An Investigation And Evaluation Of Soil Pollution Of The Farmland Near A Molybdenum Mining Area

An investigation was conducted to evaluate heavy metal and molybdenum pollution of surface soils of a field near a molybdenum mining area.51 surface soils(0-20 cm)were collected and the contents of Cd?Cu?Hg?Cr?Ni?Pb?As?Zn and Mo were determined.The heavy metal pollution of the soils were evaluated according to the secondary limits of<Environmental quality standard for soils>(GB 15618-1995)and<Standard for heavy-metal pollution classification for agricultural soils in Fujian Province>(DB35/T 859-2008),and the Mo pollution was evaluated according to the soil environmental quality guideline of French.Some proposals were also presented for remediation and rational utilization of the soils.The main results were as follows:1.The contents of the metals of the soils in A district(far from the mining area)were mainly within the geochemical background levels in this area with only 5.9%soils being slightly polluted with Cu.38.9%of the soils in B district(closer to the mining area that A district)were slightly polluted with Cu,and 2%soils were slightly polluted with Cd and Mo.57.1%of the soils in C district(very close to the mining area)were slightly polluted with Cu.13.7%of the soils in C district were polluted with Cd of which some soils were moderately or seriously polluted.15.7%of the soils in C district were polluted with Mo of which some soils were seriously polluted.2.The comprehensive pollution indices of the soils in A district were between 0.57-0.93 with an average of 0.76,belonging to clean level.The comprehensive pollution indices of the soils in B district were between 0.27-1.29 with an average of 0.72,belonging to slightly polluted level as a whole.The comprehensive pollution indices of the soils in C district were between 0.27-4.39 with an average of 1.27,which generally pertained to slightly polluted level but some soils have been seriously polluted.The degree of the comprehensive pollution of the soils in each district increased in the order of A district<B district<C district.The closer of the soils were to the mining area,the more serious pollution the soils suffered.3.The discharge of waste water and waste solids from the mining area and the excessive use of chemical fertilizers and pesticides were the possible reasons for the soil pollution in this area.Removal of the polluted soil,chemical washing and chemical immobilization were proposed to remediate the polluted soils.As for the agricultural measurements,cultivation of low-accumulation crops can be applied to the polluted soils in order to ensure the quality of agricultural products.