丙溴磷在稻田环境中的残留动态研究

确立了气相色谱法测定丙溴磷残留量的检测方法.采用该方法,丙溴磷在土壤、植株、糙米、稻壳和田水中的平均添加回收率为87.2％～103.6％,变异系数为3.20％～11.50％,最低检测质量浓度:田水为0.005 mg/kg;土壤、植株、糙米和稻壳为0.050 mg/kg.残留动态研究表明,丙溴磷在田水、植株和土壤中的半衰...     

Environmental fate of rice paddy pesticides in a model ecosystem.

The distribution and metabolic fate of several rice paddy pesticides were evaluated in a modified model ecosystem. Among the three BHC isomers, beta-isomer was the most stable and bioconcentrated in all of the organisms. Alpha- and gamma-isomers were moderately persistent and degraded to some extent during the 33 day period. Disulfoton was relatively persistent due to the transformation to its oxidation products. Pyridaphenthion was fairly biodegradable. N-Phenyl maleic hydrazide derived from the hydrolysis of pyridaphenthion was not detected in the organisms though it was found in the aquarium water after 33 days. Cartap and edifenphos were considerably biodegradable, and the ratio of the conversion to water soluble metabolites was very high. There was a distinct difference in the persistence of Kitazin P and edifenphos in the aquarium water. It appeared that the hydrolysis rate of the pesticides affected their fate in the organisms. PCP appeared to be moderately biodegradable. CNP was considerably stable and stored in the organisms though the concentration in the aquarium water was relatively low. The persistence and distribution of the pesticides in the model ecosystem were dependent on their chemical structures. In spite of the limitation derived from short experimental period, the model ecosystem may be applicable for predicting the environmental fate of pesticides.     

Model development for nutrient loading estimates from paddy rice fields in Korea

A field experiment was performed to evaluate water and nutrient balances in paddy rice culture operations during 2001-2002. The water balance analysis indicated that about half (50-60%) of the total outflow was lost by surface drainage, with the remainder occurring by evapotranspiration (490-530 mm). The surface drainage from paddy fields was mainly caused by rainfall and forced-drainage, and in particular, the runoff during early rice culture periods depends more on the forced-drainage due to fertilization practices. Most of the total phosphorus (T-P) inflow was supplied by fertilization at transplanting, while the total nitrogen (T-N) inflow was supplied by the three fertilizations, precipitation. and from the upper paddy field, which comprised 13-33% of the total inflow. Although most of the nutrient outflow was attributed to plant uptake. nutrient loss by surface drainage was substantial, comprising 20% for T-N and 10% for T-P. Water and nutrient balances indicate that reduction of surface drainage from paddy rice fields is imperative for nonpoint source pollution control. The simplified computer model, PADDIMOD, was developed to simulate water and nutrient (T-N and T-P) behavior in the paddy rice field. The model predicts daily ponded water depth, surface drainage, and nutrient concentrations. It was formulated with a few equations and simplified assumptions, but its application and a model fitness test indicated that the simulation results reasonably matched the observed data. It is a simple and convenient planning model that could be used to evaluate BMPs of paddy rice fields alone or in combination with other complex watershed models. Application of the PADDIMOD to other paddy rice fields with different agricultural environments might require further calibration and validation.     

Adsorption and desorption variability of four herbicides used in paddy rice production

