Spatio-temporal behaviour and mass balance of fluorine in forest soils near an aluminium smelting plant: short- and long-term aspects

With the help of a large number of monitoring sites, the behaviour of F in forested ecosystems of a formerly polluted area (M?hlin and Rheinfelden, Switzerland) could be studied over 30 years. An aluminium smelting plant originated the pollution of this area in the past: however, after the installation of a filtration plant in 1958 the F emissions were reduced and since 1991 almost absent the primary production of aluminium was stopped. The present-day area with elevated F contents (water-soluble F with >20 mg/kg) is restricted to a radius of about 1000 m from the plant. In 1969 this area had a radius of about 3 and 5 km. Between 1969 and 2000 a significant decrease in the soluble F content in the soil was observed together with a substantial decrease of F in the vegetation. The net losses of water-soluble F in the soil were in the range of 35 up to more than 70% of the original concentration and the F losses in the vegetation between 60 up to more than 80%. After the reduction of high F deposition rates the accumulated SOM was decomposed within the observation period 1969-1993. The combined decrease in F and humus led to chain reactions with losses of major elements and a dealumination of clay minerals, i.e. removal of interlayered Al of 2:1 minerals and consequent formation of smectites.     

Distribution and fractionation of phosphorus, cadmium, nickel, and lead in calcareous soils amended with composts

Composts improve organic carbon content and nutrients of calcareous soils but the accumulation and distribution of phosphorus and heavy metals among various fractions in soil may vary under the south Florida conditions. The accumulation of P, Cd, Ni, and Pb with depth and the distribution of water soluble, exchangeable, carbonate, Fe-Mn oxides, organic and residual forms of each element were investigated in soils amended with municipal solid waste (MSW) compost, co-compost and biosolids compost and inorganic fertilizer (as control). Total concentrations of P, Cd, Ni, and Pb were higher in the 0-22 cm soil layers and decreased considerably in the rock layers. These elements were in the decreasing order of P > Pb > Ni > Cd. Amounts of water soluble and exchangeable forms of P, Cd, Ni and Pb were negligible at 0-22 cm soil depths except for Cd in the 10-22 cm depth. Amending calcareous soil with either organic or inorganic amendments rendered phosphorus, nickle and lead in the residual form followed by Fe-Mn oxides form in the 0-10 and 10-22 cm soil layers. Cadmium was predominantly in the Fe-Mn oxides fraction followed by the residual and carbonate forms in both soil layers. A significant positive correlation was found between various organic carbon fractions and organic forms of P, Cd and Pb in the surface soil layer. Soil amended with MSW compost had higher concentration of Cd in the organic fraction whereas, co-compost and MSW compost amended soil had higher concentrations of organic Ni fraction in the 0-10 cm soil layer.     

Degradation of toxaphene in water during anaerobic and aerobic conditions

The degradation of technical toxaphene in water with two kinds of bioreactors operating in sequence was studied. One packed bed reactor was filled with Poraver (foam glass particles) running at anaerobic conditions and one suspended carrier biofilm reactor working aerobically. Chemical oxygen demand (COD), chloride, sulphate, pH, dissolved oxygen, total toxaphene and specific toxaphene isomers were measured. After 6 weeks approx. 87% of the total toxaphene was degraded reaching 98% by week 39. The majority of the conversion took place in the anaerobic reactor. The concentrations of toxaphene isomers with more chlorine substituents decreased more rapidly than for isomers with less chlorine substituents.     

Flood-risk management strategies for an uncertain future: living with Rhine River floods in The Netherlands?

Social pressure on alluvial plains and deltas is large, both from an economic point of view and from a nature conservation point of view. Gradually, flood risks increase with economic development, because the expected damage increases, and with higher dikes, because the flooding depth increases. Global change, changing social desires, but also changing views, require a revision of flood-risk management strategies for the long term. These should be based on resilience as opposed to the resistence strategy of heightening dikes. Resilience strategies for flood-risk management imply that the river is allowed to temporarily flood large areas, whereas the flood damage is minimized by adapting land use. Such strategies are thus based on risk management and 'living with floods' instead of on hazard control. For The Netherlands, one of the most densely populated deltas in the world, alternative resilience strategies have been elaborated and assessed for their hydraulic functioning and 'sustainability criteria'.     

