Chemically oxidative removal of polycyclic aromatic hydrocarbons (PAHs) in soil is related to their occurrence state. Whether the heterogeneity of natural organic matter has an effect on the occurrence of PAHs in soil and, if there is an effect, on the oxidative removal efficiency of PAHs remains unknown. In this study, the removal efficiencies of 16 priority PAHs aged in humic acids (HAs) of different soil aggregate fractions by various oxidants were investigated by combining soil fractionation and microreaction experiments. Results showed that the accumulations of PAHs in particulate HA (P-HA) and microaggregate occluded HA (MO-HA) mainly occurred in the early period of the aging time frame. In contrast, PAH accumulation in non-aggregated silt and clay associated HA (NASCA-HA) was relatively slow and tended to saturate in the late period of the aging time frame. The cumulative contents of PAHs throughout the entire aging period in MO-HA and NASCA-HA were significantly greater than that in P-HA. The aged PAHs in P-HA and NASCA-HA exhibited the highest and lowest removal efficiencies, respectively. This ranking was mainly governed by the molecular size and polarity of HAs. Sodium persulfate and potassium permanganate had the highest removal efficiencies in total PAHs in HAs, with average efficiencies of 85.8% and 79.1%, respectively, in P-HA. Hydrogen peroxide had the lowest degradation efficiency in PAHs. In particular, the degradation efficiency of total PAHs in NASCA-HA was lowered to 31.0%. PAH congeners in HAs showed a large difference in oxidative removal efficiency. Low-ring PAH was more easily degraded than medium- and high-ring PAHs, and in most treatments, fluoranthene and pyrene in the medium ring and benzo[a]pyrene in the high ring demonstrated higher efficiencies than other PAHs with the same number of rings. Our findings are useful in promoting the accurate and green remediation of PAH-contaminated soils.

Anthropogenic metal contamination can cause increased stress in exposed organisms, but it can be difficult to disentangle the anthropogenic influence from natural variation in environmental conditions. In the proximity of a closed lead (Pb)/zinc (Zn) mine in northern Sweden, the health effects of Pb exposure, essential element (calcium [Ca] and Zn) uptake, and prey availability and composition were estimated on pied flycatcher (Ficedula hypoleuca) nestlings, using hemoglobin (Hb) level as a proxy for health. Pb concentration in nestling blood range between 0.00034 and 2.21 μg/g (ww) and nestlings close to the mine had higher Pb concentrations and lower Hb, but contrary to our hypothesis, Hb was not directly related to Pb accumulation. Proportions of flying terrestrial and aquatic insects in available prey and availability of flying terrestrial insects were positively associated with nestling Hb, whereas the proportion of terrestrial ground living prey, the most common prey type, showed a negative association. This suggests that positive influence of certain prey, which does not have to be the most common in the surroundings, can counteract the negative effects from Pb contamination on bird health. Nestlings inhabiting sites adjacent to lakes had an advantage in terms of prey composition and availability of preferred prey, which resulted in higher Hb. As such, our results show that during moderate exposure to metals, variation in natural conditions, such as prey availability, can have great impact on organism health compared to Pb exposure.

Multi-layered engineered landfill consists of the bottom liner layer (mainly bentonite clay (B)) upon which the hazardous wastes are dumped. In current practice, sand (S) is mixed with bentonite to mitigate the adverse effects of using bentonite alone in the liner layer. Incorporation of waste and unutilized fly ash (FA) as an amendment material to B has been explored in terms of its hydro-mechanical properties, but not gauged its adsorption potential. Indian subcontinent primarily relies on the thermal power source, and FA dumps have already reached its full capacity. The objective of this study is to explore the adsorption characteristics of four B-FA composite mixes sourced within India, considering Pb²⁺ as a model contaminant. The effect of fly ash type, fly ash amendment rate and adsorbate concentration was explored in the current study and juxtaposed with B-S mixes, based on 960 batch adsorption tests. Both B-FA and B-S mixes reached equilibrium adsorption capacity within 65 min. At higher adsorbate concentrations (commonly observed in the liner), B-FA mixes exhibited superior adsorption capacity, mainly one mixed with Neyvelli fly ash (NFA). The effect of higher amendment rate had little impact on the adsorption capacity at different concentration, but gradually decreased the percentage removal of Pb²⁺. The B-S mix showed a drastic decrease in percentage removal at higher adsorbate concentration among all tested mixes. Systematic characterization including geotechnical properties, microstructure and chemical analysis was also done to interpret the obtained results. Both Freundlich and Langmuir models fitted the isotherm data well for all B-FA mixes. The maximum adsorption capacity from the isotherm was correlated to easily measurable Atterberg limits by two empirical relationships.

