The exploitation of thallium (Tl) resources through mining poses a significant threat to ecological systems and human health due to its high toxicity and ready assimilation by human body. We report the first assessment of the pollution, spatial distribution, source, and ecological-health risks of potentially toxic elements (PTEs) in Tl mining area of southwest Guizhou, China. Spatial distribution maps for PTEs were visualized by ArcGIS to identify their distribution trends. We use the enrichment factor (EF), correlation analysis, and principal component analysis to identify likely sources of seven PTEs mining area. The wider risk assessment was evaluated using the geoaccumulation index (Igₑₒ), potential ecological risk index (RI), human non-carcinogenic risk (HI), and carcinogenic risk (CR). The results revealed the PTEs content in the study area identifies direct mining, metal production, and domestic pollution sources. In addition, the distribution of PTEs was also affected by the topography, rain water leaching, and river dispersals. The main elements of concern are Tl and As, while Cd, Cr, Cu, Pb, and Zn do not show significant enrichment in the area despite associations with the ore deposit. Risk assessment identifies strong pollution and ecological risks and poses unacceptable human health risks to local residents, especially for children. The ecological risk in the study is identified to be predominantly from Tl (74.32%), followed by As (8.57%) and Cd (7.32%). The contribution of PTEs to the non-carcinogenic risk of humans in the study area is exclusively from As and Tl, while the carcinogenic risk is dominated by As, and the other elements pose no significant risk to human health.

Polysilicon production wastewater (PPW) is characterized by complex composition, high chemical oxygen demand (COD) concentration and poor biodegradability. An integrated process comprising of ferrate(VI) oxidation and biological aerated biofilter (BAF) was developed at lab scale for treating PPW with an initial COD of 3630 mg/L, biochemical oxygen demand (BOD₅) of 350 mg/L, suspended solids (SS) of 440 mg/L, and turbidity of 430 nephelometric turbidity units (NTU). Firstly, the potassium ferrate(VI) (K₂FeO₄) microcapsules were synthesized by using the phase separation method in cyclohexane, and ethylcellulose was used as the microcapsule wall materials (WM). The stability could be enhanced greatly when ferrate(VI) was encapsulated in the microcapsules with a mass ratio of K₂FeO₄:WM of 1:4 in the air compared with pure K₂FeO₄. The microcapsules exhibited sustained release behaviour and higher oxidation efficiency than pure K₂FeO₄. The microcapsules were used to pretreat PPW. Under the oxidation conditions of pH 6.0, microcapsule dosage 5.0 g/L and reaction time 70 min, the removal efficiency of COD, suspended solids (SS) and turbidity reached 55.1%, 61.3% and 74.2%, respectively. Subsequently, the oxidation effluent was subjected to BAF treatment. Under a hydraulic residence time of 48 h and a gas:water ratio of 6:1, the final effluent values of COD, SS and turbidity were 308 mg/L, 35 mg/L and 28 NTU, respectively, corresponding to total removal of 91.5%, 92.0% and 93.5%, respectively. Thus, this work demonstrates the feasible and potential application of encapsulated ferrate(VI) samples in the degradation of various toxic effluents.

The removal of greenhouse gas (GHG) emission from bitumen used in the construction of flexible pavement by iron-polyphenol complex nanoparticles (Fe-PNPₛ) has been examined in the study. Laboratory studies indicated the removal of carbon dioxide (CO₂) with Fe-PNPₛ is a function of the amount of additive (Fe-PNPₛ). From the experimental data, it was found that the reduction of CO₂ increases with increasing amount of additive up to a dosage of 4% (by weight of bitumen) without severely changing the basic engineering properties of the bitumen. The reduction of GHG is due to the conversion of the CO₂ to a mixture of hydrocarbon in the presence of Fe-PNPₛ. The characterization of the additive by SEM, FTIR, UV, and XRD indicated the formation of the Fe-PNPₛ. The analysis of the basic engineering properties of bitumen such as penetration value, softening point of the bitumen, flash point, fire point, and ductility in the presence of additive as well as without the additive were studied and reflected a noticeable effect in the reduction of the CO₂. The reduction of GHG by Fe-PNPₛ minimizes the environmental impact and saving energy by increasing the yield of hydrocarbons.

