Spatial and temporal analysis of the risks posed by total petroleum hydrocarbon and trace element contaminants in coastal waters of Kuwait

Marine Pollution Bulletin xxx (xxxx) xxx–xxx

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Spatial and temporal analysis of the risks posed by total petroleum hydrocarbon and trace element contaminants in coastal waters of Kuwait E.E.M. Nicolausa,⁎, S.R. Wrighta, J. Barrya, T.P.C. Bolama, K. Ghareebb, M. Ghaloomb, N. Al-Kanderib, B.F.M. Harleya, W.J.F. Le Quesnea, M.J. Devlina, B.P. Lyonsc a b c

Centre for Environment Fisheries and Aquaculture Science (Cefas), Lowestoft Laboratory, Lowestoft, Suffolk NR33 0HT, UK Environment Public Authority (EPA) Kuwait, P.O. Box 24395, Safat 13104, Kuwait Cefas Weymouth Laboratory, Weymouth, Dorset DT4 8UB, UK

A R T I C L E I N F O

A B S T R A C T

Keywords: Kuwait Trace elements TPHs Marine waters Coastal

Nine trace elements including As, Cd, Cu, Fe, Hg, Ni, Pb, V and Zn, and total petroleum hydrocarbons were analysed from water samples collected from 23 stations since 1984 from Kuwaiti coastal waters. Here it was investigated whether concentrations of these determinants are at levels above Kuwaiti and internationally established assessment criteria (AC). The results indicate that Cu and Cd had the most Kuwaiti AC breaches over time. Comparing the data of the last sampled year to the least stringent international AC, then Cu and Cd showed breaches at all stations. The trends for trace metals are significantly downwards, especially for Cd and Hg. No determinant measured showed a significant upward trend, indicating that water pollution for these contaminants is not a worsening situation. However, further sampling should be carried out to confirm these findings, especially at shoreline locations, where routine monitoring ceased in 2011 to investigate any recent changes.

The State of Kuwait, located in the most northern regions of the Arabian (also known as the Persian) Gulf, has undergone major economic, social and industrial development over the past few decades (Al-Abdulghani et al., 2013; Al-Sarawi et al., 2015; Devlin et al., 2015a). The rapid expansion of Kuwait's urban and industrial sector has mainly occurred around its coasts (Al-Rifaie et al., 2007; AlAbdulghani et al., 2013). Consequently, a variety of contaminants have been discharged directly into the marine environment, including total petroleum hydrocarbons (TPHs), metals, nutrients (from raw domestic sewage), and contaminated brine from desalination plants, which are essential for freshwater production in the region (Al-Ghadban and ElSammak, 2005; Saeed et al., 2012; Al-Sarawi et al., 2015; Devlin et al., 2015b; Lyons et al., 2015a; Lyons et al., 2015b; Smith et al., 2015). These contaminant inputs pose a risk to Kuwait's marine habitats, which serve as a primary nursery ground for many ecologically and economically important species, like Green Tiger prawn (Penaeus semisulcatus), and the fish suboor (Tenualosa ilisha), orange-potted grouper (Epinephelus coioides) and tigertooth croaker (Otolithes ruber; Al-Husaini et al., 2007; Al-Mohanna et al., 2014). The Shatt Al-Arab mudflats close to Kuwait's northern border provide ideal habitats for numerous fish species and penaeid shrimp (Al-Zaidan et al., 2013; AlHusaini et al., 2015). Kuwait Bay and Khor Al-Sabiyah are some of the most important marine ecosystems around the Kuwait coastline and are

