Detection and Quantification of Oxygenated Polycyclic Aromatic Hydrocarbons (oxy-PAHs) in Groundwater Near the Former Manufactured Gas Plant in Bay Shore, N.Y.

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Introduction As a result of storage and disposal practices at a former Manufactured Gas Plant, or MGP, in Bay Shore, NY, a variety of polycyclic aromatic hydrocarbons (PAHs) have been detected at high concentrations in the surficial, upper glacial aquifer of Long Island. Levels of PAHs initially detected over 10 years ago were in the parts-per-thousand range within a groundwater contaminant plu...

Introduction

As a result of storage and disposal practices at a former Manufactured Gas Plant, or MGP, in Bay Shore, NY, a variety of polycyclic aromatic hydrocarbons (PAHs) have been detected at high concentrations in the surficial, upper glacial aquifer of Long Island. Levels of PAHs initially detected over 10 years ago were in the parts-per-thousand range within a groundwater contaminant plume. The plume extended over a half-mile from MGP-related sources to discharge at a local estuarine tributary, Lawrence Creek, resulting, resulting in malodorous hydrocarbon sheens in this tributary and nearby storm drains. These signs of contamination revealed a larger underlying problem and prompted calls by state and local government for extensive remediation. To date, most of the source-materials (known as NAPLs, or non-aqueous phase liquids) responsible for creosote leachates, such as PAHs, have been excavated. In addition, both chemical treatments (to promote chemical oxidation) and oxygen-gas injection (OGI) lines (to spur microbial growth) have been employed to breakdown breakdown the PAHs within the plume. One breakdown product of PAHs — oxy-PAHs— may originate in part from incomplete combustion during gasification operations at the MGP or weathering of the coal-tar by-product during storage. However, several studies near other MGPs have shown that biological degradation products of PAHs can also result in the formation, and in some cases accumulation, of oxy-PAHs in soils1. Little is known about the fate and transport of oxy-PAHs in shallow, coastal aquifers and in estuarine environments, although structurally, oxy-PAHs are more soluble (and potentially more mobile) than PAHs. A literature review of available toxicity data found that some oxy-PAHs may be harmful to aquatic ecosystems, and possibly even more toxic than their parent PAH compounds1,2. Currently, a local university collaborator has begun to study the effects of various concentrations of some oxy-PAHs (found during this project) on project) on fish larvae.fish larvae.
 

Approach

Recently, an analytical method was developed at the USGS National Water Quality Laboratory (NWQL) in Denver, Colo. for detecting the  oxy-PAHs. This method has been used by the NWQL to analyze samples collected by the Suffolk County Department of Health Services  (SCDHS) and USGS from the vicinity of the Bay Shore plume for 14  oxy-PAHs, with detection limits as low as 0.04 μg/L. Each of the oxy-PAHs in the analytical method has been successfully identified in at least one sample. Recent samples indicate concentrations (when detected) of  oxy-PAHs in the parts-per-trillion range in both groundwater and surface waters. The method is an extension of  the current NWQL PAH method  (which corresponds to the EPA  “priority list” of 16 PAHs of concern) and includes seven parent-daughter compound pairs whose ratios are being used to compare before and after OGI-line values. Screening for additional oxy-PAHs to add to the method is also being investigated.
 

Benefits

The USGS has been working closely with the SCDHS to document and better understand the fate and transport of these emerging contaminants as the PAH plume is remediated by the OGI system and other technologies. Proposed future work will continue monitoring of oxy-PAH levels in existing groundwater wells to assess the OGI system treatment of PAHs, as well as potential discharges into seabed pore waters and surface waters of the adjacent estuary.

Project
Location by County

Suffolk County, NY