RESUMO
Emerging organic contaminants (EOCs) are a vast group of often (very)persistent, (very)mobile and toxic (PMT/vPvM) substances that are continuously released worldwide, posing environmental and human health risks. Research on occurrence and behavior of EOCs in karst is in its infancy, thus policy measures and legislative control of these compounds in groundwater are still lacking. The Dinaric karst aquifers are an essential source of drinking water for almost half of Croatia's territory. Intense karstification, complex heterogeneous characteristics, and high fracture-cavernous porosity result in rapid, far-reaching groundwater flow and large karst springs, but also high intrinsic vulnerability due to low contaminant attenuation. To prioritize future monitoring and establish appropriate thresholds for EOCs detected in Croatian karst drinking water resources, in silico tools based on quantitative structure-activity relationships were used in PBT (persistence, bioaccumulation, and toxicity) and PMT/vPvM analyzes, while toxicological assessment helped identify potential threats to human health. In 33 samples collected during two sampling campaigns in 2019 at 16 karst springs and one lake used for water supply, we detected 65 compounds (EOCs and some legacy chemicals), of which 7 were classified as potentially PBT or vPvB compounds (PFOS, PFHxS, PFHpA, PFOA, PFNA, boscalid, and azoxystrobin), while only 2 compounds were assessed as not PMT/vPvM. This finding underlines that most of detected EOCs potentially endanger karst (ground)water ecosystems and important drinking water sources in Croatia. Comparison of maximum concentrations with existing or derived drinking water guideline values revealed how 2 of 65 detected compounds represent a potential risk to human health at lifelong exposure (sulfadiazine and hydrochlorothiazide), while 5 chemicals warrant additional human health impacts studies and groundwater monitoring. Although most compounds do not individually pose a significant risk to human health at current environmental levels, their potential synergistic and long-term effects remain unknown.
RESUMO
Karst aquifers are globally important source of drinking water and harbor specific ecosystems that are vulnerable to anthropogenic contamination. This paper provides insights into the occurrence and ecotoxicological characterization of 21 emerging contaminants (ECs) detected in the karst catchment of Jadro and Zrnovnica springs (Dinarides, Croatia). Karst springs used for water supply, surface water, and groundwater were sampled during seven campaigns. The ECs concentration levels ranged from 0.3 ng/L (tramadol in Jadro spring) to 372 ng/L (1H-benzotriazole in Cetina River). DEET was the most frequently detected ECs with an average concentration of around 50 ng/L in both surface water and groundwater. To prioritise detected ECs, their persistence (P), bioaccumulation (B), mobility (M) and toxicity (T) were assessed based on in silico strategy for PBT assessment and recently developed REACH PMT guidelines. PBT scores ranging below the threshold of 0.5, indicated non-PBT compounds of expected low concern. However, only 4 out of 21 detected ECs were not assessed as PMT/vPvM. Concerningly, 20 ECs were categorised as very mobile. Karst springs exhibited larger proportions of ECs meeting PMT/vPvM criteria than surface water. To characterise the contamination extent and estimate the incidence of adverse effects of detected ECs, a preliminary environmental risk assessment (ERA) was conducted. Most ECs posed no environmental risk with RQ values predominantly below 0.01. The total risk quotient RQsite accentuated Cetina River as having the highest risk compared to other sampling sites. This is the first study on ECs in Croatian karst, contributing to a growing need to understand the impacts of emerging contaminants in karst aquifers, which are still largely unexplored.