3.2 Trace Metals Concentration in Plant (Vegetative Part)
Average values for element concentrations (mg kg − 1 dry weight or ppm) in the barley plant vegetative parts are presented in Table 3. Results showed the following:
Table 3
Average Heavy Metals Concentrations in Plant (Vegetative Part) [ppm]
Treatment
|
Cd
|
Cr
|
Cu
|
Fe
|
K
|
Mn
|
Ni
|
Pb
|
Zn
|
Control
|
0.54b
|
4.13c
|
36.18bc
|
1003.78a
|
354070a
|
469.96a
|
5.31b
|
3.66b
|
129.07a
|
X
|
0.74b
|
5.31c
|
48.40a
|
943.04ab
|
354070a
|
442.00ab
|
9.88ab
|
4.50b
|
124.25a
|
3X
|
0.83ab
|
6.59c
|
26.48c
|
750.33b
|
354070a
|
322.79b
|
12.30a
|
3.77b
|
159.61a
|
9X
|
0.95ab
|
15.49b
|
43.37ab
|
751.79b
|
354070a
|
427.47ab
|
6.29b
|
4.85b
|
139.55a
|
15X
|
1.27a
|
18.55a
|
39.68ab
|
960.45ab
|
298348b
|
323.90b
|
6.30b
|
7.94a
|
106.26a
|
Means in the same column with similar superscripts are not statistically different (Duncan test, P ≤ 0.05). |
- Cadmium (Cd), Chromium (Cr), and Lead (Pb) concentration in vegetative parts of barley had an increasing trend with increased metal application in irrigation water. These three metals have no nutritious capacity, but they are exceptionally toxic.
- The response of other metals in barley showed no systematic relationship to metal application. González and Lobo, (2013) reported similar results for barley planted in soils contaminated with heavy metals [37].
- Cadmium, Chrome, and Lead accumulation concentrations in barley were greater than permissible level set by WHO for these metals [38] and accordingly these plants are not sui for consumption. Other metal accumulation concentration was within permissible levels set by WHO. However, this high metal accumulation level did not affect plant growth appearance, and/or yield, a result agreed by Bigdeli and Seilsepour, 2008[39].
- Ferrous (Fe), and Manganese (Mn) concentration were higher in the control compared to all metal treated plants. This indicate that Fe and Mn accumulation in barley is not related to its metal application rate.
- Results obtained in this study agree with published research which indicated that for Cu, Zn, Fe, Mn content accumulated in barley plant irrigated with wastewater containing heavy metals was high up to 2 years of irrigation with heavy metals and the content of these metals was reduced for longer irrigation than 2 years (5–10years) [40]. Similar higher accumulation of
Fe (129–968 ppm) and Mn (19–137 ppm) [41]
Fe (116–378 ppm) and Mn (12–69 ppm) [42]
was found in vegetables irrigated with wastewater.
- No specific trend or relationship was found for the repetitive and multiple application of Cu, K, Ni, Pb, and Zn and their accumulation in barley.
- The decreasing order of the maximum average concentration of heavy metals in barley vegetative parts was: K (342926 ppm) > Fe (881.88 ppm) > Mn (397.22 ppm) > Zn (131.75).
3.3 Trace Metals Concentration in Roots
The average values of heavy (trace) elements in plant roots are presented in Table 4. In general, there were increase in metal concentration accumulation in barley's roots as a response to increased metal application in irrigation water. For Cd, Cu, Mn, Ni, Pb, and Zn metal accumulation in roots of the control was greater 'than that in some metal treatments. Metal accumulation in samples irrigated with 15X was less than that of 9X for most metal applications (except for Pb). Cd, Cu, K, Mn and Zn metal accumulation in plant vegetative parts was higher than in the roots. This result agrees with published data for different plants [43–46].