This investigation was performed to determine the effect of physicochemical soil properties on penoxsulam, molinate, bentazon, and MCPA adsorption-desorption processes. Four soils from Melozal (35° 43' S; 71° 41' W), Parral (36° 08' S; 71° 52' W), San Carlos (36° 24' S; 71° 57' W), and Panimavida (35° 44' S; 71° 24' W) were utilized. Herbicide adsorption reached equilibrium after 4 h in all soils. The Freundlich L-type isotherm described the adsorption process, which showed a high affinity between herbicides and sorption sites mainly because of hydrophobic and H-bonds interaction. Penoxsulam showed the highest adsorption coefficients (4.23 ± 0.72 to 10.69 ± 1.58 mL g?1) and were related to soil pH. Molinate showed K(d) values between 1.72 ± 0.01 and 2.3 ± 0.01 mL g?1 and were related to soil pH and organic matter, specifically to the amount of humic substances. Bentazon had a high relationship with pH and humic substances and its K(d) values were the lowest, ranging from 0.11 ± 0.01 to 0.42 ± 0.01 mL g?1. MCPA K(d) ranged from 0.14 ± 0.02 to 2.72 ± 0.01 mL g?1, however its adsorption was related to humic acids and clay content. According to these results, the soil factors that could explain the sorption process of the studied herbicides under paddy rice soil conditions, were principally humic substances and soil pH. Considering the sorption variability observed in this study and the potential risk for groundwater contamination, it is necessary to develop weed rice management strategies that limit use of herbicides that exhibit low soil adsorption in areas with predisposing conditions to soil leaching.     

Adsorption and desorption variability of four herbicides used in paddy rice production

This investigation was performed to determine the effect of physicochemical soil properties on penoxsulam, molinate, bentazon, and MCPA adsorption–desorption processes. Four soils from Melozal (35° 43′ S; 71° 41′ W), Parral (36° 08′ S; 71° 52′ W), San Carlos (36° 24′ S; 71° 57′ W), and Panimavida (35° 44′ S; 71° 24′ W) were utilized. Herbicide adsorption reached equilibrium after 4 h in all soils. The Freundlich L-type isotherm described the adsorption process, which showed a high affinity between herbicides and sorption sites mainly because of hydrophobic and H-bonds interaction. Penoxsulam showed the highest adsorption coefficients (4.23 ± 0.72 to 10.69 ± 1.58 mL g^?1) and were related to soil pH. Molinate showed K_d values between 1.72 ± 0.01 and 2.3 ± 0.01 mL g^?1and were related to soil pH and organic matter, specifically to the amount of humic substances. Bentazon had a high relationship with pH and humic substances and its K_d values were the lowest, ranging from 0.11 ± 0.01 to 0.42 ± 0.01 mL g^?1. MCPA K_d ranged from 0.14 ± 0.02 to 2.72 ± 0.01 mL g^?1, however its adsorption was related to humic acids and clay content. According to these results, the soil factors that could explain the sorption process of the studied herbicides under paddy rice soil conditions, were principally humic substances and soil pH. Considering the sorption variability observed in this study and the potential risk for groundwater contamination, it is necessary to develop weed rice management strategies that limit use of herbicides that exhibit low soil adsorption in areas with predisposing conditions to soil leaching.     

Concentration of global fallout 99Tc in rice paddy soils collected in Japan

Analysis of global fallout 99Tc in environmental samples should provide useful information for predicting the nuclide behaviour under natural conditions which is important from the viewpoint of radioecology. Concentrations of 99Tc in rice paddy soils collected in Japan have been studied. After chemical separation, 99Tc in the final solution was measured by ICP-MS. The activity ratio of 99Tc/137Cs was used to understand the 99Tc behaviour in the environment because the fission yields of 99Tc and 137Cs from 235U or 239Pu are almost the same. The theoretical activity ratio from fission which is calculated now is about 3.0 x 10(-4). Our results showed that the range of activity ratios of 99Tc/137Cs in the soil samples was (2.0-5.2) x 10(-3); these ratios were one order of magnitude higher than the theoretical one. 99Tc has been accumulating in rice paddy soil like 137Cs has, although their mechanisms might differ. One of the reasons for the high ratio in the surface soil might be the ratios in the atmospheric samples, which have increased from the order of 10(-3) to 10(-2) (García-León et al., 1993).     

