Assessing the contamination level and ecological risk of heavy metals in the Lower Danube sediments using by different pollution indices [309898]

[anonimizat]1, Cătălina Iticescu1, Maria Cătălina Țopa1, Mihaela Timofti1, Maxim Arseni1, Lucian Puiu Georgescu1, Mădălina Călmuc1, Adrian Roșu1

1”Dunarea de Jos” [anonimizat], Faculty of Sciences and Environment, 111 Domneasca Street, 800201, Galati, Romania

*Corresponding author: [anonimizat]

Abstract

This paper presents a [anonimizat] 182 and Km 60. [anonimizat] (RI) and to evaluate the contribution of anthropogenic activities on the level of heavy metal contamination in surface sediment by using different indices such as: Geoaccumulation Index (Igeo), Contamination Factor (CF), and Pollution Load Index (PLI). [anonimizat] 5 heavy metals (Cr, Ni, Zn, Pb, Cu) out of the 15 metals determined in the sediment samples were taken into account. RI, Igeo, [anonimizat] 2018 and March 2019, based on the X-ray fluorescence (XRF) technique. [anonimizat] a low toxicity factor.

Keywords: [anonimizat], [anonimizat]-[anonimizat], Pollution Load Index.

1. Introduction

Assessment of heavy metal concentration in aquatic ecosystems is a topic of interest due to their toxicity and special property to bioaccumulate in organisms [1, 2]. There are 23 [anonimizat] [3]. [anonimizat], autoimmunity and even death in some instances [4].

The Danube is a complex river that hosts a large variety of plants and animals that can be exposed to heavy metals pollution. [anonimizat], do to this reason is necessary to reduce pollution sources [5]. The main sources of Danube pollution with heavy metals are: [anonimizat], pesticides, fertilizers, [anonimizat] [6, 7]. [anonimizat].

The sediment is a natural component of the aquatic ecosystem that serves as a reservoir for a wide variety of pollutants [8]. [anonimizat]. Furthermore, many invertebrates process sediments as a food source. [anonimizat] [9] .

[anonimizat], calculating the Potential Ecological Risk Index (RI). Another objective is to evaluate the contribution of anthropogenic activities on the level of heavy metal contamination in surface sediments using different indices such us: Geo-accumulation index (Igeo), Contamination Factor (CF), and Pollution load index (PLI).

2. Experimental part

2.1 Study area

To assess the level of heavy metals sediment pollution, 15 sampling stations were selected between km 180 and km 60 of the Lower Danube. In this monitored area, the Danube River crosses 3 major cities in Romania (Brăila, Galati, Tulcea) with a large number of inhabitants and significant industrial activity (Damen Shipyard Galati, Navrom shipyard Galati, Vard shipyard Braila, Vard shipyard Tulcea). The sediment samples were collected in two different time periods, namely November 2018 and March 2019.

Fig.1 Sampling stations-Lower Danube

2.2 Metals Analysis / Methods of analysis

The surface sediment samples (first 10 cm) were collected by using a Van Veen Grab Sampler and were placed in polyethylene recipients. The transport and temporary storage (1/2 days) of the sediment samples were performed at 4 oC. In the preliminary stage, the sediment samples were dried at 105 oC until they reached a constant weight and were sieved by using a 125 m sieve. The heavy metals were determined by using the XRF (X-ray fluorescence) technique.

2.3 Methods of assessing the anthropogenic contributions to heavy metal sediments pollution

Geo-accumulation Index (Igeo)

The Geoaccumulation Index was proposed by Müller (1969) [10] to assess the pollution levels of each heavy metals in surface sediment, taking into account their background value [11]. According to Litenithy and Laszlo (1999), Woitke et al. (2003), Ilie et al. (2017) [12-14], the background values of heavy metals in sediments of Danube are: 35, 50, 25, 10, and 130 mg/kg for Cu, Cr, Pb, Ni and Zn.

Igeo = log2 (1)

Where: Igeo is the Index of geoaccumulation for each heavy metals; Cn is the measured concentration of heavy metals in sediment; Bn refers to the background value of heavy metals, K represents a constant, which has usually 1.5 value [15].

