Graphene oxide (GO) may strongly interact with toxic metal ions and mineral particles upon release into the soil environment. We evaluated the mutual effects between GO and Ni (Ni(II)) with regard to their adsorption and co-adsorption on two minerals (goethite and hematite) in aqueous phase. Results indicated that GO and Ni could mutually facilitate the adsorption of each other on both goethite and hematite over a wide pH range. Addition of Ni promoted GO co-adsorption mainly due to the increased positive charge of minerals and cation–π interactions, while the presence of GO enhanced Ni co-adsorption predominantly due to neutralization of positive charge and strong interaction with oxygen-containing functional groups on adsorbed GO. Increasing adsorption of GO and Ni on minerals as they coexist may thus reduce their mobility in soil. Extended X-ray absorption fine structure (EXAFS) spectroscopy data revealed that GO altered the microstructure of Ni on minerals, i.e., Ni formed edge-sharing surface species (at RNᵢ₋Fₑ∼3.2 Å) without GO, while a GO-bridging ternary surface complexes (at RNᵢ₋C∼2.49 Å and RNᵢ₋Fₑ∼4.23 Å) was formed with GO. These findings improved the understanding of potential fate and toxicity of GO as well as the partitioning processes of Ni ions in aquatic and soil environments.

Sediments nearby harbors are dredged regularly, and the sediments require the stringent treatment to meet the regulations on reuse and mitigate the environmental burdens from toxic pollutants. In this study, FeCl₃ was chosen as an extraction agent to treat marine sediment co-contaminated with Cu, Zn, and total petroleum hydrocarbons (TPH). In chemical extraction process, the extraction efficiency of Cu and Zn by FeCl₃ was compared with the conventional one using inorganic acids (H₂SO₄ and HCl). Despite the satisfactory level for extraction of Cu (78.8%) and Zn (73.3%) by HCl (0.5 M) through proton-enhanced dissolution, one critical demerit, particularly acidified sediment, led to the unwanted loss of Al, Fe, and Mg by dissolution. Moreover, the vast amount of HCl required the huge amounts of neutralizing agents for the post-treatment of the sediment sample via the washing process. Despite a low concentration, extraction of Cu (70.1%) and Zn (69.4%) was done by using FeCl₃ (0.05 M) through proton-enhanced dissolution, ferric-organic matter complexation, and oxidative dissolution of sulfide minerals. Ferric iron (Fe³⁺) was reduced to ferrous iron (Fe²⁺) with sulfide (S²⁻) oxidation during FeCl₃ extraction. In consecutive chemical oxidations using hydrogen peroxide (H₂O₂) and persulfate (S₂O₈²⁻), the resultant ferrous iron was used to activate the oxidants to effectively degrade TPH. S₂O₈²⁻ using FeCl₃ solution (molar ratio of ferrous to S₂O₈²⁻ is 19.8–198.3) removed 42.6% of TPH, which was higher than that by H₂O₂ (molar ratio of ferrous to H₂O₂ is 1.2–6.1). All experimental findings suggest that ferric is effectively accommodated to an acid washing step for co-contaminated marine sediments, which leads to enhanced extraction, cost-effectiveness, and less environmental burden.

Strong acid rain was recently observed over Northeastern China, particularly in summer in Liaoning Province where alkaline dust largely neutralized acids in the past. This seems to be related to the regional transboundary pollution and poses new challenges in acid rain control scheme in China. In order to delve into the regional transport impact, and quantify its potential contributions to such an “eruption” of acid rain over Liaoning, this paper employs an online source tagging model in coupling with the Nested Air Quality Prediction Modeling System (NAQPMS). Validation of predictions shows the model capability in reproducing key meteorological and chemical features. Acid concentration over Liaoning is more pronounced in August (average of 0.087 mg/m³) with strong pollutant import from regional sources against significant depletion of basic species. Seasonal mean contributions from regional sources are assessed at both lower and upper boundary layers to elucidate the main pathways of the impact of regional sources on acid concentration over Liaoning. At the upper layer (1.2 km), regional sources contribute to acid concentration over Liaoning by 67%, mainly from Shandong (16%), Hebei (13%), Tianjin (11%) and Korean Peninsula (9%). Identified main city-receptors in Liaoning are Dandong, Dalian, Chaohu, Yingkou, Liaoyang, Jinfu, Shengyang, Panjin, Tieling, Benxi, Anshan and Fushun. At lower layer (120 m) where Liaoning local contribution is dominant (58%), regional sources account for 39% in acid concentration. However, inter-municipal acid exchanges are prominent at this layer and many cities in Liaoning are revealed as important sources of local acid production. Seasonal acid contribution average within 1.2 km-120 m attains 55%, suggesting dominance of vertical pollutant transport from regional sources towards lower boundary layer in Liaoning. As direct environmental implication, this study provides policy makers with a perspective of regulating the regional transboundary environmental impact assessment in China with application to acid rain control.

