Grain size, moisture, and organic matter analysis
Sediment fractions, moisture, and OM contents of the Rayahs sediment are given in Table 3. Sand was the dominant fraction, varying in the ranges of 42.79–73.84%, 27.73–87.77%, 36.74–82.23%, and 19.23–84.20% in RT, RM, RB, and RN, respectively (Table 3 and Fig. 2). Sand was deposited through erosion of two banks and by wind (aeolian deposits, with fine to very-fine sand) with limited water movement. RB and RT were characterized by low sand deposition compared to RN and RM. Sand fraction exhibits a strong negative correlation with mud (r = −78), moisture % (r = −53; p = 0.01), and Fe (r = −0.4; P = 0.05). This is related to silt and fine-grained clays that reflect sedimentation during commonly-occurring perennial water flows and coarse-grained clastic layers in between this clay matrix; therefore, they reflect a very high energy environment, or flood events (Priyanka Raja et al. 2018).
By contrast, the main gravel fractions were in the range of 0.5–47.24%, 0.26–12.40%, 2.56–24.01%, and 1.7–20.59% in RT, RM, RB, and RN, respectively, with an order of RT > RB > RN > RM. (Table 3 and Fig. 2). Notably, gravel fraction comprised mollusca shells and fragments associated with granules deposited by banks erosion and some gravel >2 mm was transported to sub-branches by human activity at banks.
Mud fraction is the second dominant after sand in the ranges of 9.97–48.11% (average 28.39%) for RT, 9.72–65.43% (average 36.62%) for RM, 12.38–46.36% (average of 28.98%) for RB, and 6.53–60.17% (average 28.79%) for RN. Rate of mud deposition increased northward, related to the decrease of water movement. Mud (silt and clay) was deposited via water (river deposit) and wind (aeolian deposits) from the two banks. The results agreed with those obtained by Abu El-Enain et al. (1997); Abd El-Monsif (2009); Salem and Lotfy (2017); Goher et al. (2021), who stated that the dominant fractions of Nile River are sand > mud (silt and clay) > gravel. We can state that the distribution of grain size depends on the depth and energy of water movement, where mud (clay and silt) increased with depth and quite water with slow currents, while sand and gravel increased at banks with low depth and high movement water. After the establishment of the Aswan High Dam in 1964, great changes in the hydrological system in the Nile Delta led to a halt in the arrival of sediments and floodwaters to the Mediterranean Sea. The sources of sediments in the Nile River are the shore erosion and aeolian sedimentation (Stanley et al. 2004; Hamouda et al. 2014; Ghoneim et al. 2015; Elsherif et al. 2020; Goher et al. 2021). Mud exhibits a strong positive correlation with moisture % (r = 0.73, n = 31; P = 0.01) and OM% (r = 0.043; n = 31; p = 0.05); this can be related to the fermentation process, which is conducted through the sinking of dead microorganisms forming organic matter (Dinakaran and Krishnayya 2011; Farahat 2019).
OM is produced from life processes of plants and animals and is the source of fuels and raw materials such as coal, petroleum, and natural gas (Engel et al. 1993). Without organic matter, bare mineral soils are more susceptible to accelerated erosion. The horizontal distribution of OM is shown in Table 3 and Fig. 3. OM contents in the Rayahs sediments were found in the order of RN < RB < RM < RT, with mean values of 8.12%, 8.55%, 10.57%, and 11.17%, respectively (Table 3 and Fig. 3). We found that OM percentage increases with mud fraction with respect to sand and gravel fractions, which is consistent with the results obtained by Salem (2011); Goher et al. (2021). Results showed the increase of the OM in RM and RT with respect to RB and RN, which may be related to the high population, and thus, human activity, in the first two Rayahs. OM showed a strong positive correlation with moisture % (r = 0.5; n = 31; p = 0.01) that may be explained by the high porosity of mud, which stores OM and water.
Water content is one of the most important indicator properties used to establish a correlation between sediment behavior and its indicator properties. Moisture percentage has been defined as the ability of sediment to save water. Moisture contests in sediments varied in the ranges of 40.23–64.98%, 38.93–72.30%, 38.91–63.42%, and 36.53–71.28% in RT, RM, RB, and RN, respectively (Table 3 and Fig. 3). RM Sediment has a higher moisture content followed by RN, whereas RT and RB show low values.
Table (3): Texture and heavy metal contents in the four Rayahs sediments.
