A highly efficient, eco-friendly and relatively low-cost catalyst is necessary to tackle bottlenecks in the treatment of industrial wastewater laden with heavy metals and antibiotic such as livestock farm and biogas liquids. This study investigated co-oxidative removal of arsenite (As(III)) and tetracycline (TC) by iron nanoparticles (Fe NP)-impregnated carbons based on heterogeneous Fenton-like reactions. The composites included Fe NP@biochar (BC), Fe NP@hydrochar (HC), and Fe NP@HC-derived pyrolysis char (HDPC). The functions of N and S atoms and the loading mass of the Fe NP in the Fe NP@BC in heterogeneous Fenton-like reactions were studied. To sustain its cost-effectiveness, the spent Fe NP@BC was regenerated using NaOH. Among the composites, the Fe NP@BC achieved an almost complete removal of As(III) and TC under optimized conditions (1.0 g/L of dose; 10 mM H₂O₂; pH 6; 4 h of reaction; As(III): 50 μM; TC: 50 μM). The co-oxidative removal of As(III) and TC by the Fe NP@ BC was controlled by the synergistic interactions between the Fe NPs and the active N and S sites of the BC for generating reactive oxygen species (ROS). After four consecutive regeneration cycles, about 61 and 95% of As(III) and TC removal were attained. This implies that the spent carbocatalyst still has reasonable catalytic activities for reuse. Overall, this suggests that adding technological values to unused biochar as a carbocatalyst like Fe NP@BC was promising for co-oxidative removal of As(III) and TC from contaminated water.

Metal(loid)s (MLs) with natural or anthropogenic sources may cause adverse health effects in children. This study aimed to compare the childhood exposure to ΣMLs (essential, non-essential and toxic) in an industrial and an urban area in Southwest Iran using toenail tissue as a biomarker. The present study was carried out with school children in the age range of 7–12 years, who were living in an industrial area in the petrochemical and gas area (PGA) of the Central District of Asaluyeh County and in an urban area (UA) located in the Kaki District. A total of 270 boys and girls were recruited in January to April 2019. The ICP-MS was used for determination of the studied MLs. A multi-linear regression model was constructed to assess the effect of residence area on toenail ML levels. A significantly higher level of ΣMLs in toenail from the PGA was observed compared to the level in the UA (8.839 vs. 7.081 μg/g, β = -0.169 and p < 0.05). However, all of the 15 MLs studied were detected in the toenail samples from both study sites. Significant differences for the mean Cr (β = −0.563), Fe (β = −0.968), Mn (β = −0.501), Ni (β = −0.306), and Pb (β = −0.377) levels were found between toenail samples from the study areas (p < 0.05), with higher levels in the PGA. The results of this study suggest that children in industrial area are prone to a greater risk for ML exposures compared with those living in a non-industrial urban area.

Identifying effective and low-cost agents for the remediation of Pb-contaminated soil is of great importance for field-scale applications. In this study, the feasibility of reusing incinerated sewage sludge ash (ISSA), a waste rich in phosphorus, under activation by oxalic acid (OA) for the remediation of high-Pb contaminated soil was investigated. ISSA and OA were mixed at different proportions for the treatment of the high-Pb contaminated soil (5000 mg/kg). The Pb immobilization efficacy was further examined by both the standard deionized water leaching test and the toxicity characteristic leaching procedure (TCLP). The overall results showed that the use of the ISSA alone and an appropriate mixture of the ISSA and OA could effectively reduce the leachability of Pb from soil. 20% ISSA together with 30% OA (0.2 mol/L) reduced leached Pb concentration by 99%. The main stabilization mechanisms were then explored by different microstructural and spectroscopic analytical techniques including SEM, XRD and FTIR. Apparently, OA released phosphate from the ISSA and Pb from soil via acid attack, which combined and precipitated as stable lead phosphate minerals. However, excessive OA could cause high leaching of phosphate and zinc from the ISSA. Overall, this study indicates that ISSA could be used together with OA to remediate high-Pb contaminated soil, but careful design of mix proportions is necessary before practical application to avoid excessive leaching of phosphate and zinc from the ISSA.

