To prevent the spread of the COVID-19 epidemic, the Chinese megacity Wuhan has taken emergent lockdown measures starting on January 23, 2020. This provided a natural experiment to investigate the response of air quality to such emission reductions. Here, we decoupled the influence of meteorological and non-meteorological factors on main air pollutants using generalized additive models (GAMs), driven by data from the China National Environmental Monitoring Center (CNEMC) network. During the lockdown period (Jan. 23 – Apr. 8, 2020), PM₂.₅, PM₁₀, NO₂, SO₂, and CO concentrations decreased significantly by 45 %, 49 %, 56 %, 39 %, and 18 % compared with the corresponding period in 2015–2019, with contributions by S(meteos) of 15 %, 17 %, 13 %, 10 %, and 6 %. This indicates an emission reduction of NOₓ at least 43 %. However, O₃ increased by 43 % with a contribution by S(meteos) of 6 %. In spite of the reduced volatile organic compound (VOC) emissions by 30 % during the strict lockdown period (Jan. 23 – Feb. 14, 2020), which likely reduced the production of O₃, O₃ concentrations increased due to a weakening of the titration effect of NO. Our results suggest that conventional emission reduction (NOₓ reduction only) measures may not be sufficient to reduce (or even lead to an increase of) surface O₃ concentrations, even if reaching the limit, and VOC-specific measures should also be taken.

Raphidiopsis raciborskii is a diazotrophic and potentially toxic cyanobacterium. To date, this species has successfully invaded many regions from the tropics to sub-tropical and temperate regions, typically forming blooms at temperatures greater than 25 °C. However, there have been a few cases in which R. raciborskii blooms have occurred at low temperatures (below 15 °C), but its cause and mechanisms remain unclear. In this study, field investigations revealed that R. raciborskii blooms occurred at 10–15 °C in Lake Xihu, Yunnan, China. The biomass of R. raciborskii was found to be positively related to nitrate concentrations in this lake. Three strains of R. raciborskii, two isolated from Lake Xihu (CHAB 6611 and CHAB 6612) and one from Lushui Reservoir in central China (CHAB 3409), were used for growth experiments at 15 °C. The three strains exhibited genotypic (16S rRNA and ITS-L genes) and physiological differences in response to nitrogen concentrations at low temperature. The growth rates of strains CHAB 6611 and CHAB 6612 increased with nitrogen concentration while CHAB 3409 could not grow at 15 °C. Furthermore, the growth and phenotypic responses of CHAB 6611 and CHAB 6612 to nitrogen concentrations were different, despite the closer genetic relationship shared by these two strains. Thus, increased nitrogen concentration in water may enhance the biological availability and utilization of nitrogen by R. raciborskii, which is the external promoter, leading to improving the resistance of R. raciborskii to low temperature. The internal cause is the presence of ecotypes in R. raciborskii populations with adaptation to low temperature. With increasing global eutrophication, the distribution range of R. raciborskii as well as the scale of its blooms will increase. As such, the risk of exposure of aquatic biota and humans to cylindrospermopsin is also expected to increase.

Chlorinated polyfluoroalkyl ether sulfonates (Cl-PFESAs), are ubiquitous alternatives to perfluorooctane sulfonate (PFOS), a widely used poly- and perfluoroalkyl substance (PFAS). Despite in vivo and in vitro evidence of metabolic toxicity, no study has explored associations of Cl-PFESAs concentrations with metabolic syndrome (MetS) in a human population. To help address this data gap, we quantified 32 PFAS, including 2 PFOS alternative Cl-PFESAs (6:2 and 8:2 Cl-PFESAs) in serum from 1228 adults participating in the cross-sectional Isomers of C8 Health Project in China study. The odds ratios (ORs) and 95% confidence intervals (CIs) of MetS and its various components were estimated using individual PFAS as a continuous or categorical predictor in multivariate regression models. The association between the overall mixture of PFAS and MetS was examined using probit Bayesian Kernel Machine Regression (BKMR-P). Greater serum PFAS concentrations were associated with higher odds of MetS and demonstrated a statistically significant dose-response trend (P for trend < 0.001). For example, each ln-unit (ng/mL) increase in serum 6:2 Cl-PFESA was associated with a higher prevalence of MetS (OR = 1.52, 95% CI: 1.25, 1.85). MetS was also 2.26 (95% CI: 1.59, 3.23) times more common in the highest quartile of serum 6:2 Cl-PFESA concentration than the lowest, and particularly high among women (OR = 6.41, 95% CI: 3.65, 11.24). The BKMR-P analysis showed a positive association between the overall mixture of measured PFAS and the odds of MetS, but was only limited to women. While our results suggest that exposure to Cl-PFESAs was associated with MetS, additional longitudinal studies are needed to more definitively address the potential health concerns of these PFOS alternatives.

