Geochemical sediment of the tropical Pinang River, Malaysia was carried out with the aim at documenting elemental concentrations and pollution level assessment. Concentration of selected heavy metals (Cu, Cd, Cr, Pb, Zn and Mn), rare earth elements, TOC and grain size distribution of sediments were determined at 100 m sampling interval along the river. Sediment size showed a positive correlation with ∑REE and Mn and medium correlations with TOC, Zn, Cu, Cr and Pb contents showing enrichment in the clay size fraction. Results of enrichment factor and geoaccumulation index showed that most of the elemental sources were natural (especially REE) and mostly likely represented background values. However, pollution load index revealed the higher levels of Cr, Cd, Zn and Pb, and, therefore, indicating to the anthropogenic sources ( i.e. fishing activities) especially in the downstream locations. Thus, the Pinang River is classified as moderately to highly polluted.
Heavy metals and rare earths elements (REEs) are potentially toxic inorganic substances in the environment. Persistence and bioaccumulation of such elements may reach a certain threshold of toxicity to aquatic life and therefore, to the food chain systems [
Rare earth elements are being widely exploited due to the ever rising demand in modern gadgetry manufacturing such as magnet, catalyst, alloy, glasses, and related electronics [
Pinang River is one of the seven most contaminated river basins in Malaysia and is classified as Class-IV by the Interim National Water Quality Standards for Malaysia [
Pinang River is located in the northeast of Penang Island, Malaysia, as shown in
Sampling cruises were made aboard the research vessel that also served as sample processing platform. Surface sediments (0 - 10 cm depth) were collected with an interval of 100 m in July 2013 from 24 locations (
Sediment samples were dried at 60˚C in a clean oven for one week. Coarse debris and gravel in the sample were removed manually. The dried sediments samples were used to determine the concentration of heavy metals, REEs, TOC and grain size of sediments. For the total digestion about 50 mg of sample was transferred into the
Teflon cup along with 2 mL of mixed acids of HNO3, HCl and HF in the ratio of 3:3:1, respectively. The Teflon cup was enclosed in a pressure bomb and heated at 100˚C for 7 hours until a clear solution without residue obtained. After cooling down, sample was brought to volume of 10 mL using Milli-Q water (18.2 MΩ・cm). Concentration of heavy metals and REE were then measured by the multi-elements technique using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) (Method EPA 6020A; EPA, 2007).
Precautions were taken and appropriate procedures were followed as part of the QA/QC program throughout the analysis. Blank solution was prepared which only contained reagent to assess the impurity. Standard Reference Material (SRM-1646a) of sediments was used in the recovery test by comparing the measured values with the certified values to ensure accuracy. Recovery of analysis varied from 83% to 108% depending upon the metal as shown in
The organic carbon content (TOC) was determined in a 0.5 g of sample, avoiding contact with iron or steel, by wet oxidation and digestion by the Walkley-Black method. Oxidisable matter in the sediment was oxidised by 10.0 mL of 1N potassium dichromate (K2Cr2O7) solution. The reaction was assisted by the heat generated when two volumes of concentrated sulphuric acid (H2SO4) was mixed with one volume of the dichromate. The remaining dichromate was titrated with ferrous sulphate (Fe2SO4・7H2O). The titre is inversely related to the
Unit | Certified value | Analysed value | Recovery value (%) | |
---|---|---|---|---|
Li | ug・g−1 | 18 | 19.406 | 108 |
Al | % | 2.297 ± 0.018 | 2.307 | 100 |
Cr | ug・g−1 | 40.9 ± 1.9 | 41.584 | 102 |
Mn | ug・g−1 | 234.5 ± 2.8 | 194.059 | 83 |
Cu | ug・g−1 | 10.01 ± 0.34 | 9.703 | 97 |
Zn | ug・g−1 | 48.9 ± 1.6 | 48.515 | 99 |
Cd | ug・g−1 | 0.148 ± 0.007 | 0.139 | 94 |
Pb | ug・g−1 | 11.7 ± 1.2 | 11.980 | 102 |
amount of carbon present in the sediment sample.
