A study area was selected from the industrial region of Gaoshawo Town, Yanchi County, Ningxia, to explore the level of heavy metal pollution in desert grasslands due to industrial activities. A total of 82 surface soils were collected, and the concentration of heavy metals, namely, Cu, Cd, Cr, Pb, Zn, Mn, and Co, was determined by ICP-AES (atomic emission spectrometer) (HK-8100); the average values were 21.64 ± 3.26, 0.18 ± 0.02, 44.99 ± 21.23, 87.18 ± 25.84, 86.63 ± 24.98, 570.49 ± 171.57, and 17.96 ± 9.96 mg kg⁻¹. The single-factor, Nemerow pollution, and potential ecological risk index methods were used to evaluate the status of soil heavy metal pollution and the contribution from the major sources identified by the receptor model. The results showed that 9.09% of the samples were slightly polluted, 32.47% of the samples were moderately polluted, and 58.41% of the samples were heavily polluted. The comprehensive potential ecological risk index indicated that 90.79% of the samples had moderate ecological risk. It was verified from the models and spatial distribution maps that Cr, Co, Zn, and Mn are mainly contributed by the industrial sources that account for 55.04%, 92.13%, 50.05%, and 48.77% of these heavy metals, respectively. The heavily contaminated areas are distributed around the industrial park. A total of 70.63% and 77.83% of Cu and Pb are contributed by transportation sources, respectively, with the concentrations decreasing from southwest to northeast. The contribution from agricultural activities to Cd is 77.02%, with concentrations largely distributed in the north of the highway. This study showed that the existence of the Gaoshawo Industrial Zone and the corresponding industrial and transportation activities have a significant impact on the grassland soil environment.

Small geographically isolated ponds provide a multitude of ecological functions and services, but water table fluctuations alter the magnitude of these services. Understanding temporal and spatial changes of surface water levels in the watershed, and their spatial variability, is critical for restoration and protection of small ponds. A biweight spatial consistency test was employed to quantify the seasonal variability of surface water tables for 50 ponds and hydrological connectivity models, and land use metrics, topographic characteristics, and irrigation needs, for groundwater, were introduced into the model to identify influencing factors. The spatial difference of water level changes in the rice season was greater than the wheat season while water table increased in the wheat season and declined in the rice season. Continuous runoff with complete surface hydrological connectivity of ponds, which was strongly related to precipitation, occurred only one time during the study period. Water level dynamics were largely uncorrelated to surface hydrological connectivity but were linked to watershed and pond size. By evaluating irrigation water requirements, irrigation was a primary human management factor affecting the water table changes in ponds. Groundwater also enriched influence factors that estimated water level variation in ponds, and these results will provide support for improved water resource management and ponds protection purposes.

This paper presents a synthesis of mesoporous silica (MS) from natural clay as a silica source using Pluronic L35 (EO11PO16EO11) as a structure-directing agent. The prepared material was characterized by XRD, X-ray fluorescence, thermogravimetric analysis, SEM, TEM, and N2 adsorption-desorption analyses. Then, mesoporous material was used for the removal of Acid Red 337 (AR337) from aqueous solution, and the treatment of real textile effluent. The effect of pH, contact time, weight of adsorbent, and initial concentration was studied in batch adsorption. The synthesized mesoporous material showed good discoloration efficiency with a 62% percentage. Experiment with real textile wastewater showed that 39%, 40%, and 31.5% of the color, TOC, and chemical oxygen demand respectively were eliminated by using 1 g of MS per liter of wastewater.

Two pot experiments were conducted to study the effects of intercropping cadmium (Cd) accumulator plants (Stellaria media (L.) Villars, Cardamine hirsuta, Cerastium glomeratum Thuill, and Galium aparine L.) and applying their straw on the growth and Cd accumulation of Brassica chinensis L. Intercropping with four accumulator plants reduced the biomass, water content, and photosynthetic pigment content of B. chinensis compared with monoculture. Intercropping with accumulator plants increased the Cd content in the roots and shoot of B. chinensis, and the translocation factor (TF), root bioconcentration factor (root BCF), and shoot bioconcentration factor (Shoot BCF) increased. The soil pH decreased and the soil available Cd content increased by intercropping. Thus, intercropping with four accumulator plants can promote the Cd uptake of B. chinensis. The straw of four accumulator plants reduced the biomass, water content, and photosynthetic pigment content of B. chinensis compared with the control. The straw of S. media and C. hirsute increased the Cd content in the roots and shoots of B. chinensis, TF, root BCF, and shoot BCF. The straw of C. glomeratum and G. aparine decreased the Cd content in the roots and shoots of B. chinensis, TF, root BCF, and shoot BCF. The soil pH increased and the soil available Cd content decreased by application of straw. Thus, the straw of C. glomeratum and G. aparine can reduce the Cd uptake of B. chinensis.

