Fractionation of heavy metals and distribution of organic carbon in two contaminated soils amended with humic acids

The effects of humic acids (HAs) extracted from two different organic materials on the distribution of heavy metals and on organic-C mineralisation in two contaminated soils were studied in incubation experiments. Humic acids isolated from a mature compost (HAC) and a commercial Spaghnum peat (HAP) were added to an acid soil (pH 3.4; 966 mg kg(-1) Zn and 9,229 mg kg(-1) Pb as main contaminants) and to a calcareous soil (pH 7.7; 2,602 mg kg(-1) Zn and 1,572 mg kg(-1) Pb as main contaminants) at a rate of 1.1g organic-C added per 100g soil. The mineralisation of organic-C was determined by the CO(2) released during the experiment. After 2, 8 and 28 weeks of incubation the heavy metals of the soils were fractionated by a sequential extraction procedure. After 28 weeks of incubation, the mineralisation of the organic-C added was rather low in the soils studied (<8% of TOC in the acid soil; <10% of TOC in the calcareous soil). Both humic acids caused significant Zn and Pb immobilisation (increased proportion of the residual fraction, extractable only with aqua regia) in the acid soil, while Cu and Fe were slightly mobilised (increased concentrations extractable with 0.1M CaCl(2) and/or 0.5M NaOH). In the calcareous soil there were lesser effects, and at the end of the experiment only the fraction mainly related to carbonates (EDTA-extractable) was significantly increased for Zn and decreased for Fe in the humic acids treated samples. However, HA-metal interactions provoked the flocculation of these substances, as suggested by the association of the humic acids with the sand fraction of the soil. These results indicate that humic acid-rich materials can be useful amendments for soil remediation involving stabilisation, although a concomitant slight mobilisation of Zn, Pb and Cu can be provoked in acid soils.     

Modelling the dynamic air-water-sediment coupled fluxes and occurrence of polychlorinated biphenyls in a high altitude lake

The BIODEP model in terms of atmosphere-lake interactions was developed. The model was applied to an oligotrophic, dimictic high altitude lake (Lake Redo, Pyrenees) for a range of polychlorinated biphenyl (PCB) congeners. High altitude lakes, which receive their contaminant inputs uniquely from the atmosphere through long-range atmospheric transport, provide ideal controlled environments for the study of the interactions between atmospheric depositional and water column biogeochemical processes. The BIODEP model was able to predict dissolved water concentrations and PCB accumulation in the lake sediment within a factor of 2. This shows that the BIODEP model captures the essential processes driving the sink of POPs in high altitude lakes and that POP occurrence in the lake is driven by direct atmospheric inputs with limited influence from the watershed. An important seasonal variability in water column concentrations is predicted which should have important implications in sampling strategies. Furthermore, it is shown that diffusive air-water exchange dominated the PCB dynamics in the lake, especially for the less chlorinated biphenyls.     

Evaluation of Fenton and ozone-based advanced oxidation processes as mature landfill leachate pre-treatments

Fenton treatment (Fe²⁺/H₂O₂) and different ozone-based Advanced Oxidation Processes (AOPs) (O₃, O₃/OH⁻ and O₃/H₂O₂) were evaluated as pre-treatment of a mature landfill leachate, in order to improve the biodegradability of its recalcitrant organic matter for subsequent biological treatment. With a two-fold diluted leachate, at optimised experimental conditions (initial pH 3, H₂O₂ to Fe²⁺ molar ratio of 3, Fe²⁺ dosage of 4 mmol L⁻¹, and reaction time of 40 min) Fenton treatment removed about 46% of chemical oxygen demand (COD) and increased the five-day biochemical oxygen demand (BOD₅) to COD ratio (BOD₅/COD) from 0.01 to 0.15. The highest removal efficiency and biodegradability was achieved by ozone at higher pH values, solely or combined with H₂O₂. These results confirm the enhanced production of hydroxyl radical under such conditions. After the application for 60 min of ozone at 5.6 g O₃ h⁻¹, initial pH 7, and 400 mg L⁻¹ of hydrogen peroxide, COD removal efficiency was 72% and BOD₅/COD increased from 0.01 to 0.24. An estimation of the operating costs of the AOPs processes investigated revealed that Fe²⁺/H₂O₂ was the most economical system (8.2 € m⁻³ g⁻¹ of COD removed) to treat the landfill leachate. This economic study, however, should be treated with caution since it does not consider the initial investment, prices at plant scale, maintenance and labour costs.     