For the grain size analysis, sediment samples were oven dried (105˚C for 24 hours) and about 200 g of sample was passed through 14 different mesh size sieves arranged consecutively downward from 4000 µm to <63 µm. For the fine fraction (<63 µm), about 2 g of sample was diluted with distilled water and 10% of Calgon solution (Na6P6O18) was added to disperse bonded particles in sediments. The grain size sediments of sediments were analysed using laser Particle Size Analyzer (PSA). Statistical analysis was carried out using SPSS software. Geographical Information System (GIS) was used to develop spatial variation maps. All data is reported as dry weight of sediments.
In situ measurements of water column (bottom layer) included several parameters such as pH which ranged from 6.91 to 8.15, DO from 0.13 to 4.92 mg/L and salinity from 15.6‰ to 30.81‰. Upstream sampling locations (P1 to P11) registered sand size (63 - 2000 µm) fraction only (
TOC ranged from 5.33% at P10 to 0.36% at P4 with mean value of 2.16%. TOC contents remained nearly unchanged at the upstream locations (P1 to P9; <1%) but increased sharply at P10 and then remained consistent before gradually decreasing closer to the estuary. TOC (%) in Pinang River is higher than the Langat River, Yangtze River and Pearl River [
Concentrations of Cd, Cr, Cu, Mn, Pb and Zn in surficial sediments are given in
with the mean value of 142 µg・g−1. The highest Mn contents were recorded location, P24, which is close to the estuary. Mn contents showed high correlation with mean fine size sediments (r = 0.83) and Zn, Cu, Cr and Pb showed medium correlation with (r = 0.64), (r = 0.62), (r = 0.41) and (r = 0.52) respectively. Cd showed a week correlation with mean sediments size (r = 0.37). Strong correlation between Zn and Cu (0.87) points to the same source which is probably anti-fouling paints contain about 15% - 30% of metals [
TOC showed a medium to strong correlations with studied metals, Zn (r = 0.71), Cu (r = 0.70), Pb (r = 0.63), Mn (r = 0.51), Cd (r = 0.45). TOC such as humic substances and fulvic acid provides absorption, ion exchange and forms complex (chelate compound) with metal re-deposition process [
Concentration of REE and related statistical data in surficial sediments of Pinang River is shown in
Both grain size and TOC contents of sediments showed a positive correlation with ƩREE, r = 0.82 and r = 0.70, respectively, and various metals (e.g. Zn) suggesting important controlling factors of metal distributions
Cd | Cr | Cu | Mn | Pb | Zn | |
---|---|---|---|---|---|---|
P1 | 0.34 | 68.0 | 5.23 | 44.8 | 11.1 | 68.0 |
P2 | 0.49 | 65.0 | 6.89 | 76.6 | 11.2 | 90.6 |
P3 | 0.50 | 77.1 | 12.6 | 79.8 | 26.4 | 104 |
P4 | 0.40 | 33.9 | 4.88 | 39.8 | 8.42 | 77.7 |
P5 | 0.23 | 60.5 | 15.7 | 75.6 | 10.5 | 50.6 |
