Ward Collin P.

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Ward

First Name

Collin P.

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0000-0003-2979-0280

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Now showing 1 - 19 of 19

Divergent forms of pyroplastic: lessons learned from the M/V X-Press Pearl ship fire

(American Chemical Society, 2022-07-29) James, Bryan D. ; de Vos, Asha ; Aluwihare, Lihini I. ; Youngs, Sarah ; Ward, Collin P. ; Michel, Anna P. M. ; Hahn, Mark E. ; Reddy, Christopher M.

In late May 2021, the M/V X-Press Pearl container ship caught fire while anchored 18 km off the coast of Colombo, Sri Lanka and spilled upward of 70 billion pieces of plastic or “nurdles” (∼1680 tons), littering the country’s coastline. Exposure to combustion, heat, chemicals, and petroleum products led to an apparent continuum of changes from no obvious effects to pieces consistent with previous reports of melted and burned plastic (pyroplastic) found on beaches. At the middle of this continuum, nurdles were discolored but appeared to retain their prefire morphology, resembling nurdles that had been weathered in the environment. We performed a detailed investigation of the physical and surface properties of discolored nurdles collected on a beach 5 days after the ship caught fire and within 24 h of their arrival onshore. The color was the most striking trait of the plastic: white for nurdles with minimal alteration from the accident, orange for nurdles containing antioxidant degradation products formed by exposure to heat, and gray for partially combusted nurdles. Our color analyses indicate that this fraction of the plastic released from the ship was not a continuum but instead diverged into distinct groups. Fire left the gray nurdles scorched, with entrained particles and pools of melted plastic, and covered in soot, representing partial pyroplastics, a new subtype of pyroplastic. Cross sections showed that the heat- and fire-induced changes were superficial, leaving the surfaces more hydrophilic but the interior relatively untouched. These results provide timely and actionable information to responders to reevaluate cleanup end points, monitor the recurrence of these spilled nurdles, gauge short- and long-term effects of the spilled nurdles to the local ecosystem, and manage the recovery of the spill. These findings underscore partially combusted plastic (pyroplastic) as a type of plastic pollution that has yet to be fully explored despite the frequency at which plastic is burned globally.
Rapid degradation of cellulose diacetate by marine microbes

(American Chemical Society, 2021-12-08) Mazzotta, Michael G. ; Reddy, Christopher M. ; Ward, Collin P.

The persistence of cellulose diacetate (CDA), a biobased plastic used in textiles and single-use consumer products, in the ocean is currently unknown. Here, we probe the disintegration and degradation of CDA-based materials (25 μm films, 510 μm foam, and 97 g/m2 fabric) by marine microbes in a continuous flow seawater mesocosm. Photographic evidence and mass loss measurements demonstrate that CDA-based materials disintegrate in months. Disintegration is marked by the increasing esterase and cellulase activity of the biofilm community, suggesting that marine microbes degrade CDA. The natural abundance stable (13C) and radiocarbon (14C) isotopic signature of carbon dioxide respired during short-term bottle incubations confirms the rapid degradation of both acetyl and cellulosic components of CDA by seawater microbial communities. These findings challenge the paradigm set by governmental agencies and advocacy groups that CDA-based materials persist in the ocean for decades, and represent a positive step toward identifying high-utility, biobased plastics with low environmental persistence.
Plastic formulation is an emerging control of its photochemical fate in the ocean

(American Chemical Society, 2021-09-08) Walsh, Anna N. ; Reddy, Christopher M. ; Niles, Sydney F. ; McKenna, Amy M. ; Hansel, Colleen M. ; Ward, Collin P.

