Download or read book Dissolved Organic Matter DOM Concentrations and Quality for Watershed Compartments in a Forested Mid Atlantic Watershed USA written by Nina Finger and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: While the importance of dissolved organic matter (DOM) constituents is well recognized we know very little about how these constituents vary across watershed compartments, influence the transport of dissolved organic carbon (DOC) and nitrogen (DON), and determine the mobility and bioavailability of DOM. We explore the concentrations and quality of DOM for ten watershed sources in a 12 ha forested catchment over a two-year period. DOM was evaluated for throughfall, litter leachate, soil water, shallow and deep groundwater, groundwater discharged from seeps, stream water and water in the hyporheic zone. Soil water samples included both free flowing soil water (using zero tension lysimeters) as well as soil pore water (using tension lysimeters). DOM quality was characterized using a suite of indices derived from UV-visible absorbance and parallel factor analysis (PARAFAC) modeling of fluorescence excitation-emission matrices (EEMs). DOM quality displayed a pronounced trend in watershed compartments especially as a function of soil depth. The humic, aromatic, and high molecular weight constituents of DOM decreased with soil depth while there was a concomitant percent increase in the protein-like DOM moieties. Principal component analyses (PCA) revealed that the differences in surficial watershed compartments were dictated by humic components while differences in groundwater sources were dictated by % total proteins. The increase in % total proteins with increasing soil depth indicated that in groundwater a greater fraction of DOM may be bioavailable compared to DOM in litter leachate and soil water. We did not find any conclusive evidence for C or N enrichment in any particular DOM quality pools. In addition, DOM quality displayed pronounced spatial differences. DOM in wetland groundwater was more aromatic and humic than that at the riparian location. This study also suggested that some spectrofluorometric indices (e.g. the humification index, HIX) may be preferable over others (e.g. specific UV absorbance, SUVA) for characterizing DOM quality.

Download or read book Quantity and Composition of Stream Dissolved Organic Matter in the Watershed of Conesus Lake New York written by Morgan Bida and published by . This book was released on 2013 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The watershed of Conesus Lake, New York is drained by more than 18 unique streams and several smaller tributaries and has multiple land uses, varying from highly agricultural to primarily wooded, making the lake an ideal study site for analysis of the effects of land use on various water quality parameters. Previous water quality and watershed-health studies at Conesus Lake have focused on the delivery of inorganic nutrients to the lake. We know much less, however, about the effects of watershed land use on the quantity and composition of dissolved organic matter (DOM) exported to the lake. We sought to determine how stream DOM quantity and composition varied with space and time within the watershed during 2011. The concentrations of dissolved organic carbon and inorganic and organic nitrogen and phosphorus were measured seasonally in 7 streams, with a more detailed analysis of water chemistry in 12 streams during the growing season. The composition of DOM entering Conesus Lake was assessed with a suite of optical indices and with fluorescence excitation-emission matrices (EEMs) with parallel factor analysis (PARAFAC), a chemometric technique for the decomposition of characteristic fluorescence peaks. A 4-component PARAFAC model showed one allochthonous, humic-like component (C1), one semi-labile component with allochthonous and/or autochthonous origin (C2), and two autochthonous, protein-like components (C3 & C4). We showed seasonality in the composition and quantity of DOM that is consistent with abiotic seasonal controls and principal components analyses (PCA) suggest that agriculturally-dominated streams are associated with increased nitrate and phosphate, a greater proportion of protein-like PARAFAC components (C3 & C4), and that the DOM tends to be less humified. These results imply that a) seasonal controls on DOM govern the abundance of protein-like DOM and can alter the quantity of bulk DOM, b) agricultural land use may augment autochthonous production in a stream, particularly in the spring and summer, thus creating a more labile pool of DOM that is exported to the lake, and c) stream order can alter DOM quantity and composition, possibly through instream processing and variations in light availability."--Abstract.