The objective of this research is to investigate the effluent water quality of a treatment plant in Turkey fed from surface and groundwater, according to water quality index (WOI) and health risk assessment (HRA). In order to achieve this goal, the quality of the influent and effluent water of the treatment plant was monitored monthly from January 2017 to January 2019. Water quality parameter results were compared with the Turkish drinking water standards and the World Health Organization (WHO), revealing that all parameters were within approved limits. Principal component analysis (PCA) was applied to determine the water quality parameter impacts in the overall quality of water and the most attractive parameters were trace elements, heavy metals, NH₃-N, NO₃, and TKN. To evaluate water quality and the impacts on human health, WQI and HRA, including hazard quotient (HQ) and hazard index (HI), were used. The WQI values were calculated by taking into account PCA results. WQI results demonstrated that the influent and effluent of water treatment plant values have a small number of WQI ranking that expressed the water category was “excellent” for drinking purpose. Finally, metal contamination in influent and effluent waters was assessed and the associated health risks to rural populations were estimated for different age groups, children and adults in the service area of the treatment plant. The health risk assessment with similar to WQI results, the acute, sub-chronic, and chronic risks of trace elements was “negligible” level, i.e., to a level affecting 1 person in 1,000,000 inhabitants.

Laboratory snow melting experiments were conducted with actual late-winter snow samples, collected just before the final snowmelt, in two similar northern Swedish cities, Luleå and Umeå, to investigate releases of the selected heavy metals (HM) (Cu, Pb, Zn, and Cd) and 16 USEPA PAHs from melting snow. Metal concentrations were determined in three fractions: total, dissolved, and truly dissolved (defined as the fraction passing through a 3-kMWCO ultrafilter). Total HM concentrations in snowmelt were rather high at both sites and reflected the accumulation of pollutants in the roadside snowbanks over a period of about 5 months: Cd = 0.43, Cu = 303, Pb = 41.9, Zn = 817 (μg/l), and TSS = 2000 (mg/l) in Luleå samples and Cd = 1.87, Cu = 905, Pb = 165, Zn = 3150 (μg/l), and TSS = 4800 (mg/l) in Umeå samples. The difference between metal and TSS concentrations at the two sites of similar characteristics was attributed to a smaller volume snowbank in Umeå. The dissolved HM concentrations represented relatively small fractions of the total concentrations (0.3–6.9% in Luleå and 0.01–3.1% in Umeå). The truly dissolved fraction represented 71–90% of the dissolved fraction in Luleå and 74–98% in Umeå. At both sites, the dissolved fractions exhibited preferential elution from the laboratory snow piles. The PAHs studied (16 US EPA PAHs) were mostly particulate bound, with only 5–12% of the total burden contributed by the meltwater, and most dissolved concentrations below the reporting limits. PAH concentrations in the Luleå samples were about one-third to one-fourth of those in Umeå. In general, the releases of PAHs from the snowbank were delayed, compared with releases of meltwater, and showed similar release patterns as TSS.

Our goal was to reconstruct soil recovery from Acid Rain based upon removal of stemflow at beech (Fagus sylvatica) stands of known historic and recent soil status. Fourteen beech stands in the Vienna Woods were selected in 1984 and again in 2012 to study changes in soil and foliar chemistry over time. A part of those stands had been strip cut, and to assess reversibility of soil acidification, we analyzed soils around beech stumps from different years of felling, representing the years when acidic stemflow ceased to affect the soil. Furthermore, it was hypothesized that changes of soil chemistry are reflected in the stemwood of beech. Half-decadal samples of tree cores were analyzed for Ca, Mg, K, Mn, Fe, and Al. Soil analyses indicated recovery in the top soil of the stemflow area but recovery was delayed in the between trees areas and deeper soil horizons. Differences in soil pH between proximal and distal area from beech stumps were still detectable after 30 years indicating that soils may not recover fully from acidification or do so at a rather slow rate. Stemwood contents indicated mobilization of base cations during the early 80s followed by a steady decrease thereafter. Backward reconstructions of soil pH and soil nutrients, building on regressions between recent stemwood and soil chemistry, could not be verified by measured soil data in 1984, but matched with declining cation foliar contents from 1984 to 2012. Dendrochemical reconstructions showed highest values in the 1980s, but measured soil exchangeable cation contents were clearly lower in 1984. Hence, we conclude that our reconstructions mimicked soil solution rather than soil exchanger chemistry.

