Zeolite and limestone were tested for their capability of removing As and Fe from acidic water in batch and column experiments. Synthetic acidic water with 3 mg/L As and 50 or 100 mg/L Fe at pH = 2 was used in the column experiments. In the batch experiments, the As concentration, the mass of media, and the contact time were varied between 0.2 and 5 mg As/L, 0.5 and 50 g, and 0.25 and 42 h, respectively. Maximum As sorption capacity as indicated by the Langmuir model was 0.17 mg/g for zeolite and 1.3 mg/g for limestone, at 18-h contact time and 6.3 g/L medium concentration. Energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy analyses revealed that As and Fe were retained in zeolite at the end of the batch experiments. The main factors affecting As and Fe removal efficiency and pH raising capacity were the contact time and the media concentration. This was confirmed in the column experiments, since zeolite and limestone columns presented 99% As removal, under a hydraulic loading rate of 21.8 mm/day. However, limestone columns presented a higher Fe removal: 99 versus 73% for zeolite. The results indicate that limestone could be more appropriate than zeolite when As and Fe are present under acidic conditions, given its higher capacity to remove both As and Fe and to raise pH.

Arsenate (As(V)) is an analog of phosphate (Pᵢ), and previous studies have shown that As(V) and Pᵢ are absorbed via the same transport systems in some organisms. However, little is known about which periplasmic phosphate-binding proteins (PBPs) of ABC-type Pᵢ transporters play major roles in As(V) uptake by cyanobacteria. In this study, the model cyanobacterium Synechocystis sp. PCC 6803 (Synechocystis) was chosen to study the ability of PBPs to discriminate between Pi and As(V). We found that As(V) and Pᵢ competed for uptake via Pᵢ transporters when Synechocystis was treated with As(V) and/or Pᵢ in short-term incubation. The As/P molar ratios of Synechocystis wild type (WT) and mutants (∆sphX, ∆pstS2, ∆sll0540, and ∆sphXpstS1) were measured, and they were significantly different with the order WT > ∆pstS2 > ∆sll0540 > ∆sphXpstS1 > ∆sphX. Furthermore, As(V) uptake by Escherichia coli strain Transetta expressing PBP genes, particularly sphX or sll0540, was significantly increased when PBP gene (pstS1, pstS2, sphX, or sll0540) was separately expressed in Transetta at the same level. Subsequent phylogenetic analyses of PBPs showed that SphX and Sll0540 belonged to the low-affinity PBPs, while PstS1 and PstS2 were clustered with the high-affinity PBPs. These results implied that As(V) was taken up via Pᵢ transporters, and the low-affinity PBPs, SphX and Sll0540, made a significant contribution to As(V) uptake.

The intensive use of pesticides has increased exponentially in Brazil and worldwide due to the need to meet the food demands of a growing population. If the management/monitoring of the use of pesticides is adequately performed, it would not compromise the expected benefits or have negative effects on the environment as a whole. In order to examine the information available on herbicide use in Brazil and worldwide, this paper presents a review of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) and its chemical properties, action on target organisms, environmental fate, and toxicity to non-target organisms. This herbicide is a synthetic auxin used to control broad-leaved weeds, and the action in target organisms is well known. Although 2,4-D has been widely used worldwide, many studies have shown that this herbicide induces alterations in non-target organisms. Therefore, ecotoxicology studies are important to assess the risk the herbicides can be to different ecosystems. Thus, it is advised to use this herbicide and other pesticides with caution.

In this study, the degradation of benzene by the means of an optimized surface/packed-bed hybrid discharge (SPBHD) plasma combined with γ-Al₂O₃-supported MO ₓ (M = Ag, Mn, Cu, or Fe) catalysts in post plasma-catalysis (PPC) system. The effects of Ag loading amount and gas hourly space velocity (GHSV) for plasma-catalysis degradation of benzene have been systematically investigated. The experimental result showed that the benzene degradation was improved and the mineralization process was greatly enhanced towards total oxidation after the combination of plasma with all MO ₓ /γ-Al₂O₃ catalysts. The AgO ₓ /γ-Al₂O₃ catalyst exhibited the best catalytic activity in benzene degradation than the other catalysts in PPC system. The highest benzene degradation efficiency of 96% and CO ₓ selectivity of 99% can be obtained for AgO ₓ /γ-Al₂O₃ catalyst with optimum Ag loading amount and GHSV of 15% and 22,856 h⁻¹, respectively. Time course of benzene degradation during PPC process indicated that the plasma-induced catalytic activity of AgO ₓ /γ-Al₂O₃ catalyst was temporary rather than lasting over a period after the plasma off. FT-IR analysis results revealed that the intermediate products (such as CO, HCOOH) and unwanted by-products (O₃ and NO ₓ) generated in plasma process could be significantly inhibited by PPC process with AgO ₓ /γ-Al₂O₃ catalyst.