Download or read book Dissolved Organic Matter in Wetland Soils and Streams of Southeast Alaska written by Jason B. Fellman and published by . This book was released on 2008 with total page 318 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Dissolved organic matter (DOM) transported from terrestrial to aquatic ecosystems is an important source of C, N and energy for the metabolism of aquatic heterotrophic bacteria. I examined the concentration and chemical quality of DOM exported from coastal temperate watersheds in southeast Alaska to determine if wetland soils are an important source of biodegradable dissolved organic carbon (BDOC) to aquatic ecosystems. I addressed this question through a combination of high resolution temporal and spatial field measurements in three watersheds near Juneau, Alaska by using a replicated experimental design that characterized DOM export from three different soil types (bog, forested wetland and upland forest) within each of the watersheds. PARAFAC modeling of fluorescence excitation-emission spectroscopy and BDOC incubations were used to evaluate the chemical quality and lability of DOM. Overall, my findings show that wetland soils contribute substantial biodegradable DOM to streams and the response in BDOC delivery to streams changes seasonally, with soil type, and during episodic events such as stormflows. In particular, the chemical quality of DOM in streamwater and soil solution was similar during the spring runoff and fall wet season, as demonstrated by the similar contribution of protein-like fluorescence in soil solution and in streams. These findings indicate a tight coupling between wetland DOM source pools and streams is responsible for the export of BDOC from terrestrial ecosystems. Thus, seasonal changes in soil-stream linkages can have a major influence on watershed biogeochemistry with important implications for stream metabolism and the delivery of labile DOM to coastal ecosystems. Soil DOM additions in small streams draining the three soil types showed that DOM leached from watershed soils is readily used as a substrate by stream heterotrophs and at the same time modified in composition by the selective degradation of the proteinaceous fraction of DOM. These findings indicate terrestrial DOM inputs to streams are an important source of C to support stream heterotrophic production. Thus, the production of protein-rich, labile DOM and subsequent loss in stream runoff has the potential to be an important loss of C and N from coastal temperate watersheds"--Leaf iii.

Download or read book Dissolved Organic Matter in Lacustrine Ecosystems written by K. Salonen and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt: Concentrations of dissolved organic matter (DOM) in lakes are often an order of magnitude greater than concentrations of particulate organic matter; nevertheless, the biogeochemical analysis of DOM is described in only a few textbooks on limnology (most thoroughly by Wetzel). The orgins of dissolved organic substances are largely photosynthetic; DOM is either autochthonously synthesized by littoral and pelagic flora through secretions and autolysis of cellular contents, or allochthonously generated in terrestrial systems of the drainage basin, composing largely of humic substances refractory to rapid microbial degradation. The role of DOM in lacustrine ecosystems, as energy source and system regulator, however, is still poorly known. The aim of this book is: (1) to present state-of-the-art reviews of the role of dissolved autochthonous and allochthonous organic matter in pelagial and littoral zones; and (2) to focus attention on poorly understood but critical topics and hence to provide direction for future research activity.

