Stability and transport of As species in soils were investigated in three contaminated Central European regions in the Czech Republic; one of them represents naturally contaminated area, the others are results of a former mining activity. Total As content varied from 60 to <18,000 ppm depending on locality and sampling layer. Sequential extraction procedure (SEP) enabled to distinguish five main fractions of As in soils based on different chemical and binding properties. Non-specifically and weakly sorbed As, as well as As remained in solid rests of samples did not exceed 10% of total As; specifically bounded As varied from 5 to 15%. The substantial portion of As was bound to hydrated Fe oxides (HFO) in amorphous and poorly-crystalline forms (10-30% of the total As) and/or to a well-crystallized forms of the same phases (50-80%). As sorption on HFO surface, particularly on well-crystallized phases represented the most significant and stable As bond in soils. Model leaching experiments illustrated the increased mobility of As species at pH [almost equal to] 7.0 in the soil-groundwater-surface water systems.

The type and amount of indoor air pollutants affects the comfort and quality of indoor environments. Therefore, indoor air quality is an important issue with different social, economic, and health aspects because people in developing countries spend most of their time indoors being exposed to different kinds of indoor pollutants. The indoor air quality can be assessed empirically by measuring the pollutant concentrations or can be predicted by means of mathematical models. An indoor aerosol model describes the dynamic behavior of indoor air pollutants. The basic concept of indoor air models is the mass-balance-conservation where several factors that govern the indoor particle concentrations can be described. These factors may include direct emissions from indoor sources, outdoor aerosol particles penetrating indoors as a result of the ventilation and filtration processes, deposition onto indoor surfaces, and removal from indoor air by means of ventilation. Here we present principles of indoor aerosol models and we also give examples of different kind of models.

In a risk assessment study the environmental fate of the herbicide glyphosate was studied with the specific background of the presence of genetically modified (GM) plants. Aim was to simulate the environmental behaviour of glyphosate in sandy field soil lysimeters after multiple herbicide applications and under the presence of GM soybean and to test and enhance model reliability in the simulation of the herbicide fate including biodegradation in the soil and herbicide translocation in GM plants. The modelling of the herbicide behaviour in the present study was based on the pesticide transport model LEACHP and the model PLANTX to simulate the pesticide uptake by plants. Both models were implemented in the modular modelling system EXPERT-N. Glyphosate transport measurements and the mathematical modelling results indicate that due to the high sorption of glyphosate to the soil matrix and the high microbial capacities for glyphosate degradation in the lysimeter soil, leaching risk can be considered to be low. We confirmed that the introduction of more adequate conceptual descriptions of microbial response to pesticide and nutrient additions can contribute to a reduction in the uncertainty of pesticide degradation modelling. Moreover, the consideration of uncertainty in sorption, dispersivity and degradation parameters revealed a considerable variability in model output. The observed accumulation of glyphosate in roots and nodules was reproduced by the simulation results. Under the restriction that the prevailing model assumptions are valid, the simulation results indicate that glyphosate may accumulate also in beans of trangenic soybean.

Prescribed or natural drawdowns occur frequently in reservoirs but their effects on fish populations have been barely studied. As a consequence of a severe drought and the need to optimize water quality, a partial drawdown was prescribed in autumn 2005 to a eutrophic reservoir that provides water supply to a large metropolitan area (Barcelona, Spain). In order to avoid a potential massive fish kill given the reduced oxygen availability and high fish abundance, preventive purse seine fisheries were performed to reduce the fish stock. The fisheries had little effect on the fish assemblage because final population size structure and species composition did not change significantly. The species composition of the purse seine catches varied significantly during the drawdown with higher proportion of bleak (Alburnus alburnus) in pelagic water during the days of worst water quality, confirming that bleak is more tolerant than roach (Rutilus rutilus) to poor water quality and a potential good indicator of water pollution. The weight-length relationship (i.e. condition) of roach and bleak also varied significantly during the drawdown following the same tendency in both species, losing and recovering their weight (4.99% in roach and 5.96% in bleak) in only 16 days. The close relationship found between water quality and fish condition demonstrates that fish condition can be a good metric of the well being of fish, even for extreme short-term changes.

In the view of accepted ideas about the preservation of nitrite in freshwater, this short note presents experiments questioning standard laboratories procedures and tries to be a caveat to experimenters looking for sole total nitrite values more than for total nitrate plus nitrite concentrations. To validate an adequate preservation technique for nitrite, we realized a series of three experiments investigating the effect of filtration, freezing and ageing on initial nitrite concentrations found in freshwater samples collected in an agricultural watershed. Experiment results demonstrate no adsorption or dilution of NO₂ ⁻ concentrations during filtration. Nonetheless, we recommend using filtration only when sample turbidity is visible at the eye to avoid any contamination with laboratory materials during manipulations. Furthermore, results also indicate that freezing samples induces a significant decrease of NO₂ ⁻ concentrations whereas the long term storage at 4°C of samples induces a smaller variability on nitrite concentrations. In consequence, we forbid the use of freezing as a preservation technique for nitrite analysis from freshwater samples and rather recommend storage of samples at 4°C for a period of 48 h.

A new approach to vapor phase elemental mercury capture has been explored; this approach exploits an ionic liquid coating layer to oxidize elemental mercury for subsequent immobilization by chelating ligands. The room temperature ionic liquid 1-butyl-1-methyl pyrrolidinium bis(trifluoromethane sulfonyl)imide (P₁₄) was selected for study based on its oxidation potential window, thermal stability, and low vapor pressure. Tests were also completed in which KMnO₄ was added to P₁₄ to form a new ionic liquid, P₁₄-KMnO₄, with a higher oxidation potential. In room-temperature bulk liquid phase capture experiments, 59% of the elemental mercury in the inlet gas was captured using P₁₄ alone; mercury capture using P₁₄-KMnO₄ was quantitative. P₁₄ and P₁₄-KMnO₄ coatings were successfully applied to mesoporous silica substrates and to silica substrates functionalized with mercury chelating ligands. The coating layers were found to be thermally stable up to 300°C. Fixed-bed tests of nonfunctionalized silica coated with P₁₄ showed an elemental mercury uptake of 2.7 mg/g adsorbent at 160°C; at the same temperature, functionalized silica coated with P₁₄-KMnO₄ showed an elemental mercury capacity of at least 7.2 mg/g adsorbent, several times higher than that of activated carbon. The empty bed gas residence time in these tests was 0.04 s. A chelating adsorbent incorporating P₁₄ in the coating layer, may be capable of simultaneous removal of elemental and oxidized mercury from coal combustion flue gases.

Pentachlorophenol (PCP) vertical transportation in soil column during its phototransformation on the soil surface was investigated using a new designed photoreactor. Three kinds of soils were used to study the effect of soil water and soil properties. In air-dried sandy loam, no obvious PCP transportation occurred in the soil profile when PCP was phototransformed on the soil surface. And the average removal of PCP in the whole soil column was close to zero after 48 h irradiation. In the moist sandy loam, PCP in the deeper soil could transport to the soil surface with water evaporation and then be transformed during UV irradiation, thus the average PCP removal in the whole soil column was improved. When the initial water contents are 9.3 and 19.2%, the average PCP removal in the sandy loam after 48 h irradiation accounted to 20.9 and 39.9%, respectively. The improving of PCP removal induced by soil water was limited in the clay and silt soils where PCP transportation was impeded because of their higher adsorption capacity. In the silt soil where the initial water content was 19.7%, not only PCP transportation in the deeper soil but also PCP phototransformation on the surface was inhibited seriously because of the high organic matter content of 18%.

Water resources are threatened globally and declining water quality is primarily due to stormwater, agricultural, urban, and mining runoffs. Steamboat Creek in Nevada is the largest non point source (NPS) of pollution to the Truckee River. Treatment wetlands are a cost-effective and reliable technique to control NPS pollution, therefore, a large-scale wetland along Steamboat Creek has been proposed as a component of a regional watershed restoration plan. This study used ten parallel pilot-scale wetland mesocosms, and tested the effects of drying and rewetting, hydraulic retention time (HRT), and high nitrogen loading on the efficiency of nutrient and total suspended solids (TSS) removal. Drying and rewetting produced noticeable effects on nutrient retention, but the effect was short-lived. During longer HRT period nutrient removal in manipulated mesocosms with an 8 h HRT were higher than controls with a 4 h HRT. Reducing the HRT from 4 h to 30 min further decreased nutrient interception. During increased influent nitrogen loading (9.5 ± 2.4 mg l⁻¹), manipulated mesocosms functioned as sinks for total nitrogen (TN) with removal efficiency increasing from 45 ± 13% to 87 ± 9%. The average change in TN concentration was 9.1 ± 2.2 mg l⁻¹. Drying/rewetting and varying HRT influenced total phosphorus (TP) and TSS similarly, and TP removal was associated with TSS removal. Results can help make decisions regarding wetland construction, management, and operation more effective in order to reduce nutrient loads to the Truckee River.

An investigation was made into a novel system aimed at reducing the impact of highly polluting wastewaters, and based on the combined action of catalytic oxidation and microbial biotechnology. The experimental part incorporated the following three schemes: chemical treatment using Fenton's reaction for a single process (stage 1); biological treatment only (stage 2); and chemical oxidation followed by biological treatment (stage 3). Wastewaters with 2-mercaptobenzothiazole (MBT; 7,200-7,400 mg O₂ l⁻¹) were oxidized by stoichiometric amounts of dilute hydrogen peroxide (35%) in the presence of water soluble iron catalysts, either Fe (II) or Fe (III), at concentrations up to 1% w/w and above. As a result, transformation by chemical means of recalcitrant organics to more easily attackable end-products occurs, that can subsequently undergo conventional or advanced (microflora and biomass dispersed or adhered) biological treatments, with 90% of chemical oxygen demand abatement and 95% of MBT.

The US fleet of coal-fired power plants, with generating capacity of just over 300 GW, is known to be a major source of domestic mercury (Hg) emissions. To address this, in March 2005, the Environmental Protection Agency (EPA) promulgated the Clean Air Mercury Rule (CAMR) to reduce emissions of mercury from these plants. It is generally believed that most of the initial (Phase I) mercury reductions will come as a co-benefit of existing controls used to remove particulate matter (PM), SO₂, and NO X . Deeper reductions in emissions (as required in Phase II of CAMR) may require the installation of mercury-specific control technology. Duct injection of activated carbon sorbents is the mercury-specific control technology that has been most widely studied and has been demonstrated over a wide range of coal types and combustion conditions. The effectiveness of the mercury control options (both “co-benefit control” and “mercury-specific control”) is significantly impacted by site-specific characteristics such as the combustion conditions, the configuration of existing air pollution controls, and the type of coal burned. This paper identifies the role of coal properties and combustion conditions in the capture of mercury by fly ash and injected sorbents.