二氰蒽醌在几种典型土壤中的降解吸附和移动特性

采用室内模拟试验方法,研究了二氰蒽醌在国内3种典型土壤江西红壤、东北黑土和太湖水稻土中的降解、吸附和移动特性。结果表明,25℃下二氰蒽醌在江西红壤、东北黑土与太湖水稻土中的降解半衰期分别为5.614、1.939、4.767d,其在土壤中化学稳定性较弱,易于降解,且pH越高,降解越快。二氰蒽醌在江西红壤的吸附等温线可以Freundlich方程很好地拟合,在东北黑土和太湖水稻土中的则可用线性方程拟合,吸附系数Kd值分别为36.4、114.6和51.9,Koc值分别为3 661.9、6 741.1、4 119.0,二氰蒽醌在土壤中具有中等或较强的吸附性能,在环境中迁移扩散的能力较弱。采用土壤薄层试验得到二氰蒽醌在这三种土壤中的移动分配系数Rf均<0.1,属于难于淋溶的农药,对地下水影响较小。二氰蒽醌在我国的几种典型土壤中均表现出了易降解性,难迁移以及难淋溶的特性,在目前的使用情况下,二氰蒽醌的环境风险较低。     

异噁唑草酮在土壤表面光解及在土壤中的降解和淋溶特性

为合理评估除草剂异唑草酮的环境风险,在实验室模拟条件下,研究了异唑草酮在土壤 (红壤土)表面光解以及在不同质地土壤 (潮土、水稻土和红壤土) 中的降解和淋溶特性。结果表明:异唑草酮在土壤表面的光解遵循一级反应动力学方程c_t = 4.23e–0.008t (r = 0.937),半衰期为82.5 h;其在潮土、水稻土和红壤土中的降解均符合一级动力学方程,好氧条件下,异唑草酮在3种土壤中的降解半衰期分别为10.5、43.3和139 h,厌氧条件下的降解半衰期分别为19.4、18.4和158 h;其在潮土、水稻土和红壤土中的淋溶系数 (R_f) 分别为0.417 0、0.083 3和0.083 3。研究表明:异唑草酮在土壤表面光解速率较慢,而在土壤中好氧及厌氧条件下降解速率均较快,残留期短;其在土壤中淋溶性较弱,不易对周围环境及地下水造成污染风险。     

三种拟除虫菊酯类农药在砂土和壤土中的淋溶行为

采用土柱淋溶法和气相色谱法研究了3种拟除虫菊酯类农药三氟氯氰菊酯、联苯菊酯和高效氯氰菊酯在热带地区主要土壤类型砂土和壤土中的淋溶特性。结果表明:3种拟除虫菊酯类农药在砂土和壤土中主要残留于第1段土壤 (0～5 cm) 中,且驻留量随土壤深度增大而减少。三氟氯氰菊酯、高效氯氰菊酯和联苯菊酯在砂土中的R_i值分别为52.86%、94.73%和83.19%,在壤土中的R_i值分别为54.70%、77.28%和55.33%,均大于50%。根据农药在土壤中的淋溶性等级划分标准,3种药剂均属于难淋溶农药,不易对地下水造成污染。本研究结果可为热带地区土壤和地下水中农药污染修复提供参考。     

七种农药在3种不同类型土壤中的吸附及淋溶特性

采用振荡平衡法和土柱淋溶法研究了2,4-滴酸、丁噻隆、毒草胺、炔草酸、氟环唑、甲基磺草酮和烯啶虫胺7种农药在江西红壤、太湖水稻土及东北黑土3种不同理化性质土壤中的吸附及淋溶特性,探讨了农药性质及土壤理化性质对供试农药在土壤中吸附、淋溶行为的影响。结果表明:农药的水溶性越大,其在土壤中的吸附性越弱,淋溶性越强;农药在土壤中的吸附性与土壤pH值、有机质含量以及阳离子交换量之间有较好的相关性。土壤pH值、有机质含量以及农药性质是影响农药在土壤中淋溶及迁移的主要因素。     

