PM₂.₅ (particulate matter having aerodynamic diameter ≤2.5 μm) samples were collected during wintertime from two polluted urban sites (Allahabad and Kanpur) in the central Indo-Gangetic Plain (IGP) to comprehend the sources and atmospheric transformations of light-absorbing water-soluble organic aerosol (WSOA). The aqueous extract of each filter was atomized and analyzed in a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). Water-soluble organic carbon (WSOC) and WSOA concentrations at Kanpur were ∼1.2 and ∼1.5 times higher than that at Allahabad. The fractions of WSOC and secondary organic carbon (SOC) to total organic carbon (OC) were also significantly higher ∼53% and 38%, respectively at Kanpur compared to Allahabad. This indicates a higher abundance of oxidized WSOA at Kanpur. The absorption coefficient (bₐbₛ₋₃₆₅) of light-absorbing WSOA measured at 365 nm was 46.5 ± 15.5 Mm⁻¹ and 73.2 ± 21.6 Mm⁻¹ in Allahabad and Kanpur, respectively, indicating the dominance of more light-absorbing fractions in WSOC at Kanpur. The absorption properties such as mass absorption efficiency (MAE₃₆₅) and imaginary component of refractive index (kₐbₛ₋₃₆₅) at 365 nm at Kanpur were also comparatively higher than Allahabad. The absorption forcing efficiency (Abs SFE; indicates warming effect) of WSOA at Kanpur was ∼1.4 times higher than Allahabad. Enhancement in light absorption capacity was observed with the increase in f44/f43 (fraction of m/z 44 (f44) to 43 (f43) in organic mass spectra) and O/C (oxygen to carbon) ratio of WSOA at Kanpur while no such trend was observed for the Allahabad site. Moreover, the correlation between carbon fractions and light absorption properties suggested the influence of low-volatile organic compounds (OC3 + OC4 fraction obtained from thermal/optical carbon analyzer) in increasing the light absorption capacity of WSOA in Kanpur.

Carbonaceous particles play an important role in climate change, and an increase in their emission and deposition causes glacier melting in the Himalayas and the Tibetan Plateau (HTP). This implies that studying their basic characteristics is crucial for a better understanding of the climate forcing observed in this area. Thus, we investigated characteristics of carbonaceous particles at a typical remote site of southeastern HTP. Organic carbon and elemental carbon concentrations at this study site were 1.86 ± 0.84 and 0.18 ± 0.09 μg m⁻³, respectively, which are much lower than those reported for other frequently monitored stations in the same region. Thus, these values reflect the background characteristics of the study site. Additionally, the absorption coefficient per mass (α/ρ) of water-soluble organic carbon (WSOC) at 365 nm was 0.60 ± 0.19 m² g⁻¹, with the highest and lowest values corresponding to the winter and monsoon seasons, respectively. Multi-dimensional fluorescence analysis showed that the WSOC consisted of approximately 37% and 63% protein and humic-like components, respectively, and the latter was identified as the component that primarily determined the light absorption ability of the WSOC, which also showed a significant relationship with some major ions, including SO²⁻₄, K⁺, and Ca²⁺, indicating that combustion activities as well as mineral dust were two important contributors to WSOC at the study site.

The negative impact of antibiotic pollution on the agricultural system and human health is a hot issue in the world. However, little information is available on the antibiotics toxicity mechanism and the role of silicon (Si) to alleviate the antibiotics toxicity. In this study, strawberry (Fragaria ananassa) showed excitatory response to low-dose SMZ (1 mg L⁻¹), but strawberry root and photosynthetic efficiency were damaged under high level. When SMZ level exceeded 10 mg L⁻¹, H₂0₂, O₂⁻, MDA and relative conductivity increased, while SOD and CAT activities first increased and then decreased. SMZ accumulated more in roots and fruits, but less in stems, and the accumulation increased with the increase of SMZ-dose. Under 1 mg L⁻¹ SMZ, the SMZ accumulation in fruits was 110.54 μg kg⁻¹, which exceeded the maximum residue limit. SMZ can induce the expression of sul1, sul2 and intI1, and intI1 had the highest abundance. Exogenous application of Si alleviated the toxicity of SMZ, which is mainly related to the degradation of SMZ in soil and the reduction of SMZ absorption by strawberry. In addition, Si relieved root damage, promoted the increase of photosynthetic efficiency, and improved the antioxidant system to resist SMZ toxicity.

