Tropospheric ozone in the surface air has become the primary atmospheric pollutant in Hangzhou, China, in recent years. Previous analysis is not enough to decode it for better regulation. Therefore, we use the traditional atmospheric model, Weather Research and Forecasting coupled with Community Multi-scale Air Quality (WRF-CMAQ), and machine learning models, Extreme Learning Machine (ELM), Multi-layer Perceptron (MLP), Random Forest (RF) and Recurrent Neural Network (RNN) to analyze and predict the ozone in the surface air in Hangzhou, China, using meteorology and air pollutants as input. We firstly quantitatively demonstrate that the dew-point deficit, instead of temperature and relative humidity, is the predominant meteorological factor in shaping tropospheric ozone. Urban heat island, daily direct solar radiation time, wind speed and wind direction play trivial role in impacting tropospheric ozone. NO₂ is the primary influential factors both for hourly ozone and daily O₃-8 h due to the titration effect. The most environmental-friendly way to mitigate the ozone pollution is to lower the volatile organic compounds (VOCs) with the highest ozone formation potentials. We deduce that the tropospheric ozone formation process tends to be not only non-linear but also non-smooth. Compared with the traditional atmospheric models, machine learning, whose characteristics are rapid convergence, short calculating time, adaptation of forecasting episodes, small program memory, higher accuracy and less cost, is able to predict tropospheric ozone more accurately.

Reduced graphene oxide (rGO) is one of the most widely used carbon nanomaterials. When it is released into the environment, rGO can markedly affect the transformation of many pollutants, and change their fate and risk. In this work, the synergetic effects of rGO and Cu(II) on the oxidation of 2-naphthol were examined in water in the dark. It was found that the coexistence of rGO and Cu(II) significantly promoted the oxidation of 2-naphthol. Corresponding products were identified as the coupling oligomers of 2-naphthol (dimer, trimer and tetramer) and hydroxylated compounds (OH-2-naphthol, OH-dimer, di–OH–dimer and naphthoquinone derivatives). In the oxidation reaction, rGO played dual roles, i.e. adsorbent and electron-transfer mediator. rGO firstly adsorbed Cu(II) and 2-naphthol on its surface, and then transferred electrons from 2-naphthol to Cu(II) to yield 2-naphthol radicals and Cu(I). 2-Naphthol radicals coupled to each other to form different oligomers of 2-naphthol. Cu(I) was re-oxidized back to Cu(II) by dissolved oxygen, which sustained the continuous oxidation of 2-naphthol. During the autoxidation of Cu(I), reactive oxygen species were generated, which further reacted with 2-naphthol to form hydroxylated products. These findings provide new insights into the risk assessment of rGO and 2-naphthol in aquatic environments.

The challenge of sludge digester liquor treatment is its high ammonium nitrogen (NH₄⁺-N) concentration. Early reports found that complete ammonia oxidation (comammox) was not present and anaerobic ammonia oxidation (anammox) was difficult to achieve in most sludge digester liquor treatments. In this study, NH₄⁺-N removal by cooperation between partial-nitrification, comammox, and anammox processes was achieved in a sequencing batch reactor (SBR) for sludge digester liquor treatment. The results showed that 2100–2200 mg/L of NH₄⁺-N was removed in the SBR with 98.82% removal efficiency. In addition, 55.11% of NH₄⁺-N was converted to nitrite nitrogen (NO₂⁻-N) by partial-nitrification, 25.43% of NH₄⁺-N was converted to nitrate nitrogen (NO₃⁻-N) by comammox, and 18.28% of NH₄⁺-N was removed by anammox. During the operation, in the SBR, the relative abundance of the dominant ammonia-oxidizing bacteria (Chitinophagaceae) was 18.89%, that of the dominant anammox bacteria (Candidatus Kuenenia) was 0.10%, and that of the dominant comammox bacteria (Nitrospira) was 0.20%. Therefore, the high nitrogen removal efficiency in this system was considered the result of the combination of the three processes. These results showed that comammox and anammox could play very important roles in nitrogen transformation and energy-saving in nitrogen removal systems.

