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Pollution of Cd has seriously threatened environmental safety and human health. The field experiment was conducted to investigate the effects of calcium-magnesium phosphate fertilizer and water management on bioavailability of Cd in soils and its accumulation in rice. The results revealed that continuous flooding has enhanced soil pH from 5.10 to 5.72 and reduced soil redox potential (Eh) from 164 to − 60 mV. Application of calcium-magnesium phosphate fertilizer has significantly raised soil pH from 5.10 to 6.45 (P

Different amendments have diverse adsorption capacity for heavy metals. The objectives of this study were to evaluate adsorption efficiency of different kinds of amendments for heavy metals and to provide theoretical guidance for alleviation of heavy metals. The indoor oscillating experiments were carried out to investigate the adsorption efficiency of five amendments (i.e., lime, illite ilerite, ground phosphate rock, chitin, and corn straw charcoal) for adsorption capacity of heavy metals (i.e., Zn, Pb, and Cd). The adsorption efficiency of lime for Zn and Cd was 99.64% and 99.99% followed by chitin with adsorption efficiency of 74.94% and 81.63% respectively. The adsorption efficiency of amendments for Pb, Zn, and Cd was increased gradually with adsorption time. The adsorption efficiency has gradually reached a stable stage after certain time. In addition to adsorption of Pb by corn straw charcoal, the other four materials (i.e., lime, illite ilerite, ground phosphate rock, and chitin) have reached equilibrium when pH value was 3. The adsorption efficiency of lime (1%) for Zn was highest (99.98%). The adsorption efficiency of other materials for Pb was enhanced with increase in dosage except for chitin; however, the unit adsorption capacity was not decreased. It is concluded that adsorption efficiency of lime and chitin for heavy metals such as Zn, Pb, and Cd was more than illite ilerite, ground phosphate rock, and corn straw charcoal, which can be considered as an active sorption materials.

The intensive human activities are the major cause of heavy metals pollution in suburban farmland, which poses threats to soil environment and safety of agricultural products. The combination of spatial analysis (SA), principal component analysis (PCA), input fluxes analysis (IFA) and UNMIX model have precisely analyzed the sources and relative contribution of heavy metals from each source. The results revealed that average contents of Cr, Ni, Cu, Zn, Pb and Cd were 37.82, 13.65, 17.93, 93.78, 48.84 and 0.24 mg kg−1, respectively. The spatial distribution indicated that parent materials, industrial activities and traffic emissions had significant effects on contents of heavy metals in topsoil. According to UNMIX model, the contribution rates of soil parent material, industrial/ traffic emissions, and agricultural activities to heavy metals in soil were 49.15%, 35.00% and 15.85% respectively. Which indicated largest contribution of natural sources, but input of human activities including industry, transportation and agriculture could not be ignored. The input fluxes analysis (IFA) reveals that atmospheric deposition was main source of heavy metals in soil, followed by fertilizer and irrigation. This study has presented reliable methods for analysis of sources of heavy metals in suburban farmland soil. The combination of UNMIX and IFA can accurately identify and quantify pollution sources.