parameter
|
El-Tawfiky
|
El-Menoufy
|
El-Behary
|
El-Nassery
|
|
Min
|
Max
|
Av
|
Sd
|
Min
|
Max
|
Av
|
Sd
|
Min
|
Max
|
Av
|
Sd
|
Min
|
Max
|
Av
|
Sd
|
Gravel
|
0.57
|
47.24
|
15.01
|
±17.4
|
0.26
|
12.40
|
5.09
|
±4.69
|
2.56
|
24.01
|
9.93
|
±6.64
|
1.70
|
20.59
|
9.09
|
±6.68
|
Sand
|
42.79
|
73.84
|
56.62
|
±9.7
|
27.73
|
87.77
|
56.64
|
±19.4
|
36.74
|
82.24
|
60.86
|
±15.1
|
19.24
|
84.20
|
62.11
|
±19.4
|
Mud
|
9.97
|
48.11
|
28.39
|
±14.2
|
9.72
|
65.43
|
36.62
|
±19.5
|
12.38
|
46.36
|
28.98
|
±13.0
|
6.53
|
60.17
|
28.79
|
±16.6
|
Mo%
|
40.23
|
64.98
|
49.65
|
±9.27
|
38.93
|
72.30
|
54.68
|
±12.1
|
38.91
|
63.42
|
49.92
|
±8.81
|
36.53
|
71.28
|
52.97
|
±11.4
|
O.M%
|
5.87
|
16.47
|
11.17
|
±4.12
|
6.82
|
15.75
|
10.57
|
±3.38
|
4.48
|
14.15
|
8.55
|
±3.51
|
4.78
|
14.08
|
8.12
|
±3.26
|
Fe mg/g
|
6.75
|
6.75
|
10.51
|
±2.62
|
7.91
|
13.61
|
10.42
|
±2.10
|
7.12
|
14.90
|
10.58
|
±2.95
|
7.36
|
12.13
|
9.69
|
±1.77
|
Mn µg/g
|
123.2
|
201.8
|
153.85
|
±25.9
|
177.2
|
252.0
|
199.83
|
±26.1
|
239.14
|
422.50
|
316.07
|
±66.6
|
165.29
|
245.96
|
198.69
|
±25.9
|
Zn µg/g
|
16.38
|
36.36
|
23.75
|
±7.33
|
20.80
|
41.66
|
29.33
|
±7.09
|
7.12
|
109.56
|
82.50
|
±16.6
|
26.33
|
48.93
|
39.08
|
±6.59
|
Cu µg/g
|
4.96
|
12.68
|
8.76
|
±2.46
|
9.51
|
16.51
|
12.57
|
±2.39
|
20.02
|
40.05
|
28.39
|
±7.18
|
14.68
|
23.66
|
18.47
|
±2.76
|
Pb µg/g
|
4.82
|
12.90
|
7.81
|
±2.49
|
7.06
|
15.90
|
10.20
|
±3.29
|
8.14
|
27.54
|
15.61
|
±7.90
|
8.11
|
18.60
|
12.43
|
±4.01
|
Ni µg/g
|
3.22
|
5.62
|
4.07
|
±0.87
|
3.08
|
6.78
|
4.38
|
±1.20
|
2.38
|
8.54
|
4.83
|
±2.23
|
2.63
|
8.57
|
5.10
|
±1.92
|
Cr µg/g
|
3.35
|
8.79
|
5.98
|
±1.70
|
6.28
|
11.08
|
7.84
|
±1.57
|
10.70
|
33.50
|
21.03
|
±7.79
|
6.61
|
16.54
|
11.62
|
±3.66
|
Cd µg/g
|
0.42
|
1.27
|
0.703
|
±0.28
|
0.72
|
1.14
|
0.91
|
±0.18
|
0.785
|
3.07
|
1.62
|
±0.84
|
0.722
|
1.39
|
1.09
|
±0.27
|
Heavy Metals
Sediment contamination poses one of the worst environmental threats in ecosystems, which act as sinks and sources of contaminants in aquatic systems; thus, sediment analysis is critical for assessing the pollution status of the environment (Mucha et al. 2003). Geochemical analyses of Fe, Mn, Zn, Pb, Cu, Ni, Cr, and Cd were conducted, and their concentrations are listed in Table 3 and represented in Fig. 4.
Iron (Fe) is one of the major constituents of the lithosphere; it is critical in the behavior of several trace elements and is located in the intermediate position between macro and micronutrients in plants, animals, and humans (Kabata-Pendias and Arun 2007). The sediment content in Fe is controlled by several factors, including the distance from the outfall, nature of sediment, OM content, oxidation/reduction conditions, TDS levels (salinity), and pH value of water (Masoud et al. 2011; Goher et al. 2021). Concerning our results, the lowest (6.75 mg/g) and the highest (15.17 mg/g) values of Fe were recorded in RT at sites T1 and T7, respectively, which is consistent with the results obtained by Goher et al. (2021), who worked in River Nile. However, our results are lower than those regarding Ismailia Canal, Rosetta branch, and Greater Cairo, obtained by El Sayed (2015); El-Amier et al. (2015); Lasheen and Ammar (2009). Fe exhibits a strong positive correlation (n = 31; p = 0.01) with Mn (r = 0.47), Pb (r = 0.72), Ni (r = 0.67), Cr (r = 0.47), and Cd (r = 0.69) and is positively correlated (n = 31; p = 0.05) with Zn (r= 0.36) and Cu (r = 0.40), indicating the common source and association of metals with oxy-hydroxides of Fe–Mn, which is also supported by Imam et al. (2020); Goher et al. (2021). Furthermore, the positive correlation of Fe with OM (r = 40, n = 31; p = 0.05) indicates the association of Fe deposition with OM accumulation in the sediment.
Manganese (Mn) exists in sediments principally as MnO2, which is very insoluble in water under reducing conditions: Mn in the dioxide form is reduced from valence 4 to 2, and solubility occurs as with ferric oxide (Arslan et al. 2019). Mn shows irregular distribution patterns in all Rayahs sediments; the lowest value (123.16 µg/g) has been found in RT and the maximum (422.5 µg/g) in RB, with a major difference between sites. This result was lower than that obtained in previous studies in Greater Cairo (Lasheen and Ammar 2009), Rosetta branch (El-Bouraie et al. 2010), and Nasser Lake (Imam et al. 2020). The strong positive correlation (n = 31; p = 0.01) of Mn with Zn (r = 0.95), Cu (r = 0.95), Pb (r = 0.84), Ni (r = 0.57), Cr (r = 0.96), and Cd (r = 0.89) indicates that it probably represents the geochemical support phases of these metals, associated with Mn coprecipitate, adsorbed on Mn oxides, or hydroxide (Ottosen et al. 2006).
Zinc (Zn) may occur in sediments as carbonate, oxide, and sulfide (AIP 2017; Imam et al. 2020); its concentration is mainly attributed to the input of organic wastes in aquatic environments, which come from municipal sewage and dumping materials, in addition to industrial discharges, sewage effluent, and runoff sources (Alagarsamy 2006; Goher et al. 2015). In the present study, Zn content ranged between 16.38 µg/g (in RT) and 109.56 µg/g (in RB), with a high spatial significant difference. The obtained results were lower than the corresponding values found in River Nile (102.2–261 µg/g) (Abdel Satar 2005), Damietta branch (75.5–888.5µg/g) (Goher 1998), and Upper Egypt (1 - 271 µg/g, with an average of 114 µg/g) (El-Kammar et al. 2009). However, values were higher than that recorded in Nasser Lake (11.55–82.71 µg/g) (Imam et al. 2020) and close to the values ranging from 10 to 145.95 µg/g in Ismailia Canal, obtained by El Sayed (2015) and in Greater Cairo (Lasheen and Ammar 2009). Zn exhibits a strong positive correlation (n = 31; p = 0.01) with Cu (r = 0.95), Pb (r = 0.74), Cr (r = 0.92), Cd (r = 0.82), and Ni (r = 0.43, n = 31; p = 0.05).
