Assessment of chemical properties of reclaimed subsidence land by the integrated technology using Yellow River sediment in Jining, China

Land subsidence is one of the most prominent environmental problems in China. Chemical properties of reclaimed subsidence land by the integrated reclamation technology using Yellow River sediment were assessed. Reclamation engineering of mining subsidence land was conducted, and representative soil samples of the reclaimed farmland (SR) and nearby unaltered farmland (CK) were collected from Jining City, Shandong Province. Soil chemical properties, including pH, electrical conductivity (EC), organic carbon (OC), total nitrogen (TN), extractable phosphorus (EP) and potassium (EK), and eight heavy metals were measured. The results indicate that more than 95 % of mining subsidence lands can be restored to farmland, which indicates the integrated reclamation technology with Yellow River sediment was feasible. The soils of SR and CK were alkaline but non-saline. The contents of TN, EP, EK and OC of SR were less than those of CK. Cd and Hg were not detected in any soil, and the contents of Pb, Zn, Cu, Cr, Ni and As of all soil layers of SR and CK were less than the maximum contaminant values of the second level to maintain human health and third level to protect plant normal growth as suggested in the standard for soils of China. Some improved methods of the integrated reclamation technology are suggested, such as draining water after settling of the water-sediment mixture in the reclamation strip for several days (>48 h) to increase deposition of more clay and silt in SR. The return of wheat or maize residue is recommended to improve both the fertility and plant-available water capacity of SR. Conventional tillage of the reclaimed land will likely improve productivity as the sand, silt and clay particles become an integral, living, soil body.