Distribution and transport of coal tar-derived PAHs in fine-grained residuum

We investigated the distribution and transport of coal tar-derived polycyclic aromatic hydrocarbons (PAHs) in fine-grained residuum and alluvial floodplain deposits that underlie a former manufactured gas plant. All 16 USEPA priority pollutant PAHs are present at this site and have penetrated the entire 4-5m thickness of clayey sediments, which unconformably overly limestone bedrock. Concentrations of less hydrophobic PAHs (e.g., naphthalene, 0.011-384mg kg(-1)) were about 10 times higher than those of highly hydrophobic PAHs (e.g., benzo[g,h,i]perylene -0.002 to 56.03mgkg(-1)). Microscopic examination of thin-sections of the clay-rich sediments showed that fractures and rootholes, which can act as pathways for flow, occur throughout the profiles. Tarry residue was found coating some fractures and rootholes, indicating that coal tar was, in some cases, able to penetrate as an immiscible phase. However, in the vast majority of samples in which PAHs were detected, there was no detectable tar residue, suggesting that much of the transport occurred in the dissolved phase. Examination of thin-sections with an epifluorescent microscope indicated that PAHs, which fluoresce brightly when exposed to UV light, are distributed throughout the soil matrix, rather than being confined to fractures and rootholes. The widespread distribution of PAHs is most likely due to diffusion-controlled exchange between the fast-flow pathways in the fractures and rootholes and the relatively immobile water in the fine-grained matrix. This implies that fractures and rootholes can play a major role in controlling transport of highly hydrophobic compounds in fine-grained sediments, which would otherwise act as barriers to contaminant migration.     

Uptake and accumulation of cadmium, lead and zinc by Siam weed [Chromolaena odorata (L.) King & Robinson

The Siam weed, Chromolaena odorata (L.) King & Robinson, Family Asteraceae, was found to be a new Pb hyperaccumulator by means of field surveys on Pb soil and hydroponic studies. Plants from field collection accumulated 1377 and 4236mgkg(-1) Pb in their shoots and roots, respectively, and could tolerate soil Pb concentrations up to 100000 mgkg(-1) with a translocation factor of 7.62. Very low concentrations of Cd and Zn were found in plants collected from the field. Under nutrient solution culture condition, C. odorata from the contaminated site (CS) and from non-contaminated site (NCS) grew normally with all three metals (Pb, Cd, Zn) supplied. However, the relative growth rates of all treated plants decreased with increased metal concentrations. The percentage uptakes of Pb, Cd, and Zn by C. odorata increased with increasing metal concentrations. Pb concentration in shoots and roots reached its highest values (1772.3 and 60655.7mgkg(-1), respectively) at a Pb supply level of 10mgl(-1). While the maximum concentrations of Cd (0.5mgl(-1)) in shoots and roots of C. odorata were 102.3 and 1440.9mgkg(-1), and the highest concentrations of Zn (20mgl(-1)) were 1876.0 and 7011.8mgkg(-1), respectively. The bioaccumulation coefficients of Pb and Cd were greater than 1000. These results confirm that C. odorata is a hyperaccumulator which grows rapidly, has substantial biomass, wide distribution and has a potential for the phytoremediation of metal contaminated soils.     

The use of NTA and EDDS for enhanced phytoextraction of metals from a multiply contaminated soil by Brassica carinata

