To investigate and assess heavy metal contamination on the farmland soils of a typical mining city, the concentrations of Cu, Cd, Zn, Pb, As, and Cr were analyzed from four mining areas (Tongguan District (TGD), Shunan Town (SAT), Tianmen Town (TMT), and Zhongmin Town (ZMT)) and two control areas (Xilian Township (XLT), Donglian Township (DLT)) in Tongling City, China. The total metal concentrations in the soils were in the following order: Cd ˂ As ≤ Pb ˂ Cu ˂ Cr ≤ Zn. Total metal concentrations in the soils of mining areas were significantly higher than those of the control areas (P < 0.05). According to the Chinese Environmental Quality Standard for Soils (GB 15618-1995) and geo-accumulation index (Igₑₒ), Cd and As pollution in the farmland soils of the mining areas was the most severe, followed by Cu. The Igₑₒ values of soil heavy metals of TGD and SAT were the most highest, followed by those of TMT and ZMT. The health risk quotient (HQ) of heavy metals in the soils showed as follows: HQAₛ ˃ HQPb ˃ HQCᵣ ˃ HQCd ˃ HQCᵤ ˃ HQZₙ, and the total average daily exposed dose (non-carcinogenic risk) of As was the highest except that of Cd. The contribution rate of carcinogenic risk index (CR) to total carcinogenic risk index (TCR) of As and Cd in the topsoil for adults was 99.91% and 0.09% respectively, and the value for children was 99.87% and 0.13%. The CR and TCR of As in the farmland of mining areas were greater than 10⁻⁴, which showed the carcinogenic risk is an intolerable range for both adults and children. According to the results of the present study, it can help the local people know the pollution of heavy metals in farmland and adopt the best suitable agriculture practices.

This study evaluated the oxidation of toluene (TOL) by persulfate (PS) in aqueous solution in the presence of a Fe₃O₄-carbon black (CB) composite oxidant system generating sulfate radicals. The cytotoxic activity and oxidative stress generated by these materials were investigated in rat liver Clone 9 cells. The effects of various operating parameters including the pH and concentrations of PS, Fe₃O₄-CB, and TOL were evaluated to optimize the oxidation process. The results showed that Fe₃O₄-CB/PS achieved effective removal of TOL under acidic conditions. The TOL degradation efficiency was strongly pH-dependent, where pH 3.0 > 6.0 > 9.0. Additionally, the viability of Clone 9 cells exposed to 0–400 μg/mL Fe₃O₄-CB indicated that this material showed low cytotoxicity. A dichlorodihydrofluorescein diacetate assay performed to evaluate the generation of reactive oxygen species indicated that Fe₃O₄ showed relatively lower toxicity than CB in these cells. Therefore, the cytotoxicity of CB may involve the induction of oxidative stress and physical changes in cell morphology.

Aeration strategy played an important role in reactor performance. In this study, when superficial upflow air velocity (SAV) decreased from 0.16 to 0.08 cm s⁻¹, low dissolved oxygen concentration (DO) of 2.0 mg L⁻¹ occurred in reactor. The required depth for anoxic microenvironment in biofilm decreased from 902.3 to 525.9 μm, which enhanced the growth of denitrifying bacteria and total nitrogen (TN) removal efficiency. However, decreasing aeration intensity resulted in insufficient hydraulic shear stress, which led to weak biofilm matrix structure. Mass biofilm detachment and reactor deterioration then occurred after 87 days of operation. An end gas recirculation aeration strategy was proposed to separately manipulate DO and aeration intensity. Low DO and high aeration intensity were simultaneously achieved, which enhanced the metabolism of denitrifying bacteria (such as Flavobacterium sp., Pseudorhodobacter sp., and Dok59 sp.) and EPS-producing bacteria (such as Zoogloea sp. and Rhodobacter sp.). Consequently, high TN removal performance (82.1 ± 2.7%) and stable biofilm structure were achieved.