Table 4
Average Heavy Metals Concentrations in Root [ppm]
Treatment
|
Cd
|
Cr
|
Cu
|
Fe
|
K
|
Mn
|
Ni
|
Pb
|
Zn
|
Control
|
0.11b
|
10.80cd
|
10.28c
|
2566.60b
|
4530b
|
156.30b
|
13.33ab
|
4.44bc
|
45.87b
|
X
|
0.03b
|
5.88d
|
7.83c
|
1434.80c
|
4852b
|
59.68c
|
6.56c
|
1.94d
|
20.50c
|
3X
|
0.12b
|
14.85c
|
10.10c
|
1569.30c
|
6297ab
|
92.90c
|
8.09c
|
3.34cd
|
77.48a
|
9X
|
0.73a
|
68.94a
|
19.60a
|
3384.40a
|
8022 a
|
211.22a
|
15.13a
|
5.73b
|
50.89b
|
15X
|
0.68a
|
30.90b
|
13.61b
|
2898.70ab
|
7138ab
|
154.84b
|
11.25b
|
7.89a
|
39.75b
|
Means in the same column with similar superscripts are not statistically different (Duncan test, P ≤ 0.05). |
In general, the accumulation concentration of heavy metals in roots increased consistently with the metal total contents in the soil.
Although accumulated Cu levels increased in both root and shoot in response to metal application in irrigation water, Cu accumulation concentration in shoots increased more sharply than that in roots (see Table 4). It was reported [47] that Cu concentration in the shoots was significantly influenced by Cu concentration in soil and increased markedly with an increase in the soil Cu concentration. González and Lobo, 2013 [48] found that Zn concentration was higher in the roots of four varieties of barley than other parts of the plant.
The metal accumulation concentration of Cr and Fe was always higher in roots than in the vegetative parts. Similar result for the accumulation of Cr was reported [49]. This could be because Cr is immobilized in the vacuoles of the root cells, which may be a natural toxicity response of the plant [50]. For Fe, Chiroma et al.,(2014) reported similar results in Bush green and Roselle plants [51].
3.4 Trace Metals Concentration in Soil
The average values of heavy (trace) elements in soil are presented in Table 5 Metal accumulation in the control treatment showed higher accumulation concentration for all elements except for Cd and Zn.
In general, no systematic accumulation in soil was observed for all metal treatments. Also, accumulation concentration in soil beyond irrigation with 9X treatment was reduced for all metal application which indicate a limiting accumulation capacity of the soil.
No significant differences were observed for Ferrous (Fe) and Zinc (Zn) accumulation between X, 3X, 9X and 15X. This agrees with the results reported by several researchers [52–54].
Table 5
Average Heavy Metals Accumulation Concentrations in Soil [ppm]
Treatment
|
Cd
|
Cr
|
Cu
|
Fe
|
K
|
Mn
|
Ni
|
Pb
|
Zn
|
Control
|
0.07b
|
50.47a
|
19.19a
|
30812a
|
6775a
|
508.37a
|
35.36a
|
20.17a
|
94.10a
|
X
|
0.03b
|
9.21c
|
5.73c
|
6204b
|
2239b
|
106.20bc
|
8.29c
|
5.22c
|
35.90a
|
3X
|
0.00b
|
13.77c
|
5.62c
|
7393b
|
1893b
|
135.68bc
|
9.04c
|
4.97c
|
35.90a
|
9X
|
0.33a
|
32.96b
|
12.09b
|
15408b
|
6191a
|
269.17b
|
20.90b
|
12.69b
|
1607.80a
|
15X
|
0.00b
|
7.79c
|
2.90c
|
3051b
|
1563b
|
53.41c
|
4.52c
|
3.11c
|
135.50a
|
Means in the same column with similar superscripts are not statistically different (Duncan test, P ≤ 0.05). |
The highest concentration was found in soils irrigated with tap water except for Cd and Zn. This indicated that originally the soil contains elevated amounts of these elements and irrigation leached these elements down the soil profile. Previous studies reported that the movement of heavy metals in soils irrigated with wastewater is very slow [55, 56]. Other researchers showed that the amount of metal that remained in the soil was greatest for the higher concentration of Zn and Cd treatments [57].
