Predicting Pesticide Volatility Through Coupled Above- and Belowground Multiphysics Modeling

Pesticides are applied to agricultural fields to control unwanted pests but can volatilize and be transported downwind by wind currents to create the potential for non-target organism exposure. Volatilization rates change through the growing season due to pesticide application timing, meteorological differences, and the differential flux rates from soil and vegetation matrices. Field studies quantifying pesticide volatility are expensive and cannot capture the semi-infinite parameter combinations of soil, crop, management, and meteorological conditions encountered under regional agronomic practices. A numerical approach was used to simulate pesticide dissipation above- and belowground to augment field and laboratory experimental observations. Above- and belowground physics are coupled into a single numerical tool using the COMSOL Multiphysics® software package with the current emphasis on pesticide volatility into air from soil and vegetation and resulting near field neighboring air concentrations. Comparison of simulation results against experimental observations for an insecticide (chlorpyrifos) applied to potato and alfalfa fields shows good agreement (R² 0.68–0.98). Chlorpyrifos volatility from plant surfaces drives the overall volatility within the first several days post application. The maximum volatility flux rate simulated and observed were 0.79 and 0.66 μg m^?2 s^?1 for the alfalfa trial and 2.72 and 2.17 μg m^?2 s^?1 for the potato field, respectively. This coupled multiphysics tool [computational fluid dynamics (CFD), mass transfer coefficients, and variably saturated flow in soil] can be used to estimate volatility flux rates of pesticides when little or no prior knowledge is available and for extrapolating field study observations to different and diverse scenarios.     

色谱、光谱及联用技术在多农药残留检测中的应用

介绍了国内外多农药残留检测的发展状况,综述了色谱法、光谱法、色谱-质谱联用技术、色谱-光谱联用法、多维气相色谱技术的特点及在多农药残留检测中的应用,指出多农药残留检测在今后的农药残留检测中将占据主导地位.     

Assessing the Effects of Atmospheric Ethylene on Epinasty and Tuber Yield of Potato (Solanum Tuberosum L.) Near Polyethylene Manufacturing Plants

A multi-year programme was performed to assess the effects of atmospheric ethylene on potato (Solanum tuberosum L.) in the vicinity of polyethylene manufacturing plants. There was a strong temporal variation of the hourly ethylene concentrations measured close to the sources from 1982 through 1991. Growing seasonal means exceeded 12 g m^–3 ethylene, the threshold for phytotoxic effects under laboratory conditions. Young test plants of potato showed an epinastic response to enhanced levels of ethylene. This response was reversible and did not occur when atmospheric ethylene was not detected. Based on hourly observations for the growing seasons of 1984 through 1991, epinasty occurred on average during circa 5% of the growing season and varied from circa 1% in 1985 to circa 18% in 1991. At night, ethylene concentrations were higher and epinasty was more frequent than during daylight hours. The intermittent exposures to ethylene did not affect tuber yield for the growing seasons of 1982 through 1990. The occurrence of epinasty indicated that ethylene exposure levels in the vicinity of the industrial sources might be sufficiently high to affect sensitive plants.     

A multi-level assessment methodology for determining the potential for groundwater contamination by pesticides

A multi-level pesticide assessment methodology has been developed to permit regulatory personnel to undertake a variety of assessments on the potential for pesticide used in agricultural areas to contaminate the groundwater regime at an increasingly detailed geographical scale of investigation. A multi-level approach accounts for a variety of assessment objectives and detail required in the assessment, the restrictions on the availability and accuracy of data, the time available to undertake the assessment, and the expertise of the decision maker. The level 1: regional scale is designed to prioritize districts having a potentially high risk for groundwater contamination from the application of a specific pesticide for a particular crop. The level 2: local scale is used to identify critical areas for groundwater contamination, at a soil polygon scale, within a district. A level 3: soil profile scale allows the user to evaluate specific factors influencing pesticide leaching and persistence, and to determine the extent and timing of leaching, through the simulation of the migration of a pesticide within a soil profile. Because of the scale of investigation, limited amount of data required, and qualitative nature of the assessment results, the level 1 and level 2 assessment are designed primarily for quick and broad guidance related to management practices. A level 3 assessment is more complex, requires considerably more data and expertise on the part of the user, and hence is designed to verify the potential for contamination identified during the level 1 or 2 assessment. The system combines environmental modelling, geographical information systems, extensive databases, data management systems, expert systems, and pesticide assessment models, to form an environmental information system for assessing the potential for pesticides to contaminate groundwater.     

