九龙江丰水期水化学组成特征及其控制因素

Hydrogeochemical characteristics and controlling factors in Jiulong River(Fujian Province) during the flood season

为了解九龙江流域水环境状况,于2017年7月对福建九龙江河水样品进行了系统采集与分析。结果显示,九龙江丰水期河水pH在6.7~7.9,平均7.2,呈弱碱性;TDS平均含量为90.9 mg·L-1,低于世界河流平均值。电导率(EC)和溶解氧(DO)的平均值分别为116.5μS·cm-1和7.5 mg·L-1。水化学类型为HCO3-SO4-Ca型,Ca2+是主要的阳离子,占阳离子总量的47.9%,K+和Na+二者之和占总阳离子的29.6%。HCO3-和SO42-是主要的阴离子,二者之和占阴离子总当量的68.6%。采用正演法估算各端元贡献,显示碳酸盐岩和硅酸盐岩风化是九龙江水化学组成的主要控制因素,对河水总阳离子的贡献分别为50.6%和30.7%。大气降水对九龙江流域影响较大,约贡献了阳离子总量的12.9%。人为活动对河水的化学组成影响也不容忽视,特别是对SO42-和NO3-的含量影响较大。九龙江工农业布局使得北溪河水主要受工业生产影响,而西溪和南溪主要受农业活动影响。因此,在治理九龙江水环境时,除了严格控制城镇污水排放外,北溪还需加强工业废水管理,而西溪和南溪要严格控制农田化肥的使用。

To understand the environmental status of Jiulong River basin, water samples from the river were collected in July 2017. The pH value of water ranged from 6.7 to 7.9, with an average of 7.2, indicating slightly alkaline. The average value of total dissolved solids （TDS） was 90.9 mg·L-1, lower than the global mean value of the rivers. The average value of electrical conductivity and dissolved oxygen was 116.5 μS·cm-1 and 7.5 mg·L-1, respectively. Ca2＋ was the dominant cation, accounting for 47.9% of the total cations, whereas K＋ and Na＋ together accounted for 29.6% of the total cations. HCO3- and SO42- were main anions, which together accounted for 68.6% of the total anions. Those results suggested that the hydrogeochemical type of Jiulong River was HCO3SO4Ca. The forward method was used to estimate the contribution of each end member, the results of which showed that carbonate and chemical weathering of silicate contributed to 50.6% and 30.7% of the total cations, respectively. Precipitation had an obvious influence on the water chemistry, presenting a contribution of 12.9% to total cations. The influence of anthropogenic input could not be ignored, especially for the contents of SO42- and NO3-. The water chemistry of North River was heavily affected by industrial production due to the industrial and agricultural layout, while that of West River and South River were affected by agricultural activities. Therefore, the discharge of wastewater from industrial production as well as urban sewage should be strictly controlled in North River. In addition to urban sewage, the use of fertilizers also should be strictly controlled in West River and South River.