“…Similar to the current study, SPs have been frequently detected in sediments from California (Amweg et al, 2006;Holmes et al, 2008;Trimble et al, 2009;You et al, 2008;Weston et al, 2004Weston et al, , 2005, Texas (Hintzen et al, 2009), and Illinois (Ding et al, 2010) in USA, as well as the PRD in China . The OPs, however, were detected at lower frequencies and concentrations in those studies.…”