The applicability of spectral analysis in detection of freshwater metal contamination was assessed by developing and testing a novel hyperspectral imaging (HSI) application for aquatic insect larvae (Trichoptera: Hydropsychidae). Larvae were first exposed to four different cadmium (Cd) concentrations: 0, 1, 10, and 100 μg L⁻¹ for 96 h. Individual larvae were then preserved in ethanol, inspected with microscopy for the number of anomalies in larval gills, and imaged by hyperspectral camera operating with wavebands between 500 and 850 nm. Three additional larvae from each exposure were analyzed for tissue Cd concentration. Although the larval tissue Cd concentrations correlated positively with actual water concentrations, the toxicity response of larvae, i.e., frequency of gill abnormalities, did not differ among the Cd concentrations. In contrast, hyperspectral imaging data indicated some concentration-response relationship of larval spectral properties to the Cd exposure, but it was too weak for reliable automatic distinction between exposed and unexposed larvae. In this pilot study a workflow for data processing for a novel application of hyperspectral imaging was developed. Based on the results of this preliminary study, the workflow in the imaging process will be optimized and its potential for detecting metal contamination of aquatic environments reassessed.

The original publication of this paper contains an error. The correct Figure 8 is shown in this paper.

The calculation of marginal abatement costs of CO₂ plays a vital role in meeting China’s 2020 emission reduction targets by providing reference for determining carbon tax and carbon trading pricing. However, most existing researches only used one method to discuss regional and industrial marginal abatement costs, and almost no studies predicted future marginal abatement costs from the perspective of CO₂ emission efficiency. To make up for the gaps, this paper first estimates marginal abatement costs of CO₂ in three major industries of 30 provinces in China from 2005 to 2015 based on three assumptions. Second, based on the principle of fairness and efficiency, China’s 2020 emission reduction targets are decomposed by province. Based on the ZSG-C-DDF model, the marginal abatement costs of CO₂ in all provinces in China in 2020 are estimated and compared with the marginal abatement costs of 2005 to 2015. The results show that (1) from 2005 to 2015, marginal abatement costs of CO₂ in all provinces show a fluctuating upward trend; (2) compared with the marginal abatement costs of primary industry or tertiary industry, most provinces have lower marginal abatement costs for secondary industry; and (3) the average marginal abatement costs of CO₂ for China in 2020 are 2766.882 Yuan/tonne for the 40% carbon intensity reduction target and 3334.836 Yuan/tonne for the 45% target, showing that the higher the emission reduction target, the higher the marginal abatement costs of CO₂. (4) Overall, the average marginal abatement costs of CO₂ in China by 2020 are higher than those in 2005–2015. The empirical analysis in this paper can provide multiple references for environmental policy makers.

Heavy metals are a common contaminant in water supplies and pose a variety of serious health risks to nearby human populations. A promising approach to heavy metal decontamination is the sequestration of heavy metal ions in porous materials; however, current technologies involve materials which can be difficult to synthesize, are high-cost, or are themselves potentially toxic. Herein, we demonstrate that rapidly synthesized calcium carbonate (CaCO₃) microparticles can effectively remove high quantities of Pb²⁺, Cd²⁺, and Cu²⁺ ions (1869, 1320, and 1293 mg per gram of CaCO₃ microparticles, respectively) from aqueous media. The CaCO₃ microparticles were characterized with powder X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and Brunauer–Emmett–Teller (BET) N₂ sorption–desorption. It was found that the Ca²⁺ ions of the microparticles were replaced by the heavy metal ions, leading to partially recrystallized nanoparticles of new compositional phases such as cerussite (PbCO₃). The adsorption, surface dissolution/re-precipitation, and nucleation/crystal growth mechanisms were determined by investigating the Ca²⁺ released, along with the changes to particle morphology and crystal structure. Importantly, this study demonstrates that the porous CaCO₃ microparticles performed well in a system with multiple heavy metal ion species: 100% of Cu²⁺, 97.5% of Pb²⁺, and 37.0% Cd²⁺ were removed from an aqueous solution of all cations with initial individual metal concentrations of 50 mg/L and 1.5 g/L of CaCO₃ microparticles. At this concentration, the CaCO₃ microparticles significantly outperformed activated carbon. These results help to establish CaCO₃ microparticles as a promising low-cost and scalable technology for removing heavy metal ions from contaminated water. Graphical abstract ᅟ

Phosphorus (P) is an essential element for all living organisms, and plays a major role in many physiological processes. However, in recent years, excessive amounts of P discharged into aquatic environments have become one of the main causes of water eutrophication, which has negative effects on water quality. Therefore, it is desirable to implement technologies to recover P from P-containing solutions to maintain the natural P cycle and reduce the level of P entering surface waters. This work reviews the latest studies on P recovery technologies, with a specific focus on current approaches and treatment media including seed materials, microorganisms, wetland plants, and membrane materials. This review also investigates the potential for P recovery, the purity of recovered products, the technical and economic feasibility of different approaches, and the resulting ecological and economic benefits. Building upon the outcomes of previous studies, technological innovations in P recovery media and approaches were considered to evaluate their advantages, difficulties, and inherent limitations. This comprehensive review provides the basis for additional research and the future development of P recovery in response to the increasing severity of eutrophication and the imminent depletion of P reserves.

