Field Methods of Monitoring Aquatic Systems

Unit 1 – Water Analysis and Sampling

Copyright © 2011 by DBS

Distribution of Earth’s Water

Source: http://ga.water.usgs.gov/edu/waterdistribution.html

Purified via hydrologic cycle

Purified via percolation

Est. adequate water to support 20-40 billion

Still shortages due to spatial availability

Question

Write down some of the constituents found in natural river water

Ions derived from commonly occuring inorganic salts, e.g. Na+, Ca2+, Cl-, SO4

2-

Transition metal ions derived from less commonly occuring salts

Insoluble solid material, either from plants or particles from geological weathering

Soluble or colloidal compounds from decomposition of plants

Dissolved gases

Water Quality Parameters

Water properties and processes

Ions Found in Natural Waters

Conc. Range

(mg L-1)

Cations Anions

0-100 Ca2+, Na+ Cl-, SO42

-, HCO3-

0-25 Mg2+, K+ NO3-

0-1 Fe2+, Mn2+, Zn2+ PO43-

0-0.1 Other metal ions NO2-

Reeve, 2002

Ariola et al, 2004

Rain water

mg L-1

River water

mg L-1

Sea water

g l-1

similar

Ca2+/Cl-

Cl-/SO42-

Gibbs, 1970

Composition of Water is Never Static

• Weathering of rocks• Sedimentation of suspended

material• Effect of aquatic biota• Aeration• Volatilization/evaporation• Additional water volumes

River Example

Question

How would you expect the composition of groundwater to be different from surface water?

Could be more concentrated in salts leached from mineral deposits. Percolation through organic material can lower oxygen content

Primary Water Quality Standards

• EPA sets Maximum Contaminant Levels (MCL)• Primary: health hazards• Secondary: aesthetic qualities• NB: also includes organics

Inorganic Contaminant

MCL)(mg/L)

Sb 0.006

Asbestos 7 MFL

As 0.01

Ba 2

Be 0.004

Cd 0.005

Cr 0.1

Cu 1.3

CN- 0.2

F- 4

Pb 0.015

Hg 0.002

Ni 0.1

NO3- 10

NO2- 1

Se 0.05

Tl 0.002

Source: http://www.epa.gov/safewater/mcl.html

MO Contaminant MCL

Total Coliform 5%

Fecal coliform 0 per 100 mL

Giardia lambia 0 per 100 mL

Viruses 0 per 100 mL

+ organics and radionuclides

Secondary Water Quality Standards

Secondary: aesthetic qualities – taste, corrosion, staining

Source: http://www.epa.gov/safewater/mcl.html

Contaminant MCL

(mg/L)

Al 0.05-0.2

Cl- 250

Cu 1.0

F- 2.0

Na+ 20

Soaps/detergents 0.5

Fe 0.3

Mn 0.05

pH 6.5-8.5

Ag 0.10

SO42- 250

TDS 500

Zn 5

Water Qualityexample records

e.g Moon Twp 2005

Summary of Course

• We will be measuring a variety of parameters, e.g.– TDS– DO– Col. Bacteria– pH and alkalinity– Anions: F-, Cl-, NO3

-, SO42-, PO4

3-

– Cations: Na, Ca, Mg

• Goals– Design a sampling plan– understand the chemical principles used– Critically evaluate and interpret data– Write a report that effectively conveys the data to the outside world

Question

Decode the following lab notebook page

Sampling

Objective:

Collect a portion of material small enough in volume to be transported and large enough for analysis while still accurately representing the material being sampled

Representative Samples

Environment is variable (sampling strategy needs to account for this)

– no two organisms exposed in exactly the same way

– day/night cycling of factories

– hour by hour, day by day, seasonal e.g. NO3

- in river water

Different results would be found a few km downstream due to physical, chemical and biological transformations

Lab or Field Analysis?

What are the relative merits of lab and field analyses?

Lab

Pros: analyses performed under optimum conditions, leading to maximum accuracy, precision will also be maximized

Cons: transport, time delay in getting results, changes to sample during storage, cost to operate lab

Field

Pros: instantaneous results, no errors due to storage, possible to analyze in-situ, possible to use continuous monitoring

Cons: conditions may not be optimum, lower precision and accuracy,

Question

Can you guess which of the following determinations are best made in the lab or in the field?

