Globally, heavy metal (HM) pollution of soil is a serious problem that can lead to long-term toxic effects on soil. In this milieu, the present study investigated the eco-toxicological effects of three trace elements, e.g., cadmium (Cd), copper (Cu), and lead (Pb), on enzyme activities and microbial function and structural diversity in phaeozem and red soil samples. Hormesis effects of Cd, Cu, and Pb on catalase and invertase activities were observed in phaeozem soil, while for red soil, there was an inhibitory effect on the activities of catalase and invertase under Cu- and Pb-contaminated soils. The utilization of carbon sources was inhibited in Cd- and Pb-treated phaeozem soil, but higher utilization of polymers and amines exhibited in Cu-contaminated soil. Although the substrates under the contamination of Cd, Cu, and Pb had high average well color development values across incubation time, the utilization of various substrates did not exhibit a regular trend under different treatments with HMs. The denaturing gradient gel electrophoresis (DGGE) analysis showed that the HMs led to marginal changes in the number and species of soil microbes, while the similarity indices decreased in HM-treated samples, varying from 66.2 to 77.3% in phaeozem soil and from 62.8 to 66.7% in red soil. However, the sequence analysis showed that there existed metal-resistant microbial communities such as Bacillales, Bacillus, and Massilia and so on under the stress of HMs.

Photo-Fenton oxidation is one of the most promising processes to remove recalcitrant contaminants from industrial wastewater. In this study, we developed a novel heterogeneous catalyst to enhance photo-Fenton oxidation. Multi-composition (Fe-Cu-Zn) on aluminosilicate zeolite (ZSM-5) was prepared using a chemical process. Subsequently, the synthesized catalyst was characterized by using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray (spectroscopy) (EDX), and Brunauer–Emmett–Teller (BET). Activity of the synthesized catalyst is analysed to degrade an azo dye, methyl orange. Taguchi method is used to optimize color removal and total carbon content (TOC) removal. The dye completely degraded, and 76% of TOC removal was obtained at optimized process conditions. The amount of catalyst required for the desired degradation of dye significantly reduced up to 92% and 30% compared to conventional homogenous and heterogeneous Fenton oxidation processes, respectively.

Consuming drinking water contaminated with As(V) represents a hazard to human health. Adsorption of As(V) onto bone char (BC) has been studied previously, but a detailed study is required for applying BC to remove arsenate present in drinking water. The effect of the operating conditions, water matrix, and presence of fluoride onto the adsorption capacity of BC toward As(V) were thoroughly investigated. The XRD examination confirmed the presence of hydroxyapatite in BC, and the TEM examination of BC showed the random piling of the layers of hydroxyapatite. The BC adsorption capacity was contrasted with that of reagent-grade hydroxyapatite, and it was found that the BC capacity was mainly attributed to its hydroxyapatite content. The BC capacity is augmented by diminishing the solution pH because of the rise of the electrostatic attraction between the arsenate in water and the positive charge of the BC surface. The adsorption capacity was improved by incrementing the temperature so that the adsorption of As(V) was endothermic. The adsorption mechanism of As(V) on BC comprised electrostatic attraction and ion exchange. The simultaneous elimination of fluoride and arsenate in drinking water samples in San Luis Potosí, SLP, México, revealed that both pollutants could be effectively removed by adsorption on BC, and the presence of As(V) did not affect the adsorption capacity of BC toward fluoride. In contrast, the capacity of BC for adsorbing As(V) was enhanced in the drinking water compared with that of deionized water, and this synergistic behavior was due to a screening effect.

