Hydrologic and geochemical controls on pesticide and nutrient transport to two streams on the Delmarva Peninsula

Ator, Scott W.; Denver, Judith M.; Brayton, Michael J.

doi:10.3133/sir20045051

Cited by 17 publications

(58 citation statements)

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“…Nitrogen in chemical fertilizers and atmospheric deposition generally reaches the land in inorganic forms such as ammonia (NH 3 ), ammonium (NH 4 + ), or nitrate (NO 3 -), whereas nitrogen in animal wastes (such as poultry manure) and septic effluent often occur in ammonium or organic compounds. Much of the applied nitrogen is converted in the soil to nitrate, which remains stable in groundwater as long as dissolved oxygen is present, and is the most common form of nitrogen in groundwater and streams of the Eastern Shore (Denver and others, 2004;Ator, Denver, and Brayton, 2005;Debrewer and others, 2007) and elsewhere (Dubrovsky and others, 2010). Phosphorus is less soluble than nitrate and commonly occurs in solid form bound to soils or sediment particles, although some phosphorus may dissolve in streams or groundwater in the form of phosphate (PO 4 3-) (Dubrovsky and others, 2010).…”

Section: Movement Of Nitrogen and Phosphorus From Source Areas To Surmentioning

confidence: 99%

“…Nitrogen moves from source areas on the landscape to surface waters of the Eastern Shore primarily through groundwater in the form of nitrate (Böhlke and Denver, 1995;Ator, Denver, and Brayton, 2005;. Because nitrate is very soluble, it dissolves easily in rainfall or other water as it infiltrates through the soil toward the water table.…”

Section: Nitrogenmentioning

confidence: 99%

“…Although the Eastern Shore includes only 7 percent of the land area in the bay watershed, it receives more than 13 percent of the nitrogen and phosphorus applications in the form of fertilizer, manure, and (for nitrogen) direct fixation of atmospheric nitrogen by legume crops (Wieczorek and LaMotte, 2010b, c). Soils and surficial aquifer sediments are sandy and permeable over much of the area-conditions that promote the movement of nutrients from application areas to groundwater, streams, and tidal waters (Böhlke and Denver, 1995; Denver and others, 2004;Ator, Denver, and Brayton, 2005; Debrewer and others, 2007). In addition, the proximity of most areas of the Eastern Shore to tidal waters limits the opportunities for natural storage and mitigation of landapplied nutrients in upland landscapes and increases the likelihood of their delivery to the bay (Staver and Brinsfield, 2001).…”

mentioning

confidence: 99%

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Understanding nutrients in the Chesapeake Bay watershed and implications for management and restoration: The Eastern Shore

Ator¹,

Denver²

2015

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), onlineFor more information on the USGS-the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1-888-ASK-USGS For an overview of USGS information products, including maps, imagery, and publications, visit http://www.usgs.gov/pubprodTo order this and other USGS information products, visit http://store.usgs.gov Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted materials contained within this report. SEE CHAPTER 2The Eastern Shore ( fig. 1) includes only a small part of the Chesapeake Bay watershed, but contributes disproportionately large loads of the excess nitrogen and phosphorus that have contributed to ecological and economic degradation of the bay in recent decades. Chesapeake Bay is the largest estuary in the United States and a vital ecological and economic resource. The bay and its tributaries have been degraded in recent decades by excessive nitrogen and phosphorus in the water column, however, which cause harmful algal blooms and decreased water clarity, submerged aquatic vegetation, and dissolved oxygen. The disproportionately large nitrogen and phosphorus yields from the Eastern Shore to Chesapeake Bay are attributable to human land-use practices as well as natural hydrogeologic and soil conditions. Applications of nitrogen and phosphorus compounds to the Eastern Shore from human activities are intensive. Also, hydrogeologic and soil conditions promote the movement of these compounds from application areas on the landscape to groundwater and (or) surface waters, and the proximity of much of the Eastern Shore to tidal waters limits opportunities for natural removal of these compounds in the landscape. The Eastern Shore only includes 7 percent of the Chesapeake Bay watershed, but receives nearly twice as much nitrogen and phosphorus applications (per area) as the remainder of the watershed and yields greater nitrogen and phosphorus, on average, to the bay ( fig. 2). SOURCE INPUTS TO THE EASTERN SHORE Sources of Nitrogen and Phosphorus on the Eastern Shore SEE CHAPTER 3Agricultural operations contribute the vast majority of nitrogen and phosphorus to the landscape on the Eastern Shore. Land use in the area has been primarily agricultural for several hundred years. Nitrogen and phosphorus applications in support of agriculture increased substantially during the second half of the last century, however, but have since stabilized or decreased ( fig. 3). More than 90 percent of nitrogen and phosphorus reaching the land in the Eastern Shore is applied as part of inorganic fertilizers or manure, or (for nitrogen) fixed directly from the atmosphere in cropland ( fig. 4). Nonagricultural sources such as atmospheric deposition, septic systems, sewage treatment plants, or other urban sources...

