Covers of the nuclear waste repository are of great significance to the long-term safe storage and disposal of nuclear wastes. Capillary barriers have proven to be effective to resist the downward water seeping into the underlying nuclear wastes, especially in dry climate, and have been widely used worldwide. Infiltrating water is removed from the fine layer by evaporation or transpiration or through percolation into the coarse layer, which plays a critical role in preventing the water from further infiltration in the bulk wastes. In this paper, laboratory infiltration tests were conducted with an organic glass box, filled with fine-grained quartz sand in which a layer of coarse-grained quartz sand was emplaced horizontally or at various slopes (10° and 20°), and the capillary barrier effect under various conditions (different thickness, slop of coarse-grained quartz sand layer, and sprinkling intensity) was investigated in detail. The results show that the thickness of the underlying coarse layer plays a critical role in governing the performance of the capillary barrier. The efficiency of capillary barrier increases with increasing thickness and/or slope of the coarse layer, but decreases with increasing sprinkling intensity. For a sprinkling intensity of 20 mm/day, a 30-mm-thick coarse layer even emplaced horizontally can achieve 100% water diversion. In addition, a visible tracer test was performed with an inert red dyestuff to trace the streamlines; the results indicate that even with a 7-mm-thick coarse layer, the capillary barrier can offer marked ability to prevent water from percolating into the coarse layer. The findings could be useful for improving engineered uses of capillary barriers at waste repository sites.

Adsorption to biomass is a key mechanism which results in the elimination of natural estrogens and their conjugates from sewage. Freundlich model showed that the adsorption capacities of estrone and 17β-estradiol to activated sludge were the highest at neutral pH. The lower capacities at pH 2 and 11.5 could be due to the competition of sludge adsorption sites by cations or electrostatic repulsion from particles of similar charges. The lowest adsorption capacity at pH 11.5 was attributable to electrostatic repulsion, and the highest capacity at pH 2 might be due to the increased sulfate adsorbability. For estrogen conjugates such as estrone-3-sulfate and 17β-estradiol-3-sulfate, adsorption performances were similar at pH 5, 7, and 9. It was observed that mean values of log K D were 2.78, 2.61, 1.67, and 1.94 l kg TSS⁻¹; log K OM were 2.96, 2.79, 1.77, and 2.04 l kg VSS⁻¹ and those of log K OC were 3.31, 3.12, 2.21, and 2.46 l kg OC⁻¹ for estrone, 17β-estradiol, estrone-3-sulfate, and 17β-estradiol-3-sulfate, respectively.

Stable isotope analyses were performed on gas samples collected within two instrumented biocovers, with the goal of evaluating CH₄ oxidation efficiencies (f ₀). In each of the biocovers, gas probes were installed at four locations and at several depths. One of the biocovers was fed with biogas directly from the waste mass, whereas the other was fed through a gas distribution system that allowed monitoring of biogas fluxes. While the f ₀ values obtained at a depth of 0.1 m were low (between 0.0% and 25.2%) for profiles with poor aeration, they were high for profiles with better aeration, reaching 89.7%. Several interrelated factors affecting aeration seem to be influencing f ₀, including the degree of water saturation, the magnitude of the biogas flux and the temperature within the substrate. Low f ₀ values do not mean necessarily that little CH₄ was oxidized. In fact, in certain cases where the CH₄ loading was high, the absolute amount of CH₄ oxidized was quite high and comparable to the rate of CH₄ oxidation for cases with low CH₄ loading and high f ₀. For the experimental biocover for which the CH₄ loading was known, the oxidation efficiency obtained using stable isotopes (f ₀ = 55.67% for samples taken inside flux chambers) was compared to the value obtained by mass balance (f ₀ = 70.0%). Several factors can explain this discrepancy, including the high sensitivity of f ₀ to slight changes in the isotopic fractionation factor for bacterial oxidation, α ox, uncertainties related to mass flow metre readings and to the static chamber method.