Different studies have shown that livestock manure has a high potential for fertilization in plant growth and crop yield. However, the main challenge of using animal manure as fertilizer is to increase the risk of endocrine-disrupting compounds (EDCs) pollution in soil and water. Because of their adverse effects, these compounds have gained more concern. Farmland applied with manure is considered the primary source of estrogens in the environment. To manage the pollution of EDCs, manure management approaches such as aerobic composting should be utilized to degrade and remove these pollutants. Composting has attracted attention because of its rapid reaction scale and strong degradation ability against the steroidal compounds. However, estrogen removal via traditional composting needs to be improved, as the steroidal compounds that remained in the composted manure could be quickly discharged to the environment because their biodegradation rate is lower than their discharge rate. For that reason, more advanced approaches, such as inoculation with microorganisms, should be involved. Also, applying adsorbent materials such as biochar (BC) and humic acid (HA) should be considered. In the light of the modern studies, affording an overall vision and perspectives about the fate of estrogens during composting is highly valuable. This review was designed to explore the sources, properties, occurrence, half-life, degradation, and transformation of estrogens during animal manure composting. Besides, the efficiency of estrogens degrading microorganisms and adsorbent additives was also reviewed. The eventual remarks were mentioned, and their prospects were discussed.

Lead is a toxic metal, and its characterization in contaminated soils is crucial to the success of a remediation, especially for the soil washing, one of most commonly used technologies. In this study, we propose a convenient approach that combines sedimentary hydro-classification with semi-quantitative powder X-ray diffraction analysis for characterizing the Pb-bearing minerals in soils. The approach was applied to two samples (YYm and YYu-1) collected from a closed Cu–Pb–Zn mine in the Tohoku region of Japan. The samples were taken from adjacent areas but had different appearances (YYm was a gray soil and YYu-1 was a creamy colored soil). The coarser YYm fractions had higher Pb contents than the finer YYm fractions, but the finer YYu-1 fractions (diameters < 32 μm) had higher Pb contents than the coarser YYu-1 fractions. The semi-quantitative powder X-ray diffraction analysis showed that the main Pb-containing minerals in the YYm and YYu-1 samples were galena and plumbojarosite, respectively. Tessier sequential extractions were also performed, and 1 M sodium acetate leached 21% and 65% of the Pb from the YYm and YYu-1 samples, respectively. This suggested that most of the Pb in the YYu-1 sample was ion-exchangeable and was more easily leached compared with that in the YYm sample. The findings indicate that it is important to accurately characterize the Pb-bearing minerals (especially naturally occurring Pb) present in contaminated soils before selecting appropriate remediation techniques and conditions.

Surface architecting of the catalyst is a hopeful method to expand the surface property of the impetus material for upgrading their response towards the chemical reaction. In the present study, designing of the catalyst was carried out using specific transition metals to boost the simultaneous NO-CO conversion reaction catalytically. These metal oxide systems have been prepared using the combustion and wet impregnation method. Prepared oxides were characterized using XRD, BET, XPS, SEM, and TEM. Further, the surface phenomenon of the catalyst was monitored through H₂-TPR, O₂-TPO, NO-TPD, and CO-TPD studies. The highly remarkable activity was perceived by Pd-based modified manganese oxide-cobalt chromite system as compared with simple Pd-based manganese oxide and Pd-based cobalt chromite. The catalyst showed the highest activity for NO-CO redox reaction with T₁₀₀ at 170 °C. Also, good stability was observed with a runtime of 7 h.

As a recently discovered process of nitrogen cycling, anaerobic ammonium oxidation coupled to ferric iron reduction (Feammox) has attracted more attentions. This study investigated the spatial variation of Feammox in the sediment of different zones of a shallow freshwater lake and the effect of organic matter derived from algae and macrophyte on Feammox process. The potential Feammox rates showed significant differences among sediments from algae-dominated area (ADA), transitional area in the center of the lake (TDA), and macrophyte-dominated area (MDA), and in a descending order, ADA, MDA, and TDA. The potential Feammox rate ranged from 0.14 to 0.34 mg N kg⁻¹day⁻¹ in the freshwater lake sediment. The potential Feammox rates of the sediment with algae or macrophyte amendment were 12.29% and 15.31% higher than the control test without algae and macrophyte amendment. The addition of algae or macrophyte to the sediment from TDA could improve the amount of HCl-extractable total Fe, Fe(III) reduction rate, and the abundance of FeRB. These results demonstrated that organic matter is one of the key regulators of Feammox process.

