Design of Adsorption Equipment in Air Pollution Control

The purpose of this paper is to provide a helpful tool for the design of adsorption equipment, recognizing in particular the recent, more stringent regulations on air pollution. This work is based on an earlier paper by Hougen and Marshall,¹ who developed therein an analytical adsorption model. Under certain assumptions, especially that of linear adsorption equilibrium, it is possible to express the results in the form of convenient usable charts. Although more sophisticated models² have recently been developed, the numerical effort involved in solving the associated partial differential equations is such that practical application is often questionable.     

Price Determination and Efficiency in the Market for South Platte Basin Ditch Company Shares

Water scarcity presents an obstacle to economic development in the western United States. Water rights markets help improve water allocation, allowing states to derive the highest economic benefit from available resources, and supporting new uses and economic development. However, the implicit (marginal) prices of water rights attributes are uncertain. To address this problem, we apply econometric analysis to a unique dataset to estimate the implicit values that market participants place on the attributes of shares of ditch company water rights in Colorado's South Platte River Basin. Our analysis demonstrates that ditch company share buyers value proximity of water diversion, reliability of water deliveries, and temporal flexibility of water use. To assess reliability we introduce the use of the coefficient of variation to capture, in one variable, the randomness of supply from ditch company shares that are not a single water right, but a portfolio of rights with different appropriation dates. Finally, we test and correct for spatial autocorrelation for the first time in a study of water market prices.     

Charcoal production in a UK moorland wildfire – How important is it?

Wildfires are a common feature of peatland environments, but the carbon balance of these wildfires is often not considered and the production of refractory black carbon in these wildfires could be an important addition to carbon accumulation and mitigate losses of biomass during the fire. This study investigates the biomass and carbon losses during a moorland wildfire. Changes in above-ground carbon stocks were calculated using a combination of field data, laboratory measurements and literature values. The results show that approximately 14% of the carbon in the original above-ground biomass remained on the site after the burn. Black carbon production was approximately 6 gC m(-2) which constituted 4.3% of the biomass lost. The survival of biomass and black carbon may help to mitigate the loss of carbon during the fire.     

Job level risk assessment using task level ACGIH hand activity level TLV scores: a pilot study.

Existing upper extremity musculoskeletal disorder analytical tools are primarily intended for single or mono-task jobs. However, many jobs contain more than 1 task and some include job rotation. This case/control study investigates methods of modifying an existing tool, the American Conference of Governmental Industrial Hygienists (ACGIH) Hand Activity Level (HAL) Threshold Limit Value (TLV), to assess the upper extremity risk of multi-task jobs. Various methods of combining the task differences and ratios into a job level assessment were explored. Two methods returned significant odds ratios, (p < .05) of 18.0 (95% CI 1.8-172) and 12.0 (95% CI 1.2-120). These results indicate that a modified ACGIH HAL TLV may provide insight into the work-related risk of multi-task jobs. Further research is needed to optimize this process.     

Phosphorus transfer in runoff following application of fertilizer, manure, and sewage sludge

Phosphorus (P) transfer in surface runoff from field plots receiving either no P, triplesuperphoshate (TSP), liquid cattle manure (LCS), liquid anaerobically digested sludge (LDS), or dewatered sludge cake (DSC) was compared over a 2-yr period. Dissolved inorganic P concentrations in runoff increased from 0.1 to 0.2 mg L(-1) on control and sludge-treated plots to 3.8 and 6.5 mg L(-1) following application of LCS and TSP, respectively, to a cereal crop in spring. When incorporated into the soil in autumn, runoff dissolved P concentrations were typically < 0.5 mg L(-1) across all plots, and particulate P remained the dominant P form. When surface-applied in autumn to a consolidated seedbed, direct loss of LCS and LDS increased both runoff volume and P transfers, but release of dissolved P occurred only from LCS. The largest P concentrations (>70 mg L(-1)) were recorded following TSP application without any increase in runoff volume, while application of bulky DSC significantly reduced total P transfers by 70% compared with the control due to a reduced runoff volume. Treatment effects in each monitoring period were most pronounced in the first runoff event. Differences in the release of P from the different P sources were related to the amounts of P extracted by either water or sodium bicarbonate in the order TSP > LCS > LDS > DSC. The results suggest there is a lower risk of P transfer in land runoff following application of sludge compared with other agricultural P amendments at similar P rates.     

