# Assessment of the Environmental Significance of Heavy Metals Pollution in Surficial Sediments of South Brittany Waters, France: An Ecological Risk Assessment Approach

Meng Chuan Ong, Hui-Juan Pan, Noor Azhar Mohamed Shazili, David Menier, Virginie Dupont, Sidonie Révillon, Alexandra Coynel

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# Assessment of the Environmental Significance of Heavy Metals Pollution in Surficial Sediments of South Brittany Waters, France: An Ecological Risk Assessment Approach

**MENG CHUAN ONG** (✉ ong@umt.edu.my)

Universiti Malaysia Terengganu https://orcid.org/0000-0003-0095-6849

**Hui-Juan Pan**

National Taiwan Ocean University

**Noor Azhar Mohamed Shazili**

Universiti Malaysia Terengganu

**David Menier**

Universite de Bretagne-Sud

**Virginie Dupont**

Universite de Bretagne-Sud

**Sidonie Révillon**

Universite de Bretagne Occidentale

**Alexandra Coynel**

Universite de Bordeaux

## Research article

**Keywords:** Heavy metals, Bay of Quiberon, Gulf of Morbihan, sediment, sediment quality guidelines

**Posted Date:** August 6th, 2020

**DOI:** https://doi.org/10.21203/rs.3.rs-51877/v1

**License:** © This work is licensed under a Creative Commons Attribution 4.0 International License.

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1 Assessment of the Environmental Significance of Heavy

2 Metals Pollution in Surficial Sediments of South Brittany

3 Waters, France: An Ecological Risk Assessment Approach

4 Ong Meng Chuan¹,²,³

5 Email: ong@umt.edu.my

6

7 Hui-Juan Pan⁴,⁵

8 Corresponding author

9 Email: hjpan76@gmail.com

10

11 Noor Azhar Mohamed Shazili¹,²

12 Email: nazhar@umt.edu.my

13

14 David Menier⁶

15 Email: david.menier@univ-ubs.fr

16

17 Virginie Dupont⁷

18 Email: virginie.dupont@univ-ubs.fr

19
20 Sidonie Révillon<sup>8,9</sup>

21 Email: sidonie.revillon@sedisor.eu

22

23 Alexandra Coynel<sup>10</sup>

24 Email: alexandra.coynel@u-bordeaux.fr

25

26 (Institutional addresses)

27 <sup>1</sup> Faculty of Science and Marine Environment, Universiti Malaysia Terengganu, 21030 Kuala

28 Nerus, Terengganu, Malaysia

29 <sup>2</sup> Institute of Oceanography and Environment, Universiti Malaysia Terengganu, 21030 Kuala

30 Nerus, Terengganu, Malaysia

31 <sup>3</sup> Ocean Pollution and Ecotoxicology (OPEC) Research Group, Universiti Malaysia

32 Terengganu, 21030 Kuala Nerus, Terengganu, Malaysia

33 <sup>4</sup> Institute of Earth Sciences, College of Ocean Science and Resource, National Taiwan Ocean

34 University, 2 Pei-Ning Road, Keelung, Taiwan 20224, ROC

35 <sup>5</sup> Center of Excellence for Ocean Engineering, College of Engineering, National Taiwan

36 Ocean University, 2 Pei-Ning Road, Keelung, Taiwan 20224, ROC

37 <sup>6</sup> Laboratoire Géosciences Océan (LGO), Université Bretagne Sud, 56017, Vannes, Cedex,
38 France

39 ⁷ Département Sciences de la Matière et de la Vie, Université Bretagne Sud, 56017, Vannes,

40 Cedex, France

41 ⁸ UMR 6538 Laboratoire Géosciences Océan, Institut Universitaire Européen de la Mer, Place

42 Nicolas Copernic, 29280, Plouzané, France

43 ⁹ SEDISOR, Institut Universitaire Européen de la Mer, Place Nicolas Copernic, 29280,

