Mining activities are responsible for the elevated input levels of suspended sediment and hazardous metals into the riverine ecosystem. These have been shown to threaten the riverine fish populations and can even lead to localized population extinction. To date, research on the effects of mining activities on fish has been focused within metal contamination and bioaccumulation and its threat to human consumption, neglecting the effects of suspended sediment. This paper reviews the effects of suspended sediment and metal pollution on riverine ecosystem and fish population by examining the possibilities of genetic changes and population extinction. In addition, possible assessments and studies of the riverine fish population are discussed to cope with the risks from mining activities and fish population declines.

Over the last few decades, many classes of micropollutants have been detected in aquatic environments worldwide and paracetamol is one of the micropollutant agents detected in the aquatic environment. New treatment methods based on biologically produced metal and metal oxides have been developed for micropollutant removal. Biogenic manganese oxides are also one of the most important biogenic metal oxide species. In this study, biogenic manganese oxides produced by manganese-adapted Pseudomonas putida NRRL B-14878 were used for removing paracetamol. A complete removal of paracetamol could be achieved within 216 h at pH 7, biogenic manganese oxide amount of 5 g/L, and paracetamol concentration of 2 mg/L. Response surface methodology (RSM) was applied to determine interaction between solution pH, paracetamol concentration, and biogenic manganese oxide amount being individual variables and to optimize operating conditions. According to results of variance analysis (ANOVA), the second-order polynomial model was statistically significant and coefficient of determination value was high. The optimal conditions were obtained as the solution pH of 6.81, the paracetamol concentration of 9.82 mg/L, and the biogenic manganese oxide amount of 6.36 g/L. Transformation products including the dimers, higher-degree oligomers, 3-hydroxyacetaminophen, 4-aminophenol, 4-methoxyphenol, 1,4-dimethoxybenzene, and butenedioic acid were identified by LC-MS/MS. The results of this work indicate that biogenic manganese oxide is an effective material for removing micropollutants.

A comparative experiment was conducted based on a non-road diesel engine to investigate the effects of two after-treatment devices on the engine’s emission characteristics as well as their power and fuel consumption performances. The first after-treatment device is a combination of a diesel oxidation catalyst (DOC) and a catalytic diesel particulate filter (CDPF). The second device is a single CDPF-coated improved noble metal catalyst. Results showed that the two after-treatment devices had almost no effect on the power and fuel consumption performance. The gaseous and particulate emissions of the engine depended on the operation conditions including the speed and load. However, the dual DOC+CDPF system and the single CDPF reduced more than 81% of the carbon monoxide (CO) and 73% of the hydrocarbon (HC) emissions. Notably, the reduction efficiency by the single CDPF was higher than that of the DOC+CDPF system. In terms of the particulate emissions, both after-treatment devices achieved more than 96% reduction of the particle number (PN) and up to 88% reduction of the particulate mass (PM). Similarly, the single CDPF outperformed the dual DOC+CDPF system in reducing particle emissions. Although no changes occurred in the bimodal particle size distribution of the engine after the installation of the two after-treatment devices, they performed differently in reducing particles with different sizes. The particles reduction efficiency of the DOC+CDPF system was higher than that of the single CDPF for the particles smaller than 14.3 nm, and this trend converted for particles larger than 14.3 nm. Improving the noble metal catalyst load in the CDPF ensured a performance that rivaled the DOC+CDPF system. Apart from the NOx emissions, the installation of a single CDPF with an improved noble metal catalyst load can make the non-road diesel engine meet the limits of the China IV emission regulations.

