DETERMINATION OF SOME HEAVY METAL IONS AND WATER QUALITY IN GROUNDWATER OF MANY WELLS IN ASSIUT , EGYPT

1. Environmental Affairs Department, Assiut University Hospitals, Assiut University(www.aun.edu.eg), Assiut, Egypt. 2. Egyptian Environmental Affairs Agency (EEAA), Assiut branch, Assiut, Egypt. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History


Methods And Materials:-
Chemicals and reagents:-All chemicals in this study were purchased from Sigma -Aldrich (Germany), Merck (USA), Kanto Chemical CO. (Japan), (A.R.E). The atomic absorption spectroscopic standard solutions (1.0 g/L) for the elements were purchased from (Merck) which is traceable to Standard Reference Material (SRM) from National Institute of Standards and Technology (NIST). Working standard solutions were prepared by diluting the stock solution using deionized water. Argon and acetylene gas with 99.99% purity, used in Atomic Absorption Spectrophotometer (Shimadzu Corporation) Model: (AA-6800).
Analytical procedures:-Water quality parameters, their units, reference methods and methods of analysis are summarized in table (1). The various parameters were determined using standard procedures [16]. The temperature, pH, electrical conductivity, salinity, turbidity and DO of each water sample were measured at the sampling points by (water quality analyzer (HORIBA .LtD) Model U-10-2M), were measured on site by (Ultra meter (Myron L company) Model: 6P), SO 4 -2 (Turbidimetry ), TDS were determined gravimetrically at 105-110 O C. total hardness and Ca hardness were measured by EDTA complexo-metry titration , the indicators are Eriochrome Black T and muroxide at pH 10 and 12, respectively . alkalinity determined by acid titration using bromcresol green as indicator. Total organic carbon (TOC) was determined by TOC analyzer (Shimadzu Corporation Model: (TOC-V CSN ). NO 2¯ -N, NO 3¯ -N, NH 3 -N were analyzed by Colorimetric method, UV spectrophotometer, Phenate method respectively using (UV-Visible spectrophotometer (Shimadzu Corporation) Model: (UV-1650PC). Fluoride was measured using SPADNS method. . Trace and heavy metal (Cu, Fe and Mn) were determined by FAAS using acetylene air flame while (Pb, Cd, Ni and Cr) were analyzed using electro-thermal atomic absorption spectrometer (ETAAS) (Shimadzu Corporation) Model: (AA-6800).
Water Sampling:-A total number of 44 water samples from Assiut city and some countryside were collected from selected productive wells. The selected samples were taken from the wells after they have been pumped for 10-15 min, in order to remove the stagnant water. The water samples were collected in previously rinsed three 500 mL capacity polyethylene and glass bottles. These bottles were immediately transported to the laboratory under low temperature conditions in iceboxes. The samples were stored in the laboratory at 4 o C until processed/analyzed.
For the determination of trace elements a 500 mL polyethylene bottle which are good tighted were used instead of glass bottles. This reduces the leaching of the trace element from the wall containers. Also, the storage of water samples into plastic bottles eliminates the adsorption of trace elements. The samples usually acidified with concentrated nitric acid to prevent the hydrolysis of these elements. The bottles were completely filled with water samples for protection and isolation from air. Finally, they were stored in a refrigerator. pH, salinity, electrical conductivity (EC), temperature, turbidity, dissolved oxygen (DO) and oxidation reduction potential (ORP) were determined in the site. All parameter were determined using the standard procedures (APHA, 2005) [16].

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Data treatment by statistical method:-Statistical analysis was carried out using Statistical Package for Social Sciences (SPSS) version 17.0

Classification of groundwater samples:-
The level of groundwater vulnerability depends on three groups of factors, i.e., natural, human-induced, and physicochemical [4]. Groundwater depth; is one of the natural factors .
In this study we are classified the wells under investigation according to the depth of well into two group: Group A: low depth wells ( 50 -80 m) Group B: high depth wells ( 80 -100 m )

Determination of Hydro-chemical properties:-
The parameters of Hydro-Chemical such as: pH, salinity, electrical conductivity (EC), temperature, turbidity, dissolved oxygen (DO) and oxidation reduction potential (ORP) were determined in the site. The obtained data for group A, samples which collected from wells of groundwater with high depth, were recorded in Table2. Also, The obtained data for group B, samples which collected from wells of groundwater with low depth, were recorded in Table 3.  According to a salinity classification by Rabinove et al [20], the groundwater was classified as shown in Table 4. Table 4:-Classification of water on basis of Total Dissolved Solids (TDS).

