D issolved O xygen P rotocol

B ack ground

T he D O protocol described here is for sam pling surface w ater D O concentration (D E Q 1995; D E Q

T he term “ dissolved oxygen” (D O ) refers to the 1997; E PA 1996; M acD onald, Sm art, and W issm ar am ount of oxygen that is dissolved in w ater at a

1991). Intergravel D O concentration is also an given tem perature and a given atm ospheric

im portant m easure of stream habitat for salm on pressure. D O is critical to the entire biological

(M cC ullough and E spinosa 1996; M acD onald, com m unity in surface w aters and is a key elem ent

Sm art, and W issm ar 1991). Intergravel D O of healthy salm on habitat. D O is one of the

sam ples can be collected by pum ping a w ater principal param eters used to m easure w ater quality.

sam ple from the gravel near potential redds. In O regon, w ater quality criteria have been

H ow ever, D E Q does not recom m end that these developed for D O based on the life history

types of sam ples be collected by w atershed requirem ents of aquatic species, particularly

councils. A dditional inform ation of intergravel D O salm onids (D E Q 1994).

sam ple collection should be referred to the m entor.

D O is usually m easured in parts per m illion (ppm )

M entors

or the equivalent of m illigram s per liter (m g/l).

A s w ith any m onitoring project, questions w ill W ater can hold m ore dissolved oxygen (D O

com e up that are not answ ered or covered saturation) at low tem peratures than at high

sufficiently in this protocol. T herefore, a group of tem peratures. For exam ple, at 08C and 1

m entors that are agency experts in m onitoring have atm osphere of pressure, the m axim um

been identified . T hese m entors m ay be contacted concentration of D O (100% saturation) is 14.6

w ith specific questions about a particular m g/l; at 308C the sam e w ater sam ple w ould contain

m onitoring effort.

only 7.55 m g/l (H itchm an 1978). In w aters supporting salm onids, the necessary D O

For m ore inform ation on dissolved oxygen, contact: levels range from 11 m g/l in spaw ning and rearing

D r. G eorge Ice

w aters (in order to support em bryo and larval

E -m ail: gice@ w crc-ncasi.org production stages w ith no im pairm ent) to 6 m g/l in

non-spaw ning w aters (the absolute m inim um to

avoid acute m ortality). Statew ide D E Q V olunteer M onitoring C oordinator K aren W illiam s: (503) 229-5983

In addition to tem perature, various supplies and

E -m ail: w illiam s.karen@ deq.state.or.us dem ands influence the concentration of D O in

w ater. T he prim ary sources for dissolved oxygen

N orth C oast

are photosynthetic activities of aquatic plants and L arry C aton (503)229-5983; reaeration (as w ater spills and splashes

E -m ail: caton.larry@ deq.state.or.us dow nstream , atm ospheric oxygen is trapped and

dissolved in the w ater). T he m ajor dem ands on D O

South C oast & W illam ette

concentration com e from plant respiration and the

D ennis A des (503)-229-5983; biological breakdow n (or decom position) of organic

E -m ail: ades.dennis@ deq.state.or.us m aterial by bacteria and other m icroorganism s.

E astern O regon L arry M arxer (503) 229-5983;

Dissolved Oxygen Protocol

7-1

Water Quality Monitoring Guidebook

E -m ail: m arxer.larry@ deq.state.or.us

T he H A C H C om pany P.O . B ox 608

O rdering E quipm ent

L oveland, C O 80539-0608

T he sam pling m ethod for m easuring D O

1-800-227-4224

concentration outlined in this protocol is know n as the W inkler Titration M ethod (A PH A 1998). T he

N O T E : The chem icals, liquid or dry, used in the W inkler M ethod can be done w ith liquid or dry

W in k ler T itra tio n m eth o d fo r m ea su rin g D O chem ical reagents. A pproxim ate costs for

c o n c e n tra tio n s a re hazardous. M aterial Safety equipm ent and reagents are show n in T able 7-1.

D ata Sheets are provided w ith each purchase, and For inform ation about the chem ical reagents and

all safety precautions and procedures should be the other equipm ent required for this m ethod,

em ployed during use

contact:

T able 7-1. E quipm ent costs.