Nitrate, metals, temperature, pH, DO

Field

Temperature

pH

DO

Lab

Metals

Nitrate

Organics

Quality

• How to produce an accurate analysis?– Sampling should produce a representative sample– No contamination or change during storage– No contamination in laboratory or during analysis– Losses on extraction, separation and concentration

minimized– No interferences from other components– Results calculated correctly and archived for future

reference

Types of Sampling

• Judgmental– Not representative– Worst or best case scenario

• Systematic– Division of site into grids

• Random– No pattern or reason

Kegley, 1998

Sampling Devices

Van Dorn Sampler

Grab - bucket, bottle, bag, messenger (Niskin, Kemmerer or Van Dorn type), peristaltic pump Depth Integrating – verical water column

Automated – remove samples at fixed intervals

Container Choice

• Plastic is typically used• Glass – hard glass (Pyrex) recommeded for all

organics• Amber Glass – recommended for light-sensitive

compounds• 1 L sample necessary for most analyses

See p1-33 of Standard Methods Book

1-33

Standard Methods (1998)

Technique

• Fill without pre-rinsing with sample(may bias results)

• To fill or not to fill?– Organics – full– Inorganics and MO – space left for mixing

• Trace levels need special precautions• Metals require total or dissolved fractional sampling, must be

filtered immediately through 0.45 micron filters• Composite samples are not recommended for many analytes

due to instability

Bottle Technique

Source: http://www.epa.gov/volunteer/stream/vms50.html

Leave a space

Replicates

• Contaminated equipment or poor lab technique can give unexpectedly high or low results

• Could be ‘real’ but no way to know• Bottles may break or leak, not

possible to sample again under the same conditions

• May not be critical at all locations, especially inportant at inflows and outflows

• Planning is important!

Blanks

• Ensure samples are representative of the site

– no contamination

– are all pure DI water

Type Contaminant Procedure

Field air exposed to air at site

Trip container taken to site but not opened

Equipment sampling equipment rinsing solution

Background sample

- taken near site

Don’t forget also need reagent blanks during analysis!

Preparation: Acid Washing

• Inspect glassware

• If very dirty – No-chromix (H2SO4 + ammonium persulfate) and rinse

• Soap and water + scrubbing brush

• Rinse all surfaces with 25 mL 8 M HNO3, Rinse all surfaces with 25 mL 1.2 M HCl

• Rinse with DI 3 times

500 mL bottle500 mL filter flask10, 50, 100 mL cylinders100 mL volumetric flask

DO NOT REUSE RINSE WATER

Storage

• Concentration of species to be analyzed should remian unchanged during transportation and storage

• Potential problems– Volatile, degradable or reactive

species– Adsorption onto containers– Leaching from containers

• Storage before filtration should be at 4 °C no more than 2 days

• Storage after filtration should be at 4 °C no more than 30 days

Examples

NO3- - stored at 4 °C to lower MO

degradation

Pesticides - store in dark to avoid decomposition by light

Metals - acidify to prevent adsorption

BOD - no preservation is possible

Example Strategy

• What analyses are required?– Analytical technique affects size, bottle type, storage method– Is sufficient lab time available for analysis? (preservation kept to minimum)

• Decide on a programme– Variation may be periodic– Sources of pollution - site history– Effects of dilution - location of inflows and outflows, natural variations– No. of samples and timing of sampling is affected

• Decide no. of samples (see 1-31)– Each location should be done in duplicate– Take into consideration time required for analyses– Statistical treatment requires sufficient numbers of samples

• Decide location and apparatus– Ease of access, weather may not be perfect– Topography - a map is useful, bathymetrical survey for deep sampling– Composite or individual samples? Surface, sub-surface, integrated?

• Decide sample volume and container type– Volatiles/gases container must be full, others better if container not full – Check for contamination in apparatus

• Decide on storage method

What Analyses are Required?

Source Common Pollutants

Cropland Turbidity, phosphorus, nitrates, temparature, total solids

Forestry harvest Turbidity, temperature, total solids

Grazing land Fecal bacteria, turbidity, phosphorus, nitrates, temperature

Industrial discharge Temperature, conductivity, total solids, toxics, pH

Mining pH, alkalinity, total dissolved solids

Septic systems Fecal bacteria (i.e., Escherichia coli, enterococcis), nitrates, phosphorus, dissolved oxygen/biochemical oxygen demand, conductivity, temperature

Sewage treatment Dissolved oxygen and biochemical oxygen demand, turbidity, conductivity, phosphorus, nitrates, fecal bacteria, temperature, total solids, pH

Construction Turbidity, temperature, dissolved oxygen and biochemical oxygen demand, total solids, and toxics

Urban runoff Turbidity, phosphorus, nitrates, temperature, conductivity, dissolved oxygen and biochemical oxygen demand

Monitoring Discharges to Rivers

Samples should be taken downstream for the discharge to be completely mixed

Source: Reeve, 2002

Question

What variation would you expect in concentrations of DO and NO3

-?