环酰菌胺在土壤中的吸附及降解特性

为评价环酰菌胺在土壤中的生态风险,采用超高效液相色谱-串联质谱(UPLC-MS/MS)方法测定了土壤和水中环酰菌胺的残留量,研究了该农药在红壤和水稻土中的吸附及降解特性,并对其淋溶特性进行了分析,评估了该农药对地下水的污染风险。结果表明:环酰菌胺在红壤和水稻土中的吸附符合Freundlich吸附等温线方程,KOC值分别为373.69和726.86 mL/g,水稻土对环酰菌胺的吸附能力强于红壤。好氧条件下,环酰菌胺在红壤和水稻土中的降解半衰期分别为0.63和5.06 d,积水厌氧条件下的降解半衰期分别为6.80和9.24 d,表明环酰菌胺在好氧条件下降解较快。环酰菌胺在红壤和水稻土中的地下水污染指数(groundwater ubiquity score)分别为1.19和1.10,表明其对地下水的污染风险较低。结果可为环酰菌胺的生态风险评估提供参考。     

环丙酰草胺在土壤中的迁移特性

为研究环丙酰草胺在土壤中的吸附迁移规律，分别采用批平衡法和柱淋溶法测定了环丙酰草胺在江西红壤、太湖水稻土、常熟乌杉土、陕西潮土和东北黑土5种土壤中的吸附和淋溶特性，并运用数学模型对其在土壤中的吸附及迁移特性进行了分析。结果表明:环丙酰草胺在5种土壤中的等温吸附曲线符合线性吸附方程，吸附常数K_d在1.41~7.08之间；环丙酰草胺在5种土壤中的淋溶性大小依次为:东北黑土>陕西潮土>常熟乌杉土>太湖水稻土>江西红壤。通过对吸附常数K_d与土壤有机质含量和pH值的关系进行分析，发现土壤pH值在吸附过程中属主要因素，K_d与土壤pH值呈负相关。上述结果表明，环丙酰草胺在供试的5种土壤中比较容易迁移，影响其迁移的主要因素是土壤pH值。环丙酰草胺在使用过程中应关注其对地表水和地下水造成的风险。     

绿磺隆在土壤中的放射性同位素残留分析

本文综述了利用同位素元踪法研究^14C-绿磺隆在土壤中的吸附、淋溶、迁移和降解等特性，分析了^14C－绿磺隆在土壤中的残留动态。     

化学农药环境安全评价试验准则(续)

3.1.6 土壤淋溶作用试验在农业上使用的农药,都要提供淋溶特性资料。淋溶作用与吸附作用密切相关,可利用吸附常数估计农药在土壤中的移动性。淋溶试验可用土壤柱淋溶法或土壤薄层层析法测定。用土壤柱淋溶法测定时,对易降解的农药,最好同时测定降解作用。试验时可模拟农药使用地区的气温与降雨条件,并提供土     

稻丰散在土壤和水中的降解及其在土壤中的吸附

在室内模拟条件下,研究了稻丰散在土壤和水中的降解及其在土壤中的吸附行为。结果表明:稻丰散的降解速率随土壤温度的升高和土壤含水量的增加而加快;微生物的存在有利于其在土壤中的降解;在20 ℃时,稻丰散在pH为5、7、9的水溶液中的降解半衰期分别为10.66、11.65和6.53 d。3种供试土壤对稻丰散的吸附均符合Freundich方程,且有机质含量越高,土壤对稻丰散的吸附越强。     

新型杀菌剂苯菌酮在3种典型土壤中的淋溶行为

农药在土壤中的淋溶规律已成为研究热点之一,同时也是农药登记的必备数据。建立了土壤中苯菌酮残留量的超高效液相色谱-串联质谱(UPLC-MS/MS)分析方法,并通过土壤薄层层析和土柱淋溶试验,研究了苯菌酮在我国3种典型土壤中的淋溶行为。结果表明:苯菌酮在3种土壤中的平均添加回收率在81%~109%之间,相对标准偏差(RSD)为1.2%~13.4%,检出限(LOD)为0.29~0.30μg/kg。薄层层析试验表明,苯菌酮在河北潮土、湖南红壤和黑龙江黑土中的比移值(Rf)分别为0.17、0.26和0.15。土柱淋溶试验表明,苯菌酮在河北潮土、湖南红壤及黑龙江黑土第1段(0~10 cm)土柱中的含量比例(R1)分别为原始添加量的99%、80%和99%。根据我国化学农药环境安全评价标准,苯菌酮在3种土壤中的迁移特性均为不易移动,因此不易对地下水造成污染。研究结果可为苯菌酮在我国登记以及其安全使用提供基础数据。     