This study has investigated how to simultaneously remove both heavy metals (Cu, Mn, and Zn) and natural organic matters (NOM; humic acid and fulvic acid) from river water using potassium ferrate (K₂FeO₄), a multipurpose chemical acting as oxidant, disinfectant, and coagulant. In water sample including each 0.1 mM heavy metal, its removal efficiency ranged 28-99% for Cu, 22-73% for Mn, and 18-100% for Zn at the ferrate(VI) doses of 0.03-0.7 mM (as Fe). The removal efficiency of each heavy metal increased with increasing pH, whereas an overall temperature did not make any special effect on the reaction between the heavy metal and ferrate(VI). A high efficiency was achieved on the simultaneous treatment of heavy metals (0.1 mM) and NOM (10 mg/l) at the ferrate(VI) doses of 0.03-0.7 mM (as Fe): 87-100% (Cu), 31-81% (Mn), 11-100% (Zn), and 33-86% (NOM). In the single heavy metal solution, the optimum ferrate dose for treating 0.1 mM Cu or Mn was 0.1 mM (as Fe), while that for treating 0.1 mM Zn was 0.3 mM (as Fe). In the mixture of three heavy metals and NOM, on the other hand, 0.5 mM (as Fe) ferrate(VI) was determined as an optimum dose for removing both 0.1 mM heavy metals (Cu, Mn, and Zn) and 10 mg/l NOM. Prior to the addition of ferrate(VI) into the solution of heavy metals and NOM (HA or FA), complexes were formed by the reaction between divalent cations of heavy metals and negatively charged functional groups of NOM, enhancing the removal of both heavy metals and NOM by ferrate(VI).

Purpose Contamination with petroleum hydrocarbons (PHC) is a global problem with environmental implications. Physico-chemical treatments can be used for soil cleanup, but they are expensive, and can have implications for soil structure and environment. Otherwise, biological remediation treatments are cost-effective and restore soil structure. Several remediation experiments have been carried out in the lab and in the field; however, there is the challenge to achieve as good or better results in the field as in the laboratory. In the ambit of a project aiming at investigating suitable biological remediation approaches for recovering a refinery contaminated soil, we present here results obtained in bioremediation trials. The approaches biostimulation and bioaugmentation were tested, in parallel, and compared with natural attenuation. For this purpose, mesocosm experiments were carried out inside the refinery area, which constitutes a real asset of this work. Methods Soil contaminated with crude oil was excavated, re-contaminated with turbine oil, homogenised and used to fill several 0.5 m³ high-density polyethylene containers. The efficiency of procedures as follows: (1) natural attenuation; (2) manual aeration; (3) biostimulation by adding (3.1) only nutrients; and (3.2) nutrients and a non-ionic surfactant; and (4) bioaugmentation in the presence of added (4.1) nutrients or (4.2) nutrients and a non-ionic surfactant were evaluated after a 9-month period of experiment. For bioaugmentation, a commercial bacterial product was used. In addition to physico-chemical characterization, initial and final soil contents in total petroleum hydrocarbons (TPH) (by Fourier transform infrared spectrophotometry) and the total number of bacteria (by total cell counts) were carried out. For TPH degradation evaluation the soil was divided in four fractions corresponding to different depths: 0-5; 5-10; 10-15; and 15-20 cm. Mean values of percentages of PHC degradation varied between 20 and 50% at surface and between 10 and 35% below 5-cm depth. Natural attenuation was as efficient as most of the tested treatments (about 30% TPH degradation) being exceeded only by bioaugmentation combined with nutrient and surfactant amendments (about 50% TPH degradation). Higher TPH degradation at surface suggests that a combination of sufficient dioxygen, propitious for aerobically degradation, with sunlight required for production of strong photochemical oxidants like ozone, contributed for enhancing degradation. Indeed, the atmosphere of the refineries is relatively rich in volatile organic compounds and nitrogen dioxide (a side-product of the combustion of residual volatile PHC released by the chimneys), which are precursors of O₃ and other photochemical oxidants produced in sunny days, which are very common in Portugal. The fact that natural attenuation was as efficient as most of the soil treatments tested was very probably a result of the presence, in the initial soil, of physiologically adapted native microorganisms, which could be efficient in degrading PHC. Conclusions A cost-effective way to reduce half-life for the degradation of PHC of contaminated soil of the refinery will be a periodic revolving of the soil, like tillage, in order to expose to the oxidative atmosphere the different layers of contaminated soil. A combination of soil revolving with bioaugmentation together with nutrients and surfactant amendments may result in an additional improvement of PHC degradation rate. However, this last procedure will raise markedly the price of the remediation treatment.

Metal pollution is a global problem which represents a growing threat to the environment. Because of bioaccumulation and negative effects of heavy metals, their bioavailability needs to be monitored. Many studies showed accumulation of metals in crayfish tissues as dose- and time-dependent without significant differences in tissue concentration levels comparing males and females. Muscles and exoskeleton were considered as specific for accumulation of mercury and nickel, respectively. Cadmium, zinc, copper, lead, and chromium accumulated mainly in hepatopancreas. By analyzing these specific tissues, it is possible to deduce the bioavailability and, by presumption, the level of environmental pollution by specific metals. However, in the case of zinc and copper, their utility is limited to assessing bioavailability because rapid depuration of these metals renders them less useful for long-term environmental monitoring programs. The literature reporting heavy metal impacts on freshwater crayfish, with reference to accumulation levels, is reviewed and summarized with respect to their suitability as bioindicators. Summarized published data from unpolluted or control localities can be used as referential values in crayfish, and consequently help with evaluation of monitored sites.

