An evaluation of waste and well water quality for agriculture production around Erbil city, Iraq

: Erbil city is located in the northern Iraq with a population of over one million people. Due to water crises farmers usually use wastewater and well water for the agricultural production. In this study six stations were designed to sample waste water and three from well water to define waste water and ground water characteristics. In this study, Residual Na + Carbonate, Mg ++ hazard, salinity hazard, Kelley index, %sodium, total hardness, permeability index, potential salinity, sodium adsorption ratio, and Irrigation Water Quality Index (IWQI) were determined. The order of average cation concentrations in water was Mg 2+ > Ca 2+ > Na + > K + . While the proportion of main anions in water were HCO 3 >SO 4 > Cl. The highest concentrations of Ca 2+ , Mg 2+ and Na + were found in well water, while the highest concentration of K + was found in wastewater. The maximum concentration of HCO 3 and Cl recorded in well water, while the highest concentration SO 4 recorded in wastewater. Moreover, the order of trace elements was Pb > Al > Fe > Cd > As > Mn >Cr > Ag > Ni. Keeping in mind metal concentration set by US EPA and FAO (1999) and (1994) guidelines the levels of Pb, Al, Fe, Mn, Cr, Ag and Ni in the waste and well water were within the admissible limitations for irrigation schemes. Moreover, limitations of As and Cd were beyond permissible limitation need to be reduced. The IWQI ranged from 88.92 to 95.09 in the waste water samples. Overall assessment reveals that cultivated agriculture plants were secured from toxic compounds.


Introduction:
Water elements are one of the virtually important factors due to the fact that they have a direct bearing on human health and other living things 1 . Excessive water usage, together with population and economic expansion, will reduce each person's water supply and threaten the global ecosystem's fauna 2 . Water quality assessment is a crucial tool for long-term success and provides valuable information for water executives. In a number of countries with severe or semi-hard climates, the quality of surface water is a sensitive and critical issue 3 .Farmers are compelled to utilize wastewater for agriculture due to rising urbanization and a scarcity of freshwater globally, particularly in developing nations. It provides substantial advantages to farmers who lack access to treated wastewater 4 .This farmland will treble due to population growth according to 5 , Wastewaters ninety nine point ninety eight percent water, 0.02-0.03% hanging particles, and soluble biotic and abiotic components. Biotic and abiotic pollutants degrade water quality aquatic structure and abundance have improved 6,7 . Erbil's sewer system handles storm and grey water. Cesspools and septic tanks treat toilet black water. Erbil City has neither integrated nor separated sewers. In newly built communities and villages in Erbil City, small-scale wastewater treatment plants are required under investment legislation to treat wastewater. Erbil wastewater is often utilized for irrigation directly and enters the Greater-Zab River near Gwer without treatment 8 . Researchers must analyze the fluctuation of trace elements and content in the pair surface water and groundwater to reduce pollution and improve water quality. Trace elements, unlike organic contaminants, are non-biodegradable and aggregate in living being's; in addition, many ions of trace metals are poisonous or carcinogenic 7, 9 . Heavy metal bioaccumulation in food chains and their toxicity as concentrations rise have hampered their separation and purification. Due to stricter regulations, toxic metals are a major ecological problem 10 . Furthermore, composition and amount of soluble salts used to test water quality (for human and livestock consumption, crop irrigation, and so on). Sodicity, salinity, and ion toxicity are key irrigation fluid factors. It's salty. Sodicity degrades soil structure. Toxicity is the concentration at which CO3 2-, HCO -3, Cl -, Na + , Mg 2+ , and other trace ions harm plant development 11 . Horton 12 was the first to propose employing the WQI, and since then several researches have been published for various aquatic systems 2 , an irrigation water quality index (IWQI) is a single, unit less value obtained from a complex computational technique using numerous hydrochemical factors 13 , as well as well-known indices like as potential salinity (PS), permeability index (PI), Kelley index (KI), etc. 14 . In this study a comparative analysis of waste and well water quality is provided to understand whether the use of both waters for agriculture is safe. In addition, vegetable qualitative analysis is given to determine if human consumption will have no health risk. In this study a comparative analysis of waste and well water quality is provided to understand whether the use of both waters for agriculture is safe. In addition, vegetable qualitative analysis is given to determine if human consumption will have no health risk.