Manganese sulfate residue (MSR) is a by-product derived from the manganese sulfate production process. In this study, an iron hydroxide adsorbent was prepared from MSR using the hydrothermal conversion method. The adsorbent was characterized and used to remove copper(II) ions from aqueous solution. Batch experiments were performed to investigate the adsorption efficiency of copper ions at different contact times, initial concentrations, solution pH levels, and reaction temperatures. Adsorption equilibrium was observed in 3 h, and the best pH was under natural conditions (pH ∼ 5.5). Increasing the initial Cu²⁺ concentration and reaction temperature can increase the adsorption quantity. The adsorption capacity of iron hydroxide at an initial concentration of 50 mg L⁻¹ was 14.515 mg g⁻¹ Cu(II) under the conditions of a nature pH and room temperature. According to the adsorption data, the pseudo-second-order model can describe the adsorption kinetics of copper ions well, and the Freundlich model provides an excellent fit to the adsorption isotherm. XRD and FTIR were applied to characterize the raw materials and adsorbents to reveal the adsorption mechanism. The results suggest that the adsorbent converted from MSR is a promising material for the removal of Cu(II) in aqueous solutions.

Phosphorus (P) is an essential biogenic element in aquatic ecosystem, and its speciation in sediment may influence the water quality. The composition of P in suspended particular matters (SPM) and sediments were analyzed. Metal ions bonding PO₄³⁻ and chelating organic P (OP) were explored by Visual MINTEQ simulation and infrared spectroscopy. Inorganic P (IP) mainly comprises orthophosphate and pyrophosphate in SPM. OP mainly includes α-glycerol phosphate, β-Gly, monophosphate, and mononucleotides from aquatic plants in SPM. Cyclotella, Nitzschia, Amphiprore, and terrestrial C₃ plants are the main source of aquatic plants in JH, while they are from Oscillatoria and Merismopedia in JL. These aquatic plants directly determine whether OP or IP is taken to surface sediments during the setting of SPM. The bonding between PO₄³⁻ and Ca is more preferential than Al and Fe, so the excess PO₄³⁻ makes Ca compounds bonding IP (Ca-IP) and Al/Fe/Mn (hydr) oxides associated IP (Al/Fe/Mn-IP) dominant, but limited PO₄³⁻ preferentially contributes more Ca-IP. Metal ions in saline water can firmly cheat with OP via P-OH and/or P=O groups to promote the burial of OP.

Multi-element concentrations (Al, As, Cd, Cr, Hg, Ni, Pb, Se, and Sr) were analyzed in the muscle of six fish species (Hoplias malabaricus, Oligosarcus jenynsii, Rhamdia quelen, Bryconamericus iheringii, Astyanax fasciatus, and Odontesthes bonariensis) with different diets and habits from the Río Tercero Reservoir (RTR) in Córdoba, Argentina, during the wet and dry seasons. Besides, potential human health risks, associated with the consumption of these elements, have been assessed considering the average daily intake (EDI) in children and adults. Additionally, the target hazard quotient (THQ) and carcinogenic risk (CR) were evaluated taking into account the intake by the general population, fishermen, and consumption frequency recommended by the American Heart Association (AHA), the maximum scientific reference in cardiology in the USA and worldwide. All species presented quantifiable values in muscle for all the analyzed elements (Al, As, Cr, Hg, Ni, Se, and Sr), except for Cd and Pb, being Al and Sr the most accumulated elements in all species in both seasons. The consumption of edible muscles of the species studied in this reservoir represents a toxicological risk to humans. Mercury and As were the main elements that presented a health risk through the consumption of fish. Their concentrations in most fish species were above the maximum daily allowable concentrations, and THQ values were several times greater than 1. In addition, according to AHA recommendations, the cancer risk caused by As was greater than the acceptable value of 10⁻⁴ in all species studied, and in both seasons, with the exception of A. fasciatus, in the rainy season. These results indicate that the consumption of fish from the RTR exposes the inhabitants to possible health risks, especially when considering the consumption frequency recommended by the AHA. Therefore, fish intake from this reservoir should be limited to minimize potential risks to the health of consumers. Finally, the results of this study are useful for controlling pollution and developing preventive and palliative policies to protect populations in contact not only with the reservoir but also with other areas of the world with similar conditions.

