This study provides a comparison of water quality profiles taken within the screened interval of five shallow monitoring wells and those obtained from adjacent multilevel sampler clusters. Parameters compared are oxidation‐reduction potential, electrical conductivity, temperature, methylotertiary‐butyl ether (MTBE) concentrations, and chloride concentrations. The constituents were found to be relatively constant with depth within the monitoring wells, despite large variations observed with depth in the discrete samplers. Parameter homogenization in the wellbores can be explained by vertical flow conditions, as revealed by hydraulic head measurements in the multilevel samplers. The results suggest that sampling conventional shallow monitoring wells with active or passive samplers at different depths within a well screen will not provide an accurate indication of how constituents may vary in the adjacent formation with depth.
Arsenic (As) contamination in wells is common throughout the northeastern United States. It is well documented that lead‐arsenate (PbHAsO4) pesticides were widely used on fruit tree orchards from the 1890s to 1950s. This study evaluates the potential for As contamination of groundwater from former orchards in Connecticut, where there were over 47,000 orchards in 1935. A proximity analysis involving 189 orchards and 114 domestic wells was conducted to assess the spatial relationship between historic orchards and As in wells. Field studies were then conducted to characterize As and lead (Pb) distributions in soils and wells near historic orchards. The proximity analysis found that the wells with no detected As were further away from historic orchards and had fewer historic orchards within their vicinity when compared with wells that contained As. The field investigations found that elevated levels of As and Pb were widespread in soils from orchards established by 1951, with some As concentrations exceeding 200 ppm. In some soils, As and Pb were leachable at concentrations exceeding USEPA drinking water standards in synthetic precipitation laboratory tests. It was also found that the wells nearest to the impacted soils tended to contain the highest As concentrations, while the wells located in areas that were forested prior to 1970 contained no As. Overall, this study found that As and Pb from legacy pesticide residues are still abundant in former orchard soils and that a strong spatial relationship exists between As‐contaminated wells and historic orchards. Greater consideration should be given to historic orchard soils as a potential contributing nonpoint source of As to the groundwater in Connecticut, where domestic well contamination rates are high.
In rural areas of New England groundwater from fractured crystalline and sedimentary bedrock is a critical water resource. Increasingly, studies have shown that development occurring in rural areas is resulting in the impairment of water quality in fractured rock aquifers. The objective of this study was to evaluate the spatial and temporal variations in groundwater quality associated with development and evaluate the extent to which common groundwater contaminants associated with rural development may be naturally buffered. The study entailed a compilation and synthesis of over 2500 reports on domestic water quality that spanned a 30 year period. Focus was placed on the spatial distribution and temporal variations in sodium, chloride, iron, manganese, nitrate, and nitrite. Results indicate that despite significant levels of development, the amount of contamination to the bedrock has been minimal. Of the constituents examined, only the chloride concentration exhibits a systematic increase over time, but the level of chloride remained relatively low. The flux of chloride to the bedrock from deicing appears minimal despite the significant amounts of road salt used in the study area. Sodium concentrations in the bedrock remained relatively constant and appear to be buffered by ion exchange with calcium as suggested by the increase in hardness with time. Iron and manganese were present at relatively low levels but did not show any systematic trends over time. Nitrate and nitrite concentrations were very low and found to be inversely correlated with manganese and iron concentrations. This suggests that the presence of iron and manganese contribute to denitrification. This study indicated that both geochemical and biogeochemical processes are active buffering mechanisms that help shield the bedrock from contaminants associated with development.
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