Occurrence and distribution of PAHs, PCBs, and chlorinated pesticides in Tunisian soil irrigated with treated wastewater

Concentrations, phase exchanges and source apportionment of polycyclic aromatic hydrocarbons (PAHs) In Bursa-Turkey

The present study aimed to determine the pollution levels derived from polycyclic aromatic hydrocarbons (PAHs) in air, plant and soil samples and to reveal the PAH exchange at the soil-air, soil-plant and plant-air interfaces. In this context, air and soil samples were collected in approximately 10-day periods between June 2021 and February 2022 from a semi-urban area in Bursa, an industrial city with a dense population. Also, plant branch samples were collected for the last three months. Total PAH concentrations in the atmosphere (∑₁₆PAH) and soil (∑₁₄PAH) ranged from 4.03 to 64.6 ng/m³ and 13-189.4 ng/g DM, respectively. PAH levels in the tree branches varied between 256.6 and 419.75 ng/g DM. In all air and soil samples, PAH levels were low in the summer and reached higher values in the winter. 3-ring PAHs were the dominant compounds, and their distribution in air and soil samples varied between 28.9%-71.9% and 22.8%-57.7%, respectively. According to the results of diagnostic ratios (DRs) and principal component analysis (PCA), both pyrolytic and petrogenic sources were found to be effective in PAH pollution in the sampling region. The fugacity fraction (ff) ratio and net flux (F_net) values indicated that the direction of movement of PAHs was from soil to air. In order to better understand the PAH movement in the environment, soil-plant exchange calculations were also achieved. The ratio of ∑₁₄PAH values measured to modeled concentrations (1.19<ratio<1.52) revealed that the model worked well for the sampling region and produced reasonable results. The ff and F_net levels showed that branches were saturated with PAHs and the direction of PAH movement was from plant to soil. The plant-air exchange results indicated that the direction of movement of PAHs was from plant to air for low molecular weight PAHs and the opposite was true for compounds with high molecular weight ones.

Assessment of organochlorine contamination source and ecological risk in the Litani River: polychlorinated biphenyls and organochlorinated pesticides in surface sediments

In this paper, we investigate for the first time the contamination source and the ecological risk associated to organochlorinated compounds in the Litani system. For this purpose, the levels of 7 polychlorinated biphenyls (PCBs) and 13 organochlorinated pesticides (OCPs) were assessed, using a microwave-assisted extraction coupled to gas chromatography-electron capture detector (MAE/GC-ECD) method, in surficial sediments from 30 sites along the main course of the river, two major tributaries, and the Quaraoun Lake. ∑7PCBs exhibited total concentrations ranging from 0.11 to 8 ng g-1 of dry weight and are not able apparently to pose ecological risks since none of the samples showed concentration above the effects range low (ERL) guideline (22.7 ng g-1). The detected levels of OCPs in the river were significantly higher than those of PCBs; ∑13OCPs range from 0.5 to 46.5 ng g-1 of dry weight. Overall, the integrated eco-toxicological risk imposed by the organochlorine contamination in the Litani River, estimated as the mean effects range medium quotient (mERMq), is considered low with risk probability lower than 21% in all sites. The six dichlorodiphenyltrichloroethane-based pesticides (∑6DDT) contributed to more than 70% of the mERMq in 15 over the 29 included sites. Moreover, the approach of ∑6DDT/∑7PCB ratios was applied to investigate the contamination source. ∑6DDT/∑7PCB was higher than one in all samples suggesting that the organochlorine contamination result from agricultural activities set in the surrounding areas of the Litani River.

Presence of selected organochlorine pesticides (OCPs) in sediments and biota of River Satluj, Pakistan: first report

Abstract In the developed countries, the use of OCPs (organochlorine pesticides) has been banned. However, in South Asia several of them are still in use. In Pakistan and India a constant addition of OCPs into the atmosphere has been indicated by various researchers. In this study levels of selected organochlorine pesticide residues were assessed in sediment and biota collected from four (4) water reservoirs (3 Barrages & 1 Siphon) on the River Satluj Pakistan, along 231 miles (372 km) of River stretch which was further divided into 12 sampling sites. It was aimed to find out the levels of organochlorine pesticide (OCPs) residues in sediments and from selected fish species (Labeo rohita, Wallagu attu, Cyprinus carpio) of the River Satluj Pakistan. The Organochlorine residues (seven pesticides) present in samples of sediments and biota were investigated through multi residue method, using Gas Chromatograph (GC-ECD).In the current study, the concentration of DDT, was investigated in Wallago attu (0.786-3.987 ppb), Labeo rohita (0.779-4.355 ppb) and Cyprinus carpio (1.234-5.654 ppb). DDE was also found in Cyprinus carpio (1.244-6.322 ppb), Wallag attu (0.877-4.221 ppb) and Labeo rohita (2.112-5.897 ppb). Aldrin was not observed in Labeo rohita and Wallago attu. Currently, lindane and DDE was found predominately high in the sediments of study area at SZ-4 (Panjnad Barrage) ranging (2.238-8.226 ppb) and (4.234-6.876 ppb), respectively. Heaptachlor was found only at SZ-4 (Panjnad Barrage) from the sediments with concentration ranging (0.032-234 ppb). In short all other residues investigated were found below the MCL (maximum concentration level) in all the compartments of the study area set by various agencies like WHO/FAO- Codex Alimenterious.

Valorization of Traditional Alcoholic Beverages: The Study of the Sicilian Amarena Wine during Bottle Aging

Traditional alcoholic beverages have always been part of the Mediterranean culture and, lately, they have been re-evaluated to valorize both the territory and local customs. In this study, the Amarena wine, a fortified wine included in the national list of the traditional agri-food products, was characterized during bottle aging for oenological parameters, chromaticity, volatiles, and inorganic elements. Then, experimental data were visually interpreted by a principal component analysis (PCA). PCA revealed that most of oenological parameters (i.e., alcoholic grade, total dry extract, sugars, organic acids, and phenolic compounds) had a scarce discriminating power. Additionally, ethyl esters were only present in younger products, while remaining at quite constant levels. Conversely, certain metals (i.e., Mg, Na, Mn, Zn, and Cu), chromatic properties, and pH differentiated older Amarena bottles from the younger counterpart. Particularly, acetaldehyde and furanic compounds proved to be valid aging markers. A sensorial analysis highlighted that fruity and floral odors and flavors characterized younger beverages, while dried fruity, nutty, and spicy notes were displayed by older products, along with the valuable attribute of “oxidized” typically observed in aged Sherry wines. Overall, this study may encourage the production and commercialization of the Amarena wine, thus preserving the cultural heritage of the Mediterranean area.

