SrCO₃ was formed and added as a carrier into copper-based catalyst (CuZnAl catalyst) prepared by hydrothermal method before the catalyst incorporates with HZSM-5. The CuZnAlSr catalyst was characterized by SEM, BET, XRD, IR, and activity-evaluation system in a fixed-bed tubular reactor equipped with chromatograph (GC). The conversion of CO₂ reaches 30.30 %, and the overall yield of methanol and dimethyl ether is 27.80 %. Catalytic property as to CO₂ conversion has only slight decrease even up to 150 h of reaction time. The addition of SrCO₃ enhanced the activity of the catalyst through providing a tridimensional frame and electron transfer bridge.

The present work studies the remediation of a B20 (20 % biodiesel, 80 % diesel) biodiesel blend-contaminated soil (1,000 mg kg⁻¹) with persulfate activated by iron. Three different sources of iron (Fe(II)), granular zerovalent iron (gZVI), and a slurry of nanoparticles of zerovalent iron (nZVI), without pH adjustment were tested. Besides, the effect of the addition of chelating agents, such as trisodium citrate (SC), or citric acid (CiA), has been also studied. SC promotes pH under near-neutral conditions and reaction takes place at low rate at these experimental conditions. On the other hand, the use of CiA leads to an acidic pH and chelating agent is oxidized at higher rate than total petroleum hydrocarbons (TPH). Therefore, CiA addition does not seem to produce any improvement on the removal efficiency of TPH. Regarding the three different sources of iron used as activators, Fe(II), gZVI and nZVI, in absence of chelating agent, under acidic pH and by adding the same amount of iron, the highest TPH conversion was obtained with ZVI (about 60 %), while a conversion of about 40 % was obtained with the addition of Fe(II). The maximum TPH conversion value was achieved in shorter time using nZVI. Concerning the removal efficiency of each fraction of biodiesel abated, fatty acid methyl esters (FAME) were by far the easiest to oxidize, achieving 100 % of conversion, either by using Fe(II) or nZVI activated persulfate.

Biochar has great advantages and potentials on soil amendment and polluted soil remediation. In order to explore these applications, a pot experiment was carried out to research the effect of biochar on the heavy metal speciation in paddy soil and the heavy metal accumulation of paddy rice from Chengdu plain, Sichuan Province. The experimental results show that wine lees-derived biochar can efficiently increase soil pH, decrease the contents of soil exchangeable heavy metals, and promote heavy metal transformation to residual fraction. Moreover, application of biochar can reduce the accumulation of heavy metals in paddy plant, decrease the migration ability of heavy metals to the aboveground part of the plant, and consequently cut down contents of heavy metals in rice. When biochar dosage was 0.5 % in weight, the contents of soil exchangeable Cr, Ni, Cu, Pb, Zn, and Cd decreased 18.8, 29.6, 26.3, 23.0, 23.01, and 48.14 %, respectively, which all significantly differed from CK (P < 0.05), and the contents of heavy metals in plant roots, stems, leaves, rice husk, and rice all decreased accordingly, among which Zn, Cd, and Pb decreased 10.96, 8.89, and 8.33 % respectively. When biochar dosage increased to 1 %, heavy metal contents in roots, stems, leaves, rice husk, and rice decreased further. Therefore, wine lees-derived biochar shows a great potential in remediation of heavy-metal-polluted soil, and this work provides theoretical basis for restoring heavy-metal-polluted soil using biochar.