Environmental exposure to phthalates may contribute to an increased risk of asthma in children and adults. We aimed to assess the direction and strength of the association between urinary phthalates metabolites and current asthma in children and adults that participated in the National Health and Nutrition Examination Survey (NHANES) 2007–2012. Data on ten urinary phthalate metabolites, self-reported questionnaires, spirometry measures, and covariates were obtained from 7765 participants (28.1% were children aged 6–17 years) taking part in the NHANES 2007–2012. Asthma was assessed using self-reported questionnaires for children and adults, and via spirometry measures for adults alone. We used crude and adjusted logistic regression models to estimate the odds ratios (ORs) and 95% confidence interval (CI) per one log₁₀ unit change in the concentration of phthalate metabolites. We further modeled the effect modification by sex. Out of 10 metabolites, only mono-benzyl phthalate (MBzP) was positively associated with the prevalence of self-reported asthma in children, after adjusting for a range of potential confounders (odds ratio 1.54; 95% confidence interval 1.05–2.27). No significant relationship was observed for adults. The association of mono-ethyl phthalate (MEP) was modified by sex, with significantly increased odds of asthma among males [boys (2.00; 1.14–3.51); adult males (1.32; 1.04–1.69)]. While no other phthalates showed a positive relationship with current asthma in males, mono-(carboxynonyl) phthalate (MCNP) and mono-(3-carboxylpropyl) phthalate (MCPP) were inversely associated with spirometrically defined asthma in adult females. A sex-specific relationship in adults was evident when spirometry, but not self-reported measures were used to define asthma. We found no clear association between exposure to phthalates and current asthma, except for a significant relationship between MBzP metabolites and self-reported asthma in children. As a result, exposure to phthalates and asthma development and/or exacerbations remains controversial, suggesting a need for a well-designed longitudinal study.

Aging effects play a crucial role in determining applications of green-synthesised iron-based nanoparticles in wastewater treatment from laboratory scale to practical applications. In this study, iron-based nanoparticles (Ec-Fe-NPs) were synthesised using the extract of Eichhornia crassipes and ferric chloride. Scanning electron microscopy (SEM) revealed that the fresh Ec-Fe-NPs were spherical and had a narrow particle size range (50 to 80 nm). X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) demonstrated that the Ec-Fe-NPs were mainly amorphous in nature and consisted of Fe⁰, FeO, Fe₂O₃ and Fe₃O₄. As they aged, the particle size of the liquid Ec-Fe-NPs gradually increased and then tended to stabilise. Ec-Fe-NPs that were aged for 28 days were only 19% less efficient than fresh material at removing Cr(VI). Extracts aged up to 28 days were also tested, and their antioxidant capacity was found to be 15.4% lower than that of the fresh extracts. Furthermore, the removal efficiency of Cr(VI) using iron-based nanoparticles synthesised with the aged extracts was 67.2%. Finally, the active components of the extracts, which were responsible for the reactivity and stability of the iron-based nanoparticles, were identified by liquid chromatography–mass spectrometry. Overall, green-synthesised iron-based nanoparticles show promise for Cr(VI) removal from wastewater in practical applications.

An analytical methodology was developed to characterize the colloidal distribution of trace elements of interest in environmental waters sampled in a same site and enables the different colloidal distributions from waters to be compared. The purpose was to provide consistent information related to the origin and nature of colloids responsible for the transport of trace element(s). The work was motivated by the observed enhanced mobility of uranium in soil. The colloidal size continuum was investigated by a multi-technique approach involving asymmetric flow field-flow fractionation (AF4) coupled with ultraviolet spectroscopy (UV), multi angle light scattering (MALS), and atomic mass spectrometry (ICPMS). To take into consideration the size and shape variability specific to each sample, the size distributions were established from the gyration radii measured from MALS, also considering the size information from standard nanospheres fractionated by AF4. A new parameter called “shape index” was proposed. It expresses the difference in hydrodynamic behavior between analytes and spherical particles taken as reference. Under AF4 diffusion conditions, it can be considered as an evaluator of the deviation from the sphericity of the fractionated analytes. AF4-UV-MALS-ICPMS enabled the dimensional and chemical characteristics of the colloidal size continuum to be obtained. As a “proof of concept”, the developed methodology was applied at a field scale, in a reference study site. In order to have a “dynamic understanding”, the investigation was based on the joint characterization of colloids from surface waters and soil leachates from static and dynamic processes. In the water samples of the study site, the continuum of gyration radius ranged from a few nanometers up to 200 nm. Colloids containing iron, aluminum, and organic carbon were involved in the uranium transport in the soil column and surface waters. The colloidal uranium concentration in the surface water increased from the upstream location (approximately 13 ng (U) L⁻¹) to the downstream location (approximately 60 ng (U) L⁻¹).