The potential of nine different species to grow in the presence of metals (As, Cd, Cu, Pb and Zn) and to accumulate them in the shoots was assessed for each metal separately by germination and root length tests, and successively by hydroponic experiments. Of the nine species tested, Brassica carinata was the species that accumulated the highest amounts of metals in shoots without suffering a significant biomass reduction. To further evaluate the potential of B. carinata for chelant-enhanced phytoextraction of a natural, multiply metal-polluted soil (As, Cd, Cu, Pb and Zn), both hydroponic and pot experiments were carried out with nitrilotriacetic acid (NTA) or (S,S)-ethylenediamine disuccinic acid (EDDS) as complexing agents. The hydroponic study with solutions containing the five metals together showed that accumulation of Cd, Cu, Pb and Zn in shoots was higher following EDDS addition compared to NTA. EDDS was more effective than NTA in desorbing Cu, Pb and Zn from the soil, whereas As and Cd were poorly extracted. B. carinata plants were grown for 4 weeks in the multiply metal-contaminated soil and then the soil was amended with 5 mmol kg(-1) NTA or EDDS. All plants were harvested 1 week after amendment. In comparison to NTA, EDDS was more effective in enhancing the concentrations of Cu, Pb and Zn in B. carinata shoots (2- to 4-fold increase compared to the control). One week after chelant addition, the DTPA-extractable metal concentrations in the polluted soil were lower in the EDDS treatment in comparison with the NTA amendment. Even though B. carinata showed a reduced growth and a relatively low metal uptake, it demonstrated the ability to survive and tolerate the presence of more metals simultaneously.     

Acid-base properties of humic substances from composted and thermally-dried sewage sludges and amended soils as determined by potentiometric titration and the NICA-Donnan model

The acid-base properties of humic acids (HAs) and fulvic acids (FAs) isolated from composted sewage sludge (CS), thermally-dried sewage sludge (TS), soils amended with either CS or TS at a rate of 80 t ha(-1)y(-1) for 3y and the corresponding unamended soil were investigated by use of potentiometric titrations. The non-ideal competitive adsorption (NICA)-Donnan model for a bimodal distribution of proton binding sites was fitted to titration data by use of a least-squares minimization method. The main fitting parameters of the NICA-Donnan model obtained for each HA and FA sample included site densities, median affinity constants and widths of affinity distributions for proton binding to low and high affinity sites, which were assumed to be, respectively, carboxylic- and phenolic-type groups. With respect to unamended soil HA and FA, the HAs and FAs from CS, and especially TS, were characterized by smaller acidic functional group contents, larger proton binding affinities of both carboxylic- and phenolic-type groups, and smaller heterogeneity of carboxylic and phenolic-type groups. Amendment with CS or TS led to a decrease of acidic functional group contents and a slight increase of proton binding affinities of carboxylic- and phenolic-type groups of soil HAs and FAs. These effects were more evident in the HA and FA fractions from CS-amended soil than in those from TS-amended soil.     

Heavy metal-rich wastes sequester in mineral phases through a glass-ceramic process

Certain sludges generated by industry are rich in contaminating elements and are a major environmental problem. In this study, we determine the ability of these contaminating elements to be incorporated into a glass-matrix and in various mineral phases after a crystallization process. The contaminating elements studied were obtained from sewage sludges (SS) and galvanic sludges (GS), our raw materials. The sludge samples were taken from urban wastewater treatment plant in Catalonia (NE Spain) with high levels of phosphorus oxide (P(2)O(5)). In silica glasses, P(2)O(5) acts as a network former. We determined the chemical composition of both the SS and GS, as well as their thermal behaviour by differential thermal analysis and thermal gravimetric analysis (DTA-TG) to obtain their melting curves. The vitreous transition temperature of the obtained glass was established by dilatometer technique at 725 degrees C. The DTA-TG curve of the glass obtained has an exothermal wide peak at 860 degrees C corresponding to crystallization of the two phases: a spinel phase and a phosphate phase. A second exothermal wide peak at 960 degrees C was attributed to the crystallization of aluminium pyroxene, anorthite and fluor-apatite, with two exothermal phenomena attributed to the evolution of these phases. An exothermal peak at 1100 degrees C was attributed to gehlenite crystallization. Scanning electron microscope observations and energy-dispersed X-ray spectroscopy microanalyses of glass-ceramic showed that the contaminating elements were concentrated in the spinel phases, which are the first phases to crystallize during the cooling of glass. Finally, the spinel structure permits the incorporation of all the contaminating elements into it.     

