Metal Index
The interest on the effects on humans and other animals of heavy metals and metalloids like arsenic taken in through drinking and use of thermal waters has increased in recent years (Smith et al., 2002; Nordstrom, 2002; Senn and Hemond, 2002; Fewtrell et al., 2001; Lind and Glynn, 1999; Manay et al., 1999; Ramessur et al., 2001; Flaten, 2001; Gauthier et al., 2000; Veeramachaneni et al., 2001; Pedersen and Permin, 1988). The definition of the maximum allowable concentration (MAC) values for certain elements (recently classified as trace elements) in spring, drinking, thermal and surface waters has been and still is the subject of chemical and biological research, and of political debate, in several countries. For instance, the value of MACAs (arsenic, AW 74.92, Group 15, VA) in the USA was decreased from 50 to 10 mgyl in May 2001 (starting January 22, 2006) (US EPA, Office of Water, 2000, 2001). Notwithstanding, the debate on this parameter is still open. The Environmental Protection Agency (EPA), the National Research Council (NRC) and several research groups stated that chronic effects on humans may be caused by prolonged consumption of water with a concentration of As as low as 5 mgyl (EPA) or even 3 mgyl (NRC) (Hogue, 2001a,b). Arsenic is usually relatively abundant in sulfide-containing mineral deposits such as pyrite and ‘soft’-metal mineralizations, as well as in hydrous iron oxides; therefore, monitoring of waters in volcanic areas and in districts that are rich in heavy-metal sulfide ores can be important to assess possible health risks.
Increasing interest has grown on the content of vanadium in drinking and thermal waters of Italy (WHO, 2000; Giammanco et al., 1996, 1998) in the last few years. Starting on November 1999 the Italian Health Ministry fixed the MACV (vanadium, AW 50.94, Group 5, VB) value at 50 mgyl for drinking water (Decreto del Presidente della Repubblica, 1988, n. 183, Decreto Legge, 2001, n. 31, Decreto Ministeriale, 1999, Italian law). The reason of concern came after finding that V concentrations were unusually high in drinking waters from the Etna volcanic massif in Sicily (University of Catania and Italian Health Ministry, 1995; Giammanco et al., 1996, 1998). Concentrations of V as high as 50–130 mgyl for drinking waters from Mount Etna area were measured through a study performed at the University of Catania, the Italian NRC and the Superior Institute of Health (SIH) of Rome.
Another metal that is attracting increasing interest because it can affect the quality of drinking waters is Co (cobalt, AW 58.93, Group 9, VIIIB). Several reports indicated that prolonged consumption of the element from waters may cause dermatitis, asthma and failures in the cardio-vascular system, at least when ingested at 5–10 mgyday (Barceloux, 1999; Nordberg, 1994). It is noteworthy that the MACCo value is not yet defined by law in Italy (Decreto del Presidente della Repubblica, 1988, n. 183).
Previously reported geological and mineralogical analyses indicate that the geological evolution of Tuscany produced volcanic bodies and volcanites and led to a large-scale geothermal activity that is still present in southern Tuscany and Mount Amiata area. Several areas have been mined for millennia and contain Mn, Fe, Cu, Zn, Sn, Sb, As (Carmignani and Kligfield, 1990; Serri et al., 1993; Grassi and Netti, 2000; Dall’Aglio et al., 2001; RIMIN Spa-ENI, 1990; Protano et al., 1998). The structure of the aquifer at Mount Amiata has a capacity of approximately 2=109 m3 of water and the regime overall annual withdrawal in the long term is estimated at approximately 65=106 m3 (Amministrazione Provinciale di Siena, 1994).
On the basis of these premises and in accord with our interest on metal ion–biomolecule complexes (Defazio and Cini, 2002; Cini and Tamasi, 2002; Cini and Pifferi, 1999; Cini et al., 2001), we determined the concentrations of V, Co, As and other elements in the drinking waters from the Siena countryside, focusing on the Mount Amiata area, which is volcanically active and rich in sulfide-containing mineral deposits. We report here on the highlights of this work.
Uses and Limitation
It is used for drinking water, which takes into account possible additive effects of N heavy metals on the human health that helps to quickly evaluate the overall quality of drinking waters
Categorization Table
The higher the concentration of a metal compared to its respective MAC value, the worse the quality of the water. MI value >1 is a threshold of warning (Bakan et al., 2010).
Standards Required
MAC, maximum allowable concentration, for Metal Index calculations was used according to the enforced law (Decreto del Presidente della Repubblica, 1988, n. 183, Decreto Legge, 2001, n. 31, Decreto Ministeriale, 1999, Italian law).
Variables Selection
Metal Index was defined to evaluate the quality of the water based on the content of 11 heavy metals (Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd and Pb) and As.
Calculation of Metal Index:
According to (Tamasi and Cini, 2004), the Metal Index is calculated by using the following formula:
\begin{eqnarray*}
MI = \sum_{}^{} \ {[C_{i}/(MAC)_{i}]}
\end{eqnarray*}
Where MAC is maximum allowable concentration Ci is mean concentration of each metal.
Case Studies based on Metal Index
Ismailia Canal is one of the most important branches of the Nile River in Egypt. It is the main source of drinking and irrigation water for many cities. Weighted arithmetic method of water quality index (WQI) was used to evaluate the water quality of Ismailia Canal according to drinking, irrigation and aquatic life water utilizations. The objective of the index is to transform complex water quality data into understandable and usable information by the public. The WQI values of Ismailia Canal are good to poor for drinking and aquatic life utilizations, and excellent for irrigation utilization. Metal index (MI) and pollution index (PI) were calculated to assess the contaminations of the canal water with the metals (Al+3, Cd+2. Cu+2, Fe+2, Mn+2, Ni+2, Pb+2 and Zn+2). MI and PI values denote the dangerous pollution of the canal water, which is described as seriously at most sites along, in particular for drinking and fisheries utilizations. It may be attributed to the effluents of different industrial wastes arriving at the canal water. Law 48/1982 for the protection of the Nile River and its waterways against pollution must be enforced to prevent the obvious deterioration of the canal water and to improve its quality.
The present study aimed to envisage the water quality status of Diyala River (Iraq) with respect to its heavy metal concentrations by preparing the most recent heavy metal pollution index, metal index and to evolve the sources of heavy metals. Ten locations were selected along of the Diyala River, from Kalar district to the confluence with Tigris River. Six heavy metals viz. Zinc (Zn), Nickle (Ni), Cadmium (Cd), Copper (Cu), Lead (Pb) and Chromium (Cr) were analyzed using Atomic Absorption Spectroscopy (AAS). The mean HPI 2097 far above the critical value of 100, indicates that Diyala River is critically polluted with respect to heavy metals. MI revealed low quality water with MI value 71.63, suggests that the river is seriously affected with respect to heavy metal. The study revealed the impact of anthropogenic sources on the pollution load of the river water.
References
Mohamed E. Goher, Ali M. Hassan, Ibrahim A. Abdel-Moniem, Ayman H. Fahmy, Seliem M. El-sayed (2014). Evaluation of surface water quality and heavy metal indices of Ismailia Canal, Nile River, Egypt. Egyptian Journal of Aquatic Research 40, 225–233.