Five surface water samples

32 soil samples and 14 groundwater samples have been taken from the representative area of the Pearl River Delta

in order to understand arsenic origin and distribution in water and soil of this area. The results show that surface water in this area has suffered arsenic pollution. Total arsenic content of topsoil (0-10cm) is from 19.8 to 27.4 mg/kg

with an average value of 23.7 mg/kg. The most of arsenic content in topsoil is residual fraction. The sequence of arsenic average content of seven forms in topsoil is residual fraction＞weak organic fraction＞oxide fraction＞carbonate fraction＞strong organic fraction＞water soluble fraction＞ion exchange fraction. Total arsenic content of subsoil (30-40cm) is from 11.5mg/kg to 28.1 mg/kg

with an average value of 21.2 mg/kg. The most of arsenic content in subsoil also is residual fraction. The sequence of arsenic average contents of seven forms in subsoil is residual fraction＞weak organic fraction＞oxide fraction＞carbonate fraction＞strong organic fraction＞ion exchange fraction＞water soluble fraction. Average contents of all arsenic forms are higher in topsoil than in subsoil. In unsaturated zone

total arsenic content decreaseds firstly and then increases with the depth. The contents of water soluble fraction

ion exchange fraction and carbonate fraction decrease gradually with the depth. The contents of weak organic fraction

oxide fraction

strong organic fraction and residual fraction do not show regular variation with the depth.The arsenic content of groundwater is from 00028 to 0.021mg/L

with an average value of 0.0114mg/L. The arsenic content exceeds 42.9% compared with the Chinese drinking water quality standards(0.01mg/L). Industrial wastewater infiltration and original arsenic released from aquifer medium are the main origin of arsenic in groundwater.