⁎

known to be affected by anthropogenic inputs of contaminants via the Shatt Al-Arab River, coastal construction and effluent discharges (AlSarawi et al., 2015). TPHs reach the marine environment due to oil spills, fossil fuel combustion and road run-off. TPHs are acutely toxic and have mutagenic or carcinogenic properties (Ehrhardt, 1972, Klewowski et al., 1994; Hallier-Soulier et al., 1999). Metals have been shown to affect a range of invertebrate and vertebrate species inhibiting growth or being acutely toxic depending on its concentration (Leung et al., 2005; Oldham et al., 2014). Historically both TPHs and metal contamination have been perceived as a threat to the health of Kuwait's marine and coastal ecosystems. Sources of TPHs pollution in Kuwait include the 1991 Gulf War which resulted in an estimated 10 million barrels of oil being deliberately released into Kuwait's coastal waters following the sabotaged pipelines and tankers at the Al-Ahmadi terminal (Al-Abdali et al., 1996; Readman et al., 1996). Sub-sea seepage of natural oil at numerous locations around the Kuwaiti coastline is also an important natural source of oil contamination in the region (Al-Ghadban et al., 2002). Anthropogenic sources of metals include antifouling paints, such as those used on vessels and marine structures, industrial effluent from power generating and desalination plants, run-off from roads and leaching from waste materials (Jickells and Knap, 1984; Flood et al., 2005; Jones, 2011; Lyons et al., 2015a).

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

http://dx.doi.org/10.1016/j.marpolbul.2017.04.031 Received 9 March 2017; Received in revised form 11 April 2017; Accepted 13 April 2017 0025-326X/ © 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/BY/4.0/).

Please cite this article as: Nicolaus, E.E., Marine Pollution Bulletin (2017), http://dx.doi.org/10.1016/j.marpolbul.2017.04.031

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E.E.M. Nicolaus et al.

Fig. 1. EPA Kuwait shoreline and coastal water monitoring stations. Table 1 Coordinates (decimal degrees) of EPA Kuwait shoreline and coastal water monitoring stations. Station ID

Station name

Longitude

Latitude

Station ID

Station name

Longitude

Latitude

S00 S01 S02 S03 S04 S05 S06 S08 S09 S11

Al-Beda'a Al-Salam Al-Amiri Benaid Al-Gar Al-Sha'ab Ras Al-Ardh Salmiya Abo-Al-Hasaniya Al-Fintas Al-Fahaheel

48.08867 47.95742 47.98947 48.00507 48.1001 48.1001 48.09198 48.10212 48.12278 48.13872

29.28293 29.36662 29.39103 29.37707 29.34097 29.34653 29.32888 29.22782 29.17687 29.0929

Z00 Z01 Z02 Z03 Z04 Z05 Z06 Z07 Z08 Z09 Z10 Z11 Z12

Al-Beda'a Medayrah (Jal Az-Zour) Al Doha Ras Ushayrij Al-Shuwaikh Ras Ajuzah Ras Al-Ard Al-Messila Al-Fintas Al-Fahaheel Mina Abdulla Ras Al-Julayah Mina Az-Zur

48.12936 47.9111 47.78502 47.91603 47.97593 48.02331 48.0951 48.12424 48.16832 48.15883 48.16908 48.27267 48.4

29.27562 29.47746 29.39364 29.42369 29.42497 29.40115 29.39142 29.23103 29.15608 29.0994 29.0205 28.92167 28.71867

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period. To compare the metals and TPHs simply with one another the RCR was used as described by Nicolaus et al. (2016). In summary, the RCR is the ratio between the Measured Environmental Concentration (MEC) and the ASQC. If the RCR is above 1, then the determinant failed the contaminant specific ASQC, which then provides environmental managers with an indication that water quality in relation to chemical contamination may be poor. As there is currently no documented approach on the way the quality criteria were derived they should be interpreted with care. Therefore, the MECs were also compared to quality standards from other countries or organisations (Spain, the EU, USA, Australia and New Zealand, OSPAR, Canada and Norway) that were summarised in a manuscript by Durán and Beiras (2013). OSPAR, who carries out marine based contaminant assessments for western European countries, has carried out environmental assessments in sediments using the Effects Range Low and Effects Range Mid that were developed for the USA. Using assessment criteria developed in other parts of the world for local assessments is very common, but not ideal as background concentrations vary considerably on a regional basis and organisms may be more adapted to these conditions over time. In the Gulf this is particularly pertinent as background levels of sedimentary metals are already high (Al-Abdali et al., 1996). However, this approach provides added confidence to any conclusions drawn. While the spatial status assessment, using set assessment criteria and comparing them to the measured concentrations of the last sampled year, provides an annual indication of environmental harm, the trend assessment allows environmental managers to understand the form of the trend trajectory. The trend assessment conducted here was carried out using a generalized additive model (GAM; Wood, 2006) for stations where samples were available in at least 5 separate years for a specific contaminant at a specific station. The GAM models were fitted using the function gam in the R package mgcv. A linear model was used in cases with only 4 years of data availability. No trend assessment was carried out if 3 years or less data were sampled. The GAM analyses incorporate temporal variation over time and are more flexible than linear regression. The gam() function allows us to compare the fitted model against a null hypothesis of “no trend”: the null hypothesis can be rejected, if the p-value is ≤ 0.05. Fig. 2 gives an example for the variation in As concentrations over time and the fitted GAM. The pvalue for this example was < 0.05 which allowed us to reject the null hypothesis of “no trend”. To judge the direction of the trend, we examined the direction of the trend at the end of the series was examined - which was downwards in this case. This procedure was followed for all determinants at the different stations where a GAM was fitted. The results in Table 3 give an overview of all the determinants and sites that failed the mean Kuwaiti ASQC from 1984 to 2016. Cu and Pb were metals of concern in the recent past (2010) at shoreline stations, while coastal sites indicate failures for Cd, Cu, Hg and Fe in different