44 Plouzané, France

45 ¹⁰ Université de Bordeaux - UMR CNRS 5805 EPOC, Allée Geoffroy Saint Hilaire Bât NB18

46 - CS 50023, 33615 Pessac Cedex, France

47

48

49 **Abstract**

50 Distribution patterns of selected heavy metals content in sediments from the Bay of Quiberon

51 and Gulf of Morbihan were studied to understand the current heavy metals contamination due

52 to urbanization and mariculture activities in the coastal area. Therefore, a survey was

53 conducted and 196 sediments collected were characterized for heavy metals content using

54 Inductively Coupled Plasma – Mass Spectrometry (ICP-MS) after mix acid digestion process.

55 The distribution maps of the concentrations of the heavy metals studied were produced as an
isopleth map based on data interpolation by the ArcGIS software application. The association
with the adverse effects on aquatic organisms was determined by the classification of the
sediment according to the sediment quality guidelines. Therefore, two approaches were
employed namely; direct comparison with Sediment Quality Guidelines (SQGs) by USEPA
and comparison with other numerical SQGs, threshold effect level/probable effect level, and
effect range low /effect range medium. In order to estimate the effect of multiple
contaminations of heavy metals, the mean-ERM-quotient was calculated at each sampling
point.

64

65

Keywords

66 Heavy metals, Bay of Quiberon, Gulf of Morbihan, sediment, sediment quality guidelines

67

68

Introduction

69
Nowadays, estuary and coastal environments are contaminated by human activities containing
70
elevated concentrations of heavy metals, nutrients, organic pollutants, and radionuclides
71
(Clark et al. 2000; Kennish 2002). Some chemicals are highly toxic and persistent and have a
72
strong tendency to concentrate in marine food webs. The pollution of coastal zones near
73
metropolitan areas, caused by these anthropogenic wastes is due to the large human
74 population and the enormous amounts of sewage discharged into coastal waters (Sadiq 2002;

75 Bay et al. 2003). The addition of waste products into rivers and estuaries, particularly those in

76 industrial and population centres has led to a significant increase in contamination of heavy

77 metals (Jayaprakash et al. 2005). Accumulation of heavy metals in surface sediments from

78 industrial effluents and urban discharged into the river without proper cleaning is easily

79 identified by heavy metals spatial variations in sediments (Dauvalter & Rognerud 2001).

80

81 Coastal areas are sensitive to both climate changes and human impacts, which make these

82 areas ideal for studying environmental changes and the sequence of coastal sediments, and

83 have become attractive targets for documenting paleoenvironmental changes. The Bay of

84 Quiberon and Gulf of Morbihan are an excellent example of the coastal sea with high

85 terrestrial influence, a semi-enclosed bay, surrounded by densely populated areas and

86 mariculture activities. Such an investigation is required if the environmental impacts of the

87 region are to be understood quantitatively and qualitatively.

88

89 In this exploration, surficial spatial distributions of selected heavy metals; Copper (Cu), Zinc

90 (Zn), Cadmium (Cd), Lead (Pb) (identified as priority contaminants in aquatic systems by the

91 European Community (EC) Water Framework Directive 2000/60/EC; Tessier et al. 2011)
92 were characterized in the surficial sediments which reflects the recent input to evaluate the
93 contamination level resulting from anthropogenic inputs. This EC work recommends the
94 monitoring of fluvial loads of heavy metals as a tool for sustainable management in the
95 aquatic ecosystem (Masson et al. 2006).

96

97 Metals are toxic because they bioaccumulate in which the accumulate in organisms and are
98 higher than in the environment (Gupta 2013; Goretti et al. 2016; Sobihah et al. 2018; Tengku
99 Nur Alia et al. 2020). Furthermore, metals also biomagnify, amplifies through the food chain
100 and accumulates in the top predators (Storelli et al. 2005; Gu et al. 2017; Rodríguez-Jorquera
101 et al. 2017; Bonsignore et al. 2018). Trace metals are also very persistent and difficult to be
102 removed once they enter the body of the organisms (Storelli et al. 2011; Benali et al. 2017; Gu
103 et al. 2018).

