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Browsing Staff publications (ES) by Subject "37 Earth Sciences"

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    An analysis of factors that influence the spatial pattern of faecal matter flow in unsewered cities
    (Elsevier, 2025-05-25) Sultana, M. Sufia; Waine, Toby W.; Bari, Niamul; Tyrrel, Sean
    The management of sanitation systems in unsewered cities in low and middle income countries is a critical issue, yet it is unclear where the risk hotspots are and where interventions should be focused. This study utilised a prototype model, developed by the authors, to map the spatial pattern of faecal flow in Rajshahi city, a secondary city in northwest Bangladesh with a population around a million. This city serves as a representative example of 60 such secondary cities in Bangladesh and hundreds more in the economically developing region in Asia, Africa and Latin America. The model relies on assumptions that carry significant uncertainties; hence, the study employed a sensitivity analysis with multiple plausible scenarios to characterise these uncertainties, aiming to identify ways to improve the model further. Five major influencing factors on the spatial pattern of faecal flow were identified: the emptying of septic tanks, the use of soak pits, and sludge removal from drains, variations in faecal matter production by building types, and the presence or absence of toilets. These factors were shown to collectively have a significant impact (almost 50 % changed) on the model outcome, depending upon the assumptions made. The study offers insights that will guide future data collection efforts by emphasising the need to understand these specific influencing factors and their spatial pattern. Consequently, this research has broader implications for urban sanitation management as well as associated public health research like wastewater surveillance, risk assessment, and disease dynamics in similar urban settings, offering insights into areas of uncertainty that need to be addressed in future modelling efforts.
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    Nature-based stormwater management for aquifer recharge: exploring bioclogging-induced challenges
    (Elsevier, 2025-08-01) Wu, Yuhui; Lu, Ying; Yan, Zihan; Shi, Min; Wang, Qiandan; Lyu, Tao; Jia, Ruoyu; Huang, Ling; Chen, Zhiliang; Chen, Jianyu; Song, Xiaoming; Yang, Yuesuo
    Utilising excess urban stormwater to recharge groundwater can effectively mitigate the problems caused by the over-exploitation of subsurface environments while simultaneously making full use of valuable water resources. However, bioclogging can significantly reduce the efficiency of recharge projects in practical applications. This study is distinguished by its comprehensive consideration of unsaturated hydraulic conditions during stormwater recharge, which can influence microbial activities and the evolution of bioclogging, setting it apart from the predominant focus on saturated conditions in previous research. Microbial activity in the media became more vigorous under unsaturated conditions, and the cell volume decreased to 33–50 % of that under saturated conditions. Under unsaturated conditions, microbial EPS exhibited a curled morphology. At 60 % saturation, the contents of LB-EPS and polysaccharides increased by 141.23 and 187.47 μg/g sand, respectively, compared to saturated conditions. The reduction in saturation weakened microbial migration, promoted their deposition on the media surfaces, and reduced the non-uniformity of interlayer distribution. Simultaneously, unsaturated seepage conditions attenuated the effect of flow velocity (0.5–2 mL/min) changes on microbial migration and deposition. Bioclogging under unsaturated seepage conditions was governed by both EPS action and the EPS-bacterial interaction, with EPS secretion significantly influencing the degree of internal bioclogging development. This work contributes to a more comprehensive understanding of the bioclogging mechanisms under the unique hydrodynamic conditions of stormwater recharge, enabling more precise prevention and control of bioclogging during artificial stormwater recharge.
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    Optimizing the temperature sensitivity of the isoprene emission model MEGAN in different ecosystems using a Metropolis‐Hastings Markov Chain Monte Carlo method
    (American Geophysical Union (AGU), 2025-05-01) DiMaria, Christian A.; Jones, Dylan B. A.; Ferracci, Valerio; Bloom, A. Anthony; Worden, Helen M.; Seco, Roger; Vettikkat, Lejish; Yáñez Serrano, Ana Maria; Guenther, Alex B.; Araujo, A.; Goldstein, Allen H.; Langford, Ben; Cash, James; Harris, Neil R. P.; Brown, Luke; Rinnan, Riikka; Schobesberger, Siegfried; Holst, Thomas; Mak, John E.
    Isoprene is a reactive hydrocarbon emitted to the atmosphere in large quantities by terrestrial vegetation. Annual total isoprene emissions exceed 300 Tg a−1, but emission rates vary widely among plant species and are sensitive to meteorological and environmental conditions including temperature, sunlight, and soil moisture. Due to its high reactivity, isoprene has a large impact on air quality and climate pollutants such as ozone and aerosols. It is also an important sink for the hydroxyl radical which impacts the lifetime of the important greenhouse gas methane along with many other trace gas species. Modeling the impacts of isoprene emissions on atmospheric chemistry and climate requires accurate isoprene emission estimates. These can be obtained using the empirical Model of Emissions of Gases and Aerosols from Nature (MEGAN), but the parameterization of this model is uncertain due in part to limited field observations. In this study, we use ground‐based measurements of isoprene concentrations and fluxes from 11 field sites to assess the variability of the isoprene emission temperature response across ecosystems. We then use these observations in a Metropolis‐Hastings Markov Chain Monte Carlo (MHMCMC) data assimilation framework to optimize the MEGAN temperature response function. We find that the performance of MEGAN can be significantly improved at several high‐latitude field sites by increasing the modeled sensitivity of isoprene emissions to past temperatures. At some sites, the optimized model was nearly four times more sensitive to temperature than the unoptimized model. This has implications for air quality modeling in a warming climate.
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    The known unknowns of petrogenic organic carbon in soils
    (American Geophysical Union (AGU), 2025-04-01) Evans, Daniel L.; Doetterl, Sebastian; Gallarotti, Nora; Georgiadis, Eleanor; Nabhan, Sami; Wartenweiler, Stephan H.; Rhyner, Timo M. Y.; Mittelbach, Benedict V. A.; Eglinton, Timothy I.; Hemingway, Jordon D.; Blattmann, Thomas M.
    Intensifying effects of global climate change have spurred efforts to enhance carbon sequestration and the long‐term storage of soil organic carbon (OC). Current soil carbon models predominantly assume that inputs of OC are biospheric, that is, primarily derived from plant decomposition. However, these overlook the contribution of OC from soil parent material, including petrogenic organic carbon (OCpetro) from OC‐bearing (meta‐)sedimentary bedrock. To our knowledge, no soil carbon model accounts for the inputs of OCpetro to soils, resulting in significant gaps in our understanding about the roles OCpetro plays in soils. Here, we call for cross‐disciplinary research to investigate the transport and stability of OCpetro across the bedrock–soil continuum. We pose four key questions as motivation for this effort. Ignoring the inputs of OCpetro to soils has significant implications, including overestimating biospheric carbon stocks and turnover times. Furthermore, we lack information on the role that OCpetro may play in priming microbial communities, as well as the impacts of land management on OCpetro stocks.