Abstract
The aim of this study is to determine the types of heavy metals frequently present in Makkah wells and the possible environmental causes of their distribution and accumulation. Makkah lies in a mountain range dominated by different types of rocks from the Precambrian and Lower Paleozoic eras, as well as subordinate sedimentary rocks and basaltic lava flow from the Tertiary and Quaternary periods. Natural contaminants in Makkah wells water can be attributed to the unique location. Many epidemiological studies have identified associations between the ingestion of wells water contaminated with heavy metals and increased risk of some illnesses. This study presents exclusive information on the levels and distribution of 9 heavy metals—arsenic, barium, cadmium, chromium, cobalt, copper, lead, mercury, and selenium—in the wells water in various rural and urban areas of Makkah city. These naturally occurring elements are considered significant markers of water purity. More than 160 wells were involved in this three-year investigation. Water samples were collected during different seasons in order to assess any changes in the distribution and concentration of these heavy metals throughout the year. The collected water samples were filtered and digested before analysis using inductively coupled plasma mass spectrometry (ICP/MS). We found the following sequence of concentrations of heavy metals in the studied wells: Ba > Se >Cr > As > Co > Cu> Hg > Pb > Cd. Arsenic, barium, chromium, and selenium were the most abundant contaminants in the wells studied. The concentrations of the other heavy metals ranged from non-detectable to 3 μg/L. Although low, these values are also reported in comparisons with the local and international strict values and standards which govern the maximum contaminant levels permitted for long-term daily consumption.
Highlights
Water is essential for life on earth, and we can say that groundwater is generally presumed to be safe for human consumption and is used as a potential source of drinking water
Shallow aquifers are affected by rainy seasons, which result in the dilution of heavy metals and other elements
This area is dominated by different types of igneous, metamorphic, and sedimentary rocks from the Precambrian and Lower Paleozoic eras
Summary
Water is essential for life on earth, and we can say that groundwater is generally presumed to be safe for human consumption and is used as a potential source of drinking water. Groundwater in the areas of Makkah selected for this study contains water mostly from nonrenewable sources, primarily runoff which seeped from metamorphic igneous rocks through the Wadi sediment to aquifers. Metal contamination of these aquifers can be predicted based on the type and composition of igneous and/or sedimentary rocks present. The selected wells in the Makkah area are in the southern Hijaz region, the west-central Arabian Shield. This area is dominated by different types of igneous, metamorphic, and sedimentary rocks from the Precambrian and Lower Paleozoic eras. The dominant structural trend is northeast to north-northeast and reflects the three major phases of Precambrian deformation and Tertiary faulting [6]
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