Switchgrass biochar affects two aridisols

The use of biochar has received growing attention because of its ability to improve the physicochemical properties of highly weathered Ultisols and Oxisols, yet very little research has focused on its effects in Aridisols. We investigated the effect of low or high temperature (250 or 500°C) pyrolyzed switchgrass () biochar on two Aridisols. In a pot study, biochar was added at 2% w/w to a Declo loam (Xeric Haplocalcids) or to a Warden very fine sandy loam (Xeric Haplocambids) and incubated at 15% moisture content (by weight) for 127 d; a control (no biochar) was also included. Soils were leached with 1.2 to 1.3 pore volumes of deionized HO on Days 34, 62, 92, and 127, and cumulative leachate Ca, K, Mg, Na, P, Cu, Fe, Mn, Ni, Zn, NO-N, NO-N, and NH-N concentrations were quantified. On termination of the incubation, soils were destructively sampled for extractable Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P, Zn, NO-N, and NH-N, total C, inorganic C, organic C, and pH. Compared with 250°C, the 500°C pyrolysis temperature resulted in greater biochar surface area, elevated pH, higher ash content, and minimal total surface charge. For both soils, leachate Ca and Mg decreased with the 250°C switchgrass biochar, likely due to binding by biochar's functional group sites. Both biochars caused an increase in leachate K, whereas the 500°C biochar increased leachate P. Both biochars reduced leachate NO-N concentrations compared with the control; however, the 250°C biochar reduced NO-N concentrations to the greatest extent. Easily degradable C, associated with the 250°C biochar's structural make-up, likely stimulated microbial growth, which caused NO-N immobilization. Soil-extractable K, P, and NO-N followed a pattern similar to the leachate observations. Total soil C content increases were linked to an increase in organic C from the biochars. Cumulative results suggest that the use of switchgrass biochar prepared at 250°C could improve environmental quality in calcareous soil systems by reducing nutrient leaching potential.     

Bioaccumulation of Selenium by the Bryophyte Hygrohypnum ochraceum in the Fountain Creek Watershed, Colorado

Aquatic bryophytes, Hygrohypnum ochraceum, were deployed “in situ” at 14 sites in the Fountain Creek Watershed, spring and fall, 2007 to study selenium (Se) accumulation. Dissolved, total, and pore (sediment derived) water samples were collected and water quality parameters determined while plants were exposed to the water for 10?days. There was a trend showing plant tissue-Se uptake with distance downstream and we found a strong correlation between Se in the water with total hardness in both seasons. There was a modest association between Se-uptake in plants with hardness in the spring of 2007 but not the fall. Plants bioconcentrated Se from the water by a factor of 5.8?×?10³ at Green Mountain Falls and 1.5?×?10⁴ at Manitou Springs in the fall of 2007. Both are examples of the bioconcentration abilities of the plants, primarily in the upper reaches of the watershed where bioconcentration factors were highest. However, the mean minima and maxima of Se in the plants in each of the three watershed segments appeared similar during both seasons. We found direct relationships between the pore and dissolved Se in water in the spring (R ²?=?0.84) and fall (R ²?=?0.95) and dissolved Se and total hardness in the spring and fall (R ²?=?0.92). The data indicate that H. ochraceum was a suitable indicator of Se bioavailability and Se uptake in other trophic levels in the Fountain Creek Watershed based on a subsequent study of Se accumulation in fish tissues at all 14 sites.     

