Water quality standard for nitrate becomes more and more strict, and the plant carbon source is widely used for denitrification by constructed wetland (CW) and bioreactor. However, the nitrate removal efficiency by different types of plant carbon source are not evaluated comprehensively. Denitrification performance of different plant carbon sources, and the influence of dosing method and pretreatment are thoroughly reviewed in this paper, which aims to investigate the accurate utilization of plant carbon source for nitrogen (as nitrate) removal. It is concluded that plant carbon source addition for all types of CWs and bioreactors can improve the nitrate removal efficiency to some extent, and the dosing method of plant carbon source for denitrification should be further studied and optimized in the future. The popular carbon sources for CW and bioreactor denitrification enhancement are woodchip, chopped macrophytes, crop plants, macrophytes litters, etc. The recommended optimum C:N ratios for CW and bioreactor are 4.0:5.0 and 1.8:3.0, respectively. The physical and biological pretreatments are selected to supply organic carbon for long-term denitrification.

Rapid increase of CO₂ concentration in the atmosphere has forced the international community towards adopting actions to restrain from the impacts of climate change. Moreover, in India, the dependence on fossil fuels is projected to increase in the future, implying the necessity of capturing CO₂ in a safe manner. Alkaline solid wastes can be utilized for CO₂ sequestration by which its disposal issues in the country could also be met. The present work focuses to study direct mineral carbonation of steelmaking slag (SS) at room temperature and low-pressure conditions (<10 bar). Direct mineral carbonation of SS was carried out in a batch reactor with pure CO₂ gas. The process parameters that may influence the carbonation of SS, namely, CO₂ gas pressure, liquid to solid ratio (L/S) and reaction time were also studied. The results showed that maximum sequestration of SS was attained in the aqueous route with a capacity of 82 g of CO₂/kg (6 bar, L/S ratio of 10 and 3 h). In the gas-solid route, maximum sequestration capacity of about 11.1 g of CO₂/kg of SS (3 bar and 3 h) was achieved indicating that aqueous route is the better one under the conditions studied. These findings demonstrate that SS is a promising resource and this approach could be further developed and used for CO₂ sequestration in the country. The carbonation process was evidenced using FT-IR, XRD, SEM and TG analysis.

This work investigates influence of different aluminosillicate nanoparticles (NPs) which are found in air in selected workplaces on the properties of the phospholipid (DPPC) monolayer at air–saline interface considered as ex vivo model of the lung surfactant (LS). The measurements were done under physiological-like conditions (deformable liquid interface at 37 °C) for NP concentrations matching the calculated lung doses after exposure in the working environment. Measured surface pressure–area (π–A) isotherms and compressibility curves demonstrated NP-induced changes in the structure and mechanical properties of the lipid monolayer. It was shown that hydrophilic nanomaterials (halloysite and bentonite) induced concentration-dependent impairment of DPPC’s ability of attaining high surface pressures on interfacial compression, suggesting a possibility of reduction of physiological function of natural LS. Hydrophobic montmorillonites affected DPPC monolayer in the opposite way; however, they significantly changed the mechanical properties of the air–liquid interface during compression. The results support the hypothesis of possible reduction or even degradation of the natural function of the lung surfactant induced by particle–phospholipid interactions after inhalation of nanoclays. Presented data do not only supplement the earlier results obtained with another LS model (animal-derived surfactant in oscillating bubble experiments) but also offer an explanation of physicochemical mechanisms responsible for detrimental effects which arise after deposition of inhaled nanomaterials on the surface of the respiratory system.

In this study, we compared the size of the mobile Hg pool in soil to those obtained by extractions using 2 M HNO₃, 5 M HNO₃, and 2 M HCl. This was done to evaluate their suitability to be used as proxies in view of Hg uptake by ryegrass. Total levels of Hg in soil ranged from 0.66 to 70 mg kg⁻¹ (median 17 mg kg⁻¹), and concentrations of Hg extracted increased in the order: mobile Hg < 2 M HNO₃ < 5 M HNO₃ < 2 M HCl. The percentage of Hg extracted relative to total Hg in soil varied from 0.13 to 0.79 % (for the mobile pool) to 4.8–82 % (for 2 M HCl). Levels of Hg in ryegrass ranged from 0.060 to 36 mg kg⁻¹ (median 0.65 mg kg⁻¹, in roots) and from 0.040 to 5.4 mg kg⁻¹ (median 0.34 mg kg⁻¹, in shoots). Although results from the 2 M HNO₃ extraction appeared to the most comparable to the actual total Hg levels measured in plants, the 2 M HCl extraction better expressed the variation in plant pools. In general, soil tests explained between 66 and 86 % of the variability of Hg contents in ryegrass shoots. Results indicated that all methods tested here can be used to estimate the plant total Hg pool at contaminated areas and can be used in first tier soil risk evaluations. This study also indicates that a relevant part of Hg in plants is from deposition of soil particles and that splashing of soil can be more significant for plant contamination than actual uptake processes. Graphical Abstract Illustration of potential mercury soil-plant transfer routes

Hydrofluorosis in humans and domestic animals is a worldwide health problem and caused by a prolonged period of fluoride exposure through drinking of fluoride contaminated water. But in recent years, due to rapid industrialization in India, diverse serious health problems among industrial workers and residents and domestic animals living in the industrial areas due to fluoride pollution are on the rise. A number of coal-burning and industrial activities such as power-generating stations, welding operations and the manufacturing or production of steel, iron, aluminum, zinc, phosphorus, chemical fertilizers, bricks, glass, plastic, cement, and hydrofluoric acid are generally discharging fluoride in both gaseous and particulate/dust forms into surrounding environments which create a industrial fluoride pollution and are an important cause of occupational exposure to fluoride in several countries including India. An industrial emitted fluoride contaminates not only surrounding soil, air, and water but also vegetation, crops and many other biotic communities on which man and animals are generally dependants for food. Long- time of inhalation or ingestion of industrial fluoride also causes serious health problems in the forms of industrial and neighborhood fluorosis. In India, whatever research works conducted so far on the chronic industrial fluoride intoxication or poisoning (industrial and neighborhood fluorosis) in man and various species of domestic animals due to a prolonged period of industrial fluoride exposure or pollution (contamination) are critically reviewed in the present communication. Simultaneously, we are also focused the various bio-indicators and bio-markers for chronic industrial fluoride intoxication or pollution.

