Downpour dynamics: outsized impacts of storm events on unprocessed atmospheric nitrate export in an urban watershed

Downpour dynamics: outsized impacts of storm events on unprocessed atmospheric nitrate export in an urban watershed

<p>Water quality impacts of stream water nitrate (NO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M1" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><m...

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Bibliographic Details
Main Authors: J. T. Bostic, D. M. Nelson, K. N. Eshleman
Format: Article
Language:English
Published: Copernicus Publications 2023-06-01
Series:Biogeosciences
Online Access:https://bg.copernicus.org/articles/20/2485/2023/bg-20-2485-2023.pdf
Description
Summary:<p>Water quality impacts of stream water nitrate (NO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M1" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="9pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="5c4cefaf8b78d41c1ce2f2ef151f712f"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-20-2485-2023-ie00001.svg" width="9pt" height="16pt" src="bg-20-2485-2023-ie00001.png"/></svg:svg></span></span>) on downstream ecosystems are largely determined by the load of NO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M2" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="9pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="53e1f98be2cdf70dbe180d95894fc6b5"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-20-2485-2023-ie00002.svg" width="9pt" height="16pt" src="bg-20-2485-2023-ie00002.png"/></svg:svg></span></span> from the watershed to surface waters. The largest NO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M3" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="9pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="0aaab3ee324d7a9ba8e4b96f67d8036e"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-20-2485-2023-ie00003.svg" width="9pt" height="16pt" src="bg-20-2485-2023-ie00003.png"/></svg:svg></span></span> loads often occur during storm events, but it is unclear how loads of different NO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M4" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="9pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="0723f17b5be9fc41c36a5585631feb47"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-20-2485-2023-ie00004.svg" width="9pt" height="16pt" src="bg-20-2485-2023-ie00004.png"/></svg:svg></span></span> sources change during storm events relative to baseflow or how watershed attributes might affect source export. To assess the role of storm flow and baseflow in NO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M5" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="9pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="8c72af1edd6d67ed562efcaf5163d22b"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-20-2485-2023-ie00005.svg" width="9pt" height="16pt" src="bg-20-2485-2023-ie00005.png"/></svg:svg></span></span> source export and how these roles are modulated by hydrologic effects of land-use practices, we measured nitrogen (<span class="inline-formula"><i>δ</i><sup>15</sup></span>N) and oxygen (<span class="inline-formula">Δ<sup>17</sup></span>O) isotopes of NO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M8" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="9pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="7de8959157e6c258409d4c11688ca166"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-20-2485-2023-ie00006.svg" width="9pt" height="16pt" src="bg-20-2485-2023-ie00006.png"/></svg:svg></span></span> and oxygen isotopes (<span class="inline-formula"><i>δ</i><sup>18</sup></span>O) of water in rainfall and stream water samples from before, during, and after eight storm events across 14 months in two Chesapeake Bay watersheds of contrasting land use. Storms had a disproportionately large influence on the export of unprocessed atmospheric NO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M10" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="9pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="78ed0f7e81615226176402cdd6a1afd5"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-20-2485-2023-ie00007.svg" width="9pt" height="16pt" src="bg-20-2485-2023-ie00007.png"/></svg:svg></span></span> (NO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M11" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mrow><mn mathvariant="normal">3</mn><mspace linebreak="nobreak" width="0.25em"/><mi mathvariant="normal">Atm</mi></mrow><mo>-</mo></msubsup><mo>)</mo></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="28pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="9514b4a9c185f97f94d1417c44425043"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-20-2485-2023-ie00008.svg" width="28pt" height="16pt" src="bg-20-2485-2023-ie00008.png"/></svg:svg></span></span> and a disproportionately small influence on the export of terrestrial NO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M12" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="9pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="ee54bb0fff66afdafaf51bed1fde360d"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-20-2485-2023-ie00009.svg" width="9pt" height="16pt" src="bg-20-2485-2023-ie00009.png"/></svg:svg></span></span> (NO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M13" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mrow><mn mathvariant="normal">3</mn><mspace width="0.25em" linebreak="nobreak"/><mi