Study on the identification of arsenic exposure areas by 10% sampling method

Objective of this work is to study the representation of 10% sampling method in identifying the areas with high arsenic concentration. Water arsenic concentration was high due to arsenicosis in all the pump wells in 31 villages from Shanxi and Inner Mongolia regions. The actual exposed high arsenic rate (Q) was calculated. All the wells of the village were marked on the village map, and then each village was divided into 5 parts (east, south, west, north and the center). 10% of the wells were sampled randomly from each of the five parts of the village, which has got more than 50 wells. For the villages with less than 50 wells, one well was sampled randomly from each of the five parts. All the wells were selected from the village which has got less than 5 wells. 10% sample exposed high arsenic rate (R) was calculated. The relationship between Q and R was analyzed. Given the exposed high arsenic rate is not less than 5% there is no significant difference between R and Q. On the contrary, if the actual exposed high arsenic rate was below 5%, R could not represent Q. The 10% sampling method can be perfectly used for detecting high arsenic areas when the actual rate exposed to high arsenic wells is below 5%.