Affiner votre recherche
Résultats 2521-2530 de 4,938
Performance of Physically and Chemically Activated Biochars in Copper Removal from Contaminated Mine Effluents Texte intégral
2019
The increasing global demand for metals and minerals justifies the intensive study of treatment options for contaminated mine effluents. The present study evaluated the conversion of wood residues into physically and chemically activated biochars and their subsequent use in the treatment of Cu in synthetic and actual contaminated mine drainage. First, wood residues were converted into biochar by fast pyrolysis. Then, physical (using steam or CO₂) or chemical (using KOH) activation was carried out in a homemade pilot-scale furnace. After activation, highly microporous (KOH materials) and micro/mesoporous activated biochars (CO₂ and steam materials) were obtained. Batch adsorption testing was first conducted with synthetic effluents. Results showed that CO₂-activated biochar was the most Cu effective adsorbent (99% removal) at low concentrations (5–20 mg L⁻¹). The mechanisms of Cu²⁺ adsorption involved physical and chemisorption for biochars and CO₂-activated biochar, while chemisorption for KOH-activated biochars was probably due to the high proportion of functional groups connected to their surface. In multi-metal acid mine drainage, metal adsorption capacities deteriorated for most of the materials, probably due to the effects of ion competition. However, KOH-activated biochar decreased Cu²⁺ concentrations to below the authorized monthly mean allowed by Canadian law (0.3 mg L⁻¹) and decreased Co, Pb, and Mn concentrations up to 95%. These findings indicate that high porosity and oxygenated functional groups connected to the surface of activated biochars are important properties for the enhancement of interactions between carbon materials and metals from mine effluents, as well as for their performance improvement in mine drainage treatment.
Afficher plus [+] Moins [-]Nocturnal noise and habitat homogeneity limit species richness of owls in an urban environment Texte intégral
2019
Fröhlich, Arkadiusz | Ciach, M. (Michał)
Habitat loss and fragmentation are listed among the most significant effects of urbanization, which is regarded as an important threat to wildlife. Owls are the top predators in most terrestrial habitats, and their presence is a reliable indicator of ecosystem quality and complexity. However, influence of urbanization on owl communities, anthropogenic noise in particular, has not been investigated so far. The aim of this study was to identify the role of noise and landcover heterogeneity in the species richness of owl assemblage in the urban ecosystem. Owls were surveyed in the city of Kraków (southern Poland) on 65 randomly selected sample plots (1 km²). The area of main landcover types, landcover diversity index, mean size of landcover patch, and nocturnal noise level were defined within the sample plots and correlated with owl species richness. Five owl species were recorded in the study area with forests as the dominant landcover type for Tawny and Ural owls, grasslands for Long-eared and Barn owls, and gardens for Little owls. In total, 52% of sample plots were occupied by at least one species (1–3 species per plot). The number of owl species was positively correlated with landcover diversity index and negatively correlated with nocturnal noise emission. This study demonstrates that species richness of owls in urban areas may be shaped by landcover heterogeneity and limited by noise intensity. This indicates that noise changes top predator assemblage, which in consequence may disturb predator-prey interactions within human-transformed habitats.
Afficher plus [+] Moins [-]Investigating the Effect of Medicago sativa L. and Trifolium pratense L. Root Exudates on PAHs Bioremediation in an Aged-Contaminated Soil Texte intégral
2019
Davin, Marie | Starren, Amandine | Marit, Emilie | Lefébure, Kévin | Fauconnier, Marie-Laure | Colinet, Gilles
Polycyclic aromatic hydrocarbons (PAH) are persistent organic compounds of major concern that accumulate in the environment, especially soils, and require remediation. Researches to develop bioremediation and phytoremediation (alternative eco-friendly technologies) are being conducted. First, a bioaccessibility measurement protocol was adapted to a brownfield soil using Tenax® beads in order to compare PAHs bioaccessibility in soil samples. PAHs desorption kinetics were established, described by a site distribution model, and a common extraction time was calculated (48 h). Second, the role of two Fabaceae (Medicago sativa L. or Trifolium pratense L.) root exudates in enhancing PAHs bioaccessibility and biodegradation in the studied soil was evaluated during microcosms experiments (28 °C). The CO₂ emissions were significantly higher in presence of T. pratense exudates; the dehydrogenase activities showed improvements of the soil microbial activity in presence of two types of root exudates compared to untreated soil samples; the PAHs residual contents decreased more in untreated samples than in the presence of T. pratense exudates; and M. sativa exudates lowered PAHs bioaccessibility but not residual contents.
