The presence of different kinds of leaf packs (native or alien) and environmental gradients can affect the composition and abundance of macroinvertebrate assemblages in freshwater ecosystems, but little is known about the interactive effects. Here, we investigated (1) how environmental gradients could influence leaf packs macroinvertebrates and (2) which was the chief factor (among water quality, mass loss of leaf packs, and flow regime) affecting macroinvertebrate assemblages in impaired streams. We analyzed leaf packs in six sites in impaired streams, characterized by wastewater discharges and dominated by pollution-tolerant macroinvertebrate species. Using principal component analysis, we defined two environmental gradients as follows: a water quality gradient, related to anthropogenic alteration, and a hydromorphological gradient, mostly related to the catchment features. Our results pointed out that, in the tested conditions, biological metrics, such as functional groups and taxa richness, were chiefly influenced by the water quality gradient, while different leaf types in packs influenced the total taxa richness, but did not cause significant variation in the distribution and abundance of macroinvertebrate functional groups. On the contrary, the mass loss differed for different leaf types and was related to the stream and catchment features (mainly flow). This work showed that, in impaired streams, macroinvertebrate assemblages colonizing leaf packs are more influenced by water quality than by leaf types. Thus, the improvement of water quality should be the priority in restoration programs and should be achieved before any effort to restore native riparian vegetation.

Because of the existence of a semi-analytical solution, the Henry saltwater intrusion problem has been widely used for benchmarking non-reactive density-driven flow models. In this work, we extend the semi-analytical solution of Henry to reactive transport in variable-density fluid flow. Accurate semi-analytical solutions are provided for three test cases dealing with saltwater transport including dissolution and degradation reactions. About 6,195 terms are required in the Fourier series to obtain a stable solution for these test cases instead of the 78 initially used by Henry (Sea Water in Coastal Aquifers 1613-C:70–84, 1964) for the non-reactive problem. The resolution of the highly non-linear system is made possible due to the modified Powell hybrid algorithm with an analytical evaluation of the Jacobian. Numerical simulations are performed using different numerical methods and grid sizes to evaluate the benefits of these new test cases for benchmarking reactive density-driven flow models.

Major incidents involving mine waste facilities and poor environmental management practices have left the legacy of thousands of contaminated sites like in the historic mining areas in the Carpathian Basin. Associated environmental risks have triggered the development of new EU environmental legislation to prevent and minimize the effects of such incidents. The Mine Waste Directive requires the risk-based inventory of all mine waste sites in Europe by May 2012. In order to address the mining environmental problems, a standard risk-based pre-selection protocol has been developed by the EU Commission. The protocol consists of 18 simple questions about contamination source, pathway and receptor. This paper evaluates the protocol by applying it to real-life cases, adopting it to local conditions, comparing to the similar method of the European Environmental Agency standard Preliminary Risk Assessment Model (PRAMS) and by carrying out uncertainty analysis. All together, 145 ore mine waste sites have been selected for scientific testing and evaluation using the EU Mining Waste Directive (MWD) Pre-selection Protocol as a case study from Hungary. The proportion of uncertain responses to questions in the protocol for the mine waste site gives an insight of specific and overall uncertainty in the data used. Questions of the EU MWD Pre-selection Protocol are linked to a GIS system, and key parameters such as the topographic slope and distance to the nearest surface and groundwater bodies to settlements and protected areas are calculated and statistically evaluated in order to adjust the RA models to local conditions in Hungary. Results show that the adjustment of threshold values to local conditions is necessary; however, the EU MWD Pre-selection Protocol is robust and is relatively insensitive to threshold values. Results of the EU MWD Pre-selection Protocol are consistent with the pre-screening European Environmental Agency PRAMS model which further confirms that the Protocol delivers reliable selection results that are not sensitive to the selected parameters. An interesting outcome of the study is that the highest uncertainty is associated with the engineering conditions of the waste facilities, such as the heights and size.

A laboratory-scale study was conducted to determine the removal efficiencies of nine contaminants from a tannery wastewater using a number of physicochemical processes. Coagulation–flocculation using bittern as coagulant, oxidation-utilizing ozone, and adsorption using activated carbon were applied separately and in different sequences. Jar tests were utilized to conduct the experimental work. Except for arsenic, the highest removal efficiencies were recorded when coagulation/flocculation was conducted on the alkalized samples using a bittern dose of 5 mL/L. Activated carbon adsorption improved removal efficiencies of several contaminants. The coagulation/flocculation–adsorption sequence using the optimum dose of 5 mL/L of bittern resulted in high removal efficiencies for total suspended solids (TSS) (97 % ± 1), apparent color (100 % ± 0), turbidity (97 % ± 1), total nitrogen (86 % ± 1), and chromium (100 % ± 0). On the other hand, the same sequence resulted in moderate removal efficiencies for chemical oxygen demand (COD) (72 % ± 7) and total phosphorus (74 % ± 5) and relatively low removals for biochemical oxygen demand (BOD) (55 % ± 10) and arsenic (42 % ± 14). The removal efficiencies for the different tested sequences demonstrated that each sequence did improve the removal efficiencies for most of the parameters tested and consequently, the quality of tannery effluent. However, no single optimum sequence was capable of attaining high removal efficiencies for all nine parameters.

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.