E stim ated C osts

W inkler M ethod F ield S am pling E quip.: H ach D igital T itrator D O T est K it

$190.00 (50 tests) A dditional reagents

$43.00 (50 sam ples) 200 m l V olum etric F lask

F ield A udit T herm om eter

F ield N otebook (D ata S heets)

Field Protocol

conditions, therefore the frequency and total num ber of m onitoring sam ples should be based on

T he W inkler T itration M ethod is the m ost accurate the attainm ent of that goal. T he concentration of

D O in surface w aters w ill vary throughout the day co n cen tra tio n . It is based on the oxidation of

c h e m ica l m eth o d fo r m ea su rin g D O

due to oxygen production by aquatic plants, m anganese, the liberation of iodine in proportion to

respiration, and changes in w ater tem perature. If the D O present in the sam ple, and then the

5 D O sam ples are not collected frequently enough, “ titration” of the iodine w ith sodium thiosulfate.

the degree of daily D O fluctuation m ay be m issed, the im m ediate or potential problem s m ay not be

M onitoring Frequency & T im ing identified, or the long-term trends m ay not be M onitoring frequency depends on the objectives of

determ ined.

the project plan (M acD onald, Sm art, and W issm ar 1991). T he goal of D O m onitoring is to provide a

T he tim ing of collecting sam ples also depends on realistic estim ate of the stream ’s typical D O

the objectives of the project, w hich m ay target a particular tim e of day. L ow D O concentrations usually occur in the early m orning because plants

stop producing oxygen at nightfall and don’t begin "titration" is a standard analytical method that measures the

again until sunrise. D O concentrations build up

amount of one chemical or solution needed to react with another

chemical or solution. In this case, the amount of sodium thiosulfate

throughout the day follow ing the pattern of

needed to react with the iodine present in the water sample.

photosynthesis. C oncentrations usually peak in the photosynthesis. C oncentrations usually peak in the

2. R em ove the glass stopper and add the contents photosynthesis (R icklefs 1979; W illers 1991). of 1 pow der pillow of M anganous Sulfate

T he tim ing of sam ple collection m ay also be (W inkler R eagent 1), and 1 pow der pillow of

A lkaline A zide (W inkler R eagent 2). R eplace influenced by other oxygen sinks and sources that

occur at a specific tim e of day or season of the year. stopper and repeatedly invert the sam ple bottle so that the contents m ix vigorously for 15-20 seconds. A flocculent precipitate (a cloudy

For exam ple, large inputs of organic m aterial m ay substance created from the chem ical reaction) result in a significant drop in oxygen concentration

w ill form in the sam ple (brow nish-orange if due to an increase in biochem ical oxygen dem and

oxygen is present, w hite if oxygen is absent). (B O D ) .

3. A llow the sam ple to stand until the “ floc” has T he dissolved oxygen needs of salm onids vary w ith

settled approxim ately half w ay to the bottom of their life history stages, from em bryo developm ent to

the bottle. R E PE A T the vigorous m ixing for grow th and sexual m aturity. H aving experience

15-20 seconds. A llow the sam ple to stand until w ith regional w eather patterns and know ing the

the floc settles a second tim e. N ote: V igorous tim ing and length of salm onid spaw ning seasons is

m ixing is critical to dissolving the pow dered im portant if m onitoring duration m ust be lim ited.

reagents and allow ing the chem ical reactions to For exam ple, w est of the C ascades, the m ajority of

occur. N ot all of the reagents w ill dissolve, but salm on and steelhead spaw ning takes place during

large chunks of the reagents should not be the fall, w inter, and spring m onths w hen w ater levels

visible after m ixing. Inadequate m ixing in are elevated and w ater tem peratures are at a

steps 2 and 3 is a com m on error. m inim um .

4. A fter the floc has settled again, rem ove the glass stopper and add 1 pow der pillow of

R ecom m ended Sam ple C ollection &

Sulfam ic A cid. R eplace the glass stopper and

A nalysis

invert the bottle several tim es, m ixing vigorously 15-20 seconds. T he sam ple should

Field C ollection

turn a clear am ber color. (Som e of the T he sam ple containers used for collecting w ater

pow dered reagents m ay not have com pletely sam ples for D O m easurem ents are clean 300 m l

dissolved – this is norm al.) glass B O D bottles w ith glass stoppers (these bottles

com e w ith the H A C H m onitoring kits). Field staff

A fter the initial w ater sam ple has been chem ically can fill the sam ple bottle by: a) subm ersing it

preserved, it can be held for up to eight hours, in directly into the stream ; or, b) collecting the w ater

the dark at 4° C , before the titration step is sam ple from a bridge or sim ilar structure using a

perform ed.

suitable grab sam ple collection m ethod.

D issolved O xygen P rotocol