Download or read book Watershed Export of Dissolved Organic Matter in Response to Anthropogenic and Hydroclimatic Drivers in Subtropical Streams and Rivers written by Shuo Chen and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Dissolved organic matter (DOM) is an assemblage of heterogeneous organic compounds that play important roles in terrestrial and aquatic ecosystems. In this dissertation, I investigated changes in the amount, source, composition, lability, and ecological functions of stream water DOM in response to agricultural land use, hydrological events, and downstream transport and transformation in the southeastern United States. The dissertation includes three stand-alone studies presented in Chapters 2, 3 and 4, respectively. In Chapter 2, I evaluated the effects of hurricane-induced storm events on the quantity and quality of DOM exported from ten watersheds of various physical and land-use characteristics within five Gulf and South Atlantic states. We found that large storms can significantly enhance the concentrations and yields of terrestrially-derived dissolved organic carbon (DOC) and nutrients in streams and rivers but decrease the percentage bioreactive DOC. This study demonstrates that extreme weather and climate events can lead to rapid, ecosystem-level disturbances that significantly shift energy and nutrient availability within drainage networks. The objective of Chapter 3 was to quantify the relative importance of agricultural land use and natural hydroclimatic drivers in affecting the quality and quantity of DOM in a group of 15 streams draining watersheds of a gradient of agricultural land use. The partial least square path modeling (PLS-PM) identified that agricultural land use increased stream water DOM quantity primarily through increasing allochthonous carbon sources. This study demonstrates that structural equation modeling is a powerful tool that should be more widely adopted to distinguish among multiple drivers and mechanisms regulating freshwater biogeochemistry. Chapter 4 investigated the longitudinal transformations of DOM in relation to ecosystem metabolism along a fluvial section including 3rd order, 7th and 8th order streams. From upstream to downstream, DOC concentrations and the relative contributions of freshly-produced DOM increased. The gross primary productivity was positively correlated with the contributions of autochthonous DOM, yet the ecosystem respiration did not vary with the quantity or quality of DOM. This study highlights the complexity of DOM transformations in relation to stream metabolism along the river continuum. Collectively, the three independent but connected studies reveal the complexity and sensitivity of inland water DOM in response to hydroclimatic and anthropogenic drivers. The findings provide new insights into potential shifts in energy and substrates exported across the terrestrial-aquatic boundary due to human activities and climate change and how these shifts can alter water quality and fluvial biogeochemical functions.

Download or read book Source Tracing of Dissolved Organic Matter DOM in Watersheds Using UV and Fluorescence Spectroscopy written by Jessica Chi Ying Wong and published by . This book was released on 2009 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt: In aquatic ecosystems, dissolved organic matter (DOM) is an important source of detrital energy on which microorganisms rely. However, its dynamics are not well understood in an ecological context. By isolating specific watershed sources, the work reported in this thesis has attempted to characterize the seasonal patterns of DOM in the hyporheic zone of a temperate stream and to find the likely sources that contribute to this abundant pool of organic carbon. Hyporheic DOM characteristics described by UV spectroscopy indicated temporal rather than spatial dependence in relative allochthonous/autochthonous source in the fall. Excitation-emission matrices (EEMs) showed that hyporheic DOM was mainly comprised of fulvic- and humic-like fluorescence with small amounts of protein-like fluorescence. Cedar needles appeared to be an important and consistent source of this protein-like fluorescence in autumn. In contrast, DOM leached from birch litter was more dynamic in that its quality as an energy source decreased as the season progressed. Increases in dissolved organic carbon (DOC) concentrations from birch litter isolates were greater than those from cedar litter in early autumn, but less in late autumn. Although streambed biofilm was not significant in increasing DOC concentrations, it was also a source of protein-like fluorescence.

Download or read book Dissolved Organic Matter in Arctic Watersheds and Coastal Waters written by Craig Thomas Connolly and published by . This book was released on 2019 with total page 300 pages. Available in PDF, EPUB and Kindle. Book excerpt: Arctic warming is already affecting the movement of freshwater and dissolved organic matter (DOM) from watersheds to the coastal ocean in the Arctic. Improved understanding of DOM in freshwater sources and linkages to DOM characteristics in Arctic coastal waters is needed to assess responses to and feedbacks with climate change. This work focuses on DOM characteristics that couple watershed and coastal systems in the Arctic, with specific considerations of river and groundwater inputs to lagoon ecosystems along the eastern Alaska Beaufort Sea coast. We found that spring and summer river-borne concentrations of dissolved organic carbon and nitrogen (DOC and DON) are strongly linked to variations in watershed slope and soil organic matter coverage across space and scale in the Arctic. The quantities and composition of DOM in lagoons of the eastern Alaska Beaufort Sea coast vary markedly between seasons. Specifically, lagoons experience a shift from high to low DOC and DON concentrations between the late spring sea ice break-up and winter ice-covered periods, but these concentrations are more variable during the summer open water period. Distinct seasonal transitions in ice coverage, runoff from land, and water exchange with the Beaufort Sea strongly influence the availability of lagoon DOM. During the summer, concentrations of DOC and DON in supra-permafrost groundwater (SPGW) inputs to lagoons are much higher than those found in local rivers and lagoons. Late-summer fluxes of SPGW DOM to the northern Alaska coastline are substantial and may be the principal source of DOM to lagoons without river inputs. This SPGW DOM is sourced from readily leachable organic matter in surface soils and deeper soil horizons that likely extend into thawing permafrost. SPGW DOM contains aromatic carbon compounds that are largely resistant to microbial degradation on the order of days to months. While nearby river and lagoon water DOM has a similar composition and degradability, SPGW contains a portion of bioavailable and reactive DOM that is not present in river and lagoon waters. Inputs of SPGW DOM provide a potentially important source of energy for lagoon food webs along the Alaskan Beaufort Sea coast during the late summer