The Environment Public Authority (EPA) Kuwait has been conducting a long-term marine monitoring programme of chemical pollution at a series of coastal (Z-sites) and shoreline (S-sites) stations since 1984 and 2006, respectively (Fig. 1; Table 1). Generally, samples were collected using a 1 L pre-acidified polyethylene bottle and kept in an icebox (at 4 °C) and transported to the laboratory for subsequent chemical analyses. Samples for Hg were kept in a brown glass bottle. Trace elements cadmium (Cd), copper (Cu), iron (Fe), lead (Pb), nickel (Ni), vanadium (V) and zinc (Zn) were analysed using an Agilent 700 series and Varian Pro-Vista Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). For mercury (Hg) and arsenic (As), the PS Analytical Atomic Fluorescence Analyzer was used. TPHs were analysed using a Perkin Elmer LS 45 luminescence spectrometer. To ensure quality control, reference material for trace metals (Cd, Cu, Fe, Pb, Ni, V, Zn), Hg and As, and TPHs were run periodically. More detail on sample collection preparation, analysis of trace elements and TPHs, quality control and quality assurance can be found in the manuals that were published by the Shuaiba Area Authority (1989) and the Regional Organisation for the Protection of the Marine Environment (ROPME, 1999 and ROPME, 2010). This study reports and assesses concentrations of metals and total petroleum hydrocarbons (TPHs) collected as part of this long-term national monitoring programme. The concentrations of metals and TPHs were compared to water quality standards as set out by the EPA in Decision No. 210/2001 (EPA, 2001). These are national standards set by EPA that contaminant concentrations in ambient water samples should not breach. They are similar to other regional standards, including those used in other GCC states (ROPME, 2010). The results were also discussed and compared to assessment criteria that have been developed for other countries around the world, including Australia and New Zealand, Spain, OSPAR, USA, Canada, Norway and European Commission (Canadian Council of Ministers of the Environment, 1999, US EPA, 1999, ANZECC, 2000, OSPAR, 2005, Norwegian pollution control authority, 2007, US-EPA, 2009, EU, 2012). A current assessment of 9 trace elements As, Cd, Cu, Fe, Pb, Hg, Ni, V and Zn, and TPHs, from ten (seven for TPHs) shoreline (S-sites) and thirteen coastal (Z-sites; Table 1; Fig. 1) sites was carried out to investigate if they are at levels that may cause harm to the marine environment around the Kuwaiti coast. Set Ambient Seawater Quality Criteria (ASQC) developed by EPA were used as assessment criteria for metals (Table 2). The ASQC for TPHs are set at 5 ppm or 5000 μg L− 1. A spatial status assessment was carried out by comparing assessment criteria to sampled contaminant concentrations in water to investigate if these concentrations could have any impacts on marine life in a specific area. The principles of Nicolaus et al. (2015) and (2016) were followed by using a Risk Characterisation Ratio (RCR) to investigate if concentrations measured are likely to pose a toxicological threat. Additionally, a trend assessment was carried out to determine if the contaminant levels have increased or decreased over the monitoring

