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Effects of high atmospheric CO₂ concentration on root hydraulic conductivity of conifers depend on species identity and inorganic nitrogen source
2011
Gebauer, Tobias | BassiriRad, H. (Hormoz)
We examined root hydraulic conductivity (Lₚ) responses of one-year-old seedlings of four conifers to the combined effects of elevated CO₂ and inorganic nitrogen (N) sources. We found marked interspecific differences in Lₚ responses to high CO₂ ranging from a 37% increase in P. abies to a 27% decrease in P. menziesii, but these effects depended on N source. The results indicate that CO₂ effects on root water transport may be coupled to leaf area responses under nitrate (NO₃ ⁻), but not ammonium (NH₄ ⁺) dominated soils. To our knowledge, this is the first study that highlights the role of inorganic N source and species identity as critical factors that determine plant hydraulic responses to rising atmospheric CO₂ levels. The results have important implications for understanding root biology in a changing climate and for models designed to predict feedbacks between rising atmospheric CO₂, N deposition, and ecohydrology.
Show more [+] Less [-]The effect of mercury on trees and their mycorrhizal fungi
2011
Jean-Philippe, Sharon R. | Franklin, Jennifer A. | Buckley, David S. | Hughes, Karen
The Oak Ridge Reservation, established in 1942, was the designated site for the construction of the atomic bomb. During a 20-year period from 1944 to 1963 radioactive and toxic chemical pollutants, especially mercury compounds were released into the surrounding waterways. Tree diversity and mycorrhizal presence and abundance were analyzed in the mercury-contaminated floodplains of East Fork Poplar Creek Oak Ridge (EFPC) (Tennessee). A subsequent greenhouse study was conducted to assess the phytotoxic effects of different mercuric solutions on Platanus occidentalis (American Sycamore), inoculated with soils from EFPC. Total soil mercury in the field had no effect on tree diversity. Organic species of mercury proved to be more toxic than inorganic species of mercury and soil inoculants from EFPC had no protective effects against Hg toxicity in our greenhouse study. Comparison of the effects of mercury contamination in our field and greenhouse studies was difficult due to uncontrolled factors.
Show more [+] Less [-]Nitrogen deposition and its ecological impact in China: An overview
2011
Liu, Xuejun | Duan, Lei | Mo, Jiangming | Du, Enzai | Shen, Jianlin | Lu, Xiankai | Zhang, Ying | Zhou, Xiaobing | He, Chune | Zhang, Fusuo
Nitrogen (N) deposition is an important component in the global N cycle that has induced large impacts on the health and services of terrestrial and aquatic ecosystems worldwide. Anthropogenic reactive N (Nᵣ) emissions to the atmosphere have increased dramatically in China due to rapid agricultural, industrial and urban development. Therefore increasing N deposition in China and its ecological impacts are of great concern since the 1980s. This paper synthesizes the data from various published papers to assess the status of the anthropogenic Nᵣ emissions and N deposition as well as their impacts on different ecosystems, including empirical critical loads for different ecosystems. Research challenges and policy implications on atmospheric N pollution and deposition are also discussed. China urgently needs to establish national networks for N deposition monitoring and cross-site N addition experiments in grasslands, forests and aquatic ecosystems. Critical loads and modeling tools will be further used in Nᵣ regulation.
Show more [+] Less [-]Strategies for enhancing the phytoremediation of cadmium-contaminated agricultural soils by Solanum nigrum L
2011
Ji, Puhui | Sun, Tieheng | Song, Yufang | Ackland, M Leigh | Liu, Yang
Field trials contribute practical information towards the development of phytoremediation strategies that cannot be provided by laboratory tests. We conducted field experiments utilizing the Cd hyperaccumulator plant Solanum nigrum L., on farmland contaminated with 1.91 mg kg⁻¹ Cd in the soil. Our study showed that S. nigrum has a relatively high biomass. Planting density had a significant effect on the plant biomass and thus on overall Cd accumulation. For double harvesting, an optimal cutting position influenced the amount of Cd extracted from soils. Double cropping was found to significantly increase the amount of Cd extracted by S. nigrum. Fertilizing had no significant effect on plant biomass or on the Cd remediation of the soil over the short-term period. Our study indicates that S. nigrum can accumulate Cd from soils where the concentrations are relatively low, and thus has application for use in decontamination of slightly to moderately Cd-contaminated soil.
