粤北岩溶区星子河流域水化学离子特征及其时空变化分析

Analysis of Hydrochemical Ion Characteristics and Their Temporal and Spatial Variations in the Karst Basin of the Xingzi River,North Guangdong Province

星子河流域位于粤西北典型岩溶区,岩溶地貌类型发育齐全。该流域是北江最大支流连江的上游源头,其水资源状况在粤西北和珠江三角洲核心区社会和经济发展中扮演着重要的角色。因此弄清楚其水质状况及其变化规律,非常必要而且具有重要的经济和社会意义。鉴于此,分冬夏季系统采集星子河流域水样进行分析和处理。结果表明:该流域Ca2+和HCO3-含量在水化学中占绝对优势,Ca2+占阳离子平均质量浓度70%以上,HCO3-占阴离子平均质量浓度的80%以上;其次是Mg2+和SO42-,分别约占阳离子和阴离子总量的12%和8%,属于软水和弱矿化度水;星子河流域水化学类型以碳酸盐岩石风化物质和蒸发岩溶解物质来源为主的HCO3--Ca2+、HCO3--Ca2+·Mg2+型,只有很少水样表现为HCO3-·SO42--Ca2+型;从Gibbs图的分析可知:星子河流域水化学组分主要来源于岩石风化,是岩石风化控制型,大气降水输入和蒸发-浓缩作用对该流域水化学离子的贡献有限;该流域水化学时间变化上表现出明显的降水稀释效应,大部分离子组分冬季含量高于夏季;相关分析表明星子河流域水化学空间变化特征明显,岩溶地质背景深刻的影响着其水文地球化学特征。

The Xingzi river basin is located in typical karst dominated regions in northwest of Guangdong, and its karstification is better developed, and karst types are better diverse. This basin is the source of upstream of Lianjiang river which is the largest tributary of Beijiang river, and its source of water conditions plays an important role for social and economic development in northwest of Guangdong but especially in the core area of Pearl River Delta. So understanding its water quality conditions and its variation discipline in this basin, is very necessary and has important economic and social significance. Therefore, we collected water samples systematically during summer and winter across the study basin and the samples were analyzed and processed in the laboratory and the field respectively. The result shows that： Ca2＋ and HCO3- were the dominant ions, accounted for over 70% and 80% of the total cations and anions concentration respectively; Followed by the Mg2＋ and SO4 2- , accounted for about 12% and 8% respectively. Based on the nature of the water, it is divided into soft water and weakly mineralized water. Its main chemical source is dominated by carbonate rock weathering materials and evaporation karst solution materials in this basin and the water chemical type is HCO3 -Ca2＋ , HCO3 -Ca2＋ .Mg2＋ type, but only a few water samples expressed as HCO3--Ca2＋ SO42 type. And from the Gibbs distribution pattern, we conclude that the major source of hydrochemistry ions is rock weathering, and the dissolution of carbonates may play an important role in controlling the chemical composition of river water, but atmospheric precipitation input and evaporation concentrated effect had the limited contribution in this area. The temporal variation showed obvious dilution effect of precipitation, and most of the hydrochemical ion component in winter has the higher concentration than in summer. Correlation analysis showed that the spatial variation has the significant features and obvious regularity. This study suggested that carbonate rocks as well as evaporites is the dominance controlling factor of the water chemical and karst geological background has deeply affected the hydro-geochemical types in Xingzi basin.