Copper (Cu) is a micronutrient element fundamental to all forms of life. In excessive amounts, it may become toxic to organisms by inducing a reduction in enzymes activity or a random rearrangement of structural proteins (Goldman 2007; Karak et al. 2017; Goher et al. 2019). The high Cu concentrations in El-Rayahs sediments may be attributed to the high accumulation of OM and Fe–Mn oxy-hydroxides produce simultaneous accumulation of HMs in sediments (Ottosen et al. 2006). The highest value (40.05 µg/g) of Cu was recorded in RB and the lowest (4.96 µg/g) in RT, with considerable difference between locations. The obtained results were lower than the corresponding values in River Nile (average, 42 µg/g) (El-Kammar et al. 2009) and Greater Cairo 27–90 µg/g (Lasheen and Ammar 2009). However, values were close to those (1.0–40.3 µg/g) obtained by Imam et al. (2020) for Nasser Lake. Cu exhibits a strong positive correlation (n = 31; p = 0.01) with Pb (r = 0.84), Cr (r = 0.97), Cd (r = 0.88), and Ni (r = 0.56); these results are consistent with the several studies (Goher et al. 2014; El Sayed 2015; Goher et al. 202; Abou El-Anwar et al. 2021), who reported that the deposition of Cu and Zn is enhanced by the association of metals with clay minerals or the adsorption of both elements on hydrated iron and manganese oxides. These authors also added that the order of adsorption of most mobile metals fraction is Fe/Mn oxides > OM > clay.
Lead (Pb) is considered as one of the most toxic elements to humans and animals, and its toxicity is largely dependent on its solubility (Wani et al. 2015); the form of PbSO4 is much soluble than PbCO3 and has a greater toxicity, whereas PbS has a very low solubility and toxicity (Lide 2008; SCDHEC 2020). Pb enters the aquatic environment throughout precipitation of dust fall out, leaching soil, and industrial wastes discharge (Abd El-Aal 2020). Pb contents varied in the range of 4.82–27.54 µg/g in RT and RB, respectively; this result is consistent with the results obtained by (Mostafa et al. 2019) for River Nile and (Goher et al. 2014) for Nasser Lake, whereas they are higher than those obtained by Lasheen and Ammar (2009) for Nile River in Greater Cairo (2.33–7.5 µg/g) and lower than those of Upper Egypt (average, 10 µg/g) obtained by El-Kammar et al. (2009). Pb has a strong positive correlation (n = 31; p = 0.01) with Ni (r = 0.84), Cr (r = 0.87), and Cd (r = 0.95).
Nickel (Ni) is generally considered to be an essential trace element. It is subject to homeostatic regulation and mobilization in response to disease and physiological stress, and its absence (or lack) in mammalian organisms produces well-defined deficiency symptoms (Prashanth et al. 2015). The maximum (8.57 µg/g) and minimum (2.38 µg/g) values of Ni were recorded at RN and RB, respectively; they are lower than the range of 59–65 µg/g found for Greater Cairo by Lasheen and Ammar (2009), from the value of 28.56 µg/g obtained by El Sayed (2015) for Ismailia Canal, and the range of 5.2–40 µg/g obtained by Goher et al. (2021) for River Nile. Ni has a strong positive correlation (n = 31; p = 0.01) with Cr (r = 0.61) and Cd (r = 0.73).
Chromium (Cr) is a transition metal, found in water in oxidation states, ranging from Cr+6 to Cr−2; it is a nonessential element and is classified as a toxic metal, entering watercourses through both anthropogenic and natural sources, such as geogenic processes and interaction of microbes with mafic and ultramafic rocks, in addition to industrial activities, such as production of energy, chemicals, and metals manufacturing. Furthermore, different wastes release Cr compounds into the aquatic environment (Tumolo et al. 2020). Concerning our results, the highest value of Cr (33.5 µg/g) was recorded at RB, whereas the lowest (3.45 µg/g) was recorded at RT with highly significant difference between sites. These values are lower than 185.6 µg/g, obtained by El-Bourie et al. (2010) for Rosetta branch and higher than the range of 0–8.5 µg/g, obtained by Goher et al. (2021) along the River Nile, from Aswan to Cairo. On the contrary, our results are close to the 36.6–46 µg/g range found for Greater Cairo by Lasheen and Ammar (2009). Chromium has a strong positive correlation with Cd (r = 0.91, n = 31, p = 0.01).
Cadmium (Cd) precipitates as CdCO3 coprecipitation, which is similar to lead (Imam et al. 2020; Goher et al. 2021). Its content showed a maximum level (3.066 µg/g) at RB, whereas the lowest (0.421 µg/g) was recorded at RT, with highly significant difference between sites; these results were lower than the corresponding values in River Nile in Upper Egypt (average of 3µg/g) and Damietta branch (2.04–36.64µg/g), according to (El-Kammar et al., 2009; Goher, 1998), respectively. However, our values are close to the ranges of 0.1–4.3 and 1.7–3 µg/g, obtained by Lasheen and Ammar (2009) in Greater Cairo and El Sayed (2015) for Ismailia Canal, respectively.
