Environ Monit Assess (2014) 186:4289–4297 DOI 10.1007/s10661-014-3698-5
Origination and assessment of metal pollution in Qarechay River bed sediments Aida Biati & Abdulreza R. Karbassi & Zahra Keyhani
Received: 22 November 2013 / Accepted: 20 February 2014 / Published online: 14 March 2014 # Springer International Publishing Switzerland 2014
Abstract In the present investigation, bulk and chemical partitioning of elements (Cu, Mn, Ni, Zn, Fe, Ca) together with organic matter as a loss in ignition in the Qarechay River bed sediments have been studied. The concentration of metals in Qarechay River bed sediments is governed by the geological units of the study area. The study of anthropogenic portion shows that a small proportion of elemental concentration belongs to this phase. However, Mn has a large portion of anthropogenic sources (43 %). Also, Mn has a share of 13.6 % in sulfide fractions. This result indicates that Mn is a highly mobile element and can easily enter the water column. The presence of Mn in sulfide fraction might be indicative of initial stages of conversion of oxidation state into reduction in Qarechay River. Share of metals in anthropogenic portion is in the following order: Mn
(43 %)>Cu (19 %)>Zn (10 %)>Ni (3 %)>Fe (0 %). Organic metallic bonds are not significantly present in the study area. Geochemical index (Igeo), pollution index (Ipoll), enrichment factor (EF), and pollution load index (PLI) values are indicative of a clean environment throughout the river course. These values are in well agreement with results of chemical partitioning data. Eventually, based on the results of chemical partitioning, regional standard of elements for Qarechay River bed sediments has been established. Keywords Chemical partitioning . Pollution intensity index . Geochemistry . Bed sediment . Anthropogenic portion
Introduction A. Biati (*) Department of Environmental Science, Graduate Faculty of Environment and Energy, Tehran Science and Research Branch, Islamic Azad University, Tehran, Iran e-mail: [email protected] A. R. Karbassi Graduate Faculty of Environment, University of Tehran, 141556135 Tehran, Iran e-mail: [email protected] Z. Keyhani Department of Environmental Geology, Graduate Faculty of Environment and Energy, Tehran Science and Research Branch, Islamic Azad University, Tehran, Iran
Heavy metals are among the most common environmental pollutants, and their occurrence in waters and biota indicates the presence of natural or anthropogenic sources. The existence of trace metals in aquatic environments has led to serious concerns about their influence on plant and animal life (Zvinowanda et al. 2009; Sheikh et al. 2007). Many researchers have used sediments to study the behavior of metals over time of sedimentation (Bellucci et al. 2003; Bertolotto et al. 2003; Al-Masri et al. 2002; Borretzen and Salbu 2002; Weis et al. 2001; Lee and Cundy 2001; Karbassi 1989). Forstner and Muller (1973) used a sediment pollution index to evaluate the heavy metal pollution of rivers of Germany.
4290
Sediment quality values are a useful tool to screen the potential for contaminants within sediment to induce biological effects and to compare sediment contaminant concentration with corresponding quality guideline (Mohan 2000). These indexes evaluate the degree to which the sediment-associated chemical status might adversely affect aquatic organisms and are designed to assist sediment assessors and manager responsible for the interpretation of sediment quality (Borole et al. 1982). It is also to rank and prioritize the contaminated areas or the chemicals for further investigation (Adams et al. 1992). Qarechay is one of two permanent and big rivers in Markazi Province in the central part of Iran. This river is almost 540 km long, and its catchment area is 1,800 km2. It originates from the heights of Shazand and finally flows into the Qom salt lake. In recent years, due to the reduced rainfall and construction of “Alghadir” dam for agricultural purposes, the mean annual discharge of this river has been decrease. Trace element pollution in rive, lake, estuary, and bay sediments has been reported by many researchers around the world (Al-Masri et al. 2002; Coker et al. 1995; Farmer 1991). However, study on the geochemistry of Qarechay River sediments in the present study area has not been undertaken by previous researchers so far.
