1. Several CECs showed low stability in river water, at room temperature, over a 24h sampling/transport time. It is therefore recommended that, in the absence of cooling or analyte immobilization options, environmental water samples are spiked with internal standards on site, immediately after collection. Samples should then be processed to SPE cartridge as soon as possible, to be transported to analyzing laboratory. 2. iMME has proven effective in immobilizing, concentrating, and increasing the stability of CECs at room temperature (for at least 7 days storage), allowing for sample collection at remote locations. 3. The results from the River Avon and Olifants River, indicate that the pristine environment of the Olifants catchment is largely unaffected by CECs common in the urbanized River Avon, with a few exceptions: lifestyle chemicals (e.g., caffeine, nicotine, and their metabolites); paracetamol and UV filters; and carbamazepine, due to its persistent nature. 4. Whilst many CECs demonstrated themselves to be stable on cartridge at room temperature (overall average of 5 ± 24% degradation after 24 hours across both groups A and B), efforts should be made to apply cooling during transport, and cartridges should be stored at freezer temperature prior to processing. 5. Using sterilized filter housing units, it is also possible to collect on-site river samples for ARG analysis, providing potential complementary data to AA concentrations. Stability of ARGs during transport and storage were not investigated during this study. Future scoping work with a few initial samples from a river in the UK and in SA have demonstrated the potential for onsite SPE sampling to quantify a range of CECs to a good level of sensitivity. 6. Further work is required to provide full integration of the device and comprehensive assessment of performance in both chemicals and biological targets.