Sunlight exposure is a control of long-term plastic fate in the environment that converts plastic into oxygenated products spanning the polymer, dissolved, and gas phases. However, our understanding of how plastic formulation influences the amount and composition of these photoproducts remains incomplete. Here, we characterized the initial formulations and resulting dissolved photoproducts of four single-use consumer polyethylene (PE) bags from major retailers and one pure PE film. Consumer PE bags contained 15–36% inorganic additives, primarily calcium carbonate (13–34%) and titanium dioxide (TiO2; 1–2%). Sunlight exposure consistently increased production of dissolved organic carbon (DOC) relative to leaching in the dark (3- to 80-fold). All consumer PE bags produced more DOC during sunlight exposure than the pure PE (1.2- to 2.0-fold). The DOC leached after sunlight exposure increasingly reflected the 13C and 14C isotopic composition of the plastic. Ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry revealed that sunlight exposure substantially increased the number of DOC formulas detected (1.1- to 50-fold). TiO2-containing bags photochemically degraded into the most compositionally similar DOC, with 68–94% of photoproduced formulas in common with at least one other TiO2-containing bag. Conversely, only 28% of photoproduced formulas from the pure PE were detected in photoproduced DOC from the consumer PE. Overall, these findings suggest that plastic formulation, especially TiO2, plays a determining role in the amount and composition of DOC generated by sunlight. Consequently, studies on pure, unweathered polymers may not accurately represent the fates and impacts of the plastics entering the ocean.
The molecular products and biogeochemical significance of lipid photooxidation in West Antarctic surface waters

( 2018-04) Collins, James R. ; Fredricks, Helen F. ; Bowman, Jeff S. ; Ward, Collin P. ; Moreno, Carly ; Longnecker, Krista ; Marchetti, Adrian ; Hansel, Colleen M. ; Ducklow, Hugh W. ; Van Mooy, Benjamin A. S.

The seasonal depletion of stratospheric ozone over the Southern Hemisphere allows abnormally high doses of ultraviolet radiation (UVR) to reach surface waters of the West Antarctic Peninsula (WAP) in the austral spring, creating a natural laboratory for the study of lipid photooxidation in the shallow mixed layer of the marginal ice zone. The photooxidation of lipids under such conditions has been identified as a significant source of stress to microorganisms, and short-chain fatty acids altered by photochemical processes have been found in both marine aerosols and sinking marine particle material. However, the biogeochemical impact of lipid photooxidation has not been quantitatively compared at ecosystem scale to the many other biological and abiotic processes that can transform particulate organic matter in the surface ocean. We combined results from field experiments with diverse environmental data, including high-resolution, accurate-mass HPLC-ESI-MS analysis of lipid extracts and in situ measurements of ultraviolet irradiance, to address several unresolved questions about lipid photooxidation in the marine environment. In our experiments, we used liposomes — nonliving, cell-like aggregations of lipids — to examine the photolability of various moieties of the intact polar diacylglycerol (IP-DAG) phosphatidylcholine (PC), a structural component of membranes in a broad range of microorganisms. We observed significant rates of photooxidation only when the molecule contained the polyunsaturated fatty acid (PUFA) docosahexaenoic acid (DHA). As the DHA-containing lipid was oxidized, we observed the steady ingrowth of a diversity of oxylipins and oxidized IP-DAG; our results suggest both the intact IPDAG the degradation products were amenable to heterotrophic assimilation. To complement our experiments, we used an enhanced version of a new lipidomics discovery software package to identify the lipids in water column samples and in several diatom isolates. The galactolipid digalactosyldiacylglycerol (DGDG), the sulfolipid sulfoquinovosyldiacylglycerol (SQDG) and the phospholipids PC and phosphatidylglycerol (PG) accounted for the majority of IP-DAG in the water column particulate (≥ 0.2 μm) size fraction; between 3.4 and 5.3 % of the IP-DAG contained fatty acids that were both highly polyunsaturated (i.e., each containing ≥ 5 double bonds). Using a broadband apparent quantum yield (AQY) that accounted for direct and Type I (i.e., radical-mediated) photooxidation of PUFA-containing IP-DAG, we estimated that 0.7 ± 0.2 μmol IP-DAG m-2 d-1 (0.5 ± 0.1 mg C m-2 d-1) were oxidized by photochemical processes in the mixed layer. This rate represented 4.4 % (range, 3-21 %) of the mean bacterial production rate measured in the same waters immediately following the retreat of the sea ice. Because our liposome experiments were not designed to account for oxidation by Type II photosensitized processes that often dominate in marine phytodetritus, our rate estimates may represent a sizeable underestimate of the true rate of lipid photooxidation in the water column. While production of such diverse oxidized lipids and oxylipins has been previously observed in terrestrial plants and mammals in response to biological stressors such as disease, we show here that a similar suite of molecules can be produced via an abiotic process in the environment and that the effect can be commensurate in magnitude with other ecosystem-scale biogeochemical processes.
Photochemical alteration of organic carbon draining permafrost soils shifts microbial metabolic pathways and stimulates respiration

(Nature Publishing Group, 2017-10-03) Ward, Collin P. ; Nalven, Sarah G. ; Crump, Byron C. ; Kling, George W. ; Cory, Rose M.