The iron was found to be higher in comparison to all other studied metals in soil. This result agrees with the findings of zafar et al 2018 [58].
All heavy metals had concentrations in soil marginally below the WHO maximum permissible level meaning that there is no threat of soil contaminations by these metals when the effluent of the treatment plant is used for the irrigation of barely. A result indicating the appropriateness of sandy soils to minimize health and environmental risk hazards associated with irrigation with water containing heavy metals. This agrees with results reported by other researchers [59–61].
The highest Cd, Cu and K concentration for these metals was in the vegetative parts of barley while and the lowest was in soil.
It is very important to note that in reality soils used to plant barley are mostly not sandy as used in this study and therefore geochemical monitoring of and evaluation on heavy metals in other soils is important and necessary to ensure proper barley agricultural production and quality.
The average heavy metal concentrations in soils were observed in the following decreasing order: Fe > K > Zn > Mn > Cr > Ni > Pb > Cu > Cd. This sequence follows to some extent a natural progressive concentration of heavy metals in sandstones [62].
To understand soil contamination and the ability of barley or part of it to uptake/accumulate metals and to assess plant’s potential for phytoremediation purposes in response to metal inputs from anthropogenic sources several factors were investigated including enrichment factor (EF), bioconcentration factor BCF), and translocation factor (TF). The three factors were estimated based on dry weight concentration in ppm.
3.5.1 Enrichment Factor
Enrichment factor (EF) was used/estimated in order to derive the degree of soil contamination and heavy metal accumulations in soil and in plants irrigated with heavy metal contaminated water. EF was defined as the ratio of metal concentration in plant of contaminated soil to plant of uncontaminated soil (control), were listed in Tables 6 and 7 and showed the following development:
-
For Cd, Cr, Cu, Fe, K, and Ni there was an increasing trend of the EF in roots of barley observed with treatment until the 9X treatment then with higher metal treatment the EF was reduced.
-
In general, small variations of the EF in shoots of barley for all metals were observed.
-
The EF in shoots and roots for treatment 15X were significantly decreased indicating the no effect or relationship of increasing treatment level beyond 9X on all metal accumulation.
-
As most of the EF for all metals were less than 2, an indication that (i) the soil used in the experiment was deficient of minimal enrichment (which is normal for sandy soils) and (ii) the soil was moderately contaminated upon various levels of metal applications (treatment). This result agrees with the findings of [62].
-
The overall average of EF for shoots (1.13) was less than that of roots (1.47) indicating higher enrichment of metals in barley's roots than shoots.
Table 6
Enrichment factors (EF) of shoots of barley
Treatment
|
Cd
|
Cr
|
Cu
|
Fe
|
K
|
Mn
|
Ni
|
Pb
|
Zn
|
X
|
1.38
|
1.28
|
1.34
|
0.94
|
1.00
|
0.94
|
1.86
|
1.23
|
0.96
|
3X
|
1.13
|
1.24
|
0.55
|
0.80
|
1.00
|
0.73
|
1.25
|
0.84
|
1.28
|
9X
|
1.14
|
2.35
|
1.64
|
1.00
|
1.00
|
1.32
|
0.51
|
1.29
|
0.87
|
15X
|
1.34
|
1.20
|
0.92
|
1.28
|
0.84
|
0.76
|
1.00
|
1.64
|
0.76
|
Average
|
1.25
|
1.52
|
1.11
|
1.10
|
0.96
|
0.94
|
1.16
|
1.25
|
0.97
|
The average value of enrichment factor (EF) for Cd (2.27) and Cr (2.04) indicated moderate to weak enrichment in barley irrigated roots. The EF of the rest of heavy metals used were around unity indicating poor enrichment to soil and translocation to roots and shoots.
