Morning all, do we still discuss science here?

I’m “baby-sitting” and they have a year 11 high school biology assignment. The questions is:

Can you tell me about electrical conductivity within a aqua environment and how the different readings affect the environment as a whole as well as the other more individual aspects of it such as ph turbidity and macro invertebrates.

He has observed it to be low, and needs help explaining why when it is low and falling, it becomes an environmental problem (withing the observable environment)

What’s low and falling? The conductivity or the pH or the turbidity or…?

poikilotherm said:

What’s low and falling? The conductivity or the pH or the turbidity or…?

the conduictivity is falling the ph is stable mostly and the turbidity has been falling

(apparently)

I’m cutting and pasting these answers btw:

the conductivity has been like this in the last 6 or so years
1645
1935
718
760
598
638
and this year 347

the turbidity is
28
20
90
80
14
37
over the last few years each one being for each years

(what he said)

i am trying to think of a third environmental concern to write about
i have done temperature
am waiting for enlightenment about conductivity
but i can not think of what else
the pH is high but it is also stable and the sensitivity of the macro invertebrates indicate that it is not a problem

So, PH is stable, we can ignore that.

Turbidity is increasing slightly which means the water is getting cloudier with suspended solids. Not much though, so we’ll ignore that as well.

“Conductivity” (water hardness) is decreasing – which is obviously the major factor here. Water itself is not a very good conductor, and salts and minerals increase its conductivity. A reduction in hardness suggests the water is getting purer. As to why that in itself is a bad thing, I can only speculate that the invertebrates require a certain amount of stuff such as calcium to be healthy.

SqueezeBabe said:

(what he said)

i am trying to think of a third environmental concern to write about
i have done temperature
am waiting for enlightenment about conductivity
but i can not think of what else
the pH is high but it is also stable and the sensitivity of the macro invertebrates indicate that it is not a problem

Conductivity is a major issue for aquatic life, IIRC, it relates to TDS (total dissolved solids), and the amount in the water will affect organisms as they need different osmoregulation (ions/water loss gain from environment) mechanisms to cope with different conductivity levels.

Example – South American Cichlids like water that has low conductivity and a low pH, but will survive and breed at higher a pH (within reason…) as long as the conductivity is right. They won’t do this if the conductivity is high.

Things like phosphate, nitrate, magnesium, chloride, iron, calcium will affect conductivity, you could relate these to fertilisers/sewage/other pollution.

The conductivity will depend on the soils the river/stream is running through – granite = low conductivity, clay soils = high conductivity.

He says thank you, you’ve all been really helpful.

:)

SqueezeBabe said:

(what he said)

i am trying to think of a third environmental concern to write about
i have done temperature
am waiting for enlightenment about conductivity
but i can not think of what else
the pH is high but it is also stable and the sensitivity of the macro invertebrates indicate that it is not a problem

Without reading the whole discussion, sex hormone pollution springs to mind.

Need temperature figures.

Conductivity is strongly affected by temperature, as are whether the water is likely to be ‘scale forming’ or ‘corrosive’.

This stuff has significant ramifications for marine life, especially Coral.

Welcome back, squeezebabe.
SqueezeBabe said:

the conductivity has been like this in the last 6 or so years
1645
1935
718
760
598
638
and this year 347

That’s a good result. Conductivity is often referred to as “salinity”, though it can be related to the presence of electrolytes other than salt, such as phosphates and surfactants. I’m not sure what the units are for your numbers; if it’s milli-Siemens per metre then the value for seawater is 5000, and the result shows that fresh water is replacing salt water. This would be in a river system and means that the either the water flow is increasing (reducing the tidal ingress of seawater) or efforts to stem salt pollution and other forms of water pollution are successful. Biologically, this would mean a switch from saltwater and salt-tolerant species to freshwater species. Drinking water is 5 to 50 milli-Siemens per metre

If the units are micro-Siemens per metre then the water would be exceptionally pure and the biological effects negligible, which is unlikely.