H2SO4 as a marine biocide

[Gargleblaster]

The thread on red diesel has got me thinking.

In our club tearoom on the Medway there is much talk about how the fouling is getting worse every year and of course the Medway in the tearoom's opinion is the worst river for fouling on the East Coast. Having been on the Medway for five years and previously on the Roach I can't see much difference.

But it got me thinking about the fact that Sulphur was an excellent biocide in red diesel. Then I thought of that product of combustion in high sulphur diesel, Sulphuric Acid and whether the reduction of sulphur in our diesel was causing more fouling. Sulphuric Acid which is one of the products of electricity generation using coal was blamed for a great deal of defoliation, particularly in the US. Now in this country we have all but eliminated coal burning power stations and nowhere is that more evident than on the Medway as all the power stations are being demolished and we are losing all our landmarks.

So my final conclusion was that it, perhaps the reduction of sulphur in our diesel is not having an effect but the reduction of sulphuric acid emitting coal fired power stations could cause an increase in fouling in our rivers.

Still I like wind farms. Like power station chimneys they make navigation at night just that much easier.

Interestingly I only spent 3 weeks on my buoy this year in late September to mid October and noticed despite no scrubbing off between launching in late April and haul out in mid October only a light covering of slime and about 6 tiny barnacles. I had gone as low as 27deg N and had not even got any gooseneck barnacles which I have picked up as low as 39degN previously. That included a month in a marina on Madeira at 33deg N. Every year I experiment with a different antifouling and wonder if I have finally cracked it. But perhaps not for the East Coast Rivers.

 

[Malish]

seawater has about 3.7 grams per kilogram of sulphate in it (which is the stable form of sulphur in seawater) diesel and coal emissions have not really had a significant impact on that figure.

 

[Hydrozoan]

I doubt that it has any significant effect for (amongst others) the reason that RR has given. The main factors governing the general biological productivity of coastal waters are nutrient (N, P) levels, light and temperature.

Interestingly, this paper of 2007 http://onlinelibrary.wiley.com/doi/10.4319/lo.2007.52.2.0635/pdf
suggested that, as chlorophyll levels had then been rising in the North Sea despite reductions in nutrient loads, climatic variations were likely responsible through changes in temperature and water transparency. Whether that suggestion has been confirmed, and the trends continued, I do not know, but that paper is at least not paywalled and you may find it interesting background.

Of course very locally, and in respect of fouling organisms particularly, different combinations of factors and trends may apply, but I personally doubt that sulfur emissions are involved either in terms of acidity or sulfur.

 

[PeterWright]

seawater has about 3.7 grams per kilogram of sulphate in it (which is the stable form of sulphur in seawater) diesel and coal emissions have not really had a significant impact on that figure.

+1 for that simple fact.

Acid rain was much discussed in the 70's and 80's and extensive defoliation of Scandinavian forests was blamed on the UK "high stack" policy which achieved such high stack velocities that the emissions from the likes of Kingsnorth and Littlebrook went up to the upper atmosphere. These hypotheses entailed no work to find where the emissions got rained out back to the ground, which was later found to be well beyond Scandinavia. The hypotheses also included an assumption that the coal burned in the UK power stations was as high in sulphur as central European coal whereas, in fact, the UK coal contained, on average, almost ten times less sulphur than the accusers were assuming.

In the 90's, it all went quiet when more diligent research showed clearly that acid soil was a natural consequence of coniferous monoculture forests, so the timber industry had been damaging their own forests by focussing production on fast growing species. Remember the cheap wooden window frames of the 60's and 70's? Not many left now as they've all rotted away, while many Victorian ones survive. That, and the roof trusses and floor joists of that era, were the chief products of the timber industry which rushed headlong into these monocultures.

Sulphur is a mildly effective biocide, although not so much as the sulphate (SO4) ion - after all Epsom salts is magnesium sulphate, generally held to be beneficial to health. Sulphuric acid would need to be at a concentration raising other concerns to be effective in the biocide role where the problem is always finding something strong enough to prevent fouling without being so strong that it causes wider environmental damage. I'm old enough to remember the wonder of Tri Butyl Tin (TBT) in antifouling which was banned after research at the MAFF lab in Burnham showed it was causing significant environmental damage. If we didn't worry about environmental damage, it would be easy to go back to TBT or even use a chlorate ion (ClO3) based biocide to protect our hulls from fouling, but I prefer to keep fish in the sea. and leave it to biochemists with adequate research facilities to support their work to decide which antifoulings are safe to use.

Peter.


Peter