In many countries, including Morocco, groundwater contamination with pesticides such as globally banned organochlorides (e.g., dichlorodiphenyltrichloroethane (DDT)) and some accredited organophosphates and pyrethroids poses ecological and human health risks. To assess these risks, we herein monitored pesticides in Saïss plain groundwater (Morocco) during the summer of 2017 and the winter of 2018 using polar organic chemical integrative samplers. The two types of passive samplers were deployed in 22 traditional wells for 14–20 days and subjected to solid-phase extraction. The extracts were analyzed by gas chromatography-mass spectrometry and liquid chromatography-tandem mass spectrometry using a multiresidue method, and 27 pesticides were detected in total. In the summer campaign, 22 pesticides with individual concentrations ranging from <limit of quantitation (LOQ) to 243.1 ng L⁻¹ were identified, whereas 17 compounds with concentrations ranging from <LOQ to 53.8 ng L⁻¹ were detected in the winter campaign. In the summer period, the maximum individual concentrations of chlorothalonil, DDT, and α-hexachlorocyclohexane (α-HCH) equaled 111.7, 36.1, and 22.3 ng L⁻¹, respectively, with the respective values for the winter period equaling 18.14, 16.62, and 22.2 ng L⁻¹. Health risk assessment indicated that the carcinogenic α-HCH, β-HCH, DDT, and dichlorodiphenyldichloroethylene present in groundwater may also contaminate drinking water and thus pose a threat to human health, particularly to that of infants and children. Further analysis revealed that the Saïss aquifer presents a high ecological risk. Thus, the monitoring of pesticides in groundwater by passive sampling was effective and could be combined with human health and ecological risk assessment to develop ways of reducing human and environmental exposure to pesticides.

A total of 106 24-h PM₂.₅ aerosol samples were collected in an urban area (Shijiazhuang, SJZ) and a suburban area (Liulihe, LLH, Fangshan County, Beijing) in the Beijing-Tianjin-Hebei (BTH) region in 2 periods: the first is from 10 July to 10 August, which is before Sept. Third Parade (Period I); the second is from 20 Aug. to 6 Sept. 2015, which is during Sept. Third Parade (Period II). Polar organic tracers, including isoprene, α-pinene, β-caryophyllene and toluene oxidation products, as well as sugars and carboxylic acids were measured. In Period II, rigorous emission-reduction measures were taken in the BTH region. With the anthropogenic emission being cut down significantly, the average concentrations of isoprene, α-pinene, β-caryophyllene and toluene oxidation products and all carboxylic acids (except tetradecanoic, palmitic, and stearic acids), were lower in Period II than those in Period I in LLH, indicating that the SOA tracers were decreased with precursor emission volumes and yields in the atmosphere. Moreover, sugar compounds were shown with comparable levels during the two periods in LLH, suggesting that no measures were taken to reduce the intensities of the biogenic sources. On the contrary, tetradecanoic, palmitic, and stearic acids were shown with obviously higher concentrations in Period II than those in Period I, demonstrating that cooking fumes increased during Sept. Third Parade period.The positive matrix factorization (PMF) model combining with tracer-based method was applied to explore the sources of secondary organic carbon (SOC). It reveals that the sources of SOC include isoprene, α-pinene, β-caryophyllene and toluene oxidation products, fossil fuel combustion, cooking fumes and regionally transferred aged aerosols. These sources accounted for 11.3%, 9.0%, 15.5%, 10.9%, 29.2%, 2.9%, 21.1% of SOC for SJZ, and 12.7%, 11.2%, 9.7%, 14.4%, 25.3%, 0%, 26.7% of SOC for LLH, during the whole sampling periods respectively.

