Chemical extraction methods to assess bioavailable arsenic in soil and solid media

Area of Science:

• Environmental Chemistry
• Toxicology
• Soil Science

Background:

• Soil ingestion is a key exposure route for children to arsenic-contaminated soils, posing public health risks.
• Existing soil chemical extraction methods' ability to quantify bioavailable arsenic from ingestion is not well-established.

Purpose of the Study:

• To compare arsenic extracted by five common soil chemical methods with in vivo bioavailable arsenic.
• To identify soil extraction methods that accurately estimate bioavailable arsenic for risk assessment.

Main Methods:

• Fifteen arsenic-contaminated soils (233–17,500 mg kg(-1)) were analyzed.
• Arsenic was extracted using water, sodium acetate, phosphate, hydroxylamine hydrochloride, and ammonium oxalate.
• Bioavailable arsenic was determined through in vivo dosing trials with immature swine (Sus scrofa).

Main Results:

• Ammonium oxalate and hydroxylamine hydrochloride extracted the highest percentages of total arsenic.
• Hydroxylamine hydrochloride showed the strongest correlation (r = 0.88) with in vivo bioavailable arsenic.
• The trend for extracted arsenic compared to bioavailable arsenic was: ammonium oxalate, hydroxylamine hydrochloride > in vivo > phosphate, acetate > water.

Conclusions:

• Soil extraction methods dissolving amorphous iron (Fe) and manganese (Mn) oxides, like hydroxylamine hydrochloride, provide better estimates of bioavailable arsenic.
• Hydroxylamine hydrochloride extraction is a promising method for assessing arsenic bioavailability in soils relevant to children's ingestion exposure.