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排序方式: 共有1777条查询结果,搜索用时 31 毫秒
901.
Jayawickreme DH Santoni CS Kim JH Jobbágy EG Jackson RB 《Ecological applications》2011,21(7):2367-2379
Conversions of natural woodlands to agriculture can alter the hydrologic balance, aquifer recharge, and salinity of soils and groundwater in ways that influence productivity and sustainable land use. Using a land-use change chronosequence in semiarid woodlands of Argentina's Espinal province, we examined the distribution of moisture and solutes and estimated recharge rates on adjacent plots of native woodlands and rain-fed agriculture converted 6-90 years previously. Soil coring and geoelectrical profiling confirmed the presence of spatially extensive salt accumulations in dry woodlands and pervasive salt losses in areas converted to agriculture. A 1.1-km-long electrical resistivity transect traversing woodland, 70-year-old agriculture, and woodland, for instance, revealed a low-resistivity (high-salinity) horizon between approximately 3 m and 13 m depth in the woodlands that was virtually absent in the agricultural site because of leaching. Nine-meter-deep soil profiles indicated a 53% increase in soil water storage after 30 or more years of cultivation. Conservative groundwater-recharge estimates based on chloride tracer methods in agricultural plots ranged from approximately 12 to 45 mm/yr, a substantial increase from the <1 mm/yr recharge in dry woodlands. The onset of deep soil moisture drainage and increased recharge led to >95% loss of sulfate and chloride ions from the shallow vadose zone in most agriculture plots. These losses correspond to over 100 Mg of sulfate and chloride salts potentially released to the region's groundwater aquifers through time with each hectare of deforestation, including a capacity to increase groundwater salinity to >4000 mg/L from these ions alone. Similarities between our findings and those of the dryland salinity problems of deforested woodlands in Australia suggest an important warning about the potential ecohydrological risks brought by the current wave of deforestation in the Espinal and other regions of South America and the world. 相似文献
902.
Jonathon J. Valente James W. Rivers Zhiqiang Yang S. Kim Nelson Joseph M. Northrup Daniel D. Roby Carolyn B. Meyer Matthew G. Betts 《Conservation biology》2023,37(5):e14091
Understanding how habitat fragmentation affects individual species is complicated by challenges associated with quantifying species-specific habitat and spatial variability in fragmentation effects within a species’ range. We aggregated a 29-year breeding survey data set for the endangered marbled murrelet (Brachyramphus marmoratus) from >42,000 forest sites throughout the Pacific Northwest (Oregon, Washington, and northern California) of the United States. We built a species distribution model (SDM) in which occupied sites were linked with Landsat imagery to quantify murrelet-specific habitat and then used occupancy models to test the hypotheses that fragmentation negatively affects murrelet breeding distribution and that these effects are amplified with distance from the marine foraging habitat toward the edge of the species’ nesting range. Murrelet habitat declined in the Pacific Northwest by 20% since 1988, whereas the proportion of habitat comprising edges increased by 17%, indicating increased fragmentation. Furthermore, fragmentation of murrelet habitat at landscape scales (within 2 km of survey stations) negatively affected occupancy of potential breeding sites, and these effects were amplified near the range edge. On the coast, the odds of occupancy decreased by 37% (95% confidence interval [CI] –54 to 12) for each 10% increase in edge habitat (i.e., fragmentation), but at the range edge (88 km inland) these odds decreased by 99% (95% CI 98 to 99). Conversely, odds of murrelet occupancy increased by 31% (95% CI 14 to 52) for each 10% increase in local edge habitat (within 100 m of survey stations). Avoidance of fragmentation at broad scales but use of locally fragmented habitat with reduced quality may help explain the lack of murrelet population recovery. Further, our results emphasize that fragmentation effects can be nuanced, scale dependent, and geographically variable. Awareness of these nuances is critical for developing landscape-level conservation strategies for species experiencing broad-scale habitat loss and fragmentation. 相似文献
903.