P6 | 0.38 | 82.7 | 7.78 | 103 | 16.9 | 118 |
P7 | 0.30 | 22.6 | 5.99 | 99.2 | 21.4 | 100 |
P8 | 0.30 | 24.3 | 26.1 | 50.3 | 13.0 | 65.0 |
P9 | 0.66 | 20.9 | 3.98 | 45.4 | 12.5 | 59.6 |
P10 | 0.30 | 29.8 | 3.57 | 54.6 | 13.8 | 46.6 |
P11 | 0.07 | 18.8 | 8.70 | 83.9 | 17.4 | 71.1 |
P12 | 1.51 | 49.9 | 62.1 | 184 | 75.1 | 317 |
P13 | 1.11 | 48.3 | 22.2 | 135 | 23.7 | 109 |
P14 | 0.63 | 89.5 | 37.5 | 195 | 42.9 | 194 |
P15 | 0.25 | 25.9 | 7.68 | 126 | 19.1 | 67.9 |
P16 | 0.48 | 48.8 | 27.8 | 172 | 33.9 | 190 |
P17 | 0.47 | 92.3 | 44.6 | 194 | 83.5 | 252 |
P18 | 0.71 | 122 | 39.5 | 250 | 35.7 | 227 |
P19 | 0.34 | 70.3 | 40.1 | 249 | 34.2 | 242 |
P20 | 1.14 | 73.6 | 41.9 | 211 | 37.5 | 219 |
P21 | 0.47 | 77.7 | 21.1 | 301 | 24.2 | 153 |
P22 | 0.77 | 60.9 | 43.9 | 108 | 16.9 | 115 |
P23 | 0.46 | 42.5 | 8.00 | 152 | 11.7 | 91.9 |
P24 | 0.34 | 95.7 | 14.6 | 375 | 21.4 | 106 |
Average | 0.53 | 58.4 | 21.3 | 142 | 25.9 | 131 |
Std. Dev. | 0.33 | 27.8 | 16.9 | 88.8 | 19.1 | 75.2 |
Min | 0.07 | 18.8 | 3.57 | 39.8 | 8.42 | 46.6 |
Max | 1.51 | 122 | 62.1 | 375 | 83.5 | 317 |
(
Organic matter contains humic substances which provide high affinity for REE ion especially at near-neutral pH aquatic environments [
Texturally river sediments are classified as silt-sand and the sand size (>2000 µm) fraction decreases towards
river mouth. Upstream locations tend to have coarser grain size sediments due the removal of fine particles and deposition towards downstream locations deepening upon hydraulic energy and gradient. Tropical rain events are intense and significantly remove fine sediments to the sea.
Mn concentration increased gradually towards the river mouth. Downstream zone contains higher fraction of fine sediments and potentially provides larger binding sites for dissolved Mn ions in water column [
Highest concentrations of Cu and Cd were determined at location P12 closer to the jetty. The input is most likely due to the fishing boat activities such as fish delivering, leakage of petrol and lubricant as well as antifouling paint residue [
Sc | Y | La | Ce | Pr | Nd | Sm | Eu | Gd | Tb | Dy | Ho | Er | Tm | Yb | Lu | |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
P1 | 963 | 9.29 | 39.1 | 108 | 3.27 | 7.75 | 5.57 | 1.13 | 2.36 | 0.77 | 2.09 | 0.70 | 1.40 | 0.25 | 1.60 | 0.30 |
P2 | 921 | 11.2 | 40.1 | 188 | 4.46 | 10.9 | 6.51 | 1.78 | 3.24 | 0.62 | 3.60 | 0.76 | 1.95 | 0.22 | 1.14 | 0.13 |
P3 | 953 | 10.1 | 46.1 | 113 | 3.84 | 13.5 | 3.89 | 2.35 | 2.43 | 0.58 | 2.37 | 0.66 | 1.47 | 0.55 | 1.82 | 0.37 |
P4 | 850 | 4.72 | 21.5 | 74.6 | 2.98 | 4.96 | 1.45 | 1.39 | 1.88 | 0.15 | 1.19 | 0.71 | 1.23 | 0.28 | 0.93 | 0.41 |
P5 | 827 | 6.46 | 32.0 | 76.4 | 4.55 | 9.04 | 4.79 | 1.75 | 1.48 | 0.74 | 0.73 | 0.64 | 1.96 | 0.16 | 0.69 | 0.37 |
