Background, aim, and scope Aquatic microcontaminants (MCs) comprise diverse chemical classes, such as pesticides, biocides, pharmaceuticals, consumer products, and industrial chemicals. For water pollution control and the evaluation of water protection measures, it is crucial to screen for MCs. However, the selection and prioritization of which MCs to screen for is rather difficult and complex. Existing methods usually are strongly limited because of a lack of screening regulations or unavailability of required data. Method and models Here, we present a simple exposure-based methodology that provides a systematic overview of a broad range of MCs according to their potential to occur in the water phase of surface waters. The method requires input of publicly available data only. Missing data are estimated with quantitative structure-property relationships. The presented substance categorization methodology is based on the chemicals' distribution behavior between different environmental media, degradation data, and input dynamics. Results Seven different exposure categories are distinguished based on different compound properties and input dynamics. Ranking the defined exposure categories based on a chemical's potential to occur in the water phase of surface waters, exposure categories I and II contain chemicals with a very high potential, categories III and IV contain chemicals with a high potential, and categories V and VI contain chemicals with a moderate to low potential. Chemicals in category VII are not evaluated because of a lack of data. We illustrate and evaluate the methodology on the example of MCs in Swiss surface waters. Furthermore, a categorized list containing potentially water-relevant chemicals is provided. Discussion Chemicals of categories I and III continuously enter surface waters and are thus likely to show relatively steady concentrations. Therefore, they are best suited for water monitoring programs requiring a relatively low sampling effort. Chemicals in categories II and IV have complex input dynamics. They are consequently more difficult to monitor. However, they should be considered if an overall picture is needed that includes contaminants from diffuse sources. Conclusions The presented methodology supports compound selection for (a) water quality guidance, (b) monitoring programs, and (c) further research on the chemical's ecotoxicology. The results from the developed categorization procedure are supported by data on consumption and observed concentrations in Swiss surface waters. The presented methodology is a tool to preselect potential hazardous substances based on exposure-based criteria for policy guidance and monitoring programs and a first important step for a detailed risk assessment for potential microcontaminants.

Purpose The purpose of this paper is to assess fatal cancer risk after external and internal (inhalation and ingestion) exposure from natural radionuclides in soil like ²³⁸U, ²³²Th, ⁴⁰K, and ²²⁶Ra on the territory of Bela Crkva, Serbia. Although receiving doses are low from sources like natural radionuclides in soil, because of stochastic effects of ionizing radiation, risk for developing cancer exists and can be quantified. Methods Concentrations of radionuclides from 80 soil samples are measured using HPGe detector. Fatal cancer risk is assessed from calculated ambient dose rate in the target organs of body due to external and internal exposure. Monte Carlo simulations are used to obtain conversion factors which are required to calculate absorbed dose rate in target organs. Results and discussion Assessed cancer risk for ²³⁸U in the case of both inhalation and ingestion exposure is from 1.11 × 10⁻⁶ to 24 × 10⁻⁶ for minimal and maximal activity in soil samples, from 1.02 × 10⁻⁶ to 23.3 × 10⁻⁶ for exposure to ²²⁶Ra, from 1.89 × 10⁻⁶ to 50.3 × 10⁻⁶ for exposure to ²³²Th, and from 0.265 × 10⁻⁶ to 9.83 × 10⁻⁶ for exposure to ⁴⁰K. Overall risk from ⁴⁰K as external and internal source is from 0.8 × 10⁻⁶ to 31.9 × 10⁻⁶. Calculated cancer risks from both inhalation and ingestion exposure could be related to all tissues that are on the way of distribution of particles within the body but especially to deposition sites in the body. Conclusion Assessed risks for fatal cancer development from inhaled and ingested natural radionuclides originating in soil are not increased.

