State one natural origin of acid deposition.

State equations which represent chemical transformations of elemental sulfur into sulfurous acid, H₂SO₃.

Discuss the possible ways of decreasing acid deposition and its adverse effects on the environment.

volcano eruption/activity / lightning / microbial activity;

\({\text{S}} + {{\text{O}}_{\text{2}}} \to {\text{S}}{{\text{O}}_{\text{2}}}\);

\({\text{S}}{{\text{O}}_2} + {{\text{H}}_2}{\text{O}} \to {{\text{H}}_2}{\text{S}}{{\text{O}}_3}\);

washing of coal/natural gas / fluidized bed combustion / remove sulfur before/during the burning;

scrubbing exhaust gases;

using catalytic converters;

low-S diesel / fuel switching / use of alternative energy sources/wind/solar/tidal energy;

reduction in energy consumption;

Accept specific examples of energy saving (e.g. use of bicycles instead of cars).

use lime/formula of a reasonable base on rivers/lakes/soils to neutralize the acid;

Allow other methods/solutions.

Award [2 max] for adverse effects of acid deposition on environment.

This was generally answered well although in (a) some thought the natural acidity of rain, caused by dissolved CO₂, was what was required.

Part (b) was answered well (although the number of candidates who wrote elemental sulfur as a diatomic molecule was worrying).

There were some good discussions in (c). Many candidates mis-interpreted the question as asking about the effects of acid rain – credit was given.