In sunlit waters, photochemical alteration of dissolved organic carbon (DOC) impacts the microbial respiration of DOC to CO2. This coupled photochemical and biological degradation of DOC is especially critical for carbon budgets in the Arctic, where thawing permafrost soils increase opportunities for DOC oxidation to CO2 in surface waters, thereby reinforcing global warming. Here we show how and why sunlight exposure impacts microbial respiration of DOC draining permafrost soils. Sunlight significantly increases or decreases microbial respiration of DOC depending on whether photo-alteration produces or removes molecules that native microbial communities used prior to light exposure. Using high-resolution chemical and microbial approaches, we show that rates of DOC processing by microbes are likely governed by a combination of the abundance and lability of DOC exported from land to water and produced by photochemical processes, and the capacity and timescale that microbial communities have to adapt to metabolize photo-altered DOC.
Revised microbial and photochemical triple-oxygen isotope effects improve marine gross oxygen production estimates

(Oxford University Press, 2022-10-12) Sutherland, Kevin M. ; Johnston, David T. ; Hemingway, Jordon D. ; Wankel, Scott D. ; Ward, Collin P.

AbstractThe biogeochemical fluxes that cycle oxygen (O2) play a critical role in regulating Earth’s climate and habitability. Triple-oxygen isotope (TOI) compositions of marine dissolved O2 are considered a robust tool for tracing oxygen cycling and quantifying gross photosynthetic O2 production. This method assumes that photosynthesis, microbial respiration, and gas exchange with the atmosphere are the primary influences on dissolved O2 content, and that they have predictable, fixed isotope effects. Despite its widespread use, there are major elements of this approach that remain uncharacterized, including the TOI dynamics of respiration by marine heterotrophic bacteria and abiotic O2 sinks such as the photochemical oxidation of dissolved organic carbon (DOC). Here, we report the TOI fractionation for O2 utilization by two model marine heterotrophs and by abiotic photo-oxidation of representative terrestrial and coastal marine DOC. We demonstrate that TOI slopes associated with these processes span a significant range of the mass-dependent domain (λ = 0.499 to 0.521). A sensitivity analysis reveals that even under moderate productivity and photo-oxidation scenarios, true gross oxygen production may deviate from previous estimates by more than 20% in either direction. By considering a broader suite of oxygen cycle reactions, our findings challenge current gross oxygen production estimates and highlight several paths forward to better understanding the marine oxygen and carbon cycles.
Synergy between sunlight, titanium dioxide, and microbes enhances cellulose diacetate degradation in the ocean

(American Chemical Society, 2022-09-16) Walsh, Anna N. ; Mazzotta, Michael G. ; Nelson, Taylor F. ; Reddy, Christopher M. ; Ward, Collin P.

Sunlight chemically transforms marine plastics into a suite of products, with formulationthe specific mixture of polymers and additivesdriving rates and products. However, the effect of light-driven transformations on subsequent microbial lability is poorly understood. Here, we examined the interplay between photochemical and biological degradation of fabrics made from cellulose diacetate (CDA), a biobased polymer used commonly in consumer products. We also examined the influence of ∼1% titanium dioxide (TiO2), a common pigment and photocatalyst. We sequentially exposed CDA to simulated sunlight and native marine microbes to understand how photodegradation influences metabolic rates and pathways. Nuclear magnetic resonance spectroscopy revealed that sunlight initiated chain scission reactions, reducing CDA’s average molecular weight. Natural abundance carbon isotope measurements demonstrated that chain scission ultimately yields CO2, a newly identified abiotic loss term of CDA in the environment. Measurements of fabric mass loss and enzymatic activities in seawater implied that photodegradation enhanced biodegradation by performing steps typically facilitated by cellulase. TiO2 accelerated CDA photodegradation, expediting biodegradation. Collectively, these findings (i) underline the importance of formulation in plastic’s environmental fate and (ii) suggest that overlooking synergy between photochemical and biological degradation may lead to overestimates of marine plastic persistence.
Opinion: we need better data about the environmental persistence of plastic goods

(National Academy of Sciences, 2020-06-10) Ward, Collin P. ; Reddy, Christopher M.

