Using Soil Mineral Signatures to Confirm Sources of Industrial Contaminant Trespass.

The development or expansion of industrial operations in a community may be accompanied by contaminant trespass on adjacent residential properties.  While the products of smokestack emissions or wind-blown debris from some manufacturing operations can be often easily identified by microscopic analysis (e.g., coal flyash, mine wastes, etc.), proof that a site or individuals have been impacted by emissions from other processes may be more elusive and pose a challenge for an expert witness.  A mineral phase universally present in electric arc furnace stack discharges by mini steel mills, for example, is magnetite (FeO^.Fe₂O₃).  Though frequently encountered in the heavy mineral fraction of soils, magnetite from a steel mill source can be differentiated from detrital grains by both a distinctive particle morphology and an anomalously high manganese content (often three or more orders of magnitude greater than those for detrital grains).  Collectively, the two provide conclusive evidence that anthropogenically-derived, airborne contamination has taken place.

     A complicating problem arises, however, if contaminants are emitted as a mixed gas-particulate phase whose particles are <2.5 microns in size.  Emissions from paper mills may be in this form and will often contain hydrogen sulfide (H₂S) and sulphur trioxide (SO₃). Both of these rapidly combine with water vapor in the atmosphere to form sulphuric acid.  Dispersal can occur over a wide area as a toxic plume and can cause a variety of acutely or chronically harmful medical problems, especially in young children and the elderly.  Though acknowledged as present in stack emissions by the paper companies, the presence  of this vapor phase is often difficult to find on nearby residential properties (though its corrosive effects are invariably present!).  An associated particulate phase (calcite) that is used as a whitener in paper production, however, is emitted from a facility’s lime kilns and often can be used as indirect evidence to show that a variety of industrial emissions have likely impacted adjacent properties.