The evolution of microbial communities with increasing carbon tetrachloride concentrations was studied in two anaerobic columns containing sand and two different clay soils, one of which contained high levels of iron. Microbial communities were characterized through analysis of column effluents with denaturing gradient gel electrophoresis and quantitative polymerase chain reaction for archaea and eubacteria as inlet carbon tetrachloride concentrations were increased from 0.8 to 29 μM. Inhibition of microbial activity was observed in both columns, and was associated with the accumulation of chloroform at concentrations of 0.2 to 0.4 μM as inlet CT concentrations were increased to 2.4-3.0 μM in the low-iron clay column and approximately 16 μM in the iron rich clay column. Inhibition was indicated by decreasing rates of methanol and carbon tetrachloride degradation, decreases in effluent levels of DNA, and shifts in microbial communities of the columns. Even with the inhibition observed, in the iron-rich clay column CT degradation continued to the end of the study with inlet CT concentrations of 29 μM, in contrast to the low-iron clay column in which minimal CT degradation occurred once CT inlet concentrations exceeded 3 μM. The greater capacity for CT degradation in the column containing the iron-rich clay was hypothesized to be the result of reaction with biogenic ferrous iron produced by biological dissimilatory iron reduction.

The contamination of soils and waters by dye-containing effluents is of environmental concern. Due to the increasing awareness and concern of the global community over the discharge of synthetic dyes into the environment and their persistence there, much attention has been focused on the remediation of these pollutants. Among the current pollution control technologies, biodegradation of synthetic dyes by different microbes is emerging as an effective and promising approach. The bioremediation potentials of many microbes for synthetic dyes have been demonstrated and those of others to be explored in future. The biodegradation of synthetic dyes is an economic, effective, biofriendly, and environmentally benign process. Bioremediation of xenobiotics including synthetic dyes by different microbes will hopefully prove a green solution to the problem of environmental soil and water pollution in future. This review paper discusses comprehensively the science and arts of biodegradation of synthetic dyes.

Copper biosorption onto chemically modified biomass of marine alga Sargassum filipendula was investigated in a batch reactor and a fixed bed column. Experiments were carried out in the batch reactor to obtain kinetic and equilibrium data and to assess the copper desorption efficiency of different eluent solutions. The pseudo-first-order, pseudo-second-order, and Langmuir kinetic models were used to correlate kinetic data. The experimental data fitted well to the pseudo first order and Langmuir kinetic models. Langmuir and Freundlich models were applied to describe the equilibrium data obtained at a fixed temperature of 30°C and at pH values of 3.0, 4.0, 5.0, and 6.0. The maximum capacities of copper biosorption onto the algal biomass were 1.43, 1.59, 2.40, and 2.36 mequiv./g at pH 3.0, 4.0, 5.0, and 6.0, respectively. The efficiencies of two eluent solutions (calcium chloride and hydrochloric acid) for copper removal from the biomass were evaluated at different concentrations (0.1, 0.2, 0.5, and 1.0 mol/L). The efficiencies of the calcium chloride solutions varied from 1% to 14%, while efficiencies varying from 95% to 99% were obtained when hydrochloric acid solutions were applied. Three adsorption/desorption cycles were carried out in a fixed bed column using 0.1 mol/L hydrochloric acid as eluent solution. The results showed that an increase in the number of cycles led to a reduction in the adsorption capacity of the alga. The desorbed copper fraction presented no significant variation, remaining around 63% in the three adsorption/desorption cycles.

An exploratory survey of the mercury content of some common California biomass feedstocks shows that the concentrations are well below EPA toxicity levels with representative feedstock concentrations of 20 ppb for rice straw, 28 ppb for wheat straw, and 32 ppb for whole-tree wood chips. The temporal variability for rice straw (17-20 ppb) is near the analytical uncertainty (∼2 ppb). Saline-irrigated feedstock does not contain greatly higher mercury contents (17-38 ppb) compared to normally irrigated feedstock. Water leaching has likewise no detectable effects on mercury mobility, despite an up to 30% increase in the Hg concentrations attributable to mass losses during leaching. Combustion at temperatures of at least 575°C results in complete volatilization of mercury leaving solid ash and slag residuals with mercury contents at or near the lower limit of detection (5 ppb). The mercury strongly concentrated in fly ash can reach concentrations up to 40 times (<1,166 ppb) the corresponding fuel concentrations.

