不同空间尺度土地利用方式对开都河水质的影响

Effects of land use patterns at different spatial scales on water quality of Kaidu River

为探究开都河不同尺度土地利用方式对水质的影响,于2021年6月和10月对开都河的15个样点进行取样,测定TDS、TN、TP和COD 4个水质指标。结合2020年的土地利用数据,提取以水质采样点为圆心建立的100、200、500、800、1 000 m缓冲区内的土地利用,运用冗余分析(RDA)、相关性分析、线性回归模型揭示不同尺度土地利用方式对水质的影响。结果表明:开都河水质整体处于Ⅱ类水标准,主要潜在污染物为TN和TP,污染来自农业退水和放牧;RDA分析发现缓冲区尺度土地利用方式对水质指标的解释度在500 m范围内最大。丰水期,TDS、TP、TN、COD与水域和耕地呈正相关,与裸地、草地呈负相关。平水期,TP、TDS、TN与草地呈正相关,与水域和裸地表现为负相关,而COD与耕地呈正相关,与裸地、水域和草地呈负相关;不同空间尺度土地利用方式与水质指标的相关关系不同,丰水期,TN在500~1 000 m缓冲区范围内与草地呈显著负相关。平水期,COD在1 000 m缓冲区内与草地呈显著负相关。丰水期和平水期,TN、COD在100~1 000 m缓冲区范围内与耕地呈显著正相关;土地利用方式对水质的影响具有尺度效应,且对水质影响最大的是耕地面积占比,其次为草地。

To investigate the effects of land use of different scales practices on water quality in the Kaidu River,water samples were obtained from 15 sample sites in the Kaidu River in June and October 2021.Four water quality indicators,TDS,TN,TP,COD,were tested.With these test results and the data of land use in 2020,which is about the land use of buffer zones of 0 m to 100 m,100 m to 200 m,200 m to 500 m,500m to 800 m,and 800 m to 1000 m created around from sample-taking sites,the redundancy analysis(RDA),correlation analysis and linear regression model were applied to reveal the influence of land use patterns of different scales on water quality.The results showed that the overall water quality of Kaidu River fallen into the category of Class II water standard,with TN and TP as its main potential pollutants,and agricultural waste water and grazing as its main source of pollution.RDA analysis finds buffer zones within 500 m has the largest the degree of explanation in the scale of land use pattern on water quality indexes.During water abundant seasons,TDS,TP,TN and COD were positively correlated with watershed and cropland,and negatively correlated with bare land and grassland;during normal water seasons,TP,TDS,TN were positively correlated with grassland,and negatively correlated with watershed and bare land,while COD was positively correlated with cropland and negatively correlated with bare land,watershed and grassland.The correlation between land use of different spatial scales and their water quality indexes was also different.During water abundant seasons,TN was significantly negatively correlated with grassland within buffer zone of 500~1000 m;during normal water seasons,COD was negatively correlated with grassland within the 1000 m buffer zone.During water abundant seasons and normal water seasons,TN and COD were significantly and positively correlated with cropland within buffer zone of 100~1000 m.The influence of land use pattern on water quality had a scaled effect,and the largest influence on water quality was the proportion of cropland area,followed by grassland.