Soil contamination by crude oil is a major environmental and health hazard. Extraction of the total petroleum hydrocarbons (TPH) sorbed to the clay soil (kaolin) was carried out using synthetic sorbent (Desmopan®) and 2-propanol as a mobilizing agent. The crude oil-loaded polymer beads were bioregenerated in a solid–liquid two-phase partitioning bioreactor (TPPB). A central composite design under response surface methodology was employed for the experimental design and analysis of the results. The independent variables were extraction phase to soil ratio, mobilizing agent to soil ratio, and initial concentration of crude oil in polluted soil. The influences of three independent variables on the TPH reduction efficiency were determined using a statistically significant quadratic model (R ² = 0.9673). Remediation was more efficient when the mobilizing agent to the soil ratio was equal to 3.00 ml g⁻¹, compared to the higher (4.00 ml g⁻¹) and lower (2.00 ml g⁻¹) levels. The results exhibited that the interaction between the extraction phase ratio and the initial concentration of crude oil in kaolin had significantly influenced the TPH removal. The bioregeneration studies showed a significant reduction (72.07 ± 0.63 %) of low-molecular-weight (two- to three-ring) polycyclic aromatic hydrocarbons and n-alkanes (97.75 ± 0.26 %) present in the crude oil-loaded solid polymers within a 10-day experiment. These findings show that solid polymer extraction followed by bioregeneration of sorbents in a TPPB is applicable to treat crude oil-contaminated kaolin.

Previous research demonstrated that nutrient treatment in conventionally drained bioretention cells is dependent upon temperature and varying wetting and drying regimes in the media. This study examines the influence that previous events have on outflow concentrations by analyzing flow-weighted composite samples from four to six consecutive events during three different seasons for two sets of field-monitored bioretention cells in Nashville, NC. The bioretention cells had different media depths (0.6-m versus 0.9-m). As a means to analyze performance from consecutive events, the evolution of cumulative pollutant loads was presented by plotting cumulative load versus cumulative volume. This method of presenting water quality data allows for the direct analysis of event mean concentrations, load reduction, and volume reduction with one graph, as well as describing the seasonal impacts and impacts from consecutive events. Runoff and outflow concentrations were also correlated to media temperature and rainfall characteristics. The overall results of this study showed that conventionally drained bioretention cells mainly convert organic nitrogen, the predominant source of nitrogen in runoff, into nitrate in the aerobic environment present in the media. Nitrate is then exported from the media during subsequent events. The greatest export occurred during the warmer months because higher media temperatures increased microbial activity. Pollen and leaf litter were identified as organic nitrogen and total phosphorus sources because of elevated runoff concentrations that occurred in the spring and autumn. Based on these results, future bioretention studies should strongly consider monitoring consecutive events and this method of data analysis, as they reveal internal processes and allow researchers to draw conclusions that independent event monitoring could not.

Soils polluted by metals and organic compounds are a major challenge in soil remediation and environmental recovery; however, the technology to efficiently decontaminate soils polluted by both metal and organic pollutants does not yet exist. Most of these soils are disposed of in landfills. This study first evaluates chemical reagents (hydrochloric, nitric, sulfuric and lactic acids and ethanol) for leaching metals from soil. Assays were then conducted to evaluate non-ionic, ionic and amphoteric surfactants for pentachlorophenol (PCP) removal by flotation. Finally, a laboratory-scale leaching/flotation process was applied to treat four soil samples polluted with both organic ([PCP]ᵢ = 2.5–30 mg kg⁻¹) and metals ([As]ᵢ = 50–250 mg kg⁻¹, [Cr]ᵢ = 35–220 mg kg⁻¹, [Cu]ᵢ = 80–350 mg kg⁻¹) compounds. The organic compounds and metals are concentrated in the froth and liquid fractions, respectively. Removal yields of 82–93 %, 30–80 %, 79–90 % and 36–78 % were obtained from As, Cr, Cu and PCP, respectively, under optimized process conditions (H₂SO₄ = 1 N, [cocamidopropyl betaine]ᵢ = 1 % (w w⁻¹), t = 60 min, T = 60 °C, PD = 10 % (w v⁻¹)). The treatment of the produced leachate was also tested by chemical precipitation using different reagents.

