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441.
Small farm ponds: overlooked features with important impacts on watershed sediment transport
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Matthew D. Berg Sorin C. Popescu Bradford P. Wilcox Jay P. Angerer Edward C. Rhodes Jason McAlister William E. Fox 《Journal of the American Water Resources Association》2016,52(1):67-76
Despite their size, small farm ponds are important features in many landscapes. Yet hydrographical databases often fail to capture these ponds, and their impacts on watershed processes remain unclear. For a 230‐km2 portion of central Texas, United States (U.S.), we created a historical inventory of ponds and quantified the accuracy of automated detection methods under varying drought conditions. In addition, we documented pond dredging/enlargement events and identified sites that had been abandoned. We also analyzed sediment cores from downstream reservoirs to track changes in watershed sediment transport. Over 75 years, pond densities increased more than 350% — to among the highest documented in the U.S. — and the ability of automated methods to detect these ponds was highly dependent on drought severity (R2 = 0.96). Approximately 5% of ponds present in the 1950s were no longer present in 2012, while 33% were dredged between 1937 and 2012. Downstream reservoir sedimentation has decreased by an average of 55% as ponds have increased in number. These findings suggest that small ponds and the maintenance of trapping efficiency have large‐scale impacts on sediment dynamics. Accurately accounting for these storage effects is vital to water resource planning efforts. 相似文献
442.
Recycling Irrigation Reservoir Stratification and Implications for Crop Health and Production
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Haibo Zhang Patricia A. Richardson Bruk E. Belayneh Andrew Ristvey John Lea‐Cox Warren E. Copes Gary W. Moorman Chuanxue Hong 《Journal of the American Water Resources Association》2016,52(3):620-631
Recycling irrigation reservoirs (RIRs) are an emerging aquatic ecosystem and water resource of global significance. This study investigated the vertical distribution of water temperature, dissolved oxygen (DO), and pH in eight RIRs at two nurseries each in Virginia and Maryland from 2011 to 2014. Monomictic thermal stratification was observed from April to October in all RIRs, despite their shallow depths (0.75‐3.89 m). The strongest stratification had a top‐bottom temperature difference of 21.53°C. The top‐bottom temperature difference was positively correlated with water column depth, air temperature, and daily light integral (p < 0.05). Wind speed did not impact the thermal stratification, likely due to their relatively small surface areas. Thermal stratification affected the vertical distribution of DO and pH. The top‐bottom differences in DO and pH were greater during stratification periods than nonstratification periods. Water pH in all RIRs was higher at the top than at the bottom with the greatest difference of 4.16 units. Discovery and characterization of thermal stratification in RIRs helps understand water quality dynamics in this novel ecosystem and promote safe and productive water reuse for irrigation. Specifically, water withdrawal depths should be adjusted according to variations in temperature, DO, and pH during the stratification and nonstratification periods to mitigate pathogen risk and improve water treatment efficacy and crop production. 相似文献
443.
Antonio J. Castro Caryn C. Vaughn Jason P. Julian Marina García‐Llorente 《Journal of the American Water Resources Association》2016,52(1):209-221
We performed a sociocultural preference assessment for a suite of ecosystem services provided by the Kiamichi River watershed in the south‐central United States, a region with intense water conflict. The goal was to examine how a social assessment of services could be used to weigh tradeoffs among water resource uses for future watershed management and planning. We identified the ecosystem services beneficiaries groups, analyzed perception for maintaining services, assessed differences in the importance and perceived trends for ecosystem services, and explored the perceived impact on ecosystem services arising from different watershed management scenarios. Results show habitat for species and water regulation were two ecosystem services all beneficiaries agreed were important. The main discrepancies among stakeholder groups were found for water‐related services. The identification of potential tradeoffs between services under different flow scenarios promotes a dynamic management strategy for allocating water resources, one that mitigates potential conflicts. While it is widely accepted the needs of all beneficiaries should be considered for the successful incorporation of ecosystem services into watershed management, the number of studies actually using the sociocultural perspective in ecosystem service assessment is limited. Our study demonstrates it is both possible and useful to quantify social demand of ecosystem services in watershed management. 相似文献
444.
445.
Phosphorus (P) losses to surface waters can result in eutrophication. Some industrial by-products have a strong affinity for dissolved P and may be useful in reducing nonpoint P pollution with landscape-scale runoff filters. Although appreciable research has been conducted on characterizing P sorption by industrial by-products via batch isotherms, less data are available on P sorption by these materials in a flow-through context integral to a landscape P filter. The objectives of this study were to evaluate several industrial by-products for P sorption in a flow-through setting, to determine material chemical properties that have the greatest impact on P sorption in a flow-through setting, and to explore how retention time (RT) and P concentration affect P removal. Twelve materials were characterized for chemical properties that typically influence P removal and subjected to flow-through P sorption experiments in which five different RTs and P concentrations were tested. The impact of RT and P concentrations on P removal varied based on material chemical properties, mainly as a function of oxalate-extractable aluminum (Al), iron (Fe), and water-soluble (WS) calcium (Ca). Statistical analysis showed that materials elevated in oxalate-extractable Al and Fe and WS Ca and that were highly buffered above pH 6 were able to remove the most P under flow-through conditions. Langmuir sorption maximum values from batch isotherms were poorly correlated with and overestimated P removal found under flow-through conditions. Within the conditions tested in this study, increases in RT and inflow P concentrations increased P removal among materials most likely to remove P via precipitation, whereas RT had little effect on materials likely to remove P via ligand exchange. 相似文献
446.
