Contamination of groundwater by nitrate is considered a global problem. Nitrates are introduced in the groundwater from a variety of sources like agricultural activities, poor sewer system, wastewaters, and industrial activities. In the present research, a survey of wells (n = 1,060) was undertaken in all 13 regions of the Kingdom of Saudi Arabia to assess the contained nitrate (NO(3)) levels. The results indicated variation in nitrate levels from 1.1 to 884.0 mg/L as NO(3) throughout the Kingdom. The average nitrate levels in milligrams per liter as NO(3) were as follows in descending order: 65.7 (Jizan), 60.3 (Asir), 60.0 (Qassim), 51.3 (Hail), 41.8 (Makkah Al Mukaramma), 41.3 (Madina Al Munnawara), 38.0 (Al Baha), 37.0 (Najran), 30.7, (Tabouk), 25.2 (Eastern Province), 18.8 (Riyadh), 15.8 (Al Jouf), and 9.1 (Hadwed Shamalyah). The results indicated that nitrate levels exceeded the maximum contaminant limits for drinking water (45 mg/L as NO(3)) in a number of wells (n = 213) in different regions of the Kingdom. The maximum and minimum wells exceeding the maximum contaminant limits for nitrate in drinking water were in Jizan (52.6%) and Hadwed Shamalyah (4.9%), respectively. Most of the wells which exceeded the maximum allowed limits for nitrate were in the areas which were used for agricultural and residential purposes.
Water samples were collected from 400 coolers in Riyadh area. From each cooler, one feed and one cooled water samples were collected. These samples were analyzed for trace metals like Al, Cr, Cu, Fe, Mn, Ni, Pb, and Zn by Inductively Coupled Plasma (ICP) Spectrophotometer equipped with ultrasonic nebulizer. Out of 400 coolers, water from 382 (95.50%) were found to meet World Health Organization (WHO), Saudi Arabian Standards Organization (SASO), and United States Environmental Protection Agency (USEPA) drinking water standards whereas water from 18 coolers (4.50%) were found to have elevated levels of Fe, Pb, and Ni metals. In one cooler, water was allowed to stand for 12 h and a 1 L sample collected every 2 h. All the metals mentioned above with the exception of Pb were found to increase due to standing time.
The presence of elevated levels of fluoride in groundwater is considered a global problem. Fluoride in water derives mainly from dissolution of natural minerals in the rocks and soils with which water interacts. The most common fluorine-bearing minerals are fluorite, apatite and micas. Anthropogenic sources of fluoride include agricultural fertilizers and combustion of coal. In the present research, a survey of wells (n = 1,060) was undertaken in all the 13 regions of the Kingdom of Saudi Arabia to assess the contained fluoride (F) levels. The results indicated variation in fluoride levels from 0.10 to 5.4 mg/L as F throughout the kingdom. The average fluoride levels in milligrams per liter as F were as follows in descending order: 1.80 (Hadwood Shamalyah), 1.37 (Hail), 1.33 (Eastern Province), 1.16 (Al Jouf), 1.11 (Qassim), 1.01 (Riyadh), 0.90 (Madina Al Munnawara), 0.81 (Tabouk), 0.74 (Makkah Al-Mukaramma), 0.73 (Jizan), 0.66 (Asir), 0.64 (Najran), and 0.60 (Al Baha). The results indicated that fluoride levels exceeded the USEPA maximum contaminant limits for drinking water (4 mg/L) in several wells (n = 7) in different regions of the kingdom and that 13.96 % of the wells exceeded the World Health Organization recommended levels (1.5 mg/L). The results were also compared with the secondary USEPA contaminant standards of 2.0 mg/L for fluorides.
Twenty-three rain water samples were collected from 15 sampling locations in Riyadh during four rain events in 1994 and analyzed for pH, conductivity, TDS, alkalinity, Cl, NO(3), F, SO(4), Na, Mg, Ca, and 12 trace metals. The pH ranged between 6.83 and 8.21. The major cation and anion were Ca and SO(4), contributing with 30.5% and 20. 8%, respectively, to TDS. Moderate variation in major ions concentration was found to occur between different sites. The concentrations of different metals varied considerably from one sampling location to another. The dominant trace metal ions in the rain water samples were Zn, Pb, and Al. Samples collected from a site near a cement factory in Riyadh showed maximum concentrations of most of the major ions and metals. The concentrations of various ions in the first rain event were comparatively higher than the concentrations of these ions in the later rain events.
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