P6 | 969 | 26.2 | 80.7 | 151 | 8.28 | 23.1 | 5.01 | 0.89 | 4.90 | 0.73 | 3.10 | 0.99 | 3.71 | 0.65 | 1.98 | 0.67 |
P7 | 865 | 19.0 | 85.5 | 153 | 9.18 | 22.5 | 6.47 | 1.78 | 4.99 | 1.50 | 5.83 | 0.83 | 2.59 | 0.49 | 1.53 | 0.47 |
P8 | 981 | 20.9 | 60.5 | 122 | 6.87 | 18.3 | 5.89 | 2.34 | 3.97 | 0.72 | 4.23 | 0.79 | 2.48 | 0.82 | 2.26 | 0.53 |
P9 | 951 | 21.7 | 64.2 | 129 | 8.02 | 21.2 | 4.44 | 2.10 | 3.56 | 0.96 | 3.06 | 1.48 | 3.00 | 0.53 | 2.01 | 0.85 |
P10 | 974 | 18.2 | 60.2 | 119 | 9.11 | 22.6 | 4.78 | 1.49 | 3.85 | 0.70 | 3.47 | 0.77 | 2.90 | 0.87 | 2.23 | 0.37 |
P11 | 948 | 23.9 | 70.8 | 142 | 8.85 | 22.0 | 5.37 | 1.38 | 4.53 | 1.32 | 4.20 | 1.36 | 2.71 | 0.40 | 2.92 | 0.51 |
P12 | 759 | 74.8 | 355 | 662 | 38.7 | 137 | 18.4 | 3.00 | 16.0 | 3.94 | 11.8 | 3.20 | 10.3 | 1.75 | 5.49 | 1.47 |
P13 | 890 | 38.8 | 152 | 266 | 14.3 | 47.7 | 8.21 | 1.48 | 6.87 | 1.73 | 7.52 | 1.63 | 4.00 | 0.74 | 3.06 | 0.98 |
P14 | 744 | 74.0 | 234 | 721 | 31.2 | 63.9 | 22.5 | 2.69 | 15.0 | 2.66 | 10.7 | 2.55 | 7.13 | 2.31 | 7.25 | 1.26 |
P15 | 862 | 42.6 | 169 | 308 | 14.9 | 42.6 | 8.42 | 2.41 | 7.64 | 2.16 | 7.13 | 1.92 | 5.27 | 0.38 | 4.72 | 1.09 |
P16 | 834 | 89.0 | 262 | 520 | 31.5 | 86.4 | 17.5 | 3.25 | 18.3 | 4.48 | 15.7 | 4.10 | 10.8 | 1.59 | 6.11 | 1.70 |
P17 | 797 | 127 | 474 | 823 | 44.0 | 132 | 29.2 | 4.13 | 20.8 | 3.36 | 18.8 | 4.38 | 10.6 | 2.14 | 13.0 | 1.93 |
P18 | 788 | 138 | 445 | 914 | 49.1 | 159 | 21.0 | 3.99 | 23.9 | 6.29 | 25.2 | 6.00 | 17.2 | 2.06 | 13.2 | 2.58 |
P19 | 738 | 120 | 451 | 816 | 48.4 | 136 | 22.3 | 3.08 | 23.0 | 4.13 | 15.7 | 4.32 | 10.5 | 2.30 | 76.9 | 1.46 |
P20 | 748 | 121 | 401 | 827 | 42.5 | 142 | 27.4 | 3.94 | 17.4 | 5.78 | 21.1 | 4.26 | 9.8 | 1.71 | 9.8 | 1.97 |
P21 | 772 | 79.8 | 424 | 672 | 36.2 | 98.7 | 18.6 | 3.84 | 16.0 | 2.86 | 13.2 | 3.20 | 8.18 | 1.25 | 5.73 | 1.56 |
P22 | 982 | 16.3 | 75.5 | 112 | 7.00 | 21.3 | 5.25 | 2.42 | 4.89 | 1.13 | 2.37 | 0.99 | 1.76 | 0.34 | 2.45 | 0.71 |
P23 | 947 | 31.7 | 170 | 285 | 16.9 | 48.3 | 9.4 | 1.53 | 5.90 | 1.25 | 5.25 | 1.21 | 2.33 | 0.53 | 3.63 | 0.78 |
P24 | 788 | 84.0 | 428 | 894 | 39.3 | 112 | 23.9 | 3.51 | 17.1 | 4.26 | 11.6 | 3.87 | 9.12 | 1.82 | 12.8 | 1.45 |
Mean | 869 | 50.4 | 193 | 383 | 20.1 | 58.5 | 11.9 | 2.40 | 9.6 | 2.20 | 8.34 | 2.14 | 5.51 | 1.00 | 7.64 | 1.00 |
Std | 87.3 | 43.6 | 165 | 313 | 16.6 | 52.0 | 8.68 | 0.99 | 7.52 | 1.78 | 6.90 | 1.60 | 4.29 | 0.74 | 15.3 | 0.65 |
Min | 738 | 4.72 | 21.5 | 74.6 | 2.98 | 4.96 | 1.45 | 0.89 | 1.48 | 0.15 | 0.73 | 0.64 | 1.23 | 0.16 | 0.69 | 0.13 |
Max | 982 | 138 | 474 | 914 | 49.1 | 159 | 29.2 | 4.13 | 23.9 | 6.29 | 25.2 | 6.00 | 17.2 | 2.31 | 76.9 | 2.58 |
ΣREEs | LREE | REE | LREE/HREE | Ce/La | Gd/Yb | La/Yb | La/Lu | La/Sm | Ce/Ce* | Eu/Eu* | |
---|---|---|---|---|---|---|---|---|---|---|---|
P1 | 175 | 165 | 9.47 | 17.5 | 1.08 | 1.22 | 16.9 | 13.3 | 4.39 | 1.97 | 0.95 |
