大鼠全胚胎培养方法的建立及其在若干农药致畸研究中的应用

本文通过对体内、体外大鼠胚胎生长发育的对比研究，在本实验室建立植入后大鼠全胚胎培养方法，并应用该法探讨农药敌枯双和除草剂８３－１对体外大鼠胚胎的毒作用和臻致畸作用，为其安全性评价提供进一步的科学依据。     

农药在人体中的变化(二)

三、水解代谢水解代谢是农药在生物体内的代谢中研究得最多的,也是发生得最多和最普遍的一类代谢反应。水解酶的种类很多,其中关系最大的有五大类,分为二个系列:A—酯酶和B—酯酶。它们的主要区别为,前者水解有机磷酸酯类农药,而后者到则受     

生物体内有机氯农药的研究进展

有机氯农药是高残留农药，进入生物体后会长期残留，对生物体产生危害。近年来，生物体中的有机氯农药的研究越来越引起各国环境化学家、生态学家的重视，渐渐成为环境化学、生态毒理学研究的热点之一。本文总结了近年来国际上有关生物体内有机氯农药的研究进展情况，以及所取得的主要研究成果。     

谈农药的发展趋向与环境的协调

农药在防治植物病虫害和提高农产品产量方面起着重要的作用。六六六、DDT、对硫磷、和其它一些有机合成农药经常使用。在过去的40多年里,世界上由于除草剂的使用,使除草劳动效率提高了90％。据估计,到21世纪中叶,世界人口将超过100亿。为了解决人口日益增长对粮食的需要,毫无疑问,农药的有效及合理使用是极其重要的。     

83－1除草剂的主要代谢产物的毒性研究

本文检测了８３－１除草剂的主要代谢产物—２．４一二氯，６－胺基酚对大鼠、小鼠的ＬＤ＿（５０）；同时做了Ａｍｅｓ试验。用Ｈｏｒｎ′ｓ法测定ＬＤ＿（５０）结果为：大鼠雌１０００（６４２～１５６０）ｍｇ／ｋｇ，雄１０００（５５４～１８１０）ｍｇ／ｋｇ；小鼠雌８５２（５６２～１２１０）ｍｇ／ｋｇ雄１０００（６４２～１５６０）ｍｇ／ｋｇ；Ａｍｅｓ试验结果为阳性．     

磺酰脲类农药特性及国内外监测技术研究现状

随着磺酰脲类除草剂使用范围的扩大和农民为提高除草效果而擅自增加用量,其在农作物、环境中的残留及其对人类健康和环境造成的毒害越来越为人们所关注。本文主要介绍磺酰脲类农药的特性,以及目前国内外对该类农药监测技术领域的一些研究成果。该类农药的监测技术主要有高效液相色谱法、毛细管电泳法、气相和气质联用法、高效薄层析技术、酶联免疫生物测定法和放射性同位素示踪法等方法,这些检测方法为实际环境监测中选择最合适的分析方法监测磺酰脲类农药提供参考。     

农药的消失与残留的初步探讨

化学农药施用于农田后,由于物理、化学、和生物等因素的作用,逐渐分解消失,消失的快慢直接影响农药的药效,又关系农药对环境的污染。大多数农药经生物环境与非生物环境作用后,较快地分解成简单化合物而消失,但是长效性农药如DDT、六六六能在土壤和生物体内停留较长时间,形成所谓农药的“残毒”问题。     

82—1除草剂的主要代谢产物的毒性研究

本文检测了83－1除草剂的主要代射产物－2，4－二氯，6－胺基酚对大鼠，小鼠的LD50；同时做了Ames试验，用Horn‘s法测定LDLD50结果为：大鼠雌1000（642－1560）mg/kg，雌1000（554－1810）mg/kg，小鼠雌852（562－1210）mg/kg。雌1000（642－1560)mg/kg,Ames试验结果为阳性。     

生物修复技术治理农村面源水污染问题的调查研究

调查得知，随着农村化肥、农药、除草剂的大量使用以及禽畜养殖规模化的扩大，造成我国农村面源污染日趋严重。农村面源污染源分散，没有明确位置，其治理一直是个难题。本文结合成都市政府解决府南河水污染问题时采用的针对面源污染的生物修复技术，对此技术作了较深入的研究，并取得了一定的效果，对国内城市近郊农村面源污染有较好的参考价值。在对所需植物进行逐级实验后，可推广至农村以解决成都地区的面源污染问题。     

不同土类稻田环境中农药残留规律的研究

“六六六”往年是我省防治水稻虫害的主要农药品种,长期以来被农民普遍应用,由于“六六六”化学性质稳定,易造成环境污染,近年来,国内虽对有机氯农药在多种作物上残留、代谢已做了大量的研究,可是对土壤环境“六六六”迁移、转化方面的研     

