Accumulation Characteristics and Sources of Available Pb in Soils under Greenhouse Cultivation Condition in Northeast China

Greenhouse vegetable production (GVP) is one of the most effective cultivation methods, and the enrichment of heavy metals has been found in greenhouse soils. This study was conducted to determine the influence of cultivation ages on available Pb and find out pollutant sources. The concentrations of available Pb decreased with soil depth, and obviously accumulated in 0-40 cm soil profiles (P<0.05). Available Pb contents in 0-40 cm soil profiles fluctuated and did not significantly (P>0.05) correlate with cultivation duration. According to correlation analysis, there was no significant correlationship (P>0.05) between available Pb and soil properties (pH, SOM, sand, silt, clay, SiO2, Al2O3 and Fe2O3). It can be concluded that Pb in greenhouse soils might arise from comprehensive sources including anthropogenic activities and natural effects. Therefore, agricultural practices (i.e. manure and fertilizer input, pesticide spray, and application of agricultural machines) will not be a dominant factor of available Pb accumulation.