Table 7
Enrichment Factor in barely roots
Treatment
|
Cd
|
Cr
|
Cu
|
Fe
|
K
|
Mn
|
Ni
|
Pb
|
Zn
|
X
|
0.27
|
0.54
|
0.75
|
0.57
|
1.01
|
0.38
|
0.50
|
0.43
|
0.43
|
3X
|
3.77
|
2.52
|
1.29
|
1.09
|
1.30
|
1.56
|
1.23
|
1.73
|
3.78
|
9X
|
5.97
|
4.64
|
1.94
|
2.16
|
1.27
|
2.27
|
1.87
|
1.71
|
0.66
|
15X
|
0.93
|
0.45
|
0.69
|
0.86
|
0.89
|
0.73
|
0.74
|
1.38
|
0.78
|
Average
|
2.27
|
2.04
|
1.17
|
1.17
|
1.12
|
1.24
|
1.09
|
1.31
|
1.41
|
3.5.2 Bioconcentration Factor
To better evaluate the ability of barley to accumulate within its tissues the heavy metals from simulated treated wastewater, this study used a bioconcentration factor (BCF) to measure the absorption capacity of the heavy metals by barely. The values of BCF defined as the ratio of metal content in plant to the total content in soil are shown in Tables 8 and 9. In general, if the BCF is ≤ 1, then the value denotes that barley is able to absorb the heavy metals, but do not accumulate it within its tissues, accumulation within tissues occurs when BCF > 1. According to the FAO/World Health Organization (WHO) [63, 64], grains and cereals with BCF higher than 0.20 are thought to be highly contaminated by anthropogenic activities and have a high health risk.
The order of the bioconcentration factor (BCF) measured in barley's shoots was K > Cu > Cd > Mn > Zn > 1, indicating that barley possessed a strong biological enrichment ability to accumulate a variety of heavy metals.
Potassium in shoots showed the highest BCF with increasing trend to metal application followed by Cd and Cu while the rest of metals showed low BCF values. BF in roots were low for all metals. BF data in shoots and roots suggested that no direct relationship exists between BF and metal concentration in irrigation water. BCF values greater than 1 were observed in shoots and roots for most metals and applications indicating the ability and potential success of barley for phytoremediation.
Table 8
Bioconcentration Factor (BCF) in shoots
Treatment
|
Cd
|
Cr
|
Cu
|
Fe
|
K
|
Mn
|
Ni
|
Pb
|
Zn
|
Control
|
5.99
|
0.07
|
1.68
|
0.03
|
40.65
|
0.74
|
0.14
|
0.17
|
1.13
|
X
|
21.38
|
0.58
|
8.45
|
0.15
|
158.16
|
4.16
|
1.19
|
0.86
|
3.84
|
3X
|
0.00
|
0.48
|
4.71
|
0.10
|
187.05
|
2.38
|
1.36
|
0.76
|
4.45
|
9X
|
2.87
|
0.47
|
3.59
|
0.05
|
57.20
|
1.59
|
0.30
|
0.38
|
0.09
|
15x
|
0.00
|
2.38
|
13.72
|
0.31
|
190.90
|
6.06
|
1.39
|
2.55
|
0.78
|
Average
|
6.05
|
0.80
|
6.43
|
0.13
|
126.8
|
2.99
|
0.88
|
0.94
|
2.06
|
Table 9
Bioconcentration Factor (BCF) in Roots
Treatment
|
Cd
|
Cr
|
Cu
|
Fe
|
K
|
Mn
|
Ni
|
Pb
|
Zn
|
Control
|
1.35
|
0.19
|
0.48
|
0.06
|
0.55
|
0.25
|
0.34
|
0.20
|
0.42
|
X
|
0.93
|
0.64
|
1.37
|
0.23
|
2.17
|
0.56
|
0.79
|
0.37
|
0.63
|
3X
|
0.00
|
1.08
|
1.80
|
0.21
|
3.33
|
0.68
|
0.89
|
0.67
|
2.16
|
9X
|
2.19
|
2.09
|
1.62
|
0.22
|
1.30
|
0.78
|
0.72
|
0.45
|
0.03
|
15x
|
0.00
|
3.97
|
4.71
|
0.95
|
4.57
|
2.90
|
2.49
|
2.54
|
0.29
|
Average
|
0.89
|
1.59
|
2.00
|
0.33
|
2.38
|
1.03
|
1.05
|
0.85
|
0.71
|
BCF values listed in s for shoots and roots indicated that Cd, Cr, Cu, K, Mn, Ni, and Pb transfer from soils to plants is directly correlated with the available metal concentration in soils.
