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Risk of pollution by sulphur

Oil pollution is sadly all too common a type of pollution. The response techniques are well known and depend on the specific characteristics of the substances in question. It is worth noting that the quantity spilt (around 1,300 tonnes according to estimations) is greater than that spilt on 7 November by the container ship Cosco Busan in San Francisco Bay. It is however far less than that spilt by the Erika (20,000 tonnes), the Prestige (64,000 tonnes) or the Amoco Cadiz (227,000 tonnes).

Pollution by sulphur is however far less well known. According to the information provided by the local Ukrainian authorities, the sulphur was transported as granules and contained inside the three mentioned sunken ships. As reported in the literature, sulphur in granular form has a low speed of reaction with water and therefore does not pose an immediate acute risk. However, there is little practical experience with this type of accident. If sulphur reacts with seawater at a higher rate, the release of sulphur could be a concern for the marine fauna, flora and humans.

The main incident involving the transportation of sulphur is the shipwrecking of the T2 tanker converted to carry sulphur, SS Marine Sulphur Queen, which sank without sending out a mayday between the 3 and 6 February 1963 off the coast of Florida, in the infamous Bermuda triangle. A wreck, which could have been that of the Marine Sulphur Queen, was filmed by a team of divers in 2001, who discovered flourishing vegetation. No pollution impact studies were carried out.

Aware of the risks involved in the extraction of naturally occurring sulphur from deposits at Lacq in France from the port of Bayonne, Cedre published in 1989 a mini response guide in French on sulphur spills. This guide contains the basic information on the behaviour of sulphur in water and on the risks for humans and the environment. A few extracts from this guide can be found below.

What you need to know about sulphur

Sulphur can be transported in the form of a solid (in powder) or liquid (ambient pressure and temperature of at least 136°C). It is not volatile, but sulphur dust dispersed in the air can form explosive and flammable mixtures when exposed to a flame or heat.

Sulphur is flammable and burns with an almost invisible flame, giving off a very toxic gas: sulphur dioxide (SO2).

In the event of fire, responders must be equipped with protective clothing, breathing apparatus and explosimeters.

When spilt into water, liquid sulphur forms a paste and sinks, without dissolving, creating a localised deposit on the seafloor.

Solid sulphur stored in bulk naturally releases a small amount of hydrogen sulphide from the initial concentration (200 to 300 ppm) which varies according to where and how it is manufactured, but this release is very slow.

Immediate effects for the environment

Only in very exceptional cases will a sulphur spill lead to the presence of colloidal sulphur in suspension thus harming the aquatic biocenosis (effects observed at concentrations of between 1.6 and 10 g/l). On land, the biocidal properties of sulphur on plant parasites (vines in particular) are well known.

Persistence in the environment

In water, sulphur can gradually oxidise into sulphates by microbial action.

In soil, sulphur is more rapidly biotransformed by micro-organisms.

Response to spills at sea

Solid or molten sulphur sinks. In shallow waters, it can be recovered by suction or dredging. It can then be placed in temporary storage tanks for subsequent treatment.

Waste treatment/disposal

Recovered sulphur must never be directly discharged into surface waters or sewer systems.
Burning is generally advised against as its combustion releases sulphur dioxide (SO2). Sulphur can be covered or mixed with calcium carbonate (3 times the mass of sulphur in CaCO3), and buried on a site for dangerous waste.

It is strongly advised that you call upon the services of a specialised company.

Last update: 07/12/2012