The release of heavy oil from laboratory-contaminated sediments was studied in a series of kinetic and equilibrium experiments. The kinetic curves could be interpreted by a two-compartment first-order equation including rapid and slow release steps. The slow step was dominant and the rate constant was 3 orders of magnitude smaller than for the rapid step. Equilibrium experiments for the slow step revealed that the isotherms could be described by the Freundlich equation. The release of heavy oil was found to correlate with higher contamination level, larger particle size, lower salinity, and higher temperature. The effect of coexisting surfactant on the release was also investigated and the results showed that the presence of Tween-20 promoted the process. The oil release process was endothermic and the randomness at the solid–liquid interface increased during the desorption process. The values of activation energy and standard enthalpy change indicated that this process was a physical one.

Organoclays possess unique adsorption behaviour towards hydrophobic organic contaminants. They can also remediate ionic contaminants such as heavy metals and metalloids. The objective of the present study was to prepare organoclay and organoclay mixtures efficient to adsorb both cationic and anionic contaminants. The adsorbents were characterised by X-ray diffraction and infrared spectroscopy. Trivalent (Cr3+) and hexavalent (Cr2O 7 2-) chromium were selected as the model contaminants representing cationic and anionic properties. Bentonite modified with cationic surfactant hexadecyl trimethylammonium bromide at double the cation exchange capacity of the clay remarkably improved Cr2O7 2- adsorption capacity (as high as 0.49 mmol g-1). Similarly, its modification with anionic surfactant sodium dodecyl sulphate at the same dosage improved Cr3+ adsorption (as high as 0.36 mmol g -1). When these two organoclays were physically mixed in equal proportions (1:1), the resultant organoclay mixture efficiently adsorbed both Cr3+ (as high as 0.21 mmol g-1) and Cr2O 7 2- (as high as 0.32 mmol g-1) implying that the mixture could remediate both anionic and cationic contaminants simultaneously. The adsorption of Cr3+ by the organoclay and organoclay mixture fitted well to the Langmuir isothermal model whereas the adsorption of Cr2O7 2- fitted well to the Freundlich model. © 2013 Springer Science+Business Media Dordrecht.

The occurrence, as well as the environmental fate and impact, of vegetable oil spills in freshwater wetlands have until now been unreported. Thus, the largest global vegetable oil spillage in a freshwater wetland, which occurred at the Con Joubert Bird Sanctuary wetland in 2007, presented an ideal opportunity to evaluate these impacts. Five post-spill sampling sites were selected within the wetland from which a variety of abiotic and biotic samples were collected bi-monthly over a period of 12 months. Abiotic variables included the sediment and water column oil concentrations, total nitrogen, total phosphorous, biochemical oxygen demand (BOD), silica, chlorophyll a, as well as in situ measurements of pH, electrical conductivity, and dissolved oxygen. Aquatic macroinvertebrates were chosen as biotic indicators in the study field due to their wide applicability as water quality indicators and were thus collected at each site. Spatial and temporal changes in total nitrogen, total phosphorous, and chlorophyll a concentrations as well as changes in pH were observed. The oil spillage also resulted in an increase in tolerant macroinvertebrate taxa, mainly Chironomidae and Psychodidae, at the sites closest to the source of the spillage. These two taxa, and to a lesser extent, Syrphidae, were identified as potentially useful indicators to determine the extent of vegetable oil contamination within a freshwater wetland. Furthermore, monitoring of these indicator taxa can be a useful management tool to determine the recovery of freshwater wetlands after vegetable oil spills. In the study, a static battery of bioassays of different biotic trophic levels was also employed to determine the adverse effects of the spilled vegetable oil on the biotic environment. It was evident from the result of the static battery of bioassay that adverse effects of the sunflower oil differ between trophic levels. The latter was in relationship with the data obtained from the field macroinvertebrate study, indicating that certain macroinvertebrate families were more tolerant to the adverse effects of sunflower oil than other families. © 2013 Springer Science+Business Media Dordrecht.

Rural non-point source (RNPS) water pollution control is problematic in Hubei Province, which is a typical agricultural region with abundant rainfall and a developed natural surface water network. The concept of best management practices (BMP) originating from the USA has already been introduced with the aim to reduce the application of chemical fertilizers and pesticides, and water and soil loss. However, a comprehensive evaluation of rural wastewater and nutrient reutilization to benefit the rural communities and the environment has not been attempted. To fill this gap, this review paper explores the major contributors of RNPS water pollution in Hubei Province, assesses the status of watercourses and discusses the prevalent ecological engineering techniques including vegetated filter strips (VFS), ecological ditches (ED), constructed wetlands (CW), and biogas plants (BP) with respect to aspects such as water purification, energy generation, and nutrient reduction and recirculation. Findings indicate that RNPS water pollution continuously increased for the past 10 years. Chemical fertilizers, poultry and livestock breeding, aquaculture, and rural living are the major sources of elevated chemical oxygen demand, ammonia–nitrogen, total nitrogen, and total phosphorus loads discharged to receiving watercourses. Finally, ecological engineering technologies such as VFS, ED, CW, and BP are proposed for villages and communities to combat RNPS water pollution. BMP are a promising approach to create a sustainable agricultural system, improve the rural energy consumption structure and living conditions, decrease wastewater discharges, and reduce chemical fertilizer application rate.

