GROUNDWATER CONTAMINATION BY NEMATICIDES: INFLUENCE OF RECHARGE TIMING UNDER PINEAPPLE CROP1

ABSTRACT: Toxic organic compounds, such as DBCP, EDB, and c TCP, that are associated with pineapple cultivation in Hawaii have been discovered in drinking water wells on Oahu. In order to reach and contaminate the Pearl Harbor aquifer, pesticides must be transported quickly downward away from the soil surface prior to complete volatilization, degradation, or adsorption of residuals. This paper assesses the role of pesticide application timing relative to subsequent rainfall-induced recharge events in determining the amount and extent of chemical leaching from the soil. A water balance model for a pineapple crop is developed to estimate the time series of recharge from two fields for which soil contamination profiles are available. In general, the amounts of DBCP, EDB, and TCP found in the soil profiles of the two fields are consistent with expectations of leaching based on an analysis of the recharge time series. The results indicate that recharge during and immediately following the application of pesticides is important in determining whether groundwater contamination will result.     

Development of a Quality-Assessed Agrichemical Database For Monitoring Anthropogenic Impacts on Ground-Water Quality

The Quality–Assessed Agrichemical Contaminant Database for Nebraska Ground Water is a unique repository of nitrate and pesticide data collected by federal, state, and local agencies. Each contaminant concentration in the database has been evaluated based upon well–defined criteria that address completeness of the well–attribute data, analytical method and field and laboratory quality control practices and assigned to one of five quality levels. The quality assessment level always accompanies the contaminant concentration so that the end–user knows the quality assurance effort expended in the acquisition of the data, can select comparable data, and choose data whose quality assurance effort is commensurate with project objectives. The database can be viewed and queried on–line; downloaded in its entirety; or imported to a spreadsheet or a geographic information system. Setting criteria for data quality and assessing the level of quality have resulted in significant increases in the percentages of high quality (Levels 3–5) nitrate and pesticide data. These high quality data presently constitute 52% of the nitrate and 55% of the pesticide data.     

Causes of ambient toxicity in the Calleguas Creek watershed of southern California

A combination of toxicity tests, chemical analyses, andToxicity Identification Evaluations (TIEs) were used toinvestigate receiving water toxicity in the Calleguas Creekwatershed of southern California. Studies were conductedfrom 1995 through 1999 at various sites to investigatecauses of temporal variability of toxicity throughout thissystem. Causes of receiving water toxicity varied by siteand species tested. Investigations in the lower watershed(Revolon Slough, Santa Clara Drain, Beardsley Wash)indicated that toxicity of samples to the cladoceran Ceriodaphnia dubia due to elevated concentrations ofthe organophosphate pesticide chlorpyrifos, while causes ofintermittent toxicity to fathead minnows (Pimephalespromelas) and the alga Selanastrum capricornutum wereless clear. Investigations at sites in the middle and upperreaches of the watershed (Arroyo Simi and Conejo Creek)indicated that the pesticide diazinon was the probable causeof receiving water toxicity to Ceriodaphnia. Elevatedammonia was the cause of toxicity to fathead minnows in theupper watershed sites. Results of these and previousstudies suggest that biota are impacted by degraded streamquality from a variety of point and non-point pollutionsources in the Calleguas Creek watershed. Water qualityresource manager's efforts to identify contaminant inputsand implement source control will be improved with thefindings of this study.     

Effect of Common Pesticides Used in the Niger Delta Basin of Southern Nigeria on Soil Microbial Populations

The effects of eleven pesticides on the populations of bacteria, actinomycetes, fungi and protozoa was investigated by treating a garden soil with their recommended rates. The microbial populations were estimated using the standard plate-count technique. Of the ll pesticides investigated, phenylmercuric acetate (agrosan) at 50 g g^-1 inhibited bacterial density the most, i.e. from 4,600,000 to 220 cells g^-1. The pesticides were Pentachloronitrobenzene (PCNB), tetramethylmethylthiuram disulphide (thiram),1- naphthylmethylcarbamate (Vetox 85), 1,2,3,4,5,6-hexachlorocyclohexane (Gammalin 20), phenylmercuric acetate (Agrosan), tetrachloroterephthalic acid (Dacthal), 4-nitrophenyl –2-nitro-4-trifluoromethylphenyl ether (Preforan), 2-ethyl-6-methyl –N-2-methoxy –1-methyl ethyl-chloroacetanide (Dual), Benlate, Brestan and Gramoxone. Pentachloronitrobenzene (PCNB) at 240,000 g g^-1 reduced bacterial population from 4,600,000 to 2,100 cells g^-1, whereas tetramethylthiuram disulphide (thiram) at 100 g g^-1 suppressed it by 2 log orders of magnitude. Soil application of 1-naphthylmethylcarbamate (Vetox 85) at 100 g g^-1 and 1,2,3,4,5,6,-hexachlorocyclohexane (Gamalin 20) at 1,300 g g^-1 repressed the bacterial numbers by 2 log orders of magnitude each. Pentachloronitrobenzene reduced the actinomycetes density from 340,000 to 320 cells g^-1 and completely eliminated all fungal and protozoan propagules from the soil. The Gammalin 20 completely wiped out all the fungi, whereas phenylmercuric acetate totally eliminated all the protozoa and reduced the fungal population from 34,000 to 60 cells g^-1. In general, protozoa and fungi were more susceptible to fungicides than bacteria and actinomycetes. Pentachloronitrobenzene, 1,2,3,4,5,6,-hexachlorocyclohexane and phenylmercuric acetate were toxic particularly to soil microorganisms, whereas the herbicides dacthal, Preforan and Dual were quite harmless in soil at application rates of 0.1, 0.06 and 0.02 g g^-1 respectively.     

