The contamination status of rivers and their floodplains with inorganic and organic pollutants in central Russia is poorly known. We investigated the concentrations of inorganic (As, Cd, Cu, Hg, Ni, Pb and Zn) and persistent organic pollutants (hexachlorocyclohexane, PCBs, cyclodienes, DDX and other pesticides) in floodplain soils of the Oka River catchment (Russia). The level of contamination was generally lower than in the Elbe River floodplain but in the same range as in other European river systems such as floodplains of the rivers Rhine, Dřevnice and Yachroma. Only soil samples from the periphery of the city of Ryazan (200 km southeast of Moscow) had a higher anthropogenic enrichment of Cd, Cu and Zn which was comparable to the contaminated Elbe River floodplains. These soils also had the largest concentrations of persistent organic pollutants among all samples from the Oka River catchment. Therefore, the need for large-scale remediation seems to be less urgent than in Central European river catchments and mainly restricted to some “hot spot” areas.

The article presents results of a case study in northeastern Germany, where magnetic susceptibility assessment was carried out at grid-wise field measurements. The measurements were clustered into three different depth levels, which represent the humus layer, the transition zone between humus layer and mineral horizon, and the mineral horizon. Taking these three depth levels, a multiple regression-based regionalization approach was applied, testing and using additional environmental parameters derived from geology, topography, and stand type with the aim to develop a comprehensive model for spatial variability of magnetic susceptibility. Spatial variation of magnetic susceptibility was predicted with a high precision by the multiple linear regression models. A slightly differing set of model parameters was selected for the single depth levels. In tendency, magnetic susceptibility values in depth level 6-10 cm were best explained by the distance to Bitterfeld and by soil properties. In depth level 11-15 cm, variables which describe the orographic conditions and stand properties gain in importance. In depth level 21-25 cm, variables indicating soil and site properties disappear completely. Here, aspect and land surface characteristics play a major role together with stand properties. A spatial stratification of the model for a distance of up to 25 km to the former emitters provided a further improvement of the model quality considering the prediction of small-scale variations of magnetic susceptibility.

This study evaluated the impacts of three sugarcane residue management techniques, namely postharvest burning of residue (BR), shredding of residue (SR), and full postharvest retention of residue (RR), on the water quality of surface runoff from February 2006 to September 2007 in Iberia, LA. Total runoff volumes recorded were 58,418, 57,923, and 46,578 L for the BR, SR, and RR treatments, respectively. Except for total Kjeldahl nitrogen (TKN), which was higher for BR than RR or SR, there were no significant differences in total loads of total suspended solids (TSS), total dissolved solids (TDS), biological oxygen demand at 5 days (BOD₅), total phosphorus (TP), nitrate-N, nitrite-N, and sulfate among the three residue management techniques, although the RR treatment generally exported the lowest total loads. Regression analyses on the pollutant load and rainfall event showed that the load exported for each water quality parameter was positively correlated with precipitation, with the BR treatment being more sensitive to rainfall amount than the RR and SR treatments in TSS, TKN, TP, BOD, nitrate, and sulfate exports. Runoff TSS and turbidity were also highly correlated (R ² = 0.95, P < 0.001). The results suggested that the two sugarcane residue retention practices (RR and SR) had limited benefit on improving surface runoff water quality over the BR practice in subtropical region such as Louisiana.

This study is the first to report nitrite occurrence and variability in surface water across an agricultural watershed in the province of Quebec, Canada. Nitrite (NO₂ ⁻) concentrations were monitored across a 2.4 km² watershed during 2 years. Water samples were collected at the outlet from April to November and in three contrasted stream branches (six stations) during three hydrological regimes (summer low water levels, fall recharge, and snowmelt). Our study clearly demonstrates that NO₂ ⁻ levels observed at the outlet are not representative of NO₂ ⁻ variability across the micro-watershed. Surface water collected in cropped areas presents high NO₂ ⁻ concentrations during summer low water levels, often exceeding guidelines for aquatic life, with NO₂ ⁻ means ranging from 0.022 to 0.107 mg N L⁻¹ and maximum value reaching 0.156 mg N L⁻¹. Furthermore, the two stream branches in cropped area have demonstrated significant differences in NO₂ ⁻ concentrations and other water quality parameters. The importance of groundwater discharge to streams in the micro-watershed Bras d'Henri may potentially generate different in-stream sources of NO₂ ⁻ and water quality parameters. However, further studies are essential to determine sources and processes related to in-stream NO₂ ⁻ peaks.

