Soil contamination in community gardens of Philadelphia and Pittsburgh, Pennsylvania

Abstract

Community gardens have been seen sprouting up in and around urban settings such as Philadelphia and Pittsburgh over the past several decades. Due to the long histories of industrial activities and urbanization, these soils in urban regions may be at a high risk for various contaminants such as metals and metalloids. Using inductively coupled plasma mass spectrometry (ICP-MS), we measured 7 elements (lead (Pb), zinc (Zn), copper (Cu), vanadium (V), cadmium (Cd), nickel (Ni), and arsenic (As)) in soil samples collected from a total of 21 community gardens in Philadelphia City, Philadelphia suburban areas, and Pittsburgh City during September and October 2021. We found that the city areas in Philadelphia and Pittsburgh had higher elemental concentrations in community garden soils compared to the suburbs. We found that all elements except vanadium were below the Pennsylvania Department of Environmental Protection (PADEP) guidelines. When compared to more stringent Canadian Council of Ministers of the Environment (CCME) guidelines of a maximum of 140 mg/kg of lead in the soil, 36% percent of Philadelphia community gardens, 60% of Pittsburgh gardens, and 20% of the Philadelphia suburb gardens exceeded the CCME guideline. In Philadelphia city, generally, elemental concentrations exhibited a negative trend with increasing distance to historical smelter locations, although a significant correlation was observed for only zinc. We found that the soil from the raised beds had lower concentrations of lead and arsenic, but many of the samples from the raised beds had higher concentrations of zinc, copper, vanadium, and nickel. This discrepancy in raised beds is most likely attributed to these elements being actively deposited in the soil from present day sources such as vehicles on the road and active industrial sites. Understanding and recognizing such variations of these contaminants in community gardens are essential to understanding how industrial legacies and modern pollution continue to put urban communities at a disproportionate risk of health impacts.

Keywords: Community garden; Heavy metals; Lead exceedances; Raised bed; Smelter.