Non-destructive measurements of contaminated soil core samples are desirable prior to destructive measurements because they allow obtaining gross information from the core samples without touching harmful chemical species. Medical X-ray computed tomography (CT) and time-domain low-field nuclear magnetic resonance (NMR) relaxometry were applied to non-destructive measurements of sandy soil core samples from a real site contaminated with heavy oil. The medical CT visualized the spatial distribution of the bulk density averaged over the voxel of 0.31 × 0.31 × 2 mm³. The obtained CT images clearly showed an increase in the bulk density with increasing depth. Coupled analysis with in situ time-domain reflectometry logging suggests that this increase is derived from an increase in the water volume fraction of soils with depth (i.e., unsaturated to saturated transition). This was confirmed by supplementary analysis using high-resolution micro-focus X-ray CT at a resolution of ∼10 μm, which directly imaged the increase in pore water with depth. NMR transverse relaxation waveforms of protons were acquired non-destructively at 2.7 MHz by the Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence. The nature of viscous petroleum molecules having short transverse relaxation times (T2) compared to water molecules enabled us to distinguish the water-saturated portion from the oil-contaminated portion in the core sample using an M ₀-T2 plot, where M ₀ is the initial amplitude of the CPMG signal. The present study demonstrates that non-destructive core measurements by medical X-ray CT and low-field NMR provide information on the groundwater saturation level and oil-contaminated intervals, which is useful for constructing an adequate plan for subsequent destructive laboratory measurements of cores.

Polycyclic aromatic hydrocarbons (PAHs) were analyzed in 70 soils distributed in mountain areas such as Montseny (300–1,700 m), Pyrenees (1,500–2,900 m), Alps (1,100–2,500 m), and Tatras (1,400–1,960 m). Average total PAH concentrations, excluding retene and perylene, were about 400 ng/g in the Pyrenees and 1,300–1,600 ng/g in the other mountain ranges. No correlations between PAH concentrations and total organic carbon were observed. Retene was the major PAH in the Pyrenean soils of lower altitude. No altitudinal dependence was found between soil PAH concentrations and elevation for the whole dataset. However, in the Tatra soils a statistically significant correlation with altitude was observed involving higher concentrations at higher altitude. This correlation was due to the statistically significant altitudinal dependence of the more volatile PAHs. Another observed altitudinal trend concerned the benz[a]anthracene/(benz[a]anthracene + chrysene + triphenylene) and the benzo[a]pyrene/(benzo[a]pyrene + benzo[e]pyrene) ratios that exhibited a decrease in the more chemically labile compounds, benz[a]anthracene and benzo[a]pyrene, respectively, in the soils located at higher altitude. This observation is consistent with the expected higher photooxidation at higher mountain altitude.

Concrete grinding residue (CGR) is a by-product created by concrete pavement maintenance operations. The application of CGR to roadside soils is not consistently regulated by state agencies across the USA, which is partially due to the lack of science-based information on its impacts to soils and plants. The objectives of this research were to determine the impact of CGR additions to soil on both smooth brome (Bromus inermis L.) biomass and plant and soil chemical parameters. In a greenhouse study, two soils were treated with two CGR by-products at 8% and 25% by weight. Shoot biomass was significantly influenced by the main effects (Soil, CGR, and Rate) and by all two-way interactions, but not consistently positively or negatively correlated. Trace metal concentrations in the shoot biomass were variable, but 68% of these metals had the same concentration or lower in the 25% CGR treatments compared with the controls. Soil pH and electrical conductivity were significantly influenced by the main effects and two-way interactions of Soil × Rate and CGR × Rate, and soil pH was significantly greater in the CGR-treated soils. Calcium, Na, Mg, Al, and S concentrations in soils were all influenced by additions of CGR, but trace metal levels in the treatments were all within the range for uncontaminated soils. Ecosystem impact of applying CGR will be dependent upon the quality of CGR and soil characteristics. Controlling the liming potential of CGR should be considered a best management practice.

Prediction of the sorption behavior of environmental pollutants is of utmost importance within the framework of risk assessments. In this work two approaches are presented with the aim to describe sorption of aromatic substances to geosorbents. First, analytical solutions of kinetic models were fitted to experimental data of batch sorption experiments with aniline and 1-naphthylamine onto animal manure-treated soil and the soil mineral montmorillonite. The models, accounting for equilibrium and nonequilibrium sorption coupled to transformation and/or irreversible sorption processes, could well reproduce the concentration course of the sorbates. Results suggest that the amounts transformed/degraded and irreversibly bound were higher for the soil than for the clay mineral. In the second part, quantum chemical calculations were performed on aniline and 1-naphthylamine interacting with acetic acid, acetamide, imidazole, and phenol as models of functional groups present in humic substances. Molecular modeling showed that formation of hydrogen bonds is the dominating binding mechanism in all modeled complexes, which are energetically very similar between aniline and 1-naphthylamine.