Materials and methods Riverine sediments were collected from six stations in Qarechay River in winter 2012 using a Peterson grab sampler. Location of samples is shown in Fig. 1. The riverbed sediments are brownish clayey silts deposited in the recent times. These samples were instantly placed in polyethylene bags, refrigerated, and carried to the laboratory. Sediments were dried at 70 °C for 24 h and passed through a mesh smaller than 63 μm. The sediment grains were then powdered using an agate mortal and pestle. Bulk digestion was carried out by HF– HNO3–HCl–HClO4. Chemical partition studies were carried out in four sequential steps: (1) 25 %v/v acetic acid, (2) 25 %v/v acetic acid–0.1 M hydroxylamine hydrochloride, (3) 30 % H2O2 “extraction with 1 M ammonium acetate,” and (4) 50 % hot HCl (Malo 1977; Gupta and Chen 1975; Gibbs 1973; Chester and Hughes 1967). Metal concentrations were measured by the Varian SpectrAA-200 at Science and Research Branch, I.A. University, Tehran, Iran, in spring 2013.
Environ Monit Assess (2014) 186:4289–4297
Procedural blanks and duplicates were run with the samples in a similar way for quality assurance of the laboratory analysis. The accuracy of analysis was about ±5 % for all elements. A standard sample (MESS-1) was analyzed in the same manner for analysis accuracy check. Results showed that the errors in the analysis were Zn (13.5 %) > Cu (13.3 %)>Ni (12.2 %)>Fe (2.8 %) Sulfide ions Mn (13.6 %) > Zn (0.3 %) > Fe (0.2 %)>Cu,Ni (0 %) Fig. 2 Dendrogram of cluster analysis for metals in Qarechay River bed sediments
Organic ions Cu (13.4 %)>Mn (6 %)>Zn (5.5 %)> Fe (2.5 %)>Ni (0 %) Resistant ions Zn (73.6 %) > Fe (62.9 %) > Ni (58.4 %)>Cu (47.8 %)>Mn (37.3 %) Within lattice ions Fe (31.6 %)>Ni (29.4 %)>Cu (25.5 %)>Mn (14.2 %)>Zn (7.1 %). In this study, Mn is the metal showing the highest mobility (upper than 28 %) in the loose ions fraction. It can be concluded that this element might be present in the form of carbonates in the area of study. Therefore, Mn shows more concentration in the loose ions fraction. The study of anthropogenic portion shows that a large portion of total concentration of Mn is related to this
Environ Monit Assess (2014) 186:4289–4297
4293
Table 2 Chemical partitioning of metals in Qarechay River bed sediments Elements
Cu (mg/kg)
Station bond a b c d
Ni (mg/kg) e a b c d
Mn (mg/kg) e
Zn (mg/kg)
a
b
c
17
145 0
d
e
a
Fe (%)
b c d
a
b
1
3 0 3 13 3 5 0 0 22 9
2
4 0 3 11 5 6 0 0 25 10 262 0
55 200 0
6
2 0 3 8
27 107 93 16 0 9 107 19 0.06 0
9 5 0 0 33 24 107 13
167 62 26 0 6 85
e
9
1 6 87
c
d
e
4
0.04 0
6
0.05 0.01 0.07 1.14 0.39
0.01 1.06 0.44 0.06 1.13 0.94
a loosely bonded ions, b sulfide bonded ions, c organic–metallic bonded ions, d resistant bonded ions, e within lattice bonded ions
and mean world sediments, chemical partitioning proves a lithogenous source for this element (90 %), and share of anthropogenic portion is not significant. Share of anthropogenic and lithogenous portions can be summarized as follows:
phase (43 %). Also, Mn has a share of 13.6 and 6 % in sulfide and organic fractions, respectively. These results indicate that Mn is a highly mobile element and can easily enter the water column. The presence of Mn in sulfide fraction might be indicative of initial stages of conversion of oxidation state into reduction (Karbassi 1996) in Qarechay River. Further, the results of chemical partitioning were grouped into anthropogenic and lithogenous ones. As shown in Fig. 3, a small proportion of elemental concentration is in anthropogenic phase (except for Mn). Among all of the studied elements, Mn and Ni have the highest and the lowest share of anthropogenic sources, respectively, but Fe showing no anthropogenic portion remains constant in all sampling stations. Although results of bulk digestion show a higher concentration of Zn than those of shale, mean crust,
Fig. 3 Lithogenous and anthropogenic portions of trace metals in the bed sediments of Qarechay River
Lithogenous Fe (100 %)>Ni (97 %)>Zn (90 %)> Cu (81 %)>Mn (57 %) Anthropogenic Mn (43 %) > Cu (19 %) > Zn (10 %)>Ni (3 %)>Fe (0 %).
