A Field Procedure To Screen Soil for Hazardous Lead

Abstract

Soils retain lead contamination from possible sources such as mining, smelting, battery recycling, waste incineration, leaded gasoline, and crumbling paint. Such contamination is often concentrated in toxic hot spots that need to be identified locally. To address this need, a simple field procedure was designed to screen soil for hazardous Pb for use by the general public. The procedure is a modification of the in vitro soil Pb extraction described by Drexler and Brattin (Hum. Ecol. Risk Assess.2007, 13, 383) and EPA Method 1340, and uses a 0.4 M glycine solution at pH 1.5. A higher soil-to-solution ratio of 1:10 allows for classifying soil samples based on extractable Pb concentrations of <200 mg/kg (low), 200–400 mg/kg (medium), and >400 mg/kg (high) using sodium rhodizonate as a color indicator. The 1:10 soil-to-solution ratio also makes it possible to measure Pb concentrations in the glycine extract solutions on a continuous scale using a portable X-ray fluorescence analyzer. The procedure rather consistently extracts about one-third of the Pb extracted by the standard method across a wide range of Pb concentrations. Manufacturing the kit in larger quantities could reduce the cost of the materials well below the current $5/test.

Does Involving Parents in Soil Sampling Identify Causes of Child Exposure to Lead? A Case Study of Community Engagement in Mining‐Impacted Towns in Peru

“…Recent work has shown that XRF analysis of Pb in liquid extracts highly correlates with analysis by inductively coupled plasma mass spectrometer (ICP-MS; Landes et al, 2019), which was also seen for samples analyzed in the present study ( Figure S1 in the supporting information). Concentrations of Pb in water samples were analyzed in the laboratory by high-resolution ICP-MS (Thermo Scientific Element II); all fieldprocedure extracts were also analyzed by ICP-MS for confirmation.…”

“…The main difference of the field procedure used in this study relative to the later version described in Landes et al (2019) is that a test strip impregnated with sodium rhodizonate was inserted directly into the unfiltered solution after the extraction time of 1 hr instead of adding a gelatin capsule of sodium rhodizonate to the filtered extract (Landes et al, 2019). The procedure was later modified because we noticed that the Plumbtesmo® rhodizonate strips degraded with temperature and sunlight.…”

“…Bioaccessibility of Pb depends on its chemical form, size fraction, and the soil matrix (Casteel et al, 2006;Ruby et al, 1999). Lead from mining sources is often less bioaccessible than Pb from leaded-gasoline, smelters, or urban areas (Appleton et al, 2013;Casteel et al, 2006;Landes et al, 2019;Ruby et al, 1999). The lead contamination in Corcona is likely from the nearby mine and probably less extractable for that reason.…”

“…After collecting the soil samples, parents met with a researcher to analyze the samples using an earlier version of the field procedure for hazardous Pb described by Landes et al (2019). This method is based on the 0.4 M glycine extraction (pH = 1.5) of Drexler and Brattin (Drexler & Brattin, 2007) and the U.S. EPA's standard bioavailability method for Pb (U.S. EPA, 2017).…”

“…On average the field procedure extracted 38% ± 29% (±1 SD, n = 89) of the total soil Pb, after accounting for a soil-to-solution ratio of 1:10, and this proportion can be used to estimate the amount of Pb that would be released in the gastrointestinal system (Landes et al, 2019). Less Pb was extracted from samples in Corcona, 31% ± 20% (n = 49), than in Tornamesa, 45% ± 38% (n = 31), and in the car wash locations, 52% ± 11% (n = 9; p < 0.05) ( Figure 6).…”