Sampling groundwater from microwells in a Cape Cod pond during a tracer experiment. USGS.
New England's aquifers supply people and ecosystems, but in places geologic and human sources have contaminated them. The U.S. Geological Survey, working with Federal, State and local agencies, has led studies of where contaminants occur in the region's bedrock and sand-and-gravel aquifers, how vulnerable groundwater is, and how contaminants move and break down.
Science still needed
- where arsenic, lead, radon and uranium from rock occur and what mobilizes them;
- how land use — farms, industry, homes, roads, waste disposal — relates to contamination;
- new field, lab and modeling methods;
- where health risks lie in relation to contaminant sources.
Contaminants from rock
Reactions between groundwater and aquifer minerals can release arsenic, lead, radon and uranium. Arsenic has been mapped across most of New England; uranium is only beginning to be studied.
| Study | Finding |
|---|---|
| New Hampshire bedrock aquifers (2011 model) | about 39 percent of bedrock groundwater has at least a 50-percent chance of arsenic ≥1 μg/L; 7 percent, of ≥5 μg/L; about 5 percent, of ≥10 μg/L — predicted by geology, geochemistry, land use, hydrology, topography and demographics (report) |
| East-central Massachusetts private wells | of 478 random wells sampled by owners, 13 percent exceeded the public-water standard for arsenic and 3.5 percent for uranium, which rarely occurred together; an estimated 5,700 and 3,300 wells in the area exceed the standards (report) |
| Maine private wells (2005–2009 lab data, owners' privacy protected) | of 174 towns with 20 or more wells tested, 44 had more than 25 percent of wells over the 10 μg/L arsenic standard; in 19 towns, more than 10 percent exceeded 50 μg/L; in 45, at least 1 percent exceeded 100 μg/L — tied to bedrock geology (report) |
A core from the fractured bedrock aquifer beneath Great Bay National Wildlife Refuge, New Hampshire. USGS.
Land use and waste sites
As nationally, chloride, nitrate and other constituents are trending upward in New England groundwater, threatening ecosystems and drinking water. Suspected sources include roads and deicers, wastewater and septic systems, livestock and fertilizer, landfills, and hazardous waste sites.
- Cape Cod nitrogen: treated wastewater spread on land created a plume moving toward the coast. Sampling in 1994 and 2007 mapped it after disposal stopped in 1995; its nitrogen loads were ≤11 percent of the watersheds' nonpoint-source loads (report).
- A Connecticut supply well (Woodbury): most samples showed road salt or septic influence; most water reaching the well was young (under 7 years); the highest nitrate came from wells below septic drain fields (report).
- A New Hampshire Superfund site (Savage Municipal Well, Milford): a plume mostly of the solvent PCE, above 100,000 parts per billion in 1995, was contained with a barrier wall and extraction wells. From 1998 to 2004, PCE outside the wall fell by an average of 80 percent at most wells (report).
- MTBE in Maine (North Windham, July 1998–May 1999): the gasoline additive, which gives water a bad taste and smell, was in 35 percent of wells (64 percent in the aquifer's high-yield part), more in urban and residential areas. After Maine restricted it, median air levels fell from 0.25 to 0.09 ppbv; precipitation couldn't explain the aquifer's MTBE (report).
Installing a multilevel sampler on Cape Cod to track nitrogen from homes to a coastal bay. USGS.
New methods and tools
USGS labs analyze trace elements, organic compounds, isotopes, age tracers, microbes and emerging contaminants such as pharmaceuticals; new geophysical methods map plumes and bedrock beneath thick sediments.
- Septic micropollutants: next to a large septic system serving an elder care facility, pharmaceuticals, personal-care and plasticizer compounds ranged from 1 to >20 μg/L below and downgradient of the leach beds; high TBEP plasticizer levels may reflect cleaning products (paper).
- Road salt near I–93: chloride above New Hampshire's 230 mg/L standard has been measured near Interstate 93. In fall 2006, electromagnetic surveys found where salty groundwater (up to 350 mS/m) was entering Policy Brook in Salem; seven streambed piezometers confirmed it (specific conductance up to 2,630) (paper).
- Bedrock beneath Cape Cod: western Cape Cod, home to one of New England's largest contamination sites, tested the HVSR seismic-noise method — 164 sites calibrated against 559 borings — to map the bedrock surface, revealing glacially carved detail (map).
Installing continuous water-level and water-quality monitoring in a New Hampshire bedrock well. USGS.
Drinking water and health
Private wells aren't regulated under Federal law or by most States.
- Nationally, about 23 percent of 1,389 domestic wells had at least one contaminant above a drinking-water standard or USGS health-based screening level; New England's crystalline-bedrock wells had elevated arsenic, fluoride, radon and uranium (report).
- Bladder cancer: a study of cancer deaths among white men and women in 1985–1999 found a significant correlation with private well use in 1970, after adjusting for population density — in New England (r = 0.42 men, 0.48 women) and in New York and New Jersey (0.49 and 0.62) — suggesting private well water, or something closely tied to it, may help explain excess bladder cancer (paper).
Sources
Based on Groundwater Contaminant Science Activities of the U.S. Geological Survey in New England, USGS Fact Sheet 2016–3010, New England Water Science Center, U.S. Geological Survey (DOI); a work of the United States government in the public domain. The photographs come from the fact sheet's PDF.
Licence: CC0 1.0 (public domain) · Adapted from pubs.usgs.gov
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