104

105 **Aim of Research**

106 The current study aims to analyze the levels of four heavy metals (Cu, Cd, Pb and Zn) at 196
107 sampling points in the Bay of Quiberon and Gulf of Morbihan surficial sediments. The
108 adverse effects on aquatic organisms were determined by direct comparison with the
109 Sediment Quality Guidelines (SQGs) and the sediment toxicity and ecological risk indices,
namely the effect low range (ERL) / effect range median (ERM), and the threshold effect
level (TEL) / probable effect level (PEL) values. In order to estimate the effect of multiple
contaminations of heavy metals in the study area, the mean-ERM-quotient was also calculated
at each sampling point.

114

115

**Methods/Experimental**

116

**Study Area**

Bay of Quiberon is a large open-sea area on the south coast of Brittany, consisting of two additional areas with an equivalent surface area of approximately 120 km² (Figure 1). The bay is roughly triangular, almost completely surrounded by land on the north and east sides; open to the south with the Gulf of Morbihan to the north-east and the narrow peninsula of Quiberon providing protection from the Atlantic Ocean to the west. The Belle, Houat, and Hœdic islands add to the protection of the bay (Proust et al. 2001; Chaumillon et al. 2008).

123

Gulf of Morbihan ("Mor-bihan" = "little sea" in Breton) is a natural harbor located in the South Brittany, northwest France (Figure 1). It is a close sea body (11 500 ha) and a shoreline of 250 km (Menier et al. 2011). It is a shallow basin with a maximum depth of 30 m and is connected to the sea by a 900 m wide and 30 m deep tidal inlet at Port Novalo (Rossi et al.

125

126

127
128 2011). Institut Géographique National France recorded that there are 37 islands located in the gulf where the two largest islands are Moine and Arz Islands. The gulf is sheltered from the Atlantic Ocean (Bay of Biscay) by the peninsula of Quiberon, Houat, Hoëdic, and Belle Islands.

132
133 Many areas along the coast are used by the public as recreation areas. A number of shipping ports for recreational purposes and fishing activities are located in this region. In addition, the surrounding coast is successfully used for commercial shellfish (oyster and mussel) mariculture activities with a significant market around the region.

137
138 Sample Collection

139 This oceanographic fieldwork was carried out by the SEPIOLA research vessel of the
140 University of Rennes1 at the Gulf of Morbihan and vessel of the Regional Committee of
141 Conchyliculture (CRC), South Brittany at the Bay of Quiberon. A total of 196 surficial
142 sediments were collected randomly in Bay of Quiberon and Gulf of Morbihan with Orange
143 Peel Grab sampler. In addition, in order to prevent metals contamination from the wall of the
144 grab, the outermost layer of the sediment samples were removed and only the inner part was
145 kept for further analysis. After collected, the samples were stored in plastic containers and
146 kept at low temperatures until analysis was carried out.

147

148 Laboratory Analysis

149 Sediment samples were digested and analyses for total heavy metals following published
150 methodologies with some modifications (Ong & Kamaruzzaman 2009; Kamaruzzaman et al.

151 2008; Kamaruzzaman et al. 2010). The digestion method involved heating of 50mg of a finely
152 powdered sample in a sealed Teflon vessel in a mixture with a mixed acid solution of
153 concentrated HF, HNO₃ and HCl. The Teflon vessel was kept in an oven at 150°C for 6 hours.

154 After cooling at room temperature, the solution of the vessel was transferred into a
155 polypropylene test tube. An inductively coupled plasma mass spectrometer, ICP-MS (Perkin
156 Elmer Elan 9000) was used for the quick and precise determination of selected heavy metals
157 in the digested sediment samples. The accuracy was also examined by analyzing duplicate
158 Standard Reference Material 1646a Estuarine Sediment, the results of which were within ±3%
159 of certified values.

