Assessment of Cadmium in Maize and Millet of Different District using Canal and Wastewater Irrigation

The article is focused on concentration of cadmium in maize and millet collected in 20182019 from different district (Sargodha, Faisalabad, Sheikhupura, Lahore and Kasur) of Punjab under different irrigation sources Canal and wastewater. The values of Bioconcentration factor, Translocation factor, Pollution load index, Daily intake of metal, Health Risk Index and Enrichment factor were studied to evaluate the effect of heavy metal accumulation on grains quality and human health. Most of the metals observed in wastewater were present in high amount. Cd concentration increased considerably under wastewater irrigation in soil (1.06 mg/kg) and grains (1.05 mg/kg). Cd showed highest bioconcentration (3.82 mg/kg) in canal water. Wastewater irrigated soil exhibited the maximum Pollution Load Index (PLI) values as compared to control treatment. Under the influence of wastewater irrigation, Cd concentration increased considerably in soil and grains. The purpose of study is the labeling of Maize and Millets species of the area according to their toxicity/desirability for use as human food and fodder.


Introduction
Irrigation of the crops which is carried out by the wastewater affects the crops and soil properties negatively. It induces the amount of toxic chemicals in the crops and imbalance the nutrients consequently leads toward the toxicities in crops and causes harmful effect on consumers [1,2]. Human activities also play an important role in the heavy metal contaminations [3,4]. Anthropogenic activities in collaboration with the nature affects to increase the heavy metal adversely affects the life by different ways [5].
Crops cultivated by the wastewater contain different types of nutrients some are beneficial to grow crops but also contain very harmful substances involving heavy metal such as chromium, lead, cadmium, and nickel which ultimately accumulated in environment and lead to damaging effects in living beings [6].
The momentous toxicity is produced by heavy metals in any form [7]. Among the prevalent cereals Maize (Zea mays) is of significant importance as it provides the source of food and protein for human and animals in several ways. It is used for maize grains and silage for animals to use for food. Maize is also used for industrial purpose to make the fuel. High yield of maize can be obtained without compromising the quality of the crops by using the treated wastewater. The crops which were irrigated with the wastewater give the better result and the yield and the quality was also increased [8,9].
Agricultural activities are confined in areas where water is in sufficient amount, scarcity of water inhibit the agriculture. To overcome the demand of water and to meet the requirement of food for the population, farmers are using the wastewater to meet the water deficiency. Wastewater is undone by the treatment plant to enhance the food quality and safety and reduce the water pollution [10].
Many health complications arise due to the penetrating metal absorptions in soil which are captivated by the rising plants resulting in food chain contamination [11]. It was revealed by different studies that the crops which were grown by the wastewater absorb the heavy metal to such an extent that their amount grows higher than the prescribed limit affecting the consumers hazardously [12]. The aim of study is to determine the concentration of heavy metals in water, soil, plants (maize and millet) irrigated with different sources of water.

Materials and methods
Current research was performed in different districts (Sargodha, Faisalabad, Sheikhupura, Lahore and Kasur) of Punjab during the year 2018-2019. Samples of shoot, grain and soil were gathered from various sites of five districts and made composite sample or one replicate. Four replicates of soil, shoot and grain of maize and millet were collected from different sites in each district. All types of water samples irrigating these grains (canal water and sewage water) (100 mL each) were taken from 5 different districts of Punjab. All the samples placed in polypropylene bottles washed with nitric acid (1%) and later that samples were taken to the research center and stored at 4 o C until analysis [13].
Total 80 replicates of soil samples from five districts were collected. Samples of soil (one from each corner and one from center of fields) from depth 0-15cm were collected from each district. The soil trials were put into constricted bags and conveyed to test center for heavy metals analysis to avoid internal mixing and external contamination. Five composite soil samples were prepared and dried in air, and put in forced air oven for 48 h at a temperature of 72 o C. These composed samples were dehydrated, kept in categorized wrapped envelopes and kept in incubator for 5 days at a temperature of 70 o C [14]. Shoot and grain samples of maize and millet were rinsed with condensed water and placed in paper bags. Each sample was assigned identity.
Samples of soil, shoot and grain after aeration were then kept in the oven at temperature of 72 o C until it becomes completely dried. After taking away from the oven, grains were detached from the shoots and crushed in the pestle and mortar to make powder of it. Each sample weighed 1 g was used for finding heavy metals. Wet digestion method is used for the breakdown of samples of soil, shoot and grain.
The dried samples were placed in a small conical flask and digested with conc. HNO3 and H2O2 1:2 on a hot plate until a colorless solution appear and allowed to cool. After cooling, dilute all the samples in a measuring flask up to 50mL as final volume. The samples were then filtered through Whatmann filter paper No. 42. All the processed samples were then passed to Atomic Absorption Spectrophotometer (Perkin-Elmer Corp., 1980) to find the concentration of metal.The Standard solution of was made from the Stock solution, to get the standardize curve.

