Method Comparison for Bioaccessible Lead and Arsenic in Soils

Metals and Metals Speciation Analysis in Environmental Samples
Oral Presentation

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Contamination from trace metals, such as lead (Pb), in soils can lead to potential health risks from ingestion of the soil or vegetables grown in the soil. Typical risk assessment models apply an assumed bioavailability percentage ranging from 60 - 100% of contaminant metals in a soil sample. These assumptions can result in incorrect health risk assessments or unnecessarily high remediation costs, because actual bioavailability can range from 0 - 100%. Currently, in vivo animal studies are often used to determine bioavailability, which are expensive and time consuming. In vivo methods are giving way to new in vitro methods, such as EPA Method 1340 “In Vitro Bioaccessibility Assay for Lead in Soil”. A recently published method for arsenic (As) bioaccessibility, the California Arsenic Bioaccessibility (CAB) Method, was developed to improve the accuracy of risk assessments and assist regulators in making responsible remediation decisions while still protecting human health.

For this study, bioaccessible Pb and As concentrations in soil samples were determined using both EPA 1340 and the CAB Method with sample analysis by triple quadrupole ICP-MS. Pb and As were quantified in both extractions to evaluate if a streamlined method could be developed and applied to both elements. In order to evaluate if there was a correlation between the bioaccessible metals concentrations and specific As compounds, direct quantification of different molecular forms of the metal (e.g., arsenite, arsenate, etc.) were performed on the soil samples.

Both EPA 1340 and the CAB Method generate digestates with complex matrices and high total dissolved solids. Analysis of these types of samples by ICP-MS provides unique challenges. Some challenges can be mitigated by recent instrumental advances, such as reaction cells and triple quadrupole instruments, however some require further instrumental adjustments.