Environmental, ecological and health risks of trace elements, and their sources in soils of Harran Plain, Turkey

Journal Pre-proof Environmental, ecological and health risks of trace elements, and their sources in soils of Harran Plain, Turkey Memet Varol, Muhammet Raşit Sünbül, Halil Aytop, Cafer Hakan Yılmaz PII:

S0045-6535(19)32832-2

DOI:

https://doi.org/10.1016/j.chemosphere.2019.125592

Reference:

CHEM 125592

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ECSN

Received Date: 26 June 2019 Revised Date:

19 November 2019

Accepted Date: 8 December 2019

Please cite this article as: Varol, M., Sünbül, Muhammet.Raş., Aytop, H., Yılmaz, C.H., Environmental, ecological and health risks of trace elements, and their sources in soils of Harran Plain, Turkey, Chemosphere (2020), doi: https://doi.org/10.1016/j.chemosphere.2019.125592. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Ltd.

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Environmental, ecological and health risks of trace elements, and their sources in soils of

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Harran Plain, Turkey

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Memet Varola,*, Muhammet Raşit Sünbülb, Halil Aytopb, Cafer Hakan Yılmazb

4

a

5 6

b

Malatya Turgut Özal University, Faculty of Fisheries, Malatya, Turkey

East Mediterranean Transitional Zone Agricultural Research of Institute, Kahramanmaraş, Turkey

7 8

*Corresponding

author:

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[email protected]

Memet

Varol;

e-mail

addresses:

[email protected];

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Abstract

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Soil pollution with trace elements (TEs) has become an increasingly serious environmental

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concern, however, assessment of ecological and human health risks especially in intensive

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agricultural regions remains limited. In this study, the contents of ten TEs (Al, As, Pb, Cr, Cu,

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Zn, Ni, Co, Mn and Fe) in soil samples from 204 sampling sites in the Harran Plain (Turkey)

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were examined to evaluate possible sources, pollution status and environmental, ecological

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and health risks of these elements. Only As and Ni exceeded the upper continental crust

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concentrations. Among ten TEs, Ni and As had the highest mean values of enrichment factor

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(EF) and contamination factor (Cf), indicating that soils showed moderate enrichment and

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moderate contamination with these elements. Ecological risk factor and ecological risk index

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values of all samples were < 40 and < 150, respectively, indicating low ecological risk in the

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study area. Factor analysis and correlation analysis indicated that Al, Pb, Cr, Cu, Zn, Co, Mn

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and Fe mainly originated from natural sources, Ni from mixed sources of anthropogenic and

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lithogenic origins, while arsenic primarily originated from anthropogenic activities. The

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hazard quotient values for both adults and children did not exceed 1, suggesting that all TEs in

1

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soil through ingestion, dermal contact and inhalation pathways had no significant non-

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carcinogenic risks. Children were more susceptible to non-carcinogenic health effects of TEs

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in soils. The carcinogenic risk values of As, Co, Cr and Ni were within the acceptable risk

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range, indicating that carcinogenic risks were not expected.

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Keywords: Harran Plain; trace elements; soil contamination; risk assessment; multivariate

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statistical methods

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1. Introduction

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The soil is widely accepted as the part of the environment most exposed to trace element

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contamination (Marchand et al., 2011; Mazurek at al., 2017). The highest contents of trace

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elements (TEs) occur generally in the topsoils, because surface layers, especially organic

37

horizons, have the greatest ability to bond TEs (Acosta et al., 2015; Mazurek at al., 2017).

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Sources of TEs in soils can be natural (lithogenic and pedogenic processes) or anthropogenic

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(Huang et al., 2018; Wang et al., 2012; Rivera et al., 2015; Mazurek at al., 2017; Li et al.,

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2018). Nevertheless, compared with natural sources, anthropogenic inputs are the major cause

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of TE accumulation in soils (Dong et al., 2018; Ni et al., 2018). The major sources of

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anthropogenic inputs for TEs in soils are domestic wastes, industrial activities, traffic

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emissions and agricultural activities (application of pesticides and fertilizers) (Muhammad et

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al., 2011; Dong et al., 2018; Ni et al., 2018; Antoniadis et al., 2017; Kumar et al., 2019;

45

Huang et al., 2018).

46 47

Pollution of soils by TEs has become a serious concern in many regions of the world (Islam et

48

al., 2016; Jia et al., 2018; Chen et al., 2015; Yang et al., 2018; Li et al., 2017). For instance,

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16.1% of China's soil was polluted and about 82% of the contaminated soil contained trace

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elements (Teng et al., 2014; Shi et al., 2019). Therefore, many studies associated with TE

2

51

pollution in soils have focused on concentrations, possible sources, and ecological and

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environmental risk assessments of TEs (Yaylalı-Abanuz, 2011; Dartan et al., 2015; Dong et

53

al., 2018; Mazurek at al., 2017; Ni et al., 2018). Understanding the pollution characteristics of

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TEs in the soils, and assessing their environmental and ecological risks both are the basic

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preconditions for prevention and control of soil pollution, and provide important information

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for making decisions on remediation of contaminated soils (Chen et al., 2015; Ye et al.,

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2017a, 2017b, 2019). Multivariate statistical methods are conducted to identify potential

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pollution sources and to indicate relationships between trace elements (Dong et al., 2018; Ni

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et al., 2018). Environmental risk assessment of TEs in soil is an important reference for

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identifying the pollution degree and developing pollution prevention strategies (Li et al.,

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2018; Kumar et al., 2019; Mazurek et al., 2019). Enrichment factor, geoaccumulation index

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and contamination factor were frequently used for environmental risk assessment of TEs.

