Cemented paste backfill has been proposed in the mining industry for managing metal mill tailings. Low sulfide tailing (0.49 wt%) samples were prepared into different cemented pastes that were mixed with flocculants (polymerized aluminum chloride). The best mixing proportions of tailings, binder, flocculant, and filling structure (containing 0.5 wt% of ordinary Portland cement in one paste layer, 100 g/L polymerization aluminum chloride) were determined through leaching experiment. The addition of polymerization aluminum chloride improved the mechanical property of the paste. The strength of the cemented pastes by adding 100 g/L flocculant met the requirement of mine backfill. The cemented paste could also fix heavy metals, as shown in the paste leachate analysis of copper (Cu, about 0.01–0.08 mg/L of concentration) and chromium (Cr, about 0.03 mg/L of concentration). In summary, results from this study demonstrate that tailings can be managed by cemented paste backfill technique, preventing its contamination of the environment.

Phosphorus (P) release and flux at sediment-water interface was hypothesized to vary with studied catchment branches due to differences in water chemistry of recharging groundwater. Stream water, seepage water, groundwater, and resurgence groundwater were collected, and their dissolved reactive P (DRP) concentrations and related water chemistry variables (pH, dissolved oxygen, cations, and anions) were measured to identify P sources in seepage water and resurgence groundwater and to look into their impacts on stream water DRP. Results showed that the groundwater-carried P concentrations were negligible, and, thus, not a direct source of DRP to stream water. However, the upwelling groundwater could contribute to stream water DRP by dissolving calcite-bound P in top sediments of branch 15. The seepage experiment indicated that in branch14, sediment release of reducible P was minimal. Furthermore, the presence of impermeable clay layer over the streambed of branch 14 prevented the transport of water and nutrients from beneath sediments to stream water, further reducing the P flux across the sediment-water interface. This study revealed that in branch 14, the recharge of anoxic groundwater did not significantly influence stream water P, due directly to its low P concentration, or indirectly to the lack of reducible P and the poor hydrological connectivity in bottom sediments. These results showed that differences between P soluble concentrations in small catchment streams can be explained by physicochemical processes at the sediment-water interface. More investigation is needed to assess whole catchment P dynamics.

A common weed, Imperata cylindrica (cogongrass), was used as a low-cost adsorbent for the adsorption of methylene blue (MB) and the process optimized. The effects of four factors, namely, shaking speed (100–300 rpm), pH (3–9), contact time (10–40 min) and adsorbent dosage (0.4–1.0 g), on colour removal and chemical oxygen demand (COD) reduction of MB were studied and optimized using fractional factorial design and response surface methodology. The two factors that play a vital role in the adsorption process are pH and adsorbent dosage. From the results, colour removal and COD reduction recorded coefficient of determination (r ²) values of 0.9600 and 0.9594, respectively. Optimum adsorption conditions, resulting in 99.09 % colour removal and 97.87 % COD reduction, were achieved at shaking speed of 100 rpm, pH 9, 40 min contact time and adsorbent dosage of 1.0 g. The adsorption systems for MB dye were found to fit the pseudo-second order model instead of the pseudo-first order model, while equilibrium studies showed that the adsorption process followed the Langmuir isotherm.

Larval black flies (Diptera: Simuliidae), which inhabit streams and rivers, are both filter-feeders and a dominant part of the macroinvertebrate community. As filter-feeders, these insects are potentially an important entrance point for mercury into lotic food webs. The objectives of our study were to (1) document mercury concentrations in the water column, streambed sediments, and larval black fly tissue in select streams in coastal Alabama, USA, over both spatial (among streams) and temporal (across and within season) gradients and (2) determine if levels of mercury in stream ecosystems can be predicted based on stream predictors. Mercury was found consistently in both the black fly larval tissues and streambed sediments but was not detected in the water column. The range of total mercury found in larval tissue and stream sediments varied between 23.73–142.05 and 0.60–56.98 ppb, respectively. Mean mercury levels in both tissue and sediments show significant variation among summer, fall, and spring collections. In addition, mercury levels in tissue and sediments were significantly associated with dissolved oxygen, conductivity, or temperature within a season.

Air pollution contributes substantially to global health burdens; however, less is known about pollution patterns in China and whether they differ from those elsewhere. We evaluated temporal and spatial heterogeneity of air pollution in Lanzhou, an urban Chinese city (April 2009–December 2012), and conducted a systematic review of literature on air pollution and health in Lanzhou. Average levels were 141.5, 42.3, and 47.2 μg/m³for particulate matter with an aerodynamic diameter ≤10 μm (PM₁₀), NO₂, and SO₂, respectively. Findings suggest some seasonality, particularly for SO₂, with higher concentrations during colder months relative to warmer months, although a longer time frame of data is needed to evaluate seasonality fully. Correlation coefficients generally declined with distance between monitors, while coefficients of divergence increased with distance. However, these trends were not statistically significant. PM₁₀levels exceeded Chinese and other health-based standards and guidelines. The review identified 13 studies on outdoor air pollution and health. Although limited, the studies indicate that air pollution is associated with increased risk of health outcomes in Lanzhou. These studies and the high air pollution levels suggest potentially serious health consequences. Findings can provide guidance to future epidemiological studies, monitor placement programs, and air quality policies.

Pirina, a waste of olive oil factory, was used as an adsorbent for the removal of remazol brilliant blue R (RBBR) from aqueous solution by adsorption process. The pirina was pretreated with HNO₃before batch adsorption experiments. The effects of contact time, initial concentration, pH, temperature, and ionic strength on dye removal were investigated. While the amount of the dye removed by the pirina was increasing with increasing initial concentration and temperature, it decreased with an increase in pH. Moreover, commercial activated carbon (CAC) was also used to compare with the pirina in removing the RBBR. The maximum amounts of the RBBR removed by the pirina and the CAC were 23.63 and 199.45 mg g⁻¹per unit mass of the adsorbents, and the removal efficiencies of them were found as 94.52 and 99.72 %, respectively. Ionic strength in the presence of NaCl and KCl had also a reducing effect on the removal efficiency. The adsorption isotherm was in the best harmony with Langmuir, Freundlich, and Temkin models. The adsorption kinetic obeyed the pseudo-second-order and the intra-particle diffusion models. The values of the r²from the pseudo-second-order kinetic and intra-particle diffusion were between 0.984–0.999 and 0.85–0.996, respectively. From thermodynamic studies, it was seen that the adsorption was of spontaneous and endothermic nature. The values of ΔG° of the adsorption were between −3,218 and −8,867 J mol⁻¹. The values of ΔH° and ΔS° were 50,134 J mol⁻¹and 179 J mol⁻¹ K⁻¹, respectively. Moreover, SEM and FT-IR studies were also performed.

The transformation of less toxic Cr(III) species to harmful Cr(VI) is worth concerning. Compared with free Cr(III), however, the photo-oxidation of Cr(III)–organic acid complexes is seldom reported. In this study, Cr(III)–malate complex was synthesized and purified, and its photo-oxidation was investigated to reveal the potential conversion pathway of Cr(III) to Cr(VI). The results indicated that Cr(III)–malate complex could be gradually photo-oxidized to Cr(VI) through a ligand–metal charge transfer path. Higher pH and stronger light intensity promoted the conversion process. A 50-μM Cr(III)–malate complex was almost completely oxidized to Cr(VI) within 420-min irradiation of 500 W medium-pressure mercury lamp at pH 12. The introduction of H₂O₂, considered as a direct source of hydroxyl radicals (·OH) in the presence of Cr(II), markedly enhanced the yield of Cr(VI), and a complete oxidation of Cr(III)–malate complex (50 μM ) was realized within 20 min. Under a weak acidic condition, the production of Cr(VI) was coupled with the reduction of Cr(VI) by malic acid and its free radical generated from Cr(III)–malate complex, leading a gradual decrease in Cr(VI) concentration with the reaction.

Urban market gardening in Africa is suffering from increasing environmental contamination due to sources of contamination as varied as traffic, industry, and agriculture practices. A field study was therefore conducted to determine the global influence of the polluted environment (atmosphere, soil, and irrigation waters) on vegetable quality in a large urban-farming area. For leafy vegetables collected in 15 ha of squatted land belonging to the international airport of Cotonou, total concentrations of metal(loid)s measured in consumed parts of Lactuca sativa L. and Brassica oleracea were 52.6–78.9, 0.02–0.3, 0.08–0.22, 12.7–20.3, 1.8–7.9, and 44.1–107.8 mg kg⁻¹for Pb, Cd, As, Sb, Cu, and Zn, respectively. Human gastric bioaccessibility of the metal(loid)s was measured, and the obtained values varied according to the considered metal(loid) and the plant species. The results identified values that are commonly found in non-polluted soils and roots associated with contaminated edible parts, raising the possibility of atmospheric contamination. Such a hypothesis is in agreement with values of magnetic susceptibility, since iron oxides and probably their associated metal(loid)s do not translocate from the roots toward the upper parts of the plants. (Bioaccessible) estimated dose intake ((B)EDI) and total (bioaccessible) target hazard quotient (Σ(B)THQ) were calculated to assess the health risk of consuming vegetables from this area. Pb and Sb were the major risk contributors. Taking the bioaccessible fractions into account, ΣBTHQ values were lower than ΣTHQ but were all still >1 for both males and females, leading to the conclusion that consuming these vegetables from this area is not risk-free.

Microcystis aeruginosa, the most common toxic cyanobacterial bloom, could cause severe environmental problem by producing and releasing lethal cyanobacterial toxins to water body. This study investigated the electron beam irradiation for the inactivation of M. aeruginosa. The treatment process was monitored via the measurement of chlorophyll a concentration, optical density, photosynthesis, and antioxidant enzymes. At low electron beam irradiation dose (1.0 kGy), its performance is not desirable. High dosage of electron beam irradiation (2.0–5.0 kGy) can dramatically decrease chlorophyll a concentration, optical density, and photosynthesis rate and affect activities of antioxidant enzymes. The transmission electron microscopy measurement indicates that electron beam irradiation treatment cause significant damages on integrity and morphology. Our results demonstrate that electron beam irradiation is a promising technique for quick and efficient inactivation of M. aeruginosa in aqueous solution.

Environmental pollution is one of the most serious causes of degradation of Mediterranean wetlands. Mercury (Hg) and cadmium (Cd) are of particular concern due to biomagnification. Here, we used red swamp crayfish (Procambarus clarkii) to monitor the spatial and temporal patterns of these two metals in a Portuguese rice field system. We sampled the crayfish in three different sites and three different time periods in the Sado River Basin (Portugal). We measured temperature, pH, total dissolved solids and conductivity in the water. Hg and Cd were measured in the crayfish abdominal muscle tissue and exoskeleton. In muscle, a spatial pattern was found for the accumulation of Cd while for Hg, only a temporal pattern emerged. The spatial pattern for Cd seemed to reflect the mining history of the sites, whereas the temporal pattern for Hg seemed related to the flooding of rice fields. We suggest that this flooding process increases Hg bioavailability.