上海郊区稻田氮素流失研究

通过测坑和大田小区试验，研究了上海郊区稻田氮素排水流失和渗漏流失的特征、相关因素和流失负荷。结果表明，稻田综合排水TN为6.55mg／L，流失负荷为16．68kg／hm^2，以铵态氮为主，稻田氮素的排水流失负荷为16．68kg／hm^2。稻田渗漏水氮浓度与前茬作物有关，草莓和蔬菜高，麦茬低，TN为5．73mg／L，渗漏负荷为22．92kg／hm^2，其中硝态氮占50％左右。稻田氮素总流失负荷占稻季化肥用量的13．23％。测坑和大田试验都证明，施用有机肥可较多地减少稻田氮素流失量。     

果尔对水稻土中厌氧细菌的影响

探讨了各种浓度的果尔对水稻土中厌氧细菌群的影响,实验表明,低于或等于田间正常施药量的果尔,在１周内对各类氧细菌的生长具有刺激作用,随着施药后时间的延长,刺激作用逐渐消失;高于田间正常施药量的果尔,在１周内对各类厌氧细菌的生长具有明显的抑制作用,随着施药后时间的延长,果尔的降解产物能促进各类厌氧细菌的生长。     

Phosphine migration at the water-air interface in Lake Taihu, China

The diurnal atmospheric phosphine (PH₃) concentrations and fluxes at the water-air interface in Lake Taihu were reported. The results showed that the PH₃ flux at the water-air interface ranged from −69.9 ± 29.7 to 121 ± 42 ng m⁻² h⁻¹, with a mean flux of 14.4 ± 22.5 ng m⁻² h⁻¹. The fluxes were both negative and positive during the diurnal period, indicating that the lake can act as a sink and a source of PH₃. In addition, the PH₃ fluxes were positively correlated with water temperature, total soluble phosphorus and soluble reactive phosphorus, while they were negatively correlated with water redox potential. A similar diurnal variation curve of atmospheric PH₃ concentrations was observed during all four seasons, with the maximum level occurring in early morning and the minimum appearing around midday. These findings suggest that light plays an important role in the elimination of atmospheric PH₃. A significant positive correlation was also found between air temperature and atmospheric PH₃ concentration. The mean flux of PH₃ in Lake Taihu was higher than in other reported wetlands, with an estimated annual emission of PH₃ to the atmosphere of 2.94 × 10⁵ g y⁻¹.     

Seasonal variations of CH(4) and N(2)O emissions in response to water management of paddy fields located in Southeast China

Water management is one of the most important practices that affect methane (CH₄) and nitrous oxide (N₂O) emissions from paddy fields. A field experiment was designed to study the effects of controlled irrigation (CI) on CH₄ and N₂O emissions from paddy fields, with traditional irrigation (TI) as the control. The effects of CI on CH₄ and N₂O emissions from paddy fields were very clear. The peaks of CH₄ emissions from the CI paddies were observed 1-2 d after the water layer disappeared. Afterward, the emissions reduced rapidly and remained low until the soil was re-flooded. A slight increase of CH₄ emission was observed in a short period after re-flooding. N₂O emissions peaks from CI paddies were all observed 8-10 d after the fertilization at the WFPS ranging from 78.1% to 85.3%. Soil drying caused substantial N₂O emissions, whereas no substantial N₂O emissions were observed when the soil was re-wetted after the dry phase. Compared with TI, the cumulative CH₄ emissions from the CI fields were reduced by 81.8% on the average, whereas the cumulative N₂O emissions were increased by 135.4% on the average. The integrative global warming potential of CH₄ and N₂O on a 100-year horizon decreased by 27.3% in the CI paddy fields, whereas no significant difference in the rice yield was observed between the CI and TI fields. These results suggest that CI can effectively mitigate the integrative greenhouse effect caused by CH₄ and N₂O emissions from paddy fields while ensuring the rice yield.     