Download or read book Source Tracing of Dissolved Organic Matter DOM in Watersheds Using UV and Fluorescence Spectroscopy written by Jessica Wong and published by . This book was released on 2010 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In aquatic ecosystems, dissolved organic matter (DOM) is an important source of detrital energy on which microorganisms rely. However, its dynamics are not well understood in an ecological context. By isolating watershed sources, the work reported in this thesis has attempted to characterize the seasonal patterns of DOM in the hyporheic zone of a temperate stream and to find the likely sources that contribute to this pool of organic carbon. Hyporheic DOM characteristics described by UV spectroscopy indicated temporal rather than spatial dependence. Excitation-emission matrices (EEMs) showed that hyporheic DOM was mainly comprised of fulvic- and humic-like fluorescence with small amounts of protein-like fluorescence. Increases in dissolved organic carbon (DOC) concentrations from birch litter isolates were greater than those from cedar litter in early autumn, but less in late autumn. Although streambed biofilm was not significant in increasing DOC concentrations, it was also a source of protein-like fluorescence.

Download or read book Dissolved Organic Matter Bioavailability and Composition in Streams Draining Catchments with Discontinuous Permafrost written by Kelly L. Balcarczyk and published by . This book was released on 2008 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt: "We examined the influence of permafrost on dissolved organic matter (DOM) in Caribou Poker Creeks Research Watershed (CPCRW). We analyzed long-term data from watersheds underlain with varying degrees of permafrost, sampled springs and thermo karsts to capture the range of DOM concentration and quality, used fluorescence spectroscopy to examine DOM composition, and measured DOM bioavailabity. Permafrost hydrology influenced DOM patterns, with the stream draining the high permafrost watershed having the highest dissolved organic carbon and nitrogen (DOC and DON) concentrations, higher DOC:DON, and greater specific ultraviolet absorbance (SUVA). Streams, springs, and thermokarsts exhibited a wide range of DOC and DON concentrations (1.5 - 37.5 mgC/L and 0.14 - 1.26 mgN/L), DOC:DON (7.08 - 42.8), and SUVA (1.5 - 4.7 L mgC−1 m−1). All sites had fluorescence index values (1.3 - 1.4) consistent with DOM derived from terrestrial sources. Principal components analysis revealed distinct groups in our fluorescence data determined by diagenetic processing and DOM source. Bioavailability of DOM ranged from 2 - 35% and was correlated with the proportion of tyrosine and tryptophan. Our results indicate that the degradation of permafrost in CPCR W will result in a decrease in DOC and DON concentrations, a decline in DOC:DON, and a reduction in SUVA, accompanied by a change in bioavailability"--Leaf iii.