Degradation of 1,1,2,2-tetrachloroethane and accumulation of vinyl chloride in wetland sediment microcosms and in situ porewater: biogeochemical controls and associations with microbial communities

The biodegradation pathways of 1,1,2,2-tetrachloroethane (TeCA) and 1,1,2-trichloroethane (112TCA) and the associated microbial communities in anaerobic wetland sediments were evaluated using concurrent geochemical and genetic analyses over time in laboratory microcosm experiments. Experimental results were compared to in situ porewater data in the wetland to better understand the factors controlling daughter product distributions in a chlorinated solvent plume discharging to a freshwater tidal wetland at Aberdeen Proving Ground, Maryland. Microcosms constructed with wetland sediment from two sites showed little difference in the initial degradation steps of TeCA, which included simultaneous hydrogenolysis to 112TCA and dichloroelimination to 1,2-dichloroethene (12DCE). The microcosms from the two sites showed a substantial difference, however, in the relative dominance of subsequent dichloroelimination of 112TCA. A greater dominance of 112TCA dichloroelimination in microcosms constructed with sediment that was initially iron-reducing and subsequently simultaneously iron-reducing and methanogenic caused approximately twice as much vinyl chloride (VC) production as microcosms constructed with sediment that was methanogenic only throughout the incubation. The microcosms with higher VC production also showed substantially more rapid VC degradation. Field measurements of redox-sensitive constituents, TeCA, and its anaerobic degradation products along flowpaths in the wetland porewater also showed greater production and degradation of VC with concurrent methanogenesis and iron reduction. Molecular fingerprinting indicated that bacterial species [represented by a peak at a fragment size of 198 base pairs (bp) by MnlI digest] are associated with VC production from 112TCA dichloroelimination, whereas methanogens (190 and 307 bp) from the Methanococcales or Methanobacteriales family are associated with VC production from 12DCE hydrogenolysis. Acetate-utilizing methanogens (acetotrophs) appear to be involved in the biodegradation of VC. The relative abundance of Methanosarcinaceae, the only methanogen group with acetotrophic members, doubled in microcosms in which degradation of VC was observed. In addition, molecular analyses using primers specific for known dehalorespiring bacteria in the Dehalococcoides and Desulfuromonas groups showed the presence of these bacteria in microcosm slurry from the site that showed the highest VC production and degradation. Determination of biogeochemical controls and microbial consortia involved in TeCA degradation is leading to a better understanding of the heterogeneity in biodegradation rates and daughter product distribution in the wetland, improving capabilities for developing remediation and monitoring plans.     

Role of alpha-tocopherol and beta-carotene in ameliorating the fenvalerate-induced changes in oxidative stress, hemato-biochemical parameters, and semen quality of male rats

Role of alpha-tocopherol (vitamin E), beta-carotene and/or their combination as antioxidants against the toxicity of fenvalerate on blood hematology, free radicals, biochemical parameters, and semen quality were studied in male rats. Fenvalerate (20 mg/kg BW), vitamin E (100 mg/kg BW), beta-carotene (10 mg/kg BW), and vitamin E plus beta-carotene (100 + 10 mg/kg BW, respectively) were given alone or in combination with fenvalerate. The tested doses were given to rats every other day for 30 days. Results obtained showed that fenvalerate significantly (P < 0.05) induced free radicals in plasma and brain and insignificantly in liver and testes. While, vitamin E, beta-carotene alone and/or in combination decreased the levels of free radicals in plasma, liver, testes, and brain. The activities of glutathione S-transferase (liver), alkaline phosphatase (plasma and liver), aspartate aminotransferase (plasma, liver, and testes) and alanine aminotransferase (plasma and liver) were significantly (P < 0.05) increased due to fenvalerate administration. The activity of acetylcholinesterase was significantly (P < 0.05) decreased in brain and plasma, while plasma glucose, urea, creatinine, and bilirubin concentrations were significantly (P < 0.05) increased in rats treated with fenvalerate. Also, results showed a significant (P < 0.05) alterations in plasma proteins, hematological parameters, body weight, and relative weights of organs. Sperm concentration and motility (%) were significantly (P < 0.05) decreased, while dead and abnormal sperm increased in rats exposed to fenvalerate. Vitamin E, beta-carotene alone and/or in combination did not cause any changes in the investigated parameters, but improved semen quality and minimized the toxic effect of fenvalerate. The obtained results demonstrated the beneficial influences of vitamin E, beta-carotene alone and/or in combination in reducing the harmful effects of fenvalerate.     