Adsorption and degradation of four acidic herbicides in soils from southern Spain

BACKGROUND: Pesticide degradation and adsorption in soils are key processes determining whether pesticide use will have any impact on environmental quality. Pesticide degradation in soil generally results in a reduction in toxicity, but some pesticides have breakdown products that are more toxic than the parent compound. Adsorption to soil particles ensures that herbicide is retained in the place where its biological activity is expressed and also determines potential for transportation away from the site of action. Degradation and adsorption are complex processes, and shortcomings in understanding them still restrict the ability to predict the fate and behaviour of ionisable pesticides. This paper reports the sorption and degradation behaviour of four acidic pesticides in five soils from southern Spain. Results are used to investigate the influence of soil and pesticide properties on adsorption and degradation as well as the potential link between the two processes. RESULTS: Adsorption and degradation of four acidic pesticides were measured in four soils from Spain characterised by small organic matter (OM) contents (0.3-1.0%) and varying clay contents (3-66%). In general, sorption increased in the order dicamba < metsulfuron-methyl < 2,4-D < flupyrsulfuron-methyl-sodium. Both OM and clay content were found to be important in determining adsorption, but relative differences in clay content between soils were much larger than those in OM content, and therefore clay content was the main property determining the extent of herbicide adsorption for these soils. pH was negatively correlated with adsorption for all compounds apart from metsulfuron-methyl. A clear positive correlation was observed for degradation rate with clay and OM content (P < 0.01), and a negative correlation was observed with pH (P < 0.01). The exception was metsulfuron-methyl, for which degradation was found to be significantly correlated only with soil bioactivity (P < 0.05). CONCLUSIONS: Both OM and clay content were found to be important in determining adsorption, but relative differences in clay content between soils were much larger than those in OM content, and therefore clay content was the main property determining the extent of herbicide adsorption for soils of this type. pH was negatively correlated with adsorption for all compounds apart from metsulfuron-methyl. The contrasting behaviour shown for these four acidic pesticides indicates that chemical degradation in soil is more difficult to predict than adsorption. Most of the variables measured were interrelated, and different behaviours were observed even for compounds from the same chemical class and with similar structures.     

Further observations on the enhanced degradation of iprodione and vinclozolin in soil

The effects of soil pH on rates of degradation of iprodione and vinclozolin were measured in a silty clay loam soil. Little degradation of either fungicide occurred at pH 4.3 or 5.0, and degradation at pH 5.7 was slower than at pH 6.5. In both of the higher-pH soils, the rate of loss of a second application of either fungicide was faster than that of the first, and a third application degraded even more quickly. In soil with pH 6.5, for example, the times for 50% degradation of iprodione following the first, second and third applications were about 30, 12 and 4 days, and for vinclozolin were 30, 22 and 7 days respectively. Iprodione degraded very rapidly in a sandy loam that had been treated three times previously with this fungicide and also degraded rapidly in the same soil pretreated three times with vinclozolin. Vinclozolin degraded rapidly in the vinclozolin pre-treated soil, but its rate of loss in the iprodione pre-treated soil was only slightly faster than in the previously untreated control. Studies of iprodione degradation in 33 soils from commercial fields demonstrated a clear trend towards faster rates of loss in soils with an extensive history of iprodione use. The time for 90% loss from previously untreated soils varied from 22 to 93 days. It varied from 16 to 28 days in soils treated once previously and from 5.2 to 23 days in soils treated twice previously. In soils that had received three or more previous doses, the time to 90% degradation varied from 3.8 to 15 days.     

