A polyaniline-modified quartz crystal microbalance (QCM) sensor was obtained through immobilizing the polyaniline film on the silver electrode surface of quartz crystal resonator by an electrochemical method. The sensor was studied for detecting the formic acid gas of different concentrations, and the results showed that the resonant frequency of QCM decreased quickly in the beginning and tended to be constant in the end when exposed to formic acid gas. The frequency shifts decreased faster as the concentration of formic acid gas increased. And the frequency shifts of the QCM sensors were found to be linearly related to the concentration of formic acid gas, which might be used to estimate the concentration level of the formic acid gas within the range of experimental concentrations. The result of on-line monitoring test fully indicated that the QCM sensor responded effectively to the increasing concentration of formic acid and had important practical significance and broad application prospect in real-time detection of antique conservation environment in the museum.

Nonpoint stormwater runoff remains a major threat to surface water quality in the USA. More effective stormwater control measures can be designed by understanding patterns in pollutant export with respect to the runoff hydrograph. In particular, nutrient concentrations in urban stormwater can cause deleterious effects in sensitive watersheds in the Southeast and Mid-Atlantic USA. A year-long study captured stormwater samples from 36 storm events at two catchments (one primarily impermeable and the other substantially wooded) and analyzed for total suspended solids and various nutrient species. Using these data, the first flush effect (the assumption that the initial portion of a rainfall-runoff event is more polluted than the later portions) was evaluated based on several published methods and definitions. Based on an analysis of multiple methodologies, the ranking of first flush strength among the pollutants was total suspended solids (TSS) > ammonia (NH₃) > total Kjeldahl nitrogen > NO₂-NO₃ > total phosphorus > orthophosphate (O-PO₄). Nitrogen species generally displayed a stronger first flush than phosphorus species, with O-PO₄ showing the weakest first flush effect. Various relationships ° climate, land use, and the first flush strength were also explored. Of the rainfall characteristics analyzed, total rainfall and runoff volume each inversely affected the first flush strength of TSS on the more impervious catchment. Although orthophosphate did not have a strong first flush effect, the relative first flush strength for O-PO₄ increased with increasing rainfall or runoff. Land use did not influence the first flush strength of the pollutants. On average, most pollutants exhibited a slight first flush effect, but substantial pollutant loading still occurred in the latter portion of the storm’s total runoff volume. Thus, treating the majority of a storm’s total pollutant load requires capturing a commensurate fraction of runoff volume.

Phosphorus (P) releases to the environment have been implicated in the eutrophication of important water bodies worldwide. Current technology for the removal of P from wastewaters consists of treatment with aluminum (Al) or iron (Fe) salts, but is expensive. The neutralization of acid mine drainage (AMD) generates sludge rich in Fe and Al oxides that has hitherto been considered a waste product, but these sludges could serve as an economical adsorption media for the removal of P from wastewaters. Therefore, we have evaluated an AMD-derived media as a sorbent for P in fixed bed sorption systems. The homogenous surface diffusion model (HSDM) was used to analyze fixed bed test data and to determine the value of related sorption parameters. The surface diffusion modulus Ed was found to be a useful predictor of sorption kinetics. Values of Ed < 0.2 were associated with early breakthrough of P, while more desirable S-shaped breakthrough curves resulted when 0.2 < Ed < 0.5. Computer simulations of the fixed bed process with the HSDM confirmed that if Ed was known, the shape of the breakthrough curve could be calculated. The surface diffusion coefficient D ₛ was a critical factor in the calculation of Ed and could be estimated based on the sorption test conditions such as media characteristics, and influent flow rate and concentration. Optimal test results were obtained with a relatively small media particle size (average particle radius 0.028 cm) and resulted in 96 % removal of P from the influent over 46 days of continuous operation. These results indicate that fixed bed sorption of P would be a feasible option for the utilization of AMD residues, thus helping to decrease AMD treatment costs while at the same time ameliorating the impacts of P contamination.

Past mining and processing of uranium ore at a former uranium mining site near Monument Valley, AZ has resulted in nitrate contamination of groundwater. The objective of this study was to investigate the potential of ethanol addition for enhancing the reduction of nitrate in groundwater. The results of two pilot-scale field tests showed that the concentration of nitrate decreased, while the concentration of nitrous oxide (a product of denitrification) increased. In addition, changes in aqueous concentrations of sulfate, iron, and manganese indicated that the ethanol amendment caused a change in prevailing redox conditions. The results of compound-specific stable isotope analysis for nitrate–nitrogen indicated that the nitrate concentration reductions were biologically mediated. Denitrification rate coefficients estimated for the pilot tests were approximately 50 times larger than resident-condition (non-enhanced) values obtained from prior characterization studies conducted at the site. The nitrate concentrations in the injection zone have remained at levels three orders of magnitude below the initial values for many months, indicating that the ethanol amendments had a long-term impact on the local subsurface environment.

In the present paper, the Eulerian–Lagrangian localized adjoint method (ELLAM) formulation developed by Younes et al. (Advances in Water Resources 29:1056–1074, 2006) is combined with the sequential noniterative approach to accurately simulate 2D multicomponent reactive transport in saturated/unsaturated porous media. The performance and accuracy of the developed model, named ELLAM_REACT, are compared against those of an existing numerical model based on a combination of discontinuous Galerkin and multipoint flux approximation methods (DGMPFA_REACT). Three studied test cases, dealing with reactive transport in saturated and unsaturated porous media and involving chemical reactions with only aqueous species or both fixed and aqueous species, show the superiority of the ELLAM_REACT model compared to the DGMPFA_REACT model.