Table 2 Ambient Seawater Quality Criteria (ASQC) in (μg L− 1) from the EPA Kuwait and around the world as summarised by Durán and Beiras (2013). Trace element

WQC

Spain

EU AA

EU MAC

USEPA AWQC

USEPA CWQC

ANZECC 95%

OSPAR EAC

Canada

Norway II

EPA Kuwait

As Hg Cu Cd Fe Pb Zn Ni V

n.r. 1.01 1.39 3.83

n.r. 0.07 25 0.2

n.r. – n.r. 0.2

n.r. 0.07 n.r. 1.5

n.r. 1.8 4.8 40

n.r. 0.94 3.1 8.8

n.r. 0.4 1.3 5.5

1–10 0.005–0.05 0.005–0.05 0.01–0.1

n.r. 0.016 n.r. 0.12

n.r. 0.048 0.64 0.24

25.3 8.24 n.r. n.r.

7.2 60 n.r. n.r.

7.2 n.r. n.r. n.r.

14 n.r. n.r. n.r.

210 90 74 n.r.

8.1 81 8.2 n.r.

4.4 15 n.r. n.r.

0.5–5 0.5–5 n.r. n.r.

n.r. n.r. n.r. n.r.

2.2 2 n.r. n.r.

n.r. 0.37 15.5 0.7 91.3 12 n.r. 20 9.4

Water Quality Criteria (WQC) derived from Durán and Beiras (2013); and international SQCs as presented by Durán and Beiras (2013); Spanish standards (Spain); EU chronic levels or EU Annual Averages (AV) and acute EU Maximum Admissible concentration (MAC); USEPA acute WQC and USEPA chronic WQC); Australia and New Zealand trigger values at 95% of protection (ANZECC), OSPAR ecotoxicological assessment criteria ranges (OSPAR EAC); Canadian guidelines (Canada); Norwegian level II criteria (Norway II); Kuwait EPA; n.r. not recorded. Bold highlighted assessment criteria are the highest and lowest used for comparisons.

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Water Quality Criteria (WQC). For this, results were compared to the lowest and highest available EACs that were available from different countries for different contaminants (Table 2). The OSPAR EACs were mainly the lowest available ones, while the upper EACs combined depending on the determinant from different countries (Table 2). Many determinants failed the lowest available EACs, while only one Cu sample collected at site S00 failed the highest available WQC (from Spain; Table S1) in the last sampled year (2010), but the annual average stayed below the Spanish WQC. Table 4 gives an overview of the RCR for each determinant and site when using the lowest available international standard which varied with determinant. It can be seen, that Cu had the highest number of failures (highest RCR values) while Ni showed no concern. As and Zn did not have specific ASQCs, so there was benefit in comparing the results to internationally recognised WQCs. The results indicate that some S and Z-sites are breaching the less stringent OSPAR EAC marginally. Zn, which was only sampled at six out of ten S-sites failed all of them with RCRs ranging between 25.8 and 59.3. The trend assessment showed that 63 out of a possible 162 significantly negative trends were observed across the board for metals and TPHs. The shoreline S-sites only accounted for three significant downward trends which were all for As while all other contaminants appeared to remain stable (Table 4; Table S1). The coastal Z-sites contributed 60 significant downward trends. Cu, Ni and Fe only showed significant downward trends at 1 and 2 coastal sites, respectively, while all other determinants showed very strong downward trends, especially after 2000. The most significant decreases were observed for Cd (13) and Hg (11 out of 13 coastal sites). Some non-significant increases at shoreline sites were observed mainly for Cd, Fe and Pb at stations S01, S05 and S11 (Al-Salam, Ras Al-Ardh and Al-Fahaheel, respectively). A detailed overview of the status and trend assessment can be found in Table 4. For TPHs, not a single station failed the assessment criteria over the years, indicating that pollution from hydrocarbons is not a significant problem in Kuwaiti waters. Of the 20 stations sampled at S-sites and Zsites in 2010 and 2014, respectively, 9 had mean TPHs concentrations < 1 μg L− 1. The highest mean concentrations were observed at S04 and S09 with 41.9 and 10.2 μg L− 1 in their respected last sampled year of 2010. Looking at the historic data, the highest ever recorded concentrations were 191, 167 and 141 μg L− 1 observed at stations S04, S11 and Z05 in 2010, 2006 and 2011, respectively. The generally low concentrations also confirm the findings of previous studies which indicate that apart from releases related to conflicts in the region, the actual background level of hydrocarbon contamination is relatively low (for review see Al-Sarawi et al., 2015). The trend assessment also showed that while shoreline concentrations (S-sites) of TPHs remain stable there is a significant downward trend at 6 coastal (Z-sites) stations (Table 4). The stable or declining concentrations observed here as part of this long-term monitoring programme are surprising giving the multiple and increasing pressures that Kuwait's marine environment is facing (Devlin et al., 2015a). However, while the human population of Kuwait has expanded (17-fold increase since 1950) and associated waste water and industrial inputs likely increased (Al-Abdulghani et al., 2013; Devlin et al., 2015b) there have been significant reductions in the flow of the Shatt al Arab to the Northern border of Kuwait (Abdullah et al., 2015). Previous studies have shown that this was a regionally important source of diffuse pollution (AlGhadban et al., 2002; Al-Ghadban and El-Sammak, 2005). All detailed trend assessment results including p-values can be found in Table S2. The data presented here indicate that metal contaminants are above the least stringent international assessment criteria for most determinants and therefore could potentially have adverse effects on the marine environment. The greatest concern would be Cu as the concentrations are stable across all sites and not decreasing at the same rates as other metals like Cd, Hg and Pb, for example. While Cu concentrations varied between 0.02 and 104.6 μg L− 1 across all

