ORCID Profile
0000-0002-0575-8342
Current Organisation
Virginia Tech
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Publisher: University of Chicago Press
Date: 03-2016
DOI: 10.1086/685284
Publisher: American Association for the Advancement of Science (AAAS)
Date: 16-03-2018
Abstract: A combination of physical transport processes and biologically mediated reactions in streams and their sediments removes dissolved inorganic nitrogen (DIN) from the water. Although stream chemistry and biology have been considered the dominant controls on how quickly DIN is removed, Grant et al. show that physics is what sets the limits on removal rates of nitrate (a component of DIN). Residence time in the hyporheic zone (the region below the sediment surface where groundwater and surface water mix) determines the maximum rate at which nitrate can be removed from stream water. Nevertheless, at local scales, chemistry and biology modify how closely to that maximum rate removal occurs. Science , this issue p. 1266
Publisher: Wiley
Date: 11-12-2015
DOI: 10.1002/WAT2.1128
Abstract: Natural treatment systems ( NTS ), such as constructed wetlands and stormwater ponds, are multibenefit, multidisciplinary approaches to sustaining water resources and reducing contaminant loading to urban streams. Surficial thin films (called surface microlayers) are not well characterized in NTS , but may have important implications for ecosystems, public health, and pollutant fate and transport. We present results from a case study evaluating microlayer contaminant partitioning across 4 NTS in Melbourne, Australia. To our knowledge, this study provides the first direct evidence for microlayer formation and contaminant enrichment (total petroleum hydrocarbons and trihalomethanes) in NTS . Contaminated microlayers were detected in the three most stable NTS , with stability defined relative to wind speed. Fluorescent‐dissolved organic matter profiles differed between microlayer and subsurface water in these systems, suggesting that fluorescence‐based techniques are useful for microlayer detection. Although in idual fluorophores were not consistently associated with specific contaminants, fluorescence ratios were useful for identifying likely contaminant source waters, including road‐runoff and irrigation water from nearby green spaces. We evaluate our case study in light of what is known about surface microlayers in analogous systems (e.g., oceans, estuaries, and lakes), in order to identify existing research gaps and future opportunities. WIREs Water 2016, 3:269–281. doi: 10.1002/wat2.1128 This article is categorized under: Engineering Water Sustainable Engineering of Water Engineering Water Water, Health, and Sanitation Science of Water Water Quality
Publisher: Elsevier BV
Date: 10-2021
Publisher: Springer Science and Business Media LLC
Date: 05-11-2020
Publisher: American Chemical Society (ACS)
Date: 08-05-2017
Abstract: Green infrastructure (also referred to as low impact development, or LID) has the potential to transform urban stormwater runoff from an environmental threat to a valuable water resource. In this paper we focus on the removal of fecal indicator bacteria (FIB, a pollutant responsible for runoff-associated inland and coastal beach closures) in stormwater biofilters (a common type of green infrastructure). Drawing on a combination of previously published and new laboratory studies of FIB removal in biofilters, we find that 66% of the variance in FIB removal rates can be explained by clean bed filtration theory (CBFT, 31%), antecedent dry period (14%), study effect (8%), biofilter age (7%), and the presence or absence of shrubs (6%). Our analysis suggests that, with the exception of shrubs, plants affect FIB removal indirectly by changing the infiltration rate, not directly by changing the FIB removal mechanisms or altering filtration rates in ways not already accounted for by CBFT. The analysis presented here represents a significant step forward in our understanding of how physicochemical theories (such as CBFT) can be melded with hydrology, engineering design, and ecology to improve the water quality benefits of green infrastructure.
Publisher: American Geophysical Union (AGU)
Date: 05-2017
DOI: 10.1002/2016WR020048
Publisher: American Chemical Society (ACS)
Date: 10-09-2015
Abstract: Catchment urbanization perturbs the water and sediment budgets of streams, degrades stream health and function, and causes a constellation of flow, water quality, and ecological symptoms collectively known as the urban stream syndrome. Low-impact development (LID) technologies address the hydrologic symptoms of the urban stream syndrome by mimicking natural flow paths and restoring a natural water balance. Over annual time scales, the volumes of stormwater that should be infiltrated and harvested can be estimated from a catchment-scale water-balance given local climate conditions and preurban land cover. For all but the wettest regions of the world, a much larger volume of stormwater runoff should be harvested than infiltrated to maintain stream hydrology in a preurban state. Efforts to prevent or reverse hydrologic symptoms associated with the urban stream syndrome will therefore require: (1) selecting the right mix of LID technologies that provide regionally tailored ratios of stormwater harvesting and infiltration (2) integrating these LID technologies into next-generation drainage systems (3) maximizing potential cobenefits including water supply augmentation, flood protection, improved water quality, and urban amenities and (4) long-term hydrologic monitoring to evaluate the efficacy of LID interventions.
