Non-indigenous minerals as evidence of anthropogenic contamination in an urban environment

Sediment (and particulate) trespass is an ever more common cause of litigation in today's courtrooms. This stems from the fact that industrial and manufacturing operations are frequently adjacent, or in proximity, to residential sites. Runoff, or fugitive and smokestake emissions, can produce large quantities of effluent which, in many cases, contains noxious or toxic compounds that have potentially carcinogenic, mutagenic, or teratogenic effects on humans.

Often times the contaminants are emitted as a mixed gas-particulate phase that may be difficult to tie to the actual industrial source. As an example, particulate emissions from paper mills often will contain sulphur trioxide (SO3) that, because its particle size is less than 2.5 microns (i.e.< PM 2.5), will not be collected in the baghouse, but rather becomes dispersed over a wide area as a toxic plume. This compound rapidly combines with water vapor to form sulphuric acid which can cause both acute and chronic medical problems, especially in young children and the elderly. Though the compound cannot be identified on surrounding residential property, because it occurs in a vapor phase, an associated particulate, calcite, used as a whitener in paper production, is emitted from the facility's lime kiln and bears testimony that industrial emissions have taken place.

A second example is the incriminating presence of magnetite (and associated toxic heavy metals) on residential properties located near large mini-steel mills. Dust samples collected from affected properties may contain highly elevated amounts of magnetite, which is generated by electric-arc furnaces. Magnetite, as a constituent of Coastal Plain sediments, is an uncommon mineral and rarely exceeds a few hundredths of a percent. Its presence in dust and soil samples in quantities four to five orders of magnitude greater than normal can again used to show that anthropogenically-derived airborne contamination has taken place.