Overland flow caused by rainfall is one of the critical factors influencing soil erosion and loss of soil nutrients. Therefore, the study on the mechanism and controlling measures of soil nutrient transport proposed is considered important. A simulation experiment was performed to investigate the effects of polyacrylamide application rates (0, 1, 2, 4, and 8 g/m²) and flow rates (400 ml/min, 600 ml/min, and 800 ml/min) on runoff, infiltration rate, soil losses, and the concentration of ammonium nitrogen (NH₄⁺) in runoff at loess slope (0.8 m (width) × 1.5 m (length) and 5°). As the results suggest runoff, sediment loss, and soil nutrient loss increased by increasing flow rate. Applicable amount of polyacrylamide (PAM) can effectively increase infiltration and reduce soil erosion, but excess amount of dissolved PAM would plug porosity of soil which could decrease the infiltration. The ammonia nitrogen loss amount was decreased with the increase of the PAM application rate. The ammonia nitrogen loss amount respectively decreased by 40.0%, 57.0%, 59.1%, and 63.4% with the PAM application rate of 1, 2, 4, and 8 g/m². The best performance with the coefficient of determination (R²) showed that the ammonium transport with runoff can be well described by the proposed model in flow scour experiments of this study. Furthermore, the model parameter b has a significant positive exponential relation with the total amount of sediment.

We use a 32-year dataset from a rural, southeastern New York stream to describe the effect of long-term road salt use on concentrations of sodium (Na⁺) and chloride (Cl⁻). Mean annual stream Na⁺ and Cl⁻ concentrations initially increased, reached a plateau, and then increased again. Trends in summer and winter stream concentrations were similar but summer concentrations were higher than winter, indicating that salt entered the stream via groundwater discharge. Seasonal and inter-annual variability in stream Na⁺ and Cl⁻ concentrations and export were high in the latter years of the study and can be explained by increased variability in stream discharge. Stream water Na⁺ and Cl⁻ concentrations were positively correlated with conductivity, and conductivity was negatively correlated with discharge during all seasons (p < 0.001). We used road salt application data from a local agency to examine effects of best management practices. Despite reductions in salt application, there was no commensurate decrease in stream water Na⁺ and Cl⁻ concentrations. We estimate that the legacy of long-term salt accumulation in groundwater and soils may delay a decline in stream water Na⁺ and Cl⁻ concentrations by 20–30 years. Continued research to develop road salt reduction practices is important to mitigate impacts on freshwater ecosystems and drinking water supplies.

The intensity and frequency of cyanobacteria-dominated harmful algal blooms (cHABs) has been increasing. A key issue associated with cHABs is the potential to release cyanotoxins, such as microcystin. One of the primary methods for addressing cHABs in a reservoir is the application of algaecides. This research evaluated the impact of common environmental factors (i.e., Fe, total organic carbon) on the efficacy of a hydrogen peroxide-based algaecide to attain control of a targeted cyanobacterial population. The results found that sodium carbonate peroxydrate (SCP, trade name PAK®27) at half the manufacturer’s suggested application was effective at suppressing cyanobacteria for 2 weeks. For example, reactors that contained a full level of TOC and 1 mg/L Fe significantly decreased by 89% from 21,899 to 2437 ± 987 cells/mL (p < 0.05) by 2 days after treatment with half-dose SCP while reactors that contained the full-dose TOC and no SCP treatment depicted an increase in cyanobacteria population over the first week. Furthermore, as the cyanobacteria population decreased, the algal assemblage began to switch to being green algae dominant. Under the experimental conditions evaluated, Fe and total organic content did not interfere with the efficacy of SCP. SCP can provide effective control of cyanobacteria in a variety of environmental conditions.

This article presents a review of the main physical, chemical, electrochemical, and biological technologies used for treating heavy metals in the wastewater of industrial processes and in synthetic aqueous solutions which could be applied to leachate from landfills. This paper outlines the generalities, operating principles, and modifications made to the technologies described. It discusses and assesses which of these have better removal rates and higher levels of efficiency in minimizing the heavy metal concentrations contained in leachates, such as mercury, chromium, lead, nickel, and copper among others. The first part of the document presents the so-called conventional technologies, such as chemical, physical, and electrochemical treatment. These have been used to treat different wastewater, especially industrial waste, operating adequately from the technical topic, but with high costs and the secondary products’ production. The second part exposes biological treatments tend to be most widely used due to their versatility, effectiveness, and low cost, when compared with traditional technologies. It is important to note that there is no single treatment and that each of the technologies reviewed has different heavy metal decontamination rates. All technologies search to reduce concentrations of heavy metals to values that are safe for the natural resources where they are discharged or disposed, thereby complying with the regulatory limits regulated in each of the regions.