Field Evaluations on Soil Plant Transfer of Lead from an Urban Garden Soil

Abstract

Lead (Pb) is one of the most common contaminants in urban soils. Gardening in contaminated soils can result in Pb transfer from soil to humans through vegetable consumption and unintentional direct soil ingestion. A field experiment was conducted in 2009 and 2010 in a community urban garden with a soil total Pb concentration of 60 to 300 mg kg−1. The objectives of this study were to evaluate soil–plant transfer of Pb, the effects of incorporation of a leaf compost as a means of reducing Pb concentrations in vegetables and the bioaccessibility of soil Pb, and the effects of vegetable cleaning techniques on the Pb concentrations in the edible portions of vegetables. The amount of compost added was 28 kg m−2. The tested plants were Swiss chard, tomato, sweet potato, and carrots. The vegetable cleaning techniques were kitchen cleaning, laboratory cleaning, and peeling. Compost addition diluted soil total Pb concentration by 29 to 52%. Lead concentrations of the edible portions of vegetables, except carrot, were below the maximum allowable limits of Pb established by the Food and Agriculture Organization and the World Health Organization. Swiss chard and tomatoes subjected to kitchen cleaning had higher Pb concentrations than laboratory‐cleaned plants. Cleaning methods did not affect Pb concentrations in carrots. Bioaccessible Pb in the compost‐added soils was 20 to 30% less than that of the no‐compost soils; compost addition reduced the potential of transferring soil Pb to humans via vegetable consumption and direct soil ingestion. Thorough cleaning of vegetables further reduced the potential of transferring soil Pb to humans.

A Gardener's Influence on Urban Soil Quality

“…Although the use of Pb is strongly restricted today, it still represents a serious risk for human health due to its high persistence in soils (Filippelli and Laidlaw, 2010). Total Pb concentrations in urban gardens worldwide vary widely (e.g., from 60 to > 2,500 mg kg −1 ; Cheng et al, 2011;Attanayake et al, 2014), this is also confirmed in this study, whereby the concentrations ranged between 18.5 and 1,076 mg kg −1 . Nonetheless, the mean value of Pb was relatively low compared to other cities (Table 4).…”

Urban home gardens in the Global North: A mixed methods study of ethnic and migrant home gardens in Chicago, IL

“…Research suggests that the uptake of soil lead by vegetable crops may be weak 23,24 . Inhalation or consumption of contaminated soil particles, though, represents another exposure pathway.…”

Bioavailability-Based In Situ Remediation To Meet Future Lead (Pb) Standards in Urban Soils and Gardens

“…21 Studies suggest that repeated addition of organic matter in large quantities dilutes total Pb concentrations in soils and would therefore be beneficial. [55][56][57]59 However, questions remain about long-term effectiveness as the organic amendments decompose over time. Nanomaterials such as nanoscale zero-valent iron 60, 61 and nanoparticulate apatite [62][63][64] have been used for in situ remediation of many contaminants, but the usefulness for Pb in soil is highly unlikely due to relatively high cost considering the sheer volume of urban soil that has to be treated.…”

“…growing,19,55,[119][120][121][122][123][124] relatively little is known about bioavailability and in situ treatment effectiveness in urban soils at levels that may be relevant for the new BLL values.…”