Notably, the maximum values for most metals, based on mean values, have been found at RB (except for nickel at RN), whereas minimum values (on average) were recorded at RT. Furthermore, the increase of HMs in the northward sediments among all Rayahs is attributed to the impact of human activities along their sides. The data of Pearson’s correlation coefficients between the measured metals with Fe and Mn (r = 0.47–0.98, n = 31, p = 0.01) revealed the role of steeling of Fe and Mn oxides in the deposition of metals into the sediment. In the same context, the positive correlation of metals with organic matter demonstrated the relation between OM accumulation and the distribution of HMs in sediments. The present study confirmed that the order of deposition of most metals is associated with Fe and Mn oxides > OM > clay, which is consistent with the results obtained by Ottosen et al. (2006); El-Kammar et al. (2009); Goher et al. (2014); Goher et al. (2021); Abou El-Anwar et al. (2021).
Contamination factor
The level of contamination of El-Rayahs sediments by given toxic substances (metals), suggested by (Hakanson 1980), is expressed in terms of a contamination factor (CF and calculated as
CF = metal content in the sediment/background level of metal.
The pollution grade of sediments, according to CF values, is given in Table 4. The most studied metals exhibited low contamination for all samples, except Cu, that exhibited moderate contamination at site B6 in RB. However, the contamination factors of Cd exhibited spatial variation, changing from moderate in most sites to very high at site B6 in RB.
Contamination degree
The degree of contamination (Cd) was originally defined as the sum of all contamination factors: (Cd) = ∑ CF. Results showed that the degree of contamination was low at all Rayahs, except the northern part of RB (El-Mahmoudia Canal), which was very-highly contaminated (Table 4).
The pollution load index
Tomlinson et al. (1980) proposed the PLI, which can provide useful information on the level of pollution at a given location (Mohiuddin et al. 2010; Harikumar and Jisha 2010). PLI for a single site is the nth root of the product of n CF values, according to the following formula:
PLI for a site = nth√CF1 * CF2*...Fn
where CF = contamination factor and n = number of metals, whereas
PLI for a zone = nth√site1 * site2*...iten
where n equals the number of sites.
PLI data (Table 4) provide a simple comparison mean for evaluating the quality of a site or area (0.0 denotes perfection, 1.0 indicates the baseline levels of existent contaminant, and >1.0 indicates tolerant deterioration of the site) (Table 2) (Tomlinson et al. 1980; Cabrera et al. 1999). Based on PLI values of El-Rayahs sediments, which are <1 in all examined sites, they are categorized as not significantly polluted.
Table (4): Contamination factor,Degree of Contamination (Cd) and Pollution Load Index (PLI) of the studied trace metals of the four Rayahs sediments.
Site
|
Contamination Factor (Cf)
|
Degree of Contamination (Cd)
|
Pollution Load Index (PLI)
|
Fe
|
Mn
|
Zn
|
Cu
|
Pb
|
Ni
|
Cr
|
Cd
|
T1
|
0.144
|
0.130
|
0.172
|
0.124
|
0.241
|
0.052
|
0.037
|
1.404
|
2.305
|
0.151
|
T2
|
0.184
|
0.145
|
0.179
|
0.176
|
0.322
|
0.050
|
0.054
|
1.640
|
2.750
|
0.182
|
T3
|
0.210
|
0.144
|
0.183
|
0.207
|
0.367
|
0.047
|
0.063
|
1.93
|
3.151
|
0.199
|
T4
|
0.241
|
0.164
|
0.266
|
0.218
|
0.389
|
0.071
|
0.078
|
2.303
|
3.730
|
0.241
|
T5
|
0.229
|
0.178
|
0.273
|
0.228
|
0.372
|
0.062
|
0.067
|
2.474
|
3.882
|
0.236
|
T6
|
0.243
|
0.160
|
0.293
|
0.263
|
0.397
|
0.054
|
0.069
|
2.447
|
3.925
|
0.239
|
T7
|
0.325
|
0.212
|
0.383
|
0.317
|
0.645
|
0.083
|
0.098
|
4.215
|
6.277
|
0.341
|
zone
|
|
|
|
|
|
|
|
|
|
0.221
|
M1
|
0.169
|
0.187
|
0.257
|
0.238
|
0.374
|
0.053
|
0.074
|
2.453
|
3.806
|
0.227
|
M2
|
0.174
|
0.205
|
0.219
|
0.246
|
0.353
|
0.056
|
0.070
|
2.412
|
3.735
|
0.225
|
M3
|
0.194
|
0.187
|
0.247
|
0.306
|
0.395
|
0.045
|
0.081
|
2.470
|
3.924
|
0.236
|
M4
|
0.291
|
0.265
|
0.439
|
0.413
|
0.795
|
0.100
|
0.123
|
3.813
|
6.239
|
0.389
|
M5
|
0.245
|
0.220
|
0.320
|
0.325
|
0.460
|
0.065
|
0.085
|
3.291