This paper proposes a holistic approach to connect anthropogenic impacts to environmental remediation solutions. The eDPSIR (engineered-Drivers-Pressures-States-Impacts-Responses) framework aims at supporting the decision-maker in designing technological solutions for a contaminated coastal area, where the natural matrices need to be cleaned up. The eDPSIR is characterized by cause-effect relationships that are operationally implemented through three multidisciplinary toolboxes: (i) Toolbox 1, to connect driving forces with pressures, classifying the state of the system and allowing the identification of target contaminants and the extent of contamination; (ii) Toolbox 2, to quantify bioaccumulation also by identifying corresponding areas; (iii) Toolbox 3, to identify the most suitable remediation solutions for previously identified contaminated areas, named contamination scenarios. The eDPSIR was calibrated on the case study of the Mar Piccolo in Taranto (Southern Italy), one of the most complex and polluted areas in Europe. While the consolidated DPSIR allows for a strategic response by limiting the use of contaminated areas or reducing upstream pressures, the eDPSIR made it possible to structure with a semi-quantitative logic the problem of assisting the decision-makers in choosing the optimal technological remediation responses for each sediment scenario of contamination (heavy metal; organic compounds; mixed). Assisted natural attenuation was identified as the best remediation technology in terms of treatment effectiveness and smallest amount of impacts involved in the project actions. However, considering the scenario of mixed contamination, in-situ reactive capping reached a good rank with a value of the composite indicator equal to 99.5%; thermal desorption and stabilization/solidification recorded a value of 94.1% and 84.6%, respectively. The application of these toolboxes provides alternative means to interpret, manage, and solve different cases of global marine contaminated sites.

With increasing population growth and climate change, de facto reuse practices are predicted to increase globally. We investigated a longitudinal gradient within the Uhlava River, a representative watershed, where de facto reuse is actively occurring, during Fall and Spring seasons when instream flows vary. We observed human pharmaceutical levels in the river to continuously increase from the mountainous areas upstream to downstream locations and a potable intake location, with the highest concentrations found in small tributaries. Significant relationship was identified between mass flow of pharmaceuticals and the size of human populations contributing to wastewater treatment plant discharges. Advanced ozonation and granular activated carbon filtration effectively removed pharmaceuticals from potable source waters. We observed a higher probability of encountering a number of targeted pharmaceuticals during colder Spring months when stream flows were elevated compared to warmer conditions with lower flows in the Fall despite a dilution paradigm routinely applied for surface water quality assessment and management efforts. Such observations translated to greater water quality hazards during these higher Spring flows. Future water monitoring efforts should account for periods when higher chemical uses occur, particularly in the face of climate change for regions experiencing population growth and de facto reuse.