Calculation of pollution intensity The concentrations of various metals provide measures for determining the level of pollution in Qarechay sediments, based on Muller’s Index (Igeo), EF, and Ipoll. One
Fe6 0
100
Fe2 0
100
Fe1 0
100
Zn6
7
Zn2
5
Zn1
93 95 18
Mn6
82 36
Mn2
64 57
Mn1
35
65
Ni6 0 Ni2
5
95 96 14
Cu2
86 23
Cu1
77
19 0
Lithogenous
100
Ni1 4 Cu 6
Anthropogenic
43
81 20
40
60
Metals Percentile
80
100
120
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Environ Monit Assess (2014) 186:4289–4297
Table 3 Comparison of Igeo, Ipoll, and EF values for metals in Qarechay River sediments Elements
Ipoll
Igeo Stations
Mean
S1
S2
S6
Cu
0
0
0
Ni
0
0
0
Mn
0
0
Zn
0
0
EF
Stations S1
S2
S6
0
0.45
0.52
0.37
0
0.21
0.23
0.12
0
0
0.76
1.25
0
0
0.44
0.23
of the evaluation methods for the intensity of metal contamination in Qarechay sediments is the geochemical accumulation index I geo ¼ Log2 C n =ð1:5 Bn Þ
ð1Þ
where Igeo, Cn, and Bn are the geochemical accumulation index, the sediment metal concentration, and the metal concentration in the shale, respectively (Gonzalez et al. 2000; Forstner et al. 1991; Muller 1979). In this formula, the constant number 1.5 is applied as a factor for normalization to background metal concentrations. The enrichment factor can be calculated for metals using EF ¼ ðC n =C Fe Þsample =ðC n =C Fe Þcrust
ð2Þ
where (Cn/CFe)sample is the ratio of the element concentration (Cn) to the concentration of Fe (CFe). In the sediment sample, (Cn/CFe)crust is the same ratio in an unpolluted reference sample (Pekey 2006; Ergin et al. 1991; Rule 1986; Buat-Menard and Chesselet 1979). Based on the results of chemical partitioning, the anthropogenic portion of metals can be separated from their lithogenic portion. Therefore, Muller’s formula has been modified in order to correctly measure the Table 4 Contamination factor and PLI in Qarechay River bed sediments Stations
Mean
CF
PLI
Cu
Ni
Mn
Zn
Fe
S1
0.49
0.5
0.46
1.3
0.3
0.5
S2
0.5
0.6
0.6
1.1
0.35
0.6
S6
0.49
0.9
0.4
1.6
0.46
0.7
Stations
Mean
S1
S2
S6
0.45
1.16
1.14
0.82
0.97
0.19
1.19
1.26
1.45
1.3
0.79
0.9
1.09
1.24
0.68
0.97
0.26
0.31
4.3
3.6
3.77
3.5
pollution intensity of metal contamination in sediments (Nasrabadi et al. 2010; Karbassi et al. 2008) I poll ¼ Log2 Bc =Lp ð3Þ In previous equation, Ipoll is the pollution intensity, Bc is the sediment metal concentration, and Lp is the lithogenous portion. The lithogenous portion is calculated by subtraction of the anthropogenic portion of elements from their bulk concentration. As metal concentrations in the shale play no role in this equation, the constant factor (1.5) is not required for normalization. EF and Igeo formulae compare bulk concentrations of elements to their background levels in crust and shale, respectively. However, I poll shows the chemical partitioning results of the study area. Table 3 shows a comparison among various pollution indices in Qarechay River sediments. The pollution load index (PLI) is obtained by calculating concentration factors (CFs). The PLI of the stations is calculated by obtaining the n-root from the n-CFs from all metals (Soares et al. 1999; Tomlinson et al. 1980). CF ¼ C metal =C background value
PLI ¼
ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi p n ðCF1 CF2 CF3 … CFnÞ
ð4Þ
ð5Þ
where CF is the contamination factor, n is the number of metals, Cmetal is the metal concentration in contaminated sediments, and Cbackground value is the background value of that metal (shale values). Table 4 shows the contamination factor and PLI in sampling stations for Qarechay River sediments. Table 5 shows the categories of sediment pollution intensity based on the calculated indexes. According to geochemical accumulation index (Igeo), this region is unpolluted in all sampling stations. Iwuoha et al.