Mammalian polychlorinated biphenyl (PCB) metabolism has not been systematically explored with nontarget high-resolution mass spectrometry (Nt-HRMS). Here we investigated the importance of the gut microbiome in PCB biotransformation by Nt-HRMS analysis of feces from conventional (CV) and germ-free (GF) adult female mice exposed to a single oral dose of an environmental PCB mixture (6 mg/kg or 30 mg/kg in corn oil). Feces were collected for 24 h after PCB administration, PCB metabolites were extracted from pooled samples, and the extracts were analyzed by Nt-HRMS. Twelve classes of PCB metabolites were detected in the feces from CV mice, including PCB sulfates, hydroxylated PCB sulfates (OH-PCB sulfates), PCB sulfonates, and hydroxylated methyl sulfone PCBs (OH-MeSO₂-PCBs) reported previously. We also observed eight additional PCB metabolite classes that were tentatively identified as hydroxylated PCBs (OH-PCBs), dihydroxylated PCBs (DiOH-PCBs), monomethoxylated dihydroxylated PCBs (MeO-OH-PCBs), methoxylated PCB sulfates (MeO-PCB sulfates), mono-to tetra-hydroxylated PCB quinones ((OH)ₓ-quinones, x = 1–4), and hydroxylated polychlorinated benzofurans (OH-PCDF). Most metabolite classes were also detected in the feces from GF mice, except for MeO-OH-PCBs, OH-MeSO₂-PCBs, and OH-PCDFs. Semi-quantitative analyses demonstrate that relative PCB metabolite levels increased with increasing dose and were higher in CV than GF mice, except for PCB sulfates and MeO-PCB sulfates, which were higher in GF mice. These findings demonstrate that the gut microbiome plays a direct or indirect role in the absorption, distribution, metabolism, or excretion of PCB metabolites, which in turn may affect toxic outcomes following PCB exposure.

The response of freshwater invertebrates following accidental releases of oil is not well understood. This knowledge gap is more substantial for unconventional oils such as diluted bitumen (dilbit). We evaluated the effects of dilbit on insect emergence and benthic invertebrates by conducting experimental spills in limnocorrals (10-m diameter; ~100-m³) deployed in a boreal lake at the IISD-Experimental Lakes Area, Canada. The study included seven dilbit treatments (spill volumes ranged from 1.5 L [1:66,000, oil:water, v/v] to 180 L [1:590, oil:water, v/v]), two controls, and additional lake reference sites, monitored for 11 weeks. Invertebrate emergence declined at the community level following oil addition in a significantly volume-dependent manner, and by 93–100 % over the 11 weeks following the spill in the highest treatment. Dilbit altered community structure of benthic invertebrates, but not abundance. One-year post-spill and following oil removal using traditional skimming and absorption techniques, benthic richness and abundance were greater among all treatments than the previous year. These results indicate that recovery in community composition is possible following oil removal from a lake ecosystem. Research is needed concerning the mechanisms by which surface oil directly affect adult invertebrates, whether through limiting oviposition, limiting emergence, or both. The response of benthic communities to sediment tar mats is also warranted.

Trace organic compounds (TOrCs) and microplastics (MPs) have been recognized as emerging pollutants that cause severe water pollution related problems due to their non-degradable and bio-accumulative nature. Many studies on oxidation processes such as ozone have been conducted to efficiently remove TOrCs in water treatment. However, there has been a lack of research on the removal efficiency of TOrCs in the oxidation process when they co-exist with MPs and form transformation byproducts (TBPs) during this process. This study evaluates the effects of MPs on TOrC removal during ozonation at various ozone concentrations and based on the mass of MP particles in distilled water. The adsorption of TBPs and TOrCs was also evaluated using the Freundlich and Langmuir isotherm equations. The toxicity of these compounds was evaluated to confirm the risk to aquatic ecosystems. The results show that triclosan (TCS) had the highest absorption capacity amongst the TOrCs and TBPs tested. Polyvinylchloride exhibited the highest adsorption efficiency compared with polyethylene and polyethyleneterephthalate (TCS 0.341 mg/g) due to its high adsorption capacity and hydrophobicity. In the toxicity test, 2,4-dichlorophenol and 4-chloroaniline as TBPs had a relatively higher toxicity to Vibrio fischeri (a marine bacterial species) than Daphnia magna (a freshwater plankton species).

Paraquat (PQ) is a toxic, organic herbicide for which there is no specific antidote. Although banned in some countries, it is still used as an irreplaceable weed killer in others. The lack of understanding of the precise mechanism of its toxicity has hindered the development of treatments for PQ exposure. While toxicity is thought to be related to PQ-induced oxidative stress, antioxidants are limited in their ability to ameliorate the untoward biological responses to this agent. Summarized in this review are data on the absorption, distribution, metabolism, excretion, and toxicity (ADME/T) of PQ, focusing on the essential roles of individual transporters and enzymes in these processes. Based on these findings, strategies are proposed to design and test specific and effective antidotes for the clinical management of PQ poisoning.