Fig. 2. Variation in As concentrations (μg L− 1) over time and the fitted GAM model. Also shown is the 95% confidence interval for the fitted GAM model. Blue-dotted line-lowest available assessment criteria for reference. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) Table 3 All stations samples since 1984 that failed the Kuwaiti ASQC for metals. RCR-Risk Characterisation Ratio is the ratio between the Measured Environmental Concentration (MEC) and the Ambient Seawater Quality Criteria. If the RCR is above 1, then the determinant failed the particular ASQC and this determinant may cause harm to the environment. Station

Year

Determinant

MEC mean

95% CI

MEC Max

N

RCR mean

95% CI

S01 S04 S04 S05 Z00 Z00 Z01 Z01 Z02 Z02 Z02 Z04 Z05 Z06 Z07 Z08 Z09 Z10 Z11 Z11 Z12 Z12

2010 2010 2010 2010 1991 2002 2002 2004 1997 2003 2016 2002 2002 2002 2002 2002 1991 2002 2002 2007 2002 2007

Cu Cu Pb Cu Fe Cd Cd Hg Cu Cd Fe Cd Cd Cd Cd Cd Hg Cd Cd Cd Cd Cd

22.8 16.4 12.6 23.5 110.8 0.87 1 0.4 18.2 1.3 91.4 1.1 1.2 0.7 1.2 0.8 0.4 1.1 0.9 0.8 1 0.9

40.9 24.2 17.8 40.6 NA 0.09 1.06 0.63 15.8 1.97 NA 0.72 0.8 0.2 0.8 0.2 0.1 0.8 0.7 0.9 0.8 1.0

104.6 64.5 47.1 104.6 110.8 1 2.6 2 97.3 5.2 91.4 2.2 2.4 0.9 1.8 1 0.5 1.9 1.6 1.7 1.4 1.9

5 5 5 5 1 4 4 6 6 5 1 4 4 4 4 4 2 3 3 3 2 3

1.5 1.1 1.1 1.5 1.2 1.2 1.5 1.1 1.2 1.9 1 1.6 1.7 1 1.7 1.1 1.1 1.5 1.3 1.1 1.5 1.3

8.2 5.4 5.0 8.2 NA 2.8 6.2 5.8 6.4 9.4 NA 5.2 5.8 2.4 4.6 3.0 2.6 5.4 4.6 5.0 5.4 5.4

MEC = Measured Environmental Concentration in μg L− 1; 95% CI = 95% Confidence interval around the mean which is (Mean ± 2 ∗ standard deviation); RCR = Risk Characterisation Ratio.

