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Do Microplastic Contaminants Distort Our Understanding of the Ocean's Carbon Cycle?

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Do Microplastic Contaminants Distort Our Understanding of the Ocean's Carbon Cycle?/
作者:	Medina Faull, Luis Ernesto.
面頁冊數:	1 online resource (150 pages)
附註:	Source: Dissertations Abstracts International, Volume: 84-02, Section: B.
Contained By:	Dissertations Abstracts International84-02B.
標題:	Chemical oceanography. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=29328171click for full text (PQDT)
ISBN:	9798841770855

Do Microplastic Contaminants Distort Our Understanding of the Ocean's Carbon Cycle?
Medina Faull, Luis Ernesto.

Do Microplastic Contaminants Distort Our Understanding of the Ocean's Carbon Cycle? - 1 online resource (150 pages)

Source: Dissertations Abstracts International, Volume: 84-02, Section: B.

Thesis (Ph.D.)--State University of New York at Stony Brook, 2022.

Includes bibliographical references

Microplastics (MPs) have become an omnipresent component of the litter contaminating our oceans. These abundant micro-sized particles (diameters ranging from less than 0.001 to 5 mm) are either derived from the breakdown of larger plastic items or are intentionally manufactured (e.g., cosmetic microbeads, industrial pellets). Once entering the ocean through rivers, sewage discharge, and surface runoff, MPs move vertically and laterally along the coast and circulate into the open ocean. Oceanic MPs are problematic because they can bind toxic chemicals and enter the food chain. They are also possibly unintentionally included in fundamental studies of movement, chemical transformation, and storage of natural carbon in the ocean, all of which are integral to the study of climate change. To date, the effects of MPs on ocean carbon cycling measurements have not been evaluated systematically. This dissertation focuses on understanding oceanic distributions of MPs using state-of-the-art technology, and on determining the contribution of these synthetic polymers to natural organic particle pools. The main goals of this work were to: i) establish the abundance and distribution MP in different locations, ii) compute realistic estimates of MP abundances to eventually derive a mass balance of oceanic MPs, and iii) evaluate how unintentional inclusion of MPs in carbon cycling measurements might distort our models of how the ocean processes natural carbon. Addressing these objectives is crucial to understanding how plastic pollution has actually affected the ocean and biased our perceptions of how the ocean processes carbon. Firstly, an automatable methodology based on Raman microspectroscopy was developed (Chapter 2). This protocol was applied to directly detect, quantify, and chemically identify the polymeric structure of micron (1 to 300 µm) and submicron (0.46 to 0.99 µm) sized MPs in marine environmental samples collected on filters. I demonstrate that by using Raman microspectroscopy it is possible to generate spatial chemical images of the particles based on the Raman spectra of the polymers, which allows for the calculation of the volume and mass of particles. This methodology facilitates the precise chemical analysis of entire membrane filters (representing several milliliters to liters of seawater) at a spatial resolution below 1 µm. This enables detection of even the smallest (~0.46 µm) MP particles in water samples collected on a filter and allows for estimation of MP concentration, particle size, and mass. To demonstrate the technique's capabilities, environmental samples collected off the Northeast coast of Venezuela (NECV), in the Pacific Arctic Ocean (PAO), and Gulf Stream Current (GSC) were analyzed (CChapter 3). Plastics were ubiquitous at all study sites, with the highest concentrations at coastal sites; numerical abundances of MP particles in NECV samples were ~10-fold higher than in those from the PAO and GSC. The size range of most MP particles at all sites was between 1 and 43 µm equivalent spherical diameters (ESD). The most abundant polymers were polypropylene (PP) in NECV and GSC samples and polystyrene (PS) and polyethylene terephthalate (PET) in the PAO. In addition, MPs < 5 μm represented the majority of the plastic particles collected all three sites (NECV: 80%, GSC: 90%, and PAO: 86%). These methods facilitate detection of very small MP particles and calculation of their masses, which is crucial