It was observed that BCF is a variable for the various metals and applications used in this study. BCF in shoots and roots was mostly directly related to metal application concentrations in irrigation water.
The Cr, Fe, and Pb little build-up in the shoots and roots of barley with BCF < < 1 could be related to soil type but are issues that need further verification in future studies.
The overall average of BCF for shoots (19.02) was much greater than that of roots (1.40) indicating higher metal transferability, accumulation and buildup took place in the barley's shoots despite the high application of metals to the soil. However, the low BCF root values and averages were impacted by the sandy soil used in the experiment as planting medium.
BCF in shoots was the highest in K (53.79), followed by Cd (8.24), and then Mn, Cu, and Zn (3.75, 3.48, 3.38), while the lowest was Fe (0.42), according to the overall averages.
3.5.3 Translocation Factor
The Translocation factor (TF) defined as the ratio between the metal content in shoots and that in roots which explains the ability of barley plant to translocate metals from roots through shoots and leaves which is primarily responsible for phytoextraction TF values obtained were listed in Table 10 and showed the following development:
-
The TF for K was the highest among all metal ( > > 1) and showed decreasing trend with increasing treatment. It was found that Potassium plays a major role in enhancing tolerance of barley to drought by increasing translocation and maintaining water balance [66]. High TF values with less extent were also observed for Cd, Cu Mn, and Zn. For Cd, Cr, Cu, Fe, K, and Ni there was an increasing trend of the EF in roots of barley observed with treatment until the 9X treatment then with higher treatment the EF was limited.
-
In general, no specific trend of the TF was observed for other metals and treatments.
-
TF values of > > 1 in Cd Cu, K, Mn, and Zn indicate that barley is considered as strong accumulators of the corresponding metals. It also indicates that sandy soil is not suitable for barley stabilizing these metals in soil.
Table 10
Treatment
|
Cd
|
Cr
|
Cu
|
Fe
|
K
|
Mn
|
Ni
|
Pb
|
Zn
|
Control
|
4.45
|
0.38
|
3.48
|
0.40
|
73.87
|
3.00
|
0.40
|
0.82
|
2.70
|
X
|
22.92
|
0.90
|
6.18
|
0.66
|
72.97
|
7.41
|
1.51
|
2.32
|
6.06
|
3X
|
6.84
|
0.44
|
2.62
|
0.48
|
56.23
|
3.47
|
1.52
|
1.13
|
2.06
|
9X
|
1.31
|
0.22
|
2.21
|
0.22
|
44.14
|
2.02
|
0.42
|
0.85
|
2.74
|
15X
|
1.87
|
0.60
|
2.92
|
0.33
|
41.80
|
2.09
|
0.56
|
1.01
|
2.67
|
Average
|
7.48
|
0.51
|
3.48
|
0.42
|
57.8
|
3.60
|
0.88
|
1.23
|
3.25
|
According to Mellem et al. [65], transfer factor values nearer to zero imply high retention of metal in the soil and result in less movement to the plants. Thus, the low level of TF observed in the case of Cr (TF 0.22–0.90), and Fe (TF 0.22–0.66), implies that only a small portion will be available in the plant vegetative parts. This result agrees with the enrichment factors in shoots and roots for these metals in Tables 6 and 7. However TF values for all other heavy metals were much greater than unity, indicating high mobility of these metals from soil and roots to the vegetative parts of barley and thus labeling barley as heavy metal accumulator. We can consider barley as a potential candidate for phytoextraction and phytoremediation of soils contaminated with these metals.