Environmental models are frequently used within regulatory and policy frameworks to estimate environmental metrics that are difficult or impossible to physically measure. As important decision tools, the uncertainty associated with the model outputs should impact their use in informing regulatory decisions and scientific inferences. In this paper, we present a case study illustrating a process for dealing with a key issue in the use and application of air quality models, the additional error in annual mean aggregations resulting from imputation of missing data from model data sets. The case study is based on the US Environmental Protection Agency’s Multi-layer Model, which estimates the hourly dry deposition velocity of air pollutants based on hourly measurements of meteorology and site characteristics. A simulation was implemented to evaluate the effect of substituting historical hour-specific average values for missing model deposition velocity predictions on annual mean aggregations. Sensitivity studies were performed to test the effects of different missing data patterns and evaluate the relative impact of the substitution procedure on annual mean SO2 deposition velocity estimates. The substitution procedure was shown to result generally in long-term unbiased estimates of the annual mean and contributed less than 20% additional error to the estimate even when all data were missing. Consequently, it may be possible to use the historical record of deposition velocities to provide reasonably accurate and unbiased annual estimates of deposition velocities for years without meteorological measurements.

Lake Hallstättersee is a holomictic alpine lake, which is influenced by salt mining since the middle Bronze Age. Beside the constant saline waste water load, two massive brine spills loaded the lake with additional 16,900 tons sodium chloride (≈10,250 tons Cl−) from 1977 to 1979 and 3,000 tons salt (≈1,820 tons Cl−) in 2005. The effect of waste water intrusions from salt mining on stratification of Lake Hallstättersee was analysed over a period of 40 years. Water density, dissolved oxygen and total phosphorus (TP) concentrations were measured and an exponential model was fitted to describe the wash-out of chloride from Lake Hallstättersee after the brine spills. Furthermore, the time required returning to holomixis and steady chloride content after the second brine spill was estimated. During the whole sampling period the minimum and maximum volume-weighted annual mean chloride concentrations were 23.58 mg/L in 1979 and 3.19 mg/L in 1998. However, the mixing regime of Lake Hallstättersee, as well as the chloride concentrations, varied considerably and exhibited three holomictic and three meromictic periods between 1970 and 2009. Holomictic periods were observed when the yearly density gradient was below 0.06 kg/m3, deepwater oxygen in spring above 4 mg/L and consequently declining TP concentration in the deepest water layer below 60 mg/m3, otherwise meromictic periods were observed. Our study showed that Hallstättersee was 13 years ectogenic meromictic and 27 years holomictic during the study period.

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.

This study aimed to optimize two process variables, namely extractant concentration, i.e., di-2-ethylhexylphosphoric acid concentration ([D2EHPA]) and equilibrium pH (pHeq), in Cu(II) extraction from aqueous solutions with a soybean-oil-based organic solvent using response surface methodology by maximizing the percentage extraction (%E). A central composite design was applied, and a regression model for %E was developed. Adequacy of the model was examined, and it was found to be statistically significant. The optimum conditions were determined as follows: [D2EHPA] of 84.71 mM and pHeq of 4.46, which resulted in 99.78% of %E. The experimental value of %E (98.17%) obtained is found to agree satisfactorily with that (99.78%) predicted from the model.

Petroleum monoaromatics including benzene, toluene, ethylbenzene, and xylenes (BTEX) are among the notorious volatile organic compounds that contaminate water and soil. In this study, a surfactant- modified natural zeolite and its relevant granulated nanozeolites were evaluated as potential adsorbents for removal of petroleum monoaromatics from aqueous solutions. All experiments performed in batch mode at constant temperature of 20°C and pH of 6.8 for 48 h. The results revealed that the amount of BTEX uptake on granulated zeolites nanoparticles were remarkably higher than the parent micron size natural zeolite (in the order of four times). The isotherms data were analyzed using five models namely, Langmuir, Fruendlich, Elovich, Temkin, and Dubinin–Radushkevich models. It was concluded that the Langmuir model fits the experimental data. The measured adsorption capacities were 3.89 and 4.08 mg of monoaromatics per gram of hexadecyltrimethylammonium-chloride and n-cetylpyridinium bromide (CPB)-modified granulated nanozeolite, respectively. Considering the type of surfactant, adsorbents modified with CPB showed greater tendency for the adsorption of the adsorbates.

Sorption and desorption of Hg(II) on clay minerals can impact the biogeochemical cycle and bio-uptake of Hg in the environment. We studied the kinetics of the desorption of Hg(II) from kaolinite as affected by oxalate and cysteine, representing the ligands with carboxylic and thiol groups of different affinities for Hg(II). The effects of pH (3, 5, and 7), ligand concentration (0.25 and 1.0 mM), and temperature (15°C, 25°C, and 35°C) on the Hg(II) desorption were investigated through desorption kinetics. Our study showed that the Hg(II) desorption was pH dependent. In the absence of any organic ligand, >90% of the previously adsorbed Hg(II) desorbed at pH 3 within 2 h, compared to <10% at pH 7. Similar results were observed in the presence of oxalate, showing that it hardly affected the Hg(II) desorption. Cysteine inhibited the Hg(II) desorption significantly at all the pH tested, especially in the first 80 min with the desorption less than 20%, but the inhibition of the desorption appeared to be less prominent afterwards. The effect of the ligand concentration on the Hg(II) desorption was small, especially in the presence of oxalate. The effect of temperature on the Hg(II) desorption was nearly insignificant. The effect of the organic acids on the Hg(II) sorption and desorption is explained by the formation of the ternary surface complexes involving the mineral, ligand, and Hg(II). The competition for Hg(II) between the cysteine molecules adsorbed on the particle surfaces and in the solution phase probably can also affect the Hg(II) desorption.