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1.
Aida Mendez Gary R. Sands Berangere Basin Chang‐Xing Jin Paul J. Wotzka 《Journal of the American Water Resources Association》2004,40(2):385-400
ABSTRACT: Surface and subsurface drainage make crop production economically viable in much of southern Minnesota because drainage allows timely field operations and protects field crops from extended periods of flooded soil conditions. However, subsurface drainage has been shown to increase nitrate/nitrogen losses to receiving waters. When engaging in drainage activities, farmers are increasingly being asked to consider, apart from the economic profit, the environmental impact of drainage. The Agricultural Drainage and Pesticide Transport model (ADAPT) was used in this study to evaluate the impact of subsurface drainage design on the soil water balance over a two‐year period during which observed drainage discharge data were available. Twelve modeling scenarios incorporated four drainage coefficients (DC), 0.64 cm/d, 0.95 cm/d, 1.27 cm/d, and 1.91 cm/d, and three drain depths, 0.84 m, 1.15 m, and 1.45 m. The baseline condition corresponded to the drainage system specifications at the field site: a drain depth and spacing of 1.45 m and 28 m, respectively (DC of 0.64 cm/d). The results of the two‐year simulation suggested that for a given drainage coefficient, soils with the shallower drains (but equal DC) generally have less subsurface drainage and can produce more runoff (but reduced total discharge) and evapotranspiration. The results also suggested that it may be possible to design for both water/nitrate/nitrogen reduction and crop water needs. 相似文献
2.
Krista Harper Catherine Sands Diego Angarita Horowitz Molly Totman Monica Maitín Jonell Sostre Rosado 《Local Environment》2017,22(7):791-808
How do youth learn through participation in efforts to study and change the school food system? Through our participatory youth action research (YPAR) project, we move beyond the “youth as consumer” frame to a food justice youth development (FJYD) approach. We track how a group of youth learned about food and the public policy process through their efforts to transform their own school food systems by conducting a participatory evaluation of farm-to-school efforts in collaboration with university and community partners. We used the Photovoice research method, placing cameras in the hands of young people so that they themselves could document and discuss their concerns and perspectives. The research was designed to gain insight about youths’ knowledge of food, health, and community food systems. Drawing upon the youth group’s insights, we build a framework for building critical consciousness through FJYD. 相似文献
3.
Kenneth T. Gillingham Steven J. Smith Ronald D. Sands 《Mitigation and Adaptation Strategies for Global Change》2008,13(7):675-701
In the coming century, modern bioenergy crops have the potential to play a crucial role in the global energy mix, especially
under policies to reduce carbon dioxide emissions as proposed by many in the international community. Previous studies have
not fully addressed many of the dynamic interactions and effects of a policy-induced expansion of bioenergy crop production,
particularly on crop yields and human food demand. This study combines an updated agriculture and land use (AgLU) model with
a well-developed energy-economic model to provide an analysis of the effects of bioenergy crops on energy, agricultural and
land use systems. The results indicate that carbon dioxide mitigation policies can stimulate a large production of bioenergy
crops, dependent on the level of the policy. This production of bioenergy crops can lead to several impacts on the agriculture
and land use system: decreases in forestland and unmanaged land, decreases in the average yield of food crops, increases in
the prices of food crops, and decreases in the level of human demand of calories.
相似文献
Steven J. Smith (Corresponding author)Email: |
4.
Dhazn Gillig Bruce A. McCarl Ronald D. Sands 《Mitigation and Adaptation Strategies for Global Change》2004,9(3):241-259
An econometrically estimated family ofresponse functions is developed forcharacterizing potential responses togreenhouse gas mitigation policies by theagriculture and forestry sectors in theU.S. The response functions are estimatedbased on results of anagricultural/forestry sector model. Theyprovide estimates of sequestration andemission reductions in forestry andagriculture along with levels of sectoralproduction, prices, welfare, andenvironmental attributes given a carbonprice, levels of demand for agriculturalgoods, and the energy price. Sixalternative mitigation policiesrepresenting types of greenhouse gasoffsets allowed are considered. Resultsindicate that the largest quantity ofgreenhouse gas offset consistently appearswith the mitigation policy that pays forall opportunities. Restricting carbonpayments (emission tax or sequestrationsubsidy) only to aff/deforestation or onlyto agricultural sequestration substantiallyreduces potential mitigation. Highercarbon prices lead to more sequestration,less emissions, reduced consumer and totalwelfare, improved environmental indicatorsand increased producer welfare. 相似文献
5.
J. M. Sands B. K. Fink S. H. McKnight C. H. Newton J.W. Gillespie Jr. G. R. Palmese 《Clean Products and Processes》2001,2(4):228-235
The U.S. Department of Defense (DoD) has been utilizing polymer matrix composite (PMC) and structural adhesive materials in military equipment for over 20 years. However, the volume of PMCs in fielded systems has remained relatively low. Currently, however, the DoD has established strategic goals that will necessitate the use of lightweight composites in order to meet performance requirements. Therefore, the volume of composites used in DoD systems is expected to see an unprecedented 100-fold increase over the next 30 years. As production volumes increase, the need to address environmental impact increases. The major contributions to environmental degradation from composites are generation of hazardous air pollutants (HAPs) and generation of hazardous (HW) and solid wastes. HAPs result primarily during the curing of the composite. HWs arise from expiration of stockpiled resin materials and from soiled support media used during manufacturing and clean up. Due to the wide range of applications and materials systems, as well as manufacturing and repair requirements, a family of environmentally benign solutions is needed to reduce and eliminate environmental impacts from PMC manufacturing. Solutions are proposed involving use of new technologies and materials to reduce pollutants from composite manufacturing. The technologies proposed include alternative curing of thermoset composites using electron beam (E-beam) irradiation and materials substitution employing thermoplastics processed using electromagnetic irradiation. 相似文献
6.
