基于主成分分析的岩溶水水化学组成及影响因素研究--以贵州水城盆地为例

Hydrogeochemical characterization of groundwater and surface water and their influencing factors based on principal component analysis:An example in the Shuicheng basin of Guizhou

2015年9月对贵州水城盆地进行采样,共采集地下水样品12个,地表水样品10个,综合运用相关性分析、主成分分析等方法,并结合PHREEQC软件对矿物饱和度指数的计算结果,探讨了地下水、地表水水化学特征现状及其影响因素。研究结果表明:水城盆地岩溶水的水化学类型主要为HCO_3-Ca型,部分为SO_4-Ca型,地下水和地表水水化学组成主要受Ca^(2+)、K^++Na^+、HCO_3^-、SO_4^(2-)和Cl^-影响。研究区地下水和地表水中Ca^(2+)和HCO_3^-主要来源于碳酸盐岩地区的水-岩反应,水体中Cl^-、NO_3^-和Na^+主要来源于城镇生活污水、屠宰废水排放。地下水水质受水-岩反应影响,部分区域受到人类活动干扰明显;地表水水质在钟山区方向主要受沿途生活污水和农业面源污水汇入影响显著,而在水城县方向受煤矿企业排放废水影响较大。

As the major water resources for most of the settlements in karst regions, karst water could be more easily polluted in a shorter time by human activity than water in non-karst aquifers. Assessing current hydrochemical status and understanding the mineralization process in karst water are of significance to ana- lyze the influence factors from natural evolution and human activities. The Shuicheng basin, a tectonic basin with well-developed karst topography, is located at the center of the Yunnan-Guizhou Plateau, southwestern China. The NW-SE oriented basin is an area of approximately 22.5 km long, 5.5 km to 9 km wide and 208 km2 in size, with the elevation ranging from 1,700 m to 1,800 m above mean sea level. Climatically, it falls in the north subtropical monsoon zone with plentiful precipitation which is a major source recharging the karst water. Average annual precipitation in this area is 1,200 mm/year to 1,500 mm/year. Geologically, the basin predominantly consists of the Permian and Carboniferous carbonate rocks, accounting for nearly 90% of the total rock exposure. This work investigated the hydrogeoehemical characteristics and influence factors of groundwater and surface water in different regions of the Shuicheng basin, with the intension of providing references for help- ing to significantly improve the quality of the aquifer. Sampling campaigns were carried out in September 2015. Variable parameters of the sampled water were measured using a portable instrument and HCO3- was titrated with 0.01 mol/L HC1 in the field. All water samples were filtered through 0.45 μm cellulose acetate membrane filters and then collected into 50 mL high-density polyethylene bottles. The samples for cation a- nalysis were immediately acidified with pure HNO3 to a pH lower than 2. The cations and anions of the sam- ples were analyzed by the methods of atomic absorption spectrometry and ion chromatography, respectively, with the test accuracy of less than 5%. The interpretation of hydrochemical data was performed by using various methods, i.e. Piper diagram, correlation analysis, multivariate principal component analysis, and saturation mapping. The results show two hydrochemical types （HCO3- Ca and SO4- Ca） that characterize the groundwater and surface water. Natural dissolution of carbonate rock （water-rock interaction） is the primary source of Ca2＋ and HCO3- in groundwater and surface water. Domestic sewage and the wastewater from livestock and poultry industry may be the main contribution of Cl- ,NO3- and Na＋ to surface water. The main factor affecting on the quali- ty of groundwater is the water-rock reaction. The urban sewage water from Zhongshan district and coal in- dustrial wastewater from Shuicheng County and discharge from the groundwater are the main sources affect- ing the surface water quality of the basin. In conclusion, the evolution of water quality is determined by the lithology of the aquifer （dissolution and base exchanges） and by anthropogenic processes （urbanization, coal mining activities and agriculture）.