Transformations of elemental mercury to inorganic and organic forms in mercury and hydrocarbon co-contaminated soils

There are many industrial sites, such as gas processing plants, that are contaminated with both mercury and hydrocarbons. These sites tend to be localized but can have very high concentrations of mercury in the soil and heterogeneous distribution of hydrocarbons. The original form of mercury in many cases was elemental mercury from broken manometers. Over time the mercury has become redistributed within soil and has undergone chemical transformations into new forms. The forms of mercury will govern the chemical behavior and the availability of the mercury to biological receptors. The availability of the mercury is important as it will govern the risk associated with the contaminated soil and will also determine the effectiveness of any attempts at remediation. In the present study a chemical extraction protocol was used to determine the forms of mercury in soil originally contaminated by spillage of elemental mercury and petroleum hydrocarbons. Chemical extractions have been used in the past to determine the forms of mercury in uncontaminated soils and several researchers have used them to study contaminated soils. However, to date, no researchers have studied the forms of mercury in soils following years of weathering of elemental mercury after a spill. This study shows that decades after the original spill the elemental mercury has transformed and is dominantly (up to 85%) associated with soil organic matter, and to a lesser extent the mineral fraction of soil.