Due to the complex sources and fate of perfluoroalkyl substance (PFAS), their source apportionment in the environment remains a challenge. A data set of 11 straight-chain PFAS in 139 samples of fish in the Great Lakes was analyzed using positive matrix factorization (PMF) to investigate their primary sources, whose spatial variations were examined against the surrounding environmental factors. PMF analysis produced five fingerprints. Factor 1 (72% of Σ₁₁PFAS, dominated by PFOS) probably represented emissions from primary sources (such as consumer products) and secondary sources (precursors), and increased in average abundance from west to east across the Great Lakes. Factor 2 (13% of Σ₁₁PFAS) and factor 3 (7% of Σ₁₁PFAS), highly loaded with long-chain PFAS and PFNA, respectively, were thought to represent PVDF manufacture or processing in metal plating. They showed higher contributions in sparsely populated Lakes Superior and Huron. Factor 4 (5% of Σ₁₁PFAS, highly loaded with PFOS and PFHxS) presented hot spots near current and former air force bases, suggesting it was related to aqueous film-forming foams (AFFFs). Factor 5 (4% of Σ₁₁PFAS) contained primarily PFOS and PFOSA, which may imply metabolism of precursors (PFOSA) to PFOS in vivo. Unexpectedly, the spatial trends of the five sources all showed abnormally low values near the more urbanized Chicago and Milwaukee in Lake Michigan, which may be due to their unique wastewater and stormwater infrastructure or may arise from atmospheric transport of precursors. Our study indicated that PMF was an effective tool to identify sources of PFAS in fish despite absorption, distribution, metabolism, and excretion (ADME) processes which might alter fingerprints in fish relative to their surrounding environment.

It is widely recognized that green infrastructures in urban ecosystems provides important ecosystem services, including air purification. The potential absorption of nitrogen oxides (NOₓ) by urban trees has not been fully quantified, although it is important for air pollution mitigation and the well-being of urban residents. In this study, four common tree species (Sophora japonica L., Fraxinus chinensis Roxb., Populus tomentosa Carrière, Sabina chinensis (L.)) in Beijing, China, were studied. The dual stable isotopes (¹⁵N and ¹⁸O) and a Bayesian isotope mixing model were applied to estimate the sources contributions of potential nitrogen sources to the roadside trees based on leaf and soil sampling in urban regions. The following order of sources contributions was determined: soil > dry deposition > traffic-related NOₓ. The capacity of urban trees for NOₓ removal in the city was estimated using a remote sensing and GIS approach, and the removal capacity was found to range from 0.79 to 1.11 g m⁻² a⁻¹ across administrative regions, indicating that 1304 tons of NOₓ could be potentially removed by urban trees in 2019. Our finding qualified the potential NOₓ removal by urban trees in terms of atmospheric pollution mitigation, highlighting the role of green infrastructure in air purification, which should be taken into account by stakeholders to manage green infrastructure as the basis of a nature-based approach.

To prevent spreads of Coronavirus disease-2019 (COVID-19), China adopted the lockdown measures in late January 2020, providing a platform to study the response of air quality and atmospheric chemical and physical properties to strict reduced emissions. In this study, the continuous measurements of aerosol light absorption were conducted in Nanjing, east China, from January 3 to March 31, 2020. Our results showed that the contribution of black carbon (BC) to light absorption at the different wavelengths was more than 75% and the rest light absorption was contributed by brown carbon (BrC), which was mainly originated from primary emissions. Secondary BrC absorption, which was mainly produced by photochemical oxidation, constituted a minor fraction (2–7%) of the total absorption. Compared with the sampling in the pre-lockdown, the significant decreases of BC (43%) and secondary BrC absorption (31%) were found during the lockdown period, resulting in a substantial decrease of solar energy absorbance by 36% on a local scale. The control measures also changed the diurnal variations of light absorption. Due to the reduced emissions, the relative fraction of fossil fuel to BC also dropped from 78% in the pre-lockdown to 71% in the lockdown. The concentrations of BC, PM₂.₅ and NO₂ decreased 1.1 μg m⁻³, 33 μg m⁻³ and 9.1 ppb whereas O₃ concentration increased 9.0 ppb during the COVID-19 lockdown period. The decreased concentrations of BC, PM₂.₅ and NO₂ were mainly contributed by both emission reduction (51–64%) and meteorological conditions (36–49%). Our results highlighted that the balance of control measures in alleviation of particulate matter (PM) and O₃ pollution, and meteorology should be seriously considered for improvement of air quality in this urban city of China.