竹银水库库底氮磷营养盐释放潜力研究

竹银水库是珠海新建的目前最大的对澳门供水水库，总库容达4500×104 m3。氮和磷是浮游植物生长繁殖的主要限制性营养元素，氮、磷的供应很大程度决定着水生生态系统的初级生产力和有机质的微生物循环，而水体氮、磷营养盐的一个重要来源就是沉积物，即底泥。以竹银水库蓄水前库内不同区域的底泥为对象，对水库内代表不同区域的10个位点底泥进行采样，通过水库蓄水模型装置，模拟无氧条件下各区域底泥在蓄水后短期内向上覆水体释放氮、磷营养盐的情况，并对释放到水体中的总氮、总磷进行2天一次的定期监测，评估该水库底泥氮、磷营养盐的释放潜力。结果表明：竹银水库库底氮、磷营养盐的释放存在空间差异，农业种植区和畜牧养殖区附近的采样点具有较大的总氮和总磷释放潜力；各采样点的总氮平均释放潜力达15 g·m-3，总磷平均释放潜力达30 mg·m-3，磷释放的风险远低于氮，磷仍将是竹银水库最主要的限制性营养元素；预计该水库在蓄水后10 d内最多可释放近1.7×105 kg的氮和1.5×103 kg左右的磷，按满库容计算，则底泥营养盐的释放使水库水体氮、磷营养盐质量浓度分别提高4.25 mg·L^-1和0.038 mg·L^-1。建议对不同区域性质的底泥采取具有针对性的处理措施：对农业种植区与牲畜养殖场区域的底泥应以清淤为主，对于其他区域可采取底泥覆盖等技术降低其营养盐释放风险。

Nutrient Release from different soils in Zhuyin,a newly commissioned Reservoir in Macau,China.

We studied soils from various zones of Zhuyin, a newly built reservoir near Zhuhai city, intended to supply water to the city of Macau. The reservoir bottom, before its first flooding, consisted of several zones including forest, mountains, planting areas and an animal farming district. The release rates of nitrogen and phosphorus of soils from these different regions were estimated in anaerobic condition in the laboratory after a short-term storage in water, using self-designed equipment. The results showed that zonal disparities in nutrient release should be expected. The farm belt and the livestock farm released most nitrogen and phosphorus. The average potential for releasing nitrogen and phosphorus was about 15 g·m-3 and 30 mg·m-3. It is estimated that the amount of nitrogen released is close to 1.7×105 kg while phosphorus release is only about 1.5×103 kg, 10 days after storage. Thus, The phytoplankton in Zhuyin Reservoir was expected to be under phosphorus limitation. Further, the expected concentration of nitrogen and phosphorus could reach high values of about 4.25 mg·L^-1 and 0.038 mg·L^-1, respectively. Therefore, the nutrient-rich soils of the farm belt and the livestock farm should be removed before water storage, and the other regions should be rendered inactive or capped to reduce the release of nutrients from the sediments.