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Hakanson ecological risk index and ecological risk factor were widely utilized to identify the

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ecological risk of TEs (Huang et al., 2016; Yaylalı-Abanuz, 2011; Dong et al., 2018; Jia et al.,

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2018; Mazurek at al., 2017; Ni et al., 2018; Wu et al., 2018; Mazurek et al., 2019). These

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studies indicated that both index methods are reliably used for evaluation of ecological and

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environmental risks of TEs in soils.

68 69

TEs accumulated in soils can cause great threat to both human health and natural environment

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due to their high toxicity, persistency and high bioaccumulation potential (Jia et al., 2018;

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Mazurek at al., 2017). However, compared with investigations involving environmental and

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ecological risks of TEs in soils, the investigations that have been carried out for human health

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risk assessment associated with TEs in soils are much less in number (Jia et al., 2018;

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Antoniadis et al., 2019). Previous studies reported that long-term exposure to TEs in soils can

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cause serious adverse effects on human. For instance, chronic exposure to toxic elements such

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as As, Pb Cr and Cd can lead to cardiovascular diseases, dermal lesions, reproductive and

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hematological damages, nervous system disorders, developmental anomalies, liver and kidney

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dysfunctions, and skin and lung cancer in humans (Pan et al., 2016a; Adimalla and Wang,

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2018; Jia et al., 2018; Antoniadis et al., 2019; Huang et al., 2018). Thus, health risks from

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exposure to TEs in soils should not be ignored. It is necessary to conduct more studies for

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assessing human health and eco-environment risks from TEs in soils.

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Increasing investigations have been performed on TE concentrations, contamination

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assessment, source identification and human health risk assessment of TEs in agricultural and

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urban soils in many countries (Rinklebe et al., 2019; Baltas et al., 2020; Pan et al., 2016a;

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Adimalla and Wang, 2018; Dong et al., 2018; Mazurek at al., 2017; Ni et al., 2018; Jia et al.,

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2018; Wu et al., 2018). However, there have been few investigations on ecological and health

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risks of TEs in the soils of Turkey (Yaylalı-Abanuz, 2011; Baltas et al., 2020). Thus, this

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study fills an important gap by evaluating the potential effects of TEs in soils on human health

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and eco-environment. The Harran Plain, located in the province of Şanlıurfa, is one of the

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most fertile plains in Turkey. About 67% of total area of the plain is used for agricultural

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purposes (Isgin and Kara, 201). To better understand the risks of soil TEs in an important

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agricultural area, this pilot study was conducted in the Harran Plain in Southeastern Turkey.

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Thus, this area could serve as a model for monitoring other agricultural areas with similar

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characteristics. The objectives of the current study were to identify possible sources of TEs

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using multivariate statistical methods, to evaluate ecological-environmental risks of TEs using

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multiple indices, and to assess both non-carcinogenic and carcinogenic human health risks for

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local residents exposed to TEs in soils.

99 100

2. Materials and methods

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2.1. Study area

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This study was performed in the Harran Plain (36°43ʹ– 37°11ʹN; 38°39ʹ–39°30ʹE), located in

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Şanlıurfa province in Turkey (Fig. 1). This region has very fertile soils and agriculture is the

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main economic activity in the region (Bilgili et al., 2017). The soils in the plain are clayey and

105

slightly alkaline (pH 7.50–8.00). The majority of soils are classified as Vertisol. Soil organic

106

matter content is around 1% (Yanardağ et al., 2016). There are no industrial and mining

107

activities in the plain. The Harran Plain has a total land area of 225,000 ha and about 150,000

108

ha is used for agricultural production (Isgin and Kara, 2015). The soils in the plain have been

109

irrigated by water from the Atatürk Dam Reservoir. Cotton, corn and wheat are the dominant

110

crops in the area. Large amounts of pesticides and fertilizers are used in the Harran Plain

111

(Bilgili et al., 2017). The plain has a semi-arid climate. The mean annual air temperature and

112

precipitation are 18 °C and 284 mm, respectively (Atasoy and Yesilnacar, 2010).

