analytical methods
to measure the total amount of heavy metals in soil sample, the nitric acid-hydrofluoric acid digestion method was firstly utilized. then the sollar aa m6 flame atomic absorption spectrophotometer produced by thermo fisher, the usa, was adopted to detect the content of heavy metals. the total amount of heavy metals in plants was firstly detected using the nitric acid-perchloric acid digestion method, and the contents of heavy metals were tested using the same method above. the potassium dichromate-sulfuric acid oil-bath method (nyt 1121. 6-2006) was employed to detect the organic matters in soil sample. meanwhile, ph valueof the soil sample was measured using electrode method ( ny 525-2012) and the dry weight of dried crops was determined using weighing method.