Prepared by Wendy Nelson Research Officer
Environmental Quality Programme
Institute of Marine Affairs Hilltop Lane, Chaguaramas
P.O. Box 3160, Carenage Post Office
Trinidad & Tobago, W.I. Tel: (868) 634-4291/4 Fax: (868) 634-4433
© 2016 Copyright The Institute of Marine Affairs
All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording of any information storage or retrieval system without the permission in writing to the Director of the IMA. The Institute encourages fair use of this document and proper citation is mandatory. Furthermore, the Institute of Marine Affairs gives no representations or a warranty either expressed or implied, as to the appropriateness of the data for a particular purpose, and as such, is not liable for inferences, recommendations or conclusions drawn by third parties.
All queries must be addressed to:
Institute of Marine Affairs
This project was funded by the Government of the Republic of Trinidad and Tobago. I wish to acknowledge staff of the Institute of Marine Affairs: R. Kishore- collaborating researcher in Fisheries Biology; S. James- Heavy Metals Technician; C. Koon Koon, S. Ramsammy, W. Beckles-Roberts and K. Williams from the Marine Chemistry Department; A. Jute, A. Titus and K. Philip from the Fisheries and Aquaculture Research Programme; P. Ramcharan, M. Pierre and R. Robinson from the Technical and Support Services Department; and H. Asmath and A. Jehu from the Information Technology Department. Thanks also to staff of the Trinidad and Tobago Coast Guard, the Customs and Excise Division, Commodore A. Franklin and C. James
TABLE OF CONTENTS
1.1 Background...... 1
1.2 Justification...... 1
1.3 Goal and Objectives...... 1
2.1 Sampling Regime...... 2
2.2 Selection of Stations...... 3
2.3 Parameters Determined...... 5
2.4 Sample Collection and Preservation...... 5
2.5 Methods of Analysis...... 5
2.6 Quality Control...... 6
2.7 Data Analysis...... 7
3.0RESULTS AND DISCUSSION...... 7
3.1 Water...... 7
3.1.1 Physico-Chemical Parameters...... 8
3.2 Sediment...... 11
3.2.1 Total Organic Carbon...... 11
3.2.2 Heavy Metals...... 12
LIST OF TABLES
Table 1:Logistics for sampling conducted...... 2
Table 2:Heavy metal ranges in sediments from Trinidad and Tobago...... 13
Table 3:Pearson correlation matrix for sediments from Trinidad...... 15
Table 4:Pearson correlation matrix for sediments from Tobago...... 16
LIST OF FIGURES
Figure 1:Location of stations sampled in Trinidad...... 4
Figure 2:Location of stations sampled in Tobago...... 4
Figure 3:pH of water from Trinidad and Tobago...... 8
Figure 4:DO of water from Trinidad and Tobago...... 9
Figure 5:Temperature of water from Trinidad and Tobago...... 10
Figure 6:Salinity of water from Trinidad and Tobago...... 11
Figure 7:Total organic carbon in sediments from Trinidad and Tobago...... 12
Figure 8:Boxplots for metals with no significant differences between sampling areas..18
Figure 9:Boxplots for metals with significant differences between sampling areas....20
Figure 10:Heavy metals in sediments from Trinidad and Tobago (a) Plot of loadings on
PC 1 and PC 2 (b) Plot of scores in the coordinates of PC 1 and PC 2...... 22
Figure 11:Heavy metals in sediments from Trinidad and Tobago. Colour coded plot of scores in the coordinates of PC 1 and PC 2 23
Figure 12:Sediments with highest metal accumulation. Solid “X”s- outliers, hollow “X”s- Group D stations in PCA plot of scores 24
Samples used in this study were the first set of sediment samples collected as part of an ongoing research project entitled, “Preliminary Investigation on Heavy Metals in Fish and the Mobile/ Bioavailable Phase of Sediments from Trinidad and Tobago”. This project is being conducted in collaboration with the Fisheries and Aquaculture Research Programme. The main goals of this project are (1) To investigate the potential mobility and bioavailability of heavy metals in sediments from Trinidad and Tobago and (2) To determine whether metals considered mobile/ bioavailable in the sediments are bioavailable to, or accumulating in, selected commercial fish tissue.
