Concentration‐discharge (c‐Q) relations have been used to infer watershed‐scale processes governing solute fluxes. Prior studies have documented inconsistent concentration‐discharge patterns at the ...storm‐event scale driven by changes in end‐member concentrations. Other studies have evaluated c‐Q data from all periods in a composite fashion to quantify chemostasis (relatively invariant changes in concentration over several orders of magnitude variation in streamflow). Here we examine 3 years of high‐frequency nitrate and discharge data (49,861 data points) to complement 14 years of weekly data (699 data points) for an urban stream in Baltimore, MD, U.S. to quantify c‐Q relationships. We show that these relationships are variable through time and depend on the temporal scale at which they are investigated. On a storm‐event scale, the sensor data exhibit a watershed‐specific dQ/Q threshold when storms switch from counter‐clockwise to clockwise c‐Q behavior. On a seasonal scale, we show the influence of hydrologic variability and in‐stream metabolism as controls on stream nitrate concentrations and fluxes. On a composite scale, we evaluate the c‐Q data for chemostasis using analysis of both c‐Q slopes and CVc/CVQ, as a function of time. The slopes of c‐Q data for both long‐term weekly and high‐frequency data sets are in close agreement on an annual basis and vary between dry and wet years; the CVc/CVQ analysis is less sensitive to hydroclimate variability. This work highlights the value of both long‐term and high‐frequency c‐Q data collection for calculating and analyzing solute fluxes.
Key Points
Variations in c‐Q relationships exist across multiple scales of analysis: event, seasonal, annual, long‐term
Detection of c‐Q chemostasis is dependent upon frequency of data collection and the metric of analysis (slope versus CVc/CVQ)
Evaluation of c‐Q at a storm‐event scale reveals a dQ/Q threshold that separates counterclockwise versus clockwise hysteretic behavior
Distributed, infiltration‐based approaches to stormwater management are being implemented to mitigate effects of urban development on water resources. One of the goals of this type of storm water ...management, sometimes called low impact development or green infrastructure, is to maintain groundwater recharge and stream base flow at predevelopment levels. However, the connection between infiltration‐based stormwater management and groundwater recharge is not straightforward. Water infiltrated through stormwater facilities may be stored in soil moisture, taken up by evapotranspiration or contribute to recharge and eventually base flow. This study focused on a 1.1 km2 suburban, low impact development watershed in Clarksburg, Maryland, USA, that was urbanized and contained 73 infiltration‐based stormwater facilities. Continuous water table measurements were used to quantify the movement of infiltrated stormwater. Time series analyses were performed on hydrographs of 7 wells, and the episodic master recession method was used. Persistence in water levels, as measured by autocorrelation function, was found to be positively related to depth to water. Storm properties (precipitation rate and duration) and well location (proximity to the nearest stream) were significant in driving episodic recharge to precipitation ratios. The well that had the highest recharge to precipitation ratios and water table rises of up to 1.5 m in response to storm events was located furthest from the stream and down gradient of stormwater infiltration locations. This work may be considered in evaluating the effects of planned watershed‐scale infiltration‐based stormwater management on groundwater flow systems.
The literature contains contradictory conclusions regarding the relative effects of urbanization on peak flood flows due to increases in impervious area, drainage density and width function, and the ...addition of subsurface storm drains. We used data from an urbanized catchment, the 14.3 km2 Dead Run watershed near Baltimore, Maryland, USA, and the physics‐based gridded surface/subsurface hydrologic analysis (GSSHA) model to examine the relative effect of each of these factors on flood peaks, runoff volumes, and runoff production efficiencies. GSSHA was used because the model explicitly includes the spatial variability of land‐surface and hydrodynamic parameters, including subsurface storm drains. Results indicate that increases in drainage density, particularly increases in density from low values, produce significant increases in the flood peaks. For a fixed land‐use and rainfall input, the flood magnitude approaches an upper limit regardless of the increase in the channel drainage density. Changes in imperviousness can have a significant effect on flood peaks for both moderately extreme and extreme storms. For an extreme rainfall event with a recurrence interval in excess of 100 years, imperviousness is relatively unimportant in terms of runoff efficiency and volume, but can affect the peak flow depending on rainfall rate. Changes to the width function affect flood peaks much more than runoff efficiency, primarily in the case of lower density drainage networks with less impermeable area. Storm drains increase flood peaks, but are overwhelmed during extreme rainfall events when they have a negligible effect. Runoff in urbanized watersheds with considerable impervious area shows a marked sensitivity to rainfall rate. This sensitivity explains some of the contradictory findings in the literature.
