W. Dolan, T. M. Pavelsky, J. Davis, N. LaFramboise, C. A. Polik, R. M. Cory
{"title":"Effects of Total Suspended Solids on Photomineralization of Dissolved Organic Matter in the Peace-Athabasca Delta, Canada","authors":"W. Dolan, T. M. Pavelsky, J. Davis, N. LaFramboise, C. A. Polik, R. M. Cory","doi":"10.1029/2024JG008620","DOIUrl":null,"url":null,"abstract":"<p>Northern deltas receive chromophoric dissolved organic matter (CDOM) from their watersheds, which can be oxidized to carbon dioxide upon absorption of sunlight (i.e., photomineralized). These deltas also receive total suspended solids (TSS), which may shade sunlight absorption by CDOM, thus limiting photomineralization. To quantify this interaction for the first time, we measured photomineralization rates at 11 sites in the Peace-Athabasca Delta (PAD), Canada. We sampled waters during a July 2022 field campaign for TSS concentration, CDOM concentration (<span></span><math>\n <semantics>\n <mrow>\n <msub>\n <mi>a</mi>\n <mrow>\n <mtext>CDOM</mtext>\n <mo>,</mo>\n <mi>λ</mi>\n </mrow>\n </msub>\n </mrow>\n <annotation> ${a}_{\\text{CDOM},\\lambda }$</annotation>\n </semantics></math>), total downwelling sunlight attenuation coefficients (<span></span><math>\n <semantics>\n <mrow>\n <msub>\n <mi>K</mi>\n <mrow>\n <mi>d</mi>\n <mo>,</mo>\n <mtext>tot</mtext>\n <mo>,</mo>\n <mi>λ</mi>\n </mrow>\n </msub>\n </mrow>\n <annotation> ${K}_{d,\\text{tot},\\lambda }$</annotation>\n </semantics></math>), and light attenuation coefficients due to CDOM (<span></span><math>\n <semantics>\n <mrow>\n <msub>\n <mi>K</mi>\n <mrow>\n <mi>d</mi>\n <mo>,</mo>\n <mtext>CDOM</mtext>\n <mo>,</mo>\n <mi>λ</mi>\n </mrow>\n </msub>\n </mrow>\n <annotation> ${K}_{d,\\text{CDOM},\\lambda }$</annotation>\n </semantics></math>). TSS ranged from <1 to 112 mg/L with an average of 19 ± 34 mg/L (mean ± one standard deviation), an order of magnitude lower than TSS reported in rivers entering the PAD earlier in the open water season. <span></span><math>\n <semantics>\n <mrow>\n <msub>\n <mi>a</mi>\n <mrow>\n <mtext>CDOM</mtext>\n <mo>,</mo>\n <mi>λ</mi>\n </mrow>\n </msub>\n </mrow>\n <annotation> ${a}_{\\text{CDOM},\\lambda }$</annotation>\n </semantics></math> at 305 nm (<span></span><math>\n <semantics>\n <mrow>\n <msub>\n <mi>a</mi>\n <mrow>\n <mtext>CDOM</mtext>\n <mo>,</mo>\n <mn>305</mn>\n </mrow>\n </msub>\n </mrow>\n <annotation> ${a}_{\\text{CDOM},305}$</annotation>\n </semantics></math>) ranged from 23.3 to 65.2 m<sup>−1</sup>, <span></span><math>\n <semantics>\n <mrow>\n <msub>\n <mi>K</mi>\n <mrow>\n <mi>d</mi>\n <mo>,</mo>\n <mtext>CDOM</mtext>\n <mo>,</mo>\n <mn>305</mn>\n </mrow>\n </msub>\n </mrow>\n <annotation> ${K}_{d,\\text{CDOM},305}$</annotation>\n </semantics></math> ranged from 26.3 to 74.1 m<sup>−1</sup>, and <span></span><math>\n <semantics>\n <mrow>\n <msub>\n <mi>K</mi>\n <mrow>\n <mi>d</mi>\n <mo>,</mo>\n <mtext>tot</mtext>\n <mo>,</mo>\n <mn>305</mn>\n </mrow>\n </msub>\n </mrow>\n <annotation> ${K}_{d,\\text{tot},305}$</annotation>\n </semantics></math> ranged from 19.0 to 63.7 m<sup>−1</sup>. The ratio of sunlight absorbed by CDOM relative to total sunlight attenuation (<span></span><math>\n <semantics>\n <mrow>\n <mfrac>\n <mrow>\n <msub>\n <mi>K</mi>\n <mrow>\n <mi>d</mi>\n <mo>,</mo>\n <mtext>CDOM</mtext>\n <mo>,</mo>\n <mi>λ</mi>\n </mrow>\n </msub>\n </mrow>\n <mrow>\n <msub>\n <mi>K</mi>\n <mrow>\n <mi>d</mi>\n <mtext>,tot</mtext>\n <mo>,</mo>\n <mi>λ</mi>\n </mrow>\n </msub>\n </mrow>\n </mfrac>\n </mrow>\n <annotation> $\\frac{{K}_{d,\\text{CDOM},\\lambda }}{{K}_{\\mathit{d}\\text{,tot},\\lambda }}$</annotation>\n </semantics></math>) was inversely correlated with TSS concentration across all wavelengths measured (305–412 nm). TSS thus limited photomineralization rates by shading CDOM from ultraviolet A and visible wavelengths of sunlight, reducing photomineralization rates by up to 56% compared to rates in the absence of TSS or other non-CDOM particles that attenuate sunlight. Results suggest that shifts in delta hydrology that affect TSS concentration likely influence photomineralization rates within TSS-rich northern deltas.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 6","pages":""},"PeriodicalIF":3.7000,"publicationDate":"2025-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Geophysical Research: Biogeosciences","FirstCategoryId":"93","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1029/2024JG008620","RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"ENVIRONMENTAL SCIENCES","Score":null,"Total":0}
引用次数: 0
Abstract
Northern deltas receive chromophoric dissolved organic matter (CDOM) from their watersheds, which can be oxidized to carbon dioxide upon absorption of sunlight (i.e., photomineralized). These deltas also receive total suspended solids (TSS), which may shade sunlight absorption by CDOM, thus limiting photomineralization. To quantify this interaction for the first time, we measured photomineralization rates at 11 sites in the Peace-Athabasca Delta (PAD), Canada. We sampled waters during a July 2022 field campaign for TSS concentration, CDOM concentration (), total downwelling sunlight attenuation coefficients (), and light attenuation coefficients due to CDOM (). TSS ranged from <1 to 112 mg/L with an average of 19 ± 34 mg/L (mean ± one standard deviation), an order of magnitude lower than TSS reported in rivers entering the PAD earlier in the open water season. at 305 nm () ranged from 23.3 to 65.2 m−1, ranged from 26.3 to 74.1 m−1, and ranged from 19.0 to 63.7 m−1. The ratio of sunlight absorbed by CDOM relative to total sunlight attenuation () was inversely correlated with TSS concentration across all wavelengths measured (305–412 nm). TSS thus limited photomineralization rates by shading CDOM from ultraviolet A and visible wavelengths of sunlight, reducing photomineralization rates by up to 56% compared to rates in the absence of TSS or other non-CDOM particles that attenuate sunlight. Results suggest that shifts in delta hydrology that affect TSS concentration likely influence photomineralization rates within TSS-rich northern deltas.
期刊介绍:
JGR-Biogeosciences focuses on biogeosciences of the Earth system in the past, present, and future and the extension of this research to planetary studies. The emerging field of biogeosciences spans the intellectual interface between biology and the geosciences and attempts to understand the functions of the Earth system across multiple spatial and temporal scales. Studies in biogeosciences may use multiple lines of evidence drawn from diverse fields to gain a holistic understanding of terrestrial, freshwater, and marine ecosystems and extreme environments. Specific topics within the scope of the section include process-based theoretical, experimental, and field studies of biogeochemistry, biogeophysics, atmosphere-, land-, and ocean-ecosystem interactions, biomineralization, life in extreme environments, astrobiology, microbial processes, geomicrobiology, and evolutionary geobiology