In the mining sector, local communities have emerged as particularly important governance actors. Conventional approaches to mineral development no longer suffice for these communities, which have demanded a greater share of benefits and increased involvement in decision making. These trends have been spurred by the growth of the sustainable development paradigm and governance shifts that have increasingly transferred governing authority towards non-state actors. Accordingly, there is now widespread recognition that mineral developers need to gain a ‘social license to operate’ (SLO) from local communities in order to avoid potentially costly conflict and exposure to social risks. A social license can be considered to exist when a mining project is seen as having the ongoing approval and broad acceptance of society to conduct its activities. Due to the concept's relatively recent emergence, however, only a limited body of scholarship has developed around SLO. Drawing on examples from northern Canada, this paper uses governance and sustainability theories to conceptualize the origins of SLO in the mining sector and describe some of the associated implications. Further research is needed to determine governance arrangements which help facilitate establishment of SLO in different mineral development contexts. 相似文献
447.
Prion diseases, including chronic wasting disease (CWD) and scrapie, can be transmitted via indirect environmental routes. Animals habitually ingest soil, and results from laboratory experiments demonstrate prions can bind to a wide range of soils and soil minerals, retain the ability to replicate, and remain infectious, indicating soil could serve as a reservoir for natural prion transmission and a potential prion exposure route for humans. Preliminary epidemiological modeling suggests soil texture may influence the incidence of prion disease. These results are supported by experimental work demonstrating variance in prion interactions with soil, including variance in prion soil adsorption and soil-bound prion replication with respect to soil type. Thus, local soil type may be a key determinant of prion incidence. Further experimental and epidemiological work is required to fully elucidate the dynamics of soil-mediated prion transmission, an effort that should lead to effective disease management and mitigation strategies. 相似文献
448.
449.
Jason B. Fellman Eldon H. Franz Chelsea L. Crenshaw Denise Elston 《Environment, Development and Sustainability》2009,11(4):871-885
It has become increasingly well documented that human activities are enhancing the greenhouse effect and altering the global
climate. Identifying strategies to mitigate atmospheric carbon dioxide emissions on the national level are therefore critical.
Fossil fuel combustion is primarily responsible for the perturbation of the global carbon cycle, although the influence of
humans extends far beyond the combustion of fossil fuels. Changes in land use arising from human activities contribute substantially
to atmospheric carbon dioxide; however, land use changes can act as a carbon dioxide sink as well. A soil carbon model was
built using STELLA to explore how soil organic carbon sequestration (SOC) varies over a range of values for key parameters
and to estimate the amount of global soil carbon sequestration from livestock waste. To obtain soil carbon sequestration estimates,
model simulations occurred for 11 different livestock types and with data for eight regions around the world. The model predicted
that between 1980 and 1995, United States soils were responsible for the sequestration of 444–602 Tg C from livestock waste.
Model simulations further predicted that during the same period, global soil carbon sequestration from livestock waste was
2,810–4,218 Tg C. Our estimates for global SOC sequestration are modest in proportion to other terrestrial carbon sinks (i.e.
forest regrowth); however, livestock waste does represent a potential for long-term soil carbon gain. SOC generated from livestock
waste is another example of how human activities and land use changes are altering soil processes around the world.
Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue. 相似文献
450.
Stuckey JW Neaman A Ravella R Komarneni S Martínez CE 《Environmental pollution (Barking, Essex : 1987)》2009,157(1):12-16
This is the first test of a highly charged swelling mica's (Na-2-mica) ability to reduce the plant-absorbed Cu in Cu-contaminated soils from Chile. Perennial ryegrass (Lolium perenne L.) was grown in two acid soils (Sector 2: pH 4.2, total Cu = 172 mg Cu kg−1 and Sector 3: pH 4.2, total Cu = 112 mg Cu kg−1) amended with 0.5% and 1% (w/w) mica, and 1% (w/w) montmorillonite. At 10 weeks of growth, both mica treatments decreased the shoot Cu of ryegrass grown in Sector 2 producing shoot Cu concentrations above 21-22 mg Cu kg−1 (the phytotoxicity threshold for that species), yet the mica treatments did not reduce shoot Cu concentrations when grown in Sector 3, which were at a typical level. The mica treatments improved shoot growth in Sector 3 by reducing free and extractable Cu to low enough levels where other nutrients could compete for plant absorption and translocation. In addition, the mica treatments improved root growth in both soils, and the 1% mica treatment reduced root Cu in both soils. This swelling mica warrants further testing of its ability to assist re-vegetation and reduce Cu bioavailability in Cu-contaminated surface soils. 相似文献