Effects of glyphosate and two herbicide mixtures on microbial communities in prairie wetland ecosystems: a mesocosm approach

A multitrophic outdoor mesocosm system was used to mimic a wetland ecosystem and to investigate the effects of glyphosate and two herbicide mixtures on wetland microbial communities. The glyphosate concentration used was 1000 times the environmentally relevant concentration (ERC). One herbicide mixture consisted of six auxin-type herbicides (2,4-D, MCPA, clopyralid, dicamba, dichlorprop, mecoprop), each at 1000 times the ERC. The second mixture was comprised of eight herbicides, including the six auxin-type herbicides as well as bromoxynil and glyphosate. For this mixture, a dose-response approach was used to treat mesocosms with the ERCs of each herbicide as the base concentration. Algal biomass and production and bacterial production and numbers for pelagic and attached communities were measured at different times over a 22-d period. The experimental results indicate that the eight-herbicide mixture, even at low concentrations, produced negative effects on microbial communities. Glyphosate on its own suppressed algal biomass and production for the duration of the study in pelagic and biofilm communities. Algal biomass and production, although initially depressed in the auxin-type herbicide treatment, were stimulated from Day 9 until experiment end. Due to their similar modes of action, the effects of this herbicide mixture appear to be a result of concentration addition. Such negative effects, however, were brief, and microbial communities recovered from herbicide exposure. Based on evidence presented in this study, it appears that glyphosate has a higher potential to inhibit primary production and chlorophyll content in pelagic and attached wetland algal communities than the auxin-type herbicide mixture.     

SUSCEPTIBILITY OF INDIANA WATERSHEDS TO HERBICIDE CONTAMINATION1

ABSTRACT: An index of watershed susceptibility to surface water contamination by herbicides could be used to improve source water assessments for public drinking water supplies, prioritize watershed restoration projects, and direct funding and educational efforts to areas where the greatest environmental benefit can be realized. The goal of this study is to use streamflow and herbicide concentration data to develop and evaluate a method for estimating comparative watershed susceptibility to herbicide loss. United States Geological Survey (USGS) concentration data for five relatively water soluble herbicides (alachlor, atrazine, cyanazine, metolachlor, and simazine) were analyzed for 16 Indiana watersheds. Correlation was assessed between observed herbicide losses and: (1) a herbicide runoff index using GIS‐based land use, soil type, SCS runoff curve number, tillage practice, herbicide use estimates, and combinations of these factors; and (2) predicted herbicide losses from a non‐point source pollution model (NAPRA‐Web, an Internet‐based interface for GLEAMS). The highest adjusted R²value was found between herbicide concentration and the runoff curve number alone, ranging from 0.25 to 0.56. Predictions from the simulation model showed a poorer correlation with observed herbicide loss. This indicates potential for using the runoff curve number as a simple herbicide contamination susceptibility index.     

REGRESSION MODELS OF HERBICIDE CONCENTRATIONS IN OUTFLOW FROM RESERVOIRS IN THE MIDWESTERN USA, 1992–19931

ABSTRACT: Reservoirs are used to store water for public water supply, flood control, irrigation, recreation, hydropower, and wildlife habitat, but also often store undesirable substances such as herbicides. The outflow from 76 reservoirs in the midwestern USA, was sampled four times in 1992 and four times in 1993. At least one herbicide was detected in 82.6 percent of all samples, and atrazine was detected in 82.1 percent of all samples. Herbicide properties; topography, land use, herbicide use, and soil type in the contributing drainage area; residence time of water in reservoirs; and timing of inflow, release, and rainfall all can affect the concentration of herbicides in reservoirs. A GIS was used to quantify characteristics of land use, agricultural chemical use, climatic conditions, topographic character, and soil type by reservoir drainage basins. Multiple linear and logistic regression equations were used to model mean herbicide concentrations in reservoir outflow as a function of these characteristics. Results demonstrate a strong association between mean herbicide concentrations in reservoir outflow and herbicide use rates within associated drainage basins. Results also demonstrate the importance of including soils and basin hydrologic characteristics in models used to estimate mean herbicide concentrations.     

Runoff and drainage losses of atrazine, metribuzin, and metolachlor in three water management systems

Rainfall can transport herbicides from agricultural land to surface waters, where they become an environmental concern. Tile drainage can benefit crop production by removing excess soil water but tile drainage may also aggravate herbicide and nutrient movement into surface waters. Water management of tile drains after planting may reduce tile drainage and thereby reduce herbicide losses to surface water. To test this hypothesis we calculated the loss of three herbicides from a field with three water management systems: free drainage (D), controlled drainage (CD), and controlled drainage with subsurface irrigation (CDS). The effect of water management systems on the dissipation of atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine), metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazine-5(4H)-one), and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] in soil was also monitored. Less herbicide was lost by surface runoff from the D and CD treatments than from CDS. The CDS treatment increased surface runoff, which transported more herbicide than that from D or CD treatments. In one year, the time for metribuzin residue to dissipate to half its initial value was shorter for CDS (33 d) than for D (43 d) and CD (46 d). The half-life of atrazine and metolachlor were not affected by water management. Controlled drainage with subsurface irrigation may increase herbicide loss through increased surface runoff when excessive rain is received soon after herbicide application. However, increasing soil water content in CDS may decrease herbicide persistence, resulting in less residual herbicide available for aqueous transport.     

