A landscape defined by battle
The soil around the Douaumont Ossuary records the chemical history of the Battle of Verdun. In 1916, this area became the epicenter of one of World War I's longest and most brutal conflicts. Over 300 days, French and German armies fired an estimated 60 to 75 million artillery shells across a battlefield of less than 20 square kilometers. This intense bombardment fundamentally altered the landscape in a process termed "bombturbation"—the violent mixing and cratering of soil by explosives.
The shelling churned soil horizons, blasted bedrock to the surface, and created a pockmarked terrain of overlapping craters. This physical destruction was accompanied by an immense chemical assault. Millions of shells, bullets, and shrapnel fragments—composed primarily of lead (Pb), copper (Cu), zinc (Zn), and arsenic (As)—were deposited into the ground. Studies of former battlefields show that this contamination is not temporary; it persists more than a century later, locked into the soil's biogeochemical cycles.
The isotopic fingerprint of war
Scientists studying the Verdun soils have found a way to trace the contamination directly to the ammunition used in 1916. Scientists use lead isotope analysis. Lead has several stable isotopes (forms of the element with different numbers of neutrons), and the ratios between them, such as ²⁰⁶Pb/²⁰⁷Pb, vary depending on the geographic origin of the lead ore. This identifies the source for lead sourced from different countries.
Research has shown that WWI-era ammunition used by different armies can be distinguished by these isotopic signatures. By analyzing the isotopic ratios of lead in the soil around Douaumont, scientists can confirm that the contamination originates from the munitions fired during the battle, and not from other potential sources like pre-war industrial pollution.
Lead concentrations in the soil at former ammunition destruction sites near Verdun have been measured at levels as high as 26,398 mg/kg. For context, many public health guidelines consider levels above 400-600 ppm (or mg/kg) to be a potential concern in residential areas. Lead is particularly persistent, with a half-life in soil estimated to be 700 years or more. This long-lasting contamination can be taken up by plants and fungi, potentially entering the local food web. High lead levels have been found in the livers of wild boars in the forests around Verdun.