模拟酸雨对不同营养水平湖泊pH值的影响

Effects of Simulated Acid Rain on pH in Lakes With Different Trophic Levels

长江中下游湖区是全球的强酸雨中心之一,为了研究酸雨对该地区湖泊p H值的影响,通过野外调查和实验模拟展开了研究。对长江中下游68个湖泊的调查结果表明,酸雨区湖泊p H均值显著低于非酸雨区(P<0. 05)且湖泊p H值与水温、溶解氧含量和叶绿素a含量呈显著正相关,与总氮、硝酸盐、溶解性无机碳含量和浊度呈显著负相关。模拟实验结果表明,在不同p H值(2. 5、4. 0和5. 0)酸雨作用下,虽然各处理组p H值日变化趋势相同,但低营养组p H值低于高营养组且p H值增加速率慢于后者,低和高营养组不同酸雨处理p H值差异均随时间推移逐渐减小。实验结束时,实验组和对照组p H值无显著差异。湖泊富营养化会增加叶绿素a含量,增强水体对酸雨的缓冲能力,但持续性酸雨会对湖泊p H值、水生生物和生物地球化学循环产生潜在影响。

pH has important effects on aquatic organisms and element cycling in lakes.The south part of the middle and lower reaches of the Yangtze River is one of the centers of acid rain in the world.The effects of acid rain on lake pH were studied through field investigation and simulated experiment.In the 68 investigated lakes along the middle and lower reaches of the Yangtze River,lake pH had a significant positive correlation with water temperature,dissolved oxygen and chlorophyll a,and a significant negative correlation with total nitrogen,nitrate,dissolved inorganic carbon and turbidity;the average pH value of lakes in acid rain areas was significantly lower than that in non-acid rain areas(P<0.05).The results of the simulated experiment show that the pH value of the low trophic treatment(L)was lower than that of the high trophic treatment(H),and the increasing rates of pH in L treatment was slower than that in H treatment after the single addition of acid rain(pH=2.5,4.0 and 5.0).The differences of the pH values with three pH treatments of acid rain decreased over time in both L and H treatments.The daily variations of the pH values with different treatments showed the same trend.At the end of the experiment,the pH values with acid rain addition and no acid rain addition had no significant difference in the two trophic treatments.The study indicates that although the increase of the content of chlorophyll a in lakes caused by eutrophication can enhance the buffer capacity to the acid rain,the persistent acid rain could have a potential impact on pH,aquatic organisms and biogeochemical cycles in lakes of this area.