Download or read book Dissolved Organic Matter in Atmospheric Deposition written by Lidiia Iavorivska and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Dissolved organic matter (DOM) in the atmosphere affects air quality and climate. Unlike inorganic constituents that typically consist of single compounds, DOM is a mixture of multiple organic compounds having varying molecular weights, reactivity and solubility. Dissolved organic carbon (DOC) is typically used as a measure of the total DOM present in solution. In the atmosphere, DOC originates from emissions of various biogenic and anthropogenic sources, such as vegetation, incomplete combustion of fossil fuels, biomass burning, and sea-spray. The ultimate fate of atmospheric DOC is to be oxidized to inorganic forms of carbon dioxide and carbon monoxide, or to be removed from the atmosphere and transferred to the landscape through deposition. Deposition can occur as wet deposition via precipitation and as dry deposition via surface settling of particles and gases. The concentration, or quantity, of DOC in precipitation plays an important role in the carbon cycle and in other elemental cycles; while the chemical composition, or quality, of DOC in precipitation largely determines its fate in the environment. Rain and snow deposited to the landscape are a source of nutrient enrichment to ecosystems and water bodies, and are especially important as an input of carbon in coastal regions. Since DOC in precipitation is highly chemically reactive and bioavailable it influences rates of productivity in aquatic ecosystems. Despite the significance of DOC to many ecosystem processes, knowledge about its contributions to landscapes in precipitation remains limited. With anthropogenic influences on the carbon cycle now widely recognized, the need for synthesis of existing datasets on atmospheric deposition of DOC and further determining its rates and drivers is great. My dissertation is focused on wet deposition of DOC and assesses the magnitude and patterns of variation of organic matter in precipitation over space and time. The dissertation is organized into four manuscripts. Chapter 1 is a literature review where I provide a new data synthesis from 83 contemporary, peer-reviewed studies where organic carbon (OC) in precipitation was measured at sites around the world. Data regarding the concentrations of OC in precipitation and rates of atmospheric deposition were compiled in a common set of units and presented along with the summary statistics. These data give insights into the magnitude and regional variability of OC in precipitation. Organic carbon was ubiquitous in precipitation in rural and urban locations; with DOC in precipitation spanning several orders of magnitude between locations. This synthesis brings attention to atmospheric deposition as an under-sampled piece of the global carbon cycle; highlights gaps in data availability and challenges for data inter-comparison; and provides a unique data set that can be used for toward exploring future changes in the carbon cycle. Chapter 2 aims to understand how DOC concentration and composition in precipitation change temporally from storm to storm. Precipitation samples were collected at the Susquehanna Shale Hills Critical Zone Observatory watershed (Pennsylvania, USA) during 90 storm events. Observational data revealed temporal variability associated with seasonality and meteorological conditions. Using a mixed modeling statistical approach, I showed that there are multiple processes that work in synergy to influence the quantity and quality of DOC in precipitation. Factors related to storm properties, emission sources, and to the chemical composition of the atmosphere could explain more than 60% of the storm to storm variability in DOC concentrations. This study provided observations on changes in DOC that can be useful in modeling of atmospheric chemistry and in considering temporal changes in ecosystem nutrient balances and microbial activity.Chapter 3 explores how DOC concentration and composition vary throughout the course of storm events. I measured DOC in sequential samples during 13 storms at the Shale Hills watershed. The observational data generated hypotheses about potential factors that influence variability of DOC within storms. While previous studies have observed that concentrations of other elements in precipitation typically decrease over the course of individual storms, results from this study showed that DOC concentrations are highly variable. During most storms concentrations decreased towards the end of the event; however increasing concentrations in the later stages of some storms highlight that DOC removal with precipitation is not merely an exponential decay process. The variability of DOC during events is related to the balance between the cloud microphysics, atmospheric chemical transformations, and synoptic scale gradients in the abundance of organic compounds in the boundary layer. This work advances understanding of physicochemical processes occurring during storms that are relevant to studies of atmospheric chemistry, carbon cycling, and ecosystem responses.Chapter 4 quantifies spatial gradients in wet atmospheric DOC deposition across the state of Pennsylvania (USA). DOC concentrations were measured in selected precipitation samples collected for six years at a network of atmospheric deposition monitoring sites. A simple modeling approach was used to estimate the first statewide, annual estimates of wet atmospheric DOC deposition. Results showed that DOC inputs with wet deposition in Pennsylvania represented about one-third as much as literature reported values for DOC exported by rivers from watersheds in the region. The rates of DOC wet deposition showed a pronounced seasonality and spatial distribution, with highest deposition rates observed in the summer, especially at the sites located in western Pennsylvania.

