School of Natural and Social Sciences (SNSS)

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Browsing School of Natural and Social Sciences (SNSS) by Author "ALI, Fatma Khamis"

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    Occurrence and Distribution of Antifouling Biocide (Diuron) Along the Coastal Areas of Zanzibar: The Case Study of Unguja Island.
    (SUZA, 2022-12-01) ALI, Fatma Khamis
    Diuron (N-(3,4-dichlorophenyl)-N,N-dimethylurea) is one amongst the booster biocides presented to substitute tributyltin (TBT) as an antifouling agent. It has continued to be used ever since, though little is known about their levels in the maritime setting of Zanzibar. This thesis details the occurrence and distribution of Diuron around the coastline area of Unguja Island. Total of 33 samples from 11 sampling sites with different characteristics and activities such as tourisms, dockyards, fishing, coral reef areas, cargo and passengers‘ ports were collected. Samples were prepared and extracted automatically using Solid Phase Extraction (SPE) technique. Finally, Diuron was analyzed using High Performance Liquid Chromatography HPLC (an Agilent Technologies series 1260 infinity II, USA) equipped with DAD (G1315D). The concentrations of diuron in water ranged from Below Detection Limit (BDL) to 1321ng/L maximum were detected. The average concentration observed in harbor and ports (commercial and fisheries) (mean ± SD) were 1006.67 ± 90.6 ng/L (Malindi), 1321.67 ± 52.3 ng/L (Bwawani), BDL (Mtoni). Average concentration results observed in small isles and sand sandbanks were 263.67 ± 4.0 ng/L (Bawe), 1047.33 ± 45.4 ng/L (Pange), BDL (Kwale). The average concentration observed in coastal area is 449.33 ± 91.2 ng/L (Kizimkazi). Average concentration results from Coral reef islands were 1126.33 ± 31.1 ng/L (Chapwani), 620.33 ± 5.7 ng/L (Mnemba) while the results from Chumbe and Murongo were below detection limit (BDL). Majority of the sites showed higher levels of Diuron above the maximum permissible concentration (MPC) of 430 ng/L as restricted by the Dutch Authorities for marine organisms except Bawe (263.67ng/L). Average concentration between all sites and permissible concentration showed significant difference (p<0.05). In general the results of this study suggest that the long term future studies on the antifouling biocides particularly on long term monitoring, chronic exposure, risk assessment, organisms' responses and pollution models would add special value towards better understanding the mechanisms and sustainable marine ecosystem health.