3.6. General Discussion
To show metal movement and differentiation between soil, roots, and vegetative parts of barley (shoots and leaves), the values overall heavy metals averages for all treatment are listed in Table 11.
Table 11
Overall Heavy Metals Averages for All Treatments, [ppm]
Treatment
|
Cd
|
Cr
|
Cu
|
Fe
|
K
|
Mn
|
Ni
|
Pb
|
Zn
|
Vegetative Parts
|
0.87
|
10.01
|
38.82
|
882
|
342926
|
397.2
|
8.01
|
4.94
|
131.8
|
Roots
|
0.33
|
26.3
|
12.3
|
2571
|
6168
|
135.0
|
10.9
|
4.67
|
46.9
|
Soil
|
0.086
|
22.8
|
9.1
|
12574
|
3732
|
214.6
|
15.6
|
9.2
|
381.4
|
FAO/WHO*
|
0.20
|
2.30
|
73.3
|
425.5
|
300
|
0.20
|
67.9
|
0.30
|
99.4
|
Note: Vegetative Parts = Shoots + Leaves
* = in vegetables
As shown in Table 11, heavy metals (Cd, Cr, K Mn, and Pb) were mainly concentrated in the vegetative parts of barley while Cu, Fe, Ni, and Zn were concentrated in the roots of barley indicating its different extraction, biological enrichment, and accumulation ability to accumulate a variety of heavy metals. Also, the extent of heavy metals accumulation was different by the different heavy metals.
A systematic increasing trend of heavy metals, Cd, Cu, K, and Mn accumulation from soil (lowest) to shoots and leaves (highest). Other metals did not show such trend. Overall average concentration of most heavy metals in barley's vegetative parts (Table 11) exceeds the maximum FAO/WHO permissible values. These metals showed strong enrichment capacity in barley's shoots (Table 6). For such heavy metals, barley proved to be suitable to be used as a phytoremediation method for wastewater treatment.
The overall average of Cd soil, roots, and vegetative parts was 0.08, 0.33, and 0.87 ppm, respectively showed an increasing trend and most importantly large differences between the three parts: four times in roots than soil and eleven times in the vegetative parts than soil. This prove the ability of barley plant to translocate Cd from soil through roots to shoots and leaves.
Only Cd and Ni overall average concentrations in soil were below the WHO/FAO maximum permissible level of 0.2 and 67.9 ppm, respectively.
The overall average of Cr for the five treatments in soil, roots, and shoots was 22.8, 26.3, and 10.0 ppm, respectively indicating no systematic changing trend and threefold difference between the three parts. All concentrations were larger than the WHO/FAO permissible level of 2.3 ppm for Cr.
The overall average of Cu for the five treatments in soil, roots, and shoots was 9.1, 26.3, and 38.8 ppm, respectively indicating an increasing trend and large difference between the three parts. Only All concentrations were below the WHO/FAO permissible level of 73 ppm for Cu.
Among various metallic concentrations, Fe had the highest concentration. Fe maximum concentration observed in soils (12574 ppm), then in root (2571 ppm), and the least in the vegetative parts of barley (882 ppm). The bioaccumulation factor values for Fe in shoots and roots were < < 1 indicating the inability of barely to be suitable for removing Fe.
The average EF for soil for all metals in shoots were 1.52–0.94 indicating deficient or minimal enrichment of the soil. differed depending on the type and concentration of the effluents and the type of soil. Similar results were obtained for the average EF for soil for all metals in roots were 2.27–1.12.
According to Cluis (2004) [67], hyperaccumulating plants have a BCF value more than 1.0. In this study,
BCF in shoots > 1: Cd 6.05, Cu 6.43, K 126.8, Mn 2.99, and Zn 2.06
BCF in roots > 1: K 2.38, Cu 2.0, Cr 1.59, Mn 1.03, and Zn 1.05
Only Cd, Cu, and K in shoots have relatively high BCF and are hyperaccumulating. The lower BCF values in roots might be related to soil metal composition.