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal).This article has been retracted at the request of the Editors-in-Chief and Authors. The corresponding author informed the journal that full permission had not been obtained to use all the samples documented in the study. The authors apologise for any inconvenience caused.

Owing to the substantial consumption of caffeinated food, beverages, and medicines worldwide, caffeine is considered the most representative pharmaceutically active compound (PhAC) pollutant based on its high abundance in the environment and its suitability as an indicator of the anthropogenic inputs of PhACs in water bodies. This review presents a worldwide analysis of 132 reports of caffeine residues in freshwater environments. The results indicated that more than 70% of the studies reported were from Asia and Europe, which have densely populated and industrially developed areas. However, caffeine pollution was also found to affect areas isolated from human influence, such as Antarctica. In addition, the maximum concentrations of caffeine in raw wastewater, treated wastewater, river, drinking water, groundwater, lake, catchment, reservoir, and rainwater samples were reported to be 3.60 mg/L, 55.5, 19.3, 3.39, 0.683, 174, 44.6, 4.87, and 5.40 μg/L, respectively. The seasonal variation in caffeine residues in the freshwater environment has been demonstrated. In addition, despite the fact that there was a small proportion of wastewater treatment plants in which the elimination rates of caffeine were below 60%, wastewater treatment is generally believed to have a high caffeine removal efficiency. From a pharmacy perspective, we proposed to adopt effective measures to minimize the environmental risks posed by PhACs, represented by caffeine, through a new concept known as ecopharmacovigilance (EPV). Some measures of EPV aimed at caffeine pollution have been advised, as follows: improving knowledge and perceptions about caffeine pollution among the public; listing caffeine as a high-priority PhAC pollutant, which should be targeted in EPV practices; promoting green design and production, rational consumption, and environmentally preferred disposal of caffeinated medicines, foods, and beverages; implementing intensive EPV measures in high-risk areas and during high-risk seasons; and integrating EPV into wastewater treatment programs.

Significant progress has been made in reducing emissions of air pollutants in the San Joaquin Valley in California. Nevertheless, from May to October, the valley still experiences numerous exceedances of the ozone health standard. As the standards are tightened, it is becoming harder to design policies to attain them. To better understand historical emissions reductions in the context of necessary future control efforts, we analyze 25 years of hourly measurements of ozone and nitrogen oxides concentrations for the hottest one third of days in Fresno using multiple linear regression analysis. We then analyze the changing dynamics of the weekend effect over the years in order to evaluate the growing importance of day-to-day carryover on ozone concentrations. A simplified model of the day-of-week pattern of ozone concentrations is used to explore the impact of same-day and previous-day concentrations. In addition to ozone, Oₓ (O₃ + NO₂) is used to distinguish reductions of atmospheric oxidants from short-duration exchanges between O₃ and NO₂. The analysis shows that there has been a significant increase in the importance of day-to-day carryover on ozone levels, and that consequently the ozone weekend effect in Fresno has changed over the last 25 years. In the 1990s, lower NOₓ on the weekend led to increased ozone on Saturdays and Sundays but levels of Oₓ remained constant. In the 2010s, lower weekend NOₓ led to reduced ozone on Saturdays, Sundays and Mondays showing that reductions in primary pollutants are sufficient to yield immediate decreases in secondary pollutants. Overall, the photochemical regime in the atmosphere has evolved such that carryover and regional pollution will be increasingly important in determining local ozone concentrations. Policies will therefore need to pay greater attention to regional emissions as local reductions may not be sufficient to meet the health standard.

China is one of the largest coastal countries in the world, which have all kinds of marginal systems. Studies have reported the sedimentary Polycyclic aromatic hydrocarbons (PAHs) pollution status, including their concentrations, sources and risks, in localized marginal systems, which showed significant differences. Thus, a comprehensive understanding of their pollution in marginal systems along China Mainland is urgently needed on a national scale. In the present study, the concentrations of 16 priority PAHs in surface sediments from 62 different marginal systems along China Mainland were reviewed. Their sources were identified and apportioned, and the health risks and ecological risks were also evaluated. As a result, the total sedimentary PAHs varied in a wide range of 4–3700 ng/g, with the lowest values observed in Kenting National Park in East China Sea and the highest values observed in Daliao River estuary in Bohai Sea. Their concentrations suggested that they were not contaminated-weakly contaminated in most study areas, but were contaminated-heavily contaminated in some pollution hot-spots. Source identification and apportion suggested that the sedimentary PAHs were mainly originated from coal combustion, vehicular emission, natural gas combustion and petrogenic source, but the coal combustion and vehicular emission contributed most to their emission (>90%). Risk assessment suggested that the carcinogenic risks were lower than the upper limit of the acceptable range (10⁻⁴), which were acceptable at a large spatial scale. However, for sediments from Qinhuangdao coastal wetland, Daliao River estuary and Yangpu Bay, their carcinogenic risks were higher than 10⁻⁴, which will pose high carcinogenic risks for adults. The non-carcinogenic risks were acceptable in all marginal systems with values lower than the safety guideline (<1). In the ecological risk assessment, their concentrations in some pollution hot-spots were higher than the safety guidelines (effects range low, ERL), suggesting a higher potential ecological risk.

