Evaluation of heavy metal accumulation in greenhouse soils in Shenyang, Northeast China

Soil heavy metals are considered being originated from two major sources, natural and anthropogenic. With the spring-up of greenhouse farming in the suburbs of big cities, heavy metals accumulation in greenhouse soil is becoming a serious environmental problem. In order to evaluate and ascertain the accumulation status and origins of heavy metals in the greenhouse soils of Shenyang suburb, the Cu, Zn, Cd, As, Cr and Pb contents in soil samples collected from the greenhouse fields with different cultivation years were determined by using atomic absorption spectroscopy (AAS) and hydrogen-atomic fluorescence spectrometer (HG-AFS), and the origins of these heavy metals were analyzed by employing correlation analysis, principle component analysis (PCA) and hierarchical cluster analysis (HCA). No obvious soil heavy metals accumulation was observed, but the Cu, Zn, Cd and As contents in greenhouse soils increased with increasing years of cultivation. Two significant components were extracted by PCA, explaining 70.013% of total variance. The Cu, Zn, Cd and As in test soils were mainly associated with anthropogenic input, whereas Cr and Pb were related to parent rocks. HCA confirmed and completed the results obtained by PCA, classifying the data in two groups representing different origins. Cluster included Cu, Zn, Cd and As representing human inputs, while Cluster included Cr and Pb representing natural sources. Moreover, the results obtained by the correlation analysis also agreed with PCA and HCA, also helping in elucidating the relationship between heavy metals and soil properties. More attention should be paid to the anthropogenic inputs of Cu, Zn, Cd and As in Shenyang greenhouse fields, especially for those having been cultivated for 5 years or more.