Microplastics are emerging contaminants ubiquitously distributed in the environment, with rivers acting as their main mode of transport in surface freshwater systems. However, the relative importance of hydrologic processes and source-related variables for benthic microplastic distribution in river sediments is not well understood. We therefore sampled and characterized microplastics in river sediments across the Meramec River watershed (eastern Missouri, United States) and applied a hydrologic modeling approach to estimate the relative importance of river discharge, river sediment load, land cover, and point source pollution sites to understand how these environmental factors affect microplastic distribution in benthic sediments. We found that the best model for the Meramec River watershed includes both source-related variables (land cover and point sources) but excludes both hydrologic transport-related variables (discharge and sediment load). Prior work has drawn similar and dissimilar conclusions regarding the importance of anthropogenic versus hydrologic variables in microplastic distribution, though we acknowledge that comparisons are limited by methodological differences. Nevertheless, our findings highlight the complexity of microplastic pollution in freshwater systems. While generating a universal predictive model might be challenging to achieve, our study demonstrates the potential of using a modeling approach to determine the controlling factors for benthic microplastic distribution in fluvial systems.

Simulation model is very essential for predicting the environmental fate and the potential environmental consequences of chemical pollutants including those from accidental chemical spills. However very few of such simulation model is seen related to Chinese costal water body. As the first step toward our final goal to develop a simulation model for the prediction and the risk assessment of chemical pollutants in Chinese coastal water, this study developed a three-dimensional (3D) hydrodynamic model of Xiamen Bay (XMB). This hydrodynamic model was externally derived by meteorological data, river discharge and boundary conditions of XMB. We used the model to calculate the physical factors, especially water temperature, salinity and flow field, from June to September 2016 in XMB. The results demonstrated a good match between observations and simulations, which underscores the feasibility of this model in predicting the spatial-temporal concentration of chemical pollutants in the coastal water of XMB. Longitudinal salinity distributions and the mixing profile of river-sea interactions are discussed, including the obvious gradation of salinity from the river towards sea sites shown by the model. We further assumed that 1000 kg and 1000 mg/L of a virtual chemical pollutant leaked out from Jiulong River (JR) estuary (point source) and whole XMB (non-point source), respectively. The model illustrates that it takes three months for XMB to become purified when point source pollution occurs in the estuary, while half a year to be required in the case of non-point source pollution across the entire bay. Moreover, the model indicated that pollutants can easily accumulate in the western coastal zone and narrow waters like Maluan Bay, which can guide environmental protection strategies.

Polycyclic Aromatic Hydrocarbons are strongly associated with agricultural, residential, transportation, and industrial activities. This study determined by GC-MS the concentration of 15 PAHs in soil and sediments at different sites from the Awotan-Asunle dumpsite area in the Southwestern region of Nigeria, which is one of the largest dumpsites in Africa. The sources of contamination, toxicity and associated risks for human health were also evaluated. Total PAHs concentrations were from 489 to 5616 μg kg⁻¹, and 642–2159 μg kg⁻¹, for soil and sediment, respectively. For soils, the highest values were observed for indeno[1,2,3-c,d]pyrene, coronene, and phenanthrene, while for sediments, the most abundant species were pyrene, fluoranthene and phenanthrene. Diagnostic ratios were used to determine the sources of PAHs and suggested that the compounds were mainly emitted from non-traffic sources. The total BaP-TEQ and BaP-MEQ for soils did not exceed the value recommended by the Canadian guideline since the country does not present guidelines. The analysis of incremental lifetime cancer risk was high mostly for dermal and ingestion exposures in the population. This study might provide valuable information regarding exposure to PAHs in soils of a Nigerian community.

Freshwater systems serve as important sources and transportation routes for marine microplastic pollution, and inadequate attention has been paid to this situation. Data on microplastic pollution of typical seagoing rivers in northern China are lacking. In the current study, we investigated the distribution and characteristics of microplastics in the main stream of the Haihe River, which flows through a metropolis with a high population density and level of industrialization and then flows into the Bohai Sea. The microplastic samples were collected by manta trawls with pore sizes of 333 μm, and the microplastic concentrations ranged from 0.69 to 74.95 items/m³. Fibers dominated in the surface water of the Haihe River; their shapes that were categorized as fibers, film, foam, fragments, and spheres, and contributed 17.4–86.7% of the total microplastics studied. The size distribution of the microplastics was concentrated in a range of 100–1000 μm, with 54.7% of the total sizes corresponding to the 333-μm trawl. Micro-Fourier transform infrared (μ-FT-IR) spectra showed that the main components were polyethylene, poly(ethylene-propylene) copolymer, and polypropylene. Scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) measurements revealed scratches, micropores, and cracks on the surfaces of the microplastics due to mechanical friction, chemical oxidation and degradation processes. The results of this study confirmed the high abundance and high diversity of microplastics in an urban river and indicated appreciable impacts from point-source inputs on the microplastic pollution, such as effluents from wastewater treatment plants (WWTPs).