Bromide and nitrate movement through undisturbed soil columns

Field experiments often assume that Br-, 14NO3(-)-N, and 15NO3(-)-N have similar leaching kinetics. This study tested this assumption. Twenty-four undisturbed soil columns (15-cm diameter) were collected from summit-shoulder, backslope, and footslope positions of a no-tillage field with a corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] rotation. Each of the landscape positions had a different soil series. After conditioning the columns with 4 L of 0.01 M CaCl2 (2 pore volumes), 15N-labeled Ca(NO3)2 and KBr were applied to the soil surface and leached with 4 L of 0.01 M CaCl2. Leachate was collected, weighed, and analyzed for NO3(-)-N, NH4(+)-N, 15N, 14N, and Br-. The total amount of 15NO3(-)-N and 14NO3(-)-N collected in 1000, 2000, and 3000 mL of leachate was similar. These data suggest that 15N discrimination during leaching did not occur. Bromide leached faster through the columns than NO3(-)-N. The more rapid transport of Br- than NO3(-)-N was attributed to lower Br- (0.002 +/- 0.036 mg kg(-1)) than NO3(-)-N (0.17 +/- 0.03 mg kg(-1)) sorption. Results from this study suggest that (i) if Br- is used to estimate NO3(-)-N leaching loss, then NO3(-)-N leaching losses may be overestimated by 25%; (ii) the potential exists for landscape position to influence anion retention and movement in soil; and (iii) 15N discrimination was not detected during the leaching process.     

Modeling the impacts of temperature and precipitation changes on soil CO2 fluxes from a Switchgrass stand recently converted from cropland

Switchgrass(Panicum virgatum L.) is a perennial C_4 grass native to North America and successfully adapted to diverse environmental conditions. It offers the potential to reduce soil surface carbon dioxide(CO_2) fluxes and mitigate climate change. However, information on how these CO_2 fluxes respond to changing climate is still lacking. In this study, CO_2 fluxes were monitored continuously from 2011 through 2014 using high frequency measurements from Switchgrass land seeded in 2008 on an experimental site that has been previously used for soybean(Glycine max L.) in South Dakota, USA. DAYCENT, a process-based model, was used to simulate CO_2 fluxes. An improved methodology CPTE[Combining Parameter estimation(PEST) with "Trial and Error" method] was used to calibrate DAYCENT. The calibrated DAYCENT model was used for simulating future CO_2 emissions based on different climate change scenarios. This study showed that:(i) the measured soil CO_2 fluxes from Switchgrass land were higher for 2012 which was a drought year, and these fluxes when simulated using DAYCENT for long-term(2015–2070) provided a pattern of polynomial curve;(ii) the simulated CO_2 fluxes provided different patterns with temperature and precipitation changes in a long-term,(iii) the future CO_2 fluxes from Switchgrass land under different changing climate scenarios were not significantly different, therefore, it can be concluded that Switchgrass grown for longer durations could reduce changes in CO_2 fluxes from soil as a result of temperature and precipitation changes to some extent.     

Forest succession suppressed by an introduced plant-fungal symbiosis

Microbial symbionts can affect plant nutrition, defensive chemistry, and biodiversity. Here we test the hypothesis that symbionts alter the speed and direction of plant succession in communities that are shifting from grasslands to forests. A widespread C3 grass introduced to the United States, Lolium arundinaceum (tall fescue), hosts a fungal endophyte that is toxic to herbivores. In replicated experimental grasslands, the presence of the endophyte in tall fescue reduced tree abundance and size, altered tree composition, and slowed plant species turnover. In addition, consumption of tree seedlings by voles (Microtus spp.) was 65% higher in plots with the endophyte at the one grassland site where these data were collected. Despite its negligible contribution to community biomass, a microbial symbiont suppressed tree establishment, posing an important constraint on the natural transition from grasslands to forests.     

Differences in herbicide adsorption on soil using several soil ph modification techniques

Abstract

Effects of soil pH on weak acid and weak base herbicide adsorption by soil are often determined by modifying soil pH in the laboratory. Modification of soil pH with acidic or basic amendments such as HCl or NaOH can cause changes in the soil‐solution system that may affect pesticide adsorption. The partition coefficients (K_d) for atrazine and dicamba by Waukegan, Piano, and Walla Walla silt loam soils stabilized in the field at different pH levels were compared to the K_d obtained when the soil pH was adjusted with acidic or basic amendments before herbicide addition. NaOH addition to raise soil pH generally increased the soluble soil organic carbon (SSOC) concentration in solution compared to field soils at the same pH and to soil treated with Ca(OH)₂. NaOH decreased the soil solution ionic strength slightly. Acidifying soils increased the soil solution ionic strength, when compared to field soils at the same pH and had no effect on SSOC concentration. Dicamba adsorption to soil was minimal (K_d < 0.22) and not influenced by soil pH in the range of 4.1 to 6.0; adsorption by laboratory amended soils in some cases underestimated adsorption compared to nonamended soils. Atrazine adsorption increased with decreased pH in all soils, and was overestimated slightly by several laboratory treatments to reduce pH compared to adsorption by field soils. Treatments to raise the pH did not affect atrazine adsorption. Overall, herbicide adsorption differences due to pH modification were small (<30%), and were not affected by soil solution ionic strength, saturating cation, or SSOC concentration in solution.