**3. Experimental**

#### **3.1. Sample processing**

Surface sediment samples were collected with a stainless steel grab. The upper 1-3 cm of the sample were carefully removed and stored in acid rinsed polyethylene 250 mL glass bottles. Samples were transferred to the laboratory and were stored at -20ºC until sample extractions. Details of sampling areas is shown in Table 1 and description of samples as shown in Table 2. Sampling location is shown in Figure 3.

**Figure 3.** Sampling locations

Spatial and Monthly Behaviour of Selective Organochlorine Pesticides in Subtropical Estuarine Ecosystems http://dx.doi.org/10.5772/54842 431


**Table 1.** Details of sampling areas.

the coral reef ecosystems and their adjacent environments in and around the Okinawa Island are contaminated with OCPs, OTCs and PCBs (Tashiro et al.*,* 2003; Imo et al.*,* 2007; Sheikh et al.*,* 2002). However, very little is known about the behaviour of HCH and dieldrin in estuarine sediments of subtropical areas. The main objective of this chapter is provide crucial informa‐ tion on the distribution and behaviour of HCH and dieldrin compounds in protected sub‐

Surface sediment samples were collected with a stainless steel grab. The upper 1-3 cm of the sample were carefully removed and stored in acid rinsed polyethylene 250 mL glass bottles. Samples were transferred to the laboratory and were stored at -20ºC until sample extractions. Details of sampling areas is shown in Table 1 and description of samples as shown in Table

tropical estuaries in the Okinawa Island.

430 Insecticides - Development of Safer and More Effective Technologies

2. Sampling location is shown in Figure 3.

**3. Experimental**

**3.1. Sample processing**

**Figure 3.** Sampling locations


**3.2. Sample extraction**

the amount extracted before GC-MS analysis.

*3.3.1. Total Organic Carbon (TOC) in sediments*

PHM 95/ion meter, Radiometer model (± 0.001 pH).

**3.3. Environmental parameters**

8.50% and N = 14.88 %).

**4. Results and discussion**

*3.3.2. pH*

Prior to extraction, surface sediments were freeze-dried, homogenized with a stainless spatula and passed through a 63 µm sieve followed by mixing with anhydrous Na2SO4. The sediment samples were extracted by ultrasonication technique as described by (Vagi et al.*,* 2005). The surrogate standard of 5 µgL-1 was added to 40 g of sediments. Portion of this amount was used for QC analysis (i.e. each batch contained 1 sample, 1 blank, 4 spiked). For the spiked samples, various concentration of Chlorinated Mix (5, 10, 50 µgL-1) were added to each spiked sample. The samples were extracted by ultra wave sonication for 15 minutes with 10 mL of dichloro‐ methane. The extracts were then filtered using WHATMAN filters (0.45 µm) followed by centrifugation at 3000 rpm for 15 minutes. The clear organic supernants were removed then the combine extracts were evaporated on a rotary evaporator at 30-35°C near to dryness. A 1 mL of hexane was added to the dried residues. For further cleanup, the samples were then added to the florisil ENVI Carb and the samples were eluted with hexane. The residues were dissolved in 1 mL hexane. A 1mL of Internal Standard (Pentachloronitrobenzene, 50 µgL-1) in

Spatial and Monthly Behaviour of Selective Organochlorine Pesticides in Subtropical Estuarine Ecosystems

http://dx.doi.org/10.5772/54842

433

Approximately 3g sediment sample was weighed (± 0.002 g) and HCl (*2M*) was added to the sample and left over night to remove all carbonates. Milli Q water was added to rinse the acid from the sediments. To ensure that all the acid was removed from the samples, a 6*M* of HCl was added. The acid from the sample was removed by adding 2 mL of distilled water followed by centrifugation. The sediments were then dried at 60°C over night and ready for analysis (US EPA, 2012). The Total Organic Carbon (TOC) was determined using the CHNS analyser (JM 10 Model from J-Science Lab, Co. Ltd, Japan0. Calibration was performed using Antipyrine as Standard with the following compositions: C8H9NO = 135.17 (C = 70.19%, H = 6.43%, O =