Biorefineries provide a platform for different industries to produce multiple bio-products enhancing the economic value of the system. The production of these biorefineries has led to an increase in the generation of biowaste. To minimize the risk of environmental pollution, numerous studies have focused on a variety of strategies to mitigate these concerns reflected in the vast amount of literature written on this topic. This paper aims to systematically analyze and review the enormous body of scientific literature in the biowaste and biorefinery field for establishing an understanding and providing a direction for future works. A bibliometric analysis is first performed using the CorTexT Manager platform on a corpus of 1488 articles written on the topic of biowaste. Popular and emerging topics are determined using a terms extraction algorithm. A contingency matrix is then created to study the correlation of scientific journals and key topics from this field. Then, the connection and evolution of these terms were analyzed using network mapping, to determine relationships among key terms and analyze notable trends in this research field. Finally, a critical review of articles was presented across three main categories of biowaste management such as mitigation, sustainable utilization, and cleaner disposal from the perspective of the biorefinery concept. Operational and technological challenges are identified for the integration of anaerobic digestion in biorefineries, especially in developing nations. Moreover, logistical challenges in the biorefinery supply-chain are established based on the economics and collection aspect of handling biowaste.

Lakes and rivers are sources of livelihood, food and water in many parts of the world. Lakes provide natural resources and valuable ecosystem services. These aquatic ecosystems are also vulnerable to known and new environmental pollutants. Emerging water contaminants are now being studied including antibiotics because of the global phenomenon on antibiotic resistance. β-Lactam antibiotics are widely used in human and animal disease prevention or treatment. The emergence of antibiotic resistance is a public health threat when bacteria become more resistant and infections consequently increase requiring treatment using last resort drugs that are more expensive. This review summarizes the key findings on the occurrence, contamination sources, and determination of β-lactam antibiotics and β-lactam antibiotic resistant bacteria and genes in the Asian lake and river waters. The current methods in the analytical measurements of β-lactam antibiotics in water involving solid-phase extraction and liquid chromatography-mass spectrometry are discussed. Also described is the determination of antibiotic resistance genes which is primarily based on a polymerase chain reaction method. To date, β-lactam antibiotics in the Asian aquatic environments are reported in the ng/L concentrations. Studies on β-lactam resistant bacteria and resistance genes were mostly conducted in China. The occurrence of these emerging contaminants is largely uncharted because many aquatic systems in the Asian region remain to be studied. Comprehensive investigations encompassing the environmental behavior of β-lactam antibiotics, emergence of resistant bacteria, transfer of resistance genes to non-resistant bacteria, multiple antibiotic resistance, and effects on aquatic biota are needed particularly in rivers and lakes that are eventual sinks of these water contaminants.

Toxicological studies have demonstrated the associations between fine particle (PM₂.₅) components and various cytotoxic endpoints. However, few studies have investigated the toxicological effects of source-specific PM₂.₅ at the individual level. To investigate the potential impact of source-specific PM₂.₅ on cytotoxic effects, we performed repeated personal PM₂.₅ monitoring of 48 adult participants in Hong Kong during the winter and summer of 2014–2015. Quartz filters were analyzed for carbonaceous aerosols and water-soluble ions in PM₂.₅. Teflon filters were collected to determine personal PM₂.₅ mass and metal concentrations. The toxicological effects of personal PM₂.₅ exposure—including cytotoxicity, inflammatory response, and reactive oxygen species (ROS) production—were measured using A549 cells in vitro. Personal PM₂.₅ samples collected in winter were more effective than those collected in summer at inducing cytotoxicity and the expression of proinflammation cytokine IL-6. By contrast, summer personal PM₂.₅ samples induced high ROS production. We performed a series of statistical analyses, Spearman correlation and a source apportionment approach with a multiple linear regression (MLR) model, to explore the sources contributing most significantly to personal PM₂.₅ bioreactivity. Secondary inorganic species and transition metals were discovered to be weak-to-moderately associated with cytotoxicity (rₛ: 0.26–0.55; p < 0.01) and inflammatory response (rₛ: 0.26–0.44; p < 0.05), respectively. Carbonaceous aerosols (i.e., organic and elemental carbon; rₛ: 0.23–0.27; p < 0.05) and crustal material (Mg and Ca) was positively associated with ROS generation. The PMF–MLR models revealed that tailpipe exhaust and secondary sulfate contributed to ROS generation, whereas secondary nitrate was the major contributor to PM₂.₅ cytotoxicity and inflammation. These results improve and variate the arguments for practical policies designed to mitigate the risks posed by air pollution sources and to protect public health.