CLFUG: A GIS‐scaleable model of pesticide fate in the soil–groundwater system based on clearance and fugacity paradigms

A model of pesticide transport through the soil profile based on clearance and fugacity paradigms is presented, and an example of its application in a GIS environment is shown. A validation of the model at the field plot scale is presented using data obtained at a crop in a semiarid irrigated agricultural basin which was treated with Lindane. The adequacy at the regional scale is tested by inspection of the model predictions and the measured concentrations of the pesticide obtained from a regional phreatimetric net. The clearance concept is used to obtain estimates of the volumes of some environmental phases. These are further used to solve the equations of thermodynamic equilibrium at equal fugacity and obtain concentration estimates. The model closely reproduces the observed percolation trends, and is consistent with the regional pattern of Lindane distribution in groundwater. An application of the model as unitary module for the simulation of non‐point pesticide sources in a raster GIS frame is shown. Its performance (run time, data needed, etc.) is comparable to that of other existing algorithms, and presents some advantages to planners and evaluators of environmental quality in that it incorporates an explicit 2‐D approach and allows the identification of polluted areas downslope with respect to those directly treated with the pesticides. Further, it can be implemented in a variety of GIS and spatial data processors.     

我国农田农药流失现状及减控策略

农业面源污染已经成为全球水污染的主要来源,其中具有生物毒性的农药污染物对人体健康和生态环境安全构成了严重威胁。分析了我国农田农药流失现状,指出流失的主要农药品种与用药历史和特点密切相关,水体中检出的有机氯农药主要源于早期农药残留,检出的有机磷农药和长残效除草剂部分种类目前仍在使用。提出从影响农药流失的各个环节入手,制定严密的减控策略。植物缓冲带是拦截农药流失的常用措施,可以实现对农业面源污染的可持续治理。建议实行生态功能区划,严格限制高毒农药的施用,减少化学农药施用量,规范农药喷洒器械和施药技术,从源头上控制农药流失,从而降低农业非点源污染带来的危险。     

Spatial Relationships Between Water Quality and Pesticide Application Rates in Agricultural Watersheds

Pesticide applications to agricultural lands in California, USA, are reported to a central data base, while data on water and sediment quality are collected by a number of monitoring programs. Data from both sources are geo-referenced, allowing spatial analysis of relationships between pesticide application rates and the chemical and biological condition of water bodies. This study collected data from 12 watersheds, selected to represent a range of pesticide usage. Water quality parameters were measured during six surveys of stream sites receiving runoff from the selected watershed areas. This study had three objectives: to evaluate the usefulness of pesticide application data in selecting regional monitoring sites, to provide information for generating and testing hypotheses about pesticide fate and effects, and to determine whether in-stream nitrate concentration was a useful surrogate indicator for regional monitoring of toxic substances. Significant correlations were observed between pesticide application rates and in-stream pesticide concentrations (p < 0.05) and toxicity (p < 0.10). In-stream nitrate concentrations were not significantly correlated with either the amount of pesticides applied, in-stream pesticide concentrations, or in-stream toxicity (all p > 0.30). Neither total watershed area nor the area in which pesticide usage was reported correlated significantly with the amount of pesticides applied, in-stream pesticide concentrations, or in-stream toxicity (all p > 0.14). In-stream pesticide concentrations and effects were more closely related to the intensity of pesticide use than to the area under cultivation.     