The upper Great Egg Harbor River watershed in New Jersey's Coastal Plain is urbanized but extensive freshwater wetlands are present downstream. In 2006-2007, studies to assess levels of total mercury (THg) found concentrations in unfiltered streamwater to range as high as 187 ng/L in urbanized areas. THg concentrations were <20 ng/L in streamwater in forested/wetlands areas where both THg and dissolved organic carbon concentrations tended to increase while pH and concentrations of dissolved oxygen and nitrate decreased with flushing of soils after rain. Most of the river's flow comes from groundwater seepage; unfiltered groundwater samples contained up to 177 ng/L of THg in urban areas where there is a history of well water with THg that exceeds the drinking water standard (2,000 ng/L). THg concentrations were lower (<25 ng/L) in unfiltered groundwater from downstream wetland areas. In addition to higher THg concentrations (mostly particulate), concentrations of chloride were higher in streamwater and groundwater from urban areas than in those from downstream wetland areas. Methylmercury (MeHg) concentrations in unfiltered streamwater ranged from 0.17 ng/L at a forest/wetlands site to 2.94 ng/L at an urban site. The percentage of THg present as MeHg increased as the percentage of forest + wetlands increased, but also was high in some urban areas. MeHg was detected only in groundwater <1 m below the water/sediment interface. Atmospheric deposition is presumed to be the main source of Hg to the wetlands and also may be a source to groundwater, where wastewater inputs in urban areas are hypothesized to mobilize Hg deposited to soils.

Current and past industrial pollution leaves many traces in the environment, in particular along rivers in industrial and urban areas. The isotopic analysis of the lead found in soils and tree rings offers a kind of environmental archive for presenting a portrait of the pollutant distribution in the environment in both spatial and temporal terms. This study is an attempt to identify and compare the source of contamination found in soils and tree rings located along two rivers affected by pollution over several years. Specifically, the focus is on the pattern of lead concentrations and lead isotopic signatures (206Pb/207Pb, 208Pb/206Pb, and 206Pb/204Pb) detected in soils and tree rings located on polluted floodplains. The concentration of Pb in overbank sediments does not rise with the increasing distance downstream from the point source (mining area), suggesting that significant fluvial transport of the pollutant particles over 80 km is involved. For the soil profiles, Pb concentration levels range between 12.32 and 149.13 mg/kg, with the highest concentrations found at the base of the profiles (>1 m). For the lead isotope ratios in the soil profiles, the values obtained range from 0.851 to 0.872 (206Pb/207Pb), 2.081 to 2.111 (208Pb/206Pb), and 0.547 to 0.562 (206Pb/204Pb). The tree ring analysis of red ash (Fraxinus pennsylvanica Marsh.) shows average lead concentrations of 0.63 μg/g, and the lead values of all the tree specimens range between 0.03 and 11.38 μg/g. Pb concentrations varied greatly between the specimens in selected sites and lead isotope ratios in the tree rings showed a strong variability in the time series, particularly from 1945 to 1970. The greater number of variations in the lead concentration rates and isotopic ratios suggest that many more events associated with pollution and contamination have in fact occurred in this area. The study demonstrates the utility of combining stable isotope analyses (soils and tree rings) to examine the source and dispersion of contaminant Pb in fluvial systems by providing reliable and robust indicators for the detection of environmental changes on a local and regional scale.

The oxidation of di-(2-ethylhexyl) phthalate (DEHP) in solution using UV/H₂O₂ and direct UV photolysis are analyzed in this study. It was found that DEHP was 100% removal in the solution by 180-min UV/H₂O₂ treatment and 73.5% removal by 180-min direct UV photolysis. The effect of different factors, such as DEHP concentration, H₂O₂ concentration, and UV light intensity, on photochemical degradation was investigated. The degradation mechanism of DEHP and the acute toxicity of intermediates were also studied. The photochemical degradation process was found to follow pseudo-first-order kinetics. The results of our study suggested that the concentration with 40 mg/L H₂O₂ and 5 μg/mL DEHP in the solution at pH 7 with 10.0 × 10⁻⁶ Einstein l⁻¹ s⁻¹ UV was the optimal condition for the photochemical degradation of DEHP. The photochemical degradation with UV/H₂O₂ can be an efficient method to remove DEHP in wastewater.