Plastic pollution is one of the most visible and complex environmental issues today. Interested and concerned parties include researchers, governmental agencies, nongovernmental organizations, industry, media, and the general public. One key assumption behind the issue and the public outcry is that plastics last indefinitely in the environment, resulting in chronic exposure that harms animals and humans. But the data supporting this assumption are scant.
Photochemical oxidation of oil reduced the effectiveness of aerial dispersants applied in response to the Deepwater Horizon spill

(American Chemical Society, 2018-04-25) Ward, Collin P. ; Armstrong, Cassia J. ; Conmy, Robyn N. ; French-McCay, Deborah P. ; Reddy, Christopher M.

Chemical dispersants are one of many tools used to mitigate the overall environmental impact of oil spills. In principle, dispersants break up floating oil into small droplets that disperse into the water column where they are subject to multiple fate and transport processes. The effectiveness of dispersants typically decreases as oil weathers in the environment. This decrease in effectiveness is often attributed to evaporation and emulsification, with the contribution of photochemical weathering assumed to be negligible. Here, we aim to test this assumption using Macondo well oil released during the Deepwater Horizon spill as a case study. Our results indicate that the effects of photochemical weathering on Deepwater Horizon oil properties and dispersant effectiveness can greatly outweigh the effects of evaporative weathering. The decrease in dispersant effectiveness after light exposure was principally driven by the decreased solubility of photo-oxidized crude oil residues in the solvent system that comprises COREXIT EC9500A. Kinetic modeling combined with geospatial analysis demonstrated that a considerable fraction of aerial applications targeting Deepwater Horizon surface oil had low dispersant effectiveness. Collectively, the results of this study challenge the paradigm that photochemical weathering has a negligible impact on the effectiveness of oil spill response and provide critical insights into the “window of opportunity” to apply chemical dispersants in response to oil spills in sunlit waters.
Sunlight-driven dissolution is a major fate of oil at sea

(American Association for the Advancement of Science, 2022-02-16) Freeman, Danielle Haas ; Ward, Collin P.

Oxygenation reactions initiated by sunlight can transform insoluble components of crude oil at sea into water-soluble products, a process called photo-dissolution. First reported a half century ago, photo-dissolution has never been included in spill models because key parameters required for rate modeling were unknown, including the wavelength and photon dose dependence. Here, we experimentally quantified photo-dissolution as a function of wavelength and photon dose, making possible a sensitivity analysis of environmental variables in hypothetical spill scenarios and a mass balance assessment for the 2010 Deepwater Horizon (DwH) spill. The sensitivity analysis revealed that rates were most sensitive to oil slick thickness, season/latitude, and wavelength and less sensitive to photon dose. We estimate that 3 to 17% (best estimate 8%) of DwH surface oil was subject to photo-dissolution, comparable in magnitude to other widely recognized fate processes. Our findings invite a critical reevaluation of surface oil budgets for both DwH and future spills at sea.
Arctic amplification of global warming strengthened by sunlight oxidation of permafrost carbon to CO2

(Wiley, 2020-06-09) Bowen, Jennifer C. ; Ward, Collin P. ; Kling, George W. ; Cory, Rose M.

Once thawed, up to 15% of the ∼1,000 Pg of organic carbon (C) in arctic permafrost soils may be oxidized to carbon dioxide (CO2) by 2,100, amplifying climate change. However, predictions of this amplification strength ignore the oxidation of permafrost C to CO2 in surface waters (photomineralization). We characterized the wavelength dependence of permafrost dissolved organic carbon (DOC) photomineralization and demonstrate that iron catalyzes photomineralization of old DOC (4,000–6,300 a BP) derived from soil lignin and tannin. Rates of CO2 production from photomineralization of permafrost DOC are twofold higher than for modern DOC. Given that model predictions of future net loss of ecosystem C from thawing permafrost do not include the loss of CO2 to the atmosphere from DOC photomineralization, current predictions of an average of 208 Pg C loss by 2,299 may be too low by ~14%.
Oxygen isotopes (delta O-18) trace photochemical hydrocarbon oxidation at the sea surface

(American Geophysical Union, 2019-05-31) Ward, Collin P. ; Sharpless, Charles M. ; Valentine, David L. ; Aeppli, Christoph ; Sutherland, Kevin M. ; Wankel, Scott D. ; Reddy, Christopher M.