sampling years highlighted in Table 3. Fe failed the Kuwaiti environmental standard in the last sampled year at the coastal Z02 Al-Doha site, while all other annual mean MECs stayed below the ASQC (Table 4). Compared to previous years this was the lowest recorded Fe concentration at this site, which decreased from 102.5 (2013) to 91.4 μg L− 1. Additionally, twelve single samples for Cd, Cu, Hg, Fe, and Pb from four shoreline (S00, S08, S09 and S11) stations also failed the ASQC in their respected last sampled year (Table S1), but the annual mean stayed below the ASQC. To the best of our knowledge the Kuwaiti ASQC were not specifically derived following the examination of ecotoxicological data. Therefore, the results were compared to a range of international

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Table 4 Summary results of status and trend assessment for trace elements and TPHs. Status assessment: Green - result of last sampled year below Kuwaiti ASQC; Red - result of last sampled year above Kuwaiti ASQC; Pale Green - result of last sampled year below lowest Water Quality Criteria (WQC); Yellow - last sampled year above lowest WQC; Trend Assessment was carried out if four or more years were sampled: ↔ indicates there was no significant change over time (stable); ↓ indicates there was a significant downward trend; Risk Characterisation Ratio values for lowest WQC.

Stn.

As

Cd

Cu

Fe

Pb

Hg

Ni

TPHs

V

S 00 S01 S02

NA

NA

NA

NA

NA

NA

NA

NA

NA

S03

NA

NA

NA

NA

NA

NA

NA

NA

NA

S04 S05

As

Cd

Cu

Fe

Pb

Hg

Ni

TPHs

V

Zn

Last year sampled

3.4

32.1

2996

0.38

11.4

67.7

0.44

<0.1

0.1

44.9

2010; Zn 2006

0.1

7.9

720

0.07

1.2

3.4

0.2

<0.1

0.16

42.6

2011; Zn 2006; TPHs 2010

1.2

13.6

1100

0.41

1.0

3.6

0.28

NA

0.16

NA

2011

NA

0.14

NA

<0.1

0.09

1

10.2

760

0.18

1.2

3.6

0.5

1.6

8.5

580

0.72

1.8

3.4

0.35

0.8

6.7

560

0.17

2

3.6

0.22

1

8.2

780

0.11

1.2

3.8

0.2

41

2011; Zn 2006; TPHs 2010 2011; Zn 2006; TPHs 2010

<0.1

0.06

25.8

NA

0.11

NA

2011

0.21

59.3

2010; Zn 2006

0.13

NA

S06

NA

NA

NA

NA

NA

NA

NA

NA

NA

S08

NA

NA

NA

NA

NA

NA

NA

NA

NA

4.3

12.1

1090

0.64

13.3

22.5

0.31

<0.1

S09

NA

NA

NA

NA

NA

NA

NA

NA

NA

0.9

25.4

514.4

0.9

4.39

24.7

0.23

<0.1

2007 2010; Zn 2006

S 11

3.4

39.3

385

0.45

17.05

17.6

0.22

<0.1

0.19

Z00

0.1

2.88

291.9

0.1

0.4

4.05

0.18

<0.1

0.05

NA

2015; As, TPHs 2014

Z01

1.1

7.6

626

0.58

0.66

0.6

0.28

<0.1

0.14

NA

2016; TP+Hs 2014

Z02

1.2

7.7

278

1.1

0.24

0.46

0.19

<0.1

0.12

NA

2016; TPHs 2014

Z03

1.3

7.7

376

0.29

0.48

0.72

0.19

<0.1

0.14

NA

2016; TPHs 2014

Z04

0.9

7.1

342

0.14

0.24

1.0

0.19

<0.1

0.01

NA

2016; TPHs 2014

Z05

0.8

7.2

354

0.36

0.48

0.8

0.12

<0.1

0.05

NA

2016; TPHs 2014

NA

2016; TPHs 2014

NA

2015; As, TPHs 2014 2015; TPHs 2014

Z06 Z07

0.8

7.1

496

0.19

0.42

0.4

0.16

<0.1

0.02

0.1

3.76

492.7

0.13

0.72

2.36

0.21

<0.1

0.05

55

Z08

0.1

3.77

681.1

0.11

0.51

1.84

0.19

<0.1

0.08

NA

Z09

0.1

3.61

602.2

0.06

0.44

1.56

0.18

<0.1

0.04

NA

2015; TPHs 2014

Z10

0.1

4.71

331.1

0.08

0.71

1.5

0.22

<0.1

0.05

NA

2015; TPHs 2014

Z11

0.1

3.96

885.2

0.19

0.6

1.53

0.16

<0.1

0.08

NA

2015; TPHs 2014

Z12

0.2

3.48

379.6

0.1

0.49

1.54

0.3

<0.1

0.03

NA

2015; TPHs 2014