Publisher: Wiley
Date: 06-02-2022
DOI: 10.1002/PAN3.10300
Abstract: Natural treatment systems (NTS) for stormwater have the potential to provide a myriad of ecosystem services to society. Realizing this potential requires active collaboration among engineers, ecologists and landscape planners and begins with a paradigm shift in communication whereby these groups are made aware of each other's perceptions about NTS and the presence of knowledge gaps that their respective disciplines can bridge. Here we participate in the first part of what we hope will be a reciprocal exchange: presenting results from a landscape perceptions survey to urban planners, ecologists and landscape architects that illustrates how the next generation of engineers perceives NTS relative to other landscape features, and the implications of those perceptions for future infrastructure development. Our results suggest that although lawns, gardens and native ecosystems were perceived as multifunctional, providing characteristic bundles of services/disservices, perceptions of NTS were more variable (i.e. there was no social norm for their perception). Environmental worldviews, knowledge, attitudes about ecosystem services and demographics were all significant drivers of perceived services. However, students had difficulty identifying NTS correctly, and factual knowledge about NTS did not help students associate NTS with typical design services like flood reduction more than features not designed for those purposes, such as lawns. This suggests that engineering students lack familiarity with the outward appearance of NTS and have difficulty placing NTS services into a broader landscape context. Expertise from urban planning and ecology could help bridge these knowledge gaps, improving the capacity of tomorrow's engineers to co‐design NTS to meet erse community needs. Read the free Plain Language Summary for this article on the Journal blog.
Publisher: Elsevier BV
Date: 06-2018
DOI: 10.1016/J.WATRES.2018.03.020
Abstract: Constructed stormwater wetlands provide a host of ecosystem services, including potentially pathogen removal. We present results from a multi-wetland study that integrates across weather, chemical, microbiological and engineering design variables in order to identify patterns of microbial contaminant removal from inlet to outlet within wetlands and key drivers of those patterns. One or more microbial contaminants were detected at the inlet of each stormwater wetland (Escherichia coli and Enterococcus > Bacteroides HF183 > adenovirus). Bacteroides HF183 and adenovirus concentrations declined from inlet to outlet at all wetlands. However, co-removal of pathogens and fecal indicator bacteria only occurred at wetlands where microbial assemblages at the inlet (dominated by Proteobacteria and Bacteriodetes) were largely displaced by indigenous autotrophic microbial communities at the outlet (dominated by Cyanobacteria). Microbial community transitions (characterized using pyrosequencing) were well approximated by a combination of two rapid indicators: (1) fluorescent dissolved organic matter, and (2) chlorophyll a or phaeophytin a fluorescence. Within-wetland treatment of fecal markers and indicators was not strongly correlated with the catchment-to-wetland area ratio, but was diminished in older wetlands, which may point to a need for more frequent maintenance.
Publisher: American Chemical Society (ACS)
Date: 27-08-2015
Abstract: Bedforms are a focal point of carbon and nitrogen cycling in streams and coastal marine ecosystems. In this paper, we develop and test a mechanistic model, the "pumping and streamline segregation" or PASS model, for nitrate removal in bedforms. The PASS model dramatically reduces computational overhead associated with modeling nitrogen transformations in bedforms and reproduces (within a factor of 2 or better) previously published measurements and models of biogeochemical reaction rates, benthic fluxes, and in-sediment nutrient and oxygen concentrations. Application of the PASS model to a erse set of marine and freshwater environments indicates that (1) physical controls on nitrate removal in a bedform include the pore water flushing rate, residence time distribution, and relative rates of respiration and transport (as represented by the Damkohler number) (2) the biogeochemical pathway for nitrate removal is an environment-specific combination of direct denitrification of stream nitrate and coupled nitrification-denitrification of stream and/or sediment ammonium and (3) permeable sediments are almost always a net source of dissolved inorganic nitrogen. The PASS model also provides a mechanistic explanation for previously published empirical correlations showing denitrification velocity (N2 flux ided by nitrate concentration) declines as a power law of nitrate concentration in a stream (Mulholland et al. Nature, 2008, 452, 202-205).
Publisher: Elsevier BV
Date: 05-2017
DOI: 10.1016/J.WATRES.2017.03.010
Abstract: Stormwater is a major driving factor of aquatic ecosystem degradation as well as one of the largest untapped urban freshwater resources. We present results from a long-term, multi-catchment study of urban stormwater pesticides across Australia that addresses this dichotomous identity (threat and resource), as well as dominant spatial and temporal patterns in stormwater pesticide composition. Of the 27 pesticides monitored, only 19 were detected in Australian stormwater, five of which (diuron, MCPA, 2,4-D, simazine, and triclopyr) were found in >50% of s les. Overall, stormwater pesticide concentrations were lower than reported in other countries (including the United States, Canada and Europe), and exceedances of public health and aquatic ecosystem standards were rare (<10% of s les). Spatio-temporal patterns were investigated with principal component analysis. Although stormwater pesticide composition was relatively stable across seasons and years, it varied significantly by catchment. Common pesticide associations appear to reflect 1) user application of common registered formulations containing characteristic suites of active ingredients, and 2) pesticide fate properties (e.g., environmental mobility and persistence). Importantly, catchment-specific occurrence patterns provide opportunities for focusing treatment approaches or stormwater harvesting strategies.
Location: United States of America
Location: United States of America
No related grants have been discovered for Megan Rippy.