Key Points
Imperviousness is more important for moderate extreme events than extreme ones
Changes in drainage density significantly affect flood peaks over a small range
Width function is not a good predictor sensitivity, conveyance is important too
Middle–Late Ordovician sequences from the Appalachian Basin and Arbuckle Mountain regions of North America were analyzed for carbonate-associated sulfate (δ34SCAS) and pyrite (δ34Spyr) paired with ...carbonate (δ13Ccarb) and organic matter (δ13Corg) chemostratigraphy. Two major negative drops in δ34SCAS (12‰ excursions) are recognized: the older decline in δ34SCAS occurs within the Histiodella holodentata–Phragmodus polonicus Conodont Zones and the younger drop is within the Cahabagnathus sweeti–Amorphognathus tvaerensis (Baltoniodus gerdae subzone) Zones. These overall these negative shifts in δ34SCAS have an antithetical relationship with positive shifts in δ34Spyr (~+10‰) and δ13Ccarb (~+2‰) recorded in the same successions. The older negative δ34SCAS shift is coincident with the widely documented mid-Darriwilian δ13C excursion (MDICE), and the younger negative δ34SCAS shift is coincident with another positive δ13Ccarb shift in the early Sandbian. Geochemical modeling of these sulfur isotope shifts suggests that a decrease in the global rate of pyrite burial or isotope fractionation between seawater sulfate and sedimentary pyrite could account for these negative δ34SCAS trends. Additionally, a substantial increase in the weathering flux of pyrite to the global oceans could also explain these secular sulfur isotope trends. While increased crustal weathering is broadly consistent with a sea-level lowstand, and the seawater 87Sr/86Sr isotope record of change in continental weathering in the late Darriwilian Stage of the Ordovician, geologic and geochemical proxy evidence do not support distinct pulses of continental weathering required to generate two separate negative shifts in δ34SCAS. These antithetical isotope trends may be best explained by changes in the marine redox state that significantly reduced microbially mediated pyrite burial and organic matter remineralization rates. Pulses of oceanic ventilation would have expanded habitable environments for marine organisms, and thus is broadly consistent with major increases in biodiversification during this period of the Ordovician.
•Newly paired sulfur and carbon isotope data of Ordovician carbonates from Laurentia•Two large drops in δ34SCAS correspond to positive shifts in δ13Ccarb values.•First isotopic evidence for Ordovician decoupling of carbon and sulfur cycles•These data support intervals of oceanic ventilation in the Middle–Late Ordovician.•Oceanic oxygenation provides bolstering conditions for coincident GOBE pulses.
Reveals the little known history of one of history's most famous maps - and its maker
Tucked away in a near-forgotten collection, Virginia and Maryland as it is Planted and Inhabited is one of the ...most extraordinary maps of colonial British America. Created by a colonial merchant, planter, and diplomat named Augustine Herrman, the map pictures the Mid-Atlantic in breathtaking detail, capturing its waterways, coastlines, and communities. Herrman spent three decades travelling between Dutch New Amsterdam and the English Chesapeake before eventually settling in Maryland and making this map. Although the map has been reproduced widely, the history of how it became one of the most famous images of the Chesapeake has never been told.
A Biography of a Map in Motion uncovers the intertwined stories of the map and its maker, offering new insights into the creation of empire in North America. The book follows the map from the waterways of the Chesapeake to the workshops of London, where it was turned into a print and sold. Transported into coffee houses, private rooms, and government offices, Virginia and Maryland became an apparatus of empire that allowed English elites to imaginatively possess and accurately manage their Atlantic colonies.
Investigating this map offers the rare opportunity to recapture the complementary and occasionally conflicting forces that created the British Empire. From the colonial and the metropolitan to the economic and the political to the local and the Atlantic, this is a fascinating exploration of the many meanings of a map, and how what some saw as establishing a sense of local place could translate to forging an empire.
Civic Intimacies van Doorn, Niels
2019, 2019-06-07, Letnik:
12
eBook
Black queer lives often exist outside conventional civic institutions and therefore have to explore alternative intimacies to experience a sense of belonging. Civic Intimacies examines how—and to ...what extent—these different forms of intimacy catalyze the values, aspirations, and collective flourishing of Black queer denizens of Baltimore. Niels van Doorn draws on 18 months of immersive ethnographic fieldwork for his innovative cross-disciplinary analysis of contemporary debates in political and cultural theory. Van Doorn describes the way that these systematically marginalized communities improvise on citizenship not just to survive but also to thrive despite the proliferation of violence and insecurity in their lives. By reimagining citizenship as the everyday reparative work of building support structures, Civic Intimacies highlights the extent to which sex, kinship, memory, religious faith, and sexual health are rooted in collective practices that are deeply political. These systems sustain the lives of Black queer Baltimoreans who find themselves stuck in a city they cannot give up on—even though it has in many ways given up on them.
Eick explores the history of a comprehensive high school from the world views of its assorted student body, confronting issues of race, ethnicity, class, gender, nationality, and religion. Her case ...study examines the continuities and differences in student relationships over five decades. While she discusses the "dark side" of the high school experience, she also presents hopeful signs and alternatives. This history comes alive through rich oral testimonies that contribute to the ongoing search to make high school life a meaningful and constructive experience for young people living in an increasingly complex society. This book contains three parts. Part I: The Divided Generation (1950-1969), contains: (1) Memories of Class, Race, and Gender Divides: Immediate Pre and Post Desegregation Years; and (2) Cautiously Negotiating Social Divides: A Conservative Student Body. Part II: The Border-Crossing Generation (1970-1985), contains: (3) Memories of Interracial Peer-Group Affiliations: Integration Years; and (4) Bridging Social Divides through Peer-Groups: A Socially Tolerant but Politically Inactive Student Body. Part III: The Re-Divided Generation (1986-2000), contains: (5) Memories of Segregation by Class, Race, Nationality, and Religion: Destabilizing Years of Shifting Demographics; (6) Self-Segregating in Opposition To: A Student Body Sensitized to Discrimination; (7) Conclusion; and (8) Methodology: The Transparent Historian.
Phytoextraction is a green remediation technology for cleaning contaminated soils. Application of chelating agents increases metal solubility and enhances phytoextraction. Following a successful ...greenhouse experiment, a panel study under field weather elucidated the efficiency of the chelating agent ethylenediaminedisuccinic acid (EDDS) on phytoextraction of lead (Pb) by vetiver grass, a hyperaccumulator of Pb, and a nonaccumulator fescue grass from residential soils contaminated with Pb-based paint from Baltimore, MD and San Antonio, TX. Three soils from each city with Pb content between 1000 and 2400 mg kg−1 were chosen for the panel study. Sequential extraction revealed that Fe-Mn oxide (60–63%) and carbonate (25–33%) fractions of Pb dominated in Baltimore soils, whereas in San Antonio soils, Pb was primarily bound to the organic fraction (64–70%) because organic content was greater and, secondarily, to the Fe-Mn oxide (15–20%) fraction. Vetiver and fescue grasses were transplanted and grown on wood panels in the field with EDDS applied after 3 months and 13 months. Soil and leachate results indicated that EDDS applications increased Pb solubility in soils. Plant tissues results indicated enhanced the uptake of Pb by vetiver and showed that EDDS application promoted translocation of Pb from root to shoot. Average Pb concentration increased by 53% and 203% in shoots and by 73% and 84% in roots of vetiver after the first and second applications of EDDS, respectively. Concentrations in roots and shoots increased in all tested soils, regardless of soil pH or clay content. After the second application, average Pb concentrations in vetiver were higher than those in fescue by 3.6x in shoots and 8.3x in roots. Visual phytotoxic symptoms from increased bioavailable Pb from EDSS applications were observed in fescue but not in vetiver. This study demonstrated the potential of a chemically-catalyzed phytoremediation system as a cleanup method for lead-contaminated soils.
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•Lead was phytoextracted from field-collected, contaminated soils by vetiver grass under field conditions.•Ethylenediaminedisuccinic acid (EDDS), a biodegradable chelating agent, was applied to the soils.•Concentrations of lead in roots and shoots increased dramatically after EDDS applications, indicating chelation occurred.•EDDS applications did not cause any visual phytotoxic symptoms on vetiver.•Application of EDDS enhanced phytoextraction of lead from soil under realistic conditions.
Application of ethylenediaminedisuccinic acid (EDDS) to lead-contaminated residential soils enhanced phytoextraction by vetiver grass in a panel study under a field weather.
Apparent groundwater ages along two flow paths in the upper Patapsco aquifer of the Maryland Atlantic Coastal Plain, USA, were estimated using
14
C,
36
Cl and
4
He data. Most of the ages range from ...modern to about 500 ka, with one sample at 117 km downgradient from the recharge area dated by radiogenic
4
He accumulation at more than one Ma. Last glacial maximum (LGM) water was located about 20 km downgradient on the northern flow path, where the radiocarbon age was 21.5 ka, paleorecharge temperatures were 0.5–1.5 °C (a maximum cooling of about 12 °C relative to the modern mean annual temperature of 13 °C), and Cl
–
, Cl/Br, and stable isotopes of water were minimum. Low recharge temperatures (typically 5–7 °C) indicate that recharge occurred predominantly during glacial periods when coastal heads were lowest due to low sea-level stand. Flow velocities averaged about 1.0 m a
–1
in upgradient parts of the upper Patapsco aquifer and decreased from 0.13 to 0.04 m a
–1
at 40 and 80 km further downgradient, respectively. This study demonstrates that most water in the upper Patapsco aquifer is non-renewable on human timescales under natural gradients, thus highlighting the importance of effective water-supply management to prolong the resource.
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