Groundwater Sampling

Field ParametersKassidy Klink

Peak Environmental

Acceptable Groundwater Sampling Methods

Volume-Average Purge

SamplingLow-flow Sampling

Non-purge Sampling

Important Points to Consider

Well screen >5ˈ = multiple samples

Firms need to be certified

Field calibration at correct temperature

Calibration Form

Applicable Field Parameters

pH

SC

ORP

DO

NTU

What is pH?

A measure of how acidic/basic water is; Ranges from 0-14, with 7 being neutral Reported in logarithmic units (ex. pH of 5 is 10x

more acidic than 6)

Why measure pH pH of water determines solubility and biological

availability of chemical constituents Nutrients (phosphorus, nitrogen, and carbon) Heavy metals (lead, copper, cadmium, etc.) pH determines activity of organisms and there

ability to use nutrients pH determines toxicity of heavy metals Generally more toxic at lower pH (solubility)

What is Specific Conductivity? The measure of the ability of water to conduct

electrical current Conductivity + area of electrodes = SC Highly dependent on the amount of dissolved

solids (such as salt) in water A good indicator of the amount of dissolved

material in water

Why measure Specific Conductivity

Dissolved solids can affect the suitability of water for domestic, industrial, and agricultural uses

Can give drinking water unpleasant taste or odor Can cause gastrointestinal problems Can deteriorate plumbing fixtures and appliances Saline water can affect crops Very high levels can inhibit bacterial activity

What is ORP?

Oxidation → net loss of electrons, Reduction → net gain of electrons

A measure of the tendency of a chemical substance to oxidize or reduce another chemical substance

Why measure ORP Under proper ORP conditions, contaminants can

transform and/or become immobilized (ex. Heavy metals)

Cr+6 → Cr+3 under reducing conditions (good) As+5 → As+3 under reducing conditions (bad) Chlorinated solvents: Dechlorination (reducing

conditions) or ISCO (oxidizing conditions) Dechlorination of chlorinated compounds occurs

as a stepwise process with each step requiring a lower ORP

What is and why measure Dissolved Oxygen?

Oxygen dissolved in water Typical Range → 0 to 8 mg/L Indicates whether conditions are: Oxidizing (aerobic) Reducing (anaerobic) Oxygen is the first electron acceptor available for

biotic transformations and is quickly consumed If DO is low (<2 mg/L) – look at other electron

acceptors

What is and why measure Turbidity

The amount of particulate matter (i.e. clay, silt, organic matter, microscopic organisms) suspended in water

High turbidity in samples can influence analytical results

Organics/inorganics sorbed to particulates Suspended inorganics

What is and why measure Temperature

Can vary with: Depth Seasons Impacts biological activity Colder = slower Impacts probe calibrations

Wrap-up Field parameters are actually important

o Geochemistry of siteo Look at trends during remediation & MNAo Tells us if remediation might be working

Know what to expecto Historical readingso What type of remediation → geochemical impacts

Question the data If it doesn’t make sense – check calibration Once the sampling is complete – It’s too late!