Thermally robust hydroxylated biochar (HBC) and sulphonated biochar (SBC) were synthesised from paper and pulp sludge (PPS) and used for the adsorption of Zn²⁺ from synthetic wastewater through batch experiments. FTIR analyses proved successful incorporation of the hydroxyl and sulphonic functional groups in HBC and SBC, respectively. The effects of initial solution pH, initial Zn²⁺ concentration, solution temperature and equilibrium contact time were investigated. The removal efficiency of Zn²⁺ increased with increase in both solution temperature and initial Zn²⁺ concentration. Adsorption of Zn²⁺ was greatest at pH 3. HBC and SBC removed 38–99% and 68–90% of Zn²⁺ from solution, respectively. Zn²⁺ adsorption on SBC followed both Langmuir (R ² = 0.994) and Freundlich isotherm models (R ² = 0.999), while adsorption on HBC followed the Freundlich model (R ² = 0.989). Zn²⁺ adsorption on both biosorbents followed pseudo-second-order kinetics (R ² = 0.994–0.999). The increase in enthalpy of adsorption indicated the adsorption process was endothermic and a decrease in Gibbs free energy signified the spontaneity of adsorption. Positive entropy change values imply that the adsorbed Zn²⁺ ions are randomly distributed over the adsorbent surface. The research demonstrated that although their adsorption mechanisms had salient differences, HBC and SBC can effectively remove Zn²⁺ from wastewater. Development of HBC and SBC from PPS provides potential low-cost biosorbents for water and wastewater, while simultaneously minimising the environmental and public health risks associated with current disposal practices of PPS.

An aerobic denitrification system, initially bioaugmented with Pseudomonas strain T13, was established to treat coal-based ethylene glycol industry wastewater, which contained 3219 ± 86 mg/L total nitrogen (TN) and 1978 ± 14 mg/L NO₃ ⁻-N. In the current study, a stable denitrification efficiency of 53.7 ± 4.7% and nitrite removal efficiency of 40.1 ± 2.7% were achieved at different diluted influent concentrations. Toxicity evaluation showed that a lower toxicity of effluent was achieved when industry wastewater was treated by stuffing biofilm communities compared to suspended communities. Relatively high TN removal (~50%) and chemical oxygen demand removal percentages (>65%) were obtained when the influent concentration was controlled at below 50% of the raw industry wastewater. However, a further increased concentration led to a 20–30% decrease in nitrate and nitrite removal. Microbial network evaluation showed that a reduction in Pseudomonas abundance was induced during the succession of the microbial community. The napA gene analysis indicated that the decrease in nitrate and nitrite removal happened when abundance of Pseudomonas was reduced to less than 10% of the overall stuffing biofilm communities. Meanwhile, other denitrifying bacteria, such as Paracoccus, Brevundimonas, and Brucella, were subsequently enriched through symbiosis in the whole microbial network.

Increased Cd concentrations in the environment impair plant growth, but plants properly supplied with S may develop greater tolerance to the damage caused by Cd and be used in the remediation of contaminated environments. The aim of this study was to evaluate the Cd-phytoextraction potential of Panicum maximum cv. Tanzania grown with S rates and to identify alterations in the concentrations of nutrients and amino acids and in the activity of some antioxidant enzymes under Cd stress conditions. Combinations of five S rates (0.1, 1.0, 1.9, 2.8, and 3.7 mmol L⁻¹) and five Cd rates (0.0, 0.5, 1.0, 1.5, and 2.0 mmol L⁻¹) in a nutrient solution were provided in two plant growth periods. Concentrations of N, P, and Zn increased, while K, Fe, and Mn decreased with exposure to Cd. The concentration of Ca decreased as the S supply was increased. Isoleucine, leucine, proline, and valine concentrations increased with exposure to Cd and with higher levels of S. The APX activity was higher at the highest Cd exposure level. Activity and number of SOD and GR isoforms in the roots and of CAT in the shoots of the regrown plant decreased at the highest level of contamination by Cd, which was lessened by the supply of greater S rates. Tanzania guinea grass grown with an adequate supply of S has the potential for phytoextraction of Cd-contaminated environments.