Environ Monit Assess (2014) 186:4289–4297 Table 5 Categories of sediment pollution based on the calculated indexes Range of indexes Igeo and Ipoll I≥5
EF
CF
PLI
State of pollution
Extremely polluted
4≤I
Origination and assessment of metal pollution in Qarechay River bed sediments Aida Biati & Abdulreza R. Karbassi & Zahra Keyhani
Received: 22 November 2013 / Accepted: 20 February 2014 / Published online: 14 March 2014 # Springer International Publishing Switzerland 2014
Abstract In the present investigation, bulk and chemical partitioning of elements (Cu, Mn, Ni, Zn, Fe, Ca) together with organic matter as a loss in ignition in the Qarechay River bed sediments have been studied. The concentration of metals in Qarechay River bed sediments is governed by the geological units of the study area. The study of anthropogenic portion shows that a small proportion of elemental concentration belongs to this phase. However, Mn has a large portion of anthropogenic sources (43 %). Also, Mn has a share of 13.6 % in sulfide fractions. This result indicates that Mn is a highly mobile element and can easily enter the water column. The presence of Mn in sulfide fraction might be indicative of initial stages of conversion of oxidation state into reduction in Qarechay River. Share of metals in anthropogenic portion is in the following order: Mn
(43 %)>Cu (19 %)>Zn (10 %)>Ni (3 %)>Fe (0 %). Organic metallic bonds are not significantly present in the study area. Geochemical index (Igeo), pollution index (Ipoll), enrichment factor (EF), and pollution load index (PLI) values are indicative of a clean environment throughout the river course. These values are in well agreement with results of chemical partitioning data. Eventually, based on the results of chemical partitioning, regional standard of elements for Qarechay River bed sediments has been established. Keywords Chemical partitioning . Pollution intensity index . Geochemistry . Bed sediment . Anthropogenic portion
Introduction A. Biati (*) Department of Environmental Science, Graduate Faculty of Environment and Energy, Tehran Science and Research Branch, Islamic Azad University, Tehran, Iran e-mail: [email protected] A. R. Karbassi Graduate Faculty of Environment, University of Tehran, 141556135 Tehran, Iran e-mail: [email protected] Z. Keyhani Department of Environmental Geology, Graduate Faculty of Environment and Energy, Tehran Science and Research Branch, Islamic Azad University, Tehran, Iran
Heavy metals are among the most common environmental pollutants, and their occurrence in waters and biota indicates the presence of natural or anthropogenic sources. The existence of trace metals in aquatic environments has led to serious concerns about their influence on plant and animal life (Zvinowanda et al. 2009; Sheikh et al. 2007). Many researchers have used sediments to study the behavior of metals over time of sedimentation (Bellucci et al. 2003; Bertolotto et al. 2003; Al-Masri et al. 2002; Borretzen and Salbu 2002; Weis et al. 2001; Lee and Cundy 2001; Karbassi 1989). Forstner and Muller (1973) used a sediment pollution index to evaluate the heavy metal pollution of rivers of Germany.
4290
Sediment quality values are a useful tool to screen the potential for contaminants within sediment to induce biological effects and to compare sediment contaminant concentration with corresponding quality guideline (Mohan 2000). These indexes evaluate the degree to which the sediment-associated chemical status might adversely affect aquatic organisms and are designed to assist sediment assessors and manager responsible for the interpretation of sediment quality (Borole et al. 1982). It is also to rank and prioritize the contaminated areas or the chemicals for further investigation (Adams et al. 1992). Qarechay is one of two permanent and big rivers in Markazi Province in the central part of Iran. This river is almost 540 km long, and its catchment area is 1,800 km2. It originates from the heights of Shazand and finally flows into the Qom salt lake. In recent years, due to the reduced rainfall and construction of “Alghadir” dam for agricultural purposes, the mean annual discharge of this river has been decrease. Trace element pollution in rive, lake, estuary, and bay sediments has been reported by many researchers around the world (Al-Masri et al. 2002; Coker et al. 1995; Farmer 1991). However, study on the geochemistry of Qarechay River sediments in the present study area has not been undertaken by previous researchers so far.
