More than fifty percent of the population in the United States relies on groundwater as the sole source of potable water. Groundwater in Suffolk County, NY, the study area, provides all potable water to the residents. Regrettably, urban contamination is increasingly threatening groundwater supplies. Two common inorganic contaminates in urban settings are nitrate (NO3) and perchlorate (ClO4). The U.S. Environmental Protection Agency national drinking water standard is 10 mg/L for N-NO3. No national drinking water standard has been set for ClO4 but many states have set advisory levels. The contaminant planning level in New York State is 5 μg/L and the maximum allowable level is 18 μg/L.
Nitrate and perchlorate are common co-contaminants in urban settings. Both ions are mobile in groundwater, moving quickly from the source of contamination. The goal of this research is to identify likely sources of these ions in urban areas. Once identified, hopefully contamination can be reduced at the source. Urban sources are identified as residential sewage, road runoff from highways, and organic fertilizer applied to urban lawns. The lawns are dominantly turfgrass and were sampled for soil water affected by turfgrass fertilizer, lawn clippings, soil cores, and bulk precipitation. In addition to N-NO 3 and ClO4, the sources were analyzed for ion concentrations of Ca, Na, K, Mg, Cl, SO4, PO4, Br, I, B, Sr, and N-NH 4.
Perchlorate concentrations of bulk precipitation are between 0.2 to 3 μg/L, with the highest concentrations influenced by atmospheric fallout from firework displays. The ion content of bulk precipitation is predominantly influenced by sea spray with minor components (<16%) of anthropogenic contamination and terrestrial dust. The average soil water concentrations of perchlorate, collected at 100 cm, beneath lawns treated with organic fertilizer is 90 μg/L which is 45 times higher than concentrations beneath lawns treated with chemical fertilizer or lawns that were not fertilized. However, nitrate concentrations of soil water beneath the lawns treated with chemical fertilizers are statistically higher than the lawns treated with organic fertilizer, with average values of 9.7 mg/L and 6.5 mg/L respectively.
Perchlorate concentrations in sewage range from below detection (0.1 μg/L) to 260 μg/L, with an average concentration of 2.2 μg/L. Perchlorate from sewage will likely raise the concentration in the groundwater above natural levels and depending on the density of septic systems and the amount of perchlorate reduction by bacteria, the groundwater concentrations may increase to near or above the NY State advisory level of 5 μg/L. Road runoff collected in catch basins and recharge basins have, on average, 3 μg/L ClO4 and 2 mg/L Total Inorganic N (nitrate and ammonium). In areas where road runoff directly recharges to groundwater, the concentrations from these areas are of concern for groundwater quality. While the average concentration, 3 μg/L, is below the NY state drinking water planning level, some samples are above this level at concentrations as high as 18 μg/L. As a result, we have to be concerned about the risk of concentrations of perchlorate in groundwater increasing to above the New York State planning level.
Perchlorate was found in nearly all samples analyzed in this study. Concentrations of some samples are a concern for groundwater quality. However, without a clear understanding of the health impacts of perchlorate ingestion it is difficult to clearly assess impacts to groundwater quality. What is clear is that perchlorate contamination is likely widespread and more research is needed in understanding nonpoint source pollution in addition to a clear understanding of health impacts.
|School:||State University of New York at Stony Brook|
|School Location:||United States -- New York|
|Source:||DAI-B 71/05, Dissertation Abstracts International|
|Subjects:||Hydrologic sciences, Water Resource Management, Geochemistry|
|Keywords:||Groundwater, Nitrate, Nonpoint sources, Perchlorate, Precipitation, Urban land use|
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