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1

Modeling for Management of Farmland in Rural Communities —— A Large-scale Paddy Field in the Hokkaido Region  

Microsoft Academic Search

In this paper, we construct a model for management of farmland in rural communities to examine the effect of change in farm laborers. Based on the rural community data of Ishikari and Sorachi regions in Hokkaido paddy fields, we empirically found that the decrease in and aging of farm laborers negatively contributes to farm management. The results also showed that

Nobuyoshi YASUNAGA; Isao HARA

2

[Nitrogen balance and environmental impact of paddy field under different N management methods in Taihu Lake region].  

PubMed

Effects of nitrogen (N) management methods of paddy field on N export to environment and paddy N balance in Taihu lake region, China were studied. Field experiment including site-specific nitrogen management (SSNM), organic & chemical N fertilizer treatment (OCN), control released urea treatment (CRN), reduced chemical N treatment (RN) and farmer's N treatment (FN) were conducted at the Taihu lake region in 2008. N loss including runoff, leaching, ammonia volatilization and N2O were calculated, and the N balance was evaluated. Results showed the grain yield of SSNM, OCN, CRN and RN treatments was identical with FN treatment, while the total N rate reduced about 20%-40%, and N use efficiency (NUE) increased 14.5%-44%. N export of SSNM and CRN treatments decreased 52.8% and 45.4% in comparison with FN treatment. Under the same N input, N export of OCN treatment was lower than pure chemical N treatment (RN). N surplus was observed in FN treatment, while N deficit existed in SSNM treatments. CRN and SSNM treatments could increase NUE, reduce N export without sacrifice of yield and benefit, and could be as an economic and environment-friendly measure to intensify in Taihu lake region. PMID:21717759

Xue, Li-Hong; Yu, Ying-Liang; Yang, Lin-Zhang

2011-04-01

3

Field studies on 32P movement and P leaching from flooded paddy soils in the region of Taihu Lake, China.  

PubMed

Field experiments were done in two sites, Yixing and Changshu, Jiangsu province, China, to study P movement and leaching in flooded paddy soils. P movement in soil was investigated by using the KH2 32PO4 tracker method, and the amount of P leached from the soil layer in different depths was estimated by measuring P concentrations in the soil solution and saturated hydraulic conductivities in field. Determination was done about one month after P application. There was 46% and 42% of total 32P retained in the 0-5cm layer of soil in the Yixing site and in the Changshu site respectively. The 32P retained in the 25-30 cm layer was only about 1-2% of the total 32P added. Furthermore, 8.01% of 32P in the soil of Yixing site and 16.8% of 32P in the soil of Changshu site was lost from the layer 0-30 cm soil. The seasonal amounts of P leached from the top soil layer and from bottom layer are about 4.5-5.8% and 1.6-2.1% of the total P application, respectively. Changes of total P concentrations in soil solutions during rice growth showed that the fertilizer P applied before flooding of the paddy fields suffered a flash leaching loss and a slow leaching loss. We concluded that the fertilizer P could quickly move in the flooded paddy rice field and parts of it can enter into surface water and ground water. Unless the P application is well managed the risk of P loss and consequently environmental pollution exist. PMID:15499779

Xie, X J; Ran, W; Shen, Q R; Yang, C Y; Yang, J J; Cao, Z H

4

A study on pesticide runoff from paddy fields to a river in rural region—1: field survey of pesticide runoff in the Kozakura River, Japan  

Microsoft Academic Search

Runoff characteristics of nine kinds of herbicides from paddy fields were surveyed in the Kozakura River, that is one of the tributaries flowing into the Lake of Kasumigaura, over a period of 23 April to 30 June (before and after rice transplantation) of year. The flow rates of river water and the concentrations of herbicides in the river water were

Yoshio Nakano; Akane Miyazaki; Tomohiko Yoshida; Kazusa Ono; Takanobu Inoue

2004-01-01

5

Comparison of aquatic organisms communities between paddy fields under rice-duck (aigamo) farming and paddy fields under conventional farming  

Microsoft Academic Search

Farming using “aigamo” (rice-duck; crossbred of wild and domestic duck) is one of the popular organic farming methods for paddy rice in Japan. The diversity and community structure of aquatic organisms under rice-duck farming were investigated and compared with those under conventional farming. Adjacent paddy fields with these different farming methods were selected at two sites. The taxonomical groups and

Masatsugu Yamazaki; Nobuhiro Yasuda; Toshimasa Yamada; Koichi Ota; Makoto Kimura

2004-01-01

6

Nitrogen loss through lateral seepage in near-trench paddy fields.  

PubMed

A near-trench paddy field experiment with five urea application rates (0-360 kg N ha(-1) in 90-kg increments) was conducted on a paddy soil in the Taihu Lake Region of China to elucidate N losses through lateral seepage during three rice (Oryza sativa L.) growing seasons. The total N (Nt), NH4(+) -N, and NO3(-) -N concentrations in the lateral seepage water increased with increasing N rates. The seasonal Nt fluxes by lateral seepage varied from 6.8 to 25.6 kg N ha(-1) for urea application rates of 90 to 360 kg N ha(-1). Lateral seepage accounted for 4.7 to 6.6% of the Nt applied, implying that lateral seepage was an important pathway of N loss from near-trench paddy fields. The cumulative N loss via lateral seepage was significantly related to N fertilization rate (P = 0.05). Floodwater level was also identified as a main factor affecting N losses via lateral seepage from paddy fields, as indicated by a positive linear relationship (R2 = 0.43) between floodwater level and daily lateral flow during the flooded period (P = 0.05). Under the conditions of these experiments, a shallow floodwater depth of 50 mm, urea application rates of 90 kg N ha(-1) or less, and no rainfall within 1 wk after N application reduced N losses by lateral seepage from paddy fields. PMID:18396559

Liang, Xin-Qiang; Li, Hua; Chen, Ying-Xu; He, Miao-Miao; Tian, Guang-Ming; Zhang, Zhi-Jian

7

Phosphine in paddy fields and the effects of environmental factors.  

PubMed

Ambient levels of phosphine (PH3) in the air, phosphine emission fluxes from paddy fields and rice plants, and the distribution of matrix-bound phosphine (MBP) in paddy soils were investigated throughout the growing stages of rice. The relationships between MBP and environmental factors were analyzed to identify the principal factors determining the distribution of MBP. The phosphine ambient levels ranged from 2.368±0.6060ngm(-3) to 24.83±6.529ngm(-3) and averaged 14.25±4.547ngm(-3). The highest phosphine emission flux was 22.54±3.897ng(m(2)h)(-1), the lowest flux was 7.64±4.83ng(m(2)h)(-1), and the average flux was 14.17±4.977ng(m(2)h)(-1). Rice plants transport a significant portion of the phosphine emitted from the paddy fields. The highest contribution rate of rice plants to the phosphine emission fluxes reached 73.73% and the average contribution was 43.00%. The average MBP content of 111.6ngkg(-1)fluctuated significantly in different stages of rice growth and initially increased then decreased with increasing depth. The peak MBP content in each growth stage occurred approximately 10cm under the surface of paddy soils. Pearson correlation analyses and stepwise multiple regression analysis showed that soil temperature (Ts), acid phosphatase (ACP) and total phosphorus (TP) were the principal environmental factors, with correlative rankings of Ts>ACP>TP. PMID:23876504

Niu, Xiaojun; Wei, Aishu; Li, Yadong; Mi, Lina; Yang, Zhiquan; Song, Xiaofei

2013-07-19

8

Spatial variation of infiltration rate and compactness in paddy fields  

Microsoft Academic Search

Percolation loss of water in rice fields is a major cause of low water use efficiency. Variation of infiltration rate and\\u000a soil compactness in four paddy fields (with clay, silty clay, clay loam, and loam textures) was investigated in northern Iran.\\u000a In each field, in longitudinal and transverse directions, points located 0.5, 2.5, 6.5, 12.5, … m from the bunds

S. F. Mousavi; F. Kamyab-Talesh; M. R. Yazdani; S. H. Saghaian-Nejad

9

Effectiveness of a subsurface drainage system in poorly drained paddy fields on reduction of methane emissions  

Microsoft Academic Search

Intensive field experiments were conducted from 1999 to 2001 to examine the effects of farmland improvement on methane (CH4) emission from two rice paddy fields in Niigata, Japan. Rice cultivation and field management were similar in both paddy fields; however, one field had a subsurface drainage system installed 0.6–0.8 m below the soil surface (drained paddy field) and the other had

Yutaka Shiratori; Hidekazu Watanabe; Yuichiro Furukawa; Haruo Tsuruta; Kazuyuki Inubushi

2007-01-01

10

Mobility and Bioavailability of Technetium in Rice Paddy Fields  

SciTech Connect

Field observations and radiotracer experiments were carried out to investigate the behavior of 99Tc in paddy fields. The concentrations of global fallout 99Tc in soil collected from paddy fields in Japan were 6-88 milli-bequerels per kilogram (mBq/kg)-dry and activity ratios of 99Tc to 137Cs ranged from 1.1 x 10-3 to 7.0 x 10-3 with an average of (4.8 {+-} 2.1) x 10-3. (The theoretical activity ratio from nuclear fission yield is presently calculated as 3.3 x 10-4 with correction for radioactive decay.) This result implies that there was a tendency for 99Tc to accumulate in rice paddy fields. To understand the mechanisms of the accumulation, a sequential extraction method was applied over a 6-month period to waterlogged soils contaminated with TcO4-. From the results, it was clear that the TcO4- in soil under waterlogged conditions was readily changed to other insoluble physicochemical forms, such as TcO2, TcS2 and organically bound forms.

Uchida, S.; Tagami, K.

2003-02-24

11

Biodiversity and seasonal variation of the cyanobacterial assemblage in a rice paddy field in Fujian, China  

Microsoft Academic Search

Cyanobacteria are one of the main components of the microbiota in rice paddy fields and significantly contribute to its fertilization. The diversity and changes of the cyanobacterial assemblage were investigated during a rice growth season and after harvest in a paddy field located in Fujian Province, China. The cyanobacterial populations were analyzed by a semi-nested PCR, followed by denaturing gradient

Tieying Song; Lotta Mårtensson; Torsten Eriksson; Weiwen Zheng; Ulla Rasmussen

2005-01-01

12

Prediction of the environmental concentration of pesticide in paddy field and surrounding surface water bodies  

Microsoft Academic Search

Pesticides are very important in European rice production. For appropriate environmental protection, it is useful to predict the potential impact of pesticides after application, in paddy fields, in paddy runoff, and in the surrounding water, by calculating predicted environmental concentrations (PECs). In this paper, a joint simulation is described, coupling a field-scale pesticide fate model (RICEWQ) and a transportation model

Zewei Miao; Laura Padovani; Carlo Riparbelli; Amy M. Ritter; Marco Trevisan; Ettore Capri

2003-01-01

13

Simulation of pesticide in paddy field by coupling PCPF-1 and HYDRUS-2D: Tracer validation  

Microsoft Academic Search

Pesticide uses in rice cultivation take generally place during the ponded period. Their persistence in paddy field is the origin of pollution risk according two main ways: (i) directly in the runoff, (ii) moving and leachate in soil. To forecast pesticide behavior and hydraulic pathways in paddy field appear crucial in order to define non point pollution adapted management and

Julien TOURNEBIZE; Hirozumi WATANABE; Kazuhiro TAKAGI; Taku NISHIMURA

14

Evaluating Attitudes towards Changes in Rural Landscape by Grazing Cattle on Abandoned Paddy Fields  

NASA Astrophysics Data System (ADS)

The appearance of cattle grazing abandoned paddy fields can be used to evaluate attitudes towards this land-use change. The semantic differential (SD) method was used families of a university student to evaluate and compare attitudes towards five types of rural landscape: pasture, pasture grazed by cattle, rice paddy field, abandoned paddy field converted to pasture and abandoned paddy field converted to pasture grazed by cattle. Cattle grazing abandoned paddy fields were determined to have a positive effect on the landscape. However, all grazing cattle created a negative attitude because of the unclean appearance of the landscape. Grazing cattle at high stocking rates in small areas could create a negative attitude because of the oppressive appearance of the landscape. The acceptance of grazing cattle was lower if the animals ware newly introduced to the landscape.

Yasuhito, Kitai; Toshihiro, Hattori; Hiroshi, Takahashi

15

Assessment of the camellia seed meal impact on loaches in paddy fields  

Microsoft Academic Search

In Taiwan, Camellia seed meal is often sprayed on rice paddies during rice transplantation season to stop the growth of Pomacea canaliculata. However, the application of camellia seed meal endangers muciferous mollusks and fishes in paddy fields. Though researchers\\u000a have examined the effects of the saponin in the camellia seed meal on Pomacea canaliculata, previous studies ignore the effects of

Rong-Song Chen; Kuo-Liang Wang; Chia-Ying Wu

16

Effect of water management on methane emission from a Japanese rice paddy field: Automated methane monitoring  

Microsoft Academic Search

The effect of differing water management schemes on the emission of methane (CH4) from rice paddies to the atmosphere was studied in a Japanese paddy field. Using an automated sampling and analyzing system, the test site was divided into two plots: a continuously flooded plot which was maintained flooded by constant irrigation from May to August, and an intermittently drained

Kazuyuki Yagi; Haruo Tsuruta; Ken-ichi Kanda; Katsuyuki Minami

1996-01-01

17

Behavior of herbicide pyrazolynate and its hydrolysate in paddy fields after application.  

PubMed

Behavior of the herbicide pyrazolynate, 4-(2,4-dichlorobenzoyl)-1,3-dimethylpyrazol-5-yl p-toluenesulfonate, in paddy water and soil after application to paddy fields was investigated to evaluate the hydrolyzation to destosyl pyrazolynate (DTP), 4-(2,4-dichlorobenzoyl)-1,3-dimethyl-5-hydroxypyrazole. The respective maximum concentrations of pyrazolynate and DTP were 440-1,240 and 200-260 ?g/L, respectively, in the paddy water, and 610-860 ?g/kg dry and 460-730 ?g/kg dry in the paddy soil. The applied pyrazolynate was drained from the paddy fields as DTP. The runoff ratios of DTP from the paddy fields were calculated as 19 % ± 14 %. The respective mean values of the half-lives of pyrazolynate and DTP were 0.87 ± 0.091 and 17 ± 1.4 days in the paddy water and 2.2 ± 0.70 and 26 ± 2.1 days in the paddy soil, respectively. PMID:22914901

Kubo, Takuya; Ohno, Masaki; Nagasawa, Shunsuke; Kose, Tomohiro; Kawata, Kuniaki

2012-08-23

18

Immigration and Migration of Fish to Paddy Fields for Early Crop Rice  

NASA Astrophysics Data System (ADS)

Fish immigration and migration to early-planted paddy fields was investigated in Kaminanami-cho, in Matsusaka-city, Mie prefecture. Fish immigrated to paddy fields in the upper area through water inlets during the intake of water and they spawned eggs. Since it is rare that water is taken into paddy fields in the lower area, fish immigrated to there through water outlets when water from the drainage channel overflowed due to rainfall. Paddy fields in the lower area functioned as breeding and refuge areas. Oryzias latipes immigrated to paddy fields in the middle of April just after rice planting, and Misgurnus anguillicaudatus immigrated in May. The standard length of M. anguillicaudatus fries that emigrated from paddy fields to irrigation channels during mid-summer drainage in Kaminanami was significantly smaller than those in Kunitachi-city, Tokyo where rice is planted in early June. The small standard length of former may be attributed to a low water temperature; short term to be able to grow in paddy fields until mid-summer drainage. If accelerated cropping season make negative effect on fish spawning and growth, it will be more important to conserve spawning and growth areas in irrigation channels.

Minagawa, Akiko; Takaki, Kyoji; Goto, Masahiro; Taruya, Hiroyuki

19

Characteristics of water balance in a rainfed paddy field in Northeast Thailand  

Microsoft Academic Search

Rice productivity in rainfed paddy fields varies with seasonal changes of water availability in which the conditions of flooding\\u000a are affected by the water balance. Hydrometeorological measurements were performed in a rainfed paddy field in Northeast Thailand\\u000a from July 2004 to December 2006 to analyze the water balance. As a result of our measurements, climatologically conditions\\u000a were classified as semi-humid

Shinkichi Goto; Tsuneo Kuwagata; Pisarn Konghakote; Anan Polthanee; Yasushi Ishigooka; Hitoshi Toritani; Toshihiro Hasegawa

2008-01-01

20

Geochemical Transformation of Cadmium (Cd) from Creek to Paddy Fields in W Thailand  

NASA Astrophysics Data System (ADS)

Extensive Cd contamination of paddy soils in Tak Province, western Thailand, a consequence of Zn mining activities, was first established in 2005 and medical studies showed that the health of local communities was being impaired. Mae Tao, Tak Province, comprising many paddy fields and irrigation canals, has been selected for this study of the geochemical transformation of Cd from the contamination source in the mountainous region to the east of the study site through the community irrigation system to the paddy soils. The aim of this research is to (i) investigate the geochemical transformation of Cd as it is transported from the main irrigation creek through the canals and to the paddy fields, (ii) assess the availability of Cd to rice plants, which may be affected by both chemical and physical factors, and (iii) trial some practical treatments to minimise Cd concentrations in rice grains. Soils, irrigation canal sediments and water samples were collected during the dry season and at the onset of the rainy season. Rice samples were collected at harvesting time and samples of soil fertiliser were also obtained. Water samples were filtered, ultrafiltered and analysed by ICP-MS whilst sub-samples of dried, ground soils and sediments were first subjected to micro-wave assisted acid digestion (modified US EPA method 3052). XRD and SEM-EDX methods were used for mineralogical characterisation and selective chemical extractions have assisted in the characterisation of solid phase Cd associations. Soil Cd concentrations were in the range 2.5-87.6 µg g-1, with higher values being obtained for fields furthest from the main creek. Although current irrigation water Cd inputs are low (mean 1.9 ?g L-1; flood period), high loads of suspended particles still contribute additional Cd (4.2-9.8 µg L-1) to the paddy fields. For bioavailability assessment by a 3-step BCR sequential extraction, 70-90% Cd was in the exchangeable; HOAc-extractable fraction. That indicated that most of the Cd was in water soluble, exchangeable and carbonate-bound forms. For the fields with highest Cd concentration, SEM-EDX analysis identified two forms of Cd, i.e. Cd-Clay and Cd-CaCO3, in good agreement with the sequential extraction data. The predominance of easily extractable forms in the paddy field soils suggests that Cd may be readily absorbed by the rice plants. After harvesting, the Cd concentration in rice grains ranged from 0.05-4.0 µg g-1 and the concentration trends across the group of 18 fields matched well with the soil Cd data. Rice from nine out of the 18 fields contained Cd at greater than the safe level of 0.4 µg g-1.

Kosolsaksakul, Peerapat; Graham, Margaret; Farmer, John

2013-04-01

21

Assessment of nitrogen contamination of groundwater in paddy and upland fields  

Microsoft Academic Search

This study aims to assess the nitrogen contamination of groundwater in paddy and upland fields. A reactive chemical transport\\u000a model PHREEQC and a variable saturated groundwater flow and transport model FEMWATER were used to evaluate the vertical transport\\u000a of nitrogen compound in various soil types of paddy and upland. The shallow groundwater quality monitoring data of 2003, 2006,\\u000a 2009 in

Y. H. Kao; C.-W. Liu; C. S. Jang; S. W. Zanh; K. H. Lin

2011-01-01

22

Influence of bird feces to water quality in paddy fields during winter season  

NASA Astrophysics Data System (ADS)

Thousands of migratory birds such as tundra swan came to the paddy fields for overwintering in recent years in the study area. They stayed in paddy fields during night time for sleeping and used around the fields as a feeding ground during day time. During the birds stay, it was observed that water pooled in the paddy fields gradually turned green and gave off a bad smell. In this study, we tried to estimate the influence of the bird’s feces to water quality in the paddy fields. The study area is in the southeastern portion of Matsue City in Shimane Prefecture, Japan. In several paddy fields, puddling procedure was executed after harvesting rice and then water was stored in the paddy fields during winter season. This is because of being easier of farming activities such as weeding next season and of avoiding using pesticide for weeding with rising of environmental awareness. Water in the paddy fields was collected once or twice a month from the target fields and analyzed nitrogen, phosphorus, and organic carbon in 2007. In the study in 2006, as water was sampled once a week and the changes in the water quality had been grasped, we paid attention to behavior of the birds in a day in the field investigation in 2007. The number of the birds was counted once an hour from visible 7 am to 6 pm once a month. In addition to this, fresh feces were sampled from the fields and analyzed the contents of nitrogen, phosphorus, and organic carbon in the feces. As results, average water qualities of TN, TP, and TOC from November 2007 to March 2008 showed very high concentrations compared with a river water concentration used as irrigation water. More than 70% of TN in the water was ammonia nitrogen. Moreover, comparing with a standard fertilizer amount of nitrogen and phosphorus for paddy fields during irrigation period, it was estimated that the amount of nitrogen excreted by the bird’s feces during the winter season was equivalent to the standard fertilizer amount and the amount of phosphorus was about 30% of the standard amount. From these results, it was concluded that feces and urine from the birds influenced a lot to the water quality in the paddy fields.

Somura, H.; Takeda, I.; Masunaga, T.; Mori, Y.; Ide, J.

2009-12-01

23

Water Management and N, P Losses From Paddy Fields in Southern Korea  

NASA Astrophysics Data System (ADS)

Assessment and control of nutrient losses from paddy fields is important to protect water quality of lakes and streams in Korea. A four-year field study was carried out to investigate water management practices and losses of nitrogen (N) and phosphorus (P) in rice paddy irrigation fields in southern Korea. The amount and water quality of rainfall, irrigation, surface drainage, and infiltration were measured and analyzed to estimate inputs and losses of N and P. The observed irrigation amount surpassed consumptive use, and approximately 52 to 69 percent of inflow (precipitation plus irrigation) was lost to surface drainage. Field data showed that significant amounts of irrigation water and rainfall were not effectively used for rice paddy culture. Water quality data indicated that drainage from paddy fields could degrade the recipient water environment. The nutrient balance indicated that significant amounts of nutrients (29.5 percent of total N and 8.6 percent of total P compared to input) were lost through sur face drainage. Furthermore, up to half the nutrient losses occurred during nonstorm periods. The study results indicate that inadequate water management influences N and P losses during both storm and nonstorm periods. Proper water management is required to reduce nutrient losses through surface drainage from paddy fields; this includes such measures as minimum irrigation, effective use of rainfall, adoption of proper drainage outlet structures, and minimized forced surface drainage.

Yoon, Kwang-Sik; Cho, Jae-Young; Choi, Jin-Kyu; Son, Jae-Gwon

2006-10-01

24

[Characteristics of paddy field nitrogen leakage and runoff in rice-duck farming system].  

PubMed

A field experiment was conducted to study the characteristics of paddy field nitrogen (N) leakage and runoff under rice-duck farming (MRD), conventional farming (MR), and conventional farming with flooding (CK). Comparing with that under MR, the paddy field under MRD had a notable decrease of N (especially NO3- -N) concentration in its leaked liquid; but this concentration was tended to be increased, compared with that under CK. After 7-9 days of fertilization, the NH4+ -N and NO3- -N concentrations in paddy field surface water were higher under MRD than under MR. However, owing to the no draining and the higher band, the paddy field under MRD had a notable reduction of drainage, resulting in a marked decrease of N runoff than that under MR. Comparing with MR, the paddy field under MRD had an addition of nitrogen supply from duck dung, a reduction of N leakage and runoff, a lesser application of chemical nitrogen fertilizer, and more nitrogen uptake by rice plant. Both the reduction of N input and that of N output in rice-duck farming system were nearly equal in quantity. PMID:19449578

Yu, Xiang; Wang, Qiang-sheng; Wang, Shao-hua; Liu, Zheng-hui; Wang, Xia-wen; Ding, Yan-feng

2009-01-01

25

Geospatial estimation of soil moisture in rain-fed paddy fields using SCS-CN-based model  

Microsoft Academic Search

Paddy fields are characterized by standing water and saturation condition during the entire crop growth period. However, in sub-humid and semi-arid areas, scarce rainfall and intermittent dry spells often cause soil moisture depletion resulting in unsaturated condition in the fields. These distinctive characteristics of the paddy fields have significant influence on the runoff generation and soil moisture retention characteristics of

T. V. Reshmidevi; R. Jana; T. I. Eldho

2008-01-01

26

Influences of meteorological and vegetational factors on the partitioning of the energy of a rice paddy field  

Microsoft Academic Search

Observations made in a paddy field were analysed to show the influences of meteorological and vegetational factors on the crop's energy budget. Energy budget in the paddy field was characterized by the major partitioning to latent heat flux LE and by the negative Bowen ratio B mostly in the afternoon. Canopy resistance rc, estimated with the Penman-Monteith equation, was related

Hiroki Oue

2005-01-01

27

Estimation of methane and nitrous oxide emission from paddy fields and uplands during 1990–2000 in Taiwan  

Microsoft Academic Search

To investigate the greenhouse gases emissions from paddy fields and uplands, methane and nitrous oxide emissions were estimated from local measurement and the IPCC guidelines during 1990–2000 in Taiwan. Annual methane emission from 182807 to 242298 ha of paddy field in the first crop season ranged from 8062 to 12066 ton, and it was between 16261 and 25007 ton for

Shang-Shyng Yang; Chung-Ming Liu; Chao-Ming Lai; Yen-Lan Liu

2003-01-01

28

Incorporation of nitrogen from urea fertilizer into soil organic matter in rice paddy and cassava upland fields in Indonesia  

Microsoft Academic Search

Incorporation of newly-immobilized N into major soil organic matter fractions during a cropping period under paddy and upland cropping systems in the tropics was investigated in Jawa paddy fields with and without fish cultivation and a Sumatra cassava field in Indonesia. N-labelled urea (N urea) was applied as basal fertilizer, and the soil samples were collected after harvest. The percentage

Tomonori Abe; Sambudhi S. Suwandhi; Wayan Sabe Ardjasa; Ho Ando; Akira Watanabe

2002-01-01

29

Comparative environmental analyses of paddy fields in two lake catchment areas: Lake Taihu, China and Lake Biwa, Japan  

Microsoft Academic Search

Eutrophication in Taihu Lake has become a serious environmental problem. In this paper, environmental conditions in paddy fields in Taihu Lake's catchment area were compared with those in Lake Biwa's catchment area, which revealed issues on social development at different stages and raised questions over restoration of Taihu Lake from an environmental sociology perspective. Keywords-lake; eutrophication; paddy field; non-point source;

Yang Ping; Zhu Wei; Tan Xiao

2011-01-01

30

Improving the physical conditions of the paddy fields with irrigated paddy rice and upland crop rotation by no-till and no-puddled rice culture  

Microsoft Academic Search

In recent years, Japanese agriculture has been facing serious problems including overproduction of rice. Poorly drained paddy fields in the heavy soil area also have been often converted to upland fields. In these upland fields, however, productivity are lower due to many limitations such as wet injury. Recently, no-till and no-puddled rice culture have developed using rice seedlings grown by

OTA Takeshi; MURAKAMI Shou; FUJII Yoshikazu; KOBAYASHI Hitomi

31

Modelling field-data of preferential flow in paddy soil induced by earthworm burrows.  

PubMed

Dye tracer studies revealed that earthworm burrows in the compacted plough pan of a Chinese paddy rice field can serve as preferential flow paths. It is, however, unclear whether the observed bypass of the compacted soil horizon might be explained by differences in hydraulic properties between the plough pan, the worm burrows with a surrounding denser drilosphere and the un-compacted subsoil, or by lower-permeable macropore walls. The objective is to separately analyse effects of the individual flow domains and to identify possible limiting factors (bottlenecks) in the flow system for better soil drainage management. Hydraulic properties are inversely estimated from in situ measurements of pressure heads and evaporation by using HYDRUS_1D code. Field data of 2D pressure head progression after dye tracer infiltration in the vicinity of worm burrows are simulated using HYDRUS_2D. The axisymmetric 2D flow model considers a highly permeable cylindrical macropore region in the centre of the flow domain, assuming Darcy's law is valid. The match between simulated and measured pressure head fields improved after including a lower-permeable drilosphere pore domain. Scenario simulations show that the inflow into the 'bypass-flow' domain are reduced by the homogenized topsoil (i.e., after puddling) and limited if the macropore domain is relatively shallow. The results suggest that basic structural features may in this concept be considered as one possibility to describe observed preferential flow patterns. The separate consideration of soil structural effects may help developing and improving management strategies for manipulation of preferential flow in soils of paddy fields. PMID:19064301

Sander, Till; Gerke, Horst H

2008-11-17

32

Organic carbon stratification and size distribution of three typical paddy soils from Taihu Lake Region, China.  

PubMed

Developing realistic soil carbon (C) sequestration strategies for China's sustainable agriculture relies on accurate estimates of the amount, retention and turnover rates of C stored in paddy soils. Available C estimates to date are predominantly for the tilled and flood-irrigated surface topsoil (ca. 30 cm). Such estimates cannot be used to extrapolate to soil depths of 100 cm since soil organic carbon (SOC) generally shows a sharp decrease with depth. In this research, composite soil samples were collected at several depths to 100 cm from three representative paddy soils in the Taihu Lake region, China. Soil organic carbon distribution in the profiles and in aggregate-size fractions was determined. Results showed that while SOC decreased exponentially with depth to 100 cm, a substantial proportion of the total SOC (30%-40%) is stored below the 30 cm depth. In the carbon-enriched paddy topsoils, SOC was found to accumulate preferentially in the 2-0.25 and 0.25-0.02 mm aggregate size fractions. theta13C analysis of the coarse micro-aggregate fraction showed that the high degree of C stratification in the paddy topsoil was in agreement with the occurrence of lighter theta(13)13C in the upper 30 cm depth. These results suggest that SOC stratification within profiles varies with different pedogenetical types of paddy soils with regards to clay and iron oxyhydrates distributions. Sand-sized fractions of aggregates in paddy soil systems may play a very important role in carbon sequestration and turnover, dissimilar to other studied agricultural systems. PMID:18575131

Pan, Genxing; Wu, Laosheng; Li, Lianqing; Zhang, Xuhui; Gong, Wei; Wood, Yvonne

2008-01-01

33

Responses of seasonal and diurnal soil CO2 effluxes to land-use change from paddy fields to Lei bamboo (Phyllostachys praecox) stands  

NASA Astrophysics Data System (ADS)

Land-use change often markedly alters soil carbon (C) dynamics such as soil surface CO2 efflux. This study aims to test the hypotheses that converting paddy fields to bamboo stands would markedly reduce soil CO2 efflux and their temperature sensitivity (change of soil CO2 efflux rate by increasing 10 °C of temperature), and change the relationship between soil CO2 efflux and other environmental factors. A 12-month field study was conducted to measure the seasonal and diurnal soil CO2 effluxes in three adjacent paddy field-bamboo forest pairs with the automated soil CO2 flux system (LI-8100). Results showed that soil CO2 effluxes from both of the two land-uses had distinct seasonal patterns, and were reduced from 45.4 to 34.7 t CO2 ha-1 yr-1 in cumulative CO2 emissions when paddy fields were converted to bamboo stands. About 80% of the variation in soil respiration in the bamboo stands was explained by soil temperature; however, a positive relationship between soil CO2 efflux and soil temperature in the paddy field was observed only when the soil was not submerged under water, indicating that soil water saturation in the paddy fields altered the soil CO2 efflux-temperature relationship. A negative relationship (P < 0.01) between soil CO2 efflux and soil moisture was observed in the paddy fields, while no such relationship was observed in the bamboo stands. The apparent temperature sensitivity of soil respiration (Q10) was dependent on the depth of the soil temperature measurement and was increased by converting paddy fields to bamboo stands, rejecting the hypothesis. In Lei bamboo stands, the R2 for the soil respiration-temperature regression was higher using seasonal and diurnal CO2 efflux data together than using the seasonal data alone. We conclude that the conversion of paddy fields to Lei bamboo stands decreased the annual soil CO2 efflux but increased its temperature sensitivity, and altered the relationship between soil respiration and soil moisture. When calculating the Q10, the soil temperature measurement depth and data with diurnal timescale should be taken into account. If such land-use conversion effects are confirmed over the subtropical region in China in future research, this land-use conversion could increase C sequestration in the ecosystem and help mitigate climate change.

Zhang, Tao; Li, Yongfu; Chang, Scott X.; Jiang, Peikun; Zhou, Guomo; Zhang, Jiaojiao; Liu, Juan

2013-10-01

34

[Research on vertical distribution pattern and reserve of organic carbon in paddy field soil of Qianguo, Jilin].  

PubMed

Taking Qianguo paddy field of Jilin Province as investigation object, based on the soil test data of 7 different periods developed for 4 to 55 years, the vertical distribution of SOC content in the 1 m paddy field section was studied adopting the space scale method instead of time scale. The paddy soil carbon sink in last 20 years was discussed and the organic carbon storage of Qianguo paddy field soil was estimated. According to the second soil census data, the characteristics of soil SOC used in fields of different type were comparatively analyzed. The results showed that the paddy field SOC decreased from top to bottom by layer, which showed an increasing trend with the increase of development age; the organic carbon content in the surface soil layer (0-30 cm) (1 820.79 t) was 46.87% of the total organic carbon storage in deep soil (3 885.05 t), and the soil SOCD content was highly different depending on the type of field, ranked in descending order as paddy field, dry land, and saline field. The development of paddy field is a SOC accumulating carbon sink process, which is conducive to the transfer of organic carbon from the surface soil layer to the bottom soil layer. PMID:24028014

Tang, Jie; Zhang, Wen-Hui; Li, Zhao-Yang; Zhang, Nan; Hu, Meng

2013-07-01

35

Abundance of bacteriophages of common heterotrophic bacteria in the floodwater of a Japanese paddy field  

Microsoft Academic Search

Bacteriophages of 18 heterotrophic bacterial strains (four Cytophaga–Flavobacterium–Bacteroides bacteria, six ?-Proteobacteria, two ?-Proteobacteria, two ?-Proteobacteria, one Firmicute and three Actinobacteria) that were isolated from floodwater were enumerated in the floodwater of four plots (no fertilization, N, P, and K fertilizers, N, P, K and Ca fertilizers, and N, P, K and Ca fertilizers with compost) in a Japanese paddy field

Natsuko Nakayama; Mami Okumura; Katsuhiro Inoue; Susumu Asakawa; Makoto Kimura

2007-01-01

36

Effects of Fipronil Insecticide Application on Sympetrum sp. Larvae and Adults in Experimental Rice Paddy Field  

NASA Astrophysics Data System (ADS)

The effect of on sowing and before transplanting application of the phenyl pyrazole insecticide, fipronil, on the survivorship Sympetrum spp. was investigated in plots of an experimental rice paddy field. In addition, the effect of two pesticide applications on rice weevils was investigated. A total of nine paddy plots were used in this study: three were treated with fipronil at the before transplanting application , three at the on sowing application, and the three remaining plots were left untreated for use as controls. Fipronil concentrations in paddy water at the time of application in before transplanting and on sowing treatments reached 1.45 and 1.20 ?g/L, respectively. A comparison of experimental and control plots revealed a marked absence of Sympetrum frequens larvae, exuviae and adults from fipronil-treated fields. Adult density of Sympetrum sp. and members of Lestidae in paddy fields before transplanting application were considerably lower than in control plots. Our results show that before transplanting application is more effective than on sowing application for treating rice weevils, but that on sowing application may still be harm against dragonflies.

Jinguji, Hiroshi; Ueda, Tetsuyuki; Tsunoda, Manami; Aihara, Shoko; Saito, Mitsuo

37

[Determination of niclosamide ethanolamine residue in rice and paddy field by high performance liquid chromatography].  

PubMed

A high performance liquid chromatographic (HPLC) method was established for the analysis of niclosamide ethanolamine residue in rice and paddy field. The paddy water and plant were extracted with alkaline ethylacetate, while the paddy soil, rice husk and unpolished rice were first extracted with alkaline ethanol, and then with ethylacetate. The extracts were then cleaned-up by a Florisil column and detected by high performance liquid chromatography with an ultraviolet detector (UVD) on a Welchrom C18 column (250 mm x 4.6 mm, 5 microm). The calibration curve showed good linearity from 0.01 mg/L to 10.00 mg/L with the correlation coefficient more than 0. 999 8. The average recoveries of this method were from 93.47% to 100.9% with the relative standard deviations of 1.46% - 5.82% at the spiked levels of 0.01 - 5.00 mg/kg. This method is fast, simple, sensitive, reproducible and practical for the determination of niclosamide ethanolamine residue in paddy fields, and can meet the requirement of the determination of pesticide residues. PMID:22393698

Wu, Yihong; Gong, Daoxin; Peng, Xiao; Xie, Hui; Han, Baolu

2011-11-01

38

Characterization of contamination, source and degradation of petroleum between upland and paddy fields based on geochemical characteristics and phospholipid fatty acids.  

PubMed

To evaluate contamination caused by petroleum, surface soil samples were collected from both upland and paddy fields along the irrigation canals in the Hunpu wastewater irrigation region in northeast China. N-alkanes, terpanes, steranes, and phospholipid fatty acids (PLFA) in the surface soil samples were analyzed. The aliphatic hydrocarbon concentration was highest in the samples obtained from the upland field near an operational oil well; it was lowest at I-3P where wastewater irrigation promoted the downward movement of hydrocarbons. The Hunpu region was found contaminated by heavy petroleum from oxic lacustrine fresh water or marine deltaic source rocks. Geochemical parameters also indicated significantly heavier contamination and degradation in the upland fields compared with the paddy fields. Principal component analysis based on PLFA showed various microbial communities between petroleum contaminated upland and paddy fields. Gram-negative bacteria indicated by 15:0, 3OH 12:0, and 16:1(9) were significantly higher in the paddy fields, whereas Gram-positive bacteria indicated by i16:0 and 18:1(9)c were significantly higher in the upland fields (p < 0.05). These PLFAs were related to petroleum contamination. Poly-unsaturated PLFA (18:2omega6, 9; indicative of hydrocarbon-degrading bacteria and fungi) was also significantly elevated in the upland fields. This paper recommends more sensitive indicators of contamination and degradation of petroleum in soil. The results also provide guidelines on soil pollution control and remediation in the Hunpu region and other similar regions. PMID:23534234

Zhang, Juan; Wang, Renqing; Du, Xiaoming; Li, Fasheng; Dai, Jiulan

2012-01-01

39

Spatial variability of soil available Zn and Cu in paddy rice fields of China  

NASA Astrophysics Data System (ADS)

As a source of nutrient supplements, the deficiency or excess of micronutrients in soil is directly connected to the plant uptake and, thereby, status of micronutrients in the human population. Proper management of micronutrients requires an understanding of the variations of soil micronutrients across the fields. This study is to investigate the spatial patterns of soil available Zn and Cu in paddy rice fields. Four hundred and sixty three soil samples were taken in Hangzhou-Jiaxing-Huzhou (HJH) watershed in Zhejiang Province, China, and available Zn and Cu were analyzed using an atomic adsorption spectrometer. Geostatistical semivariograms analysis indicated that the available Zn and Cu were best fitted to a spherical model with a range of 40.5 and 210.4 km, respectively. There were moderate spatial dependences for Zn and Cu over a long distance and the dependence were attributed to soil types and anthropogenic activities. The overlay analysis of spatial patterns and soil types gave us greater understanding about how intrinsic factors affect the spatial variation of available micronutrients. Based on the above, macroscopically regionalized management of soil available micronutrients and the implications to potential risk were discussed.

Liu, Xingmei; Xu, Jianming; Zhang, Minghua; Si, Bingcheng; Zhao, Keli

2008-10-01

40

Purification of contaminated paddy fields by clean water irrigation over two decades.  

PubMed

Paddy fields near a mining site in north part of Guangdong Province, PR China, were severely contaminated by heavy metals as a result of wastewater irrigation from the tailing pond. The following clean water irrigation for 2 decades produced marked rinsing effect, especially on Pb and Zn. Paddy fields continuously irrigated with wastewater ever since mining started (50 years) had 1,050.0 mg kg?1 of Pb and 810.3 mg kg?1 of Zn for upper 20 cm soil, in comparison with 215.9 mg kg?1 of Pb and 525.4 mg kg?1 of Zn, respectively, with clean water irrigation for 20 years. Rinsing effect mainly occurred to a depth of upper 40 cm, of which the soil contained highest metals. Copper and Cd in the farmlands were also reduced due to clean water irrigation. Higher availability of Pb might partly account for more Pb transferred from the tailing pond to the farmland and also more Pb removal from the farmland as a result of clean water irrigation. Neither rice in the paddy field nor dense weeds in the uncultivated field largely took up the metals. However, they might contribute to activate metals differently, leading to a different purification extent. Rotation of rice and weed reduced metal retention in the farmland soil, in comparison with sole rice growth. Harvesting of rice grain (and partially rice stalk) only contributed small fraction of total amount of removed metal. In summary, heavy metal in paddy field resulting from irrigation of mining wastewater could be largely removed by clean water irrigation for sufficient time. PMID:23797601

Tai, Yiping; Lu, Huanping; Li, Zhian; Zhuang, Ping; Zou, Bi; Xia, Hanping; Wang, Faming; Wang, Gang; Duan, Jun; Zhang, Jianxia

2013-10-01

41

Distribution and identification of proteolytic Bacillus spp. in paddy field soil under rice cultivation.  

PubMed

Proteolytic bacteria in paddy field soils under rice cultivation were characterized and enumerated using azocoll agar plates. Bacillus spp. were the proteolytic bacteria that were most frequently present, comprising 59% of the isolates. They were always the numerically dominant proteolytic bacteria isolated from three kinds of fertilizer treatments (yearly application of rice-straw compost and chemical fertilizer, yearly application of chemical fertilizer, and no fertilizer application) and at three different stages of rice development (vegetative growth stage, maximal tillering stage, and harvest stage). Of the 411 proteolytic bacteria isolated, 124 isolates had stronger proteolytic activity than others on the basis of gelatin liquefaction tests and most of them were Bacillus spp. (100% in 1989 and 92.4% in 1991). Bacillus subtilis and Bacillus cereus were the main bacteria of this group and Bacillus mycoides, Bacillus licheniformis, and Bacillus megaterium were also present. We conclude that these Bacillus spp. are the primary source of soil protease in these paddy fields. PMID:8364803

Watanabe, K; Hayano, K

1993-07-01

42

Wise use of paddy rice fields to partially compensate for the loss of natural wetlands  

Microsoft Academic Search

This paper reviews the scientific information related to climate change impacts on wetlands and functions of human-made wetlands\\u000a such as paddy rice field and treatment wetland are described to partially compensate for the loss of natural wetlands. Wetlands\\u000a are among the world’s most productive environments and are cradles of biological diversity, providing the water and primary\\u000a productivity upon which countless

Chun G. Yoon

2009-01-01

43

Dynamics of dissolved ions in the soil of abandoned terraced paddy fields in Sado Island, Japan  

Microsoft Academic Search

We investigated the soil and soil water chemistry in abandoned terraced paddy fields (reed stand) and a thicket of deciduous\\u000a broad-leaved trees (thicket stand) on the same slope in Sado Island, Japan. The soils gathered from these plots were incubated\\u000a under different water conditions to examine the dynamics of dissolved ions. The organic carbon pool in the soil in the

Nobuhiro Oyanagi; Makoto Nakata

2010-01-01

44

Comparative study of the microbial diversity of bulk paddy soil of two rice fields subjected to organic and conventional farming  

Microsoft Academic Search

Two adjacent paddies of an experimental rice field, subjected to organic and conventional farming, were characterized aiming the comparative assessment of microbiological variations occurring in the bulk paddy soil over the rice cycle. This study comprehended the simultaneous characterization of general physicochemical soil properties [total carbon and nitrogen, pH (H2O and KCl), C:N ratio and water content], biochemical properties [enzymatic

Ana R. Lopes; Cátia Faria; Ángeles Prieto-Fernández; Carmen Trasar-Cepeda; Célia M. Manaia; Olga C. Nunes

2011-01-01

45

Paddy field mapping and yield estimation by satellite imagery and in situ observations  

NASA Astrophysics Data System (ADS)

Since Asian countries are responsible for approximately 90% of the world rice production and consumptions, rice is the most significant cereal crop in Asia. In order to ensure food security and take mitigation strategies or policies to manage food shortages, timely and accurate statistics of rice production are essential. It is time and cost consuming work to create accurate statistics of rice production by ground-based measurements. Hence, satellite remote sensing is expected to contribute food security through the systematic collection of food security related information such as crop growth or yield estimation. In 2011, Japan Aerospace Exploration Agency (JAXA) is collaborating with GISTDA (Geo-Informatics and Space Technology Development Agency, Thailand) in research projects of rice yield estimation by integrating satellite imagery and in situ data. Thailand is one of the largest rice production countries and the largest rice exporting country, therefore rice related statistics are imperative for food security and economy in the country. However, satellite observation by optical sensor in tropics including Thailand is highly limited, because the area is frequently covered by cloud. In contrast, Japanese microwave sensor, namely Phased-Array L-Band Synthetic Aperture Radar (PALSAR) on board Advanced Land Observing Satellite (ALOS) is suitable for monitoring cloudy area such as Southeast Asia, because PALSAR can penetrate clouds and collect land-surface information even if the area is covered by cloud. In this study, rice crop yield over Khon Kaen, northeast part of Thailand was estimated by combining satellite imagery and in-situ observation. This study consists of mainly two parts, paddy field mapping and yield estimation by numerical crop model. First, paddy field areas were detected by integrating PALSAR and AVNIR-2 data. PALSAR imagery has much speckle noise and the border of each landcover is ambiguous compared to that of optical sensor. To overcome this problem, we used AVNIR-2 data for object-based image analysis and derived each object was linked with backscatter coefficient of PALSAR. Then, paddy field areas were detected by using seasonal changes of backscatter coefficients. Derived paddy field map over Kohn Kean area was validated with ground-based measurements and it showed high accuracy. Finally, in order to estimate rice crop yield, numerical crop model was run with model parameters related to physiological aspect of rice and meteorological data collected by Automatic Weather Station (AWS) placed at study area, field survey and satellite products. This processing was implemented all over the detected paddy filed areas and overall yield was estimated by counting up each result. Consequently, it was found that the yield estimation was reasonable validated with agricultural statistics in Thailand.

Oyoshi, K.; Sobue, S.

2011-12-01

46

Modeling of Movement of Field Gudgeon, Gnathopogon elongatus elongatus, in Agricultural Canals in Yatsu Paddy Fields  

NASA Astrophysics Data System (ADS)

It is important as quantitative information for making a decision of project sites for networking of water area, to predict reproductive process of fish population when consolidating fish-ways on points dividing fish habitat. To that end, it is necessary to predict the number of individuals migrating to new habitats. Hence, modeling of movement of individuals is necessary as a first step in population modeling. We constructed a mathematical model of movement of field gudgeon in agricultural canals, comparing with observed data obtained by our surveys. A unit time span of this model is 50 days. This model is able to consider existence of 2 types of movement, namely, individuals of sedentary type and individuals of ambulant type. Parameters of the model were decided based on observed data which correspond to 1 unit span. Next, moving distances of 6 individuals for 4 unit span were calculated using those parameters. A histogram of calculated values was similar to that of observed data which correspond to 4 unit span. The model is expected to provide an important immigration component to a population dynamics model which is currently under development. The population model is needed to predict population recovery processes where areas of paddy fields are joined in larger networks through construction of fish-ways.

Takemura, Takeshi; Koizumi, Noriyuki; Mizutani, Masakazu; Mori, Atsushi; Watabe, Keiji

47

[Carbon sequestration effects of rice straw return in double season paddy field in Southern China].  

PubMed

In a long-term site-specific experiment with rice straw return (RSR) and in a short-term experiment with different RSR modes, this paper studied the effects of RSR on the soil organic carbon (SOC) sequestration, methane emission, and net carbon sink in a double season paddy field. RSR increased the SOC content, and the annual increasing rate of soil carbon sink in plow layer (0-15 cm) under long-term RSR was 0.07 t C x hm(-2) x a(-1). With the increasing amount of RSR, the apparent SOC transformation rate decreased. RSR promoted the methane emission from the paddy field significantly, and the methane emission flux in treatment RSR plus NPK during early- and late rice growth seasons increased by 75.0% and 251.5% (P < 0.01), respectively, compared with that in treatment NPK. The methane emission increased with the increasing amount of RSR. Under the similar tillage mode and rice yield, the rice straw returned had the similar apparent methane transformation rate. Considering the soil carbon sequestration and the net carbon sink after methane emission in the paddy field comprehensively, treatment RSR plus NPK had significant negative effect on the carbon sink which was basically approached to the bio-fixation of carbon by rice and increased by 158.3%, as compared with treatment NPK. Among different RSR modes, rice straw mulching plus no tillage decreased soil methane emission significantly, with the net carbon sink decreased by 50.9% as compared with the treatment high stubble plus tillage, and benefited the high and stable yielding of rice. PMID:22384587

Wu, Jia-Mei; Ji, Xiong-Hui; Peng, Hua; Shi, Li-Hong; Liu, Zhao-Bing; Tian, Fa-Xiang; Huo, Lian-Jie; Zhu, Jian

2011-12-01

48

Cinosulfuron: chemical and biological degradability, adsorption and dissipation in flooded paddy field sediment.  

PubMed

Cinosulfuron is a sulfonylurea herbicide largely used in the extensive cultures of flooded rice in North Italy. The degradation of cinosulfuron has been investigated in sterile aqueous solutions at 30 degrees C at different pH values. It was rapidly degraded at acidic pH (half-lives 3, 9 and 43 days at pH 4, 5 and 6, respectively) while the half-life was > 1 year at pH 7 and 9. Two degradation products formed by cleavage of the sulfonylurea bridge were identified by LC-MS. Degradation by selected mixed microbial cultures tested in aerobic and anaerobic conditions was very slow and attributable to chemical hydrolysis due to the acidic pH of the cultural broths. Degradation took place in freshly collected rice field water treated for two years with cinosulfuron but, in this case also, chemical hydrolysis prevailed over microbial degradation. In contrast, in flooded sediment simulating the paddy field environment, the dissipation rate of cinosulfuron was higher than expected from chemical hydrolysis according to the pH of the system, indicating the involvement of soil microflora. Although the herbicide exhibited a reduced affinity for the sediment surfaces demonstrated by the low value of the K(f) Freundlich coefficient (0.87 on a micromolar basis), the rapid dissipation observed in the simulated paddy field should prevent its leaching to ground water. PMID:15726573

Nègre, Michèle; Baiocchi, Claudio; Gennari, Mara

2005-07-01

49

Methane emission from fields with three various rice straw treatments in Taiwan paddy soils.  

PubMed

Flooded rice fields are one of the major biogenic methane sources. In this study, the effects of straw residual treatments on methane emission from paddy fields were discussed. The experimental field was located at Tainan District Agricultural Improvement Station in Chia-Yi county (23 degrees 25'08''N, 120degrees16'26''E) of southern Taiwan throughout the first and the second crop seasons in 2000. The seasonal methane fluxes in the first crop season with rice stubble removed, rice straw burned and rice straw incorporated were 4.41, 3.78 and 5.27 g CH4 m(-2), and the values were 32.8, 38.9 and 75.1 g CH4 m(-2) in the second crop season, respectively. In comparison of three management methods of rice straw residue, the incorporation of rice straw residue should show a significant tendency for enhancing methane emission in the second crop season. Moreover, stubble removed and straw burned treatments significantly reduced CH4 emissions by 28 approximately 56% emissions compared to straw incorporated plot. Concerning for air quality had led to legislation restricting rice straw burning, removing of rice stubble might be an appropriate methane mitigation strategy in Taiwan paddy soils. PMID:12856932

Liou, Rey-May; Huang, Shan-Ney; Lin, Chin-Wei; Chen, Shin-Hsiung

2003-07-01

50

Water management--a tool for methane mitigation from irrigated paddy fields.  

PubMed

Water drainage is considered to be one of the important practices that reduce the CH(4) efflux from paddy fields. In this study, four different drainage systems (continuous flooding, tillering stage drainage, mid-season drainage and multiple drainage) were compared to find out the best one, for attenuation of CH(4) emission from rice fields. Except for continuous flooding, from all the other three drainage systems, irrigation water from the paddy fields was drained out at the different stages of the crop cycle. Highest efflux of the methane was recorded from continuously flooded plots (346.6 mg/m(2)/day), followed by 9% less CH(4) efflux from tillering stage drainage (315.1mg/m(2)/day), 36.7% less efflux from mid-season drainage (219.3mg/m(2)/day) and the least 41% CH(4) efflux from multiple drainage plots (204.7 mg/m(2)/day). Among all the four different drainage systems applied, mid-season drainage and multiple drainage were found to be highly effective in mitigating methane efflux. Redox potential of the soil of the drainage system was found to be inversely proportional to the methane efflux from all the treatments. PMID:19854469

Tyagi, Larisha; Kumari, Babita; Singh, S N

2009-10-25

51

Application of FAO56 for evaluating evapotranspiration in simulation of pollutant runoff from paddy rice field in Japan  

Microsoft Academic Search

Applicability of FAO-56 method in estimation of evapotranspiration for the simulation of pollutant runoff from rice paddy field in Japan was investigated. Crop evapotranspiration and crop coefficient recommended by FAO-56 method relative to those values obtained in the field monitoring for three Japanese rice varieties, namely, Nihonbare, Mangetsumochi and Koganemochi during first three growing stages were compared. Also, the pesticide

Son Hong Vu; Hirozumi Watanabe; Kazuhiro Takagi

2005-01-01

52

Arsenic dynamics in porewater of an intermittently irrigated paddy field in Bangladesh.  

PubMed

In Bangladesh, irrigation of dry season rice (boro) with arsenic-contaminated groundwater is leading to increased As levels in soils and rice, and to concerns about As-induced yield reduction. Arsenic concentrations and speciation in soil porewater are strongly influenced by redox conditions, and thus by water management during rice growth. We studied the dynamics of As, Fe, P, Si, and other elements in porewater of a paddy field near Sreenagar (Munshiganj), irrigated according to local practice, in which flooding was intermittent. During early rice growth, As porewater concentrations reached up to 500 ?g L(-1) and were dominated by As(III), but As release was constrained to the lower portion of the soil above the plow pan. In the later part of the season, soil conditions were oxic throughout the depth range relevant to rice roots and porewater concentrations only intermittently increased to ?150 ?g L(-1) As(V) following irrigation events. Our findings suggest that intermittent irrigation, currently advocated in Bangladesh for water-saving purposes, may be a promising means of reducing As input to paddy soils and rice plant exposure to As. PMID:21166387

Roberts, Linda C; Hug, Stephan J; Voegelin, Andreas; Dittmar, Jessica; Kretzschmar, Ruben; Wehrli, Bernhard; Saha, Ganesh C; Badruzzaman, A Borhan M; Ali, M Ashraf

2010-12-17

53

Impacts of the herbicide butachlor on the larvae of a paddy field breeding frog (Fejervarya limnocharis) in subtropical Taiwan  

USGS Publications Warehouse

Butachlor is the most commonly used herbicide on paddy fields in Taiwan and throughout Southeast Asia. Since paddy fields provide habitat for pond breeding amphibians, we examined growth, development, time to metamorphosis, and survival of alpine cricket frog tadpoles (Fejervarya limnocharis) exposed to environmentally realistic concentrations of butachlor. We documented negative impacts of butachlor on survival, development, and time to metamorphosis, but not on tadpole growth. The 96 h LC50 for tadpoles was 0.87 mg/l, much lower than the 4.8 mg/l recommended dosage for application to paddy fields. Even given the rapid breakdown of butachlor, tadpoles would be exposed to concentrations in excess of their 96 h LC50 for an estimated 126 h. We also documented DNA damage (genotoxicity) in tadpoles exposed to butachlor at concentrations an order of magnitude less than the 4.8 mg/l recommended application rate. We did not find that butachlor depressed cholinesterase activity of tadpoles, unlike most organophosphorus insecticides. We conclude that butachlor is likely to have widespread negative impacts on amphibians occupying paddy fields with traditional herbicide application.

