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Climatic Controls on the Porewater Chemistry of Mid-Continental Wetlands.

紀錄類型:	書目-語言資料,手稿 : Monograph/item
正題名/作者:	Climatic Controls on the Porewater Chemistry of Mid-Continental Wetlands./
作者:	Levy, Zeno Francis.
面頁冊數:	1 online resource (161 pages)
附註:	Source: Dissertation Abstracts International, Volume: 79-01(E), Section: B.
標題:	Hydrologic sciences. -
電子資源:	click for full text (PQDT)
ISBN:	9780355120356

Climatic Controls on the Porewater Chemistry of Mid-Continental Wetlands.
Levy, Zeno Francis.

Climatic Controls on the Porewater Chemistry of Mid-Continental Wetlands. - 1 online resource (161 pages)

Source: Dissertation Abstracts International, Volume: 79-01(E), Section: B.

Thesis (Ph.D.)--Syracuse University, 2017.

Includes bibliographical references

Wetlands develop where climate and physiography conspire to maintain saturated soils at the land surface, support diverse plant and animal communities, and serve as globally important sinks for atmospheric carbon. The chemistry of wetland porewaters impacts near-surface biological communities and subsurface biogeochemical processes that influence carbon cycling in the environment. Wetland porewater chemistry is a dynamic byproduct of complex hydrogeological processes that cause meteoric waters to enter groundwater systems (recharge) or groundwater to flow to the land surface (discharge). Changes in climate can alter subsurface hydraulic gradients that determine the recharge and discharge functions of wetlands, which in turn control the hydrogeochemical evolution of wetland porewaters.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2018

Mode of access: World Wide Web

ISBN: 9780355120356Subjects--Topical Terms:

1179176
Hydrologic sciences.
Index Terms--Genre/Form:

554714
Electronic books.

Climatic Controls on the Porewater Chemistry of Mid-Continental Wetlands.
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500 $a Source: Dissertation Abstracts International, Volume: 79-01(E), Section: B.
500 $a Adviser: Donald I. Siegel.
502 $a Thesis (Ph.D.)--Syracuse University, 2017.
504 $a Includes bibliographical references
520 $a Wetlands develop where climate and physiography conspire to maintain saturated soils at the land surface, support diverse plant and animal communities, and serve as globally important sinks for atmospheric carbon. The chemistry of wetland porewaters impacts near-surface biological communities and subsurface biogeochemical processes that influence carbon cycling in the environment. Wetland porewater chemistry is a dynamic byproduct of complex hydrogeological processes that cause meteoric waters to enter groundwater systems (recharge) or groundwater to flow to the land surface (discharge). Changes in climate can alter subsurface hydraulic gradients that determine the recharge and discharge functions of wetlands, which in turn control the hydrogeochemical evolution of wetland porewaters.
520 $a The climate of mid-continental North America is influenced by competing air masses with vastly different temperature and moisture contents originating from the Pacific Coast, the Gulf of Mexico, and the Arctic. The interactions of these air masses result in large dynamic shifts of climate regimes characterized by decadal-scale oscillations between periods of drought and heavy rain. Over the course of the 20th century, a shift occurred towards wetter climate in the mid-continental region. This dissertation examines the impact of this climate shift on the porewater chemistry of two very different wetland systems, located only 350 km apart: the Glacial Lake Agassiz Peatlands (GLAP) of northern Minnesota and the Cottonwood Lake Study Area (CLSA) of North Dakota. The former study site consists of a large (7,600 km2), circumboreal peatland that developed an extensive blanket of peat over the last ~5000 years on a relatively flat glacial lake bed within a sub-humid to semi-arid climate gradient characterized by small annual atmospheric moisture surpluses and frequent droughts. The latter study site consists of a 0.92 km2 complex of small (meter-scale) "prairie pothole" wetlands located on a hummocky glacial stagnation moraine under semi-arid climate where wetlands frequently fill and dry with surface ponds over low-permeability glacial till in response to snowmelt runoff and evapotranspiration. Both sites have been the subject of long-term hydrological study since c. 1980 and are well-established examples of the sensitivity of wetland functions to changes in climate.
520 $a The first chapter of this dissertation utilizes a semi-conservative tracer suite (pH, Ca, Mg, Sr, 87Sr/86Sr) to fingerprint discharge of calcareous groundwater to GLAP peat along a ~6 km transect from a bog crest downslope to an internal fen water track and bog islands. However, stable isotopes of the peat porewaters (delta18O and delta 2H) show that the subsurface throughout the entire study area is currently flushed with recharge from the near surface peat. I hypothesize that back-diffusion of groundwater-derived solutes from the peat matrix to active pore-spaces has allowed the geochemical signal from paleo-hydrogeologic discharge to persist into the current regime of dilute recharge. This effect promotes methane generation in the peatland subsurface by allowing transport of labile carbon compounds from the land surface to depth while maintaining geochemical conditions (i.e. pH) in the deep peat favorable to biogenic methane production. The results of this study show that autogenic hydrogeochemical feedback mechanisms contribute to the resilience of peatlands systems and associated ecological functions against climate change.
520 $a The second chapter of this dissertation consists of a detailed geoelectrical survey of a well-studied, closed-basin prairie wetland (P1) in the CLSA that has experienced record drought and heavy rains (i.e. deluge) during the late 20th century. Subsurface storage of sulfate (SO4) salts allows many such closed-basin prairie wetlands to maintain moderate surface water salinities (TDS from 1 to 10 g L--1) that influence communities of aquatic biota. I imaged saline lenses of sulfate-rich porewater (TDS > 10 g L--1) in wetland sediments beneath the bathymetric low of the wetland and within the currently ponded area along the shoreline of a prior pond stand. Analyses of long-term (1979--2014) groundwater and surface water levels in the wetland suggest that the saline lenses formed during paleo-droughts when the groundwater levels dropped below the wetland bed and are stable in the subsurface on at least centennial timescales. I hypothesize a "drought-induced recharge" mechanism by which wetlands maintain moderate surface water salinity by subsurface storage during droughts when the wetlands dry and intermittent runoff events flush surface salts down secondary porosity created by desiccation fractures and terrestrial plant roots. Drought-derived saline groundwater has the potential to increase wetland salinity during record wet climate conditions currently prevalent in the Prairie Pothole Region.
520 $a The third chapter of this dissertation extends the findings of the second chapter by a detailed geochemical survey of wetland porewater, pond water, and upland groundwater in the P1 basin. (Abstract shortened by ProQuest.).
533 $a Electronic reproduction. $b Ann Arbor, Mich. : $c ProQuest, $d 2018
538 $a Mode of access: World Wide Web
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