Factors Affecting Water Factors Affecting Water QualityQuality

Chapter 6Chapter 6

IntroductionIntroduction

Many types of pollutants and many factors Many types of pollutants and many factors affecting the toxic effect of those pollutantsaffecting the toxic effect of those pollutants

Factors include Factors include physicochemical propertiesphysicochemical properties Mode and time of exposureMode and time of exposure Environmental factorsEnvironmental factors Interactions among toxicants in a mixtureInteractions among toxicants in a mixture Biological factorsBiological factors Nutritional factorsNutritional factors

Chemical Characterization of WaterChemical Characterization of Water

I. StructureI. Structure• Chemical StructureChemical Structure

1.1. InorganicInorganic

CationsCations AnionsAnions CaCa++ ++ Mg Mg++ ++ NaNa++ ++ (K(K++) ) HCOHCO--

3 3 SOSO44- - ClCl- - POPO44

- - NONO33--

bicarbonatebicarbonate

Normal environmental concentrationsNormal environmental concentrationsmg/L 15 8 6 23 mg/L 15 8 6 23 120 12 8 v. low (<1) 120 12 8 v. low (<1)

Note: because NONote: because NO33- - is not limited in freshwater is not limited in freshwater casual about disposal (i.e. Spring River) casual about disposal (i.e. Spring River)

limited in freshwater

limited in oceans

2.2. OrganicOrganic

pH is the master variable but pH of aquatic system is intricately linked to the relative abundance of carbonate, bicarbonate and carbon dioxide. 

Normal rangeCarbonate-bicarbonate

equilibrium

HardnessHardness

Degree of difficulty in precipitating soapDegree of difficulty in precipitating soap Based on combined concentrations of calcium, Based on combined concentrations of calcium,

magnesium and other cationsmagnesium and other cations Can have great effect of toxicity (increasing hard = Can have great effect of toxicity (increasing hard =

decreasing toxicity)decreasing toxicity) Units – CaCOUnits – CaCO33

2-2- mg/L (accounts for all metals which are mg/L (accounts for all metals which are +2+2)) Typical values (as CaCOTypical values (as CaCO33

2-2-))• <5- - 100 mg/L<5- - 100 mg/L softsoft• 100 - 200 mg/L moderately hard100 - 200 mg/L moderately hard• >200 “ hard>200 “ hard

Carbonate vs. Non-carbonate hardnessCarbonate vs. Non-carbonate hardness

Note: heat can change hardness -> forms scale on boilers, Note: heat can change hardness -> forms scale on boilers, coffee potscoffee pots

AlkalinityAlkalinity Measurement of the capacity to accept protons Measurement of the capacity to accept protons

(esp. H(esp. H++) ) called called buffering capacitybuffering capacity Units also expressed as CaCOUnits also expressed as CaCO33

2-2-

Really measures CaCOReally measures CaCO332- 2- (bicarbonate)(bicarbonate)

Alkalinity directly correlated with hardness in many Alkalinity directly correlated with hardness in many systemssystems

• Soft water = low alkalinitySoft water = low alkalinity• Hard water = high “ (but exceptions Hard water = high “ (but exceptions AMD) AMD)

Measured by titrating with HMeasured by titrating with H22SOSO4 4 drives drives bicarbonate to CObicarbonate to CO22

Rule of thumb Rule of thumb water of low hardness, low water of low hardness, low alkalinity (headwaters) = higher effect of alkalinity (headwaters) = higher effect of toxicants (especially true of metals, acid)toxicants (especially true of metals, acid)

Alkalinity (con’t)Alkalinity (con’t) Rule of thumb: water Rule of thumb: water

of low hardness, low of low hardness, low alkalinity (headwaters) alkalinity (headwaters) = higher effect of = higher effect of toxicants (especially toxicants (especially true of metals, acid)true of metals, acid)

Headwaters of the Hudson River

Photo by R. Grippo

OxygenOxygen Amount of oxygen that can be dissolved in water (solubility) is highly Amount of oxygen that can be dissolved in water (solubility) is highly

dependent on temperaturedependent on temperature

Note: atmosphere = 210,000 mg/L but ~10 mg/L in most water so O2 is is usually in very short supply in water

B.B. Physical structurePhysical structure

1.1. Stream order – rough numerical sequence that allows characterization of a Stream order – rough numerical sequence that allows characterization of a streamstream

11

springs

2 2

3

1

4

3

6

headwaters

Mid-reach

6-12 = river

Lower reach

Note: streams of same order have to come together to form next order

Note: headwaters generally straight, starts to wander (form bends = sinuosity) as hit order 4-6. Sinuosity is a function of slope, hardness of substrate (mud<silt<gravel)

Hard substrate = low sinuosity

Soft substrate = high sinuosity

II. FunctionII. Function- function always based on structure - function always based on structure can infer function from structurecan infer function from structure

A.A. RiversRivers1.1. River Continuum ConceptRiver Continuum Concept

- RCC based on two concepts- RCC based on two conceptsa.a. From headwaters to mouth = continuous change From headwaters to mouth = continuous change

(gradient) in physical conditions within a stream system(gradient) in physical conditions within a stream systemb.b. Gradient produces a continuous and predictable Gradient produces a continuous and predictable

change in the make-up of the assemblages of change in the make-up of the assemblages of organisms within a stream systemorganisms within a stream system

Upper reaches ---------------- mid-reach --------------------- lower reach

(headwater to 3rd order) (order 4 to 6) (>6)

Continuous and predictable changes in biotic assemblages

Use bioassessment (sample, enumerate organisms) if do not find what is predicted problem!!

BB. Lakes. Lakes systems are dynamic but slowsystems are dynamic but slow Pollution stays put (reason why sewage treatment plants Pollution stays put (reason why sewage treatment plants

are built on rivers, not lakesare built on rivers, not lakes More likely toMore likely to

• Serve a pollution sinks (bioremediation slow if lake is deep (e.g. Serve a pollution sinks (bioremediation slow if lake is deep (e.g. Great Lakes)Great Lakes)

• Can be highly influenced by aerial depositionCan be highly influenced by aerial deposition

Pollutants usuallyPollutants usually

introduced as introduced as

leachate fromleachate from

contaminated soilscontaminated soils

Dependent onDependent on

physical/chemicalphysical/chemical

properties of soils properties of soils

in addition to waterin addition to water

CC. Groundwater. Groundwater