The effects of high metal concentrations in soil-compost mixtures on soil enzymes

The study was undertaken to determine the impact of high-metal composts on the activities of four soil enzymes. High concentrations of metal salts (Cr, Cu, Ni or a Co-Mo-Pb combination) were added to feedstocks during the thermophilic stage of composting. These four metal-enriched composts and an unamended control compost were then mixed with soil collected from long-term agriculture plots under organic management or conventional management. The compost-soil mixtures were prepared at two rates (1:1 or 1:3 compost:soil, v/v) and incubated at 20°C for three weeks. These 20 combinations plus the five composts and the two soils were added to pots and incubated for three weeks. Following incubation, soil enzyme activities (acid phosphatase, arysulfatase, dehydrogenase, phosphodiesterase) were measured using traditional assay procedures. Compared to the control, none of the high-metal composts inhibited soil enzyme activity. Notably, the Cu compost treatment produced significantly higher activity of all four enzymes in the soil compared to the control. Previous soil management influenced the activity of three enzymes, arysulfatase and dehydrogenase had greater activity in the organic soil while phosphatase activity was greater in the conventional soil. Increasing the proportion of compost in the pot had a positive effect on phosphodiesterase activity only. In conclusion, the high-metal compost treatments either enhanced or caused no adverse effects on soil enzyme activity.     

Review on the use of enzymes for the detection of organochlorine, organophosphate and carbamate pesticides in the environment

Pesticides are released intentionally into the environment and, through various processes, contaminate the environment. Three of the main classes of pesticides that pose a serious problem are organochlorines, organophosphates and carbamates. While pesticides are associated with many health effects, there is a lack of monitoring data on these contaminants. Traditional chromatographic methods are effective for the analysis of pesticides in the environment, but have limitations and prevent adequate monitoring. Enzymatic methods have been promoted for many years as an alternative method of detection of these pesticides. The main enzymes that have been utilised in this regard have been acetylcholinesterase, butyrylcholinesterase, alkaline phosphatase, organophosphorus hydrolase and tyrosinase. The enzymatic methods are based on the activation or inhibition of the enzyme by a pesticide which is proportional to the concentration of the pesticide. Research on enzymatic methods of detection, as well as some of the problems and challenges associated with these methods, is extensively discussed in this review. These methods can serve as a tool for screening large samples which can be followed up with the more traditional chromatographic methods of analysis.     

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

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).     

The dynamics of arsenic in four paddy fields in the Bengal delta

Irrigation with arsenic contaminated groundwater in the Bengal Delta may lead to As accumulation in the soil and rice grain. The dynamics of As concentration and speciation in paddy fields during dry season (boro) rice cultivation were investigated at 4 sites in Bangladesh and West Bengal, India. Three sites which were irrigated with high As groundwater had elevated As concentrations in the soils, showing a significant gradient from the irrigation inlet across the field. Arsenic concentration and speciation in soil pore water varied temporally and spatially; higher As concentrations were associated with an increasing percentage of arsenite, indicating a reductive mobilization. Concentrations of As in rice grain varied by 2-7 fold within individual fields and were poorly related with the soil As concentration. A field site employing alternating flooded-dry irrigation produced the lowest range of grain As concentration, suggesting a lower soil As availability caused by periodic aerobic conditions.     

Modeling transport and fate of nitrogen from urea applied to a near-trench paddy field

A simple but comprehensive model is developed to quantify N losses from urea applied to a near-trench paddy field, considering all the N-transformations such as urea hydrolysis, volatilization, nitrification, denitrification, and all the important transportations like runoff, lateral seepage, vertical leaching and crop uptake. Seasonal average data of field observations for three crop seasons were used for model calibration and validation, which showed that ammonia volatilization accounted for 26.5-29.4% of the applied N and N uptake by crop occupied 38.2-44.8%, while N losses via surface runoff, vertical leaching and lateral seepage varied from 5.6-7.7%, 4.0-4.9% to 5.0-5.3% of the applied N, respectively. These observed results were well predicted by our model, indicating that the model performed effectively at quantifying N losses via individual processes in a wide range of urea application rates and benefit for developing water and fertilizer management strategies for near-trench paddy fields.     

Temporal trends and sources of PCDD/Fs, pentachlorophenol and chlornitrofen in paddy field soils along the Yoneshiro River basin, Japan

In order to understand the long-term behaviors of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), pentachlorophenol (PCP), and 2,4,6-trichlorophenyl-4′-nitrophenyl ether (chlornitrofen, CNP) in paddy soil, we measured their concentrations in paddy soil samples collected in 1982 and 1984 (1980s) and in 2000 and 2002 (2000s) from the Yoneshiro River basin, Japan. The concentrations of PCP and CNP decreased from the 1980s to the 2000s, whereas the concentrations of PCDD/Fs and their toxic equivalency (WHO2006-TEQ) remained. The major sources of PCDD/Fs in the paddy soil samples were attributed to impurities in PCP and CNP as a result of comparisons of homologue and congener profiles and principal component analysis. Based on the results of comparison of total input and remaining amount, it is estimated that more than 99% of PCP and CNP applied to the paddy fields had disappeared, whereas most of the applied PCDD/Fs and TEQ remained.     