P2 | 263 | 252 | 11.7 | 21.6 | 1.83 | 2.34 | 24.3 | 30.8 | 3.86 | 3.63 | 1.18 |
P3 | 193 | 183 | 10.3 | 17.8 | 0.96 | 1.11 | 17.6 | 13.0 | 7.43 | 2.32 | 2.32 |
P4 | 114 | 107 | 6.76 | 15.8 | 1.35 | 1.68 | 16.1 | 5.5 | 9.27 | 1.81 | 2.56 |
P5 | 135 | 129 | 6.76 | 19.0 | 0.93 | 1.77 | 32.2 | 8.9 | 4.19 | 1.12 | 1.99 |
P6 | 285 | 269 | 16.7 | 16.0 | 0.73 | 2.05 | 28.2 | 12.4 | 10.1 | 1.33 | 0.54 |
P7 | 297 | 279 | 18.2 | 15.3 | 0.70 | 2.69 | 38.6 | 18.8 | 8.27 | 1.52 | 0.95 |
P8 | 232 | 216 | 15.8 | 13.7 | 0.79 | 1.45 | 18.5 | 11.8 | 6.43 | 1.33 | 1.47 |
P9 | 245 | 229 | 15.5 | 14.8 | 0.78 | 1.46 | 22.1 | 7.82 | 9.06 | 1.28 | 1.60 |
P10 | 232 | 217 | 15.2 | 14.3 | 0.77 | 1.43 | 18.7 | 16.7 | 7.89 | 1.24 | 1.05 |
P11 | 269 | 251 | 18.0 | 14.0 | 0.78 | 1.28 | 16.8 | 14.5 | 8.28 | 0.65 | 0.85 |
P12 | 1268 | 1214 | 53.9 | 22.5 | 0.72 | 2.40 | 44.8 | 25.1 | 12.1 | 2.23 | 0.53 |
P13 | 516 | 490 | 26.5 | 18.5 | 0.68 | 1.86 | 34.4 | 16.1 | 11.6 | 0.93 | 0.60 |
P14 | 1123 | 1075 | 48.9 | 22.0 | 1.20 | 1.71 | 22.3 | 19.2 | 6.52 | 2.93 | 0.45 |
P15 | 576 | 545 | 30.3 | 18.0 | 0.71 | 1.34 | 24.7 | 16.1 | 12.6 | 1.01 | 0.91 |
P16 | 983 | 920 | 62.8 | 14.7 | 0.77 | 2.48 | 29.7 | 15.9 | 9.37 | 1.16 | 0.55 |
P17 | 1582 | 1507 | 75.1 | 20.1 | 0.68 | 1.33 | 25.3 | 25.4 | 10.2 | 1.29 | 0.51 |
P18 | 1688 | 1592 | 96.5 | 16.5 | 0.80 | 1.49 | 23.3 | 17.8 | 13.3 | 1.49 | 0.54 |
P19 | 1615 | 1477 | 138 | 10.7 | 0.70 | 0.25 | 4.06 | 32.1 | 12.7 | 1.41 | 0.41 |
P20 | 1515 | 1444 | 71.8 | 20.1 | 0.80 | 1.46 | 28.2 | 21.1 | 9.15 | 1.65 | 0.55 |
P21 | 1306 | 1254 | 52.1 | 24.1 | 0.62 | 2.31 | 51.3 | 28.1 | 14.3 | 2.96 | 0.68 |
P22 | 238 | 224 | 14.6 | 15.3 | 0.58 | 1.65 | 21.4 | 11.1 | 9.03 | 0.75 | 1.45 |
P23 | 552 | 531 | 20.9 | 25.4 | 0.65 | 1.34 | 32.4 | 22.6 | 11.3 | 0.83 | 0.62 |
P24 | 1564 | 1502 | 62.0 | 24.2 | 0.81 | 1.10 | 23.1 | 30.6 | 11.2 | 2.31 | 0.53 |
Mean | 707 | 670 | 37.4 | 18.0 | 0.85 | 1.63 | 25.6 | 18.1 | 9.27 | 1.63 | 0.99 |
Std | 582 | 551 | 33.5 | 3.84 | 0.28 | 0.55 | 10.0 | 7.50 | 2.87 | 0.76 | 0.61 |
Min | 114 | 107 | 6.76 | 10.7 | 0.58 | 0.25 | 4.06 | 5.45 | 3.86 | 0.65 | 0.41 |
Max | 1688 | 1592 | 138 | 25.4 | 1.83 | 2.69 | 51.3 | 32.1 | 14.3 | 3.63 | 2.56 |
Heavy metal concentration changes showed more or less three distinct trends along the river flow path (
The order of abundance of REEs in sediments was observed to be Sc > Ce > La > Nd > Y > Pr > Sm > Gd > Dy > Yb > Er > Eu > Tb > Ho > Tm > Lu. The enrichment of LREE over HREE and nearly flat pattern of
HREE is shown in
ƩLREE is more abundant as compared to ƩHREE with an average ƩLREE/ƩHREE ratio of 18.0. Estuarine environment have higher content of carbonate that leads to the enrichment ƩLREE in surficial sediments [
