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The nocturnal drainage flow of air causes significant uncertainty in ecosystem CO2, H2O, and energy budgets determined with the eddy covariance measurement approach. In this study, we examined the magnitude, nature, and dynamics of the nocturnal drainage flow in a subalpine forest ecosystem with complex terrain. We used an experimental approach involving four towers, each with vertical profiling of wind speed to measure the magnitude of drainage flows and dynamics in their occurrence. We developed an analytical drainage flow model, constrained with measurements of canopy structure and SF6 diffusion, to help us interpret the tower profile results. Model predictions were in good agreement with observed profiles of...
The project focuses on the use of analytical techniques that we have developed to support a wide range of studies in water-rock interaction, integrating solid phase mineralogy and elemental chemistry and clay mineralogy into hydrologic and contaminant studies.
Categories: Project; Tags: Contaminants, Mineralogy
The “Hydroecology of Flowing Waters” project was initiated in 1998 with the aim to improve understanding of how stream and river corridors function naturally in ways that produce valuable ecosystem services (e.g. flood attenuation, carbon and nutrient storage and contaminant removal, habitat value for fish and wildlife, recreation). The research is increasingly focused on how aquatic ecosystem services can be better protected in the face of degradation resulting from accelerating land use and climate change. Central to the research is the investigation of interactions between physical and biological processes, e.g. how land use change affects hydraulics and channel geomorphology in ways that produce cascading...
Various processes within the unsaturated zone affect ground-water availability and portability, as well as concentrations of water vapor and trace gases in the atmosphere. The rate at which precipitation or applied irrigation water infiltrates, its redistribution following infiltration, and the partitioning of the redistributed soil moisture between ground-water recharge and evapotranspiration affect the rate at which the ground-water reservoir is replenished and the degree to which ground water might be contaminated by chemical applications, spills, or disposal. Consequently, knowledge of and methods to quantitatively measure and predict these processes are needed to determine the impact of such societal practices...
The objectives of my current research are to 1. Understand the water quality effects of fire, 2. Measure the effects of fire on the carbon cycle and other biogeochemical cycles, 3. Characterize the combustion products of wildfire, mainly ash and charcoal, and 4. Link post-fire responses and the composition, physical characteristics, and reactivity of ash and charcoal to measures of burn severity detected on the ground or using remotely-sensed data. The overarching objective of my research is to understand runoff, erosion, deposition, and water quality effects after wildfire.
Watershed-scale water quality and water availability are affected by the interaction between the landscape and surface and subsurface flows at multiple scales. Wide-spread agriculture leads to diffuse non-point sources of contamination by agricultural chemicals. Localized exchanges of surface water and groundwater through highly reactive streambeds can attenuate the impact of agricultural chemicals on water quality. Thus, understanding the patterns and trends in water quality within a watershed requires analyses at multiple scales to understand hydrologic processes and the integration of hydrology and water quality information. The main objective of my research is to develop a better understanding of the role of...
Identification of a fuel released into the environment can be difficult due to biodegradation or weathering. Negative electrospray ionization/mass spectrometry was used to screen for unique polar components in a wide variety of commercial hydrocarbon products and mixtures. These fuels produced unique and relatively simple spectra. When applied to hydrocarbon samples from a large, long-term fuel spill in a relatively cool climate in which the alkane, isoprenoid, and alkylcyclohexane portions had begun to biodegrade or weather, the polar components in these samples had changed little over time. This technique provided rapid fuel identification on hydrocarbons released into the environment, without sample preparation,...
D.1 introduction; D.2 suspended-sediment concentration interpolation method; D.3 transport-curve method for suspended sediment load, bed load, and total load; D.4 equations for estimating bed load and bed-material load; D.5 toward collection of consistent, reliable fluvial-sediment data; references
Categories: Publication; Types: Citation
The Aries River basin of western Romania has been subject to mining activities as far back as Roman times. Present mining activities are associated with the extraction and processing of various metals including Au, Cu, Pb, and Zn. To understand the effects of these mining activities on the environment, this study focused on three objectives: (1) establish a baseline set of physical parameters, and water- and sediment-associated concentrations of metals in river-valley floors and floodplains; (2) establish a baseline set of physical and chemical measurements of pore water and sediment in tailings; and (3) provide training in sediment and water sampling to personnel in the National Agency for Mineral Resources and...