Liu, Wan-Yi; Wang, Ching-Yuh; Wang, Tsu-Shing; Fellers, Gary M.; Lai, Bo-Chi; Kam, Yeong-Choy

2011-01-01

54

Methane and nitrous oxide emissions from rice paddy fields as affected by nitrogen fertilisers and water management  

Microsoft Academic Search

Methane and N2O emissions affected by nitrogen fertilisers were measured simultaneously in rice paddy fields under intermittent irrigation in 1994. Ammonium sulphate and urea were applied at rates of 0 (control), 100 and 300 kg N ha-1. The results showed that CH4 emission, on the average, decreased by 42 and 60% in the ammonium sulphate treatments and 7 and 14%

Zucong Cai; Guangxi Xing; Xiaoyuan Yan; Hua Xu; Haruo Tsuruta; Kazuyuki Yagi; Katsuyuki Minami

1997-01-01

55

Effect of plastic-film mulching on leaching of nitrate nitrogen in an upland field converted from paddy  

Microsoft Academic Search

A lysimeter experiment was conducted to examine the effects of plastic film mulching on the leaching rate of nitrate nitrogen (NO 3-N) from chemical fertilizer that was applied to an upland field that had been converted from paddy rice production. Leaching was monitored in two lysimeters filled with sandy loam soil, which contained low soil organic matter content, under different

Tomokazu Haraguchi; Atsushi Marui; Kozue Yuge; Yoshisuke Nakano; Ken Mori

2004-01-01

56

Fate and Transport of Nursery-Box-Applied Tricyclazole and Imidacloprid in Paddy Fields  

Microsoft Academic Search

The fate and transport of tricyclazole and imidacloprid in paddy plots after nursery-box application was monitored. Water\\u000a and surface soil samples were collected over a period of 35 days. Rates of dissipation from paddy waters and soils were also\\u000a measured. Dissipation of the two pesticides from paddy water can be described by first-order kinetics. In the soil, only the\\u000a dissipation of

Thai Khanh Phong; Dang Thi Tuyet Nhung; Takashi Motobayashi; Dang Quoc Thuyet; Hirozumi Watanabe

2009-01-01

57

[Controlling effects of multiple species coexistence on rice diseases, pests and weeds in paddy field ecosystem].  

PubMed

Establishing a species-diversified cropping system to control crop diseases, insect pests and weeds is an important approach to sustainable agricultural development. This paper reviewed the researches on paddy field species-diversified cropping systems at home and abroad, and discussed the controlling effects and mechanisms of multiple species coexistence on rice diseases, pests and weeds control. The multiple species coexistence models such as rice-fish, rice-duck, rice-azolla-fish and rice-azolla-duck had effective controlling effects on Thanatephorus cucumeris (Frank) Donk, Nilaparata lugens Stal, Chaphalocrocis medinalis Gueneeand, and weeds. Other models like intercropping rice with Zizania caduciflora L. and with other wetland crops also had effective effects in controlling the occurrence and spread of Pyricularia grisea. It was suggested that further studies should be strengthened from the viewpoints of crop culture, molecular biology, and chemical ecolo- PMID:17650871

Wang, Han; Tang, Jian-jun; Xie, Jian; Chen, Xin

2007-05-01

58

Methanogenic archaeal communities developed in paddy fields in the Kojima Bay polder, estimated by denaturing gradient gel electrophoresis, real-time PCR and sequencing analyses  

Microsoft Academic Search

Methanogenic archaeal communities inhabiting the paddy field soils in the Kojima Bay polder were investigated using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE), real-time PCR and sequencing analyses. Soil samples of the plow and subsoil layers were collected in 2006 from four paddy fields that were reclaimed between 1692 and 1954. The DGGE band patterns of the targeted 16S rRNA

Takeshi Watanabe; Vita Ratri Cahyani; Jun Murase; Eiji Ishibashi; Makoto Kimura; Susumu Asakawa

2009-01-01

59

A comparison of isotope fractionation of carbon and hydrogen from paddy field rice roots and soil bacterial enrichments during CO 2\\/H 2 methanogenesis  

Microsoft Academic Search

To better understand the isotope biogeochemistry of paddy field CH4, we investigated carbon and hydrogen isotope fractionation during CO2 reduction by a methanogenic community enriched from California paddy field soil and rice plants. Results from analyses of terminal restriction fragment length polymorphism (T-RFLP) and sequences of the archaeal small-subunit (SSU) rRNA-encoding genes (rDNA) showed a difference in methanogenic community structure

Amnat Chidthaisong; Kuk-Jeong Chin; David L. Valentine; Stanley C. Tyler

2002-01-01

60

[Distribution characteristics of soil humus fractions stable carbon isotope natural abundance (delta 13C) in paddy field under long-term ridge culture].  

PubMed

A 16-year field experiment was conducted in a ridge culture paddy field in the hilly region of Sichuan Basin, aimed to investigate the distribution characteristics of stable carbon isotope natural abundance (delta 13C) in soil humus fractions. The soil organic carbon (SOC) content in the paddy field under different cultivation modes ranked in the order of wide ridge culture > ridge culture > paddy and upland rotation. In soil humus substances (HS), humin (HU) was the main composition, occupying 21% - 30% of the total SOC. In the extracted soil carbon, humic acid (HA) dominated, occupying 17% - 21% of SOC and 38% - 65% of HS. The delta 13C value of SOC ranged from -27.9 per thousand to -25.6 per thousand, and the difference of the delta 13C value between 0-5 cm and 20-40 cm soil layers was about 1.9 per thousand. The delta 13C value of HA under different cultivation modes was 1 per thousand - 2 per thousand lower than that of SOC, and more approached to the delta 13C value of rapeseed and rice residues. As for fulvic acid (FA), its delta 13C value was about 2 per thousand and 4 per thousand higher than that of SOC and HA, respectively. The delta 13C value of HU in plough layer (0-20 cm) and plow layer (20-40 cm) ranged from -23.7 per thousand - -24.9 per thousand and -22.6 per thousand - -24.2 per thousand, respectively, reflecting the admixture of young and old HS. The delta 13C value in various organic carbon fractions was HU>FA>SOC>rapeseed and rice residues>HA. Long-term rice planting benefited the increase of SOC content, and cultivation mode played an important role in affecting the distribution patterns of soil humus delta 13C in plough layer and plow layer. PMID:21774322

Tang, Xiao-hong; Luo, You-jin; Ren, Zhen-jiang; Lü, Jia-ke; Wei, Chao-fu

2011-04-01

61

Nannophya pygmaea (Odonata: Libellulidae), an endangered dragonfly in Korea, prefers abandoned paddy fields in the early seral stage.  

PubMed

To characterize habitats of Nannophya pygmaea Rambur (the northern pygmyfly; Odonata: Lilbellulidae), which is endangered in Korea, we analyzed characteristics of surface water and soil, landscape properties, and vegetation types in 22 habitats in eight areas of Korea where nymphs of N. pygmaea have been found since 2005. We divided the habitats into two groups: DS (dwelling site) habitats, where N. pygmaea was observed at the time of the study, and PDS (past dwelling site) habitats, where N. pygmaea recently lived but is no longer found. The habitats were mostly located in former paddy fields on mountain slopes that have been abandoned for 3-7 yr. The main water sources for these habitats were ground water and surface runoff, and the water level was stable at 3-7 cm in depth. The habitats ranged from 300 to 1000 m(2) and were dominated by Juncus effusus, which formed tussock mounds. According to the hydrosere model of succession, N. pygmaea appeared mostly in the early stages of plant succession (the period approximately 3-7 yr after the initiation of succession in former paddy fields) and N. pygmaea preferred habitats displaying the water and soil characteristics that are typical of the early stages of succession in abandoned paddy fields. These results indicate that the primary habitats of N. pygmaea in Korea are recently abandoned paddy fields that are in an oligotrophic state. As succession proceeds in these habitats, N. pygmaea disappears. A habitat management program should be launched to conserve the habitats and populations of N. pygmaea. PMID:20388254

Yoon, Jihyun; Nam, Jong Min; Kim, Heungtae; Bae, Yeon Jae; Kim, Jae Geun

2010-04-01

62

T4-type bacteriophage communities estimated from the major capsid genes (g23) in manganese nodules in Japanese paddy fields  

Microsoft Academic Search

The present study compared the capsid gene (g23) of T4-type bacteriophages (phages) in Mn nodules with those in the plow layer soil and subsoils of two Japanese paddy fields by applying the primers MZIA1bis and MZIA6 to DNA extracts from the nodules and soils. The deduced amino acid sequences of the g23 genes in the Mn nodules were similar to

Vita Ratri Cahyani; Jun Murase; Eiji Ishibashi; Susumu Asakawa; Makoto Kimura

2009-01-01

63

Density-dependent growth and reproduction of the apple snail, Pomacea canaliculata : a density manipulation experiment in a paddy field  

Microsoft Academic Search

To examine density dependence in the survival, growth, and reproduction of Pomacea canaliculata, we conducted an experiment in which snail densities were manipulated in a paddy field. We released paint-marked snails of\\u000a 15–20 mm shell height into 12 enclosures (pens) of 16 m2 at one of five densities – 8, 16, 32, 64, or 128 snails per pen. The survival

Koichi Tanaka; Tomonari Watanabe; Hiroya Higuchi; Kenji Miyamoto; Yoichi Yusa; Toru Kiyonaga; Hirotsugu Kiyota; Yoshito Suzuki; Takashi Wada

1999-01-01

64

DEVELOPMENT OF MULTI POLARIZATION SAR ALGORITHM FOR SOIL MOISTURE IN PADDY FIELD, CAMBODIA  

NASA Astrophysics Data System (ADS)

In Cambodia, agriculture is the important industry which engages many people. However, the water supplied only during rainy season is the source of water for agriculture. To use the limited water resources effectively, it is necessary to apply the water-resource management based on the meteorological prediction and the river runoff prediction. As the factor of these predictions, the soil moisture plays a key role in water and thermal transportation to the atmosphere, and the contribution of river runoff property. On the other hand, the soil moisture distribution with the paddy field scale is helpful in the agricultural activity and management. Therefore, Synthetic Aperture Radars (SAR) is expected to observe soil moisture with high spatial resolution in large area. Recently, some multi-polarization SAR have been in operation. The purpose of this study is to develop the algorithm to estimate soil moisture by using multi-polarization data acquired with the Phased Array type L-band Synthetic Aperture Radar (PALSAR) onboard the Advanced Land Observing Satellite (ALOS).

Aida, Kentaro; Koike, Toshio; Shi, Jiancheng

65

Seasonality of ecosystem respiration in a double-cropping paddy field in Bangladesh  

NASA Astrophysics Data System (ADS)

Ecosystem respiration (RE) from cultivated ecosystems is important for understanding the role of these ecosystems in the global carbon balance. To evaluate carbon dynamics in a double-rice cropping paddy field, we conducted long-term measurements at Mymensingh, Bangladesh in 2007 using a tower-based eddy covariance technique. The study objectives were to investigate the diurnal and seasonal variations in RE and to develop and evaluate empirical models for predicting variations in RE using environmental parameters. We found that the diurnal pattern of RE was driven by soil temperature (Ts) whereas the seasonal variation in RE was controlled primarily by Ts and soil water content (SWC). Under high biomass conditions, Ts plays a dominant role in the magnitude of CO2 release. Both the amount and magnitude of RE variation were larger in the "Boro" dry-season rice growing period from late winter to mid-summer than in the "Aman" wet-season rice growing period from late summer to early winter. Annually, the ratio of RE to gross primary production (GPP) was 0.67, indicating a net sink of carbon; the two growing seasons had RE/GPP ratios of 0.58 and 0.52. A model using Ts, SWC, and aboveground biomass predicted daily RE with R2 values of 0.87 and 0.62 for the Boro and Aman seasons, respectively.

Hossen, M. S.; Mano, M.; Miyata, A.; Baten, M. A.; Hiyama, T.

2011-08-01

66

Spatial and Temporal Variability of Macronutrients in a Lime-amended Acid Paddy Field  

NASA Astrophysics Data System (ADS)

Soil spatial variability is a natural occurring and or management induced feature that is important for site-specific management practices such as variable rate fertilization. Since rice paddy fields are flat and flooded, apparently they should be homogeneous and subsequently it could be thought that spatial variability in yields and soil attributes might be negligible. However, significant levels of variability in soil general properties, soil nutrients and rice yields have been observed even in small paddy fields. Describing spatial variability of within-field properties is a fundamental first step toward determining management strategies. The aim of this study was to analyze patterns of spatial variability in available macronutrients (NH4+-N, P and K) from an acid rice soil submitted to lime amendment. The experimental site was located at Corrientes province, Argentina. The climate is warm, subtropical with abundant rainfall the whole year round. The study soil was typic Plintacualf. Field trials were set up involving three treatments: control, without lime addition, plus two different dolomite doses of 625 and 1250 kg.ha-1. Before lime addition, soil pH was 3.7; organic matter content was 2.14 % and cation exchange capacity (CEC) was 21.7 Cmolc kg -1. Soil was sampled at three different stages, first before sowing in aerobic conditions and them two more times in anaerobiosis, i.e. by bunch formation and flowering. Ninety-six soil samples per treatment were taken during each of the three sampling periods. NH4+-N, P and K were routinely determined. Spatial variability was assessed through the analysis of semivariograms. Next, kriging maps were constructed and compared for successive sampling dates. The statistical variability of NH4+-N, P and K over the study period was low to medium, depending on treatment and sampling dates. Lime application produced a positive effect on the NH4+ availability at sowing time. Increased Olsen-P availability during sowing and tillering could be also attributed to lime addition, but a negative effect of liming on P availability was observed during flowering. Mehlich I extractable K was in general low to very low and decreased from sowing to flowering, irrespective of lime treatment. Semivariogram analysis showed a rather strong spatial dependence of NH4+, P and K concentrations and this all over the three study periods and for the three lime treatments. Empirical semivariograms could be adjusted quite well by a nugget component (C0) plus a spatial structure (C1), which was described by spherical or exponential models with a correlation range between 40 and 85 m. Geostatistical analysis provided insight into possible processes responsible of the observed spatial variability patterns within the rice soil. Kriging was useful in mapping macronutrient variability allowing identifying microrregions with high or low values of the target soil properties clearly showing the presence of small scale variability for the study soil attributes within each liming treatment and during each of the three sampling dates. Also the position of patches with maxima and minima values changed between successive sampling dates illustrating the lack of temporal stability of the pattern of spatial distribution for the study soil attributes. Results illustrate the potential for applying the principles of precision agriculture to control spatiotemporal variability in rice fields.

Vidal Vázquez, E.; Morales, L. A.; Paz González, A.

2012-04-01

67

Understanding the ecological background of rice agriculture on the Ningshao Plain during the Neolithic Age: pollen evidence from a buried paddy field at the Tianluoshan cultural site  

NASA Astrophysics Data System (ADS)

The progressive rise of atmospheric CH4 level since 5 ka has been hypothesized to result from human agricultural activities that turned forested lands, which would otherwise be a carbon sink, into paddy fields. Increasing numbers of Neolithic cultural sites unearthed in coastal eastern China, providing unique opportunities to test this hypothesis. Here, we present detailed pollen data from a buried paddy field at Tianluoshan cultural site on the Ningshao Plain, eastern China, to reconstruct the ecological conditions associated with the establishment of paddy fields. Stratigraphic data, radiocarbon ages, and pollen analyses show that vegetation underwent six phases of evolution and paddy fields were developed from 7000 to 4200 cal. yr BP. We found no evidence of slash-and-burn agriculture at the study site. Together with no presence of the irrigation system, our pollen data suggest the paddy fields at this site originated from wetlands. Hence, our findings do not support the hypothesis that anthropogenic-induced deforestation play ed a significant role in the rise of the atmospheric CH4 rise since the middle Holocene.

Li, Chunhai; Zheng, Yunfei; Yu, Shiyong; Li, Yongxiang; Shen, Huadong

2012-03-01

68

DIRECT AND INDIRECT EFFECTS OF MICROBES ON TECHNETIUM INSOLUBILIZATION IN PADDY FIELDS  

SciTech Connect

Direct and indirect effects of microorganisms on technetium insolubilization in water covering waterlogged soils were studied. Seven soils were waterlogged and then the water covering the soils were collected for further tracer experiments. The samples in contact with air were incubated with 95mTcO4--at 25 C for 4 to 5 days. After incubation, the samples were sequentially separated into four fractions: one insoluble fraction (> 0.2 {micro}m) and three soluble fractions (TcO4 -, cationic, and other forms). The radioactivity of 95mTc in each fraction was measured with a NaI (Tl) scintillation counter. The insolubility of Tc was observed in the untreated samples. The maximum insolubilization radioactivity was 37% of the total radioactivity in P38, which was collected from a paddy field, gray lowland soil. Microscopic observations revealed that bacteria were the dominant species in the insoluble fraction of P38. For the other samples, less than 9% of the Tc was found in insoluble form. In order to clarify biological and nonbiological factor affecting the insolubility, a reducing agent or nutrients were added to the P38 sample. The amount of insoluble Tc was enhanced by the addition of nutrients, while the addition of the reducing agent resulted in a dramatic decrease in the amount of the insoluble Tc. Most of the 95mTcO4 - added to the filtered or autoclaved samples was present in the form of the pertechnetate anion, even in P38. The filtered and autoclaved samples contained metabolites and dead cell particles, respectively. These materials, therefore, did not affect the physicochemical changes in Tc. These results suggest that specific bacteria having the ability to render Tc insoluble even under not strictly anaerobic conditions directly contribute to the insolubility of Tc.

Ishii, N.; Tagami, K.; Uchida, S.

2003-02-27

69

Dynamics of dissolved oxygen (DO) in ponded water of a paddy field  

Microsoft Academic Search

The transfer of heat and dissolved oxygen (DO) through water is important to understand the phenomenon of ponded water in a paddy soil. The heat from solar radiation is absorbed at the soil surface and transferred into the ponded water by convection. This study clarified the dynamics of DO, as well as the role of convection in water in DO

Mohamed Ismail Mohammed Mowjood; Tatsuaki Kasubuchi

1998-01-01

70

Estimating the Microbial Risk of E. coli in Reclaimed Wastewater Irrigation on Paddy Field  

Microsoft Academic Search

Microbial risk was quantified to assess human health risk as a result of exposure to E. coli in reclaimed wastewater irrigation. Monitoring data on E. coli were collected from pond water in paddy rice plots during the growing season. Five treatments were used and each was triplicated\\u000a to evaluate the changes in E. coli concentrations in experiments performed in 2003

Youn-Joo An; Chun G. Yoon; Kwang-Wook Jung; Jong-Hwa Ham

2007-01-01

71

Development of methane emission factors for Indian paddy fields and estimation of national methane budget.  

PubMed

A state-wise assessment of methane (CH(4)) budget for Indian paddies, based on a decadal measurement data across India is presented for the calendar year (CY) 1994, the base year for India's Initial National Communication (NATCOM) to the United Nations Framework Convention on Climate Change (UNFCCC), along with national trend from CY 1979 to 2006. The NATCOM CH(4) emission factors (EFs) for Indian paddy cultivation areas, generally having less than 0.7% of soil organic carbon (SOC), have been estimated as 17.48+/-4 g m(-2) for irrigated continuously flooded (IR-CF), 6.95+/-1.86 g m(-2) for rain-fed drought prone (RF-DP), 19+/-6 g m(-2) for rain-fed flood prone (RF-FP) and deep-water (DW), 6.62+/-1.89 g m(-2) for irrigated intermittently flooded single aeration (IR-IF-SA) and 2.01+/-1.49 g m(-2) for IR-IF multiple aeration (MA) paddy water regimes. The state-wise study for 1994 has indicated national CH(4) budget estimate of 4.09+/-1.19 Tg y(-1) and the trend from 1979 to 2006 was in the range of 3.62+/-1 to 4.09+/-1.19 Tg y(-1). Four higher emitting or "hot spot" states (West Bengal, Bihar, Madhya Pradesh and Uttar Pradesh) have accounted for 53.9% of total CH(4) emission with RF-FP paddy water regime as the major contributor. CH(4) emissions were enhanced by factors such as SOC ( approximately 1.5 times due to increase in SOC by approximately 1.8 times), paddy cultivars (approximately 1.5 times), age of seedlings (approximately 1.4 times), and seasons (approximately 1.8 times in Kharif or monsoon than in Rabi or winter season). PMID:18996564

Gupta, Prabhat K; Gupta, Vandana; Sharma, C; Das, S N; Purkait, N; Adhya, T K; Pathak, H; Ramesh, R; Baruah, K K; Venkatratnam, L; Singh, Gulab; Iyer, C S P

2008-11-08

72

Estimation of methane and nitrous oxide emission from paddy fields and uplands during 1990-2000 in Taiwan.  

PubMed

To investigate the greenhouse gases emissions from paddy fields and uplands, methane and nitrous oxide emissions were estimated from local measurement and the IPCC guidelines during 1990-2000 in Taiwan. Annual methane emission from 182,807 to 242,298 ha of paddy field in the first crop season ranged from 8,062 to 12,066 ton, and it was between 16,261 and 25,007 ton for 144,178-211,968 ha in the second crop season with local measurement. The value ranged from 12,132 to 17,465 ton, and from 16,046 to 24,762 ton of methane in the first and second crop season with the IPCC guidelines for multiple aeration treatments, respectively. Annual nitrous oxide emission was between 472 and 670 ton and between 236 and 359 ton in the first and second crop season, respectively. Methane and nitrous oxide emissions from uplands depend on crop, growth season, fertilizer application and environmental conditions. Annual methane emission from upland crops, vegetable, fruit, ornamental plants, forage crops and green manure crops was 138-252, 412-460, 97-100, 3-5, 4-5 and 3-51 ton, respectively. Annual nitrous oxide emission was 1,080-1,976, 1,784-1,994, 2,540-2,622, 31-54, 43-53 and 38-582 ton, respectively. Annual nitrous oxide emission ranged from 91 to 132 ton for 77,593-11,2095 ton of nitrogen-fixing crops, from 991 to 1,859 ton for 3,259,731-6,183,441 ton of non-nitrogen-fixing crops, and from 1.77 to 2.22 Gg for 921,169-1,172,594 ton of chemical fertilizer application. In addition, rice hull burning emitted 19.3-24.2 ton of methane and 17.2-21.5 ton of nitrous oxide, and corn stalk burning emitted 2.1-4.2 ton of methane and 1.9-3.8 ton of nitrous oxide. Methane emission from the agriculture sector was 26421-37914 ton, and nitrous oxide emission was 9810-11,649 ton during 1990-2000 in Taiwan. Intermittent irrigation in paddy fields reduces significantly methane emission; appropriate application of nitrogen fertilization and irrigation in uplands and paddy fields also decreases nitrous oxide emission. PMID:12852981

Yang, Shang-Shyng; Liu, Chung-Ming; Lai, Chao-Ming; Liu, Yen-Lan

2003-09-01

73

Assessment of heavy metals (Cd and Pb) and micronutrients (Cu, Mn, and Zn) of paddy (Oryza sativa L.) field surface soil and water in a predominantly paddy-cultivated area at Puducherry (Pondicherry, India), and effects of the agricultural runoff on the elemental concentrations of a receiving rivulet.  

PubMed

The concentrations of toxic heavy metals-Cd and Pb and micronutrients-Cu, Mn, and Zn were assessed in the surface soil and water of three different stages of paddy (Oryza sativa L.) fields, the stage I-the first stage in the field soon after transplantation of the paddy seedlings, holding adequate amount of water on soil surface, stage II-the middle stage with paddy plants of stem of about 40 cm length, with sufficient amount of water on the soil surface, and stage III-the final stage with fully grown rice plants and very little amount of water in the field at Bahour, a predominantly paddy cultivating area in Puducherry located on the southeast Coast of India. Comparison of the heavy metal and micronutrient concentrations of the soil and water across the three stages of paddy field showed their concentrations were significantly higher in soil compared with that of water (p?fields probably because of accumulation and adsorption in soil. The elemental concentrations in paddy soil as well as water was in the ranking order of Cd?>?Mn?>?Zn?>?Cu?>?Pb indicating concentration of Cd was maximum and Pb was minimum. The elemental concentrations in both soil and water across the three stages showed a ranking order of stage II?>?stage III?>?stage I. The runoff from the paddy fields has affected the elemental concentrations of the water and sediment of an adjacent receiving rivulet. PMID:23435848

Reddy, M Vikram; Satpathy, Deepmala; Dhiviya, K Shyamala

2013-02-24

74

Combination system of full-scale constructed wetlands and wetland paddy fields to remove nitrogen and phosphorus from rural unregulated non-point sources.  

PubMed

Constructed wetlands (CWs) have been used effectively to remove nitrogen (N) and phosphorus (P) from non-point sources. Effluents of some CWs were, however, still with high N and P concentrations and remained to be pollution sources. Widely distributed paddy fields can be exploited to alleviate this concern. We were the first to investigate a combination system of three-level CWs with wetland paddy fields in a full scale to remove N and P from rural unregulated non-point sources. The removal efficiencies (REs) of CWs reached 57.3 % (37.4-75.1 %) for N and 76.3 % (62.0-98.4 %) for P. The CWs retained about 1,278 kg N ha(-1) year(-1) and 121 kg P ha(-1) year(-1). There was a notable seasonal change in REs of N and P, and the REs were different in different processing components of CWs. The removal rates of wetland paddy fields adopt "zero-drainage" water management according to local rainfall forecast and physiological water demand of crop growth reached 93.2 kg N ha(-1) year(-1) and 5.4 kg P ha(-1) year(-1). The rice season had higher potential in removing N and P than that in the wheat season. The whole combined system (0.56 ha CWs and 5.5 ha wetland paddy fields) removed 1,790 kg N year(-1) and 151 kg P year(-1), which were higher than those from CWs functioned alone. However, another 4.7-ha paddy fields were needed to fully remove the N and P in the effluents of CWs. The combination of CWs and paddy fields proved to be a more efficient nutrient removal system. PMID:23703587

Sun, Haijun; Zhang, Hailin; Yu, Zhimin; Wu, Jiasen; Jiang, Peikun; Yuan, Xiaoyan; Shi, Weiming

2013-05-24

75

Effect of land use change from paddy to vegetable field on the residues of organochlorine pesticides in soils.  

PubMed

The effect of land use change from paddy to vegetable field on the residues of organochlorine pesticides (OCPs) was investigated. Soil residues of OCPs were analyzed in vegetable fields which had been converted from paddy fields for 0, 5, 10, 15, 20, 30, 50 year in Yixing, China in 2003. The mean concentrations of OCPs followed a sequence of: SigmaDDTs (13.7 microg kg(-1))> SigmaHCHs (8.6 microg kg(-1)) >HCB (2.09 microg kg(-1))>alpha-endosulfan (1.30 microg kg(-1))>endrin (1.08 microg kg(-1))>PCNB (0.76 microg kg(-1))>dieldrin (0.58 microg kg(-1)). The mean residues of OCPs especially DDTs increased significantly with vegetable planting time after land use change in the first 15 years, then decreased from 20 to 30 years and increased a little afterward. The time under anaerobic and aerobic conditions was suggested to control mainly the change of the residues of OCPs. PMID:18554761

Hao, Hongtao; Sun, Bo; Zhao, Zhenhua

2008-06-13

76

Phylogenetic and functional diversity of denitrifying bacteria isolated from various rice paddy and rice-soybean rotation fields.  

PubMed

Denitrifiers can produce and consume nitrous oxide (N(2)O). While little N(2)O is emitted from rice paddy soil, the same soil produces N(2)O when the land is drained and used for upland crop cultivation. In this study, we collected soils from two types of fields each at three locations in Japan; one type of field had been used for continuous cultivation of rice and the other for rotational cultivation of rice and soybean. Active denitrifiers were isolated from these soils using a functional single-cell isolation method, and their taxonomy and denitrifying properties were examined. A total of 110 denitrifiers were obtained, including those previously detected by a culture-independent analysis. Strains belonging to the genus Pseudogulbenkiania were dominant at all locations, suggesting that Pseudogulbenkiania denitrifiers are ubiquitous in various rice paddy soils. Potential denitrifying activity was similar among the strains, regardless of the differences in taxonomic position and soil of origin. However, relative amounts of N(2) in denitrification end products varied among strains isolated from different locations. Our results also showed that crop rotation had minimal impact on the functional diversity of the denitrifying strains. These results indicate that soil and other environmental factors, excluding cropping systems, could select for N(2)-producing denitrifiers. PMID:21487200

Tago, Kanako; Ishii, Satoshi; Nishizawa, Tomoyasu; Otsuka, Shigeto; Senoo, Keishi

2011-01-01

77

Actual Condition of Paddy Field Levee Maintenance by Various Farm Households including Large-scale Farming in the Developed Land Renting Area  

NASA Astrophysics Data System (ADS)

The survey of interview, resource acquisition, photographic operation, and questionnaire were carried out in the “n” Community in the “y” District in Hakusan City in Ishikawa Prefecture to investigate the actual condition of paddy field levee maintenance in the area where land-renting market was proceeding, large-scale farming was dominant, and the problems of geographically scattered farm-land existed. In the study zone, 1) an agricultural production legal person rent-cultivated some of the paddy fields and maintained the levees, 2) another agricultural production legal person rent-cultivated some of the soy bean fields for crop changeover and land owners maintained the levees. The results indicated that sufficient maintenance was executed on the levees of the paddy fields cultivated by the agricultural production legal person, the soy bean fields for crop changeover, and the paddy fields cultivated by the land owners. Each reason is considered to be the managerial strategy, the economic incentive, the mutual monitoring and cross-regulatory mechanism, etc.

Sakata, Yasuyo

78

Mosquitoes and other aquatic insects in fallow field biotopes and rice paddy fields.  

PubMed

Fallow field biotopes that develop from abandoned rice fields are man-made wetlands that provide new habitats for various aquatic animals. Although consideration of such biotopes generally focuses on their positive aspects, this study evaluated the negative aspects of establishing fallow field biotopes with regard to mosquito breeding sites. To determine whether fallow field biotopes become breeding habitats for vector mosquitoes, we evaluated mosquito fauna in fallow field biotopes and adjacent rice fields. We found larvae of Anopheles lesteri, Anopheles sinensis and Culex tritaeniorhynchus (all: Diptera: Culicidae) in the biotopes. Although abundances of mosquito larvae in the biotopes and rice fields were statistically similar, mosquito abundances in rice fields increased dramatically in August when the water level reduced after the rainy season. The abundance and variety of the mosquitoes' natural predators were greater in biotopes than in rice fields because the former are a permanent and stable aquatic environment. A generalized linear mixed model showed a negative effect of predator diversity on mosquito larvae abundance in both habitats. Although fallow field biotopes become breeding habitats for vector mosquitoes, establishing biotopes from fallow fields in order to protect various aquatic animals, including mosquito insect predators, may help to control mosquito breeding. PMID:23167444

Ohba, S Y; Matsuo, T; Takagi, M

2012-11-20

79

Emissions of CH4 and N2O under Different Tillage Systems from Double-Cropped Paddy Fields in Southern China  

PubMed Central

Understanding greenhouse gases (GHG) emissions is becoming increasingly important with the climate change. Most previous studies have focused on the assessment of soil organic carbon (SOC) sequestration potential and GHG emissions from agriculture. However, specific experiments assessing tillage impacts on GHG emission from double-cropped paddy fields in Southern China are relatively scarce. Therefore, the objective of this study was to assess the effects of tillage systems on methane (CH4) and nitrous oxide (N2O) emission in a double rice (Oryza sativa L.) cropping system. The experiment was established in 2005 in Hunan Province, China. Three tillage treatments were laid out in a randomized complete block design: conventional tillage (CT), rotary tillage (RT) and no-till (NT). Fluxes of CH4 from different tillage treatments followed a similar trend during the two years, with a single peak emission for the early rice season and a double peak emission for the late rice season. Compared with other treatments, NT significantly reduced CH4 emission among the rice growing seasons (P<0.05). However, much higher variations in N2O emission were observed across the rice growing seasons due to the vulnerability of N2O to external influences. The amount of CH4 emission in paddy fields was much higher relative to N2O emission. Conversion of CT to NT significantly reduced the cumulative CH4 emission for both rice seasons compared with other treatments (P<0.05). The mean value of global warming potentials (GWPs) of CH4 and N2O emissions over 100 years was in the order of NTregions.

Zhang, Hai-Lin; Bai, Xiao-Lin; Xue, Jian-Fu; Chen, Zhong-Du; Tang, Hai-Ming; Chen, Fu

2013-01-01

80

Modeling methane emission from rice paddies with various agricultural practices  

Microsoft Academic Search

Several models have been developed over the past decade to estimate CH4 emission from rice paddies. However, few models have been validated against field measurements with various parameters of soil, climate and agricultural practice. Thus reliability of the model's performance remains questionable particularly when extrapolating the model from site microscale to regional scale. In this paper, modification to the original

Yao Huang; Wen Zhang; Xunhua Zheng; Jin Li; Yongqiang Yu

2004-01-01

81

Isolation of Key Methanogens for Global Methane Emission from Rice Paddy Fields: a Novel Isolate Affiliated with the Clone Cluster Rice Cluster I  

Microsoft Academic Search

Despite the fact that rice paddy fields (RPFs) are contributing 10 to 25% of global methane emissions, the organisms responsible for methane production in RPFs have remained uncultivated and thus uncharacterized. Here we report the isolation of a methanogen (strain SANAE) belonging to an abundant and ubiquitous group of methanogens called rice cluster I (RC-I) previously identified as an ecologically

Sanae Sakai; Hiroyuki Imachi; Yuji Sekiguchi; Akiyoshi Ohashi; Hideki Harada; Yoichi Kamagata

2007-01-01

82

Phylogenetic diversity and assemblage of major capsid genes (g23) of T4-type bacteriophages in paddy field soils during rice growth season in Northeast China  

Microsoft Academic Search

Although bacteriophages (phages) are ubiquitous and the most abundant biological entities on Earth, the genetic information on their diversity and community composition in natural environments, particularly in soils, is limited. This study elucidated the diversity and composition of T4-type phages by analyzing partial major capsid gene (g23) sequences in DNA extracts from five paddy field soils in Northeast China during

Junjie Liu; Guanghua Wang; Qiang Wang; Judong Liu; Jian Jin; Xiaobing Liu

2012-01-01

83

Monitoring of selected pesticides residue levels in water samples of paddy fields and removal of cypermethrin and chlorpyrifos residues from water using rice bran.  

PubMed

Consumption of pesticides associated foods increased in recent decades in Bangladesh. Most of the pesticides come from paddy, as rice is the main food items here and about 70 % pesticides are used only on paddy fields. Water samples of paddy fields and Kaliganga River of Manikganj district were analyzed to provide base line data on cypermethrin, chlorpyrifos and diazinon residue by using high performance liquid chromatography. Levels of Cypermethrin, chlorpyrifos and diazinon detected in the paddy field water samples were (0.605 ± 0.011 ?g/L), (0.06 ± 0.001 ?g/L) and (0.039 ± 0.002 ?g/L), respectively. 0.11 ± 0.003 ?g/L of cypermethrin and 0.012 ± 0.0006 ?g/L of chlorpyrifos were also identified in the water samples of Kaligonga River. Diazinon residue was not detected in the river water samples. The detected concentrations of pesticide residues in the river water were below the accepted maximum residue limit (MRL) value of drinking water (0.1 ?g/l) adopted by the FAO/WHO Codex Alimentarius Commission. Cypermethrin and chlorpyrifos were chosen for decontamination through rice bran, as it was found in river water. Two gm rice bran could easily decontaminated 95.6 % and 96.4 % of cypermethrin and chlorpyrifos. The result of this study showed that pesticide residue was detected in water samples were below the MRLs value, which can easily be decontaminated through absorption of rice bran. PMID:22627618

Bhattacharjee, Shubhra; Fakhruddin, A N M; Chowdhury, M A Z; Rahman, M A; Alam, M K

2012-05-25

84

Impact of plant genotype and nitrogen level on rice growth response to inoculation with Azospirillum sp. strain B510 under paddy field conditions  

Microsoft Academic Search

Twenty rice cultivars, including three genetically-distinct groups (japonica, indica-1, and indica-2), were evaluated for their response to inoculation with Azospirillum sp. strain B510 in paddy fields with standard nitrogen (SN) and low nitrogen (LN) fertilization. In the SN field, the tiller numbers in most indica-2 cultivars, 37?days after transplanting (DAT), were significantly increased by the B510 inoculation, whereas those in

Kazuhiro Sasaki; Seishi Ikeda; Shima Eda; Hisayuki Mitsui; Eiko Hanzawa; Chiharu Kisara; Yuri Kazama; Atsuhiko Kushida; Takuro Shinano; Kiwamu Minamisawa; Tadashi Sato

2010-01-01

85

Internal aeration of paddy field rice (Oryza sativa) during complete submergence---importance of light and floodwater O2.  

PubMed

Flash floods can submerge paddy field rice (Oryza sativa), with adverse effects on internal aeration, sugar status and survival. Here, we investigated the in situ aeration of roots of rice during complete submergence, and elucidated how underwater photosynthesis and floodwater pO(2) influence root aeration in anoxic soil. In the field, root pO(2) was measured using microelectrodes during 2 d of complete submergence. Leaf gas films that formed on the superhydrophobic leaves were left intact, or experimentally removed, to elucidate their effect on internal aeration. In darkness, root pO(2) declined to very low concentrations (0.24 kPa) and was strongly correlated with floodwater pO(2). In light, root pO(2) was high (14 kPa) and primarily a function of the incident light determining the rates of underwater net photosynthesis. Plants with intact leaf gas films maintained higher underwater net photosynthesis relative to plants without gas films when the submerged shoots were in light. During complete submergence, internal aeration of rice in the field relies on underwater photosynthesis during the day and entry of O(2) from the floodwater during the night. Leaf gas films enhance photosynthesis during submergence leading to improved O(2) production and sugar status, and therefore contribute to the submergence tolerance of rice. PMID:23215967

Winkel, Anders; Colmer, Timothy D; Ismail, Abdelbagi M; Pedersen, Ole

2012-12-06

86

Comparison of phospholipid fatty acid composition in percolating water, floodwater, and the plow layer soil during the rice cultivation period in a Japanese paddy field  

Microsoft Academic Search

The composition of phospholipid fatty acids (PLFAs) in the percolating water (PW), the floodwater (FW), and the plow layer soil (PLS) in a paddy field was compared during the period of rice cultivation. The amounts of PLFAs in PW, FW, and PLS ranged from 19.2 to 40.3 ?g L, from 41.6 to 72.3 ?g L, and from 56.4 to 75.3

Miho Shimizu; Yasunori Nakajima; Kazuo Matsuya; Makoto Kimura

2002-01-01

87

Integrated nutrient management for environmental-friendly rice production in salt-affected rice paddy fields of Saemangeum reclaimed land of South Korea  

Microsoft Academic Search

This study was conducted in an attempt to determine the proper nitrogen and phosphorus application levels, nitrogen split\\u000a application ratio, and application method for environmental-friendly rice production in a salt-affected rice paddy field,\\u000a which was located in the Saemangeum reclaimed tidal belt on the western coast of South Korea, between April 1, 2003 and October\\u000a 10, 2004. All treatments were

Jae Young Cho; Jae Gwon Son; Chang Hoon Song; Seon Ah Hwang; Young Min Lee; Se Young Jeong; Byung Yeoup Chung

2008-01-01

88

A 3-year field measurement of methane and nitrous oxide emissions from rice paddies in China: Effects of water regime, crop residue, and fertilizer application  

Microsoft Academic Search

A 3-year field experiment was conducted to simultaneously measure methane (CH4) and nitrous oxide (N2O) emissions from rice paddies under various agricultural managements including water regime, crop residue incorporation, and synthetic fertilizer application. In contrast with continuous flooding, midseason drainage incurred a drop in CH4 fluxes while triggering substantial N2O emission. Moreover, N2O emissions after midseason drainage depended strongly on

Jianwen Zou; Yao Huang; Jingyan Jiang; Xunhua Zheng; Ronald L. Sass

2005-01-01

89

Influence of Temperature and Oil Content on the Soil\\/Air Partition Coefficient for Hexachlorobenzene in Oil-Contaminated Rice Paddy Field Soil  

Microsoft Academic Search

The soil\\/air partition coefficients (KSA) for hexachlorobenzene (HCB) in oil-contaminated (crude oil and diesel) rice paddy field soils were measured in a solid fugacity meter at different oil concentrations over the temperature range of 5 to 30°C at 100% relative humidity. The results showed that values of KSA increased with a decrease of temperature. As for oil content, there is

Xin He; Shuo Chen; Xie Quan; Huimin Zhao; Yazhi Zhao

2011-01-01

90

Evaluation of the management practice for controlling herbicide runoff from paddy fields using intermittent and spillover-irrigation schemes  

Microsoft Academic Search

Two water management practices, an intermittent irrigation scheme using automatic irrigation system (AI) and a spillover-irrigation\\u000a scheme (SI), were compared for the fate and transport of commonly used herbicides, mefenacet (MF) and bensulfuron-methyl (BSM)\\u000a in experimental paddy plots. Maximum mefenacet concentrations in paddy water were 660 and 540 ?g L?1 for AI and SI plot, respectively. The corresponding values for bensulfuron-methyl were

Hirozumi Watanabe; Youji Kakegawa; Son Hong Vu

2006-01-01

91

Assessing the potential impact of fly ash amendments on Indian paddy field with special emphasis on growth, yield, and grain quality of three rice cultivars.  

PubMed

Proper disposal and/or recycling of different industrial waste materials have long been recognized as a prime environmental concern throughout the world, and fly ash is major amongst them. In the present study, we tried to assess the feasibilities of possible effective and safe utilization of fly ash as soil amendment in Indian paddy field and its impact on rice plants, especially at growth and yield level. Our results showed that certain doses of fly ash amendments have significantly improved the physico-chemical and mineralogical properties of paddy field soil, and at lower level of amendments, fly ash induced the growth performances of three rice cultivars too. Grain yield and grain quality also responded similarly as per the growth responses. However, differential cultivar response was observed accordingly, and cultivar Sugandha-3 showed higher yield as compared with cultivars Sambha and Saryu-52. Based on the observed results, it was concluded that up to a certain level, fly ash amendments could be beneficial for Indian paddy field and can be utilized as feasible management strategy for the disposal of this major industrial waste. PMID:21901311

Singh, Anupama; Sarkar, Abhijit; Agrawal, S B

2011-09-08

92

Quantifying methane emissions from rice fields in the Taihu Lake region, China by coupling a detailed soil database with biogeochemical model  

NASA Astrophysics Data System (ADS)

As China has approximately 22% of the world's rice paddies, the regional quantification of CH4 emissions from these paddies is important in determining their contribution to the global greenhouse gas effect. This paper reports the use of a biogeochemical model (DeNitrification and DeComposition or DNDC) for quantifying CH4 emissions from rice fields in the Taihu Lake region of China. For this application, the DNDC model was linked to a 1:50 000 soil database derived from 1107 paddy soil profiles compiled during the Second National Soil Survey of China in the 1980s-1990s. The simulated results showed that the 2.3 Mha of paddy rice fields in the Taihu Lake region emitted the equivalent of 5.7 Tg C from 1982-2000, with the average CH4 flux ranging from 114 to 138 kg C ha-1 y-1. As for soil subgroups, the highest emission rate (660 kg C ha-1 y-1) was linked to gleyed paddy soils accounting for about 4.4% of the total area of paddy soils. The lowest emission rate (91 kg C ha-1 y-1) was associated with degleyed paddy soils accounting for about 18% of the total area of paddy soils. The most common soil in the area was hydromorphic paddy soils, which accounted for about 53% of the total area of paddy soils with a CH4 flux of 106 kg C ha-1 y-1. On a regional basis, the annual averaged CH4 flux in the Taihu Lake plain soil region and alluvial plain soil region were higher than that in the low mountainous and hilly soil region and the polder soil region. The model simulation was conducted with two databases using polygons or counties as the basic units. The county-based database contained soil information coarser than the polygon system built based on the 1:50 000 soil database. The modeled results with the two databases found similar spatial patterns of CH4 emissions in the Taihu Lake region. However, discrepancies exist between the results from the two methods. The total CH4 emissions generated from the polygon-based database is 2.6 times the minimum CH4 emissions generated from the county-based database, and is 0.98 times the maximum CH4 emissions generated from the county-based database. The average value of the relative deviation ranged from -20% to 98% for most counties, which indicates that a more precise soil database is necessary to better simulate CH4 emissions from rice fields in the Taihu Lake region using the DNDC model.

Zhang, L.; Yu, D.; Shi, X.; Weindorf, D.; Zhao, L.; Ding, W.; Wang, H.; Pan, J.; Li, C.

2009-05-01

93

Effect of Different Fertilizer Application on the Soil Fertility of Paddy Soils in Red Soil Region of Southern China  

PubMed Central

Appropriate fertilizer application is an important management practice to improve soil fertility and quality in the red soil regions of China. In the present study, we examined the effects of five fertilization treatments [these were: no fertilizer (CK), rice straw return (SR), chemical fertilizer (NPK), organic manure (OM) and green manure (GM)] on soil pH, soil organic carbon (SOC), total nitrogen (TN), C/N ratio and available nutrients (AN, AP and AK) contents in the plowed layer (0–20 cm) of paddy soil from 1998 to 2009 in Jiangxi Province, southern China. Results showed that the soil pH was the lowest with an average of 5.33 units in CK and was significantly higher in NPK (5.89 units) and OM (5.63 units) treatments (P<0.05). The application of fertilizers have remarkably improved SOC and TN values compared with the CK, Specifically, the OM treatment resulted in the highest SOC and TN concentrations (72.5% and 51.2% higher than CK) and NPK treatment increased the SOC and TN contents by 22.0% and 17.8% compared with CK. The average amounts of C/N ratio ranged from 9.66 to 10.98 in different treatments, and reached the highest in OM treatment (P<0.05). During the experimental period, the average AN and AP contents were highest in OM treatment (about 1.6 and 29.6 times of that in the CK, respectively) and second highest in NPK treatment (about 1.2 and 20.3 times of that in the CK). Unlike AN and AP, the highest value of AK content was observed in NPK treatments with 38.10 mg·kg?1. Thus, these indicated that organic manure should be recommended to improve soil fertility in this region and K fertilizer should be simultaneously applied considering the soil K contents. Considering the long-term fertilizer efficiency, our results also suggest that annual straw returning application could improve soil fertility in this trial region.

Dong, Wenyi; Zhang, Xinyu; Wang, Huimin; Dai, Xiaoqin; Sun, Xiaomin; Qiu, Weiwen; Yang, Fengting

2012-01-01

94

Environmental contamination and seasonal variation of metals in soils, plants and waters in the paddy fields around a Pb-Zn mine in Korea.  

PubMed

The objective of this study is to investigate the extent and degree of heavy metal contamination of paddy fields influenced by metalliferous mining activity. Paddy soils, rice plants and irrigation waters were sampled along six traverse lines in the vicinity of the mine and nearby control site. Soil samples were taken 30, 80 and 150 days after rice transplanting, to study seasonal variation of their chemical properties and heavy metal concentrations. Sampling of rice plants and irrigation waters was also undertaken with seasons. The analysis of the samples were carried out using ICP-AES for 25 elements including Cd, Cu, Pb and Zn. Physical and chemical properties of soils (pH, loss-on-ignition, cation exchange capacity and texture) and waters (pH, Eh and temperature) were also measured. The properties of soils were similar to the average Korean soils, with the exception of some samples taken in the vicinity of the mine. Concentrations of Cd, Cu, Pb and Zn in paddy soils, rice plants and irrigation waters sampled in the immediate vicinity of the mine were relatively high due to the seepage of metals from mining dump sites. Although there was variation between sampling sites, soil pH values under reducing conditions were on average higher than those under oxidising conditions. Relatively low content of organic matter and low cation exchange capacity of soils were found at 80 days after rice transplanting (P < 0.05). No seasonal variations in metal concentrations were found in paddy soils throughout the period of the rice growing, in which soils ranged from flooded reducing conditions through most of the growing season to drained oxidising conditions before and at harvest. Relatively high metal concentrations were found in the rice stalks and leaves under oxidising conditions. The sequential extraction analysis of selected soil samples confirmed that high proportions of exchangeable fractions of the metals were found under oxidising conditions. It was shown that Cd and Zn concentrations in rice leaves and stalks and rice grain increased with increasing metal concentrations in paddy soils to a greater extent than for Cu and Pb. This difference in uptake is in agreement with the greater proportions of Cd and Zn, compared with Cu and Pb, in the exchangeable soil fraction extracted with MgCl2. Average daily intake from locally grown rice by the residents was estimated to be 121 micrograms Cd and 126 micrograms Pb. Thus, long-term metal exposure by regular consumption of the rice poses potential health problems to residents in the vicinity of the mine, although no adverse health effects have as yet been observed. PMID:9167264

Jung, M C; Thornton, I

1997-05-30

95

Methylomonas koyamae sp. nov., a type I methane-oxidizing bacterium from floodwater of a rice paddy field.  

PubMed

A novel methane-oxidizing bacterium, strain Fw12E-Y(T), was isolated from floodwater of a rice paddy field in Japan. Cells of strain Fw12E-Y(T) were Gram-negative, motile rods with a single polar flagellum and type I intracytoplasmic membrane arrangement. The strain grew only on methane or methanol as sole carbon and energy source. It was able to grow at 10-40 °C (optimum 30 °C), at pH 5.5-7.0 (optimum 6.5) and with 0-0.1% (w/w) NaCl (no growth above 0.5% NaCl). 16S rRNA gene sequence analysis showed that strain Fw12E-Y(T) is related most closely to members of the genus Methylomonas, but at low levels of similarity (95.0-95.4%). Phylogenetic analysis of pmoA and mxaF genes indicated that the strain belongs to the genus Methylomonas (97 and 92?% deduced amino acid sequence identities to Methylomonas methanica S1(T), respectively). The DNA G+C content of strain Fw12E-Y(T) was 57.1 mol%. Chemotaxonomic data regarding the major quinone (MQ-8) and major fatty acids (C(16:1) and C(14:0)) also supported its affiliation to the genus Methylomonas. Based on phenotypic, genomic and phylogenetic data, strain Fw12E-Y(T) is considered to represent a novel species of the genus Methylomonas, for which the name Methylomonas koyamae sp. nov. is proposed. The type strain is Fw12E-Y(T) (?=?JCM 16701(T)?=?NBRC 105905(T)?=?NCIMB 14606(T)). PMID:21984674

Ogiso, Takuya; Ueno, Chihoko; Dianou, Dayéri; Huy, Tran Van; Katayama, Arata; Kimura, Makoto; Asakawa, Susumu

2011-10-07

96

Bacterial diversity and bioaugmentation in floodwater of a paddy field in the presence of the herbicide molinate.  

PubMed

This work aimed at studying variations on the diversity and composition of the bacterial community of a rice paddy field floodwater, subjected to conventional management, namely by using the herbicide molinate. The promotion of the herbicide biodegradation either by the autochthonous microbiota or by a bioaugmentation process was also assessed. This study comprehended four sampling campaigns at key dates of the farming procedures (seeding, immediately and 6 days after application of the herbicide molinate, and after synthetic fertilization) and the subsequent physic-chemical and microbiological characterization (pH, DOC and molinate contents, total cells, cultivable bacteria and DGGE profiling) of the samples. Multivariate analysis of the DGGE profiles showed temporal variations in the bacterial community structure and the Shannon's index values indicated that the bacterial diversity reached its minimum at the molinate application day. The highest bacterial diversity coincided with the periods with undetectable concentrations of the herbicide, although microcosm assays suggested that other factors than molinate may have been responsible for the decrease of the bacterial diversity. The ability of autochthonous microorganisms to degrade molinate and the influence of the herbicide on the bacterial community composition were assessed in microcosm assays using floodwater collected at the same dates. Given molinate was not degraded by autochthonous microorganisms, and considering it represents an environmental contaminant, bioaugmentation microcosms were assayed aiming the assessment of the feasibility of a bioremediation process to clean contaminated floodwater. A molinate-mineralizing culture, previously isolated, promoted molinate removal, induced alterations in the autochthonous bacterial community structure and diversity, and was undetected after 7 days of incubation, suggesting the feasibility of the process. PMID:20862524

Barreiros, Luisa; Manaia, Célia M; Nunes, Olga C

2010-09-23

97

Trees in Bangladesh paddy fields and homesteads: participatory action research towards a model design  

Microsoft Academic Search

This paper describes the background, context and process of farmer consultation and participation in research leading to a model design for planting trees in crop fields and homesteads on small private farms in Bangladesh. Planting trees in crop fields is a cultural and technical innovation under development through participatory action-research. Tree planting on homesteads was also a high priority for

D. Hocking; K. Islam

1994-01-01

98

[Change of available pool of heavy metals in paddy soils under human land use impacts from the Taihu Lake region, Jiangsu Province, China].  

PubMed

A number of representative farms under various human land uses were selected through a general survey in the Taihu Lake region, Jiangsu Province, China. The land uses covered vicinity of smelt industry and township industry, long history of high-yielding performance, long term fertilization treatments. Top layers of the paddy soils were sampled for analysis of available pool of heavy metals. A prevalent trend of increasing availability was observed of heavy metals by a degree of 30% up to 200% in the soils under these human impacts as compared with that under relative conserved conditions. This increasing trend was most remarkably exhibited in the top sub-layer of the paddy soils. The highest rise of the available pool largest was found in those under smelt industry impact and under long term chemical fertilization alone. The result showed that available pool of surface soil Cu and Pb under these impacts were 7.96-2.15 mg.kg-1, 24.7-3.47 mg.kg-1 and 8.34-4.42 mg.kg-1, 9.01-4.95 mg.kg-1 respectively. The dramatic rise of the availability with the increasing trend of the total (as previously reported) might stand for contemporary soil environmental quality and, thus, require severe concerns for agriculture and food security in this rapidly developing region. PMID:12916212

Li, Lianqing; Zheng, Jinwei; Pan, Genxing; Tian, Fuqiang; Qiu, Duosheng; Xu, Xiangdong; Chu, Qiuhua

2003-05-01

99

Behavior of bromobutide in paddy water and soil after application.  

