Pollutants from Old Glassworks Affect Groundwater Less Than Expected
High levels of metal pollutants in the soil near decommissioned glassworks do not necessarily translate to high concentrations in groundwater. Only a very small fraction of these pollutants leaches into the groundwater, according to a new doctoral thesis investigating high-risk areas in Sweden.
In Sweden, approximately 27,000 sites are so contaminated that they may pose a risk to human health and the environment, according to the Swedish Environmental Protection Agency (Naturvårdsverket). Among the highest-priority sites, nearly half are contaminated with metal pollutants. This is particularly true for many of the decommissioned glassworks in Småland’s “Kingdom of Crystal” (Glasriket), where hazardous metals such as arsenic, cadmium, and lead are present in the soil.
“Before hazardous waste management regulations were in place, residual waste from glass production was often dumped near the glassworks. While most of it ended up in landfills, some was also used as filling material in land preparation for nearby construction. As a result, many old glassworks are surrounded by heavily contaminated soil,” explains Terese Uddh Söderberg, an environmental science researcher at Linnaeus University.
Investigating High-Priority Areas
Fortunately, very little of these contaminants actually reaches the groundwater, as shown in Terese Uddh Söderberg’s doctoral thesis in environmental science. The thesis is based on investigations of approximately 200 of Sweden’s most highly prioritized contaminated sites, with a deeper focus on the glasswork sites in the Kingdom of Crystal.
“In the Kingdom of Crystal, the significant metal contamination in the soil has led both authorities and residents near the glassworks to be concerned about health risks. Despite the high levels in the soil, we observe that the amount of metal pollutants reaching the groundwater is much lower than expected. The local population is only exposed to low levels, even if they drink water from their own wells,” says Söderberg.
Lower spread than predicted
The thesis reveals a lower spread of hazardous metals into groundwater than predicted by general risk assessment models at the examined sites. One such site is the Pukeberg glassworks in Nybro Municipality, which was subject to closer examination.
“Despite high metal concentrations and a high leachability of metals in the landfill, we observed that the pollutants are effectively retained in the natural soil. The results demonstrate that relying solely on metal concentrations in soil may not provide an accurate assessment of the risk of groundwater contamination,” Söderberg explains.
Assessing Complex Risks
Assessing the risk of metals spreading from contaminated land is complex and resource intensive. Factors such as soil properties, water content, oxygen levels, and other chemical processes play a role. Therefore, simpler models with additional safety margins are often used when assessing risks at contaminated sites like old glassworks.
“The challenge lies in the fact that most general risk assessment models rely on soil metal concentrations to calculate metal levels in groundwater. We show that these models can just as easily underestimate as overestimate metal dispersion into groundwater, and both errors can lead to negative consequences.”
More efficient remediation
Today, many areas are classified as potentially hazardous to health using models that estimate the amount of metal pollution leaching into groundwater. However, with better measurement methods, it would be possible to pinpoint where remediation is most needed, thereby making the process more efficient, suggests Terese Uddh Söderberg.
“The examined glassworks are examples of areas where general risk assessment models predict significant local groundwater contamination, but this is not always the case in reality.”
Is It Safe to Eat Homegrown Vegetables?
The thesis also investigates the levels of metals contaminants in potatoes and lettuce grown in garden soils around several glassworks in Småland’s Kingdom of Crystal. It shows that the concentrations of arsenic, lead, and cadmium were only moderately elevated in the vegetables, and most of the examined vegetables remained below the threshold values for food safety.
“Even though the levels of arsenic and cadmium were low, they were still sufficiently high to result in a daily intake of these two metals above the toxicological threshold values for individuals who consume large quantities of vegetables and have a small body weight,” says Terese Uddh Söderberg.
More Information:
The doctoral thesis “Leachability and Transport of Metal(loid)s from Contaminated Land: Geochemical Processes and Health Risks” by Terese Uddh Söderberg.
Learn more about the Environmental Geochemistry research group.