Economic feasibility of no-tillage and manure for soil carbon sequestration in corn production in northeastern Kansas

This study examined the economic potential of no-tillage versus conventional tillage to sequester soil carbon by using two rates of commercial N fertilizer or beef cattle manure for continuous corn (Zea mays L.) production. Yields, input rates, field operations, and prices from an experiment were used to simulate a distribution of net returns for eight production systems. Carbon release values from direct, embodied, and feedstock energies were estimated for each system, and were used with soil carbon sequestration rates from soil tests to determine the amount of net carbon sequestered by each system. The values of carbon credits that provide an incentive for managers to adopt production systems that sequester carbon at greater rates were derived. No-till systems had greater annual soil carbon gains, net carbon gains, and net returns than conventional tillage systems. Systems that used beef cattle manure had greater soil carbon gains and net carbon gains, but lower net returns, than systems that used commercial N fertilizer. Carbon credits would be needed to encourage the use of manure-fertilized cropping systems.     

Persistence and Changes in Bioavailability of Dieldrin, DDE, and Heptachlor Epoxide in Earthworms Over 45 Years

The finding of dieldrin (88 ng/g), DDE (52 ng/g), and heptachlor epoxide (19 ng/g) in earthworms from experimental plots after a single moderate application (9 kg/ha) 45 years earlier attests to the remarkable persistence of these compounds in soil and their continued uptake by soil organisms. Half-lives (with 95 % confidence intervals) in earthworms, estimated from exponential decay equations, were as follows: dieldrin 4.9 (4.3–5.7) years, DDE 5.3 (4.7–6.1) years, and heptachlor epoxide 4.3 (3.8–4.9) years. These half-lives were not significantly different from those estimated after 20 years. Concentration factors (dry weight earthworm tissue/dry weight soil) were initially high and decreased mainly during the first 11 years after application. By the end of the study, average concentration factors were 1.5 (dieldrin), 4.0 (DDE), and 1.8 (heptachlor epoxide), respectively.     

Inputs of heavy metals due to agrochemical use in tobacco fields in Brazil’s Southern Region

Only a few studies have assessed the joint incorporation of heavy metals into agricultural systems based on the range of agrochemicals used on a specific agricultural crop. This study was conducted to assess the heavy metals input through application of the main agrochemicals used in Brazilian tobacco fields. A total of 56 samples of different batches of 5 fertilizers, 3 substrates, 8 insecticides, 3 fungicides, 2 herbicides, and 1 growth regulator commonly used in the cultivation of tobacco in Brazil’s Southern Region were collected from 3 warehouses located in the States of Rio Grande do Sul, Santa Catarina, and Paraná. The total As, Cd, Co, Cr, Cu, Hg, Fe, Mn, Ni, Pb, and Zn content of the samples was then determined and compared with the regulations of different countries and information found in the available literature. The fertilizers were identified as the primary source of heavy metals among the agrochemicals used. Application of pesticides directly to the shoots of tobacco plants contributed very little to the supply of heavy metals. The agrochemicals used in Brazilian tobacco fields provide lower inputs of the main heavy metals that are nonessential for plants than those registered in the international literature for the majority of crop fields in different regions of the world.     

Performance Characteristics of Instrumental Methods for Monitoring Sulfur Dioxide

The performance characteristics of commercially available sulfur dioxide monitors were determined. Con-ductimetric, colorimetric, and coulometric analyzers were investigated. During this phase of the study, characteristics that were more closely related to field operation were studied. These included comparability of data among the instruments over a period of time, weekly calibration drift, maintenance requirements (including operating cost), unattended operation performance, and the effect of rotameter changes on calibration. The methodology and apparatus used to determine each operational parameter are described. The results of this study should be useful in the selection of instruments for monitoring sulfur dioxide.     

Real-World Emissions from a Modern Production Vehicle Driven in Los Angeles

The emissions of hydrocarbons, nitric oxide, and carbon monoxide from one modern vehicle were measured using on-board instrumentation during about 350 miles of driving in Los Angeles, California. Emissions during on-road driving were compared to those obtained on dynamometers using the urban dynamometer driving schedule (UDDS). Although this study only used one driver and vehicle, tested over a relatively short distance, the analysis technique may be useful for a larger evaluation of off-cycle emissions.

