Nitrate retention capacity of milldam-impacted legacy sediments and relict A horizon soils
While eutrophication is often attributed to contemporary nutrient pollution, there is growing evidence that past practices, like the accumulation of legacy sediment behind historic milldams, are also important. Given their prevalence, there is a critical need to understand how N flows through, a...
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doaj-0d177938e83e44deb6652726fade4d922020-11-25T00:52:42ZengCopernicus PublicationsSOIL2199-39712199-398X2017-05-0139511210.5194/soil-3-95-2017Nitrate retention capacity of milldam-impacted legacy sediments and relict A horizon soilsJ. N. Weitzman0J. N. Weitzman1J. P. Kaye2Department of Ecosystem Science and Management, The Pennsylvania State University, University Park, PA 16802, USAnow at: CUNY Advanced Research Center, 85 St. Nicholas Terrace, 5th Floor, New York, NY 10031, USADepartment of Ecosystem Science and Management, The Pennsylvania State University, University Park, PA 16802, USAWhile eutrophication is often attributed to contemporary nutrient pollution, there is growing evidence that past practices, like the accumulation of legacy sediment behind historic milldams, are also important. Given their prevalence, there is a critical need to understand how N flows through, and is retained in, legacy sediments to improve predictions and management of N transport from uplands to streams in the context of climatic variability and land-use change. Our goal was to determine how nitrate (NO<sub>3</sub><sup>−</sup>) is cycled through the soil of a legacy-sediment-strewn stream before and after soil drying. We extracted 10.16 cm radius intact soil columns that extended 30 cm into each of the three significant soil horizons at Big Spring Run (BSR) in Lancaster, Pennsylvania: surface legacy sediment characterized by a newly developing mineral A horizon soil, mid-layer legacy sediment consisting of mineral B horizon soil and a dark, organic-rich, buried relict A horizon soil. Columns were first preincubated at field capacity and then isotopically labeled nitrate (<sup>15</sup>NO<sub>3</sub><sup>−</sup>) was added and allowed to drain to estimate retention. The columns were then air-dried and subsequently rewet with N-free water and allowed to drain to quantify the drought-induced loss of <sup>15</sup>NO<sub>3</sub><sup>−</sup> from the different horizons. We found the highest initial <sup>15</sup>N retention in the mid-layer legacy sediment (17 ± 4 %) and buried relict A soil (14 ± 3 %) horizons, with significantly lower retention in the surface legacy sediment (6 ± 1 %) horizon. As expected, rewetting dry soil resulted in <sup>15</sup>N losses in all horizons, with the greatest losses in the buried relict A horizon soil, followed by the mid-layer legacy sediment and surface legacy sediment horizons. The <sup>15</sup>N remaining in the soil following the post-drought leaching was highest in the mid-layer legacy sediment, intermediate in the surface legacy sediment, and lowest in the buried relict A horizon soil. Fluctuations in the water table at BSR which affect saturation of the buried relict A horizon soil could lead to great loses of NO<sub>3</sub><sup>−</sup> from the soil, while vertical flow through the legacy-sediment-rich soil profile that originates in the surface has the potential to retain more NO<sub>3</sub><sup>−</sup>. Restoration that seeks to reconnect the groundwater and surface water, which will decrease the number of drying–rewetting events imposed on the relict A horizon soils, could initially lead to increased losses of NO<sub>3</sub><sup>−</sup> to nearby stream waters.http://www.soil-journal.net/3/95/2017/soil-3-95-2017.pdf |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
J. N. Weitzman J. N. Weitzman J. P. Kaye |
spellingShingle |
J. N. Weitzman J. N. Weitzman J. P. Kaye Nitrate retention capacity of milldam-impacted legacy sediments and relict A horizon soils SOIL |
author_facet |
J. N. Weitzman J. N. Weitzman J. P. Kaye |
author_sort |
J. N. Weitzman |
title |
Nitrate retention capacity of milldam-impacted legacy sediments and relict A horizon soils |
title_short |
Nitrate retention capacity of milldam-impacted legacy sediments and relict A horizon soils |
title_full |
Nitrate retention capacity of milldam-impacted legacy sediments and relict A horizon soils |
title_fullStr |
Nitrate retention capacity of milldam-impacted legacy sediments and relict A horizon soils |
title_full_unstemmed |
Nitrate retention capacity of milldam-impacted legacy sediments and relict A horizon soils |
title_sort |
nitrate retention capacity of milldam-impacted legacy sediments and relict a horizon soils |
publisher |
Copernicus Publications |
series |
SOIL |
issn |
2199-3971 2199-398X |
publishDate |
2017-05-01 |
description |
While eutrophication is often attributed to contemporary nutrient
pollution, there is growing evidence that past practices, like the
accumulation of legacy sediment behind historic milldams, are also important.
Given their prevalence, there is a critical need to understand how N flows
through, and is retained in, legacy sediments to improve predictions and
management of N transport from uplands to streams in the context of climatic
variability and land-use change. Our goal was to determine how nitrate
(NO<sub>3</sub><sup>−</sup>) is cycled through the soil of a legacy-sediment-strewn stream
before and after soil drying. We extracted 10.16 cm radius intact soil
columns that extended 30 cm into each of the three significant soil horizons
at Big Spring Run (BSR) in Lancaster, Pennsylvania: surface legacy sediment
characterized by a newly developing mineral A horizon soil, mid-layer legacy
sediment consisting of mineral B horizon soil and a dark, organic-rich,
buried relict A horizon soil. Columns were first preincubated at field
capacity and then isotopically labeled nitrate (<sup>15</sup>NO<sub>3</sub><sup>−</sup>) was
added and allowed to drain to estimate retention. The columns were then
air-dried and subsequently rewet with N-free water and allowed to drain to
quantify the drought-induced loss of <sup>15</sup>NO<sub>3</sub><sup>−</sup> from the different
horizons. We found the highest initial <sup>15</sup>N retention in the mid-layer
legacy sediment (17 ± 4 %) and buried relict A soil
(14 ± 3 %) horizons, with significantly lower retention in the
surface legacy sediment (6 ± 1 %) horizon. As expected, rewetting
dry soil resulted in <sup>15</sup>N losses in all horizons, with the greatest
losses in the buried relict A horizon soil, followed by the mid-layer legacy
sediment and surface legacy sediment horizons. The <sup>15</sup>N
remaining in the soil following the post-drought leaching was highest in the
mid-layer legacy sediment, intermediate in the surface legacy sediment, and
lowest in the buried relict A horizon soil. Fluctuations in the water table
at BSR which affect saturation of the buried relict A horizon soil could lead
to great loses of NO<sub>3</sub><sup>−</sup> from the soil, while vertical flow through the
legacy-sediment-rich soil profile that originates in the surface has the
potential to retain more NO<sub>3</sub><sup>−</sup>. Restoration that seeks to reconnect
the groundwater and surface water, which will decrease the number of
drying–rewetting events imposed on the relict A horizon soils, could
initially lead to increased losses of NO<sub>3</sub><sup>−</sup> to nearby stream waters. |
url |
http://www.soil-journal.net/3/95/2017/soil-3-95-2017.pdf |
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