Systemic studies on the bioremediation of co-contaminated PAHs and heavy metals are lacking, and this paper provides an in-depth review on the topic. The released sources and transport of co-contaminated PAHs and heavy metals, including their co-occurrence through formation of cation-π interactions and their adsorption in soil are examined. Moreover, it is investigated that co-contamination of PAHs and heavy metals can drive a synergistic positive influence on bioremediation through enhanced secretion of extracellular polymeric substances (EPSs), production of biosynthetic genes, organic acid and enzymatic proliferation. However, PAHs molecular structure, PAHs-heavy metals bioavailability and their interactive cytotoxic effects on microorganisms can exert a challenging influence on the bioremediation under co-contaminated conditions. The fluctuations in bioavailability for microorganisms are associated with soil properties, chemical coordinative interactions, and biological activities under the co-contaminated PAHs-heavy metals conditions. The interactive cytotoxicity caused by the emergence of co-contaminants includes microbial cell disruption, denaturation of DNA and protein structure, and deregulation of antioxidant biological molecules. Finally, this paper presents the emerging strategies to overcome the bioavailability problems and recommends the use of biostimulation and bioaugmentation along with the microbial immobilization for enhanced bioremediation of PAHs-heavy metals co-contaminated sites. Better knowledge of the bioremediation potential is imperative to improve the use of these approaches for the sustainable and cost-effective remediation of PAHs and heavy metals co-contamination in the near future.

Plastic pollution represents the most widespread threaten throughout the world and, amongst aquatic habitats, freshwaters and in particular riparian zones seems to be highly disturbed. Since the plastic storage and accumulation on the riparian vegetation have not yet been deeply investigated, here, we focussed on the riparian zone's function in trapping plastic litter. To do so, we assessed the occurrence and density of plastics in different vegetated (arboreal, shrubby, herbaceous, reed, bush) and unvegetated types in 8 central Italian rivers, running in different land use contexts. Our results showed that plastic pieces, bags, bottles and food containers were the most abundant specific categories on the vegetated types, demonstrating the riparian vegetation role in trapping plastic litter. Specifically, the highest plastic density was found on the shrubby type suggesting that a tree shape retains plastics more easily than all other vegetated and unvegetated types. Shape and size classification of plastics are not significantly different between vegetated and unvegetated types. These findings allow to collect important information on how the riparian vegetation can be exploited in management activities for removing plastic litters from both freshwater and sea, being the former considered the main plastic source for the latter. This study highlights a further ecosystem service as mechanical filter provided by the riparian zone, even if further studies ought to be performed to understand the role of vegetation as plastic trap and the possible detrimental effects of plastics on the plant health status.

We investigated the biological response of soluble organic fraction (SOF) and water-soluble fraction (WSF) extracted from particulate matter (PM) emitted by an automotive diesel engine operating in a representative urban driving condition. The engine was fueled with ultra-low sulfur diesel (ULSD), and its binary blends by volume with 13% of butanol (Bu13), and with hydrotreated vegetable oil (HVO) at 13% (HVO13) and 20% (HVO20). Cytotoxicity, genotoxicity, oxidative DNA damage and ecotoxicity tests were carried out, and 16 polycyclic aromatic hydrocarbons (PAH) expressed as tbenzo(a)pyrene total toxicity equivalent (BaP-TEQ) were also analyzed. The Hepatocarcinoma epithelial cell line (HepG2) was exposed to SOF for 24 h and analyzed using comet assay, with the inclusion of formamidopyrimidine DNA glycosylase (FPG) and endonuclease III (Endo III) to recognize oxidized DNA bases. The WSF was evaluated through acute ecotoxicity tests with the aquatic microcrustacean Daphnia pulex (D. Pulex). Results showed that there was no cytotoxic activity for all tested SOF concentrations. Genotoxic responses by all the SOF samples were at same level, except for the HVO13 which was weaker in the absence of the enzymes. The addition of the FPG and Endo III enzymes resulted in a significant increase in the comet tail, indicating that the DNA damage from SOF for all tested fuel blends involves oxidative damage including a higher level of oxidized purines for ULSD and Bu13 in comparison with HVO blends, but the oxidized pyrimidines for HVO blends were slightly higher compared to Bu13. The WSF did not show acute ecotoxicity for any of the fuels. Unlike other samples, Bu13-derived particles significantly increase the BaP-TEQ. The contribution to the genotoxic activity and oxidative DNA from SOF was not correlated to BaP-TEQ, which means that the biological activity of PM might be affected also by other toxic compounds present in particulate phase.

