Affiner votre recherche
Résultats 411-420 de 736
Copper and Cadmium Biosorption by Dried Seaweed Sargassum sinicola in Saline Wastewater
2010
Patrón-Prado, Mónica | Acosta-Vargas, Baudilio | Serviere-Zaragoza, Elisa | Méndez-Rodríguez, Lía C.
Rates of biosorption of cadmium and copper ions by nonliving biomass of the brown macroalga Sargassum sinicola under saline conditions were studied. Batch experiments show that the ability to remove cadmium is significantly diminished (from 81.8% to 5.8%), while the ability to remove copper remains high (from 89% to 80%) at a range of salinity from 0 to 40 psu. Maximum capacity of biosorption at 35 psu was 3.44 mg g⁻¹ for cadmium and 116 mg g⁻¹ for copper. The presence of salt did not significantly affect the rate of biosorption, which was about 90% of saturation in 60 min for both metals. There is an antagonistic effect on biosorption when both metals are present in the solution.
Afficher plus [+] Moins [-]Effects of Enhanced UV-B Radiation on N₂O Emission in a Soil-Winter Wheat System
2010
Hu, Zhenghua | Jiang, Jingyan | Chen, Shutao | Liu, Qiaohui | Niu, Chuanpo
An outdoor pot experiments was conducted to investigate the effects of enhanced ultraviolet-B (UV-B) radiation on nitrous oxide (N₂O) emissions from soil-winter wheat systems. The enhanced UV-B radiation treatments were simulated by 20% increase in its intensity. N₂O fluxes were measured with a static opaque chamber-gas chromatograph method. The results showed that enhanced UV-B radiation did not change the seasonal patterns of N₂O emissions. Compared to the controls, the enhanced UV-B radiation reduced N₂O fluxes by 16.4% (p = 0.015) during the elongation-booting stage, while it had no significant effects on N₂O fluxes in the turning-green and heading-maturity phases. During the turning green-overall heading span, the accumulative N₂O was largely decreased by the enhanced UV-B radiation (p < 0.05). From the overall heading to maturity, however, the effects of enhanced UV-B on N₂O emissions were not pronounced (p > 0.10). At the elongation-booting stage, enhanced UV-B increased soluble proteins content in leaves, NO ₃ ⁻ -N and NO ₄ ⁺ -N content in rhizosphere soil, and soil microbial biomass C (C mic) and N (N mic; p < 0.05), as well as microbial biomass C:N ratio changing from 5.0 to 6.8. Our findings suggest that the effects of enhanced UV-B radiation on N₂O emissions differed with winter wheat developmental stages. To assess the overall effects of enhanced UV-B radiation on N₂O emissions from agroecosystems, nevertheless, more field measurements deserve to be carried out in various cropping systems.
Afficher plus [+] Moins [-]Assessment of ¹³⁷Cs and ²³⁹,²⁴⁰Pu Distribution in Forest Soils of the Opole Anomaly
2010
Ziembik, Zbigniew | Dołhańczuk-Śródka, Agnieszka | Komosa, Andrzej | Orzeł, Jolanta | Wacławek, Maria
Distribution of ¹³⁷Cs and ²³⁹,²⁴⁰Pu in the forest soils horizons of the Opole Anomaly was established. Gamma and alpha spectrometry was used for determination of these isotopes. It was found that the ¹³⁷Cs activity was approx. 1,000 times higher than that of ²³⁹,²⁴⁰Pu. The highest activities of both radioisotopes were found close to the boundary region in soil profile where the organic horizon turns into the inorganic one. Cluster analysis did not clearly indicate the group's existence in data in respect to ¹³⁷Cs and ²³⁹,²⁴⁰Pu activities and organic matter content. Distributions of ¹³⁷Cs and ²³⁹,²⁴⁰Pu in soil horizons were non-normal but similar to each other. These distributions were substantially different from that one for organic matter content. The data were separated into two groups, for organic and inorganic soil horizons, respectively. Data transformation using Box-Cox formula was performed following by standardization. Mutual relationships between variables were investigated using ordinary and robust regression methods. Good correlation between ¹³⁷Cs and ²³⁹,²⁴⁰Pu was found. No significant relationship between organic matter content and radioisotopes activity was asserted.
Afficher plus [+] Moins [-]Recovery from Mercury Contamination in the Second Songhua River, China
2010
Zhang, Z. S. | Sun, X. J. | Wang, Q. C. | Zheng, D. M. | Zheng, N. | Lv, X. G.