Monitoring of pesticide residues in a cotton crop soil

Abstract

This paper reports on the residues of methyl parathion (O,O‐dimethyl O‐4‐nitrophenyl phosphorothioate), trifluralin (α, α, α‐trifluoro‐2, 6‐dinitro‐N, N‐dipropyl‐p‐toluidine), endosulfan [(1, 4, 5, 6, 7, 7‐hexachloro‐8, 9, 10‐trinorborn‐5‐en‐2, 3‐ylenebismethylene) sulfite] and dimethoate (O, O‐dimethyl S‐methylcarbamoylmethyl phosphorodithioate) in a cotton crop soil. Soil samples (0–15 cm) were collected at different periods from the cotton crop farm and subjected to Soxhlet extraction. The extracted material was analysed after clean‐up by a HP5890 II gas Chromatograph equipped with a ⁶³Ni electron‐capture detector (ECD‐⁶³Ni) and fitted with a 25m x 0,2mm i.d. fused silica capillary column [Ultra‐2 (5% phenylmethyl polysiloxane)]. The recoveries of the pesticide residues from the spiked control soil were determined after Soxhlet extraction and C₁₈ cartridges clean‐up by using radiotracer techniques with the corresponding ¹⁴C‐pesticides. The results show that in the cotton crop soil the pesticide residues under study were present in the range of 0.1 to 0.4 mg ? kg^‐1. Endosulfan was found to be rapidly degraded in the soil and formed a sulfate metabolite.     

Monitoring of pesticide residues in a cotton crop soil

This paper reports on the residues of methyl parathion (O,O-dimethyl O-4-nitrophenyl phosphorothioate), trifluralin (alpha, alpha, alpha-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine), endosulfan [(1, 4, 5, 6, 7, 7-hexachloro-8, 9, 10-trinorborn-5-en-2, 3-ylenebismethylene) sulfite] and dimethoate (O, O-dimethyl S-methylcarbamoylmethyl phosphorodithioate) in a cotton crop soil. Soil samples (0-15 cm) were collected at different periods from the cotton crop farm and subjected to Soxhlet extraction. The extracted material was analysed after clean-up by a HP5890 II gas chromatograph equipped with a 63Ni electron-capture detector (ECD-63Ni) and fitted with a 25 m x 0.2 mm i.d. fused silica capillary column [Ultra-2 (5% phenylmethyl polysiloxane)]. The recoveries of the pesticide residues from the spiked control soil were determined after Soxhlet extraction and C18 cartridges clean-up by using radiotracer techniques with the corresponding 14C-pesticides. The results show that in the cotton crop soil the pesticide residues under study were present in the range of 0.1 to 0.4 mg.kg-1. Endosulfan was found to be rapidly degraded in the soil and formed a sulfate metabolite.     

重庆市郊稻米Cd风险的原位钝化削减

为筛选适合应用于重庆市郊区稻田土壤及农作物Cd污染的修复技术,采用田间小区原位钝化实验和重金属来源加密监测相结合的方法,比较了石灰、腐殖酸、硅酸钾3种常见修复剂对Cd污染稻田的土壤基本理化性质、水稻各部位Cd富集量、稻米产量和稻米品质的影响。结果表明,该区域土壤Cd污染的主要原因为该区域土壤Cd本底值含量高且土壤酸化严重。在土壤全Cd为0.66 mg·kg-1,有效Cd为0.39 mg·kg-1的污染程度下,施用3种修复剂均可显著降低土壤有效Cd和稻米中Cd含量。其中,施用腐殖酸可显著提高土壤有机质含量,收获期种植2种水稻的土壤中有效Cd含量比CK处理分别减少了32.1%和34.8%,稻米中Cd含量比CK处理分别较少了53.3%和48.2%,同时低于国家食品污染物限量标准 0.2 mg·kg -1,其作用机理主要通过提高土壤有机质含量,降低水稻根系对土壤中Cd的富集量及向茎叶部Cd的运输量。同时,相比于其他修复剂,施加腐殖酸可降低稻米直链淀粉含量,提升稻米品质,但会降低稻米产量。施用石灰可显著提高土壤pH和稻米产量,但水稻收割后稻米中Cd含量高于腐殖酸处理,低于硅酸钾处理。     