Both soil microbial nitrate (NO₃⁻-N) immobilization and denitrification are carbon (C)-limited; however, to what extent organic C addition may increase NO₃⁻-N immobilization while stimulate denitrification nitrogen (N) loss remains unclear. Here, ¹⁵N tracing coupled with acetylene inhibition methods were used to assess the effect of adding glucose, wheat straw and peanut straw on NO₃⁻-N immobilization and denitrification under aerobic conditions in an upland soil, in which NO₃⁻-N immobilization has been previously demonstrated to be negligible. The organic C sources (5 g C kg⁻¹ soil) were added in a factorial experiment with 100, 500, and 1000 mg N kg⁻¹ soil (as K¹⁵NO₃) in a 12-d laboratory incubation. Microbial NO₃⁻-N immobilization in the 12-d incubation in the three N treatments was 5.5, 7.7, and 8.2 mg N kg⁻¹ d⁻¹, respectively, in the glucose-amended soil, 5.9, 4.2, and 2.4 mg N kg⁻¹ d⁻¹, respectively, in the wheat straw-amended soil, and 4.9, 5.1 and 4.4 mg N kg⁻¹ d⁻¹, respectively, in the peanut straw-amended soil. Therefore, under sufficient NO₃⁻-N substrate, the higher microbial NO₃⁻-N immobilization in the glucose than in the crop residue treatments was likely due to the slow decomposition of the latter that provided low available C. The ¹⁵N recovery in the N₂O + N₂ pool over the12-day incubation was <2% for all treatments, indicating negligible denitrification N loss due to low denitrification rates in the aerobic incubation in spite of increasing C availability. We conclude that external C addition can enhance microbial NO₃⁻-N immobilization without causing large N losses through denitrification. This has significant implications for reducing soil NO₃⁻-N accumulation by enhancing microbial NO₃⁻-N immobilization through increasing C inputs using organic materials and subsequently mitigating nitrate pollution of water bodies.

Quantifying source apportionment of potentially toxic elements (PTEs) in soils and associated human health risk (HHR) is essential for soil environment regulation and pollution risk mitigation. For this purpose, an integrated method was proposed, and applied to a dataset consisting of As, Cd, Cr, Cu, Hg, Ni, Pb, Se, and Zn in 273 soil surface samples. Positive matrix factorization (PMF) was used to quantitatively examine sources contributions of PTEs in soils; and the HHR arising from the identified source was determined by combining source profiles and health risk assessment; at last, sequential Gaussian simulation (SGS) was used to identify the areas with high HHR. Four sources were identified by PMF. Natural and agricultural sources affected all 9 PTEs contents with contributions ranging from 19.2% to 62.9%. 41.9% of Cd, 40.8% of Pb, 58.6% of Se, and 29.8% of Zn were controlled by industrial and traffic emissions. Metals smelting and mining explained 35.5%, 30.5%, and 24.9% of Cr, Cu, and Ni variations, respectively. Hg was dominated by atmospheric deposition from coal combustion and coking (58.7%). The mean values of the total non-carcinogenic risks of PTEs were 1.55 × 10⁻¹ and 9.40 × 10⁻¹ for adults and children, and the total carcinogenic risk of PTEs had an average value of 8.86 × 10⁻⁵. Based on source-oriented HHR calculation, natural and agricultural sources were the most important factor influencing HHR, explaining 51.0% and 49.1% of non-carcinogenic risks for children and adults, and 44.2% of carcinogenic risk. SGS indicated that 1.1% of the total area was identified as hazardous areas with non-carcinogens risk for children.

Thiosulfate is frequently used as an energy source and electron donor in autotrophic denitrification (AD) for removing nitrate from wastewater. However, transforming pathways of S₂O₃²⁻ in this process is unclear. Herein, the aim of this study is to explore possible transforming pathways of sulfur compounds in thiosulfate-based AD process. After measuring the variation of NO₃⁻, NO₂⁻, and various sulfur compounds such as S⁰, SO₄²⁻, S₂O₃²⁻, acid volatile sulfide (AVS), and S²⁻ in the presence and absence of S₂O₃²⁻, the variation process of S₂O₃²⁻ and the contribution of various sulfur compounds were analyzed. The results indicated that S⁰, AVS, and S²⁻ were the intermediate products when S₂O₃²⁻ was applied as an electron donor. All S₂O₃²⁻, S⁰, AVS, and S²⁻ could act as electron donors in the nitrate removal process with the final products of SO₄²⁻. The utilization priority of these four sulfur sources was presumed in the following order: S²⁻ > S₂O₃²⁻ > AVS ≈ S⁰. Furthermore, sulfur transformation and balance in nitrate removal process was also investigated. This suggests the transforming pathways of sulfur compounds in denitrification process. Nitrogen removal and sulfur conversion process are dependent on the presence of microorganisms in the sludge.