Although photochemical oxidation is an environmental process that drives organic carbon (OC) cycling, its quantitative detection remains analytically challenging. Here, we use samples from the Deepwater Horizon oil spill to test the hypothesis that the stable oxygen isotope composition of oil (δ18OOil) is a sensitive marker for photochemical oxidation. In less than one‐week, δ18OOil increased from −0.6 to 7.2‰, a shift representing ~25% of the δ18OOC dynamic range observed in nature. By accounting for different oxygen sources (H2O or O2) and kinetic isotopic fractionation of photochemically incorporated O2, which was −9‰ for a wide range of OC sources, a mass balance was established for the surface oil's elemental oxygen content and δ18O. This δ18O‐based approach provides novel insights into the sources and pathways of hydrocarbon photo‐oxidation, thereby improving our understanding of the fate and transport of petroleum hydrocarbons in sunlit waters, and our capacity to respond effectively to future spills.
Quantifying pelagic primary production and respiration via an automated in situ incubation system

(Association for the Sciences of Limnology and Oceanography, 2023-06-16) Chen, Solomon T. ; Ward, Collin P. ; Long, Matthew H.

Pelagic photosynthesis and respiration serve critical roles in controlling the dissolved oxygen (DO) concentration in seawater. The consumption and production via pelagic primary production are of particular importance in the surface ocean and in freshwater ecosystems where photosynthetically active radiation is abundant. However, the dynamic nature and large degree of heterogeneity in these ecosystems pose substantial challenges for providing accurate estimates of marine primary production and metabolic state. The resulting lack of higher-resolution data in these systems hinders efforts in scaling and including primary production in predictive models. To bridge the gap, we developed and validated a novel automated water incubator that measures in situ rates of photosynthesis and respiration. The automated water incubation system uses commercially available optodes and microcontrollers to record continuous measurements of DO within a closed chamber at desired intervals. With fast response optodes, the incubation system produced measurements of photosynthesis and respiration with an hourly resolution, resolving diel signals in the water column. The high temporal resolution of the time series also enabled the development of Monte Carlo simulation as a new data analysis technique to calculate DO fluxes, with improved performance in noisy time series. Deployment of the incubator was conducted near Ucantena Island, Massachusetts, U.S.A. The data captured diel fluctuations in metabolic fluxes with an hourly resolution, allowed for a more accurate correlation between oxygen cycling and environmental conditions, and provided improved characterization of the pelagic metabolic state.
Distinct microbial communities degrade cellulose diacetate bioplastics in the coastal ocean

(American Society for Microbiology, 2023-12-06) Sun, Yanchen ; Mazzotta, Michael G. ; Miller, Carolyn A. ; Apprill, Amy ; Izallalen, Mounir ; Mazumder, Sharmistha ; Perri, Steven T. ; Edwards, Brian ; Reddy, Christopher M. ; Ward, Collin P.

Cellulose diacetate (CDA) is a bio-based plastic widely used in consumer products. CDA is a promising alternative to conventional thermoplastics due to its susceptibility to biodegradation in various environments. Despite widespread evidence for the degradation of CDA, relatively little is known about the microorganisms that drive degradation, particularly in the ocean. Recently, we documented the biodegradation of CDA-based materials (i.e., fabric, film, and foam) in a continuous-flow natural seawater mesocosm on the timescales of months, as indicated by mass loss, enzyme activity, and respiration to carbon dioxide. These findings paved the way for the present study aimed at identifying key microbial taxa implicated in CDA degradation. Analysis based on 16S rRNA gene amplicon sequencing of bacteria and archaea revealed that material type, incubation time, material morphology (e.g., fabric vs film), and plasticizer content significantly influenced the microbial community structure. Differential abundance analysis revealed that bacterial taxa affiliated with the families of Arenicellaceae, Cellvibrionaceae, Methyloligellaceae, Micavibrionaceae, Puniceicoccaceae, Spirosomaceae, and Thermoanaerobaculaceae, and the order of Pseudomonadales potentially initiated the degradation (i.e., deacetylation) of CDA fabric and film. These taxa were notably distinct from CDA-degrading microbes reported in non-seawater environments. Collectively, the findings lend further support for CDA as a promising next-generation, high-utility, and low-environmental persistence bioplastic material.
Diffusion-Ordered spectroscopy for rapid and facile determination of consumer plastic molecular weight

(American Chemical Society, 2023-05-25) Nelson, Taylor F. ; Ward, Collin P.

