Effectiveness of aluminum and iron-based drinking water treatment residuals in remediating soil arsenic: Mechanisms and implication.

摘要

The phenomenon of urban sprawl around metropolitan areas has given rise to serious concerns regarding the risk of human contact with arsenic (As)-contaminated soils. The utilization of a drinking-water treatment residual (WTR) was proposed as a cost-effective technology for As remediation. WTR is a by-product of the drinking water purification process and contain sediment, organic matter, Al/Fe hydr (oxides), and activated carbon. WTRs are typically amorphous and have a high affinity for oxyanions due to high specific surface area. The ultimate goal of the present study was to evaluate the effectiveness of WTR (Al- and Fe-based) in lowering the human health risk from soil As exposure. We conducted: (a) short-term laboratory studies to evaluate the detailed As adsorption mechanism of WTR and WTR-amended soils, because only a fraction of soil As is available that is not retained or adsorbed; and (b) long-term (3 years) greenhouse studies to examine the effectiveness of WTR on geochemical speciation, in-vitro (simulated human gastrointestinal conditions), and in-vivo (animal study) As bioavailability in inorganic and organic As pesticide-amended soils. Results indicated that As adsorption by WTRs was a function of solution properties. Adsorption of As onto the Al-WTRs were stronger than onto Fe-WTRs. Arsenic bioaccessibility (in-vitro) significantly decreased by ∼60% in WTR-treated soils compared to WTR-unamended controls over a 3-year time period. In-vivo (relative bioavailability) results confirmed the trend observed in in-vitro tests. Results showed that WTR amendment has the potential to develop into an effective remediation technology for As-contaminated soils.