We used the Weather Research and Forecasting Model coupled with Chemistry (WRF-Chem) to simulate elemental carbon (EC) concentrations in Thailand in 2017. The goals were to quantify the respective contributions of local emissions and regional transport outside Thailand to EC pollution in Thailand, and to identify the most effective emission control strategy for decreasing EC pollution. The simulated EC concentrations in Chiang Mai, Bangkok, and Phuket were comparable with the observation data. The correlation coefficient between the simulated and observed EC concentrations was 0.84, providing a good basis for evaluating EC sources in Thailand. The simulated mean EC concentration over the whole country was the highest (1.38 μg m⁻³) in spring, and the lowest (0.51 μg m⁻³) in summer. We conducted several sensitivity simulations to evaluate EC sources. Local emissions (including anthropogenic and biomass burning emissions) and regional transport outside Thailand contributed 81.2% and 18.8% to the annual mean EC concentrations, respectively, indicating that local sources played the dominant role for EC pollution in Thailand. Among the local sources, anthropogenic emissions (including the industry, power plant, residential, and transportation sectors) and biomass burning contributed 75.1% and 6.1% to the annual mean EC concentrations, respectively. As the anthropogenic emissions dominated the EC pollution, we performed four sensitivity simulations by reducing 30% of the emissions from each of the industry, power plant, residential, and transportation sectors in Thailand. The results indicated that controlling transportation emissions in Thailand was the most effective way in reducing the EC pollution. The 30% reduction of transportation emissions decreased the annual mean EC concentrations by 12.1%. In contrast, 30% reductions of the residential, industry, and power plant emissions caused 8.4%, 6.4%, and 4.0% decreases in the annual mean EC concentrations, respectively. The model results could potentially provide useful information for air pollution control strategies in Thailand.

Plastic mulching is suspected to be a significant source of microplastics in terrestrial environments owing to its intensive application and improper disposal. However, there has been a comparative lack of studies examining this hypothesis. In this study, the occurrence of macroplastics in agricultural soils was investigated by analysing 384 soil samples collected from 19 provinces across China. Additionally, the abundance of microplastics was investigated in potential hotspots that have carried out plastic mulching for over 30 years. Macroplastic concentrations in the soil samples ranged from 0.1 to 324.5 kg/ha, with an average of 83.6 kg/ha; the concentrations were higher in western China than in eastern China. A highly significant linear correlation (R² = 0.61) was found between the consumption of mulching film and the plastic residue in soils, indicating plastic film mulching may be a major source of macroplastics. The abundances of microplastic particles increased over time in the locations where plastic mulching was continuously employed, with concentrations of 80.3 ± 49.3, 308 ± 138.1, and 1075.6 ± 346.8 pieces/kg soil in fields with 5, 15, and 24 y of continuous mulching, respectively. Fourier transform infrared analyses revealed that the composition of the microplastics matched that of the mulching films, suggesting the microplastic particles originated from the mulching films. These findings confirm that plastic mulching is an important source of macroplastic and microplastic contamination in terrestrial environments. Further studies to investigate the microplastic hazards in soils are thus necessary.