Solar photocatalysis as strategy for on-site reclamation of agro-wastewater polluted with pesticide residues on farms using a modular facility

Environmental Science and Pollution Research - One of the consequences of phytosanitary treatments applied to crops is the generation of a great volume of agro-wastewater having pesticide residues....     

Presence of diclofenac,estradiol, and ethinylestradiol in Manzanares River (Spain) and their toxicity to zebrafish embryo development

Environmental Science and Pollution Research - Diclofenac (DCF), 17-β-estradiol (E2), and 17-α-ethinylestradiol (EE2) are emerging pollutants included in the first watch list agreed by...     

Development of a framework for fire risk assessment using remote sensing and geographic information system technologies

Forest fires play a critical role in landscape transformation, vegetation succession, soil degradation and air quality. Improvements in fire risk estimation are vital to reduce the negative impacts of fire, either by lessen burn severity or intensity through fuel management, or by aiding the natural vegetation recovery using post-fire treatments. This paper presents the methods to generate the input variables and the risk integration developed within the Firemap project (funded under the Spanish Ministry of Science and Technology) to map wildland fire risk for several regions of Spain. After defining the conceptual scheme for fire risk assessment, the paper describes the methods used to generate the risk parameters, and presents proposals for their integration into synthetic risk indices. The generation of the input variables was based on an extensive use of geographic information system and remote sensing technologies, since the project was intended to provide a spatial and temporal assessment of risk conditions. All variables were mapped at 1 km² spatial resolution, and were integrated into a web-mapping service system. This service was active in the summer of 2007 for semi-operational testing of end-users. The paper also presents the first validation results of the danger index, by comparing temporal trends of different danger components and fire occurrence in the different study regions.     

Interpopulational variation in chemosensory responses to selected steroids from femoral secretions of male lizards, Podarcis hispanica, mirrors population differences in chemical signals

Chemical signals are important for mate and species recognition. If variation in chemical signals occurs between populations of the same species, these differences could later preclude mating between populations and lead to speciation. In the Iberian wall lizard, Podarcis hispanica, the lipophilic fraction of femoral secretions of males is mainly a mix of steroids and fatty acids. Among steroids, the most abundant compounds are cholesterol and cholesta-5,7-dien-3-ol, which are implicated in intraspecific communication and sexual selection. Interpopulational differences in chemical signals of males, and in response to these chemicals, could contribute to reproductive isolation between populations, which would explain the known genetic differences between these populations. Chemical analyses indicated that five distinct populations of this lizard from Madrid (Central Spain) differed in the proportions of two steroids (cholesterol and cholesta-5,7-dien-3-ol) in femoral secretions. Moreover, lizards discriminated and had high chemosensory responses (i.e., high tongue-flick rates) to these steroids, but showed interpopulational differences. Lizards from populations with cold temperatures and high relative humidity (i.e., northern Madrid) elicited higher responses to these steroids, whereas the converse occurred for lizards from populations occupying dry and hot habitats (i.e., southern Madrid). Interestingly, the magnitude of the chemosensory responses to cholesta-5,7-dien-3-ol in each population mirrored the abundance of this compound in secretions of males of that population. These results suggest that the importance of cholesta-5,7-dien-3-ol in males’ secretions might be lower for lizards from the southern populations. These differences in the relative importance of chemical signals could explain reproductive isolation and cryptic speciation between populations of this lizard.