Conditions for tributyltin (TBT) solubilization and degradation were investigated. These conditions were optimized to remove or degrade organotin compounds (OTC) in spiked kaolin. TBT-spiked kaolin and reagents with specific chemical properties were tested in a batch reactor using a solid matrix model. The final concentrations of butyltin compounds in kaolin were determined by gas chromatography coupled with a pulsed flame photometric detector. Best results were obtained under acidic conditions (2 < pH < 5) with up to 87% TBT removal from the spiked kaolin. Acids with reducing properties were more effective (ascorbic and formic acid: 87% and 82% of TBT abatement, respectively). Moreover, final monobutyltin and dibutyltin concentrations were analyzed to determine which species predominate in the solid matrix after batch experiments. OTC speciation shows that degradation of TBT occurs simultaneously with solubilization in the presence of several reagents. These results allow choosing favorable/optimal operating conditions for OTC elimination.

Poorly constructed wells (leaky or without a gravel pack) and abandoned wells can behave as conduits for the interconnection of aquifers at different depths and facilitate the transfer of contaminants between these aquifers. This is the case with Campo de Cartagena (SE Spain) where the primary land use is intensive irrigated agriculture, along with a high density of wells. The unconfined aquifer is heavily impacted by a high concentration of nitrate associated with agricultural activities. The present work provides a methodological approach to evaluate the impact of the unconfined aquifer on the water quality of the confined aquifer caused by leaky wells in high-density areas of production wells. The research approach included the use of geochemical and isotopic tools; specifically, nitrate was used as a tracer for evaluating the impact, and the code MIX_PROGRAM was used for mixing calculations. Results show an increase of the impact of the unconfined aquifer on the confined aquifer along the groundwater flow direction toward the coast, although this general pattern is controlled by local factors (pumping, intensity of agricultural practices, density of wells, and groundwater residence time).

Environmentally safe disposal of sulfide-rich reactive mine tailings is one of the major challenges facing the mining industry in Canada, Scandinavia, USA, and many other parts of the world. Placing tailings under a water cover is one of the effective methods to reduce the influx of oxygen to the tailings. Wind-induced turbulence and subsequent resuspension of the tailings, however, are major concerns with this approach. In this paper, a study of wind-induced resuspension at the Shebandowan tailings storage facility, northwestern Ontario, Canada, is discussed. The study compares computer modeling of required water cover depths and resuspended tailings concentrations to observed field data. The calculated minimum water cover depths required to eliminate resuspension were found to be higher than the existing implemented water cover depths in each cell. The predicted resuspended tailings concentrations for the west cell were 6-22 mg/l with an average value of 15 mg/l and, for the east cell, 1-10 mg/l, with an average of 6.0 mg/l. In comparison, optical backscatter sensors, deployed in situ, recorded average resuspended tailings concentration up to 25 mg/l, indicating that the model results were similar to the field-measured values. Results from sediment trap measurements did not show any correlation between the amount of resuspended tailings and water cover depth. Sediment traps collect not only sediments eroded and suspended at the location of deployment but also those that have been transported from elsewhere and redeposited at the trap location. The amount of resuspension occurring at Shebandowan does not raise a major concern because discharge from the tailings area is collected and managed before it reports to the final effluent.

Settleability of dry and wet weather flow samples from a combined sewer system was examined by settling column tests, in order to improve understanding of settling processes and obtain information for design of settling tanks. In fact, these tests mimic the actual settling processes and allow evaluating total suspended solids (TSS) removal by settling. Therefore, it is also possible to assess, indirectly, removals of other pollutants, such as heavy metals, which are generally transported by solid particles in sewage. Towards this end, dry and wet weather flow samples were collected in the Liguori Channel catchment and analyzed in the laboratory for Water Supply and Sewerage (Acquedotti e Fognature) of the University of Calabria for TSS concentrations according to the Standard Methods. The settleability study revealed that removals of TSS in dry weather samples (i.e., sanitary sewage) were greater than in wet weather samples (WW), using the same experimental procedures. In particular, 65% of TSS was removed in dry weather samples at a depth of 3 m for a detention time of 40 min; while in wet weather samples the comparable removal efficiency was less than 60%.

