苏北浅滩海底地下水排放及其对海域营养盐通量的贡献

SUBMARINE GROUNDWATER DISCHARGE AND ITS CONTRIBUTION TO NUTRIENTS FLUXES IN THE SUBEI SHOAL, CHINA

海底地下水排放(SGD)是近海海域的一个重要的营养盐来源。本研究借助多种天然镭同位素对春季苏北浅滩海域的SGD及其携带入海的营养盐通量进行量化评估。研究发现:苏北浅滩海域的^(224)Ra、^(223)Ra和^(226)Ra等镭同位素的浓度水平较高,呈现近岸高、远岸低的分布趋势;根据^(224)Ra/^(226)Ra的"表观年龄模型"估算的水龄的分布情况推断,春季该海域表层水体主体流向为东北向,流速约为0.1m/s,这与前人物理海洋数值模拟结果一致;最终利用226Ra质量平衡模型发现海域的SGD通量为(46±29)cm/d,由其携带入海的溶解态无机氮、磷、硅营养盐(DIN、 DIP、 DSi)等的通量分别为(2.6±3.1)×1~09、(3.0±2.5)×10~6和(5.5±4.2)×10~8mol/d。

Submarine groundwater discharge(SGD)is an important nutrients source in a coastal water.Using multiple natural radium isotopes,we quantitatively evaluated the SGD and its associated nutrient fluxes in the Subei coastal zones(Jiangsu,South China)in spring.The results show that the activities of 224Ra,223Ra,and 226Ra in the study area were relatively high,presenting an increasing trend from nearshore to offshore.Based on the Apparent Radium Age Model with 224Ra/226Ra ratios,the distribution of water ages was portrayed,which indicated that the surface water mainly flowed to the northeast direction at?0.1m/s,which is consistent with a previously reported result of physical ocean numerical simulation.The SGD flux was(46±29)cm/d determined by a mass balance model of 226Ras.The SGD discharged nutrient fluxes of DIN,DIP and DSi were(2.6±3.1)×109,(3.0±2.5)×106 and(5.5±4.2)×108mol/d,respectively.