The Impact of Vehicle Traffic on Water Quality in Acadia National Park

Waterlines article and report summary:

Since 2002, Mitchell Center researchers have made visits during peak and off-peak tourist season at Acadia National Park to take water samples from streams throughout the park. Their goal — to see if traffic at Acadia is affecting water quality in the park’s streams.

Over 3 million visitors visit Acadia each year. In August alone, over 60,000 vehicles pass through the Sand Beach Gate. Establishing the effect of traffic on water quality is the important first step in determining how vehicles are impacting ecosystems. The NPS has actively pursued a long-term monitoring program to document the impact of air pollution on park resources. Although the majority of air pollution occurring at Acadia is attributed to long range transport, the relative contribution of local mobile emissions has not been quantified. The ability to differentiate between the volumes of local in-park emission sources as compared to more distant sources will enhance the ability of park managers to more effectively remedy existing air pollution impacts. This research is the first to study if local traffic can have a measurable effect on water quality.

Vehicles release a variety of organic compounds (i.e. gasoline and oil) and metals from exhaust and tire wear that can end up in surface waters through atmospheric deposition and stormwater runoff. The initial objectives of the study were to establish baseline data on surface water quality for certain organic compounds and metals related to vehicle use, and to ascertain if these concentrations were associated with roads and traffic or if they could be attributed to other sources.

Samples were collected from streams across a gradient from high-use roads to remote regions. This helped discriminate between the effects of local pollutant sources (such as traffic) and longer-range transport and atmospheric deposition. Multiple sites on the same stream were also tested on a gradient away from a road. This provided information on dispersion of vehicular contaminants away from the road. Springs were also chosen to represent pristine surface water unaffected by atmospheric deposition of contaminants.

Three rounds of samples were collected at each location. The objective was to sample during periods of low and high park visitation to compare under similar hydrological conditions. Three seasons were identified: spring (low traffic volume), early mid-summer (high traffic volume), and fall (moderate to low traffic volume). Actual sample dates were: November 16, 2002; June 3, 2003; July 9, 2003; and October 6, 2004. Monthly traffic volume counts were provided by the National Park Service for the Sand Beach gate.

Summary of Results

Results of this study are preliminary and are under review by the National Park Service. Following is an overview of our conclusions; all results are for compounds dissolved in water.

Motor Fuels. No evidence of volatile organic compounds associated with motor fuels was detected at >1 μg/L (1 ppb).

Polynuclear Aromatic Hydrocarbons. No evidence of polynuclear aromatic hydrocarbons (PAH) associated with motor fuels and tires was detected at >1 μg/L (1 ppb).

Metals. Metals associated with vehicles were found in nearly all samples and at all sample dates. Aluminum and zinc were detected in the μg/L (ppb) range, other metals (copper, molybdenum, arsenic, vanadium, lead, nickel, chromium, palladium, cadmium, ruthenium, rhenium, and platinum) were detected in the ng/L (ppt) range.

A surprising discovery was that springs had very elevated metal concentrations. One spring was found to be consistently high in molybdenum. Other locations also exhibited repeated high metal concentrations. A statistical analysis of these results are suggestive of an association with roadways and vehicle traffic. A majority of streams showed an increase in metal content downstream. Several of the downstream sample points were near or below roadways with an increased likelihood of roads and traffic to increase metals in streams.

The hypothesis that nearness to roads and higher traffic counts increase metals in streams was tested using four variables: traffic counts, distance from sample point to paved road, elevation of the sample point, and hydrological flow (stream stage). The combined statistical analyses consistently identified six metals that exhibit significant relationships with traffic, distance from roads, sample point elevation, or flow: aluminum, arsenic, cadmium, molybdenum, palladium, and zinc. Arsenic and molybdenum appear to be the most likely metals related to traffic with effects on surface water quality. Each of these metals may be found in vehicles, exhaust systems, and associated fuels or lubricants.

Full details of the project results will be published shortly. Please contact John Peckenham at 207/581-3254 for additional information

Abstract:
Acadia National Park receives over 3 million visitors per year. The impact of these vehicles on water quality is neither known nor are there any baseline environmental quality data that focus on specific emissions. Vehicles release a variety of organic compounds (MTBE, PAHs, gasoline) and metals from exhaust and tire wear that can end up in surface waters through atmospheric deposition and stormwater runoff. If vehicles are an important source of emissions then there should be a concentration gradient away from, and upslope from, major roadways. This investigation will assess the gradient between high-traffic areas and remote locations, using in part the gauged PRIMENet watershed streams. The use of these watersheds will provide cost effective supplemental data to assist in interpreting the results of this research. Samples will be collected from springs (background values least affected by atmospheric deposition), streams parallel and downhill from the Park Loop Road (highly vulnerable), and more remote streams. Streams near roads will be sampled above and below the roads. The management goal of this project is to determine if water quality issues should be included in the vehicle management plan for the Park. The results will be relevant to the future planning for the Island Explorer public transportation system.