R8 AM Contamination Source Identification and Apportionment
Thursday, 17 November 2005: 8:00 AM - 11:40 AM in 331-332

(BAR-1117-816531) Arsenic in the Wallkill River and its tributaries, northwestern New Jersey.

Barringer, J¹, Bonin, J¹, ¹ United States Geological Survey, West Trenton, NJ, USA

ABSTRACT- Arsenic concentrations in water samples from the Wallkill River in mostly rural Sussex County, New Jersey, in 2004 ranged from 0.5 to 21 micrograms per liter, exceeding the New Jersey Surface Water Quality Standard of 0.017 micrograms per liter. The arsenic sources could be geologic, anthropogenic (pesticides, wastewater), and (or) a combination (mining wastes). The New Jersey Department of Environmental Protection needs to know the types and locations of those sources in order to develop a total maximum daily load for arsenic for the watershed. The river flows north through glacial deposits in a valley that follows faulted carbonate rocks—dolomite at the headwaters and at a far downstream segment, and the Franklin Marble, host to formerly mined zinc ores (and arsenic minerals), in the middle segment. Tributaries draining gneiss and granite highlands to the east and shale lowlands to the west contribute little arsenic to the river. Arsenic concentrations in filtered samples were highest in water emanating from man-made Lake Mohawk, at the river's headwaters, decreased downstream to the Franklin Marble outcrop, and then increased slightly. Zinc concentrations at and downstream from the marble outcrop increased to three to six times those farther upstream. Sediments at the outlet of Lake Mohawk contain high concentrations of leachable arsenic. Concentrations of boron, chloride, and sodium in the river water that exceeded background levels by about 20% accompanied the high arsenic levels there, indicating possible anthropogenic inputs (such as wastewater) to the river's headwaters. The high arsenic and zinc content of sediments at and downstream from the Franklin Marble outcrop, together with bed-sediment mineralogy, indicates that weathered materials and wastes from past mining activities likely contribute to arsenic concentrations in water from the middle river segment.

Key words: Arsenic, streamwater, bed sediments, zinc