Materials and Methods:
Erbil is the capitol of Iraq's Kurdistan region. The studied area is located southwest of Erbil city till Demhat region, between 36 o 16' 95'38" E to 36 o 10' 07'62" E and longitude 43 o 92' 97'34" N to 43 o 81'22'71" N, by using GPS (Garmin type), three sites (vegetable field) were selected along Erbil wastewater channel or irrigated with Erbil waste water with three sites (vegetable field) irrigated with well water the location of well waters near the Erbil wastewater channel in general all studied sites is located on Turaq region,  15 .Calcium and Magnesium ion was determined using EDTA-titrimetric method as described by 15 . Trace elements in each water sample were determined by ICPE-9820 Shimadzu. The method was conducted according to (ICP multielement standard solution IV) at Bashmakh quality control lab, following condition spectrophotometer chosen for the determination of Cr, As, Cd, Cu, Fe, Zn, Ni, Hg, Al and Pb. To prevent mineral binding on the container walls, 4 mL of conc. HNO -3 was added to a (1-liter) retention filtered water. The levels of measurement were (milligrams per liter).

Irrigation Water Quality:
Presence of undesired attenuated salts or components is a key criterion for determining irrigation water appropriateness 14 .Sodium -Adsorption-Ratio (SAR), Permeability Index (PI), Magnesium Hazard (MH), Sodium percent (Na%), Total Hardness (TH), Potential salinity (PS), Kelly's index (KI), Residual Sodium Carbonate (RSC), Tables. 2 and 3, illustrate the irrigated agriculture water quality index (IWQI) and its categories. The formulae in Table. 2 are used to transform the analytical data of several qualities of water metrics into a single number.  16 The Design of (Irrigation Water Quality Index IWQI) The (IWQI) design given by 26 is implemented in three steps: 1-Identifying the parameters that have the greatest influence on the quality of irrigation water. 2-The Eq.1 was used to determine quality measurement (Qi) and aggregate weights (wi) for each parameter based on irrigation water quality parameters suggested by the University of California committee of consultants (UCCC) and recommendations specified by 27 . It was designed in accordance with the criteria of water quality were expressed by a non-dimensional numeric; the greater the score, the more appropriate the water qualities.
Qi = qi max -[( Xij -Xinf ) * qiamp / Xamp] ……. 1 Where; qimax : the class's maximum qi value ( unit less). xij: the parameter's actual value. xinf: the value corresponding to the lower limit of the class to which the parameter corresponds qiamp : xamp denotes the class amplitude where the parameter relates.
To assess xamp in the final class of every parameter, the upper limit was deemed to be the largest value achieved by physical-chemical and chemical examination of the water samples. 3-Establishing the weight value (wi) to every parameter according with Table.4 As indicated, the variables are transformed so that their total equaled one. IWQI is a dimensionless parameter with a range of 0 to 100, qi is the quality of the ith parameter and has a number from 0 to 100, which is a function of its concentration or measurement, and wi is the normalized weight of the i th parameter, which is a function of its significance and illustrates water quality fluctuations. The recommended water quality index is utilized to categorize the categories into their appropriate groupings. The classifications provided by summarize the hazards of water salinity, slow soil water penetration, and plant toxicity. 28,29 .

Statistical analysis and software used:
A one-way analysis of variance (ANOVA) was performed on the data of physicochemical parameters, trace metals, and quality indices that were managed to gather from the six sites. The ANOVA analysis, along with the various water parameters and trace elements from six different locations, were subjected to Pearson's correlation testing. Additionally, the data of water chemical parameters and trace elements were analyzed using the (PAST 4.03) program for principal component analysis (PCA). On the basis of cation and anion data, the piper plot was created using the Diagrammes software. The sampled sites were plotted and classified using Doneen 16 , Wilcox 24 , and US salinity Richards 17 diagrams.

