## 3 Results and Discussion
### Pesticide Residues in Water Samples  
In the present study, 20 organochlorine pesticide residues in surface water samples collected from the Charsadda district of Khyber Pakhtunkhwa, Pakistan were investigated. A typical chromatogram of pesticides contaminations in surface water samples collected from the Charsadda area is shown in Figure 3.  
Among the various pesticides analyzed, \(\beta\)-BHC, \(\gamma\)-BHC, heptachlor, aldrin, endosulfan I, dieldrin, 4,4-DDE, endrin aldehyde and endosulfan sulfate were detected in the surface water samples of Charsadda district. The concentrations of pesticides measured by the SPME-GC-ECD method, are given in Table 4. A total of 30 surface water samples were analyzed for 20 organochlorine pesticide residues. Approximately 50% of the surface water samples collected from Charsadda were contaminated with the pesticides \(\gamma\)-BHC, heptachlor, aldrin and dieldrin. The pesticide contaminants found in surface water samples were \(\gamma\)-BHC (16 samples), heptachlor (17 samples), aldrin (14 samples) and dieldrin (11 samples), with maximum concentrations of 0.023, 0.108, 0.014 and 0.013 \(\mu\)g L\({}^{-1}\), respec \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Compound** & **1 \(\mu\)g L\({}^{-1}\) (Present Study)** & **2 \(\mu\)g L\({}^{-1}\) (Present Study)** & **[PERSON]** & **[PERSON]** (**2003**) & **[PERSON] et al.,** (**2003**) & **[PERSON] et al.,** (**2009**) (10 \(\mu\)g L\({}^{-1}\))** \\  & **(Present Study)** & **(Present Study)** & **(0.4 \(\mu\)g L\({}^{-1}\))** & **(1 \(\mu\)g L\({}^{-1}\))** & **2009** (10 \(\mu\)g L\({}^{-1}\))** \\ \hline \(\alpha\)-BHC & 96.2 & 97.4 & 100.4 & 69 & 101 \\ \(\beta\)-BHC & 106.0 & 108.2 & 121.6 & 90 & 96 \\ \(\gamma\)-BHC & 98.2 & 102.9 & 100.2 & 73 & 97 \\ \(\delta\)-BHC & 97.3 & 98.1 & 104.2 & 97 & 86 \\ Hepatachlor & 90.6 & 89.4 & 74.5 & 79 & 85 \\ Aldrin & 98.1 & 96.8 & 49.7 & 98 & 81 \\ Hepatachlor & 89.9 & 91.8 & 67.6 & 102 & 79 \\ epoxide & 95.4 & 96.0 & - & 99 & - \\ \(\alpha\)-Chlordane & 92.8 & 88.5 & - & 100 & - \\ Endosulfan I & 93.5 & 95.1 & 99.7 & 105 & 83 \\ \(4.4^{\prime}\)-DDE & 91.4 & 90.2 & 57.6 & 107 & 81 \\ Dieldrin & 96.9 & 98.4 & 95.5 & 106 & 82 \\ Endrin & 101.1 & 97.0 & 104.0 & 86 & 81 \\ Endosulfan II & 103.8 & 107.9 & 95.2 & 75 & 85 \\ \(4.4^{\prime}\)-DDD & 94.8 & 95.7 & 79.9 & 50 & 84 \\ Endrin aldehyde & 98.2 & 99.5 & 101.1 & 100 & 86 \\ Endrin ketone & 103.7 & 109.2 & 96.9 & 100 & 82 \\ \(4.4^{\prime}\)-DDT & 87.5 & 90.2 & 63.9 & 104 & 75 \\ Endosulfan sulfate & 98.0 & 96.8 & 44.6 & 90 & 82 \\ Methoxychlor & 96.9 & 95.0 & 95.4 & 72 & 75 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Percent recovery values of selected pesticides at two concentration levels by using SPME-GC-ECD technique and comparison with some reported values. tively. The WHO and Australia guideline values and USA maximum contaminant levels for \(\gamma\)-BHC are 2 \(\mathrm{\SIUnitSymbolMicro\text{Hz}}\) L\({}^{-1}\), 0.05 \(\mathrm{\SIUnitSymbolMicro\text{Hz}}\) L\({}^{-1}\) and 0.2 \(\mathrm{\SIUnitSymbolMicro\text{Hz}}\) L\({}^{-1}\), and for heptachlor are 0.03 \(\mathrm{\SIUnitSymbolMicro\text{Hz}}\) L\({}^{-1}\), 0.05 \(\mathrm{\SIUnitSymbolMicro\text{Hz}}\) L\({}^{-1}\) and 0.4 \(\mathrm{\SIUnitSymbolMicro\text{Hz}}\) L\({}^{-1}\), respectively. The WHO and Australia guideline values for aldrin and dieldrin are 0.03 \(\mathrm{\SIUnitSymbolMicro\text{Hz}}\) L\({}^{-1}\) and 0.01 \(\mathrm{\SIUnitSymbolMicro\text{Hz}}\) L\({}^{-1}\), respectively. Table 5 shows a comparison of pesticide contamination in the Charsadda area with the reported data of some other countries. The organochlorine pesticide residues in the surface water samples of Ghana have been reported in the range of 0.02-0.08 \(\mathrm{\SIUnitSymbolMicro\text{Hz}}\) L\({}^{-1}\) (\(\gamma\)-BHC), 0.01-0.12 \(\mathrm{\SIUnitSymbolMicro\text{Hz}}\) L\({}^{-1}\) (\(\delta\)-BHC), and 0.02-0.04 \(\mathrm{\SIUnitSymbolMicro\text{Hz}}\) L\({}^{-1}\) (Heptachlor) [7]. [PERSON] et al. (2014)