Microbial biomarkers as indication of dynamic and heterogeneous urban water environments

Water samples for the 16S rRNA gene and water quality analyses were collected from around 155 km of river segments surrounding the urban areas in Xi'an, China. Multiple statistical analyses showed that the dynamic shifts of microbial communities in the Chan, Ba, and Feng Rivers from the spring to the summer seasons were apparent but little in the Zao River. The heterogeneity of microbial distributions was more due to the influence of hydrologic conditions and various sources of inflows in the rivers. The LEfSe analysis showed that the Chan and Zao Rivers, both more impacted by the sewage effluents, were more differentially abundant with bacteria related to polluted water, but the Ba and Feng Rivers, both on the outer side of the city, were more abundant with microbial communities in soil and freshwater environments in the summer. Multiple statistical analyses indicated that environmental variables had significant impacts on microbial communities. The geographical information system-based spatial analysis showed heterogeneity of microbial community distributions along the rivers. This study showed that the high-throughput sequencing analysis could identify some pathogenic bacteria that would significantly threaten public health and eco-environments in urban rivers.

An integrated supervision framework to safeguard the urban river water quality supported by ICT and models

Models and information and communication technology (ICT) can assist in the effective supervision of urban receiving water bodies and drainage systems. Single model-based decision tools, e.g., water quality models and the pollution source identification (PSI) method, have been widely reported in this field. However, a systematic pathway for environmental decision support system (EDSS) construction by integrating advanced single techniques has rarely been reported, impeding engineering applications. This paper presents an integrated supervision framework (UrbanWQEWIS) involving monitoring-early warning-source identification-emergency disposal to safeguard the urban water quality, where the data, model, equipment and knowledge are smoothly and logically linked. The generic architecture, all-in-one equipment and three key model components are introduced. A pilot EDSS is developed and deployed in the Maozhou River, China, with the assistance of environmental Internet of Things (IoT) technology. These key model components are successfully validated via in situ monitoring data and dye tracing experiments. In particular, fluorescence fingerprint-based qualitative PSI and Bayesian-based quantitative PSI methods are effectively coupled, which can largely reduce system costs and enhance flexibility. The presented supervision framework delivers a state-of-the-art management tool in the digital water era. The proposed technical pathway of EDSS development provides a valuable reference for other regions.

The atmospheric microplastics deposition contributes to microplastic pollution in urban waters

Identifying and understanding the potential sources delivering microplastics into the urban water environment is imperative for microplastic pollution control. However, how atmospheric deposition contributes to microplastic pollution in the urban water environment is unclear. Therefore, this study investigated the contribution of atmospheric deposition to microplastic pollution in urban waters based on the analysis of the atmospheric deposition characteristics in the urban area. The results showed that microplastic deposition fluxes during wet weather and dry weather varied from 1.1 × 10³±0.06×10³ to 3.5 × 10³±0.3 × 10³ particles/m²/day and 0.91×10³±0.09×10³ to 1.6 × 10³±0.1 × 10³ particles/m²/day, respectively. The microplastics deposition flux showed moderate to strong correlations to atmospheric particulate matter concentrations, especially the PM2.5 concentration (R² = 0.76-0.93), suggesting the regularly monitored PM2.5 concentration might be served as an indicator for microplastics deposition flux estimation. The deposited microplastics were mainly transparent fragments with an average size of 51-67 μm. Polyethylene and polypropylene were the most abundant plastic polymer, followed by polyethylene terephthalate and polyamide. The comparison of microplastics collected during different weather conditions suggested that rain events could increase microplastics deposition fluxes when air quality conditions are similar. Particularly, rains promoted the deposition of fibrous microplastics as well as smaller microplastics. The estimated daily microplastics deposition in the whole city region suggested more microplastics were deposited in summer and winter. The total quantity of microplastics deposited in the urban environment could reach 1.7-12 times of those discharged from treated wastewater. Among them, 10% would directly deposit to urban waters in the studied city region, while the others may also enter the urban waters through runoff. The results of this study highlighted that the atmospheric microplastics deposition is an important source for microplastics, especially smaller ones, to enter the urban waters, which could not be ignored during microplastics pollution control.

Exploring sustainable solutions for the water environment in Chinese and Southeast Asian cities

Water is essential for human activities and economic development, and the water environment significantly influences ecological balance and global climate. China and Southeast Asia are the most populous areas in the world, and their water resources are deteriorating day by day. We focus on five representative cities such as, Beijing, Jakarta, Hanoi, Kathmandu and Manila to investigate water-environmental problems with the ultimate goal of providing recommendations for sustainable urban water management. The study found that (1) the water environment of all cities has been polluted to varying levels, while the pollution has improved in Beijing and Jakarta, and the situation in other regions is severe. (2) The aquatic biodiversity has reduced, and its pollution is mainly caused by organic pollutants and decreasing river flow. In addition, numerous people live in megacities without access to clean surface water or piped drinking water, which greatly increases the use of groundwater. Further, frequent floods in the world leads to serious damage to urban infrastructure and further deterioration of water environment quality. To address these problems, countries and organizations have begun to construct wastewater treatment plants and develop water-saving technology to ensure healthy and sustainable development of water environment. The results and practical recommendations of this study can provide scientific insights for future research and management strategies to address water quality challenges during ongoing policy debates and decision-making processes.