AgInput: An Agricultural Nutrient and Pesticide Source Model

Agriculture can be a major nonpoint source (NPS) of nutrient and pesticide contamination in the environment. Available databases do not provide accurate and dynamic data on fertilizer and pesticide application, which limits the ability of complex watershed models to simulate contaminant loads into impaired water bodies. A model for estimating agricultural nutrient and pesticide input for watershed modeling has been developed. Climate, soils, and major agricultural operations are considered within the model, so that it can be adapted to any watershed or subregion within a watershed. The timing of the agricultural operations is a function of the weather data, providing realistic results at daily, monthly, or annual application rates. The model also predicts irrigation demand and biomass production, which can be used to calibrate the model. Model output can be used in any watershed model that considers agricultural land uses. Two case studies were evaluated, using grape vineyards in the Napa River and strawberry production in Newport Bay as examples. The predicted time to maturity corresponded well with actual data. Irrigation and fertilizer needs were very sensitive to weather input. Although the model can generate weather from long-term averages, the simulated results are best when at least observed precipitation and temperature are provided, to capture extreme events. The model has data for 98 crops and 126 pesticides, based on the California Department of Pesticide Regulation database. The databases are easily modifiable by the user to adapt them to local conditions. The output from AgInput is much needed for watershed modeling and for development of total maximum daily loads (TMDLs), based on realistic targets of irrigation, nutrient, and pesticide inputs. The model is available for free download at .     

Pesticides residues in okra (non-target crop) grown close to a watermelon farm in Ghana

The study looked at the levels of pesticides in okra grown close to a watermelon farm herein referred to as a non-target crop. The watermelon received some pesticide application in the course of its cultivation, and the okra which was not meant to be sprayed was also affected by the pesticide. About 500 okra samples were collected for a period of 6 weeks and pesticides extracted with 1:1 n-hexane and dichloromethane which was analysed with Agilent 2222 GC/MS coupled with 389 auto-sampler. The results confirmed accumulation of significant levels of pesticides in the non-target crop (okra grown close to watermelon farm). Levels of organochlorine pesticides ranged from 3.10 to 7.60 μg/kg whilst the organophosphorus pesticides had levels ranging from 2.80 to 2016.80 μg/kg. The synthetic pyrethroid pesticide mean levels also ranged from 0.10 to 4.10 μg/kg and were below World Health Organization/Food and Agriculture Organization-recommended residue levels, and though not appearing to constitute a grave threat to life, their occurrence is a concern, and pre-emptive techniques must be developed to thwart the contaminations. Though the non- target crop was not treated directly with the pesticides, some level of contamination with organochlorine and organophosphorus pesticides persisted in the crops. It can be inferred that application of pesticides affected the adjoining crops, meaning that inter-cropping and mix-cropping might not be acceptable when one of the crops requires pesticide application. It is important for the farmers to be trained to ensure proper application of pesticide to minimise its impact on the health of consumers.     

高尔夫球场农药使用情况调查及特征分析

通过对上海市高尔夫球场农药使用情况的详细调查,结果显示:当前高尔夫球场使用的农药主要包括3大类43种,包含杀菌剂20种、杀虫剂14种和除草剂9种,种类组成及施用量均以杀菌剂为主;施用农药以微毒、低毒农药为主(占69.8%),高毒农药主要为杀虫剂;不同球场农药使用种类、强度和频次等存在较大差异,主要与球场规模、草坪种类及管理水平等有关;当前高尔夫球场农药使用中仍存在农药施用强度较高,农药施用种类较多,品种结构仍有待优化等问题。     

Assessing the impact of irrigation treatments on thiram residual trends: Correspondence with numerical modelling and field-scale experiments

The present study was undertaken to study the trends of transport of thiram, a dithiocarbamate pesticide, at different time and depth in the fields under real field conditions for wheat crop. Numerical simulations were carried out by solving the coupled soil–water content movement and mass transport equations using HYDRUS- 1D. The supplementary data used for paramaterization of HYDRUS-1D comprise of irrigation treatments, climatic conditions, and soil characteristics. Results focus on the effects and influence of irrigation treatments on pesticide persistence and mobility. Modelling results were in good agreement with the experimentally determined thiram concentrations. Application of the model to measured field data of thiram movement indicates that the modelling approach can provide reliable and useful estimates of the mass flux of water and non-volatile pesticide in vadose zone. For policy-makers and planners, some regulation strategies are suggested for controlling inappropriate pesticide application under deficit irrigation or rain-fed conditions.     

