鼎湖山森林地表水水质状况分析

Analysis on Runoff Water Quality in Dinghushan Biosphere Reserve

对鼎湖山生物圈保护区内两溪流水源水质状况进行了调查 ,结果发现 :1鼎湖山地表水总体水质较好 ,符合地面水环境质量标准的 类水源水质标准。区内水体受污染程度低 ,绝大多数指标均符合饮用水卫生标准。 2水体 p H值较低 ,A l含量较高 ,总有机碳测定表现出整个水体受到一定程度的有机污染。水体中有害金属 Mn和 Pb含量略高 ,但都远低于饮用水卫生标准。 3对地表水来源过程环节的水化学分析比较表明 :大气降水、穿透水、土壤溶液 ( 30 cm层和 80 cm层 )和地表水水样的 p H值呈现“M”形变化。酸雨和土壤表层酸化是该区地表水 p H值偏低的主要原因。地表水和 30 cm土壤溶液中的 A l浓度分别是大气降水的 5倍和 8倍 ,地表水中的 Al主要来源于酸雨对土壤的淋溶。地表水中的 Na主要来源于大气降水。大气降水 Pb浓度是地表水的 17倍 ,林冠吸收富集和土壤固定吸附使地表水中的 Pb大幅度降低。穿透水和土壤溶液中的 Mn、K、Ca、Mg、Sr比大气降水和地表水浓度高 ,反映了元素被酸雨淋溶、活化和被植物、土壤吸收吸附的过程。从长远看 ,尽管在森林保存完好的地区 ,区域环境的恶化及酸雨对地表水水质的影响仍不容忽视。

Dinghushan Biosphere Reserve was in the extent of acid rain hazard. The runoff water quality in the forest can show the response of regional geochemistry conditions to the processes of environmental acidification. Three samples about the water quality background value of two streams (two from the east stream and one from the west stream) in Dinghushan Biosphere Reserve were analyzed. The total organic carbon were 0 87mg·L -1 , 1 26 mg·L -1 (for east stream) and 1.51 mg·L -1 (for west stream), which were 1 7~3 times as much as National Standard (Excellent Grade) for Drink Water Quality, indicating the two stream contaminated organically in some degree. The pH values in east stream were 4 34 and 4 78, and that in west stream was 6 74. And Al 3+ concentrations were 521 97 μg·L -1 and 393 92 μg·L -1 in east stream, 72 26 μg·L -1 in west stream. Those in east stream were higher than the National Standard (300 μg·L -1 ). However, taking all the results of other items (the total dissolved solid, NO - 3, NO - 2, NH + 4, the concentrations of mental elements) into consideration, it can be concluded that the water quality in Dinghushan Biosphere Reserve belong to the Class ⅠGlade of National Standard for Surface Water Environmental Quality. Five types of water samples from the monsoon evergreen broadleaved forest located in east stream, including precipitation, throughfall, soil solution in depth 30cm and 80cm, and runoff were collected every week from February 2001 to August 2001. In the duration, there is a dry season (October～March) and a wet season (April～September). The average pH values for the five types of sample were 4 27, 5 15, 4 38, 4 98, and 4 09 in the same sequence as above, respectively. Its coefficient of variation in runoff was the lowest (0 84%), and that in soil solution in depth 80cm was the highest (20 52%). There was significant difference ( p= 0 01) between precipitation and throughfall, throughfall and soil solution in depth 30cm, soil solution in depth 80cm and runoff. The low pH value in runoff resulted directly from the acid rain and the soil acidification in surface layer. The average concentrations of Al 3+ increased from precipitation to runoff. Those in runoff and in soil solution of depth 30cm were 5 times and 8 times about, respectively, as much as that in precipitation. Most of Al 3+ in runoff came directly from the soil due to the leaching of acid rain. The average concentrations of Na + also increased from precipitation to runoff, but Na + in runoff came mainly from precipitation. The average concentration of Pb 2+ decreased in the sequence of precipitation to runoff. It was 17 times about in precipitation as much as that in runoff. The Pb 2+ in rain can be strongly absorbed by canopy and fixed by soil. The concentrations of Mn 2+ , K +, Ca 2+ , Mg 2+ , Sr 2+ in throughfall and soil solution were higher than that in precipitation and runoff, indicating the processes of leaching and activation by acid rain, uptake by plant and absorption by soil. Based on the studies, it can be concluded that, even in well preserved forest area, the environment deterioration including acid rain in neighborhood can also affect water quality, although natural forest has some capacity of resistance to it.