USDA LTAR Common Experiment measurement: Total suspended solids (TSS) v2
Total suspended solids (TSS) refers to all the material from a well-mixed sample retained by a fi... more Total suspended solids (TSS) refers to all the material from a well-mixed sample retained by a filter media. In the case of environmental water samples, TSS is commonly used to measure sediment in surface waters (field runoff, ditches, and streams) but can also be present in subsurface flow where macropore flow or surface inlets to tile drainage systems are present. In some cases, TSS can also include algae or other plant materials that comprise volatile suspended solids (VSS) because combustion in a muffle furnace eliminates them. The recommended method for measuring TSS includes passing a known sample volume through a pre-weighed filter and measuring the oven-dry weight of the material trapped on the filter.
a Conservation Science Program, World Wildlife Fund, 1250 24th St. NW, Washington D.C. 20037, Uni... more a Conservation Science Program, World Wildlife Fund, 1250 24th St. NW, Washington D.C. 20037, United States b Department of Soil, Water and Climate, University of Minnesota, 1991 Upper Buford Circle, St. Paul, MN 55108, United States c Department of Economics, Bowdoin College, 9700 College Station, Brunswick, ME 04011, United States d Department of Applied Economics, University of Minnesota, 1994 Buford Ave, St. Paul, MN, 55108, United States e Institute on the Environment, University of Minnesota, 1954 Buford Ave, St. Paul, MN, 55108, United States
Effect of organic matter source and salinity on dissolved organic matter isolation via ultrafiltration and solid phase extraction
Aquatic Sciences, 2011
Page 1. RESEARCH ARTICLE Effect of organic matter source and salinity on dissolved organic matter... more Page 1. RESEARCH ARTICLE Effect of organic matter source and salinity on dissolved organic matter isolation via ultrafiltration and solid phase extraction Brittany R. Kruger Brent J. Dalzell Elizabeth C. Minor Received: 1 ...
Supplemental information for "Can Woodchip Bioreactors Be Used at a Catchment Scale? Nitrate Performance and Sediment Considerations
This file contains supplementary information referenced in the Journal of the ASABE peer-revie... more This file contains supplementary information referenced in the Journal of the ASABE peer-reviewed article “Can woodchip bioreactors be used at a catchment scale? Nitrate performance and sediment considerations.” The information is of three general types: Written method, tables, and figures. The first page consists of text and equations describing the methods used to determine V-notch weir discharge in the article. Pages 2 through 13 contain ten tables of detailed data documenting duration of flow events, discharge, hydraulic residence time, nitrate-N removal rate, water temperature, nutrient loads, and woodchip ash and sediment contents. Pages 14 through 21 contain seven figures; four figures contain photographs from the experimental site, two are data graphs, and one is a diagram showing the location of woodchip sampling.
Direct temperature-resolved mass spectrometry (DT-MS) was used to evaluate the molecular-level ph... more Direct temperature-resolved mass spectrometry (DT-MS) was used to evaluate the molecular-level photodegradation of dissolved organic matter (DOM) isolated from three sites in a Chesapeake Bay subestuary (swamp-and marsh-influenced up-river, midestuarine, and bay mouth). From each site, filtered (<0.1 or <0.2 mm) water samples were irradiated in solarsimulated ultraviolet light followed by isolation of the DOM using C 18-solid-phase extraction and subsequent DT-MS analysis. To provide background DOM photoreactivity data for the water samples, we also determined dissolved inorganic carbon (DIC) photoproduction and chromophoric dissolved organic matter (CDOM) photobleaching. DIC photoproduction was correlated with initial DOM light absorbance, initial dissolved organic carbon (DOC) concentration, and photobleaching. Changes in DT-MS characteristics within the extracts (in particular, the loss of an "aromatic" signal believed to be from reworked terrestrial material) were found to correlate linearly with the absorbance of the corresponding water samples. A relationship between photobleaching and DT-MS characteristics was also observed, with the upstream samples asymptotically approaching a constant "molecular-level" value as photobleaching increased. Both relationships appeared to be independent of absorbance wavelength in the ultraviolet. Following irradiation, the swamp/marsh-dominated upstream samples resembled the downstream samples in terms of absorption spectra and MS-determined molecular-level characteristics. These shifts indicate that terrestriallyderived DOM may be more difficult to differentiate from marine DOM upon photodegradation, which has implications regarding evaluating the terrestrial impact within the marine DOM pool.
Given an agricultural watershed containing a set of spatial units, and a set of land management p... more Given an agricultural watershed containing a set of spatial units, and a set of land management practices, the Geodesign Optimization (GOP) aims to find a land management practice for each spatial unit that optimizes overall water quality improvements in the watershed under both budget constraint and spatial constraints (e.g., minimum contiguous area, shape) arising from farm equipment operation practicalities. GOP is important for redesign of agricultural watersheds in Midwestern US to mitigate soil and water quality degradation and loss of habitat. The problem is computationally challenging as a large-scale combinatorial problem (NP-hard) under spatial constraints. Existing optimization techniques do not address spatial constraints, and lead to impractical solutions requiring frequent farm equipment reconfiguration. In this paper, we formalize the spatially-constrained GOP and propose a novel spatial optimizer which explores optimal solution without constraint violations. Our approach is further validated through a Geodesign case study at Seven Mile Creek watershed in Midwestern US.
