Surface soils in the CAFO zone showed higher levels of arsenic
compared to the agricultural soils in the Pearl River Delta.
Correlation matrix, CA, and PCA results indicate that the sources
of the soil arsenic were significantly different between the CAFO
zone and the agricultural lands in the Pearl River Delta. These
observations, together with the correlation between soil arsenic
and TOC contents in the surface soils of the CAFO zone, suggest
that organoarsenic feed additives in the animal wastes are an
important source of arsenic pollution in the CAFO zone. Analysis
of the arsenic species showed the presence of ASA at significant
levels in the environmental matrices of the CAFO zone, while
ROX was absent. Degradation of ASA in the surface soils was also
observed between the two sampling campaigns (about 3 months).
Even though the potential ecological risk posed by arsenic in the
surface soils of the CAFO zone was relatively low, continuous discharges
of arsenic-bearing animal wastes from CAFOs might elevate
the arsenic risk. The findings of this study shows that soil
arsenic pollution caused by the extensive use of organoarsenic feed
additives in areas concentrated with swine CAFOs is worthy of significant
attention.