In addition to being historically intentionally manufactured as commercial products, polychlorinated biphenyls (PCBs) can be unintentionally released as by-products from industrial processes. Recent studies have emphasized the importance of unintentionally produced PCBs (UP-PCBs) and have even identified them as major contributors to atmospheric PCBs. However, little is known about contributions of UP-PCBs in current soils. In this study, all 209 PCB congeners were analyzed in agricultural soils on a national scale to investigate the influence of unintentional sources on Chinese soil. The concentration of Σ₂₀₉PCBs in soils across China was in the range of 64.3–4358 pg/g. Four non-Aroclor congeners, i.e., PCB11, PCB44 + 47+65, PCB68, and PCB209, were dominant among all PCBs, averagely accounting for 26.3%, 8.83%, 3.03%, and 2.80% of total PCBs, respectively. PCB11 and PCB209 were found to be higher in East China, while PCB44 + 47+65 and PCB68 were higher in South China. Their spatial distributions were largely dependent on local sources. The results of source apportionment indicated that the legacy of historically produced and used commercial PCB mixtures was the dominant contributor to seven indicator PCBs in Chinese agricultural soils, especially high-chlorinated congeners. However, unintentional sources (i.e., pigment/paint, combustion-related sources, and polymer sealant), which contributed 57.4% of the total PCBs, are controlling PCB burdens in agricultural soils across China.

This meta-analysis systematically evaluated the effects of water improvement and defluoridation on fluorosis-endemic areas in North and South China. The study used PubMed, Embase, China National Knowledge Infrastructure, and Wanfang to retrieve relevant research studies published between January 2000 and October 2019. The data included water fluoride levels, dental fluorosis prevalence in children 8–15 years of age, urinary fluoride levels in children and adults, and skeletal fluorosis prevalence in adults. Fixed-effects and random-effects models were used in the meta-analysis. A total of 17 research articles met the inclusion criteria and had an average water improvement period of 15.8 years. With water improvement, water fluoride levels decreased from 2.72 mg/L to 0.54 mg/L (95% confidence intervals: −2.75, −1.58), which was below the standard for drinking water (1.5 mg/L). Additionally, after water improvement, the prevalence of dental fluorosis decreased from 54.5% to 36.2% (95% confidence intervals: 0.12, 0.31) in children, and the prevalence of skeletal fluorosis decreased from 13.7% to 4.2% (95% confidence intervals: 0.16, 0.40) in adults. Urinary fluoride levels decreased from 3.06 mg/L to 1.70 mg/L (OR = −2.03, 95% confidence intervals: −2.77, −1.30) in children and from 2.29 mg/L to 1.72 mg/L (OR = −0.57, 95% confidence intervals: 0.65, −0.49) in adults. The results showed that the prevalence of dental fluorosis and skeletal fluorosis and urinary fluoride levels were significantly reduced by water improvement. This study findings revealed that the effects of water improvement and defluoridation were greater in South China than in North China, and it is obviously related to the time of water improvement and reducing fluoride.

Ion sorption on soil and sediment has been reported to be potentially affected by bacteria which may interact both physically and chemically with solid surfaces. However, whether and how bacteria affect the sorption of inorganic phosphate (P) on soil colloids remains poorly known. Here, we comparably investigated the P sorption on four soil colloids (three highly weathered soils including two Oxisols and one Ultisol and one weakly weathered soil Alfisol) and their complexes with Bacillus subtilis and Pseudomonas fluorescens. Batch experiments showed a notable reduction in P sorption on the colloids of highly weathered soils by the two bacteria at varying P concentrations and pHs; whereas that on the colloids of Alfisol appeared to be unaffected by the bacteria. The inhibitory effect was confirmed by both greater decline in P sorption at higher bacteria dosages and the ability of the bacteria to desorb P pre-adsorbed on the colloids. Further evidence was given by isothermal titration calorimetric experiments which revealed an alteration in enthalpy change caused by the bacteria for P sorption on Oxisol but not for that on Alfisol. The B. subtilis was more efficient in suppressing P sorption than the P. fluorescens, indicating a dependence of the inhibition on bacterium type. After association with bacteria, zeta potentials of the soil colloids decreased considerably. The decrease positively correlated with the decline in P sorption, regardless of soil and bacterium types, demonstrating that the increment in negative charges of soil colloids by bacteria probably contributed to the inhibition. In addition, scanning electron microscopic observation and the Derjaguin–Landau–Verwey–Overbeek theory prediction suggested appreciable physical and chemical interactions between the bacteria and the highly weathered soil colloids, which might be another contributor to the inhibition. These findings expand our understandings on how bacteria mobilize legacy P in soils and sediments.