Afficher plus [+] Moins [-]Environmental variations mediate duckweed (Lemna minor L.) sensitivity to copper exposure through phenotypic plasticity Texte intégral
2019
Roubeau Dumont, Eva | Larue, Camille | Pujol, Benoît | Lamaze, Thierry | Elger, Arnaud
Environmentally mediated sensitivity of Lemna minor to copper (Cu) was evaluated for the first time in three experiments: the effects of two levels of nutrient concentration, light irradiance or Cu pre-exposure were tested. Various Cu concentrations (ranging from 0.05 to 0.25 mg/L) were used to assess the sensitivity of L. minor to this metal, using one common strain previously acclimatized to two different levels of light intensity, nutrient enrichment and Cu pre-exposure. Our results showed a phenotypic plastic response of the relative growth rates based on frond number and fresh mass production, and maximum quantum yield of photosystem II (Fᵥ/Fₘ). Growth was affected by the three environmental conditions both prior and during Cu exposure, whereas Fᵥ/Fₘ was mostly affected during Cu exposure. Copper significantly influenced all the parameters measured in the three experiments. Environmental conditions significantly modified L. minor sensitivity to Cu in all experiments, with up to twofold difference depending on the treatment. Growth rate was the parameter that was most impacted. Our study revealed for the first time the existence of phenotypic plasticity in L. minor sensitivity to chemical contamination, and implies that environmental context needs to be taken into account for a relevant risk assessment.
Afficher plus [+] Moins [-]Differential impact of anthropogenic pressures on Caspian Sea ecoregions Texte intégral
2019
Lattuada, Matteo | Albrecht, Christian | Wilke, Thomas
Over the past decades, overall ecological conditions in the Caspian Sea have deteriorated. However, a comprehensive understanding of lake-wide spatial differences in anthropogenic pressures is lacking and the biological consequences of human impacts are poorly understood. This paper therefore aims at assessing the individual and combined effects of critical anthropogenic pressures on the Caspian Sea ecoregions. First, cumulative pressure scores were calculated with a cumulative environmental assessment (CEA) analysis. Then, the individual contribution of anthropogenic pressures was quantified. Finally, ecoregion-specific differences were assessed. The analyses show that both cumulative and individual pressure scores are unevenly distributed across the Caspian Sea. The most important individual pressures are invasive species, chemical pollution and poaching. This uneven distribution of pressure scores across Caspian Sea ecoregions creates new challenges for future conservation strategies, as different ecoregions usually require different conservation measures.
Afficher plus [+] Moins [-]Nano-porous Membrane Process for Brackish Groundwater Treatment: Efficiency Analysis Using Response Surface Methodology Texte intégral
2019
Yuzheng Lv, Jihao Zhou, Zhengjun Mai and Jie Liu
Excessively high concentration of inorganic salts in the groundwater is the main threat for residents to drink directly in the remote areas of northwestern China. In this paper, nano-porous membrane process was proposed to removal of diverse ions in such raw water. Through the response surface methodology (RSM), the effects of multiple factors on permeate flux and ion rejection rates were analysed, and the application scope of nanofiltration for various water resource was evaluated. It was found that the factors affecting permeate flux, chloride removal and nitrate removal (response value) followed some typical sequences, and the operating pressure was always the most influential factor. Besides, nanoporous membrane process showed predominant performance in the removal of sulphate, chloride and fluoride; the rejection rates were over 99%, 97% and 95%, respectively, and the produced water could completely satisfy the relevant national standards for drinking water. However, nitrate removal rate was seldom over 80%, and it reduced obviously with the increasing initial concentration of nitrate, thus the nitrate content of raw water should be controlled within 40 mg.L-1.
Afficher plus [+] Moins [-]High Rate Vermicomposting of Coral Vine by Employing Three Epigeic Earthworm Species Texte intégral
2019
S.G. Antony Godson and S. Gajalakshmi
Use of the high-rate vermicomposting system and its relevant technology were successfully applied to accomplish direct vermicomposting of coral vine leaves - devoid of any pre-treatment/composting or amended with cow dung as earlier proclaimed protocols for the vermicomposting of various phytomass had necessitated. Three earthworm species tested were Eisenia fetida, Eudrilus eugeniae and Perionyx excavatus, and they had shown efficient vermicast recovery with few instances of mortality and good reproduction over the 150-day experiment. In this duration, all vermireactors were run in semi-continuous mode at the solid retention time of 15 days. This process enabled us to improve process efficacy of the reactor by the required pointers and systematic process monitoring. This paper substantiates the potential of the high-rate vermicomposting system in direct and potential vermicomposting of coral vine without any pre-treatment/composting or cow dung amendments. The observations have significance for enhancing process economics and therefore, process utility.
