Group 6

Gochoco, John Benjamin B.

Marcelino, April Adrienne G.

Posadas, Grace Catherine A.

Uy, Augustine Leonard G.

Valencia, Vivienne G.

Dissolved Oxygen (DO)-concentration of oxygen dissolved in water -expressed in mg/l or as percent saturation

DO Analysis-measures the amount of gaseous oxygen (O2) dissolved in an aqueous solution

INTRODUCTION

Winkler Method- technique used to measure dissolved oxygen in freshwater systems

Saltwater

Freshwater

Saltwater - watercontaining a largeamount of salt; orit is the body ofwater which hasover 1,000 ppm(mg/L) totaldissolved solids

Freshwater -situated in a remoteor obscure area;provincial; waterwith less than 500parts per million(ppm) of dissolvedsalts

Estuary - body ofwater formed wherefreshwater fromrivers and streamsflows into the ocean, mixing with theseawater.

Objectives1. To be able to determine the amount of

dissolved oxygen in an aquatic environment

2. To compare and contrast the measured dissolved oxygen obtained using the Winkler Method against the 5 different

sites.

METHODOLOGY

Materials:

• 300.0 ml BOD bottles or SOLA (glass) bottles with cap

• 250.0 ml graduated cylinder

• 500.0 ml Erlenmeyer flasks

•1.0 ml Pipettes

•Rubber aspirator

•Titration set-up

Field Sampling Procedure:

Collect samples in a 300 mL SOLA bottle

Add 2ml of manganous sulfate solution

Add 2 ml of alkaline-iodide-sodium azide solution

Shake the bottle by inverting several times

Add 2ml of conc. sulfuric acid

Allow solution to settle

Shake well until precipitate is dissolved

Titration Procedure:

Pour 200ml of sample from the SOLA bottle into an Erlenmeyer flask

If the solution is reddish-brown in color, titrate with 0.0250 N sodium

thiosulfate

If the solution has no reddish-brown

color, or is only slightly colored,

add a small quantity (approx. 1 mL) of starch indicator.

RESULTS AND DISCUSSION

Figure 1. D.O. in Balingasay River

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3.9

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Site A Site B Site C Site D Site EAm

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Ox

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Series 1

Oxygen gets into the water when:

• Oxygen from the atmosphere dissolves and mixes into the water’s surface

• Algae and bay grasses release oxygen during photosynthesis

• Water flows into the Bay from streams, rivers and the ocean. Ocean waters generally have more oxygen. River waters are fast-moving, which helps oxygen from the air mix in.

Factors affecting D.O. in water• High temperatures• Nutrient pollution• Flow of water

Dissolved oxygen profile of a river downstream of a discharge (Snape et al., 1995).

CONCLUSION

• Different factors affect the dissolved oxygen in thewater such as temperature, various chemicalreaction, and aquatic animals.• There are variations on the amount of dissolvedoxygen for the 5 sites and based from the results, site Ehas the highest amount of dissolved oxygen and site 3has the lowest amount of dissolved oxygen.