岷江上游典型土壤磷的迁移特性研究

通过选取岷江上游典型土壤类型褐土、黄棕壤、暗棕壤和亚高山草甸土,分析其磷组分特征及固磷能力,以期了解土壤磷的迁移特性。结果表明,H_2O-P和Na HCO3-P含量分别在3.39~10.91 mg·kg~(-1)和5.70~51.97 mg·kg~(-1)之间,这类磷易随土壤侵蚀而流失。褐土和黄棕壤以HCl-P为主,暗棕壤和亚高山草甸土则以Na H-P为主,其占全磷的比例分别为71.36%、24.75%、62.16%和53.04%。因此,当NaOH-P或HCl-P随土壤颗粒进入水体后,它们向水体迁移释放磷的能力较强。该区域土壤磷的最大吸附量、最大缓冲量和吸持指数表明,褐土和黄棕壤的磷素向液相释放迁移的风险高于暗棕壤和亚高山草甸土。磷素零点吸附平衡浓度介于19.44~24.08 mg·L~(-1)之间,均大于水体富营养化临界值0.35 mg·L~(-1)。综上,岷江上游土壤磷素迁移的风险较高。

Phosphorus movement characteristics of typical soils in the upper reaches of the Minjiang River, China

In recent years, there has been an increasing interest in the non-point source pollution caused by the movement of soil phosphorus(P). The fractions and fixation capacities of soil phosphorus of four kinds of typical soils, including cinnamon soil, yellow-brown earth, dark-brown earth, and subalpine meadow soil, were assessed in this study to explore the characteristics of P movement. The results showed that the concentrations of H₂O-P and NaHCO₃-P were 3.39~10.91 mg·kg^-1 and 5.70~51.97 mg·kg^-1, respectively. P was easily lost by runoff in the process of soil erosion. HCl-P was the main fraction in the cinnamon soil and yellow-brown earth while NaOH^-P had the largest share in dark-brown earth and subalpine meadow soil, and correspondingly the percentages of total P in these P fractions were 71.36%, 24.75%, 62.16% and 53.04%, respectively. Therefore, NaOH^-P and HCl-P in these soils had high P-release potentials. The maximum sorption capacity, maximum buffer capacity, and P sorption index of soil P demonstrated that the risks of P movement from cinnamon soil and yellow-brown earth to the liquid phase were higher than those from dark-brown earth and subalpine meadow soil. The equilibrium P concentrations at zero sorption of soil P in the four soils ranged between 19.44 mg·L^-1 and 24.08 mg·L^-1, which is larger than 0.35 mg·L^-1 for eutrophication. In summary, the soils in the Minjiang River have a higher risk of P movement.