High-surface-area activated carbons were prepared from an agroindustrial residue, Bertholletia excelsa capsules known as capsules of Para cashew (CCP), that were utilized for removing amoxicillin from aqueous effluents. The activated carbons were prepared with the proportion of CCP:ZnCl₂ 1:1, and this mixture was pyrolyzed at 600 (CCP-600) and 700 °C (CCP700). The CCP.600 and CCP.700 were characterized by CHN/O elemental analysis, the hydrophobic/hydrophilic ratio, FTIR, TGA, Boehm titration, total pore volume, and surface area. These analyses show that the adsorbents have different polar groups, which confers a hydrophilic surface. The adsorbents presented surface area and total pore volume of 1457 m² g⁻¹ and 0.275 cm³ g⁻¹ (CCP.600) and 1419 m² g⁻¹ and 0.285 cm³ g⁻¹ (CCP.700). The chemical and physical properties of the adsorbents were very close, indicating that the pyrolysis temperature of 600 and 700 °C does not bring relevant differences in the physical and chemical properties of these adsorbents. The adsorption data of kinetics and equilibrium were successfully adjusted to Avrami fractional-order and Liu isotherm model. The use of the adsorbents for treatment of simulated hospital effluents, containing different organic and inorganic compounds, showed excellent removals (up to 98.04% for CCP.600 and 98.60% CCP.700). Graphical abstract

In this paper, the application of ultrafiltration (UF) technology to treat cadmium (Cd) pollution in surface waters is investigated. The effect of the UF membrane molecular weight cut-off (MWCO), Cd ion (Cd²⁺) concentration, solution pH and ionic strength on the removal, and mass balance of Cd were explored. In addition, the effect of the solution pH on UF membrane fouling was analyzed. The results indicated that UF membranes with a low MWCO resulted in an improved Cd removal rate. In addition, as the Cd²⁺ concentration in feedwater increased, the Cd removal rate decreased, while the Cd concentration in the permeate increased. Since the solution pH and ionic strength had a notable impact on the Cd removal rate, a high pH value and low ionic strength led to a higher removal rate of Cd. Under optimal Cd removal conditions, UF reduced the influent Cd concentration from 1.0 to 0.019 mg/L. For membrane fouling, increasing the solution pH led to more serious membrane fouling. This phenomenon was the result of Cd²⁺ reacting with OH⁻ and forming a Cd (OH)₂ precipitate. The precipitate and humic acid formed compact cakes on the membrane surface and blocked membrane pores. These results provided adequate evidence for the higher removal of Cd with increasing solution pH. In addition, SEM images under different pH conditions were in agreement with the conclusion mentioned above, which provided further support for the effect of the solution pH on Cd removal and membrane fouling.

This study investigated the soil pollution level and evaluated the phytoremediation potential of 25 native plant species on a former gold mine-tailing site in Ghana. Plant shoots and associated soil samples were collected from a tailing deposition site and analyzed for total element concentration of As, Hg, Pb, and Cu. Soil metal(loid) content, bioaccumulation factor (BAFₛₕₒₒₜₛ), and hyperaccumulator thresholds were also determined to assess the current soil pollution level and phytoextraction potential. The concentration of As and Hg in the soil was above international risk thresholds, while that of Pb and Cu were below those thresholds. None of the investigated plant species reached absolute hyperaccumulator standard concentrations. Bioavailability of sampled metal(loid)s in the soil was generally low due to high pH, organic matter, and clay content. However, for Cu, relatively high bioaccumulation values (BAFₛₕₒₒₜₛ > 1) were found for 12 plant species, indicating the potential for selective heavy-metal extraction via phytoremediation by those plants. The high levels of As at the study site constitute an environmental and health risk but there is the potential for phytoextraction of Cu (e.g., Aspilia africana) and reclamation by afforestation using Leucaena leucocephala and Senna siamea.

