Geology topics

Sujay S. Kaushal

Publications and source records attributed to Sujay S. Kaushal.

7 recordsLinked to original sources

USGS2023

Stream restoration milestones: Monitoring scales determine successes and failures

Urban stream restoration is growing globally, but there is much to learn from successes, failures, and evaluating tradeoffs in restoration practices. Significant time and resources have been invested towards restoring the structure and function of urban ecosystems and understanding and slowing the drivers of degradation. However, the rapid pace of urbanization and its effects on urban waters present an ever-growing challenge to environmental managers and restoration practitioners when identifying and prioritizing effective strategies for restoration and monitoring outcomes. Here, we synthesize major findings and papers originating from the 5th Symposium on Urbanization and Stream Ecology (SUSE5) and propose a new concept for monitoring restoration based on lessons learned. Efforts from SUSE5 showed that urban disturbances and restoration activities have strong localized impacts that can be challenging to detect and disentangle across broader watershed scales and longitudinal flowpaths. Most urban stream restoration projects are monitored at only one or a few locations that do not capture significant variability across stream reaches and longer flowpaths. Based on knowledge from SUSE5, we present a new concept called ‘restoration milestones.’ The restoration milestones concept proposes that the scale of stream monitoring over space and time can influence whether a stream restoration project is considered a success or failure. Therefore, answers to questions regarding restoration effectiveness and durability can be affected by spatial and temporal monitoring scales. Setting realistic restoration milestones involves establishing monitoring strategies that account for spatial and temporal variability. Tracking restoration performance through time across stream reaches along longitudinal flowpaths could aid in more accurately assessing project performance. We explore applications for evaluating restoration milestones along longitudinal stream flowpaths including: (1) identifying target areas of improvement along drainage networks, (2) accurately accounting for tradeoffs in habitat, protection of infrastructure, and water quality along flowpaths, and (3) detecting how far downstream the effects of stream restoration and stormwater management can be propagated. Monitoring across different spatial and temporal scales is an overlooked but critical factor in determining restoration success. Additionally, the scale of the restoration project itself can determine the type and magnitude of improvements. Expectations for what a restoration project can accomplish in terms of water quality improvements should be calibrated to the project’s spatial scale and evolution over time. Longitudinal studies of stream restoration help identify successes and failures along flowpaths.

Urban Ecosystems↗

USGS2022

Urbanization and stream ecology: Moving the bar on multidisciplinary solutions to wicked urban stream problems

Decades of research on the effects of urbanization on stream ecology have shown that urban stream problems are inherently wicked. These problems are wicked in the sense that they are difficult to solve because information is incomplete, changing, or conflicting and because finding potential solutions often requires input from stakeholders who can have conflicting and competing values. The 5 th Symposium on Urbanization and Stream Ecology (SUSE5) in February 2020 brought together diverse perspectives from scientists, managers, practitioners, and local communities. Participants at SUSE5 discussed the state of the science in urban stream ecology and worked through in-depth case studies in teams to tackle complex real-world problems in urban stream management. The papers in this special series on urbanization and stream ecology include empirical research studies and synthesis papers sparked by discussions at SUSE5 and advance multidisciplinary solutions to wicked urban stream problems.

Freshwater Science↗

USGS2021

Evidence that watershed nutrient management practices effectively reduce estrogens in environmental waters

We evaluate the impacts of different nutrient management strategies on the potential for co-managing estrogens and nutrients in environmental waters of the Potomac watershed of the Chesapeake Bay. These potential co-management approaches represent agricultural and urban runoff, wastewater treatment plant effluent, and combined sewer overflow replacements. Twelve estrogenic compounds and their metabolites were analysed by gas chromatography–mass spectrometry. Estrogenic activity (E 2 Eq) was measured by in vitro bioassay. We detected estrone E 1 (0.05–6.97 ng L −1 ) and estriol E 3 (below detection-8.13 ng L −1 ) and one conjugated estrogen (estrone-3-sulfate E 1 -3S; below detection-8.13 ng L −1 ). E 1 was widely distributed and positively correlated with E 2 Eq, water temperature, and dissolved organic carbon (DOC). Among nonpoint sources, E 2 Eq, and concentrations of E 1 , soluble reactive phosphorus (SRP) and total dissolved nitrogen (TDN) decreased by 51–61%, 77–82%, 62–64%, 4–16% in restored urban and agricultural streams with best management practices (BMPs) relative to unrestored streams without BMPs. In a wastewater treatment plant (Blue Plains WWTP), >94% of E 1 , E 1 -3S, E 3 , E 2 Eq and TDN were removed while SRP increased by 305% during nitrification/denitrification as a part of advanced wastewater treatment. Consequently, E 1 and TDN concentrations in WWTP effluents were comparable or even lower than those observed in the receiving stream or river waters, and the effects of wastewater discharges on downstream E 1 and TDN concentrations were minor. Highest E 2 Eq value and concentrations of E1, E3, and TDN were detected in combined sewer overflow (CSO). This study suggests that WWTP upgrades with biological nutrient removal, CSO management, and certain agricultural and urban BMPs for nutrient controls have the potential to remove estrogens from point and nonpoint sources along with other contaminants in streams and rivers.