Atrazine contamination is of great concern due to its widespread occurrence in shallow lakes. Here, the distribution and degradation of atrazine in acidic and alkaline lake systems were investigated. Meanwhile, the bacterial communities in different sediments and the effects of environmental factors on atrazine-degrading bacteria were evaluated. In the lake systems without plants, atrazine levels in sediment interstitial water reached peak concentrations on the 4th d. More than 90% of atrazine was then degraded in all sediment interstitial water by day 30. Meanwhile, the degradation rate of atrazine in alkaline sediments was faster than that in acidic sediments. Values of hydroxylated metabolites in the acidic lake sediments tended to be greater. Moreover, the amounts of Proteobacteria, Actinobacteria, Firmicute, Nitrospinae, Aminicenantes, Ignavibacteriae and Saccharibacteria in acidic Tangxunhu Lake sediments were significantly different from alkaline Honghu Lake sediments, while the amounts of Cyanobacteria and Saccharibacteria in sediments treated with atrazine were significantly greater than those in sediments without atrazine (P < 0.05). Notably, pH was the most relevant environmental factor in the quantitative variation of atrazine-degrading bacteria, including in Clostridium-sensu-stricto, Pseudomonas, Comamonas and Rhodobacter. The Mantel test results indicated that the degradation of atrazine in different sediments was mainly affected by the sediment physicochemical properties rather than by the addition of atrazine and the cultivation of hydrophytes.

In recent years, the Chinese government has made great efforts to jointly control and prevent air pollution, especially fine particulate matter (PM₂.₅). However, these efforts are challenged by technical constraints due to the significant temporal and spatial heterogeneity of PM₂.₅ across China. In this study, the Affinity Zone Identification Approach (AZIA), which combines rotated principal component analysis (RPCA) with revised clustering analysis, was developed and employed to regionalize PM₂.₅ pollution in China based on data from 1496 air quality monitoring sites recorded from 2013 to 2017. Two clustering methods, cluster analysis with statistical test (CAST) and K-center-point (K-medoids) clustering, were compared and revised to eliminate unspecified sites. Site zonation was finally extended to the municipality scale for the convenience of the controlling measures. The results revealed that 17 affinity zones with 5 different labels from clean to heavily polluted areas could be identified in China. The heavily polluted areas were mainly located in central and eastern China as well as Xinjiang Province, with regional average annual PM₂.₅ concentrations higher than 66 μg/m³. The new approach provided more comprehensive and detailed affinity zones than obtained in a previous study (Wang et al., 2015b). The North China Plain and Northeastern China were both further divided into northern and southern parts based on different pollution levels. In addition, five affinity zones were first recognized in western China. The findings provide not only a theoretical basis to further display the temporal and spatial variations in PM₂.₅ but also an effective solution for the cooperative control of air pollution in China.

Mitigation of air pollution by plants is a well-established phenomenon. Trees planted on the roadside are known to reduce particulate matter pollution by about 25%. In an urban ecosystem, especially in a metropolitan city such as Delhi, roadside trees are constantly exposed to air pollution. We, therefore, evaluated the effect of air pollution on a common Indian roadside tree, Neem (Azadirachta indica), and its associated microbes in areas with high and low levels of particulate matter (PM) pollution in Delhi. We hypothesized that alteration in the air quality index not only influences plant physiology but also its microbiome.A 100-fold increase in the number of epiphytic and 10–100 fold increase in endophytic colonies were found with 1.7 times increase in the level of pollutants. Trees in the polluted areas had an abundance of Salmonella, Proteus and Citrobacter, and showed increased secondary metabolites such as phenols and tannins as well as decreased chlorophyll and carotenoid. The number of unique microbes was positively correlated with increased primary metabolites.Our study thus indicates that, alteration in air quality affects the natural micro-environment of plants. These results may be utilized as sustainable tools for studying plant adaptations to the urban ecosystem.