Soils containing a large proportion of industrial waste can pose a health risk due to high environmentally available concentrations of toxic metal(loid)s. Nano zero-valent iron (nZVI) and amorphous manganese oxide (AMO) were applied as immobilising amendments (1 wt%) to soils with different industrial origin of As and Sb, and leaching of As, Sb, Pb, and Zn was investigated using a single extraction with deionised water. The different industrial impact was reflected in the mineralogy, chemical composition and pH of these soils. Water-soluble As ratios positively correlated with pH in all experimental treatments. A significant decrease of water-soluble As ratios was observed in all nZVI-amended soils (~65–93% of the control) except for one sample with the lowest solution pH. Nano zero-valent iron was also successful in Sb immobilisation (~76–90% of the control). Highly variable results were obtained for AMO, which only led to a decrease of water-soluble As in soils with solution pH of ≥7 (~70–80% of the control), probably due to lower stability of AMO in acidic conditions. In each case, nZVI was more efficient at decreasing water-soluble As ratios than AMO. Dissolved Pb concentrations remained unchanged after the application of nZVI and AMO, and the decrease of Zn leaching using AMO was controlled mainly by soil pH increase induced by its application. According to the calculated saturation indices, tripuhyite (FeSbO₄) was predicted to be the key mineral controlling Sb solubility in mine soils. Secondary Fe (hydr)oxides either originally present or newly formed due to nZVI oxidation were instrumentally identified at different stages of their transformation and metal(loid) retention. To conclude, nZVI is suitable for application to contaminated soils at a wide pH range, while the use of AMO for decreasing As leaching is limited to soils with pH ≥ 7.

House dust is an important medium for exposure to persistent pollutants, such as metals. Detailed characterization of metal composition is needed to identify sources and potential health impacts of exposure. In this study we show that specific metals in dust dominate in different locations within residential homes in a mid-size Canadian city (Fort McMurray, Alberta), up to two years after a major wildfire event in 2016. Dust samples were collected in high-traffic (e.g. bedroom, N = 186), low-traffic (e.g. basement, N = 158), and entranceway areas (N = 171) of residential homes (N = 125), and analyzed for 25 trace metal elements using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The profile of metal concentrations in the entranceway resembled that of outdoor soils, especially for crustal elements. On the other hand, Cu, Zn, and Pb concentrations in dust sampled in indoor living areas were on average three to six times higher than in other indoor locations indicating indoor sources for these elements. In general, Pb concentrations were similar or lower than in an average Canadian residence, but a substantial fraction showed anomalously high concentrations in the low-traffic areas, particularly on concrete surfaces in basements. Notably, the 2016 wildfires showed limited influence on metal concentrations in indoor dust, despite the widespread concerns in the community about long term exposure. Enrichment factor ratio calculations and principal component analysis showed two classes of sources of metals in dust that represent geogenic-outdoor sources and anthropogenic-indoor sources. Overall, we demonstrate that outdoor and indoor sources of dust impact its composition, and these influences are reflected in the different areas of a home.

The European Noise Directive proposes using strategic noise maps as tools to assess populations affected by environmental noise. It recommends using computational methods instead of in situ measurements when possible. A sound source’s emission power is an important factor in the calculation of noise indicators. For traffic noise, this parameter is usually defined based on vehicle flow considering an emission spectrum that depends on the type of vehicle and its speed. This study analysed the possibility of using the categorisation method to propose an alternative method of defining a sound source’s emission power to develop noise maps. This was accomplished using previously published values of the emission power per unit length. Another method is also proposed that estimates traffic flows. To verify their estimation capacity, the results of both methods were compared with the values obtained from in situ measurements. The results demonstrated similar uncertainties in both methods and were in the range of expected average uncertainties compared to the results obtained by calculating a noise map with the measured experimental values. In particular, for the differences between calculations and measurements, in absolute values, the mean uncertainties were approximately 2 dBA in estimating different long-term noise indicators. For the differences, the mean of the uncertainties obtained via the categorisation method did not present significant differences for the null value for all the analysed noise indicators. Street stratification is a rapid and low-cost approach for road traffic noise mapping without increasing uncertainties.

This is a research comment on the ochratoxin A (OTA) degradation mechanism by Lysobacter sp. CW239 regarding the previous publication in Environmental Pollution (Wei et al., 2020). Three possible degradation mechanisms were discussed in the referred publication, but without definite evidences, it was not clear which one worked actually. Here, the gene cp4 deficient mutant CW239Δᶜᵖ⁴ was successfully constructed, and the carboxypeptidase CP4 role on OTA degradation in strain CW239 was validated in vivo. As a result, the mutant CW239Δᶜᵖ⁴ without gene cp4 showed less than 10% reduction of 24 hrs degradation ratio compared to wide-type strain CW239. After the gene cp4 complemented to CW239Δᶜᵖ⁴, the complementary strain (+)cp4 recovered the degradation ability to wide-type. The validation result indicated that the third degradation mechanism (i.e., OTA is degraded by joint action of multiple enzymes in CW239) proposed previous (Wei et al., 2020) was correct route for the degradation strain. This commentary was significant to the following studies on the pollutant detoxify strains with similar degradation characters between identified enzyme and the host strain.