三峡库区香溪河流域磷矿废石磷素释放特性研究

以三峡库区香溪河流域内所堆存的磷矿开采废石为研究对象,分别利用去离子水和人工配制的酸雨(pH=4.5)作为淋溶液,采用动态柱淋溶的试验方法,对比分析了磷矿废石在中性和酸性淋溶条件下的磷素释放特性.结果表明,在中性淋溶条件下,磷矿废石淋出液将长期处于弱碱性状态(pH=7.0~9.0),而在酸性淋溶条件下,淋出液pH值将在液固比(L/S)达到0.5mL/g后由弱碱性(pH=8.0~9.0)转变为弱酸性(pH=6.0~7.0);磷矿废石淋出液中的总磷(TP)浓度主要受淋溶环境pH值的影响,呈现出随液相pH减小而增大的趋势,而淋溶时间的增加不会对淋出液中的TP浓度形成稀释效应;当淋溶环境的pH值相对稳定时,磷矿废石将以稳定的溶解速率向液相中释放磷素;而当淋溶环境的pH值由弱碱性向酸性转变时将形成磷素加速释放期;无论是在自然淋溶条件还是在酸性淋溶条件下,磷矿废石淋出液中的TP浓度均超出超过GB 8978-1996中所规定的III类水域TP的排放限值(0.5mg/L),应将其视为II类工业固体废弃物进行相应的处置,以降低其对香溪河库湾的磷污染风险.

Phosphorus release from phosphate waste rocks deposited in Xiangxi River watershed of Three Gorges Reservoir

As the research object to phosphate waste rocks deposited within Xiangxi River watershed of Three Gorges Reservoir, Deionized water and artificial acid rain (pH=4.5) were selected as percolation solution of dynamic column leaching experiments. The phosphorus leaching characteristics under natural and acidic leaching conditions were compared and analysed. The results showed that the leachate pH of phosphate waste rock would maintain weak alkalinity (pH=7.0~9.0), while under the acidic condition the leachate pH would change from weak alkalinity (pH=8.0~9.0) to weak acidity (pH=6.0~7.0) when Liquid-to-Solid ratio (L/S) reached 0.5mL/g. The total phosphorus (TP) concentration of leachate was mainly dominated by pH of leaching environment, which increased with decrease of liquid pH. And the increase of leaching time won't dilution effect on the formation of TP concentration in the leaching liquid. The phosphate waste rocks would release phosphorus with a constant rate when the pH of leaching environment remained stable, while the accelerated released period would be formed during the pH of leaching environment changed from acidity to alkalinity. The leachate TP concentration would exceed the TP emission limit of the III type water area which stipulated by GB 8978~1996. The phosphate waste rocks deposited within Xiangxi River watershed should be managed as the II type industry solid waste in order to reduce the phosphorus pollution risk of Xiangxi Bay