PubMed

Behavior of the herbicide bromobutide, (RS)-2-bromo-N-(?,?-dimethylbenzyl)-3,3-dimethylbutyramide, in paddy water and soil after application to paddy fields was investigated to evaluate the degradation to bromobutide-debromo, N-(?,?-dimethylbenzyl)-3,3-dimethylbutyramide, and runoff of the herbicide. The respective maximum concentrations of bromobutide and the metabolite were 1,640–2,230 and 11.1–15.8 ?g/L in the paddy water, and 2,210–4,140 ?g/kg dry and 74–119 ?g/kg dry in the paddy soil, respectively. The runoff ratios of the applied bromobutide from the paddy fields were calculated as 28 ± 16%. The respective mean values of the half-lives of bromobutide in the paddy water and the soil were 2.7 ± 0.34 days and 6.9 ± 2.6 days, respectively. PMID:22297629

Morohashi, Masayuki; Nagasawa, Shunsuke; Enya, Nami; Suzuki, Kazuyuki; Kose, Tomohiro; Kawata, Kuniaki

2012-04-01

100

Phylogenetic diversity of microturbellarians in Japanese rice paddy fields, with special attention to the genus Stenostomum  

Microsoft Academic Search

Free-living fresh water Platyhelminthes except for the order Tricladida (planaria) are collectively called microturbellaria, most species of which are less than a few millimeters in length. The ecology and the fauna of microturbellarians in rice fields has not been clarified in detail since Okugawa (1932) reported the morphological and ecological characters of all microturbellarian species that had been observed in

Masatsugu Yamazaki; Susumu Asakawa; Jun Murase; Makoto Kimura

2012-01-01

101

Durability of Drainage Improvement by Combination of Main Drain and Trench Drains with Vertical Drains in Clayey Field Converted from Paddy to Upland Use  

NASA Astrophysics Data System (ADS)

The drainage efficiency of a subsurface drainage system for avoidance of standing water on the plow pan of clayey field was evaluated. A subsurface drainage system with a main drain and orthogonally adjoined rice husk trench drains joined by vertical rice husk drains was constructed on a test plot and compared to an identical control plot of paddy field converted to upland use under soybean cultivation. The ratio of total underdrain discharge to rainfall in the improved plot greatly increased over two years compared to that in a control plot. In the improved plot, the peak underdrain discharge per hour associated with some heavy rainfalls was around 3 mm/h in the first year but decreased to about 2 mm/h in the second year. By improving drainage in the paddy field, standing water on the plow pan was quickly eliminated after rain events and the period of flooding on the plow pan during the soybean growing season was greatly reduced. However, underdrain discharge in the improved plot decreased greatly in the third year to be at the same level as in the control plot, and rain water flooded the plow pan for extended periods of time.

Adachi, Kazuhide; Ohno, Satoshi; Furuhata, Masami; Ogura, Chikara; Tanimoto, Takeshi

102

Direct N2O emissions from rice paddy fields: Summary of available data  

Microsoft Academic Search

Rice cultivation is an important anthropogenic source of atmospheric nitrous oxide (N2O) and methane. We compiled and analyzed data on N2O emissions from rice fields (113 measurements from 17 sites) reported in peer-reviewed journals. Mean N2O emission ± standard deviation and mean fertilizer-induced emission factor during the rice-cropping season were, respectively, 341 ± 474 g N ha?1 season?1 and 0.22

Hiroko Akiyama; Kazuyuki Yagi; Xiaoyuan Yan

2005-01-01

103

[Comparing the ammonia volatilization characteristic of two typical paddy soil with total wheat straw returning in Taihu Lake region].  

PubMed

An experiment using monolith lysimeter was conducted to compare the characteristic of N loss by ammonia (NH3) volatilization between the gleyed paddy soil (G soil) and hydromorphic paddy soil (H soil) the Changshu National Agro-ecological Experimental Station of the Chinese Academy of Sciences(31 degrees 33' N, 123 degrees 38' E). Three treatments were designed for each soil type, i. e. control (no urea and straw applied), nitrogen solely and nitrogen plus wheat straw. Ammonia volatilization, flood water NH4(+) -N concentration, pH and top soil Eh were measured during the rice-growing season. Results showed that the NH3 volatilization flux and cumulative N losses by NH3 volatilization from G soil were significantly higher than those from H soil, the average cumulative N losses being about 41.8 kg x hm(-2) and 11.2 kg x hm(-2), or 15.2% and 3.8% of the fertilizer N, respectively. The average N loss by NH3 volatilization during the tillering stage was the highest among the three fertilization stages, accounting for 29.4% and 8.3% of the fertilizer N for G soil and H soil, respectively. Wheat straw returning significantly increased paddy filed NH3 volatilization losses. Comparing with the sole application of fertilizer-N, the cumulative N loss by NH3 volatilization of fertilizer-N in combination with wheat straw was increased by 19.8% and 20.6% for G soil and H soil, respectively. In addition, ammonia volatilization fluxes showed a positive relationship with the flood water NH4(+) -N concentration and pH for both soils, but the relationship with top soil Eh still needs further study. PMID:23487914

Wang, Jun; Wang, De-Jian; Zhang, Gang; Wang, Yuan

2013-01-01

104

[Effects of rice-duck farming on paddy field's methane emission].  

PubMed

By using closed-chamber technique, the characteristics of CH4 emission from an integrated rice-duck ecosystem were studied in 2006 and 2007. The results showed that comparing with conventional flooded rice ecosystem (CK), integrated rice-duck system (RD) was distinguished in its high dissolved oxygen (DO) in field surface water and significantly lower CH4 emission, due to the activities of duck. In 2006, the average CH4 emission flux and the total CH4 emission during the whole rice growth period of RD were 6.84 +/- 1.49 mg +/- m(-2) x h(-1) and 19.34 +/- 1.15 g x m(-2), being 32.7% and 26.3% lower than those of CK (10.17 +/- 1.25 mg x m(-2) x h(-1) and 26.25 +/- 2.17 g respectively; while in 2007, the values of the two test items of RD were 7.68 +/- 0.74 mg x m(-2) x h(-1) and 18.41 +/- 1.05 g x m(-2), being 19.0% and 19.3% lower than those of CK (9.53 +/- 0.40 mg x m(-2) x h(-1) and 22.81 +/- 0.75 g +/- m(-2)), respectively. The emission flux of CH4 had two peaks, being appeared at tillering and heading stages, respectively. The seasonal fluctuations of CH4 emission flux had significant positive correlations with soil temperature and soil dissolved organic carbon content (DOC), but no obvious correlation with soil total organic carbon. PMID:19288721

Zhan, Ming; Cao, Cou-gui; Wang, Jin-ping; Yuan, Wei-ling; Jiang, Yang; Gao, Da-wei

2008-12-01

105

Rural wastewater irrigation and nitrogen removal by the paddy wetland system in the Tai Lake region of China  

Microsoft Academic Search

Background, aim, and scope  A large area of water eutrophication in the Tai Lake region of China was associated with nitrogen (N) and phosphorus (P) pollution,\\u000a mainly due to the discharge of untreated rural wastewater (RW) into the surface water (SW) near villages of this region. A\\u000a field experiment was conducted, using irrigation of RW plus urea fertilization under equal nitrogen

Song Li; Hua Li; Xingqiang Liang; Yingxu Chen; Zhihong Cao; Zhihong Xu

2009-01-01

106

Isolation of key methanogens for global methane emission from rice paddy fields: a novel isolate affiliated with the clone cluster rice cluster I.  

PubMed

Despite the fact that rice paddy fields (RPFs) are contributing 10 to 25% of global methane emissions, the organisms responsible for methane production in RPFs have remained uncultivated and thus uncharacterized. Here we report the isolation of a methanogen (strain SANAE) belonging to an abundant and ubiquitous group of methanogens called rice cluster I (RC-I) previously identified as an ecologically important microbial component via culture-independent analyses. To enrich the RC-I methanogens from rice paddy samples, we attempted to mimic the in situ conditions of RC-I on the basis of the idea that methanogens in such ecosystems should thrive by receiving low concentrations of substrate (H(2)) continuously provided by heterotrophic H(2)-producing bacteria. For this purpose, we developed a coculture method using an indirect substrate (propionate) in defined medium and a propionate-oxidizing, H(2)-producing syntroph, Syntrophobacter fumaroxidans, as the H(2) supplier. By doing so, we significantly enriched the RC-I methanogens and eventually obtained a methanogen within the RC-I group in pure culture. This is the first report on the isolation of a methanogen within RC-I. PMID:17483259

Sakai, Sanae; Imachi, Hiroyuki; Sekiguchi, Yuji; Ohashi, Akiyoshi; Harada, Hideki; Kamagata, Yoichi

2007-05-04

107

Isolation of Key Methanogens for Global Methane Emission from Rice Paddy Fields: a Novel Isolate Affiliated with the Clone Cluster Rice Cluster I?  

PubMed Central

Despite the fact that rice paddy fields (RPFs) are contributing 10 to 25% of global methane emissions, the organisms responsible for methane production in RPFs have remained uncultivated and thus uncharacterized. Here we report the isolation of a methanogen (strain SANAE) belonging to an abundant and ubiquitous group of methanogens called rice cluster I (RC-I) previously identified as an ecologically important microbial component via culture-independent analyses. To enrich the RC-I methanogens from rice paddy samples, we attempted to mimic the in situ conditions of RC-I on the basis of the idea that methanogens in such ecosystems should thrive by receiving low concentrations of substrate (H2) continuously provided by heterotrophic H2-producing bacteria. For this purpose, we developed a coculture method using an indirect substrate (propionate) in defined medium and a propionate-oxidizing, H2-producing syntroph, Syntrophobacter fumaroxidans, as the H2 supplier. By doing so, we significantly enriched the RC-I methanogens and eventually obtained a methanogen within the RC-I group in pure culture. This is the first report on the isolation of a methanogen within RC-I.

Sakai, Sanae; Imachi, Hiroyuki; Sekiguchi, Yuji; Ohashi, Akiyoshi; Harada, Hideki; Kamagata, Yoichi

2007-01-01

108

Changes in microbial community structure and function within particle size fractions of a paddy soil under different long-term fertilization treatments from the Tai Lake region, China.  

PubMed

Greenhouse gas (GHG) production and emission from paddy soils impacts global climate change. Soil particle size fractions (PSFs) of different sizes act as soil microhabitats for different kinds of microbial biota with varying conditions of redox reactions and soil organic matter (SOC) substrates. It is crucial to understand the distribution of soil microbial community structure within PSFs and linkage to the GHG production from paddy soils of China. The change of bacterial and methangenic archaeal community and activity relating to CH(4) and CO(2) production with PSFs under different fertilizer applications was studied in this paper. The fertilization trial was initiated in a paddy soil from the Tai Lake region, Jiangsu, China with four treatments of non-fertilized (NF), fertilized with inorganic fertilizers only (CF), inorganic with pig manure (CFM) and inorganic with straw return (CFS), respectively since 1987, and the PSFs (<2 microm, 2-20 microm, 20-200 microm, and 200-2000 microm) were separated by a low energy sonication dispersion procedure from undisturbed samples. Analysis of bacterial community within different size particles was conducted by PCR-DGGE. The results indicated significant variation of bacterial community structure within different PSFs. The methane was predominantly produced in the coarser fractions, while more species and higher diversity of bacteria survived in the size of <2 microm fractions, in which the bacterial community structure was more significantly affected by fertilizer application practices than in the other coarser fractions. Higher bacterial species richness and more diversities in the smallest size fractions was due to the vicinity between microbes, access to carbon resource outside the microaggregates, and smaller pore size as protective agent suitable habitats for microbes rather than high SOC. Whereas, higher CO(2), CH(4) production and methanogenic archaeal community in coarser fractions may be contributed to storage of labile organic carbon in these fractions. It indicated that availability of SOC in PSFs is mainly factor affected survival of methanogenic archaeal community structure, whereas, bacterium community habitation more affected by physical protection of their location in PSFs. Their activity greatly depended on liability of SOC access to PSFs. Fertilizer application caused more change of bacteria community in clay fraction and greatly increased bacterium and methanogen activity in coarser fractions but only a slight effect on methanogenic archaeal community in the particle size fractions. PMID:17507207

Zhang, Pingjiu; Zheng, Jufeng; Pan, Genxing; Zhang, Xuhui; Li, Lianqing; Tippkötter, Rolf

2007-04-01

109

Effects of free-air CO2 enrichment (FACE) and soil warming on CH4 emission from a rice paddy field: impact assessment and stoichiometric evaluation  

NASA Astrophysics Data System (ADS)

Paddy fields are an important source of atmospheric CH4, the second most important greenhouse gas. There is a strong concern that the increasing atmospheric CO2 concentration ([CO2]) and global warming are further stimulating CH4 emissions, but the magnitude of this stimulation varies substantially by study, and few open-field evaluations have been conducted. Here we report results obtained at a Japanese rice free-air CO2 enrichment (FACE) site under water and soil temperature elevation during two growing seasons. Our objectives were to evaluate the effects of high [CO2] (ambient + 200 ?mol mol-1) and elevated soil temperature (+ 2 °C) on CH4 emissions under completely open-field conditions. We found about 80% enhancement in total seasonal emissions by the additive effects of FACE and warming, indicating a strong positive feedback effect of global warming. The enhancement in CH4 emission from the FACE-effect alone (+ 26%) was statistically non-significant (P = 0.19). Nevertheless, observed positive correlations between CH4 emissions and rice biomass agreed well with previous studies, suggesting that higher photosynthesis led to greater rhizodeposition, which then acted as substrates for methanogenesis. Soil warming increased the emission by 44% (P < 0.001), which was equivalent to a Q10 of 5.5. Increased rice biomass by warming could only partly explain the enhanced CH4 emissions, but stoichiometric analysis of the electron budget indicated that even a moderate enhancement in organic matter decomposition due to soil warming can cause a large increase in CH4 production under conditions where Fe(III) reduction, which was little affected by soil warming, dominates electron-accepting processes. At later rice growth stages, advanced root senescence due to elevated temperature probably provided more substrate for methanogenesis. Our stoichiometric evaluation showed that in situ Fe reduction characteristics and root turnover in response to elevated temperature should be understood to correctly predict future CH4 emissions from paddy fields under a changing climate. Challenges remain for determination of in situ root-exudation rate and its response to FACE and warming.

Tokida, T.; Fumoto, T.; Cheng, W.; Matsunami, T.; Adachi, M.; Katayanagi, N.; Matsushima, M.; Okawara, Y.; Nakamura, H.; Okada, M.; Sameshima, R.; Hasegawa, T.

2010-09-01

110

Effects of free-air CO2 enrichment (FACE) and soil warming on CH4 emission from a rice paddy field: impact assessment and stoichiometric evaluation  

NASA Astrophysics Data System (ADS)

Paddy fields are an important source of atmospheric CH4, the second most important greenhouse gas. There is a strong concern that the increasing atmospheric CO2 concentration ([CO2]) and global warming are further stimulating CH4 emissions, but the magnitude of this stimulation varies substantially by study, and few open-field evaluations have been conducted. Here we report results obtained at a Japanese rice free-air CO2 enrichment (FACE) site under water and soil temperature elevation during two growing seasons. Our objectives were to evaluate the effects of high [CO2] (ambient+200 ?mol mol-1) and elevated soil temperature (+2 °C) on CH4 emissions under completely open-field conditions. We found about 80% enhancement in total seasonal emissions by the additive effects of FACE and warming, indicating a strong positive feedback effect of global warming. The enhancement in CH4 emission (+26%, P = 0.19) from the effect of FACE alone was similar to that in rice biomass, suggesting that higher photosynthesis led to greater rhizodeposition, providing substrates for methanogenesis. Soil warming increased the emission by 44% (P < 0.001), which was equivalent to a Q10 of 5.5. Increased rice biomass by warming could only partly explain the enhanced CH4 emissions, but stoichiometric analysis of the electron budget indicated that even a moderate enhancement in organic matter decomposition due to soil warming can cause a large increase in CH4 production under conditions where Fe(III) reduction, which was little affected by soil warming, dominates electron-accepting processes. At later rice growth stages, advanced root senescence due to elevated temperature probably provided more substrate for methanogenesis. Our stoichiometric evaluation showed that in situ Fe reduction characteristics and root turnover in response to elevated temperature should be understood to correctly predict future CH4 emissions from paddy fields under a changing climate. Challenges remain for determination of in situ root-exudation rate and its response to FACE and warming.

Tokida, T.; Fumoto, T.; Cheng, W.; Matsunami, T.; Adachi, M.; Katayanagi, N.; Matsushima, M.; Okawara, Y.; Nakamura, H.; Okada, M.; Sameshima, R.; Hasegawa, T.

2010-03-01

111

Evaluation of methane emissions from Taiwanese paddies  

Microsoft Academic Search

The main greenhouse gases are carbon dioxide, methane and nitrous oxide. Methane is the most important because the warming effect of methane is 21 times greater than that of carbon dioxide. Methane emitted from rice paddy fields is a major source of atmospheric methane. In this work, a methane emission model (MEM), which integrates climate change, plant growth and degradation

Chen-Wuing Liu; Chung-Yi Wu

2004-01-01

112

[Responses of enzyme activities in different particle-size aggregates of paddy soil in Taihu Lake region of China to long-term fertilization].  

PubMed

Taking a long-term fertilized paddy soil in Taihu Lake region as research object, the enzyme activities in <2, 2-20, 20-200, and 200-2000 microm aggregates under no fertilization (NF), chemical fertilization (CF), chemical fertilization plus straw return (CFS), and chemical fertilization plus pig manure (CFM) were investigated. Fertilization promoted the formation of 200-2000 microm aggregates significantly. The enzyme activities differed with aggregates' particle-size. Urease and invertase activities were the highest in <2 microm aggregates, whereas the activities of cellulase, polyphenoloxidase and FDA hydrolase were the highest in 200-2000 microm aggregates. Fertilization, especially the combined fertilization of inorganic and organic fertilizers, increased the activities of urease, invertase, cellulase and FDA hydrolase in 200-2000 microm aggregates significantly. With the geometric mean (GMea) of the five test enzyme activities as the integrative index of soil enzyme activities, it was found that under fertilization, the GMea was significantly higher in 200-2000 microm aggregates, suggesting the high sensitivity of enzyme activities in larger particle-size aggregates to fertilization practices. Long-term inorganic plus organic fertilization could enhance the soil bio-function via the promotion of the formation of larger particle-size aggregates and the enzyme activities in these aggregates. PMID:20030140

Niu, Wen-jing; Li, Lian-qing; Pan, Gen-xing; Song, Xiang-yun; Li, Zhi-peng; Liu, Xiao-yu; Liu, Yong-zhuo

2009-09-01

113

Biogeochemistry of paddy soils  

Microsoft Academic Search

Paddy soils make up the largest anthropogenic wetlands on earth. They may originate from any type of soil in pedological terms, but are highly modified by anthropogenic activities. The formation of these Anthrosols is induced by tilling the wet soil (puddling), and the flooding and drainage regime associated with the development of a plough pan and specific redoximorphic features. Redox

Ingrid Kögel-Knabner; Wulf Amelung; Zhihong Cao; Sabine Fiedler; Peter Frenzel; Reinhold Jahn; Karsten Kalbitz; Angelika Kölbl; Michael Schloter

2010-01-01

114

Partitioning of arsenic in soil–crop systems irrigated using groundwater: A case study of rice paddy soils in southwestern Taiwan  

Microsoft Academic Search

The accumulation of As in rice due to groundwater irrigation in paddy fields represents a serious health hazard in South and Southeast Asia. In Taiwan, the fate of As in long-term irrigated paddy fields is poorly understood. Groundwater, surface soil, and rice samples were collected from a paddy field that was irrigated with As-containing groundwater in southwestern Taiwan. The purpose

Wen-Ming Hsu; Hsing-Cheng Hsi; You-Duan Huang; Chien-Sen Liao; Zeng-Yei Hseu

115

Changes in microbial community structure and function within particle size fractions of a paddy soil under different long-term fertilization treatments from the Tai Lake region, China  

Microsoft Academic Search

Greenhouse gas (GHG) production and emission from paddy soils impacts global climate change. Soil particle size fractions (PSFs) of different sizes act as soil microhabitats for different kinds of microbial biota with varying conditions of redox reactions and soil organic matter (SOC) substrates. It is crucial to understand the distribution of soil microbial community structure within PSFs and linkage to

Pingjiu Zhang; Jufeng Zheng; Genxing Pan; Xuhui Zhang; Lianqing Li; Tippkötter Rolf

2007-01-01

116

Responses of methanogen mcrA genes and their transcripts to an alternate dry/wet cycle of paddy field soil.  

PubMed

Intermittent drainage can substantially reduce methane emission from rice fields, but the microbial mechanisms remain poorly understood. In the present study, we determined the rates of methane production and emission, the dynamics of ferric iron and sulfate, and the abundance of methanogen mcrA genes (encoding the alpha subunit of methyl coenzyme M reductase) and their transcripts in response to alternate dry/wet cycles in paddy field soil. We found that intermittent drainage did not affect the growth of rice plants but significantly reduced the rates of both methane production and emission. The dry/wet cycles also resulted in shifts of soil redox conditions, increasing the concentrations of ferric iron and sulfate in the soil. Quantitative PCR analysis revealed that both mcrA gene copies and mcrA transcripts significantly decreased after dry/wet alternation compared to continuous flooding. Correlation and regression analyses showed that the abundance of mcrA genes and transcripts positively correlated with methane production potential and soil water content and negatively correlated with the concentrations of ferric iron and sulfate in the soil. However, the transcription of mcrA genes was reduced to a greater extent than the abundance of mcrA genes, resulting in very low mcrA transcript/gene ratios after intermittent drainage. Furthermore, terminal restriction fragment length polymorphism analysis revealed that the composition of methanogenic community remained stable under dry/wet cycles, whereas that of metabolically active methanogens strongly changed. Collectively, our study demonstrated a stronger effect of intermittent drainage on the abundance of mcrA transcripts than of mcrA genes in rice field soil. PMID:22101043

Ma, Ke; Conrad, Ralf; Lu, Yahai

2011-11-18

117

Comparing field and microcosm experiments: a case study on methano- and methylo-trophic bacteria in paddy soil  

Microsoft Academic Search

Methane-oxidising bacteria (MOB) play an important role in the reduction of methane emissions from rice agriculture. In rice fields, they are subjected to many environmental and field management parameters, which may have a significant impact on their community composition. To study this in greater detail, the community structure of methano- and methylo-trophic bacteria was investigated in a rice field in

Gundula Eller; Martin Krüger; Peter Frenzel

2005-01-01

118

Strategies for Controlling the Apple Snail Pomacea canaliculata (Lamarck) (Gastropoda: Ampullariidae) in Japanese Direct-Sown Paddy Fields  

Microsoft Academic Search

The apple snail Pomacea canaliculata becomes a much more serious pest in direct-sown rice fields than in transplanted fields. In south Japan, it represents an important constraint on the implementation of direct seeding. Described here are possible measures to control the snails and suggestions for its management in Japanese direct-sown rice fields. Crop rotation with upland crops is a practical

Takashi WADA

2004-01-01

119

Active Region Magnetic Fields. I. Plage Fields  

NASA Astrophysics Data System (ADS)

We present observations taken with the Advanced Stokes Polarimeter (ASP) in active-region plages and study the frequency distribution of the magnetic field strength (B), inclination with respect to vertical ( gamma ), azimuthal orientation ( chi ), and filling factor (f). The most common values at disk center are B = 1400 G, gamma < 10 deg, no preferred east-west orientation, and f = 15%. At disk center, there is a component of weak (<1000 G), more horizontal fields that corresponds to arching field lines connecting footpoints of different polarities. The center-to-limb variation (CLV) of the field strength shows that, close to the limb ( mu = 0.3), the field strength is reduced to 800 G from its disk-center value. This can be interpreted as a gradient of B with height in solar plages of around -3 G km-1. From this CLV study, we also deduce that magnetic field lines remain vertical for the entire range of heights involved. A similar analysis is performed for structures found in active regions that show a continuous distribution of azimuths (resembling sunspots) but that do not have a darkening in continuum. These "azimuth centers" show slightly larger values of B than normal plages, in particular at their magnetic center. Filling factors are also larger on average for these structures. The velocities in the magnetic component of active regions have been studied for both averaged Stokes profiles over the entire active region and for the spatially resolved data. The averaged profiles (more representative of high filling factor regions) do not show any significant mean velocities. However, the spatial average of Doppler velocities derived from the spatially resolved profiles (i.e., unweighted by filling factor) show a net redshift at disk center of 200 m s-1. The spatially resolved velocities show a strong dependence on filling factor. Both mean velocities and standard deviations are reduced when the filling factor increases. This is interpreted as a reduction of the p-mode amplitude within the magnetic component. Strong evidence for velocities transverse to the magnetic field lines has been found. Typical rms values are between 200 and 300 m s-1, depending on the filling factor. The possible importance of these transverse motions for the dynamics of the upper atmospheric layers is discussed. The asymmetries of the Stokes profiles and their CLV have been studied. The averaged Stokes V profiles show amplitude and area asymmetries that are positive at disk center and become negative at the limb. Both asymmetries, and for the two Fe I lines, are maximized away from disk center. The spatially resolved amplitude asymmetries show a clear dependence on filling factor: the larger the filling factor, the smaller the amplitude asymmetry. On the other hand, the area asymmetry is almost independent of the filling factor. The only observed dependence is the existence of negative area-asymmetry profiles at disk center for filling factors smaller than 0.2. Around 20% of the observed points in a given plage have negative area asymmetry. The amplitude asymmetry of Stokes V is, on the other hand, always positive. The amplitude asymmetries of the linear polarization profiles are observed to have the same sign as the Stokes V profiles. Similarly, the same CLV variation of the linear polarization amplitude asymmetries as for Stokes V has been found. The scenarios in which this similarity can exist are studied in some detail.

Martinez Pillet, V.; Lites, B. W.; Skumanich, A.

1997-01-01

120

Effects of Tillage and Nitrogen Fertilizers on CH4 and CO2 Emissions and Soil Organic Carbon in Paddy Fields of Central China  

Microsoft Academic Search

Quantifying carbon (C) sequestration in paddy soils is necessary to help better understand the effect of agricultural practices on the C cycle. The objective of the present study was to assess the effects of tillage practices [conventional tillage (CT) and no-tillage (NT)] and the application of nitrogen (N) fertilizer (0 and 210 kg N ha?1) on fluxes of CH4 and

Li Cheng-Fang; Zhou Dan-Na; Kou Zhi-Kui; Zhang Zhi-Sheng; Wang Jin-Ping; Cai Ming-Li; Cao Cou-Gui

2012-01-01

121

Effect of land use change from paddy rice cultivation to upland crop cultivation on soil carbon budget of a cropland in Japan  

Microsoft Academic Search

Effect of land use change from paddy rice cultivation to upland crop cultivation on soil carbon budget (SCB) was studied by comparing three types of cropping system (single cropping of paddy rice (PR), single cropping of upland rice (UR) and double cropping of soybean and wheat (SW)) in an experimental field having the same history as consecutively cultivated paddy rice

Seiichi Nishimura; Seiichiro Yonemura; Takuji Sawamoto; Yasuhito Shirato; Hiroko Akiyama; Shigeto Sudo; Kazuyuki Yagi

2008-01-01

122

Pendimethalin in surface waters of rivers in the proximity of irrigated paddy fields by solid phase microextraction and gas chromatography  

Microsoft Academic Search

The aim of this study was to develop an analytical methodology for the determination of the herbicide pendimethalin in river waters in the towns of Turvo and Meleiro in the southern region of Santa Catarina State, Brazil. The method, based on solid phase microextraction (SPME) followed by separation and detection by gas chromatography (GC) and electron capture detection (ECD), respectively,

Léa L. Freitas; Ernani S. Sant’Anna; Eliane A. Suchara; Vanira S. Benato; Eduardo Carasek

2012-01-01

123

Pendimethalin in surface waters of rivers in the proximity of irrigated paddy fields by solid phase microextraction and gas chromatography  

Microsoft Academic Search

The aim of this study was to develop an analytical methodology for the determination of the herbicide pendimethalin in river waters in the towns of Turvo and Meleiro in the southern region of Santa Catarina State, Brazil. The method, based on solid phase microextraction (SPME) followed by separation and detection by gas chromatography (GC) and electron capture detection (ECD), respectively,

Léa L. Freitas; Ernani S. Sant’Anna; Eliane A. Suchara; Vanira S. Benato; Eduardo Carasek

2011-01-01

124

Parameter estimation and uncertainty analysis of a large-scale crop model for paddy rice: Application of a Bayesian approach  

Microsoft Academic Search

A Bayesian approach, the Markov Chain Monte Carlo (MCMC) technique, was applied to a newly developed large-scale crop model for paddy rice to optimize a new set of regional-specific parameters and quantify the uncertainty of yield estimation associated with model parameters. The developed large-scale model is process-based and up-scaled from a conventional field-scale model to meet the intended spatial-scale of

Toshichika Iizumi; Masayuki Yokozawa; Motoki Nishimori

2009-01-01

125

Problem Soils of the Paddy Fields in the Eastern Coastal Plain of the Red River Delta, Vietnam  

Microsoft Academic Search

Although the Red River Delta is one of the grain cradles in the rice-producing areas of Vietnam, this area contains salt-affected area. In this study, we aim to clarify the distribu- tion and characteristics of problem soils which have led to the land use condition as follows. The salt-affected land in the eastern region of the Red River Delta can

Shigeko HARUYAMA; Hung Thai DINH; Van Tiem LE

126

Sources Of Atmospheric Methane: Measurements in Rice Paddies and a Discussion  

Microsoft Academic Search

We have made field measurements of methane fluxes from rice paddies, fresh water lakes, and saltwater marshes to infer estimates of the size of these sources of atmospheric methane. The rice-paddy measurements, the first of their kind, show that the principal means of methane escape is through the plants themselves as opposed to transport across the water-air interface via bubbles

Ralph J. Cicerone; James D. Shetter

1981-01-01

127

Transformation of marine sediment to paddy soil: Primary marine, lacustrine, and land plant lipids  

Microsoft Academic Search

More than fifty percent of the world's population feeds on rice. The continuous population increase and urban sprawl leads to an ever-increasing demand for new rice cultivation area, in particular China. For centuries suitable coastal areas in China have been exploited for land reclamation, i.e. conversion of coastal marine and lacustrine marshlands into rice paddy fields. Flooded rice paddies are

Cornelia Mueller-Niggemann; Zhihong Cao; Lorenz Schwark

2010-01-01

128

Impact of six transgenic Bacillus thuringiensis rice lines on four nontarget thrips species attacking rice panicles in the paddy field.  

PubMed

As a key component of ecological risk assessments, nontarget effects of Bacillus thuringiensis (Bt) rice have been tested under laboratory and field conditions for various organisms. A 2-yr field experiment was conducted to observe the nontarget effects of six transgenic rice lines (expressing the Cry1Ab or fused protein of Cry1Ab and Cry1Ac) on four nontarget thrips species including Frankliniella intonsa (Trybom), F. tenuicornis (Uzel), Haplothrips aculeatus (F.), and H. tritici (Kurd), as compared with their rice parental control lines. Two sampling methods including the beat plate and plastic bag method were used to monitor the population densities of the four thrips species for 2 yr. The results showed that the seasonal average densities of four tested thrips species in Bt rice plots were significantly lower than or very similar to those in the non-Bt rice plots depending on rice genotypes, sampling methods, and years. Among all six tested Bt rice lines, transgenic B1 and KMD2 lines suppressed the population of these tested thrips species the most. Our results indicate that the tested Bt rice lines are unlikely to result in high population pressure of thrips species in comparison with non-Bt rice. In some cases, Bt rice lines could significantly suppress thrips populations in the rice ecosystem. In addition, compatibility of Bt rice, with rice host plant resistance to nontarget sucking pests is also discussed within an overall integrated pest management program for rice. PMID:23339799

Akhtar, Z R; Tian, J C; Chen, Y; Fang, Q; Hu, C; Peng, Y F; Ye, G Y

2013-02-01

129

Abundance and community composition of methanotrophs in a Chinese paddy soil under long-term fertilization practices  

Microsoft Academic Search

Background, aim, and scope  As the second most important greenhouse gas, methane (CH4) is produced from many sources such as paddy fields. Methane-oxidizing bacteria (methanotrophs) consume CH4 in paddy soil and, therefore, reduce CH4 emission to the atmosphere. In order to estimate the contribution of paddy fields as a source of CH4, it is important to monitor the effects of fertilizer

Yong Zheng; Li-Mei Zhang; Yuan-Ming Zheng; Hongjie Di; Ji-Zheng He

2008-01-01

130

Analysis of percolation and seepage through paddy bunds  

Microsoft Academic Search

This study investigates percolation and seepage through the bunds of flat and terraced paddies. Field experiments were conducted in Hsin-Pu of Hsin-Chu County, Taiwan, to measure the soil water content of various types of bund. Measurements revealed that the soil was unsaturated along the sloped surface of the terrace. Experimental results also indicated that seepage face flow did not develop

Han-Chen Huang; Chen-Wuing Liu; Shih-Kai Chen; Jui-Sheng Chen

2003-01-01

131

Pesticide exposure assessment in rice paddies in Europe: a comparative study of existing mathematical models.  

PubMed

A comparative test was undertaken in order to identify the potential of existing mathematical models, including the rice water quality (RICEWQ) 1.6.4v model, the pesticide concentration in paddy field (PCPF-1) model and the surface water and groundwater (SWAGW) model, for calculating pesticide dissipation and exposure in rice paddies in Europe. Previous versions of RICEWQ and PCPF-1 models had been validated under European and Japanese conditions respectively, unlike the SWAGW model which was only recently developed as a tier-2 modelling tool. Two datasets, derived from field dissipation studies undertaken in northern Italy with the herbicides cinosulfuron and pretilachlor, were used for the modelling exercise. All models were parameterized according to field experimentations, as far as possible, considering their individual deficiencies. Models were not calibrated against field data in order to remove bias in the comparison of the results. RICEWQ 1.6.4v provided the highest agreement between measured and predicted pesticide concentrations in both paddy water and paddy soil, with modelling efficiency (EF) values ranging from 0.78 to 0.93. PCPF-1 simulated well the dissipation of herbicides in paddy water, but significantly underestimated the concentrations of pretilachlor, a chemical with high affinity for soil sorption, in paddy soil. SWAGW simulated relatively well the dissipation of both herbicides in paddy water, and especially pretilachlor, but failed to predict closely the pesticide dissipation in paddy soil. Both RICEWQ and SWAGW provided low groundwater (GW) predicted environmental concentrations (PECs), suggesting a low risk of GW contamination for the two herbicides. Overall, this modelling exercise suggested that RICEWQ 1.6.4v is currently the most reliable model for higher-tier exposure assessment in rice paddies in Europe. PCPF-1 and SWAGW showed promising results, but further adjustments are required before these models can be considered as strong candidates for inclusion in the higher-tier pesticide regulatory scheme. PMID:16718738

Karpouzas, Dimitrios G; Cervelli, Stefano; Watanabe, Hirozumi; Capri, Ettore; Ferrero, Aldo

2006-07-01

132

Identification of vivianite formed on the roots of paddy rice grown in pots  

Microsoft Academic Search

An understanding of the phosphate (P) dynamics in paddy rice fields is the basis for improving P fertilizer efficiency and reducing P loss from paddy fields. During the ripening stage of rice plants cultivated in pots, we identified vivianite on the roots. We placed 3?kg of air-dried soil in a pot with coated urea (1?g N), coated potassium sulfate (1?g

Masami Nanzyo; Hidenori Yaginuma; Kana Sasaki; Kumiko Ito; Yoshio Aikawa; Hitoshi Kanno; Tadashi Takahashi

2010-01-01

133

Assessing energy efficiencies and greenhouse gas emissions under bioethanol-oriented paddy rice production in northern Japan  

Microsoft Academic Search

To establish energetically and environmentally viable paddy rice-based bioethanol production systems in northern Japan, it is important to implement appropriately selected agronomic practice options during the rice cultivation step. In this context, effects of rice variety (conventional vs. high-yielding) and rice straw management (return to vs. removal from the paddy field) on energy inputs from fuels and consumption of materials,

Nobuhisa Koga; Ryosuke Tajima

2011-01-01

134

Methane emission from rice paddies  

Microsoft Academic Search

Methane release rates from rice paddies have been measured in Andalusia, Spain, during almost a complete vegetation period in 1982 using the static box system. The release rates ranged between 2 and 14 mg\\/m2\\/h and exhibited a strong seasonal variation with low values during the tillering stage and shortly before harvest, while maximum values were observed at the end of

W. Seiler; A. Holzapfel-Pschorn; R. Conrad; D. Scharffe

1983-01-01

135

Anaerobic ammonia oxidation in a fertilized paddy soil  

PubMed Central

Evidence for anaerobic ammonium oxidation in a paddy field was obtained in Southern China using an isotope-pairing technique, quantitative PCR assays and 16S rRNA gene clone libraries, along with nutrient profiles of soil cores. A paddy field with a high load of slurry manure as fertilizer was selected for this study and was shown to contain a high amount of ammonium (6.2–178.8?mg?kg?1). The anaerobic oxidation of ammonium (anammox) rates in this paddy soil ranged between 0.5 and 2.9?nmolN per gram of soil per hour in different depths of the soil core, and the specific cellular anammox activity observed in batch tests ranged from 2.9 to 21?fmol per cell per day. Anammox contributed 4–37% to soil N2 production, the remainder being due to denitrification. The 16S rRNA gene sequences of surface soil were closely related to the anammox bacteria ‘Kuenenia', ‘Anammoxoglobus' and ‘Jettenia'. Most of the anammox 16S rRNA genes retrieved from the deeper soil were affiliated to ‘Brocadia'. The retrieval of mainly bacterial amoA sequences in the upper part of the paddy soil indicated that nitrifying bacteria may be the major source of nitrite for anammox bacteria in the cultivated horizon. In the deeper oxygen-limited parts, only archaeal amoA sequences were found, indicating that archaea may produce nitrite in this part of the soil. It is estimated that a total loss of 76?g?N?m?2 per year is linked to anammox in the paddy field.

Zhu, Guibing; Wang, Shanyun; Wang, Yu; Wang, Chaoxu; Risgaard-Petersen, Nils; Jetten, Mike SM; Yin, Chengqing

2011-01-01

136

Fertilization increases paddy soil organic carbon density*  

PubMed Central

Field experiments provide an opportunity to study the effects of fertilization on soil organic carbon (SOC) sequestration. We sampled soils from a long-term (25 years) paddy experiment in subtropical China. The experiment included eight treatments: (1) check, (2) PK, (3) NP, (4) NK, (5) NPK, (6) 7F:3M (N, P, K inorganic fertilizers+30% organic N), (7) 5F:5M (N, P, K inorganic fertilizers+50% organic N), (8) 3F:7M (N, P, K inorganic fertilizers+70% organic N). Fertilization increased SOC content in the plow layers compared to the non-fertilized check treatment. The SOC density in the top 100 cm of soil ranged from 73.12 to 91.36 Mg/ha. The SOC densities of all fertilizer treatments were greater than that of the check. Those treatments that combined inorganic fertilizers and organic amendments had greater SOC densities than those receiving only inorganic fertilizers. The SOC density was closely correlated to the sum of the soil carbon converted from organic amendments and rice residues. Carbon sequestration in paddy soils could be achieved by balanced and combined fertilization. Fertilization combining both inorganic fertilizers and organic amendments is an effective sustainable practice to sequestrate SOC.

Wang, Shao-xian; Liang, Xin-qiang; Luo, Qi-xiang; Fan, Fang; Chen, Ying-xu; Li, Zu-zhang; Sun, Huo-xi; Dai, Tian-fang; Wan, Jun-nan; Li, Xiao-jun

2012-01-01

137

Quantifying methane emissions from rice paddies in Northeast China by integrating remote sensing mapping with a biogeochemical model  

NASA Astrophysics Data System (ADS)

The Sanjiang Plain located in Northeastern China is one of the major rice producing regions in the country. However, differing from the majority rice regions in Southern China, the Sanjinag Plain possesses a much cooler weather. Could the rice paddies in this domain be an important source of global methane? To answer this question, we calculated methane (CH4) emissions from the region by integrating remote sensing mapping with a process-based biogeochemistry model, Denitrification and Decomposition or DNDC. To quantify regional CH4 emissions from the plain, we first tested the model against a two-year dataset of CH4 fluxes measured at a typical rice field within the domian. A sensitivity test was conducted to find out the most sensitive factors affecting CH4 emissions in the region. Based on the understanding gained from the validation and sensitivity tests, a geographic information system (GIS) database was constructed to hold the spatially differentiated input information to drive DNDC for its regional simulations. The GIS database included a rice map derived from the Landsat TM images, which provided crucial information about the spatial distribution of the rice fields within the domain of 10.93 million hectares. The modeled results showed that the total 1.44 million ha of rice paddies in the plain emitted 0.43-0.58 Tg CH4-C per year with spatially differentiated annual emission rates ranging between 100-800 kg CH4-C/ha, which are comparable with that observed in Southern China. The modeled data indicated that the high SOC contents, long crop season and high rice biomass enhanced CH4 production in the cool paddies. The modeled results proved that the northern wetland agroecosystems could make important contributions to global greenhouse gas inventory.

Zhang, Y.; Wang, Y. Y.; Su, S. L.; Li, C. S.

2011-01-01

138

Magnetic Fields in Solar Active Regions.  

National Technical Information Service (NTIS)

The report is a review and interpretation of solar active region observations obtained principally with magnetographs. Most of these instruments measure the line-of-sight component of the magnetic field. A few instruments can also measure the transverse c...

D. M. Rust

1970-01-01

139

The effect of water management based on soil redox potential on methane emission from two kinds of paddy soils in Japan  

Microsoft Academic Search

Paddy fields are major sources of the global methane (CH4) emission. Water management of paddy fields affects rice yield and CH4 emission. There is need for improvement in the management to achieve a balance between them. We suggest the water management based on soil redox potential (Eh), which was named Eh control. The effects of Eh control on rice yield

Kazunori Minamikawa; Naoki Sakai

2005-01-01

140

Intra- versus inter-site macroscale variation in biogeochemical properties along a paddy soil chronosequence  

NASA Astrophysics Data System (ADS)

In order to assess the intrinsic heterogeneity of paddy soils, a set of biogeochemical soil parameters was investigated in five field replicates of seven paddy fields (50, 100, 300, 500, 700, 1000, and 2000 yr of wetland rice cultivation), one flooded paddy nursery, one tidal wetland (TW), and one freshwater site (FW) from a coastal area at Hangzhou Bay, Zhejiang Province, China. All soils evolved from a marine tidal flat substrate due to land reclamation. The biogeochemical parameters based on their properties were differentiated into (i) a group behaving conservatively (TC, TOC, TN, TS, magnetic susceptibility, soil lightness and colour parameters, ?13C, ?15N, lipids and n-alkanes) and (ii) one encompassing more labile properties or fast cycling components (Nmic, Cmic, nitrate, ammonium, DON and DOC). The macroscale heterogeneity in paddy soils was assessed by evaluating intra- versus inter-site spatial variability of biogeochemical properties using statistical data analysis (descriptive, explorative and non-parametric). Results show that the intrinsic heterogeneity of paddy soil organic and minerogenic components per field is smaller than between study sites. The coefficient of variation (CV) values of conservative parameters varied in a low range (10% to 20%), decreasing from younger towards older paddy soils. This indicates a declining variability of soil biogeochemical properties in longer used cropping sites according to progress in soil evolution. A generally higher variation of CV values (>20-40%) observed for labile parameters implies a need for substantially higher sampling frequency when investigating these as compared to more conservative parameters. Since the representativeness of the sampling strategy could be sufficiently demonstrated, an investigation of long-term carbon accumulation/sequestration trends in topsoils of the 2000 yr paddy chronosequence under wetland rice cultivation restricted was conducted. Observations cannot be extrapolated to global scale but with coastal paddy fields developed on marine tidal flat substrates after land reclamation in the Zhejiang Province represent a small fraction (<1%) of the total rice cropping area. The evolutionary trend showed that the biogeochemical signatures characteristic for paddy soils were fully developed in less than 300 yr since onset of wetland rice cultivation. A six-fold increase of topsoil TOC suggests a substantial gain in CO2 sequestration potential when marine tidal wetland substrate developed to 2000 yr old paddy soil.

Mueller-Niggemann, C.; Bannert, A.; Schloter, M.; Lehndorff, E.; Schwark, L.

2012-03-01

141

Clomazone dissipation, adsorption and translocation in four paddy topsoils.  

PubMed

Laboratory experiments about the dissipation, adsorption and translocation in four paddy topsoils were conducted in this paper. From the results it can be concluded as follows: the dissipation rate of clomazone differed greatly in different paddy soil derived from different parent materials. The half-lives for clomazone degradation in paddy soils ranged from 5.7 to 22.0 d. The order of clomazone dissipation rate was reddish yellow paddy soil > alluvial sandy paddy soil > yellow clayey paddy soil > purple sandy paddy soil. Clomazone sorption quantity was significantly correlated with organic carbon (R2 = 0.62) and clay content(R2 = 0.67) in the tested paddy soils. Positive correlation was found between apparent Kd value and cation exchange content(CEC). The consequences for the adsorption of different soils were purple sandy paddy soil > yellow clayey paddy soil > reddish yellow paddy soil > alluvial sandy paddy soil. Under the simulated rainfall of 200 mm through four different unsaturated soil lysimeters over 24 h, clomazone was readily to be leached into lower surface soil and there was about 2.6%--4.2% of applied clomazone leached out of 20 cm cultivated soil layer. Translocation experiments showed that the order of clomazone leaching ability was: alluvial sandy paddy soil > reddish yellow paddy soil > yellow clayey paddy soil > purple sandy paddy soil. Simple regression results manifested that factors like CEC, organic carbon, clay, and adsorption rate constant had been negatively correlated with the percentage of clomazone loss from soil lysimeters. PMID:15495980

Li, Lian-fang; Li, Guo-xue; Yang, Ren-bin; Guo, Zheng-yuan; Liao, Xiao-yong

2004-01-01

142

Basin-wide Projection for Paddy Irrigation in Monsoon Asia Based on a Distributed Hydrological Model and Climate Change Scenarios  

NASA Astrophysics Data System (ADS)

1. Introduction A large amount of water in Monsoon Asia is used for rice paddy, and the mechanism of water use varies widely by region. Agricultural water exerts a great influence on the hydrological cycle in river basins and modeling of this process is crucial to understand the hydrological cycle especially in areas where irrigated agriculture is dominant. Such agricultural water uses, however, were not fully combined in the previous runoff models, although this process is essential for assessing the impact of climate change on agriculture in Monsoon Asia. In this study, impact assessment of climate change on paddy field irrigation was carried out in the Seki River basin located in the northern part of Japan, using a distributed hydrological model incorporating various paddy water uses. 2. Distributed hydrological model incorporating various agricultural water uses The model used in this study consists of four sub-models, such as evapotranspiration, cropping pattern/area, agricultural water use, and runoff, so that it enables to estimate cropping area, paddy water requirements, actual intake at main irrigation facilities at any point of the basin, in addition to actual evapotranspiration, soil water content, runoff amount that are normally calculated by many prevailing runoff models. A target basin is divided into 1km-messhed cells and each cell contains the ratio of 5 land-use category as forest, rain-fed paddy, irrigated paddy, upland field and water area. Irrigation and crop patterns are also set as agricultural practices in each cell, and then irrigation amount and actual evapotranspiration can be estimated according to cropping stage and soil moisture. 3. Climate change scenarios and its bias correction Future climate scenarios simulated by MIROC (SRES-A1B), which is one of the GCMs developed by CCSR/NIES/FRCGC in Japan, were used as input data into the hydrological model. Coarse resolution by GCM was nested into 1km resolution by a simple linear interpolation. Bias correction was carried out by a statistical method for the meteorological elements such as precipitation, temperature, relative humidity and wind velocity which were calculated by MIROC. Furthermore, monthly daily-maximum precipitation as extreme events was corrected with the Gumbel distribution. 4. Results and discussion The results in this study are as follows: 1) Snow water equivalence during the winter season will decrease by global warming in near future (2046-2065) and the end of 21th century (2081-2100). As a result, this will lead to a decrease in snowmelt runoff in early spring. 2) Agricultural intake at the “Itakura” head works would decrease especially on May and June owing to the decrease in snowmelt runoff mentioned above. 3) The agricultural water would not be supplied in lower part of irrigated area sufficiently, while increasing in evapotranspiration from paddy field. Therefore, this may result in imbalance of agricultural water in these areas.4) The distributed hydrological model incorporating various agricultural water uses can foretell detailed impacts of climate change on irrigation as well as that of discharge.

Kudo, R.; Masumoto, T.; Yoshida, T.; Horikawa, N.

2010-12-01

143

[Simulation of methane emissions from rice fields in the Taihu Lake region, China by using different unit of soil database with the DNDC model].  

PubMed

Application of a biogeochemical model, DeNitrification and DeComposition or DNDC, was discussed to assess the impact of CH4 emissions on different soil database from rice fields in Taihu Lake region of China. The results showed that CH4 emissions of the polygon-based soil database of 1:50000, which contained 52034 polygons of paddy soils representing 1107 paddy soil profiles extracted from the latest national soil map (1:50000), were located within the ranges produced by the county-based soil database of 1:50000. However, total emissions of the whole area differed by about 1680 Gg CH4-C. Moreover, CH4 emissions of the polygon-based soil database of 1:50000 and the county-based soil database of 14,000,000, which was the most popular data source when DNDC model was applied in China, have a big estimation discrepancy among each county-based unit in spite of total emissions of the whole area by a difference of 180 Gg CH4-C. This indicated that the more precise soil database was necessary to better simulate CH4 emissions from rice fields in Taihu Lake region using the DNDC model. PMID:19799272

Zhang, Li-ming; Yu, Dong-sheng; Shi, Xue-zheng; Zhao, Li-min; Ding, Wei-xin; Wang, Hong-jie; Pan, Jian-jun

2009-08-15

144

Arsenic bioavailability to rice is elevated in Bangladeshi paddy soils.  

PubMed

Some paddy soils in the Bengal delta are contaminated with arsenic (As) due to irrigation of As-laden groundwater, which may lead to yield losses and elevated As transfer to the food chain. Whether these soils have a higher As bioavailability than other soils containing either geogenic As or contaminated by mining activities was investigated in a pot experiment. Fourteen soils varying in the source and the degree (4-138 mg As kg 1?¹) of As contamination were collected, 10 from Bangladeshi paddy fields (contaminated by irrigation water) and two each from China and the UK (geogenic or mining impacted), for comparison. Bangladeshi soils had higher percentages of the total As extractable by ammonium phosphate (specifically sorbed As) than other soils and also released more As into the porewater upon flooding. Porewater As concentrations increased with increasing soil As concentrations more steeply in Bangladeshi soils, with arsenite being the dominant As species. Rice growth and grain yield decreased markedly in Bangladeshi soils containing > 13 mg As kg 1?¹, but not in the other soils. Phosphate-extractable or porewater As was a better indicator of As bioavailability than total soil As. Rice straw As concentrations increased with increasing soil As concentrations; however, As phytotoxicity appeared to result in lower grain As concentrations. The relative proportions of inorganic As and dimethylarsinic acid (DMA) in grain varied among soils, and the percentage DMA was larger in greenhouse-grown plants than grain samples collected from the paddy fields of the same soil and the same rice cultivar, indicating a strong environmental influence on As species found in rice grain. This study shows that Bangladeshi paddy soils contaminated by irrigation had a higher As bioavailability than other soils, resulting in As phytotoxicity in rice and substantial yield losses. PMID:20977268

Khan, K Asaduzzaman; Stroud, Jacqueline L; Zhu, Yong-Guan; McGrath, Steve P; Zhao, Fang-Jie

2010-11-15

145

Vector Magnetic Field in Emerging Flux Regions  

NASA Astrophysics Data System (ADS)

A crucial phase in magnetic flux emergence is the rise of magnetic flux tubes through the solar photosphere, which represents a severe transition between the very different environments of the solar interior and corona. Multi-wavelength observations with Flare Genesis, TRACE, SoHO, and more recently with the vector magnetographs at THEMIS and Hida (DST) led to the following conclusions. The fragmented magnetic field in the emergence region - with dipped field lines or bald patches - is directly related with Ellerman bombs, arch filament systems, and overlying coronal loops. Measurements of vector magnetic fields have given evidence that undulating "serpentine" fields are present while magnetic flux tubes cross the photosphere. See the sketch below, and for more detail see Pariat et al. (2004, 2007); Watanabe et al. (2008):

Schmieder, B.; Pariat, E.

146

Complex magnetic fields in an active region  

NASA Astrophysics Data System (ADS)

High-resolution observations of the full Stokes vector in Fe\\sc i spectral lines around 5250 Angstroms obtained at the Swedish Vacuum Solar Telescope on La Palma with the ZIMPOL I Stokes polarimeter in a complex active region reveal the presence of anomalously shaped Stokes profiles indicating the coexistence of at least two magnetic components within the same spatial resolution element. These Stokes profiles have been analyzed with an inversion code based on a 3-component atmospheric model with two magnetic and one field-free component. The fits to the observations in a magnetic region that resembles a small penumbra reveal the presence of a horizontal magnetic field component with an average field strength of /line{B}=840 G, a mean filling factor of /line?=0.12, and an average temperature /line{T}=5400 K at log {tau_ {5000}}=-1.5 embedded in the main ``penumbral'' magnetic field that has /line{B}=1500 G, /line?=0.56, and /line{T}=4900 K. The horizontal component exhibits a mean outflow of 2.7 km s(-1) which is mainly due to the Evershed flow. In a region where there are strong downflows up to 7 km s(-1) , we infer the possible presence of a shock front whose height changes along the slit. The height variation can be explained by a change of the gas pressure at the base of the photosphere below the shock front as proposed by Thomas & Montesinos (1991). Small plages with field strengths below 900 G have been observed in the vicinity of some pores. Finally, we present a puzzling field structure at the boundary between two adjacent pores. Ambiguous results suggest that although the inversion code is able to successfully invert even very complex Stokes profiles, we are far from a complete description of the field structure in complex magnetic regions. We warn that magnetograms and fits to data involving only a single magnetic component may hide the true complexity of the magnetic structure in at least some parts of active regions.

Bernasconi, P. N.; Keller, C. U.; Solanki, S. K.; Stenflo, J. O.

