Search

Your search keyword '"Blake, William H."' showing total 150 results
Start Over Author "Blake, William H." Publication Type Academic Journals
150 results on '"Blake, William H."'

13. An Exploratory Data Analysis (EDA) Tool for Tracer Selection in Sediment and Pollution Fingerprinting Studies.

Author

Ovando-Fuentealba, Luis, Blake, William H., Taylor, Alex, Clason, Caroline, and Bravo-Linares, Claudio

Subjects
*DECISION trees, *DATA analysis, *WORK design, *POLLUTION, *PRIOR learning, *POLLUTION source apportionment
Abstract

Tracer selection is a critical step for any mixing model that uses the information of multiple variables to find the most likely solution for sediment or pollution source apportionment. The purpose of this work was to design an Exploratory Data Analysis (EDA) tool for qualitative and quantitative interpretation of tracer selection based on boxplots. This tool establishes a set of conditions presented as a decision tree to support the user in tracer selection decisions where current systems are either too statistically driven, which limits user interaction with the data, or rely too heavily on judgement and prior knowledge of tracer behaviour. This method extends upon the classical "range test" by incorporating a set of conditions and thresholds, creating a semi-quantitative method with a visual component to improve the tracer selection process and enable targeted consideration of geochemical behaviours for conservativism purposes. We present the results from experimental mixtures using the mixing model MixSIAR to demonstrate the method and illustrate the value of this approach for improved tracer selection. The tool, which is written in R, is freely available for use across a wide range of source apportionment applications. [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

14. Anthropogenic and climatic impacts on historic sediment, carbon, and phosphorus accumulation rates using 210Pbex and 137Cs in a sub-watershed linked to Zarivar Lake, Iran.

Author

Khodadadi, Maral, Gibbs, Max, Swales, Andrew, Toloza, Arsenio, and Blake, William H.

Subjects
ANTHROPOGENIC effects on nature, CLIMATE extremes, WATERSHED management, TERRACES (Geology), CLIMATE change, LAKE sediments
Abstract

To estimate a watershed's response to climate change, it is crucial to understand how human activities and climatic extremes have interacted over time. Over the last century, the Zarivar Lake watershed, Iran, has been subjected to various anthropogenic activates, including deforestation and inappropriate land-management practices alongside the implementation of conservation measures like check dams. To understand the effects of these changes on the magnitude of sediment, organic carbon (OC), and phosphorus supplies in a small sub-watershed connected to the lake over the last century, a lake sediment core was dated using 210Pbex and 137Cs as geochronometers. The average mass accumulation rate (MAR), organic carbon accumulation rates (OCAR), and particulate phosphorus accumulation rates (PPAR) of the sediment core were determined to be 6498 ± 2475, 205 ± 85, and 8.9 ± 3.3 g m−2 year−1, respectively. Between the late 1970s and early 1980s, accumulation rates were significantly higher than their averages at 7940 ± 3120, 220 ± 60, and 12.0 ± 2.8 g m−2 year−1 respectively. During this period, the watershed underwent extensive deforestation (12%) on steep slopes, coinciding with higher mean annual precipitations (more than double). Conversely, after 2009, when check dams were installed in the sub-watershed, the sediment load to the lake became negligible. The results of this research indicate that anthropogenic activities had a pronounced effect on MAR, OCAR, and PPAR, causing them to fluctuate from negligible amounts to values twice the averages over the last century, amplified by climatic factors. These results imply that implementing climate-smart watershed management strategies, such as constructing additional check dams and terraces, reinforcing restrictions on deforestation, and minimum tillage practices, can facilitate protection of lacustrine ecosystems under accelerating climate change conditions. [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

39. A deconvolutional Bayesian mixing model approach for river basin sediment source apportionment

Author

Blake, William H., Boeckx, Pascal, Stock, Brian C., Smith, Hugh G., Bodé, Samuel, Upadhayay, Hari R., Gaspar, Leticia, Goddard, Rupert, Lennard, Amy T., Lizaga, Ivan, Lobb, David A., Owens, Philip N., Petticrew, Ellen L., Kuzyk, Zou Zou A., Gari, Bayu D., Munishi, Linus, Mtei, Kelvin, Nebiyu, Amsalu, Mabit, Lionel, Navas, Ana, and Semmens, Brice X.

Published
2018
Full Text
View/download PDF

50. Quantifying sediment and particulate phosphorus accumulation in restored floodplain wetlands using beryllium‐7 as a tracer.

Author

Blake, William H., Hoffmann, Carl Christian, Poulsen, Jane Rosenstand, Taylor, Alex, and Kronvang, Brian

Subjects
FLOODPLAINS, WETLANDS, WETLAND restoration, WETLAND management, WATERSHEDS, STREAM restoration
Abstract

Floodplain wetlands in agricultural river basins provide critical ecosystem services such as nutrient retention, flood mitigation, carbon sequestration and ecological habitats and are a key component of a nature‐based solution approach to restoration. In the context of the global challenge to reducing impact increasingly intensive food production on downstream ecosystems, restoration of wetlands in river floodplains offers a practical means for downstream retention and mitigation of P flux from upstream agricultural land. Data on short term, flood event related, accretion rates are, however, difficult to acquire via conventional monitoring yet such information is essential for restoration planning and scenario testing. Here, we evaluate a promising approach that applies naturally‐occurring short‐lived fallout radionuclide (FRN) 7Be as a tracer to quantify sediment and, by association, particulate phosphorus retention rates in restored floodplain wetlands. Following a series of major inundation events, a restored floodplain unit was sampled to determine 7Be inventories of the floodplain relative to an undisturbed reference site. This was undertaken in conjunction with direct measurement of sedimentation as an independent check of FRN results. Accretion rates up to 27 kg m−2 were recorded using 7Be for recent deposition events compared to a longer term annual average rate of ca. 6 kg m−2 derived from 137Cs measurements. While accretion rates varied spatially and temporally, there was excellent coherence between FRN‐based measurements and direct measurements once rigorous correction for particle size effects on tracer properties had been undertaken. The study demonstrates the important contribution that FRN technology can make to support wetland management and restoration initiatives and the essential need for a systems thinking approach across the soil‐sediment continuum. Such decision support tools will become increasingly important in the 21st century with growing anthropogenic pressure on aquatic ecosystems related to upstream food production, and implementation of more nature‐based solutions such as restored wetlands to counteract these pressures. [ABSTRACT FROM AUTHOR]

Published
2022
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results