Show more [+] Less [-]Can arbuscular mycorrhizal fungi improve grain yield, As uptake and tolerance of rice grown under aerobic conditions?
2011
The effects of arbuscular mycorrhizal fungi (AMF) –Glomus intraradices and G. geosporum on arsenic (As) and phosphorus (P) uptake by lowland (Guangyinzhan) and upland rice (Handao 502) were investigated in soil, spiked with and without 60mgAskg⁻¹. In As-contaminated soil, Guangyinzhan inoculated with G. intraradices or Handao 502 inoculated with G. geosporum enhanced As tolerance, grain P content, grain yield. However, Guangyinzhan inoculated with G. geosporum or Handao 502 inoculated with G. intraradices decreased grain P content, grain yield and the molar ratio of grain P/As content, and increased the As concentration and the ratio of grain/straw As concentration. These results show that rice/AMF combinations had significant (p<0.05) effects on grain As concentration, grain yield and grain P uptake. The variation in the transfer and uptake of As and P reflected strong functional diversity in AM (arbuscular mycorrhizal) symbioses.
Show more [+] Less [-]Polybrominated diphenyl ethers (PBDEs) in soils along a rural-urban-rural transect: Sources, concentration gradients, and profiles
2011
Gevao, Bondi | Ghadban, Abdul Nabi | Uddin, Saif | Jaward, Foday M. | Bahloul, Majed | Zafar, Jamal
This study reports concentrations of PBDEs in surface soil samples collected along a 140km transect across Kuwait to assess the role of urban centers as sources of persistent organic pollutants to the surrounding environment. The ΣPBDE concentrations varied by a factor of ∼250 and ranged from 289 to 80,078pgg⁻¹d.w. The concentrations of PBDEs in Kuwait City were significantly higher (p<0.01) than those collected from sites outside the city supporting the hypothesis that urban centers are sources of PBDEs. The congener profiles were dominated by BDE-209, accounting for 93% of the PBDEs in the soil samples. The concentrations of all congeners (except BDE-209) were highly correlated with percent organic carbon (%OC) (p>0.05) when the data from Kuwait City was omitted from the analysis. These findings suggest that soil concentrations outside the urban centers were close to equilibrium with the atmosphere.
Show more [+] Less [-]Monitoring of heavy metal concentrations in home outdoor air using moss bags
2011
Rivera, Marcela | Zechmeister, Harald | Medina-Ramón, Mercedes | Basagaña, Xavier | Foraster, Maria | Bouso, Laura | Moreno, Teresa | Solanas, Pascual | Ramos, Rafael | Köllensperger, Gunda | Deltell, Alexandre | Vizcaya, David | Künzli, Nino
One monitoring station is insufficient to characterize the high spatial variation of traffic-related heavy metals within cities. We tested moss bags (Hylocomium splendens), deployed in a dense network, for the monitoring of metals in outdoor air and characterized metals’ long-term spatial distribution and its determinants in Girona, Spain. Mosses were exposed outside 23 homes for two months; NO₂ was monitored for comparison. Metals were not highly correlated with NO₂ and showed higher spatial variation than NO₂. Regression models explained 61–85% of Cu, Cr, Mo, Pb, Sb, Sn, and Zn and 72% of NO₂ variability. Metals were strongly associated with the number of bus lines in the nearest street. Heavy metals are an alternative traffic-marker to NO₂ given their toxicological relevance, stronger association with local traffic and higher spatial variability. Monitoring heavy metals with mosses is appealing, particularly for long-term exposure assessment, as mosses can remain on site many months without maintenance.
