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Typical pollutants in stormwater runoff

Soil & Water Conservation Society of Metro Halifax (SWCSMH)

Treatment of stormwater runoff

Updated: July 01, 2016                                                                  Select Pollutants

"Laser particle sizing has also indicated that a considerable proportion of the particulates in road runoff are less than 10 m. This size fraction is difficult to capture in current stormwater pollution control devices and has been shown to contain significant quantities of heavy metals, which are of concern in aquatic ecosystems." (Drapper et al)


Unit Loadings (Nonpoint and Point sources), and Bacteriological Contamination

Some examples of the post-development pollutants are as follows:

Street Surface Pollutants associated with various particle sizes:

(USEPA, 1976 [Source: Sartor and Boyd, 1972])
Measured PollutantParticle size
<43 43 - 246 >246
(% by weight)
 TS5.9 37.5 56.5
 BOD524.3 32.5 43.2
 COD22.7 57.4 19.9
 VS25.6 34.0 40.4
 Phosphates56.2 36.0 7.8
 Nitrates31.9 45.1 23.0
 Kjeldahl Nitrogen18.7 39.8 41.5
 All heavy metals 51.2 48.7 
 All pesticides 73 27 
 PCB 34 66 

Typical distribution of dissolved and particulate runoff fractions for residential runoff:

(Herr and Harper [Source: Harper, H.H. 1988. Effects of Stormwater Management Systems on Groundwater Quality. Final Report for Project SM 190, submitted to the Florida Department of Environmental Regulation.])
ParameterTypical Distribution (%)
 Total N4060
Total P5050
Total Cd7030
Total Cr6535
Total Cu7030
Total Ni7030
Total Pb2575
Total Zn3565

Common road runoff pollutants and sources:

(Drapper et al [Source: Kobringer, N.P. 1984. Volume I. Sources and Migration of Highway Runoff Pollutants- Executive Summary. FHWA/RD-84/057. Federal Highway Administration, Rexnord, EnviroEnergy Technology Center, Milwaukee, WI])
ConstituentPrimary Sources
ParticulatesPavement wear, vehicles, atmosphere, maintenance, snow/ice abrasives, sediment disturbance
Nitrogen, PhosphorusAtmosphere, roadside fertiliser use, sediments
LeadLeaded gasoline, tire wear, lubricating oil and grease, bearing wear, atmospheric fallout
ZincTire wear, motor oil, grease
IronAuto body rust, steel highway structures, engine parts
CopperMetal plating, bearing wear, engine parts, brake lining wear, fungicides and insecticides use
CadmiumTire wear, insecticide application
ChromiumMetal plating, engine parts, brake lining wear
NickelDiesel fuel and gasoline, lubricating oil, metal plating, brake lining wear, asphalt paving
ManganeseEngine parts
CyanideAnticake compound used to keep deicing salt granular
Sodium, CalciumDe-icing slats, grease
ChlorideDe-icing salts
SulphateRoadway beds, fuel, de-icing salts
PetroleumSpills, leaks, blow-by motor lubricants, antifreeze, hydraulic fluids, asphalt surface leachate
PCBs, pesticidesSpraying of highway right of ways, atmospheric deposition, PCB catalyst in synthetic tires
Pathogenic bacteriaSoil litter, bird droppings, trucks hauling livestock/stockyard waste
RubberTire wear
Asbestos*Clutch and brake lining wear
* No mineral asbestos has been identified in runoff, however some breakdown products of asbestos have been measured

Mean pollutant concentrations (g/l) in runoff from urban and rural highways:

(Drapper et al [Source: Driscoll, E., Shelley, P.E., and Strecker, E.W. 1990. Pollutant Loadings and Impacts from Highway Stormwater Runoff. Volumes I-IV. FHWA/RD-88-006-9, Federal Highway Administration, Woodward-Clyde Consultants, Oakland, CA])
PollutantUrban (ADT> 30,000)Rural (ADT< 30,000)
TSS (Total Suspended Solids)142,00041,000
VSS (Volatile Suspended Solids)39,00012,000
TOC (Total Organic Carbon)25,0008,000
COD (Chemical Oxygen Demand)114,00049,000
NO3/NO2 (Nitrate + Nitrite)760570
TKN (Total Kjeldahl Nitrogen)1,830870
Phosphorus as PO4400160
Cu (Total Copper)5422
Pb (Total Lead)40080
Zn (Total Zinc)32980

Approximate relationship between Unit Areal Loadings from Nonpoint Sources in North America:

(The table was derived by the USEPA from extensive literature in North America, and it is interesting to note that any local values export coefficients developed in Nova Scotia to date do indeed fall within the ranges in the following table)

Approximate relationship between Unit Areal Loadings from Nonpoint Sources (USEPA, 1976)
 Average (Kg/ha/yr) Range (Kg/ha/yr)
Forest2.50.2250 1-100.005-140-400
Range/Pasture 50.3400 2-100.2-0.610-1,000
Cropland100.61,600 1-400.03-0.7300-4,000
Urban50.8 2,000 2-200.25-5200-5,000
Feedlots1,000250--- 700-1,500100-400---
Precipitation100.25--- 1-1000.05-1---
Lake Sediments
   Aerobic Conditions
   Anaerobic Conditions

Unit Urban Phosphorus Export Coefficients in Dartmouth and Cole Harbour, HRM, NS:

Unit Urban Phosphorus Export Coefficients (kg/ha.yr) (Vokey, 1998)
Local watershedStorm sewer catchment area (ha)TP Export Coefficient (kg/ha.yr)
Settle Lake7.30.53
Bissett Lake57.60.57

Toxicants found in Priority Pollutant Scans

(Stormceptor [Source: Schueler and Shepp, 1993])


* = Found in water column also                                             (G) = Observed predominantly in gas station sampling

** = Observed only in water column samples                                     (NG) = Observed predominantly in non-gas station sampling

(S) = Suspected (a result of gas                                              (AS) = Observed in both sampling
                chromatography testing)                                                        

Potential Toxicant

Typical Use

Probable Pathway to Oil-Grit Separator (OGS)

--------------------  Sediment Samples  --------------------




Semi-volatile Organics




Component of gasoline, fossil fuel.

Incomplete combustion of fossil fuels. Atmospheric deposition of the vapours, Gasoline spillage, crankcase motor oil drippings. (G)



















Benzo (b) fluoranthene



Indeno (123-cd) pyrene



Benzo (g,h,i) perylene



Di-nbutyl phthalate

Plasticizer- component of plastics, polymeric substances.

Leaches from plastic products such as garden hoses, floor tiles, plastic containers and food packaging. (NG)
May leach into motor oils and other automotive fluids from their plastic containers. (G)
Motor oil is a suspected source of compound of OGS. (AS)

Butylbenzyl phthalate



Bis (2-Ethylhexyl) phthalate*









Volatile Organics




Used as solvent and in chemical synthesis.

Improper disposal of industrial waste. Atmospheric deposition of vapours resulting from incomplete combustion of fuels. (AS)


Intermediate in chemical synthesis, solvent component of antifreeze.

Antifreeze spillings. (AS)

Total Xylenes*



Methylene Chloride

Used as refrigerant. Component of PVC.

Improper disposal of industrial waste. Refrigerant leakage. (S)
Car air conditioners, coolants. (S)









Used in farming, gardening and landscaping.











Component of lead alloys, rubber, matches, ceramics, enamel, paints, lacquers and textiles.

Leaches from painted and rubber waste articles. Household and industrial waste erosion from rocks and soils. (G)


Component of fossil fuel, insecticide, food preservatives.
Used in treatment of leukemia and as a tonic.

Product of incomplete combustion of fossil fuels and incomplete atmospheric deposition of vapours. (AS)


Used to manufacture non-sparking alloys for tools, nuclear reactors and lightweight alloys.

Erosion from rocks and soils. (AS)


Used in manufacture of batteries, paints and plastics. Used to plate iron products such as nuts and bolts for corrosion prevention.

Waste from plating processes. Motor vehicle exhaust. Leached from galvanized copper and plastic pipes. (G)


Used to make alloys, catalysts and refractories. Used in plating processes. Used in paints, leather tanning, plastics.

Improper disposal of industrial waste. Corrosion of alloys and plated surfaces. (AS)
Spillage of brake fluid.


Used as alloy component. Sulphate salt used as algicide in water supply reservoirs. Component of fungicide. Used in electroplating industry. Found in coolant, brake fluid, motor oil, gasoline.

Corrosion of copper pipes and fittings. Improper disposal of waste from industry. Algicide. (AS)
Spillage of listed automobile products.


Used as an additive to gasoline, motor oil, brake fluid and coolant. Component of pipes, paints and dyes. Used in manufacture of batteries, insecticide.

Atmospheric deposition of motor vehicle exhaust. Gasoline, motor oil, brake fluid and coolant leakage. Leaching from paints, stains, plastics. Improper disposal of batteries and insecticides.


Used in electroplating, food processing (gelatin, baking powder). Present in gasoline, transmission fluid, motor oil, brake fluid, coolants.

Wastewater from electroplating operations. Product of incomplete combustion of fossil fuels and atmospheric deposition. Gasoline leakage, coolant, motor oil and brake fluid spillage. (AS)


Used in electroplating industry. Silver halides are used in photography. Component of germicide, antiseptic and astringent. Found in diesel fuel.

Improper disposal of industrial waste. (AS)


Used in electroplating industry. Component of bronze, rubber, enamel, glass and paper. Component of automobile tires, road salt and paint.

Wastewater from electroplating operations. Weathering and abrasion of galvanized iron and steel. Leaching from road salt, automobile tires. (AS)








Product of plating operations. Anticaking ingredient in road salts. Intermediate in production resins.

Waste from coal coking and refinery operations. Leaching from road salt. (AS)







--------------------  Water Column Samples**  --------------------




Semi-volatile Organics



Benzyl alcohol

Component of gasoline, fossil fuel.

Incomplete combustion of fossil fuel and atmospheric deposition of vapours. (G)













Volatile Organics




Used as gasoline additive. Solvent for paints, resins, lacquers and plastics.

Leaching of paints and plastics. Automobile product, motor oil leakage.








* = Found in water column also                                        (G) = Observed predominantly in                                                                                                                                      gas station sampling

** = Observed only in water column                                (NG) = Observed predominantly in
                samples                                                                  non-gas station sampling

(S) = Suspected (a result of gas                                         (AS) = Observed in both sampling
                chromatography testing)   




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