1998-01-01

147

Intra-versus inter-site macroscale variation in biogeochemical properties along a paddy soil chronosequence  

NASA Astrophysics Data System (ADS)

In order to assess the intrinsic heterogeneity of paddy soils, a set of biogeochemical soil parameters was investigated in five field replicates of seven paddy fields (50, 100, 300, 500, 700, 1000, and 2000 yr of wetland rice cultivation), one flooded paddy nursery, one tidal wetland (TW), and one freshwater site (FW) from a coastal area at Hangzhou Bay, Zhejiang Province, China. All soils evolved from a marine tidal flat substrate due to land reclamation. The biogeochemical parameters based on their properties were differentiated into (i) a group behaving conservatively (TC, TOC, TN, TS, magnetic susceptibility, soil lightness and colour parameters, ?13C, ?15N, lipids and n-alkanes) and (ii) one encompassing more labile properties or fast cycling components (Nmic, Cmic, nitrate, ammonium, DON and DOC). The macroscale heterogeneity in paddy soils was assessed by evaluating intra- versus inter-site spatial variability of biogeochemical properties using statistical data analysis (descriptive, explorative and non-parametric). Results show that the intrinsic heterogeneity of paddy soil organic and minerogenic components per field is smaller than between study sites. The coefficient of variation (CV) values of conservative parameters varied in a low range (10 % to 20 %), decreasing from younger towards older paddy soils. This indicates a declining variability of soil biogeochemical properties in longer used cropping sites according to progress in soil evolution. A generally higher variation of CV values (>20-40 %) observed for labile parameters implies a need for substantially higher sampling frequency when investigating these as compared to more conservative parameters. Since the representativeness of the sampling strategy could be sufficiently demonstrated, an investigation of long-term carbon accumulation/sequestration trends in topsoils of the 2000 year paddy chronosequence under wetland rice cultivation was conducted. The evolutionary trend showed that the biogeochemical signatures characteristic for paddy soils were fully developed in less than 300 yr since onset of wetland rice cultivation. A six-fold increase of topsoil TOC suggests a substantial gain in CO2 sequestration potential when marine tidal wetland substrate developed to 2000 year old paddy soil.

Mueller-Niggemann, C.; Bannert, A.; Schloter, M.; Lehndorff, E.; Schwark, L.

2011-10-01

148

Modelling the fate of pesticides in paddy rice-fish pond farming systems in northern Vietnam.  

PubMed

BACKGROUND: In Vietnam, paddy rice fields have been identified as a major non-point source of pesticide pollution of surface- and groundwater which is often directly used for domestic purposes. One strategy to assess the risk of pesticide pollution is to use process-based models. Here, we present a new model developed for simulating short-term pesticide dynamics in combined paddy rice field-fish pond farming systems. The model was calibrated using the Gauss-Marquardt-Levenberg algorithm and validated against measured pesticide concentrations of a paddy field-fish pond system typical for northern Vietnam. RESULTS: In the calibration period, model efficiencies were 0.82 for dimethoate and 0.87 for fenitrothion. In the validation period, modelling efficiencies slightly decreased to 0.42 and 0.76 for dimethoate and fenitrothion, respectively. Scenario simulations revealed that a field closure period of 1?day after pesticide application considerably reduces the risk of pond and surface water pollution. CONCLUSION: These results indicate that the proposed model is an effective tool to assess and evaluate management strategies, such as extended field closure periods, aiming to reduce the loss of pesticides from paddy fields. © 2013 Society of Chemical Industry. PMID:23483671

La, Nguyen; Lamers, Marc; Nguyen, Vien V; Streck, Thilo

2013-03-01

149

Localized modeling of regional geomagnetic field attributes  

NASA Astrophysics Data System (ADS)

Geomagnetic features have been modeled by spherical harmonics. However, this global approach is best applied where the data are uniformly distributed over the globe. Satellite observations meet this requirement, but unequally distributed data cannot be easily adopted in global modeling. A spherical cap analysis has been used as an alternative in regional modeling for geopotential fields and recently this technique was well updated by Thebault et al. (2006) and Thebault (2008). In this study, we introduce a localized analysis technique that has been effectively used to model satellite gravity data for small cap regions of the Earth and Moon (Han et al.,2008; Han, 2009). The orthogonality of basis functions is valid in the area of interest so that the spectral properties are maintained with a considerably fewer number of coefficients that are basically transformed spherical harmonic coefficients. These so-called, Slepian functions (eigenvectors) also have been used as multitapers to model signals over windowed areas of the globe as well as the 2-D Fourier plane. As an application, we consider the regional secular variations since the year of 1590 from the geomagnetic Gauss coefficients of the gufm1 model (Jackson et al.2000), over South America and Antarctica.

Kim, H.; von Frese, R. R.

2009-12-01

150

Carbon dioxide flux from rice paddy soils in central China: effects of intermittent flooding and draining cycles.  

PubMed

A field experiment was conducted to (i) examine the diurnal and seasonal soil carbon dioxide (CO(2)) fluxes pattern in rice paddy fields in central China and (ii) assess the role of floodwater in controlling the emissions of CO(2) from soil and floodwater in intermittently draining rice paddy soil. The soil CO(2) flux rates ranged from -0.45 to 8.62 µmol.m(-2).s(-1) during the rice-growing season. The net effluxes of CO(2) from the paddy soil were lower when the paddy was flooded than when it was drained. The CO(2) emissions for the drained conditions showed distinct diurnal variation with a maximum efflux observed in the afternoon. When the paddy was flooded, daytime soil CO(2) fluxes reversed with a peak negative efflux just after midday. In draining/flooding alternating periods, a sudden pulse-like event of rapidly increasing CO(2) efflux occured in response to re-flooding after draining. Correlation analysis showed a negative relation between soil CO(2) flux and temperature under flooded conditions, but a positive relation was found under drained conditions. The results showed that draining and flooding cycles play a vital role in controlling CO(2) emissions from paddy soils. PMID:23437170

Liu, Yi; Wan, Kai-yuan; Tao, Yong; Li, Zhi-guo; Zhang, Guo-shi; Li, Shuang-lai; Chen, Fang

2013-02-20

151

Ancient paddy soils from the Neolithic age in China's Yangtze River Delta  

NASA Astrophysics Data System (ADS)

Identifying prehistoric irrigated rice fields and characterizing the beginning of paddy soil development are important for a better understanding of human development and agricultural history. In 2003, paddy soils and irrigated rice fields buried at a depth of 100-130 cm were excavated at Chuo-dun-shan in the Yangtze River Delta, close to Suzhou, China. The fields of sizes between 1.4 and 16 m2 were surrounded with ridges that were connected to ditches/ponds via outlets to control the water level within the fields. Many carbonized and partly carbonized rice grains with an age of 3,903 B.C.(measured 14C age 5,129±45 a BP) were recovered. The surface layers of these buried paddy fields showed a high content of soil organic matter and a considerable high density of rice opals. The latter were identified to derive from Oryza spp. Solid-state 13C nuclear magnetic resonance spectroscopy revealed aromatic carbon (C) as the predominant organic C form in the fossil surface layer. This is expected, if the major source represents burnt rice and straw. In summary, our data are in agreement with new evidences indicating that in China, paddy soils and irrigated rice cultivation were initiated and developed more than 6,000 years ago.

Cao, Z. H.; Ding, J. L.; Hu, Z. Y.; Knicker, H.; Kögel-Knabner, I.; Yang, L. Z.; Yin, R.; Lin, X. G.; Dong, Y. H.

2006-05-01

152

Detection and estimation of mixed paddy rice cropping patterns with MODIS data  

NASA Astrophysics Data System (ADS)

In this paper, we developed a more sophisticated method for detection and estimation of mixed paddy rice agriculture from Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data. Previous research demonstrated that MODIS data can be used to map paddy rice fields and to distinguish rice from other crops at large, continental scales with combined Enhanced Vegetation Index (EVI) and Land Surface Water Index (LSWI) analysis during the flooding and rice transplanting stage. Our approach improves upon this methodology by incorporating mixed rice cropping patterns that include single-season rice crops, early-season rice, and late-season rice cropping systems. A variable EVI/LSWI threshold function, calibrated to more local rice management practices, was used to recognize rice fields at the flooding stage. We developed our approach with MODIS data in Hunan Province, China, an area with significant flooded paddy rice agriculture and mixed rice cropping patterns. We further mapped the aerial coverage and distribution of early, late, and single paddy rice crops for several years from 2000 to 2007 in order to quantify temporal trends in rice crop coverage, growth and management systems. Our results were validated with finer resolution (2.5 m) Satellite Pour l'Observation de la Terre 5 High Resolution Geometric (SPOT 5 HRG) data, land-use data at the scale of 1/10,000 and with county-level rice area statistical data. The results showed that all three paddy rice crop patterns could be discriminated and their spatial distribution quantified. We show the area of single crop rice to have increased annually and almost doubling in extent from 2000 to 2007, with simultaneous, but unique declines in the extent of early and late paddy rice. These results were significantly positive correlated and consistent with agricultural statistical data at the county level ( P < 0.01).

Peng, Dailiang; Huete, Alfredo R.; Huang, Jingfeng; Wang, Fuming; Sun, Huasheng

2011-02-01

153

Persistence Behaviour of Thiamethoxam and Lambda Cyhalothrin in Transplanted Paddy  

Microsoft Academic Search

A field study was conducted in Pre-Kharif season 2007 on paddy to determine the persistence of thiamethoxam (12.6%) and lambda\\u000a cyhalothrin (9.4%) [in a ‘Readymix’ formulation Alika 247 ZC], following the application of 33 g. a.i. ha?1 (T1) and 66 g. a.i. ha?1 (T2). Spraying of insecticide was done during milking stage of the crop (63 days after transplantation). Thiamethoxam and lambda\\u000a cyhalothrin

Suhrid Ranjan Barik; Pritam Ganguly; Samir Kumar Kunda; Ramen Kumar Kole; Anjan Bhattacharyya

2010-01-01

154

Geostatistical Estimations of Regional Hydraulic Conductivity Fields  

NASA Astrophysics Data System (ADS)

Direct and indirect measurements of hydraulic conductivity (K) are commonly performed, providing information on the magnitude of this parameter at the local scale (tens of centimeters to hundreds of meters) and at shallow depths. By contrast, field information on hydraulic conductivities at regional scales of tens to hundreds of kilometers and at greater depths is relatively scarce. Geostatistical methods allow for sparsely sampled observations of a variable (primary information) to be complemented by a more densely sampled secondary attribute. Geostatistical estimations of the hydraulic conductivity field in the Carrizo aquifer, a major groundwater flow system extending along Texas, are performed using available primary (e.g., transmissivity, hydraulic conductivity) and secondary (specific capacity) information, for depths up to 2.2 km, and over three regional domains of increasing extent: 1) the domain corresponding to a three-dimensional groundwater flow model previously built (model domain); 2) the area corresponding to the ten counties encompassing the model domain (County domain), and; 3) the full extension of the Carrizo aquifer within Texas (Texas domain). Two different approaches are used: 1) an indirect approach are transmissivity (T) is estimated first and (K) is retrieved through division of the T estimate by the screening length of the wells, and; 2) a direct approach where K data are kriged directly. Prediction performances of the tested geostatistical procedures (kriging combined with linear regression, kriging with known local means, kriging of residuals, and cokriging) are evaluated through cross validation for both log-transformed variables and back-transformed ones. For the indirect approach, kriging of log T residuals yields the best estimates for both log-transformed and back-transformed variables in the model domain. For larger regional scales (County and Texas domains), cokriging performs generally better than univariate kriging procedures when estimating both (log T)* and T*. Among univariate procedures using the direct approach, the best prediction performances are obtained using simple kriging of log K with known local means. Cross validation also indicates that the indirect approach leads to smaller prediction errors than the direct approach, which is likely due to fewer available K primary data as well as a weaker correlation between primary and secondary attributes in the direct case. Although all procedures used log-transformed variables and incorporate secondary information derived from specific capacity data, none of the investigated techniques provides systematically better predictions for all scales, which stresses the importance of using cross validation to compare performances of alternative approaches and assess the unbiasedness of the back-transform procedure. Overall, estimation of the hydraulic conductivity field at such large regional scales through the tested geostatistical methods appears to be difficult due to both scarcity of sampling in the deeper portions of the formation (> 1 km) and preferential emplacement of well screens in the most productive portions of the aquifer. For example, in the deepest portions of the aquifer in the model domain, the estimated hydraulic conductivity field is obtained by extrapolation and gives origin to unrealistically high hydraulic conductivity values.

Patriarche, D.; Castro, M. C.; Goovaerts, P.

2004-12-01

155

Methanogenic Pathway and Fraction of CH4 Oxidized in Paddy Fields: Seasonal Variation and Effect of Water Management in Winter Fallow Season.  

PubMed

A 2-year field and incubation experiment was conducted to investigate ?(13)C during the processes of CH4 emission from the fields subjected to two water managements (flooding and drainage) in the winter fallow season, and further to estimate relative contribution of acetate to total methanogenesis (Fac ) and fraction of CH4 oxidized (Fox ) based on the isotopic data. Compared with flooding, drainage generally caused CH4, either anaerobically or aerobically produced, depleted in (13)C. There was no obvious difference between the two in transport fractionation factor (?transport ) and ?(13)C-value of emitted CH4. CH4 emission was negatively related to its ?(13)C-value in seasonal variation (P<0.01). Acetate-dependent methanogenesis in soil was dominant (60-70%) in the late season, while drainage decreased Fac -value by 5-10%. On roots however, CH4 was mostly produced through H2/CO2 reduction (60-100%) over the season. CH4 oxidation mainly occurred in the first half of the season and roughly 10-90% of the CH4 was oxidized in the rhizosphere. Drainage increased Fox -value by 5-15%, which is possibly attributed to a significant decrease in production while no simultaneous decrease in oxidation. Around 30-70% of the CH4 was oxidized at the soil-water interface when CH4 in pore water was released into floodwater, although the amount of CH4 oxidized therein might be negligible relative to that in the rhizosphere. CH4 oxidation was also more important in the first half of the season in lab conditions and about 5-50% of the CH4 was oxidized in soil while almost 100% on roots. Drainage decreased Fox -value on roots by 15% as their CH4 oxidation potential was highly reduced. The findings suggest that water management in the winter fallow season substantially affects Fac in the soil and Fox in the rhizosphere and roots rather than Fac on roots and Fox at the soil-water interface. PMID:24069259

Zhang, Guangbin; Liu, Gang; Zhang, Yi; Ma, Jing; Xu, Hua; Yagi, Kazuyuki

2013-09-12

156

Methanogenic Pathway and Fraction of CH4 Oxidized in Paddy Fields: Seasonal Variation and Effect of Water Management in Winter Fallow Season  

PubMed Central

A 2-year field and incubation experiment was conducted to investigate ?13C during the processes of CH4 emission from the fields subjected to two water managements (flooding and drainage) in the winter fallow season, and further to estimate relative contribution of acetate to total methanogenesis (Fac) and fraction of CH4 oxidized (Fox) based on the isotopic data. Compared with flooding, drainage generally caused CH4, either anaerobically or aerobically produced, depleted in 13C. There was no obvious difference between the two in transport fractionation factor (?transport) and ?13C-value of emitted CH4. CH4 emission was negatively related to its ?13C-value in seasonal variation (P<0.01). Acetate-dependent methanogenesis in soil was dominant (60–70%) in the late season, while drainage decreased Fac-value by 5–10%. On roots however, CH4 was mostly produced through H2/CO2 reduction (60–100%) over the season. CH4 oxidation mainly occurred in the first half of the season and roughly 10–90% of the CH4 was oxidized in the rhizosphere. Drainage increased Fox-value by 5–15%, which is possibly attributed to a significant decrease in production while no simultaneous decrease in oxidation. Around 30–70% of the CH4 was oxidized at the soil-water interface when CH4 in pore water was released into floodwater, although the amount of CH4 oxidized therein might be negligible relative to that in the rhizosphere. CH4 oxidation was also more important in the first half of the season in lab conditions and about 5–50% of the CH4 was oxidized in soil while almost 100% on roots. Drainage decreased Fox-value on roots by 15% as their CH4 oxidation potential was highly reduced. The findings suggest that water management in the winter fallow season substantially affects Fac in the soil and Fox in the rhizosphere and roots rather than Fac on roots and Fox at the soil-water interface.

Zhang, Guangbin; Liu, Gang; Zhang, Yi; Ma, Jing; Xu, Hua; Yagi, Kazuyuki

2013-01-01

157

Matrix-bound phosphine and phosphorus fractions in paddy soils.  

PubMed

Phosphine (PH(3)) is a natural gaseous carrier of phosphorus (P) in its geochemical cycles, and it might be important to the P balance of natural ecosystems. Paddy fields are thought to be one of the main sources responsible for the production and emission of PH(3) in to the environment. The relationships between matrix-bound PH(3) (MBP) and different P fractions, as well as selected metals were investigated to explore the possible production of MBP and its link to P cycle in the paddy soils. MBP range from 20.8 (-1) to 502 ng kg(-1) with an average of 145 ng kg(-1). Concentrations at the milk stage are significantly higher than at the jointing stage. The total P range from 333 mg kg(-1) to 592 mg kg(-1). Average P fractions decrease in the order: Ca-P (69.9%) > Organic P (16.5%) > occluded P (6.50%) > Fe-P (5.93%) > dissolved P (0.80%) > exchangeable P (0.32%) > Al-P (0.02%). Different levels of nitrogen fertilizer have little effect on the contents of MBP, P fractions and metals. A significant positive correlation between MBP and Ca-P (p = 0.002), as well as between MBP and Ca (p = 0.008) could be observed, suggesting that Ca-P mainly affects the production of MBP in the paddy soils. It is suggested that soil MBP is strongly linked to Ca-P fertilizer use because soil spiked with P-fertilizer produced an additional 758 ± 142 ng of MBP per kg of soil, compared to only 81.7 ± 12.3 ng of MBP per kg of unspiked soil. No correlations are found between MBP and other P fractions, or between MBP and Al, Fe and Mn. PMID:21359385

Han, Chao; Geng, Jinju; Zhang, Rui; Wang, Xiaorong; Gao, Shixiang

2011-02-28

158

Atmospheric methane observed from space over the Asian monsoon: implications for emission from Asian rice paddies  

NASA Astrophysics Data System (ADS)

More than 40% of anthropogenic emissions of methane, the second most important greenhouse gas, is estimated to be from agricultural sources, including rice cultivation. Unfortunately, the strength of individual sources of methane remains uncertain, despite the importance of its effect in global warming. Here we focus on the Asian monsoon region to improve our understanding of methane emission from rice paddy fields. This region contains about 90% of the world’s rice fields. We analyze the temporal and spatial distribution of atmospheric methane concentrations observed from space and compare it with ground-based measurements and bottom-up emission inventory data coupled with rice field maps. Recently, Frankenberg et al. [2008] derived an updated version of methane concentration from the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY: SCIA hereafter) instrument onboard ENVISAT. This showed a clear signature of methane enhancement over the Asian monsoon. As SCIA retrievals include all involve column densities, we carefully examined potential biases and variability due to the gradient of methane concentration over source regions by comparing these data with ground-based measurements at 53 stations of the WDCGG network. After evaluating the bias and variability of methane concentration over the source regions, we examined selected areas where rice paddies were highly concentrated, and the methane emission inventories were estimated to be large. The sampled areas were North and South India, Bangladesh, Myanmar, Thailand, South China, and the Sichuan Basin. All of these are known to be major rice cultivation areas. The time series of monthly mean SCIA retrievals were compared with the emission inventory data for rice cultivation archived in the GISS dataset and Yan et al. [2009], as well as with precipitation data (Huffman et al., 1997). The phase of seasonal variation of SCIA retrievals corresponded closely to those of emission inventories. High methane concentrations were observed in the later period of the rainy season for each area. The amplitude of seasonal variation was large compared with the possible bias over the source regions, demonstrating the reliability of the analysis. We are planning to extend the analysis to the methane data observed by the Thermal And Near infrared Sensor for carbon Observations Fourier Transform Spectrometer (TANSO-FTS) onboard the Greenhouse gases Observing SATellite (GOSAT). GOSAT was launched successfully on January 23, 2009, and has been operating continuously since then. The TANSO-FTS will provide important information on methane emission from rice paddies with good spatial resolution (10 km in diameter). Preliminary results from this instrument will also be presented. References: Frankenberg, et al. (2008), Geophys. Res. Lett., 35, doi:10.1029/2008GL034300. Huffman et al. (1997), Bull. Am. Meteorol. Soc. Vol. 78, 5-20. Yan et al., (2009), Global Biogeochem. Cycles, 23, GB2002, doi:10.1029 /2008GB003299.

Hayashida, S.; Yoshizaki, S.; Frankenberg, C.; Yan, X.

2010-12-01

159

Sequential modeling of fluidized bed paddy dryer  

Microsoft Academic Search

A sequential method was developed to model a continuous plug flow fluidized bed dryer. The method is based on dividing the dryer into sections in series with ideal mixing for both solid and gas phases in each section. In order to determine the proper number of sections, drying experiments were carried out using paddy at different operating conditions. It was

Navid Bizmark; Navid Mostoufi; Rahmat Sotudeh-Gharebagh; Hossein Ehsani

2010-01-01

160

Central Region Library Field Records Collection  

USGS Multimedia Gallery

The USGS Denver Library, Field Records Collection is an archive of unpublished field notes, maps, correspondence, manuscripts, analysis reports, and other data created or collected by USGS Geologic Discipline scientists during field studies and other project work. Materials in the collection represe...

2009-04-09

161

Arsenic release from paddy soils during monsoon flooding  

NASA Astrophysics Data System (ADS)

Bangladesh relies heavily on groundwater for the irrigation of dry-season rice. However, the groundwater used for irrigation often contains high concentrations of arsenic, potentially jeopardizing the future of rice production in the country. In seasonally flooded fields, topsoil arsenic concentrations decrease during the monsoon season, suggesting that flooding attenuates arsenic accumulation in the soils. Here we examine the chemistry of soil porewater and floodwater during the monsoon season in rice paddies in Munshiganj, Bangladesh, to assess whether flooding releases significant quantities of arsenic from the soils. We estimate that between 51 and 250mgm-2 of soil arsenic is released into floodwater during the monsoon season. This corresponds to a loss of 13-62% of the arsenic added to soils through irrigation each year. The arsenic was distributed throughout the entire floodwater column by vertical mixing and was laterally removed when the floodwater receded. We conclude that monsoon floodwater removes a large amount of the arsenic added to paddy soils through irrigation, and suggest that non-flooded soils are particularly at risk of arsenic accumulation.

Roberts, Linda C.; Hug, Stephan J.; Dittmar, Jessica; Voegelin, Andreas; Kretzschmar, Ruben; Wehrli, Bernhard; Cirpka, Olaf A.; Saha, Ganesh C.; Ashraf Ali, M.; Badruzzaman, A. Borhan M.

2010-01-01

162

Fate of pesticides in combined paddy rice-fish pond farming systems in northern Vietnam.  

PubMed

During the last decades, high population growth and export-oriented economics in Vietnam have led to a tremendous intensification of rice production, which in turn has significantly increased the amount of pesticides applied in rice cropping systems. Since pesticides are toxic by design, there is a natural concern on the impact of their presence in the environment on human health and environmental quality. The present study was designed to examine the water regime and fate of pesticides (fenitrothion, dimethoate) during two consecutive rice crop seasons in combined paddy rice-fish pond farming systems in northern Vietnam. Major results revealed that 5 and 41% (dimethoate), and 1 and 17% (fenitrothion) of the applied mass of pesticides were lost from the paddy field to the adjacent fish pond during spring and summer crop seasons, respectively. The decrease of pesticide concentration in paddy surface water was very rapid with dissipation half-life values of 0.3 to 0.8 and 0.2 d for dimethoate and fenitrothion, respectively. Key factors controlling the transport of pesticides were water solubility and paddy water management parameters, such as hydraulic residence time and water holding period. Risk assessment indicates that the exposure to toxic levels of pesticides for aquaculture (, ) is significant, at least shortly after pesticide application. PMID:22370414

Anyusheva, Maria; Lamers, Marc; La, Nguyen; Nguyen, Van Vien; Streck, Thilo

163

Effect of biochar amendment on yield and methane and nitrous oxide emissions from a rice paddy from Tai Lake plain, China  

Microsoft Academic Search

A field trial was performed to investigate the effect of biochar at rates of 0, 10 and 40tha?1 on rice yield and CH4 and N2O emissions with or without N fertilization in a rice paddy from Tai Lake plain, China. The paddy was cultivated with rice (Oryza sativa L., cv. Wuyunjing 7) under a conventional water regime. Soil emissions of

Afeng Zhang; Liqiang Cui; Gengxing Pan; Lianqing Li; Qaiser Hussain; Xuhui Zhang; Jinwei Zheng; David Crowley

2010-01-01

164

Paleostress field reconstruction in the Oslo region  

Microsoft Academic Search

The geodynamic history of a region is archived in its geologic record which, in turn, may reflect deformation patterns that causally can be related to certain configurations of paleostresses. In the Oslo Region, the exposed geological record ranges from Precambrian high-grade metamorphic rocks through Cambro-Silurian sedimentary rocks to Permo-Carboniferous sedimentary and magmatic rocks, the latter being related to the development

Judith Sippel; Aline Saintot; Michel Heeremans; Magdalena Scheck-Wenderoth

2010-01-01

165

Small Field: dosimetry in electron disequilibrium region  

NASA Astrophysics Data System (ADS)

Small fields are more commonly used for radiation therapy because of the development of IMRT, stereotactic radiosurgery, and other special equipments such as Cyberknife and Tomotherapy. The dosimetry in the sub-centimeter field can result in substantial uncertainties because of the presence of electron disequilibrium due to the large dose gradients in the field. It is further complicated by the introduction of various radiation detectors, which usually perturb the conditions of disequilibrium. Hence additional corrections are required to maintain the dosimetric accuracy previously achieved for standard radiation dosimetry. A review of small field dosimetry provides some insights into the methods to characterize the detector convolution kernel and other methods to characterize detector perturbation effect.

Zhu, Timothy C.

2010-11-01

166

An analysis of the flow field in the region of the ASRM field joints  

Microsoft Academic Search

The flow field in the region of a solid rocket motor field joint is very important since fluid dynamic and mechanical propellant stresses can couple to cause a motor failure at a joint. Presented here is an examination of the flow field in the region of the Advanced Solid Rocket Motor (ASRM) field joints. The analyses were performed as a

Richard A. Dill; Harold R. Whitesides

1992-01-01

167

STOCHASTIC METHODOLOGY FOR REGIONAL WIND FIELD MODELING  

EPA Science Inventory

Three-dimensional regional scale (1000 km) air quality simulation models require hourly inputs of U and V wind components for each vertical layer of the model and for each grid cell in the horizontal. he standard North American meteorological observation network is used to derive...

168

PADDY CREEK WILDERNESS STUDY AREA, MISSOURI.  

USGS Publications Warehouse

The Paddy Creek Wilderness study area, Missouri was investigated by geologic and mineral surveys. There is no known record of mineral production, development, or prospecting in the area. Several rock units that underlie the study area are known to be the host rocks for important lead-zinc-silver-copper-nickel-cobalt deposits and magnetic iron-ore deposits of the Southeast Missouri district, about 52 mi east of the study area. Similar occurrences may exist in the Paddy Creek Wilderness study area, but the mineral-resource potential cannot be adequately evaluated without further study, specifically, deep drilling within or close to the area to test the potential for base-metal mineralization, and detailed magnetic surveys of the area to test for magnetic anomalies.

Pratt, Walden, P.; Ellis, Clarence

1984-01-01

169

Phospholipid fatty acid composition of microbiota in the percolating water from a rice paddy microcosm  

Microsoft Academic Search

The microbiota in the percolating water from the plow layer soil in paddy fields was studied based on the composition of phospholipid fatty acids (PLFAs) in a pot experiment. The mean concentrations of PLFAs in the percolating water were 17±5 and 11±4 µg L in the planted and non-planted pots, respectively. The dominant PLFAs in the percolating water were 16:

Makoto Kimura; Hirokazu Kishi; Akiko Okabe; Nagamitsu Maie

2001-01-01

170

Changes in soil phosphorus fractions in a calcareous paddy soil under intensive rice cropping  

Microsoft Academic Search

We conducted a 4-year field experiment on a calcareous paddy soil in Zhejiang province of China to measure the changes in chemically extracted soil P fractions in an irrigated double-cropping rice system. Treatments included four fertilizer combinations (unfertilized control, NK, NP, and NPK) as main-plots and two rice cultivar types (inbred vs. hybrid rice) as sub-plots. Total plant P uptake

Q. Zhang; G. H. Wang; Y. K. Feng; Q. Z. Sun; C. Witt; A. Dobermann

2006-01-01

171

CH 4 emission and oxidation in Chinese rice paddies  

Microsoft Academic Search

In the paper, the characteristics of CH4 emission from the rice paddies, its temporary and spatial variations as well as factors regulating CH4 emission and oxidation are reviewed with an emphasis on CH4 emission from rice paddies in China. The observed four types of diel variation and two type of seasonal variation can be explained by the variations of methane

Wang Mingxing; Li Jing

2002-01-01

172

Enzyme2linked immunosorbent assay used to detect the food relationships of the ar2 thropods in paddy f ields  

Microsoft Academic Search

The double antibody sandwich technique , an enzyme2linked immunosorbent assay ( ELISA) , was developed to detect the food relationships among 19 species of predators , 4 pest insects and 1 neutral insect in paddy fields in Dasha Township , Sihui County , Guangdong Province. The results indicated that 15 and 11 species of predatory arthropods preyed on the white2back

EL ISA

2002-01-01

173

Sources, Replacement and Management of Paddy Seed by Farmers in Punjab  

Microsoft Academic Search

The study has reported different sources of paddy seed, seed replacement rate of paddy growers, and management of paddy seed by the farmers in two selected districts of Punjab. Amongst different sources of paddy seed, the share of private seed dealers has been found maximum (H†48 per cent), followed by authorized seed dealer (H†19 per cent), self-retained (11.5

Sangeeta Verma; M. S. Sidhu

2009-01-01

174

Impact of Rice Paddies Plantation on Surface Water Quality in Kelantan, Malaysia  

Microsoft Academic Search

Many parts of the agricultural land in Kelantan, Ma laysia are used for paddy and most of developed wat er resources are used for paddy irrigation. A study on the impact of rice paddies plantation on surface w ater quality was carried out in paddy plantation at Lada ng Merdeka Ismail Mulong, Kelantan. The objective of the study was to

Abdul Manaff Mahmood; Noriah Abdullah

175

Transformation of marine sediment to paddy soil: Primary marine, lacustrine, and land plant lipids  

NASA Astrophysics Data System (ADS)

More than fifty percent of the world's population feeds on rice. The continuous population increase and urban sprawl leads to an ever-increasing demand for new rice cultivation area, in particular China. For centuries suitable coastal areas in China have been exploited for land reclamation, i.e. conversion of coastal marine and lacustrine marshlands into rice paddy fields. Flooded rice paddies are considered one of the major biogenic sources of methane into the atmospheric. Methane is thought to be about 30 times more efficient as greenhouse gas, when compared to carbon dioxide. Overall, rice fields are assumed to contribute app. 10-25% to global CH4 production. It is thus paramount importance to study the effects of increasing rice cultivation and land reclamation in China. For global carbon cycle investigation, it is crucial whether paddy soils, due to their large extent and higher carbon turnover, serve as carbon (CO2) sinks or sources. Here we present results from a chronosequence study of paddy soils with different and well known starting dates of cultivation, in the Zhejiang province (Yangtze River delta) by land reclamation through the building of protective dikes over the past 2000 years. Two end members of natural sediments subjected to land reclamation, a marine tidal mudflat in the Yangtze delta and a coastal lake, represent the substrate on which the paddy soil evolution started. Dike systems were constructed 2000, 1000, 700, 300, 100, and 50 years before present. We are thus able to follow the evolution of rice paddy soils developed on marine sediments using eight well defined tie-points. This chronosequence is then used for assessing the relative proportion of primary marine or lacustrine organic matter preserved in present day soils and to identify the amount and composition of organic matter added since cultivation started. Paddy soil management introduces rice plants debris and exudates as well as rice-associated microbial biomass (covered in a separate contribution) into soils. Management practises involve burning of rice straw on fields, thus adding biomass combustion residues that either may be particularly stable (e.g. PAH) or highly reactive (alkenes resulting from dehydration of alcohols). Bulk parameters reveal that the five field replicates taken at each site are highly compatible, with standard deviations usually between 0.1 to 5.0 % depending on site and/or parameter. This is better than expected and proves that the samples are representative for each cropping site. The n- and isoalkane composition also proved to be very systematic and reproducible. The marine end-member shows a broad n-alkane envelope from nC13 to nC40, with a maximum of nC31 and low abundance of nC17 and nC32+ alkanes. The lacustrine site also reveals a broad n-alkane envelope and a maximum of nC31 but shows higher relative abundance of nC17, nC23 and nC25 alkanes in addition to a C20-HBI. These biomarkers for aquatic macrophytes and diatoms were also found in minor proportions in paddy soils due to flooding with lacustrine water. Paddy n-alkane patterns were dominated by nC29 which systematically increased in abundance for older paddy soils. Paddy soil n-alkane patterns from the chronosequence are similar and related to the marine pattern. Combustion of rice straw on the field is a common management practise for nutrient return to soils. A rice straw ash sample collected in the field revealed a series of nC13 to nC37 n-alkane/alkene doublets with low odd over even predominance. As no alkenes were found in paddy soils, very fast diagenetic conversion of reactive alkenes must occur. Soil organic matter and aliphatics content increased six fold over a cultivation time of 2000 years, identifying paddies as CO2 sinks in the global carbon cycle.

Mueller-Niggemann, Cornelia; Cao, Zhihong; Schwark, Lorenz

2010-05-01

176

Identification and isolation of active N2O reducers in rice paddy soil.  

PubMed

Dissolved N(2)O is occasionally detected in surface and ground water in rice paddy fields, whereas little or no N(2)O is emitted to the atmosphere above these fields. This indicates the occurrence of N(2)O reduction in rice paddy fields; however, identity of the N(2)O reducers is largely unknown. In this study, we employed both culture-dependent and culture-independent approaches to identify N(2)O reducers in rice paddy soil. In a soil microcosm, N(2)O and succinate were added as the electron acceptor and donor, respectively, for N(2)O reduction. For the stable isotope probing (SIP) experiment, (13)C-labeled succinate was used to identify succinate-assimilating microbes under N(2)O-reducing conditions. DNA was extracted 24 ?h after incubation, and heavy and light DNA fractions were separated by density gradient ultracentrifugation. Denaturing gradient gel electrophoresis and clone library analysis targeting the 16S rRNA and the N(2)O reductase gene were performed. For culture-dependent analysis, the microbes that elongated under N(2)O-reducing conditions in the presence of cell-division inhibitors were individually captured by a micromanipulator and transferred to a low-nutrient medium. The N(2)O-reducing ability of these strains was examined by gas chromatography/mass spectrometry. Results of the SIP analysis suggested that Burkholderiales and Rhodospirillales bacteria dominated the population under N(2)O-reducing conditions, in contrast to the control sample (soil incubated with only (13)C-succinate). Results of the single-cell isolation technique also indicated that the majority of the N(2)O-reducing strains belonged to the genera Herbaspirillum (Burkholderiales) and Azospirillum (Rhodospirillales). In addition, Herbaspirillum strains reduced N(2)O faster than Azospirillum strains. These results suggest that Herbaspirillum spp. may have an important role in N(2)O reduction in rice paddy soils. PMID:21677691

Ishii, Satoshi; Ohno, Hiroki; Tsuboi, Masahiro; Otsuka, Shigeto; Senoo, Keishi

2011-06-16

177

Paddy soil nutrient assessment using visible and near infrared reflectance spectroscopy  

NASA Astrophysics Data System (ADS)

The ability of obtaining soil properties estimations from time and cost efficient remotely sensed techniques has been identified as a valuable technique as there is a great demand for larger amounts of good quality and inexpensive soil data to be used in environmental monitoring, modelling and precision agriculture. Visible (Vis) and Near Infrared (NIR) spectroscopy provides a good alternative that may be used to enhance or replace conventional methods of soil analysis. The aim of this paper is to evaluate the abilities of Vis (350-700 nm) and near infrared (700-2500 nm) for prediction of soil nutrients. In this instance we implemented Savitzky-Golay algorithm and Stepwise Multiple Linear Regression (SMLR) to construct calibration models. The soil nutrients examined were soil Total Nitrogen (N), Available Phosphorus (P) and Exchangeable Potassium (K). Our results revealed the accuracy of SMLR prediction in each of the Vis and NIR spectral regions. The NIR produced more accurate predictions for N and K; however, higher significant correlation was obtained using the Vis for available P. This work demonstrated Vis and NIR spectroscopy could be considered as a good tool to assess soil nutrients in Malaysian paddy fields.

Gholizadeh, A.; Saberioon, M. M.; Amin, M. S. M.

178

[Effects of heavy metals pollution on paddy soil aggregates composition and heavy metals distribution].  

PubMed

Topsoil samples were collected from a polluted and an adjacent non-polluted paddy field in the Taihu Lake region of China. Different particle size fractions of soil aggregates were separated by low-energy dispersion procedure, and their mass composition and Pb, Cd, Hg, and As concentrations were determined. Under heavy metals pollution, the mass composition of sand-sized fractions reduced, while that of clay-sized fractions increased. The concentrations of test metals in different particle size fractions differed, with the highest in < 0.002 mm fraction, followed by in 2-0.2 mm fraction. In 0.02-0.002 mm and 0.2-0.02 mm fractions, all the test metals were relatively deficient, with an enrichment index of 0.56-0.96. The present study showed that the aggregation of fine particles could be depressed by heavy metals pollution, which in turn, led to a relative increase in the mass composition of fine particles and the associated allocation of heavy metals in weakly aggregated silt particles, and further, increased the risks of heavy metals translocation from polluted farmland into water and atmosphere. Further studies should be made on the impacts of heavy metals pollution on soil biophysical and biochemical processes and related mechanisms. PMID:20136020

Zhang, Liang-Yun; Li, Lian-Qing; Pan, Gen-Xing; Cui, Li-Qiang; Li, Hong-Lei; Wu, Xiao-Yan; Shao, Jie-Qi

2009-11-01

179

[Humus composition and stable carbon isotope natural abundance in paddy soil under long-term fertilization].  

PubMed

Soil samples were collected from an experimental paddy field with long-term (26 years) fertilization in Taihu Lake region of Jiangsu Province to study the effects of different fertilization on the organic carbon distribution and stable carbon isotope natural abundance (delta 13C) in the soil profile, and on the humus composition. The results showed that long-term fertilization increased the organic carbon content in top soil significantly, and there was a significantly negative exponential correlation between soil organic carbon content and soil depth (P < 0.01). The organic carbon content in 10-30 cm soil layer under chemical fertilizations and in 20-40 cm soil layer under organic fertilizations was relatively stable. Soil delta 13C increased gradually with soil depth, its variation range being from -24% per thousand to -28 per thousand, and had a significantly negative linear correlation with soil organic carbon content (P < 0.05). In 0-20 cm soil layer, the delta 13C in treatments organic manure (M), M + NP, M + NPK, M + straw (R) + N, and R + N decreased significantly; while in 30-50 cm soil layer, the delta 13C in all organic fertilization treatments except R + N increased significantly. Tightly combined humus (humin) was the main humus composition in the soil, occupying 50% or more, and the rest were loosely and stably combined humus. Long-term fertilization increased the content of loosely combined humus and the ratio of humic acid (HA) to fulvic acid (FA). PMID:19102308

Ma, Li; Yang, Lin-Zhang; Ci, En; Wang, Yan; Yin, Shi-Xue; Shen, Ming-Xing

2008-09-01

180

Sources of atmospheric methane - Measurements in rice paddies and a discussion  

NASA Astrophysics Data System (ADS)

Field measurements of methane fluxes from rice paddies, fresh water lakes, and saltwater marshes have been made to infer estimates of the size of these sources of atmospheric methane. The rice-paddy measurements, the first of their kind, show that the principal means of methane escape is through the plants themselves as opposed to transport across the water-air interface via bubbles or molecular diffusion. Nitrogen-fertilized plants release much more methane than unfertilized plants but even these measured rates are only one fourth as large as those inferred earlier by Koyama (1963, 1964) and on which all global extrapolations have been based to date. Measured methane fluxes from lakes and marshes are also compared to similar earlier data and it is found that extant data and flux-measurement methods are insufficient for reliable global extrapolations.

Cicerone, R. J.; Shetter, J. D.

1981-08-01

181

Subsurface Return Flow and Ground Water Recharge of Terrace Fields in Northern Taiwan  

NASA Astrophysics Data System (ADS)

This study estimates subsurface return flow and effective ground water recharge in terraced fields in northern Taiwan. Specifically, a three dimensional model, FEMWATER, was applied to simulate percolation and lateral seepage in the terraced fields under various conditions. In the terraced paddy fields, percolation mainly moves vertically downward in the central area, while lateral seepage is mainly focused around the bund. Although the simulated lateral seepage rate through the bund exceeded the percolation rate in the central area of the paddy field, annual subsurface return flow at Pei-Chi and Shin-Men was 0.17x106 m3 and 0.37x106 m3, representing only 0.17 percent and 0.21 percent of the total irrigation water required for rice growth at Pei-Chi and Shin-Men, respectively. For upland fields, the effective ground water recharge rate during the second crop period (July to November) exceeded that during the first crop period (January to May) because of the wet season in the second crop period. Terraced paddy fields have the most efficient ground water recharge, with 21.2 to 23.4 percent of irrigation water recharging to ground water, whereas upland fields with a plow layer have the least efficient ground water recharge, with only 4.8 to 6.6 percent of irrigation water recharging to ground water. The simulation results clearly revealed that a substantial amount of irrigation water recharges to ground water in the terraced paddy, while only a small amount of subsurface return flow seeps from the upstream to the downstream terraced paddy. The amounts of subsurface flow and ground water recharge determined in the study are useful for the irrigation water planning and management and provide a scientific basis to reevaluate water resources management in the terrace region under irrigated rice.

Liu, Chen-Wuing; Huang, Han-Chen; Chen, Shih-Kai; Kuo, Yi-Ming

2004-06-01

182

The solar active region magnetic field and energetics  

NASA Astrophysics Data System (ADS)

Motivated by increasingly more advanced solar observations, we recently develop a method of coronal magnetic field extrapolation, especially for an active region (sunspot region). Based on a more complex variational principle, the principle of minimum (energy) dissipation rate (MDR), we adopt and solve a more complex equation governing the coronal magnetic field that is non-force-free in general. We employ the vector magnetograms from multiple instruments, including Hinode, NSO, and HSOS, and particularly observations at both photospheric and chromospheric levels for one active region. We discuss our results in the context of quantitative characterization of active region magnetic energy and magnetic topology. These quantitative analyses aid in better understanding and developing prediction capability of the solar activity that is largely driven by the solar magnetic field.

Hu, Qiang; Deng, Na; Choudhary, Debi P.; Dasgupta, B.; Su, Jiangtao

2011-08-01

183

[Influence of double rice cropping system innovation on paddy soil profile form and soil characteristics].  

PubMed

Field experiments were conducted on the double rice cropping paddy field in red soil area to evaluate the influence of cropping system innovation on soil profile form and related soil characteristics. Four cropping systems of rice-rice-Chinese Milkvetch (Astragalus sinicus Linn.), forage, paddy-upland rotation, and upland were substituted for the double rice cropping system. The results indicated that compared with those under double rice cropping system, the thickness of cultivated horizon under upland cropping system increased by 4 cm, that of plow pan declined by 2 cm, > 2 mm aggregates in wet-sieved particle-size fractions increased by 6.94%, wet-sieved mean-mass diameter increased by 0.37 mm, contents of humic acid carbon and fulvic acid carbon increased by 0.15 and 0.49 g kg(-1), respectively, and quotient of aggregates water stability was 0.78 times higher. Under paddy-upland rotation, the quotient of aggregates water stability was higher (95.86), while soil nutrient contents changed a little. Under rice-rice-Chinese Milkvetch system, soil organic matter content increased by 1.3 g kg(-1), quotient of aggregates water stability declined by 8.82, but other parameters had less changes. Under forage system, the thickness of cultivated and transitional horizons increased by 2 cm and 9 cm, respectively, quotient of aggregates water stability increased by 1.39, while the contents of soil organic matter and total potassium decreased by 5.6 and 2.8 g kg(-1), respectively. Among all test cropping systems, forage system had the greatest changes in soil characteristics. It was completely feasible to substitute the local double rice cropping system for paddy-upland rotation or upland cropping, particularly in the areas where full irrigation was not available. However, attention should be paid to the decrease of soil potassium content when the cropping system innovation was practiced. PMID:18655589

Zeng, Xi-Bai; Sun, Nan; Gao, Ju-Sheng; Li, Lian-Fang; Wang, Bo-Ren; Bai, Ling-Yu

2008-05-01

184

Transient horizontal magnetic fields in solar plage regions  

NASA Astrophysics Data System (ADS)

Aims:We report the discovery of isolated, small-scale emerging magnetic fields in a plage region with the Solar Optical Telescope aboard Hinode. Methods: Spectro-polarimetric observations were carried out with a cadence of 34 s for the plage region located near disc center. The vector magnetic fields are inferred by Milne-Eddington inversion. Results: The observations reveal widespread occurrence of transient, spatially isolated horizontal magnetic fields. The lateral extent of the horizontal magnetic fields is comparable to the size of photospheric granules. These horizontal magnetic fields seem to be tossed about by upflows and downflows of the granular convection. We also report an event that appears to be driven by the magnetic buoyancy instability. We refer to buoyancy-driven emergence as type 1 and convection-driven emergence as type 2. Although both events have magnetic field strengths of about 600 G, the filling factor of type 1 is a factor of two larger than that of type 2. Conclusions: Our finding suggests that the granular convection in the plage regions is characterized by a high rate of occurrence of granular-sized transient horizontal fields.

Ishikawa, R.; Tsuneta, S.; Ichimoto, K.; Isobe, H.; Katsukawa, Y.; Lites, B. W.; Nagata, S.; Shimizu, T.; Shine, R. A.; Suematsu, Y.; Tarbell, T. D.; Title, A. M.

2008-04-01

185

Identification of active denitrifiers in rice paddy soil by DNA- and RNA-based analyses.  

PubMed

Denitrification occurs markedly in rice paddy fields; however, few microbes that are actively involved in denitrification in these environments have been identified. In this study, we used a laboratory soil microcosm system in which denitrification activity was enhanced. DNA and RNA were extracted from soil at six time points after enhancing denitrification activity, and quantitative PCR and clone library analyses were performed targeting the 16S rRNA gene and denitrification functional genes (nirS, nirK and nosZ) to clarify which microbes are actively involved in denitrification in rice paddy soil. Based on the quantitative PCR results, transcription levels of the functional genes agreed with the denitrification activity, although gene abundance did not change at the DNA level. Diverse denitrifiers were detected in clone library analysis, but comparative analysis suggested that only some of the putative denitrifiers, especially those belonging to the orders Neisseriales, Rhodocyclales and Burkholderiales, were actively involved in denitrification in rice paddy soil. PMID:22972387

Yoshida, Megumi; Ishii, Satoshi; Fujii, Daichi; Otsuka, Shigeto; Senoo, Keishi

2012-09-05

186

Assessing energy efficiencies and greenhouse gas emissions under bioethanol-oriented paddy rice production in northern Japan.  

PubMed

To establish energetically and environmentally viable paddy rice-based bioethanol production systems in northern Japan, it is important to implement appropriately selected agronomic practice options during the rice cultivation step. In this context, effects of rice variety (conventional vs. high-yielding) and rice straw management (return to vs. removal from the paddy field) on energy inputs from fuels and consumption of materials, greenhouse gas emissions (fuel and material consumption-derived CO(2) emissions as well as paddy soil CH(4) and N(2)O emissions) and ethanol yields were assessed. The estimated ethanol yield from the high-yielding rice variety, "Kita-aoba" was 2.94 kL ha(-1), a 32% increase from the conventional rice variety, "Kirara 397". Under conventional rice production in northern Japan (conventional rice variety and straw returned to the paddy), raising seedlings, mechanical field operations, transportation of harvested unhulled brown rice and consumption of materials (seeds, fertilizers, biocides and agricultural machinery) amounted to 28.5 GJ ha(-1) in energy inputs. The total energy input was increased by 14% by using the high-yielding variety and straw removal, owing to increased requirements for fuels in harvesting and transporting harvested rice as well as in collecting, loading and transporting rice straw. In terms of energy efficiency, the variation among rice variety and straw management scenarios regarding rice varieties and rice straw management was small (28.5-32.6 GJ ha(-1) or 10.1-14.0 MJ L(-1)). Meanwhile, CO(2)-equivalent greenhouse gas emissions varied considerably from scenario to scenario, as straw management had significant impacts on CH(4) emissions from paddy soils. When rice straw was incorporated into the soil, total CO(2)-equivalent greenhouse gas emissions for "Kirara 397" and "Kita-aoba" were 25.5 and 28.2 Mg CO(2) ha(-1), respectively; however, these emissions were reduced notably for the two varieties when rice straw was removed from the paddy fields in an effort to mitigate CH(4) emissions. Thus, rice straw removal avers itself a key practice with respect to lessening the impacts of greenhouse gas emissions in paddy rice-based ethanol production systems in northern Japan. More crucially, the rice straw removed is available for ethanol production and generation of heat energy with a biomass boiler, all elements required for biomass-to-ethanol transformation steps including saccharification, fermentation and distillation. This indicates opportunities for further improvement in energy efficiency and reductions in greenhouse gas emissions under whole rice plant-based bioethanol production systems. PMID:21126818

Koga, Nobuhisa; Tajima, Ryosuke

2010-12-03

187

VECTOR MAGNETIC FIELDS OF A SOLAR POLAR REGION  

SciTech Connect

We study the vector magnetic fields of a solar polar region (PR) based on Solar Optical Telescope/Spectro-Polarimeter measurements. To better understand the polar magnetic properties, we compare the observed polar field with that in two solar quiet regions at the limb (QRL) and the disk center (QRD), and with that in a region of a low-latitude coronal hole (CHR). The following results are discussed: (1) The average vertical flux density of PR is 16 G, while the average horizontal flux density is 91 G. If we assume that the observed polar field suffers the same amount of limb weakening in polarization measurements as the Sun's quiet region, the average unsigned flux density in the pole would be 54 G, 60% stronger than that in the CHR. (2) The kG field in the PR occupies 6.7% of the region. The magnetic filling factor in the PR is characterized by a two-peak distribution, which appears at a field strength close to 100 G and 1000 G, respectively. (3) For the network elements, a correlation holds between the vertical and horizontal flux densities, suggesting the same physical entity is manifested by the observed stronger vertical and horizontal components. (4) The ratio of the magnetic flux in the minority polarity to that in the dominant polarity is approximately 0.5, implying that only 1/3 of the magnetic flux in the PR opens to the interplanetary space. Exemplified with CHR by a quasi-linear force-free extrapolation of the observed magnetic field, we find that the photospheric open flux is not always associated with strong vertical magnetic elements.

Jin Chunlan; Wang Jingxiu, E-mail: cljin@nao.cas.cn, E-mail: wangjx@nao.cas.cn [Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

2011-05-01

188

Oxygen input controls the spatial and temporal dynamics of arsenic at the surface of a flooded paddy soil and in the rhizosphere of lowland rice ( Oryza sativa L.): a microcosm study  

Microsoft Academic Search

The impact of oxygen (O2) input at the soil surface and in the rhizosphere of rice (Oryza sativa L.) on the spatial and temporal dynamics of arsenic (As) was investigated in a flooded paddy soil. A soil microcosm and root-mat\\u000a technique were designed to mimic submerged conditions of paddy fields. Water-filled containers with (planted) or without (unplanted)\\u000a 27-day-old rice seedlings

Matthieu N. Bravin; Fanny Travassac; Martine Le Floch; Philippe Hinsinger; Jean-Marie Garnier

2008-01-01

189

Magnetic Field Structure in High-Mass Star Formation Regions.  

National Technical Information Service (NTIS)

We present a preliminary analysis of far-IR polarimetric observations, which were made to study the magnetic field structure in the high-mass star formation regions of M42, NGC2024, and W3. These observations were made from the Kuiper Airborne Observatory...

J. A. Davidson D. Schleuning J. L. Dotson C. D. Dowell R. H. Hildebrand

1995-01-01

190

Plasma Equilibrium in a Magnetic Field with Stochastic Regions.  

National Technical Information Service (NTIS)

The nature of plasma equilibrium in a magnetic field with stochastic regions is examined. It is shown that the magnetic differential equation that determines the equilibrium Pfirsch-Schluter currents can be cast in a form similar to various nonlinear equa...

A. H. Reiman J. A. Krommes

2009-01-01

191

Active Regions and the Global Magnetic Field of the Sun  

NASA Astrophysics Data System (ADS)

The Sun follows an 11 year activity cycle, over which the global magnetic field begins highly dipolar, and becomes more complex at cycle maximum, until reverting back to a dipole state, but with reversed polarity. Many magnetic structures of varying complexity (active regions) are observed to emerge, evolve, and decay over the cycle. Beyond location and orientation, the dependence of active region magnetic properties on the phase of the solar cycle is not well known. Here, we use automated feature detection methods to detect and characterize thousands of active region detections and statistically investigate their physical properties. We find that the mean size and flux of magnetic features on the solar disk is dependent on the phase of the cycle. We establish a direct connection between the spatial distribution of active regions on the solar disk and the configuration of the global solar magnetic field by investigating the polarity imbalance of feature magnetic flux. Using a global potential field source surface model, we find that the shape of the global field is strongly dependent on the large scale distribution of imbalanced flux.

Higgins, P. A.; Bloomfield, D. S.; Gallagher, P. T.

2011-12-01

192

Neolithic rice paddy from the Zhaojiazhuang site, Shandong, China  

Microsoft Academic Search

To identify and study the Neolithic rice paddy in Shandong, eastern China, is not only an important issue in the development\\u000a of Chinese rice agriculture, but also a key part of the study on rice spread in East Asia. Due to the limitation of archaeological\\u000a materials and the research methods, there have been no discoveries about the Neolithic rice paddy

GuiYun Jin; ShengDong Yan; Tetsuro Udatsu; YuFu Lan; ChunYan Wang; PeiHua Tong

2007-01-01

193

Managing Biodiversity Of Rice Paddy Culture In Urban Landscape  

Microsoft Academic Search

Cultivated land in the Kangnam area of Seoul is for the most part dispersed. The large area paddies are distributed around\\u000a the western boundary of Seoul, but the small area paddies are located at the southeast boundary of Seoul. Review of the land\\u000a use trends of these cultivated lands, large areas have been converted into development areas or converted for

I.-J. Song; Y.-R. Gin

194

Pedogenic evolution of paddy soils in different soil landscapes  

Microsoft Academic Search

Paddy soils are Hydragric Anthrosols and are an important soil resource for food production. They are widely distributed in China and Asia. Soils that can be used for paddy cultivation vary considerably but basically are grouped into three kinds of landscape, i.e., well-drained sloping uplands, alluvial plains with groundwater fluctuation, and poorly drained polder areas with a near-surface water table.