The atmosphere as a temporary habitat for airborne microbial communities is a valuable topic to explore, and it is through aerobiological studies that the diversity of biological particles and their release, emission, transport, deposition, and impact are assessed. Specific microorganisms are involved in meteorological processes, and phytosanitary and public health concerns. Airborne microbial composition is related to factors such as geographic region and weather conditions.In this study a metagenomic approach was used to determine the composition of bacterial and fungal communities in the air of two different land-use areas (urban area and semi-rural area), during dry and rainy seasons in Mexico City. Air sampling was carried out with a Hirst-type spore trap, collecting the samples simultaneously in both study areas. Forty-two bioaerosol samples were collected, and the DNA obtained was sequenced using Next-Generation Sequencing. The results indicated that the bacterial communities were represented mainly by the phyla Actinobacteria, Proteobacteria, Firmicutes, Bacteroidetes, Cyanobacteria, and the fungal communities by the phyla Ascomycota followed by Basidiomycota. The evident changes in microbial composition were related more to seasonality than to locality, since both UA and SRA showed a high degree of urbanization, despite some differences in land use. Continuous monitoring of atmospheric bioaerosols is essential to determine the influence of meteorological factors on the composition of the aerial microbiota.

The levels and characteristics of atmospheric metals vary in time and location, can result in various health impacts, which increases the challenge of air quality management. We aimed to investigate PM₂.₅-bound metals in multiple locations and propose a methodology for comparing metal elements across study regions and prioritizing source contributions through integrated health risk assessments. PM₂.₅-bound metals were collected in the urban, suburban, rural, and industrial regions of Taiwan between 2016 and 2018. We incorporated the positive matrix factorization (PMF) with health risk assessments (considering estimates of the margin of exposure (MOE) and excess cancer risk (ECR)) to prioritize sources for control. We found that the concentrations of Fe, Zn, V, Cu, and Mn (industry-related metals) were higher at the industrial site (Kaohsiung) and Ba, Cr, Ni, Mo, and Co (traffic-related metals) were higher at the urban site (Taipei). The rural site (Hualian) had good air quality, with low PM₂.₅ and metal concentrations. Most metal concentrations were higher during the cold season for all study sites, except for the rural. Ambient concentrations of Mn, Cr, and Pb obtained from all study sites presents a higher health risk of concern. In Kaohsiung, south Taiwan, PM₂.₅-bound metals from the iron ore and steel factory is suggested as the first target for control based on the calculated health risks (MOE < 1 and ECR > 10⁻⁶). Overall, we proposed an integrated strategy for initiating the source management prioritization of PM₂.₅-bound metals, which can aid an effort for policymaking.

The Sichuan Basin (SCB) in southwestern China is largely affected by air pollution. Understanding the responses of air pollutant concentrations to emission changes is critical for designing and evaluating effective control strategies. Thus, this study used the Community Multi-scale Air Quality (CMAQ) model to simulate PM₂.₅ (i.e., particulate matter with an aerodynamic diameter ≤ 2.5 μm) in winter (January 2015) and ozone (O₃) in summer (July 2015) under nine emission reduction scenarios. For each scenario, the anthropogenic emissions of each air pollutant in each SCB grid cell were reduced by the same percentage, ranging from 10% to 90%. We found that approximately 30–70% emission reductions are required to reduce the January mean PM₂.₅ concentrations in all the SCB urban centers to a value that is less than the Chinese standard for daily mean PM₂.₅ (24-h PM₂.₅: 75 μg m⁻³). However, the January mean PM₂.₅ concentrations under 90% emission reduction still exceeded the World Health Organization (WHO) guideline (25 μg m⁻³) in 16 SCB urban centers. Moreover, reducing both SCB and non-SCB emissions were critical for achieving the PM₂.₅ level recommended by WHO. An 80% emission reduction was required to prevent the occurrence of 8-h O₃ (i.e., daily maximum 8-h mean O₃) non-attainment days in all SCB urban centers. Under 90% emission reduction, July mean 8-h O₃ concentrations still exceeded the WHO guideline of 47 ppb in approximately 35% of the SCB areas. In conclusion, this study suggests that (1) compared with the governmental emission reduction targets for 2015–2020 (2–27%), more significant emission reductions are required to meet the Chinese and WHO pollution standards; and (2) both SCB and non-SCB emissions must significantly reduce to achieve the desired pollution targets.

