基于近岸系列分层竖井的海底地下水排泄及其营养盐输入研究

Submarine Groundwater Discharge and Dependent Nutrient Input Based on a Series of Layered Monitoring Wells

摘要:

以广西北海市近岸系列分层竖井为研究对象，通过现场地下水监测和采样分析，结果显示竖井含水层整体上为靠近海边咸化明显，其中I承压水咸化程度较大，咸化程度差异主要受海水入侵及海水高位养殖影响。地下水SiO₃-Si由于受“盐效应”影响导致其自内陆向海岸浓度升高，而低含量的PO₄-P含量可能是铁氧化物的吸附清除作用引起的；潜水层中的NH₄-N和NO_x-N含量整体高于承压水的，高位养殖池塘水的下渗造成NH₄-N在近海岸的潜水层含量最高，而NO_x-N受反硝化过程影响，导致自内陆至海岸明显减小。研究区地下水氮磷比（N/P）平均值为595.85，高N/P比值地下水排泄进入海洋，将促进浮游生物营养盐结构由N限制转向P限制。

Abstract:

The submarine groundwater of a series of stratified vertical wells near the coast of Beihai， Guangxi was monitored and analyzed on-site. The monitoring and sampling analysis show that the salinity in the groundwater in Confined I which is close to the seaside is relatively high， and the difference in salinity is mainly affected by seawater intrusion and high-level mariculture. The concentration of SiO₃-Si in groundwater increases from inland to coastal area due to the “salt effect”， and the low content of PO₄-P which may have been caused by the adsorption and removal of iron oxides. The NH₄-N and NO_x-N concentrations in the phreatic layer are higher than those in confined water. The infiltration of high-level aquaculture pond water results in the highest NH₄-N concentration in the nearshore phreatic layer， while NO_x-N is affected by denitrification. The average N / P ratio of groundwater in the studied area is 595.85， and the discharge of groundwater with a high N / P ratio into the ocean will promote the transformation of nutrient structure of plankton from N limitation to P limitation.