Desiccation of the Namak Lake (NL) can result in the release of fine-grained dust contaminated with heavy metals, while there is little information available on the propagation of metals in the bed sediments of this lake. In this study, contamination of metals in the surface sediments of the NL was analyzed and the pollution status of sediments was assessed using geo-accumulation index (Igₑₒ), enrichment factor (EF), the consensus-based sediment quality guidelines (CBSQGs), and mean probable effect concentration quotient (mPECQ). Results indicated that metal concentrations at the southern part were higher than at the middle and northern parts of the lake. Possible reasons are (i) pollution loads mainly entered the lake through the rivers at the west and northwest, but accumulated at the southern parts, (ii) hard layer of salt covering the bottom of the NL at the northern part suppresses adsorption of metals to the sediment, and (iii) the muddy nature of sediments at the southern part makes it easier for metals to be absorbed. EF results showed that sediments at the southern part of the lake were moderately enriched with lead (Pb). The low Igₑₒ values suggested no pollution with the metals, and CBSQG values showed that the sediments of the NL were not toxic, while the mPECQ index suggested a toxicity probability of less than 25%. Cluster analysis classified the metals into two clusters. In general, the results showed that metal pollution in the surface sediments of NL was generally low although the concentration of Pb at the southern part of the lake was worrisome.

Mercury (Hg), the environmental toxicant, is present in the soil, water, and air as it is substantially distributed throughout the environment. Being extremely toxic even at low concentration, its remediation is utterly important. Therefore, it is necessary to detoxify the contaminant within the acceptable limits before threatening the environment. Although various conventional methods are being used, irrespective of high cost, it produces intermediate toxic by-product too. Biological methods are eco-friendly, clean, greener, and safer for the remediation of heavy metals corresponding to the conventional remediation due to their economic and high-tech constraints. Bioremediation is now being used for Hg (II) removal, which involves biosorption and bioaccumulation mechanisms or both, also mercuric ion reductase, exopolysaccharide play significant role in detoxification of mercury by acting a potential instrument for the remediation of heavy metals. In this review paper, we shed light on problems caused by mercury pollution, mercury cycle, and its global scenario and detoxification approaches by biological methods and result found in the literature.

Ambient air pollution (AAP) has been widely associated with increased morbidity of ischemic heart disease (IHD). However, no prior studies have investigated the effects of AAP exposure on the length of stay (LOS) due to IHD. Hospital data during 2015–2017 were obtained from hospital information system in five cities of Hubei province, China. We collected daily mean concentrations of air pollutants, including PM₂.₅, PM₁₀, SO₂, NO₂, O₃, and CO, and meteorological data during the same time period. Poisson regression was applied to estimate the acute impacts of AAP on the LOS of IHD inpatients. A total of 42,114 inpatients with primary diagnosis of IHD were included, 50.63% of which were chronic IHD inpatients. Annual average concentrations of PM₂.₅, PM₁₀, SO₂, NO₂, O₃, and CO were 61.93 μg/m³, 95.47 μg/m³, 18.59 μg/m³, 35.87 μg/m³, 100.30 μg/m³, and 1.117 mg/m³, respectively. After adjusting for temperature, relative humidity, gender, age group, payment method, number of hospital beds, location of hospital, and surgery or not, exposures to PM₂.₅, PM₁₀, SO₂, O₃, and CO were associated with increased LOS for all IHD patients in both single- and multi-pollutant models, and stronger associations were observed among chronic IHD patients. In addition, subgroup analyses demonstrated that males and the group aged 65+ years were more vulnerable to air pollution, and the adverse effects were also promoted by low temperature in cold season. This study provides the first investigation of the adverse effects of AAP on the LOS for IHD patients. In order to shorten the LOS of IHD, measures should be taken to strengthen the AAP management and protect the high-risk population.