Acetochlor is a widely used chloroacetanilide herbicide and has posed environmental risks in soil and water due to its toxicity and high leaching capacity. Earthworm represents the dominant invertebrate in soil and can promote the decomposition of organic pollutants. The effect of earthworm on acetochlor degradation in soil was studied by soil column experiment with or without acetochlor and earthworm in sterile and natural soils. The degradation capacities of drilosphere components to acetochlor were investigated by microcosm experiments. Bacterial and fungal acetochlor degraders stimulated by earthworm were identified by high-throughput sequencing. The degradation kinetics of acetochlor suggested that both indigenous microorganisms and earthworm played important roles in acetochlor degradation. Acetochlor degradation was quicker in soil with earthworms than without earthworms, with the degradation rates increased by 62.3 ± 15.2% and 9.7 ± 1.7% in sterile and natural treatments respectively. The result was related to the neutralized pH, higher enzyme activities and enhanced soil microbial community diversity and richness in the presence of earthworms. Earthworm cast was the degradation hotpot in drilosphere and exhibited better anaerobic degradation capacity in microcosm experiments. The acetochlor degradation rate of cast in anaerobic environment was 12.0 ± 0.1% quicker than that in aerobic environment. Residual acetochlor in soil conferred a long-term impairment on fungal community, and this inhibition could be repaired by earthworm. Earthworm stimulated indigenous degraders like Sphingomonas and Microascales and carried suspected intestinal degraders like Mortierella and Escherichia_coli to degradation process. Cometabolism between nutrition cycle species and degraders in casts also contributed to its faster degradation rates. The study also presented some possible anaerobic degradation species like Rhodococcus, Pseudomonas_fulva and Methylobacillus.

Neutralization is the necessary operation to ensure the Fenton effluent pH. In situ coagulation can be induced during neutralization. In this study, three types of alkaline neutralizers (Ca(OH)₂, NaOH, and Ca(OH)₂ + NaOH) were added into the Fenton oxidized PSE to control the effluent pH of 6 to 9. The coagulation behavior, floc structure, and properties were investigated. The results indicated that the coagulation with the adding of three neutralizers can remove 9.68 to 24.02% of the TOC. Ca(OH)₂ exhibited the highest TOC removal efficiency at the dosage of 0.4 g/L. Charge neutralization ability was in the following order: Ca(OH)₂ > Ca(OH)₂ + NaOH > NaOH. Ca(OH)₂ and Ca(OH)₂ + NaOH showed the increase of floc growth rate with the increase of agent dosage, especially for Ca(OH)₂ + NaOH. Moreover, Df of NaOH flocs was higher than that of Ca(OH)₂ and Ca(OH)₂ + NaOH, indicating the floc formed by NaOH was more compact than that of Ca(OH)₂. The main coagulation process of three neutralizers was different, and it was also affected by the agent dosage (or pH). When the dosage was 0.35 g/L (pH 6–7.5), the complexation, adsorption, and bridging were the predominant processes while charge neutralization gradually became the main coagulation process for Ca(OH)₂ and Ca(OH)₂ + NaOH with the increase of dosage (pH 7.5–9).

Mojave yucca (Yucca schidigera) is widely grown in the deserts. This herb is commercially used because it is rich in saponins and phenolic compounds with antioxidant effect. Y. schidigera or its derivatives are included as nontoxic food supplements, in cosmetics, and in the pharmaceutical industry. Saponins originated from Y. schidigera have anti-inflammatory, antioxidant, immunostimulatory, growth promoter, hypocholesterolemic, and hypoglycemic effects. To date, the key role of Y. schidigera or its products in animal nutrition is to reduce the ammonia content in the atmosphere and fecal odor in poultry excreta. Mitigating ammonia by using this plant could be achieved by the modification of gut microbiota, enhancement in digestion, and absorption of nutrients, leading to a better growth and production performance of animals and poultry. Various methods were applied to mitigate the emission of odor from the litter by different strategies including biofilters, litter treatments, air scrubbers, neutralizing agents, windbreak walls, etc., but these techniques are expensive. This article provides a new insight to scientists and poultry breeders to use Y. schidigera plant or its products as inexpensive and safe sources of a feed supplement to overcome the ammonia and fecal odor problems, as well as reduce environmental pollution in poultry houses.