Show more [+] Less [-]Direct and indirect impact of sewage sludge compost spreading on Quercus coccifera monoterpene emissions in a Mediterranean shrubland
2011
Olivier, Romain | Staudt, Michael | Lavoir, Anne-Violette | Ormeño, Elena | Rizvi, Syed Hussain | Baldy, Virginie | Rivoal, Annabelle | Greff, Stephane | Lecareux, Caroline | Fernandez, Catherine
Monoterpene emissions of Quercus coccifera L. were repeatedly measured during the two years following the spreading of a sewage sludge compost at rates of 50Mgha⁻¹ and 100Mgha⁻¹, in a twelve-year-old post-fire Mediterranean shrubland. We also monitored the patterns of change in soil and leaf nutrient content, plant water potential, chlorophyll fluorescence, and plant growth. Compost spreading resulted in weak changes in leaf nutrient content and plant water status, and therefore no significant effect on monoterpene emissions at leaf scale, except during one summer sampling, probably related to advanced leaf maturity with the highest compost rate. However, compost increased plant growth, particularly the leaf biomass. The results suggest that compost spreading in Mediterranean shrublands has no strong short-term effect on Q. coccifera monoterpene emissions at leaf level, but may indirectly increase volatile organic compound fluxes at the stand scale, which may contribute to regional ozone pollution.
Show more [+] Less [-]Changes in the chemistry of acidified Adirondack streams from the early 1980s to 2008
2011
Lawrence, G.B. | Simonin, H.A. | Baldigo, B.P. | Roy, K.M. | Capone, S.B.
Lakes in the Adirondack region of New York have partially recovered in response to declining deposition, but information on stream recovery is limited. Here we report results of Adirondack stream monitoring from the early 1980s to 2008. Despite a 50% reduction in atmospheric deposition of sulfur, overall increases in pH of only 0.28 and ANC of 13 μeq L⁻¹ were observed in 12 streams over 23 years, although greater changes did occur in streams with lower initial ANC, as expected. In the North Tributary of Buck Creek with high dissolved organic carbon (DOC) concentrations, SO₄ ²⁻ concentrations decreased from 1999 to 2008 at a rate of 2.0 μmol L⁻¹ y⁻¹, whereas in the neighboring South Tributary with low DOC concentrations, the decrease was only 0.73 μmol L⁻¹ y⁻¹. Ca²⁺ leaching decreased in the North Tributary due to the SO₄ ²⁻ decrease, but this was partially offset by an increase in Ca²⁺ leaching from increased DOC concentrations.
Show more [+] Less [-]On airborne nano/micro-sized wear particles released from low-metallic automotive brakes
2011
Kukutschová, Jana | Moravec, Pavel | Tomášek, Vladimír | Matějka, Vlastimil | Smolík, Jiří | Schwarz, Jaroslav | Seidlerová, Jana | Šafářová, Klára | Filip, Peter
The paper addresses the wear particles released from commercially available “low-metallic” automotive brake pads subjected to brake dynamometer tests. Particle size distribution was measured in situ and the generated particles were collected. The collected fractions and the original bulk material were analyzed using several chemical and microscopic techniques. The experiments demonstrated that airborne wear particles with sizes between 10nm and 20μm were released into the air. The numbers of nanoparticles (<100nm) were by three orders of magnitude larger when compared to the microparticles. A significant release of nanoparticles was measured when the average temperature of the rotor reached 300°C, the combustion initiation temperature of organics present in brakes. In contrast to particle size distribution data, the microscopic analysis revealed the presence of nanoparticles, mostly in the form of agglomerates, in all captured fractions. The majority of elements present in the bulk material were also detected in the ultra-fine fraction of the wear particles.
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