Effect of bound residues of metsulfuron-methyl in soil on rice growth

A pot experiment was conducted to appraise the hazards of bound residues of metsulfuron-methyl in soil at six levels (0, 0.050, 0.089, 0.158, 0.281, and 0.500 mg kg(-1)) to the growth of four rice varieties (Xiushui 63, Eryou 810, Liangyoupeijiu, and Zhenong 952). The morphological characteristics of rice roots like root number, total length, surface area of rice roots, and rice biomass were determined. The results showed that the bound residues of metsulfuron-methyl in soil impacted the growth of rice. Root number, total length of roots, surface area of roots, and biomass were restrained by bound residues of metsulfuron-methyl in soil. The inhibition rate of root growth increased from 69.46-81.32% to 85.18-95.97% with the increasing of levels of bound residues of metsulfuron-methyl from 0.05 mg kg(-1) to 0.50 mg kg(-1). The number of rice roots could be taken as a sensitive index to screen the rice varieties endurable to bound residues of metsulfuron-methyl in soil and to predict the potential hazards of bound residues of metsulfuron-methyl in soil to rice. The level of bound residues of metsulfuron-methyl in soil causing the root numbers decreased by 50% (IC50) followed the order of Xiushui 63 < Eryou 810 < Liangyoupeijiu < Zhenong 952.     

Loss of carbofuran from rice paddy water: Chemical and physical factors

Abstract

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 10 (t_1/2 = 1.2 hr.) than at pH 7 (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.     

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

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.     

成都东郊稻田土中汞的分布特征研究

选取成都东郊唯一的火力发电厂周围的稻田土为研究对象,对稻田土中各种形态汞的分布特征进行了调查与研究,探讨稻田土中汞的分布规律,为分析和判断稻田土中汞的迁移和转化行为及该区汞污染土壤的修复提供重要依据。结果表明,处于火力发电厂烟尘排污口下风向的1#、2#、3#、4#采样点土样受到了严重的汞污染,呈现出高含汞特征,总汞平均质量浓度在9～41mg/kg,平均值为24.546mg/kg,远远超出《土壤环境质量标准》(GB 15618—1995)二级标准所规定的限值(0.5mg/kg),而处于排污口上风向的5#、6#、7#、8#土样没有受到明显的汞污染,大部分土样的总汞含量与成都市土壤汞平均含量接近;1#、2#、3#、4#土样中5种形态汞的垂直分布均呈现出随着土壤深度增加而减少的特征;1#、2#、3#、4#土样中的各形态汞平均百分比为有机结合态汞>硝酸溶汞>残渣态汞>铁锰氧化态汞>水溶和可交换态汞,土壤中含有的大部分汞化学性质比较稳定,难以被植物吸收利用,而易被植物吸收利用的水溶和可交换态汞虽然仅占极小一部分,但含量还是高于成都市土壤中水溶和可交换态汞的背景值。     

The abundances of rarer trace elements in paddy (rice) soils of Sri Lanka

Concentrations of Ti, Ga, As, Sc, Zr, Sn, Hf, Th, U and Y have been determined for 70 paddy soils from 14 villages, selected throughout Sri Lanka by means of ICP-MS. The mean elemental contents of all paddy soil samples were 6120 Ti, 14.1 Ga, 0.84 As, 7.26 Sc, 129 Zr, 2.27 Sn, 3.64 Hf, 12.71 Th, 1.53 U, and 13.35 Y (all data in microg/g). Paddy soils were classified into groups based on morphology and climate. Higher contents of Th and U were found in the wet zone lowland soils whereas the higher Ti contents were observed in dry zone soils. Arsenic, Zr and Hf contents were comparatively similar in all regions. Factor analysis was used to identify the relationships between the contents of elements.     

Long-term effects of fertilization on the forms and availability of soil phosphorus in rice paddy

The changes in total P accumulation and P compounds with time in the plough layer in a paddy soil in southern Korea were investigated in relation to the continuous application of chemical fertilizers (NPK), straw based compost (Compost), combination these two (NPK+Compost) for 31 years. Continuous fertilization increased the total and inorganic P contents in plough layers. In NPK, inorganic P fraction did not change with time, but organic P content increased significantly. Long-term application of chemical fertilizer together with compost accelerated the decrease in the organic P fraction, presumably due to promoting microbial activity in the plow layer, and then increased significantly inorganic P fraction. Compost application decreased the residual P and Fe-P fractions and then increased inorganic P fraction, in spite of continuous compost application. Increase in total, inorganic and extractable P with time may be closely related to the increase in the availability of accumulated P for rice growth.     