The pH was measured using a portable pH meter at room temperature in the laboratory using

The highest concentration of HCH was found in the sampling month of October (213 ng/g) (Manko estuary) and Dieldrin (98 ng/g) (Okukubi estuary) followed by the month of Novem‐ ber (HCH-199 ng/g) (Manko estuary) and (Dieldrin-90 ng/g) (Okukubi estuary). The status of HCH and dieldrin in sediments in this study was compared with those in other rivers. The levels of OCPs in this study are lower than that of Er-jen river, Taiwan (80-8200 ng/g (dw))

**Table 2.** Description of surface sediment samples

### **3.2. Sample extraction**

**Sample**

432 Insecticides - Development of Safer and More Effective Technologies

**Table 2.** Description of surface sediment samples

K-26s-05 mud K-27s-05 mud K-28s-05 mud K-29s-05 mud K-30s-05 mud K-31s-05 mud K-32s-05 mud K-33s-05 mud K-34s-05 mud-sandy K-35s-05 sandy K-36s-05 sandy K-37s-05 sandy K-38s-05 sandy K-39s-05 sandy K-40s-05 sandy O-26s-05 sandy O-27s-05 sandy O-28s-05 sandy O-29s-05 sandy O-30s-05 sandy O-31s-05 sandy O-32s-05 sandy O-33s-05 sandy O-34s-05 sandy O-35s-05 sandy O-36s-05 sandy O-37s-05 sandy O-38s-05 sandy O-39s-05 sandy O-40s-05 sandy

**Surface river sediments Sample sketch**

Prior to extraction, surface sediments were freeze-dried, homogenized with a stainless spatula and passed through a 63 µm sieve followed by mixing with anhydrous Na2SO4. The sediment samples were extracted by ultrasonication technique as described by (Vagi et al.*,* 2005). The surrogate standard of 5 µgL-1 was added to 40 g of sediments. Portion of this amount was used for QC analysis (i.e. each batch contained 1 sample, 1 blank, 4 spiked). For the spiked samples, various concentration of Chlorinated Mix (5, 10, 50 µgL-1) were added to each spiked sample. The samples were extracted by ultra wave sonication for 15 minutes with 10 mL of dichloro‐ methane. The extracts were then filtered using WHATMAN filters (0.45 µm) followed by centrifugation at 3000 rpm for 15 minutes. The clear organic supernants were removed then the combine extracts were evaporated on a rotary evaporator at 30-35°C near to dryness. A 1 mL of hexane was added to the dried residues. For further cleanup, the samples were then added to the florisil ENVI Carb and the samples were eluted with hexane. The residues were dissolved in 1 mL hexane. A 1mL of Internal Standard (Pentachloronitrobenzene, 50 µgL-1) in the amount extracted before GC-MS analysis.

#### **3.3. Environmental parameters**

#### *3.3.1. Total Organic Carbon (TOC) in sediments*

Approximately 3g sediment sample was weighed (± 0.002 g) and HCl (*2M*) was added to the sample and left over night to remove all carbonates. Milli Q water was added to rinse the acid from the sediments. To ensure that all the acid was removed from the samples, a 6*M* of HCl was added. The acid from the sample was removed by adding 2 mL of distilled water followed by centrifugation. The sediments were then dried at 60°C over night and ready for analysis (US EPA, 2012). The Total Organic Carbon (TOC) was determined using the CHNS analyser (JM 10 Model from J-Science Lab, Co. Ltd, Japan0. Calibration was performed using Antipyrine as Standard with the following compositions: C8H9NO = 135.17 (C = 70.19%, H = 6.43%, O = 8.50% and N = 14.88 %).

#### *3.3.2. pH*

The pH was measured using a portable pH meter at room temperature in the laboratory using PHM 95/ion meter, Radiometer model (± 0.001 pH).