Table 1. Level of pollution with heavy metals according to Igeo [16]

Contamination factor (CF)

The contamination factor describes the pollution level of sediment with a given heavy metal and it is calculated as the ratio between concentration of each heavy metal measured (Cn) and its background value ( Cbn) (Eq.2) [17].

CF= (2)

Table 2. Contamination level of sediment according to CF value [18]

Pollution load index (PLI)

The Pollution Loading Index is a tool used to assess the global level of sediment contamination taking into account the concentrations of several heavy metals. This is calculated based on the Contamination Factor of each metal (Eq 3) [19]

PLI=(𝐶𝐹Me1×𝐶𝐹Me2 ×…×𝐶𝐹Me𝑛)1/𝑛 (3) [20, 21]

Where: PLI is Pollution load index, CFMe1, 2, 3, ..n represents the Contamination Factor of each metal Me1, 2, 3,..n and n is the number of metals.

The values of PLI<1 indicate the absence of heavy metal contamination, whereas PLI >1 shows the presence of heavy metal pollution [14]

2.4 Methods of evaluating the potential risks of heavy metals in surface sediments

Potential Ecological Risk Index (RI)

The Potential Ecological Risk Index was developed by Hakänson (1980) [22] to evaluate the potential risk of heavy metal contamination in sediments. This method takes into account the toxicity and combined effects of heavy metals on the aquatic ecosystem [23]. According to Hakänson (1980) [22] the toxic response factors for heavy metals analyzed, such us: Pb, Cu, Cr, Zn and Ni are 5, 5, 2, 1 and 5. The final value of RI is obtained by calculating the following formulas:

RI= (4)

ErMe = TrMe * Cf Me (5)

Cf Me = CMe/CSCM Me (6)

Where: RI is the sum of potential risk of individual heavy metal; ErMe is the potential ecological risk of metal Me; TrMe refers to the toxic-response factor for each metal Me; Cf Me is the contamination factor for each metal Me; CMe is the measured level of heavy metal in sediment; CSCM Me is standard value of each heavy metal concentration according with Romanian Order 161/2006 [24, 25].

Table 3. Values of Potential Ecological Risk Index

Table 4. Standard value of each heavy metal concentration in sediment according with Romanian Order 161/2006 [26]

4. Results And Discussion

Spatial distribution of Geo-accumulation Index (Igeo)

Based on the Geo-accumulation Index values obtained in November, the intensity of Cr pollution was strongly (Class 4) in the S1, S2, S4 stations, moderately to strongly (Class 3) in S6 station and moderately polluted (Class 2) in all other stations. The main sources of environmental pollution with Cr are: fertilizers, sewage, metallurgy, production of paints and pigments, chemical production, pulp and paper production [27]. The high chromium concentrations may be caused by the former chemical plant at Chiscani, which produced fibers, cellulose and paper (CEPROHART), this metal is very much persistent in water sediments. In March, the highest values of Igeo Cr were recorded in the S4 and S5 stations and it showed that the sediments were highly polluted with Cr.

Fig. 2. Spatial distribution of Geoaccumulation Index for each heavy metals in November 2018 and March 2019

The Igeo Zn values registered variations between -0.79 – 0.41 (November, 2018) and -0,73 – 0.62 (March, 2019). Also, Igeo Pb results were situated in November, 2018 within the range of -0.46-0.53 and -0.47-1.03 in March 2019. For Igeo Cu were identified values between -0.02-1.07 (November 2018) and 0,17-1.30 (March, 2019). According to these results, the Geo-accumulation Index values showed that Danube sediments were unpolluted and unpolluted to moderately with Cu, Zn, Pb in most of the sampling stations, except for S11 station, when in March the sediment was moderately polluted with Pb and Cu.

From the calculation of Geo-accumulation index at all sampling stations of Lower Danube, a strong Ni pollution was observed in November (2018). The highest value of Igeo Ni ​​was obtained in March (2019) in S11 station (4,61). The sediment sample at this station had a similar consistency to cement, which may indicate that there were discharges of different ​​materials that changed the sediments composition in that area. Similarly, Ilie et al.( 2017) [14] obtained high values of the Geo-accumulation index for Ni in the Danube sediments.

