三门湾水体营养盐变化及其对人类活动的响应

    VARIATION OF NUTRIENTS IN SANMEN BAY AND ITS RESPONSE TO HUMAN ACTIVITIES

    • 摘要: 我国沿海重点海湾水体富营养化与陆源输入和海湾开发活动密切相关,海湾特殊的弱交换水动力环境使得水体环境治理面临更为严峻的挑战,浙江省近年来实施陆域生态环境治理“千万工程”和海域“蓝色海湾整治”工程,陆域和海湾水环境提升显著。以浙江省第2大海湾三门湾为研究对象,对近30年三门湾海域水体营养调查监测数据进行对比分析,结合2019年9月在三门湾开展的流域-海域水体质量联合调查取得的54个流域水样、30个海域水样和6个雨水样的营养盐分析结果(NO3,NO2,NH4+,PO43−),分析了三门湾水体营养盐的空间分布特征和影响因素,分析营养盐长期变化特征和人类活动的影响。目前三门湾水体富营养化的问题依然突出,湾内海域DIN和DIP含量在0~439和18~59 μg/L,平均值分别为233和37 μg/L,河流DIN和DIP含量在77~1586和3~126 μg/L,平均值分别为466和48 μg/L。河流中氮、磷营养盐含量整体上呈现由上游到下游增长的趋势,其中农业生产对水体NH4+-N、NO3-N影响大,城镇生活和工业生产排放对水体中NH4+-N、NO2-N和DIP影响大。海域中氮磷营养盐的高值区主要分布在水体交换弱的港汊顶部和河流入海处,营养盐浓度呈现由近岸高值向外海逐渐降低的趋势,海水养殖是近岸营养盐的主要贡献者。三门湾水体营养盐在1987—2007年中处于持续增长趋势,2010年后随着海陆生态环境治理政策的实施,DIN和DIP呈现明显下降趋势,海湾水环境状况得到较大改善。

       

      Abstract: Some key gulfs in China are facing eutrophication related to terrigenous input and human activities. The weak hydrodynamics of the gulf brings about more serious challenges to the water management organizations. In recent years, many projects have been lunched in Zhejiang province to improve the water environment of gulfs. As the result, water qualities are significantly improved. Sanmen Bay, the second largest in the province has been a key research object of nutrition survey for almost 30 years. Based on the monitoring data in the past 30 years and the joint survey results conducted in September 2019, acquired are 54 samples from river basins, 30 samples from sea water and 6 samples from precipitation. All the samples are analyzed for nutrient contents, such as NO3 and NO2, NH4+, PO43−. Based on the results and the spatial distribution patterns of the nutrients in the bay, the influence factors on the nutrient spatial distribution patterns are revealed, especially the long-term changes of nutrients and their response to human activities. At present, the eutrophication problem remains prominent in Sanmen Bay. The contents of DIN and DIP in the sea sample range from 0 to 439 μg/L and from 18 to 59 μg/L, with an average of 233 μg/L and 37 μg/L, respectively. The contents of DIN and DIP in the river sample range from 77 to 1 586 μg/L and from 3 to 126 μg/L, with an average of 466 μg/L and 48 μg/L, respectively. The contents of nitrogen and phosphorus increased from the upstream to the downstream. Agriculture has great influences on NH4+-N and NO3-N, while urban living and industrial production have great influences on NH4+-N, NO2-N and DIP. The high values of nitrogen and phosphorus in the bay were mainly distributed at the head of the bay and the entrance to the sea where water exchanges are rather weak. The nutrient concentration shows a decreasing trend from the high values nearshore to the low value offshore. The mariculture was the main contributor of nutrients to the environment nearshore. During the period of 1987-2007, Sanmen Bay suffered a continuous increase in water nutrients. After 2010, with the enforcement of marine and land ecological environmental management policies, DIN and DIP have showed an obvious decreasing trend, and the water environment of the bay is greatly improved.

       

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