Monitoring of organochlorine pesticide residues in the Indian marine environment.

Organochlorine pesticide residues in sediment and fish samples collected from the east and west coasts of India are presented. HCH isomers and DDT and its metabolites are the predominantly identified compounds in most of the samples. Despite the higher quantity of consumption, HCH and DDT levels in fish in India were lower than those in temperate countries suggesting a lower accumulation in tropical fish, which could be due to rapid volatilization and degradation of these insecticides in the tropical environment. The predominance of alpha- and beta-HCH reflect the use of technical grade HCH in India. The high temperature in the tropics also enhances the elimination rate of chemicals in fish, as the biological half-lives of semivolatile compounds such as DDT are short at high temperature.     

Loss of carbofuran from rice paddy water: chemical and physical factors.

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.     

Methane emission from fields with differences in nitrogen fertilizers and rice varieties in Taiwan paddy soils

Flooded rice fields are one of the major biogenic methane sources. In this study, methane emission rates were measured after transplanting in paddy fields with application of two kinds of nitrogen fertilizers (ammonium sulfate, NH4+-N and potassium nitrate, NO3(-)-N) and with two kinds of rice varieties (Japonica and Indica). The experiment was conducted in fields located at Tainan District Agricultural Improvement Station in Chia-Yi county (23 degrees 25'08"N, 120 degrees 16'26"E) of southern Taiwan throughout the first and the second crop seasons in 1999. The seasonal methane flux in the first crop season with NH4+-N and NO3(-)-N ranged from 2.48 to 2.78 and from 8.65 to 9.22 g CH4 m(-2); and the values ranged 24.6-34.2 and 36.4-52.6 g CH4 m(-2) in the second crop season, respectively. In the first crop season, there were significantly increased 3.1-3.7-fold in methane emission fluxes due to plantation of Indica rice. In comparison of two rice varieties, the Indica rice variety showed a tendency for larger methane emission than the Japonica rice variety in the second crop season. Moreover, ammonium sulfate treatment significantly reduced CH4 emissions by 37-85% emissions compared to potassium nitrate plots. It was concluded that the CH4 emission was markedly dependent on the type of nitrogen fertilizer and rice variety in Taiwan paddy soils.     

Sustainable reuse of rice residues as feedstocks in vermicomposting for organic fertilizer production

Over the past decade, rice (Oryza sativa or Oryza glaberrima) cultivation has increased in many rice-growing countries due to the increasing export demand and population growth and led to a copious amount of rice residues, consisting mainly of rice straw (RS) and rice husk (RH), being generated during and after harvesting. In this study, Eudrilus eugeniae was used to decompose rice residues alone and rice residues amended with cow dung (CD) for bio-transformation of wastes into organic fertilizer. Generally, the final vermicomposts showed increases in macronutrients, namely, calcium (11.4–34.2 %), magnesium (1.3–40.8 %), phosphorus (1.2–57.3 %), and potassium (1.1–345.6 %) and a decrease in C/N ratio (26.8–80.0 %) as well as increases in heavy metal content for iron (17–108 %), copper (14–120 %), and manganese (6–60 %) after 60 days of vermicomposting. RS as a feedstock was observed to support healthier growth and reproduction of earthworms as compared to RH, with maximum adult worm biomass of 0.66 g/worm (RS) at 60 days, 31 cocoons (1RS:2CD), and 23 hatchlings (1RS:1CD). Vermicomposting of RS yielded better results than RH among all of the treatments investigated. RS that was mixed with two parts of CD (1RS:2CD) showed the best combination of nutrient results as well as the growth of E. eugeniae. In conclusion, vermicomposting could be used as a green technology to bio-convert rice residues into nutrient-rich organic fertilizers if the residues are mixed with CD in the appropriate ratio.