Categories: Publication; Types: Citation
Geochemists have long recognized a correlation between rates of physical denudation and chemical weathering. What underlies this correlation? The Critical Zone can be considered as a feed-through reactor. Downward advance of the weathering front brings unweathered rock into the reactor. Fluids are supplied through precipitation. The reactor is stirred at the top by biological and physical processes. The balance between advance of the weathering front by mechanical and chemical processes and mass loss by denudation fixes the thickness of the Critical Zone reactor. The internal structure of this reactor is controlled by physical processes that create surface area, determine flow paths, and set the residence time of...
A 21-yr gridded monthly fire-starts and acres-burned dataset from U.S. Forest Service, Bureau of Land Management, National Park Service, and Bureau of Indian Affairs fire reports recreates the seasonality and interannual variability of wildfire in the western United States. Despite pervasive human influence in western fire regimes, it is striking how strongly these data reveal a fire season responding to variations in climate. Correlating anomalous wildfire frequency and extent with the Palmer Drought Severity Index illustrates the importance of prior and accumulated precipitation anomalies for future wildfire season severity. This link to antecedent seasons' moisture conditions varies widely with differences in...
Categories: Publication; Types: Citation
Spatial and temporal variations in pore water compositions are characterized for a deep regolith profile developed on a marine terrace chronosequence near Santa Cruz California. Variations are resolved in terms of the dominance of either a lithogenic process, i.e. chemical weathering, or a biogenic process, i.e. plant nutrient cycling. The concept of elemental fractionation is introduced describing the extent that specific elements are mobilized and cycled as a result of these processes.
In August 2004, a National Forest fire crew extinguished a 1.2 ha fire in a wilderness area ~40 km northeast of Santa Barbara, California. Examination revealed that the fire originated on a landslide dotted with superheated fumaroles. A 4 m borehole punched near the hottest (262 °C) fumarole had a maximum temperature of 307 °C. Temperatures in this borehole have been decreasing by ~0.1 °C/d, although the cooling rate is higher when the slide is dry. Gas from the fumaroles and boreholes is mostly air with 3–8 vol% carbon dioxide and trace amounts of carbon monoxide, methane, ethane, and propane. The carbon dioxide is 14C-dead. The ratios of methane to ethane plus propane [C1/(C2 + C3)] range from 3.6 to 14. Carbon...
Categories: Publication; Types: Citation
This study evaluated the chemical fractionation of Cu and Zn from source to deposition in a stormwater system. Cu and Zn concentrations and chemical fractionation were determined for roadway dust, roadway runoff and pond sediments. Stormwater Cu and Zn concentrations were used to generate cumulative frequency distributions to characterize potential exposure to pond-dwelling organisms. Dissolved stormwater Zn exceeded USEPA acute and chronic water quality criteria in approximately 20% of storm samples and 20% of the storm duration sampled. Dissolved Cu exceeded the previously published chronic criterion in 75% of storm samples and duration and exceeded the acute criterion in 45% of samples and duration. The majority...
Abstract Statistical relationships between annual floods at 200 long-term (85–127 years of record) streamgauges in the coterminous United States and the global mean carbon dioxide concentration (GMCO2) record are explored. The streamgauge locations are limited to those with little or no regulation or urban development. The coterminous US is divided into four large regions and stationary bootstrapping is used to evaluate if the patterns of these statistical associations are significantly different from what would be expected under the null hypothesis that flood magnitudes are independent of GMCO2. In none of the four regions defined in this study is there strong statistical evidence for flood magnitudes increasing...