Mercury pollution in the Second Songhua River (SSR) was serious in the last century due to effluent from a chemical corporation. Effects of riverine self-purification on mercury removal were studied by comparing monitoring data of mercury concentrations varieties in water, sediment, and fish in the past, about 30 years. The present work suggested that a river of such a size like the SSR possessed the potential ability to recover from mercury pollution under the condition that mercury sources were cut off, though it needs a very long time, which might be several decades or even a century of years. During the 30 years with no effluent containing mercury input, total mercury (T-Hg) of water and sediment in some typical segments, mostly near the past effluent outlet, had decreased radically but still higher than the background values, though the decrease amplitudes were over 90% compared with that in 1975. T-Hg had decreased by more than 90% in most fishes, but some were still not suitable for consumption. Methylmercury concentrations (MeHg) of water, sediment, and fish were higher or close to the background levels in 2004. In the coming decades, the purification processes in the SSR would be steady and slow for a long period.
Afficher plus [+] Moins [-]Long-Term Monitoring of Infiltration Trench for Nonpoint Source Pollution Control
2010
Maniquiz, Marla C. | Yi, So-yŏng | Kim, Lee-Hyung
Nonpoint source pollution management initiated by the Ministry of Environment (MOE) in Korea resulted to the construction of 25 pilot facilities termed Best Management Practices (BMPs) until 2005. The national nonpoint sources control projects were employed to fulfill the Total Maximum Daily Load programs. The long-term monitoring being conducted at the sites which began in 2006 is providing detailed insight into the performance of the BMPs. The experience and performance data will be used to better understand and implement similar structural BMPs in the future as well as to assist the MOE in developing the design and maintenance guidelines of BMPs. This study presents the results gathered from the monitoring field tests and experiments over 22 rainfall events between the June 2006 and September 2008 period investigating the pollutant removal efficiency of the infiltration trench BMP that is one of the 25 pilot projects of the MOE. In addition, it includes the development of simple linear regression models to estimate constituent event mean concentration. The results reveal high treatment efficiencies for total suspended solids (89%); biochemical oxygen demand, chemical oxygen demand, and dissolved organic carbon (89-93%); oil and grease (100%); cadmium, lead, and zinc (89-93%); total nitrogen (84%); and total phosphorus (82%). The monitoring data and results will represent a step forward to a better prediction of impacts in the environment and to the national development of BMPs for sustainable watershed management in the country.
Afficher plus [+] Moins [-]Salinization of Mirror Lake by Road Salt
2010
Likens, Gene E. | Buso, Donald C.
The salinization of Mirror Lake in the White Mountains of New Hampshire has been ongoing steadily since Interstate 93 (I-93) was built through the NE subcatchment of the lake in the fall and winter of 1969-1970. Salt added to I-93 during winter as a deicer has been transported to the lake by different quantified, hydrologic pathways, but primarily from the Northeast Tributary, which was intersected by I-93. Now, surprisingly, after the New Hampshire Department of Transportation has spent more than $500,000 on recent structural modifications to divert salt from I-93 away from the Northeast subcatchment of Mirror Lake, applications of salt to a small, town road traversing the other two subcatchments for the lake and servicing a new housing development, have become the major source of salt to the lake. Streamflow from these two subcatchments currently provides more than three times as much salt to the lake as from I-93, and the salt concentration in the lake continues to rise.
Afficher plus [+] Moins [-]Trace Elements in Soils of Urban Areas
2010
Ajmone-Marsan, Franco | Biasioli, Mattia
Urban soils are an essential element of the city environment. However, studies on urban soils are scattered in terms of geographical distribution, sampling pattern, analytical dataset, etc. One of the major issues arising from the studies on this ecosystem is the diffusion of its contamination. In cities, in fact, the proximity to humans may cause a serious danger for citizens. In the present study, results from the literature about trace elements in urban soils are presented to compare methodologies and results and to offer a basis for the harmonization of investigation approaches and establishment of remediation thresholds. A total of 153 studies on the urban ecosystem published in the last 10 years were collected and data on trace elements in soils of 94 world cities were compared and discussed. Data highlights the discrepancies among different studies (sampling strategies, analytical procedures) and the extreme variability of urban soils. Most cities are contaminated by one or more trace elements, revealing the environmental relevance of the urban soil system. While Pb is still one of the major concerns in many locations, new contaminants are on the rise and would deserve more attention from the researchers. While in fact some contaminants are almost ubiquitous in world cities and could be used as tracers for urban contamination, some traffic-related elements such as platinum, rhodium, and palladium, whose reactivity and toxicity is still unknown, are becoming of concern. Collation of literature data highlights the need for the harmonization of sampling, analytical, and rendering procedures for regulatory purposes and provides a useful dataset for environmental scientists dealing with the urban ecosystem and for city planners. A sampling design adapted to local urban patterns, a prescribed sampling depth, and a minimum set of elements that deserve to be measured could be the core of a common methodology.
