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流域水化学特征作为研究化学风化作用过程的主要手段,主要离子特性可以反映来源、风化速率以及对气候变化的影响[1-2],其时空变化能够反映一定的水文情势,对流经地区的环境具有指示意义。西南喀斯特地区地质岩性特殊、河流化学侵蚀较强,深入研究喀斯特地区河流水化学对该区域环境变化、离子地球化学关系有重要意义。
早期喀斯特地区河流水化学主要研究水化学类型和基础的物理化学特征(硬度、电导、总溶解质固体、pH值等)[3-4],随着研究的深入,水化学研究逐渐往离子组成及来源、演化过程、水质特征和人类活动影响方向转移[5-8]。目前研究河流水化学的方法[9-13]很多,其中Gibbs图法、三角图法、端元图法属于定性化描述;质量平衡法、同位素追踪法属于定量化方法;评价方法包括多元统计、描述性统计、因子分析、方差分析等,而综合运用各类方法进行水化学特征的研究较少。区域上,喀斯特地区河流水化学研究主要集中于大流域,相关学者对乌江[14]、三岔河[15]、桂江[16]、西江[17]等做了研究,而小流域和库区研究鲜为报道。内容上,喀斯特地区河流水化学主要研究水化学特征,而关于工农业化发展对上游流域水化学的影响并不深入。黔中水利枢纽工程建设、平寨水电站的开发,改变了天然水溶质的运移过程,厘清平寨水库水化学离子的运移规律,有助于库区水资源有效开发利用和保护。蒋翼等[18]对贵州省平寨水库库区的水化学特征进行了研究,但对于平寨水库上游的水化学定量分析不足。
本文根据黔中水利枢纽工程水源地平寨水库上游不同时期采样分析结果,研究库区和入库河流季节性水化学特征、主要离子浓度空间变化特征及成因,以期为深入认识库区水文特征、水资源合理开发和保护提供科学依据。
喀斯特地区河流水化学季节变化特征及成因分析——以平寨水库上游流域为例
Seasonal variation characteristics and causes of river water chemistry in Karst——Taking the area of Pingzhai Reservoir as an example
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摘要: 为探究平寨水库上游水化学沿程变化情况,采用因子分析、Piper三线图、Gibbs及离子关系对比等经典地质化学分析方法,分析平寨水库上游水化学变化特征及成因。结果表明,水化学类型主要为HCO3 - Ca型,沿程河段区-河库区-库区水化学呈现由SO4·Cl—Na·Ca·Mg型到HCO3·NO3 – Ca·Mg再到HCO3 - Ca·Mg型的演变特征。离子浓度季节变化明显,冬季高于夏季;空间上,除Na+和
${\rm{SO}}_4^{2-} $ 外,其余离子浓度整体表现为库区、河-库区大于各河段。Gibbs图表明水体水化学组成受岩石风化影响显著,离子关系对比图表明河段区水体受人为活动影响较强,因子分析结果表明研究区四季水化学组分主要受自然盐岩风化以及较小程度的人类源污染。Abstract: In order to explore the variation of water chemistry, the characteristics and causes of water chemistry variation were analyzed by some classical geochemical analysis methods (such as factor analysis, Piper, Gibbs and ion relation comparison) in the upstream of Pingzhai Reservoir. The results show that: 1) the hydrochemistry type is mainly HCO3 – Ca type. From the River to the River-Reservoir and then to the Reservoir, it presents the evolution characteristics from SO4·Cl-Na·Ca·Mg type to HCO3·NO3 - Ca·Mg type and then to HCO3 – Ca·Mg type. 2) The seasonal variation of ion concentration is obvious, and it in winter was higher than that in summer. Spatially, except for Na+ and${\rm{SO}}_4^{2-} $ , the overall ion concentration shows that the Reservoir and the River-Reservoir were larger than the River. 3) Analysis by Gibbs indicated that hydrochemistry characteristics in the study area is significantly affected by rock weathering. Ion relationship comparison chart shows that water bodies are strongly affected by human activities in River section. Factor analysis shows that the chemical components of the four season’s water are mainly affected by the natural weathering of salt rocks and a lesser extent of human sources.-
Key words:
- Karst /
- upstream of Pingzhai reservoir /
- chemical characteristics /
- land use /
- seasonal variation /
- factor analysis
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表 1 不同时期研究区水化学组分统计表
Table 1. Statistics of hydro-chemical parameters of water samples in different periods
时期
Time项目
ProjectWT pH DO EC Ca2+ Mg2+ Na++K+ ${\rm{HCO}}_3^{-} $ Cl− ${\rm{SO}}_4^{2-} $ ${\rm{NO}}_3^{-} $ Sr2+ SiO2 TDS 秋季