Download or read book Linking Optical and Chemical Properties of Dissolved Organic Matter in Natural Waters written by Christopher L. Osburn and published by Frontiers Media SA. This book was released on 2017-01-17 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt: A substantial increase in the number of studies using the optical properties (absorbance and fluorescence) of dissolved organic matter (DOM) as a proxy for its chemical properties in estuaries and the coastal and open ocean has occurred during the last decade. We are making progress on finding the actual chemical compounds or phenomena responsible for DOM’s optical properties. Ultrahigh resolution mass spectrometry, in particular, has made important progress in making the key connections between optics and chemistry. But serious questions remain and the last major special issue on DOM optics and chemistry occurred nearly 10 years ago. Controversies remain from the non-specific optical properties of DOM that are not linked to discrete sources, and sometimes provide conflicting information. The use of optics, which is relatively easier to employ in synoptic and high resolution sampling to determine chemistry, is a critical connection to make and can lead to major advances in our understanding of organic matter cycling in all aquatic ecosystems. The contentions and controversies raised by our poor understanding of the linkages between optics and chemistry of DOM are bottlenecks that need to be addressed and overcome.

Download or read book Hydrologic Dynamics Control Dissolved Organic Matter Export from Watersheds written by Rebecca Anne Bellmore and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Dissolved organic matter (DOM) is an important component of nutrient cycling and energy transfer within and between ecosystems. Understanding controls over the magnitude and quality of DOM that is transferred from soils to surface water is needed to better characterize the terrestrial-aquatic carbon flux and effects of terrestrial DOM on downstream ecosystems. A meta-analysis of the response of in-stream dissolved organic nitrogen concentration (DON) to high flow events indicates that DON typically increases with flow across a wide range of ecosystem types, likely as novel DOM sources in the landscape are mobilized and transported to streams and rivers. Mechanisms controlling DOM export, including dissolved organic carbon (DOC) and DON concentrations and the quality of DOM, were examined in a small agricultural catchment in eastern Washington State. In the soil column, DOC concentration declined and source of DOM shifted from humic-like and plant-derived to microbially-derived with depth through the profile. Across seasons and years, DOM exported via drain discharge during low flows resembled that found deep in the soil profile, and DOM exported during high flows suggests topsoil and litter sources contribute to export. A simple mixing model suggests that litter leachate can contribute over 50% of DOM during peak flow. Based on modeled contributions of litter, topsoil and subsoil DOM during storm events, DOC concentration is over-predicted, except for peak flows, suggesting removal via sorption and/or microbial decomposition in the soil column control DOC export on the timescale of events. Although the character of exported DOM shifts with flow conditions, laboratory incubations suggest bioavailability to the stream sediment microbial community is consistently low, with a maximum of 7% loss over 6 days, indicating exported DOM is likely transported beyond the immediate stream reach. An analysis of anticipated effects of climate change on the flow regime in the catchment projects the wettest years to become more variable, with non-linear effects on the magnitude of DOC export. Finally I explore how climate change assessments can be incorporated into nonpoint source nutrient management plans, despite current uncertainty about the magnitude and timeframe of climate effects on nutrient loading.