113 114

2.2. Sampling and analysis

115

In this study, the sampling points were selected to represent the entire study area. Thus, a total

116

of 204 surface (0-20 cm) soil samples in the Harran Plain (Fig. 1) were collected in summer

117

2015. The sampling was carried out randomly from agricultural soils far away from people’s

118

habitats as possible. A composite soil sample at each sampling point was obtained by mixing

119

four random subsamples. The collected soil samples were placed in nylon bags for

120

transportation to the laboratory. All samples were naturally air-dried; then, the dried samples

121

were passed through a 2 mm nylon sieve to remove stones, pebbles and plant fragments. The

122

sieved samples were powdered with mortar and pestle, passed through a 0.5 mm nylon sieve

123

and stored in clean polyethylene bottles.

124

5

125

In the present study, ten TEs, including Pb, As, Cr, Ni, Al, Fe, Co, Mn, Cu and Zn, were

126

analyzed in the soil samples. These elements were selected based on their significant

127

contribution to soil contamination and health risk (Rinklebe et al., 2019). The contents of ten

128

TEs were analyzed by the following method in an authorized laboratory of the Ministry of

129

Agriculture and Forestry of Turkey. Soil samples were digested in teflon vessels including a

130

mixture of concentrated HNO3 and HCl (1:1) using a microwave digestion system (CEM

131

MARS 6, USA). Then the solutions were diluted with ultrapure water to a final volume of 50

132

mL. Concentrations of ten TEs were measured by an Inductively Coupled Plasma – Optical

133

Emission Spectrometry (Agilent 5100, USA).

134 135

Quality assurance and quality control were performed using duplicates, method blanks and

136

certified reference material (CRM) (LGC6187, river sediment). Standard solutions obtained

137

by Merck (Darmstadt, Germany) were used for calibration curves. The ultrapure water was

138

used to prepare all solutions. The analytical precision was within ±10%. In this study, one

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CRM was digested and analyzed with every 21 soil samples. The recoveries of TEs in the

140

CRM varied from 90.9% to 108.3% (Table S1). The limit of detection (LOD) and limit of

141

quantification (LOQ) for each element were calculated (Table S1). All analyses were done in

142

duplicate, and the mean values were used for data analysis.

143 144

2.3. Evaluation of environmental risks

145

2.3.1. Enrichment factor (EF)

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EF is applied to assess the possible impact of human activities on TE concentrations in soils

147

(Wu et al., 2018). The EF is computed using the relationship below:

148

EF =       









(1)

6

149

where Ci is the measured concentration of element (i) in soil samples and Cref is the

150

concentration of reference element for geochemical normalization (Mazurek at al., 2017). In

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our study, Al was chosen as the reference element due to its abundant content and stability in

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soil (Jia et al., 2018). Because of the unavailability of local geochemical background

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concentrations of TEs, upper continental crust values reported by Rudnick and Gao (2004)

154

were used as geochemical background. The EF classes are given in Table S2.

155 156

2.3.2. Geoaccumulation index (Igeo)

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Igeo is employed to assess the pollution levels of TEs in soils. This index is based on the

158

comparison of concentrations of TEs in soils with their respective geochemical background

159

values (Mazurek at al., 2017). It is defined by the following equation (Müller, 1969):

160

 Igeo = log2 ".$×& 

161

where Bi is the geochemical background value of trace element (i) (Rudnick and Gao, 2004)

162

and Ci is the concentration of trace element (i). The Igeo classes are presented in Table S2.



(2)

163 164

2.3.3. Contamination factor (Cf)

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Cf is used to assess the degree of TE contamination in soils. Cf is calculated by the following

166

equation (Hakanson, 1980):

167

C  = (

(

(3)

)

168

Where Ci is the concentration of trace element (i) and Cni is the background (pre-industrial)

169

value of trace element (i) (Rudnick and Gao, 2004). In Table S2, the Cf classes are given.

170 171

2.4. Evaluation of ecological risks

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2.4.1. Potential ecological risk factor (Er)

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Er is used to assess the potential ecological risk of a single element in soils (Hakanson, 1980),

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which is expressed as follows:

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E = T × C 

176

where Tri is the toxic-response factor of trace element (i), they are 10, 2, 5, 5, 5 and 1 for As,

177

Cr, Cu, Ni, Pb and Zn, respectively (Hakanson, 1980). Cfi is the contamination factor of trace

178

element (i). The Er classes are presented in Table S2.

(4)

179 180

2.4.2. Potential ecological risk index (RI)

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RI is used to assess the ecological risk of multielement in soils. It is defined as the sum of the

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ecological risk factors (Hakanson, 1980).

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+-." E = +-." T × C 

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Where Eri is the potential ecological risk factor of trace element (i) and n i the number of trace

185

elements (it is 6 in this study). In Table S2, the RI classes are given.

,

,

(5)

186 187

2.5. Human health risk assessment

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In the current study, human health risks of TEs in soils of the Harran Plain were calculated for

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residental adults and children. For soils, residents are exposed to TEs through accidental

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ingestion, inhalation and dermal contact exposure pathways (USEPA, 2019a; Li et al., 2017).

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Therefore, in the present study, health risks of TEs in soils of the Harran Plain were evaluated

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using carcinogenic and non-carcinogenic risks through these three pathways. Carcinogenic

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health risks were calculated only for As, Co, Cr and Ni due to the lack carcinogenic slope

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factors of other TEs. Non-carcinogenic health risks from TEs in soil were estimated using the

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hazard quotients (HQs) (Jia et al., 2018; Wu et al., 2018).