Materials and methods Riverine sediments were collected from six stations in Qarechay River in winter 2012 using a Peterson grab sampler. Location of samples is shown in Fig. 1. The riverbed sediments are brownish clayey silts deposited in the recent times. These samples were instantly placed in polyethylene bags, refrigerated, and carried to the laboratory. Sediments were dried at 70 °C for 24 h and passed through a mesh smaller than 63 μm. The sediment grains were then powdered using an agate mortal and pestle. Bulk digestion was carried out by HF– HNO3–HCl–HClO4. Chemical partition studies were carried out in four sequential steps: (1) 25 %v/v acetic acid, (2) 25 %v/v acetic acid–0.1 M hydroxylamine hydrochloride, (3) 30 % H2O2 “extraction with 1 M ammonium acetate,” and (4) 50 % hot HCl (Malo 1977; Gupta and Chen 1975; Gibbs 1973; Chester and Hughes 1967). Metal concentrations were measured by the Varian SpectrAA-200 at Science and Research Branch, I.A. University, Tehran, Iran, in spring 2013.
Environ Monit Assess (2014) 186:4289–4297
Procedural blanks and duplicates were run with the samples in a similar way for quality assurance of the laboratory analysis. The accuracy of analysis was about ±5 % for all elements. A standard sample (MESS-1) was analyzed in the same manner for analysis accuracy check. Results showed that the errors in the analysis were Zn (13.5 %) > Cu (13.3 %)>Ni (12.2 %)>Fe (2.8 %) Sulfide ions Mn (13.6 %) > Zn (0.3 %) > Fe (0.2 %)>Cu,Ni (0 %) Fig. 2 Dendrogram of cluster analysis for metals in Qarechay River bed sediments
Organic ions Cu (13.4 %)>Mn (6 %)>Zn (5.5 %)> Fe (2.5 %)>Ni (0 %) Resistant ions Zn (73.6 %) > Fe (62.9 %) > Ni (58.4 %)>Cu (47.8 %)>Mn (37.3 %) Within lattice ions Fe (31.6 %)>Ni (29.4 %)>Cu (25.5 %)>Mn (14.2 %)>Zn (7.1 %). In this study, Mn is the metal showing the highest mobility (upper than 28 %) in the loose ions fraction. It can be concluded that this element might be present in the form of carbonates in the area of study. Therefore, Mn shows more concentration in the loose ions fraction. The study of anthropogenic portion shows that a large portion of total concentration of Mn is related to this
Environ Monit Assess (2014) 186:4289–4297
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Table 2 Chemical partitioning of metals in Qarechay River bed sediments Elements
Cu (mg/kg)
Station bond a b c d
Ni (mg/kg) e a b c d
Mn (mg/kg) e
Zn (mg/kg)
a
b
c
17
145 0
d
e
a
Fe (%)
b c d
a
b
1
3 0 3 13 3 5 0 0 22 9
2
4 0 3 11 5 6 0 0 25 10 262 0
55 200 0
6
2 0 3 8
27 107 93 16 0 9 107 19 0.06 0
9 5 0 0 33 24 107 13
167 62 26 0 6 85
e
9
1 6 87
c
d
e
4
0.04 0
6
0.05 0.01 0.07 1.14 0.39
0.01 1.06 0.44 0.06 1.13 0.94
a loosely bonded ions, b sulfide bonded ions, c organic–metallic bonded ions, d resistant bonded ions, e within lattice bonded ions
and mean world sediments, chemical partitioning proves a lithogenous source for this element (90 %), and share of anthropogenic portion is not significant. Share of anthropogenic and lithogenous portions can be summarized as follows:
phase (43 %). Also, Mn has a share of 13.6 and 6 % in sulfide and organic fractions, respectively. These results indicate that Mn is a highly mobile element and can easily enter the water column. The presence of Mn in sulfide fraction might be indicative of initial stages of conversion of oxidation state into reduction (Karbassi 1996) in Qarechay River. Further, the results of chemical partitioning were grouped into anthropogenic and lithogenous ones. As shown in Fig. 3, a small proportion of elemental concentration is in anthropogenic phase (except for Mn). Among all of the studied elements, Mn and Ni have the highest and the lowest share of anthropogenic sources, respectively, but Fe showing no anthropogenic portion remains constant in all sampling stations. Although results of bulk digestion show a higher concentration of Zn than those of shale, mean crust,
Fig. 3 Lithogenous and anthropogenic portions of trace metals in the bed sediments of Qarechay River
Lithogenous Fe (100 %)>Ni (97 %)>Zn (90 %)> Cu (81 %)>Mn (57 %) Anthropogenic Mn (43 %) > Cu (19 %) > Zn (10 %)>Ni (3 %)>Fe (0 %).