Chemical methods have been used for the remediation of arsenic (As)-contaminated water; however, ecological consequences of these methods have not been properly addressed. The present study evaluated the effects of the Fe-oxide-coated sand (IOCS) remediation method on As toxicity to freshwater organisms (Lemna disperma, Chlorella sp. CE-35, and Ceriodaphnia cf. dubia). The As removal efficiency by IOCS decreased substantially with time. The IOCS remediation method was less effective at suppressing the toxicity of Asⱽ than Asᴵᴵᴵ to L. disperma but was highly effective in reducing both the Asᴵᴵᴵ and Asⱽ toxicity to C. cf. dubia. The growth of Chlorella sp. was significantly higher (p < 0.05) in remediated and pre-remediated water than in controls (non-As-contaminated filtered Colo River water) for Asᴵᴵᴵ, while the opposite was observed for Asⱽ, indicating that Asⱽ is more toxic than Asᴵᴵᴵ to this microalga. Although the IOCS can efficiently remove As from contaminated water, residual As and other constituents (e.g. Fe, nitrate) in the remediated water had a significant effect on freshwater organisms.

Peatlands serve as important stores of organic matter and regulators of nutrient and metal export to surface waters, yet relatively little is known regarding the impact of more than a century of metal, sulfur, and acid deposition on microbial activity in acidic, nutrient-poor peatlands that are common features around Sudbury, Ontario. In this study, eight peatlands were selected at varying distances from the Copper Cliff Smelter that was once the largest point source of sulfur dioxide and sampled for analysis of nutrient and metal content. Basal microbial respiration, relative response to substrate addition (four synthetic and four natural substrates) assessed as CO₂production rates and microbial biomass were assessed in surface (0–10 cm) peat samples. Bacterial and fungal communities within the peat samples were profiled using terminal restriction fragment length polymorphism analysis. Basal respiration (i.e., carbon mineralization in absence of substrate addition) was lowest and Cu and Ni concentrations and the degree of humification (assessed by the von Post scale) in surface peat samples were highest close to the smelter. Each peatland had a unique bacterial community when assessed using non-metric multidimensional scaling, whereas the fungal community was variable with no consistent patterns across the sites. Despite differences in microbial communities, substrate-induced respiration rates did not differ among peatlands as sites generally responded similarly to carbon substrate additions. Basal respiration rates were related to the humification status of the peat, which was potentially related to environmental degradation in the peatlands or surrounding terrestrial systems closer to the Sudbury smelters.

A multivariate analysis was performed in the city of Florence (Italy) to investigate the influence of road traffic and meteorology on air pollution levels at urban traffic stations. Focussing on main traffic-related pollutants (CO, NO, NO₂, NO ₓ and PM₁₀), two typical urban road configurations were analysed: a street canyon and an open road. In addition to traffic flows, basic meteorological parameters were considered: wind speed, air temperature and relative humidity. The influence of all drivers by period of the year and day of the week was analysed with correlation analysis, while a statistical model was developed to predict concentrations at traffic stations by using predictors as urban background concentrations, traffic flows and a site-specific constant. Trained on a 1-year period (2008), the model was validated over an independent 1-year period (2007). The highest correlation of urban traffic concentrations was found vs. background concentrations, markedly for PM₁₀ (r = 0.85–0.87). The influence of road traffic was the highest for NO₂ (r = 0.51–0.58) and the lowest for PM₁₀ (r = 0.36–0.40). Urban-scale poor advection conditions proved to affect PM₁₀ peak levels more significantly than local traffic increase. For all pollutants, good forecasting capability was achieved by the developed statistical model, generally performing better at the street canyon (r = 0.79–0.86) than at the open road (r = 0.72–0.82).

A pure clay ball and surface-modified clay ball were investigated to remove phosphate from synthetic wastewater; phosphate causes eutrophication in hydro-ecological systems. Adsorption tests of phosphate from aqueous solutions onto two types of adsorbents were conducted. The maximum phosphate adsorption capacities of the pure and surface-modified clay ball were found to be 0.084 and 8.869 mg/g, respectively. In a fixed-bed column packed with surface-modified clay balls, the first breakthrough of phosphate appeared after approximately 4000 min. In addition, the phosphate adsorbed on the surface-modified clay ball was effectively desorbed using a 1 M zirconium sulfate solution, and the adsorbent was regenerated for four adsorption and three desorption cycles by maintaining the adsorption capacity at the value before regeneration. X-ray diffraction (XRD), scanning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy (EDX), and Brunauer-Emmett-Teller (BET) analysis method were performed to reveal the characteristics of the surface-modified clay ball. Cytotoxicity experiment was conducted on the developed adsorbents, and as a result, these showed low cytotoxic effect on the human cells. These results indicated that the surface-modified clay ball, due to the low cost, high adsorption capacity, and non-toxicity, has the potential to be utilized in the cost-effective removal of phosphate from aqueous solutions.

