Metal contamination of freshwater bodies resulting from mining activities or deactivated mines is a common problem worldwide such as in Portugal. Braçal (galena ore) and Palhal (pyrrhotite, chalcopyrite, galena, sphalerite, and pyrite ore), located in a riverside position, are both examples of deactivated mining areas lacking implemented recovery plans since their shutdown in the early mid-1900s. In both mining areas, effluents still flow into two rivers. The purpose of this work was to evaluate the potential hazard posed by the mining effluents to freshwater communities. Therefore, short- and long-term ecotoxicological tests were performed on elutriates from river sediments collected at each site using standard test organisms that cover different functional levels (Vibrio fischeri, Pseudokirchneriella subcapitata, Lemna minor, and Daphnia sp.). The results show that elutriates from the sediments of Palhal were very toxic to all tested species, while in contrast, elutriates from Braçal showed generally no toxicity for the tested species. Our study highlights the usefulness of using an ecotoxicological approach to help in the prioritization/scoring of the most critical areas impacted by deactivated mines. This ecotoxicological test battery can provide important information about the ecological status of each concerning site before investing in the application of time-consuming and costly methods defined by the Water Framework Directive or can stand as a meaningful complementary analysis.

Spherical particles have been sampled from soils and silica-rich rock coatings close to major smelter centers at Coppercliff, Coniston, and Falconbridge in the Sudbury area, Canada. Detailed analyses employing optical microscopy, scanning electron microscopy, transmission electron microscopy, micro-Raman spectroscopy, and Mössbauer spectroscopy have been conducted to elucidate their nature, origin and potential alteration. The spherical particles are on the nano- to millimeter-size range and are composed principally of magnetite, hematite, Fe-silicates (olivine, pyroxenes), heazlewoodite, bornite, pyrrhotite, spinels (including trevorite and cuprospinel), delafossite, and cuprite or tenorite. The spinels present have variable Cu and Ni contents, whereas delafossite and cuprite are Ni free. Texturally, the spherical particles are composed of a Fe-oxide–Fe-silicate matrix with sulfide inclusions. The matrix displays growth features of a Fe-rich phase that commonly form during rapid cooling and transformation processes within smelter and converter facilities. Examination of weathered spherical particles indicates that some sulfide inclusions have dissolved prior to the alteration of the Fe-silicates and oxides and that the weathering of Fe-silicates occurs simultaneously with the transformation of magnetite into hematite. A higher proportion of Cu vs. Ni in the clay and organic fraction noted in the Sudbury soils is explained by (1) the formation of stronger adsorption complexes between Cu and the corresponding surface species and (2) the preferential release of Cu vs. Ni by smelter-derived particles. The latter mechanism is based on the observations that (a) cuprospinels have higher dissolution rates than Ni spinels, (b) a larger proportion of Cu occurs in the nanometer-size (and thus more soluble) fraction of the emitted particles, and (c) Ni spinels of relatively low solubility form in the alteration zone of heazlewoodite inclusions.

A simple spectrophotometric method was developed to quantify chlorophenol (CP) concentrations after reaction with potassium permanganate and quenching with sodium sulfite. Other quenching agents (peroxide, sodium thiosulfate and hydroxylamine hydrochloride) were found to create absorbance in the spectral range required for CP quantification. Analysis at pH 12 gave greater absorption and sensitivity for the method compared with pH 5.6. The calibration curves of the proposed methods were linear in the concentration ranges 0.0061–0.61 and 0.0078–0.78 mM with detection limit of 0.0006 and 0.0008 mM for dichlorophenols and monochlorophenols, respectively. The oxidation kinetics of five chlorophenols in aqueous solution with excess potassium permanganate were evaluated using the analytical method. The pseudo-first-order reaction rates were found to be relatively rapid 1.42 × 10−3 to 0.024 s−1 and followed the sequence 2-chlorophenol (2-CP) > 2,6-dichlorophenol (2,6-DCP) > 4-chlorophenol (4-CP) > 2,4-dichlorophenol (2, 4-DCP) > 3-chlorophenol (3-CP). The apparent second-order rate constant was calculated from the measured pseudo-first-order rate constant with respect to CP with initial KMnO4 concentration (1.5 mM) and follows the same sequence of pseudo-first-order rate constant. This shows that chlorine atoms in the structure of chlorophenol had a significant influence on the oxidation of chlorophenols by potassium permanganate. Permanganate can be used for the treatment of chlorophenol-contaminated soil and groundwater.

Arthrobacter sp. Sphe3 and Bacillus sphaericus cells were used for Cu(II) biosorption. The effect of contact time, biosorbent dose, equilibrium pH, temperature and the presence of other ions on the efficiency of the process were extensively studied. Optimum pH value and biomass concentration were determined at 5.0 and 1.0 g/l, whereas contact time was found to be 5 and 10 min for Arthrobacter sp. Sphe3 and Bacillus sphaericus biomass, respectively. Equilibrium data fitted very well to Freundlich model (R ²â€‰= 0.996, n = 2.325, K f = 8.141) using Arthrobacter sp. Sphe3. In the case of B. sphaericus, a Langmuir adsorption model [R ²â€‰= 0.996, Q ₘₐₓ = 51.54 mg-Cu(II)/g] showed to better describe the results. Potentiometric titration and Fourier transform infrared (FTIR) spectroscopy showed that amine, carboxyl and phosphate groups participate in Cu(II)-binding. The calculated thermodynamic parameters indicated the spontaneous and feasible nature of Cu(II) biosorption on both biosorbents. Selectivity of Cu(II) biosorption was examined in binary and multi-ions systems with various anions and cations which are commonly found in municipal and industrial wastewater. A specificity towards Cu(II) was observed in binary mixtures with Cl⁻, CO ₃ ⁻² , NO ₃ ⁻ , SO ₄ ⁻² , PO ₄ ⁻³ , Mg+² and Ca+², and As(V) with the maximum uptake capacity remaining constant even at high competitive ion’s concentrations of 200 mg/l. Desorption studies showed that Cu(II) could be completely desorbed from Cu(II)-loaded Arthrobacter strain Sphe3 and B. sphaericus biomass using 1.0 and 0.8 M HCl, respectively, and both bacterial species could be effectively reused up to five cycles, making their application in wastewater detoxification more attractive.

Soil pollution with heavy metals is a worldwide environmental problem. Phytoremediation through phytoextraction and phytostabilization appears to be a promising technology for the remediation of polluted soils. It is important to strongly emphasize that the ultimate goal of a heavy metal remediation process must be not only to remove the heavy metals from the soil (or instead to reduce their bioavailability and mobility) but also to restore soil quality. Soil quality is defined as the capacity of a given soil to perform its functions. Soil microbial properties are increasingly being used as biological indicators of soil quality due to their quick response, high sensitivity, and, above all, capacity to provide information that integrates many environmental factors. Indeed, microbial properties are among the most ecologically relevant indicators of soil quality. Consequently, microbial monitoring of the recovery of soil quality is often carried out during heavy metal phytoremediation processes. However, soil microbial properties are highly context dependent and difficult to interpret. For a better interpretation of microbial properties as indicators of soil quality, they may be grouped within categories of higher ecological relevance, such as soil functions, ecosystem health attributes, and ecosystem services.

Frequently, sulfonamide antibiotic agents reach arable soils via excreta of medicated livestock. In this study, accumulation and phytotoxicity indicators were analyzed to evaluate the effects of sulfonamides on plants. In a greenhouse experiment, willow (Salix fragilis L.) and maize (Zea mays L.) plants were grown for 40 days in soil spiked with 10 and 200 mg kg⁻¹ sulfadiazine (SDZ). Distribution of SDZ and major metabolites among bulk and rhizosphere soil, roots, leaves, and stems was determined using accelerated solvent extraction and LC − MS/MS analysis. Accumulation of SDZ was stronger in willow. The antibiotic was mainly stored inside roots and 4-hydroxy-sulfadiazine presence increased with the administered SDZ concentration. SDZ altered root geotropism, increased the lateral root number, and affected plant water uptake. The high concentration caused serious stress in willow (e.g., reduced C/N ratio and total chlorophyll content) and the death of maize plants. Even at environmentally relevant soil concentrations (10 mg kg⁻¹), SDZ exhibited adverse effects on root growth, while at artificially high concentrations (200 mg kg⁻¹), it showed a strong potential to impair plant performance and biomass. Willow, a fast growing tree species, showed potential for possible phytoremediation purposes.

Polybrominated diphenyl ethers (PBDEs) have been found at high levels, up to 7.6 × 106 pg/g, in biosolids commonly applied to agricultural soils. A field investigation was carried out in this study to measure concentrations of PBDEs in biosolid-amended agricultural soils in which various amounts of biosolids (20 and 80 t/ha) had been applied. Concentrations of PBDEs in surface soils that had received a single application of 80 t/ha biosolids were one to two orders of magnitude greater than that in soil, which had received a single application of 20 t/ha of biosolids. Assessment of PBDEs levels at different depths, between 0.05 and 1.05 m, in soils that received 80 t/ha biosolids, showed that PBDEs were mobilized from the surface soil to lower depths. Total PBDEs concentrations decreased from 10,250 pg/g dry weight basis (dw) in the 0.05 m soil layer to 220 pg/g dw at a depth of 1 m. The distribution of PBDEs with depth and cation exchange capacity of the soil could be described as exponential functions. The coefficients of correlation ranged from 0.47 to 0.57 and 0.47 to 0.67, respectively. Despite the deviation in the experimental measurements induced by variables, such as non-uniform biosolid application, heterogeneity of the soil, and the uneven surface of the field, variations of PBDEs along the soil profile in the biosolid-amended soil were clearly demonstrated.

The performance of the magnetic anion exchange resin, MIEX®, in the pretreatment of reclaimed water for managed aquifer recharge (MAR) was investigated. MIEX® can effectively remove aromatic organic substances with molecular weights above 10 kDa and between 1 and 5 kDa, which are always present recalcitrant during soil infiltration. The removal of organic substances is accompanied by the elimination of other undesirable components in MAR, such as nitrogen and phosphorus. The optimal process parameters are at resin doses of 5–10 mL L⁻¹ and contact time of 10–15 min, as determined via jar tests. The efficiency of the MAR pilot system was consistent throughout the long running time, during which the MIEX® treatment significantly contributed (30 to 60 %) to the removal of both organic and inorganic materials (i.e., dissolved organic carbon, ultraviolet absorbance at 254 nm, color, nitrate, ammonia, phosphorus, and sulfate). The quality of the MAR final effluent is lower than the groundwater standard for drinking sources (type III in GB/T 14848-93). Based on this study, MIEX® treatment is a suitable and efficient pretreatment method for the removal of extra dissolved organic matters and nitrates in reclaimed water for MAR.

Synthetic and persistent endocrine disrupting chemicals (EDCs) such as 17α-ethinylestradiol (EE2) have been frequently detected in the effluent of wastewater treatment plants and induce hazards to humans and wildlife. In this study, biogenic Mn oxides were tested for the removal of EE2, and factors affecting the reaction were also investigated. The biogenic Mn oxides produced by Pseudomonas putida strain MnB1 were nano-sized and poorly crystallized particles. A concentration of 7.9 mg l−1 biogenic Mn oxides showed 87% EE2 (1 mg l−1) removal efficiency in 2 h, which confirms the excellent potential of biogenic Mn oxides for removal of estrogens. EE2 removal was enhanced at high Mn oxide doses and at low pH. Co-existing heavy metals significantly inhibit EE2 removal, due to their competition for the reactive sites of biogenic Mn oxides. Humic acid (HA) also obstructed EE2 removal, but the adverse effect was alleviated as HA concentration increased, possibly due to the formation of soluble complexes with the released Mn2+, of which adsorption onto Mn oxides reduces surface reactive sites.

Two types of hydrogels with different functional groups, trimethylamine on quaternary ammonium and dimethylethoxyamine on quaternary ammonium, were synthesized. Type 1 and type 2 hydrogels were characterized with Fourier transform infrared, X-ray photoelectron spectroscopy and zeta potential analysis. The anion selectivity of these two hydrogels was investigated. The surface charges of the type 2 hydrogel were lower than those of type 1, probably because of the presence of the hydroxyl group in the ethoxy group. The Cr(VI) removal capacity of type 2 hydrogel was, therefore, less than that of type 1 hydrogel, although their adsorption rates were similar. The anion selectivity of the hydrogels was found to have a similar order: Cr(VI) > sulphate > bromide > As(V). Under the co-presence of Cr(VI) and sulphate conditions, type 2 hydrogel shows a higher selectivity towards Cr(VI). The higher hydrophobicity was caused by the presence of the ethoxy group on the quaternary ammonium in type 2 hydrogel and thus increased in selectivity towards monovalent ions (i.e. HCrO 4 − ). In addition, the hydrogels have a high reusability. Compared with type 1 hydrogel, type 2 hydrogel has an advantage for applications in Cr(VI) removal and recovery processes.