黄河三角洲新生湿地磷分布特征及吸附解吸规律

采用改进的 Hedley 磷分级方法研究了黄河三角洲新生湿地由河向海过渡带表层土壤磷形态变化和分布特征，并通过等温吸附解吸实验阐明了沿程土壤对外源磷的持留能力和释放风险。结果表明，各样点无机磷占总磷93%以上，是磷的主要存在形态。土壤中有机磷含量较低，可能与较低的有机质含量有关。无机磷中稀盐酸磷是最主要存在形态，与各样点Ca/Al含量密切相关。有效磷含量在18.6~33.4 mg/kg之间，仅占总磷的3.2%~5.9%，可能会限制湿地植物的生长。覆有植被的土壤中有效磷含量显著高于河滩和海滩土壤，说明植被存在对有效磷的积累有一定促进作用。由吸附解吸实验可知，加入较低浓度（0.05~5 mg/L）的外源磷时，随着初始磷浓度的升高，土壤对磷的吸附量增加，吸附率为70%~99%，解吸率小于7%，这说明各样点土壤的除磷能力较强，且流失风险较低。

Fractionation and adsorption-desorption characteristics of phosphorus in newly formed wetland soils of Yellow River Delta,China

A modified Hedley phosphorus （P） fractionation was used to study the P distribution seaward in the newly formed wetlands soils of Yellow River Delta. In addition, the adsorption-desorption experiments were performed to evaluate the ability of P retention and release in the sampled soils. The results showed that inorganic P remained the largest portion of total P （TP）, accounting for more than 93% of TP. Due to the lower content of organic matter, the organic P was relatively low in these soils. Among the inorganic P, Dilute HCl-P was the dominated form, related with the content of Ca in soils. The content of available P was 18.6~33.4 mg/kg, accounting for only 3.2%~5.9% of TP in soils, which might restrict the growth of plants in the wetland system. Furthermore, it was found that the content of available P in the sampling site covered with plants was higher than that in the beach soils, indicating that the vegetation cover may enhance the accumulation of soil available P. According to the adsorption-desorption experiments, when the concentration of initial P addition was in the range of 0.05~5 mg/L, the P adsorption increased with the increase of initial P concentration. Moreover, the percentage of adsorption was 70%~99%while desorption rate was less than 7%. It could be concluded that in these soils, the capacity of P retention was high and the release potential was relatively low.