172-1 Temporal Analysis of Freshwater Salinization Syndrome Solute Delivery from Four Suburban Headwater Streams Affected by Roadway Deicing Application

Session: Urban Geochemistry

Presenting Author:

Authors:

Abstract:

The “freshwater salinization syndrome” (FSS), which refers to long-term increases in salinity, alkalinity, major ion, and metal concentrations resulting primarily from roadway deicing salt applications, can have profound effects on aquatic ecosystem health and drinking water resources in urbanized watersheds. For example, elevated chloride (Cl^-) concentrations in streams compared to background are associated with decreases in aquatic species richness and diversity, as well as impacts on drinking water infrastructure. Elevated sodium (Na⁺) in drinking water can impact individuals with hypertension. Yet, little is known about the timing of delivery of FSS solutes to suburban headwater streams, despite these systems providing a source of drinking water for downstream communities.  Additionally, the impact of salt application on metal threshold exceedances remains largely unexplored. To address these knowledge gaps, we performed weekly synoptic sampling over the 2025 water year from four suburban headwater streams in the greater Philadelphia, PA area with varying impervious surface cover (ISC). Samples were analyzed for major cations (Na⁺, NH₄⁺, K⁺, Ca²⁺, Mg²⁺), anions (Cl^-, Br^-, NO₃^-, SO₄^2-), and select trace metals (Cr, Mn, Cu, Zn, As, Sr, and Pb). A temporal analysis of FSS solute concentrations was performed to assess FSS solute responses (such as Cl, Na, Ca and Zn) and molar ratios (such as (Cl^- /Na⁺) and Cl^-/(Na⁺ + Ca²⁺) to the relative amount of ISC and road salt application in the upstream area. We also report the results of high-frequency conductivity measurements and Cl^- sampling at two of the four locations. Lastly, we explored the number of exceedances of Cl^-, Na⁺, and trace metals above freshwater aquatic toxicity and drinking water criteria. Study results contribute to the understanding of FSS solute origin and transport in suburban watersheds, particularly those in road salt-affected regions. 

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-6742

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