Dissipation and residue behavior of mepiquat on wheat and potato field application

A modified LC-MS method for the analysis of mepiquat residue in wheat, potato, and soil was developed and validated. A hydrophilic interaction liquid chromatographic column has been successfully used to retain and separate the mepiquat. Mepiquat residue dynamics and final residues in supervised field trials at Good Agricultural Practice (GAP) conditions in wheat, potato, and soil were studied. The limits of quantification for mepiquat in all samples were all 0.007 mg kg^?1, which were lower than their maximum residue limits. At fortification levels of 0.04, 0.2, and 2 mg kg^?1 in all samples, recoveries ranged from 77.5 to 116.4 % with relative standard deviations of 0.4–7.9 % (n?=?5). The dissipation half-lives (T _1/2) of mepiquat in soil (wheat), wheat plants, soil (potato), and potato plants were 4.5–6.3, 3.0–5.6, 2.2–4.6, and 2.4–3.2 days, respectively. The final residues of mepiquat were below 0.153 mg kg^?1 in soil (wheat), 0.052–1.900 mg kg^?1 in wheat, below 0.072 mg kg^?1 in soil (potato), and below 1.173 mg kg^?1 in potato at harvest time. Moreover, pesticide risk assessment for all the detected residues was conducted. A maximum 0.0012 % of acceptable daily intake (150 mg kg^?1) for national estimated daily intake indicated low dietary risk of these products.     

The effects of pesticide mixtures on degradation of pendimethalin in soils

Most agronomic situations involve a sequence of herbicide, fungicide, and insecticide application. On the other hand, use of pesticidal combinations has become a standard practice in the production of many agricultural crops. One of the most important processes influencing the behavior of a pesticide in the environment is its degradation in soil. It is known that due to several pesticide applications in one vegetation season, the pesticide may be present in mixtures with other pesticides or xenobiotics in soil. This study examines the role which a mixture of chemicals plays in pesticide degradation. The influence of other pesticides on the rate of pendimethalin (PDM) degradation in soil was measured in controlled conditions. Mixtures of PDM with mancozeb or mancozeb and thiamethoxam significantly influenced the degradation of pendimethalin under controlled conditions. The second type of mixtures, with metribuzin or thiamethoxam, did not affect the behavior of pendimethalin in soil. Also, we determined the influence of water content on the rate of pendimethalin degradation alone in two soils and compared it to the rate in three pesticide mixtures. We compared two equations to evaluate the predictors of the rate of herbicide dissipation in soil: the first-order kinetic and the non-linear empirical models. We used the non-linear empirical model assuming that the degradation rate of a herbicide in soil is proportional to the difference of the observed concentration of herbicide in soil at time and concentration of herbicide in the last day of measurement.     

江苏省主要农药产品的环境残留监测方法研究

介绍了江苏省生产的主要农药品种,综述了草甘膦、丁草胺、乙草胺、百草枯和氟乐灵等5种除草剂,代森锰锌、戊唑醇、百菌清、甲基硫菌灵和三环唑等5种杀菌剂,毒死蜱、吡虫啉、氯氰菊酯等3种杀虫剂,以及乙烯利、多效唑等2种植物生长调节剂的生产现状及危害,以及上述农药在水、土壤等环境介质中的检测方法。以期为相关农药残留的检测方法标准化、环境中控制限值的制定、农药类环境事故应急监测以及农药生产与使用的环境监管提供技术支持。     

occurrence and distribution of nitrate and pesticides in bowdle aquifer, south dakota

A shallow aquifer in central South Dakota was monitored for thepresence of nitrate and pesticides. A total of 593 nitrate samples and428 pesticide samples were analyzed from nine different sites and 14wells between 1989 and 1994. Nested wells were installed at four sitesto characterize the distribution pattern of nitrate and pesticidemovement in ground water. Nitrate concentrations and pesticidedetections were qualitatively compared with area precipitation and watertable fluctuations. The results indicate that nitrates tend to betransported by a leaching mechanism in a matrix flow and may appearin ground water within months after the fertilizer application in thefields. The pesticide movement is primarily controlled by geologicaland chemical characteristics of medium and pesticides.     

