## 4 Discussion
The correlation analysis between \(f_{\mathrm{CM}}\) and \(K_{\mathrm{d}}\) showed that the two had good correlation (\(r>0.99\)), and combined what was shown in Figure 3, the conclusion could be drawn that the sorption capacity of sediments was closely related to the content of SC [36; 37; 38; 39]. The values of \(K_{\mathrm{F}}\) reflected the sorption capacity of natural solids to some extent [40], when the proportion of CMs in TOC increased from 0 to 60%, the \(K_{\mathrm{F}}\) values of lindane sorption increased from 7.38 to 35.69, increased by 3.8 times, and the \(K_{\mathrm{F}}\) values of \(p\),\(p^{\prime}\)-DDE sorption increased from 21.83 to 94.19, increased by 3.3 times, which also confirmed the importance of SC content in the sorption of lindane and \(p\),\(p^{\prime}\)-DDE by the sediments. The contribution of SC to the sorption of the sediments was calculated as follows: the difference between the amount of pesticides sorbed by the sediments with different contents of SC and natural sediments was taken as the amount of pesticides sorbed by SC; the ratio of the amount of pesticide sorbed by the sediments with different contents of SC was recorded as the contribution of SC to the sorption of lindane and \(p\),\(p^{\prime}\)-DDE by the sediments. Figure 4 shows the relationship between the ratio of CMs and TOC (\(f_{\rm CM}\)/\(f_{\rm OC}\)) and the sorption contribution rate of SC. When the ratios of \(f_{\rm CM}\)/\(f_{\rm OC}\) were 0.10, 0.22, 0.35, 0.46, and 0.60, the contribution rates of SC to the sorption of lindane were 16.4%, 28.9%, 43.1%, 57.1%, and 64.7%, respectively; the contribution rates of SC to the sorption of \(p\),\(p^{\prime}\)-DDE were 40.7%, 41.1%, 50.0%, 55.3%, and 61.7%, respectively, which was similar to the results reported by [PERSON] et al. and [PERSON] et al. (2014); [PERSON] et al. (2014), indicating that the ratio of \(f_{\rm CM}\)/\(f_{\rm OC}\) was an important factor affecting the sorption of lindane and \(p\),\(p^{\prime}\)-DDE by the sediments. The organic carbon standardized partition coefficient (\(K_{\rm OC}\)) reflects the sorption capacity of the sediments for organic pollutants ([PERSON] et al., 1986). The values of \(K_{\rm OC}\) and the ratios of \(f_{\rm CM}\)/\(f_{\rm OC}\) are listed in Table 3. When the ratio of \(f_{\rm CM}\)/\(f_{\rm OC}\) in the sediments was low, as in 0.10-0.22, the change of \(f_{\rm CM}\) had little effect on the value of \(K_{\rm OC}\), and the contribution rate of SC was below 50%. At this time, CMs played a minor role in the sorption of lindane and \(p\),\(p^{\prime}\)-DDE by the sediments; when \(f_{\rm CM}\)/\(f_{\rm OC}\) was higher, as in 0.35-0.60, CMs gradually played a leading role in the sorption, the contribution rate of SC even went up to 64.7%, and the higher the \(f_{\rm CM}\), the greater the effect on the values of \(K_{\rm OC}\). This indicates that \(f_{\rm CM}\)/\(f_{\rm OC}\) could be a principal parameter for assessing the sorption capacity of sediments and CMs for the hydrophobic OCPs. Figure 4: The relationship between the ratio of \(f_{\rm CM}\)/\(f_{\rm OC}\) and sorption contribution rate of SC. \begin{table}
\begin{tabular}{c c c c c c c} \hline  & **Sediments** & **0.5\% SC** & **1.5\% SC** & **3.0\% SC** & **5.0\% SC** & **9.0\% SC** \\ \hline \(f_{\rm CM}\) (\%) & 0.17 & 0.67 & 1.67 & 3.17 & 5.17 & 9.17 \\ \(f_{\rm OC}\) (\%) & 6.16 & 6.66 & 7.66 & 9.16 & 11.16 & 15.16 \\ \(f_{\rm CM}\)/\(f_{\rm OC}\) & 0.03 & 0.10 & 0.22 & 0.35 & 0.46 & 0.60 \\ \([\)(ug\(\cdot\)g\(\cdot\)g\(\cdot\)i)(ug\(\cdot\)L\(\cdot\)i\(\cdot\))\({}^{-1}\)\({}^{-n}]\) & 119.82 & 180.81 & 186.17 & 228.41 & 253.94 & 235.44 \\ \(K_{\rm OC}\)-\(p\),\(p^{\prime}\)-DDE & 346.23 & 718.90 & 688.12 & 801.81 & 731.11 & 621.31 \\ \([\)(ug\(\cdot\)g\(\cdot\)g\(\cdot\)i\(\cdot\)g\(\cdot\)L\(\cdot\)i\(\cdot\))\({}^{-n}]\) & 14.00 & 1.00 & 1.00 & 1.00 & 1.00 & 1.00 \\ \([\)(ug\(\cdot\)g