Contaminated soil doesn't always poison groundwater, study finds
Swedish researchers discovered that high levels of toxic metals in soil don't reliably predict groundwater contamination—challenging how regulators assess environmental risk. The finding could reshape cleanup priorities and reduce unnecessary remediation costs at industrial sites across Europe.
Originaltitel: Leachability and transport of metal(loid)s from contaminated land: Geochemical processes and health risks
<p>Heavy metal contamination of land poses severe risks to human health and the environment on a global scale. This thesis aims, firstly, to fill knowledge gaps regarding the general risk of metals spreading from contaminated soil into local groundwater across Sweden. Secondly, it addresses the conditions affecting metal solubility and migration into groundwater specifically around Swedish glassworks sites. To understand the spread of metal from contaminated soil, detailed geochemical studies of the main study object (Pukeberg glasswork) were conducted. These studies complemented analyses of metal solubility in the waste zone with analyses of the underlying soil.</p><p>We found that high metal concentrations in soil alone are generally not reliable indicators of the risk of groundwater contamination. For instance, the investigated glassworks sites are examples where generic risk assessment models would predict a significant deterioration in groundwater quality, but this is not actually the case. Despite high concentrations and a high leachability of the waste zone material at Pukeberg, metal cations are efficiently immobilized in the natural soil underneath the source. Anions have a higher leachability, but are also retained close to the source area. The geochemical model used, however, had clear difficulties in predicting the observed solubility of most metal(loid)s, and was thus unable to fully uncover the processes behind the observed retention/solubility of metals. Our results underscore the necessity of developing methods and understanding which adsorbent phases are most influential under different scenarios.</p><p>The thesis also assesses the risks associated with consumption of vegetables grown near glassworks sites, or drinking water from private wells. The results showed that concentrations of As, Cd and Pb in vegetables were moderately elevated in glassworks villages, but still high enough to result in a daily intake of As and Cd above toxicological values for high-exposure individuals. Regarding drinking water exposure, As was the only metal out of five (As, Cd, Sb, Ba, Pb) that resulted in an intake above tolerable levels for high-exposure individuals, but this was not because of As concentrations in drinking water being elevated relative regional background concentrations, but rather because of the low doses that are tolerated for this element.</p>