160

161 Results and Discussion

162 All the analyzed data were visualized using ArcGIS software and presented in the form of a
163 concentration isopleth map to identify the sediment concentration hotspot as shown in Figure
164

2. Visualization by overlaying maps using a geographical information system makes this presentation even easier and more successful (Caeiro et al. 2005).

165

166

167

Tomlison et al. (1980) elaborated that the application of the pollution load index (PLI) provides a simple way to assess the quality of estuarine and coastal sediment. This assessment is a quick tool for comparing the status of pollution at different locations (Karbassi et al.

168

169

170

2006). PLI represents the number of times the concentration of heavy metals in the sediment exceeds the background concentration and provides a summary indication of the overall level of heavy metal toxicity in a particular sample or location (Rabee et al. 2011). The PLI can provide the public in the surrounding area with some understanding of the quality of the components in their environment, indicating the trend both spatially and temporarily (Harikumar & Jisha, 2010). In addition, it provides valuable information to decision-makers towards better management of pollution levels in the Bay of Quiberon and Gulf of Morbihan regions.

171

172

173

174

175

176

177

178

179

PLI is obtained as contamination factors (CF). This CF is the quotient obtained by dividing the concentration of each metal with the background value of the metal proposed by Wedepohl (1995). The PLI can be expressed in the following calculation:

180

181
$$182 \qquad \text{Pollution load index (PLI)} = (CF_1 \times CF_2 \times CF_3 \times CF_n)^{1/n}$$

183 where, n is the number of metals (4 in the present study) and CF is the contamination factor.

184 Background value : Cu 55 µg/g; Cd 0.2 µg/g; Pb 20 µg/g; Zn 70 µg/g

185 The CF can be calculated from:

$$186 \qquad \text{Contamination factor (CF)} = \frac{\text{Element concentration in the sediment}}{\text{Background value of the element}}$$

186 The background value (of the elements were adopted from Wedepohl (1995) to calculate the

187 CF. The PLI value > 1 is categorized as polluted, while <1 indicates no pollution at the

188 sampling point (Chakravarty & Patgiri 2009; Seshan et al. 2010).

189

190 PLI values of the analyzed surficial sediments were visualized by ArcGIS software and shown

191 in Figure 3, which confirms that either Bay of Quiberon or Gulf of Morbihan is not seriously

192 polluted with the heavy metals studied. PLI was found to be generally low (<1) in all the

193 studied locations in the Bay of Quiberon, apart from Trinité-sur-Mer area. The eastern zone

194 and rivers (Auray, Marle and Noyalo) zones also have a PLI value above 1; therefore these

195 areas can be classified as moderate contamination factors (Seshan et al. 2010).

196

197 Two approaches were used to assess sediment toxicity and ecological risk to benthic

198 organisms for heavy metals studied in Bay of Quiberon and Gulf of Morbihan surficial
sediments. The first approach was to compare the concentrations of heavy metals to the
Sediment Quality Guidelines (SQGs) promulgated by the United States Environmental
Protection Agency (USEPA) which were reviewed by Giesy et al. (1990). This approach was
used only to screen contaminants of concern in aquatic ecosystems. On the other hand, the
second approach was to apply two sets of SQGs developed for marine and estuarine
ecosystems (Long & McDonald 1998) to the assessment the ecotoxicology of the
concentration of heavy metals in sediments, namely, (a) the effect range low (ERL)/effect
range median (ERM) and (b) the threshold effect level (TEL)/probable effect level (PEL).

207

Based on the SQGs proposed by USEPA from Giesy et al. (1990), sediment contamination is
defined as three classes, non-polluted, moderately polluted and heavily polluted (Table 1).

This classification of SQGs does consider the natural background or multiple elements (Luo
et al. 2010). By comparing the mean concentrations of heavy metals in Bay of Quiberon and
Gulf of Morbihan surficial sediments with SQGs, sediments in both areas were classified as
non-polluted for Zn, and Pb, and moderately polluted by Cu and Cd where these metals
exceed SQGs. Surficial sediments from Trinité-sur-Mer zone in Bay of Quiberon, Auray,
Marle, Noyalo river zones, and the eastern in Gulf of Morbihan catchment area were
moderately enriched with these metals. However, no surficial sediments from both sampling
217 areas were classified as heavily polluted with the heavy metals studied according to SQGs
218 classification.

