Compositional changes in sediments of subalpine lakes,Uinta Mountains (Utah): evidence for the effects of human activity on atmospheric dust inputs     

Richard L. Reynolds  Jessica S. Mordecai  Joseph G. Rosenbaum  Michael E. Ketterer  Megan K. Walsh  Katrina A. Moser 《Journal of Paleolimnology》2010,44(1):161-175

Sediments in Marshall and Hidden Lakes in the Uinta Mountains of northeastern Utah contain records of atmospheric mineral-dust deposition as revealed by differences in mineralogy and geochemistry of lake sediments relative to Precambrian clastic rocks in the watersheds. In cores spanning more than a thousand years, the largest changes in composition occurred within the past approximately 140 years. Many elements associated with ore deposits (Ag, As, Bi, Cd, Cu, In, Mo, Pb, S, Sb, Sn, and Te) increase in the lake sediments above depths that correspond to about AD 1870. Sources of these metals from mining districts to the west of the Uinta Mountains are suggested by (1) the absence of mining and smelting of these metals in the Uinta Mountains, and (2) lower concentrations of most of these elements in post-settlement sediments of Hidden Lake than in those of Marshall Lake, which is closer to areas of mining and the densely urbanized part of north-central Utah that is termed the Wasatch Front, and (3) correspondence of Pb isotopic compositions in the sediments with isotopic composition of ores likely to have been smelted in the Wasatch Front. A major source of Cu in lake sediments may have been the Bingham Canyon open-pit mine 110 km west of Marshall Lake. Numerous other sources of metals beyond the Wasatch Front are likely, on the basis of the widespread increases of industrial activities in western United States since about AD 1900. In sediment deposited since ca. AD 1945, as estimated using ^239+240Pu activities, increases in concentrations of Mn, Fe, S, and some other redox-sensitive metals may result partly from diagenesis related to changes in redox. However, our results indicate that these elemental increases are also related to atmospheric inputs on the basis of their large increases that are nearly coincident with abrupt increases in silt-sized, titanium-bearing detrital magnetite. Such magnetite is interpreted as a component of atmospheric dust, because it is absent in catchment bedrock. Enrichment of P in sediments deposited after ca. AD 1950 appears to be caused largely by atmospheric inputs, perhaps from agricultural fertilizer along with magnetite-bearing soil.  相似文献   

Airborne detection of ecosystem responses to an extreme event: Phytoplankton displacement and abundance after hurricane induced flooding in the Pamlico-Albemarle Sound system,North Carolina     

Patricia?A.?TesterEmail author  Sabrina?M.?Varnam  Mary?E.?Culver  David?L.?Eslinger  Richard?P.?Stumpf  Robert?N.?Swift  James?K.?Yungel  Megan?D.?Black  R.?Wayne?Litaker 《Estuaries and Coasts》2003,26(5):1353-1364

Airborne laser-induced fluorescence measurements were used to detect and monitor ecosystem wide changes in the distribution and concentration of chlorophyll biomass and colored dissolved organic matter in the Pamlico-Albemarle Sound system, North Carolina, U.S., following massive flooding caused by a series of three hurricanes in the late summer of 1999. These high-resolution data provided a significantly more detailed representation of the overall changes occurring in the system than could have been achieved by synoptic sampling from any other platform. The response time for the distribution of chlorophyll biomass to resume pre-flood conditions was used as a measure of ecosystem stability. Chlorophyll biomass patterns were reestablished within four mo of the flooding, whereas higher chlorophylla biomass concentrations persisted for approximately 6 mo. The primary trophic level in the Pamlico-Albemarle Sound system returned to equilibrium in less than a year of a major perturbation.  相似文献   

Meteorological controls on particle growth events in Beltsville,MD, USA during July 2011     

Megan K. Payne  Everette Joseph  Ricardo Sakai  Jose D. Fuentes  William R. Stockwell 《Journal of Atmospheric Chemistry》2015,72(3-4):423-440

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Clashing strategic cultures and climate policy     

Megan Ceronsky  Cameron Hepburn  Michael Obersteiner  Yoshiki Yamagata 《Climate Policy》2013,13(4):347-357

Abstract

Kagan (2002) argues that the different responses of Europeans and Americans to major strategic and international challenges is not simply due to differences in the current administrations, but rather results from (i) a power gap and (ii) differing ideologies. This article applies Kagan's theory to climate policy, employing terrorism policy as a point of comparison. We argue that the power gap between Europe and America is unable to explain the differences in climate policy. In contrast, the ideology gap may indeed have some explanatory value. Furthermore, we argue that one additional feature is critical—the costs and benefits imposed by climate change and terrorism prevention, and the process by which such costs and benefits are evaluated, differ between America and Europe.  相似文献   

Nonnative Species in British Columbia Eelgrass Beds Spread via Shellfish Aquaculture and Stay for the Mild Climate     

Megan E. Mach  Colin D. Levings  Kai M. A. Chan 《Estuaries and Coasts》2017,40(1):187-199

Nonnative species cause economic and ecological impacts in habitats they invade, but there is little information on how they spread and become abundant. This is especially true for nonnative species in native Zostera marina eelgrass beds in coastal British Columbia, Canada, which play a vital role in estuarine ecosystems. We tested how nonnative species richness and abundance were related to both arrival vectors and environmental factors in northeast Pacific eelgrass. Using correlation tests and generalized linear models, we examined how nonnative macroinvertebrates (benthic, epifaunal, and large mobile) and some algae species were related to arrival vectors (shipping and aquaculture) and environmental factors (climate variables, human population density, and native richness and abundance). We found 12 nonnative species, 50 % with known negative impacts within eelgrass habitats. For benthic organisms, both nonnative richness and abundance were strongly correlated with shellfish aquaculture activities, and not with shipping activity. For epifaunal nonnative richness and abundance, neither vector was significantly correlated. Climate (temperature and salinity) helped explain nonnative richness but not abundance; there was no relationship of nonnative richness or abundance to native species richness and abundance or population density. Results suggest that aquaculture activities are responsible for many primary introductions of benthic nonnative species, and that temperature and salinity tolerances are responsible for post-introduction invasion success. While aquaculture and shipping vectors are becoming increasingly regulated to prevent further international spread of nonnative species, it will be important when managing nonnatives to consider secondary spread from intraregional transport through local shellfish aquaculture and shipping.  相似文献