The geochemical baseline of near-ground air dust in Chengdu economic region

The heavy metals distribution of near-ground air dust in Chengdu economic region shows that the content of heavy metals in the middle-east part is higher than that in the west part, and that in the heavy industry city is higher than that in the comprehensive city and tourist city. The heavy metal content is totally high in industry and mine influencing areas, and that in the plain terrain of dense population is higher than that in the mountain area. The standard limit method was used to determine the element limiting concentration in near-ground air dust, and the statistics of values below the limiting concentration value was employed to determine the geochemical baseline values, and the values obtained are as follows: As 28.6mg/kg, Hg 0.63mg/kg, Cd 2.94 mg/kg, Cr 110 mg/kg, Pb 281 mg/kg, Ni 32 mg/kg and Zn 535 mg/kg. Elements in geochemical baseline of near-ground air dust are related to regional geological background and mineral development. Mining activity, industrial activity and residents' lives constitute the main factors responsible for the relatively high content of artificial disturbance elements of near-ground air dust.