Occurrence and distribution of emerging contaminants in surface water and biota: An integrated analytical-statistical...

Pharmaceuticals and pesticides are key contaminants of emerging concern (CECs) that threaten aquatic ecosystems due to their high mobility and persistence. Accurate environmental monitoring requires robust analytical strategies supported by rigorous statistical validation. This study presents a novel analytical-statistical framework for CEC quantification, evaluating different linear model fitting, matrix effects, and calibration methodologies: post-sample treatment standard addition (ESAC) and ESAC with internal standards (ISC). Our findings demonstrate that weighted least squares (WLS) regression provided the most accurate model fitting. The ISC methodology, combined with WLS, outperformed other approaches in linearity and validation parameters, effectively minimizing matrix interference. This validated framework was subsequently applied to surface water and biota samples. Surface water analysis revealed significant anthropogenic pressure linked to tourism and maritime activities. In certain areas the level of pharmaceuticals was lower (8.4 μg kg^-1), in contrast to pesticides (6.2 μg kg^-1). Among biota, crabs exhibited the highest bioaccumulation (334 μg kg^-1), followed by adult mussels (247 μg kg^-1); notably, no direct correlation with trophic levels was observed. These results confirm that the proposed ISC-WLS approach provides a reliable and high-precision tool for the environmental assessment of CECs in complex matrices.