Results and Discussion:
Waste and well water characteristics The hydrochemical characteristics of surface water and well water samples were determined, collected from six sites are listed in Table. 5. Three sites along Erbil's wastewater and three sites on well water were monitored, with the water from six sites being used for vegetable irrigation. The pH fluctuated from 7.63 in S5 to 7.92 in S6, with an average of 7.80, indicating that the waters were neutral to alkaline. pH changes are connected to changes in conductivity and bicarbonate content 18 . EC ranges from 809 to 1078 S/cm. EC may be used to determine the total quantity of dissolved salts in water. Temperature, concentration, and ion types affect outcomes. 30 All examined locations have satisfactory EC ratings 31 . TDS concentrations ranged from 517.76 to 689.92 mg/l, with a mean of 586.13 mg/l. The fundamental hydrochemical characteristics of surface water are mostly determined by the main ions that are present 32 . All samples exceeded the 500 mg/l TDS limit 32 . Major cations make up around 60% of the total dissolved solids (TDS). Magnesium and calcium are the most frequent cations, accounting for 33% and 17% of TDS, respectively. Major ion concentrations control the basic hydrochemical characteristics of surface water. Except for Mg 2+ , the mean of the examined anions and cations is below permissible limits, the amount of Mg 2+ in three sites especially the well water samples are over acceptable limits 33 leaching of rocks into well water may contribute, 34 as well as the soil containing a high quantity of dolomite, which is high in magnesium, or it might be owing to the higher quantities of magnesium coming from fertilizer used by farmers to boost output, and then the magnesium ion seeping into ground water, although high concentrations of magnesium may also cause dispersion with some clays, while K + ions in three sites of waste water are over acceptable limits 33 , as shown in Table. 5, may be as material disintegration as a consequence of the decomposition of plant material and the runoff from agricultural activities 10 . In surface water, the main cations were Mg 2+ (58.95), Ca 2+ (40.11), Na + (33.68), and K + (3.55).  The domains of magnesium ion on other cations documented in this research are partly attributable to the local soil and watershed's geology. Well water has more magnesium than waste water due to Clay minerals, a source of magnesium ion in water and ferromagnetic igneous rocks. It's possible that the low amount of K + in comparison to Mg 2++ , Ca 2++ , and Na + is related to the fact that clay minerals may easily fix it 35 . In studied samples the sequence of major anions were HCO3 -(442.66 mg l -1 ) > SO4 (65.79 mg l -1 ) > Cl -(29.66mg l -1 ) > CO3 2-(0.00 mg l -1 ). The most common dissolved ions are bicarbonate, sulphate and chloride. It contributes for 82 %, 12%, and 6 %, sequentially, of the total anions. In the corresponding unit, the chloride concentration provides 5.5 percent of the total anionic concentration. All Clscores are below those recommended by WHO. 32 The recommended limit of 250 mg l -1 while HCO3concentrations are within the WHO except Site 5 well water are above the WHO's recommended levels., 500 mg l -1 32 . It's possible that this is due to the presence of natural produce in the aquifer, which is oxidized to create carbon dioxide and encourages mineral dissolution 36 . Half of the HCO3 ions would come from the fossilized carbon in the calcite and dolomite in the aquifer. The amount of calcium, magnesium, and bicarbonate ions in the groundwater goes up because of the process of weathering. When silicate minerals break down over time, bicarbonate ions may be made 37 . The concentration of CO3 all studied samples was 0.00 mg.l -1 the reason is due to the pH value is less than 8.2 14   According to this diagram, HCO3. Na was found to be the most prevalent water type across the research sites. The hydrochemical surfaces of six distinct water sources were affected by ion exchange, evaporation, and concentration 40 . With respect to major anions, water belonging to HCO3 dominant Fig.2. The highest SO4 − concentrations are found at the sites of S1, S2 and S3. Regarding the major cations, the water belonging to Mg dominant type except for at S1 where it was no dominant. The above results may be due to the type of soil,, ,the nature of sewage discharge and the solubility of calcite rock which is abundant in the study area is more rapidly than dolomite or visversa. 12