Relationships Between Nitrogen Transformation Rates and Gene Abundance in a Riparian Buffer Soil

Denitrification is a critical biogeochemical process that results in the conversion of nitrate to volatile products, and thus is a major route of nitrogen loss from terrestrial environments. Riparian buffers are an important management tool that is widely utilized to protect water from non-point source pollution. However, riparian buffers vary in their nitrate removal effectiveness, and thus there is a need for mechanistic studies to explore nitrate dynamics in buffer soils. The objectives of this study were to examine the influence of specific types of soluble organic matter on nitrate loss and nitrous oxide production rates, and to elucidate the relationships between these rates and the abundances of functional genes in a riparian buffer soil. Continuous-flow soil column experiments were performed to investigate the effect of three types of soluble organic matter (citric acid, alginic acid, and Suwannee River dissolved organic carbon) on rates of nitrate loss and nitrous oxide production. We found that nitrate loss rates increased as citric acid concentrations increased; however, rates of nitrate loss were weakly affected or not affected by the addition of the other types of organic matter. In all experiments, rates of nitrous oxide production mirrored nitrate loss rates. In addition, quantitative polymerase chain reaction (qPCR) was utilized to quantify the number of genes known to encode enzymes that catalyze nitrite reduction (i.e., nirS and nirK) in soil that was collected at the conclusion of column experiments. Nitrate loss and nitrous oxide production rates trended with copy numbers of both nir and 16s rDNA genes. The results suggest that low-molecular mass organic species are more effective at promoting nitrogen transformations than large biopolymers or humic substances, and also help to link genetic potential to chemical reactivity.     

Prediction of Streamflow Regime and Annual Runoff for Ungauged Basins Using a Distributed Monthly Water Balance Model1

Moore, R.D. (Dan), J.W. Trubilowicz, and J.M. Buttle, 2011. Prediction of Streamflow Regime and Annual Runoff for Ungauged Basins Using a Distributed Monthly Water Balance Model. Journal of the American Water Resources Association (JAWRA) 48(1): 32‐42. DOI: 10.1111/j.1752‐1688.2011.00595.x Abstract: Prediction of streamflow in ungauged basins is a global challenge, but is particularly an issue in physiographically complex regions like British Columbia (BC), Canada. The objective of this study was to assess the accuracy of a simple water balance model that can be run using existing spatial datasets. The model was developed by modifying an existing monthly water balance model to account for interception loss from forest canopy, glacier melt, and evaporation from lakes. The model was run using monthly climate normals from the ClimateBC application, which have a horizontal resolution of 400 m. Each ClimateBC grid cell was classified as forest, open land, glacier or water surface based on provincial scale digital maps of biogeoclimatic zones, glaciers, and water. The output was monthly mean runoff from each grid cell. These values were integrated within the catchment boundaries for streams gauged by the Water Survey of Canada. Annual runoff was predicted with modest accuracy: after updating the predicted runoff by interpolating errors from neighboring gauged streams, the mean absolute error was 25.4% of the gauged value, and 52% of the streams had errors less than 20%. However, the model appears to be quite robust in distinguishing between pluvial, hybrid, and melt‐dominated hydroclimatic regimes, and therefore has promise as a tool for catchment classification.     

Watershed Regressions for Pesticides (warp) Models for Predicting Atrazine Concentrations in Corn Belt Streams1

Stone, Wesley W. and Robert J. Gilliom, 2012. Watershed Regressions for Pesticides (WARP) Models for Predicting Atrazine Concentrations in Corn Belt Streams. Journal of the American Water Resources Association (JAWRA) 48(5): 970‐986. DOI: 10.1111/j.1752‐1688.2012.00661.x Abstract: Watershed Regressions for Pesticides (WARP) models, previously developed for atrazine at the national scale, are improved for application to the United States (U.S.) Corn Belt region by developing region‐specific models that include watershed characteristics that are influential in predicting atrazine concentration statistics within the Corn Belt. WARP models for the Corn Belt (WARP‐CB) were developed for annual maximum moving‐average (14‐, 21‐, 30‐, 60‐, and 90‐day durations) and annual 95th‐percentile atrazine concentrations in streams of the Corn Belt region. The WARP‐CB models accounted for 53 to 62% of the variability in the various concentration statistics among the model‐development sites. Model predictions were within a factor of 5 of the observed concentration statistic for over 90% of the model‐development sites. The WARP‐CB residuals and uncertainty are lower than those of the National WARP model for the same sites. Although atrazine‐use intensity is the most important explanatory variable in the National WARP models, it is not a significant variable in the WARP‐CB models. The WARP‐CB models provide improved predictions for Corn Belt streams draining watersheds with atrazine‐use intensities of 17 kg/km² of watershed area or greater.     

