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Floodplain surficial soil samples (10 cm depth) were collected from 18 streams in the urbanized Piedmont region of northern Virginia, representing a chronosequence of time (1-10 yrs.) since stream restoration as well as unrestored and reference streams. The samples were analyzed for total carbon (TC), total nitrogen (TN) and total phosphorus (TP) storage, whereas CO2 mineralization potential and equilibrium phosphorus concentration (EPC0) were measured as metrics of nutrient and carbon loss. Samples also were analyzed for soil moisture, pH, particle size, organic matter content, and degree of phosphorus saturation.
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This dataset includes monthly dissolved silicon (DSi) concentration data from 198 rivers across the Northern Hemisphere. Concentration and discharge data were sourced from public and/or published datasets and the Weighted Regressions on Time, Discharge, and Season model (Hirsch et al. 2010) was used to estimate monthly concentrations and flow-normalized concentrations for all sites over their period of record. Sites span eight climate zones, ranged from 18 degrees N to 70 degrees N, and vary in drainage area from < 1 km2 to nearly 3 million km2. These monthly concentration data were then used to cluster sites into average (i.e., average of all years) and annual (i.e., each year individually) seasonal regimes using...
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Note: This data release has been superseded by version 2.0, available here: https://doi.org/10.5066/P9MDXR3M. The Cache Creek Settling Basin (CCSB) is a 13.3 km2 leveed basin located at the terminal drainage of the Cache Creek watershed, immediately NE of the town of Woodland (Yolo County), California and approximately 18 km NW of Sacramento, California. The basin was constructed by the U.S. Army Corps of Engineers (completed in 1937 and modified in 1993) for the purpose of trapping suspended sediment transported from the upper Cache Creek watershed during high-flow events, thus preventing sediment from entering the Yolo Bypass, a larger downstream floodwater conveyance and agricultural zone. In addition to trapping...
To advance understanding of the factors controlling the environmental fate of elements which may be toxic or of other concern (e.g. greenhouse gases). For instance, microbes influence the partitioning of group 15 and 16 elements (Phosphorus, Arsenic, and Antimony; Sulfur, Selenium, and Tellurium) between dissolved and adsorbed phases, strongly affecting the quality of drinking water in aquifers around the world. On another topic, it is well known that methane and nitrous oxide are strong absorbers of IR radiation and act as greenhouse gases near the Earth’s surface. Bacteria in lakes, wetlands, and soils both facilitate and mitigate the flux of these gases and in so doing, shape our world. The primary goal of the...
A lower limit for nitrogen loss from desert ecosystems in the southwestern United States was estimated by comparing nitrogen inputs to the amount of nitrogen stored in desert soils and vegetation. Atmospheric input of nitrogen for the last 10 000 years was conservatively estimated to be 2.99 kg N/m2. The amount of nitrogen stored in desert soils was calculated to be 0.604 kg N/m3 using extant data from 212 profiles located in Arizona, California, Nevada, and Utah. The average amount of nitrogen stored in desert vegetation is approximately 0.036 kg N/m2. Desert conditions have existed in the southwestern United States throughout the last 10 000 years. Under such conditions, vertical leaching of nitrogen below a depth...
Over the past 50 years, conceptual developments in stream ecology and ecosystem ecology have converged, thanks to biogeochemistry and the recognition that in situ processing on one hand and spatial translation of materials, processes, and influence along flowpaths on the other, unite to generate a holistic picture of ecosystem functioning at the landscape level. Early emphases in stream biogeochemistry involved organic carbon dynamics and whole-ecosystem budgets. These approaches were holistic but cumbersome and laborious and ignored several crucial issues, such as variation in organic matter quality. Nutrient-spiraling approaches rectified this shortcoming and provided a flowpath-specific technique for resolving...
The effect of snow cover on surface-atmosphere exchanges of nitrogen oxides (nitrogen oxide (NO) + nitrogen dioxide (NO2); note, here ?NO2? is used as surrogate for a series of oxidized nitrogen gases that were detected by the used monitor in this analysis mode) was investigated at the high elevation, subalpine (3,340 m asl) Soddie site, at Niwot Ridge, Colorado. Vertical (NO + NO2) concentration gradient measurements in interstitial air in the deep (up to ~2.5 m) snowpack were conducted with an automated sampling and analysis system that allowed for continuous observations throughout the snow-covered season. These measurements revealed sustained, highly elevated (NO + NO2) mixing ratios inside the snow. Nitrogen...