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Classification of groundwater TDS (mg/L) Non-saline <1000 Slightly saline 1000-3000 Moderately saline 3000-10000 Very saline >10000 The presence of high levels of TDS in water may be objectionable to consumers owing to the resulting taste and to excessive scaling in water pipes, heaters, boilers and household appliances [21].
Applying the classification from table 4 on the obtained data it is found that:  On group A (high depth wells), there are 13 wells ( less than 1000 mg/L) Non-Saline water. While, there are 5 wells ( 1000-3000 mg/L) Slightly saline water.  On group B, (Low depth wells), there are 25 wells ( less than 1000 mg/L) Non-Saline water. While, there are only one well ( 1000-3000 mg/L) Slightly-Saline water.
This means that, the depth of well can affect on the TDS of water . The low depth groundwater wells have Nonsaline water more than high depth well. Relatively high salinity may be due to the lithologic composition of these locations, in addition the leaching and dissolution of the soil salts and chemical fertilizers by irrigation water. The lower salinity was observed in the group B, wells no. (4,5) this due to the seepage of the Nile water into these regions (the wells are near to the river Nile stream for about 400 m).  [22] classification, , shown in Table  5. Total Hardness (T.H.) were determined for two groups of wells and summarized in Fig.3 WHO Limit : 500 Egyptian Limits: 500

Determination of Some Metal Ions:-
The suitability of the water from the groundwater sources for the drinking and domestic uses was analyzed by comparing the values of different water quality parameters with Egyptian guideline standard for drinking water [23]. WHO (World Health Organization) standards [24].  However, concentration of total Fe (0.09-4.1 mg/L), Mn (0.01-1.7 mg/L) and Cu (0.0024-1.7 mg/L) were relatively high, Relatively high concentration of these metal are due to the mobility of trace metals in presence of high concentration of chloride ion. Chloride complexation increases the metals mobility [18] and decreases adsorption [19].

Suitability of the groundwater in Assiut city and countryside for irrigational purposes:-
Groundwater in the study region finds intensive use in irrigation. Its suitability for irrigational purposes can be assessed using the indices for salinity [25]. Salinity index of the groundwater samples was computed using the measured electrical conductivity values. Water exhibiting low to moderate salinity (classes I and II) are not considered very harmful to soils or crops, whereas, those exhibiting high salinity (class III) are suitable for irrigating the medium and high salt tolerant crops.
High salinity water (class IV) is suitable for irrigating high salt tolerant crops, whereas, water of salinity (class V) or above is generally unsuitable for irrigation. Majority of the groundwater samples (73%) in the study region are categorized as class I or II, and thus, may be considered as suitable for irrigation. However, about 27% of the water samples are found to exhibit high salinity (classes III), and are suitable for irrigation ( Figure 13).
Low salt tolerance crops are usually chloride sensitive. The chlorinity index of the groundwater sources was calculated using the measured chloride ion concentration in water ( Figure 5). Majority of the groundwater samples (100%) are found to be suitable (classes I and II) for irrigation. Low salt tolerance crops are usually chloride sensitive. The chlorinity index of the groundwater sources was calculated using the measured chloride ion concentration in water ( Figure 5). Majority of the groundwater samples (100%) are found to be suitable (classes I and II) for irrigation.

Suitability of the groundwater in Assiut city and countryside for industrial purposes:-
Water is considered safe for industrial use, if it is neither scale forming nor corrosive in nature. The saturation index of water is an important parameter for assessing its tendency for precipitating out or dissolving calcium carbonate.