In this study, an iron–zirconium binary oxide with a molar ratio of 4:1 was synthesized by a simple coprecipitation process for removal of phosphate from water. The effects of contact time, initial concentration of phosphate solution, temperature, pH of solution, and ionic strength on the efficiency of phosphate removal were investigated. The adsorption data fitted well to the Langmuir model with the maximum P adsorption capacity estimated of 24.9 mg P/g at pH 8.5 and 33.4 mg P/g at pH 5.5. The phosphate adsorption was pH dependent, decreasing with an increase in pH value. The presence of Cl⁻, SO ₄ ²⁻ , and CO ₃ ²⁻ had little adverse effect on phosphate removal. A desorbability of approximately 53 % was observed with 0.5 M NaOH, indicating a relatively strong bonding between the adsorbed PO ₄ ³⁻ and the sorptive sites on the surface of the adsorbent. The phosphate uptake was mainly achieved through the replacement of surface hydroxyl groups by the phosphate species and formation of inner-sphere surface complexes at the water/oxide interface. Due to its relatively high adsorption capacity, high selectivity and low cost, this Fe–Zr binary oxide is a very promising candidate for the removal of phosphate ions from wastewater.

We present in this paper a new strategy based on the use of polynomial chaos expansion (PCE) for both global sensitivity analysis and parameter optimization. To limit the number of evaluations of the direct model, we develop a simple and efficient procedure to construct a sparse PCE where only coefficients that have a significant contribution to the variance of the model are retained. Parameter estimation is performed using an adaptive procedure where the intervals of variation of the parameters are progressively reduced using information from sensitivity analysis calculated using the sparse PCE. The strategy is shown to be effective for the parameter estimation of two reactive transport problems: a synthetic reactive transport problem involving the Freundlich sorption isotherm and a field experiment of Valocchi et al. (Water Resources Research 17:1517–1527, 1981) involving nonlinear ion exchange reactions.

The environmental impacts of 16 different contaminants originating from the E18 Highway (17,510 annual average daily traffic) were studied over the initial months of the highway’s operational life. Investigative methods used included electrical resistivity surveying, water chemistry analyses, soil analyses, distribution modeling, and transportation modeling of contaminants. The study conclusively showed a year-round infiltration due to melting of the snowpack from road salt, and a strong preferential, anthropogenic pathway due to increased hydraulic conductivities of road construction materials relative to in situ soils. The resistivity surveys produced values well below the expected values for the highway materials, indicating increased ionic content within the unsaturated zone. Time lapse resistivity modeling showed a clear downwards spreading of contamination from the roadway to subsurface distances greater than 5 m. Elevated concentrations of nearly every studied contaminant relative to baseline values were observed, with many metal concentrations within the snow pack averaging values in excess of the Swedish Environmental Protection Agency’s groundwater limitations. Distribution modeling demonstrated a potential offset of peak values from the road surface due to plowing and splash transport processes, and indicated different distribution behavior during winter months than during summer months. One-dimensional transport modeling demonstrated the importance of adsorption and other retentive factors to the migration of contaminants to groundwater and provided an estimate for potential long-term contaminant concentrations.

The feasibility of using nanoscale zerovalent iron (nZVI) treatment for reducing the acute toxicity of explosive wastewater, such as 2,4,6-trinitrotoluene (TNT) red water which contains highly toxic nitroaromatic compounds (NACs), has been investigated. The water quality was evaluated before and after nZVI treatment using several different analytical techniques, including UV–Vis spectroscopy, X-ray photoelectron spectroscopy, high-performance liquid chromatography, and gas chromatography/mass spectroscopy. The acute toxicity of the wastewater was tested using a luminescence bacterium bioarray. The results indicated that the most significant toxic NACs, such as dinitrotoluene sulfonates, had been effectively removed from the TNT red water by nZVI together with the small amounts of other NACs. Following 1 h of the nZVI processing treatment, the acute toxicity of the TNT wastewater was reduced by approximately 94 %. This treatment would therefore be useful for the pretreatment of wastewaters prior to the application of a biological process. The reduction in the biotoxicity of the wastewater was based on the reductive conversion processes and adsorption behaviors of nZVI.

Arsenic and heavy metal (specifically Cd, Cr, Cu, Ni, Pb, and Zn) uptake, translocation, and accumulation in ten native plant species spontaneously growing in soils polluted by mining activities were studied, with a focus on future phytoremediation work in polluted soils. Plant and soil samples were collected in the vicinity of the Mónica mine (NW Madrid, Spain). Soil analysis showed the ability of native plants for growing in soils with high concentration levels of Cd, Cu, Pb, Zn, and especially As. From these elements, the highest percentage of extractable elements was found for Cd and the lowest for Pb. A highly significant correlation was observed between total and extractable element concentrations in soils, except for Cu, indicating that total concentration is the most relevant factor for element mobility in these soils. Extractable elements in soils were better correlated with concentrations in plants than total elements in soils; thus, extraction methods applied are suitable to estimate the element phytoavailable fraction in soils, which depends on the plant species and not only on the element mobility in soils. High element concentrations were found in the aboveground parts of Corrigiola telephiifolia (As and Pb), Jasione montana (Cd and Zn), and Digitalis thapsi (As, Cd, Cu, Pb and Zn). However, considering the translocation and accumulation factors, together with the concentration levels found in roots and aboveground parts, only C. telephiifolia could be considered a Pb accumulator and an As hyperaccumulator plant, which could be used for future phytoremediation work in soils polluted with As.