Much of the research on the chemistry of snow and surface waters of the western US, Europe, and Asia has been conducted in high-elevation catchments above treeline. Here we provide information on the solute content of the seasonal snowpack at the Soddie site on Niwot Ridge, Colorado, a subalpine site near treeline. We focus on the storage and release of both inorganic and organic solutes to the soils underneath the snowpack, and subsequent effects on the chemical and nutrient content of the underlying soil solution and the adjacent headwater stream. The concentration of inorganic nitrogen (N) stored in the seasonal snowpack at the Soddie site of about 11 Î&frac14;eq L−1 was on the upper end of values reported...
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This dataset includes shallow surface sediment (top 0–2 cm interval) constituent concentration data (primarily) and microbial methylmercury production potential rate data (limited) collected from the Cache Creek Settling Basin (CCSB), Yolo County, California, between April 2010 and November 2019. The dataset includes up to 723 observations (including field replicates) per sediment parameter, reflecting 93 unique sampling locations, with each location having been sampled from 1 to 29 times (excluding field replicates) over this 10-year period. There were four spatially intensive field campaigns conducted (February–March 2013, May 2013, October–November 2014, and January–March 2015), during which at least 90 sites...
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The study is comprised of daily survey data consisting of high resolution mapping and discrete sample collection of nutrients, phytoplankton, and related water quality constituents conducted in the Sacramento River, Georgiana Slough, and the North and South Forks of the Mokelumne River on August 28 and September 10-12, 2019, coincident with planned holds of treated wastewater effluent from Sacramento Regional Wastewater Treatment Plant (SRWTP) on August 27 and September 9-11, 2019.
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This dataset contains carbon and nitrogen stable isotope values, percent carbon and percent nitrogen, algal pigment data, and diatom taxonomy from lake sediment layers dating back to 1749 Common Era (CE) for Santa Fe lake, New Mexico. Subalpine and alpine lakes are typically sensitive indicators of anthropogenically driven global change. Lake sediment records in the western United States have documented increases in percent carbon (%C), percent nitrogen (%N), and primary productivity during the 20th century. Eutrophication of mountain lakes reflects the influences of atmospheric nutrient deposition and warming. We analyzed a short (49 cm) sediment core from Santa Fe Lake, NM to investigate patterns of change in...
The overarching objective of my research is to integrate hydrology, pedology, chemistry, and physics to develop an improved process-level understanding of fluid, solute, and heat transport in unsaturated zones with applications ranging from geologic hazards to carbon storage in soils. I try to develop multi-disciplinary understanding of unsaturated zones in diverse settings with respect to groundwater-recharge and contaminant-transport determining processes, soil formation, and soil-water-plant-atmospheric interactions. I lead teams and work with others to generate individual and multidisciplinary synthesis products that address long-standing problems of fundamental importance to water resources, such as groundwater...
Micro-organisms alter the chemistry and productivity of aquatic environments by performing complex transformations of organic and inorganic molecules. In many cases, microbes can affect the speciation, mobility, bioavailability, and toxicity of toxic elements, such as Se, Hg, and As. The mechanisms by which these reactions proceed, the in situ rates of the transformation, their quantitative significance to element cycling, the responsible microorganisms and their physiology are only poorly understood. In this project, conceptual models of biogeochemical transformations will be developed by the combination of lab and field experimental work. Laboratory work will focus on identification of biochemical pathways, isolation...
Aqueous chemical models have become popular tools for the interpretation of natural water chemistry. Unfortunately, these models have deficiencies because of (1) incorrect or inconsistent thermodynamic data, (2) invalid assumption regarding the equilibrium state, (3) inappropriate or invalidated corrections for nonideality, (4) inadequate expressions for temperature dependence, (5) invalidated limitations for ionic strength, composition and temperature, and (6) lack of data on solid solution solubility. The plethora of models and databases has prompted federal agencies, especially hazardous waste and nuclear waste managers, to request geochemical code validation. Acid mine waters are a major source of water pollution...
I conduct long-term investigations on the fate and geochemical effect of organic contaminants in subsurface environments. I use a combined field and laboratory approach in a variety of hydrogeologic environments in order to meet these objectives. The principal questions being addressed by this project are: 1. How do long-term changes in biogeochemical processes affect the fate of organic and inorganic constituents in aquatic environments? and 2. Does availability of electron acceptors and electron donors control the progress of degradation reactions? My overarching objective is to increase our understanding of the transformation of contaminants from hydrocarbon spills, wastewaters from oil and gas development,...