Maryland↗

USGS2020

Making ‘chemical cocktails’ – Evolution of urban geochemical processes across the periodic table of elements

Urbanization contributes to the formation of novel elemental combinations and signatures in terrestrial and aquatic watersheds, also known as ‘chemical cocktails.’ The composition of chemical cocktails evolves across space and time due to: (1) elevated concentrations from anthropogenic sources, (2) accelerated weathering and corrosion of the built environment, (3) increased drainage density and intensification of urban water conveyance systems, and (4) enhanced rates of geochemical transformations due to changes in temperature, ionic strength, pH, and redox potentials. Characterizing chemical cocktails and underlying geochemical processes is necessary for: (1) tracking pollution sources using complex chemical mixtures instead of individual elements or compounds; (2) developing new strategies for co-managing groups of contaminants; (3) identifying proxies for predicting transport of chemical mixtures using continuous sensor data; and (4) determining whether interactive effects of chemical cocktails produce ecosystem-scale impacts greater than the sum of individual chemical stressors. First, we discuss some unique urban geochemical processes which form chemical cocktails, such as urban soil formation, human-accelerated weathering, urban acidification-alkalinization, and Freshwater Salinization Syndrome. Second, we review and synthesize global patterns in concentrations of major ions, carbon and nutrients, and trace elements in urban streams across different world regions and make comparisons with reference conditions. In addition to our global analysis, we highlight examples from watersheds in the Baltimore-Washington DC area, USA, which show increased transport of major ions, trace metals, and nutrients across streams draining a well-defined land-use gradient. Urbanization increased the concentrations of multiple major and trace elements in streams draining human-dominated watersheds compared to reference conditions. Chemical cocktails of major and trace elements were formed over diurnal cycles coinciding with changes in streamflow, dissolved oxygen, pH, and other variables measured by high-frequency sensors. Some chemical cocktails of major and trace elements were also significantly related to specific conductance (p < 0.05), which can be measured by sensors. Concentrations of major and trace elements increased, peaked, or decreased longitudinally along streams as watershed urbanization increased, which is consistent with distinct shifts in chemical mixtures upstream and downstream of other major cities in the world. Our global analysis of urban streams shows that concentrations of multiple elements along the periodic table significantly increase when compared with reference conditions. Furthermore, similar biogeochemical patterns and processes can be grouped among distinct mixtures of elements of major ions, dissolved organic matter, nutrients, and trace elements as chemical cocktails. Chemical cocktails form in urban waters over diurnal cycles, decades, and throughout drainage basins. We conclude our global review and synthesis by proposing strategies for monitoring and managing chemical cocktails using source control, ecosystem restoration, and green infrastructure. We discuss future research directions applying the watershed chemical cocktail approach to diagnose and manage environmental problems. Ultimately, a chemical cocktail approach targeting sources, transport, and transformations of different and distinct elemental combinations is beneficial to more holistically monitor and manage the emerging impacts of chemical mixtures in the world's fresh waters.

Applied Geochemistry↗

USGS2018

Watershed ‘chemical cocktails’: forming novel elemental combinations in Anthropocene fresh waters