Trace elements concentration
The mean concentrations of Ag, Al, Cd, Cr, Fe, Mn, Ni, Pb, Zn, As, in the surface water samples collected on three sited of wastewater channel and three well water are shown in Table 6. The following is the sequence of mean metals concentrations in water: (in mg l -1 ) Pb (1.2933)< Al   Table 6. Concentrations of metals in waste water sampled from six locations.
In general, most metals had larger concentrations in waste water sites, with the exception of Cd and As, which had high concentrations in site 2 (well water). The causes for this may be traced back to the fact that waste waterways take massive volumes of agricultural drainage and sewage, as well as industrial wastewater 10,42 . The quick movement of contaminants and the ability of metals to attach onto clays, biological matter, iron, and manganese oxides, as well as other particles in water 43,44 .Other causes include the hydrogeological and geochemical features of the examined region of well may impact metal transport in groundwater 44 , 45 . According to the US EPA and FAO 33,45 , Ag, Al, Cr, Fe, Mn, Ni, Pb, and Zn concentrations in all analyzed locations are below the recommended limit for irrigation, however Cd and As concentrations are greater than those reported by US EPA and FAO. The reason is that oil refineries and iron production plants are only a few kilometers away from the study site. This means that the amount of cadmium in each water sample is getting higher. Cadmium can get into water systems through the movement of groundwater and the release of chemicals from the materials that contain it. Pesticides are used by farmers to safeguard their crops and maximize yields. Arsenic appears to be extremely widespread since it was once used in pesticides. Arsenic may get into water systems through runoff from nearby farms, making the amount of arsenic in the water go up 41 .

Correlation among Chemical Characteristics of Water and Trace elements:
To investigate their effect on the kinetics of trace elements in the water body, a Pearson correlation matrix was employed. Table. 7 Correlation analysis may be used to determine the strength of a link between any two variables 46 . There are many things, both natural and man-made, that can change the pH of water. Most natural changes happen when things touch the earth's crust. In aquatic systems, salinity may show how much land imports affect water streams to some degree 47 . pH and Mg 2+ exhibited a positive connection with a value of r = 8.00. TDS had a positive connection with EC and Cd, with r = 1 and 0.926, respectively. (Table 9). The concentration, distribution, and transit of trace elements throughout the estuary were affected by pH, temperature, dissolved oxygen, and salinity 48,49 .
The principal replaceable ions at the sites that were investigated had substantial connections with a wide variety of cations and anions. Table 7    Ag showed appositive correlation with Zn, r = 0.927. Fe and Ni had a 0.923 and 0.964 correlation with Mn and Pb, respectively. Even though pH is thought to be a key factor in determining how much metal is available 50 , the present data demonstrated a negative correlation between pH and the examined trace elements, with the exception of Cd, for which no significant correlation was seen. PCA was used to link the trace elements with the investigated locations, Principal Component Analysis waste water and well waters had PC1 described 42.21% of the components in waste water and well waters, PC2 explained 26.89 %, five Principal Components were required to describe 95% of the overall variation, as seen on the screen plot of Fig. 3. The large proportion of PC1 indicates that the variables are substantially connected already Principal Components having an eigenvalue > 1 were selected for further analysis using the Kaiser criteria 51 . Table 8's eigenvalues supply this information, and PC1 and PC2 will be utilized depending on it. It disregards PC5 since its eigenvalue is less than 1, the eigenvalue of PC3 and PC4, is much smaller than PC1 and PC2, and shows few variables. Bi plots can be seen in (Fig. 4)   Cd and As exhibited a strong association in our study Fig. 4, indicating that they posed health hazards. Using polluted water to irrigate leads to heavy metal contamination of the soil, which is then transferred to the crops or plants. There are two ways trace elements which may enter vegetables: first, they can be absorbed from polluted soils; second, they can be deposited on the surfaces of vegetables that are exposed to polluted surroundings 52 . When consumed on a consistent basis, trace elements may lead to a variety of adverse health effects in humans as well as in other species 53 . A number of different malignancies have been linked to long-term exposure to very small levels of carcinogenic trace elements 54 . According to the criteria set by the International Agency for Research on Cancer (IARC), arsenic, cadmium, and chromium are all "carcinogenic to humans" 55 . Because of this, these three cancer-causing substances were analyzed to determine the chronic health hazards they posed, both carcinogenic and non-carcinogenic.

Irrigation Suitability Assessment: Permeability Index (PI)
Doneen 16 presented a PI-based classification scheme for irrigation water. This takes into account the soil's concentrations of Na + , Ca ++ , Mg ++ , and HCO3. The PI scores in the research region vary from 37.86 % in S2 to 66.30 % in S1, as shown in Fig. 5 16 . The PI may also be used to determine whether or not the water is suitable for use in irrigation 30 .

