Fig. 2b shows the levels of arsenic pollution for the agricultural
soils in the CAFO zone and the Pearl River Delta. Based on the classification
criteria in the Environmental Quality Standard for Soils in
China (SEPA, 1995), the fraction of polluted (i.e., Class II, Class III,
and Heavily polluted) soils accounted for 50.0% (n = 72) of the agricultural
soil samples in the CAFO zone. In contrast, 35.4% (n = 65)
of the agricultural soils in the Pearl River Delta were polluted by
arsenic, which is comparable to that of all types of soils (34.8%,
n = 227) in the region. These results indicate that arsenic pollution
of agricultural soils was more prevalent in the CAFO zone compared
to the other soils in the Pearl River Delta.