Environmental and human health risk assessments of polycyclic aromatic hydrocarbons in particulate matter in Nigeria

Polycyclic aromatic hydrocarbons (PAHs) are an important organic group in particulate matter which has attracted much attention among the scientific community in terms of health risk because of their carcinogenic, mutagenic, and ubiquitous nature in the environment. In this study, PAHs in particulate matter in Okitipupa were determined. Indoor and outdoor particle samples were sampled with the aid of SKC Air Check XR5000 high-volume gravimetric sampler, and analyzed using gas chromatography flame ionization detector (GC-FID). The results obtained showed that high molecular weight PAHs (5-ring, 6-ring PAHs) had higher mean concentration than low molecular weight PAHs (2-ring, 3-ring PAHs), in both indoor and outdoor particulate matter. Health risk assessments from exposure to these PAHs were also determined using toxicity equivalence quotient (TEQ), mutagenicity equivalence quotient (MEQ), incremental life cancer risk (ILCR), and hazard quotient (HQ). Dibenz(a,h)anthracene had the highest mean concentration across the sample location in both indoor and outdoor with values ranging from 33 to 31 and 90 to 93 µg/m³ respectively. The total mean concentration in outdoor PAHs ranged from 280 to 329 µg/m³, while total mean concentration in indoor PAHs ranged from 74 to 104 µg/m³. The incremental lifetime cancer risk in indoor ranged from 6.9 × 10^-7 to 1.2 × 10^-5, while the ILCR in outdoor ranged from 8.5 × 10^-6 to 1.0 × 10^-5. The hazard quotient in indoor ranged from 7.6 × 10^-5 to 2.2 × 10^-3, while the HQ in outdoor ranged from 10 × 10^-4 to 1.4 × 10^-3. These values are within the WHO permissible limit, and therefore underscores the danger associated with the inhalation of polycyclic aromatic hydrocarbons in Okitipupa.

A novel chitosan-urea encapsulated material for persulfate slow-release to degrade organic pollutants

A novel eco-friendly material (CS-U@PS) for persulfate slow-release to effectively degrade organic pollutants (methyl orange and pyrene) was synthesized using chitosan and urea as the encapsulated framework materials via an emulsion cross-linking method for the first time. The obtained CS-U@PS exhibits spherical shapes with a uniform size of approximately 2-3 µm according to the particle-size distribution and SEM image results. The slow-release mechanism was proposed through a kinetics model study and the Ritger-Peppas model fit well (r² = 0.9699) to indicate that the slow-release process is non-Fickian diffusion. The influences of urea and PS dosages and oxidative conditions on methyl orange degradation were studied, and all the results suggested that urea played an important role in PS slow-release and can also catalyze the activation of PS by iron to further produce radicals and improve the removal efficiency of pollutants. A pyrene removal rate of 90.53% was achieved in aqueous solutions and an above 80% removal rate was obtained in weakly acidic or neutral soil environments by CS-U@PS activated by Fe²⁺ with citric acid as the chelating agent. Therefore, the fabricated slow-release oxidation materials exhibit application potential for the remediation of organic polluted groundwater and soil.

Phycoremediation of wastewater for pollutant removal: A green approach to environmental protection and long-term remediation

Surface and water bodies in many parts of the world are affected due to eutrophication, contamination and depletion. The approach of wastewater treatment using algae for eliminating nutrients and other pollutants from domestic wastewater is growing interest among the researchers. However, sustainable treatment of the wastewater is considered to be important in establishing more effective nutrient and pollutant reduction using algal systems. In comparison to the conventional method of remediation, there are opportunities to commercially viable businesses interest with phycoremediation, thus by achieving cost reductions and renewable bioenergy options. Phycoremediation is an intriguing stage for treating wastewater since it provides tertiary bio-treatment while producing potentially valuable biomass that may be used for a variety of applications. Furthermore, the phycoremediation provides the ability to remove heavy metals as well as harmful organic substances, without producing secondary contamination. In this review, the role of microalgae in treating different wastewaters and the process parameters affecting the treatment and future scope of research have been discussed. Though several algae are employed for wastewater treatment, species of the genera Chlamydomonas, Chlorella, and Scenedesmus are extensively utilized. Interestingly, there is a vast scope for employing algal species with high flocculation capacity and adsorption mechanisms for the elimination of microplastics. In addition, the algal biomass generated during phycoremediation has been found to possess high protein and lipid contents, promising their exploitation in biofuel, food and animal feed industries.

A review on occurrence of emerging pollutants in waters of the MENA region

Little is known about the occurrence of emerging pollutants (EPs) in waters in the Middle East and North Africa (MENA) region despite the extensive use of low-quality water there. Available data dealing with the sources, occurrence and removal of EPs within the MENA region in different categories of water is collected, presented and analyzed in this literature review. According to the collected database, the occurrence and removal efficiency of EPs in the water matrix in the MENA region is available, respectively, for 13 and six countries of the 18 in total; no available data is registered for the rest. Altogether, 290 EPs have been observed in different water matrices across the MENA countries, stemming mainly from industrial effluents, agricultural practices, and discharge or reuse of treated wastewater (TWW). Pharmaceutical compounds figure among the most frequently reported compounds in wastewater, TWW, surface water, and drinking water. Nevertheless, pesticides are the most frequently detected pollutants in groundwater. Worryingly, 57 cases of EPs have been reported in different fresh and drinking waters, exceeding World Health Organization (WHO) and European Commission (EC) thresholds. Overall, pharmaceuticals, organic compounds, and pesticides are the most concerning EP groups. The review revealed the ineffectiveness of treatment processes used in the region to remove EPs. Negative removals of some EPs such as carbamazepine, erythromycin, and sulfamethoxazole were recorded, suggesting their possible accumulation or release during treatment. This underlines the need to set in place and strengthen control measures, treatment procedures, standards, and policies for such pollutants in the region.

Application of constructed wetlands in the PAH remediation of surface water: A review

Polycyclic aromatic hydrocarbons (PAHs) pose adverse risks to ecosystems and public health because of their carcinogenicity and mutagenicity. As such, the extensive occurrence of PAHs represents a worldwide concern that requires urgent solutions. Wastewater treatment plants are not, however, designed for PAH removal and often become sources of the PAHs entering surface waters. Among the technologies applied in PAH remediation, constructed wetlands (CWs) exhibit several cost-effective and eco-friendly advantages, yet a systematic examination of the application and success of CWs for PAH remediation is missing. This review discusses PAH occurrence, distribution, and seasonal patterns in surface waters during the last decade to provide baseline information for risk control and further treatment. Furthermore, based on the application of CWs in PAH remediation, progress in understanding and optimising PAH-removal mechanisms is discussed focussing on sediments, plants, and microorganisms. Wetland plant traits are key factors affecting the mechanisms of PAH removal in CWs, including adsorption, uptake, phytovolatilization, and biodegradation. The physico-chemical characteristics of PAHs, environmental conditions, wetland configuration, and operation parameters are also reviewed as important factors affecting PAH removal efficiency. Whilst significant progress has been made, several key problems need to be addressed to ensure the success of large-scale CW projects. These include improving performance in cold climates and addressing the toxic threshold effects of PAHs on wetland plants. Overall, this review provides future direction for research on PAH removal using CWs and their large-scale operation for the treatment of PAH-contaminated surface waters.