高效除草尿素(药肥)对稻区非目标生物影响研究

研究了高效除草尿素（药肥）对稻区水生生物的影响。结果表明,药肥对蟾 Ｂｕｆｏｂｕｆｏｇａｒｇａｒｉｚａｎｓ蝌蚪、棘胸蛙Ｒａｎａｓｐｉｎｏｓａ蝌蚪、食蚊鱼Ｇａｍｂｕｓｉａａｆｆｉｎｉｓ、虹鳟Ｓａｌｍｏｇａｉｒｄｎｅｒｉ、湖螺Ｂａｌｌａｍｙａｓｐ和蚤状蚤Ｄａｐｈｎｉａｐｕｌｅｘ的９６ｈＬＣ５０分别分别为５４３６、１５７９、４０７３、５６８、４１３９和９７８１ｍｇ／Ｌ。按照用量和目前国内外普遍采用的评价     

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

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: ∑DDTs (13.7 μg kg⁻¹) > ∑HCHs (8.6 μg kg⁻¹) > > HCB (2.09 μg kg⁻¹) > α-endosulfan (1.30 μg kg⁻¹) > endrin (1.08 μg kg⁻¹) > PCNB (0.76 μg kg⁻¹) > dieldrin (0.58 μg 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.     

Mass balance and long-term fate of PCDD/Fs in a lagoon sediment and paddy soil, Niigata, Japan

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in a sediment core and in samples of surface sediment and paddy soil collected from the Toyano lagoon and Kameda basin in Niigata, Japan, were analyzed to elucidate the temporal trends of their concentrations in the lagoon sediment and the relationship between the sediment and the paddy soil. The mass balance of these pollutants was also estimated to determine their long-term fate in surface waters. An analysis by chemical mass balance identified the agrochemicals pentachlorophenol and 2,4,6-trichlorophenyl 4-nitrophenyl ether as the major sources of PCDD/Fs. On the basis of the findings regarding the mass balance in the Kameda basin over the last 40 years, we estimate that more than half the input of PCDD/Fs to the Kameda basin has disappeared. We suggest that the PCDD/Fs that flowed out from the paddy fields have been transferred to the lower basin.     

Physicochemical forms of technetium in surface water covering paddy and upland fields

The behavior of an element in the environment depends on its physicochemical form. Basic data for the behavior of technetium in an agricultural environment were obtained by determining the physicochemical forms of Tc in 28 surface water samples from paddy and upland fields. Most of the (95m)Tc was present as TcO(4)(-) in the samples. The relative amount of this chemical form was 72% on average. A significant amount of insoluble Tc (particles more than 0.2 microm in size), however, was found in some samples. The maximum amount of the insoluble Tc was 91%. Other forms were found in insignificant amounts. The amount of insoluble Tc was relatively high in paddy soil samples. Paddy soils, gley soils and gray lowland soils were particularly effective in the insolubilization of Tc. Among the soil characteristics studied, cation exchange capacity, anion exchange capacity, and active aluminum showed significant correlations with the relative amount of insoluble Tc. When microorganisms were eliminated from the surface water samples before the addition of (95m)TcO(4)(-), little insoluble Tc was found, suggesting that microorganisms cause the physicochemical transformation. These results showed that the physicochemical form of Tc changes from TcO(4)(-) to insoluble forms in surface water covering paddy fields. The insoluble forms would restrict the mobility of Tc in paddy fields.     

Photolytic and photocatalytic degradation of quinclorac in ultrapure and paddy field water: identification of transformation products and pathways

Quinclorac (QNC) is an effective but rather persistent herbicide commonly used in rice production. This herbicide presents a mean persistence in the environment so its residues are considered of environmental relevance. However, few studies have been conducted to investigate its environmental behavior and degradation. In the present work, direct photolysis and TiO₂ photocatalysis of the target compound in ultrapure and paddy field water were investigated. After 10 h photolysis in ultrapure water, the concentration of QNC declined 26% and 54% at 250 and 700 W m⁻², respectively. However, the amount of quinclorac in paddy field water remained almost constant under the same irradiation conditions. QNC dissipated completely after 40 min of TiO₂ photocatalysis in ultrapure water, whereas 130 min were necessary to degrade 98% of the initial concentration in paddy field water.Possible QNC photolytic and photocatalytic degradation pathways are proposed after structure elucidation of the main transformation products, through liquid chromatography-electrospray ionization-quadrupole time-of-flight mass spectrometry and exact mass measurements. Pyridine ring hydroxylation at C-9 followed by ring opening and/or oxidative dechlorination were the key steps of QNC degradation.     