The test vehicle had low warmed-up running emissions over the UDDS and for most of the on-road testing where the air-to-fuel ratio was maintained at the stoichiometric point. However, occasional heavily-loaded conditions during the on-road testing led to richerthan-stoiehiometric operation.

During these brief enrichment events, which lasted up to 29 seconds, CO emissions were increased by a factor of 2500 and HC by a factor of 40 over closed-loop stoichiometric operation. Nitrogen oxide emissions were similar during low-load stoichiometric operation and high-load enriched operation. The relatively constant gram-per-second emission rate of CO and HC observed during enriched operation suggests that such information can be combined with determinations of the frequency of enrichment for a large number of vehicles with similar calibrations to estimate the impact of the additional emissions from enrichment on emissions inventories.     

Modeling the photo-oxidation of dissolved organic matter by ultraviolet radiation in freshwater lakes: implications for mercury bioavailability

Uncertainties in projected ultraviolet (UV) radiation may lead to future increases in UV irradiation of freshwater lakes. Because dissolved organic carbon (DOC) is the main binding phase for mercury (Hg) in freshwater lakes, an increase in DOC photo-oxidation may affect Hg speciation and bioavailability. We quantified the effect of DOC concentration on the rate of abiotic DOC photo-oxidation for five lakes (DOC=3.27-12.3 mg L(-1)) in Kejimkujik National Park, Canada. Samples were irradiated with UV-A or UV-B radiation over a 72-h period. UV-B radiation was found to be 2.36 times more efficient at photo-oxidizing DOC than UV-A, with energy-normalized rates of dissolved inorganic carbon (DIC) production ranging from 3.8×10(-5) to 1.1×10(-4) mg L(-1)J(-1) for UV-A, and from 6.0×10(-5) to 3.1×10(-4) mg L(-1)J(-1) for UV-B. Energy normalized rates of DIC production were positively correlated with DOC concentrations. Diffuse integrated attenuation coefficients were quantified in situ (UV-A K(d)=0.056-0.180 J cm(-1); UV-B K(d)=0.015-0.165 J cm(-1)) and a quantitative depth-integrated model for yearly DIC photo-production in each lake was developed. The model predicts that, UV-A produces between 3.2 and 100 times more DIC (1521-2851 mg m(-2) year(-1)) than UV-B radiation (29.17-746.7 mg m(-2) year(-1)). Future increases in UV radiation may increase DIC production and increase Hg bioavailability in low DOC lakes to a greater extent than in high DOC lakes.     

Insights from years of performance that are shaping injection‐based remediation systems

Research and field experience from the past 15 years has allowed remediation professionals to purposefully design injection‐based remediation systems with a high potential for success. Industry professionals can now claim a number of achievements that were unthinkable just a few years ago: (1) we have demonstrated that maximum contaminant levels (MCLs) can be achieved for multiple contaminants; (2) we have successfully targeted dense nonaqueous‐phase liquid (DNAPL) source zones; (3) we have expanded our understanding of injection hydraulics to treat large plumes; and (4) we have collected sufficient data on rates of treatment to be more predictive regarding outcomes. The next decade will continue to evolve the design and execution of these types of systems for application to more complex problems. At this point on the timeline, questions regarding the mechanisms of treatment have largely been addressed, allowing a shift in focus to operational enhancements. Specific operational insights arising from the body of work to date that arguably will continue to shape and influence the design and execution of injection‐based remediation systems include: (1) the fact that delivery does not always equal distribution, (2) treatment optimization requires aquifer tuning, and (3) life‐cycle costs can be reduced with remedy‐optimized investigation. The number of examples that support these concepts and their ramifications to future technology refinement is already increasing, demonstrating how the refinements that can be made around these areas of focus will enhance our ability to effectively tackle larger and more complicated plumes, and do so with maximum efficiency. © 2011 Wiley Periodicals, Inc.