COLD FRONT SEDIMENT RESUSPENSION, AGE, AND RESIDENCE TIMES OF SUSPENDED SEDIMENT USING 7BE/210PBXS RATIO IN GALVESTON BAY
Abstract
Winds associated with the passage of meteorological fronts cause wave-induced sediment resuspension, especially in shallow estuaries such as Galveston Bay. With a warming climate, the intensity of all meteorological events is increasingly having greater impacts on ecosystems. To better understand the effects that the passage of meteorological fronts has on the resuspension of sediment, water samples were collected during frontal passages at two locations in Galveston Bay. One in the middle portion of the bay, and one closer to the mouth of the bay. Additionally, a Conductivity, Temperature, Depth (CTD) data logger with an Optical Backscatter (OBS) turbidity sensor was deployed in Trinity Bay. We found stronger frontal winds are attributed to higher total suspended sediment (TSS) due to more sediment being resuspended from the bottom. This may, at least in part, be a result of the bay sediment in the middle bay having a finer grain size than the sediment within the lower bay. Additionally, ebb tide has higher TSS concentrations when there is a north wind in the middle bay, resulting from the addition of tidal current coupled with wind waves and wind-driven current imparting greater shear stress to the seabed. By collecting precipitation, water samples in both the middle and lower bay, and measuring the ratio of beryllium-7/lead-210 excess (7Be/210Pbxs) in these samples; we can quantify the residence times of TSS in middle and lower Galveston Bay. Based on two sampling events on 1/29/2020, the age of the sediment in the middle bay was 70 ± 10 days (sampled on 1/29/2020), and 51 ± 7.8 days (sampled on 2/21/2020), where the lower bay had older suspended sediments, with 105 ± 15 days-old particles and 66 ± 10 days-old particles, respectively. This indicates that there are longer residence times when the water is trapped within the bay. Our estimated residence time of suspended sediments (51-105 days) suggests the particle-bound contaminants adsorbed to suspended sediment may spend months suspended in the bay before exiting the bay or being accreted into the bay sediment column, increasing the exposure time of living organisms to various particle-bound contaminants.
Citation
Schmidt, Nicole Mari (2021). COLD FRONT SEDIMENT RESUSPENSION, AGE, AND RESIDENCE TIMES OF SUSPENDED SEDIMENT USING 7BE/210PBXS RATIO IN GALVESTON BAY. Master's thesis, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /195237.