es9b04316_si_001.pdf (1.49 MB)
High-Frequency Data Reveal Deicing Salts Drive Elevated Specific Conductance and Chloride along with Pervasive and Frequent Exceedances of the U.S. Environmental Protection Agency Aquatic Life Criteria for Chloride in Urban Streams
journal contribution
posted on 2019-12-31, 16:07 authored by Joel Moore, Rosemary M. Fanelli, Andrew J. SekellickIncreasing specific conductance (SC) and chloride concentrations
[Cl] negatively affect many stream ecosystems. We characterized spatial
variability in SC, [Cl], and exceedances of Environmental Protection
Agency [Cl] criteria using nearly 30 million high-frequency observations
(2–15 min intervals) for SC and modeled [Cl] from 93 sites
across three regions in the eastern United States: Southeast, Mid-Atlantic,
and New England. SC and [Cl] increase substantially from south to
north and within regions with impervious surface cover (ISC). In the
Southeast, [Cl] weakly correlates with ISC, no [Cl] exceedances occur,
and [Cl] concentrations are constant with time. In the Mid-Atlantic
and New England, [Cl] and [Cl] exceedances strongly correlate with
ISC. [Cl] criteria are frequently exceeded at sites with greater than
9–10% ISC and median [Cl] higher than 30–80 mg/L. Tens
to hundreds of [Cl] exceedances observed annually at most of these
sites help explain previous research where stream ecosystems showed
changes at (primarily nonwinter) [Cl] as low as 30–40 mg/L.
Mid-Atlantic chronic [Cl] exceedances occur primarily in December–March.
In New England, exceedances are common in nonwinter months. [Cl] is
increasing at nearly all Mid-Atlantic and New England sites with the
largest increases at sites with higher [Cl].