摘要:

AbstractGround water studies that require long data collection periods may be affected by temporal changes in ground water chemistry. Seasonal fluctuations in ground water chemistry are particularly apparent in shallow aquifers. Of specific interest is the inclusion of temporal variability in the design of statistical surveys of agricultural chemicals in well water. Statistical treatment of temporal variability involves selecting a probability sample from temporal units. The selection strategy may include repeating the same spatial units in each temporal stratum or choosing an independent sample of spatial units for each temporal stratum. The appropriate strategy depends on the specific study objectives. Failure to account for temporal variability may compromise the validity of study conclusions. An example of a large‐scale retrospective survey designed to estimate temporal averages of water quality across all wells is presente

ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1990.tb00331.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractAtrazine, cyanazine, alachlor, and metolachlor in the surface water of a recharge structure, which impounds runoff from row‐cropped farmland in Nebraska, are transported with seepage to the shallow ground water flow system and to the locally confined regional aquifer. All wells in the shallow flow system and all those in the regional flow system impacted by seepage from the structure had detectable concentrations of at least one of the four pesticides.The detectable concentrations of cyanzine, alachlor, and metolachlor in the two flow systems ranged from 0.1 to 0.9 ppb. These concentrations were an order of magnitude lower than those in the surface water. Concentrations in the regional aquifer clustered at the lower end of this concentration range. These three pesticides were not detected in the baseline study of the regional aquifer.Unlike alachlor, cyanzine, and metolachlor, atrazine was always present in the wells impacted by seepage from the recharge structure. In the shallow flow system, concentrations ranged from 0.3 to 8.8 ppb and from 0.1 to 2.5 ppb in the regional aquifer. The average of the detectable atrazine concentrations in the baseline study was 0.04 ± 0.05 p

ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1990.tb00332.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractScientists and regulators in the United States began emphasizing the study of pesticides in ground water in 1979 and 1980. The scientific community began to emphasize the study of nitrates in ground water as a result of fertilization in the mid to late 1970s. By the mid 1980s. tens of thousands of wells were found to contain elevated nitrate concentrations and detectable concentrations of pesticides. Few, if any, of the data were collected from wells associated with the nation's 13,000 golf courses.Golf is popular on Cape Cod, an area that depends on a hydrogeologically vulnerable aquifer system as its principal source of drinking water. Pesticides and fertilizers are applied to golf courses, often at high rates on greens and tees. Therefore the EPA, the Barnstable County government, and several local golf course superintendents collaborated on a study of the impact of golf course turf management on ground water quality.Nineteen monitoring wells were installed upgradient and in greens, tees, and fairways on four golf courses. Selected soil core samples were collected and analyzed. Four to six rounds of ground water samples were collected over one and a half years and analyzed for 17 pesticides and related chemicals; nitrate‐N samples were collected at least monthly. Seven of the 17 chemicals were never detected. The most frequently detected chemical‐dichlorobenzoic acid ‐ probably had been an impurity in herbicide formulations. Chlordane was detected in several wells at concentrations exceeding the health advisory level, perhaps due either to repeated heavy applications coupled with preferential flow of the bound/particulate phase and /or cross contamination during well installation. The results show no cause for concern about use of these currently registered pesticides.Nitrate‐N concentrations were generally below the 10 ppm federal MCL, with some exceptions. Overall, nitrate‐N concentrations decreased in response to lower application rates and use of slow‐release fertilizer f

ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1990.tb00333.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY