State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China; National Joint Research Center for Ecological Conservation and High Quality Development of the Yellow River Basin, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China; Northwest University College of Urban and Environmental Sciences, Northwest University, Xi'an, 710127, China.
State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China; National Joint Research Center for Ecological Conservation and High Quality Development of the Yellow River Basin, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China.
J Environ Manage. 2024 Dec;371:123232. doi: 10.1016/j.jenvman.2024.123232. Epub 2024 Nov 12.
Urbanization development often leads to significant changes in the extent in area and fragmentation of built-up land landscape pattern (BLLP) in river basins, which greatly impact the processes of rainfall runoff and pollutant migration. Understanding the spatial scale effects and driving mechanisms of BLLP changes on water quality in large river basins is a challenging research topic and an international frontier in the interdisciplinary fields of geography and environment. This study analyzes the spatial variations of BLLP and water quality throughout the Yellow River Basin (YRB) during the rainy seasons from 2019 to 2021 (4 h scale). Utilized the random forest model to quantitatively separates the contributions of rainfall processes to surface runoff and water pollution, revealing the scale effects and non-linear driving mechanisms of BLLP impacts on water environment changes. The results indicate that: 1) The YRB exhibits great spatial heterogeneity in terms of both BLLP and water quality, with places with lower water quality displaying bigger areas and higher degrees of BLLP fragmentation. 2) The patch density and built-up land area (PD.B and CA.B) have a major impact on changes in water quality in the YRB, with notable impacts noted in circular buffer zones with radii of 20 km and 5 km, respectively. 3) PD.B is sensitive to water quality in the YRB, explaining 39.1%-49.5% of the variance under different rainfall conditions, and exhibits a significant non-linear relationship, with an impact threshold of 0.38 (n/100 ha). The study suggests that for large-scale regions like the YRB, the degree of BLLP fragmentation is more likely to lead to degradation of water environmental quality compared to its area. BLLP fragmentation due to higher PD.B and CA.B disrupts the original ecosystem and hydrological connectivity, resulting in poorer retention and filtration of pollutants carried by rainfall runoff, while increasing the export of other pollutants. However, once urbanization surpasses a certain threshold, the BLLP fragmentation can enhance water quality by reducing the impermeable surface connectivity, as they are no longer impacted by expanding areas. To achieve ecologically sustainable development, it is necessary to apply rational landscape management and water resource management policies that consider the dual process of how BLLP fragmentation affects the water environment.
城市化发展常常导致流域范围内建设用地景观格局（BLLP）的面积和破碎度发生显著变化，从而极大地影响降雨径流和污染物迁移过程。理解大流域 BLLP 变化对水质的空间尺度效应和驱动机制是地理和环境等多学科交叉领域的一个具有挑战性的研究课题和国际前沿。本研究分析了 2019 年至 2021 年（4 小时尺度）雨季黄河流域（YRB）BLLP 和水质的空间变化。利用随机森林模型定量分离降雨过程对地表径流和水污染的贡献，揭示了 BLLP 对水环境变化影响的尺度效应和非线性驱动机制。结果表明：1）YRB 在 BLLP 和水质方面均表现出较大的空间异质性，水质较差的地区具有更大的面积和更高的 BLLP 破碎度。2）斑块密度和建设用地面积（PD.B 和 CA.B）对 YRB 水质变化有较大影响，在半径为 20km 和 5km 的圆形缓冲区中表现明显。3）PD.B 对 YRB 水质敏感，在不同降雨条件下解释了 39.1%-49.5%的方差，呈显著的非线性关系，其影响阈值为 0.38（n/100 ha）。研究表明，对于像 YRB 这样的大规模区域，BLLP 破碎度的程度比其面积更有可能导致水环境质量的退化。由于较高的 PD.B 和 CA.B 导致的 BLLP 破碎度破坏了原有的生态系统和水文连通性，导致降雨径流携带的污染物保留和过滤能力下降，而其他污染物的输出增加。然而，一旦城市化超过一定的阈值，BLLP 破碎度可以通过减少不透水面的连通性来提高水质，因为它们不再受到扩展区域的影响。为了实现生态可持续发展，有必要应用合理的景观管理和水资源管理政策，考虑 BLLP 破碎度如何影响水环境的双重过程。