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8

197

Non-carcinogenic risks (HQs) and carcinogenic risks (CRs) of TEs for residential receptors

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through ingestion, dermal absorption and inhalation pathways are calculated using the

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following equations (USEPA, 2019b).

200

Non-carcinogenic risks:

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HQ121 =

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HQ  = 3 &; × 7< × 5 :

203

3 HQ1ℎ  21 = 7< × 5  × C89

3 × 456 ×5&7× 89 × 8: &; × 7< × 5 :=×">?

(6)

 ×67×79×7&6@ ×89 × 8: ? =×A47&6 ×">

(7)

 ×89 × 8:

204

Carcinogenic risks:

205

CR121 =

206 207

208 209

3 × 496 ×5&7×69= 7< × ">?

Where: IFS = CR  =

(8)



89× 8:F × 456F &;F

(9) +

89× 8:H × 456H &;H

3 ×:96× 7&6@ ×69= 7< ×A47&6 ×">?

Where: DFS = CR1ℎ  21 =

89 × 8:F ×67F ×79F &;F

(10) +

89 × 8:H ×67H ×79H &;H

3 ×89×8:×4J5×">>>

(11)

7< ×C89

210 211

The total non-carcinogenic risks for each receptor were assessed by hazard index (HI), which

212

was the sum of the HQs for all exposure pathways. In addition, total carcinogenic risks (TCR)

213

were obtained by the sum of carcinogenic risks (CRs) for all pathways. Hazard index and total

214

carcinogenic risk are calculated using the following equations:

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HI = HQ121 + HQ  + HQ1ℎ  21

(12)

216

TCR = CR121 + CR  + CR1ℎ  21

(13)

217 218

If HQ and HI values are below one, non-carcinogenic health effects are not expected. If the

219

values are above one, adverse non-carcinogenic health effects may occur (USEPA, 1989, 9

220

2004). The carcinogenic risks that range between 10-4 and 10-6 are considered to be acceptable

221

(USEPA, 1991a).

222 223

The values and units associated with these equations are given detailed in Tables 1 and 2. All

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HQ, HI and CR values found in this study were confirmed using the USEPA RSL calculator

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(USEPA, 2019c).

226 227

2.6. Statistical analyses

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Pearson correlation analysis was performed to reveal the relationships among TEs (p<0.05).

229

Principal component analysis (PCA)/factor analysis (FA) was conducted to identify potential

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sources of TEs in soils. Prior to PCA/FA, all analyzed data were standardized by z-scale

231

transformation. Bartlett’s sphericity and Kaiser-Meyer-Olkin (KMO) tests were employed to

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test the suitability of the data for PCA/FA. All statistical analyses were performed by using

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SPSS 11.5.

234 235

3. Results and discussion

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3.1. The concentrations of trace elements (TEs) in soils

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Basic statistics of ten TEs in soils of the Harran Plain are shown in Table 3. The pH values of

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all soil samples were >7. As expected, Al was the most abundant trace element, followed by

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Fe and Mn, which consistent with their concentrations in the upper continental crust (Table

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3). Arsenic, Pb and Co were the less abundant trace elements. Overall, the mean values of all

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TEs except Ni were below their respective limit values established by Turkish Soil Pollution

242

Control Regulation (SPCR, 2005) (Table 3). Maximum concentrations of Cr and Ni were

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about 2.1 and 4.5 times higher than their corresponding limit values (Table 3). Concentrations

10

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of Cr in 44 samples (21.6%) and Ni in 203 samples (99.5%) exceeded their limit values

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(Table 3).

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When compared with upper continental crust (UCC) values of TEs (Rudnick and Gao, 2004),

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the concentrations of Zn and Cu were of the same order of magnitude, As and Ni were about

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1.3 and 1.9 times higher than their respective UCC values, while Al, Co, Cr, Fe, Mn and Pb

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were lower than their respective UCC values (Table 3). High concentrations of TEs respective

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to UCC values might be a consequence of anthropogenic activities (Jia et al., 2018).

252 253

In comparison with world soil average values of TEs, the concentrations of As and Zn were of

254

the same order of magnitude, Co, Cr and Mn were slightly higher, which were about 1.4 times

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higher than their corresponding worldwide average values (Kabata-Pendias, 2011), Ni,

256

however, was about 3.1 times greater than its worldwide average value (Table 3). Also, the

257

concentrations of Ni, Co, Cu and Mn were about 2.4, 1.5, 1.6 and 1.3 times higher than their

258

respective average values in European soils (Kabata-Pendias, 2011) (Table 3).