The average translocation factor (TF) for K > Cd > Mn > Cu > Zn > Pb > 1 indicating the ability of barley to translocate these heavy metals to shoots and leaves.
The translocation factor (TF) values decreased in the order of Ni > Cr > Fe, all of which were lower than 1, which showed that the absorption of these heavy metals by barley was mainly accomplished in the roots.
It is important to note that it is difficult to assess the impact of each heavy metal separately due to the joint application of metals. A deficiency of this research and a recommendation for future works.
The overall risk calculation of the three factors reveals that
-
Hyper accumulation of metals in shoots, Cd, Cu, and K
-
High metal translocation from soil to shoots indication the suitability of barley to be used as phytoremediation agent or plant
-
Barely irrigated with treated effluent containing heavy metals is unsafe for human or animal consumption
-
On the long-term metal accumulation in barley increase, increasing plant toxicity
-
The is no flexibility or possibility of no metal accumulation in barley upon its irrigation with wastewater containing heavy metals
And therefore, the health and environmental risk is high on barley's consumers and water and land resources.
To evaluate the long-term human health risk of exposure of cows and sheep to carcinogen heavy metals in barley grown/irrigated with simulated treated wastewater via ingestion, the following equations was used:
To assess the overall carcinogenic effects of exposure to multiple carcinogen heavy metals via different pathways, the sum of the HQ values representing the health hazard index of all heavy metals was estimated [68, 69]:
Hazard Index (HI) ∑ n i= ∑ HQ
Health Risk = HI * SF
Where,
AT is the averaging time, days = lifetime × 365 days
IR the daily ingestion rate, kg/day
EF is the exposure frequency (days/year)
ED is the exposure duration (years);
BW animal weight (kg)
C is the concentration of heavy metal in vegetative parts, ppm (mg/kg)
RfD is reference oral dose, (mg/kg bw/day)
HRI = Hazard risk index
HQ = Hazard Quotients
HI = Health Index
SF = carcinogenic slope factor (SF)
The carcinogen heavy metals in this study simulated wastewater were Cd, Pb, and Ni. An indicative estimation of hazard quotients and health index for carcinogen heavy metal exposure of cows and sheep from ingesting vegetative parts of barley was presented in Table 12. As shown in Table 12 the estimated health index for cows was 7.49 > > 1 and for sheep was 28.38 > > 1 which indicate without multiplying it with the carcinogen slope factor SF to obtain the health risk (SF for Cd = 6.1) that the vegetative parts of barley grown and irrigated with simulated wastewater in this study are carcinogen for cows and sheep and should not be used for feeding them.
Table 12
Estimation of Hazard Quotients and Health Index for Carcinogen Heavy Metal exposure of Cows and Sheep from Ingesting Vegetative Parts of Barley
Metal
|
C veg parts,
ppm
|
RfD mg/kg-day
|
IR,
kg/day
|
BW,
kg
|
ED
year
|
EF days/yr
|
AT,
days
|
HI for Cows
|
Cd
|
0.87
|
0.0005
|
2
|
910
|
2
|
350
|
730
|
3.67
|
Ni
|
8.01
|
0.02
|
2
|
910
|
2
|
350
|
730
|
0.84
|
Pb
|
4.94
|
0.038
|
2
|
910
|
2
|
350
|
730
|
2.97
|
Total
|
7.49
|
Metal
|
C veg parts
|
RfD
|
IR
|
BW
|
ED
|
EF
|
AT
|
Hqi for Sheep
|
Cd
|
0.87
|
0.0005
|
0.5
|
60
|
2
|
350
|
730
|
13.9
|
Ni
|
8.01
|
0.02
|
0.5
|
60
|
2
|
350
|
730
|
3.2
|
Pb
|
4.94
|
0.038
|
0.5
|
60
|
2
|
350
|
730
|
11.28
|
Total
|
28.38
|
Data Source: [70–72] |