Age Dating Oil and Gas Wastewater Spills Using Radium Isotopes and Their Decay Products in Impacted Soil and Sediment

Abstract

Spills from oil and gas operations can contaminate water resources, sediment, and soil, but in many cases, information about spill sources and environmental impacts is not available. Here we present age dating methods to estimate the time since the accumulation of radium in impacted soils and sediments from oil and gas wastewater spills. The retention of unsupported 226Ra and 228Ra from spill water to soil and sediment and the ingrowth of Ra progeny result in three independent age dating methods using the 228Th/228Ra, 210Pb/226Ra, and 228Ra/226Ra activity ratios. We tested the 228Th/228Ra method on spill sites in North Dakota and West Virginia, where the dates of the spills are known. The 228Th/228Ra method yields ages similar to the documented spill ages and can reveal the initial 228Ra/226Ra ratios of the spill waters, validating the notion that Ra isotopes and their decay products in contaminated soils and sediments can reveal the ages and origins of spills.