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Document Type |
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Article In Journal |
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Document Title |
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geochemical processes and pollution of groundwater beneath the highly urbanized coastal area of north jeddah , saudi arabia العمليات الجيوكيميائية وتلوث المياه الجوفية تحت المنطقة الساحلية الحضرية للغاية من شمال جدة ، السعودية جزيره العرب |
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Subject |
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geochemical processes and pollution of groundwater beneath the highly urbanized coastal area of north jeddah , saudi arabia |
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Document Language |
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English |
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Abstract |
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The exponential rise in the urban population of the developing countries during the past few decades, coupled with accelerated urbanization phenomenon, has brought the necessity to develop environmentally sustainable and efficient urban population . Rapid urbanization and lack of efficient sewage networks in the City of Jeddah, Saudi Arabia, has led to adverse influences on both groundwater levels and groundwater quality. Groundwater in the coastal aquifer of north Jeddah occurs at shallow depths under unconfined conditions within highly permeable formations. Different sources of recharge have led to a serious problem of groundwater level rise beneath the city (0.10 to 0.12 m/year). Leakage of sewage from septic systems is a prominent source of groundwater pollution. In the present study, groundwater samples for water quality analysis were collected from 56 shallow wells scattered in the city. Results showed variable values for salinity and chemical composition of groundwater. Groundwater salinity ranges from 803 to 74765 mg/l, generally increases northward, where the dominant water type is Na-Cl. It appeared that mixing between groundwater and the Red Sea water could be the main factor for salinization of groundwater. Some samples have Na/Cl molar ratio of 1.00 and very close to one indicating the possibility of halite dissolution in the aquifer matrix or may be possibly due to continuing modification of water chemistry by sewage leakage, where most of these samples were collected from the residential area. The study showed that silicate weathering is not the main source for release of sodium into groundwater. Excess of Ca and Mg in the groundwater revealed that it may be due to the exchange of sodium in the water by calcium and magnesium in clay materials (reverse ion exchange) instead of being derived from the dissolution of carbonate minerals. The saturation index of the most common carbonate minerals showed noticeable variability. It ranges from -0.88 to 0.53 for aragonite, from -0.74 to 0.66 for calcite and from -1.10 to 1.48 for dolomite. Significantly elevated levels of nitrates in most parts of the settlement (up to 1050 mg/l) can be related to nitrification of ammonium-rich municipal wastewater that is disposed just to the east of the study area in an open pond as well as to irrigation by raw wastewater in vegetable farms to the east of the study area. High NH sub(4) levels were observed at the southern more densely settled areas, with a higher density of septic tanks. These high levels indicate that continuous input from septic tank is a prominent source of pollution. The general groundwater flow direction, from east towards west, indicates that polluted groundwater of north Jeddah is ultimately discharged into the sea at the coastline. This process will increase the nutrients flux into the sea, which has detrimental effects on the aquatic ecosystem in north Jeddah. |
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ISSN |
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1687-4285 |
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Journal Name |
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Egyptian Journal of Aquatic Research |
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Volume |
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34 |
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Issue Number |
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2 |
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Publishing Year |
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1427 AH
2008 AD |
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Article Type |
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Article |
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Added Date |
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Saturday, February 19, 2011 |
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Researchers
| مسعود الاحمدي | alahmadi, massoud | Researcher | Doctorate | |
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