219
220 The concentration of heavy metals were evaluated in a screening-level ecological risk
221 assessment by comparing them to another numerical SQGs, namely the threshold effect level
222 (TEL)/probable effect level (PEL), and the effect range low (ERL)/effect range medium
223 (ERM) which were proposed by Long and McDonald (1998). Low range values (i.e., ERL
224 and TEL) are less than expected to have adverse effects on sediment dwelling fauna. In
225 contrast, ERM and PEL represent chemical concentrations above which adverse effects are
226 likely to occur in the aquatic ecosystem (Long & MacDonald 1998).

227
228 The SQG values for heavy metals studied in the surficial sediments from the Bay of Quiberon
229 and Gulf of Morbihan and the sediment classification based on these guidelines are shown in
230 Table 2. Results of SQGs classification suggest that all heavy metals in sediments would
231 rarely be expected to cause adverse effects on biota that living in the area.

232
233 The majority of heavy metals studied did not exceed the corresponding ERL and TEL
234 guideline values and therefore do not pose a risk to marine organisms living in Bay of
235 Quiberon and Gulf of Morbihan. Only a small percentage of surficial sediments would be
236 classified as possibly posing an occasional threat to the organism due to concentrations of Cu.

237 However, Cr, Cu, and Pb in a certain location exceeded the TEL value, particularly from the
238 Gulf of Morbihan surficial sediments. Thus, at a concentration greater than the TEL, the toxic
239 effect of long-term exposure to these heavy metals would be predicted to occur in the station
240 sampled.

241
242 In order to estimate the effect of multiple contaminations on heavy metals, mean–ERM–
243 quotient (M–ERM–Q) was calculated for each surficial sediment in the Bay of Quiberon and
244 Gulf of Morbihan according to Long et al. (1998a), Larrose et al. (2010) and Tessier et al.

245 (2011) as follows:

$$
M - ERM - Q = \frac{\sum_{i=1}^{n} (C_i / ERM_i)}{n}
$$

246
247
248 Where Ci is the surficial sediment concentrations of element (i), ERMi is the ERM for
249 element (i) and n is the number of elements, e.g. four heavy metals in this study.
250

250
251 Long et al. (1998b) have defined several classes of toxicity probability for biota organisms in
252 their study from US coast based on amphipod survival test: m-ERM-Q < 0.1 has a 9%
probability of toxicity); 0.1 < m-ERM-Q < 0.5 has a 21% probability of being toxic; 0.5 < m-ERM-Q < 1.5 has a 49% of being toxic; and m-ERM-Q > 1.5 has a 76% probability of toxicity. Using the concentrations of the heavy metals studied, the m-ERM-Q value was calculated, and the obtained distribution visualized by ArcGIS software in Bay of Quiberon and Gulf of Morbihan is shown in Figure 4.

The m-ERM-Q distribution pattern in the Bay of Quiberon surficial sediments showed that the inner bay zone had values below 0.1, which indicated a 9% probability of being toxic to the benthic organisms in that area. In the outer bay, the m-ERM-Q values slightly exceed 0.1, but not more than 0.2 indicate that this zone is between 9% and 21% probability to be toxic to benthic organisms. However, in Trinité-sur-Mer area, m-ERM-Q ranged from 0.2 and 0.3; therefore, this area can be categorized as 21% probability of toxicity to the benthic organisms according to Long et al. (1998b) classification.

