Factors Influencing The Distribution And Accumulation Of Heavy Metals In Topsoil Across Beibu Gulf Of Guangxi

A survey was performed in this study to determine concentration and distribution of heavy metals in topsoil across Beibu Gulf of Guangxi. 7327 topsoil samples and 400 rock samples were collected, and the concentration of the heavy metals and other main elements or comical index, such as As, Cd, Cr, Hg, Ni, Cu, Pb, Zn, K2 O, Na2 O, CaO, MgO, SiO2, Al2O3, TFe2O3, Mn and SOC, were analyzed. Base on the analyses of the concentration and distribution of heavy metals, we discuss the relationship between the heavy metals and parent rock, weathering process, main elements and comical index to confirm the influence factors of heavy metals in our study area. Moreover, we attempted to delineate the primary and secondary relationships between these factors. The following conclusions are obtained.1. All the concentration of the heavy metals, except for Ni, Cu and Zn, was slightly lower than the background value of the Guangxi province, and the As, Hg, Cd were 1.3 times than background value of Chinese topsoil.2. The distribution of the heavy metals showed similar characteristics to each other, that was the high-concentration areas mainly distributed in the north and central of study area, and background concentration were mainly distributed in the central of study area and low-concentration areas mainly appeared in the southern erea.3. The order of metal concentration in parent rock was clasolite > intermediate acid rocks > carbonate rock. However, the opposite order, carbonate rock > quaternary sediments> clasolite> intermediate acid rocks, presented in topsoil. This phenomenon showed that the influence of parent rock to topsoil was not significant.4. The relationship between parent rock, weathering process and heavy metals showed that the pedogenesis play an more important role in the accumulation of heavy metals than parent rock. The pearson analyses showed that Al-bearing mineral, Fe-bearing mineral, SOC and pH were mainly influence factors of heavy metal, Ca-bearing mineral, K-bearing mineral, Na-bearing mineral Mg-bearing mineral were weakly influence on heavy metal. On the contrary, the SiO2 was disadvantage for the accumulation of metal.5. The result of pearson analyses and principal component analysis showed Al-bearing mineral, Fe-bearing mineral and SOC plays a primary role in accumulation of heavy metals, while pH and Ca-bearing mineral plays weakly role in the accumulation of heavy metals. The role of K-bearing mineral, Na-bearing mineral Mg-bearing mineral in accumulation of heavy metals can be negligible.