Investigation and evaluation of the acidity and heavy metals pollution in the vegetable field in Lanzhou City

A survey was conducted to investigate the soil of 5 different vegetable field in Anning District of Lanzhou City.The pH values of the samples were measured using potentiometry,the heavy metals such as Cu,Pb,As,Zn,Cr and Ni in soils were measured using inductive coupled plasma-optical emission spectrometry(ICP).According to the soil environment quality standard(GB 15618-1995),the determined results were further assessed using methods of combining single quality index and comprehensive quality index.The results indicated that the soil quality of vegetable fields in Anning District of Lanzhou City belonged to the first to second class,which was considered to be clean,indicating that they met the requirements of soil environment for producing pollution free food.But the heavy metal concentrations among samples were much different,this indicated that human activities obviously effected the heavy metal concentrations in soil,so we should tighten the screw on environmental protection.