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Section: Movement Of Nitrogen and Phosphorus From Source Areas To Surmentioning

confidence: 99%

Section: Nitrogenmentioning

confidence: 99%

mentioning

confidence: 99%

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Understanding nutrients in the Chesapeake Bay watershed and implications for management and restoration: The Eastern Shore

Ator¹,

Denver²

2015

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“…Previous work has shown that multiple sources of data, for example, redox conditions, major-ion chemistry, and isotopic information, are necessary to more accurately determine N sources and the potential for transformations and losses of N during travel through an aquifer and into streams (Ator et al, 2005;Böhlke, 2002;Böhlke and Denver, 1995;Puckett, 2004;Tesoriero et al, 2009 (Denver, 1989;Hamilton et al, 1993 (Denver, 1989;Hamilton et al, 1993). In contrast, the geochemical signature of groundwater beneath turfgrass in residential lawns has not been determined in this region.…”

Section: Introductionmentioning

confidence: 99%

Suburban Groundwater Quality as Influenced by Turfgrass and Septic Sources, Delmarva Peninsula, USA

Kasper

Denver²,

York

2015

J. Environ. Qual.

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“…Shallow groundwater flow systems around wetlands and other surface water bodies are commonly transient and complex and reflect influences of local geology, variable precipitation and recharge, and groundwater flow systems at local to regional scales (Winter 1983(Winter , 1999 is also delivered to streams along flow paths at depths beneath the influence of riparian forests or wetlands (Böhlke and Denver 1995;Hill 1996;Puckett 2004;Ator et al 2005a). Where depressional wetlands collect rainfall and surface runoff, focused recharge may cause reversals in shallow groundwater flow, and wetlands may alternately provide recharge to or receive discharge from adjacent shallow groundwater within relatively short time periods (Winter 1983;Leibowitz and Nadeau 2003).…”

mentioning

confidence: 99%

Nitrate fate and transport through current and former depressional wetlands in an agricultural landscape, Choptank Watershed, Maryland, United States

Denver¹,

Ator²,

Lang³

et al. 2014

Journal of Soil and Water Conservation

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Understanding local groundwater hydrology and geochemistry is critical for evaluating the effectiveness of wetlands at mitigating agricultural impacts on surface waters. The effectiveness of depressional wetlands at mitigating nitrate (NO 3 ) transport from fertilized row crops, through groundwater, to local streams was examined in the watershed of the upper Choptank River, a tributary of Chesapeake Bay on the Atlantic Coastal Plain. Hydrologic, geochemical, and water quality data were collected from January of 2008 through December of 2009 from surface waters and networks of piezometers installed in and around current or former depressional wetlands of three major types along a gradient of anthropogenic alteration: (1) natural wetlands with native vegetation (i.e., forested); (2) prior-converted croplands, which are former wetlands located in cultivated fields; and (3) hydrologically restored wetlands, including one wetland restoration and one shallow water management area. These data were collected to estimate the orientation of groundwater flow paths and likely interactions of groundwater containing NO 3 from agricultural sources with reducing conditions associated with wetlands of different types. Natural wetlands were found to have longer periods of soil saturation and reducing conditions conducive to denitrification compared to the other wetland types studied. Because natural wetlands are typically located in groundwater recharge areas along watershed divides, nitrogen (N) from nearby agriculture was not intercepted. However, these wetlands likely improve water quality in adjacent streams via dilution. Soil and geochemical conditions conducive to denitrification were also present in restored wetlands and prior-converted croplands, and substantial losses of agricultural NO 3 were observed in groundwater flowing through these wetland sediments. However, delivery of NO 3 from agricultural areas through groundwater to these wetlands resulting in opportunities for denitrification were limited, particularly where reducing conditions did not extend throughout the entire thickness of the surficial aquifer allowing NO 3 to pass conservatively beneath a wetland along deeper groundwater flow paths. The complexity of N fate and transport associated with depressional wetlands complicates the understanding of their importance to water quality in adjacent streams. Although depressional wetlands often contribute low NO 3 water to local streams, their effectiveness as landscape sinks, for N from adjacent agriculture varies with natural conditions, such as the thickness of the aquifer and the extent of reducing conditions. Measurement of such natural geologic, hydrologic, and geochemical conditions are therefore fundamental to understanding N mitigation in individual wetlands.Key words: agriculture-Chesapeake Bay-denitrification-depressional wetlandsgroundwater-wetland conservation practices Local hydrologic and geochemical conditions control the movement of nitrate (NO 3 ) through and around depressional wetlands...

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Hydrologic and geochemical controls on pesticide and nutrient transport to two streams on the Delmarva Peninsula

Cited by 17 publications

References 0 publications

Understanding nutrients in the Chesapeake Bay watershed and implications for management and restoration: The Eastern Shore

Understanding nutrients in the Chesapeake Bay watershed and implications for management and restoration: The Eastern Shore

Suburban Groundwater Quality as Influenced by Turfgrass and Septic Sources, Delmarva Peninsula, USA

Nitrate fate and transport through current and former depressional wetlands in an agricultural landscape, Choptank Watershed, Maryland, United States

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