Eutrophication and nutrient enrichment bioassays in the waters of the Huainan and Huaibei coal mining subsidence areas,Anhui Province

Abstract

选取两淮采煤沉陷区内3个不同营养水平的水域为研究站点,即淮北南湖站(HBNH)、淮南潘谢顾桥站(PXGQ)和潘谢谢桥站(PXXQ),首先分析了水体营养盐含量、比例结构和营养状态指数,3个站点TP浓度的年均值分别为0.056、0.064和0.092 mg/L,TN浓度年均值则为1.00、0.94和2.67 mg/L,3个站点水体呈现中营养-轻度富营养和中度富营养2种营养状态,总体上表现出P相对N缺乏的特征.设置对照组、加氮组、加磷组和加氮磷组开展秋季氮、磷限制模拟实验研究.结果表明:HBNH、PXXQ两个站点为P限制,而PXGQ站点则为N限制.尽管水体正磷酸盐浓度较低,但由于藻类具有利用有机磷或储备P库的能力,3个研究站点依然保持了较高的初级生产力,HBNH、PXGQ和PXXQ 3个站点的叶绿素a浓度年均值分别为13.07、26.95和46.25 mg/m³,与各水体的营养水平保持一致.两淮采煤沉陷区水体富营养化控制关键可能在于调控磷元素的水平.;Three waters of different trophic states in the Huaibei and Huainan coal mining subsidence areas,including sites HBNH, PXGQ and PXXQ,were chosen to address their nutrient content,ratio of nitrogen to phosphorus (N: P),and nutrient limitation.Averaged annual concentrations of total phosphorus (TP) in the three sites are 0.056,0.064 and 0.092 mg/L,while the total nitrogen (TN) concentrations are 1.00,0.94 and 2.67 mg/L,respectively.The three studied waters present two trophic levels of meso-trophic to light eutrophication and meso-eutrophciation with deficiency of phosphorus.Nutrient enrichment bioassays were performed by four groups' experiments.Three treatments were cultured with additions of nitrogen (+N),phosphorus (+P),and nitrogen plus phosphorus (+N+P),with raw water without additions as control.HBNH and PXXQ show features of P limitation,and the other one,PXGQ presents N limitation due to its lower available inorganic nitrogen.Although very low phosphate concentrations,the three sites still have rather high primary production,with their chlorophyll-a concentrations of 13.07 (HBNH),26.95(PXGQ) and 46.25 mg/m³ (PXXQ),which are in accordance with their nutrient states.The results of this research give implication of the importance of P control to these waters in the Huainan and Huaibei coal mining subsidence areas.