The concentrations and seasonal variations of polycyclic aromatic hydrocarbons (PAHs) in air and seawater dissolved samples from the coastal area of Dalian were investigated, as well as their air-water exchanges. The average concentrations of PAHs were 27.5 ± 14.6 ng/m³ and 49.5 ± 20.5 ng/L in the air and water, respectively. Phenanthrene was the dominant congener in both air and water dissolved phase. Seasonality was discovered in the air with the concentrations higher in winter than in summer, but not in the water dissolved phase. Air-water exchange trends also displayed apparent seasonality with 3–4 ring PAHs generally being volatilization or equilibrium in summer but deposition in winter, which highlighted the important influence of temperature on the air-water exchange direction of PAHs. The air-water exchange fluxes of individual PAH congeners ranged from −24331 to 6541 ng/m²/d, and the highest deposition and volatilization fluxes both appeared at the industrial areas, which emphasized the influence of point source emission to the magnitude of air-water diffusion flux of PAHs. Multivariate source apportionment approaches, including principle component analysis, diagnostic ratios, and positive matrix factorization, were conducted, which suggested that PAHs in water originated from multiple sources. Frequent port transport correlated vehicle/ship emission rather than coal combustion may be the primary contributor of PAHs to the coastal air and water.

Limited research has examined the impacts of coal mine fire smoke on human health. The aim of this study was to assess the association between prolonged smoke PM₂.₅ exposure from a brown coal mine fire that burned over a seven week period in 2014 and medications dispensed across five localities in South-eastern Victoria, Australia. Spatially resolved PM₂.₅ concentrations were retrospectively estimated using a dispersion model coupled with a chemical transport model. Data on medications dispensed were collected from the national Pharmaceutical Benefits Schedule database for 2013–2016. Poisson distributed lag time series analysis was used to examine associations between daily mine fire-related PM₂.₅ concentrations and daily counts of medications dispensed for respiratory, cardiovascular or psychiatric conditions. Factors controlled for included: seasonality, long-term trend, day of the week, maximum ambient temperature and public holidays. Positive associations were found between mine fire-related PM₂.₅ and increased risks of medications dispensed for respiratory, cardiovascular and psychiatric conditions, over a lag range of 3–7 days. A 10 μg/m³ increase in coal mine fire-related PM₂.₅ was associated with a 25% (95%CI 19–32%) increase in respiratory medications, a 10% (95%CI 7–13%) increase in cardiovascular medications and a 12% (95%CI 8–16%) increase in psychiatric medications dispensed. These findings have the potential to better prepare for and develop more appropriate public health responses in the event of future coal mine fires.

The bioavailability of the metalloid arsenic (As) in paddy soil is controlled by microbial cycling of As and other elements such as iron (Fe) and sulfur (S), which are strongly influenced by water management in paddy fields. In this study, we evaluated how water management affects As bioavailability by growing rice plants in a geogenic As-contaminated soil. We determined As speciation in soil porewater and the diversity of the associated microbial community. Continuous flooding enhanced the release of Fe and As and increased arsenite (As(III)) and methylated As species concentrations in the rice grain compared with aerobic treatment. Total inorganic and organic As in the grain was 84% and 81% lower, respectively, in the aerobic treatment compared with the continuous flooding treatment. The amounts of Fe(III)-reducing bacteria (FeRB) increased in the flooded rhizosphere soil. The abundance of FeRB in the soil correlated with the dissolution of Fe and As. Among the As-transformation genes quantified, the aioA gene for As(III) oxidation and arsM gene for As(III) methylation were most abundant. The arsM copy number correlated positively with the levels of dsrB (dissimilatory (bi) sulfite reductase β-subunit), suggesting that dissimilatory sulfate-reducing bacteria (SRB) may play an important role in dimethylarsenate (DMAs(V)) production in soil. Our results show that decreased populations of rhizosphere FeRB and SRB contributed to a lower bioavailability of As, and decreased production of methylated arsenicals under oxic conditions.

Microplastics (MPs) contamination in water environment has recently been documented as an emerging environmental threat due to their negative impact on the ecosystem. Their sources are many, but all of them are from synthetic materials. The sources of MPs are cosmetics and personal care products, breakdown or abrasion processes of other plastic products, textile and tyre, bitumen and road marking paints. Because of their low density and small particle size, they are easily discharged into the wastewater drainage systems. Therefore, the municipal wastewater treatment plants (WWTPs) are indicated to be the main recipients of MPs before getting discharged into the natural waterbodies. Therefore, understanding the occurrence and fate of MPs in WWTPs are of great importance towards its control. The aim of this article is to provide a comprehensive review to better understand the pathways of MPs before entering the WWTPs, characteristics of MPs in wastewater, and the removal efficiency of MPs of the existing wastewater treatment technologies adopted by the WWTPs. This review also covers the development of potential microplastics treatment technologies investigated to date. Based on the review of existing literature, it is found that the existing WWTPs are inefficient to completely remove the MPs and there is a risk that they may get discharged into the ambient water sources.