The objective of this article is to describe the effect of precipitation and temperature on the drought characteristics of Yunnan province in China. The rainfall and temperature data from 10 national meteorological stations in Yunnan province during 1969 to 2018 were used to investigate the spatial and temporal evolution of drought in Yunnan province and the difference of drought index based on Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI) at nearly 50a different time scales. The results showed that Yunnan province had a frequent alternation of drought and flood, and the larger the time scale, the gentler the SPI and SPEI changes. The recent 50a drought mainly occurred in 1980–1982, 1988–1990, 2003–2007, and 2010–2015, and there was continuous drought and the duration was prolonged. The changes of SPI and SPEI showed a downward trend in different seasons. The linear slopes of SPI and SPEI in spring, summer, autumn, and winter were − 0.0064, − 0.0088, − 0.0057 and − 0.0.0111, respectively, and the drought trend was the most serious in winter. Continuous spring drought occurred in 2009–2010 and 2012–2014. The SPEI values in 2009–2010 and 2012–2014 were − 0.80, − 0.64, − 0.75, − 1.23, and − 1.17, respectively. The spatial distribution of drought frequency in Yunnan province was greatly different, and its distribution rule was more in the north and east, less in the south and west. The drought frequency in Zhaotong (northeast Yunnan) was the highest at 36.53%, the drought frequency in Deqin and Lijiang (northwest Yunnan) were 33.11% and 33.28%, and the drought frequency in Kunming (central Yunnan) Lincang, Lancang, and Simao (southwest Yunnan) were 29.35%, 30.73%, 32.77%, and 28.35%, respectively. This study provided a scientific basis for revealing the spatial and temporal variation rules, evolution trends, regional drought, and drought impact assessment and risk management of drought in Yunnan province.

In this study, a new ecological dam based on the microbial fuel cell principle (MFCED) was designed to remove pollutants from river sediments and water bodies. Sediment organics were better removed in the MFCED mode in comparison with the other two modes (ecological dam with open circuit (OCED) and ecological dam filled with gravel in cathode chamber (GMFCED)). The difference of nitrogen source in water had little effect on the removal of chemical oxygen demand (COD) (70–80%), while nitrate was more readily removed in the MFCED. The voltage curve and power curve were measured to understand the bioelectricity generation of MFCED. During the stable operation phase of MFCED, the voltage was stabilized between 0.09–0.15 V. The results of high-throughput sequencing indicated that the anode and cathode diversities of MFCED were more than the other systems, and the species diversity of the anode was more than that of the cathode in the MFCED. Graphical abstract

The implementation of the extended producer responsibility (EPR) for e-waste is an important measure to develop an ecological civilization. In order to advance manufacturing enterprises to effectively implement resource and environmental responsibility, this study investigates the main causes of environmental regulation failure from the perspective of government and enterprises. The game theory was used to establish an evolutionary game model between government regulatory departments and electronic and electrical products’ manufacturing enterprises. A system dynamic model was utilized to construct the stock-flow graph of the game between government and enterprises, and to carry out simulation analysis under different strategies. The results found that the probability of an enterprise undertaking extended responsibility gradually increased and stabilized with the increase of government supervision and punishment intensity; the government’s regulatory probability and punishment are important factors affecting the enterprises’ compliance with regulations and responsibilities. The study suggests that government should focus on strengthening environmental regulations from the aspects of improving laws and regulations, establishing a regular monitoring system and innovating incentive and constraint mechanism.

Li₂CuO₂ and different iron-containing Li₂CuO₂ samples were synthesized by solid state reaction. On iron-containing samples, atomic sites of copper are substituted by iron ions in the lattice (XRD and Rietveld analyses). Iron addition induces copper release from Li₂CuO₂, which produce cationic vacancies and CuO, due to copper (Cu²⁺) and iron (Fe³⁺) valence differences. Two different physicochemical conditions were used for analyzing CO₂ capture on these samples; (i) high temperature and (ii) low temperature in presence of water vapor. At high temperatures, iron addition increased CO₂ chemisorption, due to structural and chemical variations on Li₂CuO₂. Kinetic analysis performed by first order reaction and Eyring models evidenced that iron addition on Li₂CuO₂ induced a faster CO₂ chemisorption but a higher thermal dependence. Conversely, CO₂ chemisorption at low temperature in water vapor presence practically did not vary by iron addition, although hydration and hydroxylation processes were enhanced. Moreover, under these physicochemical conditions the whole sorption process became slower on iron-containing samples, due to metal oxides presence.