Legacy persistent organochlorine pollutants and polycyclic aromatic hydrocarbons in the surface soil from the industrial corridor of South India: occurrence, sources and risk assessment

Conversion of agricultural fields into the industrial corridor under the State Industries Promotion Corporation of Tamil Nadu Limited (SIPCOT) necessitated the investigation of soil-borne organic contaminants. This study is the first attempt to evaluate the occurrence of organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) in soils from Mambakkam and Cheyyar SIPCOT belt, along the residential, industrial and agricultural transects. Concentrations of Σ₂₈PCBs, Σ₁₆PAHs and OCPs were in the range 0.3-9 ng/g, 33-2934 ng/g and nd-81.4 ng/g, respectively. Residential areas showed higher OCP concentrations than other site types, probably due to their frequent use in vector control programmes. DDT isomers and α-isomer of endosulfan showed low concentrations indicating past usage of these OCPs. Principal component analysis indicated that high-temperature combustion and industrial processes might be the major sources of high molecular weight PAHs, while low-temperature combustion processes might be responsible for low molecular weight PAHs. PCBs in soil were probably attributed to unaccounted combustion processes of e-waste in the region. Carcinogenic PAHs and Σ₂₈PCBs were higher in the industrial sites. Mean Σ₂₈PCBs at Mambakkam (4.8 ng/g) was significantly higher (p < 0.05) than that at the incipient industrial corridor Cheyyar (2.7 ng/g). Lower chlorinated PCBs (3-Cl and 4-Cl) amounted to more than half of Σ₂₈PCBs in 75% of the sites. Total toxic equivalents (TEQs) of PAHs (total BaP_eq) were found to be maximum in industrial areas. Maximum contribution to TEQs due to dioxin-like-PCBs was from PCB-157, followed by PCB-189.

Evaluation of Polycyclic Aromatic Hydrocarbons (PAHs) in Bamboo Shoots from Soil

The toxicity, carcinogenicity and persistence of polycyclic aromatic hydrocarbons (PAHs) pose a great threat to the ecological system and human health. The contamination levels, translocation and source analysis of 16 PAHs in bamboo shoot and its planted soil were investigated. The average concentrations of total PAHs were 18.80 ± 1.90 µg/kg and 123.98 ± 113.36 µg/kg in bamboo shoots and soils, respectively. The most abundant PAH was Phenanthrene (PHE), with the detected average concentrations of 5.85 µg/kg in bamboo shoots and 19.28 µg/kg in soils. The highest detected types of PAHs were 3 rings and 4 rings, with the proportions of 80.69% (bamboo shoots) and 35.23% (soils). The transfer factors of PAHs were ranged from 0.011 to 0.895, in which PAHs with 3 rings showed the strongest transfer ability. The combustion of biomass and petroleum might be the main source of PAHs in the planted soils of bamboo shoots.

Comparative study on the pollution status of organochlorine pesticides (OCPs) and bacterial community diversity and structure between plastic shed and open-field soils from northern China

The pollution status of organochlorine pesticides (OCPs) and microbial community in plastic shed and open-field soils may be different due to the significant variations in environmental factors between the two cultivation modes. However, the differences remain unclear. We conducted a regional-scale survey to investigate the pollution level, distribution, and sources of 20 OCPs, and to evaluate the soil physicochemical properties and bacterial community in soils from plastic shed and open-field locating the north areas of China. We found that levels of total OCPs in the plastic shed soils were significantly higher than those in the nearby open-field soils. Most of these OCPs were attributed to historical application, except for dichlorodiphenyltrichloroethanes (DDTs) due to the fresh input along with dicofol application. Soil pH (for both cultivation modes) and total organic carbon (TOC) content (only for plastic sheds) were significantly correlated with the total OCP concentrations. Additionally, microbial diversity and richness were generally lower in plastic shed soils than in nearby open-field soils for each region. The bacterial community variation among different regions might be principally determined by the soil type. Soil pH had the greatest impact on the microbial community across all plastic shed and open-field samples. These results provide a better understanding of the environmental impact and ecological risk of OCPs in soils with different cultivation modes.

Fe3+-NTA as iron source for solar photo-Fenton at neutral pH in raceway pond reactors

This work presents, for the first time, a kinetic study of the solar photo-Fenton process at neutral pH mediated by the Fe³⁺-NTA complex (molar ratio 1: 1) applied to remove contaminants of emerging concern (CECs). To this end, wastewater treatment plant (WWTP) secondary effluents were treated in a raceway pond reactor (RPR) at pilot plant scale with 0.1 mM Fe³⁺-NTA and 0.88 mM H₂O₂ under average solar UVA irradiance of 35 W/m². Sulfamethoxazole and imidacloprid, at 50 μg/L of initial concentration each, were selected as model CECs. Up to 40% of the sum of both model CECs was removed from simulated WWTP effluent by the Fe³⁺-NTA Fenton-like process, and >80% was removed by solar photo-Fenton. The effect of liquid depth in the reactor was evaluated, showing an increase of the treatment capacity from 12 mg CEC/m²·h to 18 mg CEC/m²·h when liquid depth increased from 5 to 15 cm. Afterwards, these results were validated with real WWTP effluents and compared with the results obtained with the Fe³⁺-EDDS complex under the same operating conditions. The same CEC removal rates were obtained with Fe³⁺-NTA and Fe³⁺-EDDS at 5 cm of liquid depth (kinetic constants of 0.110 min^-1 and 0.046 min^-1 for sulfamethoxazole and imidacloprid, respectively). Conversely, at 15 cm of liquid depth, the degradation rates were lower with Fe³⁺-NTA (kinetic constants of 0.034 min^-1 for sulfamethoxazole and 0.017 min^-1 for imidacloprid), whereas with Fe³⁺-EDDS the values were 0.076 min^-1 and 0.047 min^-1 for sulfamethoxazole and imidacloprid, respectively. Regarding process cost estimation, the use of NTA as iron chelate for solar photo-Fenton at neutral pH at pilot plant scale resulted very cost-effective (0.13-0.14 €/m³) in comparison with the use of EDDS (0.46-0.48 €/m³) at the two liquid depths tested.

The occurrence and levels of polycyclic aromatic hydrocarbons (PAHs) in African environments-a systematic review

In the African continent, several studies have been conducted to determine PAH pollution levels with their associated health risks in the environment. However, these studies are very much disconnected. The objective of this study is to conduct a systematic review that serves as a comprehensive report on the PAH-related studies conducted in the African continent. Data sources are from Google Scholar and PubMed. English language studies that reported on PAH levels in smoked fish and meat, soils and dust, aquatic environments, indoor and outdoor air, and ready-to-eat food items were selected. Specific PAHs included the following: 33 PAHs comprising of the 16 USEPA PAHs, non-alkylated PAHs, non-alkylated PAHs, oxygenated PAHs (OPAHs), and azaarenes (AZAs). Study appraisal and synthesis methods: The Newcastle-Ottawa Scale (NOS) was adapted to assess the quality of the selected studies basing on their sampling methods, analytical techniques, and results. A total of 121 studies were reviewed, with the majority (56) being from Nigeria. PAH levels in smoked fish and meat, soils and dust, aquatic environments, indoor and outdoor air, and ready-to-eat food items recorded total concentrations of PAHs ranging from 5 to 3585 μg/kg, BDL to 6,950,000 μg/kg, 0 to 10,469,000 μg/kg, 0 to 7.82 ± 0.85 μg/m³, and 2.5 to 7889 ± 730 μg/kg respectively. Carcinogenic risk assessment for children and adults ranged from very low to very high levels when compared to the ILCR range (10^-6 to 10^-4) defined by the USEPA. Out of 54 African countries, only 19 were represented. The majority of selected studies failed to apply any standard protocols for sample collection and analysis. The low to very high PAH levels reported in studies calls for effective actions on environmental health. Similar systematic reviews are expected to be performed in other continents for a global assessment of PAH pollution.

