Microplastics and PPCPs occurrence in karst groundwaters of Illinois

Groundwater in karst aquifers throughout the world constitutes about one quarter of all drinking water sources. The carbonate aquifers of northwestern and southwestern Illinois are fractured, creviced and contain open conduits and caves. Loess, ranging in thickness up to 4 m in northwestern Illinois and up to 10 m in southwestern Illinois, overlie much of the bedrock, and cover-collapse sinkholes are found in both regions. Because of these features and the open nature of the bedrock, the karst aquifers are particularly susceptible to the introduction and rapid transport of both dissolved and particulate pollutants. In order to assess the susceptibility of karst aquifers to surface-borne contaminants, 8 springs and 3 shallow wells in Illinois’ Driftless Area in northwestern Illinois were sampled for groundwater chemistry, a suite of pharmaceuticals and personal care products (PPCPs), and microplastics in November 2017. In addition, 6 springs in Illinois’ sinkhole plain in southwestern Illinois that were previously sampled for chemistry and PPCPs (Dodgen et al. 2017) were sampled for microplastics. Springs and wells in these areas commonly contain contaminants from various sources, including road salt runoff, septic effluent (including enteric bacteria), and N-fertilizers. The results of the most recent sampling of springs and wells in these areas indicated the presence of both PPCPs and microplastics within the karst aquifers. PPCPs found in 15 of 17 sites included caffeine, carbamazepine, sufamethoxazole and triclosan. All but one of the 17 groundwater samples contained microplastics with a maximum concentration of 15.2 pieces per liter or 15,217 pieces per m3. Based on this and previous investigations, the most likely source of PPCPs and microplastics in the karst aquifers is septic effluent. This is the first time we are aware of that microplastics have been detected in groundwater.