Bacteria biodegradation of immiscible oil requires cell-droplet encounters, surface attachment, and hydrocarbon metabolism. Chemical dispersants are applied to oil spills to reduce the mean dispersed droplet size, thereby increasing the available surface area for attachment, in attempts to facilitate bacterial biodegradation. However, their effectiveness remains contentious as studies have shown that dispersants can inhibit, enhance, or have no effect on biodegradation. Therefore, questions remain on whether dispersants affect surface attachment or cell viability. Here, using microfluidics and time-lapse microscopy, we directly observe the attachment and growth of the marine bacterium, Alcanivorax borkumensis, on stationary crude oil droplets (5 μm <R < 150 μm) in the presence of Corexit 9500. We show that the average colonization time, or the time comprised of encounters, attachment, and growth, is dependent on droplet size and primarily driven by diffusive encounters. Our results suggest that dispersants do not inhibit or enhance these biophysical processes.

The ubiquitous presence of microplastics (MPs) and trace elements in the marine environment is regarded as a global threat to marine organisms. The current study aims to assess MP levels and trace element (Cu, Zn, Cd, Pb, Se, and Fe) accumulation in the shellfish Arca noae collected from five locations along the southeastern Mediterranean coasts, Alexandria, Egypt. The frequency of the occurrence of ingested MPs in A. noae soft tissues was 48%, whereas the abundance of MPs was 1.65 ± 0.28 MP/individual and 0.58 ± 0.04 items g¹ of the wet weight of tissue. Polyethylene was the most abundant polymer in A. noae, followed by polypropylene and polystyrene. The concentration levels of Zn, Cd, and Pb detected in the soft tissues of A. noae are higher than the maximum permissible limits. This study provides baseline data for further environmental assessments, with the use of A. noae as an early warning indicator in biomonitoring programs.

Quantification of four toxic metals (As, Cr, Cd, and Pb) in water and sediments at the Sitakunda ship breaking area in Bangladesh was studied. Along with this, sediment quality and ecological risk were evaluated for the metal intrusion to the study area. A total sample number of 120 (water; n = 60 and sediment; n = 60) were analyzed for both winter and summer seasons using atomic absorption spectrophotometer (AAS). The trace metal concentration in both water and sediment showed decreasing trend as follows; Cr (mean-W: 0.118 mg/L; mean-S:121.87 mg/kg) > Pb (mean-W: 0.064 mg/L; mean-S: 65.31 mg/kg) > As (mean-W: 0.03 mg/L; mean-S: 32.53 mg/kg) > Cd (mean-W: 0.004 mg/L; mean-S: 4.81 mg/kg). However, in both segments, the concentrations of the toxic metals exceeded the recommended acceptable limits. As and Cd showed significant variation (water and sediment) between the seasons, while Pb and Cr had no seasonal impact. Metal pollution index (MPI) and contamination factor (CF) was evaluated and revealed that the study area exhibited the critical score of water quality (MPI > 100). The cumulative effect of the metal concentrations was high (CI > 3). The assessed mean geoaccumulaiton index (Igₑₒ) revealed that the study area was moderate to strongly polluted except for Cr. According to the contamination factor (CF), the sediment samples were moderate to highly contaminated by Cd, Pb, and As. Moreover, the explored range of pollution load index (PLI) in all sampling sites in the ship breaking region was from 1.75 to 3.10, suggesting that the sediment in the study area was highly polluted by heavy metals (PLI > 1). The risk index and the potential ecological risk index (PERI) suggested that the study area was at high risk due to metals pollution. Therefore, it is obligatory to maintain some crucial efforts for the betterment of the surrounding environment near the investigated sites.

Laizhou Bay is plagued by many environmental problems (e.g., acidification and eutrophication) that are likely to increase in the coming decades along with social and demographic trends. We thus conducted 12 cruises from July 2019 to December 2021 in the Laizhou Bay to evaluate the potential influences of human activities on its eutrophication status. The results showed that the parameters of dissolved inorganic nitrogen (DIN) and oxygen (DO) exceeded the water quality standard in some cases during the past 3 years, suggesting DIN and DO were the crucial factors controlling water quality in the bay. Meanwhile, DIN was identified as a major pollutant in the region, and played an important role in driving the phytoplankton dynamics. Furthermore, with the increases in human-related nutrient inputs (especially DIN), the bay environment reached the mild eutrophication level and was probably at risk from excessive nutrient loads at present, further evidencing the ecosystem degradation.