Meanwhile, in the gulf of Morbihan sediments, the m-ERM-Q values at the western zone of the gulf were lower than 0.1m, and therefore this zone can be categorized as 9% probability of being toxic to the benthic organisms. Towards the inner gulf of eastern zone, the values of m-ERM-Q were increased but do not exceed the 21% probability of toxicity to the benthic
271 organisms, 0.2. Generally, some sampling locations located at the rivers zone (Auray, Marle and Noyalo) had the m-ERM-Q value higher than 0.3, which meant a 21% probability of toxicity to the benthic organisms. The impact of contaminated sediment probably on aquatic ecosystems is likely to be due to re-suspension and remobilization processes (Tankere-Muller et al. 2007; Kalnejais et al. 2010)

276

277 **Abbreviations**

278 Cd: Cadmium; CF: contamination factors; CRC: Regional Committee of Conchyliculture; Cu: Copper; EC: European Community; ERL: effect low range; ERM: effect range median; HCl : Hydrochloric acid; HF: Hydroflouric acid; HNO₃: Nitric acid; ICP-MS: Inductively Coupled Plasma - Mass Spectrometry, M-ERM-Q: mean-ERM-quotient; Pb: Lead; PEL: probable effect level; PLI: pollution load index; SQGs: Sediment Quality Guidelines; TEL: threshold effect level; USEPA: United States Environmental Protection Agency; Zn: Zinc

284

285 **Declarations**

286 **Availability of data and material**

287 Data sharing not applicable to this article as no datasets were generated or analyzed during the current study. Please contact author for data requests.

288
289

290

**Competing interests**

291

The authors declare that they have no competing interest.

292

293

**Funding**

294

This work was supported by Laboratoire Géosciences Marines et Géomorphologie du Littoral,

295

Université de Bretagne Sud, France and Institute of Oceanography (INOS) under Higher

296

Institution Centre of Excellence (HICoE), Universiti Malaysia Terengganu.

297

298

**Authors' contributions**

299

Meng-Chuan Ong proposed the topic, carried out the experimental study, analyzed the data

300

and writing the original draft. Hui-Juan Pan review and editing the manuscript. Noor Azhar

301

Mohamed Shazili, David Menier and Virginie Dupont supervised Meng-Chuan Ong and

302

review and editing the manuscript. Sidonie Révillon and Alexandra Connell help in

303

commenting the manuscript and interpret the results All authors read and approved the final

304

manuscript.

305
306 Acknowledgements

307 The authors wish to acknowledge their gratitude to the anonymous reviewers who gave freely

308 time and effort, constructive recommendations that enhanced the value of this manuscript.

309 The authors also would like to thank to Mr. Joseph Bidai for his assistance in the detection of

310 heavy metals using ICPMS at Institute of Oceanography and Environment.

311

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392 **Figure legends**

393

394 Figure 1. Map showing surficial sediment sampling points in South Brittany waters

395 Figure 2. Concentration map for heavy metals distribution in South Brittany coastal waters

396 surficial sediment
397 Figure 3. Contamination category based on PLI values in Bay of Quiberon and Gulf of

398 Morbihan surficial sediments

399 Figure 4. Contamination category based on m-ERM-Q values in Bay of Quiberon and Gulf

400 of Morbihan surficial sediments

401

402 **Table legends**

403 Table 1. Classification of sediment samples (µg/g) based on the proposed SQGs by USEPA

404 Table 2. Classification of sediment samples based on the SQGs
## Figures

<figure><img src="image_3.png" /><figcaption>**Figure 1**</figcaption></figure>

Map showing surficial sediment sampling points in South Brittany waters

<figure><img src="image_4.png" /><figcaption>**Figure 2**</figcaption></figure>

Concentration map for heavy metals distribution in South Brittany coastal waters surficial sediment
<figure><img src="image_5.png" /><figcaption>Figure 3</figcaption></figure>

Contamination category based on PLI values in Bay of Quiberon and Gulf of Morbihan surficial sediments

<figure><img src="image_6.png" /><figcaption>Figure 4</figcaption></figure>

Contamination category based on m-ERM-Q values in Bay of Quiberon and Gulf of Morbihan surficial sediments

**Supplementary Files**

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* GraphicAbstract.jpg