|
5.012
|
0.288
|
M6
|
0.248
|
0.194
|
0.336
|
0.332
|
0.540
|
0.060
|
0.087
|
3.308
|
5.105
|
0.290
|
M7
|
0.239
|
0.214
|
0.343
|
0.340
|
0.654
|
0.071
|
0.090
|
3.577
|
5.529
|
0.312
|
zone
|
|
|
|
|
|
|
|
|
|
0.276
|
B1
|
0.167
|
0.299
|
0.702
|
0.541
|
0.518
|
0.057
|
0.186
|
2.615
|
5.084
|
0.358
|
B2
|
0.153
|
0.268
|
0.828
|
0.583
|
0.421
|
0.041
|
0.154
|
3.383
|
5.832
|
0.340
|
B3
|
0.177
|
0.267
|
0.762
|
0.500
|
0.407
|
0.035
|
0.157
|
3.363
|
5.670
|
0.329
|
B4
|
0.209
|
0.252
|
0.748
|
0.565
|
0.503
|
0.045
|
0.119
|
3.582
|
6.022
|
0.348
|
B5
|
0.176
|
0.307
|
0.666
|
0.660
|
0.448
|
0.050
|
0.228
|
3.346
|
5.880
|
0.377
|
B6
|
0.319
|
0.445
|
1.153
|
1.001
|
1.377
|
0.126
|
0.372
|
10.220
|
15.014
|
0.757
|
B7
|
0.276
|
0.378
|
0.886
|
0.808
|
1.062
|
0.086
|
0.283
|
7.738
|
11.516
|
0.591
|
B8
|
0.266
|
0.363
|
0.956
|
0.822
|
1.037
|
0.092
|
0.276
|
5.759
|
9.571
|
0.572
|
B9
|
0.298
|
0.416
|
1.114
|
0.907
|
1.252
|
0.108
|
0.328
|
8.509
|
12.932
|
0.683
|
zone
|
|
|
|
|
|
|
|
|
|
0.368
|
N1
|
0.182
|
0.198
|
0.417
|
0.420
|
0.405
|
0.064
|
0.106
|
2.815
|
4.606
|
0.289
|
N2
|
0.181
|
0.192
|
0.359
|
0.423
|
0.448
|
0.081
|
0.098
|
2.719
|
4.501
|
0.291
|
N3
|
0.195
|
0.189
|
0.427
|
0.422
|
0.488
|
0.045
|
0.099
|
3.324
|
5.189
|
0.289
|
N4
|
0.158
|
0.174
|
0.277
|
0.367
|
0.441
|
0.039
|
0.073
|
2.407
|
3.936
|
0.232
|
N5
|
0.192
|
0.259
|
0.515
|
0.592
|
0.930
|
0.126
|
0.178
|
4.644
|
7.435
|
0.442
|
N6
|
0.245
|
0.208
|
0.428
|
0.482
|
0.742
|
0.099
|
0.152
|
4.281
|
6.638
|
0.387
|
N7
|
0.260
|
0.220
|
0.416
|
0.489
|
0.814
|
0.072
|
0.143
|
4.626
|
7.040
|
0.382
|
N8
|
0.248
|
0.232
|
0.451
|
0.500
|
0.703
|
0.074
|
0.184
|
4.112
|
6.504
|
0.388
|
zone
|
|
|
|
|
|
|
|
|
|
0.282
|
Ecological risk factor and Potential ecological risk
An ecological risk factor (Er) is a numerical expression of a contaminant’s potential ecological risk:
Er = T * CF,
where T is the toxic response factor for a specific substance and CF is the contamination factor. T equals 1 for Fe, Mn, and Zn; 2 for Cr; 5 for Cu, Pb, and Ni; and 30 for Cd (Hakanson 1980). Er values of El-Rayahs sediments showed that all sites have a low ecological risk for all analyzed metals, except Cd that showed moderate to considerable risk at RT, RM, and RN, with a noticeable increase northward; a high ecological risk exists in RB especially, at the northern segment (El-Mahmoudia Canal) (Table 5). In the same context, the potential ecological risk (RI), which is defined as the sum of risk factor (RI = ∑ Er), showed a low ecological risk for all Rayahs except the north of RB, which had a high ecological risk (Table 5).
Table (5): Ecological Risk Factor (Er), Potential Ecological Risk Index (RI) of the studied trace metals of the four Rayahs sediments.
Site
|
Ecological Risk Factor (Er)
|
Potential Ecological Risk Index (RI)
|
Fe
|
Mn
|
Zn
|
Cu
|
Pb
|
Ni
|
Cr
|
Cd
|
|
T1
|
0.144
|
0.130
|
0.172
|
0.620
|
1.204
|
0.262
|
0.074
|
42.125
|
44.73
|
T2
|
0.184
|
0.145
|
0.179
|
0.880
|
1.609
|
0.252
|
0.107
|
49.185
|
52.54
|
T3
|
0.210
|
0.144
|
0.183
|
1.034
|
1.833
|
0.237
|
0.126
|
57.910
|
61.68
|
T4
|
0.241
|
0.164
|
0.266
|
1.091
|
1.945
|
0.353
|
0.156
|
69.100
|
73.32
|
T5
|
0.229
|
0.178
|
0.273
|
1.140
|
1.859
|
0.309
|
0.134
|
74.208
|
78.33
|
T6
|
0.243
|
0.160
|
0.293
|
1.313
|
1.985
|
0.269
|
0.137
|
73.405
|
77.80
|
T7
|
0.325
|
0.212
|
0.383
|
1.585
|
3.226
|
0.413
|
0.195
|
126.450
|
132.79
|
M1
|
0.169
|
0.187
|
0.257
|
1.189
|
1.871
|
0.265
|
0.148
|
73.600
|
77.69
|
M2
|
0.174
|
0.205
|
0.219
|
1.231
|
1.764
|
0.282
|
0.140
|
72.350
|
76.37
|
M3
|
0.194
|
0.187
|
0.247
|
1.528
|
1.973
|
0.227
|
0.162
|
74.100
|
78.62
|
M4
|
0.291
|
0.265
|
0.439
|
2.064
|
3.976
|
0.499
|
0.246
|
114.400
|
122.18
|
M5
|
0.245
|
0.220
|
0.320
|
1.626
|
2.301
|
0.327
|
0.169
|
98.725
|
103.93
|
M6
|
0.248
|
0.194
|
0.336
|
1.662
|
2.702
|
0.301
|
0.174
|
99.225
|
104.84
|
M7
|
0.239
|
0.214
|
0.343
|
1.701
|
3.271
|
0.356
|
0.180
|
107.300
|
113.61
|
B1
|
0.167
|
0.299
|
0.702
|
2.706
|
2.588
|
0.283
|
0.371
|
78.450
|
85.57
|
B2
|
0.153
|
0.268
|
0.828
|
2.916
|
2.105
|
0.207
|
0.309
|
101.500
|
108.29