This study evaluated the effect of crude oil on the intraradical structures and morphospecies of arbuscular mycorrhizal fungi (AMF) and on the aerial and root dry matter of the grass Leersia hexandra Swartz in order to propose indicators of toxicity. An experiment was conducted in a microtunnel for 180 days. The concentrations (g kg⁻¹) of crude oil in the Gleysol were 0.693 (control), 3, 10, 30, 60, 90, 120, 150, and 180. The growth of intraradical hyphae, arbuscules, vesicles, and spores in soil was stimulated by crude oil concentrations of 3, 10, 30 and 60 g, but concentrations of 90, 120, 150, and 180 g kg⁻¹ inhibited it. Eight morphospecies of AMF were identified. The number of spores of Rhizophagus fasciculatus, Rhizophagus intraradices, Funneliformis geosporum, Diversispora eburnea, and Ambispora gerdemannii showed sensitivity to the concentration of crude oil (index values were lower than one). The number of spores of Diversispora sp. was stimulated by exposure to crude oil, with non-toxic values for the eight concentrations. The index based on the aerial dry matter of L. hexandra showed toxicity values lower than one with crude oil concentrations of 60, 90, 120, 150, and 180 g kg⁻¹, but the root dry matter showed non-toxic values with the eight concentrations. We suggest using the number of spores and morphospecies as an index of toxicity of crude oil and recommend using Diversispora sp. and L. hexandra for the phytoremediation of Gleysol contaminated with crude oil in the Mexican humid tropics.

The objective of this study was to examine the degradation of pharmaceutical compounds diclofenac, ketoprofen, and carbamazepine in a bench-scale batch type advanced oxidation treatment system combining non-thermal plasma and UV photocatalysis. The key factors affecting pollutant decomposition were studied in a dielectric barrier discharge (DBD) plasma reactor. This was followed by the comparative assessment of various advanced oxidation processes (O₃; UV+O₃; TiO₂+O₃; TiO₂+UV+O₃) in a UV-photocatalysis reactor. The overall effectiveness of the treatment process was established according to the decomposition efficiency of the individual compound determined by high-performance liquid chromatography with ultraviolet detection (HPLC/UV), removal of total organic carbon (TOC), energy consumption, and acute toxicity test with Chironomus sp. larvae. Depending on the pharmaceutical compound and oxidation system, complete decomposition of the target compound was reached within 3–6 min. The TOC removal ranged between 25 and 100% with energy consumption varying 3.1–10.6 MJ/g. TiO₂+UV+O₃ revealed slightly higher toxicity of treated water as compared to TiO₂+O₃ (22–50% vs 17–33% mortality rate of Chironomus sp. larvae). TiO₂+O₃ and TiO₂+UV+O₃ systems proved as an efficient combination of AO processes for the decomposition of pharmaceuticals in water, as long as the treatment duration is sufficient to fully mineralize organic substances.

The aim of this study was to evaluate the genotoxic and mutagenic potential of contaminated soil diluted in acidic solutions and not acidic, in the offspring of rats exposed during pregnancy and neonatal periods. To this end, a comet assay and micronucleus test were performed. Soil samples were solubilized in the following three solvents: distilled water (control group), acid solvent at pH 5.2, and acid solvent at pH 3.6. Soil and solvent were mixed in a rate of 1:2 in g/mL, and hydrofluoric acid was used in the acid solvents. In the comet assay, the tail length, percentage of DNA within the tail and tail moment was analyzed in the whole blood of the pups that were studied. The number of micronuclei found in the bone marrow cells was counted in the micronucleus test. In all parameters evaluated in the comet assay, the group exposed to the lowest pH value when associated with contaminated soil (p < 0.05) had the most damage. However, the micronucleus test showed differences between all exposed groups and the control group (p < 0.05). These results reaffirm the health risks related to the exposure to soil contaminants.