北京工业废水和城市污水中有机氯农药残留分析

建立了基于HLB固相萃取柱和气相色谱-电子捕获(GC-ECD)测定水体中有机氯农药的方法,并对方法的回收率、灵敏度进行了评价,同时分析了北京市七类典型污染点源50个采样点位有机氯农药的浓度,检测到的有机氯农药包括γ-六六六、β-六六六、4,4’-滴滴涕、α-六六六、δ-六六六、硫丹Ⅰ、4,4’-滴滴伊、艾氏剂和异狄氏剂,它们的检出率分别为90%、60%、50%、46%、26%、8%、6%、2%和2%。主要有机氯农药污染残留为γ-六六六、β-六六六和4,4’-滴滴涕。检出有机氯农药浓度范围是0.20~76.40ng/L。方法对有机氯农药的回收率达到60.93%~141.50%,方法检测限为0.27~2.90ng/L。     

水体沉积物中有毒有机污染物的监测研究进展

介绍了水体沉积物中有毒有机污染物监测的预处理技术,重点评述了我国水体沉积物中主要有毒有机污染物多环芳烃、多氯联苯和有机氯农药的监测研究现状,认为水体沉积物中有毒有机污染物研究领域今后发展的重点和方向是广泛开展国内主要河流、湖泊、海洋的监测研究和其在水体环境中的迁移及转化机理、生殖毒性以及污染消减与修复技术研究;加强新型预处理技术及其与大型仪器联用技术的研究;尽早建立水体沉积物中有毒有机污染物的监测方法标准及污染评价标准。     

Occurrence of Sediment-Bound Pyrethroids in Danish Streams and their Impact on Ecosystem Function

In a total of 189 water samples collected from Danish streams no traces of the pyrethroid esfenvalerate were detected. However, pyrethroids have previously been found in sediments in 9 out of 30 streams investigated. We found that the shredding activity of the Trichopteran Sericostoma personatum and the amphipod Gammarus pulex was significantly reduced with increased concentration of the pyrethroid lambda-cyhalohtrin adsorbed to the leaves on which they fed. Predation rate on the Plecopteran Leuctra nigra by the leech Erpobdella octoculata increased significantly with increasing concentration of lambda-cyhalothrin on the leaves on which L. nigra was fed. Our results clearly indicate that the ongoing monitoring of pesticides is likely to underestimate pyrethroid occurrence and that sediment-bound pyrethroids have a potential negative impact on ecosystem function and biotic interactions in streams.     

REGRESSION MODELS FOR ESTIMATING HERBICIDE CONCENTRATIONS IN U.S. STREAMS FROM WATERSHED CHARACTERISTICS1

ABSTRACT: Regression models were developed for estimating stream concentrations of the herbicides alachlor, atrazine, cyanazine, metolachior, and trilluralin from use‐intensity data and watershed characteristics. Concentrations were determined from samples collected from 45 streams throughout the United States during 1993 to 1995 as part of the U.S. Geological Survey's National Water‐Quality Assessment (NAWQA). Separate regression models were developed for each of six percentiles (10th, 25th, 50th, 75th, 90th, 95th) of the annual distribution of stream concentrations and for the annual time‐weighted mean concentration. Estimates for the individual percentiles can be combined to provide an estimate of the annual distribution of concentrations for a given stream. Agricultural use of the herbicide in the watershed was a significant predictor in nearly all of the models. Several hydrologic and soil parameters also were useful in explaining the variability in concentrations of herbicides among the streams. Most of the regression models developed for estimation of concentration percentiles and annual mean concentrations accounted for 50 percent to 90 percent of the variability among streams. Predicted concentrations were nearly always within an order of magnitude of the measured concentrations for the model‐development streams, and predicted concentration distributions reasonably matched the actual distributions in most cases. Results from application of the models to streams not included in the model development data set are encouraging, but further validation of the regression approach described in this paper is needed.     

长江武汉段水体悬浮物中有机氯农药的残留状况

以α-HCH,β-HCH,γ-HCH,δ-HCH,p,p′-DDE,p,p′-DDD,o,p′-DDT,p,p′-DDT和HCB等9种有机氯农药为目标污染物,采用索氏提取和气相色谱法,对长江武汉段水体悬浮物中有机氯农药的残留进行调查分析。调查发现,在长江武汉段水体悬浮物中,六氯苯(HCB)、六六六(HCHs)和滴滴涕(DDTs)类有机氯农药均被检出,其中六氯苯(HCB)在表层沉积物中的残留量(质量分数)为0 37～9 06ng g,平均为2 89ng g;六六六类农药在悬浮物中的残留量(质量分数)为0 23～1 90ng g,平均为0 76ng g;滴滴涕类在悬浮物中的残留量(质量分数)为0 18～4 67ng g,平均为1 31ng g。在长江武汉段水体悬浮物中,HCB,p,p′-DDE和γ-HCH的被检出率和残留量均最高,为主要污染物。