Polychlorinated biphenyls (PCBs) are a class of persistent organic pollutants (POPs) that have adverse effects on human health. However, the long-term health effects and potential mechanism of neonatal exposure to PCBs are still unclear. In this study, nursing male mice exposed to PCB138 at 0.5, 5, and 50 μg/kg body weight (bw) from postnatal day (PND) 3 to PND 21 exhibited increased serum uric acid levels and liver uric acid synthase activity at 210 days of age. We also found an increased kidney somatic index in the 50 μg/kg group and kidney fibrosis in the 5 and 50 μg/kg groups. Mechanistically, PCB138 induced mitochondrial dysfunction and endoplasmic reticulum (ER) stress, which might have led to inflammatory responses, such as activation of the NF-κB (nuclear factor kappa-B) and NLRP3 (NOD-like receptor protein 3) pathways. The inflammatory response might regulate renal fibrosis and hypertrophy. In summary, this study reports a long-term effect of neonatal PCB exposure on uric acid metabolism and secondary nephrotoxicity and clarifies the underlying mechanism. Our work also indicates that early life pollutant exposure may be an important cause of diseases later in life.

Low-molecular-weight (LMW) phthalate acid esters (PAEs) tend to enter the atmosphere, flying for several kilometers, so it is easy to endanger human health. This work is the first to use quantum chemistry calculations (Gaussian 16 program) and computational toxicology (ECOSAR, TEST, and Toxtree software) to comprehensively study the ozonolysis mechanism of six LMW PAEs (dimethyl phthalate (DMP), diethyl phthalate (DEP), dipropyl phthalate (DPP), diisopropyl phthalate (DIP), dibutyl phthalate (DBP), and diisobutyl phthalate (DIBP)) in the atmosphere and the toxicity of DMP (take DMP as an example) in the conversion process. The results show that the electron-donating effect of the ortho position of the LMW PAEs has the most obvious influence on the ozonolysis. We summarized the ozonation reaction law of LMW PAEs at the optimal reaction site. At 298 K, the law of initial ozonolysis total rate constant of the LMW PAEs is kDIP > kDPP > kDIBP > kDMP > kDEP > kDBP, and the range is 9.56 × 10⁻²⁵ cm³ molecule⁻¹ s⁻¹ — 1.47 × 10⁻²² cm³ molecule⁻¹ s⁻¹. According to the results of toxicity assessment, the toxicity of products is lower than DMP for aquatic organisms after ozonolysis. But those products have mutagenicity, developmental toxicity, non-genotoxicity, carcinogenicity, and corrosiveness to the skin. The proposed ozonolysis mechanism promotes our understanding of the environmental risks of PAEs and provides new ideas for studying the degradation of PAEs in the tropospheric gas phase.