|
B3
|
0.177
|
0.267
|
0.762
|
2.502
|
2.035
|
0.175
|
0.315
|
100.880
|
107.11
|
B4
|
0.209
|
0.252
|
0.748
|
2.824
|
2.515
|
0.224
|
0.238
|
107.450
|
114.46
|
B5
|
0.176
|
0.307
|
0.666
|
3.299
|
2.241
|
0.249
|
0.455
|
100.375
|
107.77
|
B6
|
0.319
|
0.445
|
1.153
|
5.006
|
6.886
|
0.628
|
0.745
|
306.621
|
321.80
|
B7
|
0.276
|
0.378
|
0.886
|
4.038
|
5.310
|
0.430
|
0.565
|
232.140
|
244.02
|
B8
|
0.266
|
0.363
|
0.956
|
4.111
|
5.186
|
0.458
|
0.553
|
172.778
|
184.67
|
B9
|
0.298
|
0.416
|
1.114
|
4.536
|
6.258
|
0.542
|
0.656
|
255.275
|
269.10
|
N1
|
0.182
|
0.198
|
0.417
|
2.099
|
2.026
|
0.319
|
0.211
|
84.443
|
89.89
|
N2
|
0.181
|
0.192
|
0.359
|
2.116
|
2.238
|
0.405
|
0.197
|
81.575
|
87.26
|
N3
|
0.195
|
0.189
|
0.427
|
2.108
|
2.438
|
0.225
|
0.198
|
99.725
|
105.51
|
N4
|
0.158
|
0.174
|
0.277
|
1.835
|
2.207
|
0.194
|
0.147
|
72.200
|
77.19
|
N5
|
0.192
|
0.259
|
0.515
|
2.958
|
4.651
|
0.630
|
0.356
|
139.325
|
148.88
|
N6
|
0.245
|
0.208
|
0.428
|
2.410
|
3.709
|
0.495
|
0.304
|
128.425
|
136.23
|
N7
|
0.260
|
0.220
|
0.416
|
2.445
|
4.071
|
0.360
|
0.286
|
138.775
|
146.83
|
N8
|
0.248
|
0.232
|
0.451
|
2.502
|
3.516
|
0.371
|
0.368
|
123.350
|
131.04
|
Enrichment factor
The EF is a commonly used method for determining enrichment ratios and the degree of anthropogenic pollution (Zakir et al. 2008):
EF = [CM/CX)sample /)CM/CX)Earth's crust]
where CM is the concentration of the analyzed metal and CX is the concentration of the immobile element, such as Al, Fe, Ti, Mn, Li, Sc, or Zr (Blaser et al. 2000; Liu et al., 2005; Chatterjee et al. 2007; Zhang et al., 2007; Goher et al. 2014; Tiomo et al. 2021). In the present study, Fe has been selected as the immobile element. Furthermore, ASVs levels are used as background concentrations; several authors indicated the degree of metal pollution with metal levels according to average shale (Muller 1969; Forstner and Muller 1973; Goher et al. 2014; Goher et al. 2021; Nasir et al. 2021).
According to Table 2, four contamination groups are commonly diagnosed based on the enrichment factor (Sutherland 2000): EF > 1 indicates high metal content in the sample relative to its level in the Earth’s crust. In contrast, EF values > 5 define sediments as polluted (Atgin et al. 2000). According to Zhang and Liu (2002), EF values between 0.5 and 1.5 suggest that the source of metals in sediments is because of crustal materials or natural processes, whereas EF values > 1.5 indicate an anthropogenic effect. Based on the above considerations, values of EF of Ni, Cr, and Mn did not cause remarkable contamination in the El-Rayahs sediments; however, Cu and Zn in RB and RN, and Pb in all Rayahs, except RT, showed moderate contamination. Only Cd showed high EF values, indicating significant to very high enrichment at all El-Rayahs, signifying the anthropogenic source of Cd (Table 6).
Table (6): Enrichment Factor (EF) of the studied trace metals of the four Rayahs sediments.
Site
|
Enrichment Factor (EF)
|
Fe
|
Mn
|
Zn
|
Cu
|
Pb
|
Ni
|
Cr
|
Cd
|
T1
|
|
0.897
|
1.193
|
0.858
|
1.668
|
0.362
|
0.258
|
9.721
|
T2
|
|
0.789
|
0.973
|
0.955
|
1.746
|
0.273
|
0.29
|
8.894
|
T3
|
|
0.687
|
0.875
|
0.986
|
1.747
|
0.226
|
0.3
|
9.204
|
T4
|
|
0.678
|
1.103
|
0.904
|
1.612
|
0.292
|
0.323
|
9.545
|
T5
|
|
0.78
|
1.194
|
0.998
|
1.626
|
0.27
|
0.294
|
10.82
|
T6
|
|
0.661
|
1.208
|
1.083
|
1.637
|
0.222
|
0.283
|
10.09
|
T7
|
|
0.654
|
1.178
|
0.976
|
1.986
|
0.254
|
0.3
|
12.98
|
M1
|
|
1.101
|
1.519
|
1.403
|
2.208
|
0.313
|
0.437
|
14.48
|
M2
|
|
1.177
|
1.255
|
1.412
|
2.023
|
0.323
|
0.4
|
13.83
|
M3
|
|
0.962
|
1.271
|
1.574
|
2.033
|
0.233
|
0.417
|
12.72
|
M4
|
|
0.91
|
1.505
|
1.417
|
2.729
|
0.342
|
0.422
|
13.09
|
M5
|
|
0.896
|
1.306
|
1.325
|
1.875
|
0.266
|
0.344
|
13.41
|
M6
|
|
0.785
|
1.355
|
1.342
|
2.181
|
0.243
|
0.352
|
13.35
|
M7
|
|
0.897
|
1.434
|
1.422
|
2.735
|
0.297
|
0.377
|
14.95
|
B1
|
|
1.794
|
4.206
|
3.243
|
3.102
|
0.339
|
1.113
|
15.67
|
B2
|
|
1.755
|
5.432
|
3.824
|
2.76
|
0.271
|
1.012
|
22.18
|
B3
|
|
1.509
|
4.3
|
2.822
|
2.295
|
0.197
|
0.887
|
18.96
|
B4
|
|
1.207
|
3.589
|
2.708
|
2.412
|
0.215
|
0.57