REGIONAL PATTERNS OF PESTICIDE CONCENTRATIONS IN SURFACE WATERS OF NEW YORK IN 19971

ABSTRACT: The predominant mixtures of pesticides found in New York surface waters consist of five principal components. First, herbicides commonly used on corn (atrazine, metolachlor, alachlor, cyanazine) and a herbicide degradate (deethylatrazine) were positively correlated to a corn‐herbicide component, and watersheds with the highest corn‐herbicide component scores were those in which large amounts of row crops are grown. Second, two insecticides (diazinon and carbaryl) and one herbicide (prometon) widely used in urban and residential settings were positively correlated to an urban/residential component. Watersheds with the highest urban/residential component scores were those with large amounts of urban and residential land use. A third component was related to two herbicides (EPTC and cyanazine) used on dry beans and corn, the fourth to an herbicide (simazine) and an insecticide (carbaryl) commonly used in orchards and vineyards, and the fifth to an herbicide (DCPA). Results of this study indicate that this approach can be used to: (1) identify common mixtures of pesticides in surface waters, (2) relate these mixtures to land use and pesticide applications, and (3) indicate regions where these mixtures of pesticides are commonly found.     

FACTORS AFFECTING HERBICIDE YIELDS IN THE CHESAPEAKE BAY WATERSHED,JUNE 19941

ABSTRACT: Median concentrations and instantaneous yields of alachlor, metolachlor, atrazine, cyanazine, and simazine were generally highest at sites in the Lower Susquehanna River Basin and in agricultural subbasins. Instantaneous herbicide yields are related to land use, hydrogeologic setting, streamflow yield, and agricultural row cropping practices. The significance of these relations may be affected by the interdependence of the factors. The percentage of basin area planted in corn is the most influential factor in the prediction of herbicide yield. Instantaneous yields of all five herbicides measured in June 1994 related poorly to averaged 1990–94 herbicide use. Annually averaged herbicide-use data are too general to use as a predictor for short-term herbicide yields. An evaluation of factors affecting herbicide yields could be refined with more-current land use and land cover information and a more accurate estimate of the percentage of basin area planted in corn. Factors related to herbicide yields can be used to predict herbicide yields in other basins within the Chesapeake Bay watershed and to develop an estimate of herbicide loads to Chesapeake Bay.     

Herbicide selection of Italian ryegrass under different levels of UVB radiation

Ultraviolet-B radiation is an environmental stress for plants and this situation could become aggravated in the next decades. In this study we used Italian ryegrass (Lolium multiflorum Lam.) as a model system to test whether an environmental stress derived from global change, such as UVB, can influence the efficacy of control procedures and evolution toward herbicide resistance. We grew three generations of Italian ryegrass plants with and without UVB light and subjected them to a series of diclofop-methyl [(+/-)-2-[4-(2,4-dichlorophenoxy) phenoxy] propanoic acid, methyl ester] doses. The effect of selection history was tested with herbicide dose response. The effect of herbicide application on plant survival and biomass varied significantly among herbicide doses and with absence or presence of UVB light. In the absence of herbicide, the decrease in individual fecundity with increasing plant density was similar under both no-UVB and UVB light treatments. Only plants growing without UVB light increased production of reproductive structures in response to the decrease in density caused by herbicide application. Our study shows that UVB light was a weak stress factor for the ryegrass plants. However, when herbicide selection pressure was high, UVB light reduced the evolution toward herbicide tolerance. When selection pressure on the parental plants was lower, the two stress factors had a synergistic effect, causing changes in herbicide efficacy that in turn had demographic and evolutionary consequences. In the field, these interactions between stress factors might be of significance for annual weeds in which seed output is a major determinant in fitness.     