The potential effect of gestational exposure to phthalates on the lung function levels during childhood is unclear. Therefore, we examined this association at different ages (from 4 to 11 years) and over the whole childhood. Specifically, we measured 9 phthalate metabolites (MEP, MiBP, MnBP, MCMHP, MBzP, MEHHP, MEOHP, MECPP, MEHP) in the urine of 641 gestating women from the INMA study (Spain) and the forced vital capacity (FVC), forced expiratory volume in 1 s (FEV₁) and FEV₁/FVC in their offspring at ages 4, 7, 9 and 11. We used linear regression and mixed linear regression with a random intercept for subject to assess the association between phthalates and lung function at each study visit and for the overall childhood, respectively. We also assessed the phthalate metabolites mixture effect on lung function using a Weighted Quantile Sum (WQS) regression. We observed that the phthalate metabolites gestational levels were consistently associated with lower FVC and FEV₁ at all ages, both when assessed individually and jointly as a mixture, although most associations were not statistically significant. Of note, a 10% increase in MiBP was related to lower FVC (−0.02 (−0.04, 0)) and FEV₁ z-scores (−0.02 (−0.04, −0.01) at age 4. Similar significant reductions in FVC were observed at ages 4 and 7 associated with an increase in MEP and MnBP, respectively, and for FEV₁ at age 4 associated with an increase in MBzP. WQS regression consistently identified MBzP as an important contributor to the phthalate mixture effect. We can conclude that the gestational exposure to phthalates was associated with children's lower FVC and FEV₁, especially in early childhood, and in a statistically significant manner for MEP, MiBP, MBzP and MnBP. Given the ubiquity of phthalate exposure and its established endocrine disrupting effects in children, our findings support current regulations that limit phthalate exposure.

The dispersion of microplastics (MPs) in coastal and marine environments and their potential harmful effects on organisms and ecosystems makes MPs pollution an emerging problem that has gained increasing attention from the scientific community. Despite the recent increase in the number of studies on MPs presence in different marine environments, investigations in Latin America and the Caribbean (LAC) are still relatively limited. This review presents the spatial distribution (where) and the methods applied (how) in assessing MPs contamination on LAC sandy beaches, identifying the challenges to be faced in advancing the understanding of this emerging contaminant. Most of the 39 papers reviewed were published between 2020 and 2021 (51%) and conducted on Brazilian beaches (43%). The LAC investigations apply spot sampling (69%) on shoreline stretches between 10 and 1000 km (59%). These works used inconsistent sampling methods, incomparable techniques for MPs extraction from sediments, and different measurement units to report their data. The MPs presence on LAC beaches is not negligible, as it varies significantly in its distribution and concentration (0–2457 MP/dw kg and 0–5458 MP/m²). Its highest accumulation is on ocean island beaches; however, there are still large stretches of coastline (Cuba, Venezuela, Argentina) with no data on MPs presence and a small number of studies exploring these contaminants' temporal variability. The lack of standardization in the studies’ methodologies, particularly their measurement units, hinders their quantitative comparison and our ability to establish baseline values regarding MPs abundance on LAC beaches. In this sense, future works should direct efforts towards the spatial and temporal expansion of their sampling, as well as protocol standardization to facilitate result comparability on MPs on LAC sandy beaches.

Size-fractionated particulate matters (SPMs) in a range of 9.0 to 0.43 μm, classified based on aerodynamic diameter (dₐₑ) as fine PMs (0.43 μm ≤ dₐₑ < 2.1 μm) and coarse PMs (2.1 μm ≤ dₐₑ < 9.0 μm) were collected by cascade impactors (7 fractions) during smoke haze (SH) and non-smoke haze (NSH) seasons in urban and rural areas of Chiang Mai, Thailand. Their polycyclic aromatic hydrocarbons (PAHs) compositions were determined for respiratory health risk assessment. During SH episode, concentrations of SPMs and PAHs in the rural area were approximately two times higher than in the urban area and about 62–68% of the SPMs were fine particles. Conversely, during NSH season the concentrations in the urban area were higher due to traffic emission. The finest particle sizes (0.65–0.43 μm) contained the highest PAHs concentrations among the other PM sizes. Benzo[b]fluoranthene was a main PAH component found during SH season suggesting biomass burning is a major pollutant source. High molecular weight (5–6 rings) PAHs with high carcinogenicity were likely to concentrate in fine particles. Distribution patterns of SPMs and PAHs during SH season were bimodal with the highest peak at a fine size range (0.65–0.43 μm) and a small peak at a coarse size range (5.8–4.7 μm). Respiratory health risk was estimated based on toxicity equivalent concentrations of PAHs bound-SPMs and inhalation cancer risk (ICR). Relatively high ICR values (1.14 × 10⁻⁴ (rural) and 6.80 × 10⁻⁵ (urban)) were found during SH season in both areas, in which fine particles played an important role. It revealed that high concentration of fine particles in ambient air is related to high respiratory health risk due to high content of carcinogenic substances.