Communities in low-income and middle-income countries (LMIC) are disproportionally affected by industrial pollution compared to more developed nations. This study evaluates the dispersal and associated health risk of contaminant-laden soil and dust at a copper (Cu) smelter in Tsumeb, Namibia. It is Africa’s only smelter capable of treating complex Cu ores that contain high arsenic (As) contents (<1%). The analyses focused on the primary trace elements associated with ore processing at the smelter: As, Cu, and lead (Pb). Portable X-Ray fluorescence spectrometry (pXRF) of trace elements in soils (n = 83) and surface dust wipes (n = 80) showed that elemental contamination was spatially associated with proximity to smelter operations. Soil concentrations were below US EPA soil guidelines. Dust wipe values were elevated relative to sites distal from the facility and similar to those at other international smelter locations (As = 1012 μg/m² (95% CI 687–1337); Cu = 1838 μg/m² (95% CI 1191–2485); Pb = 1624 μg/m² (95% CI 862–2385)). Source apportionment for Pb contamination was assessed using Pb isotopic compositions (PbIC) of dust wipes (n = 22). These data revealed that the PbIC of 73% (n = 16/22) of these wipes corresponded to the PbIC of smelter slag and tailings, indicating contribution from industrial emissions to ongoing exposure risk. Modeling of carcinogenic risk showed that dust ingestion was the most important pathway, followed by inhalation, for both adults and children. Dermal contact to trace elements in dust was also determined to pose a carcinogenic risk for children, but not adults. Consequently, contemporary smelter operations remain an ongoing health risk to the surrounding community, in spite of recent efforts to improve emissions from the operations.

For most birds, energy efficiency and conservation are paramount to balancing the competing demands of self-maintenance, reproduction, and other demanding life history stages. Yet the ability to maximize energy output for behaviors like predator escape and migration is often also critical. Environmental perturbations that affect energy metabolism may therefore have important consequences for fitness and survival. Methylmercury (MeHg) is a global pollutant that has wide-ranging impacts on physiological systems, but its effects on the metabolism of birds and other vertebrates are poorly understood. We investigated dose-dependent effects of dietary MeHg on the body composition, basal and peak metabolic rates (BMR, PMR), and respiratory quotients (RQ) of zebra finches (Taeniopygia guttata). Dietary exposure levels (0.0, 0.1, or 0.6 ppm wet weight) were intended to reflect a range of mercury concentrations found in invertebrate prey of songbirds in areas contaminated by atmospheric deposition or point-source pollution. We found adiposity increased with MeHg exposure. BMR also increased with exposure while PMR decreased, together resulting in reduced metabolic scope in both MeHg-exposed treatments. There were differences in RQ among treatments that suggested a compromised ability of exposed birds to rapidly metabolize carbohydrates during exercise in a hop-hover wheel. The elevated BMR of exposed birds may have been due to energetic costs of depurating MeHg, whereas the reduced PMR could have been due to reduced oxygen carrying capacity and/or reduced glycolytic capacity. Our results suggest that environmentally relevant mercury exposure is capable of compromising the ability of songbirds to both budget and rapidly exert energy.

Respiratory diseases, exacerbated through point source pollution, are currently among the leading causes of hospitalization of children in the United States. This paper investigates the relationship between the proximity of hazardous air pollutants (HAPs) emitted from Toxic Release Inventory (TRI) facilities and the number of children diagnosed in hospitals with a respiratory disease in Tennessee. The importance of controlling for toxicity of those HAPs is of particular interest. Hospital discharge, socioeconomic, TRI emission, and HAP toxicity data are used to estimate, via Generalized Linear Methods, a logistic regression model describing the relationship between the percent of children living in a zip code area treated for respiratory illness and the average annual emissions over the previous 10 years of HAPs from TRI sites in that area. Controlling for area socioeconomic characteristics, we find that accounting for toxicity is important in uncovering the relationship between HAP emissions and respiratory health of children. A one standard deviation increase in toxicity-weighted emissions per 100 square miles is associated with an increase in the number of children diagnosed with asthma (chronic bronchitis) by about 1205 (260). The evidence suggests that, with a goal to improving children’s respiratory health, monitoring the toxicity of chemicals being emitted is at least as important as simply monitoring total emission levels. This suggests that the EPA should consider making efforts toward establishing toxicity adjusted emission guidelines.

Comparative studies of biomonitors of trace metal contamination are relatively scarce. We took advantage of a point source pollution in a reservoir (Flix, Spain) to compare trace metal (Hg, Pb, Cd, Se, As, Zn, Cu, Cr) bioaccumulation patterns among 16 food web components. Our results indicate that most organisms are suitable for Hg biomonitoring, whereas other metals are better monitored by only some of them. Biofilms and zebra mussel were the organisms with larger and more diverse biomonitoring capacity. However, we show that using groups of biomonitors increase the scope and strengths of the conclusions and specific goals can be better addressed. We conclude providing an overview of the strengths and weaknesses of the main organisms considered for biomonitoring trace metals in rivers and reservoirs.