Leather industry generates huge amount of chrome-containing leather solid waste which creates major environment problems to tanners worldwide. Chrome-tanned leather solid waste is primarily chromium complex of collagen protein. The presence of chromium limits its protein application in animal feed industry. The purified protein hydrolysate with zero chromium could be used in poultry feed. In this study, an attempt has been made to assess performance of poultry with purified protein hydrolysate as a feed derived from chrome-tanned leather waste as partial replacement of soyabean meal as a sole source of protein for growing broiler chickens. Growth study was conducted to evaluate the effect of feeding protein hydrolysate on performance and physiochemical characteristics of meat of broiler chickens. Two experimental diets containing various levels of protein hydrolysate (EI—20 % and EII—30 %) were evaluated. The comparative study was performed as control with soyabean meal. Daily feed intake, body weight gain and feed conversion ratio were measured from day 8 to day 35. At the end of the study, birds were randomly selected and slaughtered to evaluate for physiochemical characteristics of meat. Diet had significant effects on feed intake and body weight gain. Birds fed with 20 and 30 % protein hydrolysate consumed 9.5 and 17.5 % higher amount of feed and gained 6.5 and 16.6 % higher than soyabean meal-fed birds. The current study produced evidence that protein hydrolysate can replace up to 75 % of soyabean meal in broiler diets without affecting either growth performance or meat characteristics.

Co-composting biowastes such as manures and biosolids can be used to stabilize carbon (C) without impacting the quality of these biowastes. This study investigated the effect of co-composting biowastes with alkaline materials on C stabilization and monitored the fertilization and revegetation values of these co-composts. The stabilization of C in biowastes (poultry manure and biosolids) was examined by their composting in the presence of various alkaline amendments (lime, fluidized bed boiler ash, flue gas desulphurization gypsum, and red mud) for 6 months in a controlled environment. The effects of co-composting on the biowastes’ properties were assessed for different physical C fractions, microbial biomass C, priming effect, potentially mineralizable nitrogen, bioavailable phosphorus, and revegetation of an urban landfill soil. Co-composting biowastes with alkaline materials increased C stabilization, attributed to interaction with alkaline materials, thereby protecting it from microbial decomposition. The co-composted biowastes also increased the fertility of the landfill soil, thereby enhancing its revegetation potential. Stabilization of biowastes using alkaline materials through co-composting maintains their fertilization value in terms of improving plant growth. The co-composted biowastes also contribute to long-term soil C sequestration and reduction of bioavailability of heavy metals.

Exposed mine tailing wastes with considerable heavy metals can release hazardous colloidal particles into soil under transient chemical and physical conditions. Two-layered packed columns with tailings above and soils below were established to investigate mobilization and transport of colloidal particles from metal-rich mine tailings into soil under transient infiltration ionic strength (IS: 100, 20, 2 mM) and flow rate (FR: 20.7, 41, and 62.3 mm h⁻¹), with Cu and Pb as representatives of the heavy metals. Results show that the tailing particles within the colloidal size (below 2 μm) were released from the columns. A step-decrease in infiltration IS and FR enhanced, whereas a step-increase in the IS and FR restrained the release of tailing particles from the column. The effects of step-changing FR were unexpected due to the small size of the released tailing particles (220–342 nm, being not sensitive to hydrodynamic shear force), the diffusion-controlled particle release process and the relatively compact pore structure. The tailing particles present in the solution with tested IS were found negatively charged and more stable than soil particles, which provides favorable conditions for tailing particles to be transported over a long distance in the soil. The mobilization and transport of Cu and Pb from the tailings into soil were mediated by the tailing particles. Therefore, the inherent toxic tailing particles could be considerably introduced into soil under certain conditions (IS reduction or FR decrease), which may result in serious environmental pollution.

Giant reed was used as precursor for making biochar in order for the adsorption of NH₄ ⁺–N from aqueous solution. And the adsorption of the product to NH₄ ⁺–N was examined. The surface features of biochar were investigated by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy/energy dispersive spectrometer (SEM-EDS), and X-ray diffraction (XRD). XRD patterns showed several peaks and correspond to the high amount of crystalline material. The crystals contain KCl, K₂O, CaO, MgO, and SiO and possess high surface area which enhances adsorption. The influence of different parameters such as initial concentration, adsorption time, pH, and ionic strength has been carried out. The adsorption could reach equilibrium through 24 h reaction and had the best adsorption amount at the solution pH values from 7 to 9. The cation has great influence on the adsorption of NH₄ ⁺–N, whereas the anion exerted a weaker effect. The adsorption followed pseudo-first-order and pseudo-second-order models. And the intraparticle diffusion and desorption studies further elucidated that the mechanism of adsorption on the product was ion exchange. The product equilibrium data was well described by the Langmuir and Freundlich model. The maximum adsorption capacities were 1.490 mg/g. Biochar derived from giant reed at 500 °C was suggested as a promising adsorbent for the removal of NH₄ ⁺–N from slightly polluted wastewater.