Molecular weight (MW) is a key control of plastic polymer properties and their fate in the environment. However, the primary tool used to determine plastic MW, gel permeation chromatography (GPC), has major limitations, such as low precision and accuracy, requirements for dedicated instrumentation, production of high volumes of hazardous waste, and large sample sizes. In this study, we describe, validate, and apply a diffusion-ordered spectroscopy (DOSY) method for polymer MW determinations, with a focus on applications for consumer plastics. Several experimental conditions were systematically optimized and tested to validate the DOSY method, including the selection of pulse sequences, the effect of sample concentration, cross-validation with multiple sets of external standards, and long-term instrumental stability. Validation was performed for a wide range of polymers, solvents, and temperatures, highlighting its potential for broad applicability. A preliminary screening of polystyrene and polyethylene terephthalate consumer products revealed widely varying MWs (up to two-fold) for products made of the same polymer type. A preliminary experiment was also conducted to track the decrease in polystyrene MW via photochemical chain scission reactions, finding a 20% reduction in MW after less than 1 week of irradiation. Collectively, our results demonstrate the potential for DOSY to provide high-throughput, accurate, and precise measures of polymer MW, as well as the evolution of polymer MW during environmental weathering processes, such as photochemical degradation. We conclude with a discussion of (i) the many advantages of DOSY compared to GPC, (ii) future developments to enhance the depth of information obtained from DOSY, and (iii) approaches to broaden the accessibility of this promising analytical method to the research community.
Identification of next-generation International Humic Substances Society reference materials for advancing the understanding of the role of natural organic matter in the Anthropocene

(Springer, 2023-01-09) Chin, Yu-Ping ; McKnight, Diane M. ; D’Andrilli, Juliana ; Brooks, Nicole ; Cawley, Kaelin ; Guerard, Jennifer ; Perdue, E. Michael ; Stedmon, Colin A. ; Tratnyek, Paul G. ; Westerhoff, Paul ; Wozniak, Andrew S. ; Bloom, Paul R. ; Foreman, Christine M. ; Gabor, Rachel ; Hamdi, Jumanah ; Hanson, Blair ; Hozalski, Raymond M. ; Kellerman, Anne M. ; McKay, Garrett ; Silverman, Victoria ; Spencer, Robert G. M. ; Ward, Collin P. ; Xin, Danhui ; Rosario-Ortiz, Fernando ; Remucal, Christina K. ; Reckhow, David

Many challenges remain before we can fully understand the multifaceted role that natural organic matter (NOM) plays in soil and aquatic systems. These challenges remain despite the considerable progress that has been made in understanding NOM’s properties and reactivity using the latest analytical techniques. For nearly 4 decades, the International Humic Substances Society (IHSS, which is a non-profit scientific society) has distributed standard substances that adhere to strict isolation protocols and reference materials that are collected in bulk and originate from clearly defined sites. These NOM standard and reference samples offer relatively uniform materials for designing experiments and developing new analytical methods. The protocols for isolating NOM, and humic and fulvic acid fractions of NOM utilize well-established preparative scale column chromatography and reverse osmosis methods. These standard and reference NOM samples are used by the international scientific community to study NOM across a range of disciplines from engineered to natural systems, thereby seeding the transfer of knowledge across research fields. Recently, powerful new analytical techniques used to characterize NOM have revealed complexities in its composition that transcend the “microbial” vs. “terrestrial” precursor paradigm. To continue to advance NOM research in the Anthropocene epoch, a workshop was convened to identify potential new sites for NOM samples that would encompass a range of sources and precursor materials and would be relevant for studying NOM’s role in mediating environmental and biogeochemical processes. We anticipate that expanding the portfolio of IHSS reference and standard NOM samples available to the research community will enable this diverse group of scientists and engineers to better understand the role that NOM plays globally under the influence of anthropogenic mediated changes.
Strategies to reduce the environmental lifetimes of drinking straws in the coastal ocean

(American Chemical Society, 2024-01-30) James, Bryan D. ; Sun, Yanchen ; Izallalen, Mounir ; Mazumder, Sharmistha ; Perri, Steven T. ; Edwards, Brian ; de Wit, Jos ; Reddy, Christopher M. ; Ward, Collin P.