Gan-Lin Zhang; Zi-Tong Gong

2003-01-01

195

Mineralization of metsulfuron-methyl in Chinese paddy soils  

Microsoft Academic Search

A laboratory study was conducted to investigate the mineralization of metsulfuron-methyl (MSM) in paddy soils in response to soil moisture, temperature and soil properties. The results indicated that MSM mineralization was relatively limited in the paddy soils when soil temperature was low. Only 2.2–6.0% of the applied 14C mineralized after 84d of incubation at 15°C. The mineralization of MSM was

Haizhen Wang; Jianming Xu; Scott R. Yates; Jiabao Zhang; Jay Gan; Jincai Ma; Jianjun Wu; Richeng Xuan

2010-01-01

196

The Spatial Region of Photoionization in a Strong Laser Field  

NASA Astrophysics Data System (ADS)

In the framework of the Keldysh-Faisal-Reiss theory in the velocity gauge we investigate the magnitude of the space region, where photoionization in a strong laser field takes place. We find substantial differences between the short-range and the long-range (Coulomb) potentials, and between linear and circular polarizations of incident radiation. It appears that only for the initial state in the Coulomb potential the region of space, where ionization is held, expands significantly with increasing intensity for a typical optical frequency and non-relativistic but strong circularly polarized laser field. As a result of our considerations, we suggest to modify the idea of Reiss and Krainov of a certain simple Coulomb correction to the Volkov wave function. We show that photoionization rate calculated for the H(1s) atom, using our approach, is in better agreement with other theoretical results for moderately strong circularly polarized laser field.

Bauer, J. H.

2008-10-01

197

ABRUPT LONGITUDINAL MAGNETIC FIELD CHANGES IN FLARING ACTIVE REGIONS  

SciTech Connect

We characterize the changes in the longitudinal photospheric magnetic field during 38 X-class and 39 M-class flares within 65{sup 0} of disk center using 1 minute GONG magnetograms. In all 77 cases, we identify at least one site in the flaring active region where clear, permanent, stepwise field changes occurred. The median duration of the field changes was about 15 minutes and was approximately equal for X-class and for M-class flares. The absolute values of the field changes ranged from the detection limit of {approx}10 G to as high as {approx}450 G in two exceptional cases. The median value was 69 G. Field changes were significantly stronger for X-class than for M-class flares and for limb flares than for disk-center flares. Longitudinal field changes less than 100 G tended to decrease longitudinal field strengths, both close to disk center and close to the limb, while field changes greater than 100 G showed no such pattern. Likewise, longitudinal flux strengths tended to decrease during flares. Flux changes, particularly net flux changes near disk center, correlated better than local field changes with GOES peak X-ray flux. The strongest longitudinal field and flux changes occurred in flares observed close to the limb. We estimate the change of Lorentz force associated with each flare and find that this is large enough in some cases to power seismic waves. We find that longitudinal field decreases would likely outnumber increases at all parts of the solar disk within 65{sup 0} of disk center, as in our observations, if photospheric field tilts increase during flares as predicted by Hudson et al.

Petrie, G. J. D. [National Solar Observatory, 950 N. Cherry Avenue, Tucson, AZ 85719 (United States); Sudol, J. J. [West Chester University, West Chester, PA 19383 (United States)

2010-12-01

198

The regional intraplate stress field in South America  

Microsoft Academic Search

The paper presents a compilation of lithospheric stress directions for continental South America and the inferred major patterns of the regional intraplate stress field. Stress orientations are based primarily on earthquake focal mechanisms and quaternary fault slip inversion published in the literature. In the Andean plateau, N-S extensional stresses predominate. E-W compressional stresses are observed in the sub-Andean and platform

Marcelo Assumpcao

1992-01-01

199

The Regional Intraplate Stress Field in South America  

Microsoft Academic Search

A compilation of lithospheric stress directions for continental South America and the inferred major pat- terns of the regional intraplate stress field are presented. Stress orientations are based primarily on earthquake focal mechanisms and Quaternary fault slip inversion published in the literature. Four new focal mechanisms based on short-period P wave modeling, and selected centroid-moment-tensor solutions (published by U.S. Geological

IRCELO ASSUMPCAO

1992-01-01

200

Chiral Effective Field Theory in the $\\Delta$-resonance region  

SciTech Connect

I discuss the problem of constructing an effective low-energy theory in the vicinity of a resonance or a bound state. The focus is on the example of the $\\Delta(1232)$, the lightest resonance in the nucleon sector. Recent developments of the chiral effective-field theory in the $\\Delta$-resonance region are briefly reviewed. I conclude with a comment on the merits of the manifestly covariant formulation of chiral EFT in the baryon sector.

Vladimir Pascalutsa

2006-09-18

201

Baseline soil variation is a major factor in arsenic accumulation in Bengal Delta paddy rice.  

PubMed

Factors responsible for paddy soil arsenic accumulation in the tubewell irrigated systems of the Bengal Delta were investigated. Baseline (i.e., nonirrigated) and paddy soils were collected from 30 field systems across Bangladesh. For each field, soil sampled at dry season (Boro) harvest i.e., the crop cycle irrigated with tubewell water, was collected along a 90 m transect away from the tubewell irrigation source. Baseline soil arsenic levels ranged from 0.8 to 21. mg/kg, with lower values found on the Pliestocene Terrace around Gazipur (average, 1.6 +/- 0.2 mg/kg), and higher levels found in Holecene sediment tracts of Jessore and Faridpur (average, 6.6 +/- 1.0 mg/kg). Two independent approaches were used to assess the extent of arsenic build-up in irrigated paddy soils. First, arsenic build-up in paddy soil at the end of dry season production (irrigated - baseline soil arsenic) was regressed against number of years irrigated and tubewell arsenic concentration. Years of irrigation was not significant (P = 0.711), indicating no year-on-year arsenic build-up, whereas tubewell As concentration was significant (P = 0.008). The second approach was analysis of irrigated soils for 20 fields over 2 successive years. For nine of the fields there was a significant (P < 0.05) decrease in soil arsenic from year 1 to 2, one field had a significant increase, whereas there was no change for the remaining 10. Over the dry season irrigation cycle, soil arsenic built-up in soils at a rate dependent on irrigation tubewell water, 35* (tubewell water concentration in mg/kg, triple bond mg/L). Grain arsenic rises steeply at low soil/shoot arsenic levels, plateauing out at concentratations. Baseline soil arsenic at Faridpur sites corresponded to grain arsenic levels at the start of this saturation phase. Therefore, variation in baseline levels of soil arsenic leads to a large range in grain arsenic. Where sites have high baseline soil arsenic, further additional arsenic from irrigation water only leads to a gradual increase in grain arsenic concentration. PMID:19368163

Lu, Ying; Adomako, Eureka E; Solaiman, A R M; Islam, M Rafiqul; Deacon, Claire; Williams, P N; Rahman, G K M M; Meharg, Andrew A

2009-03-15

202

Phase unwrapping using region-based markov random field model.  

PubMed

Phase unwrapping is a classical problem in Magnetic Resonance Imaging (MRI), Interferometric Synthetic Aperture Radar and Sonar (InSAR/InSAS), fringe pattern analysis, and spectroscopy. Although many methods have been proposed to address this problem, robust and effective phase unwrapping remains a challenge. This paper presents a novel phase unwrapping method using a region-based Markov Random Field (MRF) model. Specifically, the phase image is segmented into regions within which the phase is not wrapped. Then, the phase image is unwrapped between different regions using an improved Highest Confidence First (HCF) algorithm to optimize the MRF model. The proposed method has desirable theoretical properties as well as an efficient implementation. Simulations and experimental results on MRI images show that the proposed method provides similar or improved phase unwrapping than Phase Unwrapping MAx-flow/min-cut (PUMA) method and ZpM method. PMID:21096819

Dong, Ying; Ji, Jim

2010-01-01

203

Continuous model of the regional velocity field for Poland  

NASA Astrophysics Data System (ADS)

The poster presents modern determinations of the regional velocity field for Poland. The research is based on the ASG-EUPOS, Polish multifunctional GNNS network and performed within the developmental project of the Polish Ministry of Science and Higher Education. The network of the satellite-based sites consisted of above 130 Polish sites together with the selected number of European sites operating within EPN (EUREF Permanent Network). Data came from three-year period, which is the minimum number for the horizontal velocity determinations. The velocities were calculated within the discrete network related to the GNSS sites' distribution and then interpolated to the regular grid. The discussion on the interpolation methods is also included. To the interpolation of the velocity field kriging, spline and other functions were used. Assessment of the accuracy of the velocity on the interpolated points and tests of significance were also described. Developed models of the velocities field could indicate geodynamical activity on the area of Poland.

Bogusz, J.; Figurski, M.; Kontny, B.; Grzempowski, P.; Klos, A.

2012-04-01

204

Equatorial E and F region zonal electric fields in the postsunset period  

Microsoft Academic Search

The E and F region eastward electric fields in the postsunset period obtained from VHF backscatter radar and ionosonde observations respectively at the magnetic equatorial station at Trivandrum are colnpared. It is found that the F region eastward electric field is greater than the E region electric field indicating latitudinal gradients in the E region electric field. Enhancement of equatorial

S. S. Hari; K. S. Viswanathan; K. S. V. Subbarao; B. V. Krishna Murthy

1996-01-01

205

The effects of irrigation regimes on the water use, dry matter production and physiological responses of paddy rice  

Microsoft Academic Search

In most cases, rice production is associated with flooding irrigation and the efficiency of irrigated water use (WUEi) is\\u000a generally lower for production of rice than for other crops. We have examined the effects of various irrigation regimes on\\u000a water consumption in a well-puddled paddy field, as well as on dry matter production, grain yield and physiological responses\\u000a of the

Jun Lu; Taiichiro Ookawa; Tadashi Hirasawa

2000-01-01

206

MORPHOLOGICAL ANALYSIS OF FLOOD INUNDATED REGIONS IN PADDY AREAS USING ALOS\\/PALSAR DATA AND ITS DISTRIBUTION ON THE GOOGLE EARTH DESIGN OF THE FUTURE DISASTER MANAGEMENT SYSTEM (FDMS)  

Microsoft Academic Search

Large floods occurred at the northern part of the Central Plain of Thailand in May of 2006. The ordinary class flood appeared in October of 2006 in the middle stream region of the Chao Phraya river of Thailand. The ALOS satellite obtained the PALSAR radar data at the flood by the emergency observation requests. The PALSAR data can easily to

Yasuharu Yamadaa

207

Optimisation of point grids in regional gravity field analysis  

NASA Astrophysics Data System (ADS)

In contrast to spherical harmonics, which realise global uniform resolution, regional basis functions have the advantage to be adaptable to the local data density and variability. But how to choose adequately their spatial configuration? Estimating the location of basis functions represents a non-linear problem, which is difficult to solve by ordinary statistical tools, especially when treating their number as an unknown too. For that reason, most of the regional approximation approaches define the point grid in advance. In this contribution, we propose a Monte Carlo algorithm in a Bayesian framework to optimise the configuration of local basis functions jointly with their scaling coefficients. The problem can be formulated as a quasi-linear model. Quasi-linear models are non-linear ones, but linearity holds for a subset of the searched-for parameters. This allows us to utilise the analytical solution of the linear model, while the unknown parameters in the design matrix are kept fix. As a particular advantage of this approach, already existing gravity recovery software can be used in a black-box manner. The new method is analysed theoretically, followed by a demonstration of its applicability and performance by examples from the field of regional gravity field recovery from GOCE satellite data.

Schall, J.; Kusche, J.; Eicker, A.

2012-04-01

208

Pulsed star labeling of arterial regions (PULSAR): a robust regional perfusion technique for high field imaging.  

PubMed

Regional perfusion imaging (RPI) has recently been introduced as a potentially powerful technique to map the perfusion territories of patients with vascular diseases in a fully noninvasive manner. However, this technique suffers from the problems of the transfer insensitive labeling technique upon which it is based. In particular, RPI is very sensitive to magnetic field inhomogeneities, and therefore the definition of the labeled bolus can deteriorate at field strength higher than 1.5 T. Furthermore, the slab-selective triple-pulse postsaturation sequence used originally will also be impaired due to the same problem, rendering RPI unusable at higher field. In this work, an adiabatic-based signal targeting with alternating radiofrequency pulses sequence is proposed as a labeling scheme to solve the problems related to variations in local magnetic field, together with an improved four-pulse water suppression enhanced through T(1) effects technique as a presaturation scheme. PMID:15690497

Golay, Xavier; Petersen, Esben T; Hui, Francis

2005-01-01

209

A 3-year continuous record on the influence of daytime, season, and fertilizer treatment on methane emission rates from an Italian rice paddy  

Microsoft Academic Search

CH4 emission rates have been measured in an Italian rice paddy between 1984 and 1986, covering three vegetation periods. For these measurements a fully automated, computerized sampling and analyzing system was developed which allowed the simultaneous determination of CH4 emission rates at 16 different field plots. CH4 emission rates showed strong diurnal and seasonal variations. Diurnal changes correlated with changes

H. Schuetz; A. Holzapfel-Pschorn; R. Conrad; H. Rennenberg; W. Seiler

1989-01-01

210

Monitoring tricyclazole residues in rice paddy watersheds.  

PubMed

Pesticide application to rice paddies may affect the quality of environmental resources such as groundwater and surface water. The distribution of residues of tricyclazole, an environmentally persistent fungicide used widely in Italy, was monitored in the network of surface water bodies surrounding the main rice production area in Italy. The location of monitoring sites was based on the potential risk for contamination with tricyclazole. This was determined as a function of the area of rice grown, the geographical distribution of rice crops susceptible to the pest, and sales of tricyclazole. Monitoring sites were also located to represent different spatial scales (farm, catchment and basin). For water samples taken shortly after application in July and August, the highest concentrations of tricyclazole were measured at the farm sites. However, residues were also detected at the catchment and basin scale. The 95% of the measured residue levels was below 9.80, 1.20 and 1.15 microg l(-1), at the farm, catchment and basin scales, respectively. In sediment, tricyclazole residues were detected in 12 out 176 samples collected with the 95% of the measured residue levels below the concentration of 0.03 mg kg(-1). Residues were sporadically detected in samples taken after the crop was harvested in November and December. Variables such as the scale of sampling, the season and the year, were significant in determining pesticide residue distribution. The type of water body was less significant. PMID:15996714

Padovani, Laura; Capri, Ettore; Padovani, Caterina; Puglisi, Edoardo; Trevisan, Marco

2005-07-05

211

Two-field high-scale inflation in a sub-Planckian region of field space  

SciTech Connect

We present a simple two-field model of inflation and show how to embed it in string theory as a straightforward generalization of axion monodromy models. Phenomenologically, the predictions are equivalent to those of chaotic inflation, and, in particular, include observably large tensor modes. The whole high-scale large-field inflationary dynamics takes place within a region of field space that is parametrically sub-Planckian in diameter, hence improving our ability to control quantum corrections and achieve slow-roll inflation.

Berg, Marcus [Oskar Klein Center for Cosmoparticle Physics and Department of Physics, Stockholm University, Albanova University Center, SE-106 91 Stockholm (Sweden); Pajer, Enrico [Institute for High Energy Phenomenology, Newman Laboratory of Elementary Particle Physics, Cornell University, Ithaca, New York 14853 (United States); Sjoers, Stefan [Oskar Klein Center for Cosmoparticle Physics and Department of Physics, Stockholm University, Albanova University Center, SE-106 91 Stockholm (Sweden); Institute for High Energy Phenomenology, Newman Laboratory of Elementary Particle Physics, Cornell University, Ithaca, New York 14853 (United States)

2010-05-15

212

Magnetic Field Structures in a Facular Region Derived from THEMIS and Hinode Vector Magnetic Field  

NASA Astrophysics Data System (ADS)

In order to compare vector magnetic fields obtained by two spectral polarimeters (THEMIS/MTR and Hinode SOT/SP) and two inversion codes (UNNOFIT and MELANIE), we observed a facular region in the active region NOAA 10996 on 2008 May 23. We found that they give consistent results concerning the distributions of field strengths, azimuth and inclination angles. SOT/SP could resolve small magnetic polarities with sizes of 1'' to 2'', and detect convergence and divergence of the horizontal components of magnetic fields in the facular cells. These findings support the models suggesting the existence of flux tube bundles in faculae. With this model and multi spectral line observations, we could infer the relative formation heights of those spectral lines.

Guo, Y.; Schmieder, B.; Bommier, V.; Mein, P.

2012-05-01

213

Effect of moisture regime on the redistribution of heavy metals in paddy soil.  

PubMed

Sequential extraction procedure was applied to assess the dynamics of solid-phase transformation of added Cu, Pb, Cd, and Hg in a typical Chinese paddy soil incubated under three moisture regimes (75% field capacity, wetting-drying cycle, and flooding). The heavy metals spiked in the soil were time-dependently transferred from the easily extractable fraction (the exchangeable fraction) into less labile fractions (Fe-Mn oxide- and organic matter-bound fractions), and thus reduced lability of the metals. No significant changes were found for the carbonate-bound and residual fractions of the heavy metals in the soil during the whole incubation. Change rate of the mobility factor (MF), a proportion of weakly bound fractions (exchangeable and carbonate-bound) in the total metal of soil, reflected the transformation rate of metal speciation from the labile fractions toward stable fractions. It was found that soil moisture regime did not change the direction and pathways of transformation of metal speciation, but it significantly affected the transformation rate. In general, the paddy soil under flooding regime had higher metal reactivity compared with 75% field capacity and wetting-drying cycle regimes, resulting in the more complete movement of metals toward stable fractions. This might be related to the increased pH, precipitation of the metals with sulfides and higher concentration of amorphous Fe oxides under submerged condition. PMID:21520813

Zheng, Shunan; Zhang, Mingkui

2011-01-01

214

MultiPADDI-2 board for image processing  

NASA Astrophysics Data System (ADS)

We have constructed a prototype image processing board containing 384 processors in 8 VLSI chips. The goal of the prototype is to show how fine grain parallelism present in image processing applications can be exploited by using lots of simple processors interconnected in clever ways. Each processor has a 16-bit data path, a simple instruction set containing 12 instructions, a simple control unit, and a scan chain for loading data and program. Each VLSI chip, called PADDI-2, contains 48 processors. The programing model used for the processors in MIMD. Each processor has 8 words in the instruction memory. There are internal registers and queues in a processor for storing data and partial results. Data is assumed to be entering the system as a stream and processed by the processors. Each VLSI chip is connected to an external memory (64 K by 16). A hardware synchronization mechanism is used for communication between processors, memory, and the external environment. If a sender and receiver is within the same chip, communication can be done in one cycle by the hierarchical interconnect bus structure. Programming the processors and the interconnections are done at compile time. The board is interfaced to a Sun SPARCstation using the SBus. Video input and output is supported by the board and field buffers are used for buffering. Software tools for checking the board, running test programs at the assembly language level, and libraries for application development have been produced. Image processing applications are currently under development. The board is available for experimentation over the Internet. Further details are available from the project web page (http://infopad.eecs.berkeley.edu/spartan).

Srini, Vason P.; Chow, Nelson; Sutton, Roy A.; Rabaey, Jan M.

1997-09-01

215

An analysis of the flow field in the region of the ASRM field joints  

NASA Astrophysics Data System (ADS)

The flow field in the region of a solid rocket motor field joint is very important since fluid dynamic and mechanical propellant stresses can couple to cause a motor failure at a joint. Presented here is an examination of the flow field in the region of the Advanced Solid Rocket Motor (ASRM) field joints. The analyses were performed as a first step in assessing the design of the ASRM forward and aft field joints in order to assure the proper operation of the motor prior to further development of test firing. The analyses presented here were performed by employing a two-dimensional axisymmetric assumption. Fluent/BFC, a three dimensional full Navier-Stokes flow field code, was used to make the numerical calculations. This code utilizes a staggered grid formulation along with the SIMPLER numerical algorithm. Wall functions are used to determine the character of the laminar sublayer, and a standard kappa-epsilon turbulence model is used to close the fluid dynamic equations. The analyses performed to this date verify that the ASRM field joint design operates properly. The fluid dynamic stresses at the field joints are small due to the inherent design of the field joints. A problem observed in some other solid rocket motors is that large fluid dynamic stresses are generated at the motor joint on the downstream propellant grain due to forward facing step geometries. The design of the ASRM field joints are such that this is not a problem as shown by the analyses. Also, the analyses of the inhibitor stub left protruding into the port flow from normal propellant burn back show that more information is necessary to complete these analyses. These analyses were performed as parametric analyses in relation to the height of the inhibitor stub left protruding into the motor port. A better estimate of the amount of the inhibitor stub remaining at later burn times must be determined since the height which the inhibitor stub protrudes into the port flow drastically affects the fluid dynamics induced stresses on the propellant grain at the field joints.

Dill, Richard A.; Whitesides, Harold R.

1992-07-01

216

Evaluation of thermophilic fungal consortium for paddy straw composting.  

PubMed

Out of 10 thermophilic fungi isolated from wheat straw, farm yard manure, and soil, only three showed highest cellobiase, carboxymethyl cellulase, xylanase, and FPase activities. They were identified as Aspergillus nidulans (Th(4)), Scytalidium thermophilum (Th(5)), and Humicola sp. (Th(10)). A fungal consortium of these three fungi was used to compost a mixture (1:1) of silica rich paddy straw and lignin rich soybean trash. The composting of paddy straw for 3 months, during summer period in North India, resulted in a product with C:N ratio 9.5:1, available phosphorus 0.042% and fungal biomass 6.512 mg of N-acetyl glucosamine/100 mg of compost. However, a C:N ratio of 10.2:1 and highest humus content of 3.3% was achieved with 1:1 mixture of paddy straw and soybean trash. The fungal consortium was effective in converting high silica paddy straw into nutritionally rich compost thereby leading to economical and environment friendly disposal of this crop residue. PMID:17874191

Kumar, Adesh; Gaind, Sunita; Nain, Lata

2007-09-12

217

Seasonal transition of active bacterial and archaeal communities in relation to water management in paddy soils.  

PubMed

Paddy soils have an environment in which waterlogging and drainage occur during the rice growing season. Fingerprinting analysis based on soil RNA indicated that active microbial populations changed in response to water management conditions, although the fundamental microbial community was stable as assessed by DNA-based fingerprinting analysis. Comparative clone library analysis based on bacterial and archaeal 16S rRNAs (5,277 and 5,436 clones, respectively) revealed stable and variable members under waterlogged or drained conditions. Clones related to the class Deltaproteobacteria and phylum Euryarchaeota were most frequently obtained from the samples collected under both waterlogged and drained conditions. Clones related to syntrophic hydrogen-producing bacteria, hydrogenotrophic methanogenic archaea, rice cluster III, V, and IV, and uncultured crenarchaeotal group 1.2 appeared in greater proportion in the samples collected under waterlogged conditions than in those collected under drained conditions, while clones belonging to rice cluster VI related to ammonia-oxidizing archaea (AOA) appeared at higher frequency in the samples collected under drained conditions than in those collected under waterlogged conditions. These results suggested that hydrogenotrophic methanogenesis may become active under waterlogged conditions, whereas ammonia oxidation may progress by rice cluster VI becoming active under drained conditions in the paddy field. PMID:24005888

Itoh, Hideomi; Ishii, Satoshi; Shiratori, Yutaka; Oshima, Kenshiro; Otsuka, Shigeto; Hattori, Masahira; Senoo, Keishi

2013-09-05

218

Eco-stoichiometric alterations in paddy soil ecosystem driven by phosphorus application.  

PubMed

Agricultural fertilization may change processes of elemental biogeochemical cycles and alter the ecological function. Ecoenzymatic stoichiometric feature plays a critical role in global soil carbon (C) metabolism, driving element cycles, and mediating atmospheric composition in response to agricultural nutrient management. Despite the importance on crop growth, the role of phosphorous (P) in compliance with eco-stoichiometry on soil C and nitrogen (N) sequestration in the paddy field remains poorly understood in the context of climate change. Here, we collected soil samples from a field experiment after 6 years of chemical P application at a gradient of 0 (P-0), 30 (P-30), 60 (P-60), and 90 (P-90) kg ha(-1) in order to evaluate the role of P on stoichiometric properties in terms of soil chemical, microbial biomass, and eco-enzyme activities as well as greenhouse gas (GHG: CO2, N2O and CH4) emissions. Continuous P input increased soil total organic C and N by 1.3-9.2% and 3%-13%, respectively. P input induced C and N limitations as indicated by the decreased ratio of C:P and N:P in the soil and microbial biomass. A synergistic mechanism among the ecoenzymatic stoichiometry, which regulated the ecological function of microbial C and N acquisition and were stoichiometrically related to P input, stimulated soil C and N sequestration in the paddy field. The lower emissions of N2O and CH4 under the higher P application (P-60 and P-90) in July and the insignificant difference in N2O emission in August compared to P-30; however, continuous P input enhanced CO2 fluxes for both samplings. There is a technical conflict for simultaneously regulating three types of GHGs in terms of the eco-stoichiometry mechanism under P fertilization. Thus, it is recommended that the P input in paddy fields not exceed 60 kg ha(-1) may maximize soil C sequestration, minimize P export, and guarantee grain yields. PMID:23667435

Li, Xia; Wang, Hang; Gan, Shaohua; Jiang, Daqian; Tian, Guangming; Zhang, Zhijian

2013-05-07

219

High-field AC conduction in electron beam irradiated crosslinked polyethylene films in high temperature region  

Microsoft Academic Search

High-field AC conduction was investigated in electron-beam irradiated cross-linked polyethylene (IR-XLPE) film in the high-field and high-temperature region. Measurements of the electric field dependence of tan ?, dissipation current waveform, and DC absorption current were carried out. In the high-temperature and high-field region where the increment tan ? of IR-XLPE with electric field becomes large, the dissipation current waveforms have

K. Tohyama; T. Tokoro; M. Nagao; M. Kosaki

1993-01-01

220

Sensor Measurements and Sediment Incubations Indicate Diurnal Redox Cycling Associate With Arsenic Mobilization at a Bangladeshi Rice Paddy  

NASA Astrophysics Data System (ADS)

The presence of arsenic in the groundwater has led to the largest environmental poisoning in history; tens of millions of people in the Ganges Delta continue to drink groundwater that is dangerously contaminated with arsenic (As). Rice fields receive large loads of arsenic with irrigation water and provide recharge to the underlying aquifer. It is currently not known whether rice fields are a sink or source of arsenic in the hydrologic system. In the dry season, as As(III)-containing minerals are oxidized, As(V) is released and will adhere to Fe hydr(oxide) minerals. When sediments are inundated with water, reducing conditions will then drive reduction of Fe hydr(oxides) and release of As. We have been intensively studying a field site in Munshiganj, Bangladesh with extremely high levels of arsenic in groundwater (up to 1.2 mg/L). To better understand geochemical and microbial processes leading to As mobilization in surface sediment, we deployed sensors to take temporally dense measurements across our experimental rice paddy. Data collected in both 2006 and 2007 showed trends in geochemical parameters indicating that diurnal, possibly plant-induced, processes may be important. Over a two month period, nitrate concentrations decrease consistently each day as ammonium levels increase, presumably through temperature driven reductive processes. Nitrate concentrations in the subsurface then increase while ammonium levels decrease, possibly due to root oxygen leakage or rapid infiltration of oxygen rich surface water. Using sediment from the rice paddy and artificial irrigation water, laboratory microcosms were constructed to simulate the diurnal cycles observed at the field site. In carbon-ammended treatments, Fe and As cycling can occur on the order of days. Oscillations in redox conditions on diurnal as well as seasonal time scales may be important in the mobilization of arsenic into aquifers. By elucidating As mobilization mechanisms at an experimental rice paddy, this work could ultimately lead to solutions that minimize As exposure in critical populations.

Lin, T.; Lin, C.; Ramanathan, N.; Neumann, R.; Harvey, C.; Jay, J.

2007-12-01

221

TRANSITION REGION MAGNETIC FIELD AND POLAR MAGNETIC DISTURBANCES  

Microsoft Academic Search

The Explorer 12 measurements of the magnetic field outside the magnetosphere are compared with ground magnetograms from arctic observatories. Results indicate that an exterior field with a southerly component tends to be associated with ground disturbance, whereas a northward field is associated with quiet conditions. Examples are presented show- ing how a north-to-south field-direction change accompanies an increase in ground

D. H. Fairfield; L. J. Jr. Cahill

1966-01-01

222

Lignocellulolytic enzyme production from submerged fermentation of paddy straw  

Microsoft Academic Search

Five strains of cellulolytic bacteria and four strains of Phanerochaete chrysosporium were evaluated for the lignocellulolytic enzyme production during submerged fermentation (SmF) of paddy straw. Extra-cellular\\u000a enzyme assay for CMCase, FPase, Cellobiase, Xylanase, Lignin peroxidase and Laccase enzymes was performed after 7 and 15 days\\u000a of submerged fermentation. Cellulomonas cellulans MTCC 23, Cytophaga hutchinsonii NCIM 2338 and Phanerochaete chrysosporium MTCC

B. K. Mishra; A. K. Pandey Lata

2007-01-01

223

Seasonal Variation of Methane Flux From a California Rice Paddy  

Microsoft Academic Search

To allow increased understanding of the global budget of atmospheric methane, individual methane sources require investigation. We have measured methane emissions from a California rice paddy during the entire 1982 growing season. A very strong seasonal dependence was observed. Methane emissions were highest in the last 2-3 weeks before harvest; daily emissions reached 5 g CH,\\/m 2. Over the 100-day

R. J. Cicerone; J. D. Shetter; C. C. Delwiche

1983-01-01

224

ESTIMATION OF KOREAN PADDY FIELD SOIL PROPERTIES USING OPTICAL REFLECTANCE  

Technology Transfer Automated Retrieval System (TEKTRAN)

An optical sensing approach based on diffuse reflectance has shown potential for rapid and reliable on-site estimation of soil properties. Important sensing ranges and the resulting regression models useful for soil property estimation have been reported. In this study, a similar approach was applie...

225

Partitioning of arsenic in soil-crop systems irrigated using groundwater: a case study of rice paddy soils in southwestern Taiwan.  

PubMed

The accumulation of As in rice due to groundwater irrigation in paddy fields represents a serious health hazard in South and Southeast Asia. In Taiwan, the fate of As in long-term irrigated paddy fields is poorly understood. Groundwater, surface soil, and rice samples were collected from a paddy field that was irrigated with As-containing groundwater in southwestern Taiwan. The purpose of this study is to elucidate the source and sink of As in the paddy field by comparing the As fractions in the soils that were obtained by a sequential extraction procedure (SEP) with the As uptake of rice. The risks associated with eating rice from the field can thus be better understood. The concentration of As in groundwater varied with time throughout the growing seasons of rice, but always exceeded the permitted maximum (10 ?g L(-1)) for drinking water by the WHO. The As concentration increased with the concentration of Fe in the groundwater, supporting the claim that a large amount of As was concentrated in the Fe flocs collected from the internal wall of the groundwater pump. The results of the SEP revealed that As bound with amorphous and crystalline hydrous oxides exhibited high availability in the soils. The root of rice accumulated the largest amount of As, followed by the straw, husk, and grain. Although the As concentration in the rice grain was less than 1.0 mg kg(-1), the estimated intake level was close to the maximum tolerable daily intake of As, as specified by the WHO. PMID:22094052

Hsu, Wen-Ming; Hsi, Hsing-Cheng; Huang, You-Tuan; Liao, Chien-Sen; Hseu, Zeng-Yei

2011-11-16

226

Interferometric mapping of magnetic fields in star- forming regions  

Microsoft Academic Search

Magnetic fields are thought to play a significant role in all stages of star formation. However, there are few observations that measure magnetic fields at the relevant scale for the star formation process. In this thesis, I present the results from a survey of linear polarization in molecular cores at 1.3 mm wavelength with the BIMA millimeter interferometer. The linear

Shih-Ping Lai

2001-01-01

227

Reduced methane emissions from large-scale changes in water management of China's rice paddies during 1980-2000  

Microsoft Academic Search

Decreased methane emissions from paddy rice may have contributed to the decline in the rate of increase of global atmospheric methane (CH4) concentration over the last 20 years. In China, midseason paddy drainage, which reduces growing season CH4 fluxes, was first implemented in the early 1980s, and has gradually replaced continuous flooding in much of the paddy area. We constructed

Changsheng Li; Jianjun Qiu; Steve Frolking; Xiangming Xiao; William Salas; Berrien Moore; Steve Boles; Yao Huang; Ronald Sass

2002-01-01

228

Heavy metal concentrations and their possible sources in paddy soils of a modern agricultural zone, southeastern China  

Microsoft Academic Search

In a typical modern agricultural Zone of southeastern China, Haining City, 224 topsoil samples were collected from paddy fields\\u000a to measure the total concentrations of copper (Cu), lead (Pb), zinc (Zn), cadmium (Cd), chromium (Cr), mercury (Hg), arsenic\\u000a (As) and cobalt (Co). The total concentrations ranged from 15.30 to 78.40 mg kg?1 for Cu, 20.10 to 41.40 mg kg?1 for Pb, 54.98 to 224.4 mg kg?1

Chunfa Wu; Limin Zhang

2010-01-01

229

Electric Fields and Plasma Processes in the Auroral Downward Current Region, Below, Within, and Above the Acceleration Region  

Microsoft Academic Search

The downward field-aligned current region plays an active role in magnetosphere-ionosphere coupling processes associated with\\u000a aurora. A quasi-static electric field structure with a downward parallel electric field forms at altitudes between 800 km\\u000a and 5000 km, accelerating ionospheric electrons upward, away from the auroral ionosphere. A wealth of related phenomena, including\\u000a energetic ion conics, electron solitary waves, low-frequency wave activity,

G. T. Marklund

2009-01-01

230

Comparison of observed and calculated magnetic field structures for a potential model for two active regions  

Microsoft Academic Search

We present results of observations of longitudinal magnetic fields in two active regions on the sun. The observations were carried out in the lines Fe I 525.3 nm and H-beta by means of the double magnetograph of the Crimean Astrophysical Observatory. In our analysis, we compare the observed magnetic field with the potential field. The strong magnetic fields in the

S. I. Gopasyuk; S. I. Gandzha; O. S. Gopasyuk; T. N. Tarasova; A. N. Shakhovskaya

1997-01-01

231

Methane emission from Texas rice paddy soils. 1. Quantitative multi-year dependence of CH4 emission on soil, cultivar and grain yield  

Microsoft Academic Search

Methane emissions at different rice productivity levels were observed from Texas rice paddy soils during the years 1991-95. Analysis of field measurements showed that seasonal methane emission (E) was strongly dependent on soil, cultivar, and rice grain yield. The relationship can be quantitatively described by E (g m-2) J 0.048 H SI H VI H GY. SI is a soil

L. S ASS; F RANK; M. F ISHER

1997-01-01

232

Effect of long-term application of inorganic fertilizer and organic amendments on soil organic matter and microbial biomass in three subtropical paddy soils  

Microsoft Academic Search

Soil organic matter (SOM), microbial carbon (Cmic), and microbial nitrogen (Nmic) status affected by the application of inorganic fertilizer and organic amendments in subtropical paddy soils were investigated.\\u000a Soil samples were collected from the plow layer of three long-term (17 years) field experiments at Xinhua, Ningxiang, and\\u000a Taojiang counties in Hunan Province, China. Results showed that, compared to the control, application

X. H. Hao; S. L. Liu; J. S. Wu; R. G. Hu; C. L. Tong; Y. Y. Su

2008-01-01

233

Efficacy of Aquatain, a Monomolecular Film, for the Control of Malaria Vectors in Rice Paddies  

Microsoft Academic Search

BackgroundRice paddies harbour a large variety of organisms including larvae of malaria mosquitoes. These paddies are challenging for mosquito control because their large size, slurry and vegetation make it difficult to effectively apply a control agent. Aquatain, a monomolecular surface film, can be considered a suitable mosquito control agent for such breeding habitats due to its physical properties. The properties

Tullu Bukhari; Willem Takken; Andrew K. Githeko; Constantianus J. M. Koenraadt; Georges Snounou

2011-01-01

234

Artificial cooling to control coleopterans in paddy rice stored in metallic silo  

Microsoft Academic Search

Stored paddy rice may be infested with insect pests that reduce its quality and quantity, causing economic losses to the grain industry. The objective of this research was to evaluate the use of chilling aeration to control insects in stored rice. In a 5,000 t metallic silo filled with paddy rice, a commercial grain chiller was installed to insufflate cold

F. A. Lazzari; S. M. N. Lazzari; A. F. Karkle

235

Geology and regional setting of Kuparuk Oil Field, Alaska  

SciTech Connect

The Kuparuk oil field is located on the Alaskan Arctic plain in the Colville-Prudhoe basin, 10 to 30 mi (16 to 48 km) west of the Prudhoe Bay field. The 24/sup 0/ API crude is similar in type to that in the Permo-Triassic reservoirs in the Prudhoe Bay field; however, it is from the Lower Cretaceous Kuparuk Formation. This reservoir is located in a basin between the Colville and Prudhoe highs. The origin of the oil is believed to be predominantly Lower sequence formations with migration occurring possibly via the Prudhoe Bay field. The dominant trapping mechanism is stratigraphic pinch-out and truncation of the reservoir at a local unconformity along the southern and western flanks of a southeast-plunging antiform. Structural dip closure exists along the northern and eastern flanks. The reservoir sandstones occur within sequences which become cleaner and coarser upward, and are thought to be shallow marine in origin with a provenance to the northeast. They are interpreted to be infrarift sediments on what is now a passive, Atlantic-type continental margin. Two of the four major lithostratigraphic units mapped within the Kuparuk Formation exhibit good reservoir characteristics and extend over an area in excess of 200 mi/sup 2/ (518 km/sup 2/). The cumulative net pay in the Kuparuk field ranges up to 90 ft, and the estimate of movable oil-in-place is 4.4 billion stock tank bbl. There is no gas cap. The field exhibits a variable oil-water contact ranging from -6,530 ft (-1,990 m) in the southeast to -6,700 ft (-2,042 m) in the north. After secondary waterflooding, the potential recoverable reserves are estimated to be about 1.0 to 1.5 billion stock tank bbl. Kuparuk field, therefore, ranks as one of the largest oil fields in the United States.

Carman, G.J.; Hardwick, P.

1983-06-01

236

Combined impacts of freeze-thaw processes on paddy land and dry land in Northeast China.  

PubMed

The quantity of spring snowmelt infiltration and runoff, which affects the hydrology of the freeze zone, depends on the antecedent soil water content (SWC) conditions at the time of the soil's freezing. An understanding of the characteristics of frozen soil is essential for spring sowing in the agricultural freeze zones. The main goal of this study was to evaluate the differences in the freeze-thaw process and the freeze-thaw-induced water redistribution between the paddy and dry lands in a freeze zone. For this purpose, a field study was conducted in the winter of 2011-2012 for two types of farmlands in Northeast China. To illustrate the soil's frost dynamics over time, the measured SWCs at different depths (15, 30, 60, and 90 cm) were transformed into different expressions including the SWC dynamic, the frozen soil's profile, and the freezing and thawing front trace. The freezing characteristics in the paddy land, in contrast to that in the dry land, had a higher freezing point temperature, a larger amount of water movement to the upper layer, and a 2.76 mm larger accumulation of water in the upper layer. However, the increase of SWC (which is equivalent to thawing) was evidently faster than the decrease of SWC (which is equivalent to freezing). The water in the frozen soil's profile was most likely redistributed towards the freezing front before soil temperature (ST) falls below the freezing point. The findings may partially explain the soil's freeze-thaw characteristics for the different stages as well as the combined impact of these characteristics with farmland use types on soil hydrology; the findings may also provide a foundation for forecasting the hydrologic response of the freeze-thaw process and provide guidance for management strategies dealing with seasonally frozen agricultural soils. PMID:23584030

Chen, Siyang; Ouyang, Wei; Hao, Fanghua; Zhao, Xuchen

2013-04-10

237

Field alignment of quadrupole magnets for the LHC interaction regions  

Microsoft Academic Search

High-gradient superconducting quadrupole magnets are being developed by the US LHC Accelerator Project for the Interaction Regions of the Large Hadron Collider. Determination of the magnetic axis for alignment of these magnets will be performed using a single stretched wire system. These measurements will be done both at room and cryogenic temperatures with very long wire lengths, up to 20

J. DiMarco; H. Glass; M. J. Lamm; P. Schlabach; C. Sylvester; J. C. Tompkins; I. Krzywinski

2000-01-01

238

Convective-region geometry as the cause of Uranus' and Neptune's unusual magnetic fields  

Microsoft Academic Search

The discovery of Uranus' and Neptune's non-dipolar, non-axisymmetric magnetic fields destroyed the picture-established by Earth, Jupiter and Saturn-that planetary magnetic fields are dominated by axial dipoles. Although various explanations for these unusual fields have been proposed, the cause of such field morphologies remains unexplained. Planetary magnetic fields are generated by complex fluid motions in electrically conducting regions of the planets

Sabine Stanley; Jeremy Bloxham

2004-01-01

239

On-farm assessment of organic amendments effects on nutrient status and nutrient use efficiency of organic rice fields in Northeastern Japan  

Microsoft Academic Search

Animal compost, organic fertilizer and straw management are among the factors affecting soil fertility in organic cropping systems. However, few studies have compared the effects of organic amendments on soil fertility of organic paddy fields. We conducted a survey of organic farmers’ paddy fields to compare soil nutrients (N, P, K, Ca and Mg), nutrient budgets and partial factor productivity

H. Hasegawa; Y. Furukawa; S. D. Kimura

2005-01-01

240

Field-aligned currents and magnetic disturbances in the dayside polar region  

NASA Astrophysics Data System (ADS)

A model is developed for the cusp-region field-aligned currents which takes into account all known data on the relationship between the field-aligned currents and the interplanetary magnetic field (IMF). The model regards the field-aligned currents as the superposition of various current sheets under the influence of different solar wind parameters which form a pattern of a specific region 3 of field-aligned currents located poleward of region 1 and affected by both the azimuthal and northward components of the IMF. It is shown that the recent measurements obtained from experiments on the TRIAD satellite (Saflekos and Potemra, 1979) unambiguously point to the existence of region 3. In addition, the data on the transverse magnetic disturbances from the S3-2 satellite Doyle et al., 1981) are found to accord with this model by taking into account the relations between the IMF parameters and the field-aligned current intensity.

Troshichev, O. A.; Gizler, V. A.; Shirochkov, A. V.

1982-10-01

241

The stress field of Vrancea region from fault plane solution (FPS)  

NASA Astrophysics Data System (ADS)

The fault plane solutions (FPS) of 247 seismic events were used for stress field investigation of the region. The eigenvectors t, p, b, and moment tensor M components for each FPS were defined and computed numerically. The obtained results confirm the hypothesis of subduction-type intermediate depth earthquakes for the Vrancea seismic region and this may be considered the first approximation of the stress field for the whole of the Vrancea (intermediate depth) region.

Telesca, L.; Alcaz, V.; Sandu, I.

2011-10-01

242

Lignocellulolytic enzyme production from submerged fermentation of paddy straw.  

PubMed

Five strains of cellulolytic bacteria and four strains of Phanerochaete chrysosporium were evaluated for the lignocellulolytic enzyme production during submerged fermentation (SmF) of paddy straw. Extra-cellular enzyme assay for CMCase, FPase, Cellobiase, Xylanase, Lignin peroxidase and Laccase enzymes was performed after 7 and 15 days of submerged fermentation. Cellulomonas cellulans MTCC 23, Cytophaga hutchinsonii NCIM 2338 and Phanerochaete chrysosporium MTCC 787 were found to produce higher lignocellulolytic enzyme activities than rest of the cultures after 15 days of fermentation. PMID:23100663

Mishra, B K; Pandey Lata, A K

2007-07-08

243

Cumulative ecological impacts of two successive annual treatments of imidacloprid and fipronil on aquatic communities of paddy mesocosms.  

PubMed

Agricultural landscapes, including paddies, play an important role in maintaining biodiversity, but this biodiversity has been under the threat of toxic agro-chemicals. Our knowledge about how aquatic communities react to, and recover from, pesticides, particularly in relation to their residues, is deficient, despite the importance of such information for realistic environmental impact assessment of pesticides. The cumulative ecological impacts on aquatic paddy communities and their recovery processes after two successive annual applications of two systemic insecticides, imidacloprid and fipronil, were monitored between mid-May and mid-September each year. The abundance of benthic organisms during both years was significantly lower in both insecticide-treated fields than in the controls. Large-impacts of fipronil on aquatic arthropods were found after the two years. Growth of medaka fish, both adults and their juveniles, was affected by the application of the two insecticides. A Principal Response Curve analysis (PRC) showed the escalation and prolongation of changes in aquatic community composition by the successive annual treatments of each insecticide over two years. Residues of fipronil in soil, which are more persistent than those of imidacloprid, had a high level of impact on aquatic communities over time. For some taxonomic groups, particularly for water surface-dwelling and water-borne arthropods, the second annual treatment had far greater impacts than the initial treatment, indicating that impacts of these insecticides under normal use patterns cannot be accurately assessed during short-term monitoring studies, i.e., lasting less than one year. It is concluded that realistic prediction and assessment of pesticide effects at the community level should also include the long-term ecological risks of their residues whenever these persist in paddies over a year. PMID:22521688

Hayasaka, D; Korenaga, T; Suzuki, K; Saito, F; Sánchez-Bayo, F; Goka, K

2012-04-21

244

Detection of Field-Aligned Current Signatures in Martian Auroral Regions  

NASA Astrophysics Data System (ADS)

We present the results of a manual survey of magnetic field data from the Mars Global Surveyor spacecraft for magnetic field perturbations, which can be signatures of magnetic currents. We analyzed approximately three years of magnetic field data recorded at ˜400 km altitudes above the entire Martian surface. We identified over 5,000 perturbations and determined the locations and intensities of each. Perturbations tend to occur in regions of strong crustal magnetic field, in cusps between regions of closed magnetic field. Perturbation intensities averaged ˜15nT and ranged up to 50nT. Perturbations were almost always in the horizontal magnetic field component, in regions of radial crustal field. In addition, perturbations seemed to be more common and stronger farther from the center of magnetic field cusps. These observed features are consistent with the perturbations resulting from field-aligned currents in cusps, near the boundary between open and closed field lines. Field-aligned currents are associated with aurora on Earth, suggesting that the perturbations may be a signature of auroral processes operating on Mars. Ultraviolet auroral emissions have been previously reported in the cusps of Martian crustal fields, and auroral-like electrons have also been measured in these regions. The observations presented here may help to determine which mechanisms are responsible for Martian aurora and how often they operate.

Fischer, S. R.; Ulusen, D.; Brain, D. A.; Halekas, J. S.; Hurley, D. M.

2010-12-01

245

[Land cover and landscape pattern changes in Poyang Lake region of China in 1980-2010].  

PubMed

Based on the land cover datasets of Poyang Lake region in 1980, 2005, and 2010, and by using GIS, RS, and landscape ecology approaches, this paper studied the land cover and landscape pattern changes in this region from 1980 to 2010, and quantitatively analyzed the land cover types change degree, patch area index, patch shape index, margin density index, and landscape diversity index. In 1980-2010, the main land cover types in this region were paddy field, inland water, evergreen broadleaf forest, and urban built-up area, and their areas and spatial patterns varied dramatically. Overall, the areas of inland water and urban built-up area had a significant increase, while those of paddy field and dry farmland decreased somewhat. Due to the effects of population growth and economic development, the landscape fragmentation degree and landscape diversity index presented a decreasing trend, but the decrement was small, which implied that the previous environmental management of this region had exerted important roles, but a long term challenge was still faced with between the regional environmental protection and sustainable development. PMID:23898669

Wang, Juan-le; Ran, Ying-ying; Zhang, Yong-jie; Cao, Xiao-ming; Yang, Fei

2013-04-01

246

Field Trip to Enfield Glen, NY Finger Lakes Region  

NSDL National Science Digital Library

Ithaca NY is currently located in a tranquil mid-continental geologic setting. But Ithaca's past was anything but tranquil. Would you believe that we once sat beneath a mile-thick sheet of ice? Or that it was once the bottom of the ocean? In a zone of high seismic activity? Or volcanic eruptions? It's all true. On this field trip to Enfield Glen, in Upper Treman State Park, we will make measurements and observations that allow us to reconstruct some of the events in the geologic past of this locality. Was New York always on the east coast of North America? Come on, let's find out.

Moore, Alexandra

247

Magnetic Field Improvement in End Region of Rectangular Planar DC Magnetron Based on Particle Simulation  

NASA Astrophysics Data System (ADS)

For a rectangular planar direct current (DC) magnetron, anomalous target erosion may occur in the curve-out region and inner side of the curved region. One key factor is that the magnetic field in the end region is weaker than that in the straight region, and another important factor may be that there is a circumferential component of the magnetic field in the curved region. Through a calculation of three-dimensional magnetic field for the rectangular magnetron, a magnet structure shimmed by permanent magnet bars and ferromagnetic bars is proposed to solve the above problems. Through a three-dimensional non-self-consistent particle simulation and the Yamamura/Tawara formula, the target erosion profile could be predicted. The simulation results show that for an improved uniformity in magnetic field, the entire target utilization could be much enhanced.

Qiu, Qingquan; Li, Qingfu; Su, Jingjing; Jiao, Yu; Jim, Finley

2008-12-01

248

H II REGION DRIVEN GALACTIC BUBBLES AND THEIR RELATIONSHIP TO THE GALACTIC MAGNETIC FIELD  

SciTech Connect

The relative alignments of mid-infrared traced Galactic bubbles are compared to the orientation of the mean Galactic magnetic field in the disk. The orientations of bubbles in the northern Galactic plane were measured and are consistent with random orientations-no preferential alignment with respect to the Galactic disk was found. A subsample of H II region driven Galactic bubbles was identified, and as a single population they show random orientations. When this subsample was further divided into subthermal and suprathermal H II regions, based on hydrogen radio recombination linewidths, the subthermal H II regions showed a marginal deviation from random orientations, but the suprathermal H II regions showed significant alignment with the Galactic plane. The mean orientation of the Galactic disk magnetic field was characterized using new near-infrared starlight polarimetry and the suprathermal H II regions were found to preferentially align with the disk magnetic field. If suprathermal linewidths are associated with younger H II regions, then the evolution of young H II regions is significantly affected by the Galactic magnetic field. As H II regions age, they cease to be strongly linked to the Galactic magnetic field, as surrounding density variations come to dominate their morphological evolution. From the new observations, the ratios of magnetic-to-ram pressures in the expanding ionization fronts were estimated for younger H II regions.

Pavel, Michael D.; Clemens, D. P., E-mail: pavelmi@bu.edu, E-mail: clemens@bu.edu [Institute for Astrophysical Research, Boston University, 725 Commonwealth Ave., Boston, MA 02215 (United States)

2012-12-01

249

Mineralization of metsulfuron-methyl in Chinese paddy soils.  

PubMed

A laboratory study was conducted to investigate the mineralization of metsulfuron-methyl (MSM) in paddy soils in response to soil moisture, temperature and soil properties. The results indicated that MSM mineralization was relatively limited in the paddy soils when soil temperature was low. Only 2.2-6.0% of the applied (14)C mineralized after 84d of incubation at 15 degrees C. The mineralization of MSM was enhanced by increasing soil moisture and soil temperature. Soil moisture would have different impact on the response of MSM mineralization to variation in soil temperature. An increase of 10 degrees C accelerated the average rate of MSM mineralization by 2.3 times at 50% water-holding capacity (WHC) and 1.9 times at 40% WHC. Regression analysis showed that soil pH, organic carbon contents, microbial biomass carbon contents, and silt/clay fractions were the dominant factors affecting MSM mineralization, with pH as the most important factor. The relatively slow mineralization rate of MSM suggested long persistence of this herbicide in soil, thus increasing its potential ecological risk, especially when applied in alkaline soils and in cold areas. PMID:19906402

Wang, Haizhen; Xu, Jianming; Yates, Scott R; Zhang, Jiabao; Gan, Jay; Ma, Jincai; Wu, Jianjun; Xuan, Richeng

2009-11-10

250

Comparison of transient horizontal magnetic fields in a plage region and in the quiet Sun  

NASA Astrophysics Data System (ADS)

Aims: The properties of transient horizontal magnetic fields (THMFs) in both plage and quiet Sun regions are obtained and compared. Methods: Spectro-polarimetric observations with the Solar Optical Telescope (SOT) on the Hinode satellite were carried out with a cadence of about 30 s for both plage and quiet regions located near the disk center. We selected THMFs that have net linear polarization (LP) higher than 0.22%, and an area larger than or equal to 3 pixels, and compared their occurrence rates and distribution of magnetic field azimuth. We obtained probability density functions (PDFs) of magnetic field strength and inclination for both regions. Results: The occurrence rate in the plage region is the same as for the quiet Sun. The vertical magnetic flux in the plage region is ~8 times more than in the quiet Sun. There is essentially no preferred orientation for the THMFs in either region; however, THMFs in the plage region with higher LP have a preferred direction consistent with that of the plage-region's large-scale vertical field pattern. PDFs show that there is no difference in the distribution of field strength of horizontal fields between the quiet Sun and the plage regions when we avoid the persistent vertical flux concentrations for the plage region. Conclusions: The similarity between the PDFs and the occurrence rates in plage and quiet regions suggests that a local dynamo process due to the granular motion may generate THMFs all over the Sun. The preferred orientation for higher LP in the plage indicates that the THMFs may be somewhat influenced by the larger-scale magnetic field pattern of the plage. A movie is only available in electronic form at http://www.aanda.org

Ishikawa, R.; Tsuneta, S.

2009-02-01

251

Vertical Lorentz Force and Cross-Field Currents in the Photospheric Magnetic Fields of Solar Active Regions  

NASA Astrophysics Data System (ADS)

We demonstrate that the vertical Lorentz force and a corresponding lower limit of the cross-field electric current density can be calculated from vector magnetograms of solar active regions obtained at a single height in the solar atmosphere, provided that the vertical gradient of the magnetic field strength is known at this height. We use a predicted vertical magnetic field gradient derived from a previous analysis. By testing various force-free solutions, we find that the numerical accuracy of our method is satisfactory. Applying the method to active region photospheric vector magnetograms, we find vertical Lorentz forces ranging from several hundredths to a few tenths of the typical photospheric gravitational force, and typical cross-field current densities up to several times 10 mA m-2. The typical vertical current density is found to be 2-3 times smaller, on the order of 10-15 mA m-2. These differences are above the associated uncertainties. The values of the cross-field currents decrease in an averaged vector magnetogram, but the ratio of the cross-field to the vertical current density increases, also above the uncertainties. We conclude that the photospheric active region magnetic fields are not force-free, contrary to the conjectures of some recent studies.

Georgoulis, Manolis K.; LaBonte, Barry J.

2004-11-01

252

Comparison of observed and calculated magnetic field structures for a potential model for two active regions  

NASA Astrophysics Data System (ADS)

We present results of observations of longitudinal magnetic fields in two active regions on the sun. The observations were carried out in the lines Fe I 525.3 nm and H-beta by means of the double magnetograph of the Crimean Astrophysical Observatory. In our analysis, we compare the observed magnetic field with the potential field. The strong magnetic fields in the chromosphere have a smaller inclination to the vertical line than those fields in the photosphere. The difference of this inclination decreases with magnetic intensity. The observed magnetic field structure in the chromosphere differs from the potential one at the same height.

Gopasyuk, S. I.; Gandzha, S. I.; Gopasyuk, O. S.; Tarasova, T. N.; Shakhovskaya, A. N.