Heavy metals are often defined as elements with densities greater than 5g cm-3. Although these elements occur naturally, anthropogenic activities increase the bioavailable concentrations in the environment. Major sources of heavy metals include industrial effluent, sewage and domestic waste, agricultural run-off and urban run-off. While some of these elements are essential elements, i.e. they are required for important biochemical functions in an organism, all can have toxic effects in organisms when present in excess. Heavy metals present in the environment can bioaccumulate in aquatic organisms, posing a threat to consumers, including man. Depending on the metal, there can be neurological, systemic, carcinogenic effects, or birth defects. Very little information is available for Trinidad and Tobago on heavy metals in commercial fish species. Similarly, very little information is available on heavy metal distribution among the various geochemical phases in sediments, which is useful in assessing potential impacts in the environment.
1.3 GOAL AND OBJECTIVES
The main goal of this study was to assess the extent of heavy metal contamination in coastal sediments from Trinidad and Tobago. The objectives of the study were:
- To obtain physico-chemical parameters for seawater in the nearshore coastal area
- To determine concentrations of total organic carbon in surficial sediments from the nearshore coastal area
- To determine heavy metal concentrations in surficial sediments from the nearshore coastal area
- To identify metal enriched regions and possible land- based sources of heavy metals for Trinidad and Tobago
2.1 SAMPLING REGIME
Sampling was conducted once between October and December 2011. Samples for Trinidad were collected using the R.V. Kanawa (which was equipped with a winch) and samples for Tobago were collected using the R.V. Pelagica. Sampling logistics are shown in Table 1.
TABLE 1: LOGISTICS FOR SAMPLING CONDUCTEDTrip / Date / Station Sampled / Overnight Mooring
1 (trial sailing) / 28.10.11 / W2 / Not required
2 / 9.11.11 / W3-W8 / Not required
3 / 22.11.11 / T1-T5 / Buccoo- Fisheries Division Jetty
4 / 23.11.11 / T6-T10 / Buccoo- Fisheries Division Jetty
(around Trinidad) / 12.12.11 / W1, N1-N5 / Grande Riviere- off Le Grande Almandier Guest House
13.12.11 / N6-E4 / Guayaguayare- TT Coast Guard Jetty
14.12.11 / S1-S6 / Cedros- Customs/ Excise Division Jetty
15.12.11 / W9 / Not required
Surficial sediment samples were collected and physico-chemical parameters were measured at each station. Geographic co-ordinates and depths were also recorded at each station (Appendices A and B). Photos taken during field work in Trinidad are shown in Appendix C.
2.2 SELECTION OF STATIONS
Sampling stations were selected in order to ensure that:
- there was a good distribution over the nearshore coastal area
- the distance from the coastline was as consistent as possible for each island
- some samples were within areas used for fishing
A total of 35 stations were selected for sampling. 25 stations were selected for Trinidad- nine on the west coast, six on the north coast, four on the east coast and six on the south coast (Figure 1). Ten stations were selected for Tobago- five on the Windward side and five on the Leeward/ Caribbean side of the island (Figure 2).
- Samples were collected using a grab sampler, which does not work well for the sandy/ stony substrates off the east and north coasts of Trinidad. Fewer stations, which were further away from the coastline compared with other stations for Trinidad, were therefore established on the east coast.
- In order to keep stations at a consistent distance from the coast, the station depth had to be varied. A vessel equipped with a winch had to be used for sample collection in Trinidad due to the depths at some stations.
- The vessel used to collect samples in Tobago was smaller than the vessel used in Trinidad and was not equipped with a winch. Stations in Tobago were therefore established closer to the coast compared with those in Trinidad. In addition, divers were sent down to inspect the seafloor in Tobago to ensure that the grab sampler was not deployed in coralline/ rocky areas; the diver depth limit (i.e. maximum station depth) was approximately 70 feet.
FIGURE 1:LOCATION OF STATIONS SAMPLED IN TRINIDAD
FIGURE 2:LOCATION OF STATIONS SAMPLED IN TOBAGO
2.3 PARAMETERS DETERMINED
The following physico-chemical parameters were determined in water:
- Dissolved oxygen
The following parameters were determined in sediment:
- Total organic carbon (TOC)
- Total recoverable metals- vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), arsenic (As), selenium (Se), cadmium (Cd), barium (Ba), lead (Pb)
- Total recoverable metal is the metal fraction that can become available under normal environmental conditions (USEPA, 1996).
2.4 SAMPLE COLLECTION AND PRESERVATION
Surficial sediment samples were collected using a Ponar grab sampler and composite samples were prepared using a minimum of two grabs per station. Sediment samples were homogenized and transferred to polyethylene bags. Samples were held and transported back to the laboratory on ice where they were stored frozen until analysis.
