SOURCES AND CHARACTERISTICS OF LEAD AND LEAD-ISOTOPE COMPOSITIONS IN URBAN SOILS OF JERSEY CITY, NEW JERSEY

Adverse interactions between humans and their surroundings are inevitable, especially in urban settings. Urban soil, a primary receptor of chemical contaminants, is a critical indicator of surface environmental quality. Source partitioning is a crucial element in the formulation and implementation of long-term strategies and environmental policies for reducing chemical contamination. This is particularly valid in areas where there have been extensive historical and contemporary anthropogenic activities, such as Jersey City, NJ. One of the most common techniques for deciphering the potential sources of chemical contaminants in urban soils is based on their Pb-isotope ratios.

In our previous studies, urban soils around a 5 km radius of New Jersey City University, where there were at least 10 known smelters, metal works and foundries, were analyzed for their heavy metal content (As, Cu, Cr, Pb, Zn, Fe and Mn) both in the coarse- (< 2 mm and > 63µm) and fine-size (< 63µm) fractions. Pb-isotope compositions of selected fine-sized soil samples revealed a relatively narrow range of variations and fall within the modern environmental range of ^206/207Pb (1.185-1.215). In this study, heavy metals and Pb-isotope compositions of the background soil samples (Boonton Series) from a soil profile representing O, A and E horizons are compared with those of the urban soils. In addition, Pb-isotope compositions of selected urban soils in the fine-sized fraction are compared with those of the corresponding coarse-sized fractions. Although heavy metals are primarily accumulated in the fine-sized fraction, Pb-isotope compositions of the urban soils in both size fractions are similar. The background sample from the E-horizon has significantly more radiogenic Pb-isotope composition compared to those of the urban top soils. The overall trend of the Pb-isotope ratios suggests potential mixing of geogenic (background soil) and anthropogenic sources including historical Pb-ore based industrial activities, coal burning practices, as well as past vehicular emission (i.e., re-suspended leaded gasoline). Compared to the published ^206/208Pb ratios of USA coals, ^206/207Pb compositions of urban soils in Jersey City are within the range of the isotope ratios reported for Pennsylvania coal deposits.