Further understanding the mechanisms of landscape–water interactions is of great importance to water quality management in the Xitiaoxi catchment. Pearson's correlation analysis, stepwise multiple regression and redundancy analysis were adopted in this study to investigate the relation between water quality and landscape at the sub-catchment and 200 m riparian zone scales during dry and wet seasons. Landscape was characterized by natural environmental factors, land use patterns and four selected landscape configuration metrics. The obtained results indicated that land use categories of urban and forest were dominant landscape attributes, which influenced water quality. Natural environment and landscape configuration were overwhelmed due to land management activities and hydrologic conditions. In general, the landscape of the 200 m riparian zone appeared to have slightly greater influence on water than did the sub-catchment, and water quality was slightly better explained by all landscape attributes in the wet season than in the dry season. The results suggested that management efforts aimed at maintaining and restoring river water quality should currently focus on the protection of riparian zones and the development of an updated long-term continuous data set and higher resolution digital maps to discuss the minimum width of the riparian zone necessary to protect water quality.

The order and connectivity of streams influence phosphorus distribution extensively. In this work, the space-and-time variabilities of total phosphorus (TP), particulate phosphorus (PP), total dissolved phosphorus (TDP), dissolved reactive phosphorus (DRP), and dissolved unreactive phosphorus (DUP) in streams of three orders (Ⅰ, Ⅱ, III) were analyzed during each spring of 2016-2018 in a plain river network area, China. The results show that: ① PP was the main form of TP and DRP was the main form of TDP. ② The average concentrations of phosphorus in the order Ⅰ streams were significant larger than those in the order III streams. ③ The concentrations of TP, PP, TDP, and DRP in the poor-connected streams were considerably higher than those in the well-connected streams. Therefore, it is essential to implement effective practices to improve the protection and appropriate connectivity of small streams in plain river network areas.

This study aimed to investigate the effects of HDPE and Cd on forms of carbon (C) and nitrogen (N) by measuring the changes in enzymatic activities and physicochemical properties of Spartina alterniflora soil samples from coastal regions of China. Over three incubation periods (14, 28, and 56 days), a soil incubation experiment was conducted to investigate the effects of HDPE (0, 0.5, 1, and 2 g per 100 g of soil) and Cd (0, 2, 4, and 8 mg kg⁻¹) on soil physicochemical properties. The results demonstrated that the sole presence of HDPE had a notable impact on enhancing the C-related physicochemical properties of the soil, particularly by elevating the concentration of Total Organic Carbon (TOC). The sole addition of Cd significantly suppressed enzymic activities in the soil, leading to a considerable reduction in the concentration of NH₄⁺-N and NO₃⁻-N. Under identical Cd treatment conditions, the introduction of 1 g HDPE led to an increase in the concentration of TOC, and the inhibitory effect of Cd on enzymic activities was decreased; thus, an elevated consumption of soluble organic carbon (DOC) was identified. However, upon adding 2 g of HDPE, while the TOC concentration continued to rise, the stimulatory effect on enzymic activities diminished. In conclusion, the addition of HDPE inhibits, to a certain extent, the influence of Cd on the carbon and nitrogen cycling in soil.

Urban landscape waters (ULWs) are important components of ecological city; however, eutrophication has become increasingly serious. In Yancheng city, an eco-civilized city, the spatiotemporal characteristics of water quality indexes and the eutrophication degree were evaluated in Julong lake (JL) artificial ecological restoration and campus natural landscape (YCIT) waters. Since ecological restoration in 2016, the seasonal average concentrations of N, P in JL waters have been significantly decreased by more than 70%, satisfying the standards for water quality with light eutrophication. Conversely, the European Flower Street (EFS) and YCIT waters were hyper eutrophic, severely exceeding the Grade V water quality standard. The spatial distribution of ULWs quality deterioration in the plain area indicated that the human activities and endogenous pollutions contributed to ULWs eutrophication because of sluices controlling and low flow rate. This study provided a scientific basis for controlling the ULWs eutrophication via integrated eco-remediation technology in plain cities.