不同地貌条件下景观对河流水质的影响差异

景观对河流水质的影响在不同地区、不同空间尺度上存在差异。以赤水河流域为研究对象,根据地貌特征将研究区分为喀斯特地貌和非喀斯特地貌,在划分的29个子流域内采集测试水质数据,所选用的水质指标有溶解氧(DO)、电导率(EC)、总氮(TN)和总磷(TP),运用空间分析及数理统计方法,分析流域内不同地貌区景观之间的差异,探究不同空间尺度上景观与水质指标之间的关系。结果表明:(1)流域内景观组成以林地和灌草为主,建设用地和耕地次之,景观组成在不同地貌区各空间尺度上存在差异。建设用地和耕地对水质具有负面影响,且在碳酸盐岩地区更显著;林地对水质具有正面影响;灌草对水质的影响相对复杂。(2)流域内水质表现为碳酸盐岩地区优于碎屑岩地区。景观破碎化指数与总氮(TN)、总磷(TP)呈正相关,是水质变化的重要影响因素;景观聚集度指数与溶解氧(DO)呈正相关;景观破碎化指数和景观聚集度指数与电导率(EC)的关系在两个地区呈相反的结果。(3)不同地貌区景观对河流水质具有不同程度的影响。在两个地区,景观组成对河流水质解释能力最大空间尺度均为河岸带尺度,解释率分别为53.4%和59.1%;景观格局对河流水质解释能力最大的空间尺度在碳酸盐岩地区为河岸带尺度,解释率为62.9%,在碎屑岩地区为圆形缓冲区尺度,解释率为82.4%。因此,在不同地貌区应采取不同的景观优化措施以减少对流域水质的污染。

Influences of landscape on river quality under different geomorphological conditions

The impact of landscape on river water quality varies in different regions and different spatial scales. This study was conducted along Chishui River Watershed. We divided the study area into Karst landform and Non-Karst. The basin was divided into 29 sub-watersheds, Water samples were collected for monitoring of water quality. Water variables include DO, EC, TN and TP. The choice of landscape indices was at three scales based on previous research. We used Fragstas 4.5 software to obtain landscape indices of each watershed, then performed a correlation analysis. The Spatial analysis and mathematical statistic methods were used to reveal the differences between landscapes under geomorphic regions in the basin, and explore the linkage between landscape and water quality in different spatial scales. The results show that:(1) The landscape composition in the basin is dominated by forest and shrub, followed by construction land and cultivated land. The Landscape composition has a difference in different spatial scales under different geomorphic regions. Construction land and cultivated land have negative impact on water quality, and the impact on water quality is more significant in carbonate rock areas. Forest has a positive impact on water quality. The impact of shrub on water quality is relatively complex. (2) Water quality in clastic rock area is better then that in carbonate rock area. The landscape fragmentation and TN, TP showed a positive correlations;The Landscape aggregation is positively correlated with DO;The relationship between landscape fragmentation and landscape aggregation and EC are opposite in both regions. (3) The Landscape in different geomorphic regions have different effects on river water quality. Landscape composition of riparian scale can well explain 53.4% and 59.1% of the variation of water quality respectively. Landscape pattern of riparian scale can explain 62.9% in carbonate rock area, and explain 82.4% in circular buffer in clastic rock area. Therefore, different landscape optimization measures should be taken in different geomorphic regions to reduce water pollution in Chishui River basin.