Increasing Chloride in Vermont Surface Waters:

1. Increasing Chloride in Vermont Surface Waters: The tip of the iceberg? Angela Shambaugh Water Quality Division Vermont Department of Environmental Conservation

2. Background • All water has dissolved ions • Salinity describes ionic composition • Chloride dominant in seawater, not in freshwater • Result of weathering and atmospheric deposition • Chloride is “conservative” • Used to distinguish among pollution sources • Used to track movement of water masses

3. Road Salt and the Environment • Used since the 1940s • Salt + plowing are most efficient in keeping roads clear • Least expensive of currently available options • Application frequency and amount are weather-related • ~16 million tons used in the US during 2004 • Evidence that application at current rates is changing historical water concentrations

4. From USGS WRRI report 03-0412

5. Irondequoit Bay NY (on L. Ontario) Bubeck and Burton 1989 Chloride chemocline, loss of annual mixing, bottom anoxia Management of road salt applications restored normal patterns Toronto Canada Bowen and Hinton 1998 45 – 55% of road salt enters groundwater and is released during base flow Background 18 – 25 mg/L >1000 mg/L found in streams draining highly urbanized areas

6. Groundwater in Sweden Thunqvist 2003 • [Cl] increasing in surface and groundwater • number of affected drinking water supplies increasing

7. Canadian Environmental Protection Act Environment Canada 2001 • Road salt declared “toxic” • 2800 mg/L in groundwater • 2000 – 5000 mg/L in urban lakes • 18,000 mg/L in runoff • Regional scale groundwater contamination (>250 mg/L) likely under high density road systems • Northeastern surface waters Kauschal et al. 2005 • Selected streams in MD, NY and NH reached ~5000 mg/L • High concentrations persisted through the summer • Increasing road density and salt applications to blame • Surface waters will become unpotable and toxic to freshwater organisms in the 21st century if not controlled

8. Environmental Effects • Terrestrial • Soils • Compacted and unstable • Salt is retained in the soil and released over time • Plants • Severe root, shoot and leaf damage • Reproduction and recruitment • Plant composition changes as sensitive taxa replaced by insensitive • Large wildlife • attracted to road sides by applied salt and formation of artificial salt licks • Increased frequency of collisions • Physiological effects? • Birds are impaired or killed • by ingesting road salt • after drinking salt laden water

9. Environmental Effects • Lakes • Changes in water density • Changes in stratification and mixing • Streams • Increased [Cl] downstream of salted roads • Increased [Ca], [Mg], [K] as [Na] increases • BMPS for particulate management will not affect [Cl]

10. Toxicity to Aquatic Biota • sublethal effects not well studied • Organism response varies with conditions • Small changes in [Cl] may cause taxa shifts

11. Sensitivity of Aquatic Biota Environment Canada EPA Aquatic Life Criteria Acute: 1hr avg not to exceed 860 mg/L once every 3 years on avg Chronic: 4 day avg not to exceed 230 mg/L once every 3 years on avg

12. Vermont – high elevation watershedsWemple et al. 2002 – West Branch of the Waterbury River 100μmol/L = 3.5 mg/L chloride

13. Forester Pond – Jamaica, Vermont 100μeq = 3.5 mg/L chloride -Road upgrade in 1989 -Na, Cl and conductivity only parameters to respond to road change

14. Vermont streams and developmentVT DEC Biological and Aquatic Studies Section (BASS) N = 431 2003 – 2004 data Many streams with high development density have reaches that have been designated as stormwater “impaired”

15. Not significant at P<0.001 at alpha = 0.05 Lake Champlain The Lake Champlain Long-Term Water Quality Monitoring Program Chloride concentrations have increased at 11 of 14 lake stations not at levels of biological concern

16. Trends are significant in all 8 New York tributaries sampled

17. Trends are significant in 5 of 9 tributaries in Vermont and Quebec Blue stars indicate non-significant trends.

18. Conclusions about Chloride in Vermont • Chloride levels have been increasing in Lake Champlain • Not biologically significant in the open waters • Major lake tributaries carry more chloride • Tributary monitoring doesn’t target chloride • Development density influences chloride concentrations • Urban streams are likely to be most affected • Road salt can affect chloride concentrations in Vermont

19. Now what….. • more data and monitoring • ? Is there a widespread problem • ? Sources other than road salt • ? summer vs winter concentrations • ? biological response • ? groundwater Get the word out: More salt is not always better “Smart” application of salt maintains road safety and water quality