Afficher plus [+] Moins [-]Influence of Air Pollution and Humidity on Limestone Materials Degradation in Historical Buildings Located in Cities Under Tropical Coastal Climates
2010
Corvo, F. | Reyes, J. | Valdes, C. | Villaseñor, F. | Cuesta, O. | Aguilar, D. | Quintana, P.
Climatic changes and the increased air pollution intensify the atmospheric degradation of stone, affecting the aspect and integrity of valuable historical buildings constructed using limestone and located in tropical coastal sites. This paper analyzes limestone degradation process due to air pollution and humidity in tropical humid conditions in historical buildings located in the cities of Havana, Cuba and San Francisco de Campeche, Mexico. Havana shows higher pollution level than San Francisco de Campeche, which presents pollution levels as a consequence of a multipollutant situation along with the presence of airborne salinity. Temperature and humidity data were recorded from the walls of historical buildings in the city of Havana: the Minor Basilica and the convent of San Francisco. Changes in dry/wet cycles due to the absence of direct sun radiation as well as a high level of SO₂ allow the formation of a black crust (mainly composed of gypsum) in the lower part of the surface of the facade of the Basilica Minor in Havana; however, crusts formed in historical buildings located in San Francisco de Campeche City are mainly composed of calcium carbonate, indicating the importance of natural degradation mechanisms mainly due to dissolution in water. In the last case, the influence of water plays an important role in the development of biodegradation, which induces the formation of calcium oxalates. Caves and cracks were found in the walls of military buildings caused by water infiltration. The influence of air contamination, humidity, and construction materials determine the type of degradation that historical buildings undergo.
Afficher plus [+] Moins [-]Cadmium Accumulation and Translocation in Four Emergent Wetland Species
2010
Zhang, Zhenhua | Rengel, Zdenko | Meney, Kathy
Emergent wetland plant species may exhibit different capacity for phytoremediation when used in constructed wetlands. To evaluate cadmium (Cd) remediation capacity of four emergent wetland species [Baumea juncea (R.Br.) Palla, Baumea articulata (R.Br.) S.T. Blake, Schoenoplectus validus (M.Vahl) A. & D.Löve, and Juncus subsecundus N.A. Wakef.], a glasshouse experiment was conducted in hydroponics to investigate the effects of Cd (0, 5, 10, and 20 mg L⁻¹) on plant growth and Cd uptake and translocation as well as uptake of other nutrients after 14 days. The relative growth rates of the three species changed little in various Cd treatments, but was severely inhibited for B. juncea at 20 mg Cd per liter treatment. Hence, the Cd tolerance index (root length in Cd treatment vs. control) was significantly lower in B. juncea compared to other species. Among the species, the highest concentration of Cd was in the roots of J. subsecundus, followed by S. validus, B. articulata, and B. juncea, while the lowest concentration of Cd was in the S. validus shoots. Of all the species, J. subsecundus had the highest bioconcentration factor (BCF) in shoots, whereas S. validus and B. juncea had the lowest BCF in rhizomes and roots, respectively. The translocation factor was significantly lower in S. validus compared to the other species. J. subsecundus had a higher Cd accumulation rate than the other species regardless of the Cd supply. The lowest allocation of Cd in shoots was recorded for S. validus and in roots for B. juncea. The concentrations of other elements (P, S, Ca, Fe, Cu, and Zn) in shoots decreased with Cd additions, but the interactions between Cd and other elements in roots varied with the different species. These results indicate that the four wetland species have good tolerance to Cd stress (except B. juncea at high Cd exposure), varying in Cd accumulation and translocation in tissues. These properties need to be taken into account when selecting species for wetlands constructed for phytoremediation.
Afficher plus [+] Moins [-]Removal of Nickel by Means of Micellar-Enhanced Ultrafiltration (MEUF) Using Two Anionic Surfactants
2010
Samper, Encarnacion | Rodríguez, Manuel | Sentana, Irene | Prats, Daniel
Micellar-enhanced ultrafiltration (MEUF) is an effective separation technique for removing metal ions from aqueous environments. The critical micellar concentration (CMC) of two anionic surfactants, sodium dodecyl sulfate (SDS) and linear alkylbenzene sulfonate (LAS), was determined by means of conductometry. The effects of pH, conductivity, and surfactant concentration on the permeate flow, retention of surfactants and nickel by MEUF, was studied. Results showed that for surfactant concentrations beyond the CMC, Ni(II) retention with SDS was slightly higher than with LAS (S/M = 45: Ni(II) retention was 70% and 55% for SDS and LAS, respectively). LAS surfactant was always retained in higher quantities than SDS. An increase in conductivity produced large reduction in Ni(II) retention and slightly increased surfactant retention. pH values between 4 and 8 did not affect nickel retention but enhanced the SDS and LAS surfactant retentions.
Afficher plus [+] Moins [-]