THE IMPACT OF VEHICLE TRAFFIC
ON WATER QUALITY
IN
ACADIA NATIONAL PARK

Technical Report NPS/NER/NRTR—2006/035

John M. Peckenham¹, J. Steven Kahl², and Aria Amirbahman<sup>3

1,2</sup>Senator George J. Mitchell Center for Environmental and Watershed Research
³Department of Civil and Environmental Engineering
University of Maine
Orono, Maine 04469

² current address:
Center for the Environment
Plymouth State University
MSC 63, 17 High Street
Plymouth, New Hampshire 03264

March 2006

U.S. Department of the Interior
National Park Service
Northeast Region
Boston, Massachusetts

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Executive Summary

The objectives of this study were to establish baseline data on surface water quality for certain organic compounds and metals and to ascertain if background concentrations under ambient conditions can be related to roads and traffic. Samples were collected across a gradient from immediately below high-use roads to remote regions in the Park. This experiment design used differences between busy roads and remote sites to discriminate between the effect of local pollutant sources (based on presumed high concentration-gradients near roads) versus longer-range transport and atmospheric deposition that was expected to produce more uniform concentrations across the Park. The hypothesis that vehicular contaminants become more dispersed away from roadways was tested by sampling at multiple sites on the same stream on a gradient away from a road. Springs were chosen to represent a pristine chemistry of groundwater in equilibrium with bedrock and soil, absent any recent atmospheric
input.

Motor Fuels. No volatile organic compounds, which may be associated with motor fuels, were detected at >1 µg/L (1 ppb).
Polynuclear Aromatic Hydrocarbons. No polynuclear aromatic hydrocarbons (PAH), which may be associated with motor fuels and tires, were detected at >1 µg/L (1 ppb).

Metals. Metals which may be associated with vehicles were found in nearly all samples and on all sample dates. Aluminum and zinc were detected in the µg/L (ppb) range; the other metals were detected in the ng/L (ppt) range. In terms of the mean of detected concentrations, the rankings for metals in declining concentration are: aluminum, zinc, copper, molybdenum, arsenic, vanadium, lead, nickel, chromium, palladium, cadmium, ruthenium, rhenium, and platinum. In order to discriminate against one or two hot spots biasing the concentrations, the metals were ranked by frequency of occurrence. In order of decreasing frequency of detection, they are: aluminum=zinc, arsenic=copper=chromium=molybdenum=vanadium, palladium, cadmium, lead, nickel=rhenium=ruthenium, platinum. The concentration ranking and occurrence frequencies agree closely for all metals but lead. There does not seem to be a localized source of any one metal in the study area and the variations in metal concentrations observed are proportional in most samples.

A surprising discovery was that the springs had elevated metal concentrations. The Sieur de Monts Spring was found to be consistently high in molybdenum and Birch Spring had relatively high total metal concentrations. Several streams exhibited repeated high metal concentrations: Canon-Cadillac Brook (near the summit of Cadillac Mountain), Little Hunters Brook, Canon Brook, Kebo Brook, Hunters Brook, and Richardson Brook. A majority of streams had increasing metal content downstream and closer to roads. Several of the downstream sample points were near or below roadways with an increased likelihood of roads and traffic to increase metals in streams. This is suggestive of an association between water quality, roadways, and vehicle traffic.

The hypothesis that proximity to roads and higher traffic counts increased metals in streams was tested using four variables: traffic counts, distance from sample point to paved road, elevation of the sample point, and stream flow as referenced to USGS stream gauges and observations made during sample collection. The combined statistical analyses identified six metals that exhibited significant relationships with traffic, distance from roads, sample point elevation, or flow: aluminum, arsenic, cadmium, molybdenum, palladium, and zinc. Aluminum was identified statistically in this analysis, but is not considered an anthropogenic contaminant because of the large pool of aluminum in rocks and soils, and the mobilization of this aluminum is based on the relationship with pH of the water. The most commonly detected metals directly associated with traffic were arsenic and molybdenum. Another key finding was that enhanced metal concentrations occurred well away from roadways. This suggests that atmospheric transport of contaminants from vehicles is an important phenomenon controlling their distribution in surface waters in the Park.

The concentrations of the metals detected were low, mostly in the part-per-trillion range, and below existing known limits of ecological importance. An investigation of salt loading to surface waters from the ocean and winter road maintenance was not
part of this study.

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