Environmental Pollution：矿物改良剂添加对土壤磷酸盐的吸附

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　　中国农业大学资源与环境学院陈清教授团队对矿物改良剂添加下土壤中磷的吸附动力学和机理以及土壤中有效磷进行了研究。相关成果发表于Environmental Pollution（IF=5.714）。

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　　Highlights

　　P sorption on poorly-crystalline Al hydroxides was mainly through displacement of inner-sphere Al–OH groups.

　　Higher alum rates and P concentrations contributed to the inner-sphere P sorption.

　　Mg in dolomite inhibited the formation of hydroxylapatite (HAP) at higher P concentrations.

　　Dolomite addition decreased soil CaCl2–P, but increased Olsen-P.

　　Abstract

　　In China, excessive phosphorus (P) application in protected vegetable fields has led to high legacy P stores. Soil amendment with alum or dolomite is one of many best management practices (BMPs) used to reduce P losses in calcareous soils. However, both the kinetics and mechanisms of P sorption and soil available P in amended soils are understudied. Herein, both aspects were looked at under controlled conditions. Firstly, a sorption study which coupled P concentrations with poorly-crystalline Al hydroxides and dolomite was conducted. Results from this batch experiment showed that P sorption on poorly-crystalline Al hydroxides was homogenous and occurred mainly via displacement of inner-sphere hydroxyl (Al–OH) instead of the formation of AlPO4. However, the amount of sorbed P reached maximum sorption of 73.1 mg g-1 and did not change with further increase in P concentration. It was observed that P adsorbed onto the dolomite surface at low P concentrations, whereas hydroxyl replacement and uneven cluster precipitation of Ca3(PO4)2 occurred at high P concentrations. A second 90 day incubation experiment investigated changes to soil available P and sorption-desorption across variable rates of amendments (0–50 g kg-1). Results showed that alum amendment at a rate of 50 g kg-1 decreased soil CaCl2–P and Olsen-P concentrations by 91.9% and 57.8%, respectively. However, Olsen-P increased when the dolomite rates were <20 g kg-1. Phosphorus sorption-desorption of the amended soil showed alum had higher P sorption efficiency than dolomite at low addition rates (<10 g kg-1). However, soil amended with high dolomite rates (>10 g kg-1) could sorb more P in comparison with alum when P concentrations were increased. The P status of the amended soil was closely connected to the P sorption mechanisms on mineral amendments, soil P concentrations and soil properties.

　　在我国，保护地土壤中磷（P）的过量施用导致了P高残留。用明矾或白云石改良土壤是减少石灰性土壤中P流失的管理措施之一。然而，对改良土壤中P的吸附动力学和机理以及土壤中有效P的研究都还比较少。本研究在控制条件下对这两个方面进行了试验。首先研究了P浓度与低晶体铝氢氧化物和白云石添加的关系。该试验结果表明，低晶体铝氢氧化物对P的吸附是均匀的，主要通过内球氢氧化物（Al-OH）的置换而不是形成AlPO4。但P的吸附量最大为73.1 mg·g-1，且随P浓度的进一步增加不再发生变化。此外还观察到在低P浓度下，P吸附在白云石表面，而在高P浓度下则发生羟基置换和不均匀的Ca3（PO4）2团簇沉淀。另一个90d的培养试验研究了不同改良剂添加量（0-50 g·kg-1）下的土壤有效P和吸附-解吸的变化。结果表明，添加50 g·kg-1的明矾可使土壤CaCl2-P和Olsen-P浓度分别降低91.9%和57.8%。当白云石添加量<20 g·kg-1时，Olsen-P增加。P的吸附-解吸变化表明，在低添加量（<10 g·kg-1）条件下，明矾对P的吸附效率高于白云石。然而，当P浓度增加时，高白云石添加量（>10 g·kg-1）处理的土壤比明矾能吸收更多的P。土壤P状况与矿物改良剂对P的吸附机制、土壤P浓度和土壤性质密切相关。