In this study, low-cost siderite was used to activate peroxydisulfate (PDS, S2O82-)-inactivated Enterococcus faecalis to study the inactivation characteristics and mechanism of siderite/PDS. The results showed that the siderite/PDS had a better inactivation effect on Enterococcus faecalis at pH 3. The sterilization effect increases with the increase of siderite dosage, PDS concentration and temperature. The inactivation rate is decreased with the increase of initial bacterial concentration. Inorganic ions and natural organic matter (NOM) can inhibit the inactivation effect of this technology, and the inhibition intensity is NOM > HCO3− > NO3−. The free radical quenching test shows that HO• is the main oxidizing substance in the sterilization process of siderite/PDS technology. In addition, the main disinfection mechanism is highly reactive oxygen species destroying the cell wall of bacteria and releasing organic compounds in cells. After siderite was reused for four times, simply washing siderite would recover almost 80% of the removal of Enterococcus faecalis in siderite/PDS, indicating that siderite has the potential of recycling.

The eutrophication of river-type urban landscape (RTUL) lakes is different from that of natural lakes. In this study, Xiaofu Lake, a typical RTUL lake with high anthropogenic interference, was used as the study area. Monitoring data from 2018 to 2020 were used to analyze the temporal and spatial distribution characteristics of chlorophyll a (Chl-a) concentrations with meteorological, hydrodynamic, and nutrient factors. Correlation and regression analyses were used to identify the relationship between the factors influencing eutrophication and the Chl-a. The MIKE21 model is used to simulate changes in water quality indicators. The study determined the relationship between river water quality and environmental factors and explored the causes of eutrophication in the water bodies of Xiaofu Lake. The results showed that from 2018 to 2020, the water quality showed seasonal variation and differences in spatial distribution. Except for total nitrogen, which remained at a high level (average 8.23 mg/L), other water qualities remained between classes II and IV. The proportions of mild, moderate, and severe eutrophication in the study area were 25%, 69%, and 6%, respectively. Indicators that were highly correlated with water eutrophication were turbidity, water temperature, total phosphorus, and permanganate index. The contribution of water temperature, ammonia nitrogen, and permanganate index to eutrophication was 30.5%, 22.6%, and 20.9%, respectively. The high proportion of sewage in the source of recharge water is one of the reasons for the deterioration of water quality. In addition, the change in water eutrophication was closely related to the gate operation in the region. Practitioner Points• There are differences between river-type urban landscape (RTUL) lakes and natural lakes, and the conditions that cause eutrophication are different.• RTUL are subject to strong human interference and rely on water transfer and gate scheduling to maintain water quantity.

In recent years, water crisis caused by human activities has attracted much more attention from the public, and the water security problem has become a hot spot in the world. In this paper, applying the theory of system dynamics, a system dynamic model for urban water cycle was developed to simulate the conversion and consumption processes of water resources between a regional social system and water system. To improve the guarantee capacity of water security, three types of industrial development patterns were designed. Moreover, an optimization model for water security regulation schemes was developed. Based on simulation of the key indexes on regional water security status, the value of water security degree was evaluated under different industrial development patterns, and the optimal scheme obtained according to these assessment results. Results from investigation and research in Zhengzhou City, China found that all seven regulation schemes could increase water security degree to different extents; and water security degree of the schemes with compound patterns was higher than the schemes with a single pattern. Scheme 7 was recommended as the ideal scheme for Zhengzhou City.

The complicated biogeochemical behavior of matters in the water environment caused by sluice scheduling result in the transformation of water quality to present the characteristics of multi-media, multi-phase and multi-form. Based on the complex reaction mechanism induced by sluice scheduling in water environment system, a mathematical expression describing the mass transfer process of water components between various phases was proposed, a multi-phase transformation model of water quality with certain physical mechanism was established, and the water quality concentration under different sluice scheduling situations were simulated. By comparing with the no sluice scenario, the water quality concentration change rate under different sluice scheduling situations was calculated; the role of sluice scheduling in the transformation process of water quality was quantitatively evaluated; the driving effect of sluice scheduling on various reaction mechanisms in water was analyzed; and the dominant driving mechanism was identified. This study found that the change in pollutant concentration was significantly affected by sluice scheduling. Furthermore, the water quality concentration change rate was inversely associated with the change in the gate opening height, and the water quality concentration change rate in dissolved phase was larger than that in other phases. The strength and weakness of different dominant reaction mechanisms changed alternately with a change in sluice scheduling. For Huaidian Sluice, when the gate was fully open at 18 holes and the opening was approximately 40 cm, the contribution ratio of each corresponding reaction mechanism in water quality transformation was approximately same, and the dominance was relatively balanced, which could effectively suppress an increase in the nitrogen content and reduce the risk of nitrogen pollution.

Landslide and debris flows are typically triggered by rainfall-related weather conditions, including short-duration storms and long-lasting rainfall. The critical precipitation of landslide and debris flow occurrence is different under various hydrometeorological conditions. In this study, the daily hydrological states were evaluated by the SWAT model, and the trigger sensitivities of different daily hydrological variables were assessed with 50 days recorded landslide and debris flows between 2010 and 2013.