Contamination Factor (CF)

The results of the Contamination Factor of each metal show that the Danube sediments were low contaminated with metals such as Pb and Zn at all sampling stations, in both monitored periods, except for S11 station. Also, the CF values of Cu of stations S3, S8, S10, S11, S13, S14, S15 show that sediments were moderate polluted by this metal. Furthermore, from the determination of contamination factor (CF) in Lower Danube sediments was found a very hight contamination with Cr in stations S1, S2, S4, a considerable contamination in S6 and a moderate polutionin the other sampling stations.

Table 5. Contamination Factor values

Similar to the Igeo values ​​of Ni, the Contamination Factor results ​​were very high at all sampling stations in both monitoring periods. The Ni concentrations exceed the maximum admissible concentration (35 mg/kg) set by Order 161/2006 [26] across the monitored Danube sector. These results reveal the presence of a persistent Nickel pollution of Danube Lower sediments. This pollution with Nickel may be due to the transport, industry, municipal and industrial waste [28].

Spatial distribution of Pollution load index (PLI)

Figure 3 illustrates the values ​​of the Pollution load index (PLI) for the two monitoring periods, namely November 2018 and March 2019. The contribution of individual heavy metals to the Pollution load index was highlighted by a PCA representation (Figure 4).

Fig. 3. Spatial distribution of Pollution Load Index in november 2018 (a) and march 2019 (b)

Fig.4 Contributions of heavy metals to Pollution load index (PLI)

In November, the PLI values were in the range 1.27(S9) – 2.06 (S1), indicating the presence of heavy metals pollution in the Lower Danube sediments. According to the CF values (Table 5), chromium and nickel had the largest contribution to the final result of the Pollution load index (Fig.4). Also, the results obtained in March 2019, revealed the presence of heavy metals pollution in all sampling stations. The highest value of PLI was recorded at S11 station (2.49). This is due to the hight concentration of Ni measured in the sediment.

Spatial distribution of Potential Ecological Risk Index (RI)

Taking into account the metals Pb, Zn, Cr, Cu and Ni, the results of the PLI index were low in both monitoring periods. Although, according to the Igeo and CF indices, there was a contamination with Ni and Cr in the sediments of the Lower Danube, all the sampling stations were at low ecological risk level. This can be explained by the low values of the toxic response factors for heavy metals analyzed in the present study.

Fig. 5 Spatial distribution of Potential Ecological Risk Index in november 2018 (a) and march 2019 (b)

Fig. 6 Contributions of heavy metals to Potential Ecological Risk Index (RI)

According to the results of the calculation of the potential environmental risk indicator (RI), the highest value was 36.08 and was recorded in March at S11 station. The Ni and Cr potential ecological risk values (Er) had a major influence on the RI final results (Fig. 6). Similar to the values ​​of IgeoCr, IgeoNi, CF Cr, CF Ni and PLI, in November (2018), the highest values ​​of the RI index were obtained in the Danube sector adjacent to the Braila City.

5. Conclusions

The results of the Geo-accumulation Index (Igeo), the Contamination Factor (CF) and the Pollution load index (PLI) indicated that for certain heavy metals such as Ni and Cr, the anthropogenic activities had a significant influence on the pollution of Lower Danube surface sediments. However, the Potential Ecological Risk Index (RI) values revealed the existence of a low ecological risk on sediments. In addition, the pollution indices results calculated in the present study indicated the existence of a fluctuations of certain heavy metal concentrations in some sampling stations. This may be due to different factors that will represent a future subject of research.

Acknowledgement: This work was supported by the project "Strategy and actions for preparing the national participation in the DANUBIUS-RI Project" acronym "DANS" financed by the Romanian Ministry of Research and Innovation.

6. References

BURADA, A., TOPA, C. M., GEORGESCU, L. P., TEODOROF, L., NASTASE, C., SECELEANU-ODOR, D., ITICESCU, C., Rev. Chim. (București), 66, no. 1, 2015, p.48.

JAVED, T., AHMAD, N., MASHIATULLAH, A., Pol. J. Environ. Stud., 27, no. 2, 2018, p. 675.