Biodegradation kinetics of 3-chlorophenol (3-CP) were studied in two identical lab scale sequencing batch reactors (SBR) fed with the compound as the sole energy and carbon source and operated at different filling time (1 h for SBR1 and 2 h for SBR2). High removal efficiency was always obtained in both SBRs in the range of feed concentration of 300-960 mg L⁻¹. Increased feed load to 1,200 mg L⁻¹ 3-CP could also be removed in SBR1 despite the presence of inhibition, whereas determined failure of SBR2. Long filling time and high biomass concentration were shown to have beneficial effect on process kinetics since they allowed to avoid substrate concentration peaks at the end of the fill phase. However, longer filling time (in the present case higher than 1 h) did not allow to select and enrich robust microbial population. The Haldane equation well fitted the kinetic test data measured in the presence of inhibition, i.e., at 960 and 1,200 mg L⁻¹ 3-CP in SBR1.

This work describes the evolution of NO₂ and O₃ levels from January to December of 2007, covering the four seasonal periods in the urban air of Ciudad Real in the central-southern Spain. The measurements were carried out by means of passive samplers (Radiello® samplers). Eleven samples were collected weekly, placed at different monitoring site locations. The data indicate that the mean levels obtained during this period for O₃ and NO₂ were 38.5 ± 3.5 and 20.8 ± 3.8 μg/m³, respectively. These measurements were compared with other studies in Ciudad Real. Meteorological conditions (temperature, pressure, humidity relative, wind speed and direction) were also investigated.

In this paper, the effect of nitrogen addition on the aerobic bioremediation of a diesel-contaminated soil was studied. Soil was artificially contaminated with diesel at an initial 2% concentration (on a dry soil basis). Nitrogen was added as NH₄Cl in a single load at the start of the experiment at concentration levels of 0, 100, 250, 500, 1,000, and 2,000 mg N/dry kg soil, and uncontaminated and unamended soil O₂ consumptions were studied. Diesel degradation was indirectly studied via measurements of O₂ consumption and CO₂ production, using manometric respirometers. Results showed that the 250 mg N/dry kg concentration resulted in the highest O₂ consumption among all runs, whereas O₂ consumption was reduced by N additions greater than 500 mg N/dry kg. Zero to 0.6 order degradation kinetics appeared to prevail, as was calculated via the oxygen consumption rates. A theoretical biochemical reaction for diesel degradation was developed, based on measurement of the final diesel concentration in one of the runs. According to the stoichiometry, the optimal N requirements to allow complete diesel degradation should be approximately 0.15 g N/g diesel degraded or 1,400 mg N/dry kg of soil, based on the initial diesel concentration used in this study. This implies that N should be added in incremental loads.

Alkanolamines in the wastewater from gas treating plants are not readily biodegradable. In this work, we have investigated the effectiveness of the Fenton's reagent (H₂O₂-Fe²⁺) to treat monoethanolamine (MEA) as a model compound in simulated wastewater. Degradation studies were carried out in a jacketed glass reactor. The effects of concentrations of ferrous sulfate, hydrogen peroxide, and the pH of a solution on the rate of reaction were determined. A pH of 3 was found to be the optimum. The degradation reaction proceeds very fast at the beginning but slows down significantly at a longer time. A larger fractional degradation of the organics in solution was observed if the initial chemical oxygen demand (COD) of the feed solution was high. Gradual addition of H₂O₂ to the reaction mixture increased the COD removal by about 60% compared to one-time addition of the reagent at the beginning of the process. A rate equation for mineralization of the amine was developed on the basis of a simplified mechanistic model, and the lumped value of the rate constant for COD removal was determined. A partially degraded MEA solution as well as “pure” MEA was subjected to biological oxidation by activated sludge. The former substrate degraded much faster. The degradation rate and biomass generation data could be fitted by the Monod kinetic equations.

