Heavy Metal Contamination in Urban Soils of Newark, New Jersey.

Urban farming is a growing trend aiding in reclamation of abandoned spaces to develop green zones, and acting as an additional source of locally grown, fresh produce. Post-industrial urban landscapes are however far from pristine, having been subject to historical and continuing anthropogenic stresses. Newark, New Jersey, has a legacy of contamination, being an important industrial center close to major cities, and the presence of a major seaport and airport. Newark has over 30 community gardens spread out over five wards. This study investigates the extent of contamination in community gardens in Newark, and studies the association of lead (Pb) in various mineral fractions of the soil. A secondary objective of this study is to investigate the feasibility of using struvite (MgNH₄PO₄·6H₂O), a wastewater recovered phosphate mineral, as an amendment to immobilize Pb from the mobile soil fractions. Soil samples were collected from three community gardens in Newark. Total metal concentrations after acid extraction and analysis of extractant using Inductively Coupled Plasma-Optical Emission Spectrometer (ICP-OES) reveal that Pb is present in the majority of samples in the range of ppm 72-830 ppm, with a few samples exceeding the NJDEP guidance value of 400 ppm. Trace concentrations of other heavy metals such as zinc (Zn), copper (Cu), and nickel (Ni) are also detected. The possible sources of Pb in Newark’s soils include emission from industrial and vehicular sources; Pb based paints, and old pipes. The distribution of Pb in exchangeable, acid-soluble, reducible and oxidizable soil fractions of the soil is determined using the Tessier extraction method. Concentrations range from 1-948 ppm in exchangeable and acid soluble fractions, and 20-2240 ppm in reducible and oxidizable fractions. Laboratory scale experiments demonstrate that struvite has a potential to be used as an amendment to immobilize Pb and the reuse of wastewater resource makes this material sustainable.