1997-02-01

253

Field emission studies of novel ZnO nanostructures in high and low field regions  

NASA Astrophysics Data System (ADS)

A study of the field emission characteristics of novel structures of ZnO, namely marigolds, multipods and microbelts, has been carried out in both the close proximity configuration and the conventional field emission microscope. The use of a conventional field emission microscope overcomes the drawback of arc formation at high field values. The nonlinearity in the Fowler-Nordheim (F-N) plot, a characteristic feature of semiconductors has been observed and explained on the basis of electron emission from both the conduction and the valence bands. The current stability exhibited by these structures is also promising for future device applications.

Ramgir, Niranjan S.; Late, Dattatray J.; Bhise, Ashok B.; Mulla, Imtiaz S.; More, Mahendra A.; Joag, Dilip S.; Pillai, Vijayamohanan K.

2006-06-01

254

Effect of Long-Term Paddy-Upland Yearly Rotations on Rice (Oryza sativa) Yield, Soil Properties, and Bacteria Community Diversity  

PubMed Central

A 10-year-long field trial (between 2001 and 2010) was conducted to investigate the effect of paddy-upland rotation on rice yield, soil properties, and bacteria community diversity. Six types of paddy-upland crop rotations were evaluated: rice-fallow (control; CK), rice-rye grass (RR), rice-potato with rice straw mulches (RP), rice-rapeseed with straw incorporated into soil at flowering (ROF), rice-rapeseed incorporated in soil after harvest (ROM), and rice-Chinese milk vetch (RC). Analysis of terminal restriction fragment length polymorphism (T-RFLP) was used to determine microbial diversity among rotations. Rice yield increased for upland crops planted during the winter. RC had the highest average yield of 7.74?t/ha, followed by RR, RP, ROM, and ROF. Soil quality differences among rotations were found. RC and RP improved the soil mean weight diameter (MWD), which suggested that rice rotated with milk vetch and potato might improve the paddy soil structure. Improved total nitrogen (TN) and soil organic matter (SOM) were also found in RC and RP. The positive relationship between yield and TN/SOM might provide evidence for the effect of RC rotation on rice yield. A strong time dependency of soil bacterial community diversity was also found.

Chen, Song; Zheng, Xi; Wang, Dangying; Chen, Liping; Xu, Chunmei; Zhang, Xiufu

2012-01-01

255

Test Particle Calculation of Electric Currents In Magnetic Field-Reversed Regions.  

National Technical Information Service (NTIS)

A wide range of important plasma phenomena can take place in boundary layers between regions of oppositely directed magnetic fields where collisionless particles can execute magnetized and unmagnetized motion sequentially. We present in this paper an algo...

J. Chen D. L. Holland

1996-01-01

256

Blindness Due to Sellar Region Tumor Caused Apoplexy; Visual Field Investigation Helps the Diagnosis.  

National Technical Information Service (NTIS)

Chiasmal region tumor caused apoplexy is not uncommon. As its clinical picture varies and is complicated, early diagnosis is usually difficult. 7 cases are reported with marked visual loss, the presenting symptom. Visual fields all revealed definite chias...

L. Yuanxiu

1980-01-01

257

HELIOSHEATH MAGNETIC FIELDS BETWEEN 104 AND 113 AU IN A REGION OF DECLINING SPEEDS AND A STAGNATION REGION  

SciTech Connect

We examine the relationships between the magnetic field and the radial velocity component V{sub R} observed in the heliosheath by instruments on Voyager 1 (V1). No increase in the magnetic field strength B was observed in a region where V{sub R} decreased linearly from 70 km s{sup -1} to 0 km s{sup -1} as plasma moved outward past V1. An unusually broad transition from positive to negative polarity was observed during a Almost-Equal-To 26 day interval when the heliospheric current sheet (HCS) moved below the latitude of V1 and the speed of V1 was comparable to the radial speed of the heliosheath flow. When V1 moved through a region where V{sub R} Almost-Equal-To 0 (the 'stagnation region'), B increased linearly with time by a factor of two, and the average of B was 0.14 nT. Nothing comparable to this was observed previously. The magnetic polarity was negative throughout the stagnation region for Almost-Equal-To 580 days until 2011 DOY 235, indicating that the HCS was below the latitude of V1. The average passage times of the magnetic holes and proton boundary layers were the same during 2009 and 2011, because the plasma moved past V1 during 2009 at the same speed that V1 moved through the stagnation region during 2011. The microscale fluctuations of B in the stagnation region during 2011 are qualitatively the same as those observed in the heliosheath during 2009. These results suggest that the stagnation region is a part of the heliosheath, rather than a 'transition region' associated with the heliopause.

Burlaga, L. F. [NASA Goddard Space Flight Center, Code 673, Greenbelt, MD 20771 (United States); Ness, N. F., E-mail: lburlagahsp@verizon.net, E-mail: nfnudel@yahoo.com [Institute for Astrophysics and Computational Sciences, Catholic University of America, Washington, DC 20064 (United States)

2012-04-10

258

Longitudinal variation of the E-region electric fields caused by atmospheric tides  

Microsoft Academic Search

Polarization electric fields created by the E- and F-region dynamos cause the uplift of F-region plasma. The subsequent redistribution of that plasma along the magnetic field lines creates the equatorial ionospheric anomaly (EIA). Observations of the post-sunset EIA made by the IMAGE and TIMED satellites are compared here with CHAMP, Ørsted and SAC-C observations of the noontime equatorial electrojet (EEJ).

S. L. England; S. Maus; T. J. Immel; S. B. Mende

2006-01-01

259

Impact of the solar wind dynamic pressure on the Region 2 field-aligned currents  

Microsoft Academic Search

The relationship between the Region 2 field-aligned currents and the solar wind dynamic pressure is investigated using magnetic field data from Defense Meteorological Satellite Program-F13 (DMSP-F13). The generation of the Region 2 currents is associated with the direction of the magnetic pressure gradient in the magnetosphere, in relation to that of the thermal pressure gradient. Past spacecraft observations have suggested

S. Nakano; G. Ueno; S. Ohtani; T. Higuchi

2009-01-01

260

Electromagnetic field of a vertical electric dipole in the presence of a three-layered region  

Microsoft Academic Search

The electromagnetic field generated by a vertical electric dipole in the air over the surface of a two-layered region is determined for continuous-wave excitation. The region of interest consists of a conductor or dielectric with high permittivity, coated with an electrically thin layer of a dielectric under a half-space of air. Simple explicit formulas are derived for the field at

Ronald W. P. King; Sheldon S. Sandler

1994-01-01

261

Estimation of local and regional components of drain - flow from an irrigated field.  

National Technical Information Service (NTIS)

The contribution of regional ground water and deep percolation from a furrow irrigated field to total drain flow was estimated using salt load analysis. It was found that 64% of the drain flow comes from regional ground water flow. The electrical conducti...

S. O. Eching J. W. Hopmans W. W. Wallender J. L. Macyntyre D. Peters

1995-01-01

262

Relationship between Region 2 field-aligned current and the ring current: Model results  

Microsoft Academic Search

Detailed investigations on the relationship between the ring current and Region 2 field-aligned currents (FACs) have been tenuous. Using the Comprehensive Ring Current Model (CRCM), we first studied their relationship for two GEM storm events (22 April 2001 and 21 October 2001) through model and data comparison. The simulated Region 2 FACs for two different magnetic storm events capture major

Y. Zheng; A. T. Y. Lui; M.-C. Fok; B. J. Anderson; P. C. Brandt; T. J. Immel; D. G. Mitchell

2006-01-01

263

Three-dimensional magnetic field topology in a region of solar coronal heating  

Microsoft Academic Search

Flares and X-ray jets on the Sun arise in active regions where magnetic flux emerges from the solar interior amd interacts with the ambient magnetic field. The interactions are believed to occur in electric current sheets separating regions of opposite magnetic polarity. The current sheets located in the corona or upper chromosphere have long been thought to act as an

S. K. Solanki; A. Lagg; J. Woch; N. Krupp; M. Collados

2003-01-01

264

Flexible gas insulated transmission line having regions of reduced electric field  

DOEpatents

A gas insulated transmission line having radially flexible field control means for reducing the electric field along the periphery of the inner conductor at predetermined locations wherein the support insulators are located. The radially flexible field control means of the invention includes several structural variations of the inner conductor, wherein careful controlling of the length to depth of surface depressions produces regions of reduced electric field. Several embodiments of the invention dispose a flexible connector at the predetermined location along the inner conductor where the surface depressions that control the reduced electric field are located.

Cookson, Alan H. (Pittsburgh, PA); Fischer, William H. (Wilkins Township, Allegheny County, PA); Yoon, Kue H. (Pittsburgh, PA); Meyer, Jeffry R. (Penn Hills Township, Allegheny County, PA)

1983-01-01

265

Regional stress field in the lesser Antilles between Guadeloupe and Barbuda Islands  

Microsoft Academic Search

Microtectonic and extensometric measurements on the island of Basse-Terre in Guadeloupe are coherent with a homogeneous stress system (Julein and Bonneton, 1984).In order to compare the stress field obtained from the deep seismicity and the stress directions deduced from superficial observations, a method for determining the aspect ratio and the principal directions of the regional stress field from a set

Philippe Julien; Jean-Roger Bonneton

1989-01-01

266

Regional stress field in the Lesser Antilles between Guadeloupe and Barbuda Islands  

Microsoft Academic Search

Microtectonic and extensometric measurements on the island of Basse-Terre in Guadeloupe are coherent with a homogeneous stress system (Julien and Bonneton, 1984). In order to compare the stress field obtained from the deep seismicity and the stress directions deduced from superficial observations, a method for determining the aspect ratio and the principal directions of the regional stress field from a

Philippe Julien; Jean-Roger Bonneton

1989-01-01

267

Velocity, Density, and Magnetic Field Structure in High-Mass Star Forming Regions  

Microsoft Academic Search

To understand the detailed structure of four representative high-mass star forming regions, we have performed a comparative analysis of magnetic field structure; mass and velocity structure; and local features such as HII regions, outflows, and infrared sources. This work considers areas 5-15arcmin on a side in Orion A (BN\\/KL and Bar regions), NGC 2024, W3 Main, and M17. Primary data

S. J. Kannappan; A. A. Goodman

1995-01-01

268

Effects of conservation tillage on soil organic matter in paddy rice cultivation  

Microsoft Academic Search

In this study, the effect of conservation tillage on soil organic matter (SOM) in paddy rice cultivation after 10 yr was investigated. Four treatments, disk till-fallow (DTF), disk till-wheat (DTW), conservation till-fallow (CTF) and conservation till-wheat (CTW) were used. The results indicated that the combinative application of no-tillage, ridge culture and wheat cultivation was a sound conservation practice in paddy

Shao Jing'an; Tang Xiaohong; Wei Chaofu; Xie Deti

2007-01-01

269

Effect of bioaugmentation and nitrogen supplementation on composting of paddy straw  

Microsoft Academic Search

A composting experiment was conducted to evaluate the effect of a hyperlignocellulolytic fungal consortium and different nitrogen\\u000a amendments on paddy straw composting in terms of changes in physicochemical and biological parameters. A fungal consortium\\u000a comprising four lignocellulolytic mesophilic fungal cultures was used as inoculum for bioaugmentation of paddy straw in perforated\\u000a pits. The comparative effect of farmyard manure (FYM), soybean

Alok Kumar Pandey; Sunita Gaind; Arif Ali; Lata Nain

2009-01-01

270

Dehydration by Successive Pressure Drops for Drying Paddy Rice Treated by Instant Controlled Pressure Drop  

Microsoft Academic Search

The aim of the present work was to study the application of the dehydration by successive pressure drops (DDS) process to different varieties of paddy rice initially treated by the instantaneous controlled pressure drop (DIC), which is a high-temperature, short time postharvest treatment (moisture content about 20–25% dry basis) and takes less than 30 s. DIC paddy rice is dried by

Duong Thai Cong; Mazen Al Haddad; Zoulikha Rezzoug; Laurent Lefevre; Karim Allaf

2008-01-01

271

Numerical analyses of trapped field magnet and stable levitation region of HTSC  

SciTech Connect

Stable levitation with a permanent magnet and a bulk high {Tc} superconductor (HTSC) is examined numerically by using the critical state model and the frozen field model. Differences between a permanent magnet and a trapped field magnet are first discussed from property of levitation force. Stable levitation region of the HTSC on a ring magnet and on a solenoid coil are calculated with the numerical methods. Obtained results are discussed from difference of the magnetic field configuration.

Tsuchimoto, M.; Kojima, T.; Waki, H.; Honma, T. [Hokkaido Univ., Sapporo (Japan)

1995-05-01

272

The Evolution of Vector Magnetic Fields in an Emerging Flux Region  

NASA Astrophysics Data System (ADS)

Collaborative observations of NOAA Active Region 9231 were carried out during 9 days in 2000 November using the Advanced Stokes Polarimeter (ASP), Yohkoh/SXT, TRACE, and SOHO/MDI, in order to record the evolution of the photospheric magnetic field and its related coronal response. During this period an emerging flux region (EFR) appeared in the photosphere near the well-developed leading sunspot of this region, and subsequently bright bundles of coronal loops formed between the main concentrations of opposite magnetic polarity. The structure of the photospheric field comprising the EFR is classified into three regions: (1) the main bipolar magnetic flux of the EFR; (2) two small, rapidly emerging bipoles within the EFR; and (3) the remainder of the EFR excluding the other two regions. Two small, rapidly emerging bipoles are observed within a few hours of their first appearance at the photosphere. Examination of the vector magnetic field, its filling factor, and Doppler motion within the EFR shows that the young emerging magnetic field is nearly horizontal, the intrinsic field strength is weaker than that of the surrounding magnetic field (~500 G), and the weak field has a high filling factor (>80%) and upward motion (<1 km s-1). At both ends of the horizontal field structure we find that the magnetic field strength increases to about 1500 G and the filling factor drops to about 40% as the magnetic field becomes vertical in orientation during its first 12 hr. This field strength is typical of the field within the main bipolar magnetic flux, but the filling factor increases to 80% during the following 2 days. The process for organizing magnetic field configuration including convective collapse and flux concentration provides one possible explanation of the evolution of the field strength and the filling factor in the EFR. In addition, aymmetric surface distributions of magnetic field inclination were observed in the horizontal magnetic field area in the EFR. These asymmetric distributions were also observed in the small, young, emerging bipoles. This may mean that the magnetic field of the EFR is affected by the preexisting magnetic environment surrounding the EFR and that the emerging magnetic loops are deformed before or at the time they reach the photospheric level.

Kubo, M.; Shimizu, T.; Lites, B. W.

2003-09-01

273

Observations with the digital Crimean magnetograph of magnetic fields in active regions on the Sun.  

NASA Astrophysics Data System (ADS)

Presents the results of investigations of magnetic field structure in active regions outside spots. The observations of longitudinal magnetic fields were made with a new digital Crimean magnetograph in three lines, Fe I 525.3 nm, Fe II 523.4 nm, and Ti I 519.3 nm over eight days in 1997 and 1998. The magnetic flux in the smallest element was 4×109Wb and accounts for 4 - 9% of the total flux in active regions outside spots. The greatest part of the magnetic flux in active regions outside spots is concentrated in elements of size 1?- 8? The results of the observations are briefly discussed.

Gopasyuk, S. I.; Gopasyuk, O. S.; Zalesov, I. P.; Karkach, D. V.; Svistel'Nikov, V. V.; Shakhovskaya, A. N.

274

Development of bulk density, total C distribution and OC saturation in fine mineral fractions during paddy soil evolution  

NASA Astrophysics Data System (ADS)

Paddy soils are described as important accumulator for OM (Zhang and He, 2004). In southeast China, paddy soils have the second highest OM stocks (Zhao et al, 1997) and thus a large proportion of the terrestrial carbon is conserved in wetland rice soils. The paddy soil management is believed to be favorable for accumulation of organic matter, as its content in paddy soils is statistically higher than that of non-paddy soils (Cai, 1996). However, the mechanism of OM storage and the development of OM distribution during paddy soil evolution is largely unknown. The aim of the project is to identify the role of organo-mineral complexes for the stabilization of organic carbon during management-induced paddy soil formation in a chronosequence ranging from 50 to 2000 years of paddy soil use. The soil samples were analysed for bulk density, total organic carbon (TOC) and total inorganic carbon (TIC) concentrations of bulk soils and the concentration of organic carbon as well as the organic carbon stocks of physical soil fractions. First results indicate distinctly different depth distributions between paddy and non-paddy (control) sites. The paddy soils are characterized by relatively low bulk densities in the puddled layer (between 0.9 and 1.3 g cm-3) and high values in the plough pan (1.4 to 1.6 g cm-3) and the non-paddy soils by relatively homogeneous values throughout the profiles (1.3 to 1.4 g cm-3). In contrast to the carbonate-rich non-paddy sites, we found a significant loss of carbonates during paddy soil formation, resulting in decalcification of the upper 20 cm after 100 yr of paddy soil use, and decalcification of the total soil profile in 700, 1000 and 2000 yr old paddy soils. The calculation of the organic carbon stocks of each horizon indicate that paddy sites always have higher values in topsoils compared to non-paddy sites, and show increasing values with increasing soil age. The capacity of fine mineral fractions to preserve OC was calculated according to Hassink (1997). The potential capacity of paddy soil fraction to preserve OC is independently from soil age between 30 and 35.4 g OC (kg soil)-1. However, the calculated saturation level increases from 11.7 to 19.9 g OC (kg soil)-1 from 50 to 2000 y old paddy sites respectively. With increasing duration of paddy soil use, the fine fractions indicate an increasing saturation level from 33.1% to 56.2% of the potential capacity to preserve OC. This underlines the importance of fine fractions for increasing OC storage during paddy soil evolution. Conclusively, paddy soil management leads to an accelerated soil development compared to non-irrigated cropland sites. In addition, increasing OC stocks, especially in the fine mineral associated OM fractions underline the relevance of paddy soil management for OC sequestration. References Cai Z. (1996). Effect of land use on organic carbon storage in soils in eastern China. Water Air Soil Pollut 91, 383-393. Hassink J. (1997). The capacity of soil to preserve organic C and N by their association with clay and silt particles. Plant and Soil 191, 77-87. Zhang M., He Z. (2004). Long-term changes in organic carbon and nutrients of an Ultisol under rice cropping in southeast China. Geoderma 118, 167-179. Zhao C. (1996). Effect of land use on organic carbon storage in soils in eastern China. Water Air Soil Pollut 91, 383-393.

Wissing, Livia; Kölbl, Angelika; Cao, Zhi-Hong; Kögel-Knabner, Ingrid

2010-05-01

275

Convective-region geometry as the cause of Uranus' and Neptune's unusual magnetic fields.  

PubMed

The discovery of Uranus' and Neptune's non-dipolar, non-axisymmetric magnetic fields destroyed the picture--established by Earth, Jupiter and Saturn--that planetary magnetic fields are dominated by axial dipoles. Although various explanations for these unusual fields have been proposed, the cause of such field morphologies remains unexplained. Planetary magnetic fields are generated by complex fluid motions in electrically conducting regions of the planets (a process known as dynamo action), and so are intimately linked to the structure and evolution of planetary interiors. Determining why Uranus and Neptune have different field morphologies is not only critical for studying the interiors of these planets, but also essential for understanding the dynamics of magnetic-field generation in all planets. Here we present three-dimensional numerical dynamo simulations that model the dynamo source region as a convecting thin shell surrounding a stably stratified fluid interior. We show that this convective-region geometry produces magnetic fields similar in morphology to those of Uranus and Neptune. The fields are non-dipolar and non-axisymmetric, and result from a combination of the stable fluid's response to electromagnetic stress and the small length scales imposed by the thin shell. PMID:15014493

Stanley, Sabine; Bloxham, Jeremy

2004-03-11

276

Magnetic Field Topology and the Thermal Structure of the Corona over Solar Active Regions  

NASA Astrophysics Data System (ADS)

Solar extreme ultraviolet (EUV) images of quiescent active-region coronae are characterized by ensembles of bright 1-2 MK loops that fan out from select locations. We investigate the conditions associated with the formation of these persistent, relatively cool, loop fans within and surrounding the otherwise 3-5 MK coronal environment by combining EUV observations of active regions made with TRACE with global source-surface potential-field models based on the full-sphere photospheric field from the assimilation of magnetograms that are obtained by the Michelson Doppler Imager (MDI) on SOHO. We find that in the selected active regions with largely potential-field configurations these fans are associated with (quasi-)separatrix layers (QSLs) within the strong-field regions of magnetic plage. Based on the empirical evidence, we argue that persistent active-region cool-loop fans are primarily related to the pronounced change in connectivity across a QSL to widely separated clusters of magnetic flux, and confirm earlier work that suggested that neither a change in loop length nor in base field strengths across such topological features are of prime importance to the formation of the cool-loop fans. We discuss the hypothesis that a change in the distribution of coronal heating with height may be involved in the phenomenon of relatively cool coronal loop fans in quiescent active regions.

Schrijver, Carolus J.; DeRosa, Marc L.; Title, Alan M.

2010-08-01

277

Spatial Pattern of Glaucomatous Visual Field Loss Obtained with Regionally Condensed Stimulus Arrangements  

PubMed Central

Purpose. To assess the spatial distribution of glaucomatous visual field defects (VFDs) obtained with regionally condensed stimulus arrangements. Methods. Sixty-three eyes of 63 glaucoma subjects were examined with threshold-estimating automated static perimetry (full threshold 4-2-1 dB strategy with at least three reversals) on an automatic campimeter or a full-field perimeter. Stimuli were added by the examiner to regionally enhance spatial resolution in regions that were suspicious for a glaucomatous VFD. These regions were characterized by contiguous local VFDs, attributable to the retinal nerve fiber bundle course according to the impression of the examiner. The added stimulus locations were subsets of a predefined, dense perimetric grid. All VFD locations with P < 0.05 (total deviation plots) were assessed by superimposing the visual field records of all participants. Results. Glaucomatous VFD loss occurred more frequently in the upper than in the lower hemifield, with a typical retinal nerve fiber-related pattern and a preference of the nasal step region. More than 50% of the eyes with predominantly mild to moderate glaucomatous field loss showed defective locations in the immediate superior paracentral region within an eccentricity of 3°. Conclusions. Conventional thresholding white-on-white perimetry with regionally enhanced spatial resolution reveals that glaucomatous visual field loss affects the immediate paracentral area, especially the upper hemifield, in many eyes with only mild to moderate glaucomatous visual field loss. Detailed knowledge about the spatial pattern and the local frequency distribution of glaucomatous VFDs is an essential prerequisite for creating regionally condensed stimulus arrangements for adequate detection and follow-up of functional glaucomatous damage.

Papageorgiou, Eleni; Sample, Pamela A.; Pascual, John P.; Selig, Bettina; Krapp, Elke; Paetzold, Jens

2010-01-01

278

[Dynamics of polycyclic aromatic hydrocarbons (PAHs) in the paddy-soil system during the crop rotation process].  

PubMed

The concentrations of polycyclic aromatic hydrocarbons (PAHs) in the paddy root-soil system were determined to study the dynamic and the influencing factors during crop rotation period. It showed that the dynamic of PAHs in paddy roots was most correlative with the factor of root surface area, but less correlated with PAHs in air and particles, which indicates that the physiological characters rather than the environment media are the main factors influencing the PAHs accumulation in paddy roots. According to the EPA risk standard about BaP and sigma PAHs, the PAHs accumulation in the paddy seeds won't decrease the food security to human being. The PAHs concentrations in paddy soil showed a declined trend during the period of paddy growth, which was affected not only by the processes of water elution and microbe degradation, but also depended on the absorption rate of paddy roots. When the crop rotation begins and paddy planting rolls into the next growing period, the PAHs in the paddy soil will again increase into a higher level which is correlated with the TOC content in the soil. PMID:20825036

Jiao, Xing-chun; Ye, Chuan-yong; Chen, Su-hua; Yang, Yong-liang; Wu, Zhen-yan

2010-07-01

279

Surface electrostatic field below weak precipitation and stratiform regions of mid-latitude storms  

NASA Astrophysics Data System (ADS)

The electrostatic field is measured below thunderstorms at two sites in south-western France thanks to a field mill. It is recorded with a 1-s time resolution, simultaneously to the precipitation current measured with a specific sensor. The variations of both parameters are analyzed for two cases out of three storms considered in the study. Cloud-to-Ground (CG) lightning data from Météorage network and scans from a C-band radar included in the French network ARAMIS are used to characterize the storms. The magnitude of the electrostatic field can reach large values below the weak precipitation regions compared to the convective regions: between 5 and 6 kV m? 1, and between 2 and 3 kV m? 1, respectively. The field polarity is commonly negative (downward field) but it can reverse as the rainfall carries positive charge to the ground. So, the mirror effect is generally observed between the electrostatic field and the precipitation current. The electrostatic field magnitude can indicate the presence of large amounts of charge within the weak precipitation region above, although the lightning ground strokes remain relatively far. The fast field variations produced by CG flashes are analyzed. A strong dissymmetry for both CG polarities is observed: the + CG flashes can produce larger field discontinuities (~ 10 kV m? 1) even when their striking points are at about a distance of 40 km from the sensor, while the ? CG flashes produce discontinuities lower than 4 kV m? 1 even when the striking points are within 4 km around the sensor. This indicates that either the charge removed by a + CG flash can be horizontally displaced with respect to the ground stroke location, or it can be much larger compared to that removed by a negative CG flash. Our observations suggest the surface electrostatic field measured below these regions may provide valuable information for estimating local lightning risk.

Soula, S.; Georgis, J. F.

2013-10-01

280

Stationary large-scale magnetic fields generated by turbulent motion in a spherical region  

SciTech Connect

Stationary large-scale magnetic fields generated by an electrically conducting fluid in a spherical region are examined analytically, using the concept of the turbulent dynamo based on helicity and cross-helicity effects. Under this concept, the toroidal magnetic field is induced through the combination of a rotational motion and the turbulent cross-helicity effect. This field generates the poloidal one through the turbulent residual-helicity (alpha) effect. A new magnetic-field generation mechanism in the vicinity of the poles is also described. These findings are discussed in the context of the dimension of the convection part of a stellar object. {copyright} {ital 1996 American Institute of Physics.}

Yoshizawa, A.; Yokoi, N. [Institute of Industrial Science, University of Tokyo, Roppongi, Minato-ku, Tokyo 106 (Japan)

1996-10-01

281

Measurement evaluations of static and low frequency magnetic fields in the near field region  

Microsoft Academic Search

Manmade electromagnetic (EM) field in the low frequency range of the spectrum, from static to 200kHz has caused interference with electronic equipment and poses a possible public health risk. Typical sources of these EM emissions include television sets, video display terminals (VDT), electric appliances, fluorescent lights, certain medical devices, walk-through and hand-held detectors, radio stations, induction heating, wireless electricity delivered

Saba A. Hanna; Yuichi Motai; Walter Varhue; Steve Titcomb

2011-01-01

282

Twistness and Connectivity of Magnetic Field Line in the Solar Active Region NOAA 10930  

NASA Astrophysics Data System (ADS)

Solar active regions are the primary driver of the solar active phenomena, and therefore the understanding of the three-dimensional (3D) magnetic structure on active regions is crucially important to reveal the mechanism of the solar active phenomena. The purpose of this study is to clarify the topological features in magnetic field such as the connectivity and the twistness of magnetic field lines on the solar active region NOAA 10930, which had produced an X3.4 class flare on Dec.13, 2006, and coronal mass ejection (CME) causing the substorm and ionospheric storm in our geo-space. 3D magnetic field was reconstructed in term of the Non-Linear Force-Free Field (NLFFF) approximation and the vector magnetic field data observed by the solar physics satellite Hinode. First, we reconstructed the typical field lines of the NLFFF corresponding to six hours prior to the flare onset, and compared them with the flare ribbons of Ca II images observed in the early phase of flare by Hinode/SOT. As a result, it was found that the location of the two foot-points of magnetic field lines well corresponds to the flare ribbons. This result indicates that the NLFFF well capture the 3D structure of magnetic field in the flaring region, even though the structure was very complicated. Second, we have performed the quantitative analysis of twistness of magnetic field, and found that the twist of magnetic field lines was less than one turn, although the twistness increased until the onset of the flare. This result implies that the active region might be stable to the kink mode instability at least six hours prior to the flare onset. Finally, it is also found that the twistness of field lines rootedon the regions where the ribbons had been strongly illuminated was drastically weakened after the flare. It can be explained well as a consequence of reconnection of twisted magnetic field. We will also report the relationship between the time evolution of the two-ribbon structure and Qusi-Separatrix Layer (QSL), to discuss reconnection dynamics in flare.

Inoue, S.; Kusano, K.; Magara, T.

2010-12-01

283

Unitary inhibitory field potentials in the CA3 region of rat hippocampus  

PubMed Central

Glickfeld and colleagues (2009) suggested that single hippocampal interneurones generate field potentials at monosynaptic latencies. We pursued this obervation in simultaneous intracellular and multiple extracellular records from the CA3 region of rat hippocampal slices. We confirmed that interneurones evoked field potentials at monosynaptic latencies. Pyramidal cells initiated disynaptic inhibitory field potentials, but did not initiate detectable monosynaptic excitatory fields. We confirmed that inhibitory fields were GABAergic in nature and showed they were suppressed at low external Cl?, suggesting they originate at postsynaptic sites. Field potentials generated by a single interneurone were detected at multiple sites over distances of more than 800 ?m along the stratum pyramidale of the CA3 region. We used arrays of extracellular electrodes to examine amplitude distributions of spontaneous inhibitory fields recorded at sites orthogonal to or along the CA3 stratum pyramidale. Cluster analysis of spatially distributed inhibitory field events let us separate events generated by interneurones terminating on distinct zones of somato-dendritic axis. Events generated at dendritic sites had similar amplitudes but occurred less frequently and had somewhat slower kinetics than perisomatic events generated near the stratum pyramidale. In records from multiple sites in the CA3 stratum pyramidale, we distinguished inhibitory fields that seemed to be initiated by interneurones with spatially distinct axonal arborisations.

Bazelot, Michael; Dinocourt, Celine; Cohen, Ivan; Miles, Richard

2010-01-01

284

Magnetic fields, stellar feedback, and the geometry of H II regions  

NASA Astrophysics Data System (ADS)

Magnetic pressure has long been known to dominate over gas pressure in atomic and molecular regions of the interstellar medium. Here I review several recent observational studies of the relationships between the H+, H0 and H2 regions in M42 (the Orion complex) and M17. A simple picture results. When stars form they push back surrounding material, mainly through the outward momentum of starlight acting on grains, and field lines are dragged with the gas due to flux freezing. The magnetic field is compressed and the magnetic pressure increases until it is able to resist further expansion and the system comes into approximate magnetostatic equilibrium. Magnetic field lines can be preferentially aligned perpendicular to the long axis of quiescent cloud before stars form. After star formation and pushback occurs ionized gas will be constrained to flow along field lines and escape from the system along directions perpendicular to the long axis. The magnetic field may play other roles in the physics of the H II region and associated PDR. Cosmic rays may be enhanced along with the field and provide additional heating of atomic and molecular material. Wave motions may be associated with the field and contribute a component of turbulence to observed line profiles.

Ferland, Gary J.

2009-04-01

285

Flat field concave holographic grating with broad spectral region and moderately high resolution.  

PubMed

In order to deal with the conflicts between broad spectral region and high resolution in compact spectrometers based on a flat field concave holographic grating and line array CCD, we present a simple and practical method to design a flat field concave holographic grating that is capable of imaging a broad spectral region at a moderately high resolution. First, we discuss the principle of realizing a broad spectral region and moderately high resolution. Second, we provide the practical method to realize our ideas, in which Namioka grating theory, a genetic algorithm, and ZEMAX are used to reach this purpose. Finally, a near-normal-incidence example modeled in ZEMAX is shown to verify our ideas. The results show that our work probably has a general applicability in compact spectrometers with a broad spectral region and moderately high resolution. PMID:22307123

Wu, Jian Fen; Chen, Yong Yan; Wang, Tai Sheng

2012-02-01

286

Regional long-term co-operation in the field of nuclear and radiation emergency preparedness.  

PubMed

Emergency preparedness is generally covered by methodical and coordinative activities of the International Atomic Energy Agency (IAEA) in Member States of the IAEA and by the European Commission (EC) in EU Member and EU Accession Countries. However, the regional harmonisation of emergency arrangements is an important trend of emergency preparedness. The present paper gives a couple of illustrative examples for a regional co-operation in the field of emergency preparedness in Central Europe and an overview on international exercises in this region. The penultimate section contains an outlook on future activities regarding regional co-operation in Central Europe. The following topics have been suggested inter alia: the harmonisation of intervention criteria and countermeasures, co-ordination in the field of information of the public, comprehensive bi lateral and multilateral exercises, exchange of experts between the national nuclear emergency centres and inter-comparison calculations of the computer codes. PMID:15238659

Sladek, V; Metke, E; Janko, K; Hohenberg, J-K; Hofer, P

2004-01-01

287

Downward carbon transport in a 2000-year rice paddy soil chronosequence traced by radiocarbon measurements  

NASA Astrophysics Data System (ADS)

Paddy and non-paddy soils from a chronosequence of 50–2000 years of agricultural use, developed on former estuarine sediments of the Yangtze River, were sampled near Cixi, Zhejiang Province, China, in the framework of the Research Unit "Biogeochemistry of paddy soil evolution" of the German Research Foundation (DFG). In addition samples of Yangtze River estuarine sediments were obtained. The parent sediment shows a fairly homogeneous composition with ca. 0.3% TOC and a 14C concentration of ca. 50 pMC. After being diked-in, gradients in soil organic carbon and 14C concentration develop under the influence of vegetation and cultivation. In the non-paddy soil, a 14C gradient with concentration decreasing with increasing depth from modern (>100 pMC) to original sediment values around 50 pMC is already established after 50 years and can also be observed in the older sites. In contrast, the 50 years old paddy soil shows organic carbon and 14C enrichment only in the A-horizon and a nearly constant TOC and 14C stock of original sediment below the plough pan. To test the basic approach that the soil profile development started on homogeneous sediment, an isotope and mass balance calculation was used. The results show a quite similar age composition of different sample sites. Paddy rice cultivation quickly leads to a dense plough pan, which seriously reduces, but not totally prevents, downward transport of organic matter. The equilibrium times for TOC and 14C in paddy soil profiles are short (decades) in the topsoil and in the order of centuries in the subsoil, underlining the dynamic character of soil organic carbon.

Bräuer, T.; Grootes, P. M.; Nadeau, M.-J.; Andersen, N.

2013-01-01

288

FAST observations of perpendicular DC electric field structures in downward current regions : Implications  

NASA Astrophysics Data System (ADS)

FAST electric field data and ion drift moments are combined to allow full DC E field studies of auroral return current regions. Statistical comparison of 71 return current potential structures showed several differences between linearly structured perpendicular E field events, where the ratio of the two E field components remains constant during the spacecraft crossing, and curved structures where the ratio varies. Linear structures can be interpreted as straight arcs, but curved structures require gradients in another dimension. We define a parameter eta, which is a comparison of the potential at the spacecraft and the upgoing electron characteristic energy. eta implies how much ionospheric fields which map up from the lower ionosphere are overlapped on typical U-shaped potentials. The influence of ionospheric fields on return current potential structures has been seen in previous numerical predictions. From our parameter study, it is found that ionospheric effects are dominant in linear structures and U-shaped potential models are mostly consistent with curved events. This result implies that the divergent electric fields of the downward current region seen by FAST are caused by both ionospheric fields and by U-shaped potentials. The spatial structure of the events, as indicated by the ratio of the E field components, allows us to distinguish them. Statistical studies of scale sizes, magnitudes of electric fields and magnetic perturbations and downward current density, sorted by the parameter eta, reveal various interesting features. We attempt to explain these properties on the basis of different potential models for linear and curved structures, which have important implications for models of the formation and evolution of potential structures for downward current regions.

Hwang, K.; Lynch, K. A.; Carlson, C. W.; Bonnell, J. W.; Peria, W. J.

2005-12-01

289

Evaluation of origins of CH4 carbon emitted from rice paddies  

NASA Astrophysics Data System (ADS)

Possible carbon sources for CH4 emitted from rice paddies are organic matter applied to the fields, such as rice straw (RS), soil organic matter (SOM), and carbon supplied from rice plants (RP), such as exudates and sloughed tissues. To estimate the contribution of each carbon source to CH4 emission, a pot experiment was conducted using 13C-enriched soil sample and 13C-enriched RS as tracers. The percentage contribution of RP carbon was estimated by subtraction. When RS was applied at a rate corresponding to 6 t ha-1, the percentage contributions of RS, SOM, and RP carbon to CH4 emission throughout the period of rice growth were 42%, 18-21%, and 37-40%, respectively. The values for SOM and RP carbon for the treatment in which RS was not applied were 15-20% and 80-85%, respectively. Seasonal variations in the percentage contribution of soil organic carbon to CH4 emission were small in the range between 13% and 30% for the pots with RS and between 15% and 24% for the pots without RS. In the RS-applied treatment, RS and SOM accounted for almost 100% of the CH4 carbon early in the period of rice growth, while 65-70% of the CH4 emission in the milky stage was derived from RP carbon.

Watanabe, Akira; Takeda, Takuya; Kimura, Makoto

1999-10-01

290

[Dynamics of active organic carbon in a paddy soil under different rice farming modes].  

PubMed

A field experiment was conducted to study the dynamics of dissolved organic carbon (DOC), readily oxidizable organic carbon (ROC), and microbial biomass carbon (MBC) in a paddy soil under integrated rice-duck farming (RD), intermittent irrigation (RW), and conventional flooded irrigation (CK), the three rice farming modes typical in southern China. Under these three farming modes, the soil DOC and MBC contents reached the highest during the period from rice booting to heading, while the soil ROC content had less change during the whole rice growth period. Two-factor variance analysis showed that soil MBC was greatly affected by rice growth stage, soil DOC was greatly affected by rice growth stage and farming mode, and soil ROC was mainly affected by farming mode. Comparing with CK, RD significantly increased the soil DOC and ROC contents and their availability, while RW significantly decreased the soil DOC content and its availability but increased the soil ROC content and its availability. No significant differences were observed in the soil MBC and microbial quotient among RD, RW, and CK. PMID:21043109

Zhan, Ming; Cao, Cou-Gui; Jiang, Yang; Wang, Jin-Ping; Yue, Li-Xin; Cai, Ming-Li

2010-08-01

291

Observations of PC5 pulsations near field-aligned current regions  

Microsoft Academic Search

Examples of long period Pc5 magnetic field pulsations near field-aligned current (FAC) regions in the high-latitude magnetosphere,\\u000a observed by INTERBALL-Auroral satellite during January 11, April 11 and June 28, 1997 are shown. Identification of corresponding\\u000a magnetosphere regions and subregions is provided by electrons and protons in the energy-range of 0.01–100 keV measured simultaneously\\u000a onboard the spacecraft. The examined Pc5 pulsations

Alexander Z. Bochev; Karel Kudela; Iren A. Dimitrova; Petko Nenovski; Ashwini K. Sinha; Marián Slivka

2009-01-01

292

Velocity, Density, and Magnetic Field Structure in High-Mass Star Forming Regions  

NASA Astrophysics Data System (ADS)

To understand the detailed structure of four representative high-mass star forming regions, we have performed a comparative analysis of magnetic field structure; mass and velocity structure; and local features such as HII regions, outflows, and infrared sources. This work considers areas 5-15arcmin on a side in Orion A (BN/KL and Bar regions), NGC 2024, W3 Main, and M17. Primary data include (13) CO J=1-0 maps with 50arcsec spatial resolution and 0.1 km\\:s(-1) velocity resolution as well as 100 micron dust emission polarization maps with 35arcsec resolution (provided by J.L. Dotson, C.D. Dowell, D. Schleuning, and R.H. Hildebrand). These recently obtained emission polarization maps represent reliable probes of the projected magnetic field direction in dense clouds. We isolate velocity components in the spectra and then go on to analyze patterns in linewidth, component velocity, column density, polarization percentage, polarization direction, and dispersion in polarization position angle. Our analysis also makes use of field strength measurements and other data in the literature to form a coherent physical picture of what is happening in each source. By comparing the relative importance of magnetic, kinetic, and gravitational energies as well as the dynamical significance of such energetic features as HII regions and outflows, we evaluate the role of the magnetic field in each region.

Kannappan, S. J.; Goodman, A. A.

1995-12-01

293

Phase space structure of the electron diffusion region in reconnection with weak guide fields  

NASA Astrophysics Data System (ADS)

Kinetic simulations of magnetic reconnection provide detailed information about the electric and magnetic structure throughout the simulation domain, as well as high resolution profiles of the essential fluid parameters including the electron and ion densities, flows, and pressure tensors. However, the electron distribution function, f(v), within the electron diffusion region becomes highly structured in the three dimensional velocity space and is not well resolved by the data available from the particle-in-cell (PIC) simulations. Here, we reconstruct the electron distribution function within the diffusion region at enhanced resolution. This is achieved by tracing electron orbits in the fields taken from PIC simulations back to the inflow region where an analytic form of the magnetized electron distribution is known. For antiparallel reconnection, the analysis reveals the highly structured nature of f(v), with striations corresponding to the number of times electrons have been reflected within the reconnection current layer, and exposes the origin of gradients in the electron pressure tensor important for momentum balance. The structure of the reconnection region is strongly tied to the pressure anisotropy that develops in the electrons upstream of the reconnection region. The addition of a guide field changes the nature of the electron distributions, and the differences are accounted for by studying the motion of single particles in the field geometry. Finally, the geometry of small guide field reconnection is shown to be highly sensitive to the ion/electron mass ratio applied in the simulation.

Ng, J.; Egedal, J.; Le, A.; Daughton, W.

2012-11-01

294

Phase space structure of the electron diffusion region in reconnection with weak guide fields  

SciTech Connect

Kinetic simulations of magnetic reconnection provide detailed information about the electric and magnetic structure throughout the simulation domain, as well as high resolution profiles of the essential fluid parameters including the electron and ion densities, flows, and pressure tensors. However, the electron distribution function, f(v), within the electron diffusion region becomes highly structured in the three dimensional velocity space and is not well resolved by the data available from the particle-in-cell (PIC) simulations. Here, we reconstruct the electron distribution function within the diffusion region at enhanced resolution. This is achieved by tracing electron orbits in the fields taken from PIC simulations back to the inflow region where an analytic form of the magnetized electron distribution is known. For antiparallel reconnection, the analysis reveals the highly structured nature of f(v), with striations corresponding to the number of times electrons have been reflected within the reconnection current layer, and exposes the origin of gradients in the electron pressure tensor important for momentum balance. The structure of the reconnection region is strongly tied to the pressure anisotropy that develops in the electrons upstream of the reconnection region. The addition of a guide field changes the nature of the electron distributions, and the differences are accounted for by studying the motion of single particles in the field geometry. Finally, the geometry of small guide field reconnection is shown to be highly sensitive to the ion/electron mass ratio applied in the simulation.

Ng, J.; Egedal, J.; Le, A. [Department of Physics, and Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Daughton, W. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2012-11-15

295

Low-Frequency Noise Generated from High-Field Region in AlGaAs\\/InGaAs HEMTs  

Microsoft Academic Search

We have investigated the effects of a high-field region on low-frequency noise (LFN) in AlGaAs\\/InGaAs HEMTs using a two-region model and experiments. The negative cross-correlation between the LFN generated from a low-field region and that from a high-field region is found for the first time. This negative cross-correlation depends on gate and drain voltages, and increases with gate voltage. Due

Masanori Wada; Takayuki Nakamoto; Shinichi Hamayoshi; Katsuhiko Higuchi

2005-01-01

296

Open-pit coal-mining effects on rice paddy soil composition and metal bioavailability to Oryza sativa L. plants in Cam Pha, northeastern Vietnam.  

PubMed

This study quantified Cd, Pb, and Cu content, and the soil-plant transfer factors of these elements in rice paddies within Cam Pha, Quang Ninh province, northeastern Vietnam. The rice paddies are located at a distance of 2 km from the large Coc Sau open-pit coal mine. Electron microprobe analysis combined with backscattered electron imaging and energy-dispersive spectroscopy revealed a relatively high proportion of carbon particles rimmed by an iron sulfide mineral (probably pyrite) in the quartz-clay matrix of rice paddy soils at 20-30 cm depth. Bulk chemical analysis of these soils revealed the presence of Cd, Cu, and Pb at concentrations of 0.146?±?0.004, 23.3?±?0.1, and 23.5?±?0.1 mg/kg which exceeded calculated background concentrations of 0.006?±?0.004, 1.9?±?0.5, and 2.4?±?1.5 mg/kg respectively at one of the sites. Metals and metalloids in Cam Pha rice paddy soils, including As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, and Zn, were found in concentrations ranging from 0.2?±?0.1 to 140?±?3 mg/kg, which were in close agreement with toxic metal contents in mine tailings and Coc Sau coal samples, suggesting mining operations as a major cause of paddy soil contamination. Native and model Oryza sativa L. rice plants were grown in the laboratory in a growth medium to which up to 1.5 mg/kg of paddy soil from Cam Pha was added to investigate the effects on plant growth. A decrease in growth by up to 60 % with respect to a control sample was found for model plants, whereas a decrease of only 10 % was observed for native (Nep cai hoa vang variety) rice plants. This result suggests an adaptation of native Cam Pha rice plants to toxic metals in the agricultural lands. The Cd, Cu, and Pb contents of the native rice plants from Cam Pha paddies exceeded permitted levels in foods. Cadmium and Pb were highest in the rice plant roots with concentrations of 0.84?±?0.02 and 7.7?±?0.3 mg/kg, suggesting an intake of these metals into the rice plant as shown, for example, by Cd and Pb concentrations of 0.09?±?0.01 and 0.10?±?0.04 mg/kg respectively in the rice grain endosperm. The adaptation of native rice plants, combined with bioaccumulation ratios of 1?±?0.6 to 1.4?±?0.7 calculated for Cd transfer to the rice grain endosperm, and maximum Cd transfer factors of 4.3?±?2.1 to the plant roots, strongly suggest a continuous input of some toxic metals from coal-mining operations to agricultural lands in the region of Cam Pha. In addition, our results imply a sustained absorption of metals by native rice plant varieties, which may lead to metal accumulation (e.g., Cd) in human organs and in turn to severe disease. PMID:23990254

Martinez, Raul E; Marquez, J Eduardo; Hòa, Hoàng Th? Bích; Gieré, Reto

2013-08-30

297

Fast Auroral Snapshot observations of perpendicular DC electric field structures in downward auroral current regions: Morphology  

NASA Astrophysics Data System (ADS)

We present an analysis of Fast Auroral Snapshot perpendicular electric field observations using both ion distributions and electric field measurements in auroral downward current regions to study the full DC E? (electric field perpendicular to the geomagnetic field) and potential structures. We use the electric field data from the field instrument for the spin-plane component of E?, and the ion drift measurements for the axial DC E?. Examining 71 return current region crossings, a significant fraction (more than half) show E? signatures during strong field events indicative of curved potential structures rather than idealized straight arcs. We define sheetlike structured events as those for which the ratio of the two E? components remains constant during the spacecraft crossing, and curved structures as those where the ratio varies. Sheetlike structures can be interpreted as straight arcs, but curved structures require gradients in another dimension. A statistical comparison shows parametric differences between sheetlike and curved structures; however, the distinction between sheetlike and curved events cannot be sorted clearly using j?, E?, or scale length. Using the full DC electric field vector, we can investigate the morphology of auroral return current potential structures and inconsistencies with idealized static return current models. In this paper we present the observed spatial structures; in a companion paper we explore the implications of these observations.

Hwang, K.-J.; Lynch, K. A.; Carlson, C. W.; Bonnell, J. W.; Peria, W. J.

2006-09-01

298

Contextual detection of ischemic regions in ultra-wide-field-of-view retinal fluorescein angiograms  

Microsoft Academic Search

We report a novel prototype algorithm using contextual knowledge to locate ischemic regions in ultra- wide-field-of-view retinal fluorescein angiograms. We use high- resolution images acquired by an Optos ultra-wide-field-of- view (more than 200 degrees) scanning laser ophthalmoscope. We leverage the simultaneous occurrence of ischemia with a number of other signs, detected automatically, typical for the state of progress of the

E. Trucco; C. R. Buchanan; T. Aslam; B. Dhillon

2007-01-01

299

Observations with the digital Crimean magnetograph of magnetic fields in active regions on the Sun  

Microsoft Academic Search

Presents the results of investigations of magnetic field structure in active regions outside spots. The observations of longitudinal magnetic fields were made with a new digital Crimean magnetograph in three lines, Fe I 525.3 nm, Fe II 523.4 nm, and Ti I 519.3 nm over eight days in 1997 and 1998. The magnetic flux in the smallest element was 4×109Wb

S. I. Gopasyuk; O. S. Gopasyuk; I. P. Zalesov; D. V. Karkach; V. V. Svistel'Nikov; A. N. Shakhovskaya

1999-01-01

300

Phase variations of ULF magnetic field in the region of fault tectonics  

NASA Astrophysics Data System (ADS)

The experiment on phase measurements of three components of a ULF magnetic field generated by a high-power controlled source in the region dominated by fault tectonics is described. The measurements were carried out along two orthogonal directions. It is established that the phase sharply varies by about 180° between some measurement points. The phase jumps are found to be confined to the conductive geological faults, which opens the possibility of locating the faults using the phases of ELF magnetic fields.

Tereshchenko, E. D.; Poluyanov, S. V.; Grigor'ev, V. F.; Tereshchenko, P. E.; Sidorenko, A. E.

2012-09-01

301

On a plasma sheath separating regions of oppositely directed magnetic field  

Microsoft Academic Search

Summary  An exact solution of the Vlasov equations is found which describes a layer of plasma confined between two regions of oppositely\\u000a directed magnetic field. The electrons and ions have Maxwellian distributions on the plane where the magnetic field vanishes.\\u000a In the coordinate system, in which the electron and ion drift velocities are equal in magnitude but opposite in direction,\\u000a the

E. G. Harris

1962-01-01

302

Periodic auroral forms and geomagnetic field oscillations in the 1400 MLT region  

SciTech Connect

The UV images obtained with the Viking satellite often show bright features which resemble beads or pearls aligned in the east-west direction between noon and 1800 MLT. Viking acquired a series of 25 UV images during a 28-min period on July 29, 1986, which showed a distinct series of periodic bright features in this region. Magnetic field and hot plasma measurements obtained by Viking confirm that the UV emissions are colocated with the field line projection of an upward-flowing region 1 Birkeland current and precipitating energetic ({approximately}200 eV) electrons. The magnetic field and electric field measurements show transverse oscillations with a nearly constant period of about 3.5 min from 67{degree} invariant latitude equatorward up to the location of the large-scale Birkeland current system near 76{degree} invariant latitude. The electric field oscillations lead the magnetic field oscillations by about a quarter-period. The authors interpret the observed oscillations as standing Alfven waves driven at a frequency near the local resonance frequency by a large-scale wave in the boundary layer. They propose that the energy flux of the precipitating low-energy electrons in this afternoon region is modulated by this boundary wave and produces the periodic UV emission features. The results of this study support the view that large-scale oscillations of magnetospheric boundaries, possibly associated with the Kelvin-Helmholtz instability, can modulate currents, particles, and auroral forms.

Potemra, T.A. (Johns Hopkins Univ., Laurel, MD (United States)); Vo, H.; Venkatesan, D.; Cogger, L.L. (Univ. of Calgary, Alberta (Canada)); Erlandson, R.E.; Zanetti, L.J.; Bythrow, P.F.; Anderson, B.J. (Johns Hopkins Univ., Laurel, MD (United States))

1990-05-01

303

Knob fields in the Terra Cimmeria/Terra Sirenum region of Mars: Stratigraphy, mineralogy and morphology  

NASA Astrophysics Data System (ADS)

We investigate the stratigraphy, morphology and mineralogy of five major knob fields in the region between Terra Cimmeria and Terra Sirenum on Mars based on HRSC, CTX, MOC and HiRISE imagery together with hyperspectral data from CRISM. The knob fields comprise Ariadnes Colles, Atlantis Chaos and Gorgonum Chaos and further, unnamed fields of mounds. They have been mapped in previous studies as Hesperian or Amazonian units and are located within the shoreline of the proposed "Eridania lake", the putative source of Ma'adim Vallis. The mounds contain Mg/Fe-bearing phyllosilicates and locally Al-rich phyllosilicates. Our geological mapping shows that the knob fields have a late Noachian age, which indicates later phyllosilicate formation than typically observed on Mars. The knob fields formed by alteration of the "Electris deposit", an airfall deposit possibly rich in basaltic glass (Grant, J.A., Schultz, P.H. [1990]. Icarus 84, 166-195), in local depressions, possibly in the Eridania lake. The spectroscopic detection of phyllosilicates here may indicate that liquid water persisted longer in this region than elsewhere on Mars. The knob fields are embayed by the Hesperian ridged plains. Numerous valleys carve into the ridged plains and document that the aqueous history of this region continued into the Hesperian and Amazonian. The study area is traversed by the Sirenum Fossae. These graben appear to post-date the aqueous activity in the study area except in the Gorgonum basin, where a lake developed after their formation.

Wendt, Lorenz; Bishop, Janice L.; Neukum, Gerhard

2013-07-01

304

Entanglement entropy in conformal field theory: new results for disconnected regions  

NASA Astrophysics Data System (ADS)

The study of the entanglement properties of the ground-state of extended quantum systems has propelled an intense research activity at the crossroads of different disciplines such as statistical mechanics, quantum information, and quantum field theory. Quantifying the entanglement allowed an elegant and more precise characterization of many extended quantum systems. I present the results for one-dimensional systems at a quantum critical point that are described by a conformal invariant field theory. In particular, I present some recent results on the entanglement of disconnected regions and I discuss how these investigations reveal important features of the underlying conformal field theory.

Calabrese, Pasquale

2010-09-01

305

Low-Frequency Noise Generated from High-Field Region in AlGaAs/InGaAs HEMTs  

NASA Astrophysics Data System (ADS)

We have investigated the effects of a high-field region on low-frequency noise (LFN) in AlGaAs/InGaAs HEMTs using a two-region model and experiments. The negative cross-correlation between the LFN generated from a low-field region and that from a high-field region is found for the first time. This negative cross-correlation depends on gate and drain voltages, and increases with gate voltage. Due to this negative cross-correlation, the observed LFN is almost constant because the cross-correlation cancels out the increase in the LFN generated from the low-field region.

Wada, Masanori; Nakamoto, Takayuki; Hamayoshi, Shinichi; Higuchi, Katsuhiko

2005-04-01

306

Martian ionospheric conductivities in the magnetic pileup and crustal field regions  

NASA Astrophysics Data System (ADS)

The Martian ionosphere is permeated by an extremely variable magnetic field that results from both the interplanetary magnetic field and the palaeomagnetic fields that emanate from magnetized portions of the planet's crust. This spatially and temporally varying magnetic field directly affects the ion and electron gyrofrequencies. In turn, the magnetic field and gyrofrequencies, together with the collision frequencies and the electron concentration, determine the parallel, Pedersen and Hall conductivities that characterize current flow in the ionosphere. We present the findings of an investigation of these conductivities undertaken using data obtained by the Mars Global Surveyor (MGS) and Mars Express (MEX) spacecraft. The magnetic field data were collected by MGS during the aerobraking phase of its mission, while the modelled electron concentration is consistent with data obtained by MEX. Results are shown from a region with strong crustal fields and also from an area where the magnetic pileup region may be identified clearly. The altitudinal dependence of the calculated conductivities is generally characterized by three maxima, corresponding to ion Pedersen, electron Hall and electron Pedersen conductivity layers.