The purpose of this study was to understand the dynamic conditions of soil/organic mixtures in order to contribute to the study of remediation processes at hydrocarbon spill sites. Induced polarization (IP) and physical, chemical, and microbiological parameters for uncontaminated and artificially contaminated soil samples with diesel oil were evaluated under controlled conditions (constant temperature and soil moisture) during a period of 12 months. In contaminated samples, the resistivity and IP parameters (chargeability and polarizability) decreased during 8 months and remained relatively stable between 8 and 12 months. The observed reduction on resistivity and IP parameters was related to the increase on the granular aggregation of the soil and a decrease on total porosity, caused by diesel-degrading microorganisms. The behavior of the IP parameters observed after 8 months can be explained by a reduction in the microbial activity and, consequently, a decrease of the degradation rate of diesel. In the studied loamy soil with high content of organic matter (96.16 g/kg), the results demonstrate that IP time domain measurements can be used in the evaluation of the evolution of the hydrocarbon degradation even when the concentration is not very high.

The goal of this work was to investigate the occurrence of emerging contaminants in drinking water of the city of Campinas, Brazil. Tap water samples were analyzed using SPE-GC-MS for 11 contaminants of recent environmental concern. Six emerging contaminants (stigmasterol, cholesterol, bisphenol A, caffeine, estrone, and 17β-estradiol) were found in the samples. The latter two were detected only during the dry season, with concentrations below quantification limits. Stigmasterol showed the highest average concentration (0.34 ± 0.13 µg L⁻¹), followed by cholesterol (0.27 ± 0.07 µg L⁻¹), caffeine (0.22 ± 0.06 µg L⁻¹), and bisphenol A (0.16 ± 0.03 µg L⁻¹). In Campinas, where surface drinking water supplies receive large amounts of raw sewage inputs, the emerging contaminants levels in drinking waters were higher than median values compiled for drinking and finished water samples around the world.

We investigated concentrations of dissolved organic carbon (DOC) in throughfall and soil solutions at 5, 15 and 40-cm depth in 16 Norway spruce and two Scots pine plots throughout Norway between 1996 and 2006. Average DOC concentrations ranged from 2.3 to 23.1 mg/l and from 1.1 to 53.5 mg/l in throughfall water and soil solutions, respectively. Concentrations of DOC in throughfall and soil waters varied seasonally at most plots with peaks in the growing season. By contrast to recently reported positive long-term trends in DOC concentrations in surface waters between 1986 and 2003, soil water data from 1996 to 2006 showed largely negative trends in DOC concentrations and no significant trends in throughfall. However, regression analysis for individual sites, particularly at 5- and 15-cm soil depths, showed that DOC concentrations in soil water were significantly and negatively related to non-marine sulphate (SO₄) and chloride (Cl⁻). The lack of a long-term increase in DOC in soil water in the period May 1996-December 2006 may be due to the relatively small changes in the deposition of SO₄ and Cl⁻ in this period.

Mining wastes may pose risk nearby urban and agricultural areas. We investigated a lettuce crop land close to a former capped mine tailing in order to determinate the metal uptake by crops. Soil plot sampling design within the crop area and two transects along the tailing were performed. In addition, lettuces (root and leaves) were analyzed after transplant and harvest. The results showed a pH of around 7-8 for all the soil samples. Total metal concentrations were as follows: 190-510 mg kg⁻¹ Pb, 13-21 mg kg⁻¹ Cu, and 210-910 mg kg⁻¹ Zn. Diethylene triamine pentaacetic acid-extractable Pb was around 18% of the total Pb in some samples. Transects along the base and on the plateau of the tailing showed high metal concentrations of Pb (up to 5,800 mg kg⁻¹) and Zn (up to 4,500 mg kg⁻¹), indicating that capping layer had been eroded. Lettuce leaves showed Pb concentrations within standard for human health (<0.3 mg kg⁻¹ in fresh weight). For essential micronutrients such as Cu and Zn, leaves had optimal content (10-28 mg kg⁻¹ Cu, 60-85 mg kg⁻¹ Zn). A continued monitoring in metal uptake is needed in crop lands close to mining wastes in order to prevent risks in food safety. Capped tailings must be monitored and rehabilitation works performed from time to time.

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.

A set of ten heavy metals (Al, As, Cd, Cr, Cu, Hg, Ni, Pb, V, and Zn) was investigated in surface sediments (0-5 cm) collected in 21 sites of the Gulf of Trieste, Northern Adriatic Sea (Italy). The aim of this work was to obtain a preliminary assessment about the levels and spatial distribution of these selected elements. Ancillary parameters such as grain size, total organic carbon, and total nitrogen were also determined. The enrichment factor was calculated to discriminate if a natural condition or a status of anthropogenic contamination occurs. In addition, a set of sediment quality guidelines, mean effect low range and effect medium range quotients, was also applied in order to predict the probability of adverse biological effects on the benthic community.