Given an agricultural watershed containing a set of spatial units, and a set of land management p... more Given an agricultural watershed containing a set of spatial units, and a set of land management practices, the Geodesign Optimization (GOP) aims to find a land management practice for each spatial unit that optimizes overall water quality improvements in the watershed under both budget constraint and spatial constraints (e.g., minimum contiguous area, shape) arising from farm equipment operation practicalities. GOP is important for redesign of agricultural watersheds in Midwestern US to mitigate soil and water quality degradation and loss of habitat. The problem is computationally challenging as a large-scale combinatorial problem (NP-hard) under spatial constraints. Existing optimization techniques do not address spatial constraints, and lead to impractical solutions requiring frequent farm equipment reconfiguration. In this paper, we formalize the spatially-constrained GOP and propose a novel spatial optimizer which explores optimal solution without constraint violations. Our appr...
The Influence of Landscape Drainage on Biogeochemical Cycling of Carbon in Agricultural Ecosystems
The movement of water through agricultural ecosystems is often modified by the presence of open d... more The movement of water through agricultural ecosystems is often modified by the presence of open ditches and subsurface tile drainage systems. Despite the common occurrence of these practices, particularly in the corn- and soybean-producing regions of the midwestern United States, much remains unknown about how altered drainage patterns may influence carbon export from agricultural landscapes. In this study, we examined
Global demand for commodities prompted the expansion of row crop agriculture in the 25 Upper Midw... more Global demand for commodities prompted the expansion of row crop agriculture in the 25 Upper Midwest, USA with unknown consequences for multiple ecosystem services. The 26 Conservation Reserve Program (CRP) was designed to protect these services by paying farmers 27 to retire environmentally sensitive land. Here we assessed whether the benefits provided by 28 CRP's targeted retirement of agricultural land are equal to or greater in value than the cost of 29 rental payments to farmers. We quantified the benefits of CRP lands for reducing flood damages, improving water quality and air-quality, and contributing to greenhouse gas mitigation in the Indian Creek watershed in Iowa. We found that for all assessed scenarios of CRP implementation, the ecosystem service benefits provided by CRP lands exceed the cost of payments to farmers. Expanding CRP implementation under one of three potential scenarios
Despite its importance for aquatic ecosystem function and watershed carbon budgets, little is kno... more Despite its importance for aquatic ecosystem function and watershed carbon budgets, little is known about how land use influences dissolved organic matter (DOM) export. We investigated the influence of subsurface soil drainage, widespread in the Midwestern United States, on DOM export from agricultural fields designed to drain water at either 13 mm d -1 (conventional) or 51 mm d -1 (intense). Intense drainage exported 55% (±22%) more dissolved organic carbon (DOC) per year than conventional drainage due to both increased concentration and water yield. DOC export from plots was strongly dependent on precipitation and showed considerable interannual variability. Mean DOC concentrations in drainage water were low (1.62 and 1.87 mg L -1 for conventional and intense treatments), and fluorescence index (FI) measurements showed that it had a microbial source with little evidence of terrestrially derived material, suggesting that flow through deeper, organic-poor soil horizons is important in regulating DOC export from these plots. We compared DOM in subsurface drains with downstream ditch and stream sites. Increases in DOC concentration and molecular weight accompanied by decreasing FI values at downstream sites showed that streams gain a large amount of terrestrially derived DOM during base flow transport through agricultural landscapes, probably from riparian zones. These results show that DOM compositional characteristics change with catchment area and that the relevant observation scale for DOM dynamics is likely to vary among watersheds. This study also demonstrates that land management practices can directly affect DOC via changes to water flow paths. These results are critical for improving model estimates of DOM export from agricultural landscapes as well as predicting how DOC export will respond to changing land use and climate.
This article presents a modelling system for synthesising heterogeneous productivity and nutrient... more This article presents a modelling system for synthesising heterogeneous productivity and nutrient loading potentials inherent in agricultural cropland for policy use. Phosphorus abatement cost functions for cropland farmers in a southeastern Minnesota watershed are metamodelled using frontier analysis. These functions are used to evaluate policies aimed at reducing non point phosphorus discharges into the Minnesota River. Results indicate an efficiently targeted policy to reduce phosphorus discharge by 40% would cost US$ 167,700 or 844 per farm.
Integrated assessment modeling reveals near-channel management as cost-effective to improve water quality in agricultural watersheds
Proceedings of the National Academy of Sciences
Despite decades of policy that strives to reduce nutrient and sediment export from agricultural f... more Despite decades of policy that strives to reduce nutrient and sediment export from agricultural fields, surface water quality in intensively managed agricultural landscapes remains highly degraded. Recent analyses show that current conservation efforts are not sufficient to reverse widespread water degradation in Midwestern agricultural systems. Intensifying row crop agriculture and increasing climate pressure require a more integrated approach to water quality management that addresses diverse sources of nutrients and sediment and off-field mitigation actions. We used multiobjective optimization analysis and integrated three biophysical models to evaluate the cost-effectiveness of alternative portfolios of watershed management practices at achieving nitrate and suspended sediment reduction goals in an agricultural basin of the Upper Midwestern United States. Integrating watershed-scale models enabled the inclusion of near-channel management alongside more typical field management a...
Climate change, land clearing, and artificial drainage have increased the Minnesota River Basin’s... more Climate change, land clearing, and artificial drainage have increased the Minnesota River Basin’s (MRB) stream flows, enhancing erosion of channel banks and bluffs. Accelerated erosion has increased sediment loads and sedimentation rates downstream. High flows could be reduced through increased water storage (e.g., wetlands or detention basins), but quantifying the effectiveness of such a strategy remains a challenge. We used the Soil and Water Assessment Tool (SWAT) to simulate changes in river discharge from various water retention site (WRS) implementation scenarios in the Le Sueur watershed, a tributary basin to the MRB. We also show how high flow attenuation can address turbidity issues by quantifying the impact on near-channel sediment loading in the watershed’s incised reaches. WRS placement in the watershed, hydraulic conductivity (K), and design depth were varied across 135 simulations. The dominant control on site performance is K, with greater flow reductions allowed by h...
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