本文以位于平原河网区的常州市河流为研究对象，基于该区域土地利用遥感影像数据，以及河流水生态系统调查数据（59个采样点），在圆形缓冲区和汇水区两个空间尺度上，分析不同尺度常州市土地利用结构特征。采用WQI和ETI方法评价常州市河流水质状况。在上述分析的基础上，运用相关分析、冗余分析等方法分析土地利用组成和景观格局对河流水质的影响，得出如下研究结论：

（1）常州市土地利用以水域、水田和建设用地为主，三者约占总面积的79%。在100m-500m圆形缓冲区内，不同土地利用类型占比情况为：水域>建设用地>水田>林地>旱地>未利用地，在1000m后，水田、旱地和林地面积增加，在2000m圆形缓冲区和汇水区尺度上，土地利用类型的组成为：水田>水域>建设用地>林地>旱地>未利用地。

（2）景观指数在圆形缓冲区、汇水区尺度上呈现出不同特征。在圆形缓冲区尺度上，随着离岸距离的增加，景观的破碎度增加，景观多样性增加，斑块连通性增强，景观形状越复杂，优势类型的聚集度降低。汇水区的景观格局特点和1000-2000m的圆形缓冲区相似。

（3）常州市河流COD_MN、TP的平均浓度达到Ⅲ类水质标准，DO、NH₃-N的平均浓度均值达到Ⅳ类，TN的平均浓度达到Ⅴ类。主成分分析结果显示，第一主成分和TN、NH₃-N密切相关，表征营养盐污染，第二主成分与COD_MN和Chla有很强的正相关，表征工业废水引起的有机物污染。

（4）常州市河流水质WQI评估平均得分为53.2，EIT评估平均得分为0.53，两种评价结果均显示河流整体状况为一般。ETI的评价结果分布在优秀、良好、一般、差和极差5个等级上，WQI评估结果分布在良好、一般和差三个等级上。ETI评估结果主要受到TN、NH₃-N、EC、NO₃-N、TP、SS等水质指标影响，影响WQI评估结果的主要水质指标为EC、SS、NH₃-N、NO₃-N、SS、COD_MN（p<0.05）。WQI评估结果可与历史数据进行比较，可其可用于河流水环境改善效果的评价，ETI评估更能体现河流水质状况的区分度。

（5）建设用地、林地和水田是影响常州市河流水质的主要土地利用类型。建设用地与TP、TN、NO₃-N、SS呈较强的正相关，与DO呈负相关，林地与NH₃-N、NO₃-N、TN、EC、SS呈显著负相关，水田与COD_MN、Chla呈较强的负相关。土地利用景观指数和水质指标的相关性分析结果表明，SHDI与主要水质指标均呈显著负相关，ED、NP、PD、LSI与COD_MN、Chla呈显著正相关，AI、COHESION与TN、TP呈显著正相关。

（6）土地利用格局对河流水质的影响具有尺度效应，在100m宽度上，对河流水质产生重要影响的土地利用类型为水田和林地，在200-2000m宽度以及汇水区上为林地和建设用地。在100-2000m不同宽度圆形缓冲区，土地利用对河流水质的解释率在12%—17%之间，其中500米宽度圆形缓冲区土地利用对河流水质的解释率最高，达到了0.05显著性水平，说明近岸带500m内的土地利用是影响河流水质的“敏感带”。在汇水区尺度上，土地利用对河流水质的解释率为12%。从土地利用景观格局角度来看，在100-200m宽度上，景观指数对水质影响不显著，在500-2000m宽度上，对水质影响较大的景观指数为NP、PD和COHESION，在汇水区上为PD、AI和ED，不同宽度圆形缓冲区景观格局指数对河流水质的解释率在10.3%-17.5%之间，汇水区解释率为13.1%。

In this study, the Changzhou River was selected as a case to explore the the characteristics of land use structure at circular buffer and catchment scales based on remote sensing data and river water ecosystem survey data (59 sampling points) .WQI and ETI were applied to evaluate the water quality of Changzhou River. Based on the above analysis, the correlation analysis, redundancy analysis and other methods were used to analyze the impact of land use composition and landscape pattern on river water quality. Major results and conclusions are as follows:

(1) The land use of Changzhou was mainly water area, paddy field and urban, which account for 79% of the total area. In 100m-500m circular buffer , the proportion of different land use types was as follows: water area > urban > paddy field > forested land > dry land > unused land. After 1000m, the area of paddy field, dry land and forested land increased. On the scale of 2000m circular buffer and catchment, the composition of land use type was as follows: paddy field > water area > urban > forested land > dry land > unused land.

(2) The landscape index showed different characteristics on the scale of circular buffer and catchment. In the buffer of 500m width, the fragmentation of land use was higher, and then decreased with the increase of offshore distance. At the same time, with the increase of the width of the circular buffer , the diversity of landscape increased, the connectivity of patches increased,  the shape of landscape complicated, the aggregation of dominant types decreased. The landscape pattern of catchment was similar to that of circular buffer of 1000-2000m width.

(3) The average concentration of COD_MN and TP in Changzhou River reached Class III water quality standards, the average concentration of DO and NH3-N reached Class IV, and the average concentration of TN reached Class V. The principal component analysis results showed that the first principal component was closely related to TN and NH₃-N, which characterized nutrient pollution, and the second principal component had a strong positive correlation with COD_MN and Chla, which characterized the organic matter pollution caused by industrial wastewater.

(4) The average score of WQI assessment for river water quality in Changzhou was 53.2, and that of EIT was 0.53. Both evaluation results showed that the overall status of the river was fair. The evaluation results of ETI were distributed in five levels of excellent, good, fair, poor and very poor, and the results of WQI evaluation were distributed in three levels of good, fair and poor. ETI assessment results were mainly affected by water quality indicators such as TN, NH₃-N, EC, NO₃-N, TP, and SS. The main water quality indicators that affect WQI assessment results were EC, SS, NH₃-N, NO₃-N, SS, COD_MN ( p <0.05). The results of WQI assessment can be compared with historical data, which can be used to evaluate the improvement effect of river water environment. ETI assessment can better reflect the differentiation of river water quality status.

(5) Urban, forested land and paddy field are the main land use types that affect the water quality of Changzhou river. Urban has a strong positive correlation with TP, TN, NO₃-N and SS, a negative correlation with DO, forested land has a significant negative correlation with NH₃-N, NO₃-N, TN, EC and SS, paddy field has a strong negative correlation with COD_MN and Chla. SHDI was negatively correlated with main water quality indexes, ED, NP, PD, LSI was positively correlated with COD_MN and Chla, AI, COHESION was positively correlated with TN and TP.

(6) The impact of land use on river water quality had scale effects. On the 100m width, the land use types that had an important impact on the river water quality were paddy fields and forested land, and on the 200-2000m width and catchment scales were forested land and urban. On circular buffer with different widths of 100-2000m, the interpretation rate of land use for river water quality was between 12% and 17%, of which the 500m wide buffer had the highest interpretation rate for river water quality, reaching a significance level of 0.05, indicating that the land use within 500m of the coastal zone was a "sensitive zone" that affected the river water quality. On the catchment, the rate of land use interpretation of river water quality was 12%. From the perspective of land use landscape pattern, the landscape index had no significant effect on water quality in the width of 100-200m, and the landscape index that had the greatest impact on water quality in the width of 500-2000m were NP, PD and COHESION, and on the catchment were PD, AI and ED. The interpretation rate of the landscape pattern index of circular buffer with different widths was between 10.3% and 17.5%, and the interpretation rate of the catchment was 13.1%.