The use of aqueous suspension of nanoparticles of titanium dioxide for photocatalytic removal of pollutants is not suitable for industrial applications due to the inconvenient and expensive separation of nanoparticles of titanium dioxide for reuse. The nanosized titanium dioxide needs to be immobilized on the support for improving the efficiency and economics of the photocatalytic process. In the present paper, nanoparticles of titanium dioxide have been immobilized on the surface of the support using three different techniques. The immobilized films of titanium dioxide have been characterized using X-ray diffraction and scanning electron microscopy to notice any change in the phase composition and photocatalytic properties of the titanium dioxide after immobilization on the support. A photocatalytic test has been performed under similar reaction conditions to compare the photocatalytic performance of the films of immobilized titanium dioxide prepared using different techniques.

Radionuclide and heavy metal contamination influences the composition and diversity of bacterial communities, thus adversely affecting their ecological role in impacted environments. Bacterial communities from uranium and heavy metal-contaminated soil environments and mine waste piles were analyzed using 16S rRNA gene retrieval. A total of 498 clones were selected, and their 16S rDNA amplicons were analyzed by restriction fragment length polymorphism, which suggested a total of 220 different phylotypes. The phylogenetic analysis revealed Proteobacteria, Acidobacteria, and Bacteroidetes as the most common bacterial taxa for the three sites of interest. Around 20-30 % of the 16S rDNA sequences derived from soil environments were identified as Proteobacteria, which increased up to 76 % (mostly Gammaproteobacteria) in bacterial communities inhabiting the mine waste pile. Acidobacteria, known to be common soil inhabitants, dominated in less contaminated environments, while Bacteroidetes were more abundant in highly contaminated environments regardless of the type of substratum (soil or excavated gravel material). Some of the sequences affiliated with Verrucomicrobia, Actinobacteria, Chloroflexi, Planctomycetes, and Candidate division OP10 were site specific. The relationship between the level of contamination and the rate of bacterial diversity was not linear; however, the bacterial diversity was generally higher in soil environments than in the mine waste pile. It was concluded that the diversity of the bacterial communities sampled was influenced by both the degree of uranium and heavy metal contamination and the site-specific conditions. © 2013 Springer Science+Business Media Dordrecht.

There are concerns over the environmental risks posed by Cu-based fungicide use, and there is community and regulatory pressure on viticultural industries to restrict the use of Cu-based fungicides. This study assesses the relative environmental risks posed by Cu-based and alternative synthetic organic fungicide compounds used in Australian vineyards, giving particular consideration to their adverse effects on soil microbial activity and how risks vary across different viticultural regions. The study was guided by key steps in the ecological risk assessment framework to analyse the risks of Cu-based fungicides towards soil organisms and involved four key steps: (1) problem formulation, (2) analysis (characterise exposure and effects), (3) risk characterisation and (4) risk assessment. There is evidence of a build-up of Cu-based fungicide residues in Australian vineyard soils, although this has occurred over many years, thus allowing the availability of Cu in the soil to be attenuated over time due to aging processes. On the whole, it appears that Cu-based fungicide residues are currently unlikely to pose a significant risk to soil organisms in Australian vineyard soils. However, there are indicators that continued applications of Cu-based fungicides may well have implications on the use of impacted land for sustainable agricultural production. Further detailed studies are required to enable a more definitive characterisation of the risks posed by Cu-based fungicide residues, such as establishing a clearer link between the laboratory and agricultural settings, investigating effects on other indicators of microbial activity and biodiversity and understanding the resilience of soil microbes to additional stressors. The challenge for agricultural industries and governments, both in Australia and globally, is to formulate appropriate plans to reduce the risks associated with Cu-based fungicide use. Further research is required to consider the relative risks of a wide range of alternative fungicide compounds to ensure that they pose a lower environmental risk than the Cu-based fungicides they may replace.