Hundreds of millions of people are at risk from drinking arsenic (As)-contaminated groundwater in the world, making As removal from aquatic systems of utmost importance. However, characteristics of As removal by bacteria-induced ferrihydrite and coupled with redox processes are still not clear. Two-line ferrihydrite was formed in the presence of aerobic Fe(II)-oxidizing bacterium, Pseudomonas sp. strain GE-1. Arsenic co-precipitation with and adsorption onto ferrihydrite induced by Pseudomonas sp. strain GE-1 and redox processes of As were investigated. Results demonstrated that co-precipitation performed better in As(V) removal than As(III) removal, while adsorption showed higher capacity for As(III) removal. X-ray absorption near-edge spectroscopy (XANES) indicated that As(III) oxidation occurred in solid phases during co-precipitation and adsorption. Detection of As species in solution showed that As(V) was reduced to As(III) during co-precipitation, although no As(V) reduction occurred during adsorption. Arsenic immobilization by Pseudomonas sp. strain GE-1-induced ferrihydrite in the presence of the strains may be applied as an alternative remediation strategy.

Calcium alginate beads entrapping a mixture of Fe(0) and nanosized magnetite (NMT) were prepared and evaluated for their capability to reduce nitrate in groundwater. Microscopic and spectroscopic analyses of the beads revealed that clusters of Fe(0)/NMT were entirely embedded in alginate polymer matrix containing a large number of carboxylic and hydroxyl functional groups. The extent of nitrate reduction increased with increasing content of Fe(0) and NMT in the beads, but there was a critical NMT mass limit relative to Fe(0) mass where no further increase in nitrate reduction occurred. The beads showed slower nitrate reduction kinetics than bare Fe(0)/NMT but had comparable capacity in overall nitrate removal. Nitrate reduction increased proportionally with an increase in bead dosage to give a maximum removal of 94.5 % at 37.5 g L⁻¹ in 48 h. Nitrate reduction with 50 g L⁻¹ beads achieved completion of two reduction cycles in 72 h to reduce 2.19 mM nitrate to less than 0.71 mM (10 mg-N L⁻¹) in each cycle. The overall results demonstrated that the beads developed in this study have a potential utility in remediation of nitrate in groundwater.

This work describes the experimental determination of the major degradation and sorption parameters of polycyclic aromatic hydrocarbons (PAHs) in a sensitive marine environment, the Northern Adriatic Sea (Mediterranean Sea). The persistence and sorption of complex PAH mixtures were analysed in the laboratory in conditions mimicking open-sea and coastal sediments, which differ in grain size and organic carbon content and are characterized by different oceanographic conditions including abiotic influences. The study investigated how sediment type and texture and salinity, temperature and solar irradiation conditions affect the partitioning of low molecular weight (LMW) and high molecular weight (HMW) PAHs into aqueous and solid phase, which critically influence their behaviour. With regard to the change from offshore to coastal conditions, HMW PAHs were found to be more sensitive to the increased salinity (from 21 to < 37 parts per thousand), whereas LMW PHAs were more sensitive to the temperature increase (from 11 to 22 °C). HMW PAHs were more affected by sediment type changes in terms of distribution coefficient (K d). Since the physicochemical properties of organic pollutants affect their distribution, transport, bioavailability and toxicity, analysing the accumulation and persistence of dissolved pollutants can provide useful information for environmental risk assessment and management.