259 260

Compared with mean concentrations of TEs in agricultural soils of different regions in

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Turkey, Cr, Cu, Mn, Ni, Pb and Zn concentrations in our study were much lower than those in

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Bursa province (Aydinalp and Marinova, 2003). Also, Co and Ni concentrations in this study

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were lower that those in Amik Plain (Karanlık et al., 2011), while Pb concentration was

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higher. Arsenic, Co, Cu, Fe, Mn, Ni and Zn concentrations in soils of Thrace region were

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lower than those in this study (Çoskun et al., 2006), whereas Cr and Pb concentrations were

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higher (Table 3). In addition, Cr, Fe, Pb and Cu concentrations in soils of the Harran Plain

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were lower than those in agricultural soils of Sinop province (Baltas et al., 2020), while Zn,

268

As and Ni concentrations were comparable. These results revealed that different regions had

11

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different soil TE concentrations due to heterogeneity in human activities and natural mineral

270

weathering.

271 272

3.2. Environmental risk assessment

273

The descriptive statistics of EF, Igeo and Cf are given in Fig 2. And Table S3. The mean Igeo

274

values followed the descending order: Ni>Zn>Cu>Fe>Co>Cr=As>Mn>Pb and Al. The mean

275

Igeo value (0.3 ±0.3) for Ni was positive, while mean Igeo values for other elements were

276

negative, indicating that soils were unpolluted to moderately polluted by Ni, and soils were

277

unpolluted by other elements. Among ten trace elements, Ni and As had the highest mean

278

values of EF (2
279

other elements showed minimal enrichments with mean EF values below 2. Cf showed

280

consistent results with EF. Nickel and As showed the highest mean values of Cf (1
281

demonstrating moderate contamination with Ni and As, however, Cu, Cr, Pb and Zn showed

282

low contamination, as reflected by their Cf values below 1. Ungureanu et al. (2017) reported

283

that Ni content in agricultural soils can be influenced by fertilizers. The application of

284

fertilizers and pesticides is recognized as a significant factor in enhancing the level of arsenic

285

in agricultural soils (Zhou et al., 2018). Thus, Ni and As contamination in soils of the plain

286

can be closely related to the application of fertilizers and pesticides.

287 288

3.3. Ecological risk assessment

289

The basic statistics of potential ecological risk factor (Er) and ecological risk index (RI) are

290

given in Fig. 2. and Table S3. In general, Zn and Cr were trace elements, which had the least

291

ecological risk, while As and Ni had the highest Er values. However, both mean and

292

maximum Er values of As, Cr, Cu, Ni, Pb and Zn for all soil samples were less than 40,

293

indicating that 100% of the study area had low ecological risk. In this study, RI values ranged

12

294

from 15.8 to 59.4. Because RI values of all samples were < 150, soils of the Harran Plain had

295

low ecological risk. High RI values for soils are rarely reported in the literature. For instance,

296

Kumar et al. (2019) reported that agricultural soils of India showed high ecological risk (RI =

297

544) due to application of chemical fertilizers and pesticides. Similarly, Wu et al. (2019)

298

reported very high RI values in agricultural soils near a smelter in China.

299 300

3.4. Multivariate statistical methods

301

The relationships among TEs were examined using Pearson correlation matrix (Table S4).

302

Trace elements with high correlations may have a common source and mutual dependence

303

(Baltas et al., 2020; Dong et al., 2018; Pan et al., 2016b). The results showed that high

304

positive correlations existed among Al, Fe, Co, Cr, Cu, Ni, Zn, Pb and Mn (r>0.4; p<0.01),

305

indicating that these TEs in the soils of the Harran Plain were derived from similar sources.

306

However, As was negatively correlated with Al, Co, Cr, Cu, Fe, Ni and Zn (Table S4).

307 308

The KMO score (0.84) and Bartlett’s sphericity test value (p < 0.001) indicated that the data

309

set was appropriate for PCA/FA. In the present study, two varifactors (VFs) with eigenvalues

310

>1 which explained 75.5% of the total variance were obtained through FA (Table S5).

311 312

The first varifactor (VF1) had strong positive loadings (≥0.6) on Al, Cr, Co, Cu, Pb, Fe, Mn,

313

Ni and Zn, and VF1 accounted for 62.3% of the total variance (Table S5). The mean values of

314

Al, Cr, Co, Cu, Pb, Fe, Mn and Zn were comparable to or slightly lower than their

315

corresponding UCC values. Also, these eight elements exhibited significant positive

316

correlations with each other. Thus, they were mainly controlled by natural sources. This was

317

supported by low Igeo, EF and Cf values of these elements. However, the mean concentration

318

of Ni was 1.9 fold higher than its respective UCC value. Also, Ni showed higher Igeo, EF and

13

319

Cf values than other trace elements. High Ni concentrations in soils can originate from

320

various agricultural fertilizers (Ungureanu et al., 2017; Molina et al., 2009; Cai et al., 2015).

321

Nevertheless, Ni had strong positive correlations with Fe and Al, which are abundant trace

322

elements in earth crust. These findings suggested that Ni originated from both natural sources

323

and anthropogenic sources, similar to the findings by Baltas et al. (2020) and Ungureanu et al.

324

(2017). Thus, VF1 was primarily attributable to lithogenic sources although agricultural

325

activities partly contributed to Ni.

