摘要：Farmed urban soils often bear legacies of historic contamination from anthropogenic and
industrial sources. Soils from seven community farms in Newark, New Jersey (NJ), USA, were analyzed to determine the concentration and speciation of lead (Pb) depending on garden location and
cultivation status. Samples were evaluated using single-step 1 M nitric acid (HNO3
) and Tessier
sequential extractions in combination with X-ray absorption fine structure spectroscopy (XAFS)
analysis. Single-step extractable Pb concentration ranged from 22 to 830 mg kg−1
, with 21% of
samples reporting concentrations of Pb > 400 mg kg−1
, which is the NJ Department of Environmental
Protection (NJDEP) limit for residential soils. Sequential extractions indicated lowest Pb concentrations in the exchangeable fraction (0–211 mg kg−1
), with highest concentrations (0–3002 mg kg−1
)
in the oxidizable and reducible fractions. For samples with Pb > 400 mg kg−1
, Pb distribution was
mostly uniform in particle size fractions of <0.125–1 mm, with slightly higher Pb concentrations
in the <0.125 mm fraction. XAFS analysis confirmed that Pb was predominantly associated with
pyromorphite, iron–manganese oxides and organic matter. Overall results showed that lowest
concentrations of Pb are detected in raised beds, whereas uncultivated native soil and parking lot
samples had highest values of Pb. As most of the Pb is associated with reducible and oxidizable
soil fractions, there is a lower risk of mobility and bioavailability. However, Pb exposure through
ingestion and inhalation pathways is still of concern when directly handling the soil. With increasing
interest in urban farming in cities across the USA, this study highlights the need for awareness of soil
contaminants and the utility of coupled macroscopic and molecular-scale geochemical techniques to
understand the distribution and speciation of soil Pb.
关键词：community farms; urban soil; Pb contamination; metal sorption; spectroscopy; XAFS; Newark; NJ community farms ; urban soil ; Pb contamination ; metal sorption ; spectroscopy ; XAFS ; Newark; NJ