mathvariant="normal">Terr</mi></mrow><mo>-</mo></msubsup><mo>)</mo></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="27pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="341113ab75fbe4206273a3461be5102c"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-20-2485-2023-ie00010.svg" width="27pt" height="16pt" src="bg-20-2485-2023-ie00010.png"/></svg:svg></span></span> relative to baseflow in the developed urban watershed. In contrast, baseflow and storm flow had similar influences on NO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M14" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mrow><mn mathvariant="normal">3</mn><mspace width="0.25em" linebreak="nobreak"/><mi mathvariant="normal">Atm</mi></mrow><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="24pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="c0317f6ec721e17a6789623e2e5db62c"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-20-2485-2023-ie00011.svg" width="24pt" height="16pt" src="bg-20-2485-2023-ie00011.png"/></svg:svg></span></span> and NO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M15" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mrow><mn mathvariant="normal">3</mn><mspace width="0.25em" linebreak="nobreak"/><mi mathvariant="normal">Terr</mi></mrow><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="23pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="c6d582a56792fded2e68a608adaf0646"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-20-2485-2023-ie00012.svg" width="23pt" height="16pt" src="bg-20-2485-2023-ie00012.png"/></svg:svg></span></span> export in the mixed agricultural–forested watershed. An equivalent relationship between NO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M16" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mrow><mn mathvariant="normal">3</mn><mspace linebreak="nobreak" width="0.25em"/><mi mathvariant="normal">Atm</mi></mrow><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="24pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="1a3c003a46c3b6482fa8a8b7b1b65180"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-20-2485-2023-ie00013.svg" width="24pt" height="16pt" src="bg-20-2485-2023-ie00013.png"/></svg:svg></span></span> deposition on impervious surfaces and event NO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M17" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mrow><mn mathvariant="normal">3</mn><mspace linebreak="nobreak" width="0.25em"/><mi mathvariant="normal">Atm</mi></mrow><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="24pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="10b1537e5e03e8d6082fcb78275dc75e"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-20-2485-2023-ie00014.svg" width="24pt" height="16pt" src="bg-20-2485-2023-ie00014.png"/></svg:svg></span></span> stream water export in the urban watershed suggests that impervious surfaces that hydrologically connect runoff to channels likely facilitate the export of NO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M18" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mrow><mn mathvariant="normal">3</mn><mspace width="0.25em" linebreak="nobreak"/><mi mathvariant="normal">Atm</mi></mrow><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="24pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="79cb312466c10021b4f7bb5bfac3932f"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-20-2485-2023-ie00015.svg" width="24pt" height="16pt" src="bg-20-2485-2023-ie00015.png"/></svg:svg></span></span> during rainfall events. Additionally, larger rainfall events were more effective at exporting NO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M19" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mrow><mn mathvariant="normal">3</mn><mspace width="0.25em" linebreak="nobreak"/><mi mathvariant="normal">Atm</mi></mrow><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="24pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="35996e5a90939ae316cd043c0b28f172"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-20-2485-2023-ie00016.svg" width="24pt" height="16pt" src="bg-20-2485-2023-ie00016.png"/></svg:svg></span></span> in the urban watershed, with increased rainfall depth resulting in a greater fraction of event NO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M20" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mrow><mn mathvariant="normal">3</mn><mspace linebreak="nobreak" width="0.25em"/><mi mathvariant="normal">Atm</mi></mrow><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="24pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="ec1e01414f483dc9b931b5497627696e"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-20-2485-2023-ie00017.svg" width="24pt" height="16pt" src="bg-20-2485-2023-ie00017.png"/></svg:svg></span></span> deposition exported. Considering both projected increases in precipitation amounts and intensity and urban/suburban sprawl in many regions of the world, best management practices that reduce the hydrologic connectivity of impervious surfaces will likely help to mitigate the impact of storm events on NO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M21" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mrow><mn mathvariant="normal">3</mn><mspace width="0.25em" linebreak="nobreak"/><mi mathvariant="normal">Atm</mi></mrow><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="24pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="d5242401365ac8a6b03918e82fd5c130"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-20-2485-2023-ie00018.svg" width="24pt" height="16pt" src="bg-20-2485-2023-ie00018.png"/></svg:svg></span></span> export from developed watersheds.</p>
ISSN:1726-4170
1726-4189

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