to further refine plastic budgets for a wide array of marine environments. My results demonstrate that MP particle numbers are not robust proxies for accurately determining plastic loadings to natural waters.In Chapter 4, I address whether MP contamination aliases biogenic organic matter (OM) measurements by being co-combusted with autochthonous natural OM during routine analyses. If plastic is indistinguishable from autochthonous OM, then MP contamination could lead to significant errors in our observations of natural OM inventories and their associated interpretations. The widely used elemental analysis (EA) which flash combusts small volumes of solid OM to CO2 in an atmosphere of excess oxygen was evaluated for plastic inclusion. Experiments were designed to demonstrate how direct EA observations (carbon yield, % carbon and isotopic fractionation) were consistent with predictions for OM samples contaminated with known amounts of plastic. Yield and % C data demonstrate that MPs in sedimentary POM admixtures were completely oxidized (100%) and predictably detected as CO2. Consequently, MPs inadvertently collected and analyzed with routine POM samples will lead to biased δ13C and Δ14C values because petroleum-based plastics have isotopic signatures distinctly different from those of modern autochthonous OM. MP-induced biases in isotope signatures were computed from MP carbon contributions to OM inventories, their typical isotopic signatures, and by applying conservation of mass. This exercise demonstrated that observed MP inventories (1-3% of POM) could lead to a Δ14C error of ~ -11 to -30‰ because the Δ14C of plastics is -1000‰, which is equivalent to 80 to 240 age errors (conventional 14C ages). In Chapter 5, I document the ubiquitous presence of suspended MPs and black carbon (BC) throughout the water column at a Southern Ocean (SO) station and in surface waters at 9 stations in the coastal New York Bight (NYB). BC is a refractory organic residue (soot) produced by incomplete combustion of fossil fuels and vegetation and is also globally dispersed. After CO2 and CH4, MP and BC may be among the most important drivers of climate warming due to their light absorbing properties which can contribute to snow and ice melting. Allochthonous BC and MP particles in complex environmental samples often inadvertently contribute to measurements of autochthonous carbon pools. In pyrolytic and optical analyses of bulk carbon samples, carbon signals from particles comprised of BC, MP, and autochthonous biogenic materials are indistinguishable from one another. This complicates our understanding of global carbon budgets because global distributions of MPs and BC are poorly constrained. Analytical methods that enable distinguishing and quantifying co-occurring particles in all three pools are necessary. Raman microspectroscopy enabled the identification and quantification of co-occurring BC and MP particles between 0.5 and 300 μm in diameter. At the SO station, MP and BC particles were most abundant in surface waters and decreased exponentially with depth. BC particles were numerically more abundant than MP particles at all depths and all stations by about 10-fold. After factoring in particle volumes and specific densities, MP and BC particles respectively contributed ~2 - 4 % and ~3 - 5% of total POC masses in the water column of the SO. In NYB samples, the contribution of MP and BC particles to total POC inventories varied from ~3 to 5 % and ~3 to 7%, respectively. MPs are derived almost exclusively from petroleum and an indeterminant amount of BC is derived from fossil fuel combustion, thus these particles are totally depleted in radiocarbon (14C). BC produced from burning vegetation, however, has a modern radiocarbon signature. Thus, MPs and some indeterminate fraction of BC inventories will artificially increase the radiocarbon age of the total POC pool. Considering MP inventories alone, inescapable inclusion in POC measurements corresponds to possible 14C age errors ~ 240 to 400 14C-years for SO samples and ~400-560 14C-years for NYB samples. A better understanding of allochthonous MP and BC particles in environmental samples is critical in assessing carbon cycling throughout the ocean and the effects of these particles on climate.Finally, the work presented here advances the study of MPs in aquatic environments, and for the first time accounts for MP particles ≤300 µm.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2023

