秦岭火地塘森林水质的季节性变化特征

在秦岭火地塘林区选择2个闭合小流域及2个支沟集水区,对流域出口径流及支沟集水区溪流水pH值及水化学成分进行了8 a的测试,采用机理分析方法,就森林水质的季节性变化特征进行了研究.结果表明,林区径流pH值在7.1～8.4之间,冬、春季较高,夏、秋季较低,总体上水呈弱碱性;NO-3浓度春季和初夏较高,NH 4冬季和初春较高,PO3-4冬季与夏季较高;K 浓度春、秋季较高,Na 浓度则9月最大,8月最小;Ca2 浓度以6月和10月较高,年内变化范围19.4～44.3 mg·L-1,Mg2 则3月较高,年内变化范围2.18～5.25 mg·L-1;Cd浓度随季节的变化以1～4月较高,Pb浓度12、1月较高,但Cd、Pb均以秋季较低,年内变化范围分别为0.019～0.326 5 μg稬-1和0.217～3.886 μh稬-1;Mn浓度5、12月较高,Fe浓度春季较高,Zn则以3、8月较高.林区径流水质属Ⅰ类,相对而言,水质随季节的变化以秋季较好,冬、春季较差.

Seasonal Water Quality Changes in the Huoditang Forest Region of the Qinling Mountain Range

This study was conducted in the Huoditang forest region of Shaanxi Province. The region is located in the Qinling Mountain range. We collected stream water samples at the outlets of two small watersheds and two tributaries each month across an eight year period. The samples were analyzed for pH and water chemistry. Changes in pH and water chemistry with season were studied by using contributing factor analyses. The results of the study showed that stream water was slightly alkaline, with the pH ranging from 7.1 to 8.4 throughout the year. Stream water pH was higher in winter and spring and lower in summer and autumn. The NO3- concentrations in stream water were highest in spring and early summer, while NH4+ concentrations were highest in winter and early spring, and PO4(3-) concentrations were highest in winter and summer. K+ concentrations were highest in spring. Na+ concentrations were highest in September and lowest in August. Ca2+ concentrations in stream water were highest in June and September and ranged from 19.4 mg x L(-1) to 44.3 mg x L(-1) during the year. Mg2+ concentrations were highest in March and ranged from 2.18 mg x L(-1) to 5.25 mg x L(-1) during the year. Cd concentrations were highest from January to April, while Pb concentrations were highest in November and January. The concentration of both Cd and Pb was lowest in autumn. The concentration of Cd ranged from 0.019 microg x L(-1) to 0.3265 microg x L(-1) and the concentration of Pb ranged from 0.217 microg x L(-1) to 3.886 microg x L(-1). Mn concentrations were highest in May and December, while Fe concentrations were highest in spring and Zn concentrations were highest in March and August. According to environmental quality standards for surface water, stream water quality in the Huoditang forest region met the requirements for water quality standard I. Water quality was best in autumn and poorest in winter and spring.