Currently there are no standardized procedures for collecting environmental samples from surface waters . As a result, sampling protocols can vary significantly between studies as observed by table S1. These differences have included: (i) the shipping and storage temperature of samples; (ii) duration of transport, (ii) addition of internal standard (IS); (iii) type of containers used (PP or PE plastic versus glass); (iv) pre-extraction filtration. All these different factors can contribute to analyte stability during sampling, resulting in challenges when making comparisons between studies and temporal trends.