Background, aim, and scope Zinc is an essential micronutrient element but its concentrations found in contaminated soils frequently exceed those required by the plant and soil organisms, and thus create danger to animal and human health. Phytoremediation is a technique, often employed in remediation of contaminated soils, which aims to remove heavy metals or other contaminants from soils or waters using plants. Arabidopsis (A.) halleri ssp. gemmifera is a plant recently found to be grown vigorously in heavy metal contaminated areas of Japan and it contained remarkably high amount of heavy metals in its shoots. However, the magnitude of Zn accumulation and tolerance in A. halleri ssp. gemmifera need to be investigated for its use as a phytoremediation plant. Materials and methods A. halleri ssp. gemmifera was grown for 3 weeks into half-strength nutrient solution with Zn (as ZnSO₄) levels ranging from 0.2 to 2,000 µM. The harvested plants were separated into shoots and roots, dried in the oven, and ground. The plant tissue was digested with nitric-perchloric acid, and the Zn concentration in the digested solution was measured by atomic absorption spectrophotometer. Results and discussion The results showed no reduction in shoot and root dry weight when plants were grown at 0.2 to 2,000 µM Zn in the solution. The highest Zn concentration measured in the shoots was 26,400 mg kg⁻¹ at 1,000 µM Zn, while in the roots, it was 71,000 mg kg⁻¹ at 2,000 µM Zn treatment. Similar to the Zn concentration in plant parts, maximum Zn accumulation of 62 mg plant⁻¹ in the shoots and 22 mg plant⁻¹ in the roots was obtained at 1,000 and 2,000 µM Zn in the solution. The percentage of Zn translocation in shoot varied from 69% to 90% of the total Zn, indicating that the shoot was the major sink of Zn accumulation in this plant. Conclusions The results of this study indicate that the growth of A. halleri ssp. gemmifera was not affected by the Zn level of up to 2,000 µM in the nutrient solution. The concentration of Zn found in shoot indicated that A. halleri ssp. gemmifera has an extraordinary ability to tolerate and accumulate Zn and hence a good candidate for the phytoremediation of Zn-polluted soil. Recommendations and outlook Based on the results presented in this study and earlier hydroponics, and field study, A. halleri ssp. gemmifera seems to be a potential heavy metals hyperaccumulator, and could be recommended to use for phytoremediation of Cd- and Zn-contaminated soils.

Background, aim, and scope Transport of bacteria through natural porous media is an issue of increasing concern arising in several very important environmental processes. These include the percolation of bacteria from fecal waste to drinking water reservoirs, thus leading to a risk for human health, or the bioremediation of contaminated soils in which the bacteria are expected to travel long distances underground in order to reach contaminated areas and degrade chemicals originating from accidental spills. An understanding of bacterial retention and transport mechanisms in porous media would be of great help in the development of models able to predict the distance covered by bacterial suspensions in these situations. Materials and methods Experiments were carried out preparing columns filled of soil and sand, introducing bacteria culture (Escherichia coli, Pseudomona putida, and Listeria innocua) solutions by the top of the column. Breakthrough curves were obtained to see the transport of the bacteria in the column. Results The transport of different bacteria in the two soils aimed at establishing the relative importance of straining in different conditions. This has enabled us to obtain certain parameters, such as the sticking coefficients derived from the filtration theory or bacterial recoveries after multi-step elution, which aid our understanding of how bacteria are retained by mechanisms different to those usually included in the physico-chemical filtration theory. Discussion Several indicators may be used to determine the degree of relevance of straining as a mechanism acting during bacterial transport through porous media. Usually, in natural media, neither straining nor physico-chemical filtration is the sole mechanism contributing to bacterial retention. The retention of bacteria by straining mechanisms can be assessed by means of elution profiles under varying conditions. The inversion of flow in our experiments gave rise to secondary elution peaks, probably originating from bacteria retained in narrow pores Conclusions According to experimental observations, straining was shown to contribute highly to bacterial retention in all the soils tested, in particular in the soils with a broader grain size distribution and more irregular shape. In both media, an increase in ionic strength did not lead to significant differences in bacterial retention, possibly due to the lack of relevance of ionic repulsion as a barrier to physico-chemical attachment of particles Recommendation and perspectives The study of bacteria transport in natural soil is an important step in the development of decontamination processes. The importance of the straining in the transport process has been revealed in the work carried out in this paper.