Download or read book Seasonal and Spatial Variation in the Chemical Character of Dissolved Organic Matter Within a Small Boreal Forest Watershed written by Alexander W. Newman and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Dissolved organic matter (DOM) is a significant carbon reservoir and component of the terrestrial-to-aquatic flux (Qualls et al., 1991). The terrestrial-to-aquatic carbon flux, a relatively new addition to global carbon models, is currently estimated to transfer a total of 1.7 petagrams (Pg) carbon (C) yr−1 globally (IPCC, 2013). Terrestrially derived DOM has been identified as a significant pool of organic matter in the aquatic environment. However, the quantity and chemical composition of DOM transferred, as well as the mechanisms driving its transfer, are less understood. This thesis focuses on expanding our knowledge of the processing DOM undergoes as it is transferred from terrestrial-to-aquatic environments by: 1) developing a standardized extraction methodology that can yield representative eluates when applied to sourced samples from throughout the terrestrial-to-aquatic interface and 2) applying the designed methodology to conduct a year long study of DOM quantity and composition in the terrestrial-to-aquatic interface in a boreal forest watershed. Experimental results suggest that although solid phase extraction with a divinyl benzene sorbent (SPE-PPL) yields high extraction efficiencies when applied to DOM, it is subject to selectivity. Extractions performed at high loading volumes were found to select against O-alkyl DOM hydrogen constituents, additionally all SPE-PPL experiments were found to select against nitrogenous DOM components. However, by considering proper extraction parameters, SPE-PPL can produce bulk representative eluates for nuclear magnetic resonance (NMR) analysis from land positions spanning the terrestrial-to-aquatic interface. Results from the field study revealed that DOM transferred from terrestrial-to-aquatic land positions in a boreal forest watershed is both temporally and regionally variable, however, proximity immediately downstream of ponds appeared to be a major hydrologic control, while seasonal variation in hydrologic flow paths may represent another control in boreal forest watersheds. Dissolved organic matter chemical composition and quantity in traditional boreal forest streams related to shifts in the hydraulic flow path of the watershed, indicated by changes in riverine DOM chemical composition that correlated to seasonal wet and dry periods. Increases in both dissolved organic carbon (DOC) concentration and the presence of O-alkyl DOM hydrogen functionalities in the stream indicated a shift from groundwater sources during the dry period to soil water sources during the wet period. Conversely streams downslope of ponds seemed to be buffered against shifts in DOM chemical composition associated with changes in hydrologic flow paths. Dissolved organic matter chemical composition of streams downslope of ponds were relatively constant throughout the year resembling the characterization of pond outflows, even during periods of high hydraulic conductivity, via additions of autochthonous DOM produced in the pond. These additions of autochthonous DOM are negligible in streams not downslope of ponds. Further application of this approach during key periods of DOM export, such as spring snowmelt and fall rain periods may prove help to reveal the processes controlling the terrestrial-to-aquatic carbon flux in boreal forest landscapes.

Download or read book Characteristics of Dissolved Organic Matter DOM and Its Stabilization in Forest Soil written by Yuriko Yano and published by . This book was released on 2002 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dissolved organic matter (DOM) plays an important role in transport of C and essential nutrients such as N, P and S. DOM is also critical for the formation of soil organic matter (SOM), which is the largest terrestrial C pool. Nonetheless, we lack a basic understanding of what controls immobilization and mobilization of DOM. I conducted a parallel laboratory and field study to examine: 1) the effect of litter quality on DOM chemistry, and 2) the effect of DOM chemistry on immobilization in the mineral soil. For field study, an ongoing long-term manipulation of litter inputs (Double Litter=doubled annual leaf litter inputs; Double Wood=doubled woody litter inputs; and Control= normal litter inputs) in a Douglas-fir old-growth forest in the Pacific Northwest was chosen. In the lab study, degree of litter decomposition strongly influenced the chemical composition of the water extracts. For both needle and wood extracts, the hydrophobic acid fraction increased and the hydrophilic neutral fraction decreased from newly-fallen to well-decomposed DOC sources. Contrary to the laboratory results, no difference was found in composition of the 0-horizon leachate among Double Litter, Double Wood and Control treatments after 4 years of litter manipulation, in spite of significant differences in total C, total N and C:N ratios of the 0-horizon material. Possibly, microbial degradation decreased differences in DOM chemistry. Alternately, DOM production from native 0-horizon material may be much greater than from newly added litter. In field and lab studies, the removal of two acid fractions (hydrophobic and hydrophilic acids) accounted for most of the total DOC decrease. Because the hydrophobic neutral fraction was little sorbed, ligand exchange rather than hydrophobic interaction was suggested to be the major mechanism of DOM sorption. Concentrations of DOM in incoming water and DOM removal were positively correlated with a slope of ~1.0 and negative intercept regardless of season and %hydrophilic neutral, the most biodegradable fraction, of incoming DOM, suggesting that the removal was mainly abiotic (sorption) and that there was constant net release of DOM from the soil layers independent of sorption.