Modeled Summer Background Concentration of Nutrients and Suspended Sediment in the Mid‐Continent (USA) Great Rivers1

Angradi, Ted R., David W. Bolgrien, Matt A. Starry, and Brian H. Hill, 2012. Modeled Summer Background Concentration of Nutrients and Suspended Sediment in the Mid‐Continent (USA) Great Rivers. Journal of the American Water Resources Association (JAWRA) 48(5): 1054‐1070. DOI: 10.1111/j.1752‐1688.2012.00669.x Abstract: We used regression models to predict summer background concentration of total nitrogen (N), total phosphorus (P), and total suspended solids (TSS), in the mid‐continent great rivers: the Upper Mississippi, the Lower Missouri, and the Ohio. From multiple linear regressions of water quality indicators with land use and other stressor variables, we determined the concentration of the indicators when the predictor variables were all set to zero — the y‐intercept. Except for total P on the Upper Mississippi River, we could predict background concentration using regression models. Predicted background concentration of total N was about the same on the Upper Mississippi and Lower Missouri Rivers (430 μg l^?1), which was lower than percentile‐based values, but was similar to concentrations derived from the response of sestonic chlorophyll a to great river total N concentration. Background concentration of total P on the Lower Missouri (65 μg l^?1) was also lower than published and percentile‐based concentrations. Background TSS concentration was higher on the Lower Missouri (40 mg l^?1) than the other rivers. Background TSS concentration on the Upper Mississippi (16 mg l^?1) was below a threshold (30 mg l^?1) designed to protect aquatic vegetation. Our model‐predicted concentrations for the great rivers are an attempt to estimate background concentrations for water quality indicators independent from thresholds based on percentiles or derived from stressor‐response relationships.     

Constitutional tolerance to heavy metals of a fiber crop, ramie (Boehmeria nivea), and its potential usage

It is observed that ramie (Boehmeria nivea), an economic fiber crop, can establish and colonize metal-contaminated sites in China. Metal tolerance and accumulation by ramie originating from 13 metal-contaminated and 4 “clean” sites in China were compared under field and hydroponic conditions. All selected populations and germplasms displayed good growth performance under diverse metal-contaminated habitats; while growth responses, metal accumulation and tolerance were similar among the 8 populations and 2 germplasms when exposed to solutions containing elevated As, Cd, Pb, or Zn in the laboratory. These revealed that ramie possesses a certain degree of constitutional metal tolerance. To our knowledge, this is the first report of constitutional metal tolerance possessed by a fiber crop. Ramie can be considered as a good candidate for both fiber production and phytoremediation of sites contaminated by multi-metals, as it accumulates relative low metal concentrations, but possesses both high biomass and high economic value.     

Mobility of radium and trace metals in sediments of the Winterbeek: Application of sequential extraction and DGT techniques

For several decades, phosphate ores containing ²²⁶Ra as well as several trace metals have been processed in Belgium to produce calcium phosphate for use in cattle food. The waste water is discharged in two small rivers, the Laak and the Winterbeek.In this study, the levels of ²²⁶Ra and trace metals in surface water and sediments of the Winterbeek were investigated and the mobility of these compounds was assessed using DGT (Diffusive Gradient in Thin Films) and sequential extraction techniques.The concentrations of ²²⁶Ra and trace metals in water and sediment indicate a decreasing trend in inputs to the Winterbeek.The mobility of ²²⁶Ra, assessed by DGT, is related to the reductive mobilization of Fe. The sequential extraction technique shows that at some stations an important fraction of ²²⁶Ra is found to labile sediment phases.Diffusive ²²⁶Ra sediment fluxes, are however, relatively small and have only a minor contribution to the water column concentration of ²²⁶Ra.