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Creator: Dr. Michael Chase, 16th Might 2019


This text describes the tactic and PRELIMINARY final result of a comparatively low price “laboratory” (kitchen) experiment on the response of seawater pH to will increase in atmospheric CO2.

When further CO2 is added to the air above seawater the chemistry of the water is anticipated to vary, and there may be a lot give attention to the pH measure of acidity. I discover that the change in pH when equilibrium is established is quickly detectable with a low price transportable pH meter with zero.01 decision, however the measured measurement of the impact seems to be considerably smaller than reported within the current scientific literature. This text offers largely with the experimental methodology and outcomes.

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A schematic plan of the experimental equipment is proven within the following determine. A 2-litre “hermetic” meals storage jar comprises seawater and air, and transportable (battery powered) devices to measure seawater pH and atmospheric CO2 degree, with alterations to the latter by injection of pulses of further CO2. The water is blended constantly by a magnetic stirrer.

The precise experimental system used is proven within the following photograph, the pH meter is white, and the CO2 meter is gray, with its air consumption seen simply above the water floor. Meals storage know-how supplied the 2-litre hermetic container, the plastic “desk” that holds the CO2 meter simply above the water floor, and “Cling Movie” to guard the CO2 meter from getting moist, with a gap reduce for the air consumption. Particulars of the meters used, and of the magnetic stirrer, are given on the finish of the article.

The unique plan was to make use of a small transportable electrical fan to mix-up the air, nevertheless it was discovered that the batteries ran-out after about an hour, inadequate time to realize pH equilibrium, which is discovered to take round 10 hours.


CO2 was generated by including vinegar to bicarbonate of soda in a beaker (with splash guard), injected by way of an unused ear syringe, a plastic syringe or eye drop dispenser may very well be substituted:

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In a draft-free room the CO2 generated within the beaker may be considered a comparatively dense fluid which stays there, and which may be drawn into an appropriate system and injected into the 2-litre glass container. The goal is to get round 1000 ppm of CO2 within the 2-litre glass container, which is 1 half in a thousand, i.e. 2 ml of CO2 at atmospheric stress, which may be simply generated and captured.


Seawater samples of round 450 ml every time have been obtained from the shoreline close to Weymouth in Dorset, on the South coast of England. The shoreline had some seaweed, which can affect the pH. Every pattern was saved in a sealed 500 ml plastic bottle within the “laboratory” in a single day to heat it to the laboratory air temperature.


Every run of the experiment lasts round 12 hours, which is roughly the noticed time required for pH equilibrium to be achieved, with information recording at 15-minute intervals. The runs begin mid-morning and run to round 10 pm, a interval during which the room temperature stays pretty fixed.

The next determine reveals early outcomes for three runs, one with no injected CO2 (uppermost information), one with injected CO2 such that round 820 ppm was measured (proven in blue with a continuing +zero.2 shift in all pH values), and one the place the ultimate CO2 degree was round 1500 ppm:


If the current progress fee of round 2.four ppm per yr of atmospheric CO2 is maintained then the extent on the finish of the 21st century will likely be round 600 ppm, with a change in seawater pH of round zero.15, which is significantly decrease than figures quoted within the scientific literature. Observe that the change of zero.15 in pH applies to seawater of eight.eight pH, which is on the excessive finish of the noticed vary. Hydrogen ion focus at a pH of seven.eight is ten instances greater than for a pH of eight.eight, so the change of pH in 7.eight pH seawater could also be even decrease than zero.15.


· pH meter: Hanna Devices HI 98108

· CO2 meter: Kane-alert-CO2

· Magnetic Stirrer: Hanna Devices HI 190M

Observe: Water in a sealed container provides 100% humidity, and condensation might finally injury the electrics of the meters, all the things is totally dried on the finish of every run.


Readers can observe developments, and make feedback, on the following web site:

An Ocean Acidification Experiment

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