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)