326 327

The second varifactor (VF2) had strong negative loading (-0.89) on As, and VF2 explained

328

13.2% of the total variance (Table S5). Arsenic was negatively correlated with Al, Co, Cr, Cu,

329

Fe, Ni and Zn, suggesting that As was derived from different sources. The mean concentration

330

of As was 1.3 fold higher than its respective UCC value. Also, soils of the Harran Plain had

331

moderate enrichment and moderate contamination with As in terms of mean EF and Cf values

332

of As, thus suggesting that arsenic was controlled by anthropogenic activities. There are no

333

industrial activities in the study area, where agriculture is the main activity. High As

334

concentrations were frequently reported in agricultural soils due to fertilizers, pesticides and

335

livestock manures (Zhou et al., 2018; Cai et al., 2015; Adimalla and Wang, 2018; Kabata-

336

Pendias, 2011). The Harran Plain is a significant agricultural area, and fertilizers, livestock

337

manures and pesticides are widely used in soils of the plain (Bilgili et al., 2017). VF2 was

338

hence mainly attributable to anthropogenic contribution.

339 340

3.5. Human health risk assessment

341

In this study, HQ, HI and total HI (THI) values for both adults and children were lower than 1

342

(Table 4), suggesting that all TEs in soil through ingestion, dermal contact and inhalation

343

pathways had no significant non-carcinogenic risks. Similar results were obtained by

14

344

Praveena et al. (2018), who studied surface soils of Klang district in Malaysia and reported

345

the THI values < 1 for adults and children. However, Jiang et al. (2017), studying health risk

346

assessment of TEs in soils of Jiangsu Province in China, reported that the THI values were

347

3.62 and 6.21 for adults and children, respectively. In our study, among TEs, Fe for ingestion,

348

Cr for dermal contact and Mn for inhalation had highest HQ values for both adults and

349

children, whereas Zn for ingestion and dermal contact, and As for inhalation had lowest HQ

350

values for both adults and children (Table 4). HQingestion values decreased in the order of

351

Fe>Co>Al>Cr>Mn>As>Pb>Ni>Cu>Zn for both adults and children, HQdermal values followed

352

the order of Cr>Mn>As>Ni>Fe>Co>Al>Pb>Cu>Zn for both adults and children, and

353

HQinhalation values were found in the order of Mn>Al>Co>Ni>Cr>As for both adults and

354

children (Table 4). Cumulative HQ (CHQ) values of three exposure pathways for adults

355

followed the order of CHQingestion> CHQdermal> CHQinhalation, whereas CHQ values for children

356

were followed the order of CHQingestion> CHQinhalation> CHQdermal (Table 4). In the present

357

study, total HI (THI) value calculated for children was 8.6 times higher that for adults (Table

358

4). Thus, we concluded that children are more sensitive to adverse health effects of TEs in

359

soils. High THI values for children were reported by many studies (Wu et al., 2018; Jia et al.,

360

2018; Pan et al., 2016a; Rinklebe et al., 2019; Baltas et al., 2020). HI values for adults

361

decreased in the order of Mn>Al>Co>Fe>Cr>As>Ni>Pb>>Cu>Zn, while HI values for

362

children followed the order of Co>Fe>Al>Cr>Mn>As>Pb>Ni>Cu>Zn (Table 4). Cumulative

363

HQ values of all TEs through ingestion accounted for 65.5% and 87.7% of THI for adults and

364

children, respectively.

365 366

The carcinogenic risk (CR) values of As, Co, Cr and Ni through ingestion, dermal contact and

367

inhalation pathways and total carcinogenic risk (TCR) values were within USEPA’s

368

acceptable risk range of 1×10−4 and 1×10−6 (Table 4), indicating that carcinogenic risks for

15

369

residential receptors were not expected. Similar were the findings in other areas in Turkey,

370

e.g., in Sinop province studied by Baltas et al. (2020). However, high carcinogenic risks were

371

determined in soils of the Qinghai-Tibet Plateau (Wu et al., 2018). In this study, TCR values

372

decreased in the order of Cr>As>Co>Ni. The cumulative carcinogenic risk (CCR) values for

373

three exposure pathways followed the order of CCRingestion> CCRdermal> CCRinhalation. The

374

CCRingestion value was 2.3 and 13.5 times higher than CCRdermal and CCRinhalation values,

375

respectively. The CCRingestion value accounted for 66.5% of cumulative TCR (CTCR) value.

376

Chromium was the main contributor for the CTCR through ingestion and dermal contact, with

377

the highest contributions of 64.6% and 27.4%, respectively.

378 379

4. Conclusions

380

Among trace elements, only the mean value of Ni was above its respective limit value

381

established by Turkish Soil Pollution Control Regulation. Cobalt, Cr and Mn were 1.4 times

382

higher than their corresponding worldwide average values, while Ni was 3.1 times greater.

