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Discussion Starter · #1 ·
After the recent snowfall, something has come to my attention, and I think you're the man to ask or put to the task. I know this is something you dabble in, and you seem to love numbers and statistics.

Is there any research ongoing, or in the past, that looks at the effects of road salt and its input into the Chesapeake Bay and its tributaries after runoff? Are there any qualitative or quantitative statistics? Do they show any correlation to fisheries' good and bad years? Does the input have that much an effect on the overall salinity numbers and, as most of our Bay's species are dependent on such, does it limit their production or their migration patterns? Anything else?

Get to work.
 

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Discussion Starter · #2 ·
Oh yeah, any effects on plant life also? Did I forget anything?
 

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You forgot to ask about my hourly fee.
 

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Greg -

There is loads of information about the general environmental impacts from road salt. Most road salt is some form of chloride, with sodium chloride (table salt) being the predominant form. Deicing operations also use calcium, potassium, and magnesium chlorides.

I typed [stormwater runoff road salt] into Google and got more than 400,000 hits.

One of the first ones I looked at gave some useful information: http://www.forester.net/sw_0107_environmental.html. The section on aquatic biota is shown below.

Aquatic Biota. Road-salt loadings in surface waters vary with regional climate conditions, season, and air temperature fluctuation. Snowmelt may proceed gradually overall, but it increases dramatically following application of road salt. Shock loads of salt to aquatic ecosystems might last less than a day following application, with concentration decreasing thereafter. Salt held in solution in snow or deposited on surface soil layers is readily dissolved by rain and can be transported to receiving waters in runoff. Prolonged retention of salt in streambeds or lakebeds decreases dissolved oxygen and can increase nutrient loading, which in turn promotes eutrophication.

Toxicity responses of aquatic organisms to NaCl vary. Laboratory studies report that the LC50 for six freshwater fish and crustacean species exposed to NaCl for one day ranged from 2,724 to 14,100 mg/l with a mean of 7,115 mg/l (Cowgill et al., 1990). These values decreased significantly as exposure time increased. The LC50 for 17 species of fish, amphibians, and crustaceans exposed to NaCl for seven days ranged from 1,440 to 6,031 mg/l with a mean of 3,345 mg/l (EC, 2000).

Reports of chloride concentrations in highway runoff run as high as 19,135 mg/l. Salt tolerance of fishes ranges from 400 to 30,000 mg/l, greater than the salt concentration of seawater. A seven-day exposure of 1,000 mg/l is lethal to rainbow trout (NRC, 1991). While an estimated 10% of aquatic species will exceed their critical tolerance values for chloride with prolonged exposure to concentrations above 220 mg/l, many of the macroinvertebrates upon which the more tolerant species feed might exhibit lower tolerances. Stream studies in northern New York revealed that benthic diversity decreases as salinity increases and dominance of salt-tolerant invertebrates is synchronous with periods of road-salt application. Salinity stresses the periphyton community upon which benthic grazers forage and inhibits microbial processing of leaf litter (EC, 2000). Reduction of primary productivity causes repercussions at the top of the food chain in addition to the stress salinity imposes on the organisms themselves. The presence of salt in aquatic ecosystems also releases toxic metals from sediment into the water column and impairs distribution and cycling of oxygen and nutrients.


Our local Severn River streams and creeks are part of the overall bay estuary. At any given estuarine location, salinity naturally fluctuates throughout the year due to rainfall, tides, winds, etc. The species of plants and animals living here generally are euryhaline (in other words, they tolerate a range of salinities) far better than plants and animals that live in a purely freshwater environment.

I do not have any statistics on fishery results following heavy snow years. Although heavy or frequent winter storms mean more salt entering the estuary, they also mean that more moisture can soak in the ground, recharge the shallow aquifers (e.g., water table), and eventually move out into the creeks as base groundwater flow.
 

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Thanks, John, for bailing me out. Interesting stuff.
 

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Discussion Starter · #7 ·
Nice. Thanks John.
 
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