A multi-lysimeter investigation on the mobility and persistence of pesticides in the loam soil of the Fucino Plain (Italy)

In order to evaluate the impact of intensive horticulture on the water resources of the Fucino Plain, one of the most important agricultural settlements of Central Italy, the mobility and persistence in the soil of five commonly used pesticides was investigated by means of multi-lysimeter experiments. The fate of simazine, carbaryl, dicloran, linuron and procymidone was evaluated in the laboratory under experimental conditions simulating as closely as possible both pesticide application and irrigation practices required by the local crops. An efficient extraction procedure followed by chromatographic analysis, allowing the simultaneous determination of the applied chemicals, was used to monitor the pesticide residues in the soil columns as a function of time from application and depth. The experiment, carried out for about 60 days, revealed that soil contamination apparently involves only the surface layer since none of the investigated pesticides was detected at depths greater than 20-30 cm. However, the five pollutants exhibit a quite different behaviour that can be related to their physico-chemical properties.     

巢湖水质状况及污染防治措施

简述了娟湖湖区水质状况,指出工业废水和生活污水以及农田过量地使用化肥和农药等是导致巢湖水质经的主要原因,并担子同相应的防治措施。     

Dermal exposure to pesticides in greenhouses workers: discrimination and selection of variables for the design of monitoring programs

Dermal exposure to pesticides is one of the main sanitaryproblems which greenhouses workers face. With the dual aimsof establishing both the body part that receives the greatestexposure and the variable that has greatest influence on this exposure level, 22 pesticide application trials were performed. Trials were carried out in different greenhouse vegetable crops,using different pesticides and different spray diameters from the spray gun. In order to determine dermal exposure, the wholebody method was used. Pieces of the applicator suit were subject to an extraction procedure and their pesticide contentdetermined using GC-NPD analysis. Multivariate analysis were applied to the data obtained. Principal component analysis showed that all trials produced a high exposure level on lowerleft leg and lower right leg. Cluster analysis distinguished between three sample groups. The most and the least affectedparts were clearly distinguished. Discriminant analysis indicated that the thin drop size of the spray gun is responsible for both the differences between groups and the minimum or maximum exposure level measured on the applicatorsuit. Therefore, selecting the variables, lower legs and thindrop size, is considered fundamental in designing programs formonitoring pesticide exposure.     

Pesticide vapours in confined atmospheres. Determination of dichlorvos by SPME-GC-MS at the microg m(-3) level

A method based on SPME is described for assessing the gaseous dichlorvos concentration in confined atmospheres like a greenhouse after a pesticide application. Sampling was made by using SPME with PDMS fibres immersed into a 250 mL sampling flask into which air samples were dynamically pumped from the analysed atmosphere. Sampling duration was 40 min and samples were then analysed by GC-MS. Calibration was performed from a vapour saturated air sample and gas phase diluted samples, and this procedure afforded a curve with a regression coefficient (R2) higher than 0.98. The repeatability of these measurements was observed with an RSD of 2.5%. This analysis procedure was then applied for the determination of gaseous dichlorvos concentrations versus time, in the atmosphere of an experimental 8 m2 and 20 m3 greenhouse. The pesticide was sprayed according to real cultivation conditions and measurements were made from 2 up to 74 h after application affording observed concentrations in the range of decades and hundreds of microg m(-3) (corresponding limits of detection and quantification were found at the level of a few microg m(-3)).     

环境样品中农药的前处理及检测技术研究进展

综述了近年来农药环境样品的前处理及检测技术,介绍了各种前处理和检测技术的应用情况,在此基础上对环境中残留农药的前处理及检测技术的发展进行了展望.