湖北丹江口水库主要离子化学季节变化及离子来源分析

Seasonal Variation in the Major Ion Chemistry and Their Sources in the Hubei Danjiangkou Reservoir,China

2004--2006年对丹江口水库中的5个点位水质的t、pH、EC、TDS、ORP、SO4^2-、Cl^-、NO3^-、HCO3^-、Ca^2＋、Mg^2＋、Na^＋、K^＋和Si进行了测定.综合运用方差分析及主成分分析对它们的季节变化及其来源进行了研究.结果表明,丹江口库区水体呈弱碱性,属于弱矿化度水,水质类型为HCO3--Ca型水.主要阴、阳离子浓度范围为：Cl^-,（4.0±0.5--6.9±1.8）mg.L^-1;NO3^-,（4.6±0.9--6.8±1.7）mg.L^-1;SO4^2-,（24.3±2.7--35.4±6.9）mg.L^-1;HCO3^-,（133.0±11.7--153.5±29.6）mg.L^-1;Na^＋,（2.0±0.3--5.3±1.0）mg.L^-1;K＋,（0.7±0.09--1.6±0.7）mg.L^-1;Ca^2＋,（33.0±2.1--46.6±0.8）mg.L^-1;Mg^2＋,（8.0±2.5--10.5±3.2）mg.L^-1.方差分析显示除HCO3-和Si外,t、pH、EC、TDS、ORP、SO4^2-、Cl^-、NO3^-、Na^＋、K^＋、Ca^2＋、Mg^2＋都表现出了显著的季节性差异,主要离子化学汛期浓度均小于对应的非汛期浓度.Na^＋和Mg^2＋的浓度只表现出秋汛〈秋季,NO3^-和SO4^2-浓度却呈现出秋汛〉秋季,这主要归因于降雨的大气沉降对水化学的贡献不同.HCO3-占主要阴离子的75%--88%,Ca^2＋和碱土金属分别占主要阳离子的60%--80%和87%--96%,表明碳酸盐岩风化是水体质子的主要来源及主要化学风化类型.参照我国及世界卫生组织饮用水标准,主要离子的浓度并未对人体产生危害.

Water temperature, pH, EC, TDS, ORP, Si and major anions （Cl^- , NO; and SO4^2- ） and major cations （Na^＋ , K^＋ , Ca^2＋ and Mg^2＋ ） in the Danjiangkou Reservoir, the water source area of the Middle Route of the South to North Water Transfer Project of China were monitored during the period of 2004-2006. Analysis of variance （ANOVA） and principal component analysis （PCA） were performed to explore their seasonal variations and origins. The results show that the water is slightly alkaline with an average pH ranging from 7.9 to 8.4. The water is HCO3^- -Ca type with low mineralized degree, and its total dissolved solid ranges from 174.6-209.1 mg. L^-1 . The major ions range are as follows： Cl^- , from （4.0±0.5） mg.L^-1 to （6.9± 1.8） mg.L^-1; NO3^- , from （4.6±0.9） mg.L^-1 to （6.8＋ 1.7） tug.L^-1 ; SO4^2- , from （24.3± 2.7） mg.L^-1 to （35.4± 6.9） mg.L^-1; HCO3^- , from （133.0± 11.7） mg.L^-1 to （153.5± 29.6） mg.L^-1; Na^＋ , from （2.0± 0.3） mg.L^-1 to （5.3±1.0） mg.L^-1; K^＋ , from （0.7±0.09） mg.L^-1 to （1.6±0.7）mg.L^-1; Ca^2＋ , from （33.0±2.1） mg.L^-1 to （46.6 ± 0.8）mg.L^-1 ; Mg^2 ＋ , from （ 8.0 ± 2.5 ） mg.L^-1 to （ 10.5 ± 3.2） mg.L^-1. Statistical analyses indicate that the water quality variables display significant seasonal differences except HCO3 and Si. In general, major ion concentrations in flood season are relatively lower due to the dilution of precipitation. HCO3^- accounts for 75%-88% of the total major anions, while Ca^2＋ and alkali-earth metals （Ca^2＋ ＋ Mg^2＋） account for 60%-80% and 87%-96% of the total major cations respectively, reflecting that carbonic acid weathering is the main proton producer in the water. The major ions have no adverse effects on human according to water drinking quality guidelines of China and WHO.