Sodium Adsorption Ratio (SAR):
Irrigation water with high extents of salt is of particular concern because sodium has negative impacts on soil, bearing a sodium hazard. Additionally, the SAR categorizes salt threats, which may lessen the soil's permeability and hinder plants from taking up water 57 . Soil particles absorb sodium and become bonded to it. Whenever the soil is dried, it dries out and becomes hard and tight.
Making water penetration more difficult. Soils having a fine texture, particularly those that include a significant amount of clay, are more vulnerable to the effects of this activity. For the preservation of soils with high SAR levels, certain amendments could be necessary. If appropriate concentrations of Ca ++ and Mg ++ are present in the soil, they will work to mitigate the consequences of Na + exposure and contribute to the upkeep of good soil properties 58,59 . SAR is used to categorize surface water into four categories: excellent (SAR < 10), good (10 < SAR < 18), doubtful (18 < SAR< 26), and unsuitable (SAR > 26). Water samples' SAR ranged from 3.33 to 6.34, with an average of 4.94. Table 9. As a result, according to Wilcox 24 and Richards 17 , all studied samples are excellent Table 10. By comparing the SAR to the EC on a USSL diagram, one might get more insight into whether or not water should be used for irrigation 17 . All of the water samples in Fig. 6a are of the high salinity/low sodium type (C3-S1, acceptable for irrigation; S1). The amount of sodium that is soluble in surface water is expressed as a percentage called the Na percent. This measurement is also used in calculating the risk of sodium exposure. Na + percent is a common statistic used in the determination of the viability of natural waters for irrigation because sodium interacts with the soil and reduces permeability 24 Water with an Na percent concentration is more than 60%, according to 58 . This may create salt accumulations and soil deterioration. Alkali soils arise when sodium combines with carbonate; saline soils form when sodium combines with chloride. The percent Na + in the study area's surface waters ranges from 17.54 percent in S5 to 38.71 percent in S1, with an average value of 28.31 percent, Table. 9. Therefore, according to Ravikumar, et al. 19 and Eaton 25 , the sampling sites of the Erbil wastewater Canal and well water are good/safe for S1, S3, S4 and S6 sites and Excellent/safe for S2 and S5 sites, Table 10. The Wilcox 24 diagram linking sodium percent and EC shows the sites S1, S3 and S4 wastewater samples fall in the "excellent" region While the sites S2, S5 and S6 well water samples fall under the "Good" region Fig. 6b.

Residual Sodium Carbonate (RSC)
Because it determines whether or not there is a correlation between the amount of carbonate and bicarbonate present and the overall concentration of calcium and magnesium, RSC is a good measure for analyzing the adequacy of irrigation water 39 . When the water content of the soil becomes more concentrated, waters that include high concentrations of HCO3 have a greater propensity to precipitate Ca 2+ and Mg 2+ . As a consequence of the formation of sodium carbonate, soils that are watered with water that has a high RSC risk becoming unproductive 46 . When the RSC levels are lower than 1.25 meq L -1 , it is deemed safe to conduct irrigation. The usage of water with a relative salinity concentration (RSC) ranging from 1.25 to 2.5 meq L -1 is regarded marginal and may be done so with proper irrigation planning and laboratory soil salinity testing. RSC concentrations that are higher than 2.5 meq L -1 are regarded as being inappropriate for irrigation 24,25 . The analysis found that all of the samples could be used for irrigation, with the RSC of the well water being excellent and that of the wastewater being medium. Table. 10.

Magnesium, Hazard(MH):
In most waterways, calcium and magnesium are in a condition of balance. Soil alkalinity is caused by a high level of MH (>50%) in a water sample; also, a significant amount of water is adsorbed among mag nesium and clay particles, decreasing the soil's infilt ration potential and consequently damaging crop yie lds 19,39 . Water samples had an MH ranging from 47 .63 to 82.81 percent (mean = 59.40 percent), Table9 . Except for S1 and S2, which are below 50%, all o f the samples are over 50%, making S1 and S2 suita ble for irrigation and S3 to S6 unsuitable Table 10, may be as a result of the presence of magnesium in ground water and wastewater that has been in interaction with particular of geological materials, particularly limestone and gypsum. Magnesium is released as a byproduct of the dissolution of these materials. 39