The transport and biodegradation of 12 organic compounds (toluene, phenol, o-cresol, 2,6-, 3,5-dimethylphenol, naphthalene, 1-methylnaphthalene, benzothiophene, dibenzofuran, indole, acridine, and quinoline) were studied at a field site located on the island of Funen, Denmark, where a clayey till 10–15 m deep overlies a sandy aquifer. The upper 4.8 m of till is highly fractured and the upper 2.5 m contains numerous root and worm holes. A 1.5–2 m thick sand lens is encountered within the till at a depth of 4.8 m. Sampling points were installed at depths of 2.5 m, 4 m, and in the sand lens (5.5 m) to monitor the downward migration of a chloride tracer and the organic compounds. Water containing organic compounds and chloride was infiltrated into a 4 m×4.8 m basin at a rate of 8.8 m3 day−1 for 7 days. The mass of naphthalene relative to chloride was 0.39–0.98 for the sampling points located at a depth of 2.5 m, 0.11–0.61 for the sampling points located at a depth of 4 m, and 0–0.02 for the sampling points located in the sand lens. A similar pattern was observed for eight organic compounds for which reliable results were obtained (toluene, phenol, o-cresol, 2,6-, 3,5-dimethylphenol, 1-methylnaphthalene, benzothiophene, and quinoline). This shows that the organic compounds were attenuated during the downward migration through the till despite the high infiltration rate. The attenuation process may be attributed to biodegradation. 相似文献
904.
Chang-Keun Kang Eun Jung Choy Yongsoo Son Jae-Young Lee Jong Kyu Kim Youngdae Kim Kun-Seop Lee 《Marine Biology》2008,153(6):1181-1198
Loss of macroalgae habitats has been widespread on rocky marine coastlines of the eastern Korean peninsula, and efforts for
restoration and creation of macroalgal beds have increasingly been made to mitigate these habitat losses. Deploying artificial
reefs of concrete pyramids with kelps attached has been commonly used and applied in this study. As a part of an effort to
evaluate structural and functional recovery of created and restored habitat, the macroalgal community and food web structure
were studied about a year after the establishment of the artificial macroalgal bed, making comparisons with nearby natural
counterparts and barren ground communities. Dominant species, total abundance, and community structure of macroalgal assemblage
at the restored macroalgal bed recovered to the neighboring natural bed levels during the study period. The main primary producers
(phytoplankton and macroalgae) were isotopically well separated. δ13C and δ15N values of consumers were very similar between restored and natural beds but varied greatly among functional feeding groups.
The range of consumer δ13C was as wide as that of primary producers, indicating the trophic importance of both producers. There was a stepwise trophic
enrichment in δ15N with increasing trophic level. A comparison of isotope signatures between primary producers and consumers showed that, while
suspension feeders are highly dependent on pelagic sources, invertebrates of other feeding guilds and fishes mainly use macroalgae-derived
organic matter as their ultimate nutritional sources in both macroalgal beds, emphasizing the high equivalency of trophic
structure between both beds. Isotopic signatures of a few mollusks and sea urchins showed that they use different dietary
items in macroalgal-barren grounds compared with macroalgal beds, probably reflecting their feeding plasticity according to
the low macroalgal biomass. However, isotopic signatures of most of the consumers at the barren ground were consistent with
those at the macroalgal beds, supporting the important trophic role of drifting algae. Our results revealed the recoveries
of the macroalgal community and trophic structure at the restored habitat. Further studies on colonization of early settlers
and the following succession progress are needed to better understand the process and recovery rate in the developing benthic
community. 相似文献
905.
906.