2.5 METHODS OF ANALYSIS
In Trinidad, temperature (± 0.1 oC) and pH (± 0.1 pH unit) were measured in situ using the YSI Model 60 Meter. Salinity (± 0.1 ppt) and dissolved oxygen (± 0.3 mg l-1) were measured in situ using the YSI Model 85 Meter. In Tobago, temperature (± 0.1 oC), pH (± 0.01 pH unit), salinity (± 0.01 ppt) and dissolved oxygen (± 0.1 mg l-1) were measured in situ using the YSI Professional Plus Meter.
Samples were dried at 60oC, then sieved to obtain the <180μm size fraction, in which the dependence of metal content on surface area is removed (Hawkes and Webb, 1962; Oliver, 1973). Total organic carbon was determined according to the method outlined in Buchanan and Kain (1971). 1g sample was digested in K2Cr2O7 and H2SO4 and titrated against standardised ferrous ammonia solution. Detection limit: 0.01%.
Samples for total recoverable metals were prepared using microwave assisted acid digestion according to a modified version of USEPA Method 3051A (USEPA, 2007). 10 ml of concentrated HNO3 was added to 1g of sediment and allowed to pre-digest at room temperature for 30 minutes or until the initial reaction subsided. The mixture was then heated up to 175oC over a 30 minute period and held at this temperature for 4.5 minutes using the CEM Microwave Accelerated Reaction System (MARS) 6. Samples were allowed to cool and then centrifuged at 5000 rpm for 20 minutes. Samples were decanted and made up to a fixed volume using volumetric ware.
Analysis was performed using the Thermo X Series II Inductively Couple Plasma/ Mass Spectrometer using the standard mode with fully quantitative calibration. Internal standards (Tb and Ho at 3 μg l-1) were added to all samples to correct for physical interferences/ instrument drift. Detection limits were as follows- V 0.02 μg g-1, Cr 0.1 μg g-1 , Mn 0.05 μg g-1, Fe 0.1 μg g-1 , Co 0.02 μg g-1, Ni 0.02 μg g-1, As 0.05 μg g-1, Se 0.2 μg g-1, Cd 0.02 μg g-1, Ba 0.1 μg g-1 , Pb 0.1 μg g-1.
2.6 QUALITY CONTROL
Samples were analysed in batches with each sample analysed at least in duplicate. Procedural blanks were analysed with each batch of samples. Certified reference materials for water TM 24.3 and TMDA 70 (Environment Canada) were used to verify the calibration. Continuing calibration blanks were used and verification samples were used to check accuracy and drift. Precision of the total recoverable metals in sediment method was assessed using percentage relative standard deviation (RSD) of seven
replicates of a typical marine sediment. Percentage RSDs obtained were as follows: V 7.9, Cr 8.3, Mn 4.5, Fe 4.6, Co 6.5, Ni 9.2, As 9.8, Cd 14.2, Ba 10.3, Pb 7.5. Se was
below the detection limit. Grade 1 de-ionized water was used to prepare aqueous reagents and solutions used. Analytical reagents and compounds used in analysis were of Aristar or AnalaR grades. Glassware and plastic ware for heavy metals analysis were soaked overnight in 20% HNO3, rinsed with distilled water, then de-ionized water. Glassware for TOC analysis was soaked with Nochromix acid, rinsed with distilled water, then de-ionized water.
2.7 DATA ANALYSIS
Data was analysed using Minitab Statistical Software (Release 16). Statistical tests were performed on the untransformed data. One-way ANOVA and the Tukey multiple comparisons test were used to assess differences between sampling areas. Pearson correlation was used to assess relationships between parameters in sediment; data for Trinidad and Tobago was analyzed separately. Multivariate analysis- Principal Component Analysis- was performed on the data to assist in pattern detection. This is a means of data reduction in which samples with common characteristics are grouped together, and is quite useful in the analysis of multivariate environmental data (Zitko, 1994).