Kelly's Index (KI):
Kelly 34 introduced Kelly's index as an important criterion for assessing irrigation water quality. This value is calculated using the Na, Ca, and Mg levels in the water. When it comes to irrigation, water that has a KI value that is higher than one (KI > 1) is seen as unsuitable, while water that has a KI value that is lower than one (KI 1) is regarded as being appropriate. Throughout the course of this inquiry, the KI of the water sample varied anywhere from 3.33 to 6.64, with a mean value of 4.94 Table. 9. As a result of Kelly's ratio Table. 10, all of the analyzed locations are declared inappropriate for irrigation, which might be owing to high cation exchange, which supplies sufficient Na + 60 .

Total Hardness (TH):
The distinctive flavor and texture of hard water is due to the natural buildup of calcium, magnesium ions, and salts, or both. The total hardness equals the product of calcium and magnesium hardness. The total hardness (TH) categorization of groundwater categorized all wastewater canal and well water samples as soft water. After examining the samples, this conclusion was reached. The hardness values vary from 4.80 meq L -1 to 9.40 meq L -1 , with the mean value being 6.85 meq L -1 Table. 9. According to Durfor and Becker 23 , the maximum amount of TH permitted for use irrigation is 60 meq L -1 , while 120 meq L -1 is deemed to be the most appropriate limit. Table 10 indicates that the study locations are all deemed soft.

Potential Salinity (PS):
The potential salinity of a water body is equal to the concentration of Cl -, 50 % of the concentration of SO4-(PS). The PS value is a parameter-based water quality indicator that is used for categorizing irrigation water. 16 . Salts with limited solubility are known to precipitate and concentrate in the soil, making them suitable for irrigation. In contrast, salts with hydrophilic properties tend to increase soil salinity 61 .This analysis found that the amounts of PS in the water samples varied from 1.24 to 2.06 meq L -1 . with a mean of 1.52 meq L-1 Table 9. That is to say, all samples are rated Excellent to Good Table. 10.

Irrigation Water Quality Index (IWQI)
IWQI defines irrigation water quality as a single number, eliminating the requirement for huge data intervals. IWQI compares water quality measurements to criteria 21 . The irrigation water quality index is calculated using water consumption restrictions for each soil type. Ionic composition estimates irrigation water quality 62 . The categorization of the water's quality according to the IWQI measurements is indicated in Table. 9, which shows the WQI calculation for water samples. The IWQI value in water samples in this investigation ranged from 91.60 to 94.61, with a mean of 93.52. All of the places that were investigated were sampled (No restriction) 28,29 indicating that most plants and soils have negligible toxicity concern, with a low likelihood of generating salinity and sodicity problems. With the exception of soils that have an exceptionally low permeability, it is suggested that irrigation strategies include leaching 28,29 .

Conclusion:
Based on the overall assessment, it is concluded that anions and cations examined in this study are within the permissible limits. The domains of magnesium ion on other cations recorded in present study as well as the level of magnesium in well water are larger than in wastewater. The sequence of major anions is bicarbonate, sulphate and chloride. The ternary diagram is plotted in a piper plot, and the results showed that the most common kind of water is HCO3.Na in all the studied sites, Ag, Al, Cr, Fe, Mn, Ni, Pb, and Zn levels in all studied sites are within allowable limits reviewed for irrigation purposes, according to the US EPA and FAO. However, the levels of two carcinogenic metals, including Cd and As, are discovered in higher concentrations than those documented in the US EPA and FAO; this is the case even though the permissible limit is within the acceptable range. Most metals have larger concentrations in waste water sites, with the exception of Cd and As, which had high concentrations recorded in site 2 (well water).The positive correlation found among pH with Mg 2+ ,TDS -EC and Cd, K -SO4, Mg-Cl, K -Fe, K -Mn, Fe -SO4 and Mn-SO4 , Cr shows a significant positive correlation with Ni and Pb , Ag showing a positive correlation with Zn and Fe and Ni is in a positive correlation with Mn and Pb. According to PI, SAR, Sodium percent, RSC, TH,PS and IWQI indexes the studied sites water is suitable for irrigation purpose for depend on KI index water of the studied sites which is unsuitable. According to MH index S3,S4,S5 and S6 is unsuitable for irrigation