Concentrations, distributions, sources, and risk assessment of polycyclic aromatic hydrocarbons in topsoils around a petrochemical industrial area in Algiers (Algeria)

Fifty-five samples were collected from topsoils around a petrochemical industrial area at the east of Algiers (Algeria) and analyzed for 16EPA priority PAHs in the aim to determine the concentrations, the distributions, and the possible sources of polycyclic aromatic hydrocarbons (PAHs). The results of the quantification are then devoted to the assessment of the potential risks as the toxicity, the risk for the ecosystem, and the risk for the human health. The sampling sites were classified into four categories: rural, suburban, urban, and industrial-urban. A new extraction method based on the insertion of a preliminary step, using hot water, was proposed to improve the extraction efficiency. Principal component analysis (PCA) and selected diagnostic ratio of PAHs were used to investigate the source apportionment of these PAHs. The potential toxicity, the ecological, and human health risk of PAHs in soil were estimated using the toxic equivalent quotient, the risk quotient, and the total lifetime cancer risk (TLCR) methods, respectively. The proposed new protocol gave improved recovery rates for the sixteen EPA PAHs particularly for low molecular weight PAHs, with satisfactory repeatability (RSD < 10%). The Σ16PAHs concentrations were varied from 143.73 to 4575.65 μg kg^-1 with a mean value of 1209.56 μg kg^-1. Σ16PAH concentrations found for the industrial areas would be 2 times higher than for urban soils and 3 times higher than for the rural soils. The biplots of PCA and the five diagnostic ratios suggested that the most sources of PAHs in the rural, the suburban, and the urban areas are traffic emissions, biomass burning, and coal combustion sources. Some points of the urban-industrial area are from the petroleum source. The found Σ16PAH concentrations and theirs calculated TEQs showed the following trend: industrial-urban > urban > suburban >rural. The potential cancer of human health risks calculated through TLCR results indicated that the exposure to the 7EPA PAH-contaminated soils produces negligible cancer risk to human health.

A review of the impact of wastewater on the fate of pesticides in soils: Effect of some soil and solution properties

Reuse of wastewater (WW) as an agricultural irrigation source is being considered with increasing interest, mainly in arid and semiarid zones. However, due to the complex nature of WW its reuse can have an impact on the fate of the pesticides added to the soils and crops for pest control. This review provides a detailed insight about the main processes involved in pesticide-soil-WW interactions (adsorption/desorption, degradation, transport, plant uptake and field assays) focusing on the role of dissolved organic matter and salt content in the mentioned processes. The influence of pesticide and soil properties in these processes is also discussed. The review explores current research gaps in the pesticide-soil-WW interactions and identifies areas that merit further research, providing a perspective for further scientific exploration.

Occurrence, risk and influencing factors of polycyclic aromatic hydrocarbons in surface soils from a large-scale coal mine, Huainan, China

Coal is one of the most important fossil fuels for energy, but it can cause serious polycyclic aromatic hydrocarbon (PAH) pollution to the environment. In this work, the distribution, sources, influencing factors, and risk assessment of PAHs were studied in a soil of typical coal resource city, Huainan, China. The total concentration of 16 PAHs classified by USEPA in 47 soils ranged from 109.94 to 1105.30 ng/g with a mean concentration of 528.06 ng/g. The PAH concentration was higher in soil of this area than most of the agricultural, urban and industrial soils and lower than some coal mine and coal-fired power plant areas in the world. The principal component analysis (PCA) and diagnostic ratios demonstrated that PAHs in soils were mainly from the coal combustion and refined petroleum products. The total organic carbon (TOC, p < 0.01) and black carbon (BC, p < 0.01) can significantly influence PAH inventories in soils, particularly for PAHs with high molecular weight. In addition, the significantly positive correlations between PAHs in feed coal (p < 0.05), fly ash (p < 0.01), particulate matter (PM_1-2.5 and PM_2.5-10, p < 0.01) and PAHs in soils revealed that the emission sources and deposition processes were also the main factors affecting PAH contents in soils. The estimated values of incremental lifetime cancer risk (ILCR) for children and adults were higher than 10^-4 at all sampling sites, suggesting high carcinogenic risks for local residents, and the most important exposure route for PAHs was dermal absorption. These findings are valuable for assessing the health risk of PAHs in soils around typical coal mine and coal-fired power plants and highlight the urgency of taking actions to control and reduce the carcinogenic risks for local residents.

Organochlorine pesticides contamination in agricultural soils of southern Iran

There is limited information about pesticide contamination in Iran's agricultural land, particularly in plains producing exportable fruits. The aim of this investigation was to evaluate the concentration of organochlorine pesticides (OCPs) including hexachlorocyclohexane (HCH), heptachlor, dichloro-diphenyl-trichloroethane (DDT), chlordane (CHL), and their isomers compounds in agricultural soils of southern Iran. A total of 28 topsoil samples were collected from agricultural lands of Dalaki and Shabankare areas, Bushehr, Iran. In Dalaki area, the mean value of ΣHCH (α, β, γ, δ), ΣDDT (o,p-DDE, o,p-DDD, o,p-DDT, p,p-DDE, p,p-DDD, p,p-DDT, and DDT), and ΣCHL (Trans-chlordane, Cis-chlordane, Heptachlor-exo-epoxide, and Heptachlor) was found to be 0.411 ng/g (dry weight, dw), 4.37 ng/g dw, and 2.04 ng/g dw, respectively. In Shabankare area the mean value of ΣHCH, ΣDDT, and ΣCHL was measured to be 1.38 ng/g dw, 11.99 ng/g dw, and 1.62 ng/g dw, respectively. The concentration trend of pesticides in both areas was as follows: DDT > CHL > HCH. Source identification indicated recent usage of HCH and DDT in the studied areas. Obtaining a cis-chlordane/trans-chlordane ratio greater than one in Shabankare farmlands showed that chlordane was not used recently. The health risk assessment showed that children and adults groups in both areas are exposed to negligible cancer risk. More serious attempts are necessary to reduce usage of OCPs during the agricultural process and the protection of soil and human health in the studied areas.

Assessment of polychlorinated biphenyls (PCBs) in the Himalayan Riverine Network of Azad Jammu and Kashmir

The emission of polychlorinated biphenyls (PCBs) in South Asian countries is one of the great environmental concerns and has resulted in the contamination of surrounding high altitude regions such as Azad Jammu and Kashmir (AJK), Pakistan. This first investigation of Polychlorinated Biphenyl (PCBs) concentrations in the ambient air, water and surface soil was conducted along the extensive stream network in the AJK valley of the Himalayan Region. In 2014, surface soil samples were taken and passive air and water samplers were deployed along the four main rivers, namely Jhelum, Neelum, Poonch and Kunhar, and analysed for PCBs (33 congeners) using GC-MS/MS. The ∑₃₃PCBs concentrations ranged from 31.17 to 175.2 (mean ± SD: 81 ± 46.4 pg/L), ND to 1908 (1054 ± 588.5 pg/g), and 29.8 to 94.4 (52.9 ± 22.7 pg/m³) in surface water, soil and air matrices, respectively. The levels of dioxin-like PCBs (∑₈DL-PCBs) contributed considerably towards the total PCBs concentrations: 60.63% (water), 43.87% (air) and 13.76% (soil). The log transformed air-water fugacity (log fa/fw) ratios ranged from -9.37 to 2.58; with 86.3% of the sampling sites showing net volatilization of selected PCB congeners. Similarly, the fugacity fractions for air-soil exchange exhibited narrow variation (0.8 to < 1) indicating net volatilization of PCBs. The ecological risk assessment showed low potential ecological risks (E_rⁱ  = 1.58-7.63) associated with PCB contamination. The present findings provide baseline data that suggest cold trapping of POPs in the remote mountainous areas of Pakistan and can support environmental management of POPs at the regional level. This pioneer investigation campaign to assess the PCBs concentrations in Himalayan Riverine Network of Azad Jammu and Kashmir, Pakistan helps to develop baseline data of PCBs from the strategically important riverine environment that would help in future regional as well as global ecological studies. However, the effects of temperature variations on the sampling rates of chemicals across a wide spectrum of volatility along the elevation gradient were not taken under consideration for PCBs atmospheric concentrations.