Large amounts of Gd-based contrast agents are used in magnetic resonance imaging (MRI) that are then excreted in urine. These agents are subsequently discharged into the environment because they are difficult to remove by usual sewage treatment techniques. In this study, changes of the Gd anomaly during wastewater treatment processes were determined by analyzing wastewater samples and the possibility for future prediction of the changes was evaluated based on the relationship between the Gd anomaly and the number of MRI devices in use. After the wastewater treatment processes, the values of final effluent were increased 1.8 times compared to those of influent, and the Gd anomaly of effluent had a positive correlation to the number of MRI devices. The finding suggested that the changes of environmental impact were predictable based on the number of MRI devices.

PM₂.₅ is one of the major air pollutants in port cities of the Yangtze River Delta (YRD) of China. Understanding the driving factors of PM₂.₅ is essential to guide air pollution prevention and control. We selected 17 major port cities in YRD to study the driving factors of PM₂.₅ in 2019 and 2020. Generalized Additive Models were built to model the non-linear effects of single, multiple and interactions of driving factors on the variations of PM₂.₅. NO₂, SO₂ and the day of year are most strongly associated with the variation of PM₂.₅ concentration when used alone. Anthropogenic emissions play complicated roles in regulating PM₂.₅ concentration. Although the effect of cargo throughput (CT) on PM₂.₅ concentration is non-monotonic, higher PM₂.₅ levels are found to be associated with higher levels of SO₂ and CT. This work can potentially provide a scientific basis for formulating PM₂.₅ prevention and control policies in the region.

PURPOSE OF REVIEW: The utilization of attached microalgae and bacteria to degrade wastewater has become a more promising treatment process to replace traditional methods. That is because the algae-bacteria biofilm can not only remove nutrients from the water but also achieve the effect of carbon fixation. Besides, the attached microalgae are easy to harvest and can be used for the processing of high value-added products. This paper reviews the knowledge of microalgae biofilm combined with bacteria to treat wastewater and provides insights into the bioremediation of the ecosystem by algae and bacteria. RECENT FINDINGS: Due to the photosynthesis of algae and the oxidative decomposition of bacteria, the symbiotic system of algae biofilm and bacteria from wastewater has significant advantages in harvesting and degradation. To further improve wastewater utilization efficiency and carbon fixation, it is necessary to understand the algae-bacteria symbiotic system of mechanism and influencing factors of nitrogen and phosphorus removal and carbon fixation. The photobioreactor for microalgae cultivation is gradually developed and optimized, laying a solid foundation for actual production and application. The algae-bacteria symbiotic system is more effective compared to individual microalgae treatment since the algae-bacteria biofilm has better removal efficiency and adsorption capacity as well as easy to harvest. This article introduces the mechanism and influencing factors of the algae-bacteria symbiotic system to remove nutrients and organic pollutants from water in detail. Furthermore, the research progress of photobioreactors is summarized as well. Finally, the application prospect of microalgae biofilm in wastewater treatment was prospected.

Bioelectrochemical system (BES) is an emerging technology for wastewater treatment. The urgent requirement for dealing with water shortage, wastewater treatment and reuse, energy generation, and resources recovery has promoted intensive research in BES during the last decade. This review summarizes the latest typical BES configurations based on specific functions, including microbial fuel cells (MFC), microbial electrolysis cells (MEC), microbial electrosynthesis systems (MSS), microbial desalination cells (MDC), microbial recycling cells (MRC), microbial solar cells (MSC), and microbial electrochemical snorkel (MES). The removal of contaminants, particularly emerging organic, non-metallic, metallic, and metalloid contaminants, and the recovery of resources in the form of bioenergy, biofuel, nutrients, metals, and metalloids in wastewater treatment using BES technology have been reviewed in this work. Limitations of BES technology in terms of reactor performance, scale-up, and construction costs for real-world wastewater treatment applications are discussed and future research directions needed for the successful deployment of BES technology are proposed.

This study helps understand the ballast water-mediated species spread risk dynamics in the Mediterranean and examine potential policy options for ballast water management to further reduce species spread risk in the region. Results show that Gibraltar, Suez, and Istanbul remained high-risk ports from 2012 to 2018, and they are hub ports connecting several clusters. We reveal ballast water management implications for both the Mediterranean region and individual hub ports respectively. To further reduce the risks of individual Mediterranean hub ports beyond the IMO standards, the most effective (cost-effective) regulatory method is to set more stringent regulation towards such hub ports besides the IMO regulation. To further reduce the risks of the Mediterranean as a whole, the most effective (cost-effective) regulatory scenario is to set more stringent regulation towards all Mediterranean ports besides the IMO regulation. The barge-based method is the most cost-effective technology to achieve stricter regulations.