Bio concentration factor
To found the outcome of transference of metals from soil to plant portions BCF was done by [15]. BCF= Level of metal in food crop/Level of metal in soil

Translocation factor
Heavy metal have the means of translocation from shoot to grain concentration was calculated by the translocation factor with the resulting formula of [16].

Pollution load index
PLI is calculated by the method given by [17].

Daily intake of metals
The (DIM) was calculated as given by Sajjad et al. [19].

Daily intake of metal (DIM) = Cmetal × Cfactor× Dfood intake ∕ Baverage weight
where Cmetal, Cfactor,Dfood intake and Baverage weight are concentration of heavy metals (mg/kg) daily intake of maize and millet grains (kg person/day) and normal body weight correspondingly. The conversion factor 0.085 was used to convert fresh green weight to dehydrated weight as given by Rattan et al. [20].The DIM by consumption of maize and millet was 0.242 kg individual /day as given by Wang et al. [21] and average body weight 55.9 kg was specified by Wang et al. [22].

Health Risk Index
HRI is defined as the proportion of daily intake of metals in the food crop to oral reference dose (RfD) and was calculated with the formula [23].

Health risk index (HRI) = DIM / RfD
DIM = Daily intake of heavy metal RfD = Oral reference dose An HRI > 1.0 for any single metal indicates that the health of consumer population is at risk or it is carcinogenic [23].

Water
ANOVA of Cadmium for water show significant effect in Irrigation source, District and Irrigation source x District but showed non-significant variation in Forage, Irrigation source x Forage, District x Forage, Irrigation source x District x Forage (Table 1). Water in different districts in forages ranged from 0.26-3.9. Minimum level of cadmium in water was present in maize of Faisalabad irrigated with canal water, while maximum level of cadmium was present in maize of Sargodha irrigated with wastewater. The heavy metals absorption in canal water and wastewater varied significantly (Table 2, Figure 1). The range of cadmium (0.38-0.44) was greater than our values according to Khan et al. [24]. The level of cadmium in current findings was greater given by NEQS [25] and it was 0.01mg/L. All water samples (sewage water and canal water) showed the higher concentration of cadmium than its permissible limit. Heavy metals are transported from the mud to the plant plus the cob and are likely health problems to humans and animals feeding upon them. The Cadmium has higher mobility and absorbing capacity hence it is easily absorbed by plant and translocate toward upper parts of plant [26].

Soil
ANOVA of Cadmium for soil show significant effect in Irrigation source, District and Irrigation source x District but showed non-significant variation in Forage, Irrigation source x District x Forage. Significant and least significant effect was show in Irrigation source x Forage and District x Forage ( Table 1). Absorption of Cadmium in mud ranges from 0.063-1.06. Maize of Kasur irrigated with wastewater has high level of cadmium while the minimum concentration was present in the maize of Sargodha irrigated with canal water (Table 2, Figure 2).

Figure 2. Mean Concentration of Cadmium in soil of different districts (mg/kg)
The persistent wastewater irrigation caused many-fold increase in absorption of contaminants in the soil. In wastewater moistened soil, the Cd absorption was 1.06mg/kg which was more than those of the permissible limits of WHO [27]. The value of Cd was higher to present value that is 2.8 mg/kg proposed by Hassan et al. [28].The amount of Cd was lesser that was 0.20mg/kg given by Rattan et al. [20] as compared to present study. Geochemically Cd was relatively movable element in soil and it was easily taken up by plants.

Figure 3. Mean Concentration of Cadmium in shoot of different districts (mg/kg)
Cadmium was accumulated in shoot also. Our outcomes were comparable to the conclusions of Farhat et al. [29]. The present study values also exceed the PML of Codex Alimentarius Commission [30]. The reason of high concentration of cadmium in sewage water irrigated maize plants was due to the presence of higher concentration of Cd in water. Earlier studies completed by Mapanda et al. [31] on vegetables showing increasing attentions of heavy metals (cadmium, zinc, copper, lead, chromium and nickel) in soils irrigated with wastewater for ten years. There is therefore necessity for threatening peoples about harmful effects of metals later some of these metals such as Cr, Cd and Pb are considered risky impurities that can gather in the human body, with a moderately long half-life.