Enhanced degradation of iprodione and vinclozolin in soil

Residues of iprodione and vinclozolin were measured following repeated application of the fungicides to a sandy loam soil in the laboratory. There was a progressive increase in rates of degradation with successive treatments. With iprodione, for example, the times for 50% loss of the first and second applications were about 23 and 5 days respectively. When treated for the third time, less than 10% of the applied dose remained in the soil after just 2 days. Similar results were obtained with vinclozolin in the same soil, and with both compounds in a second soil. In a third soil, which had relatively low pH, degradation of both compounds occurred only slowly and the rate of degradation of a second application was the same as that of the first. Degradation rates in this soil were increased by addition of 100 g kg^?1 of a soil in which degradation occurred more readily, and they were markedly increased by addition of 100 g kg^?1 of a soil in which enhanced degradation had been previously induced. Residues of both fungicides were also measured following repeated application in the field. When iprodione was applied to previously untreated plots, about 3% of the initial dose remained in the soil after 77 days. When applied to plots treated once before, less than 1% remained after 18 days, and when applied to plots treated twice previously less than 1% remained after 10 days. Similar results were obtained with vinclozolin. Enhanced degradation of subsequent soil treatments was also observed following a sequence of low-dosage sprays in the field.     

Field effectiveness and biodegradation of cyclic imides in lettuce field soils

When 42 field trials, carried out from 1975 to 1989 in the Perpignan region (France) for control of lettuce drop caused by Sclerotinia minor, were compared, a decrease in the field effectiveness of cyclic imides was perceptible, beginning approximately in 1985. Moreover, in 15 out of 46 commercial lettuce fields surveyed in 1988 and 1989, the effectiveness of iprodione was less than 80%, the level of acceptability for the growers. In these fields, fungicide degradation, estimated by 3,5-dichloroaniline formation, was faster than in soils in which S. minor was adequately controlled. Statistical analyses showed that the iprodione degradation index was strongly linked to the history of fungicide treatment and was weakly correlated to soil pH or clay content. All the fields characterized by low iprodione effectiveness were associated with high levels of fungicide treatment and high degradation index. Moreover, we observed that soil from a field which had received iprodione for more than ten years did not degrade vinclozolin quickly, while soil from another part of the same field which had been treated with vinclozolin for eight years degraded vinclozolin faster than iprodione.     

嗪吡嘧磺隆在土壤中的吸附特性及其吸附过程模型的建立

磺酰脲类除草剂是应用较为广泛的农药之一,其在土壤中迁移、降解、转化和滞留等多个过程受其吸附、解吸行为的影响。本文以嗪吡嘧磺隆为研究对象,采用批量平衡法研究了其在8种不同类型土壤中的吸附、解吸附行为。结果表明:嗪吡嘧磺隆与土壤溶液接触4 h内为快速吸附阶段。Freundlich模型可较好地拟合嗪吡嘧磺隆在土壤中的等温吸附解吸过程,相关系数 (r) 值在0.9584~0.9973之间。8种土壤对嗪吡嘧磺隆的吸附能力均为弱,吸附常数 (K_f-ads) 在0.281~3.515之间。其中,以黑龙江白浆土对嗪吡嘧磺隆的吸附能力最强,且远高于其他土壤。除广西赤红壤外,嗪吡嘧磺隆在其他7种类型土壤中的滞后系数 (H) 均小于1,解吸过程存在滞后现象,存在潜在环境风险。单因素试验结果表明,嗪吡嘧磺隆在土壤中的吸附行为受腐殖酸的影响极显著 (P＜0.01),受pH值和Mn2 + 的影响显著 (P＜0.05),受高岭土和稻壳生物炭的影响不显著 (P＞0.05)。采用中心复合试验设计,建立了具有一定预测功能的嗪吡嘧磺隆在土壤中的吸附过程BP神经网络模型,并进行了验证,拟合结果较好。     

Degradation of the dicarboximide fungicides iprodione,vinclozolin and procymidone in Patumahoe clay loam soil,New Zealand

An enhanced rate of degradation of the dicarboximide fungicides iprodione and vinclozolin was induced in the laboratory in Patumahoe clay loam soil by adding three successive applications of fungicide. Enhanced degradation of the dicarboximide fungicide procymidone could not be induced. Following the first fungicide treatment, the time to 50% loss of iprodione was greater than 35 days; for vinclozolin the time to 50% loss was 22 days. The rate of degradation accelerated with successive applications until, after a third successive application of fungicide, the time to 50% loss of iprodione was only two days and none was detectable at seven days. For vinclozolin, after the third successive application of fungicide, 50% loss occurred after 35 days. By comparison, minimal loss of procymidone was detected after 35 days following each of two successive soil treatments. The induction of enhanced degradation of iprodione and vinclozolin in this soil in the laboratory may explain the observed loss of field control of onion white rot disease. Degradation of iprodione occurred in non-sterile soil but not in sterile soil, indicating that microbial involvement may be responsible for the degradation of iprodione and vinclozolin in soil.     