Nonpersistence in natural environments with benign degradation products is a growing design criterion for consumer plastics. However, data on their biodegradation rates and environmental lifetimes in the coastal ocean are lacking, limiting informed engineering and regulatory decisions. Single-use drinking straws, a common marine litter relevant to key stakeholders, exemplify this. To fill this knowledge gap, commercial drinking straws made of cellulose diacetate (CDA), polyhydroxyalkanoates (PHA), paper, polylactic acid (PLA), and polypropylene (PP) were incubated for 16 weeks in a flow-through seawater mesocosm and monitored for degradation and microbial community composition. CDA, PHA, and paper straws reduced in mass by up to 50%, projecting environmental lifetimes of 10–20 months in the coastal ocean. PP and PLA showed no measurable mass loss. Lifetimes depended on the material and dimensions of the straw, demonstrating the need to balance function and degradation properties. The materials that biodegraded exhibited unique microbial communities driven by chemical structure, whereas those materials that were persistent exhibited similar communities despite substantial differences in chemical structure. To reduce the persistence of drinking straws, we hypothesized that changing the product form (i.e., surface area), not just the material, can reduce their environmental lifetimes. To test our hypothesis, we evaluated the biodegradation of a prototype foamed CDA straw. Its specific surface degradation rate was more than double that of its solid counterpart, resulting in a shorter projected environmental lifetime than the paper straws. Our findings provide the initial constraints of the environmental lifetimes of several commercial drinking straws and identify strategies to design next-generation bioplastic consumer products with reduced persistence.
Minimizing the environmental impacts of plastic pollution through ecodesign of products with low environmental persistence

(American Chemical Society, 2024-01-08) James, Bryan D. ; Ward, Collin P. ; Hahn, Mark E. ; Thorpe, Steven J. ; Reddy, Christopher M.

While plastic pollution threatens ecosystems and human health, the use of plastic products continues to increase. Limiting its harm requires design strategies for plastic products informed by the threats that plastics pose to the environment. Thus, we developed a sustainability metric for the ecodesign of plastic products with low environmental persistence and uncompromised performance. To do this, we integrated the environmental degradation rate of plastic into established material selection strategies, deriving material indices for environmental persistence. By comparing indices for the environmental impact of on-the-market plastics and proposed alternatives, we show that accounting for the environmental persistence of plastics in design could translate to societal benefits of hundreds of millions of dollars for a single consumer product. Our analysis identifies the materials and their properties that deserve development, adoption, and investment to create functional and less environmentally impactful plastic products.
Controls on the respiration of ancient carbon draining from permafrost soils into sunlit Arctic surface waters

(American Geophysical Union, 2024-05-08) Rieb, Emma C. ; Polik, Catherine A. ; Ward, Collin P. ; Kling, George W. ; Cory, Rose M.

The thawing of ancient organic carbon stored in arctic permafrost soils, and its oxidation to carbon dioxide (CO2, a greenhouse gas), is predicted to amplify global warming. However, the extent to which organic carbon in thawing permafrost soils will be released as CO2 is uncertain. A critical unknown is the extent to which dissolved organic carbon (DOC) from thawing permafrost soils is respired to CO2 by microbes upon export of freshly thawed DOC to both dark bottom waters and sunlit surface waters. In this study, we quantified the radiocarbon age and 13C composition of CO2 produced by microbial respiration of DOC that was leached from permafrost soils and either kept in the dark or exposed to ultraviolet and visible wavelengths of light. We show that permafrost DOC most labile to microbial respiration was as old or older (ages 4,000–11,000 a BP) and more 13C-depleted than the bulk DOC in both dark and light-exposed treatments, likely indicating respiration of old, 13C-depleted lignin and lipid fractions of the permafrost DOC pool. Light exposure either increased, decreased, or had no effect on the magnitude of microbial respiration of old permafrost DOC relative to respiration in the dark, depending on both the extent of DOC oxidation during exposure to light and the wavelength of light. Together, these findings suggest that photochemical changes affecting the lability of permafrost DOC during sunlight exposure are an important control on the magnitude of microbial respiration of permafrost DOC in arctic surface waters.

Ward Collin P.

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