The effect of EDTA and citric acid on phytoremediation of Cd, Cr, and Ni from soil using Helianthus annuus

The possibility to clean heavy metal contaminated soils with hyperaccumulator plants has shown great potential. One of the most recently studied species used in phytoremediation applications are sunflowers. In this study, two cultivars of Helianthus annuus were used in conjunction with ethylene diamine tetracetic acid (EDTA) and citric acid (CA) as chelators. Two different concentrations of the chelators were studied for enhancing the uptake and translocation of Cd, Cr, and Ni from a silty-clay loam soil. When 1.0 g/kg CA was used, the highest total metal uptake was only 0.65 mg. Increasing the CA concentration posed a severe phytotoxicity to both cultivars as evidenced by stunted growth and diminished uptake rates. Decreasing the CA concentration to 0.1 and 0.3 g/kg yielded results that were not statistically different from the control. EDTA at a concentration of 0.1 g/kg yielded the best results for both cultivars achieving a total metal uptake of approximately 0.73 mg compared to approximately 0.40 mg when EDTA was present at 0.3 g/kg.     

Electrochemical decolourisation of structurally different dyes

The electrochemical decolourisation of structurally different dyes (bromophenol blue, indigo, poly R-478, phenol red, methyl orange, fuchsin, methyl green and crystal violet) by means of the application of DC electric current was assessed. It was found that the electrochemical process allowed a colour removal of all dyes studied, although the decolourisation rate largely depended on the chemical structure of the different dyes. Nearly complete decolourisation was achieved for bromophenol blue followed by methyl orange and methyl green, whereas phenol red was hardly decolourised (30% in 60 min). In mixtures of two dyes, the decolourisation rate became similar for both dyes. However, the addition of a redox mediator, (Co(2+/3+)) clearly enhanced the degradation rate of all tested dyes, but the simplest dye molecules were attacked firstly, followed by dyes with more complex chemical structures. The results revealed the suitability of the process to effectively decolourise wastewaters from dyeing process.     

Biosensors for detection of mercury in contaminated soils

Biosensors based on whole bacterial cells and on bacterial heavy metal binding protein were used to determine the mercury concentration in soil. The soil samples were collected in a vegetable garden accidentally contaminated with elemental mercury 25 years earlier. Bioavailable mercury was measured using different sensors: a protein-based biosensor, a whole bacterial cell based biosensor, and a plant sensor, i.e. morphological and biochemical responses in primary leaves and roots of bean seedlings grown in the mercury-contaminated soil. For comparison the total mercury concentration of the soil samples was determined by AAS. Whole bacterial cell and protein-based biosensors gave accurate responses proportional to the total amount of mercury in the soil samples. On the contrary, plant sensors were found to be less useful indicators of soil mercury contamination, as determined by plant biomass, mercury content of primary leaves and enzyme activities.     

Sorption and oxic degradation of the explosive CL-20 during transport in subsurface sediments

The abiotic sorption and oxic degradation processes that control the fate of the explosive CL-20, Hexanitrohexaazaisowurtzitane, in the subsurface environment were investigated to determine the potential for vadose and groundwater contamination. Sorption of aqueous CL-20 is relatively small (K(d) = 0.02-3.83 cm3 g(-1) for 7 sediments and 12 minerals), which results in only slight retardation relative to water movement. Thus, CL-20 could move quickly through unsaturated and saturated sediments of comparable composition to groundwater, similar to the subsurface behavior of RDX. CL-20 sorption was mainly to mineral surfaces of the sediments, and the resulting isotherm was nonlinear. CL-20 abiotically degrades in oxic environments at slow rates (i.e., 10s to 100s of hours) with a wide variety of minerals, but at fast rates (i.e., minutes) in the presence of 2:1 phyllosilicate clays (hectorite, montmorillonite, nontronite), micas (biotite, illite), and specific oxides (MnO2 and the ferrous-ferric iron oxide magnetite). High concentrations of surface ferrous iron in a dithionite reduced sediment degraded CL-20 the fastest (half-life < 0.05 h), but 2:1 clays containing no structural or adsorbed ferrous iron (hectorite) could also quickly degrade CL-20 (half-life < 0.2 h). CL-20 degradation rates were slower in natural sediments (half-life 3-800 h) compared to minerals. Sediments with slow degradation rates and small sorption would exhibit the highest potential for deep subsurface migration. Products of CL-20 oxic degradation included three high molecular weight compounds and anions (nitrite and formate). The 2-3.5 moles of nitrite produced suggest CL-20 nitro-groups are degraded, and the amount of formate produced (0.2-1.2 moles) suggests the CL-20 cage structure is broken in some sediments. Identification of further degradation products and CL-20 mineralization rates is needed to fully assess the impact of these CL-20 transformation rates on the risk of CL-20 (and degradation product) subsurface movement.