High-efficiency nanophotocatalysts with large specific surface areas have a broad range of application prospects in the catalytic oxidation treatment of organic pollutants in wastewater. A chemical method was used to synthesize a TiO₂ nanophotocatalyst with a mesoporous structure upon which a rare earth metal (Nd) was deposited, namely Nd-TiO₂-SBA-15 (NTS). The prepared NTS was characterized using X-ray diffractometry, transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectrometry. The photocatalytic mechanism was explored using scavenger experiments with photoinduced carriers combined with total organic carbon and UV–Vis measurements. At the same time, the kinetic properties of the NTS photocatalytic degradation of methyl orange (MO) were evaluated. The results showed that the deposition of TiO₂ nanoparticles on the surface of the SBA-15 molecular sieve did not change the mesoporous structure, and Nd was uniformly distributed on the surface of the nanophotocatalyst. The photogenerated holes of the NTS played an important role in the photocatalysis process. In addition, the synthesized NTS had good adaptability in the range of pH 2–10. At pH 4, the reaction rate constant (k) of the MO photocatalytic degradation by NTS was 0.011825 mg·(L·min)⁻¹, and the adsorption equilibrium constant (K) was 0.051359 L mg⁻¹. In addition, the photocatalytic degradation rate of MO by NTS remained above 70%, even when the NTS was recycled four times. The NTS showed a good performance after recycling. This work provides a good foundation for the large-scale application of NTS.

The consequences of indoor and outdoor air pollution on human health are of great concern nowadays. In this study, we firstly evaluated indoor and outdoor air pollution levels (CO, CO₂, NO, NO₂, PM₁₀) at an urban site in Dakar city center and at a rural site. Then, the individual exposure levels to selected pollutants and the variations in the levels of biomarkers of exposure were investigated in different groups of persons (bus drivers, traders working along the main roads and housemaids). Benzene exposure levels were higher for housemaids than for bus drivers and traders. High indoor exposure to benzene is probably due to cooking habits (cooking with charcoal), local practices (burning of incense), the use of cleaning products or solvent products which are important emitters of this compound. These results are confirmed by the values of S-PMA, which were higher in housemaids group compared to the others. Urinary 1-HOP levels were significantly higher for urban site housemaids compared to semirural district ones.Moreover, urinary levels of DNA oxidative stress damage (8-OHdG) and inflammatory (interleukin-6 and -8) biomarkers were higher in urban subjects in comparison to rural ones.The air quality measurement campaign showed that the bus interior was more polluted with PM₁₀, CO, CO₂ and NO than the market and urban or rural households. However, the interior of households showed higher concentration of VOCs than outdoor sites confirming previous observations of higher indoor individual exposure level to specific classes of pollutants.

Nanoplastics have attracted increasing attention in recent years due to their widespread existence in the environment and the potential adverse effects on living organisms. In this paper, the toxic effects of nanoplastics on organisms were systematically reviewed. The translocation and absorption of nanoplastics, as well as the release of additives and contaminants adsorbed on nanoplastics in the organism body were discussed, and the potential adverse effects of nanoplastics on human health were evaluated. Nanoplastics can be ingested by organisms, be accumulated in their body and be transferred along the food chains. Nanoplastics showed effects on the growth, development and reproduction of organisms, and disturbing the normal metabolism. The toxic effects on living organisms mainly depended on the surface chemical properties and the particle size of nanoplastics. Positively charged nanoplastics showed more significant effects on the normal physiological activity of cells than negatively charged nanoplastics, and smaller particle sized nanoplastics could more easily penetrate the cell membranes, hence, accumulated in tissues and cells. Additionally, the release of additives and contaminants adsorbed on nanoplastics in organism body poses more significant threats to organisms than nanoplastics themselves. However, there are still knowledge gaps in the determination and quantification of nanoplastics, as well as their contaminant release mechanisms, degradation rates and process from large plastics to nanoplastics, and the transportation of nanoplastics along food chains. These challenges would hinder the risk assessment of nanoplastics in the environment. It is necessary to further develop the risk assessment of nanoplastics and deeply investigate its toxicological effects.