Dhillon, Ranvir; Opgenoorth, Hermann; Rosenqvist, Lisa; Lester, Mark; Brain, David; Withers, Paul; Edberg, Niklas; Milan, Steve

2010-05-01

307

Regional And Global Evolution Of Mars: Insights From Geologic, Topographic, and Magnetic Field Observations  

NASA Astrophysics Data System (ADS)

Johnson and Phillips (2005) used magnetic field observations from Mars Global Surveyor (MGS), the ages of geologic units, and topographic data to provide constraints on the thermal and magmatic evolution of the Tharsis volcanic province on Mars. They conclude that Tharsis is underlain by a Noachian crust that was previously more magnetic than at present. Here, we extend these analyses to other regions and to the entire planet. We investigate the distributions of magnetic field intensities and directions (or the inferred magnetizations) as a function of geological age, where the latter is assessed via global maps of surface unit ages. Available global geological maps have higher spatial resolution (0.125°) compared with global magnetic field models ( 2° at best). The geologic data are grouped into bins of the same size as the magnetic field data and a modal age is assigned to the bin. The number of magnetic observations (magnetic field or magnetization), the mean value, standard deviation, and maximum values are computed for each bin. We test whether magnetic anomaly and/or inferred magnetization distributions are consistent with an ancient global dipolar magnetizing field. Geologic age data provide constraints on the timing of events that may have magnetized or subsequently modified the crust. Topographic data provide information related to processes that affect topography, such as uplifting. Analyses of the combined magnetic field, geologic age, and topographic data, will help to constrain regional and global models of Martian evolution. This research is supported in part by a NASA Graduate Student Research Program fellowship.

Milbury, Colleen A.; Johnson, C. L.; Schubert, G.

2006-09-01

308

Biodegradation of bensulfuron-methyl and its effect on bacterial community in paddy soils.  

PubMed

Bensulfuron-methyl (BSM) is a new kind of sulfonylurea herbicide widely used to control broad-leaf weeds in rice paddies. The aim of this work was to study BSM biodegradation in paddy soils with BSM-degrading bacteria Bacillus megaterium L1 and Brevibacterium sp. BH and its effect on the structures of soil bacterial community. More than 90 % of BSM could be degraded in paddy soils with 0.0355 mg kg?¹ BSM concentration. Addition of BSM-degrading bacterial strains Bacillus megaterium L1 into BSM contaminated paddy soil could have the half-life time of BSM compared to treatment without Bacillus megaterium L1 inoculation. Denaturing gradient gel electrophoresis and principle component analysis indicated that the diversity of the soil microbial community structure changed along with the addition of BSM, which recovered at the end of the experiment (5 weeks). Addition of BSM-degrading bacteria Bacillus megaterium L1 enriched the diversity of soil microbial community structure in paddy soils. This study provides information on the biodegradation of BSM and BSM's influences on the soil bacteria microbial community structures. PMID:22430059

Lin, Xiao-Yan; Yang, Yu-Yi; Zhao, Yu-Hua; Fu, Qing-Lin

2012-03-20

309

Periodic auroral forms and geomagnetic field oscillations in the 1400 MLT region  

Microsoft Academic Search

The UV images obtained with the Viking satellite often show bright features which resemble 'beads' or 'pearls' aligned in the east-west direction between noon and 1800 MLT. Viking acquired a series of 25 UV images during a 28-min period on July 29, 1986, which showed a distinctive series of periodic bright features in this region. Magnetic field and hot plasma

T. A. Potemra; R. E. Erlandson; D. Venkatesan; L. L. Cogger; L. J. Zanetti; P. F. Bythrow; B. J. Anderson

1990-01-01

310

Statistical analysis of multipole components in the magnetic field of the RHIC arc regions  

SciTech Connect

The existence of multipolar components in the dipole and quadrupole magnets is one of the factors limiting the beam stability in the RHIC operations. Therefore, the statistical properties of the non-linear fields are crucial for understanding the beam behavior and for achieving the superior performance in RHIC. In an earlier work [1], the field quality analysis of the RHIC interaction regions (IR) was presented. Furthermore, a procedure for developing non-linear IR models constructed from measured multipolar data of RHIC IR magnets was described. However, the field quality in the regions outside of the RHIC IR had not yet been addressed. In this paper, we present the statistical analysis of multipolar components in the magnetic fields of the RHIC arc regions. The emphasis is on the lower order components, especially the sextupole in the arc dipole and the 12-pole in the quadrupole magnets, since they are shown to have the strongest effects on the beam stability. Finally, the inclusion of the measured multipolar components data of RHIC arc regions and their statistical properties into tracking models is discussed.

Beebe-Wang,J.; Jain, A.

2009-05-04

311

Inferred electric field variability in the polarization jet from Millstone Hill E region coherent scatter observations  

Microsoft Academic Search

We investigate the fine-scale structure of the subauroral electric field in the vicinity of the polarization jet and subauroral ion drift (SAID) using coherent E region backscatter observed with the Millstone Hill 440 MHz UHF radar during a moderately disturbed period (Kp = 5) on 13 November 1998. We use a combination of data obtained at high time and spatial

P. J. Erickson; J. C. Foster; J. M. Holt

2002-01-01

312

Field and plasma configuration of a filament overlying a solar bipolar magnetic region  

Microsoft Academic Search

This paper presents an analytic model for a finite-size straight filament suspended horizontally in a steady state over a bipolar magnetic region. The equations of magnetostatic equilibrium are integrated exactly. The solution obtained illustrates the roles played by the electric current, magnetic field, pressure, and plasma weight in the balance of force everywhere in space. Basic properties are discussed. We

B. C. Low

1981-01-01

313

Thermodynamic coupling of heat and matter flows in near-field regions of nuclear waste repositories  

Microsoft Academic Search

In near-field regions of nuclear waste repositories, thermodynamically coupled flows of heat and matter can occur in addition to the independent flows in the presence of gradients of temperature, hydraulic potential, and composition. The following coupled effects can occur: thermal osmosis, thermal diffusion, chemical osmosis, thermal filtration, diffusion thermal effect, ultrafiltration, and coupled diffusion. Flows of heat and matter associated

Carnahan

1983-01-01

314

On some properties of force-free magnetic fields in infinite regions of space  

Microsoft Academic Search

Techniques for solving boundary value problems (BVP) for a force free magnetic field (FFF) in infinite space are presented. A priori inequalities are defined which must be satisfied by the force-free equations. It is shown that upper bounds may be calculated for the magnetic energy of the region provided the value of the magnetic normal component at the boundary of

J. J. Aly

1984-01-01

315

Experimental verification of the far field criteria for AFWAL's compact range in the quiet zone region  

Microsoft Academic Search

In past years the radiation and scattering properties of aerospace components have been tested on large outdoor measurement ranges. The distance between the transmitting and receiving antenna (for radiation measurements) or target (for scattering measurements) is normally dictated by the far field criteria. Recent interest in the millimeter wavelength region and the need to measure larger targets requires longer distances

H. M. Chizever; B. M. Kent

1985-01-01

316

The peculiarities of wind field in the upper middle atmosphere in the East Siberian region  

NASA Astrophysics Data System (ADS)

The climatology of wind field in height range 85-95 km over East Siberia on the base of continuous measurements during 1975-1990 is described and compared with analogous data over Central Europe and Canada. The longitudinal effects and coupling to regions above and below are discussed.

Kazimirovsky, E. S.

1994-09-01

317

Horizontal structure of the electric field in the stratiform region of an Oklahoma mesoscale convective system  

Microsoft Academic Search

This analysis combines vertical electric field components Ez observed by two research aircraft flying horizontally at two levels, with vertical soundings of thermodynamic parameters and Ez made by five balloons, to produce a quasi-three-dimensional view of the space charge distribution in the trailing stratiform cloud region behind a mesoscale convective system (MCS) that developed in central Oklahoma late in the

Qixu Mo; Andrew G. Detwiler; John Hallett; Robert Black

2003-01-01

318

Investigations on magnetic field in the interface regions between plasma armature and rail electrodes in a railgun  

Microsoft Academic Search

The key to controlling rail ablation lies in the interface regions between plasma armature and rails. The distribution of plasma in this region is affected by many factors, the magnetic field being the dominant one. In this paper, we analyze the magnetic field generated by rails and plasma armature in the interface regions, study the pattern and distribution of plasma

Jiyan Zou; Junjia He; Shihong Qin; Lichun Cheng

1999-01-01

319

Diazinon accumulation and dissipation in Oryza sativa L. following simulated agricultural runoff amendment in flooded rice paddies  

Technology Transfer Automated Retrieval System (TEKTRAN)

Flooded post-harvest rice paddies were examined as potential best management practices for reducing diazinon (organophosphate insecticide) concentrations in stormwater runoff. Two rice paddies were cultivated in Oryza sativa L. and amended with a 3hr, 0.1% simulated stormwater diazinon runoff event....

320

Mapping and modelling of greenhouse gas emissions from rice paddies with satellite radar observations and the DNDC biogeochemical model  

Microsoft Academic Search

Rice is an important agricultural production system with more than 80 million ha of irrigated rice paddies in annual production globally. As water resources become scarcer, the competition between urban development and agriculture for available water will intensify. Paddy rice cropland distribution and management intensity will need to evolve over the coming decades to accommodate increased production demand with decreasing

WILLIAM SALASa; Stephen Boles; Changsheng Li; Jagadeesh Babu Yeluripati; Xiangming Xiao; Steve Frolking; Pamela Green

2007-01-01

321

Accumulation of heavy metals in soil and paddy crop (Oryza sativa), irrigated with water of Ramgarh Lake, Gorakhpur, UP, India  

Microsoft Academic Search

Heavy metals, a highly polluting group of constituents known to exert adverse effects, tend to accumulate in living organisms. The objective of this study was to determine the accumulation and translocation of heavy metals in soil and in paddy crop irrigated with lake water compared to soil and paddy crop irrigated with bore-well water. The quantities of heavy metals (Cd,

Jaswant Singh; Suraj K. Upadhyay; Rajaneesh K. Pathak; Vidhu Gupta

2011-01-01

322

Regional Field Verification -- Case Study of Small Wind Turbines in the Pacific Northwest: Preprint  

SciTech Connect

The U.S. Department of Energy/National Renewable Energy Laboratory's (DOE/NREL) Regional Field Verification (RFV) project supports industry needs for gaining initial field operation experience with small wind turbines and verify the performance, reliability, maintainability, and cost of small wind turbines in diverse applications. In addition, RFV aims to help expand opportunities for wind energy in new regions of the United States by tailoring projects to meet unique regional requirements and document and communicate the experience from these projects for the benefit of others in the wind power development community and rural utilities. Between August 2003 and August 2004, six turbines were installed at different host sites. At least one year of data has been collected from five of these sites. This paper describes DOE/NREL's RFV project, reviews some of the lessons learned with regards to small wind turbine installations, summarizes operations data from these sites, and provides preliminary BOS costs.

Sinclair, K.

2005-05-01

323

Thermal instabilities in the edge region of reversed-field pinches  

SciTech Connect

Thermal stability of the edge region of reversed-field pinch configurations is analyzed within the context of a two-fluid model. Two major sources of instability are identified in combination with a parallel electric field: either an electron temperature gradient and/or a density gradient that leads to rapid growth (of several to many ohmic heating rates) over a region of several millimeters around the mode-rational surfaces in the edge region. The basic signature of both instabilities is electrostatic. In the case of the density gradient mode, the signature relies on the effects of electron compressibility, whereas the temperature gradient mode can be identified as the current-convective instability by taking the limit of zero diamagnetic drift, density gradient, thermal force, drift heat flux, and electron compressibility.

Goedert, J.; Mondt, J.P.

1984-04-01

324

F-region dynamo current as deduced from the magnetic-field observations by CHAMP  

NASA Astrophysics Data System (ADS)

Thermospheric neutral winds generate dynamo currents through ion-neutral collision. In ease of the equatorial F-region dynamo the current forms a meridional circuit in each hemisphere, leading to asymmetric zonal deflections of the geomagnetic field [Lühr and Maus, 2006]. Us-u ing magnetic observations of the CHAMP satellite, we investigate variations of the F-region dynamo current with season, longitude, local time, and solar activity. Dynamo currents show pronounced seasonal/longitudinal (S/L) variations. Around noon they show different longitu-dinal structures in each season. At dusk its S/L variation shows a rough correlation with that of the evening pre-reversal enhancement (PRE) of vertical drift. The dynamo current increases with solar activity. All the results imply that magnetic field data can be a useful proxy for ionospheric E-fields. Precise magnetic observations and accurate models will further improve this technique.

Park, Jaeheung; Luehr, Hermann; Rother, Martin; Min, Kyoung; Michaelis, Ingo

325

Evidence of regional structural controls on vent distribution - Springerville volcanic field, Arizona  

NASA Astrophysics Data System (ADS)

Several quantitative methods (including univariate statistics, cluster analysis, the Hough transform, and the two-point azimuth method) are used to search for vent clusters and alignments in the late Tertiary-Quaternary Springerville volcanic field (SVF) in Arizona. The results of the vent distribution analysis are compared with structural data collected in the field, showing that there is a relationship between observed patterns in the cinder cone distribution and the regional crustal structure. The results of the analysis clarify the relationship beetween the SVF volcanism and the neotectonic structures which dominate the geology of the region and yield clues regarding the mechanism governing the timing and the location of the cinder cone emplacement within the field.

Connor, Charles B.; Condit, Christopher D.; Crumpler, Larry S.; Aubele, Jayne C.

1992-08-01

326

The relation between the magnetic fields and the coronal activities in the solar polar region  

NASA Astrophysics Data System (ADS)

The telescopes aboard Hinode satellite showed new views in solar physics. One of new discoveries obtained by Hinode is the activities in the polar region of the sun. Savcheva et al. (2007) investigated the coronal hole around the south pole using the high-cadence X-ray images, and they found that the appearance of X-ray jets in the polar coronal holes occurs at very high frequency -- about 60 jets/day on average. The other of new results obtained by Hinode is the magnetic field measurements of the solar polar region with high accuracy. Tsuneta et al. (2008) found that many vertically-oriented magnetic flux tube with field strength as strong as 1--1.2 kG that are scattered in latitude between 70 -- 90. If the trumpet-like magnetic structures extend to interplanetary space, there is possibility that they are the guide field of X-ray jets, coronal plumes and fast-solar wind. Thus, in order to understand the polar phenomena, it is very important to investigate the relation between the magnetic field distribution and the coronal structures. We examined the co-alignment between the Stokes-V maps of Na, the Stokes-Q maps of Fe, the X-ray images and the EUV images of the north polar region. At the result, we found that most of the trumpet-like magnetic structures around the pole do not associate with the coronal structures. It suggests that the energy injection for the fast-solar wind is not taking place in the corona. The other finding from the co-alignment is that X-ray jets are produced by the emerging/canceling fluxes. It is same as the jets in the active regions. The existence of the emerging flux near the pole suggests that the magnetic fields around the pole are provided from not only the active regions but also the emerging fluxes near the pole.

Shimojo, M.

2008-12-01

327

Global Methane Emissions From Wetlands, Rice Paddies, and Lakes  

NASA Astrophysics Data System (ADS)

The current concentration of atmospheric methane is 1774+/-1.8 parts per billion, and it accounts for 18% of total greenhouse gas radiative forcing [Forster et al., 2007]. Atmospheric methane is 22 times more effective, on a per-unit-mass basis, than carbon dioxide in absorbing long-wave radiation on a 100-year time horizon, and it plays an important role in atmospheric ozone chemistry (e.g., in the presence of nitrous oxides, tropospheric methane oxidation will lead to the formation of ozone). Wetlands are a large source of atmospheric methane, Arctic lakes have recently been recognized as a major source [e.g., Walter et al., 2006], and anthropogenic activities-such as rice agriculture-also make a considerable contribution. However, the quantification of methane emissions still has large uncertainties. In this article, we identify some causes for the uncertainty; illustrate the challenges of reducing the uncertainty; and highlight opportunities for research from the global perspective and also from the perspective of three principal sources of methane: the Arctic, the Amazon basin, and rice paddies.

Zhuang, Qianlai; Melack, John M.; Zimov, Sergey; Walter, Katey M.; Butenhoff, Christopher L.; Khalil, M. Aslam K.

2009-02-01

328

Calm before the spawn: global coral spawning patterns are explained by regional wind fields.  

PubMed

Most corals in tropical localities broadcast their gametes into the water column, yet we have a poor understanding of what forces reproductive schedules. Moreover, recent studies show considerable geographical variation in the duration of the coral spawning season. For example, on the Great Barrier Reef, corals display tight coupling, while corals in Kenya spawn over seven months. This study reconciles the regional variance by testing the hypothesis that regional wind fields are the corals' ultimate reproductive proxy. Regions with short calm periods should be more tightly coupled than regions with calm periods extending for several months. Regional wind fields were assessed at seven localities, between 1997 and 2006, using the 11 GHz channel radiometer tropical microwave imager (TMI) onboard the tropical rainfall measuring mission (TRMM). There was a direct positive relationship between the duration of regional calm periods and the coupling of mass coral spawning. Ultimate long-term evolutionary advantages of releasing gametes during calm periods ensure fertilization and facilitate larval retention and local recruitment. Coupling mass spawning with seasonally calm periods agrees strongly with recent genetic evidence of local dispersal and high local retention. PMID:19892757

van Woesik, R

2009-11-05

329

Magnetic field and dynamic pressure ULF fluctuations in coronal-mass-ejection-driven sheath regions  

NASA Astrophysics Data System (ADS)

Compressed sheath regions form ahead of interplanetary coronal mass ejections (ICMEs) that are sufficiently faster than the preceding solar wind. The turbulent sheath regions are important drivers of magnetospheric activity, but due to their complex internal structure, relatively little is known on the distribution of the magnetic field and plasma variations in them. In this paper we investigate ultra low frequency (ULF) fluctuations in the interplanetary magnetic field (IMF) and in dynamic pressure (Pdyn) using a superposed epoch analysis of 41 sheath regions observed during solar cycle 23. We find strongest fluctuation power near the shock and in the vicinity of the ICME leading edge. The IMF and Pdyn ULF power have different profiles within the sheath; the former is enhanced in the leading part of the sheath, while the latter is increased in the trailing part of the sheath. We also find that the ICME properties affect the level and distribution of the ULF power in sheath regions. For example, sheath regions associated with strong or fast ICMEs, or those that are crossed at intermediate distances from the center, have strongest ULF power and large variation in the power throughout the sheath region. The weaker or slower ICMEs, or those that are crossed centrally, have in general considerably weaker ULF power with relatively smooth profiles. The strong and abrupt decrease of the IMF ULF power at the ICME leading edge could be used to distinguish the ICME from the preceding sheath plasma.

Kilpua, E. K. J.; Hietala, H.; Koskinen, H. E. J.; Fontaine, D.; Turc, L.

2013-09-01

330

Extensive lava flow fields on Venus: Preliminary investigation of source elevation and regional slope variations  

NASA Astrophysics Data System (ADS)

Large-volume lava flow fields have been identified on Venus, the most areally extensive of which are known as fluctus and have been subdivided into six morphologic types. Sheetlike flow fields (Type 1) lack the numerous, closely spaced, discrete lava flow lobes that characterize digitate flow fields. Transitional flow fields (Type 2) are similar to sheetlike flow fields but contain one or more broad flow lobes. Digitate flow fields are divided further into divergent (Types 3-5) and subparallel (Type 6) classes on the basis of variations in the amount of downstream flow divergence. As a result of our previous analysis of the detailed morphology, stratigraphy, and tectonic associations of Mylitta Fluctus, we have formulated a number of questions to apply to all large flow fields on Venus. In particular, we would like to address the following: (1) eruption conditions and style of flow emplacement (effusion rate, eruption duration), (2) the nature of magma storage zones (presence of neutral buoyancy zones, deep or shallow crustal magma chambers), (3) the origin of melt and possible link to mantle plumes, and (4) the importance of large flow fields in plains evolution. To answer these questions we have begun to examine variations in flow field dimension and morphology; the distribution of large flow fields in terms of elevation above the mean planetary radius; links to regional tectonic or volcanic structures (e.g., associations with large shield edifices, coronae, or rift zones); statigraphic relationships between large flow fields, volcanic plains, shields, and coronae; and various models of flow emplacement in order to estimate eruption parameters. In this particular study, we have examined the proximal elevations and topographic slopes of 16 of the most distinctive flow fields that represent each of the 6 morphologic types.

Magee-Roberts, K.; Head, James W., III; Lancaster, M. G.

1992-12-01

331

Electron/ion precipitation differences in relation to region 2 field-aligned currents  

SciTech Connect

The question of the mechanism producing the premidnight region 2 currents is investigated using magnetic field and precipitating particle data from the Defense Meteorological Satellite Program F7 satellite. In this study, the variations in the extent and intensity of the region 2 currents on the nightside, in the darkened hemisphere, are determined for a small, isolated substorm on January 18, 1984, and the variations related to the characteristics of the latitudinal profile in electron and ion precipitation. The region 2 currents are found to collocate with a steep slope in the ion energy density. The ion energy density decreases with decreasing latitude. The region 2 current intensity increases proportionally to the increase in the ion energy density gradient. In the premidnight sector the equatorward boundary of auroral ion precipitation generally extends to lower latitudes than that for electrons, suggesting charge imbalance in the right sense to drive region 2 currents. We find no correlation between the extent of the latitudinal separation of the two boundaries and the strength of the region 2 currents. In fact there was one pass with a clear region 2 current where this boundary behavior reversed. The observations are consistent with an azimuthal gradient in the ion energy density near the inner edge of the plasma sheet being an important factor in the generation of the premidnight region 2 currents if the increase in the azimuthal gradient is proportional to the increase in the radial gradient there. {copyright} American Geophysical Union 1989

Heinemann, N.C. (Department of Physics, Boston College, Chestnut Hill, Massachusetts (USA)); Gussenhoven, M.S.; Hardy, D.A.; Rich, F.J. (Air Force Geophysics Laboratory, Hanscom Air Force Base, Massachusetts (USA)); Yeh, H.-C. (Haystack Observatory, Massachusetts Institute of Technology, Westford (USA))

1989-10-01

332

Alfvenic Generation of Parallel Electric Fields and Low Density Cavities in the Auroral Acceleration Region  

NASA Astrophysics Data System (ADS)

The generation of parallel electric fields and associated low density cavities in auroral acceleration regions is a result of Alfvenic interactions in the M-I coupling system. The focus of this presentation is the mechanism of the generation of parallel electric fields. The dynamic generation of parallel electric fields in discrete auroral arcs may be the result of nonlinear Alfvenic interactions. Due to the approximate conservation of total magnetic helicity and angular momentum, the nonlinear interaction between incident and reflected Alfvén wave packets in the auroral acceleration region causes a local enhancement of azimuthal magnetic flux. This local dynamo effect supports and maintains parallel electric fields, which deepen the auroral density cavity. We will present new developments in the theory of two fluid kinetic Alfven waves (KAW). In the existing linear two fluid KAW theory, the generation of parallel electric fields associated with Alfven waves has not been completely given. Our approach emphasizes the physics of the generation of parallel electric field, which is particularly important in the nonlinear regime. This theory is able to explain the formation of not only Alfvénic auroral arcs but also inverted-V auroral arcs, which have larger spatial scales and can produce higher energy electrons than Alfvenic acceleration.

Song, Y.; Lysak, R. L.

2011-12-01

333

Fast Auroral Snapshot observations of perpendicular DC electric field structures in downward current regions: Implications  

NASA Astrophysics Data System (ADS)

FAST electric field data and ion drift moments are combined to allow full DC E? (electric field perpendicular to the geomagnetic field) studies of auroral return current regions. Statistical comparison of 71 return current potential structures showed several differences between sheetlike structured perpendicular E? field events, where the ratio of the two E? components remains constant during the spacecraft crossing, and curved structures where the ratio varies. Sheetlike structures can be interpreted as straight arcs, but curved structures require gradients in another dimension. We define a parameter ?, which is a proxy for the ratio of the potential at the spacecraft and the upgoing electron characteristic energy. Thus ? is a measure of the extent to which the potential contours are closed below the spacecraft. Statistical comparison shows that U-shaped closed-potential models are mostly consistent with curved events and ionospheric effects are dominant in sheetlike structures. This result implies that the spatial structure of the events, as indicated by the ratio of the E? components, allows us to distinguish ionospheric fields and U-shaped potentials. Statistical studies of scale sizes, magnitudes of electric fields and magnetic perturbations, and downward current density, sorted by the parameter ?, reveal various interesting features. We attempt to explain these properties on the basis of different potential closure models for sheetlike and curved structures, which have important implications for models of the formation and evolution of potential structures for downward current regions.

Hwang, K.-J.; Lynch, K. A.; Carlson, C. W.; Bonnell, J. W.; Peria, W. J.

2006-09-01

334

Regional modeling of the geomagnetic field in Europe from 6000 to 1000 B.C.  

NASA Astrophysics Data System (ADS)

We have developed a first low-degree regional geomagnetic model for the European continent valid for the period 6000-1000 B.C. from a selected compilation of sedimentary and archeomagnetic data (the SCHA.DIF.8K model). This model provides information about both direction (declination and inclination) and intensity of the Earth's magnetic field. By connecting it with our previous model, SCHA.DIF.3K, valid from 1000 B.C. to 1900 A.D., and the IGRF, we furnish continuous geomagnetic field information for the last 8000 years in Europe. It has been developed using the Revised Spherical Cap Harmonic Analysis in 2 Dimensions technique (R-SCHA2D) and using the norm of the Earth's magnetic field to constrain the inversion problem. The size of the cap is 22°, and the maximum degree of the expansion is 2. The linearization problem was solved by using the truncated Taylor's series applied to the expressions representing the relationship between the declination, inclination, and intensity data and the Cartesian components of the geomagnetic field. We used the geocentric axial dipole (GAD) field as our initial or reference field. For time, we used the classical sliding overlapping window method. The size of the window was set to 100 years shifted by 50 years. We compared the model's prediction with the input data, with the global CALS7K.2 model, and with new independent data. The regional model shows a better fit to the input and to the independent data than the global model, especially in terms of intensity, and agrees with the virtual axial dipole moment given by other studies. For the last 8000 years, the European geomagnetic field has recorded rapid changes or archeomagnetic jerks. The average field for the last 8000 years in Europe is indistinguishable from the GAD field.

Pavón-Carrasco, F. Javier; Osete, Maria Luisa; Torta, J. Miquel

2010-11-01

335

ARE DECAYING MAGNETIC FIELDS ABOVE ACTIVE REGIONS RELATED TO CORONAL MASS EJECTION ONSET?  

SciTech Connect

Coronal mass ejections (CMEs) are powered by magnetic energy stored in non-potential (current-carrying) coronal magnetic fields, with the pre-CME field in balance between outward magnetic pressure of the proto-ejecta and inward magnetic tension from overlying fields that confine the proto-ejecta. In studies of global potential (current-free) models of coronal magnetic fields-Potential Field Source Surface (PFSS) models-it has been reported that model field strengths above flare sites tend to be weaker when CMEs occur than when eruptions fail to occur. This suggests that potential field models might be useful to quantify magnetic confinement. One straightforward implication of this idea is that a decrease in model field strength overlying a possible eruption site should correspond to diminished confinement, implying an eruption is more likely. We have searched for such an effect by post facto investigation of the time evolution of model field strengths above a sample of 10 eruption sites. To check if the strengths of overlying fields were relevant only in relatively slow CMEs, we included both slow and fast CMEs in our sample. In most events we study, we find no statistically significant evolution in either (1) the rate of magnetic field decay with height, (2) the strength of overlying magnetic fields near 50 Mm, or (3) the ratio of fluxes at low and high altitudes (below 1.1 R{sub Sun }, and between 1.1 and 1.5 R{sub Sun }, respectively). We did observe a tendency for overlying field strengths and overlying flux to increase slightly, and their rates of decay with height to become slightly more gradual, consistent with increased confinement. The fact that CMEs occur regardless of whether the parameters we use to quantify confinement are increasing or decreasing suggests that either (1) the parameters that we derive from PFSS models do not accurately characterize the actual large-scale field in CME source regions, (2) systematic evolution in the large-scale magnetic environment of CME source regions is not, by itself, a necessary condition for CMEs to occur, or both.

Suzuki, J. [Department of Astronomy, University of California, Berkeley, CA 94720-7450 (United States); Welsch, B. T.; Li, Y. [Space Sciences Laboratory, University of California, Berkeley, CA 94720-7450 (United States)

2012-10-10

336

Variations of the atmospheric electric field in the near-pole region related to the interplanetary magnetic field  

NASA Astrophysics Data System (ADS)

Variations in the atmospheric, near-surface vertical electric field component Ez measured at the Russian Antarctic station Vostok in 1998 are analyzed in conjunction with changes of the interplanetary magnetic field (IMF). A total of 134 days were selected which satisfied the ``fair weather'' conditions, that is, days with absence of high winds, falling or drifting snow, clouds, and electric field ``pollution'' from the station's power plant. It is shown that the average diurnal variation of Ez for these days follows the global geoelectric field ``fair-weather'' diurnal variation: the ``Carnegie'' curve, which describes the global electric circuit formed by the thunderstorm activity occurring mostly over equatorial regions. The Ez diurnal variation shows strong seasonal dependence: it is maximal (~40% of the average daily magnitude) in summer but gradually reduces through the equinoctial months and is almost negligible during the austral winter. Ez at Vostok is strongly affected by variations in both the IMF By and Bz components. The influence of By is dominant during geomagnetic daytime hours (1100-1400 UT at Vostok): Ez increases with By in the range from -10 to +10 nT. The IMF Bz effect is mainly seen at dawn (Ez decreases with Bz) and dusk (Ez increases with Bz).

Frank-Kamenetsky, A. V.; Troshichev, O. A.; Burns, G. B.; Papitashvili, V. O.

2001-01-01

337

TWIST AND CONNECTIVITY OF MAGNETIC FIELD LINES IN THE SOLAR ACTIVE REGION NOAA 10930  

SciTech Connect

Twist and connectivity of magnetic field lines in the flare-productive active region NOAA 10930 are investigated in terms of the vector magnetograms observed by the Solar Optical Telescope on board the Hinode satellite and the nonlinear force-free field (NLFFF) extrapolation. First, we show that the footpoints of magnetic field lines reconstructed by the NLFFF correspond well to the conjugate pair of highly sheared flare ribbons on the Ca II images, which were observed by Hinode as an X3.4 class flare on 2006 December 13. This demonstrates that the NLFFF extrapolation may be used to analyze the magnetic field connectivity. Second, we find that the twist of magnetic field lines anchored on the flare ribbons increased as the ribbons moved away from the magnetic polarity inversion line in the early phase of the flare. This suggests that magnetic reconnection might commence from a region located below the most strongly twisted field. Third, we reveal that the magnetic flux twisted more than a half turn and gradually increased during the last one day prior to the onset of the flare, and that it quickly decreased for two hours after the flare. This is consistent with the store-and-release scenario of magnetic helicity. However, within this active region, only a small fraction of the flux was twisted by more than one full turn and the field lines that reconnected first were twisted less than one turn. These results imply that the kink mode instability could hardly occur, at least before the onset of flare. Based on our results, we discuss the trigger process of solar flares.

Inoue, S. [National Institute of Information and Communications Technology (NICT), 4-2-1, Nukui-Kitamachi, koganei, Tokyo 184-8795 (Japan); Kusano, K.; Yamamoto, T. T. [Solar-Terrestrial Environment Laboratory, Nagoya University Furo-cho, Chikusa-ku, Nagoya, 464-8601 (Japan); Magara, T. [Department of Astronomy and Space Science, School of Space Research, Kyung Hee University, 1, Seocheon-dong, Giheung-gu, Yongin, Gyeonggi-do, 446-701 (Korea, Republic of); Shiota, D., E-mail: inosato@nict.go.jp [Advanced Science Institute, RIKEN - Institute of Physics and Chemical Research, Wako, Saitama 351-0198 (Japan)

2011-09-10

338

Nitrogen cycling in rice paddy environments: past achievements and future challenges.  

PubMed

Nitrogen is generally the most limiting nutrient for rice production. In rice paddy soils, various biochemical processes can occur regarding N cycling, including nitrification, denitrification, and nitrogen fixation. Since its discovery in the 1930s, the nitrification-denitrification process has been extensively studied in Japan. It may cause N loss from rice paddy soils, while it can also reduce environmental pollutions such as nitrate leaching and emission of nitrous oxide (N(2)O). In this review article, we first summarize the early and important findings regarding nitrification-denitrification in rice paddy soils, and then update recent findings regarding key players in denitrification and N(2)O reduction. In addition, we also discuss the potential occurrence of other newly found reactions in the N cycle, such as archaeal ammonia oxidization, fungal denitrification, anaerobic methane oxidation coupled with denitrification, and anaerobic ammonium oxidation. PMID:22008507

Ishii, Satoshi; Ikeda, Seishi; Minamisawa, Kiwamu; Senoo, Keishi

2011-10-19

339

Improved regional gravity fields on the Moon from Lunar Prospector tracking data by means of localized spherical harmonic functions  

Microsoft Academic Search

An approach to enhance regional gravity fields of the planets using the line-of-sight (LOS) Doppler range-rate measurements is presented. Instead of representing the gravity fields as nonlocalized spherical harmonic functions, I introduced a lumped harmonic representation for obtaining regionally concentrated orthogonal basis functions. Without any regularization or spectral power control, the gravity fields over the four spherical cap regions with

Shin-Chan Han

2008-01-01

340

Three-dimensional magnetic field topology in a region of solar coronal heating.  

PubMed

Flares and X-ray jets on the Sun arise in active regions where magnetic flux emerges from the solar interior amd interacts with the ambient magnetic field. The interactions are believed to occur in electric current sheets separating regions of opposite magnetic polarity. The current sheets located in the corona or upper chromosphere have long been thought to act as an important source of coronal heating, requiring their location in the corona or upper chromosphere. The dynamics and energetics of these sheets are governed by a complex magnetic field structure that, until now, has been difficult to measure. Here we report the determination of the full magnetic vector in an interaction region near the base of the solar corona. The observations reveal two magnetic features that characterize young active regions on the Sun: a set of rising magnetic loops and a tangential discontinuity of the magnetic field direction, the latter being the observational signature of an electric current sheet. This provides strong support for coronal heating models based on the dissipation of magnetic energy at current sheets. PMID:14562096

Solanki, S K; Lagg, A; Woch, J; Krupp, N; Collados, M

2003-10-16

341

Electric field measurements in a NLC/PMSE region during the MASS/ECOMA campaign  

NASA Astrophysics Data System (ADS)

We present results of electric field measurements made during the MASS rocket campaign in Andøya, Norway into noctilucent clouds (NLC) and polar mesospheric summer echoes (PMSE) on 3 August 2007. The instrument used high input-impedance preamps to measure vertical and horizontal electric fields. No large-amplitude geophysical electric fields were detected in the cloud layers, but significant levels of electric field fluctuations were measured. Within the cloud layer, the probe potentials relative to the rocket skin were driven negative by incident heavy charged aerosols. The amplitude of spikes caused by probe shadowing were also larger in the NLC/PMSE region. We describe a method for calculating positive ion conductivities using these shadowing spike amplitudes and the density of heavy charged aerosols.

Shimogawa, M.; Holzworth, R. H.

2009-04-01

342

The closure of region-1 field-aligned current in MHD simulation  

NASA Astrophysics Data System (ADS)

We have studied the closure path of Region-1 field-aligned current system in our global MHD simulation and found some interesting results. After leaving the ionosphere on the eveningside the current deviates from the field-aligned direction rather early and bends towards the Sun. After passing through the velocity shear region near the magnetopause, which is a generator region, it climbs up along the magnetopause, being more or less field-aligned. Because of this it again bends sunward. When approaching the noon-midnight meridian plane (Y=0 plane in GSM coordinates), however, the current becomes more perpendicular to the magnetic field. It passes through the Y=0 plane at about X=2±1, Z=11±1. On the morningside the closure path is a mirror reflection of that on the evening side. Thus the closure path seems to reside more on the dayside than perhaps usually thought. We give a simple physical explanation for the dayside bending, which is based on the MHD pressure balance equation.

Janhunen, P.; Koskinen, H. E. J.

343

Modulation of the midlatitude ionospheric E region by atmospheric gravity waves through polarization electric field  

NASA Astrophysics Data System (ADS)

We have studied coupling between the neutral atmosphere and the ionospheric E region in the midlatitude by combining two numerical simulation models. Atmospheric gravity waves generated in the troposphere propagate through the stratosphere and the mesosphere and can reach the lower thermosphere. When a zonal wind shear that can accumulate a sporadic-E (Es) layer (eastward below and westward above) is applied, the accumulated Es layer is strongly modulated by the gravity waves, and polarization electric field due to the modulated Es layer produces wave-like patterns of plasma density in the upper E region. Since the eastward wind below the shear node filters out gravity waves with eastward phase velocity, those with westward phase velocity are dominant where the Es layer is accumulated. Because of the angle between phase front of gravity waves and the geomagnetic field line, gravity waves with southward phase velocity is more effective to generate polarization electric field than those with northward phase velocity. Since gravity waves with southwestward phase velocity have phase fronts aligned from northwest to southeast, polarization electric field also has the similar structure. This mechanism can explain the spatial structure of quasi-periodic (QP) echoes associated with plasma irregularities in the midlatitude E region which often shows northwest-southeast alignment.

Yokoyama, T.; Horinouchi, T.; Yamamoto, M.; Fukao, S.

2004-12-01

344

[Distribution characteristics of soil cadmium in different textured paddy soil profiles and its relevance with cadmium uptake by crops].  

PubMed

Adopting atomic absorption spectrometry (novAA400), the present study investigated the distribution characteristics of soil cadmium (Cd) in different textured paddy soil profiles under rice-wheat rotation and its correlation with Cd uptake by rice and wheat in Chengdu Plain through repeatedly taking soil and plant samples at the fixed sites in the field. The results revealed that Cd in the paddy soil profiles was mainly concentrated at the plough layer (0-15 cm) that obviously featured 'Cd accumulates towards the rooting layer'. Soil total Cd and available Cd (1 mol x L(-1) MgCl2 extraction) in the profile declined with soil depths and its average values at 30-45 cm only accounted for 47.60% and 39.49% of those at 0-15 cm. The potential downward movement of Cd in the different textured soil profiles was observed as sandy loam > heavy loam > loam. There was no significant correlation between soil pH and available Cd(r = - 0.46) at 0-15 cm soil depth, while significantly negative correlations between soil pH and available Cd were observed at 15-30 cm (r = -0.78) and 30-45 cm (r = -0.86). The results further demonstrated that the Cd contents in either grain or straw of rice and wheat were not well correlated with soil total Cd at any soil depth (r = -0.092-0.383 for rice and r = 0.174-0.424 for wheat), but significantly correlated with soil available Cd at 0-15 cm and at 15-30 cm (r = 0.766*-0.953**) despite insignificant correlation at 30-45 cm (r = 0.526-0.584). It is strongly suggested that the soil available Cd can be used as a better criterion than the total soil Cd to rate Cd contaminated soils in relation to safety of agricultural products. PMID:23697136

Qin, Yu-Sheng; Zhan, Shao-Jun; Yu, Hua; Tu, Shi-Hua; Wang, Zheng-Yin

2013-02-01

345

SITE IVESTIGATIONS (SI) AND FIELD INVESTIGATIONS (FI) OF REGION 4 SUPERFUND HAZARDOUS WASTE SITES: OCTOBER 2005 â?? SEPTEMBER 2006  

EPA Science Inventory

Site Investigations (SIs) and expanded Field Investigations (FIs) conducted by the Region 4 Science and Ecosystem Support Division (SESD) require developing and implementing work plans which include a Project Operations Plan, Field Sampling and Analysis Plan, Quality Assurance Pl...

346

SITE INVESTIGATIONS (SI) AND FIELD INVESTIGATIONS (FI) OF REGION 4 SUPERFUND HAZARDOUS WASTE SITES: OCTOBER 2006 â?? JULY 2007  

EPA Science Inventory

Site Investigations (SIs) and Field Investigations (FIs) conducted by the Region 4 Science and Ecosystem Support Division (SESD) require developing and implementing work plans which include a Project Operations Plan, Field Sampling and Analysis Plan, Quality Assurance Project Pla...

347

SITE IVESTIGATIONS (SI) AND FIELD INVESTIGATIONS (FI) OF REGION 4 SUPERFUND HAZARDOUS WASTE SITES: AUGUST 2007 â?? SEPTEMBER 2008  

EPA Science Inventory

Site Investigations (SIs) and Field Investigations (FIs) conducted by the Region 4 Science and Ecosystem Support Division (SESD) require developing and implementing work plans which include a Project Operations Plan, Field Sampling and Analysis Plan, Quality Assurance Project Pla...

348

Modeling of regional meteorological fields with high spatial resolution for West Siberia  

NASA Astrophysics Data System (ADS)

As well known, global climate changes are inhomogeneous that is most clearly pronounced in the northern regions of the Earth. To study these inhomogeneities and trends, it is necessary to analyze climate changes in the ?? century in the specific region. Now data of different reanalyses (USA, Europe, Japan), as well as observational data from weather stations, are used for such an analysis. Modeling data validity is mostly determined by amount of assimilated measurement data and by weather station network density. For example, for the 2nd edition of USA reanalysis, data of only 300 weather stations of Russian Federation have been used, where most stations are located in European part of the country. Comparison of meteorological fields obtained using reanalysis to measurements of Rosgidromet weather stations gives significant discrepancy. Reanalyses spatial resolution does not allow studying local inhomogeneities that inherent to regional climate changes. Therefore to study local climate dynamics in Siberian region, it is necessary to calculate meteorological fields with higher spatial resolution. Modern mesoscale meteorological models that use reanalyses archives and assimilate measurements of weather stations can solve this problem. We calculated fields of climatic characteristics for West Siberia for the period from 1960 to 2000. The regional weather forecast WRF model (http://www.mmm.ucar.edu/modeling/wrf/index.php) and data assimilation system WRF-VAR (WRFDA) have been installed and debugged on the base of multiprocessor computational complex. Vertical boundary conditions, as well as initial conditions are formed using ERA-40 reanalysis data. NCEP data and USGS map with spatial resolution of 9.25 km are used for the lower boundary, measurements of weather stations, located within calculation area, are used for observation nudging. As a result of the model run, we have meteorological fields, which are reanalysis fields' projections with high spatial resolution (10 km) corrected by weather stations' measurements. Primary analysis of the data obtained allows us to depict changes of climatic characteristics in local areas not as smoothed disturbances (as in reanalysis fields), but as local inhomogeneities that have specific geographical reference to specific regional ecosystem. Key parameters characterizing the main local climate dynamics trends will be chosen for further analysis and processing. The work has been partially supported by SB RAS integration projects Nos. 50 and 66.

Bogomolov, Vasiliy; Gordov, Evgeny

2010-05-01

349

Soil mineral surfaces of paddy soils are accessible for organic carbon accumulation after decalcification  

NASA Astrophysics Data System (ADS)

We studied organic carbon (OC) accumulation due to organo-mineral associations during soil development on calcareous parent material. Two chronosequences in Zhejiang Province, PR China, were investigated; one under paddy cultivation with a maximum soil age of 2000 years, and the other under upland crops where the oldest soil was 700 years old. Bulk soils and soil fractions of the uppermost A horizons were analyzed for OC concentrations and radio carbon contents. Total pedogenic iron (Fed) concentration was determined by dithionite extraction and the proportion of oxalate extractable iron (Feox) was extracted by using the method of Schwertmann (1964). The specific surface area (SSA) of soil minerals was measured by the BET-N2 method (Brunauer et al., 1938) under four conditions: untreated, after organic matter removal, after iron removal and after removal of both. Within 700/2000 years of pedogenesis, we observed no change in clay mineral composition and no additional formation of the SSA of soil minerals. But the soils differed in the degree of decalcification, OC accumulation and in the formation of iron. Paddy soil management led to an enhanced decalcification and larger OC accumulation. Management-induced redox cycles caused larger proportions of Feox in paddy soils. Their large SSA, added to the surface area of clay minerals, provided additional options for OC covering. Unexpectedly, there was no evidence of formation of secondary minerals during soil development, which could provide new surfaces for OC accumulation. However, the study revealed higher OC coverings of mineral surfaces after decalcification in paddy soils. As carbonate and Ca2+ ions seemed to interconnect clay minerals, making their surface accessible to OC, the faster dissolution of carbonate and leaching of Ca2+ ions in paddy soils made additional clay mineral surfaces available to OC. In contrast, the surface area of minerals in non-paddy soils, in which decalcification was much lower, seemed to be partly inaccessible for OC covering due to strong microaggregation by cementation with carbonate and Ca2+-bridging. The smaller accumulation of mineral-associated SOM in non-paddy soils was additionally confirmed by the retarded replacement of the inherited carbon. The accelerated decalcification of paddy soils led to enhanced accessibility of mineral surfaces for OC covering, which intensified OC accumulation from the early stages of soil formation onward. References Brunauer, S., Emmett, P.H., Teller, E., (1938). Adsorption of gases in multimolecular layers. J. Am. Chem. Soc. 60 (2), 309-319. Schwertmann, U., 1964. Differenzierung der Eisenoxide des Bodens durch Extraktion mit Ammoniumoxalat-Lösung. Zeitschrift für Pflanzenernährung, Düngung, Bodenkunde 105 (3), 194-202.

Wissing, Livia

2013-04-01

350

Evaporating very small grains as tracers of the UV radiation field in photo-dissociation regions  

NASA Astrophysics Data System (ADS)

Context. In photo-dissociation regions (PDRs), polycyclic aromatic hydrocarbons (PAHs) may be produced by evaporation of very small grains (VSGs) by the impinging UV radiation field from a nearby star. Aims: We quantitatively investigate the transition zone between evaporating VSGs (eVSGs) and PAHs in several PDRs. Methods: We studied the relative contribution of PAHs and eVSGs to the mid-IR emission in a wide range of excitation conditions. We fitted the observed mid-IR emission of PDRs by using a set of template band emission spectra of PAHs, eVSGs, and gas lines. The fitting tool PAHTAT (PAH Toulouse Astronomical Templates) is made available to the community as an IDL routine. From the results of the fit, we derived the fraction of carbon feVSG locked in eVSGs and compared it to the intensity of the local UV radiation field. Results: We show a clear decrease of feVSG with increasing intensity of the local UV radiation field, which supports the scenario of photo-destruction of eVSGs. Conversely, this dependence can be used to quantify the intensity of the UV radiation field for different PDRs, including unresolved ones. Conclusions: PAHTAT can be used to trace the intensity of the local UV radiation field in regions where eVSGs evaporate, which correspond to relatively dense (nH = [100,105] cm-3) and UV irradiated PDRs (G0 = [100,5 × 104] ) where H2 emits in rotational lines.

Pilleri, P.; Montillaud, J.; Berné, O.; Joblin, C.

2012-06-01

351

E region electric fields at the dip equator and anomalous conductivity effects  

NASA Astrophysics Data System (ADS)

Zonal and vertical electric fields were estimated at E region heights in the Brazilian sector. Zonal electric fields are obtained from the vertical electric fields based on their relation through the Hall-to-Pedersen ionospheric conductivities ratio. The technique for obtaining the vertical electric field is based on its proportionality to the Doppler velocities of type 2 irregularities as detected by coherent radars. The 50 MHz backscatter coherent (RESCO) radar was used to estimate the Doppler velocities of the type 2 irregularities embedded in the equatorial electrojet. A magnetic field-line integrated conductivity model was developed to provide the conductivities. It considers a multi-species ionosphere and a multi-species neutral atmosphere, and uses the IRI 2007, the MISIS 2000 and the IGRF 10 models as input parameters for ionosphere, neutral atmosphere and Earth's magnetic field, respectively. The ion-neutral collision frequencies of all the species are combined through the momentum transfer collision frequency equation, and different percentages of electron-neutral collisions were artificially included for studying the implication of such increase in the zonal electric field, which resulted ranging from 0.13 to 0.49 mV/m between the 8 and 18 h (LT), under quiet magnetic conditions.

Denardini, C. M.; Aveiro, H. C.; Sobral, J. H. A.; Bageston, J. V.; Guizelli, L. M.; Resende, L. C. A.; Moro, J.

2013-05-01

352

Evaluation of Atmospheric Electric Field as Increasing Seismic Activity Indicator on the example of Caucasus Region  

NASA Astrophysics Data System (ADS)

The present paper deals with reliability of a gradient of atmospheric electric field potential as an indicator of seismic activity increase. With this in view, records of atmospheric electric field potential gradients of Caucasus region for 1953-1992 with respect to periods before average and large earthquakes, which took place in the same time interval, were considered. It is worth to pay attention to the fact that the avalanche-like unstable model of fault formation based on theoretical model of self-generated seismo-electromagnetic oscillations of LAI system explains convincingly spectral succession of electromagnetic emission frequency of the periods preceding earthquakes.

Kachakhidze, M. K.; Kereselidze, Z. A.; Kachakhidze, N. K.

2013-01-01

353

Monitoring rice cropping systems using China environment satellite data in Poyang Lake region  

NASA Astrophysics Data System (ADS)

Threshold method was utilized to discriminate rice cropping systems based on the noticeable variation of Normalized Difference Vegetation Index (NDVI) during key growth stages in Poyang Lake Region, China. This area is dominated by double- and single rice cropping systems which tend to change due to the frequent ecosystem management policies. We used a new satellite data from the CCD camera sensor with 30 m spatial resolution onboard the China Environmental Satellite HJ-1A and B. The HJ -1A/B with a better temporal resolution of four days provides more data options for effective and timely agriculture monitoring. The result showed that there is evident difference of NDVI between single and late rice during mid October when they are in different growth stages. The areas of single and late rice in 2011 were 2988.6 km2 and 3105.9 km2, respectively. Paddy field distribution map and local paddy rice calendar are requisite to move the threshold method into other multiple rice cropping regions. The study suggests that the China Environmental Satellite HJ-1A/B have the potential to rice cropping system in the double to triple rice cropping systems area. With many advantages of HJ-1A/B, like, finer spatial and temporal resolution, bigger imaging swath, it may make rice cropping system monitoring more feasible and operational.

Li, Peng; Jiang, Luguang; Feng, Zhiming

354

First VHF radar observations of tropical latitude E-region field aligned irregularities  

NASA Astrophysics Data System (ADS)

Indian MST radar at Gadanki (13.5°N, 79.2°E, 12.5° dip) was operated during July/August 1994, to observe the 3-m scale size field aligned irregularities associated with the lower E region. Irregularity structure was studied by using height-time variation of the echo intensity and weighted mean Doppler velocity. In this paper results of three diurnal cycles of observation are presented. Field perpendicular echoes were observed both during daytime and nighttime. A layered irregularity structure extending down to altitude below 86 Km was seen during the nighttime. The daytime structure showed a narrow echoing region with significant downward slope. Doppler velocity was in the range of 20-50 ms-1, both during day and night and was, in general, consistent with the slope of scattering structure observed in the height-time-intensity plots.

Choudhary, R. K.; Mahajan, K. K.; Singh, Sachchidanand; Kumar, Keshav; Anandan, V. K.

355

Integral Field Spectroscopy of the Extended Emission-Line Region of 4C 37.43  

Microsoft Academic Search

We present Gemini integral field spectroscopy and Keck II long-slit spectroscopy of the extended emission-line region (EELR) around the quasar 4C 37.43. The velocity structure of the ionized gas is complex and cannot be explained globally by a simple dynamical model. The spectra from the clouds are inconsistent with shock or ``shock + precursor'' ionization models, but they are consistent

Hai Fu; Alan Stockton

2007-01-01

356

An improved permanent magnet quadrupole design with larger good field region for high intensity proton linacs  

NASA Astrophysics Data System (ADS)

The Low Energy High Intensity Proton Accelerator (LEHIPA), being developed at the Bhabha Atomic Research Centre (BARC) will produce a 20 MeV, 30 mA, continuous wave (CW) proton beam. At these low velocities, space-charge forces dominate, and could lead to larger beam sizes and beam halos. Hence in the design of the focusing lattice of the LEHIPA drift tube linac (DTL) using permanent magnet quadrupoles (PMQs), a larger good field region is preferred. Here we study, using the two dimensional (2D) and three dimensional (3D) simulation codes PANDIRA and RADIA, four different types of cylindrical PMQ designs: 16-segment trapezoidal Halbach configuration, bullet-nosed geometry and 8- and 16-segment rectangular geometries. The trapezoidal Halbach geometry is used in a variety of accelerators since it provides very high field gradients in small bores, while the bullet-nosed geometry, which is a combination of the trapezoidal and rectangular designs, is used in some DTLs. This study shows that a larger good field region is possible in the 16-segment rectangular design as compared to the Halbach and bullet-nosed designs, making it more attractive for high-intensity proton linacs. An improvement in good-field region by ˜16% over the Halbach design is obtained in the optimized 16-segment rectangular design, although the field gradient is lower by ˜20%. Tolerance studies show that the rectangular segment PMQ design is substantially less sensitive to the easy axis orientation errors and hence will be a better choice for DTLs.

Mathew, Jose V.; Rao, S. V. L. S.; Krishnagopal, S.; Singh, P.

2013-11-01

357

Spatial distribution and controlling factors of heavy metals contents in paddy soil and crop grains of rice-wheat cropping system along highway in East China.  

PubMed

There is consensus concerning the heavy metal pollution from traffic emission on roadside agricultural land. However, few efforts have been paid on examining the contamination characteristics of heavy metals in roadside paddy-upland rotation field, and especially in combination with detailed quantitative analysis. In this study, we investigated the concentrations of heavy metals (Pb, Cd, Cr and Zn) in soil and crop grains of the rice-wheat cropping system along a major highway in East China in 2008 and analyzed the spatial distribution characteristics of heavy metals and their influencing factors with GIS and Classification and Regression Trees (CART). Significantly elevated levels of heavy metals in soil, rice and wheat grains indicated the heavy metals contamination of traffic emission in roadside rice-wheat rotation field. The contamination levels of Cd, Cr and Zn in wheat grain were higher than rice grain, while that of Pb showed an opposite trend. Obvious dissimilarities in the spatial distributions of heavy metals contents were found between in the soil, rice and wheat grains, indicating that the heavy metals contents in the roadside crop grains were not only determined by the concentrations of heavy metals in the paddy soil. Results of CART analysis showed that the spatial variation of the heavy metals contents in crop grains was mainly affected by the soil organic matter or soil pH, followed by the distance from highway and wind direction. Our findings have important implications for the environmental assessment and crop planning for food security along the highway. PMID:22527116

Feng, Jinfei; Zhao, Jian; Bian, Xinmin; Zhang, Weijian

2012-04-17

358

Computational Analysis of the Flow Field Near the Boat-tail Region of Annular Plug Nozzles  

NASA Astrophysics Data System (ADS)

Flow fields over annular plug nozzles are computationally simulated and the boat-tail drag characteristics are clarified and discussed based on the simulation results. The plug nozzle configuration is taken from the ATREX (Air Turbo Ramjet) engine under development at the ISAS. The simulations are carried out for the axi-symmetric nozzle configuration using compressible Navier-Stokes equations. The computed result shows that there exists a low pressure region downstream of the Prandtl-Meyer expansion on the boat-tail region and the separation shock wave appears due to the interaction of the main flow and the nozzle plume downstream. The result also shows that the primary cause of the boat-tail drag turns out to be the low pressure region downstream of the Prandtl-Meyer expansion. The flow field with the secondary flow injection is then simulated and the computed result shows that the pressure in the region in front of the separation shock wave increases and the secondary flow injection successfully reduces the boat-tail drag. The effect of the turbulence model used in the computation is discussed to ensure the reliability of the solutions.

