WRRC 2024 Fall Seminar

October 11, 2:00pm - 3:00pm
Mānoa Campus, Hawaii Institute of Geophysics (HIG), Room 210 & Zoom

Reading the Aquifer in the Stream: In-Stream Measurements at Low-Flow Reveals Transport and Denitrification Patterns in the Sub-Surface

by Dr. Camille Vautier

Excess nitrogen in surface and groundwater leads to the degradation of drinking water resources and eutrophication of ecosystems. The export of nitrogen from inland to the coast is strongly determined by the transport and denitrification processes occurring in headwater catchments. Yet, most regulatory frameworks impose the monitoring of medium-to-large rivers while smaller streams, too numerous to be systematically monitored, remain poorly understood. Headwaters are often characterized by strong connections between surface water and shallow aquifers. Understanding the processes occurring in the sub-surface is thus necessary to predict river water quality. To face the difficult access to the subsurface, we propose to infer soils and aquifers’ removal capacity from in-stream measurements of nitrate and silica, which is used as a proxy for water residence time in the aquifer. In parallel, we estimate the respiration and denitrification potential of the stream and the hyporheic zone by monitoring dissolved gases (O2, CO2, N2, N2O) with membrane inlet mass spectrometry. Our approach opens new perspectives for a broadly applicable method of characterizing sub-surface transport and nitrate removal capacity.

How Do Tetracycline and Ciprofloxacin Affect Nitrate Reduction in Coastal Sediments?

by Dr. Anniet Laverman

Fluoroquinolones and tetracyclines are frequently detected antibiotics in aquatic sediments. We investigated the transport and fate of ciprofloxacin (CIP) and tetracycline (TC) as well as their impact on nitrogen transformations in sediments from the Seine Estuary (France). Flow through reactor experiments showed that although TC and CIP strongly interacted with the sediment components through adsorption and (bio)-chemical transformation, they kept their antimicrobial activities. Less nitrate reduction was observed during the first week of the experiment, while TC and CIP were absent in the column effluent. Whereas TC is to a large extent chemically transformed and little adsorbed in the sediment, CIP was less transformed and more adsorbed, most likely due to the great reactivity of TC with redox-active mineral surfaces. Our findings show the strong capacity of natural sediment to retain and transform antibiotics, while still maintaining their antimicrobial activity or inhibitory effect of nitrate reducing activity.

Register for meeting:

https://hawaii.zoom.us/meeting/register/tJMocemhrjIrHNaAzoeKOQaIEtkRfp03l8nC


Event Sponsor
WRRC, Mānoa Campus

More Information
Chris Shuler, 8087229785, cshuler@hawaii.edu

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