383

Based on mean Igeo values, soils were unpolluted to moderately polluted by Ni, and soils

384

were unpolluted by other TEs. Soils of the Harran Plain had moderate enrichment and

385

moderate contamination with Ni and As, while other trace elements showed minimal

386

enrichment and low contamination. According to Er and RI values, 100% of the study area

387

had low ecological risk. In terms of HQ values, children were more susceptible to non-

388

carcinogenic health effects of TEs. However, non-carcinogenic health effects from TEs in soil

389

through ingestion, dermal contact and inhalation pathways were not expected for both adults

390

and children. Also, the carcinogenic risk values of As, Co, Cr and Ni were within the

391

acceptable risk range, indicating that there were no significant carcinogenic risks for

392

residential receptors. The PCA/FA and correlation analysis demonstrated that Al, Pb, Cr, Cu,

393

Zn, Co, Mn and Fe were controlled by natural sources, Ni by both anthropogenic and natural

16

394

sources, whereas arsenic was controlled by anthropogenic sources (agro-chemicals). These

395

findings show that our study may serve as a model when addressing contamination-related

396

risk in agricultural areas where agro-chemicals are intensively used. Also, further studies

397

concerning TE contamination risk in common crops in the plain and the potential health

398

hazards are recommended. In addition, routine monitoring programs should be performed in

399

the plain.

400 401

Acknowledgements

402

Special thanks are given to the editor Professor Martine Leermakers and anonymous

403

reviewers for their constructive comments and suggestions for improving this manuscript.

404 405

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24

Table 1. Parameters and their values associated with health risk assessment for trace elements in soils Parameters Metal concentration Body weight-adult Body weight-child Exposure duration-child Exposure duration-adult Exposure frequency Skin surface area-adult Skin surface area-child Soil intake ratio-adult Soil intake ratio-child Averaging time-child Averaging time-adult Skin adherence factor-adult Skin adherence factor-child Soil ingestion ratio Soil dermal contact factor Life time Averaging time

Symbols Cs BW a BW c EDc EDa EF SAa SAc IRSa IRSc ATc ATa AFa AFc IFS DFS LT AT

Units mg/kg kg kg years years days/year 2 cm 2 cm mg/day mg/day days days 2 mg/cm 2 mg/cm mg/kg mg/kg years days

Values 70 15 6 20 350 6032 2373 20 50 365 x EDc (non-carcinogenic) 365 x EDa (non-carcinogenic) 0.07 0.2 Age-adjusted Age-adjusted 76 365 × LT = 27740 (carcinogenic)

References Site-specific Site-specific USEPA (1991b) USEPA (1991b) USEPA (2019d) USEPA (1991b) USEPA (2011) USEPA (2011) Jia et al. (2018) Jia et al. (2018) USEPA (1989) USEPA (1989) USEPA (2002) USEPA (2002) USEPA (2019d) USEPA (2019d) Site-specific Site-specific

Table 2. Relative bioavailability factor, dermal absorption fraction, oral reference dose, oral slope factor, gastrointestinal absorption, inhalation reference concentration, particulate emission factor and inhalation unit risk values for each trace element

Metal

Al As

a

Relative bioavailability factor (RBA) (unitless) 1 0.6

Dermal absorption fraction (ABSd) (unitless) 0.001 0.03

Oral reference dose (RfDo) (mg/kg-day)

Oral slope factor (CSFo) -1 (mg/kg-day)

Gastrointestinal absorption (GIABS) (unitless)

1

-

1

0.0003

1.5

1

Co

1

0.001

0.0003

-

1

b

1

0.001

0.003

0.5

0.025

Cu

1

0.001

0.04

-

1

Cr

Fe Mn Ni Pb Zn References a b

Inorganic As Cr(VI)

1 1 1 1

0.001 0.001 0.001 0.001

1

0.001

USEPA (2019d)

USEPA (2004)

0.7 0.024 0.02 0.0014 0.3 USEPA (2019e), Jia et al. (2018)

-

1 0.04 0.04 1

Inhalation reference concentration (RFC) 3 (mg/m ) 0.005000 0.000015 0.000006 0.000100 0.000050 0.000090 -

Particulate emission factor (PEF) 3 (m /kg)

Inhalation unit risk (IUR) 3 -1 (µg/m )

9

-

9

0.0043

9

0.0090

9

0.0840

9

-

9

-

9

-

9

0.0003

9

-

9

1.36×10 1.36×10 1.36×10

1.36×10 1.36×10 1.36×10 1.36×10 1.36×10

1.36×10

-

1

-

1.36×10

-

USEPA (2019e)

USEPA (2019e)

USEPA (2019e)

USEPA (2019e)

USEPA (2019e)

Table 3. Summary statistics of trace elements in soils of Harran Plain and comparison with other studies, regulation and average values in upper crust, Europe soils and worldwide soils Harran Plain