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

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 μg 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.     

Arsenic release from flooded paddy soils is influenced by speciation, Eh, pH, and iron dissolution

Arsenic (As) is highly mobilized when paddy soil is flooded, causing increased uptake of As by rice. We investigated factors controlling soil-to-solution partitioning of As under anaerobic conditions. Changes in As and iron (Fe) speciation due to flooded incubation of two paddy soils (soils A and B) were investigated by HPLC/ICP-MS and XANES. The flooded incubation resulted in a decrease in Eh, a rise in pH, and an increase in the As(III) fraction in the soil solid phase up to 80% of the total As in the soils. The solution-to-soil ratio of As(III) and As(V) (R_L/S) increased with pH due to the flooded incubation. The R_L/S for As(III) was higher than that for As(V), indicating that As(III) was more readily released from soil to solution than was As(V). Despite the small differences in As concentrations between the two soils, the amount of As dissolved by anaerobic incubation was lower in soil A. With the development of anaerobic conditions, Fe(II) remained in the soil solid phase as the secondary mineral siderite, and a smaller amount of Fe was dissolved from soil A than from soil B. The dissolution of Fe minerals rather than redox reaction of As(V) to As(III) explained the different dissolution amounts of As in the two paddy soils. Anaerobic incubation for 30 d after the incomplete suppression of microbial activity caused a drop in Eh. However, this decline in Eh did not induce the transformation of As(V) to As(III) in either the soil solid or solution phases, and the dissolution of As was limited. Microbial activity was necessary for the reductive reaction of As(V) to As(III) even when Eh reached the condition necessary for the dominance of As(III). Ratios of released As to Fe from the soils were decreased with incubation time during both anaerobic incubation and abiotic dissolution by sodium ascorbate, suggesting that a larger amount of As was associated with an easily soluble fraction of Fe (hydr) oxide in amorphous phase and/or smaller particles.     

利用响应曲面法研究蓖齿眼子菜克藻效应的环境因子

水生植物的克藻效应受到多种环境因子的影响.利用响应曲面法,对影响沉水植物蓖齿眼子菜对铜绿微囊藻克藻效应的3个环境因子进行实验研究.通过对曲面模型分析,得出蓖齿眼子菜对铜绿微囊藻的藻细胞个数的相对抑制率在温度、光照强度、全盐莒3个环境因子分别为24℃、2 891 lx、4 407 mg/L时达到最大值.曲面模型经过方差分...     

Aquatic toxicity of glyphosate-based formulations: comparison between different organisms and the effects of environmental factors

Glyphosate-based herbicides (e.g. Roundup) are extensively used in the aquatic environment, but there is a paucity of data on the toxicity of the formulated products and the influences by environmental factors. In this study, the acute toxicity of technical-grade glyphosate acid, isopropylamine (IPA) salt of glyphosate, Roundup and its surfactant polyoxyethylene amine (POEA) to Microtox bacterium (Vibrio fischeri), microalgae (Selenastrum capricornutum and Skeletonema costatum), protozoa (Tetrahymena pyriformis and Euplotes vannus) and crustaceans (Ceriodaphnia dubia and Acartia tonsa) was examined and the relative toxicity contributions of POEA to Roundup were calculated. The effects of four environmental factors (temperature, pH, suspended sediment and algal food concentrations) on the acute toxicity of Roundup to C. dubia were also examined. Generally, the toxicity order of the chemicals was: POEA>Roundup>glyphosate acid>IPA salt of glyphosate, while the toxicity of glyphosate acid was mainly due to its high acidity. Microtox bacterium and protozoa had similar sensitivities towards Roundup toxicity (i.e. IC50 from 23.5 to 29.5 mg AE/l). In contrast, microalgae and crustaceans were 4-5 folds more sensitive to Roundup toxicity than bacteria and protozoa. Except photosynthetic microalgae, POEA accounted for more than 86% of Roundup toxicity and the toxicity contribution of POEA was shown to be species-dependent. Increase in pH (6-9) and increase of suspended sediment concentration (0-200 mg/l) significantly increased the toxicity of Roundup to C. dubia, but there were no significant effects due to temperature change and food addition.