Download or read book Sources Transportation and Utilization of Dissolved Organic Matter in Groundwater and Streams written by P. M. Wallis and published by Canada. Inland Waters Directorate, Water Quality Branch. This book was released on 1979 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt: "It has long been recognized that streams in their natural state support a great deal more biomass than can be justified by primary production. This is believed to be the result of energy inputs to streams from terrestrial plants and animals which take the form of either Dissolved Organic Matter (DOM.45μ spherical diameter), or Particulate Organic Matter (POM.45μ)"--Introduction, page 1.

Download or read book Dissolved Organic Matter Discharge in the Six Largest Arctic Rivers chemical Composition and Seasonal Variability written by Amanda J. Rinehart and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The vulnerability of the Arctic to climate change has been realized due to disproportionately large increases in surface air temperatures which are not uniformly distributed over the seasonal cycle. Effects of this temperature shift are widespread in the Arctic but likely include changes to the hydrological cycle and permafrost thaw, which have implications for the mobilization of organic carbon into rivers. The focus of this research was to describe the seasonal variability of the chemical composition of dissolved organic matter (DOM) in the six largest Arctic rivers (Yukon, Mackenzie, Ob, Yenisei, Lena and Kolyma) using optical properties (UV-Vis Absorbance and Fluorescence) and lignin phenol analysis. We also investigated differences between rivers and how watershed characteristics influence DOM composition. Dissolved organic carbon (DOC) concentrations followed the hydrograph with highest concentrations measured during peak river flow. The chemical composition of peak-flow DOM indicates a dominance of freshly leached material with elevated aromaticity, larger molecular weight, and elevated lignin yields relative to base-flow DOM. During peak flow, soils in the watershed are still frozen and snowmelt water follows a lateral flow path to the river channels. As the soils thaw, surface water penetrates deeper into the soil horizons leading to lower DOC concentrations and likely altered composition of DOM due to sorption and microbial degradation processes. The six rivers studied here shared a similar seasonal pattern and chemical composition. There were, however, large differences between rivers in terms of total carbon discharge reflecting the differences in watershed characteristics such as climate, catchment size, river discharge, soil types, and permafrost distribution. The large rivers (Lena, Yenisei), with a greater proportion of permafrost, exported the greatest amount of carbon. The Kolyma and Mackenzie exported the smallest amount of carbon annually, however, the discharge weighted mean DOC concentration was almost 2-fold higher in the Kolyma, again, indicating the importance of continuous permafrost. The quality and quantity of DOM mobilized into Arctic rivers appears to depend on the relative importance of surface run-off and extent of soil percolation. The relative importance of these is ultimately determined by watershed characteristics.

Download or read book dissolved organic carbon concentrations and compositions and trihalomethane formation potentials in waters from agricultural peat soils sacramento san joaquin delta california implications for drinking water quality written by and published by DIANE Publishing. This book was released on with total page 81 pages. Available in PDF, EPUB and Kindle. Book excerpt: