5 research outputs found
Seismic Observations of Fluvial Energy Dissipation
Observing microseismic waves excited by turbulent flow is an emerging way to document river dynamics during extreme flood events. This thesis records fluvial-seismic observations in two contrasting systems at different scales. Two single-seismometer particle motion methods are introduced to characterize the seismic signal produced by rivers. In the large-scale system, the Oroville Dam spillway is observed when it is a simple rectangular channel and when it is damaged by erosion. The small-scale system is along the cobble-bed Northwest Branch of the Anacostia River. Particle motion analyses and the scaling between seismic power and discharge are suitable to characterize flow turbulence at the large-scale system. In the small-scale system, particle motion methods are found to be unsuitable and the scaling of seismic power is unable to resolve observed variability in flow dynamics within the study reach. This work suggests that methods of fluvial seismology are best suited to large-scale systems
Watershed ‘chemical cocktails’: forming novel elemental combinations in Anthropocene fresh waters
Este artÃculo contiene 25 páginas, 9 figuras.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.This work was funded by USDA (award
# 2016-67019-25280) and NSF-EPSCoR (#1641157) for
supporting collaborations at the AGU Chapman Conference
on Extreme Climate Events. Significant funding for data
collection/analyses in this paper was provided by NSF
EAR1521224, NSF CBET1058502, NSF Coastal
SEES1426844, NSF DEB-0423476 and DEB-1027188, NSF
RI EPSCoR NEWRnet Grant No. IIA-1330406, EPA ORD,
Chesapeake Bay Trust, and Multi-state Regional Hatch Project
S-1063.Peer reviewe