Al

As

Co

Cr

Cu

Fe

Mn

Ni

Pb

Zn

References

Mean

42692

6.36

16

85

27

37505

679

89

10.6

68

This study

Median

41946

5.6

16

83

27

37225

640

86

10.5

64

This study

Standard deviation

9069

4.3

3.4

18

5.6

6992

162

24

2

18

This study

Standard error

635

0.3

0.24

1.27

0.39

490

11.3

1.7

0.137

1,26

This study

Minimum

23850

0.13

9

55

15

21859

420

47

5.8

40

This study

Maximum

85916

65237

18.31

34

214

47

1409

334

16.5

197

This study

Worldwide soils

6.83

11.3

59.5

38.9

488

29

27

70

(Kabata-Pendias, 2011)

Europe soils

11.6

10.4

94.8

17.3

524

37

32

68.1

(Kabata-Pendias, 2011)

100

140

4.8

17.3

92

28

125

40

173

20

26900

194.73

43.19

38849

Turkish Soil Pollution Control Regulation Upper continental crust (UCC)

81500

Amik Plain, Turkey

39200

75

300

300

(SPCR, 2005)

774

47

17

67

(Rudnick and Gao, 2003)

274

5.6

1667

158

81

477

(Aydinalp and Marinova, 2003)

20.4

Bursa city, Turkey Thrace region, Turkey

8

Sinop province, Turkey

5.66

11

600

(Karanlık et al., 2011)

50

33

45

(Çoskun et al., 2006)

85.02

17.01

65.1

(Baltas et al., 2020)

Table 4. Non-carcinogenic (HQ, CHQ, HI and THI) and carcinogenic (CR, CCR, TCR and CTCR) risks for residential receptors

Al

Noncarcinogenic risks for child

Noncarcinogenic risks for adult

HQ ingestion

HQ HQ dermal inhalation

THI

CR ingestion

CR dermal

CR inhalation

TCR

HQ dermal

HQ inhalation

HI

HQ ingestion

Carcinogenic risks

1.36E-01

1.30E-03

6.02E-03

1.44E-01

1.17E-02

2.47E-04

6.02E-03

1.80E-02

-

-

-

-

a

4.07E-02

1.93E-02

2.99E-04

6.03E-02

3.48E-03

3.68E-03

2.99E-04

7.46E-03

1.86E-06

1.12E-06

6.60E-09

2.98E-06

b

9.06E-02

3.44E-02

6.00E-04

1.26E-01

7.76E-03

6.56E-03

6.00E-04

1.49E-02

6.33E-05

2.69E-05

4.77E-06

9.50E-05

Co

1.70E-01

1.62E-03

1.88E-03

1.74E-01

1.46E-02

3.08E-04

1.88E-03

1.68E-02

-

-

3.48E-08

3.48E-08

Cu

2.16E-03

2.05E-05

-

2.18E-03

1.85E-04

3.90E-06

-

1.89E-04

-

-

-

-

Fe

1.71E-01

1.63E-03

-

1.73E-01

1.47E-02

3.10E-04

-

1.50E-02

-

-

-

-

Pb

2.42E-02

2.30E-04

-

2.44E-02

2.07E-03

4.38E-05

-

2.12E-03

-

-

-

-

Mn

9.04E-02

2.15E-02

9.58E-03

1.21E-01

7.75E-03

4.09E-03

9.58E-03

2.14E-02

-

-

-

-

Ni

1.42E-02

3.38E-03

6.98E-04

1.83E-02

1.22E-03

6.43E-04

6.98E-04

2.56E-03

-

-

5.58E-09

5.58E-09

Zn

7.25E-04

6.88E-06

-

7.31E-04

6.21E-05

1.31E-06

-

6.34E-05

-

-

-

-

CHQ

CHQ

CHQ

THI

CHQ

CHQ

CHQ

THI

CCR

CCR

CCR

CTCR

7.40E-01

8.34E-02

1.91E-02

8.44E-01

6.35E-02

1.59E-02

1.91E-02

9.85E-02

6.52E-05

2.80E-05

4.82E-06

9.80E-05

As Cr

HQ: hazard quotient; CHQ: cumulative HQ; HI: hazard index; THI: total HI; CR: carcinogenic risk; CCR: cumulative CR; TCR: total CR; CTCR: cumulative TCR a Inorganic As b Cr(VI)

Fig. 1. Location and sampling sites of the study area

Fig. 2. Boxplots of enrichment factor (EF) (a), geoaccumulation index (Igeo) (b), contamination factor (Cf) (c) and potential ecological risk factor (Er) (d) for trace elements in the study area

Highlights ► Ecological risk index values indicated that study area had low ecological risk ► All metals except Ni and As showed minimal enrichment and low contamination. ► Children were more susceptible to non-carcinogenic health effects than adults ► According to risk assessment methods, Harran Plain soils are safe for human health ► PCA/FA indicated that As and Ni derived from anthropogenic sources

Author Contribution Statement Halil Aytop and Cafer Hakan Yılmaz collected the soils samples. Muhammet Raşit Sünbül, Halil Aytop and Cafer Hakan Yılmaz performed trace element analysis of the samples by ICP-OES. Memet Varol analysed the data, completed data interpretation, and drafted the manuscript. All the authors contributed to manuscript writing.

Declaration of interests ☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. ☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: