Comprehensive study on metal contents and their ecological risks in beach sediments of KwaZulu-Natal province, South Africa

Marine Pollution Bulletin 149 (2019) 110555

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Comprehensive study on metal contents and their ecological risks in beach sediments of KwaZulu-Natal province, South Africa

T

⁎

E. Vetrimurugana, V.C. Shrutib, M.P. Jonathanc, , Priyadarsi D. Royd, S.K. Sarkare, B.K. Rawlinsa, Lorena Elizabeth Campos Villegasc a

Department of Hydrology, University of Zululand, Private Bag x1001, KwaDlangezwa 3886, South Africa Centro Mexicano para la Producción más Limpia (CMP+L), Instituto Politécnico Nacional (IPN), Av. Acueducto s/n, Col. Barrio la Laguna Ticomán, Del Gustavo A. Madero, C.P. 07340 Ciudad de México, Mexico c Centro Interdisciplinario de Investigaciones y Estudios sobre Medio Ambiente y Desarrollo (CIIEMAD), Instituto Politécnico Nacional (IPN), Calle 30 de Junio de 1520, Barrio la Laguna Ticomán, Del. Gustavo A. Madero, C.P.07340 Ciudad de México, Mexico d Instituto de Geología, Universidad Nacional Autónoma de México (UNAM), Ciudad Universitaria, C.P. 04510, Del. Coyoacán, Ciudad de México, Mexico e Department of Marine Science, University of Calcutta, 35 Ballygunge Circular Road, Kolkata 700019, India b

A R T I C LE I N FO

A B S T R A C T

Keywords: Sediment Metal concentration Ecological risks Geochemical indices South Africa

Sediment metal concentrations were assessed in five different beach regions (n = 183) of KwaZulu-Natal (KZN) province in South Africa. Metal distribution revealed that Cr, Cu, Mo, Cd, Zn, Hg and As exceed the background upper continental crust values suggesting their anthropogenic origin (mining, agricultural and industrial) apart from natural geological inputs (gold placer deposits and heavy minerals). Various geochemical indices (Geoaccumulation index, Enrichment factor and Degree of contamination) confirmed that the sediment samples are extremely contaminated with Cr, Cd and Hg. Further, Hg and Cd were main contributors (60–90%) to the ecological threat in sediments. Hazard index estimated a high hazard potential of Hg in near future. Finally, present study together with our previous results portray the status of KZN coast with special significance to Hg contamination/enrichment. Thus, future researches are recommended to investigate the environmental and human health implications of mercury exposure in this coastal province.

1. Introduction

of these regions. The present study is part of a larger project “Blue Flag Beaches: Vision 2030” of metal enrichments and baseline database establishment in different tourist beaches around the globe.

Coastal environments involve different physical, chemical and biological processes that play important roles in metal biogeochemical cycle. The association of anthropogenic metal input with urban development and industrialization in coastal areas has increased dramatically on a global scale. In coastal ecosystems, metals accumulate in sediments due to particle scavenging and settling (Temara et al., 1998; Clark, 1999; Sharifuzzaman et al., 2016). Consequently, a higher magnitude of metal concentrations is often found in sediments of coastal areas (Chakraborty et al., 2014, 2015). Thus, the investigation of coastal beach sediments being repository of metals that is often used to assess the anthropogenic and industrial impacts, environmental contamination and risk posed by metals on the coastal ecosystems (Chakraborty et al., 2019; Sarkar et al., 2004). The beach sediments are resources that need to be preserved for all beach recreation related activities as the loss of these sediments (or) contamination would lead to long term financial losses, which often affects the economical values

⁎

1.1. Information about KwaZulu-Natal coast, South Africa KwaZulu-Natal (KZN) coast of South Africa is a rich and diverse asset, providing valuable economic, social and ecological resources. It owns two world heritage sites (iSimangaliso Wetland Park and uKhahlamba Drakensberg Park) and nine beaches with blue flag status (Ray Nkonyeni Marina, Trafalgar, Lucien, Southport, Umzumbe, Hibberdene, Ramsgate, Ushaka and Westbrook) (Blue Flag, 2018). The Gross Domestic Product (GDP) of KZN reached R 322.2 billion in 2012, equivalent to 16.6% of South Africa's total GDP, which is driven mainly by its ports and tourism (van der Elst and Goble, 2014). The ports of Durban and Richards Bay in KZN, together handle 63% of South Africa's sea cargo and > 50% of vessel traffic. The Port of Durban is South Africa's largest and busiest port in terms of cargo values which is

Corresponding author. E-mail address: [email protected] (M.P. Jonathan).

https://doi.org/10.1016/j.marpolbul.2019.110555 Received 15 July 2019; Received in revised form 27 August 2019; Accepted 27 August 2019 0025-326X/ © 2019 Elsevier Ltd. All rights reserved.

Marine Pollution Bulletin 149 (2019) 110555

E. Vetrimurugan, et al.

approximately 250 km stretch were covered in this study.

estimated to have reached more than R160 billion per annum. These ports not only reinforce much of the KZN economy, but also stimulate and support high levels of employment associated with manufacture, sea trade and transport (Jones, 2014). The second macro-economic driver of KZN is tourism, especially coastal tourism. It contributes approximately R20 billion to the province's GDP. Nearly, 8 million tourists and among them 850,000 foreigners visited KZN in 2013 (Department of Tourism, 2014). KZN coast continues to experience the growth of urban and peri-urban development and the coastlineseems to provide an opportunity for economic development, with two major ports and vast stretches of magnificent beaches that has tremendous potential for tourism. Recently, our research group conducted studies to understand the consequential impacts of industrial and tourism development on the coastal environments of KZN in terms of metal contamination (Vetrimurugan et al., 2016, 2017, 2018). The results demonstrated enrichments of Cr, Cd and Hg in the beach sediments (Vetrimurugan et al., 2016, 2017, 2018) of Richards Bay, South Durban, Sodwana Bay and St Lucia. Given the potential accumulation of toxic elements along the KZN coast, still significant areas such as Mtunzini, Tugela, Zinkwazi, Ballito and Durban North remain unexplored. The main objective of this work is the estimation of spatial distribution/enrichment of some metals along Mtunzini, Tugela, Zinkwazi, Ballito and Durban North areas of KZN and to compare the status of enrichment with previously reported values in other coastal regions of KZN and worldwide.

a) Mtunzini (MTU) (Sample numbers: 1–15; Fig. 1a) The coastal town of Mtunzini also known as “a place in the shade”, is a leafy village, situated on the banks of the uMlalazi River bordering the uMlalazi Nature Reserve. The dominant soil types are clay loamy and sandy soils, derived from sandstone and quartzite parental rocks of the Natal Group (Sudan, 1999). A variety of over 350 bird species and approximately 75 waterbird species are found in Mtunzini, making it one of the best bird-watching locations in South Africa. Agriculture is the main economic activity dominated by sugarcane and timber production. b) Tugela (TUG) (Sample numbers: 16–22; Fig. 1b) This coastal town is situated on the lower catchment area of the Tugela River, which is one of the largest river of KZN province. The total catchment area of the Tugela River is approximately 29,036 km2 and only 4183 km2 forms part of the Lower Tugela catchment. Geology of the region comprises diamictite of the Dwyka Formation as well as shales and sandstones of the Pietermaritzburg Formation. At the coast, shales of the Vryheid Formation are unconformably overlain by PlioPleistocene coastal dunes, consisting of Berea red sand (McCourt et al., 2003; Bisnath et al., 2008). The principal land use is agriculture and timber production. The biggest pulp and paper mill in Africa, SAPPI, along with Isithebe industrial area are located close to the Tugela River mouth.

2. Study area and sampling information One hundred and eighty-three sediment samples were collected from five different beach sites of KZN during August 2014 (Fig. 1). Mtunzini, Tugela, Zinkwazi, Ballito and Durban North coastal regions of

c) Zinkwazi (ZINK) (Sample numbers: 23–32; Fig. 1c)

Fig. 1. Map showing the sampled sites of Mtunzini, Tugela, Zinkwazi, Ballito and Durban North areas of KwaZulu-Natal, South Africa. 2

Marine Pollution Bulletin 149 (2019) 110555

E. Vetrimurugan, et al.

It incorporates the greater Durban area of KZN offering beautiful beaches, nature reserves, animal parks etc. The Umgeni River in the south and La Lucia River in the north border DN, and previously, most of this region was a coastal dune forest system. The main industrial areas of DN include Briardene, Red Hill and Glen Anil. Natal Group of rocks comprising arkosic, quartz-arenitic sandstones and conglomerates overlies the basement rocks of Durban (Smith, 1990; Smith et al., 1993; Singh, 2009). It also constitutes of carbonaceous shales, siltstone and sandstones of Ecca Group (Johnson et al., 2006). DN is the most booming region of KZN in both economic and touristic point of view.

no data on background concentrations from the study area, the elemental abundances of UCC values (Wedepohl, 1995) were used as the reference baselines and for the calculation of geochemical indices. Geoaccumulation index (Igeo): We employed geochemical indices like geoaccumulation index (Igeo) developed by Muller (1979), is a useful metric of metal contamination in sediments (Sun et al., 2019; He et al., 2019). It is evaluated as follows: Igeo = (log2 Cn/1.5 Bn), where Cn is the concentration of the element “n”, Bn is the background concentration for the element and 1.5 is the background matrix correction factor for lithogenic effects. Muller (1979) established seven classes of geoaccumulation index (Igeo): Class 0 (< 0) = absence of contamination; Class 1 (0–1) = uncontaminated to moderately contaminated; Class 2 (1–2) = moderately contaminated; Class 3 (2–3) = moderately to strongly contaminated; Class 4 (3–4) = strongly contaminated; Class 5 (4–5) = strongly to extreme contamination and; Class 6 (> 5) = extremely contaminated. Enrichment factor (EF) is a quantitative method used to distinguish natural and anthropogenic sources of metals (Omar et al., 2018; Saher and Siddiqui, 2019). It is calculated as: EF = (Me/Fe)sample/(Me/ Fe)baseline where, (Me/Fe)sample/(Me/Fe)baseline represent ratio of metal to Fe concentrations in the studied samples and in the background sample, respectively. In this research, Fe was employed as normalizing element due to its relative abundance in crustal materials and represent negligible anthropogenic inputs (Dragović et al., 2008; Ye et al., 2011; Poh and Mohd Tahir, 2017). To assess an overall degree of contamination in sediments, Hakanson (1980) proposed a diagnostic tool named as “Degree of conn tamination” (Cd) and it is determined as: Cd = ∑i = 0 Cf where, Cf = Ms/ Mb, Ms is the metal concentration in the sediment, Mb is the background value of the same metal. It includes four tiers of classification: 1) low degree of contamination (Cd < 8), 2) moderate degree of contamination (8 ≤ Cd < 16), 3) high degree of contamination (16 ≤ Cd < 32) and, 4) extremely high degree of contamination (Cd ≥ 32) (El-Sayed et al., 2015; Sivakumar et al., 2016).

3. Analytical methods

3.2. Ecotoxicological analysis

Zinkwazi is a narrow beach with rocky outcrops and found to have high levels of population growth and a ‘good supply’ of public recreational space. This town is recognized for its lagoon, which is an estuary of the Zinkwazi River. It is underlain predominantly by Carboniferous to Permian aged tillites of the Dwyka Group, Karoo Supergroup and deep sand (Cooper and Smith, 2014; Anderson, 2017). Surfing and snorkeling, specifically Cray fishing, are very popular in this region. d) Ballito (BAL) (Sample numbers: 33–136; Fig. 1d) Ballito is a beautiful coastal town situated on the north coast of Durban in KZN. It is also known as, ‘Pearl of the Dolphin coast’, as bottlenose Dolphins are frequent in its waters. The geological basement of this coastal stretch includes granite, Natal Group Sandstone, Dwyka Tillite, Lower and Middle Ecca shales and sandstones (Archaeology and Natural Resources of Natal, 1951). The rock outcrops along the shore are often dolerite sills or they belong to the Natal Group Sandstone, Dwyka and Middle Ecca or coal-bearing series (Pistorius, 1962; Govender, 2000). The rocky shores rich in wildlife, secluded coves and bays, and in addition, presence of dolphins and whales marks the top tourist attractions of Ballito. e) Durban North (DN) (Sample numbers: 137–183; Fig. 1e)

Sediment samples were collected from the intertidal zone at five different beach locations (MTU, TUG, ZINK, BAL & DN) in KZN using a plastic spatula. Samples (n = 183) were oven dried below 40 °C, after which they were ground and passed through ASTM 200 sieve prior to analysis. Sediment samples (1 g) were digested with 2.5 ml of HNO3, 0.8 ml of HCl and 1 ml of H2O2 acids (all analytical grade) at 119 ± 1.5 °C for 40 min (EPA 3051A method, 2007; Navarrete-López et al., 2012). Digests were made up to 10 ml after filtration and the final solution was analyzed for 13 metals (Fe, Mn, Mg, Cr, Cu, Co, Mo, Ni, Pb, Cd, Zn, Hg, As) in inductively coupled plasma optical emission spectroscopy (PerkinElmer ICP-OES Plasma Optima 8300 DV). Strict control measures were implemented in the analyses to mitigate airborne and lab contamination. Milli-Q water was used for cleaning all the equipment used in analysis, preparation of metal standard solutions and dilution of samples. The quality and accuracy of the analytical procedure were ensured by the analysis of standard reference materials namely SRM No. 691029, Loam soil B and Marine Reference Standard (SRM 2702 – Inorganics in marine sediment). The recoveries were as follows (in %): Fe: 98.85; Mn: 98.11; Mg: 77.67; Cr: 84.99; Cu: 96.22; Co: 106.95; Mo: 92.70; Ni: 87.65; Pb: 88.62; Zn: 92.96; Cd 101.39; Hg: 106.01 and As: 110.42 respectively. Statistical analysis was applied (Statistica Version 12) separately for all the five regions and a correlation matrix data set was generated for the Kwa-Zulu-Natal region.

The ecological risk analysis was done by comparing the results with Sediment Quality Guidelines (SQGs), ecotoxicological values which includes threshold effect concentration (TEC), probable effect concentration (PEC), lowest effect level (LEL), severe effect level (SEL), effect range low (ERL) and effect range medium (ERM). Hazard quotient (HQ) developed by Urban and Cook (1986) was used in this study to estimate the potential biological adverse effect of SMC metal contaminants in sediments. It is defined as: HQ= SQG , where SMC is the sediment metal concentration and SQG is the concentration defined by sediment quality guidelines. Since ERL is more reasonably predictive of non-toxic condition (SQGs), the SQG is set at ERL levels (Long et al., 1995). If HQ < 0.1, no adverse effects are expected; if 0.1 < HQ < 1, low potential hazards are expected; in the range of 1.0 < HQ < 10, moderate hazards are probable; and when HQ > 10, high hazard potential is anticipated (Wang et al., 2002; Filgueiras et al., 2004; Qian et al., 2015). Potential ecological risk (RI) proposed by Hakanson (1980), is a widely used to evaluate the ecological risk of metals in sediments (Lin et al., 2016; Zhuang et al., 2018; Elias et al., 2018). It is expressed as: i

RI ∑ f ERfi ; ERfi = Tr i × Cfi = Tr i ×

( ) where, ER Csi

Cni

f

i

is the potential

ecological risk factor for a given element i; Tri is the biological toxicity factor for element i; which is defined as Mn = 1, Cr = 2, Cu = Ni = Pb = 5, Cd = 30, Zn = 1, Hg = 40 and As = 10 (Hakanson, 1980); Cfi, Csi and Cni are the contamination factor, the concentration in the sediment and the background reference value for element i respectively. RI < 150 indicate low ecological risk; 150 ≤ RI ≤ 300 moderate ecological risk; 300 ≤ RI ≤ 600 high ecological risk; and RI > 600 significantly high ecological risk.

3.1. Geochemical indices Geochemical enrichment for both natural and external (anthropogenic) input was identified using three types of indices. As there are 3

Marine Pollution Bulletin 149 (2019) 110555

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Fig. 2. a–m Metal distribution pattern in beach sediments of Mtunzini (MTU) (S.Nos: 1–15); Tugela (TUG) (S.Nos: 16–22); Zinkwazi (ZINK) (S.Nos: 23–32); Ballito (BAL) (S.Nos: 33–136) and Durban North (DN) (S.Nos: 137–183) areas of KwaZulu-Natal, South Africa.

among other metals are: Cu vs Ni (r2 = 0.90), Co (r2 = 0.95), Zn (r2 = 0.70), Hg (r2 = 0.87) and As (r2 = 1.00) respectively. The extensive agricultural activities in and around the Mtunzini areas discharge their wastewaters into the uMlalazi River, that ultimately reaches the coastal sediments resulting in enhancement of aforementioned metals (Umlalazi Nature Reserve, 2009; Department of Water and Sanitation, 2015). Cd did not show any relationship with other metals, suggesting its independent behavior in sediments. Apart from human activities, the presence of ilmenite, zircon, rutile, other heavy minerals and gold placer deposits in the dunes off the coastline of MTU results in natural elevation of Cr, Cu, Mo, Ni, Co, Cd, Zn, Hg and As metals (e.g. Humby, 2012; Wanless, 2014). The sediments of TUG beach have the highest concentration (in μg g−1) of Cu (71.34), Mo (5.37) and Co (16.56). However, in relation to UCC, metals like Cr, Cu, Mo, Ni, Co, Cd, Zn, Hg and As are significantly enhanced. Similar to MTU sediments, Cr and Mo are correlated (r2 = 0.92) with each other indicating their industrial source. There exists a good correlation (r2) among Cu vs Ni (0.85), Co (0.97), Zn (0.77), Hg (0.83), Cd (0.84) and As (0.84), suggesting their common origin. Tugela River drains in this region, which is largely influenced by three main sources: 1) Drainage from Natal coalfields via the Sundays and Buffalo Rivers; 2) Domestic effluents, fertilization and pesticides run off from farmlands adjacent to the river and 3) Effluents from the largest paper processing plant at Mandini (e.g. Felhaber, 1984;

4. Results and discussion 4.1. Metal distribution Metal distribution pattern in sediments from Mtunzini, Tugela, Zinkwazi, Ballito and Durban North beaches are illustrated in Fig. 2a–m. The relative abundance of metals in sediments maintained the following descending order: 1) MTU: Fe > Mg > Cr > Mn > Zn > Cu > Ni > Co > Pb > Mo > As > Cd < Hg; 2) TUG: Fe > Mg > Cr > Mn > Cu > Zn > Ni > Co > Pb > Mo > As > Hg > Cd; 3) ZINK: Fe > Mg > Cr > Mn > Zn > Cu > Ni > Pb > Co > Mo > As > Hg > Cd; 3) BAL: Fe > Mg > Cr > Mn > Zn > Cu > Ni > Pb > Co > Mo > As > Hg > Cd; and 4) DN: Fe > Mg > Cr > Ni > Zn > Mn > Cu > Pb > Co > As > Hg > Mo > Cd respectively. Correlation analysis was performed for each region to identify the possible sources of metals and the results are presented in Table 1. Moreover, the metal concentrations were also compared with upper continental crust (UCC) background values to understand the enrichment pattern (Table 2). The results show that MTU sediments are enriched with metals Cr, Cu, Mo, Ni, Co, Cd, Zn, Hg and As when compared to UCC values. Cr and Mo display a strong positive correlation of r2 = 0.71 (Table 1), indicating their source originated from metal based industries, where they used as anti-corrosive agent. Other noteworthy interrelationships 4

Marine Pollution Bulletin 149 (2019) 110555

E. Vetrimurugan, et al.

Table 1 Correlation matrix analysis of beach sediments from Mtunzini, Tugela, Zinkwazi, Ballito and Durban North areas of KwaZulu-Natal, South Africa. Fe Mtunzini (n = 15)

Tugela (n = 7)

Zinkwazi (n = 10)

Ballito (n = 104)

Durban North (n = 47)

⁎ † ‡

Fe Mg Mn Cr Cu Mo Ni Co Pb Cd Zn Hg As Fe Mg Mn Cr Cu Mo Ni Co Pb Cd Zn Hg As Fe Mg Mn Cr Cu Mo Ni Co Pb Cd Zn Hg As Fe Mg Mn Cr Cu Mo Ni Co Pb Cd Zn Hg As Fe Mg Mn Cr Cu Mo Ni Co Pb Cd Zn Hg As

1.00 0.84⁎,†,‡ 0.93⁎,†,‡ – 0.79⁎,†,‡ −0.57⁎,‡ 0.84⁎,†,‡ 0.95⁎,†,‡ 0.88⁎,†,‡ – 0.70⁎,† 0.77⁎,†,‡ 0.76⁎,† 1.00 0.94⁎,† 0.92⁎,† – 0.93⁎,† – 0.84⁎ 0.93⁎,† 0.90⁎,† – 0.84⁎ 0.85⁎ 0.85⁎ 1.00 0.99⁎,†,‡ 0.92⁎,†,‡ – 0.96⁎,†,‡ – 0.94⁎,†,‡ 0.99⁎,†,‡ 0.95⁎,†,‡ 0.77⁎,† 0.89⁎,†,‡ – – 1.00 0.43⁎,†,‡ −0.29⁎,† 0.67⁎,†,‡ 0.37⁎,†,‡ 0.82⁎,†,‡ 0.27⁎,† – −0.29⁎,† 0.81⁎,†,‡ −0.26⁎,† −0.34⁎,†,‡ – 1.00 0.81⁎,†,‡ 0.61⁎,†,‡ 0.87⁎,†,‡ 0.61⁎,†,‡ −0.50⁎,†,‡ 0.81⁎,†,‡ 0.88⁎,†,‡ 0.59⁎,†,‡ – 0.57⁎,†,‡ 0.68⁎,†,‡ 0.68⁎,†,‡

Mg

Mn

Cr

Cu

Mo

Ni

Co

Pb

Cd

Zn

Hg

As

1.00 0.92⁎,†,‡ – 0.66⁎,† – 0.71⁎,† 0.84⁎,†,‡ 0.58⁎ – 0.91⁎,†,‡ 0.88⁎,†,‡ 0.88⁎,†,‡

1.00 – 0.76⁎,† – 0.73⁎,† 0.90⁎,†,‡ 0.80⁎,†,‡ – 0.84⁎,†,‡ 0.87⁎,†,‡ 0.86⁎,†,‡

1.00 – 0.71⁎,† – – – – – – –

1.00 – 0.90⁎,†,‡ 0.89⁎,†,‡ 0.73⁎,† – 0.57⁎ 0.60⁎ 0.60⁎

1.00 – – −0.57⁎ – – – –

1.00 0.95⁎,†,‡ 0.76⁎,† – 0.53⁎ 0.68⁎,† 0.67⁎,†

1.00 0.86⁎,†,‡ – 0.70⁎ 0.81⁎,†,‡ 0.81⁎,†,‡

1.00 – – 0.65⁎,† 0.65⁎,†

1.00 – – –

1.00 0.87⁎,†,‡ 0.87⁎,†,‡

1.00 1.00⁎,†,‡

1.00

1.00 0.96⁎,†,‡ – 0.79⁎ – – 0.82⁎ 0.79⁎ – 0.95⁎,† 0.85⁎ 0.85⁎

1.00 – 0.82⁎ – – 0.88⁎,† 0.88⁎,† – 0.93⁎,† 0.85⁎ 0.85⁎

1.00 – 0.92⁎,† – – – – – – –

1.00 – 0.85⁎ 0.91⁎,† 0.95⁎,†,‡ 0.78⁎ – 0.76⁎ 0.76⁎

1.00 – – – – – – –

1.00 0.97⁎,†,‡ 0.90⁎,† – – – –

1.00 0.95⁎,†,‡ – 0.77⁎ 0.77⁎ 0.77⁎

1.00 0.79⁎ – 0.77⁎ 0.77⁎

1.00 – 0.84⁎ 0.84⁎

1.00 0.83⁎ 0.83⁎

1.00 1.00⁎,†,‡

1.00

1.00 0.90⁎,†,‡ – 0.94⁎,†,‡ – 0.92⁎,†,‡ 0.96⁎,†,‡ 0.91⁎,†,‡ 0.77⁎,† 0.86⁎,† – –

1.00 – 0.85⁎ −0.80⁎ 0.74⁎ 0.97⁎,‡ 0.97⁎,‡ 0.87⁎ 0.86⁎ – –

1.00 – – – – – – – – –

1.00 – 0.97⁎,†,‡ 0.95⁎,†,‡ 0.93⁎,†,‡ – 0.90⁎,†,‡ – –

1.00 – −0.66⁎ −0.71⁎ −0.79⁎,† – – –

1.00 0.89⁎,†,‡ 0.84⁎,† – 0.81⁎,† – –

1.00 0.98⁎,†,‡ 0.81⁎,† 0.89⁎,†,‡ – –

1.00 0.78⁎,† 0.93⁎,†,‡ – –

1.00 – – –

1.00 – –

1.00 1.00⁎,†,‡

1.00

1.00 0.50⁎,†,‡ 0.60⁎,†,‡ 0.29⁎,† – 0.59⁎,†,‡ 0.57⁎,†,‡ 0.46⁎,†,‡ 0.23⁎ 0.31⁎,† – 0.53⁎,†,‡

1.00 0.41⁎,†,‡ 0.37⁎,†,‡ −0.50⁎,†,‡ 0.64⁎,†,‡ 0.88⁎,†,‡ 0.61⁎,†,‡ – 0.57⁎,†,‡ 0.47⁎,†,‡ 0.61⁎,†,‡