This study examined the relationship between abundance of submerged aquatic vegetation (SAV) and the water trophic status of a group of lakes located in northwestern Hillsborough county. SAV abundance was expressed by the percent of lake volume infested with SAV (PVI) and the percent of lake area covered with SAV (PAC). The group of lakes was divided into two subgroups based on SAV abundance less than 20 PVI (PVI < 20) and lakes with more than 20 PVI (PVI > 20). Mean concentrations of total phosphorus (TP), total nitrogen (TN), and chlorophyll-α in lake water were used as indicators of trophic status, with the concentration of each nutrient in one group of lakes compared to its corresponding concentration in the other group. Lakes with PVI < 20 had a mean concentration of TP and chlorophyll-α of 28 and 11 µg/l, respectively, while those with a PVI > 20 had a mean concentration of 18 and 4 µg/l for the same parameters, respectively. The results of a t test and one-way ANOVA performed at the 95% confidence level indicated that the differences were significant for the concentrations of TP and chlorophyll-α but not for TN, the last of which had a mean lake water concentration of 0.8 and 0.7 mg/l for the PVI < 20 and PVI > 20 subgroups, respectively.

The purpose of this study was to determine the impacts of regional historical uranium mining activities within sediments of the Bowman–Haley reservoir of southwestern North Dakota. The extent of anthropogenic-influenced watershed impacts were quantified through the determination of sediment metals concentrations and metal enrichment factors to evaluate the potential of geochemically influenced As and U remobilization within the reservoir sediments. Sediment cores were collected and analyzed for total metal concentrations at five locations within the reservoir: Spring Creek delta, Alkali Creek delta, two locations within the North Fork of the Grand River confluence, and adjacent to the reservoir outfall. Pearson-moment correlations were used to establish inter-core metal correlations, while sediment enrichment factors were determined relative to background concentrations. Enrichment factor results suggest all sampling sites are classified as minor to moderately enriched for As and U. Metal behavior for the three reservoir inlets indicated similar metal loading sources and post-depositional behavior, while metals migration within the vicinity of the reservoir outlet appear to be controlled by geochemical and/or physical processes. For the reservoir outlet, As and U normalized to Al suggest the occurrence of vertical migration of As, while surface-bound U remobilization was apparent within the water column immediately above the sediments. Elevated U was found within the Spring Creek inlet, and appear attributed to historical uranium processing operations located in Griffin, North Dakota. While the reservoir As and U sediment concentrations may be considered low, their presence appears directly attributed to historical uranium mining activities within the Bowman–Haley reservoir watershed.

The objective of this research was the evaluation of the effects of exogenous added surfactants on hydrocarbon biodegradation and on cell surface properties. Crude oil hydrocarbons are often difficult to remove from the environment because of their insolubility in water. The addition of surfactants enhances the removal of hydrocarbons by raising the solubility of these compounds. These surfactants cause them to become more vulnerable to degradation, thereby facilitating transportation across the cell membrane. The obtained results showed that the microorganism consortia of bacteria are useful biological agents within environmental bioremediation. The most effective amongst all, as regards biodegradation, were the consortia of Pseudomonas spp. and Bacillus spp. strains. The results indicated that the natural surfactants (rhamnolipides and saponins) are more effective surfactants in hydrocarbon biodegradation as compared to Triton X-100. The addition of natural surfactants enhanced the removal of hydrocarbon and diesel oil from the environment. Very promising was the use of saponins as a surfactant in hydrocarbon biodegradation. This surfactant significantly increases the organic compound biodegradation. In the case of those surfactants that could be easily adsorbed on cells of strains (e.g., rhamnolipides), a change of hydrophobicity to ca. 30-40% was noted. As the final result, an increase in hydrocarbon biodegradation was observed.