Biochar application into paddy is an improved strategy for addressing methane (CH₄) stimulation of straw biomass incorporation. Whereas, the differentiative patterns and mechanisms on CH₄ emission of straw biomass and biochar after long years still need to be disentangled. Considering economic feasibility, a seven-year of field experiment was conducted to explore the long-term CH₄ mitigation effect of annual low-rate biochar incorporation (RSC, 2.8 t ha⁻¹), with annual rice straw incorporation (RS, 8 t ha⁻¹) and control (CK, with no biochar or rice straw amendment incorporation) as a comparation. Results showed that RSC mitigated CH₄ emission while RS stimulated CH₄ significantly (p < 0.05) and stably over 7 experimental years compared with CK. RSC mitigated 14.8–46.7% of CH₄ emission compared with CK. In comparison to RSC, RS increased 111–950.5% of CH₄ emission during 7 field experimental years. On the 7th field experimental year, pH was significantly increased both in RS and RSC treatment (p < 0.05). RSC significantly (p < 0.05) increased soil nitrate (NO₃⁻-N) compared with RS while RS significantly (p < 0.05) increased dissolved carbon (DOC) compared to RSC. Soil NO₃⁻-N inhibition on methanogens and promotion on methanotrophs activities were verified by laboratory experiment, while soil pH and DOC mainly promoted methanogens abundance. Significantly (p < 0.05) increased DOC and soil pH enhanced methanogens growth and stimulated CH₄ emission in RS treatment. Higher soil NO₃⁻-N content in RSC than CK and RS contributed to CH₄ mitigation. Soil NO₃⁻-N and DOC were identified as the key factors differentiating CH₄ emission patterns of RS and RSC in 2019. Collectively, soil NO₃⁻-N impacts on CH₄ flux provide new ideas for prolonged effect of biochar amendment on CH₄ mitigation after years.

The significant reduction in PM₂.₅ mass concentration after the outbreak of COVID-19 provided a unique opportunity further to study the formation mechanism of secondary inorganic aerosols. Hourly data of chemical components in PM₂.₅, gaseous pollutants, and meteorological data were obtained from January 1 to 23, 2020 (pre-lockdown) and January 24 to February 17, 2020 (COVID-lockdown) in Zhengzhou, China. Sulfate, nitrate, and ammonium were the main components of PM₂.₅ during both the pre-lockdown and COVID-lockdown periods. Compared with the pre-lockdown period, even though the concentration and proportion of nitrate decreased, nitrate was the dominant component in PM₂.₅ during the COVID-lockdown period. Moreover, nitrate production was enhanced by the elevated O₃ concentration, which was favorable for the homogeneous and hydrolysis nitrate formation despite the drastic decrease of NO₂. The proportion of sulfate during the COVID-lockdown period was higher than that before. Aqueous-phase reactions of H₂O₂ and transition metal (TMI) catalyzed oxidations were the major pathways for sulfate formation. During the COVID-lockdown period, TMI-catalyzed oxidation became the dominant pathway for aqueous-phase sulfate formation because the elevated acidity favored the dissolution of TMI. Therefore, the enhanced TMI-catalyzed oxidation affected by the elevated particle acidity dominated the sulfate formation, resulting in the slight increase of sulfate concentration during the COVID-lockdown period in Zhengzhou.