Background, aim, and scope Atmospheric pollution is a worldwide problem. Exposure to atmospheric pollutants causes toxic cellular effects. One of the mechanisms of toxicity by these pollutants is the promotion of oxidative stress. Several signaling pathways control cellular redox homeostasis. In this respect, nuclear factor erythroid 2-related factor 2 (Nrf2) is a crucial transcription factor in the cell's response to oxidative stress. Main features In cellular animal models, exposure to atmospheric pollutants activates Nrf2, attenuating its toxic and even its carcinogenic effects. Therefore, we have reviewed the scientific literature in order to indicate that air pollutants, such as particulate matter, polycyclic aromatic hydrocarbons, and gaseous matter, are Nrf2 pathway inductors, triggering self-defense through the establishment of proinflammatory and antioxidant responses. Results and discussion Exposure to reactive molecules as atmospheric pollutants causes the activation of Nrf2 and the subsequent regulation of the expression of cytoprotective and detoxifying enzymes, as well as antioxidants. Moreover, induction of Nrf2 prior to exposure reduces the harmful effects of pollutants. The present article discusses the protective role of the Nrf2 pathway against different atmospheric pollutant insults. Conclusions Nrf2 regulates the expression of numerous cytoprotective genes that function to detoxify reactive species produced during atmospheric pollutant metabolic reactions. From the papers highlighted in this review, we conclude that Nrf2 has an important role in the defense against atmospheric pollutant-induced toxicity. Perspectives Further studies are needed to understand the signaling events that turn on the system in response to atmospheric pollutant stress. This could allow for the possibility of targeting the pathway for prevention benefits in the near future.

Background, aim, and scope Riverine retention decreases loads of nitrogen (N) and phosphorus (P) in running water. It is an important process in nutrient cycling in watersheds. However, temporal riverine nutrient retention capacity varies due to changes in hydrological, ecological, and nutrient inputs into the watershed. Quantitative information of seasonal riverine N and P retention is critical for developing strategies to combat diffuse source pollution and eutrophication in riverine and coastal systems. This study examined seasonal variation of riverine total N (TN) and total P (TP) retention in the ChangLe River, an agricultural drainage river in east China. Methods Water quality, hydrological parameters, and hydrophyte coverage were monitored along the ChangLe River monthly during 2004-2006. Nutrient export loads (including chemical fertilizer, livestock, and domestic sources) entering the river from the catchment area were computed using an export coefficient model based on estimated nutrient sources. Riverine TN and TP retention loads (RNRL and RPRL) were estimated using mass balance calculations. Temporal variations in riverine nutrient retention were analyzed statistically. Results and discussion Estimated annual riverine retention loads ranged from 1,538 to 2,127 t year⁻¹ for RNRL and from 79.4 to 90.4 t year⁻¹ for RPRL. Monthly retention loads varied from 6.4 to 300.8 t month⁻¹ for RNRL and from 1.4 to 15.3 t month⁻¹ for RPRL. Both RNRL and RPRL increased with river flow, water temperature, hydrophyte coverage, monthly sunshine hours, and total TN and TP inputs. Dissolved oxygen concentration and the pH level of the river water decreased with RNRL and RPRL. Riverine nutrient retention ratios (retention as a percentage of total input) were only related to hydrophyte coverage and monthly sunshine hours. Monthly variations in RNRL and RPRL were functions of TN and TP loads. Conclusions Riverine nutrient retention capacity varied with environmental conditions. Annual RNRL and RPRL accounted for 30.3-48.3% and 52.5-71.2%, respectively, of total input TN and TP loads in the ChangLe River. Monthly riverine retention ratios were 3.5-88.7% for TN and 20.5-92.6% for TP. Hydrophyte growth and coverage on the river bed is the main cause for seasonal variation in riverine nutrient retention capacity. The total input TN and TP loads were the best indicators of RNRL and RPRL, respectively. Recommendations and perspectives High riverine nutrient retention capacity during summer due to hydrophytic growth is favorable to the avoidance of algal bloom in both river systems and coastal water in southeast China. Policies should be developed to strictly control nutrient applications on agricultural lands. Strategies for promoting hydrophyte growth in rivers are desirable for water quality management.

Global warming has become a source of awareness regarding the potential deleterious effects of extreme abiotic factors (e.g., temperature, dissolved oxygen (DO) levels) and also their influence on chemicals toxicity. In this work, we studied the combined effects of nickel and temperature (low and high levels) and nickel and low levels of DO to Daphnia magna, and concentration addition and independent action concepts as well as their deviations for synergism/antagonism, dose ratio and dose level dependency, were applied to survival and feeding rate data. Nickel single exposure showed an LC₅₀ value for 48 h of 7.36 mg l⁻¹ and an EC₅₀ value for feeding impairment at 2.41 mg l⁻¹. In the acute exposures to high and low temperatures, 50% of mortality was observed, respectively, at 30.7°C and 4.2°C whereas 50% reduction on the feeding activity was recorded at 22.6°C and 16.0°C. Relatively to low DO levels, a LC₅₀ value for 48 h of 0.5 mg l⁻¹ was obtained; feeding activity EC₅₀ value was 2 mg l⁻¹. On acute combined experiments, antagonism was observed for the combination of nickel and extreme temperatures, whereas a synergistic behaviour was observed in the combined exposure of nickel and low DO levels. At sublethal levels, nickel showed to be the main inducer of toxicity at high and low temperatures but not at low levels of dissolved oxygen. Toxicokinetics and toxicodynamics modelling studies should be made in the future to understand the toxicological pathways involved on complex combinations of stressors and to validate any conclusions.

Background, aim, and scope Primitive wax refining techniques had resulted in almost 50,000 tonnes of acidic oily sludge (pH 1-3) being accumulated inside the Digboi refinery premises in Assam state, northeast India. A novel yeast species Candida digboiensis TERI ASN6 was obtained that could degrade the acidic petroleum hydrocarbons at pH 3 under laboratory conditions. The aim of this study was to evaluate the degradation potential of this strain under laboratory and field conditions. Materials and methods The ability of TERI ASN6 to degrade the hydrocarbons found in the acidic oily sludge was established by gravimetry and gas chromatography-mass spectroscopy. Following this, a feasibility study was done, on site, to study various treatments for the remediation of the acidic sludge. Among the treatments, the application of C. digboiensis TERI ASN6 with nutrients showed the highest degradation of the acidic oily sludge. This treatment was then selected for the full-scale bioremediation study conducted on site, inside the refinery premises. Results The novel yeast strain TERI ASN6 could degrade 40 mg of eicosane in 50 ml of minimal salts medium in 10 days and 72% of heneicosane in 192 h at pH 3. The degradation of alkanes yielded monocarboxylic acid intermediates while the polycyclic aromatic hydrocarbon pyrene found in the acidic oily sludge yielded the oxygenated intermediate pyrenol. In the feasibility study, the application of TERI ASN6 with nutrients showed a reduction of solvent extractable total petroleum hydrocarbon (TPH) from 160 to 28.81 g kg⁻¹ soil as compared to a TPH reduction from 183.85 to 151.10 g kg⁻¹ soil in the untreated control in 135 days. The full-scale bioremediation study in a 3,280-m² area in the refinery showed a reduction of TPH from 184.06 to 7.96 g kg⁻¹ soil in 175 days. Discussion Degradation of petroleum hydrocarbons by microbes is a well-known phenomenon, but most microbes are unable to withstand the low pH conditions found in Digboi refinery. The strain C. digboiensis could efficiently degrade the acidic oily sludge on site because of its robust nature, probably acquired by prolonged exposure to the contaminants. Conclusions This study establishes the potential of novel yeast strain to bioremediate hydrocarbons at low pH under field conditions. Recommendations and perspectives Acidic oily sludge is a potential environmental hazard. The components of the oily sludge are toxic and carcinogenic, and the acidity of the sludge further increases this problem. These results establish that the novel yeast strain C. digboiensis was able to degrade hydrocarbons at low pH and can therefore be used for bioremediating soils that have been contaminated by acidic hydrocarbon wastes generated by other methods as well.

Background, aim, and scope Acrylate and methacrylate esters are α,β-unsaturated esters that contain vinyl groups directly attached to the carbonyl carbon (CH₂=CHCOO- and CH₂=CCH₃COO-, respectively) and are widely used in the polymer plastic and resin production. Rate coefficients for Cl reactions for most of the unsaturated esters have not been previously determined, and a good understanding is needed of all the atmospheric oxidation processes of these compounds in order to determine lifetimes in the atmosphere and to evaluate the impact of these reactions on the formation of photo-oxidants and therefore on health and environment. Materials and methods The relative rate technique has been used to obtain rate coefficients for the reactions between the Cl atom and a series of unsaturated esters. The experiments have been carried out in a static Teflon reactor at room temperature and atmospheric pressure (N₂ as bath gas) using gas chromatography with flame ionization detection as detection system. Results The following rate coefficients are obtained (in cubic meter per molecule per second): methyl acrylate + Cl = 1.71 ± 0.13 × 10⁻¹⁰; methyl methacrylate + Cl = 2.30 ± 0.18 × 10⁻¹⁰; ethyl acrylate + Cl = 1.82 ± 0.13 × 10⁻¹⁰; ethyl methacrylate + Cl = 2.71 ± 0.21 × 10⁻¹⁰; butyl acrylate + Cl = 2.94 ± 0.23 × 10⁻¹⁰; butyl methacrylate + Cl = 3.83 ± 0.30 × 10⁻¹⁰; methyl 3-methyl acrylate + Cl = 2.21 ± 0.17 × 10⁻¹⁰; and methyl 3,3-dimethyl acrylate + Cl = 3.58 ± 0.28 × 10⁻¹⁰. Discussion Rate coefficients calculated for Cl reactions are around one order of magnitude higher than OH ones. The effect in the reactivity of increased substitution at the carbon-carbon double bond is analyzed and also the effect of the identity of the alkyl group R in the -C(O)OR. Atmospheric lifetimes of the compounds against the attack by the major oxidants are estimated and the atmospheric implications are discussed. Conclusions The dominant atmospheric loss process for acrylate esters is clearly their daytime reaction with the hydroxyl radical. However, in coastal areas and in the marine boundary layer and in some industrial zones, Cl-atom-initiated degradation of the unsaturated esters considered here can be a significant if not dominant homogeneous loss process. Recommendations and perspectives Product analysis should be necessary in order to evaluate the real environmental impact of these reactions. OH and ozone reactions of most of the considered compounds have already been studied and products determined, but kinetic and products information for NO₃ radical reactions is especially scarce.

BACKGROUND, AIM, AND SCOPE: This study focuses on the factors that affect trihalomethane (THMs) formation when dissolved organic matter (DOM) fractions (colloidal, hydrophobic, and transphilic fractions) in aqueous solutions were disinfected with chlorine. MATERIALS AND METHODS: DOM fractions were isolated and fractionated from filtered lake water and were characterized by elemental analysis. The investigation involved a screening Placket-Burman factorial analysis design of five factors (DOM concentration, chlorine dose, temperature, pH, and bromide concentration) and a Box-Behnken design for a detailed assessment of the three most important factor effects (DOM concentration, chlorine dose, and temperature). RESULTS: The results showed that colloidal fraction has a relatively low contribution to THM formation; transphilic fraction was responsible for about 50% of the chloroform generation, and the hydrophobic fraction was the most important to the brominated THM formation. DISCUSSION: When colloidal and hydrophobic fraction solutions were disinfected, the most significant factors were the following: higher DOM fraction concentration led to higher THM concentration, an increase of pH corresponded to higher concentration levels of chloroform and reduced bromoform, higher levels of chlorine dose and temperature produced a rise in the total THM formation, especially of the chlorinated THMs; higher bromide concentration generates higher concentrations of brominated THMs. Moreover, linear models were implemented and response surface plots were obtained for the four THM concentrations and their total sum in the disinfection solution as a function of the DOM concentration, chlorine dose, and temperature. Overall, results indicated that THM formation models were very complex due to individual factor effects and significant interactions among the factors. CONCLUSIONS: In order to reduce the concentration of THMs in drinking water, DOM concentrations must be reduced in the water prior to the disinfection. Fractionation of DOM, together with an elemental analysis of the fractions, is important issue in the revealing of the quality and quantity characteristics of DOM. Systematic study composed from DOM fraction investigation and factorial analysis of the responsible parameters in the THM formation reaction can, after an evaluation of the adjustment of the models with the reality, serves well for the evaluation of the spatial and temporal variability in the THM formation in dependence of DOM. However, taking into consideration the natural complexity of DOM, different operations and a strict control of them (like coagulation/flocculation and filtration) has to be used to quantitatively remove DOM from the raw water. RECOMMENDATIONS AND PERSPECTIVES: Assuming that this study represents a local case study, similar experiments can be easily applied and will supply with relevant information every local water treatment plant meeting problems with THM formation. The coagulation/flocculation and the filtration stages are the main mechanisms to remove DOM, particularly the colloidal DOM fraction. With the objective to minimize THMs generation, different unit operation designed to quantitatively remove DOM from water must be optimized.