In the Anthropocene, watershed chemical transport is increasingly dominated by novel combinations of elements, which are hydrologically linked together as ‘chemical cocktails.’ Chemical cocktails are novel because human activities greatly enhance elemental concentrations and their probability for biogeochemical interactions and shared transport along hydrologic flowpaths. A new chemical cocktail approach advances our ability to: trace contaminant mixtures in watersheds, develop chemical proxies with high-resolution sensor data, and manage multiple water quality problems. We explore the following questions: (1) Can we classify elemental transport in watersheds as chemical cocktails using a new approach? (2) What is the role of climate and land use in enhancing the formation and transport of chemical cocktails in watersheds? To address these questions, we first analyze trends in concentrations of carbon, nutrients, metals, and salts in fresh waters over 100 years. Next, we explore how climate and land use enhance the probability of formation of chemical cocktails of carbon, nutrients, metals, and salts. Ultimately, we classify transport of chemical cocktails based on solubility, mobility, reactivity, and dominant phases: (1) sieved chemical cocktails (e.g., particulate forms of nutrients, metals and organic matter); (2) filtered chemical cocktails (e.g., dissolved organic matter and associated metal complexes); (3) chromatographic chemical cocktails (e.g., ions eluted from soil exchange sites); and (4) reactive chemical cocktails (e.g., limiting nutrients and redox sensitive elements). Typically, contaminants are regulated and managed one element at a time, even though combinations of elements interact to influence many water quality problems such as toxicity to life, eutrophication, infrastructure corrosion, and water treatment. A chemical cocktail approach significantly expands evaluations of water quality signatures and impacts beyond single elements to mixtures. High-frequency sensor data (pH, specific conductance, turbidity, etc.) can serve as proxies for chemical cocktails and improve real-time analyses of water quality violations, identify regulatory needs, and track water quality recovery following storms and extreme climate events. Ultimately, a watershed chemical cocktail approach is necessary for effectively co-managing groups of contaminants and provides a more holistic approach for studying, monitoring, and managing water quality in the Anthropocene.

Biogeochemistry↗

USGS2018

Changes in long-term water quality of Baltimore streams are associated with both gray and green infrastructure

The steadily rising global urban population has placed substantial strain on urban water quality, and this strain is projected to increase for the foreseeable future. Considerable attention has been given to the hydrological and physico-chemical effects of urbanization on stream ecosystems. However, due to the relative infancy of the field of urban ecology, long-term water quality analyses in urban streams are sparse. Using a 15-year stream chemistry monitoring record from Baltimore, MD, USA, we quantified long-term trends in nitrate, phosphate, total nitrogen, total phosphorus, chloride, and sulfate export at several sites along a rural-urban gradient. We found no significant change in solute export at most sites, although we did find specific patterns of interest for certain solutes. For example, nitrogen export declined at the most headwater urban site, while phosphorus export declined at the most downstream urban site. Coupling long-term monitoring with data on gray and green infrastructure management throughout the landscape, we established relationships between solute export at the most downstream urban monitoring site and sanitary sewer overflows (SSOs), best management practice (BMP) implementation, and road salt application rates. Phosphorus export was correlated with BMP implementation in the watershed, whereas nitrogen export was related to SSOs. Despite highly urbanized watersheds, water quality does not appear to be declining at most of these sites, suggesting that current management may have limited further impairment. Results of our study suggest that both gray and green infrastructure are key for maintaining and improving water quality in this highly urbanized watershed.

Maryland↗

USGS2011

Tracking nonpoint source nitrogen pollution in human-impacted watersheds

Nonpoint source nitrogen (N) pollution is a leading contributor to U.S. water quality impairments. We combined watershed N mass balances and stable isotopes to investigate fate and transport of nonpoint N in forest, agricultural, and urbanized watersheds at the Baltimore Long-Term Ecological Research site. Annual N retention was 55%, 68%, and 82% for agricultural, suburban, and forest watersheds, respectively. Analysis of δ 15 N-NO 3 – , and δ 18 O-NO 3 – indicated wastewater was an important nitrate source in urbanized streams during baseflow. Negative correlations between δ 15 N-NO 3 – and δ 18 O-NO 3 – in urban watersheds indicated mixing between atmospheric deposition and wastewater, and N source contributions changed with storm magnitude (atmospheric sources contributed &sim;50% at peak storm N loads). Positive correlations between δ 15 N-NO 3 – and δ 18 O-NO 3 – in watersheds suggested denitrification was removing septic system and agriculturally derived N, but N from belowground leaking sewers was less susceptible to denitrification. N transformations were also observed in a storm drain (no natural drainage network) potentially due to organic carbon inputs. Overall, nonpoint sources such as atmospheric deposition, wastewater, and fertilizer showed different susceptibility to watershed N export. There were large changes in nitrate sources as a function of runoff, and anticipating source changes in response to climate and storms will be critical for managing nonpoint N pollution.

Environmental Science & Technology↗