Polyaromatic hydrocarbons in biochars and human health risks of food crops grown in biochar-amended soils: A synthesis study

Soil amendment with biochars is currently being studied worldwide as a sustainable agricultural practice to improve soil and water quality, increase crop productivity, and augment soil carbon storage. However, the formation of polyaromatic hydrocarbons (PAHs) during biochar production is inevitable. Therefore, it is crucial to assess the risks in food safety and human health of crops grown in biochar-amended soils. This paper performed a synthesis study of PAH concentrations in biochars and estimated the risks of soils amended with biochars, based on refereed articles published between 2012 and 2018. The PAH concentrations in biochars ranged greatly, with the dominant proportion being 2-3 ringed PAHs (40%-71%). Biochar application increased the PAH levels in soils at drastically varying extents (0.02-3574 μg/kg), which led to a broad range of PAH concentrations in food crops grown in biochar-amended soils. A five-step method was then introduced to assess the toxicity of biochar-borne PAHs to human health. The total mean incremental lifetime cancer risk for adults was estimated to range between 2.0 × 10^-6-1.9 × 10^-5 via direct contact with and ingestion (inhalation) of contaminated soils or consumption of tainted crops. These results indicated that biochar amendment in soils might pose potential risks to food safety and human health, but the overall cancer risks through exposure to biochar-borne PAHs in soils and food crops were low. Higher application rates (e.g. ≥20 t/ha) of biochars with high PAH contents can be avoided to minimize human cancer risks. Although biochar application in arable farmlands has many environmental and agronomic benefits, holistic and systematic approaches are required to fully assess the benefits and risks before their large-scale adoption. PAHs in biochar may be reduced by improving the biochar production process and developing a cost-effective post-manufacturing treatment.

Effect of liquid depth on microcontaminant removal by solar photo-Fenton with Fe(III):EDDS at neutral pH in high salinity wastewater

In arid Mediterranean countries, such as Tunisia, wastewater often has high salinity, being an obstacle to the elimination of microcontaminants for the reuse of water in agriculture. In this paper, the photo-Fenton process in raceway pond reactors (RPRs) has been successfully applied to a simulated secondary effluent from a Tunisian urban wastewater treatment plant (WWTP), with high chloride load. A mixture of three contaminants of emerging concern (CECs) was used as model pollutants at 50 μg/L each (one antibiotic, sulfamethoxazole and two pesticides, pyrimicarb and imidacloprid). All the assays were conducted at neutral pH with 0.1 mM Fe(III):EDDS at 1:1 molar ratio. The effect of hydrogen peroxide initial concentration (20, 30, and 90 mg/L) on microcontaminant removal was studied. Different liquid depths (5 and 15 cm) were selected to assess the relationship between the microcontaminant removal and the volumetric rate of photon absorption (VRPA). Although the reaction rate was initially photo-limited, after a short reaction time of 15 min, the final yield (≈ 80% of CEC removal) was limited by the photo-degradation of the Fe(III):EDDS complex and excess H₂O₂ was found at all concentrations used. Therefore, treatment times below 15 min should be used. The treatment capacity was three times higher when the liquid depth was increased from 5 to 15 cm. For the first time, these results show that the operation of a 15 cm-deep RPR in continuous flow mode would be suitable for large-scale implementation of the solar photo-Fenton process.

PCDD/PCDFs and PCBs in the irrigation water in Egypt: levels, patterns, and potential sources

The contamination levels of PCDD/PCDFs in irrigation water are the most rarely studied throughout the world. The major problem in Egypt is the lack of studies and statistics about these contaminants of POPs in irrigation water. Therefore, this study is the first comprehensive report to elucidate the estimation and sources of PCDD/PCDFs and PCBs in irrigation water from Egypt and rare for worldwide may provide a reference to future studies of POPs compounds in irrigation water of Egypt. A total of 24 irrigated water samples were collected from different irrigation canals which are adjacent to industrial areas from six Egyptian governorates (Bani Swef, El-Giza, El-Sharkeya, El-Menoufeya, El-Gharbeya, and Alexandria). The study shows that irrigation water canals were contaminated with low levels of PCDDs/PCDFs, which were 0.95 pgWHO-TEQ/l, and the total of PCDD/PCDFs and dl-PCBs were 2.06 pgWHO-TEQ/l with contamination ranging between 0.88 to 2.97 pgWHO-TEQ/l while the levels of indicator PCBs were 18.52 ng/l and ranged between 0.39 to 165.6 ng/l. The most predominant dioxins congeners were HpCDD, OCDD, HpCDF, and OCDF while for dl-PCBs were PCB105 and PCB118, and for ndl-PCBs was PCB138. The areas with recent urbanization and industrialization were more contaminated with PCBs than the unindustrialized area. Lightly to moderately chlorinated congeners dominated the PCB profiles. The major sources for these contaminants were fire bricks followed by textile industries closer to the located sampling sites. The detected pattern was found to be similar to the patterns reported in the air by other studies. Although the concentrations of the studied POPs are found to be low in irrigated water, it may be considered as a potential source of soil pollution due to their accumulation process in the agricultural land and may lead to risk on human health by consuming the agricultural products irrigated by contaminated water.

Stable-Isotope Probing-Enabled Cultivation of the Indigenous Bacterium Ralstonia sp. Strain M1, Capable of Degrading Phenanthrene and Biphenyl in Industrial Wastewater

To identify and obtain the indigenous degraders metabolizing phenanthrene (PHE) and biphenyl (BP) from the complex microbial community within industrial wastewater, DNA-based stable-isotope probing (DNA-SIP) and cultivation-based methods were applied in the present study. DNA-SIP results showed that two bacterial taxa (Vogesella and Alicyclobacillus) were considered the key biodegraders responsible for PHE biodegradation only, whereas Bacillus and Cupriavidus were involved in BP degradation. Vogesella and Alicyclobacillus have not been linked with PHE degradation previously. Additionally, DNA-SIP helped reveal the taxonomic identity of Ralstonia-like degraders involved in both PHE and BP degradation. To target the separation of functional Ralstonia-like degraders from the wastewater, we modified the traditional cultivation medium and culture conditions. Finally, an indigenous PHE- and BP-degrading strain, Ralstonia pickettii M1, was isolated via a cultivation-dependent method, and its role in PHE and BP degradation was confirmed by enrichment of the 16S rRNA gene and distinctive dioxygenase genes in the DNA-SIP experiment. Our study has successfully established a program for the application of DNA-SIP in the isolation of the active functional degraders from an environment. It also deepens our insight into the diversity of indigenous PHE- and BP-degrading communities.IMPORTANCE The comprehensive treatment of wastewater in industrial parks suffers from the presence of multiple persistent organic pollutants (POPs), such as polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs), which reduce the activity of activated sludge and are difficult to eliminate. Characterizing and applying active bacterial degraders metabolizing multiple POPs therefore helps to reveal the mechanisms of synergistic metabolism and to improve wastewater treatment efficiency in industrial parks. To date, SIP studies have successfully investigated the biodegradation of PAHs or PCBs in real-world habitats. DNA-SIP facilitates the isolation of target microorganisms that pose environmental concerns. Here, an indigenous phenanthrene (PHE)- and biphenyl (BP)-degrading strain in wastewater, Ralstonia pickettii M1, was isolated via a cultivation-dependent method, and its role in PHE and BP degradation was confirmed by DNA-SIP. Our study provides a routine protocol for the application of DNA-SIP in the isolation of the active functional degraders from an environment.

Identification and characterization of a meta-cleavage product hydrolase involved in biphenyl degradation from Arthrobacter sp. YC-RL1

Polychlorinated biphenyls (PCBs) are a group of persistent organic pollutants (POPs) widely existing in the environment. Arthrobacter sp. YC-RL1 is a biphenyl-degrading bacterium that shows metabolic versatility towards aromatic compounds. A 2-hydroxy-6-oxo-6-phenylhexa-2, 4-dienoate (HOPDA) hydrolase (BphD) gene involved in the biodegradation of biphenyl was cloned from strain YC-RL1 and heterologously expressed in Escherichia coli BL21 (DE3). The recombinant BphD_YC-RL1 was purified and characterized. BphD_YC-RL1 showed the highest activity at 45 °C and pH 7. It was stable under a wide range of temperature (20-50 °C). The enzyme had a K_m value of 0.14 mM, K_cat of 11.61 s^-1, and V_max of 0.027 U/mg. Temperature dependence catalysis exhibited a biphasic Arrhenius Plot with a transition at 20 °C. BphD_YC-RL1 was inactivated by SDS, Tween 20, Tween 80, Trition X-100, DTT, CHAPS, NBS, PMSF, and DEPC, but insensitive to EDTA. Site-directed mutagenesis of the active-site residues revealed that the catalytic triad residues (Ser115, His275, and Asp247) of BphD_YC-RL1 were necessary for its activity. The investigation of BphD_YC-RL1 not only provides new potential enzyme resource for the biodegradation of biphenyl but also helps deepen our understanding on the catalytic process and mechanism.

The occurrence of OCPs, PCBs, and PAHs in the soil, air, and bulk deposition of the Naples metropolitan area, southern Italy: Implications for sources and environmental processes

I am often reminded of the famous saying of Goethe: "Vedi Napoli e poi muori! - See Naples and die!". Sadly, Naples is now confronted with a number of serious, ongoing problems with a need to alleviate pressure on the worsening environment. One serious problem facing the environment is the presence of the potentially hazardous persistent organic pollutants (POPs), although few systematic studies at regional scale have been conducted. In this study, samples of soil, air, and bulk deposition were collected in Naples metropolitan area (NMA) to characterize the status of POPs, including organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs). The results obtained showed that most of these compounds are pervasive in all the studied environmental matrices, especially in some hotspot areas, such as the Bagnoli Brownfield Site and the infamous "Triangle of the Death", where unwanted ecological risk conditions for PAHs and Endosulfan were determined, respectively. The interactional complexity between urban and the surrounding rural areas was also confirmed, as is the role that urban areas play in the migration and transformation process of POPs. High urban-rural gradients for atmospheric PAHs and PCBs were observed in the NMA, and the urban areas were identified as the emission source of these contaminants. Similarly, the OCP residues, historically originated from the nearby agricultural regions, experience long-term soil re-emission and continuously influence the connected urban environment via atmospheric transport processes.

Organic contamination of Italian and Tunisian culinary herbs and spices

Contaminants belonging to various classes, as polychlorobiphenyls, polycyclic aromatic hydrocarbons, organochlorine pesticides, organophosphorous pesticides, pyrethroid insecticides, fungicides, herbicides, synergists, carbamates, acaricides and insect growth regulators were simultaneously analysed by GC-MS/MS in 118 Italian and Tunisian culinary herbs and spices. The results obtained in Italian samples shown that laurel samples were the most contaminated with the presence of 15 residues on 140, whereas in rosemary (max value of 35 ng/g for cis-chlorfenyvinphos) and oregano (max value of 118.16 ng/g for ethion) some occasional residues can be observed, but always lower than the maximum residue levels; all the others samples shown no contamination. Among Tunisian samples, only rosemary contains a notably high content of pollutants exceeded the EU maximum residue limits (i.e., alachlor and phosalone with level of 359.2 and 43.3 ng/g, respectively), while oregano was determined to be free of contaminant residues. Considering the comparison among the different organic pollutants in Italian and Tunisian spices and herbs evaluated and the differences observed in this study a harmonization of regulation on contaminant residues in herbs and spices for human consumption should be needed, considering their increased use in diet and cooking.

Presence and distributions of POPS in soil, atmospheric deposition, and bioindicator samples in an industrial-agricultural area in Turkey

In this study, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and organochlorine pesticides (OCPs) were detected in the soil, lichen pine needle, and total deposition samples in the Meriç-Ergene Basin, which is one of the most important regions in terms of industrial and agricultural activities in Turkey. POP concentrations were measured in 192 samples selected to represent four seasons over a 1-year period across four different regions: an intensive industrial area, an industrial + residential area, an agricultural area, and a background area. Total PAH concentrations are found in the range of 69.6-887.6 ng/g, 74.6-1277.7 ng/g, 113.4-588.9 ng/g, and 0.00-937.8 ng/m²-day; total PCB concentrations are 9.98-62.9 ng/g, 6.8-68.1 ng/g, 11.3-32.7 ng/g, and 0.00-144.4 ng/m²-day; total OCPs concentrations are 5.9-83.2 ng/g, 7.3-85.6 ng/g, 9.9-97.1 ng/g, and 0.00-137.6 ng/m²-day respectively for soil, lichen, pine needles, and bulk samples. The data were evaluated according to pollutant groups and spatial and temporal changes. The highest PAH and PCB values were detected in lichen samples from industrial areas. The highest OCP values were detected for total deposition and soil samples and in the agricultural area. The results showed that two- to three-ring PAHs, hepta-PCBs, and cyclodienes were the most widespread pollutant groups. Statistical analyses were performed to evaluate the accumulation and indication properties of the matrices in the study for 0.05 significance level. The pollutant group in which matrices are most similar is PAHs. Total deposition samples showed the most different pattern in terms of indications, especially for PCBs. For OCP results, the concentration values obtained in soil samples were different from all other matrices. It was determined that the indication properties of the matrices identified as pollutant indicators differ markedly from the pollutant type, and this difference is at the lowest level for PAH pollutants. Graphical abstract ᅟ.

Exploring bacterial communities and biodegradation genes in activated sludge from pesticide wastewater treatment plants via metagenomic analysis

Activated sludge (AS) has been regarded as the main driver in the removal of organic pollutants such as pesticides due to a high diversity and abundance of microorganisms. However, little is known about the biodegradation genes (BDGs) and pesticide degradation genes (PDGs) harbored in the AS from wastewater treatment plants (WWTPs). In this study, we explored the bacterial communities and BDGs/PDGs in the AS from five WWTPs affiliated with pesticide factories across four consecutive seasons based on high-throughput sequencing. The AS in pesticide WWTPs exhibited unique bacterial taxa at the genus level. Furthermore, a total of 17 BDGs and 68 PDGs were explored with a corresponding average relative abundance of 0.002-0.046% and 2.078-7.143% in each AS sample, respectively, and some BDGs/PDGs clusters were also identified in the AS. The bacterial communities and BDGs/PDGs were season-dependent, and the total variations of 50.4% and 76.8% were jointly explained by environmental variables (pesticide types, wastewater characteristics, and temperature). In addition, network analysis and distribution patterns suggested that the potential hosts of BDGs/PDGs were Thauera, Stenotrophomonas, Mycobacterium, Hyphomicrobium, Allochromatium, Ralstonia, and Dechloromonas. Our findings demonstrated the linkages of bacterial communities and BDGs/PDGs in the AS, and depended on the seasons and the pesticide wastewater characteristics.

Organic pollution in PGI and non-PGI lemons and related soils from Italy and Turkey

In this work 67 organic contaminants in Protected Geographical Indication (PGI) and non-PGI Interdonato Lemon pulps, peels, leave and related soils were evaluated by GC/MS-MS. It is possible to highlight that in Italian pulps and peels the residues were under LODs (0.10-10.30 ng·g^-1), whereas the leaves showed piperonyl butoxide in 33% of samples (11.76 ± 1.24 ng·g^-1) and cypermethrins in 33% of samples (Cypermethrin I, 6.12 ± 0.35 ng·g^-1; Cypermethrin II, 8.67 ± 0.48 ng·g^-1; Cypermethrin III, 8.90 ± 1.52 ng·g^-1; Cypermethrin IV, 12.25 ± 2.46 ng·g^-1). Turkish samples were mainly contaminated by piperonyl butoxide: it was revealed in the 33% of pulps (3.35 ± 1.03 ng·g^-1), in 100% of peels (23.46 ± 17.69 ng·g^-1) and in 100% of leaves (1302.44 ± 527.40 ng·g^-1). In both soils a different contamination was detected. This study confirms that the European brand (PGI) of Interdonato Lemon Messina is a valuable instrument for the consumer protection.

Levels and risk assessment of hydrocarbons and organochlorines in aerosols from a North African coastal city (Bizerte, Tunisia)

The aim of this study was to assess, for the first time, the concentrations, sources, dry deposition and human health risks of polycyclic aromatic hydrocarbons (PAHs), aliphatic hydrocarbons (AHs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in total suspended particle (TSP) samples collected in Bizerte city, Tunisia (North Africa), during one year (March 2015-January 2016). Concentrations of PAHs, AHs, PCBs and OCPs ranged 0.5-17.8 ng m^-3, 6.7-126.5 ng m^-3, 0.3-11 pg m^-3 and 0.2-3.6 pg m^-3, respectively, with higher levels of all contaminants measured in winter. A combined analysis revealed AHs originating from both biogenic and petrogenic sources, while diesel vehicle emissions were identified as dominant sources for PAHs. PCB potential sources included electronic, iron, cement, lubricant factories located within or outside Bizerte city. The dominant OCP congeners were p,p'-DDT and p,p'-DDE, reflecting a current or past use in agriculture. Health risk assessment showed that the lifetime excess cancer risk from exposure to airborne BaP was negligible in Bizerte, except in winter, where a potential risk to the local population may occur.

Seasonal occurrence, source evaluation and ecological risk assessment of polycyclic aromatic hydrocarbons in industrial and agricultural effluents discharged in Wadi El Bey (Tunisia)

Polycyclic aromatic hydrocarbons are of great concern due to their persistence, bioaccumulation and toxic properties. The occurrence, source and ecological risk assessment of 26 polycyclic aromatic hydrocarbons in industrial and agricultural effluents affecting the Wadi El Bey watershed were investigated by means of gas chromatographic/mass spectrometric analysis (GC/MS). Total PAHs (∑ 26 PAH) ranged from 1.21 to 91.7 µg/L. The 4- and 5-ring compounds were the principal PAHs detected in most of 5 sites examined. Diagnostic concentration ratios and molecular indices were performed to identify the PAH sources. Results show that PAHs could originate from petrogenic, pyrolytic and mixed sources. According to the ecotoxicological assessment, the potential risk associated with PAHs affecting agricultural and industrial effluents ranged from moderate to high for both aquatic ecosystem and human health. The toxic equivalency factor (TEF) approach indicated that benzo[a]pyrene and benz[a]anthracene were the principal responsible for carcinogenic power of samples.

Solubilization of polycyclic aromatic hydrocarbons (PAHs) with phenol in coking wastewater treatment system: Interaction and engineering significance

Polycyclic aromatic hydrocarbons (PAHs) are accumulated in the sludge collected from the coking wastewater treatment. Phenol with its efficient degradation observed in biological treatment promotes the solubility of PAHs in aqueous phase. The interaction mechanism of phenol and PAHs in aqueous and sludge phases was systematically studied in two full-scale engineering projects composed of anaerobic-oxic-oxic (A-O₁-O₂) and anaerobic-oxic-hydrolytic-oxic (A-O₁-H-O₂) sequences. The results showed that reasonable use of phenol facilitates solubilization of PAHs alleviating their emission problems. The ΔPAHs/Δphenol mass ratio in the sludge phase of A-O₁-H-O₂ system (146.3) exceeded that in A-O₁-O₂ one (63.80), exhibiting a good solubilization effect on PAHs with their more efficient degradation in the former. The full-scale observations were verified in laboratory solubilization experiments using phenanthrene (Phen), pyrene (Pyr) and benzo[a]pyrene (Bap) as the models of 3-, 4- and 5-ring PAHs, respectively. The binding energies of [phenol^-PAHs] complexes were calculated using computational density functional theory showing consistency with the experimentally observed phenol-facilitated solubilization efficiencies in the row of Phen>Pyr>Bap. The results showed the fate and distribution of PAHs in coking wastewater treatment affected by the presence of phenol serving as a cost effective reagent for enhanced solubilization of PAHs from the coking wastewater sludge.