Calculation of pollution intensity The concentrations of various metals provide measures for determining the level of pollution in Qarechay sediments, based on Muller’s Index (Igeo), EF, and Ipoll. One
Fe6 0
100
Fe2 0
100
Fe1 0
100
Zn6
7
Zn2
5
Zn1
93 95 18
Mn6
82 36
Mn2
64 57
Mn1
35
65
Ni6 0 Ni2
5
95 96 14
Cu2
86 23
Cu1
77
19 0
Lithogenous
100
Ni1 4 Cu 6
Anthropogenic
43
81 20
40
60
Metals Percentile
80
100
120
4294
Environ Monit Assess (2014) 186:4289–4297
Table 3 Comparison of Igeo, Ipoll, and EF values for metals in Qarechay River sediments Elements
Ipoll
Igeo Stations
Mean
S1
S2
S6
Cu
0
0
0
Ni
0
0
0
Mn
0
0
Zn
0
0
EF
Stations S1
S2
S6
0
0.45
0.52
0.37
0
0.21
0.23
0.12
0
0
0.76
1.25
0
0
0.44
0.23
of the evaluation methods for the intensity of metal contamination in Qarechay sediments is the geochemical accumulation index I geo ¼ Log2 C n =ð1:5 Bn Þ
ð1Þ
where Igeo, Cn, and Bn are the geochemical accumulation index, the sediment metal concentration, and the metal concentration in the shale, respectively (Gonzalez et al. 2000; Forstner et al. 1991; Muller 1979). In this formula, the constant number 1.5 is applied as a factor for normalization to background metal concentrations. The enrichment factor can be calculated for metals using EF ¼ ðC n =C Fe Þsample =ðC n =C Fe Þcrust
ð2Þ
where (Cn/CFe)sample is the ratio of the element concentration (Cn) to the concentration of Fe (CFe). In the sediment sample, (Cn/CFe)crust is the same ratio in an unpolluted reference sample (Pekey 2006; Ergin et al. 1991; Rule 1986; Buat-Menard and Chesselet 1979). Based on the results of chemical partitioning, the anthropogenic portion of metals can be separated from their lithogenic portion. Therefore, Muller’s formula has been modified in order to correctly measure the Table 4 Contamination factor and PLI in Qarechay River bed sediments Stations
Mean
CF
PLI
Cu
Ni
Mn
Zn
Fe
S1
0.49
0.5
0.46
1.3
0.3
0.5
S2
0.5
0.6
0.6
1.1
0.35
0.6
S6
0.49
0.9
0.4
1.6
0.46
0.7
Stations
Mean
S1
S2
S6
0.45
1.16
1.14
0.82
0.97
0.19
1.19
1.26
1.45
1.3
0.79
0.9
1.09
1.24
0.68
0.97
0.26
0.31
4.3
3.6
3.77
3.5
pollution intensity of metal contamination in sediments (Nasrabadi et al. 2010; Karbassi et al. 2008) I poll ¼ Log2 Bc =Lp ð3Þ In previous equation, Ipoll is the pollution intensity, Bc is the sediment metal concentration, and Lp is the lithogenous portion. The lithogenous portion is calculated by subtraction of the anthropogenic portion of elements from their bulk concentration. As metal concentrations in the shale play no role in this equation, the constant factor (1.5) is not required for normalization. EF and Igeo formulae compare bulk concentrations of elements to their background levels in crust and shale, respectively. However, I poll shows the chemical partitioning results of the study area. Table 3 shows a comparison among various pollution indices in Qarechay River sediments. The pollution load index (PLI) is obtained by calculating concentration factors (CFs). The PLI of the stations is calculated by obtaining the n-root from the n-CFs from all metals (Soares et al. 1999; Tomlinson et al. 1980). CF ¼ C metal =C background value
PLI ¼
ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi p n ðCF1 CF2 CF3 … CFnÞ
ð4Þ
ð5Þ
where CF is the contamination factor, n is the number of metals, Cmetal is the metal concentration in contaminated sediments, and Cbackground value is the background value of that metal (shale values). Table 4 shows the contamination factor and PLI in sampling stations for Qarechay River sediments. Table 5 shows the categories of sediment pollution intensity based on the calculated indexes. According to geochemical accumulation index (Igeo), this region is unpolluted in all sampling stations. Iwuoha et al.
Environ Monit Assess (2014) 186:4289–4297 Table 5 Categories of sediment pollution based on the calculated indexes Range of indexes Igeo and Ipoll I≥5
EF
CF
PLI
State of pollution
Extremely polluted
4≤I