Fluoride in Antarctic marine crustaceans 总被引:2,自引:0,他引:2
The concentration of fluoride in the body parts of a range of Antarctic crustaceans from a variety of habits was examined
with the aim of determining whether fluoride concentration is related to lifestyle or phylogenetic grouping. Euphausiids had
the highest overall fluoride concentrations of a range of Antarctic marine crustaceans examined; levels of up to 5477 μg g−1 were found in the exoskeleton of Euphausia crystallorophias. Copepods had the lowest fluoride levels (0.87 μg g−1 whole-body); some amphipods and mysids also exhibited relatively high fluoride levels. There was no apparent relationship
between the lifestyle of the crustaceans and their fluoride level; benthic and pelagic species exhibited both high and low
fluoride levels. Fluoride was concentrated in the exoskeleton, but not evenly distributed through it; the exoskeleton of the
head, carapace and abdomen contained the highest concentrations of fluoride, followed by the feeding basket and pleopods,
and the eyes. The mouthparts of E.␣superba contained almost 13 000 μg F g−1 dry wt. Antarctic krill tail muscle had low levels of fluoride. After long-term (1 to 5 yr) storage in formalin, fluoride
was almost completely lost from whole euphausiids.
Received: 1 April 1998 / Accepted: 29 July 1998 相似文献
7.
Three cases of intrathoracic hyperechogenic areas on fetal ultrasound are described. Two apparently resolved spontaneously and the infants are alive at 1 year and 7 months, respectively. The third infant was found to have a pulmonary sequestration of the extra-lobar variety which required surgical resection. 相似文献
8.
Peter Miehle Michael Battaglia Peter J. Sands David I. Forrester Paul M. Feikema Stephen J. Livesley Jim D. Morris Stefan K. Arndt 《Ecological modelling》2009
In forest management and ecological research, consideration of the impacts and risks of climate change or management optimisation is complex. Computer models have long been applied as tools for these tasks. Process-based forest growth models claim to overcome the limitations of empirical statistical models, but the capacity of different process-based models and modelling approaches have rarely been compared directly. This study evaluates stepwise multiple regression models in comparison to four process-based modelling approaches (3-PG, 3-PG+, CABALA and Forest-DNDC) for greenfield predictions of Eucalyptus globulus plantation growth from 2 to 8 years after planting throughout southern Australia. 相似文献
9.
Water quality modeling of fertilizer management impacts on nitrate losses in tile drains at the field scale 总被引:2,自引:0,他引:2
Nitrate losses from subsurface tile drained row cropland in the Upper Midwest U.S. contribute to hypoxia in the Gulf of Mexico. Strategies are needed to reduce nitrate losses to the Mississippi River. This paper evaluates the effect of fertilizer rate and timing on nitrate losses in two (East and West) commercial row crop fields located in south-central Minnesota. The Agricultural Drainage and Pesticide Transport (ADAPT) model was calibrated and validated for monthly subsurface tile drain flow and nitrate losses for a period of 1999-2003. Good agreement was found between observed and predicted tile drain flow and nitrate losses during the calibration period, with Nash-Sutcliffe modeling efficiencies of 0.75 and 0.56, respectively. Better agreements were observed for the validation period. The calibrated model was then used to evaluate the effects of rate and timing of fertilizer application on nitrate losses with a 50-yr climatic record (1954-2003). Significant reductions in nitrate losses were predicted by reducing fertilizer application rates and changing timing. A 13% reduction in nitrate losses was predicted when fall fertilizer application rate was reduced from 180 to 123 kg/ha. A further 9% reduction in nitrate losses can be achieved when switching from fall to spring application. Larger reductions in nitrate losses would require changes in fertilizer rate and timing, as well as other practices such as changing tile drain spacings and/or depths, fall cover cropping, or conversion of crop land to pasture. 相似文献
10.
M. Battaglia E.A. PinkardP.J. Sands J.L. BruceA. Quentin 《Ecological modelling》2011,222(17):3193-3202
After presenting a short review of process-based model requirements to capture the plant dynamic response to defoliation, this paper describes the development and testing of a model of crown damage and defoliation for Eucalyptus. A model that calculates light interception and photosynthetic production for canopies that vary spatially and temporally in leaf area and photosynthetic properties is linked to the forest growth model CABALA. The process of photosynthetic up-regulation following defoliation is modelled with a simple conditional switch that triggers up-regulation when foliar damage or removal causes the ratio of functional leaf area to living tissue in the tree to change.We show that the model predicts satisfactorily when validated with trees of Eucalyptus nitens and Eucalyptus globulus from a range of sites of different ages, subject to different types of stress and different types of defoliation events (R2 = 0.96 across a range of sites). However, the complexity of particular situations can cause the model to fail (e.g. very heavy defoliation events where branch death occurs).It is concluded that while the model will not cope with all situations, an appropriate level of generality has been captured to represent many of the physiological processes and feedbacks that occur following defoliation or leaf damage. This makes the model useful for guiding management interventions following pest attack and allows the development of scenarios including climate change impact analyses and decision-making on the merits of post-defoliation fertilisation to expedite recovery. 相似文献