Modeling spatial patterns in soil arsenic to estimate natural baseline concentrations

Area of Science:

• Environmental Science
• Geochemistry
• Public Health

Background:

• Arsenic in soil poses a public health risk.
• Regulatory standards should consider natural background concentrations to avoid excessive remediation.
• Understanding arsenic distribution is crucial for accurate risk assessment.

Purpose of the Study:

• To assess the spatial distribution of arsenic (As) in Ohio soils and stream sediments.
• To compare measured As concentrations with existing regulatory screening levels.
• To evaluate the utility of current soil screening levels based on natural background data.

Main Methods:

• Utilized soil and stream sediment samples from the USGS National Geochemical Survey.
• Analyzed total As using sodium peroxide fusion and hydride-generation atomic absorption spectrometry.
• Employed sequential Gaussian simulation to map As concentration and uncertainty.

Main Results:

• Arsenic concentrations in Ohio ranged from 2.0 to 45.6 mg/kg.
• Elevated As concentrations (>10 mg/kg) were common, particularly in central and west-central Ohio.
• Measured As levels frequently exceeded the generic soil screening level of 0.39 mg/kg.

Conclusions:

• Natural background arsenic concentrations in Ohio often surpass established screening levels.
• Current regulatory standards may not adequately reflect natural conditions, potentially leading to unnecessary remediation.
• Risk assessments should incorporate baseline concentration data for more practical environmental management.