环境pH对香溪河流域磷矿废石释磷特性的影响

为了评价三峡库区香溪河流域内所堆存的磷矿废石对地表水体的磷污染风险,以香溪河支流高岚河流域内具有不同风化时间的6座磷矿废石堆体为研究对象,依据US EPA Method 1313所规定的实验方法,开展了9种不同pH(2.0~13.0)条件下磷矿废石磷素浸出特性的实验研究,探讨了液相环境pH对磷矿废石磷素浸出浓度的影响。结果表明:在酸性环境下磷矿废石的磷素浸出浓度与pH呈负相关关系;中性及碱性环境下的磷素浸出浓度总体上低于酸性条件,其大小与环境pH之间无显著关系存在,但在pH=10.5±0.5范围内存在小幅升高;自然条件下磷矿废石堆体内部的液相环境为弱碱性(pH=7.8~8.8),且不会受当地酸雨长期淋滤的影响,在此条件下6种磷矿废石的磷素平均浸出浓度为0.7 mg/L,超标率为33 %。因此,研究区内的磷矿废石堆体可以形成点源形式的磷污染。在香溪河库湾水体富氧化问题日趋严重的前提下,应考虑将流域内堆存的磷矿废石作为第II类一般工业固体废物进行妥善处置,以降低其对香溪河库湾水体环境的磷污染风险。

Effects of environmental pH on phosphorus leaching characteristics of phosphate waste rock deposited within Xiangxi River watershed

To evaluate the potential phosphorus pollution risk of phosphate waste rocks deposited within Xiangxi River watershed of the Three Gorges Reservoir, six phosphate waste rocks with different weathering degrees stacked in Gaolan River, which is one tributaries of Xiangxi River, were selected as the study objectives. The leaching behaviors of the phosphate waste rock under nine different pH conditions (2.0 to 13.0) were characterized following the US EPA Method 1313 and the effect of liquid environmental pH on phosphorus leaching concentration was discussed. The results indicate that the phosphorus released from phosphate waste rocks inversely depended on liquid pH in acidic environment. While in neutral and alkaline environment, there was no significant relationship between the phosphorus leaching concentrations and environmental pH values. The phosphorus leaching concentrations were found to be generally smaller than that under acidic condition, while a slightly increase presented around the pH 10.5±0.5. The inner environment of phosphate waste rock piles would remain in weak alkaline (pH is 7.8 to 8.8) under natural conditions and would not be changed by long-term leaching of local acid rain. Under natural conditions, the average phosphorus leaching concentration of six phosphate waste rock samples was 0.7 mg/L with 33% standard-exceeding rate. Therefore, the phosphate waste rock piles dumped in study area could form phosphorus pollution as point sources. Considering the increasing problem of water eutrophication of Xiangxi River bay, the phosphate waste rocks should be considered as the second type of general industrial solid waste to reduce their environmental pollution risk.