Grain
Analysis of variance of Cadmium for grain show significant effect in Irrigation source, District, Forage, Irrigation source x District and least significant effect in Irrigation source x Forage, Irrigation source x District x Forage ( Table 1). The cadmium varied from 0.13-1.05 in grain. Higher value was present in forages grown in sewage water of maize of Kasur while lower value was found in maize of Sheikupura irrigated with canal water (Table 2, Figure 4). These values of cadmium were higher than the range (0.002 to 0.004 mg/kg) reported by Edem et al. [32]. The main absorbing structure in plants is through roots and then it is transferred into the edible https://doi.org /10.37358/Rev. Chim.1949 Rev. Chim., 71 (7) portions of plants that is leaves, fruits and seeds. It collects in animal milk and flashy tissues. Phosphate compost also added Cadmium into the soil is of the concern heavy metal. Its transfer from soil to the eatable portions of farming food yields is significantly larger than other contamination elements. Cadmium also may be damaging to soil bacterial populations [28]. In current study the value of cadmium was higher as compared to value 0.062mg/kg given by Yu et al. [33]. The concentration of Cadmium exceeded the Permissible limits of of 0.4 mg/kg proposed by Codex Alimentarius Commission [30].

Bio concentration factor
BCF for cadmium transmission from soil to grain varies from 0.61 to 3.82 mg/kg (Table 3, Figure  5). Highest and lowest content was present in maize of Sargodha and Sheikhupura irrigated with canal water. (FigureCurrent findings of BCF for Cd in all samples were lower as compared to that given by Asdeo [34]. Our findings were greater than Khan et al. [2]. Lokeshwari and Chandrappa [35] defined that Cd is supplementary transportable than other heavy metals hence it fixes less strongly to soil.

Translocation factor
The ability of the plants to move and accumulate the heavy metals from one part to the other part is determined through translocation factor [36], which it is calculated as the ratio of heavy metal content of one part to the other. Translocation factor is a key component to determine the exposure of human to metals via food chain. Translocation factor of cadmium from shoot to grain varies from 0.41 to 2.43 (Table 3, Figure 6). Highest concentration was found in maize of Sargodha and lowest was observed in maize of Sheikhupura irrigated with canal water. Asdeo [34] reported the lower translocation factor values for Cd in relation to our study. Lokeshwari and Chandrappa [35] have investigated that Cd is not strongly bound by soil and therefore it is easily uptake by the plants. https://doi.org /10.37358/Rev. Chim.1949 Rev. Chim., 71 (7)

Pollution load index
Pollution severity of soil is well estimated by determining pollution load index. The PLI for cadmium in different districts fluctuated from 0.042 to 0.712 (Table 3, Figure 7). The extreme concentration was noticed in maize of Kasur irrigated with wastewater while low content was noticed in maize of Sargodha in canal water. The pollution in soil was discovered using method Pollution load index [37]. This method gives an easy and relative source for calculating the different irrigation systems. Tomlinson et al. [38] explained that if value comes in zero that this shows no harm, however if value comes in one and greater than one than it would be harmful. In the present study the PLI was higher than that of Khan et al. [2].  Highest and lowest concentration was found in maize of Kasur and Sheikhupura irrigated by wastewater and canal water. The values of daily intake of metals for Cd, was lower as related to tolerable daily intake limit (0.07 mg/kg) by USEPA [23]. The daily intake of metals depends on equally the metal attention in crops and the amount of consumption of the particular food crop. Daily intake of Cd for all types of samples was found much lower than the findings (0.001 mg/kg/day) of Chaoua et al. [39]. Khan et al. [2] suggested the higher Daily intake (0.01, 0.01 mg/kg/day) for Cd. Wang et al. [22] had given the lower Daily intake (0.0002 mg/kg/day) for Cd. Daily intake rate for Cd investigated in the present research for all types of samples were below than the maximum tolerable limit (0.07 mg/kg/day) suggested by USEPA [23]. Radwan and Salama [40] have also reported the same results that there is no risk caused by the consumption of wastewater irrigated wheat grains.

Health risk index
The range of HRI for Cd via intake of grains in various districts of different forages was 0.59-4.55 mg/kg (Table 3, Figure 9). Maximum and minimum value was found in Maize of Kasur and Sheikhupura using irrigation of waste water and canal water. HRI value for Cd (5.86) given by Singh et al. [41] was higher than the range of current investigation. Wheat is known as an important way of dietary exposure to heavy metals. However, features of metals and high-risk areas are other important sources of heavy metal exposure. Due to this reason, potential health risk associated with heavy metals might be different as compared to present estimation [42].

Enrichment factor
The Enrichment factor of cadmium in different districts varied from 4.6-28.4 mg/kg (Table 3, Figure 10). Highest value of EF is recorded in maize of Sargodha watered with stream water and lowest in maize of Sheikhupura watered with canal water. Alghobar and Suresha [43] investigated the lower EF value (1.50) for Cd. All the samples in present research had the higher Enrichment factor value than that value (4.57), which was given by Singh et al. [41]. Higher value of EF for Cd showed its lower retention in the soil and high mobility.