Comparison of field-scale herbicide runoff and volatilization losses: an eight-year field investigation

An 8-yr study was conducted to better understand factors influencing year-to-year variability in field-scale herbicide volatilization and surface runoff losses. The 21-ha research site is located at the USDA-ARS Beltsville Agricultural Research Center in Beltsville, MD. Site location, herbicide formulations, and agricultural management practices remained unchanged throughout the duration of the study. Metolachlor [2-chloro--(2-ethyl-6-methylphenyl)--(2-methoxy-1-methylethyl) acetamide] and atrazine [6-chloro--ethyl--(1-methylethyl)-1,3,5-triazine-2,4-diamine] were coapplied as a surface broadcast spray. Herbicide runoff was monitored from a month before application through harvest. A flux gradient technique was used to compute volatilization fluxes for the first 5 d after application using herbicide concentration profiles and turbulent fluxes of heat and water vapor as determined from eddy covariance measurements. Results demonstrated that volatilization losses for these two herbicides were significantly greater than runoff losses ( < 0.007), even though both have relatively low vapor pressures. The largest annual runoff loss for metolachlor never exceeded 2.5%, whereas atrazine runoff never exceeded 3% of that applied. On the other hand, herbicide cumulative volatilization losses after 5 d ranged from about 5 to 63% of that applied for metolachlor and about 2 to 12% of that applied for atrazine. Additionally, daytime herbicide volatilization losses were significantly greater than nighttime vapor losses ( < 0.05). This research confirmed that vapor losses for some commonly used herbicides frequently exceeds runoff losses and herbicide vapor losses on the same site and with the same management practices can vary significantly year to year depending on local environmental conditions.     

Alachlor and bentazone losses from subsurface drainage of two soils

Atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine) is frequently detected at high concentrations in ground water. Bentazone [3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide] plus alachlor (2-chloro-2',6'-diethyl-N-methoxymethylacetanilide) is a potential herbicide combination used as a substitute for atrazine. Thus, the objective of this study was to assess the environmental risk of this blend. Drainage water contamination by bentazone and alachlor was assessed in silty clay (Vertic Eutrochrept) and silt loam (Aquic Hapludalf) soils under the same management and climatic conditions. Drainage volumes and concentrations of alachlor and bentazone were monitored after application. Herbicides first arrived at the drains after less than 1 cm of net drainage. This is consistent with preferential flow and suggests that about 3% of the pore volume was active in rapid transport. During the monitoring periods, bentazone losses were higher (0.11-2.40% of the applied amount) than alachlor losses (0.00-0.28%) in the drains of the silty clay and silt loam. The rank order of herbicide mass losses corresponded with the rank order of herbicide adsorption coefficients. More herbicide residues were detected in drainage from the silty clay, probably due to preferential flow and more intensive drainage in this soil than the silt loam. Surprisingly, herbicide losses were higher in the drains of both soils in the drier of the two study years. This could be explained by the time intervals between the treatments and first drainage events, which were longer in the wetter year. Results suggest that the drainage phases occurred by preferential flow in the spring-summer period, with correspondingly fast leaching of herbicides, and by matrix flow during the fall-winter period, with slower herbicide migration.     

Modeling potential herbicide loss to surface waters on the Swiss plateau

Lack of sufficiently detailed data often limits the applicability of complex transport-reaction models for estimating potential herbicide loss to surface waters. Therefore, there is also a need for simple models that are easy to apply but still capture the main features of the underlying processes.In this study, a simple regression model was developed to assess the vulnerability of catchments in the Swiss Plateau to diffuse herbicide loss to surface waters. The model is designed as a screening tool to rank the catchments in a relative sense and not to calculate Predicted Environmental Concentrations (PEC) of pesticides. The main goal is to capture two dominating factors controlling diffuse herbicide transport into streams and rivers. These factors are herbicide application and fast flow processes that are mainly responsible for herbicide transport. In a first step vulnerability of sites to herbicide loss is estimated based on site-specific conditions irrespective of actual herbicide application. In the second step, this vulnerability assessment is combined with actual herbicide application data to estimate the potential herbicide loss.The fast flow index (FFI), derived from discharge data using a base flow separation method, was applied as a proxy for the amount of fast flow occurring. The influence of catchment attributes (including topographic, climatic and soil data) on the FFI was analyzed using a multiple regression approach based on data from 57 catchments of the Swiss Plateau. By combining regression analysis with mechanistic knowledge, a two factor non-linear model based on river density and soil permeability as dominant input factors was selected as the best model for FFI prediction given the available data. Higher dimensional models had to be excluded because the strong correlation between the potential input factors led to unrealistic dependences while only minimally improving the quality of the fit.The spatial pattern of the predicted FFI as a measure for the vulnerability to diffuse herbicide losses shows a clearly increasing trend from the western to the eastern part of the Swiss Plateau and towards the pre-alpine/alpine regions in the south.In general the pattern of herbicide use corresponds to site conditions typical of a low FFI. However, the spatial analysis revealed exceptions, namely areas in which high actual herbicide use coincides with a high FFI.Despite the uncertainties in the model, this simple approach seems to be useful for supporting site-adapted agricultural practice whenever the higher accuracy of more detailed models is not required or too expensive to achieve. In addition, in combination with data on actual herbicide application, it can support the design of monitoring strategies by identifying critical areas of actual herbicide loss.