人类活动影响下的龙口海岸带海底地下水排泄通量研究

在沿海地区,以²²³Ra和²²⁴Ra为示踪剂建立的镭质量平衡模型已广泛应用于海底地下水排泄量(SGD)的研究中,然而目前国内外关于在人类活动复杂影响较大情况下的SGD研究却极为少见。本文对比研究了在有防渗墙(A区)和填海造陆(B区)两种不同人为因素影响下的龙口海岸带水体表现年龄、海底地下水排泄量及其携带的氮磷营养盐通量。结果表明,A区平均水体表现年龄为14.26 d,B区平均水体表现年龄为10.64 d。此外,B区沿岸地下水以及近岸海水中的Ra活度均普遍高于A区,而盐度低于A区。在SGD方面,A区的SGD速率为1.26~1.60 cm·d^-1,B区为1.43~1.82 cm·d^-1,考虑SGD在评估方法上存在一定的误差,因此两个区域的SGD速率相差不大。但与我国其他自然海域相比,这两个区域的SGD速率均处于较低水平。此外,B区的氮磷营养盐浓度普遍高于A区,而且由SGD驱动的氮磷营养盐通量不同,地下水输入的不平衡的营养盐极易改变龙口海域的营养盐结构,对海洋生态环境产生不利影响,这也进一步证实SGD在沿海生态环境以及水体污染治理中的重要地位。

Submarine groundwater discharge in Longkou coastal zones under the influence of human activities

The radium mass balance model based on ²²³Ra and ²²⁴Ra tracers has been widely used in the study of submarine groundwater discharge (SGD) in coastal zones. However, few researches are currently done to study the influence of human activities on SGD. In this paper, the water residence time, SGD flux and nutrient flux carried by SGD were compared between the Longkou coastal zones A and B, under the influence of two different human activities, namely an impervious dam in Zone A and land reclamation in Zone B. Results showed that the average water residence time in Zone A was 14.26 days and in Zone B 10.64 days. In addition, radium activities in groundwater and seawater in Zone B were generally higher than that in Zone A; whereas salinities were lower in Zone B than in Zone A. The discharge rates for SGD in Zone A ranged from 1.26 to 1.60 cm/d and in Zone B from 1.43 to 1.82 cm/d. Therefore the discharge rates for SGD in these two zones were comparable within the margin of error. However, the discharge rates for SGD were relatively low in these two zones compared to other natural coastal areas in the country. Moreover, the nitrogen and phosphorus nutrient concentrations in Zone B were generally higher than that in Zone A. The nitrogen and phosphorus nutrient fluxes carried by SGD were different in the two zones. Such unbalanced nutrient inputs from SGD could easily change the nutrient structure of the Longkou coastal zones, which has an adverse impact on the marine ecological environment, further confirming that SGD is important for coastal ecological environment and water pollution control.