1.00 0.65⁎,†,‡ 0.47⁎,†,‡ 0.74⁎,†,‡ 0.71⁎,†,‡ – 0.72⁎,†,‡ – – 0.22⁎

1.00 0.25⁎ 0.55⁎,†,‡ 0.55⁎,†,‡ 0.23⁎ 0.59⁎,†,‡ – – 0.21⁎

1.00 – – −0.50⁎,†,‡ 0.56⁎,†,‡ −0.38⁎,†,‡ −0.32⁎,†,‡ −0.28⁎,†

1.00 0.79⁎,†,‡ 0.30⁎,† 0.39⁎,†,‡ 0.27⁎,† 0.24⁎ 0.38⁎,†,‡

1.00 0.39⁎,†,‡ 0.24⁎ 0.46⁎,†,‡ 0.41⁎,†,‡ 0.49⁎,†,‡

1.00 – 0.36⁎,†,‡ 0.26⁎,† 0.66⁎,†,‡

1.00 −0.22⁎ −0.20⁎ –

1.00 0.27⁎,† 0.49⁎,†,‡

1.00 0.45⁎,†,‡

1.00

1.00 0.67⁎,†,‡ 0.65⁎,†,‡ 0.67⁎,†,‡ −0.39⁎,† 0.57⁎,†,‡ 0.63⁎,†,‡ 0.70⁎,†,‡ – 0.30⁎ 0.62⁎,†,‡ 0.62⁎,†,‡

1.00 0.58⁎,† 1.00⁎,† −0.36⁎,† 0.47⁎,† 0.46⁎,† 0.65⁎,†,‡ – 0.39⁎,† 0.68⁎,†,‡ 0.68⁎,†,‡

1.00 0.58⁎,†,‡ −0.62⁎,†,‡ 0.93⁎,†,‡ 0.91⁎,†,‡ 0.54⁎,†,‡ – 0.51⁎,†,‡ 0.68⁎,†,‡ 0.68⁎,†,‡

1.00 −0.36⁎ 0.47⁎,† 0.46⁎,† 0.65⁎,†,‡ – 0.39⁎,† 0.68⁎,†,‡ 0.68⁎,†,‡

1.00 −0.59⁎,†,‡ −0.60⁎,†,‡ −0.34⁎ – −0.25⁎ −0.34⁎ −0.34⁎

1.00 0.92⁎,†,‡ 0.56⁎,†,‡ – 0.52⁎,†,‡ 0.67⁎,†,‡ 0.67⁎,†,‡

1.00 0.52⁎,†,‡ – 0.55⁎,†,‡ 0.67⁎,†,‡ 0.67⁎,†,‡

1.00 – 0.31⁎ 0.73⁎,†,‡ 0.73⁎,†,‡

1.00 – – –

1.00 0.44⁎,† 0.44⁎,†

1.00 1.00⁎,†,‡

1.00

p < 0.05. p < 0.01. p < 0.001.

(24.03), Cd (0.83), Zn (85.85) and As (2.50) compared to all other beach regions. Additional metals like Cr, Cu, Mo, Cd, Zn Hg and As are elevated than UCC background values. In case of Pb, only the sediments of ZINK displayed higher concentrations with respect to UCC. Nearly,

Ntanganedzeni et al., 2018). The above mentioned sources are principal contributors for elevated concentrations of Cr, Cu, Mo, Ni, Co, Cd, Zn, Hg and As in TUG sediments. ZINK sediments exhibit higher concentrations (in μg g−1) of Pb 5

2779 – 1017 1072–27,190 30,964

HCl + HNO3 HCl + HNO3 – HCl + HNO3 HCl + HNO3

6

TEC 22 PEC 23 LEL 23 SEL 24 ERL 24 ERM

22

– – – – – – –

HCl + HNO3

– 29,000 600.6 33,000-51,100 5693 4812 7783 7320 6393 6291 6001 2692 4111 5098 31,792 – – 20,000 40,000 – –

– – – – – 917 1008 943 953 1021 1041 577 805 879 13,871 – – – – – –

– – –

– – 17,833

HCl + HNO3 + HClO4 – HCl + HNO3 – HCl + HNO3 HCl + HNO3 HCl + HNO3 + HF HCl + HNO3

–

437,900

–

– 120 42.43 256.6–615.7 65 64 72 76 93 97 113 105 27 87 542 – – 460 1100 – –

399 479 383

927.38

– 6.85–586 416.82

54.84 153.30

– – – – 10,752

344 – –

Mn

– – –

Mg

93.90 –

47.8 28.6 52.93

6.6–91 81 12.89 – 9.11 298 426 521 379 378 359 303 92 302 35 43.4 111 26 110 81 370

18.5 21.6 26.62

40.23

123.4 0.64–105.50 269.17

Cr

3.56 3.55

20 49.2 32

4.8–100 200 13.73 2.8–29.1 2.69 33.63 4.53 5.03 67.39 71.34 60.43 35.78 17.69 50.53 14 31.6 149 16 110 34 270

31.8 21 50.22

30.73

77.41 0.76–26.97 53.93

Cu

– – – – – 3.99 6.01 6.87 5.25 5.37 4.46 3.53 1.17 3.96 1.4 – – – – – –

– 0.6 –

–

– – –

– –

– – –

Mo

6.44 –

38.6 – –

1.3–28 20 53.59 34.2–79.9 6.41 101.98 15.16 16.56 35.03 35.78 31.55 11.73 52.49 33.32 19 22.7 48.6 16 75 20.9 51.6

13.8 – 6.88

19.27

51.31 0.33–16.35 –

Ni

– –

– – –

– – 26.44 18.1–31.7 5.32 48.52 6.90 7.71 16.24 16.56 15.74 6.33 12.22 13.42 12 – – – – – –

9.4 6.4 66.05

–

18.38 – 109.08

Co

5.67 76.63

25.4 36.3 25.78

5.4–235 360 49.25 35.1–447.8 8.68 16.06 1.27 1.49 10.56 10.55 24.03 10.03 14.84 14.00 17 35.8 128 31 250 46.7 218

22.2 23 662

48.19

42.39 0.13–20.46 409.67

Pb

0.72 –

0.50 1.5 0.14

– 2.8 5.8 0.1–0.3 0.74 0.41 0.34 0.30 0.73 0.75 0.83 0.52 0.66 0.70 0.102 0.99 4.98 – – 1.2 9.6

0.30 0.2 22.12

–

1.46 0.10–12.51 –

Cd

14.20 28.84

43 202.1 93.08

10.6–433 1000 48.59 65.7–115.3 78.11 44.57 2.81 3.29 67.72 70.87 85.85 46.17 52.17 64.56 52 121 459 120 820 150 410

70.2 56 1609

133.64

111.3 3.54–96.23 125.80

Zn

– 1.4 – – 0.003 1.57 1.14 1.31 0.70 0.95 1.00 0.78 1.46 0.98 0.056 0.18 1.06 0.2 2 0.15 0.71

– – –

–

– – –

– –

– – 0.048

Hg

– – 8.38

1.5–27 21 – – – – – – 1.73 2.39 2.50 1.40 2.19 2.04 1.30

7.1 15.8 19.23

–

– 0.09–5.40 –

– 20.74

As

All values are expressed in (μg g−1). UCC = Upper Continental Crust (Wedepohl, 1995); TEC: Threshold effect concentration; PEC: Probable effect concentration; LEL: Lowest effect level; SEL: Severe effect level; ERL: Effects range low; ERM: Effects range medium. 1) Topcuoğlu et al. (2004); 2) Lee et al. (2008); 3) Jiang et al. (2018); 4) Ganugapenta et al. (2018); 5) ELTurk et al. (2018); 6) Saher and Siddiqui (2016); 7) Jonathan et al. (2011); 8) Gutiérrez-Mosquera et al. (2018); 9) Kim et al. (2016); 10) Alkan et al. (2014); 11) Adamo et al. (2005); 12) Chakraborty and Owens (2014); 13) Alyazichi et al. (2015); 14) McCready et al. (2006); 15) El Nemr et al. (2006); 16) Omar et al. (2015); 17) Vetrimurugan et al. (2016); 18) Vetrimurugan et al. (2017); 19) Vetrimurugan et al. (2018); 20) Vetrimurugan et al. (2018); 21) Wedepohl (1995); 22) MacDonald et al. (2000); 23) USEPA (2001); 24) Long et al. (1995).

21 UCC values Sediment quality guidelines Ecotoxicological values

Present study

South Africa

Africa

Australia

Europe

North America South America

10,909 24,000 –

HCl + HNO3 – HCl + HNO3 + HF

3

2

Marmara Sea, Turkey Youngil bay, Korea East Zhejiang coast, China 4 Tupilipalem Coast, India 5 Kuala Selangor estuary, Malaysia 6 Coastal Pakistan 7 Acapulco beach, Mexico 8 Bahia Solano Beaches, Colombia 9 Baixada Santista, Southeastern Brazil 10 Spain 11 Naples City Port, Italy 12 South Australian coastline 13 Kogarah Bay 14 Sydney Harbour 15 Suez Gulf, Egypt 16 North Morocco 17 Richards Bay beaches 18 South Durban beaches 19 Sodwana Bay 20 St Lucia Mtunzini Tugela Zinkwazi Ballito Durban North Avg.

Asia

Fe

1

Metal concentrations

Extraction type

Country/region

Continent

Table 2 Metal concentrations in coastal sediments around KwaZulu-Natal province of South Africa and other countries worldwide.

E. Vetrimurugan, et al.

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Mn in all the beach sites. Noticeably, Hg is most enriched in sediments reaching the maximum contamination level (extremely severe) in all the sediment samples. The second most enriched element Cr is categorised as extremely severe at MTU, TUG, ZINK and BAL regions. Moreover at two sites (BAL & DN) Cd was classified as extremely severe enrichment. Cu and Mo are severely enriched in sediments of MTU, TUG and ZINK whereas, the metals Ni, Pb, Zn and As are moderately to severely enriched at all sites. Overall, the geoaccumualtion index and enrichment factor results reveal the extreme contamination levels of Cr, Cd and Hg in all the beach sediments. These metals are primarily sourced from natural geological formations, while the exceeding concentrations adsorbed to the sediments when compared to background values, clearly reflect their sources are from increasing human activities especially agricultural, mining and industrial sectors. Degree of contamination (Cd) showed a considerable enrichment of metal contamination in the examined sediments of KZN beaches, i.e. all the five beach regions showed Cd values > 16 (Fig. 3b). Cd showed extremely high degree of contamination (Cd ≥ 32) of metals in the sediments of MTU, TUG, ZINK and DN, while the BAL beach sediments exhibited a high degree of contamination (16 ≤ Cd < 32) in most of the sampling sites (Fig. 3b).

67% of the Zinkwazi wetland is covered with sugarcane agricultural fields and high levels of effluent and pesticides in the waters around the Zinkwazi estuary has been observed (e.g. Howarth, 2008; Meyer, 2011; Matavire, 2015). There exists a strong correlation (r2) between Pb vs Cd (0.78) vs Zn (0.93) indicating their common source from agricultural activities (e.g. Atafar et al., 2010; Wuana and Okieimen, 2011). It is observed that extensive sugarcane farming in this region resulting in wetland loss as well as deterioration of water has consequently enhanced the metals in ZINK sediments. The distribution pattern reflects low concentrations of metals in BAL sediments compared to all other regions (Fig. 2a–m). However, the metals Cr, Cu, Mo, Cd, Hg and As exceed UCC values. They are derived from a common source as they display a positive correlation (r2) among each other, Cr vs Cu (0.65), Mo (0.47), Cd (0.72) and Hg vs As (0.45). In recent years, there has been a population boom in Ballito and presently it caters to a growing industrial community on the north coast. The entire land resource was transformed from agricultural use to that for residential development (e.g. Appelcryn, 2007). Constructional activities along with domestic sewage effluents significantly influence the metal concentrations (Cr, Mo, Cd) in BAL sediments. DN sediments generally present lower concentration (in μg g−1) of metals in comparison with other regions except for Ni (52.49), Hg (1.46) and As (2.19). However, when compared to UCC, Cr, Cu, Ni, Hg and As are enhanced significantly. Likewise, these metals are strongly inter-related to each other as observed in correlation (r2) results (Table 2), where Cr vs Cu (0.58), Ni (0.93), Hg (0.68) and As (0.68) signifying a similar source. The elevated concentrations of Cr, Cu, Ni, Hg and As are sourced from Umgeni River draining in this region that has been significantly affected by agricultural drainage, urban wash-off, effluents from industries, mining, leachate from landfills and human settlements (Department of Environmental Affairs and Tourism, 2006; Olaniran et al., 2013). Likewise, Hg presents significantly higher concentrations in DN sediments compared to all other sites. Importantly, Hg wastes have been discharged into the Umgeni River situated in close proximity to the former mercury processing plant (Thor Chemicals Pty Ltd) in KZN (e.g. Clarke, 1994; Papu-Zamxaka et al., 2010; Williams et al., 2011). The observations in this study affirm that the historically Hg contaminated river still represents a potential Hg source to the surrounding environment. In addition, the sand mining activities in this region play an important role in mercury assimilation into the sediment beds. Overall, the sources of metals in coastal sediments of KZN were identified as geological (gold placer deposits and heavy minerals), past mining activities, agricultural, and industrial discharges.

4.3. Ecotoxicological assessment Once the level of metal contamination was established, the ecological risks due to the presence of these metals in sediments were evaluated using sediment quality guidelines (SQGs), ecotoxicological values, hazard quotient (HQ) and ecological risk index (RI). The metal concentrations were compared with SQGs and ecotoxicological values which include threshold effect concentration (TEC), probable effect concentration (PEC), lowest effect level (LEL), severe effect level (SEL), effect range low (ERL) and effect range medium (ERM) (Table 3). The values below TEC, LEL and ERL suggest no adverse effects, whereas values above PEC, SEL and ERM indicate harmful effects on the biological community (MacDonald et al., 2000; USEPA, 2001; Long et al., 1995). The concentrations of Cr in MTU, TUG, ZINK and BAL sediments are above PEC and SEL. Likewise, in MTU and TUG sediments the values of Cr are above ERM. Ni concentrations are above PEC and ERM exclusively in DN sediments. Similarly, DN sediments present Hg values higher than PEC. This means that the concentrations of Cr, Ni and Hg in beach sediment of KZN will cause adverse biological effects in due course of time. Results of the Hazard quotient (HQ) values for the beach sediments decreased in the following order: 1) MTU: Cr (4.68) > Hg (4.67) > Cu (1.98) > Ni (1.68) > Cd (0.61) > Zn (0.45) > Pb (0.23); 2) TUG: Hg (6.36) > Cr (4.67) > Cu (2.10) > Ni (1.71) > Cd (0.62) > Zn (0.47) > Pb (0.23); 3) ZINK: Hg (6.65) > Cr (4.43) > Cu (1.78) > Ni (1.51) > Cd (0.69) > Zn (0.57) > Pb (0.51); 4) Ballito: Hg (5.19) > Cr (3.74) > Cu (1.05) > Ni (0.56) > Cd (0.43) > Zn (0.31) > Pb (0.21) and 5) DN: Hg (9.75) > Ni (2.51) > Cr (1.13) > Cd (0.55) > Cu (0.52) > Zn (0.35) > Pb (0.32). The calculated HQ values reveal low potential hazards (0.1 < HQ < 1) for Cd, Zn and Pb in KZN beach sediments. However, all the other remaining metals (Cr, Hg, Cu and Ni) present moderate hazard potential (1.0 < HQ < 10) in the studied regions. Eventhough, Hg exhibits moderate hazard conditions in all the studied regions, the HQ values are close to 10 indicating the probability of high hazard potential in near future. Potential ecological risk (RI) of metals in all sampling sites is illustrated in Fig. 4a–e. According to the classification of RI, Cd and Hg in the sediments pose significantly high ecological risk (RI > 600). Cr and Cu exhibit moderate ecological risk in the sediments of MTU, TUG, ZINK and BAL. Likewise, the sediments of DN display a moderate ecological risk by As. Overall, in the studied samples, Hg alone presents nearly 65–90% of the ecological threat in sediments (Fig. 4a–e).

4.2. Geochemical indices We employed geochemical indices like geoaccumulation index (Igeo), enrichment factor (EF) and degree of contamination (Cd) to determine the level of metal contamination/enrichment in the sediments. The calculated geoaccumulation index (Igeo) values for the present study are illustrated in Fig. 3a. Here, our results provide strong evidences of Cd and Hg contamination in all the five beach destinations. The contamination status of Hg is entirely non-comparable with other metals as it falls in Class 4 (strongly contaminated) for TUG, ZINK, BAL and Class 5 (strongly to extremely contaminated) for DN. Cr and Cd show higher Igeo values (2–3) suggesting moderately to strongly contaminated for MTU, TUG and ZINK sites and moderate contamination (Igeo values = 1–2) for BAL and DN respectively. The Igeo values of Cu and Mo fall in class 2 indicating their moderate contamination in MTU, TUG and ZINK sediments. In contrast, the majority of the other studied metals display their levels below the baseline values within the Class 0 demonstrating that they are uncontaminated sediments. Enrichment Factor (EFs) are identified and the results of this study are presented in Table 3. Based on the EF values, the results suggest that there is no obvious geogenic deviation (EF < 1.5) for the metals Mg and 7

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Fig. 3. a–b a) Igeo values; b) degree of contamination values for Mtunzini, Tugela, Zinkwazi, Ballito and Durban North areas of KwaZulu-Natal, South Africa.

the concentrations of Cr (302 μg g−1) obtained in this study was higher than other sites. It is mainly attributed from Quaternary beach sand deposits along the KZN coast characterized with heavy minerals like ilmenite, rutile, zircon and chrome-bearing spinels as typical gangue minerals (Sudan et al., 2004; Pownceby and Bourne, 2006; Barath and Dunlevey, 2010). Cu concentration (50.53 μg g−1) was found to be lower in this area than in coastal Pakistan, Bahia Solano Colombia, Kogarah Bay Australia, Sydney Harbor and yet higher than other sites. Higher concentration of Ni (33.32 μg g−1) was found in this study than in other regions except Turkey, coastal Pakistan, Egypt and Morocco. Pb concentration (14 μg g−1) was lower in this study compared to other sites except India. The concentration of Cd (0.70 μg g−1) in this study was higher than the other results reported excluding India, coastal Pakistan, Mexico, Southern Australian Coastline, Sydney Harbor and Egypt. Hg concentration (0.98 μg g−1) was higher compared to China and lower than Sydney Harbor. Overall this analysis indicated that the

Overall, sediment assessment and its focus towards health risk aspects based on the two types of analysis done in the present study indicate that some toxic elements (Cr, Cd and Hg) could pose a threat to the human health as well as marine organisms along the coastal regions in near future. Based on earlier reports and our results it is recommended that these elements should be continuously monitored as there are several mining operations still operating as open mining and also drain their effluents directly or indirectly into the rivers and also deposit the finer particles in aquatic environment during different periods through wind transportation processes (Davies and Mundalamo, 2010; Pownceby and Bourne, 2006).