Mode of access: World Wide Web

ISBN: 9798841770855Subjects--Topical Terms:

516760
Chemical oceanography.
Subjects--Index Terms:

Carbon budgetIndex Terms--Genre/Form:

542853
Electronic books.

Do Microplastic Contaminants Distort Our Understanding of the Ocean's Carbon Cycle?
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520 $a Microplastics (MPs) have become an omnipresent component of the litter contaminating our oceans. These abundant micro-sized particles (diameters ranging from less than 0.001 to 5 mm) are either derived from the breakdown of larger plastic items or are intentionally manufactured (e.g., cosmetic microbeads, industrial pellets). Once entering the ocean through rivers, sewage discharge, and surface runoff, MPs move vertically and laterally along the coast and circulate into the open ocean. Oceanic MPs are problematic because they can bind toxic chemicals and enter the food chain. They are also possibly unintentionally included in fundamental studies of movement, chemical transformation, and storage of natural carbon in the ocean, all of which are integral to the study of climate change. To date, the effects of MPs on ocean carbon cycling measurements have not been evaluated systematically. This dissertation focuses on understanding oceanic distributions of MPs using state-of-the-art technology, and on determining the contribution of these synthetic polymers to natural organic particle pools. The main goals of this work were to: i) establish the abundance and distribution MP in different locations, ii) compute realistic estimates of MP abundances to eventually derive a mass balance of oceanic MPs, and iii) evaluate how unintentional inclusion of MPs in carbon cycling measurements might distort our models of how the ocean processes natural carbon. Addressing these objectives is crucial to understanding how plastic pollution has actually affected the ocean and biased our perceptions of how the ocean processes carbon. Firstly, an automatable methodology based on Raman microspectroscopy was developed (Chapter 2). This protocol was applied to directly detect, quantify, and chemically identify the polymeric structure of micron (1 to 300 µm) and submicron (0.46 to 0.99 µm) sized MPs in marine environmental samples collected on filters. I demonstrate that by using Raman microspectroscopy it is possible to generate spatial chemical images of the particles based on the Raman spectra of the polymers, which allows for the calculation of the volume and mass of particles. This methodology facilitates the precise chemical analysis of entire membrane filters (representing several milliliters to liters of seawater) at a spatial resolution below 1 µm. This enables detection of even the smallest (~0.46 µm) MP particles in water samples collected on a filter and allows for estimation of MP concentration, particle size, and mass. To demonstrate the technique's capabilities, environmental samples collected off the Northeast coast of Venezuela (NECV), in the Pacific Arctic Ocean (PAO), and Gulf Stream Current (GSC) were analyzed (CChapter 3). Plastics were ubiquitous at all study sites, with the highest concentrations at coastal sites; numerical abundances of MP particles in NECV samples were ~10-fold higher than in those from the PAO and GSC. The size range of most MP particles at all sites was between 1 and 43 µm equivalent spherical diameters (ESD). The most abundant polymers were polypropylene (PP) in NECV and GSC samples and polystyrene (PS) and polyethylene terephthalate (PET) in the PAO. In addition, MPs < 5 μm represented the majority of the plastic particles collected all three sites (NECV: 80%, GSC: 90%, and PAO: 86%). These methods facilitate detection of very small MP particles and calculation of their masses, which is crucial to further refine plastic budgets for a wide array of marine environments. My results demonstrate that MP particle numbers are not robust proxies for accurately determining plastic loadings to natural waters.In Chapter 4, I address whether MP contamination aliases biogenic organic matter (OM) measurements by being co-combusted with autochthonous natural OM during routine analyses. If plastic is indistinguishable from autochthonous OM, then MP contamination could lead to significant errors in our observations of natural OM inventories and their associated interpretations. The widely used elemental analysis (EA) which flash combusts small volumes of solid OM to CO2 in an atmosphere of excess oxygen was evaluated for plastic inclusion. Experiments were designed to demonstrate how direct EA observations (carbon yield, % carbon and isotopic fractionation) were consistent with predictions for OM samples contaminated with known amounts of plastic. Yield and % C data demonstrate that MPs in sedimentary POM admixtures were completely oxidized (100%) and predictably detected as CO2. Consequently, MPs inadvertently collected and analyzed with routine POM samples will lead to biased δ13C and Δ14C values because petroleum-based plastics have isotopic signatures distinctly different from those of modern autochthonous OM. MP-induced biases in isotope signatures were computed from MP carbon contributions to OM inventories, their typical isotopic signatures, and by applying conservation of mass. This exercise demonstrated that observed MP inventories (1-3% of POM) could lead to a Δ14C error of ~ -11 to -30‰ because the Δ14C of plastics is -1000‰, which is equivalent to 80 to 240 age errors (conventional 14C ages). In Chapter 5, I document the ubiquitous presence of suspended MPs and black carbon (BC) throughout the water column at a Southern Ocean (SO) station and in surface waters at 9 stations in the coastal New York Bight (NYB). BC is a refractory organic residue (soot) produced by incomplete combustion of fossil fuels and vegetation and is also globally dispersed. After CO2 and CH4, MP and BC may be among the most important drivers of climate warming due to their light absorbing properties which can contribute to snow and ice melting. Allochthonous BC and MP particles in complex environmental samples often inadvertently contribute to measurements of autochthonous carbon pools. In pyrolytic and optical analyses of bulk carbon samples, carbon signals from particles comprised of BC, MP, and autochthonous biogenic materials are indistinguishable from one another. This complicates our understanding of global carbon budgets because global distributions of MPs and BC are poorly constrained. Analytical methods that enable distinguishing and quantifying co-occurring particles in all three pools are necessary. Raman microspectroscopy enabled the identification and quantification of co-occurring BC and MP particles between 0.5 and 300 μm in diameter. At the SO station, MP and BC particles were most abundant in surface waters and decreased exponentially with depth. BC particles were numerically more abundant than MP particles at all depths and all stations by about 10-fold. After factoring in particle volumes and specific densities, MP and BC particles respectively contributed ~2 - 4 % and ~3 - 5% of total POC masses in the water column of the SO. In NYB samples, the contribution of MP and BC particles to total POC inventories varied from ~3 to 5 % and ~3 to 7%, respectively. MPs are derived almost exclusively from petroleum and an indeterminant amount of BC is derived from fossil fuel combustion, thus these particles are totally depleted in radiocarbon (14C). BC produced from burning vegetation, however, has a modern radiocarbon signature. Thus, MPs and some indeterminate fraction of BC inventories will artificially increase the radiocarbon age of the total POC pool. Considering MP inventories alone, inescapable inclusion in POC measurements corresponds to possible 14C age errors ~ 240 to 400 14C-years for SO samples and ~400-560 14C-years for NYB samples. A better understanding of allochthonous MP and BC particles in environmental samples is critical in assessing carbon cycling throughout the ocean and the effects of these particles on climate.Finally, the work presented here advances the study of MPs in aquatic environments, and for the first time accounts for MP particles ≤300 µm.
520 $a Importantly, I generated data on the 1 to 20 µm MP fraction, which current sampling and analytical methods omit. In addition, I was able to measure not only the number of MP particles but determine their identities, sizes and masses. This is critical because mass-based inventories will permit more accurate and meaningful estimations of global oceanic plastic budgets than simply enumerating plastic particles.
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