**2. Materials and methods**

 Water and sediment samples were collected from the estuarine areas of Ramisi-Vanga system in the Kenyan South Coast; peri-urban creeks of Mombasa; and estuarine areas of the North Coast (**Figure 1**). Ramisi-Vanga system (Ramisi, Mwena, and Umba) is a low-lying coastal plain submergent complex (below 30 m contour) with extensive cover of mangrove forest, intertidal areas covered with seagrass beds and shallow water lagoons harboring the coral reefs. These critical systems are interlinked through the exchange of water, nutrients, and carbon by the tidally controlled circulation and river discharge [29]. The Kisite-Mpunguti Marine Protected Area (KMMPA) and Shimoni are situated approximately 90 km south of Mombasa with very few scattered fringe mangrove cover on the shoreline though there is no river input into this system apart from sewage and runoff [30]. The area constitutes an important tourist attraction and important resource for the surrounding communities [31]. The main characterizing features of interest around Mombasa peri-urban creeks (Makupa, Kilindini, Mtwapa, and Tudor creeks) include the Kilindini port and the Mombasa Municipal refuse dumpsite, (Kibarani), both of which are found in the vicinity of the Makupa creek stations and the Kenya Meat Commission (KMC) beef factory located within the vicinity of the Tudor creek [32]. Mtwapa creek is situated 25 km north of Mombasa. It is a tidal creek lined by mangrove forests and extensive mud banks. The creek receives freshwater input through seasonal rivers and it is reported to be relatively eutrophic due to direct release of raw sewage into the creek at the vicinity of Shimo la Tewa government prison [30]. These peri-urban creeks were chosen due to anthropogenic activities in the adjacent areas while riverine estuarine systems were chosen given that river-derived material like water, sediments, and pollutants have a tremendous ecological and toxicological influence on coastal zones [35]. North Coast sites comprised of estuarine areas of River Tana which arises from Aberdare range and Mount Kenya passing through the arid and semiarid areas of the eastern part of the country and finally drain into the Indian Ocean in a fan-shaped delta [34] while Sabaki river originates from Athi river where it joins Tsavo river and forms river Galana where it also discharges into the sea. These two rivers affect the marine ecological conditions of Watamu, Malindi, and Lamu [33].

 Nutrient sample collection, preservation, shipment, storage, and analysis were done following procedures described by Parsons [36], APHA [37] and measured using Genesys 10S Vis spectroscopy (Thermo Scientific™). Sediment samples were collected using Uwitec corer (fitted with a 50-cm plastic sampler, Ø 8 cm) following the procedures provided in IAEA TECDOC-1415. The samples were transported to the laboratory awaiting analysis.

**Figure 1.** 

*Map showing sampling sites: Estuaries (Umba, Ramisi, Sabaki, Mwena, and Tana); north coast (Kilifi, Malindi, and Lamu); south coast (Kibuyuni, Shimoni, Wasini, Sii Island, Gazi, and Kisite); and peri-urban creeks of Mombasa (Mtwapa, Tudor, and Makupa).* 

For analysis of trace metals and alpha-emitter 210Po radionuclide, top 5 cm of sediment for each site were pooled, mixed by hand, and freeze-dried, homogenized sieved, dry-weighed, and then digested in a microwave (Microwave Accelerated Reaction system). Elemental analysis of Cu, Zn, Mn, Pb, Cd, and Cr was carried out using inductively coupled plasma mass spectrometer (ICP-MS) (Varian, Australia) while 210Po activity was measured using alpha-spectrometry with silicon surface barrier detectors (EG and G) coupled to a PC running Maestro TM data acquisition software [38].

PCBs, OCPs, and PAH were analyzed as described by Thompson et al. [39] where wet samples were freeze-dried using Heto powerdry LL3000 freeze dryer (Thermo

*Decadal Pollution Assessment and Monitoring along the Kenya Coast DOI: http://dx.doi.org/10.5772/intechopen.82606* 

Scientific), then known weight of the sediment sample was spiked with internal standard for PCBs (PCB 30, PCB 103, PCB 155, PCB 198 from Promochem, Dr. Ehrenstorfer GmbH, France), OCPs (d8 4,4′ DDT from Cambridge Isotope Laboratory, France), and PAH (per-deuterated PAHs; Phenanthrene-d10, benzo [a]pyrene- d12, benzo [e] pyrene d12 and benzo [g, h, i]perylene-d12 from Cambridge Isotope Laboratories, Andover, USA; and Fluoranthene-d10, chrysene-d12 and pyrene-d10 from MSD isotopes, Division of Merck Frost Canada INC, Montreal, CND) to quantify the recoveries. The samples were then extracted using START E microwave-assisted extraction system (Milestone, Italy). The extract was concentrated using Rapidvap LABCONCO (Serlabo Technologies, France) and then concentrated samples were subjected to the clean-up process. Thereafter, the extracts were finally concentrated under nitrogen, transferred to 100-μl container and analyzed using GC-MS.