Autumn最小值 12.47 7.86 7.35 238.00 35.00 2.24 2.09 42.70 1.16 22.00 4.21 0.34 0.59 73.49 最大值 16.77 8.63 9.27 616.00 77.00 8.62 11.81 172.95 16.28 103.46 12.55 0.74 10.05 240.40 平均值 15.10 8.25 8.25 365.71 58.26 6.06 6.94 97.21 5.52 58.97 9.91 0.45 5.95 158.92 标准差 1.36 0.18 0.49 81.52 11.79 1.77 2.24 33.57 3.39 17.65 2.50 0.09 2.47 38.11 变异系数 9.01 2.18 5.94 22.29 20.24 29.21 32.28 34.53 61.41 29.93 25.23 20.00 41.51 23.98 冬季
Winter最小值 9.20 7.81 4.96 244.00 46.00 2.34 2.05 112.85 1.53 23.48 4.93 0.33 4.02 88.09 最大值 13.30 8.83 10.23 653.00 79.50 9.15 12.71 247.10 15.23 118.69 15.15 0.76 9.41 313.57 平均值 11.11 8.12 7.45 405.18 66.35 6.54 7.95 161.60 6.21 61.04 10.39 0.48 6.00 172.98 标准差 1.05 0.32 1.88 86.50 10.18 1.81 2.32 33.08 3.77 19.41 2.39 0.10 1.72 46.65 变异系数 9.45 3.94 25.23 21.35 15.34 27.68 29.18 20.47 60.71 31.80 23.00 20.83 28.67 26.97 春季
Spring最小值 10.83 8.02 7.92 248.00 47.00 2.04 1.96 125.05 1.15 21.89 3.90 0.30 2.01 84.02 最大值 18.05 8.84 11.43 600.00 78.50 8.22 11.95 210.45 14.78 96.78 16.93 0.78 9.01 201.17 平均值 13.16 8.46 9.72 394.59 67.74 5.99 8.13 164.34 5.77 56.19 10.15 0.47 4.81 162.00 标准差 1.80 0.21 1.08 79.54 9.57 1.72 2.51 25.47 3.57 15.43 2.81 0.11 2.67 29.57 变异系数 13.68 2.48 11.11 20.16 14.13 28.71 30.87 15.50 61.87 27.46 27.68 23.40 55.51 18.25 夏季
Summer最小值 16.77 7.74 7.03 204.00 40.50 1.71 1.40 82.35 1.22 21.68 3.46 0.26 0.82 74.31 最大值 27.17 9.03 10.17 378.00 68.50 6.76 12.16 164.70 14.90 108.80 17.20 0.55 8.52 220.08 平均值 22.34 8.43 8.44 307.35 50.74 5.00 6.14 111.77 7.45 60.86 9.50 0.36 4.36 146.97 标准差 3.19 0.39 1.09 43.85 8.04 1.55 2.85 20.684 4.16 18.72 2.97 0.06 3.19 33.14 变异系数 14.28 4.63 12.91 14.27 15.85 31.00 46.42 18.51 55.84 30.76 31.26 16.67 73.17 22.55 注:T单位为℃,电导率EC单位为μS/cm,pH为无量纲,变异系数为%,其余单位均为mg·L−1.
Note: Unit of T is ℃, EC is μS/cm, pH is dimensionless, coefficient of variation is %, and other units are mg·L−1.表 2 各季节水化学组分主成分分析
Table 2. Principal Component analysis of water chemical components in each season
项目
Project秋季 Autumn 冬季 Winter 春季 Spring 夏季 Summer 1 2 3 1 2 3 1 2 3 1 2 3 Ca2+ 0.81 0.10 −0.25 0.82 −0.44 −0.29 0.73 −0.39 −0.46 0.27 0.73 0.52 Mg2+ 0.87 −0.36 0.04 0.77 −0.54 0.23 0.79 −0.54 −0.02 0.76 0.18 −0.46 ${\rm{HCO}}_3^{-} $ 0.25 −0.65 0.53 0.77 0.56 −0.17 0.89 0.27 −0.18 −0.20 0.89 0.05 ${\rm{NO}}_3^{-} $ 0.63 0.09 −0.59 0.81 −0.05 −0.32 0.56 −0.24 0.55 0.59 0.68 −0.09 ${\rm{SO}}_4^{2-} $ 0.57 0.55 0.47 0.59 0.56 0.53 0.73 0.45 0.35 0.82 −0.21 0.46 Cl- 0.60 0.72 0.15 0.83 0.37 0.18 0.81 0.37 0.17 0.91 0.06 0.21 K+ 0.92 −0.33 −0.10 0.85 −0.43 0.07 0.73 −0.44 0.40 0.75 0.10 −0.62 Na+ 0.88 −0.42 −0.00 0.76 −0.44 0.31 0.92 −0.08 −0.02 0.82 −0.55 0.08 SiO2 −0.30 −0.17 0.76 −0.53 −0.02 0.77 −0.64 0.09 −0.72 −0.61 0.18 0.66 Sr2+ 0.16 0.79 0.21 0.17 0.87 −0.16 0.33 0.86 −0.14 0.33 −0.73 0.48 TDS 0.92 0.01 0.37 0.93 0.31 0.14 0.98 0.14 0.03 0.84 0.34 0.41 特征值 5.12 2.26 1.71 6.04 2.50 1.32 6.32 1.88 1.39 4.94 2.87 1.99 累计贡献/% 46.54 67.10 82.63 54.92 77.58 89.62 57.42 74.53 87.16 44.95 71.01 89.13 -
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