3.0RESULTS AND DISCUSSION
Water quality guidelines (WQGs) for the protection of marine aquatic life from the Canadian Council of Ministers of the Environment (CCME, 2007) were used to assess water quality parameters, as no ambient water quality guidelines are available for Trinidad and Tobago. These WQGs were developed for a temperate climate and are not necessarily applicable to a tropical environment. They were therefore used solely as benchmarks in this study.
pH of water from Trinidad and Tobago ranged from 7.2 to 8.8 (Figure 3). Two stations (Stations E4 and S3) were slightly more alkaline than the recommended CCME (2007) range of 7.0 - 8.7 for the protection of aquatic life, however, pH of water from the five sampling areas (west, north, east and south coasts of Trinidad, and Tobago) were not significantly different (p > 0.05).
FIGURE 3:PH OF WATER FROM TRINIDAD AND TOBAGO
Dissolved oxygen (DO) concentrations in water from Trinidad and Tobago ranged from
5.1 to 7.8 mg l-1 (Figure 4). All concentrations were below the CCME (2007) WQG of
>8 mg l-1 unless due to natural processes. DO in water off the west coast of Trinidad was significantly lower than DO in water from Tobago (p < 0.05). There are quite likely two main reasons for this: (1) the Gulf of Paria- the body of water off the west coast of Trinidad- is subject to the greatest quantity of organic pollutants such as sewage, agricultural runoff and food waste; these pollutants would utilize oxygen in the water
during decomposition and (2) the Gulf of Paria is semi-enclosed and more sheltered compared with the other sampling areas so there would be less aeration of this water body.
FIGURE 4:DO OF WATER FROM TRINIDAD AND TOBAGO
Temperature in water from Trinidad and Tobago ranged from 27.6 to 29.7 oC (Figure 5). The CCME (2007) water quality guideline for the protection of aquatic life is narrative. It states that, “Human activities should not cause changes in ambient temperature of marine and estuarine waters exceeding ±1ºC at any time, location, or depth”. Essentially, large fluctuations from ambient conditions (such as appears to be the case particularly off the west coast of Trinidad, perhaps due to industrial/ anthropogenic activities), should be avoided. The temperature of water off the west, south and east coasts were significantly higher than off the north coast of Trinidad (p < 0.05). This may be due in part to the land-based runoff/ discharge from the Orinoco River in South America. The temperature of water off the west, south and east coasts were not significantly different from the temperature of water from Tobago (p > 0.05).
FIGURE 5:TEMPERATURE OF WATER FROM TRINIDAD AND TOBAGO
Salinity ranged from 20.0 to 35.4 ppt (Figure 6). As with temperature, the CCME guideline is narrative and states that, “Human activities should not cause the salinity of marine and estuarine waters to fluctuate by more than 10% of the natural level expected at that time and depth” i.e. large fluctuations from ambient conditions should be avoided.
The salinity of open ocean water is typically about 35 ppt; the salinity values recorded in the twenties are suggestive of significant freshwater input. Salinity of water off the west, south and east coasts of Trinidad were significantly lower than salinity of water off the north coast of Trinidad, and off Tobago (p < 0.05). Although there is some variation in salinity, the values can be considered ambient as Trinidad and Tobago is subject to substantial freshwater discharge from the Orinoco River in South America, particularly during the wet season.
FIGURE 6:SALINITY OF WATER FROM TRINIDAD AND TOBAGO
Sediment quality guidelines (SQGs) for the protection of aquatic life from the Canadian Council of Ministers of the Environment (CCME, 2007) were used to assess sediment quality parameters, as no ambient sediment quality guidelines are available for Trinidad and Tobago. There is no sediment quality guideline for Total Organic Carbon. SQGs available for total metals in surficial sediment are being used solely as benchmarks to highlight the relative toxicity of the metals for two reasons: (1) the SQGs were developed for a temperate climate and are not necessarily applicable to a tropical environment; and (2) sediments were analyzed for the environmentally available total recoverable metal, however the SQGs were developed for the total metal concentration.
3.2.1 Total Organic Carbon
Total organic carbon (TOC) is the carbon found in organic matter and can be used as an indicator of organic matter (Schumacher, 2002), which is an important factor controlling metal abundance (Rubio et al. 2000). TOC can be due to natural sources i.e. decomposition of plant and animal matter, or anthropogenic sources such as sewage effluent, fish farm effluents and some industrial effluents (Cole et al., 1999). TOC
ranged from 0.15 to 2.08% (Figure 7). There is no sediment quality guideline for TOC. TOC in sediments off the north and west coasts of Trinidad were significantly higher than in sediments off the east and south coasts of Trinidad and off Tobago. It is likely that natural sources are contributing to the elevated TOC concentrations on the north coast of Trinidad as there is little anthropogenic activity on this coast.