Sources of Contaminants to Congaree National Park—USGS and National Park Service Working Together Completed

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The NPS manages many of our Nation's most highly valued aquatic systems, including Congaree National Park, South Carolina, which is the largest remaining contiguous tract of old-growth bottomland forest in the southeastern United States. This park consists almost entirely of flood-plain/aquatic environments and is located downstream from multiple urban and agricultural areas that are potential sources of contaminants.

The USGS and others have documented organic chemicals that we use in our everyday lives (for example, medicines, personal hygiene products, chemical additives, and pesticides) in streams throughout the Nation. Because of the likelihood of upstream and within park sources, it is important to understand the origins, concentrations, and persistence of contaminants at Congaree National Park to begin to define exposure of humans and other organisms in the park.

The USGS–NPS Water Quality Partnership Program (WQPP) supports research to address a broad range of policy and management needs related to high-priority water-quality issues in national parks. Since 1998, the WQPP has enabled the NPS to make informed management decisions based on USGS data analyses and interpretations.

Under the WQPP, the USGS assessed organic contaminants that may originate in Congaree National Park from visitation and waste-handling or may be transported by rivers and tributaries into the park from upstream sources. Scientists measured the concentrations of a range of organic contaminants in 72 samples collected from 16 locations throughout the park during 2013 to 2015 to assess exposure and potential sources of 199 and 81 targeted organic contaminants in water and sediment samples, respectively. The potential for biodegradation was also measured for eight radiolabeled model contaminants to understand the environmental persistence of contaminants, which is one driver of the timing and duration of organism exposure.

More than one-half of the water and sediment analytes measured in this study were not detected or potentially had natural sources. Many other distinctly anthropogenic (human-sourced) contaminants, including insect repellent, antibacterials, phosphate flame retardants, pesticides, plasticizers, alkyl-phenol detergent metabolites, and pharmaceuticals, were detected in water and sediment throughout Congaree National Park.

Results from this study indicate that transport of contaminants into the park from upstream sources. For example, pharmaceutical contaminants were detected (49 total) more frequently and at higher concentrations at Congaree and Wateree River sites that are downstream from major urban areas. Multiple lines of evidence, however, indicate that park visitation also is a possible source of contamination. The insect repellent N,N-diethyl-m-toluamide (DEET) was detected frequently, with the highest concentrations near locations in the park used by visitors, including areas that were not connected to streams at the time of sampling. Assessment of the biodegradation potentials of eight model contaminants in sediment indicated good potential for biodegradation of most chemicals under aerobic conditions. The biodegradation potential was poor for some contaminants, such as the antibiotic sulfamethoxazole (detected in 69 percent of the incoming stream samples), under the anaerobic conditions expected to dominate saturated flood-plain sediment.

NPS units encompass a wide range of ecosystems; external-development pressures; internal visitor pressures; and, by extension, risks for organic-contaminant exposure and potential adverse effects. Protected public lands such as national parks can play an important economic role for local communities. U.S. Secretary of the Interior Ryan Zinke announced that the 2016 record visitation of 331 million visitors at America's 417 NPS sites contributed \$34.9 billion to the U.S. economy in 2016—a \$2.9 billion increase from 2015.

The USGS promotes the Department of the Interior's stewardship of trust obligations by providing science support for the NPS. This study provides information about sources and exposures of commonly used contaminants as first steps to understand the health risks to humans and organisms nationwide.

The USGS's Environmental Health Program (Toxic Substances Hydrology and Contaminant Biology) and USGS-NPS WQPP supported this study.