Fujii, Kozo; Imai, Kazuhiro; Sato, Tetsuya

359

Regional electric field induced by electroconvulsive therapy: a finite element simulation study.  

PubMed

The goal of this study is to investigate the regional distribution of the electric field (E-field) strength induced by electroconvulsive therapy (ECT), and to contrast clinically relevant electrode configurations through finite element (FE) analysis. An FE human head model incorporating tissue heterogeneity and white matter anisotropy was generated based on structural magnetic resonance imaging (MRI) and diffusion tensor MRI (DT-MRI) data. We simulated the E-field spatial distributions of three standard ECT electrode placements [bilateral (BL), bifrontal (BF), and right unilateral (RUL)] and an investigational electrode configuration [focal electrically administered seizure therapy (FEAST)]. A quantitative comparison of the E-field strength was subsequently carried out in various brain regions of interests (ROIs) that have putative role in the therapeutic action and/or adverse side effects of ECT. This study illustrates how the realistic FE head model provides quantitative insight in the biophysics of ECT, which may shed light on the differential clinical outcomes seen with various forms of ECT, and may guide the development of novel stimulation paradigms with improved risk/benefit ratio. PMID:21096148

Lee, Won Hee; Deng, Zhi-De; Kim, Tae-Seong; Laine, Andrew F; Lisanby, Sarah H; Peterchev, Angel V

2010-01-01

360

The temperature and density structure in the closed field regions of the solar corona  

NASA Astrophysics Data System (ADS)

In this paper we study the temperature and density structure in the closed field region of the solar corona using a dipole plus current sheet model to simulate the global solar magnetic field and a heating function of the same type used in models of the fast wind. The heat equation, describing the redistributing effects of heat conduction on the heat input in the presence of radiative losses, is solved simultaneously with hydrostatic pressure balance. At the base we prescribe the temperature and assume that the heat flux is zero there. We also insist that the heat flux is zero at the equator. This ensures that whatever heat has been added is radiated away. From the mathematical viewpoint this additional requirement sets up an eigenvalue problem which implies that the density at the base must be chosen in just the right way to fulfill the condition of zero heat flux at the equator. Thus our model not only provides the temperature and density structure in the closed regions of a global solar magnetic field appropriate to solar minimum but also predicts the latitudinal variation of the base density whose characteristic value is determined by the ratio of the amplitudes of the heating to the cooling. However it should be stressed that this last prediction represents, at best, an approximation to the real stale of affairs which is more complex and involves the connection of the coronal field lines to the magnetic funnels of the chromospheric network.

McKenzie, J. F.; Sukhorukova, G. V.; Axford, W. I.

1999-10-01

361

Effects of water management, connectivity, and surrounding land use on habitat use by frogs in rice paddies in Japan.  

PubMed

In Japan, rice paddies play an important role as a substitute habitat for wetland species, and support rich indigenous ecosystems. However, since the 1950s, agricultural modernization has altered the rice paddy environment, and many previously common species are now endangered. It is urgently necessary to evaluate rice paddies as habitats for conservation. Among the species living in rice paddies, frogs are representative and are good indicator species, so we focused on frog species and analyzed the influence of environmental factors on their habitat use. We found four frog species and one subspecies (Hyla japonica, Pelophylax nigromaculatus, Glandirana rugosa, Lithobates catesbeianus, and Pelophylax porosa brevipoda) at our study sites in Shiga prefecture. For all but L. catesbeianus, we analyzed the influence of environmental factors related to rice paddy structure, water management and availability, agrochemical use, connectivity, and land use on breeding and non-breeding habitat use. We constructed generalized additive mixed models with survey date as the smooth term and applied Akaike's information criterion to choose the bestranked model. Because life histories and biological characteristics vary among species, the factors affecting habitat use by frogs are also expected to differ by species. We found that both breeding and non-breeding habitat uses of each studied species were influenced by different combinations of environmental factors and that in most cases, habitat use showed seasonality. For frog conservation in rice paddies, we need to choose favorable rice paddy in relation to surrounding land use and apply suitable management for target species. PMID:22943781

Naito, Risa; Yamasaki, Michimasa; Lmanishi, Ayumi; Natuhara, Yosihiro; Morimoto, Yukihiro

2012-09-01

362

Validation of GOCE global gravitational field models by comparison with regional geoid and gravity anomaly surfaces  

NASA Astrophysics Data System (ADS)

The satellite gravitational gradiometry mission GOCE provides various products related to the Earth's gravitational field. One of these products is a global gravitational field model, i.e. representation of the Earth's gravitational field in terms of spherical harmonic coefficients. Such a model is used in realizing vertical reference frames in geodesy, exploring the interior of the Earth in geophysics and geology, studying the behavior of currents in oceanography, or discovering sea level rise and ice-melting in climatology. Numerous Earth's gravitational field representations have already been derived from GOCE. These representations differ according to the time span of GOCE measurements and the theoretical approach used in the harmonic analysis. To assess the quality of the GOCE models validation by independent knowledge of the gravitational field has to be performed. Global gravitational field models with limited spectral/spatial resolution are validated by terrestrial data. In this case, spectral inconsistency between the two sources of data has to be treated properly. An intuitive approach to perform the validation in a consistent way is offered by an adequate filtering. Transformation of the regional data into the spectral domain is performed firstly. Then a low-pass filter is applied to generate a smoothed version of the regional model with the same spectral content as the global GOCE model. Subsequently, the filtered signal is transformed back into the space domain where comparison with a GOCE geoid surface is performed. Despite its conceptual simplicity, the development of an optimal filtering procedure is still challenging. In this contribution we address some aspects of the filtering method. Firstly, a simulation study based on EGM2008 is performed to investigate the accuracy of the direct transformation from space to frequency domain and its inverse. Moreover, various mathematical filters are considered to filter out the short wavelengths. Secondly, the most accurate filtering procedure is applied in validation of real GOCE models. The validation experiment is performed with respect to gravity anomalies and geoid undulations over the territory of Scandinavia.

Sprlak, M.; Gerlach, C.; Pettersen, B. R.; Omang, O. C. D.

2012-04-01

363

[Seasonal dynamics of soil active carbon pool in a purple paddy soil in southwest China].  

PubMed

The seasonal dynamics of soil organic carbon (SOC), readily oxidized carbon (ROC), dissolved organic carbon (DOC) and microbial biomass carbon (MBC) in a purple paddy soil were studied in a long-term field experimental station in Chongqing, China. The results showed that the seasonal variations of the contents of SOC, ROC and MBC had similar trends in the rape growing season. The contents were much higher in the early and late stages than in the middle stage of the rape growth. SOC, ROC and MBC all achieved the highest values of 16.20 g x kg(-1), 3.58 g x kg(-1) and 309.70 mg x kg(-1) at the end of the growing period, respectively. The seasonal change of DOC content presented as a single peak and reached to the highest value of 37.64 mg x kg(-1) at the middle stage of the rape growth. The temporal dynamics of the allocation ratios of ROC, MBC and DOC were similar to that of their contents. The allocation ratios of ROC, MBC and DOC were 15.49%-23.93%, 1.44%-2.06% and 0.11%-0.32% during the rape growing season, respectively. The influencing factors of SOC and ROC contents were the soil temperature at 5 cm soil depth, soil total nitrogen content and pH. MBC content was jointly impacted by the soil temperature at 5 cm soil depth, root biomass and its C and N contents. DOC content was mainly affected by soil moisture. PMID:23213908

Wu, Yan; Jiang, Chang-sheng; Hao, Qing-ju

2012-08-01

364

Magnetic Field Diagnostics and Spatio-Temporal Variability of the Solar Transition Region  

NASA Astrophysics Data System (ADS)

Magnetic field diagnostics of the transition region from the chromosphere to the corona faces us with the problem that one has to apply extreme-ultraviolet (EUV) spectro-polarimetry. While for the coronal diagnostics techniques already exist in the form of infrared coronagraphy above the limb and radio observations on the disk, one has to investigate EUV observations for the transition region. However, so far the success of such observations has been limited, but various current projects aim to obtain spectro-polarimetric data in the extreme UV in the near future. Therefore it is timely to study the polarimetric signals we can expect from these observations through realistic forward modeling. We employ a 3D magneto-hydrodynamic (MHD) forward model of the solar corona and synthesize the Stokes I and Stokes V profiles of C uc(iv) (1548 Å). A signal well above 0.001 in Stokes V can be expected even if one integrates for several minutes to reach the required signal-to-noise ratio, and despite the rapidly changing intensity in the model (just as in observations). This variability of the intensity is often used as an argument against transition region magnetic diagnostics, which requires exposure times of minutes. However, the magnetic field is evolving much slower than the intensity, and therefore the degree of (circular) polarization remains rather constant when one integrates in time. Our study shows that it is possible to measure the transition region magnetic field if a polarimetric accuracy on the order of 0.001 can be reached, which we can expect from planned instrumentation.

Peter, H.

2013-04-01

365

Regional gravity field modeling by the free-positioned point mass method  

NASA Astrophysics Data System (ADS)

The remove-compute-restore technique can be regarded as a state-of-the-art procedure for regional gravity field modeling, in which the long and short wavelength contributions from a spherical harmonic model and a DTM are first removed from the observations, then gravity field modeling techniques are applied to the residuals, and finally the corresponding long and short wavelength contributions are restored back. In this contribution the emphasis is on the second step, i.e., the compute or modeling step. Besides the classical integral and least-squares collocation (LSC) methods, the estimation based on radial basis functions is another interesting approach for regional gravity field modeling. The point mass method belongs to the latter category, where the basis functions with respect to the disturbing potential are the reciprocal distances between the function and observation locations. The choice of the positions and number of the point masses plays a crucial role in this method, and even in other related estimation methods. In order to solve this problem, the concept of the free-positioned point masses proposed by Barthelmes (1986) seems to be a good choice, in which the point masses are searched stepwise with simultaneous determination of the corresponding point mass positions and magnitudes within an iterative nonlinear least-squares approach. In this study, four different nonlinear iterative algorithms (Levenberg-Marquardt, L-BFGS, L-BFGS-B, and NLCG) have been implemented for regional gravity field modeling. The applicability and performance of each algorithm is demonstrated by two numerical tests with simulated and real data, respectively. In each test, different aspects (e.g., the use of original or reduced basis functions, the use of 2 or 4 parameters for each point mass), affecting the quality of the solutions, are discussed. Furthermore, the results are compared to the classical LSC solutions.

Lin, Miao; Denker, Heiner; Müller, Jürgen

2013-04-01

366

Influences of indigenous phototrophs on methane emissions from a straw-amended paddy soil  

Microsoft Academic Search

A pot experiment was conducted to investigate the influences of indigenous phototrophs on methane (CH 4) emissions from a paddy soil where rice straw was incorporated or was surface-applied. During the cultivation, half of the pots were covered with aluminum foil, except for the minimum space for rice plants, to prevent ambient light reaching the floodwater or the soil surface.

Naoki Harada; Shigeto Otsuka; Masaya Nishiyama; Satoshi Matsumoto

2005-01-01

367

Cadmium Speciation and Release Kinetics in a Thai Paddy Soil Subjected to Varying Redox Regimes  

Technology Transfer Automated Retrieval System (TEKTRAN)

Understanding the factors controlling Cd speciation and bioavailability in flooded, drained, and alternate flooded/drained paddy soil will be crucial to developing and implementing best management practices needed for productive agricultural areas. Transformation of Cd species can occur in response...

368

CADMIUM SOLUBILITY IN PADDY SOILS: EFFECTS OF SOIL OXIDATION, METAL SULFIDES AND COMPETITIVE IONS.  

EPA Science Inventory

Cadmium (Cd) is a non-essential element for human nutrition and is an agricultural soil contaminant. Cadmium solubility in paddy soils affects Cd accumulation in the grain of rice. This is a human health risk, exacerbated by the fact that rice grains are deficient in iron (Fe) an...

369

Loss of carbofuran from rice paddy water: chemical and physical factors.  

PubMed

The loss of carbofuran was studied from rice paddy water treated with a granular formulation of the insecticide, and from ponds filled with drainage from the paddy. The average half-life (t 1/2) for carbofuran loss was 57 hr. Controlled experiments indicated that pH was the predominating factor governing carbofuran loss from water in the environment studied. The loss due to hydrolysis was over 700 times more rapid at pH (t 1/2 = 1.2 hr.) than at pH (t 1/2 = 864 hr.) in buffered deionized water. The average pH of the rice paddy was 8, but diurnal fluctuations of 7 to 9.5 are common in similar environments. Impurities in the water, sunlight, and temperature influence the rate of carbofuran loss but not nearly so much as pH. There was no evidence for significant loss due to evaporation or oxidation. The results have important implications for the duration of the insecticide's activity and the effect on fish within or downstream from treated paddies. PMID:25291

Seiber, J N

1978-01-01

370

Burma Soils. A Study of the Effects of Lime and Cement on Paddy and Laterite Material.  

National Technical Information Service (NTIS)

Laboratory tests were performed on samples of paddy and laterite soils obtained from the proposed right-of-way of the Rangoon-Mandalay Highway, Burma. These tests were conducted to determine the basic engineering properties of the soils and to evaluate th...

N. B. Schomaker R. E. Aufmuth

1971-01-01

371

Flux estimates from soil methanogenesis and methanotrophy: Landfills, rice paddies, natural wetlands and aerobic soils  

Microsoft Academic Search

Present and future annual methane flux estimates out of landfills, rice paddies and natural wetlands, as well as the sorption capacity of aerobic soils for atmospheric methane, are assessed. The controlling factors and uncertainties with regard to soil methanogenesis and methanotrophy are also briefly discussed.

Pascal Boeckx; OSWALD VAN CLEEMPUT

1996-01-01

372

BIOAVAILABILITY AND SAFETY ISSUES OF HEAVY METALS IN PADDY SOIL-RICE CONTINUUM IN KOREA  

Microsoft Academic Search

There is an increasing concern over heavy metal contamination of agricultural soils and the successive translocation of metals to rice in Korea. Rice is one of the most important crops in the country. Thus, it is very important to monitor the status and trend of heavy metal contamination in paddy soils and rice periodically. It is also important to verify

Won-Il Kim; Jae E. Yang; Goo-Bok Jung; Byung-Jun Park; Sang-Won Park; Jin-Kyoung Kim; Oh-Kyung Kwon; Gab-Hee Ryu

373

Aging well: methanotrophic potential and community structure along a paddy soil chronosequence of 2000 years.  

NASA Astrophysics Data System (ADS)

Given that rice paddies are anthropogenic methane sources and the inevitable need to increase rice production to sustain human population growth, it is pertinent to identify the effects of long term agriculture on the selection of methanotrophs. Methanotrophs play a crucial role in mitigating methane emission from rice paddies. Therefore, we analyzed the methanotroph community along a chronosequence of paddy soils from China covering recently reclaimed sites to paddies under permanent agriculture since 2000 years (Cheng et al., 2009; doi:10.1016/j.geoderma.2009.03.016). Maximum potential methane oxidation rate (PMOR) increased monotonically with age. Our results also showed that long-term agriculture imposes a selection pressure on different groups of methanotrophs. In contrast to younger soils, type Ib methanotrophs were observed to multiply in correspondence with increasing PMOR in ancient soils, while other groups showed a relatively stable community composition as revealed by pmoA-based fingerprints (T-RFLP) and quantitative PCR. Cloning and sequencing the pmoA (a key gene in methane oxidation), the soils were found to harbour known and putative methanotrophs, ammonium-oxidizing bacteria, and interestingly, sequences affiliated to Crenothrix, a methane oxidizer with an unusual pmoA (Stoecker et al., 2006; doi:10.1073/pnas.0506361103). In summary, long-term agriculture shapes the community and allows for an elevated level of potential methane oxidation.

Ho, Adrian; Frenzel, Peter

2010-05-01

374

Soil type determines the abundance and community structure of ammonia-oxidizing bacteria and archaea in flooded paddy soils  

Microsoft Academic Search

Purpose  Ammonia oxidation plays an important role in global nitrogen cycle. However, little information is available on ammonia oxidizers\\u000a in paddy soils. This study aimed to understand the controlling factors of ammonia oxidizers in the paddy soils.\\u000a \\u000a \\u000a \\u000a \\u000a Materials and methods  Three types of paddy soils were collected from southwest [Chongqing City (CQ)], central [Honghu City (HH)], and northeast\\u000a [Panjin City (PJ)] of

Xin Chen; Li-Mei Zhang; Ju-Pei Shen; Zhihong Xu; Ji-Zheng He

2010-01-01

375

Characterization of the IMF By-dependent field-aligned currents in the cleft region based on DE 2 observations  

NASA Astrophysics Data System (ADS)

The magnetic field and plasma data from 47 passes of DE-2 are used to study the IMF By-dependent distribution of field-aligned currents in the cleft region. It is proposed that the low-latitude cleft current (LCC) region is not an extension of the region 1 or region 2 current system and that a pair of LCCs and high-latitude cleft currents (HCCs) constitutes the cleft field-aligned current regime. The proposed pair of cleft field-aligned currents is explained with a qualitative model in which this pair of currents is generated on open field lines that have just been reconnected on the dayside magnetopause. The electric fields are transmitted along the field lines to the ionosphere, creating a poleward electric field and a pair of field-aligned currents when By is positive; the pair of field-aligned currents consists of a downward current at lower latitudes and an upward current at higher latitudes. In the By negative case, the model explains the reversal of the field-aligned current direction in the LCC and HCC regions.

Taguchi, S.; Sugiura, M.; Winningham, J. D.; Slavin, J. A.

1993-02-01

376

Neuroplastic changes following rehabilitative training correlate with regional electrical field induced with tDCS.  

PubMed

Transcranial direct current stimulation (tDCS) has recently emerged as a promising approach to enhance neurorehabilitative outcomes. However, little is known about how the local electrical field generated by tDCS relates to underlying neuroplastic changes and behavior. To address this question, we present a case study analysis of an individual with hemianopia due to stroke and who benefited from a combined visual rehabilitation training and tDCS treatment program. Activation associated with a visual motion perception task (obtained by functional magnetic resonance imaging; fMRI) was used to characterize local changes in brain activity at baseline and after training. Individualized, high-resolution electrical field modeling reproducing precise cerebral and lesioned tissue geometry, predicted distortions of current flow in peri-lesional areas and diffuse clusters of peak electric fields. Using changes in fMRI signal as an index of cortical recovery, correlations to the electrical field map were determined. Significant correlations between the electrical field and change in fMRI signal were region specific including cortical areas under the anode electrode and peri-lesional visual areas. These patterns were consistent with effective tDCS facilitated rehabilitation. We describe the methodology used to analyze tDCS mechanisms through combined fMRI and computational modeling with the ultimate goal of developing a rationale for individualized therapy. PMID:21620985

Halko, M A; Datta, A; Plow, E B; Scaturro, J; Bikson, M; Merabet, L B

2011-05-18

377

Fault patterns in Benin River and Makaraba Fields: A regional play type for the Niger Delta  

SciTech Connect

Using 830 km{sup 2} of excellent 3-D seismic data, we determined the fault patterns that are responsible for hydrocarbon entrapment in the Benin River and Makaraba fields, onshore northwestern Niger Delta. Both fields are trapped downthrown to the major listric GbokoMaka growth fault system, which trends E18{degrees}S for over 40 km, and has at least 2000 m of displacement to the southwest. Several major splay faults break off the main trend in a southeasterly direction, creating a series of fault-bounded structural compartments. Each of these compartments opens to the southeast and has a structural attic at the junction of the splay fault with the main fault trend. These compartments create large-scale traps for hydrocarbons migrating from east to west up the gentle regional dip within the Miocene Ughelli depobelt. The Benin River field is trapped in the major compartment between the GbokoMaka fault and the Benin River splay fault. The large Makaraba field is similarly trapped between the GbokoMaka and MakaWest faults. Such traps require an upthrown fault seal at the master fault and a downthrown fault seal at the splay fault. In the Makamba field, the trap potential is enhanced by rollover into the GbokoMaka fault. The same structural style is also evident along several other major fault trends to the north and the south, and probably represents an important play type in the onshore western Niger delta.

Adeyekun, A.B.; Faparusi, B.D.; Nunns, A.G. [Chevron Nigeria Ltd., Lagos (Nigeria)] [and others

1995-08-01

378

Methane emissions from rice paddies natural wetlands, and lakes in China: synthesis and new estimate.  

PubMed

Sources of methane (CH4 ) become highly variable for countries undergoing a heightened period of development due to both human activity and climate change. An urgent need therefore exists to budget key sources of CH4 , such as wetlands (rice paddies and natural wetlands) and lakes (including reservoirs and ponds), which are sensitive to these changes. For this study, references in relation to CH4 emissions from rice paddies, natural wetlands, and lakes in China were first reviewed and then reestimated based on the review itself. Total emissions from the three CH4 sources were 11.25 Tg CH4  yr(-1) (ranging from 7.98 to 15.16 Tg CH4  yr(-1) ). Among the emissions, 8.11 Tg CH4  yr(-1) (ranging from 5.20 to 11.36 Tg CH4  yr(-1) ) derived from rice paddies, 2.69 Tg CH4  yr(-1) (ranging from 2.46 to 3.20 Tg CH4  yr(-1) ) from natural wetlands, and 0.46 Tg CH4  yr(-1) (ranging from 0.33 to 0.59 Tg CH4  yr(-1) ) from lakes (including reservoirs and ponds). Plentiful water and warm conditions, as well as its large rice paddy area make rice paddies in southeastern China the greatest overall source of CH4 , accounting for approximately 55% of total paddy emissions. Natural wetland estimates were slightly higher than the other estimates owing to the higher CH4 emissions recorded within Qinghai-Tibetan Plateau peatlands. Total CH4 emissions from lakes were estimated for the first time by this study, with three quarters from the littoral zone and one quarter from lake surfaces. Rice paddies, natural wetlands, and lakes are not constant sources of CH4 , but decreasing ones influenced by anthropogenic activity and climate change. A new progress-based model used in conjunction with more observations through model-data fusion approach could help obtain better estimates and insights with regard to CH4 emissions deriving from wetlands and lakes in China. PMID:23504718

Chen, Huai; Zhu, Qiu'an; Peng, Changhui; Wu, Ning; Wang, Yanfen; Fang, Xiuqin; Jiang, Hong; Xiang, Wenhua; Chang, Jie; Deng, Xiangwen; Yu, Guirui

2012-10-26

379

A NEW RECORD AND A REDESCRIPTION OF POLYPEDILUM PRUINA FREEMAN (DIPTERA: CHIRONOMIDAE) WITH A KEY TO INDIAN SPECIES ASSOCIATED WITH RICE FIELDS  

Microsoft Academic Search

Polypedilum pruina Freeman is recorded for the first time from the rice paddy area of India and redescribed in light of modern taxonomic usages. A new dichotomous key to rice field species of genus Polypedilum Kieffer is also presented.

Sailesh Chattopadhyay

380

Regional modelling of the Geomagnetic Field in Europe for the last 8000 years  

NASA Astrophysics Data System (ADS)

From a selected compilation of sedimentary and archaeomagnetic data a new low-degree regional geomagnetic model for the European Continent valid for the period 6000 BC to 1000 BC has been developed. This model provides information about the direction (declination and inclination) and intensity of the Earth's Magnetic Field in Europe during 5000 years, from 6000 BC to 1000 BC. By connecting it with our SCHA.DIF.3K previous model valid from 1000 BC to 1900 AD and the IGRF, we furnish continuous geomagnetic field information for the last 8000 years. The new model is called SCHA.DIF.8K. It has been developed using the Revised Spherical Cap Harmonic Analysis in 2 Dimensions technique (R-SCHA2D, Thébault, 2008, GJI) and the norm of the Earth's Magnetic Field to constrain the inversion problem. The size of the cap is 22°. The maximum degree of the expansion is 2. The linearization problem has been solved using the truncation Taylor's series applied to the expressions of the relationship between the declination, inclination and intensity data and the Cartesian component of the geomagnetic field. As initial or reference we used the Geocentric Axial Dipole field. In time, we used the classical sliding overlapping window method. The size of the window was set to 100 years shifted 50 years. We have compared the model's prediction with the input data and with the global CALS7K.2 model. The regional model shows a better fitting to the input data than the global model, especially for the intensity data.

Pavon-Carrasco, Francisco Javier; Osete, Maria Luisa; Miquel Torta, J.

2010-05-01

381

Inputs of heavy metals due to agrochemical use in tobacco fields in Brazil's Southern Region.  

PubMed

Only a few studies have assessed the joint incorporation of heavy metals into agricultural systems based on the range of agrochemicals used on a specific agricultural crop. This study was conducted to assess the heavy metals input through application of the main agrochemicals used in Brazilian tobacco fields. A total of 56 samples of different batches of 5 fertilizers, 3 substrates, 8 insecticides, 3 fungicides, 2 herbicides, and 1 growth regulator commonly used in the cultivation of tobacco in Brazil's Southern Region were collected from 3 warehouses located in the States of Rio Grande do Sul, Santa Catarina, and Paraná. The total As, Cd, Co, Cr, Cu, Hg, Fe, Mn, Ni, Pb, and Zn content of the samples was then determined and compared with the regulations of different countries and information found in the available literature. The fertilizers were identified as the primary source of heavy metals among the agrochemicals used. Application of pesticides directly to the shoots of tobacco plants contributed very little to the supply of heavy metals. The agrochemicals used in Brazilian tobacco fields provide lower inputs of the main heavy metals that are nonessential for plants than those registered in the international literature for the majority of crop fields in different regions of the world. PMID:22729828

Zoffoli, Hugo José Oliveira; do Amaral-Sobrinho, Nelson Moura Brasil; Zonta, Everaldo; Luisi, Marcus Vinícius; Marcon, Gracioso; Tolón-Becerra, Alfredo

2012-06-23

382

Analyses of disking phenomenon and stress field in the region of an underground powerhouse  

NASA Astrophysics Data System (ADS)

The large underground power chambers of Ertan Hydropower Station will be built near the abutment on the left bank in a region with high initial stresses. In this paper, a statistical analysis is presented for the phenomenon of core disking in the dam site. On the basis of a number of stress measurements, the region of the river valley could be divided into three different geostress zones. It is shown that there exists a rather high horizontal stress of up to 30 MPa, and even over 60 MPa at the bottom of the river bed. A least square method has been introduced to get a continuous field of stress, which approximates the variable measured stress data.

Zhu, Weishen; Li, Guangyu; Wang, Kejun

1985-01-01

383

Chiral effective-field theory in the Delta(1232) region : II. radiative pion photoproduction  

SciTech Connect

We present a theoretical study of the radiative pion photoproduction on the nucleon ($\\gamma N \\rightarrow \\pi N \\gamma'$) in the $\\De$-resonance region, with the aim to determine the magnetic dipole moment (MDM) of the $\\Delta^+(1232)$. The study is done within the framework of chiral effective-field theory where the expansion is performed (to next-to-leading order) in the $\\delta$ power-counting scheme which is an extension of chiral perturbation theory to the $\\Delta$-resonance energy region. We present in detail the results for the absorptive part of the $\\Delta$ MDM, as well as a sensitivity study for the radiative pion photoproduction observables on the real part of the $\\Delta$ MDM. We find that an asymmetry for circular polarization of the photon beam may provide a model-independent way to measure the $\\Delta$ MDM.

Vladimir Pascalutsa; Marc Vanderhaeghen

2007-10-12

384

A modified technique for field measurements of dry deposition fluxes of polychlorinated biphenyls in tropical regions.  

PubMed

This report focused on the development of a technique to measure dry deposition fluxes of PCBs in tropical environments. Temperature resistant double-adhesive tape has been used as a new surrogate surface for collection of deposited PCBs. The new technique includes the measurement of field blanks for the entire sampling period. A sonication-assisted extraction procedure has been validated for the extraction of PCBs from the tape. The new technique has been used in the field for a period of 4 months in the tropical region of Singapore. The average dry deposition flux measured for total PCBs was 15.3 ng m(-2) day(-1) and, on a global scale, this can be considered to be low. PMID:17765946

Wurl, Oliver; Obbard, Jeffrey Philip

2007-09-04

385

Biochar amendment decreased global warming potential of a Cd/Pb contaminated paddy ecosystem from the Tai Lake plain, China  

NASA Astrophysics Data System (ADS)

Nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4) are concerned as the predominant biogenic greenhouse gases (GHGs) in the net GHGs balance of agro-ecosystems. Predicting the net exchanges of these gases in a systemic approach would be critical for assessing the effects on GHGs mitigation of environmental conditions and crop management. Previous studies have shown a great potential of biochar amendment to mitigate GHGs emission from croplands. Here, we report a field experiment on biochar effects on rice production, net ecosystem exchange (NEE) and global warming potential (GWP) in cadmium (Cd) and lead (Pb) contaminated paddy field. Biochar was amended in 2009 before rice transplanting at rate of 0, 10, 20 and 40 t ha-1 and soil emission of CO2, ecosystem emissions of CH4 and N2O were monitored with closed chamber method at 7 days interval throughout the whole rice growing season (WRGS) in 2010. Soil samples were collected after rice harvest in 2010 for analysis of soil property changes with biochar amendment. Biochar amendment increased soil pH, soil organic carbon, total N but decreased soil bulk density. DTPA Cd and Pb were decreased by 25.3%, 21.3% and 48.7%, and by 11.9%, 17.3% and 23.6% under biochar amendment at rates of 10 t ha-1, 20 t ha-1 and 40 t ha-1, respectively. Total soil CO2 emission of WRGS was decreased by 16% and 24% under biochar amendment respectively at 20 and 40 t ha-1. There was a weak correlation of total CO2 emission with DTPA Pb concentration (p=0.0642). Total WRGS ecosystem emission of N2O was reduced by 11%, 33% and 50% under biochar amendment at 10 t ha-1, 20 t ha-1 and 40 t ha-1, respectively while an increase by 31% in that of CH4 emission was observed only under biochar amendment at 40 t ha-1.Overall, an consistent increase in ecosystem carbon sink was observed across all treatments of biochar amendment as the overall GWP of the ecosystem was decreased by 54% and 63% under biochar amendment at 20 t ha-1 and 40 t ha-1, respectively. Key words: biochar, net ecosystem exchange, global warming potential, cadmium and lead contaminated paddy field

Zhang, A.; Hussian, Q.; Li, L.; Zheng, J.; Pan, G.; Zhang, X.; Bian, R.

2012-04-01

386

The existence region of the Hg0.8Cd0.2Te phase field  

NASA Astrophysics Data System (ADS)

The existence region of the Hg0.8Cd0.2Te phase field has been re-examined using three techniques: Hall measurements, p-n junction depth measurements on material which had been annealed to produce an n-type skin following equilibration at high temperature, and quantitative modelling of experimental observations of gettering of silver in (Hg,Cd)Te. The results we obtain are generally in good agreement with previously reported measurements, although some systematic disagreement is found, particularly under tellurium saturated conditions for temperatures less than 450‡C.

Schaake, H. F.

1985-09-01

387

Coronal Magnetic Field Extrapolation from Photospheric Measurements Applied to an Active Region  

NASA Astrophysics Data System (ADS)

We outline an MHD relaxation method that permits to extrapolate photospheric vector magnetograms into coronal nonlinear force-free fields. The method is applied to a magnetogram taken before an eruptive event in NOAA AR 7792 on 25 October 1994. The event produced a coronal mass ejection (CME) and eruptive flare with a prominent sigmoidal soft X-ray source. Multiwavelength observations as well as theoretical modeling indicate the importance of twisted magnetic configurations in solar active regions(ARs) in the initiation of such events. Manoharan et al. (1996) proposed a model for this event that included the merging of two slightly twisted flux bundles near the polarity inversion line into a flux rope of larger total twist and an overlying flux system much closer to a potential-field state. For the extrapolation we use a vector magnetogram taken at the Mees Solar Observatory 16 hours before the actual event. The magnetic field extrapolation is able to recover main parts of the structures suggested in the model by Manoharan et al. We find the overlying nearly potential flux and part of the sigmoidal field, i.e., one of the suggested weakly twisted flux bundles, in the location observed. This supports the notion that sigmoids are coronal manifestations of twisted magnetic flux tubes which start expanding in eruptive events and may exist even before the onset of such events. We tentatively attribute the incomplete reconstruction of the sigmoidal field structure to the strong evolution of the photospheric field at the suggested location of flux tube merging between the time of the magnetogram and the eruption, as indicated by a magnetogram on the following day.

Fuhrmann, M.; Kliem, B.; Valori, G.; Seehafer, N.

2008-09-01

388

Regional geological and tectonic structures of the North Sea area from potential field modelling  

NASA Astrophysics Data System (ADS)

The spatial distribution of large-scale crustal domains and their boundaries are investigated in the North Sea area by combining gravity, magnetic and seismic data. The North Sea is situated on the plates of three continents, Avalonia, Laurentia and Baltica, which collided during the Caledonian orogeny in the middle Palaeozoic. The location and continuation of the collisional sutures are debated. We apply filters and transformations to potential field data to focus on the crystalline crust and uppermost mantle on a regional scale in order to extract new information on continental sutures. The transformations reveal intrinsic features of crustal transitions between the Caledonian plates and their relation to later extensional structures. The transformations include the Hough Transform applied to the gravity field, calculation of fractional derivatives and integrals of the gravity and magnetic fields, the pseudogravity field and the horizontal gradient field as well as upward continuation. The results indicate a fundamental difference between the lithosphere of Avalonia, Laurentia and Baltica. The location of the Mesozoic rift system (the Central Graben and Viking Graben), may have been partly determined by the presence of the sutures between these three plate, indicative of extensional reactivation of compressional structures. A significant lineament across the entire North Sea between Scotland and North Germany indicates that the lower crust of Baltica provenance may extend as far south-westward as to this lineament. Comparison of the power spectra of the gravity field in five selected areas shows significant differences in the long wavelength components between the areas north and south of the lineament corresponding to differences in crustal properties. This lineament could represent the suture between lithosphere of Caledonian origin (Avalonia) versus lithosphere of Precambrian origin (Baltica) in the lower crust and upper mantle. If this is the case, the lineament is the missing link in the reconstruction of the triple plate collision.

Lyngsie, S. B.; Thybo, H.; Rasmussen, T. M.

2006-02-01

389

Generation of parallel electric fields in the Jupiter-Io torus wake region  

NASA Astrophysics Data System (ADS)

Infrared and ultraviolet images have established that auroral emissions at Jupiter caused by the electromagnetic interaction with Io not only produce a bright spot, but an emission trail that extends in longitude from Io's magnetic footprint. Electron acceleration that produces the bright spot is believed to be dominated by Alfvén waves whereas we argue that the trail or wake aurora results from quasi-static parallel electric fields associated with large-scale, field-aligned currents between the Io torus and Jupiter's ionosphere. These currents ultimately transfer angular momentum from Jupiter to the Io torus. We examine the generation and the impact of the quasi-static parallel electric fields in the Io trail aurora. A critical component to our analysis is a current-voltage relation that accounts for the low-density plasma along the magnetic flux tubes that connect the Io torus and Jupiter. This low-density region, ˜ 2 R J from Jupiter's center, can significantly limit the field-aligned current, essentially acting as a “high-latitude current choke.” Once parallel electric fields are introduced, the governing equations that couple Jupiter's ionosphere to the Io torus become nonlinear and, while the large-scale behavior is similar to that expected with no parallel electric field, there are substantial deviations on smaller scales. The solutions, bound by properties of the Io torus and Jupiter's ionosphere, indicate that the parallel potentials are on the order of 1 kV when constrained by peak energy fluxes of a few milliwatts per square meter. The parallel potentials that we predict are significantly lower than earlier reports.

Ergun, R. E.; Ray, L.; Delamere, P. A.; Bagenal, F.; Dols, V.; Su, Y.-J.

2009-05-01

390

Reconstruction of the solar coronal magnetic field, from active region to large scale  

NASA Astrophysics Data System (ADS)

The low solar corona is dominated by the magnetic field which is created inside the sun by a dynamo process and then emerges into the atmosphere. This magnetic field plays an important role in most structures and phenomena observed at various wavelengths such as prominences, small and large scale eruptive events, and continuous heating of the plasma, and therefore it is important to understand its three-dimensional properties in order to elaborate efficient theoretical models. Unfortunately, the magnetic field is difficult to measure locally in the hot and tenuous corona. But this can be done at the level of the cooler and denser photosphere, and several instruments with high resolution vector magnetographs are currently available (THEMIS, Imaging Vector Magnetograph (IVM), the Advanced Stokes Polarimeter (ASP), SOLIS, HINODE, Solar Dynamics Observatory (SDO), or will be shortly available by future telescopes such as EST and solar missions as SOLAR-ORBITER. This has lead solar physicists to develop an approach which consists in " reconstructing" the coronal magnetic field from boundary data given on the photosphere. We will discuss some of the issues encountered in solving this problem as well our recent progress and results at the scale of active region scales or the larger one such as full sun scale.

Amari, T.; Canou, A.; Delyon, F.; Aly, J. J.; Frey, P.; Alauzet, F.

2011-12-01

391

Velocity Fields in H II Regions Using High Resolution Imaging Fabry-Perot Spectrometer  

NASA Astrophysics Data System (ADS)

The thesis comprises of two parts: I. Instrumentation II. Observations, results and discussion. An imaging Fabry-Perot spectrometer (IFPS) is designed and constructed for the studies on kinematics of extended astronomical objects (Seema et al., 1992). IFPS comprises of a field aperture, collimating lens and a two dimensional imaging sensor called Imaging Photon Detector (IPD). It is the first time that IPD which uses a resistive anode for position determination is being used in the spectroscopic studies of astronomical objects. Observations were made on Orion and Trifid nebula covering a wide field of view using a 35cm Celestron-14 telescope (f/11 cassegrain) at Gurushikhar, Mt.Abu, India. Orion Nebula: Observations were made in [OIII] 5007A, line with a spectral resolution of 6 km/sec and spatial resolution of 4" covering a field of view of 10.5', to study (i) general velocity flow (ii) high velocity flow and (iii)random motions. Line profiles generated for about 2000 positions showed an asymmetric shape with (a)a narrow component 20 +- 3 km/sec and (b) a broad component 50 +- 3 km/sec. The two components could be interpreted in terms of the interaction of the ionized gas (from the trapezium stars) with the condensations present in the nebula, resulting in the secondary flows. The iso-velocity contour map generated for both the components showed velocity flow in agreement with the champagne flow model (Tenorio-Tagle 1982). A model emission line profile constructed assuming a champagne flow in [OIII] 5007A, line for a position 2' away from theta-1 C Ori showed a reasonably good agreement with the narrow component of the observed profile. Certain high velocity flow (~50 km/s) regions are observed to be superimposed on the main flow of the narrow component. These flows are either radiation pressure driven stellar winds or jets generated during the formation phase of Young stellar objects. The radial velocity was found to be low with no high velocity flow regions in the dark bay indicating that there could be obstructing material to the expanding gas in this region. Velocity profile was generated for the first time across the Orion 'bar' ionization front. The high velocity flows are found only in certain clumps along the bar showing that the bar ionization front is found to be diffuse in [OIII] 5007A, line. The actual velocity obtained by us around the bar ionization front is estimated to be more than 100 km/s, indicating that O++ is produced by shock ionization (at least in part). Turbulence: The structure function B for a region r about 100" around theta-1 C Ori for both the narrow and the broad components showed a correlation of the form B proportional to r. We interpret that this deviation from the standard Kolmogorov model (1941) could be caused due to the presence of compressibility in the fluid (i.e., violation of one of the assumptions in Kolmogorov's model). For regions around theta-2 A Ori, the behaviour of the structure function is found to be irregular. Trifid nebula: Velocity field studies were made for about 48 positions on the nebula in [OIII] 5007A, line covering a field of view of 24'. The isovelocity map in a region 2' around the central hot star HD 164492 showed a picture of symmetric flow in velocities with no density gradients as was observed in the case of Orion nebula. A general red-shift in the radial velocities is observed in the south west direction with a velocity change of 50 km/s. There is a symmetric localized flow with a red-shift velocity of 40 km/s observed about 2.3' southwest of HD 164492 corresponding to a bow shock feature adjoining a condensation. (SECTION: Dissertation Summaries)

Seema, P.

1996-05-01

392

Analyses of the warm season rainfall climatology of the northeastern US using regional climate model simulations and radar rainfall fields  

NASA Astrophysics Data System (ADS)

We examine the warm season (April-September) rainfall climatology of the northeastern US through analyses of high-resolution radar rainfall fields from the Hydro-NEXRAD system and regional climate model simulations using the weather research and forecasting (WRF) model. Analyses center on the 5-year period from 2003 to 2007 and the study area includes the New York-New Jersey metropolitan region covered by radar rainfall fields from the Fort Dix, NJ WSR-88D. The objective of this study is to develop and test tools for examining rainfall climatology, with a special focus on heavy rainfall. An additional emphasis is on rainfall climatology in regions of complex terrain, like the northeastern US, which is characterized by land-water boundaries, large heterogeneity in land use and cover, and mountainous terrain in the western portion of the region. We develop a 5-year record of warm season radar rainfall fields for the study region using the Hydro-NEXRAD system. We perform regional downscaling simulations for the 5-year study period using the WRF model. Radar rainfall fields are used to characterize the interannual, seasonal and diurnal variation of rainfall over the study region and to examine spatial heterogeneity of rainfall. Regional climate model simulations are characterized by a wet bias in the rainfall fields, with the largest bias in the high-elevation regions of the model domain. We show that model simulations capture broad features of the interannual, seasonal, and diurnal variation of rainfall. Model simulations do not capture spatial gradients in radar rainfall fields around the New York metropolitan region and land-water boundaries to the east. The model climatology of convective available potential energy (CAPE) is used to interpret the regional distribution of warm season rainfall and the seasonal and diurnal variability of rainfall. We use hydrologic and meteorological observations from July 2007 to examine the interactions of land surface processes and rainfall from a regional perspective.

Yeung, June K.; Smith, James A.; Villarini, Gabriele; Ntelekos, Alexandros A.; Baeck, Mary Lynn; Krajewski, Witold F.

2011-02-01

393

Quantitative relationships between éeld-measured leaf area index and vegetation index derived from VEGETATION images for paddy rice éelds  

Microsoft Academic Search

In an eVort to develop the quantitative relationships between éeld- measured leaf area index (LAI) and VEGETATION-derived vegetation indices for paddy rice é elds, we have measured LAI of paddy rice é elds at 10-day intervals at é ve sampling sites in Jiangning County, Jiangsu Province of China during the rice growing season (July to October) of 1999, using a

X. XIAO; L. HE; W. SALAS; C. LI; B. MOORE III; R. ZHAO; S. FROLKING; S. BOLES

2002-01-01

394

Three field photometer observations of gravity waves in the 80 to 100 km height region  

NASA Astrophysics Data System (ADS)

A three field photometer (3FP) for making observations of airglow in the Mesosphere Lower Thermosphere (MLT) region has been installed at the centre of the large MF aerial array located near Adelaide since 1993. Observations of the 558 nm airglow emitted by atomic oxygen at height near 97 km and the 732 nm airglow emitted by Hydroxyl near 85 km have been made simultaneously with MF Spaced Antenna observations of wind velocities in the 80-100 km height region. The 3FP measures the intensity of the 558 nm and 732 nm airglow in three fields separated by about 13 km. These data have been analysed to yield gravity wave phase speeds and horizontal wavelengths. Simultaneous MF radar data have been analysed to yield measurements of the neutral wind velocity in 2 km height steps in the 80-100 km height interval every two minutes, and these have been used together with the observed wave parameters to calculate intrinsic gravity wave parameters. This paper presents a very brief overview of the system, the motivation for the work, and presents results from 1995 until 2000.

Reid, I. M.; Woithe, J. M.

2003-04-01

395

Radar observations of artificial E-region field-aligned irregularities  

NASA Astrophysics Data System (ADS)

Artificial E region field aligned plasma density irregularities (FAIs) were generated using HAARP in four different experimental modes and observed with a coherent scatter radar imager located 450 km to the southwest where it could detect field-aligned backscatter. The experiments were conducted in July of 2008, during the Polar Aeronomy and Radio Science Summer School (PARS), during quiet conditions in the daytime when the E layer was dense and absorption was modest. The echoes observed during zenith and magnetic zenith heating experiments were deflected from their nominally anticipated horizontal positions toward the midpoint position. The occurrence of hysteresis when heating with amplitude modulated pulses implied the development of the resonance instability, although the threshold for the onset of instability appeared to be higher than what has been predicted theoretically. Heating experiments involving pump frequencies slightly above and below the second electron gyroharmonic frequency produced no significant differences in the observed echoes. Finally, heating with a pump frequency slightly above the E region critical frequency appears to have produced FAIs at two distinct altitudes where the upper-hybrid resonance condition could be satisfied.

Nossa, E.; Hysell, D. L.; Fallen, C. T.; Watkins, B. J.

2009-07-01

396

Fine Scale Magnetic Fields in and Around a Decaying Active Region  

NASA Astrophysics Data System (ADS)

A very high resolution spectro-polarimetric observation of a decaying spot was observed with the Diffraction Limited Spectro-Polarimeter (DLSP). The spatial resolution achieved in this observation is close to the diffraction limit (0.18arcsec) of the Dunn Solar Telescope operated by the National Solar Observatory at Sacramento Peak, Sunspot, New Mexico. The fine scales present inside the decaying active region as well as surrounding areas of the active region will be presented. There are two interesting phenomenon observed which will be described in detail. They are: (i) There are opposite polarity loops present all around the spot and some of them do connect the main spot and the surrounding magnetic features, (ii) Canopy like structures are likely to be present in the umbral dots as well as in the light bridges present providing evidence for field-free intrusion. The conclusion from the time variation of the intensity structures of this spot is that the spot is disrupted in to several fragments by the formation of light bridges and the fragmented magnetic fields later disappear under the visible photosphere.

Sankarasubramanian, K.; Hagenaar, M.

2006-11-01

397

Magnetic Field Structures in a Facular Region Observed by THEMIS and Hinode  

NASA Astrophysics Data System (ADS)

The main objective of this paper is to build and compare vector magnetic maps obtained by two spectral polarimeters, i.e. THEMIS/MTR and Hinode SOT/SP, using two inversion codes (UNNOFIT and MELANIE) based on the Milne - Eddington solar atmosphere model. To this end, we used observations of a facular region within active region NOAA 10996 on 23 May 2008, and found consistent results concerning the field strength, azimuth and inclination distributions. Because SOT/SP is free from the seeing effect and has better spatial resolution, we were able to resolve small magnetic polarities with sizes of 1? to 2?, and we could detect strong horizontal magnetic fields, which converge or diverge in negative or positive facular polarities. These findings support models which suggest the existence of small vertical flux tube bundles in faculae. A new method is proposed to get the relative formation heights of the multi-lines observed by MTR assuming the validity of a flux tube model for the faculae. We found that the Fe i 6302.5 Å line forms at a greater atmospheric height than the Fe i 5250.2 Å line.

Guo, Y.; Schmieder, B.; Bommier, V.; Gosain, S.

2010-03-01

398

NOTE: Dosimetric effects on the penumbra region of irregular multi-leaf collimated fields  

NASA Astrophysics Data System (ADS)

The dosimetric effect in the penumbra region for multi-leaf collimator (MLC) fields was studied using a Varian 21 EX linear accelerator. The beam profiles in the cross-line and in-line directions for MLC field configurations of varying lengths of protruded leaves, which are adjacent (on one or both sides) to the beam profile axes, were measured using a 6 MV photon beam. It was found that there is a decrease of dose in the 'edge' region of the protruded leaves' side in the cross-line profile, when the protruded leaves (upper and/or lower side) were moved out from 0.5 cm to 3 cm towards the central beam axis. When both the upper and lower portions of leaves were moved out forming a gap for the profile, the dose at the 'edge' region in the cross-line direction was decreased by about 20% and 6%, with the protruded length of leaves being 0.5 cm and 1 cm, respectively. The penumbra width of the cross-line profile increased with the protruded length of leaves when the gap width was 0.5 cm, and it was independent of the length when the width was increased larger than 1 cm. The Pinnacle treatment planning system could calculate the decrease of dose observed experimentally in the cross-line profile, but an underestimation of about 30% was found when using version 6.2b, which did not consider the leaf rounded end and tongue-and-groove effect. While the newly commissioned 7.4f, which considered the two aforementioned effects, made an improvement, it still underestimated the dose by 25% compared to the measurement. For the in-line profiles, both versions estimated the penumbra width well.

Chow, James C. L.; Wettlaufer, Brent; Jiang, Runqing

2006-02-01

399

[Profile of soil microbial biomass carbon in different types of subtropical paddy soils].  

PubMed

The soil microbial biomass carbon (C(mic)), one of the most active components of soil organic carbon (C(org)), is an effective indicator of soil quality. In the present study, five subtropical paddy soils developed from different parent materials were selected, and the distribution of C(mic) through the profiles was studied, as well as the relationship of C(mic) with C(org) and soil nutrients. The results showed that the contents of C(org) and C(mic) decreased markedly with increasing soil depth, ranging from 2.45 g x kg(-1) to 26.19 g x kg(-1) and from 4.55 mg x kg(-1) to 1 691.75 mg x kg(-1), respectively. They mainly concentrated in the surface layer (plough horizon and plough pan). The content of C(mic) varied significantly in paddy soils developed from different parent materials, with the highest one in yellow clayey soil, and the lowest ones in alluvial sandy soil and reddish yellow clayey soil. This was on the contrary to the distribution of C(org) in the surface paddy soils, since the reddish yellow clayey soil and alluvial sandy soil showed higher contents while other types of paddy soils exhibited similar contents of C(org). Notwithstanding, C(mic) was still controlled by the quantity of C(org) and positively correlated with C(org). The ratio of C(mic) to C(org)(C(mic)/C((org)) decreased with increasing soil depth and differed in the plough horizon between different paddy soils, with lower values in alluvial sandy soil (2.11%) and reddish yellow clayey soil (1.37%) but higher value in reddish yellow clayey soil I (8.24%). It indicated that the microbial substrate availability in alluvial sandy soil and reddish yellow clayey soil was lower than those in reddish yellow clayey soils. The content of C(mic) was significantly positively correlated with total nitrogen, alkali-hydrolyzable N and Olsen-P, but was irrelevant to available K. It is implied that the C(mic) was not only controlled by C(org), but also complicatedly interacted with soil nutrients in paddy soils. PMID:23798145

Sheng, Hao; Zhou, Ping; Yuan, Hong; Liao, Chao-Lin; Huang, Yun-Xiang; Zhou, Qin; Zhang, Yang-Zhu

2013-04-01

400

Anaerobic N mineralization in paddy soils in relation to inundation management, physicochemical soil fractions, mineralogy and soil properties  

NASA Astrophysics Data System (ADS)

Anaerobic N mineralization measured from (saturated) repacked soil cores from 25 paddy fields in Bangladesh and was previously found to negatively related to soil N content on a relative basis. This suggests that other factors like soil organic matter (SOM) quality or abiotic factors instead control the anaerobic N mineralization process. We therefore assessed different physical and chemical fractions of SOM, management factors and various soil properties as predictors for the net anaerobic N mineralization. 1° First, we assessed routinely analyzed soil parameters (soil N and soil organic carbon, texture, pH, oxalate- and pyrophosphate-extractable Fe, Al, and Mn, fixed-NH4 content). We found no significant influences of neither soil mineralogy nor the annual length of inundation on soil N mineralization. The anaerobic N mineralization correlated positively with Na-pyrophosphate-extractable Fe and negatively with pH (both at P<0.01). At this stage it is, however, not known if these relations between net evolution of NH4 and pH and Fe content are causal or indirect. 2° Second, the 25 samples collected from farmers' fields were physically fractionated into particulate OM and silt and clay associated OM. The silt and clay sized OM was further chemically fractionated by oxidation with 6%NaOCl to isolate an oxidation-resistant OM fraction, followed by extraction of mineral bound OM with 10%HF thereby isolating the HF-resistant OM. None of the physicochemical SOM fractions were found useful predictors anaerobic N mineralization. The linkage between these chemical soil N fractions and N supplying processes actually occurring in the soil thus appears to be weak. Regardless, we hypothesize that variation in strength of N-mineral and N-OM linkages is likely to explain variation in bio-availability of organic N and proneness to mineralization. Yet, in order to separate kinetically different soil N fractions we then postulated that an alternative approach would be required, which instead isolates soil N fractions on the basis of bonding strength. In this respect bonding strength should be seen as opposite of proneness to dissolution of released N into water, the habitat of soil microorganisms mediating soil N mineralization. We hypothesize that soil N extracted by water at increasing temperatures would reflect such N fractions with increasing bonding strength, in turn equivalent to decreasing bio-availability. Although water has frequently been used to extract labile SOM, its use has mostly been limited to 100°C. 3° Third we developed sub critical water extraction (SCWE) at 100°C, 150°C and 200°C to isolate SOM fractions from the set of 25 paddy soil samples. In all cases, SCWE organic carbon (SCWE-OC) and N (SCWE-N) increased exponentially with the increase of temperature. SCWE preferentially extracted N over OC with increasing temperature. The efficiency of SCWE and the selectivity towards N were both lower in soils with increasingly reactive clay mineralogy. No correlations were found between the SCWE fractions and anaerobic N mineralization rate. In conclusion, SOM quantity and SOM quality, here represented by C and N distribution over physicochemical fractions, don't seem to dominantly determine anaerobic N mineralization in primarily young floodplain paddy soils. Other factors with exceeding control (pH and pyrophosphate extractable Fe) appear to exist. Possibly, the specific young genesis stage of most of the soils included (termed 'floodplain' soils) results in a limited availability of readily reducible Fe. Being an important alternative electron acceptor under submerged conditions, the availability of Fe, which is also controlled by pH, may be a bottleneck in the anaerobic N mineralization process. This needs to be further investigated by controlled incubation experiments with detailed follow-up of pH, redox potential, Fe in solution and mineral N.

Sleutel, Steven; Kader, Mohammed Abdul; Ara Begum, Shamim; De Neve, Stefaan

2013-04-01

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