My research objectives include characterization of dissolved and particulate natural organic acid influence on the reactivity, bioavailability, and mobility of metal ions and inorganic surfaces in aquatic environments. An important research objective of my project is examination of formation and dissolution rates of carbonate minerals. Biocalcification is a significant carbon sink in the world carbon budget and requires further investigation. I study aspects of biocalcification processes that proceed through a highly unstable calcium carbonate polymorph – amorphous calcium carbonate (ACC) stabilized by organic acids. I use chemical thermodynamics and kinetics to better describe and predict the fate and distribution...
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Microbial biomass nitrogen was measured in unamended (dry) and wetted soils in ten shrubland and grassland communities of the Chihuahuan desert, southern New Mexico, by the fumigation-extraction method. Microbial biomass-N in dry soils was undetectable. Average microbial biomass-N in wetted soils among all plant communities was 15.3 ?g g-1 soil. Highest values were found in the communities with the lowest topographic positions, and the minimum values were detected in the spaces between shrubs. Microbial biomass was positively and significantly correlated to soil organic carbon and extractable nitrogen (NH4 + + NO3 -). In a stepwise multiple regression, organic carbon and extractable nitrogen accounted for 40.9 and...
The broad objective of my research is to determine rates and controls of organic carbon metabolism as a fundamental component of the terrestrial-aquatic-atmospheric exchange of carbon. I quantify the relative importance of intrinsic substrate properties and environmental variables to carbon metabolism, and the impact of climate change and other disturbances. I combine field and laboratory study approaches to understand the numerous controls on carbon cycling processes. Much of my research has focused on boreal and arctic systems, where nearly &frac12; of the global soil organic pool resides and is vulnerable to climate change. My research objectives in boreal and arctic regions include: 1) quantifying the release...
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Boreal ecosystems comprise about one tenth of the world’s land surface and contain over 20 % of the global soil carbon (C) stocks. Boreal soils are unique in that the mineral soil is covered by what can be quite thick layers of organic soil. These organic soil layers, or horizons, can differ in their state of decomposition, source vegetation, and disturbance history. These differences result in varying soil properties (bulk density, C content, and nitrogen (N) content) among soil horizons. These data were used in a manuscript (https://doi.org/10.5194/essd-2019-114) where these soil properties, as represented by over 3000 samples from Interior Alaska, were summarized. We also examined how soil drainage and stand...
map background search result map search result map Carbon and nitrogen limitations of soil microbial biomass in desert ecosystems Cottonwood Lake Study Area - Water Chemistry - Wells - In Situ Measurements Shallow Sediment Geochemistry in a Mercury-Contaminated Multi-Habitat Floodplain: Cache Creek Settling Basin, Yolo County, California, 2010–17 Data Supporting Generalized models to estimate carbon and nitrogen stocks of organic layers in Interior Alaska Assessing spatial variability of nutrients, phytoplankton, and related water quality constituents in the California Sacramento-San Joaquin Delta during treated wastewater effluent holds: August and September 2019 high resolution mapping surveys Shallow Sediment Geochemical Data for the Cache Creek Settling Basin, Yolo County, California Data of floodplain soil carbon and nutrient retention along a chronosequence of urban stream restorations in Northern Virginia (2022) Paleoecological data from sediment collected in 2020 from Santa Fe Lake, New Mexico Paleoecological data from sediment collected in 2020 from Santa Fe Lake, New Mexico Cottonwood Lake Study Area - Water Chemistry - Wells - In Situ Measurements Shallow Sediment Geochemical Data for the Cache Creek Settling Basin, Yolo County, California Shallow Sediment Geochemistry in a Mercury-Contaminated Multi-Habitat Floodplain: Cache Creek Settling Basin, Yolo County, California, 2010–17 Carbon and nitrogen limitations of soil microbial biomass in desert ecosystems Data of floodplain soil carbon and nutrient retention along a chronosequence of urban stream restorations in Northern Virginia (2022) Assessing spatial variability of nutrients, phytoplankton, and related water quality constituents in the California Sacramento-San Joaquin Delta during treated wastewater effluent holds: August and September 2019 high resolution mapping surveys Data Supporting Generalized models to estimate carbon and nitrogen stocks of organic layers in Interior Alaska