Linear anionic polyacrylamide (LA-PAM) is being considered as a soil amendment to reduce seepage and infiltration in unlined earthen canals. While polyacrylamides have been extensively used for potable water treatment, dewatering sewage sludge, coal and mine processing, paper manufacturing, and agriculture, little is known about its ecological impact to aquatic ecosystems. Acute toxicity (LC₅₀, 24 and 48 h) and chronic exposure tests (limited and continuous exposures) were conducted on Daphnia magna. In the chronic limited exposure experiments, Daphnia were exposed to LA-PAM for only 24 h whereas for the chronic continuous exposure the concentrations of 0, 0.5, 1, 5, 10, and 100 mg/L were tested and the endpoints of growth, onset to reproduction, fecundity, and mortality were measured for the duration of 32 days. There was no significant difference among the chronic, limitedly exposed organisms. The acute toxicity for LA-PAM was measured at 100, 150, 200, 250, and 300 mg/L. The acute test showed that the LC₅₀ for LA-PAM was at 152 mg/L. Overall in the chronic, continuous exposure test, D. magna was negatively impacted by LA-PAM at levels as low as 1 mg/L. Growth was reduced by 37% and 89% at 1 and 100 mg/L, respectively. Fecundity and onset to reproduction was impaired at 10 and 100 mg/L. Kinematic viscosity ranged from 0.98 cSt at 1 mg/L to 2.9 at 100 mg/L. At these levels, mechanical and physiological impairments due to the viscous properties of LA-PAM are the proposed mechanisms of reduction in the life history traits of D. magna.

Background, aim and scope The applicability of the Whole Effluent Assessment concept for the proof of compliance with the “best available techniques” has been analysed with paper mill wastewater from Germany by considering its persistency (P), potentially bio-accumulative substances (B) and toxicity (T). Materials and methods Twenty wastewater samples from 13 paper mills using different types of cellulose fibres as raw materials have been tested in DIN or ISO standardised bioassays: the algae, daphnia, luminescent bacteria, duckweed (Lemna), fish-egg and umu tests with lowest ineffective dilution (LID) as test result. The potentially bio-accumulative substances (PBS) were determined by solid-phase microextraction and referred to the reference compound 2,3-dimethylnaphthalene. Usually, a primary chemical-physical treatment of the wastewater was followed by a single or multi-stage biological treatment. One indirectly discharged wastewater sample was pre-treated biologically in the Zahn-Wellens test before determining its ecotoxicity. Results No toxicity or genotoxicity at all was detected in the acute daphnia and fish egg as well as the umu assay. In the luminescent bacteria test, moderate toxicity (up to LIDlb = 6) was observed. Wastewater of four paper mills demonstrated elevated or high algae toxicity (up to LIDA = 128), which was in line with the results of the Lemna test, which mostly was less sensitive than the algae test (up to LIDDW = 8). One indirectly discharged wastewater sample was biodegraded in the Zahn-Wellens test by 96% and was not toxic after this treatment. Low levels of PBS have been detected (median 3.27 mmol L⁻¹). The colouration of the wastewater samples in the visible band did not correlate with algae toxicity and thus is not considered as its primary origin. Further analysis with a partial wastewater stream from thermomechanically produced groundwood pulp (TMP) revealed no algae or luminescent bacteria toxicity after pre-treatment of the sample in the Zahn-Wellens test (chemical oxygen demand elimination 85% in 7 days). Thus, the algae toxicity of the respective paper mill cannot be explained with the TMP partial stream; presumably other raw materials such as biocides might be the source of algae toxicity. Discussion Comparative data from wastewater surveillance of authorities confirmed the range of ecotoxicity observed in the study. Wastewater from paper mills generally has no or a moderate ecotoxicity (median LID 1 and 2) while the maximum LID values, especially for the algae and daphnia tests, are considerably elevated (LIDA up to 128, LIDD up to 48). Conclusions Wastewater from paper mills generally is low to moderately ecotoxic to aquatic organisms in acute toxicity tests. Some samples show effects in the chronic algae growth inhibition test which cannot be explained exclusively with colouration of the samples. The origin of elevated algae ecotoxicity could not be determined. In the algae test, often flat dose-response relationships and growth promotion at higher dilution factors have been observed, indicating that several effects are overlapping. Recommendations and perspectives At least one bioassay should be included in routine wastewater control of paper mills because the paper manufacturing industry is among the most water consuming. Although the algae test was the most sensitive test, it might not be the most appropriate test because of the complex relationship of colouration and inhibition and the smooth dose-effect relationship or even promotion of algae growth often observed. The Lemna test would be a suitable method which also detects inhibitors of photosynthesis and is not disturbed by wastewater colouration.