WATER QUALITY OF TWO SEMI-CLOSED AREAS IN THE UNITED ARAB EMIRATES COAST ALONG THE ARABIAN GULF – A COMPARATIVE STUDY

Abstract

A comparative study was carried out between the two biggest creeks along the Arabian Gulf coast of the United Arab Emirates to evaluate impacts of sewage and industrial effluents on their hydrochemical characteristics. Surface and bottom water samples were collected from Abu Dhabi and Dubai creeks during the period from October 1994 to September 1995. The hydrochemical parameters studied were: temperature (21.10-34.00ºC), salinity (37.37-47.09‰), transparency (0.50-10.0 m), pH (7.97-8.83), dissolved oxygen (1.78-13.93 mg/l) and nutrients ammonia (ND - 13.12µg-at N/1), nitrite (ND-6.66 µg-at N/1), nitrate (ND- 41.18 µg-at N/1), phosphate (ND- 13.06 µg-at P/1), silicate (0.68-32.50 µg-at Si/1), total phosphorus (0.26 - 21.48 µg-at P/1), and total silicon (0.95 - 40.32 µg-at Si/1).
The present study indicates clearly that seawater of Abu-Dhabi Creek was warmer (28.12ºC) than Dubai (27.56ºC) resulting in a higher rate of evaporation. Owing to more evaporation, salinity levels showed higher levels at Abu Dhabi (43.33‰) compared to Dubai (39.03‰) seawater. The study also revealed higher secchi disc readings at Abu Dhabi Creek (4.68 m) as compared to Dubai Creek (2.60 m) suggesting more transparency at Abu Dhabi Creek. Whereas, seawater of Dubai exhibited higher levels of pH (1.03 times), and dissolved oxygen (1.05 times) than Abu Dhabi seawater due to an increase in productivity. Meantime, seawater of Dubai showed higher tendency to accumulate ammonia (8.22 times), nitrite (10.93 times), nitrate (5.85 times), phosphate (10.64 times), silicate (1.60 times), total phosphorus (3.19 times), and total silicon (1.54 times) compared to Abu Dhabi seawater due to the enrichment of seawater at Dubai with domestic sewage waters which has distinctly elevated the levels of the nutrient salts particularly in inner-most parts of the creek leading to eutrophication signs. The changes occurred in the receiving creek water of Dubai as a result of waste-water disposal that have also reflected on the atomic ratios of nit: Effect of pollution rogen: phosphorus: silicon.