Desorption characteristics of kaolin clay contaminated with zinc from electrokinetic soil processing 总被引:1,自引:0,他引:1
A number of bench scale laboratory column tests were carried out using a newly designed and developed electrokinetic cell
to investigate the fundamental behavior of zinc-spiked kaolin clay subjected to an electric field. Laboratory investigations
focused on (i) zinc migration by the combined effects of electromigration and electro-osmosis and (ii) the electrically induced
desorption characteristics of zinc-contaminated kaolin that occurred during processing. The correlations of the applied voltage
gradient, electro-osmotic flow rate, and the development of a pH gradient were examined and evaluated. The results showed
that the removal efficiency was high during the early stage of processing due to rapid desorption by electrokinetic effects
in the cathode region. However, the majority of zinc migrating from the anode was precipitated due to the high pH environment
in the cathode region. 相似文献
907.
Hua Jiang Jeong-Nam Kim Yi Luo 《Environmental Communication: A Journal of Nature and Culture》2019,13(5):582-602
This study applied a situational approach to understanding an environmental problem: PM2.5 (its resulted haze and smog air pollution) in China. Based on a national sample of 374 citizens living in China, it tested a situational model of problem solving and extended it by adding citizens’ environmental engagement behaviour as an immediate consequence of their communicative action. Results of a structural equation modelling analysis supported all the causal links in the conceptual model. Moreover, communicative action significantly mediated the relationship between referent criterion and environmental engagement. Problem recognition, constraint recognition, and involvement recognition did not influence environmental engagement directly, but exerted their significant indirect impact via two key mediators in the model: situational motivation in problem solving and communicative action in problem solving. Theoretical and practical implications of the present study were discussed. 相似文献
908.
ABSTRACTDisaster management spans actions before, during, and after disaster events. Changes in the roles and functions of local governments before a disaster can influence other stages of disaster management. After a chemical spill in 2012, South Korean hazardous chemical management tasks were returned to the central government and local governments’ roles and functions were reduced. To identify associated issues and enhance the hazardous chemical management system, this study analyzed changes in laws and policies and conducted interviews with stakeholders. While the changes helped with centralization, reinforcement, and specification, some loopholes were discovered. The information and human resource capacities of local governments and intra – and intergovernmental relations issues have hindered their active participation before and during chemical disasters. These loopholes can be addressed through institutional enhancements for local governments, such as including them in monitoring hazardous chemical handling facilities, developing codes articulating the division of tasks among departments within them, and providing adequate incentives for them to increase their personnel. This study provides empirical data that informs ongoing debates about the centralization and devolution of disaster management by linking local governments’ ordinary management systems to their disaster management activities. 相似文献
909.
Faheem Du Jiangkun Kim Sang Hoon Hassan Muhammad Azher Irshad Sana Bao Jianguo 《Environmental science and pollution research international》2020,27(30):37286-37312
Environmental Science and Pollution Research - The advanced oxidation processes (AOPs), especially sulphate radical (SO4•−)–based AOPs (SR-AOPs), have been considered more... 相似文献
910.
Jiyun Kim Hye-Bin Choi Uikyu Choi In-Jae Yang Jong-Sik Ryu 《Environmental Forensics》2020,21(1):59-70
AbstractThe purpose of this study is to evaluate what sources principally affect the chemical compositions in the catchment of the upper Nakdong River, South Korea where bedrock mostly consists of silicates as a natural factor. From October 7th to 9th, 2015, thirty-three water samples were collected, including samples from tributaries which run alongside mines. We analyzed the major anions, cations, trace elements and water isotopes of the samples and the analyzed data are divided into four groups by principle component analysis (PCA). We determined that most of the water samples are influenced by water-rock interactions when we consider the PCA results and the chemical weathering equation line. However, six samples have excess concentrations of sulfate and plot below the equation line. These samples were mostly from streams beside a zinc-cadmium smelter, which was also consistent with the PCA results. Samples near populated area could also be separated into a group via domestic pollution. Based on the PCA and chemical results, the chemical compositions of the river can be affected by two anthropogenic inputs: mine wastes and domestic contaminants. 相似文献