This study aimed to assess the chemical composition of the rainwater in three areas of different environmental impact gradients in Southern Brazil using the receptor model EPA Positive Matrix Factorization (EPA PMF 5.0). The samples were collected in a bulk sampler, from October 2012 to August 2014, in three sampling sites along with the Sinos River Basin: Caraá, Taquara, and Campo Bom. The major ions NH₄⁺, Na⁺, K⁺, Ca²⁺, Mg²⁺, F⁻, Cl⁻, NO₃⁻, SO₄²⁻, and pH were analyzed, as well as identify the main emission sources. The most abundant cations and anions were Ca²⁺, Na⁺, Cl⁻, and SO₄²⁻, respectively. The mean pH value in the Sinos River Basin during the study period was 6.07 ± 0.49 (5.13–7.05), which suggests inputs of alkaline species into the atmosphere. The most important neutralizing agents of sulfuric and nitric acids in the Sinos River Basin are Ca²⁺ (NF = 1.36) and NH₄⁺ (NF = 0.57). The source apportionment provided by the EPA PMF 5.0 resulted in four factors, which demonstrate the influence of anthropogenic and natural sources, in the form of (a) industry/combustion of fossil fuels (F⁻ and SO₄²⁻), (b) marine contribution (Na⁺ and Cl⁻), (c) crustal contribution (K⁺, Ca²⁺, and NO₃⁻), and (d) agriculture/livestock (NH₄⁺). Therefore, this study allows a more appropriate understanding of factors that contribute to rainwater chemical composition and also to possible changes in air quality.

Leachates emanating from bauxite residue disposal areas are alkaline and require neutralisation prior to discharge. The use of passive technologies such as constructed wetlands has received increasing interest as possible treatments for alkaline leachates, including bauxite residues. Mechanisms proposed for wetland effectiveness have included calcite precipitation but it is not clear if such a pathway is feasible in the relatively low Ca residue leachates. Carbonation of Ca-spiked residue leachate treatments was conducted to observe rates of pH decrease and precipitate formation. For all treatments, carbonation effectively decreased pH to ca. 10.5 which remained stable following aeration. Decreases in Al content of 83–93% were also observed. Precipitates retrieved from carbonation experiments and from a constructed wetland trial were characterised using XRD, SEM, XPS and EDX. Calcium carbonates formed in Ca-spiked treatments and dawsonite precipitation occur in the absence of Ca. Rinsing of precipitates removes surface calcium indicating soluble forms adsorbed on precipitates. The results demonstrate that carbonation of bauxite residue leachate is an important component of passive treatments and neutralisation.

Water fog composition was investigated at a fog harvesting installation in the coast of Atacama (North Chile). Chañaral is historically affected by mining contamination discharges. Hydro-chemical characterization of fog water from top of the mountain (where capture installation is located) and at the bottom of the mountain (after vertical transportation where an aquaponic system is located) revealed many compositional differences that compromise the use of water. High acidity and high concentrations in Cu and As in water collected on top of the mountain were found; meanwhile, acidity and Cu decreased, and As levels overpassed the drinking water standards after the vertical transportation. Collected data was assessed according to national and international regulatory standards, neutralization factors (NF), sodium adsorption ratio (SAR), and ion ratios to determine origin of contamination and suitability of destined for human consumption, irrigation, or aquaculture purposes.

An intensive sampling campaign of airborne fine particles (PM₂.₅) was conducted at Sanya, a coastal city in Southern China, from January to February 2012. Chemical analyses and mass reconstruction were used identify potential pollution sources and investigate atmospheric reaction mechanisms. A thermodynamic model indicated that low ammonia and high relative humidity caused the aerosols be acidic and that drove heterogeneous reactions which led to the formation of secondary inorganic aerosol. Relationships among neutralization ratios, free acidity, and air-mass trajectories suggest that the atmosphere at Sanya was impacted by both local and regional emissions. Three major transport pathways were identified, and flow from the northeast (from South China) typically brought the most polluted air to Sanya. A case study confirmed strong impact from South China (e.g., Pearl River Delta region) (contributed 76.8% to EC, and then this result can be extended to primary pollutants) when the northeast winds were dominant. The Weather Research Forecasting Black carbon model and trace organic markers were used to apportion local pollution versus regional contributions. Results of the study offer new insights into the atmospheric conditions and air pollution at this coastal city.