|
17.18
|
B5
|
|
1.744
|
3.791
|
3.754
|
2.55
|
0.284
|
1.295
|
19.03
|
B6
|
|
1.394
|
3.615
|
3.138
|
4.316
|
0.394
|
1.167
|
32.03
|
B7
|
|
1.366
|
3.205
|
2.922
|
3.843
|
0.311
|
1.023
|
28
|
B8
|
|
1.367
|
3.601
|
3.097
|
3.906
|
0.345
|
1.041
|
21.69
|
B9
|
|
1.398
|
3.739
|
3.046
|
4.203
|
0.364
|
1.101
|
28.57
|
N1
|
|
1.09
|
2.292
|
2.31
|
2.23
|
0.351
|
0.581
|
15.49
|
N2
|
|
1.061
|
1.983
|
2.336
|
2.472
|
0.447
|
0.543
|
15.02
|
N3
|
|
0.97
|
2.191
|
2.161
|
2.499
|
0.23
|
0.508
|
17.04
|
N4
|
|
1.104
|
1.758
|
2.328
|
2.8
|
0.246
|
0.466
|
15.27
|
N5
|
|
1.352
|
2.689
|
3.089
|
4.857
|
0.658
|
0.928
|
24.25
|
N6
|
|
0.849
|
1.744
|
1.964
|
3.022
|
0.403
|
0.619
|
17.44
|
N7
|
|
0.848
|
1.603
|
1.883
|
3.136
|
0.278
|
0.551
|
17.82
|
N8
|
|
0.938
|
1.821
|
2.02
|
2.839
|
0.299
|
0.742
|
16.6
|
Geo-accumulation index
The geo-accumulation index (Igeo) values are calculated for the studied metals, as introduced by Muller (1981), as follows:
Igeo=log2 [Cn/(1.5*bn)]
where Cn is the content of analyzed element (n) in the sample and bn is the geochemical background. Muller (1981) proposed seven grades (or classes) of the geo-accumulation index (Table 2). According to the Igeo of the analyzed metals (Table 7), El-Rayahs sediments are classified as unpolluted for all metals at all sites, except Cd, which exhibited moderate pollution in most sites, with a remarkable enrichment northward, particularly in RB.
Table (7): Index Geo-Accumulation (I geo ) of the studied trace metals of the four Rayahs sediments.
Site
|
Index Geo-Accumulation (Igeo)
|
Fe
|
Mn
|
Zn
|
Cu
|
Pb
|
Ni
|
Cr
|
Cd
|
T1
|
-3.38
|
-3.53
|
-3.12
|
-3.597
|
-2.64
|
-4.84
|
-5.33
|
-0.1
|
T2
|
-3.02
|
-3.37
|
-3.06
|
-3.091
|
-2.22
|
-4.9
|
-4.81
|
0.128
|
T3
|
-2.84
|
-3.38
|
-3.03
|
-2.859
|
-2.03
|
-4.98
|
-4.57
|
0.364
|
T4
|
-2.64
|
-3.2
|
-2.49
|
-2.781
|
-1.95
|
-4.41
|
-4.26
|
0.619
|
T5
|
-2.71
|
-3.07
|
-2.46
|
-2.717
|
-2.01
|
-4.6
|
-4.48
|
0.722
|
T6
|
-2.63
|
-3.23
|
-2.36
|
-2.514
|
-1.92
|
-4.8
|
-4.45
|
0.706
|
T7
|
-2.21
|
-2.82
|
-1.97
|
-2.242
|
-1.22
|
-4.18
|
-3.94
|
1.491
|
M1
|
-3.15
|
-3.01
|
-2.54
|
-2.657
|
-2
|
-4.82
|
-4.34
|
0.71
|
M2
|
-3.1
|
-2.87
|
-2.78
|
-2.607
|
-2.09
|
-4.73
|
-4.43
|
0.685
|
M3
|
-2.95
|
-3.01
|
-2.6
|
-2.296
|
-1.93
|
-5.05
|
-4.21
|
0.72
|
M4
|
-2.36
|
-2.5
|
-1.77
|
-1.861
|
-0.92
|
-3.91
|
-3.61
|
1.346
|
M5
|
-2.61
|
-2.77
|
-2.23
|
-2.206
|
-1.7
|
-4.52
|
-4.15
|
1.133
|
M6
|
-2.6
|
-2.95
|
-2.16
|
-2.174
|
-1.47
|
-4.64
|
-4.1
|
1.141
|
M7
|
-2.65
|
-2.81
|
-2.13
|
-2.141
|
-1.2
|
-4.4
|
-4.06
|
1.254
|
B1
|
-3.17
|
-2.33
|
-1.1
|
-1.471
|
-1.54
|
-4.73
|
-3.01
|
0.802
|
B2
|
-3.3
|
-2.49
|
-0.86
|
-1.363
|
-1.83
|
-5.18
|
-3.28
|
1.173
|
B3
|
-3.08
|
-2.49
|
-0.98
|
-1.584
|
-1.88
|
-5.42
|
-3.25
|
1.165
|
B4
|
-2.85
|
-2.58
|
-1
|
-1.409
|
-1.58
|
-5.07
|
-3.66
|
1.256
|
B5
|
-3.09
|
-2.29
|
-1.17
|
-1.185
|
-1.74
|
-4.91
|
-2.72
|
1.157
|
B6
|
-2.23
|
-1.75
|
-0.38
|
-0.583
|
-0.12
|
-3.58
|
-2.01
|
2.768
|
B7
|
-2.44
|
-1.99
|
-0.76
|
-0.893
|
-0.5
|
-4.12
|
-2.41
|
2.367
|
B8
|
-2.5
|
-2.05
|
-0.65
|
-0.867
|
-0.53
|
-4.03
|
-2.44
|
1.941
|
B9
|
-2.33
|
-1.85
|
-0.43
|
-0.725
|
-0.26
|
-3.79
|
-2.19
|
2.504
|
N1
|
-3.05
|
-2.92
|
-1.85
|
-1.837
|
-1.89
|
-4.56
|
-3.83
|
0.908
|
N2
|
-3.05
|
-2.97
|
-2.06
|
-1.826
|
-1.74
|
-4.21
|
-3.93
|
0.858
|
N3
|
-2.94
|
-2.99
|
-1.81
|
-1.831
|
-1.62
|
-5.06
|
-3.92
|
1.148
|
N4
|
-3.25
|
-3.11
|
-2.44
|
-2.031
|
-1.76
|
-5.28
|
-4.35
|
0.682
|
N5
|
-2.97
|
-2.53
|
-1.54
|
-1.342
|
-0.69
|
-3.57
|
-3.08
|
1.63
|
N6
|
-2.61
|
-2.85
|
-1.81
|
-1.638
|
-1.02
|
-3.92
|
-3.3
|
1.513
|
N7
|
-2.53
|
-2.77
|
-1.85
|
-1.617
|
-0.88
|
-4.38
|
-3.39
|
1.625
|
N8
|
-2.6
|
-2.69
|
-1.73
|
-1.584
|
-1.09
|
-4.34
|
-3.03
|
1.455
|
Notably, based on different indices data, Cd represented the source of higher environmental risk in all El-Rayahs sediments, which is consistent with (Goher et al. 2021) for sediments of the Nile River from Aswan to Cairo. However, our results differ from (Abou El-Anwar 2019), who indicated that Zn, Ni, Cr, and Cd are the most possible sources of pollution in sediments of Nile in Upper Egypt.