5. Comparison studies A comparison of the studied metals with those reported in KZN and worldwide are presented in Table 2. Globally, it has been observed that

Table 3 Calculated Enrichment Factor (EF) values for five different coastal regions in KZN province, South Africa. EF values

Classification

Mtunzini

Tugela

Nkwazi

Ballito

Durban North

< 1.5 <3 3–5 5–10 10–25 25–30 > 50

No enrichment Minor enrichment Moderate enrichment Moderately severe enrichment Severe enrichment Very severe enrichment Extremely severe enrichment

Mg, Mn – Pb Ni, Co, Zn, As Cu, Mo Cd Cr, Hg

Mg, Mn – Pb Ni, Co, Zn, As Mo Cu, Cd Cr, Hg

Mg, Mn – – Ni, Co, Pb, Zn Cu, Mo, As Cd Cr, Hg

Mg – Mn Co Ni, Pb, Zn, As Mo Cr, Cu, Cd, Hg

Mg, Mn – – Mo, Co, Pb, Zn Cr, Cu, Ni, As – Cd, Hg

8

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Fig. 4. a–e Contribution of different metals to potential ecological risk indices in beach sediments of: a) Mtunzini, b) Tugela, c) Zinkwazi, d) Ballito and e) Durban North.

of metal concentrations due to rapidly growing anthropogenic activities (Vetrimurugan et al., 2017). 2) Based on the contamination assessment, Kwambonambi Long, Nhlabane, Five Mile, Alkanstrand, Port Durnford, Ballito and Durban North beaches have levels of Cd displaying extreme contamination. However, South Durban, Sodwana Bay, Mtunzini, Tugela, Zinkwazi, Ballito, Durban North and Durban South beaches exhibit severe contamination of Cr and Hg (Vetrimurugan et al., 2016, 2017, 2018). 3) Moreover, based on the potential ecological risk index assessment, KZN sediments have been contaminated at a very high-risk level by Hg, with other metals presenting a low degree of potential ecological risk. Hotspots with higher ecological risk are mainly located in Sodwana Bay, St Lucia, Durban North and Durban South contributing nearly 86–97% of threat. Our study identifies the coast of KZN as Hg potential “hotspot” and urges adequate remediation techniques to control mercury contamination in this province. Once deposited in aquatic environments, mercury is vulnerable for microbial transformations into soluble and mobile methyl‑mercury form, which tends to bioaccumulate and biomagnify in food chains,

degree of contamination by metals in KZN coastal sediments is relatively severe, especially for Cr, Cd and Hg. 6. Conclusion In summary, the present study on metal concentration levels in five different beach sediments of KZN show enhancements of Cr, Cu, Mo, Cd, Zn, Hg and As. These metals are primarily sourced from natural geological formations of the study area, which is rich in heavy minerals and gold placer deposits. In the same time, the originated enhanced concentrations of these metals exceeding the background values represent their sources significantly from past gold mining, agricultural and industrial activities. As the data set is being complete with this study for all the beaches of KZN, we point out the current status of this coast on various aspects that are described as follows: 1) The overall data on metal concentrations showed that KZN coastal sediments are enriched with metals like Cr, Cd and Hg. Especially, the coastal stretch of Durban South is experiencing a higher degree 9

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ultimately exposing severe threat to biota and human health. Further investigations focusing the fractionation and detailed study of Hg in different compartments of environment (air, water, organisms and human health) are highly recommendable. 4) Our study identified that metals such as Cr, Cd and Hg in KZN sediments are derived from both natural and anthropogenic sources. Among them, primary anthropogenic sources include mining and mineral exploitation, industrial wastewater discharges and port activities (Fair and Jones, 1991; KMT, 2004; Jaggernath, 2010; Greenfield et al., 2011).

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Accordingly, KwaZulu-Natal faces the challenging task of balancing economic development with the protection of its beaches and the coastal environments. In this regard, relevant government and regional agencies must take measures to alleviate the pressure of metal contamination/enrichment necessary in the coastal environments of KZN. CRediT authorship contribution statement E. Vetrimurugan: Project administration, Funding acquisition. V.C. Shruti: Methodology, Software, Validation, Formal analysis, Investigation, Data curation, Writing - original draft, Writing - review & editing, Visualization. M.P. Jonathan: Conceptualization, Investigation, Writing - original draft, Writing - review & editing, Supervision, Project administration. Priyadarsi D. Roy: Conceptualization, Visualization. S.K. Sarkar: Conceptualization, Writing - review & editing, Visualization. B.K. Rawlins: Resources, Funding acquisition. Lorena Elizabeth Campos Villegas: Methodology, Validation, Formal analysis, Resources, Data curation. Acknowledgements EVM thanks the University of Zululand, South Africa for their financial assistance through Research and Innovation Scheme (Grant S186/14). MPJ wishes to express their thanks to IPN (COFAA, EDI), Mexico. VCS, MPJ and PDR thank Sistema Nacional de Investigadores (SNI), CONACyT, México. VCS acknowledges CONACYT project Grant No. 274276 “Fase I De La Remediación de Áreas Contaminadas con Hidrocarburos en la Refinería Gral. Lázaro Cárdenas” for postdoctoral fellowship. This article is part of the “Blue Flag Beaches: Vision 2030” and is 105th partial contribution from Earth System Science Group (ESSG), Chennai, India. Appendix A. Supplementary data Supplementary data associated with this article can be found in the online version, at https://doi.org/10.1016/j.marpolbul.2019.110555. These data include the Google map of the most important areas described in this article. References Adamo, P., Arienzo, M., Imperato, M., Naimo, D., Nardi, G., Stanzione, D., 2005. Distribution and partition of heavy metals in surface and sub-surface sediments of Naples city port. Chem 61, 800–809. Alkan, N., Alkan, A., Akbaş, U., Fisher, A., 2014. Metal pollution assessment in sediments of the southeastern Black Sea coast of Turkey. Soil Sediment Contam. Int. J. https:// doi.org/10.1080/15320383.2015.950723. Alyazichi, Y.M., Jones, B.G., McLean, E., 2015. Source identification and assessment of sediment contamination of trace metals in Kogarah Bay, NSW, Australia. Environ. Monit. Assess. 187 (2) (20-1 - 20-10). Anderson, G., 2017. Scoping Heritage Survey of the Zinkwazi Main Beach – Upgrade to the Septic Tank for Triplo4 Sustainable Solutions. Umlando: Archaeological surveys and Heritage Management (Report, 1-26 pp). Appelcryn, A., 2007. Environmental Impacts of the Construction Phase of an Intensive Development Project on a Coastal Forest Wetland. Case Study: Seaward Estates· Ballito. Thesis of Master of Science degree in the Civil Engineering Programme. University of KwaZulu-Natal, Durban, pp. 1–135. Archaeology and Natural Resources of Natal, 1951. Natal Regional Survey. vol. 1 Oxford University Press, Cape Town.

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