Thermal power generating industries affect the surrounding environment in various ways. Fly ash escapes along with flue gases and can be found in undesirable quantities in soil and water sources in the region. The water quality of an area must be evaluated regularly to ensure the quality of potable water. The present study evaluates the pre-monsoon and post-monsoon concentrations of several important physico-chemical parameters and heavy-metal contents of groundwater samples collected from sites near the Koradi Thermal Power Plant, a major source of power generation in the Nagpur Region. The maximum amount of total dissolved solids observed during the two seasons studied were 1571 mg/l and 1591 mg/l which is within the desirable limit implying that fly ash contamination did not affect this water quality parameter. The total hardness of samples from GW-3, GW-5 and GW-9 were 844 mg/l, 775 mg/l and 675 mg/l during pre-monsoon season, while GW-3 and GW-5 along with GW-4 continued to show high levels of total hardness at 1015 mg/l, 741 mg/l and 650 mg/l, respectively. These values are higher than the permissible limit due to the high levels of ions of bicarbonate, calcium, sodium and sulphate derived from fly ash leachate. Statistical analysis showed that sulphides, total hardness, electrical conductivity and total dissolved solids were the significant water quality parameters of the region. The evaluation of the parameters found that the three water sources (GW-3, GW-5 and GW-9) out of 10 are the most affected groundwater sources of fly ash pollution.

Accelerating greenhouse gas emission particularly carbon dioxide (CO₂) in the atmosphere has become a major concern. Adsorption process has been proposed as a promising technology for CO₂ adsorption from flue gas, and the carbonaceous adsorbent is a potential candidate for CO₂ adsorption at atmospheric pressure and ambient temperature. Biochar derived from palm kernel shell waste was applied as a potential precursor for activated carbon production. This research study employed the response surface methodology coupled with Box-Behnken design to optimize the parameters involved in producing exceptional activated carbon with high yield (Y₁) and CO₂ adsorptive characteristics (Y₂). Specifically, parameters studied include the activation temperature (750–950 °C), holding time (60–120 min), and CO₂ flow rate (150–450 mL/min). The activated carbon at the optimum conditions was characterized using various analytical instruments, including elemental analyzer, nitrogen (N₂) physisorption analyzer, and field emission scanning electron microscopy. Overall, utilization of biochar as the activated carbon precursor is practical compared with the traditional non-renewable materials, due to its cost efficiencies and it being more environment-friendly ensuring process sustainability. Besides, this research study that incorporates physical activation with CO₂ as the activating agent is attractive, because it directly promotes CO₂ utilization and capture, in addition to the absence of any chemicals that may result in the secondary pollution problems.

In this work, malachite green was degraded using different advanced oxidation processes (Fenton, photo-Fenton, sono-Fenton and electrochemical process). Malachite green is used as biocide in aquaculture and is usually discarded with the effluents. On higher pollutant concentration, all the Fenton-based reactions achieved excellent absorbance reduction up to 10 min. Classic Fenton was faster after 10 min of reaction and photo-Fenton acting faster before this point. The photocatalytic effect was better on the oxygen demand reduction (COD) with 86.91% against 79.19% of sono-Fenton and 62.72% of Fenton. All four methodologies had excellent absorbance reduction following the order: photo-Fenton (100% up to 30 min) > electrochemical (99.27%) > Fenton (98.11%) > sono-Fenton (73.99%). Despites the slowly initial degradation obtained for electrochemical process, the reaction achieved high capacity after 60 min. Toxicity tests, using Lactuca sativa seeds, indicated a significant reduction in the effluent toxicity following this sequence: sono-Fenton > photo-Fenton > Fenton > electrochemical. The results showed that all processes studied provided high levels of malachite green removal; however, the adequate use of each technique should be conduct with an accurate evaluation of the needed treatment considering the particularity of each method. Such techniques were successfully applied before to remove dye basic blue 99 and the hormone 17-α-methyltestosterone and corroborated by Lactuca sativa toxicity assays. Graphical Abstract