O2 produced by photosynthesis in daytime, continuously consumed by oxidation of organics. Continuous input from atmosphere. Drop at night is expected

NO3- more complicated. If no inputs it would decrease in

spring and increase in winter. May be increased by fertilizer inputs

Text Books

• Artiola, J.F., Pepper, I.L., and Brusseau, M. (2004) Environmental Monitoring and Characterization. Elsevier, Amsterdam.

• Clesceri, L.S., Greenberg, A.E., and Eaton, A.D., eds. (1998) Standard Methods for the Examination of Water and Wastewater, 20th Edition. Published by American Public Health Association, American Water Works Association and Water Environment Federation.

• Kegley, S.E. and Andrews, J. (1998) The Chemistry of Water. University Science Books.

• Narayanan, P. (2003) Analysis of Environmental Pollutants : Principles and Quantitative Methods. Taylor & Francis.

• Keith, L.H. and Keith, K.H. (1996) Compilation of EPA's Sampling and Analysis Methods. CRC Press.

• Nollet, L.M. and Nollet, M.L. (2000) Handbook of Water Analysis. Marcel Dekker.

• Reeve, R.N. (2002) Introduction to Environmental Analysis. Wiley.

• Rump, H.H. (2000) Laboratory Manual for the Examination of Water, Waste Water and Soil. Wiley-VCH.

• Van der Leeden, F., Troise, F.L., and Todd, D.K. (1991) The Water Encyclopedia. Lewis Publishers.

Natural Constituentstypical analysis

Constituent Major Sources Conc. (mg/L) Issues

CO32- Limestone, dolomite SW: 0

GW: <10

CaCO3 scale retards heat and liquid flow in pipes

HCO3- < 500

> 1000 with excess CO2

SO42- Oxidation of sulfide ores,

gypsum, industrial wastes< 1000

~ 200,000 in brines

CaSO4 similar to above

> 500 bitter taste

> 1000 cathartic

Cl- Weathering of edimentary and igneous rocks

< 10 in humid regions

200,000 in brines

> 100 salty taste

> Physiological damage

F- Amphiboles, apatite, fluorite, mica

GW: < 10

SW: < 1.0

Up to 1600 in brines

0.6 – 1.7 beneficial

> 1.5 ‘mottled enamel’

> 6 disfiguration

NO3- Atmosphere, legumes, plant

debris, animal waste, fertilizersSW: 1.0 - 5.0

GW: up to 1000

> 100 bitter taste

> 45 methemoglobinemia

Kegley, 1998 Appendix A

Natural Constituentstypical analysis

Constituent Major Sources Conc. (mg/L) Issues

Dissolved solids Minerals SW: < 3000

GW: < 5000

> 500 undesirable for drinking

< 300 manufacturing

Silica (SiO2) Feldspars, ferromagnesium and clay minerals, amorphous silica, chert, opal

1.0 - 30 (sometimes 100) With Ca and Mg scale retards heat and liquid flow

Fe Igneous rocks, sandstone rocks

Objects made from cast iron or stell

< 0.50

pH < 8 ~ 10

> 0.1 ppts with air contact Stains, bad taste, discolors

Mn Soils and sediments, metamorphic and sedimentary rocks

< 0.20

GW: 10

> 0.2 ppts with air contact

Stains, bad taste, builds up in pipes

Natural Constituentstypical analysis

Constituent Major Sources Conc. (mg/L) Issues

Ca Amphiboles, feldspars, gypsum, clay minerals etc.

As much as 600 in W streams

Scale retards heat, combine with fatty acid ions to form suds

Mg has a laxative effectMg Amphiboles, olivine, pyroxenes, dolomite, magnesite, clay minerals

Several hundred in W streams

Na Feldspars, clay minerals, evaporites

Up to 1000 in W streams > 50 with suspended solids causes foaming accl. Scale formation

> 65 Na causes problems with ice manufactureK Feldspars, feldpathoids,

clay minerals< 10