Diffused petroleum and chlorinated hydrocarbon contamination was detected in a sandy aquifer below a chemical plant in Southern Italy. The contamination was due to underground leaking tanks and pipes. The site is located near the shore line and is bordered by canals which, in combination with pumping wells, control the groundwater flow direction toward the sea. In this study, a comprehensive three-dimensional flow model was developed and calibrated to simulate the general groundwater flow system and to individuate a flow line. On this latter, a detailed field investigation was performed in order to determine the fate of dissolved hydrocarbons. Depth profiles obtained from multi-level samplers located along the modelled flow line, including measurements of hydrocarbons, all major ions and dissolved gasses, were used to constrain the conceptual model. These data were then included into a two-dimensional transport model in order to verify the efficacy of the hydraulic barrier (HB) in preventing the hydrocarbon plume to reach the shore line. Two different approaches were used in the transport simulation, one accounting for density-dependent flow and the other not. The calibrated models show that the plume length and consequently, the submarine groundwater discharge of contaminants is slightly different for the two approaches. For the simulation not accounting for the density contrast between freshwater and saltwater, the mass of contaminant discharged downstream to the HB was underestimated and also the reconstructed plume geometry was different than the observed. Moreover, the reconstruction of the saltwater intrusion interface (SWII) with the two different approaches was substantially different. This study demonstrates that at field site, variable density processes should be carefully taken into account not only when the modelling is devoted to the reconstruction of the SWII but also when the modelling is targeting the fate of hydrocarbons at sites affected by SWII, in order to provide accurate data on which soundly environmental management of the coastal zone can be based.

A major input in intensive organic agriculture is nutrient-rich liquid fertilizers. Guano and other fowl manure are frequently digested in water extracts, and the supernatant is supplied as fertilizer. The resultant manure biowaste (MBW) is commonly disposed of to the environment, posing potential pollution and health risks. The study aims were to determine two types of fowl MBWs for their chemical properties before and after lime treatment and to test their reuse potential as soil amendment. Guano and layer manure were digested, and the residues’ chemical properties were analyzed before and after lime treatment. MBWs were then air-dried and used as a soil amendment in a parsley-growing experiment. The lime-treated MBW composition met the European standards for high-quality biowaste compost. Both digested and lime-treated MBWs had residual nitrogen, 3% and 1% in guano and layer manure, respectively. Parsley grown in soil amended with layer MBW had 100% survival, high yield, and good crop quality compared with controls. Plants grown with soil amended with guano biowaste exhibited lower yield and only 50% survival. These findings indicate that the current practice of disposing guano biowaste to the environment may pollute soil and water bodies, while the land spread of lime-treated layer MBW is safe and may improve soil fertility.

Assessment of native plants and laboratory-scale phytoextraction tests are fundamental and preliminary steps in checking the feasibility and practice of low-cost and low-impact phytoremediation. In this study, we investigated the absorption of B by plants as a tool to remove boron in sediments from different areas of the Cecina River basin in Tuscany, Italy. The investigation was performed analyzing total and available B fraction in sediment samples as well as the B content in different tissues of native plants colonizing the contaminated areas. In laboratory scale, a phytoextraction screening test was performed. Selected high biomass crops (Brassica juncea, Zea mays, and Helianthus annuus) were evaluated in the most contaminated sample in two consecutive growing cycles. Results from field survey showed no hyperaccumulator native plant was present in the investigated areas although, high accumulation levels were found in native species from Bulera dump (Rumex crispus—259 mg kg−1 and Poa spp—203 mg kg−1). Results from laboratory phytoextraction tests showed a higher ability of B. juncea which removed about 18.5 mg B kg−1 sediment in after the two consecutive growing cycles, representing on the whole 45% of the initial available B fraction. The sediment characteristics affected by the phytoextraction processes were also discussed.