Most of the data detailing metals concentration in the environment is for total metals. For many applications it is important to know the probable molecular form or chemical form of the metal of interest as it may exist under a specified set of environmental conditions. The particular chemical form of the elemental constituent may affect such chemical and physical parameters as its volatility, aqueous solubility, bioavailability, toxicity, etc, and thus affect its impact on human and ecological health. These same parameters may determine the way that the constituents will respond to remediation technologies. An example is mercuric sulfide, a relatively nonvolatile, highly stable form of mercury that has a low bioavailability, which represents a much lower health risk than other forms of toxic mercury such as methyl mercury. Similarly, hexavalent chromium is a much greater hazard than trivalent chromium.
The MCLinc laboratory has an extensive history of applying solid state characterization methods, in conjunction with process design, to understand the extent, limit, and nature of the interaction between materials. Using electron microscopy (scanning, digital, environmental, ultra-high resolution, and/or transmission) in combination with micro x-ray fluorescence (energy or wavelength) and electron diffraction the size, elemental associations, matrix association, and composition of micro-particulates can be determined. Using x-ray diffraction and x-ray fluorescence, the phase composition and elemental analysis of the materials can be determined. These solid state characterization technologies combined with specific sample preparation, vibrational spectroscopy, ion chromatography, and radiological spectroscopy (if required) allow for the species specific ‘fingerprints’ to be determined for a variety of metal based species. Thus, utilizing this array of micro and macro characterization tools, MCLinc can provide metals speciation, particulate analysis, and source profiling.
MCLinc’s ability to provide detailed metals speciation and materials interaction support has proven valuable in support of various environmental technologies. Understanding the nature of particulates formed during incineration, their interaction with the process equipment, and their interaction with the environment has helped to ensure that the technologies being used to mitigate environmental legacies are in full environmental compliance.
Knowing the speciation of metals in RCRA contaminated soils has allowed a more accurate determination of the risks of human exposure. MCLinc identified the speciation of mercury at an Oak Ridge remediation site. Based upon the results, the EPA action limit was increased to reflect the lower risk to human health. This speciation information helped to save over $100M in remediation cost.