that many invertebrate larvae showed effects during EC10 and LC50 toxicity tests at Cu concentrations between 1.5 and 32.5 μg L− 1, which is within range of concentrations observed in this study. Comparing the MECmax concentrations of Hg, Cd, Pb and Zn observed in this study to the EC10 and LC50 test results presented by Durán and Beiras (2013) then there should not be an immediate concern as all MECs were below any observed effects results. Although, these determinants failed the least stringent internationally available EACs at almost all sites, the trends indicate that the determinant concentrations are decreasing steadily or stay stable at many stations, which is very positive considering the industrial and population expansion in Kuwait. The trends at stations S11 and Z09 next to the main industrial area of Shuaiba are also mainly stable or downward for many determinants indicating that the environment is improving steadily in relation to metal pollution. Further sampling at S-sites which stopped in 2011 would be advantageous to increase the power for trend assessments and to review the current status assessment. 11 sites also indicated mean TPHs concentrations above 1 μg L− 1 (a concentration of > 1 μg L− 1 was considered above the background concentration of TPHs in the Golf of Mexico after the Deepwater Horizon oil spill; Wade et al., 2016), which could be resampled to see if the concentations improved since then.

stations and sampled years, the mean Cu concentration was 3.07 ± 0.26 μg L− 1 ( ± 95% confidence interval), higher than the concentrations observed by Bu-Olayan et al. (1998; 0.6–2.2 μg L− 1), but lower than the mean concentrations observed by Al-Sarawi et al. (2002; mean concentration of 4 μg L− 1). Furthermore, Bu-Olayan and Thomas (2014) also reported high Cu levels in wastewater drain outfall samples, which were attributed to the effluents discharged from power plants, automobiles, paint industries, lubricants and domestic wastes from residential areas around the Kuwaiti coast. The mean Hg, Cd, Pb and Zn concentration (0.07 ± 0.0054; 0.3 ± 0.012, 1.87 ± 0.14 and 22.38 ± 5.8 μg L− 1 respectively) were similar to concentrations reported by Al-Sarawi et al. (2002) in respect of Pb (2 μg L− 1), but much lower for Zn (36 μg L− 1). Bu-Olayan et al. (1998) observed mean Cd concentrations ranging from 0.2 to 0.7 μg L− 1 which confirms the results observed here. No previous studies from Kuwaiti waters included any As or Hg concentrations in the water column, making direct comparisions difficult. Youssef et al. (2016) reported mean Hg concentrations of 0.3 μg L− 1 around Tarut Island, Saudi Arabia, Arabian Gulf and Al-Taani et al. (2014) overserved mean Hg concentrations of 0.063 μg L− 1 in the Gulf of Aqaba, Saudi Arabia, which are similar to our results. Al-Taani et al. (2014) also measured As and observed mean concentrations of 0.82 μg L− 1 which is much lower than our mean concentrations of 1.53 μg L− 1. The highest concentration observed in their study was 1.55 μg L− 1 in the northern Gulf of Aqaba. Their sampling was undertaken in January 2013, and comparing their results to ours collected between 2013 and 2016, then our mean is 0.3 μg L− 1 with a maximum of 1.25 μg L− 1. This shows how much the As concentrations decreased in our study between 2003 and 2016. Multiple studies summarised by Durán and Beiras (2013) indicate

Acknowledgements The authors wish to thank the staff of the Water Pollution Monitoring Department and the Central Analytical Laboratory of the Environment Public Authority (EPA) Kuwait for access to the data used within this paper. This work was funded by the EPA eMISKMarine Project (C6332). We would also like to thank Robin Law for editorial advice 5

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