The leachability of bottom medical waste ash from a Jordanian incinerator was studied in this work. The ash was characterized in terms of particle size distribution, chemical and mineralogical composition followed by leaching of several size fractions at different conditions (leaching time, temperature, initial pH, particle size, and solid liquid ratio). The major elements found in the ash were Ca, Si, Al, Cl, Na, Fe, Ti, S, Mg, Ba, and K, while the main mineral phases found in the ash were calcite, halite, sylvite, anhydrite, hematite, hydrochlorborite, cristobalite, melanterite, and chlormayenite. Leaching data indicates that as leaching time and S/L increased, the concentration of metals increased in the leachate. The highest leaching level was at a S/L ratio of 60 mg/ml. As the particles sizes decreased, the concentration of the majority of metals studied increased. Meanwhile, the effect of particle size on other metals was not regular due to the fact that sieving resulted in more concentrated metals in certain particle size fractions. Leachability results also indicate that variation in the initial pH has a slight effect on the degree of leaching. The concentration of some metal ions increased with temperature, while others increased initially but subsequently decreased. The extracted quantities of all the heavy metals were less than the limits set by EPA.

Nitrogen removal from wastewater is usually severely inhibited under low temperatures. The wastewater enrichment using an external carbon source has the influence on the stability and efficiency of the nitrification and denitrification processes during the biological wastewater treatment. This paper reports the results of the study where the effect of temperature and addition of an external carbon source on the efficiency of wastewater treatment process were investigated. Nitrification and denitrification rates were determined in the laboratory-scale treatment system, operating under low-temperature conditions, ranging from 6 up to 15 °C. Ethanol was used as an external carbon source. The addition of ethanol resulted in the increase during the nitrification rate at lower temperature (up to 71% at 6 °C and up to 11% at 15 °C). Similar tendency was observed during the denitrification process. Denitrification rate increased up to 81% at 6 °C and up to 10% at 15 °C, respectively. Nitrification rate was slightly higher compared to the denitrification rate. Two-variable model equations for calculation of an external carbon amount required were based on the experimental data and in order to reach desirable process rate at particular wastewater temperature were developed. The independency from wastewater temperature and the amount of loaded carbon explicit interdependence between nitrification and denitrification rates were observed.

Red sand is the by-product of aluminum refinery processing. It is susceptible to wind erosion and the emitted particles may cause serious environmental and safety issues. Lignosulfonate stabilizers are one of the promising non-traditional stabilizers to mitigate such issues. However, the contribution of the improvement on each mechanical property to the modification of the final erosion resistance was rarely analyzed, especially for coarse sandy bauxite residue. Thus, this study was conducted to analyze the relationship between improved mechanical properties and corresponding dust control performance of bauxite residue by applying two lignosulfonate stabilizers LS-S and LS-C. Results show that both of them provide improved water retention with higher concentration. However, the improvement is not substantial when the concentration is more than 4%. Two stabilizers generate nearly the same results in the optimum moisture content (OMC) and maximum dry density (MDD) tests, in which both of them reduce the OMC by about 10% and slightly increase the MDD. The addition of LS has virtually no influence on the density of the formed crust, but the crust thickness reduces with the increase of LS concentration. Furthermore, both penetration resistance and unconfined compressive strength (UCS) evidently increase with LS concentration, and LS-S apparently outperforms LS-C. Wind erosion tests have demonstrated that both LS-S and LS-C improve wind erosion resistance, and LS-S-treated sample can withstand longer period of wind attack, which is consistent with the penetration and UCS results that LS-S outperforms LS-C. Importantly, evidences presented in this paper illustrate that the improved mechanical properties appear to increase dust control performance.

This study focuses on the transient analysis of diffusion of a contaminant ejected by an external source into a laminar flow of recovered water. The influence of density variation with contaminant concentration is approximated according to the Boussinesq approximation. On the basis of momentum conservation and mass conservation theory, recovered water flow and mass transfer partial differential equations (PDEs) describing contaminant diffusion are obtained. This problem under three kinds of boundary conditions is solved analytically using Laplace transform method. By comparing the actual measured concentration in horizontal well of X shale gas reservoir and the concentration obtained from the models, the type of boundary conditions of X shale gas reservoir is determined. After that, sensitivity analysis of the influence of each parameter on the concentration of contaminant is presented. The determination of boundary condition type can determine the fracture form, which provides the basis for the flow and diffusion of the fluid in the fracture. The model also can be quite useful for available necessary early warning methods for detecting or predicting contaminant concentration and hence help mitigate related environmental pollution by earlier instituting relevant decontamination measures.