USING SANDS AS A POTENTIAL INDICATOR OF HEAVY METAL POLLUTION: LESSONS LEARNED FROM MOUNT BALDY

Quantifying metal contamination and identifying pollution sources within sand can be difficult due to grain size and sorting effects, as well as mineralogical complexity. The ubiquitous of sand makes it a medium that requires special attention, particularly because of its ease of exposure to children and adults. Playgrounds, beaches, national parks, and dunes are places where sand is found, and people interact intensively with it. An initial scanning electron microscope (SEM) and transmission electron microscope (TEM) investigation of samples from Mt. Baldy in Indiana Dunes National Park demonstrated the presence of several pollutants, including heavy metals. The size range of observed heavy metal bearing particles is from several tens of micrometers to tens of nanometers, thus enabling possible exposure through both inhalation and ingestion. The sources of heavy metals may be from multiple sources. TEM identified Zn observed with Fe-rich particles, which may be from vehicular sources, while Mn-bearing anthropogenic spherules are consistent with anthropogenic spherules observed in road sediment associated with steel manufacturing. Northwest Indiana is well recognized as a major steel producing region with large facilities and extensive supporting infrastructure throughout the region. Thus, steel facility pollution emissions in general are recognized as a significant potential source of metal pollution near our study.

This investigation opens questions regarding electron microscopy investigations of sand as both a medium for environmental monitoring but also as an exposure medium for adults and children. Investigating pollution in the sands throughout the region would help evaluate the efficiency of sand in capturing pollutants, the nature and extent of the contamination, and risks to the population. This study provides critical context for defining the type and sources of pollutants in Northwest Indiana.