Afficher plus [+] Moins [-]Life Cycle Assessment of the Oil Palm Production in the Philippines: A Cradle to Gate Approach Texte intégral
2019
Ma. Theresa M. Espino, Rocky Marius Q. de Ramos and Luzvisminda M. Bellotindos
Despite its small share of 0.15% in the global market, the oil palm production in the Philippines is being contested with environmental issues on continued deforestation, increased emissions from illegal burning of trees, and the marginalization of indigenous communities. As a developing industry, there is a need to further conduct of social and environmental impact studies to gain more acceptance, thereby, pursue growth and expansion. In view of the environmental concerns, this study aimed to conduct a life cycle assessment of the crude oil palm with North Cotabato, Philippines as the case study. Using cradle to gate approach, the potential environmental impacts were established: non-renewable energy of 0.394 MJ/kg oil, carbon footprint of 1.150 kgCO2/kg oil, ozone creation potential of 2.429×10-3 kg NOx /kg oil, acidification potential of 0.0138×10-3 kg SO2 /kg oil and water footprint of 5,797.3 L/kg oil. Compared to six locations in Indonesia, Malaysia and Thailand, the environmental impacts and performance of the oil palm production in North Cotabato were satisfactory given the same topographical conditions. Opportunities to mitigate and decrease the impacts were also identified, namely improving oil extraction rates; increasing ratio of shell as biomass fuel; prudent application of nitrogen fertilizers and optimizing delivery loads and schedules. The results of this study can be a reference for future environmental assessments in other locations.
Afficher plus [+] Moins [-]The Effect of Sublethal Exposure of Chlorpyrifos to Nile Tilapia (Oreochromis niloticus): Case Study of Twin Lakes of West Sumatra, Indonesia Texte intégral
2019
Taufiq Ihsan, Tivany Edwin and Rahma Desri Yanti
Chlorpyrifos is one of the toxic organophosphate insecticides that is often used by farmers in West Sumatra Province. This research was conducted with the aim to analyse the level of consumption, conversion ratio, and growth rate in fish cultivated in the twin lakes of West Sumatra. The concentration variations are 1/7 and 1/14 LC50-96h of chlorpyrifos. The study was conducted for 14 days. Research data analysis found the values of R = 0.75-1 for the relationship of oxygen level, conversion ratio, and growth of tilapia to the duration of exposure which means having a strong correlation. The results obtained were due to chlorpyrifos insecticide exposure on day 1 to day 14. At a concentration of 0.0054 mg/L, there was a decrease in the level of oxygen consumption of 0.0159 mgO2 /L, an increase in feed conversion ratio of 0.8253, and the deviation flow of 2.7048%. Whereas at a concentration of 0.0108 mg/L, there was a decrease in the oxygen level of 0.0213 mgO2 /L, increase in feed conversion ratio of 0.8201, and deviation growth by 2.7048%.
Afficher plus [+] Moins [-]Biomass and Soil Organic Carbon Stocks Under Cedrus deodara Forests in Mandi District of Himachal Pradesh Texte intégral
2019
Manoj Thakur and R. K. Verma
The estimation of carbon sequestration in forest ecosystem is necessary to plan for mitigating the impacts of climate change. The present study was conducted in the Cedrus deodara (CD) forests of Mandi district in Himachal Pradesh to estimate the biomass and soil organic carbon stock at various sites of the study area. Overall, 18 plots of 0.1 ha were laid at six sites randomly in the year 2014-15. In CD forest, the mean stem density was 354 trees/ha and the mean basal area and mean volume were 62.28 m2/ha and 719.71 m3/ha respectively. The mean carbon stock for tree aboveground, tree belowground, understorey and litter were 189.93 ton/ha, 37.99 ton/ha, 1.71 ton/ha and 0.72 ton/ha respectively. The soil organic carbon percentages varied from 1.98-2.83%, 1.72-2.11% and 1.56-1.74% at soil depth of 0-15cm, 15-30cm and 30-45cm respectively, and the soil organic carbon stocks ranged from 24.41-32.22 ton/ha, 21.59-29.03 ton/ha and 19.17-26.78 ton/ha at soil depths of 0-15cm, 15-30cm and 30-45cm respectively. The total mean soil organic carbon (SOC) stock up to a depth of 0-45cm was found to be 76.16 ton/ha. The organic carbon percentage showed a decreasing trend with increasing soil depth.
Afficher plus [+] Moins [-]