Determination of Langelier Saturation Index (LSI):-
The LSI is defined as the difference of actual measured pH of water (pH w ) and calculated pH which the water would have when in equilibrium with calcium carbonate (pH s ) as follows: Where pH s , the pH at saturation in calcium carbonate is calculated as LSI = pH w − pH s (1) pH s = (9.    Res. 4(10), 503-521 517

Determination of the Ryznar Stability Index (RSI):-
The RSI is calculated as: RSI = 2(pH s ) − pH w (2) Where pH S is the pH at saturation in calcium carbonate and pH w is the measured pH of water. RSI value of< 6 indicates increasing tendency for scale formation with a Decreasing index value, whereas, a value of > 7 suggests formation of no corrosion protective films. Water with RSI > 8 suggests tendency for dissolution of CaCO 3 , and thus corrosive in nature. The RSI values of the groundwater samples are shown in Figure (16).

Water Quality Index(WQI):-
The water quality index (WQI) allows the reduction of vast amounts of data on a range of physico-chemical and biological parameters to a single number in a simple reproducible manner. The assessment of heavy metals is included with water quality parameters in order to assess overall pollution of water. WQI is calculated from the point of view of stream water quality criteria with regard to all uses [27][28]. Fourteen water quality parameters (NO 2 ‾, NO 3 ‾, NH 3 , F ‾, Cl ‾, TDS, T.H, Cd, Fe, Mn, Cr, Cu, Ni, and Pb) were considered according to their importance as water quality assessment indicators. The overall water quality index can be calculated as follows: Where: n = number of parameter, qi = quality rating for the i th water quality parameter. The quality rating can be obtained by the following relation: qi = 100 (Vi/Si) where Vi = observed value of the i th parameter at a given sampling site and Si = water quality standard for i. The permissible or critical pollution index value is 100. The average water quality index (AWQI) for n parameters can be calculated using the following equation: The AWQI = 0 when all pollutants are absent, and the AWQI = 100 when all pollutants reach their permissible limits. Values of AWQI exceeding 100 indicate that the water sample may suffer from serious pollution problems. 518 The computed AWQI value ranges from 18 to 137 and therefore, can be categorized into five types "excellent water" to "water unsuitable for drinking". Table (6) shows the water quality classification based on WQI,  The high value of AWQI at this case has been found to be mainly from the higher values of iron, total dissolved solids, manganese, fluorides, and hardness. The AWQI for all wells was below the value (100) which refers to the water manly good water.    [15].

Correlation of quality variables among groundwater:-
Also, positive correlation value (r = 0.657) between Mg and SO 4 -2 , indicate that the main water type in samples is (Mg SO 4 ).
Fe correlates inversely with ORP (r = -0.4, table 20) indicate that the concentration of dissolved Fe would be influenced principally by the redox potentials of groundwater systems. The presence of high levels of (Fe) is possibly a result from the reductive dissolution of Fe oxides under the lower redox levels of groundwater [29]. The occurrence of trace elements is possibly influenced by redox levels and nature of underlying sediment.
Fe & Mn correlates inversely with DO (r = -0.27,-0.23 respectively) indicate that the extent to which Fe and Mn dissolve in groundwater depends on the amount of oxygen in the water. When at higher dissolved oxygen levels, iron occurs as Fe 3+ , while at lower dissolved oxygen levels, the iron occurs as Fe 2+ .Where Fe 2+ is very soluble in water and Fe 3+ will not dissolve in water.
In addition, there was no correlation of Mn with other elements (Table 8) indicate that the manganese in water samples probably originated from amorphous state, [30].
No correlation of Cd with other elements, indicating that the dissolution of mineral phase could not be the source of cadmium. Where don't find any manufactures producing Cdcontaining wastes in study area [30]. High positive correlation (r =0.93) are observed between TOC & COD indicate to COD and TOC specify the loading of organic matter in water samples.

Conclusion:-
The study clearly indicate the most ground water of Assiut city and some countryside suitable for drinking and human use in accordance with the limits of law of the Egyptian drinking water with exception of wells No.[(9, 10, 11, 12, and 13) from group A, while only well No. 9 from group B ) . Most of wells should be treated for Fe and Mn. Most groundwater samples can be used for irrigation and industrial purposes (negative values of sat. index) and for different uses (WQI). The depth of well can affect on some parameters of water quality such as, the TDS of water. The low depth groundwater wells have Non-saline water more than high depth well. Statistical analyses confirm results of chemical analysis and exhibits good and interesting correlations lead to interpretation these results.