Polybrominated diphenyl ethers (PBDEs) are listed as persistent organic pollutants (POPs) in the Stockholm Convention. It has been established that PBDEs may be released into the environment during improper handling and disposal of e-waste and other products containing PBDEs that is prevalent in developing countries. This research work assessed the status of PBDE contamination at dumpsites in Nigeria. Soil and edible plant samples were collected from the dumpsites and control sites for analysis. The concentrations of ∑₇PBDE in the topsoils around the dumpsites at 0–15 cm depth ranged from 112 to 366 ng/g dry weight (dw) while that of the topsoil of the control site 500 m from the dumpsite ranged from 26.8 to 39.7 ng/g dw. These high concentrations stem likely from open burning of waste including electronic waste on the landfills. Plant samples (bentgrass, spinach, tomatoes, pumpkin and sweet potatoes) around the dumpsites were found to be contaminated by PBDEs with levels ranging from 25.0 to 60.5 ng/g dw in plant roots and from 8.45 to 32.2 ng/g dw in plant shoots for ∑₇PBDE. This suggests that consumption of vegetables by humans and ingestion of contaminated soils and feed by chickens and cows can transfer PBDEs into the human food chain around the dumpsites. The comparison of PBDE levels in soils and the PBDE levels in chicken eggs from the former study indicate that PBDE levels in the soils are sufficient to explain the levels in the chicken eggs with a reasonable carry-over rate for PBDEs of 0.28 on average. The PBDE contamination in the soil was sufficient to result in a relevant exposure of humans via accumulation in eggs. The study shows that a better management of end-of-life products containing PBDEs is needed to reduce PBDE exposure risk in Africa.

This paper reports the chemical and light extinction characteristics of fine aerosol (PM₂.₅) during the winter period (2017–18) at Lumbini, Nepal, a rural site on the Indo Gangetic Plains. A modified IMPROVE algorithm was employed to reconstruct light extinction by chemical constituents of aerosol. The fine aerosol levels impacted visibility adversely during daytime, but during nighttime visibility was controlled by fog droplets rather than by aerosols. The PM₂.₅ chemical constituents showed varying characteristics during clear and polluted days. The average NO₃⁻/SO₄²⁻ concentration ratio was 0.57 during clear and 1.36 and polluted days, signifying a change in secondary inorganics and formation processes mainly due to decreasing photochemical production and due to increased partitioning of nitrate particles at a lower temperature. The increased secondary organics contribution and the higher OM/OC ratio (2.2) during polluted days showed the vital role of aqueous processing and biomass burning emissions in determining the concentration of organics. Total light extinction was 2.3 times higher on polluted days compared to clear days, while the PM₂.₅ mass concentration was 1.5 times higher. This variation in mass and extinction order signifies that various chemical components in fine particles have a more considerable impact on light extinction. On clear days we found that carbonaceous particles (OM and EC) made a major contribution to light extinction. In contrast, the extinction contribution by secondary inorganic (especially NH₄NO₃) increased significantly during polluted days, with hygroscopic growth and enhanced scattering efficiency at higher RH conditions playing a major role. The comparison between clear and polluted days altogether suggests that regulating the nitrate sources can help significantly in improving the visibility levels and restrict fog haze development during wintertime in rural IGP.