Sediment quality guidelines
In recent years, the effect of contaminated sediments on sediment-dwelling organisms (such as invertebrates and plants), aquatic-dependent wildlife (such as mammals, birds, fish, reptiles, and amphibians), and human health has become more intelligible. There are three levels of potential toxic effect on benthic creatures that depend on the continuous, long-term impact of pollutants: the first is “no effect levels,” at which no hazardous effect on aquatic creatures has been documented and where no biomagnification via food chain is anticipated; the second is the “lowest effect level,” which denotes a level of sediment pollution that the majority of benthic organisms can tolerate or at which the levels of contaminant exhibit a low possible risk effect; the third is the “severe effect level,” which denotes the levels of pollutant that has a high potential effect and may harm the majority of benthic species. Moreover, the sediment-dwelling community is likely to be significantly disrupted.
There are different approaches for the sediment quality guidelines set by several authors and organizations (Persaud et al. 1993; Smith et al. 1996; Long and Morgan 1991; USEPA 1996b, 1997; SLC/MOVIE 1992). In the present study, the screening level concentration approach (SLCA), recommended by (Persaud et al. 1993) for the lowest effect level (LEL) and severe effect level (SEL), is used to assess the quality of El-Rayahs sediments and the potential risk of HMs on benthic organisms. Table 8 shows that Fe, Mn, Zn, Ni, and Pb were below their LEL levels: thus, they did not have any adverse effect on benthic organisms in all El-Rayahs. However, Cd exceeded LEL in 47% of RT and all other sites, confirming that Cd has the greatest toxic effect on benthic creatures. Furthermore, Cu exceeded LEL and showed adverse effect in 14.3%, 100%, and 75%, in RM, RB, and RN samples, respectively, whereas Cr recorded values above its LEL in 100% of RB samples.
Table (8). The levels of heavy metals in El-Rayah sediment in µg/g compared to the levels of Sediment Quality Guidelines ( SQGs)
|
Metal
|
Cd
|
Cr
|
Cu
|
Fe1
|
Pb
|
Mn1
|
Ni
|
Zn
|
SQGs(1)
|
LEL
|
0.6
|
26
|
16
|
20000
|
31
|
460
|
16
|
120
|
SEL
|
10
|
110
|
110
|
40000
|
250
|
1100
|
75
|
820
|
El-Tawfiky
|
present result
|
|
0.421-1.265
|
3.35-8.79
|
4.96-12.68
|
6750-15170
|
4.82-12.9
|
123.16-201.81
|
3.22-5.62
|
16.83-36.36
|
Samples <LEL
|
%
|
43
|
100
|
100
|
100
|
100
|
100
|
100
|
100
|
<SEL samples >LEL
|
%
|
57
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
Samples>SEL
|
%
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
El-Menoufy
|
present result
|
|
0.724-1.144
|
6.28-11.08
|
9.51-16.51
|
7910-13610
|
7.06-15.9
|
177.2-252.04
|
3.08-6.78
|
20.8-41.66
|
Samples <LEL
|
%
|
0
|
100
|
85.7
|
100
|
100
|
100
|
100
|
100
|
<SEL samples >LEL
|
%
|
100
|
0
|
14.3
|
0
|
0
|
0
|
0
|
0
|
Samples>SEL
|
%
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
El-Behary
|
present result
|
|
0.785-3.056
|
10.7-33.5
|
20.02-40.05
|
7120-14900
|
8.14-27.54
|
239.14-422.5
|
2.38-8.54
|
7.12-109.56
|
Samples <LEL
|
%
|
0
|
77.8
|
0
|
100
|
100
|
100
|
100
|
100
|
<SEL samples >LEL
|
%
|
100
|
22.2
|
100
|
0
|
0
|
0
|
0
|
0
|
Samples>SEL
|
%
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
El-Nassery
|
present result
|
|
0.722-1.393
|
6.61-16.54
|
14.68-23.66
|
7360-12130
|
8.11-18.6
|
165.29-245.96
|
2.63-8.57
|
26.33-48.93
|
Samples <LEL
|
%
|
0
|
100
|
25
|
100
|
100
|
100
|
100
|
100
|
<SEL samples >LEL
|
%
|
100
|
0
|
75
|
0
|
0
|
0
|
0
|
0
|
Samples>SEL
|
%
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
SQG = Sediment Quality guidelines; LEL= lowest effect level; SEL= severe effect level;, (1) according to Persaud et al. (1993), |