JAISHANKAR, M., TSETEN, T., ANBALAGAN, N., MATHEW, B. B., BEEREGOWDA, K. N., Interdiscip. Toxicol., 7, no. 2, 2014, p. 60.

MALASSA, H., AL-QUTOB, M., AL-KHATIB, M., AL-RIMAWI, F., J. Environ. Prot., 4, 2013, p. 818.

MILENKOVIC, N, DAMJANOVIC, M., RISTIC, M., Pol. J. Environ. Stud. 14, no. 6, 2005, p. 781.

ITICESCU, C., GEORGESCU, L.P., ȚOPA, C., MURARIU, G., 2014, J Environ Prot Eco, 15, no. 1., 2014, p. 30.

GASPAROTTI C., Euro Economica, 33, no.1, 2014, p. 91-106

IORDACHE, M., POPESCU, L. R., PASCU, L. F., IORDACHE, I., Rev. Chim. (Bucharest), 66 , no. 8, 2015, p.1247.

DEMIRAK, A., YILMAZ, F., TUNA, A. L., OZDEMIR, N., Chemosphere, 63, 2006 p. 1451.

MULLER, G. Geojournal, 2, no. 3, 1969, p. 108.

WEI, Z., WANG, D., ZHOU, H , QI, Z., Procedia. Environ. Sci. 10, 2011, p.1946.

LITENITHY, P., LASZLO, F., War. Sci. Tech. 40, no.10, p. 17.

WOITKE, P., WELLMITZ, J., HELM, D., KUBE, P., LEPOM , P., LITHERATY, P., Chemosphere, 51, 2003, p. 633.

ILIE, M., MARINESCU, F., SZEP, R., GHIȚA, G., DEAK, G., ANGHEL, A. M., PETRESCU, A., URIȚESCU, B., Carpath J Earth Env, 12, no.2, 2017, p. 437.

HOUNKPÈ, J. B., KÉLOMÈ, N. C., ADÈCHINA, R., LAWANI, R. N., JMES, 8, no. 12, 2017, p. 4369.

ÇEVIK, F., GÖKSU, M. Z. L., DERICI, O. B., FINDIK, Ö, Environ Monit Assess, 152, 2008, p.309.

OUCHIR, N., LASSAÂD, B. A., MABROUK, B., ABDELWAHEB, A., , Arab J Geosci, 539, no. 9, 2016, p. 1.

CHANDRASEKARAN, A., MUKESH, M. V., CHIDAMBARAM, S., SINGARASUBRAMANIAN, S. R., RAJENDRAN, S., MUTHUKUMARASAMY, R., TAMILSELVI, M., 2015, Environ Earth Sci , 73, 2015, p. 2441.

JAHAN, S., STREZOV, V., Mar. Pollut. Bull. 128, 2018, p. 295.

IORDACHE, M., MEGHEA, A., NEAMTU, S., POPESCU, L. R., IORDACHE, I., Rev. Chim. (București), 65, no. 1, 2014, p.81.

GANUGAPENTA, S., NADIMIKERI, J, CHINNAPOLLA, S. R. R. B. M, BALLARI, L., MADIGA, R., NIRMALA, K., TELLA, L. P., 2018, Int J Sediment Res, 33, 2018, p. 294.

HAKÄNSON, L., Water Res., 14, 1980, p. 975. AQ

XU, J., CHEN, Y., ZHENG, L., LIU, B., 1,2, LIU, J., WANG, X., Water, 1060, no.10 2018, p. 1.

TEODOROF, L., BURADA, A., DESPINA, C., SECELEANU-ODOR, D., TUDOR, A. I.-M., IBRAM, O. I., NAVODARU, I., TUDOR, M., JEPE, 17, no. 1, 2016, p. 42.

WU, B., WANG, G., WU, J., FU, Q., LIU, C., 2014, PLoS ONE 9, no. 7, 2014, p.1.

Order 161/2006, regarding the classification of surface water quality to determine the ecological status of water bodies.

JAISHANKAR, M., TSETEN, T., ANBALAGAN, N., MATHEW, B. B., BEEREGOWDA, K. N., Interdiscip Toxicol., 7, no. 2, 2014, p. 60.

HARASIM, P., FILIPEK, T., J. Elem., 20, no. 2, 2015, p. 525.