Mechanisms of biochar reducing the bioaccumulation of PAHs in rice from soil: Degradation stimulation vs immobilization

This study aimed to elucidate the mechanisms by which biochar reduces the bioaccumulation of polycyclic aromatic hydrocarbons (PAHs) in rice under anaerobic conditions. Corn straw- or bamboo-derived biochar pyrolyzed at 300 °C and 700 °C (CB300 or BB700), respectively, was amended into flooded PAH-contaminated soil. After harvest, 2% CB300, 0.5% BB700 or 2% BB700 amendments reduced the bioaccumulation of PAHs in rice root, especially that of high-molecular-weight PAHs (p < .05). Total PAH concentrations were higher, and their bioavailable concentrations were lower in BB700-amended soils than the control. The stimulation of PAH desorption from BB by low-molecular-weight organic acids (LMWOAs) was gentle and did not significantly retard the adsorption of PAHs on BB700, indicating that BB700 reduced PAH bioavailability primarily via immobilization. The total and bioavailable concentrations of PAHs were both lower in the 2% CB300-treated soils than the control. LMWOAs facilitated PAH release from CB300-amended soils, thus increasing the bioavailability of immobilized PAHs. The relative abundances of the bacteria, functional genes, and methanogens involved in PAH anaerobic degradation were significantly higher in the 2% CB300 treatment than other treatments. Fast PAH dissipation in soil amended with 2% CB300 may be attributed to the increased bioavailability of immobilized PAHs and enhanced biodegradation, both of which were induced by LMWOAs and CB. In summary, biochar types and root presence jointly affected the mechanisms by which biochar reduced the bioaccumulation of PAHs in rice under anaerobic conditions.

Uptake and translocation of polycyclic aromatic hydrocarbons (PAHs) and heavy metals by maize from soil irrigated with wastewater

By investigating the uptake of 16 priority polycyclic aromatic hydrocarbons (PAHs) and five heavy metals from soils to maize at the farmlands with industrial wastewater irrigation, this study revealed the effects of heavy metals on PAHs uptake in terms of co-contamination. The results of 15 investigated soils showed medium contamination level and the vertical PAHs distribution in soils indicated that 2-3 rings PAHs with low octanol-water partition coefficient (log Kow < 4.5) were easier to transport in soils, causing a great potential risk immigrating to the groundwater. The 3-ring PAHs were most likely to be taken up by maize roots whereas 2- and 4-6 ring PAHs had the lower likelihood. The translocation of PAHs in maize tissues has positive relationship with log Kow less than 4.5, while negatively correlated otherwise. Redundancy analysis indicated the unexpected results that, except for soil PAHs concentration, the PAHs translocation by maize was reduced by Pb uptake, but not significantly affected by soil organic matters, pH or the other four heavy metals (Cr, Cu, Ni and Zn). This study for the first time provides the restricted factors of PAHs and heavy metal acropetal translocation by maize when they co-exist at wastewater irrigation sites.

Pesticide residues in nut-planted soils of China and their relationship between nut/soil

Twenty-nine pesticide residues in nut-planted soils from China were investigated. One organophosphate (chlorpyrifos) was detected in 5.3% soils, and the residue levels of 7.2 μg/kg to 77.2 μg/kg. The concentrations of six organochlorines (DDT, HCH, endosulfan, quintozene, aldrin and dieldrin) detected in 78.9% soils were 0.6 μg/kg to 90.1 μg/kg. The residue levels of six pyrethroids (bifenthrin, fenpropathrin, cyhalothrin, cypermethrin, fenvalerate and deltamethrin) detected in 65.8% soils were 1.5 μg/kg to 884.3 μg/kg. Triadimefon and buprofezin were found in 71.1% and 52.6% samples, respectively, with the corresponding concentrations of 9.8 μg/kg to 193.7 μg/kg and 87.9 μg/kg to 807.4 μg/kg. The multiple residues were found in 76.3% soils. A significant correlation between pesticide residues in nuts and soils was observed, with the correlation coefficient (r) 0.83 (P < 0.001). In addition, the bioconcentration factor (BCF) values for the explanation of pesticides from soils into nuts were ranged from 0.8 to 16.5. The results showed that some pesticides could accumulate in nut by the uptake effect from soil.

Efficient phytoremediation of organic contaminants in soils using plant-endophyte partnerships

Soil pollution with organic contaminants is one of the most intractable environmental problems today, posing serious threats to humans and the environment. Innovative strategies for remediating organic-contaminated soils are critically needed. Phytoremediation, based on the synergistic actions of plants and their associated microorganisms, has been recognized as a powerful in situ approach to soil remediation. Suitable combinations of plants and their associated endophytes can improve plant growth and enhance the biodegradation of organic contaminants in the rhizosphere and/or endosphere, dramatically expediting the removal of organic pollutants from soils. However, for phytoremediation to become a more widely accepted and predictable alternative, a thorough understanding of plant-endophyte interactions is needed. Many studies have recently been conducted on the mechanisms of endophyte-assisted phytoremediation of organic contaminants in soils. In this review, we highlight the superiority of organic pollutant-degrading endophytes for practical applications in phytoremediation, summarize alternative strategies for improving phytoremediation, discuss the fundamental mechanisms of endophyte-assisted phytoremediation, and present updated information regarding the advances, challenges, and new directions in the field of endophyte-assisted phytoremediation technology.

Effects of untreated and treated wastewater at the morphological, physiological and biochemical levels on seed germination and development of sorghum (Sorghum bicolor (L.) Moench), alfalfa (Medicago sativa L.) and fescue (Festuca arundinacea Schreb.)

Wastewater reuse in agriculture may help mitigate water scarcity. This may be reached if high quality treatments removing harmful pollutants are applied. The aim of the present study was to compare the effect of untreated (UTW) and treated wastewater (TW) on germination and seedlings development of alfalfa (Medicago sativa L.), fescue (Festuca arundinacea Schreb.) and sorghum (Sorghum bicolor (L.) Moench). UTW presented high turbidity (130 NTU), chemical and biological oxygen demand (COD, 719mgL^-1, BOD_5, 291mgL^-1) and metal concentrations. These levels caused mortality (18% for fescue), decreased germination speed in seeds (37.5% for alfalfa) and reductions of root and stem length in seedlings (80% and 22% respectively for alfalfa). Adverse effects on seeds germination were reflected at the biochemical level by increased H₂O₂ levels (6 times for sorghum after 5days) and by increased Malondialdehyde (MDA) levels (more than 600 times for sorghum roots) during seedlings development. When TW was used, these parameters were close to control seeds ones. They were also dependent on plant species and developmental stage. Therefore, for efficient reclaimed wastewater reuse in irrigation, suitable crops, displaying wide tolerance to toxic contents during germination and later seedling development stages have to be selected.

Removal and transformation of polycyclic aromatic hydrocarbons during electrocoagulation treatment of an industrial wastewater

Polycyclic aromatic hydrocarbons (PAHs) are an important class of water pollutants because of their known ecological and human toxicity. Electrocoagulation (EC) is a promising technology for mitigating industrial wastewater pollution, but the removal and transformation of PAHs during EC treatment has not yet been understood. Therefore, a paper-making wastewater effluent (PMWW) was employed in this study to investigate the relationship between PAHs' removal and transformation during EC treatment. The results show that 86% of PAHs were effectively removed not only by the electro-oxidation reactions, but also by adsorption onto Fe hydroxide flocs. The removal and transformation of PAHs were related to the number of rings in their structures. Some PAHs composed of two aromatic rings (e.g., naphthaline and dimethylnaphthalene) were produced from humic acid-like and fulvic acid-like organics in PMWW, while PAHs with three to four rings were degraded, thus being removed efficiently. Therefore, PAH transformation during EC treatment exerted double-sided effects on the removal of PAHs; the net effect appeared to be positive. Overall, this study revealed the existence and importance of PAH transformation during EC treatment and provided useful guidance for pulp and paper mills to improve the design and operation of wastewater treatment facilities.