大亚湾海底地下水排泄及营养盐和重金属通量的评估

发布时间：2018-02-07 10:03

本文关键词： 镭同位素海底地下水排泄海底地下淡水排泄营养盐涡动扩散系数大亚湾　出处：《中国地质大学(北京)》2017年硕士论文　论文类型：学位论文

【摘要】：海底地下水排泄(SGD)是地下水与海水交换的研究重点,它包括了两个部分,一部分是海底地下淡水排泄(SFGD),另一部分是再循环海水(RSGD)。作为水循环的重要组成部分,SGD是陆地输入海洋化学物质的重要通道之一,同时也是各种污染物质输入到海水中的一个隐蔽通道。近年来,已经有许多的报道证明了由SGD驱动的物质通量是不可被忽视的。本文以未被研究过SGD的大亚湾为研究对象,采集并分析了大亚湾区域的镭同位素数据,发现镭同位素在海湾内由东北部的子湾向西南湾口逐渐递减。考虑了河流和外海影响,利用镭同位素对水体刷新时间进行了估计,得到的结果是13.41~18.85 d,并利用纳潮量模型(结果是18.83 d)验证了镭同位素的水体刷新时间估计。同时,我们利用水体表观年龄模型得出水体表观年龄是:9.35~26.72。三者结果基本一致,相互得到验证。对于水体混合过程,我们根据~(224)Ra在海湾内的分布状况和一维~(224)Ra扩散模型,计算了大亚湾内的水平涡动扩散系数,结果为(7.80~11.65)×10~6cm2/s。同时,根据湾内和湾口一个站点计算的垂直分布状况,估算出垂直涡动扩散系数为(1.12~4.44)cm2/s。在估计水体刷新时间的基础上,构建了海湾内的镭同位素质量平衡模型,估计出大亚湾内SGD为(2.68~3.34)×10~7 m~3/d。通过耦合海湾内水、盐质量平衡模型,估算出2015年7月大亚湾海底地下淡水排泄量为(3.98~7.12)×10~6 m~3/d。同时在年平均的意义上建立了稳态区域水均衡模型,估算出海底地下淡水排泄为(1.23~2.41)×10~6m~3/d或(0.22~0.43)cm/d。两个不同模型得出的海底地下淡水排泄量非常接近,结果得到相互验证。估算了由SGD输入到海湾的营养盐与重金属物质通量。结果显示由SGD输入到海湾的重金属通量明显大于河水输入,SGD驱动的营养盐通量与河流输入通量相当。确定了SGD携带化学物质入海中所起的重要作用,在对海湾生态系统的研究中必须考虑SGD的影响。
[Abstract]:Submarine groundwater discharge (SGD) is the focus of research on the exchange of groundwater and seawater, which consists of two parts. One is the discharge of underwater fresh water, the other is the recycling of sea water, RSGD. As an important part of the water cycle, SGD is one of the important channels for terrestrial input of marine chemicals. In recent years, there have been many reports that the matter flux driven by SGD can not be ignored. In this paper, Daya Bay, which has not been studied on SGD, has been studied. The radium isotopic data in the Daya Bay area are collected and analyzed. It is found that the radium isotopes gradually decrease from Ziwan in the northeast to the mouth of the southwest bay in the Gulf. Considering the influence of rivers and the open sea, the refresh time of water body is estimated by using radium isotopes. The result obtained is 13.41 ~ 18.85 days, and the water refresh time estimate of radium isotope is verified by the model of tidal absorption (18.83 days). At the same time, the apparent age of water body is: 9.35 ~ 26.72 by using the water body apparent age model. The results are basically consistent with each other. For the mixing process of water body, we calculate the horizontal eddy diffusion coefficient in Daya Bay according to the distribution situation of Gui 224Ra in the bay and the one-dimensional diffusion model. The results show that the diffusion coefficient is 7.80 ~ 11.65) 脳 10 ~ (6) cm ~ (2 / s) 路s ~ (-1). At the same time, the horizontal vortex diffusion coefficient in Daya Bay is calculated. According to the vertical distribution calculated at a station in the bay and the mouth of the bay, the vertical eddy diffusion coefficient is estimated to be 1.124.44 cm ~ 2 / s. Based on the estimation of the water refresh time, a radium isotope mass balance model is established in the bay. The SGD in Daya Bay is estimated to be 2.68 ~ 3.34) 脳 10 ~ (7) m ~ (-1) 路d ~ (3 / d). By coupling the mass balance model of water and salt in the bay, it is estimated that in July 2015 the amount of underground fresh water discharged from the bottom of Daya Bay is 3.987.12) 脳 10 ~ (6) m ~ (3 / d) d. At the same time, a steady regional water balance model is established in the sense of annual average. It is estimated that the subsea freshwater discharge is 1.23 ~ 2.41) 脳 10 ~ (6) m ~ (-1) / d or 0.22 ~ 0.43 cm / d 路d. The two different models are very close to each other. The results show that the flux of nutrients and heavy metals from SGD to the bay is obviously larger than that from the river to the bay, and the flux of nutrient and heavy metal from the river to the bay is higher than that from the river. The flux is equivalent. The important role that SGD plays in carrying chemicals into the sea is determined. The effects of SGD must be considered in the study of the Gulf ecosystem.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P734;X820;P641

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