The continuous deterioration of the aquatic environment in rivers and streams is increasingly causing social and political tensions. To alleviate aquatic environmental problems, especially for the nonpoint source pollution, establishment of riparian forest buffers has been demonstrated as an effective control measure. However, few comprehensive studies of the reduction effects of riparian reforestation on the aquatic environment have been performed, particularly in identifying the suitable widths of reforestation projects. In this paper, the Annualized Agricultural Non-Point Source (AnnAGNPS) model was used to simulate the reduction effects of riparian reforestation on runoff and nutrient loads in Wucun watershed, China. The results showed that 20-m, 40-m, and 60-m widths of riparian buffer reforestation had significant effects on the yearly loads of total nitrogen (TN) and total phosphorus (TP), with reduced rates of 23.21 to 56.2% and 18.16 to 52.14%, respectively. The reduction effect on annual runoff varied from 2.8 to 5.4%. Furthermore, the reduction effect of nutrients performed best during the transition period, while the best runoff reduction was found during the dry period. These distinct reductions indicated that the implementation of riparian forest buffers was capable of reducing the risk and frequency of flooding and eutrophication, especially during the wet and transition periods. Additionally, the 20-m width of riparian buffer reforestation achieved the highest reduction efficiency for runoff, and the 40-m width was the most suitable reforested riparian buffer width for TN and TP. Therefore, 40 m may be the optimum buffer width for the implementation of riparian reforestation in the Wucun watershed. These research results provided scientific information on selecting the optimum buffer width for aquatic environmental regulators and managers as the reduction effects of different widths of riparian buffers on runoff and nutrients were different when considering buffer reforestation.

This study aims to identify the analytical and radiological characterization of scale TENORM waste produced from oil and natural gas productions in the western desert in Egypt and evaluates their radiological impacts. The mean activity concentration of ²³⁸U, ²²⁶Ra, ²¹⁰Pb, ²²⁸Ra, ²²⁴Ra, and ⁴⁰K measured in scale TENORM samples is 660 ± 63, 1979 ± 435, 1399 ± 211, 645 ± 104, 794 ± 116, and 556 ± 86 Bq/kg, respectively. Radiological hazard parameters (Raₑq, Hex, Hin, etc.) were estimated form the scale TENORM waste sample. All the calculated hazard parameters were found greater than the permissible and recommended safe levels. So the exposure to radiations released from the accumulation of the petroleum scale TENORM waste may cause health risks to the operators and who inhale radioactive radon gases and/or ingest contaminants by radiotoxic nuclides of U, Th, Ra, and Pb. Also, the risks may be extended to the near and/or the general environment.

This paper presents a demonstration of an integrated risk assessment and site investigation for groundwater contamination through a case study, in which the geologic and hydrogeological feature of the site and the blueprint of the fossil power plant (FPP) were closely analyzed. Predictions for groundwater contamination in case of accidents were performed by groundwater modeling system (GMS) and modular three-dimensional multispecies transport model (MT3DMS). Results indicate that the studied site area presents a semi-isolated hydrogeological unit with multiplicity in stratum lithology, the main aquifers at the site are consisted of the filled karst development layer with a thickness between 6.0 and 40.0 m. The poor permeability of the vadose zone at the FPP significantly restricted the infiltration of contaminants through the vadose zone to the subsurface. The limited influence of rarely isotropic porous karstified carbonate rocks on the groundwater flow system premised the simulate scenarios of plume migration. Analysis of the present groundwater chemistry manifested that that the groundwater at the site and the local area are of the HCO₃–Ca, HCO₃, and SO₄–Ca types. A few of the water samples were contaminated by coliform bacteria and ammonia nitrogen as a result of the local cultivation. Prediction results indicate that the impact of normal construction and operation processes on the groundwater environment is negligible. However, groundwater may be partly contaminated within a certain period in the area of leakage from the diesel tanks, the industrial wastewater pool, and the cooling tower water tank in case of accidents. On a positive note, none of the plumes would reach the local sensitive areas for groundwater using. Finally, an anti-seepage scheme and a monitoring program are proposed to safeguard the groundwater protection. The integrated method of the site investigation and risk assessment used in this case study can facilitate the protection of groundwater for the construction of large-scale industrial project.

Developing low cost and efficient method for the treatment of electroplating wastewater containing heavy metals complexed with chelating agent has attracted increasing attention in industrial wastewater treatment. This study involved a system combining Fenton oxidation (FO) and recycled ferrite (RF) process for treating synthetic solution containing Ni(II)-EDTA at ambient temperature. In this system, the FO reaction can produce hydroxyl radicals with high redox potential to decomplex the metal-organic complexes and degrade the organics, thereby enhancing the removal efficiency of heavy metals. The RF process is to incorporate the non-iron metal into the spinel ferrites at room temperature, and stabilize the sludge. As a result, the toxicity characteristic leaching procedure can fulfill the relevant standards. Furthermore, the ferrous ions in Fenton reaction could be used as the source of irons in RF process. After treatment by the combined process, the effluent water fulfills the relevant standard in China. In comparison with conventional alkaline precipitation, the sludge sedimentation velocity of FO-RF is 2.16 times faster than that of conventional alkaline precipitation and the volume of sludge is reduced by half, which strongly demonstrated the advantages of the presented FO-RF system and indicated the huge potential for the treatment of EDTA-chelated nickel.