Biodegradability of alkylates as a sole carbon source in the presence of ethanol or BTEX

The biodegradability of alkylate compounds in serum bottles was investigated in the presence and absence of ethanol or benzene, toluene, ethylbenzene, and p-xylene (BTEX). The biomass was acclimated to three different alkylates, 2,3-dimethylpentane, 2,4-dimethylpentane and 2,2,4-trimethylpentane in porous pot reactors. The alkylates were completely mineralized in all three sets of experiments. They degraded more slowly in the presence of BTEX than in their absence because BTEX inhibited the microbial utilization of alkylates. However, in the presence of ethanol, their slower biodegradation was not related to inhibition by the ethanol. Throughout the experiments alkylates, ethanol, and BTEX concentrations did not change in the sterile controls.     

Biodegradation of heavy crude oil Maya using spent compost and sugar cane bagasse wastes

Experiments were carried out to evaluate the use of some agroindustrial wastes as supports in solid state cultures for the biodegradation of crude oil Maya in static column reactors over 15-20 days periods. Spent compost and cane bagasse wastes showed superior qualities over peat moss waste as support candidates with the advantage that they contain appreciable densities of autochthonous microorganisms in the order of 10(2) cfu g(-1). Mercuric chloride (2%) was able to completely inhibit growth of these microfloras. Biodegradation was enhanced in the presence of the IMP consortium and highest when microflora from cane bagasse only was the bioaugmentation partner (180.7 mg kg(-1) day(-1)). Combination of these waste materials (3:1 ratio, respectively) was observed to significantly biodegrade the crude oil by approximately 40% in 15 days from an initial concentration of 10,000 mg kg(-1) with a four order of magnitude increase in microbial density during this period. Spent compost and cane bagasse wastes are veritable solid support candidates for use in the biodegradation of crude oil polluted systems.     

Binding affinity of proanthocyanidin from waste Pinus radiata bark onto proline-rich bovine achilles tendon collagen type I

Binding affinity of proanthocyanidin (PA) purified from Pinus radiata bark waste onto bovine Achilles tendon collagen (type I) was studied. Adsorption of PA onto the collagen was optimized by examining pH, contact time and temperature. The adsorption was pH-dependent. The maximum adsorption capacity (Q(0)) of PA on collagen was found to be 211 mg g(-1) using the Langmuir isotherm. Comparison between two adsorbents also showed that collagen had higher adsorptivity of approximately 20% more than PVPP (polyvinyl polypyrrolidone). The high affinity between PA and collagen was further confirmed in solvent solubility experiments. The observed solvent resistance was thought to be mainly due to a hydrophobic stacking mechanism reinforced by hydrogen bonding. FT-IR spectra clearly indicated the presence of PA adsorbed on collagen. The results have interesting implications that PA can be a good protective agent for collagen against collagenase and other enzymes.     

Future climate scenarios and rainfall--runoff modelling in the Upper Gallego catchment (Spain)

Global climate change may have large impacts on water supplies, drought or flood frequencies and magnitudes in local and regional hydrologic systems. Water authorities therefore rely on computer models for quantitative impact prediction. In this study we present kernel-based learning machine river flow models for the Upper Gallego catchment of the Ebro basin. Different learning machines were calibrated using daily gauge data. The models posed two major challenges: (1) estimation of the rainfall-runoff transfer function from the available time series is complicated by anthropogenic regulation and mountainous terrain and (2) the river flow model is weak when only climate data are used, but additional antecedent flow data seemed to lead to delayed peak flow estimation. These types of models, together with the presented downscaled climate scenarios, can be used for climate change impact assessment in the Gallego, which is important for the future management of the system.     

Promoting the O3 flux concept for European forest trees

Tropospheric ozone (O3) levels are predicted to stay high, being a factor within "global change" with potential effects on the carbon sink strength of forest trees. Hence, new approaches to O3 risk assessment and their validation are required, although appropriate databases for adult trees are scant. Approaches based on external O3 exposure are presently being evaluated against the ones on O3 flux into leaves, as the cumulative uptake has the capacity for deriving O3 risk from cause-effect relationships. The effective dose, however, needs to account for the trees' O3 defence and tolerance in addition to O3 uptake. The current status of promoting the preferable mechanistic O3 flux concept is highlighted for major regions of Europe, addressing refinements and simplifications needed for routine use. At the pan-European scale, however, the flux-based concept is ready for use in O3 risk assessment and has the potential of meso-scale application at the forest ecosystem level.