The pesticide module of the Root Zone Water Quality Model (RZWQM): testing and sensitivity analysis of selected algorithms for pesticide fate and surface runoff

The Root Zone Water Quality Model (RZWQM) is a one-dimensional, numerical model for simulating water movement and chemical transport under a variety of management and weather scenarios at the field scale. The pesticide module of RZWQM includes detailed algorithms that describe the complex interactions between pesticides and the environment. We have simulated a range of situations with RZWQM, including foliar interception and washoff of a multiply applied insecticide (chlorpyrifos) to growing corn, and herbicides (alachlor, atrazine, flumetsulam) with pH-dependent soil sorption, to examine whether the model appears to generate reasonable results. The model was also tested using chlorpyrifos and flumetsulam for the sensitivity of its predictions of chemical fate and water and pesticide runoff to various input parameters. The model appears to generate reasonable representations of the fate and partitioning of surface- and foliar-applied chemicals, and the sorption of weakly acidic or basic pesticides, processes that are becoming increasingly important for describing adequately the environmental behavior of newer pesticides. However, the kinetic sorption algorithms for charged pesticides appear to be faulty. Of the 29 parameters and variables analyzed, chlorpyrifos half-life, the Freundlich adsorption exponent, the fraction of kinetic sorption sites, air temperature, soil bulk density, soil-water content at 33 kPa suction head and rainfall were most sensitive for predictions of chlorpyrifos residues in soil. The latter three inputs and the saturated hydraulic conductivity of the soil and surface crusts were most sensitive for predictions of surface water runoff and water-phase loss of chlorpyrifos. In addition, predictions of flumetsulam (a weak acid) runoff and dynamics in soil were sensitive to the Freundlich equilibrium adsorption constant, soil pH and its dissociation coefficient.     

宝鸡地区典型农田土壤中微塑料赋存特征及其环境效应研究

地膜覆盖被普遍应用于农业生产中,形成大量的微塑料,对农田土壤环境产生重要的影响.本文通过野外调查取样与室内实验分析相结合的方法,研究了宝鸡地区辣椒地、玉米地和猕猴桃地三种典型农田土壤中微塑料赋存特征及其对土壤环境的影响.研究结果显示:不同农田土壤中微塑料41％～48％为＜1mm粒径,其次为1-2mm和2-5mm粒径.其...     

高效液相色谱法测定二甲四氯在铁铝土中的吸附特征

二甲四氯 (MCPA) 是铁铝土区域广泛使用的一种除草剂,生物毒性大。吸附是控制MCPA在土壤中迁移/转化的关键过程。本研究建立了以C₁₈为色谱柱、V(甲醇):V[水 (乙酸调pH值至2.5)] = 80 : 20为流动相、PDA为检测器 (检测波长280 nm) 的MCPA高效液相色谱检测方法,并结合批量平衡法评估MCPA在铁铝土中的吸附特征。结果表明:在0.5~40 mg/L内,MCPA的质量浓度与对应的峰面积间呈良好线性关系 (R2 = 0.999 9),检出限为0.2 mg/L,定量限为0.5 mg/L;回收率为98%~103%,相对标准偏差为3.5%~4.0%,适用于MCPA吸附试验的测定。铁铝土对MCPA的等温吸附过程符合Freundlich模型,吸附自由能△G<0,|△G|为9.34~14.73 kJ/mol,是一个自发的、非均质的、多层的物理吸附过程。吸附常数K_f值在0.85~4.24 L/kg之间,属于难吸附污染物,对地下水具有环境风险。不同铁铝土对MCPA的吸附作用受土壤pH值、有机质、矿物影响,表现为水稻土>暗红湿润铁铝土>简育湿润铁铝土。氢键结合、偶极间作用是吸附发生的关键作用力。