| Popis: |
With the existing and anticipated expansion in the Jebel Ali Free Zone (JAFZ), Dubai, there is concern regarding the degradation of water resources in the area. This study was conducted to assess the water quality of the harbor in the JAFZ area, with an emphasis on the impact of discharged pollutants into the harbor. To do so, an extensive sampling protocol was followed to identify target pollutants. The protocol covered sampling of all discharge locations, several harbor stations, and a reference point in the Arabian Gulf. Over 90 parameters were analyzed for most collected samples. During the study, four industries discharged treated wastewater into the harbor. Also, part of the sewage treatment plant (STP) effluent on-site had been discharged in early stages of the project but was then terminated. Generally, discharged treated wastewater from the five sources that were examined met allowable discharge limits set by the Ports, Customs and Free Zone Corporation at the JAFZ area but sometimes marginally exceeded limits for a few parameters. Diversion of STP effluent for landscape purposes significantly reduced the annual discharge load of several pollutants. Overall, average increases in harbor water concentration caused by discharges from known industrial sources were not significant. Results of harbor water quality showed that water temperature, pH, and total dissolved solids were lower than harbor objective limits whereas total suspended solids slightly exceeded the limit. As for the dissolved oxygen, its level was generally higher than the minimum objective limit. Ammonia, however, was generally higher than that at the reference location, with an apparent increase in its level at deeper depths and in the inner and outer basins. The level of sulfide in harbor water at several locations was lower than the harbor water objective limit, except in the inner basin. Similarly, phosphorus exceeded the objective limit at the east and west corners of the inner basin. Among the metals tested, the levels of Fe, Zn, and Al were higher than those at the reference location. However, only iron and Cu exceeded the harbor water objective limits. Total petroleum hydrocarbons levels, on the other hand, typically exceeded the harbor objective limit by orders of magnitude, especially in the west corner of the inner basin. As to the other organic matter indicators, biochemical oxygen demand and total organic carbon were higher near the bottom and highest in the inner and outer basins. Trace organics were generally below the limit of quantitation at many stations, except for detectable bromoform, chloroform, and toluene. The phytoplankton communities found in our study matched those commonly known along the coastal area of the Arabian Gulf. However, the observed high algae concentration in harbor water could be a result of the nutrient-rich environment caused by organic discharge and bacterial action. The highest values were found at the east and west corners of the inner basin. On the other hand, the phytoplankton diversity and density dropped over time owing to a probable reduction in waste discharge from the STP, seasonal variations, or dredging of harbor bottom sediments that may have reduced its organic contents. The presence of high coliform bacteria in marine water (as is the case in the inner basin) is uncommon unless it receives discharge from domestic sources. |