A multivariate assessment of surface sediments contamination included determination of enrichment factor (EF), Index of Geoaccumulation (Igeo) and Pollution Load Index (PLI). Assessments were calculated using upper continental crust (UCC) values of elements as background.
For Enrichment Factor (EF) calculation, Li was used a reference element to normalize the metal concentrations. Concentration of Li showed a positive correlation with mean sediment grain size and most of the metals measured. EF was used to estimate whether metal input is natural or anthropogenic An EF value of less than 2.0 is considered natural. The EF is calculated as presented by Buat-Menard and Chesselet [
where,(
EF value followed order Cd > Zn > Cr > Pb > Cu > Mn. The moderate anthropogenic of metal Cd at P2 (2.43), P4 (2.67), P9 (3.01), P12 (4.16), P13 (4.56), P20 (2.28), P22 (4.29) might relate to local point discharge. EF for REE was less than 2 and therefore, all sources of REE are natural. Anthropogenic enrichment of REE is mainly caused by ore mining activities and through observation the Pinang River catchments do not have mining activities.
Geo-accumulation Index (Igeo) is used to assess the quality of sediments [
Where, Cn is concentrations of a heavy metal element in the sample, Bn is background value, 1.5 is the correction factor.
An Igeo value of ≥1 is considered unpolluted to moderate level. Pollution level of Cr (Igeo = 2.1) showed moderately to strongly polluted and Igeo Cd was found to be 1.54. The calculated Igeo values followed the order of Cr > Cd > Zn > Pb > Cu > Mn.
Pollution load index (PLI) gives better understanding for the level of contamination of heavy metals [
PLI is calculated as:
where, CF is contamination factor which (C)sample is concentration of metal in sample, (C)background is background value of the metal. “n” is the number of metals measured.
The PLI varied from 0.60 to 3.09 (average ~1.44). A PLI value above 1 indicates contamination. Sampling station with PLI value above 1 are in the order of P12 > P17 > P18 > P20 > P14 > P19 > P21 > P16 > P22 > P13 > P24 > P23 were mostly found at the downstream of river. This might be caused by the higher anthropogenic input at downstream than the upstream and due to the accumulative build up in sediments (i.e. sink) of metals. Fishing activities were found at P12 and there are high possibilities of major sources of metals were derived from boat activities. Retention of metals in sediments is due to the multi factors including grain size, TOC and pH-redox conditions and when conditions change metals can become mobile (i.e. source) in the aquatic ecosystem.
Among the elements measured in surface sediments of Penang River, Cd, Cr, Zn and Pb concentrations were found to be significantly elevated and, therefore, might pose a threat to the aquatic ecosystem. A multivariate assessment indicated moderately to highly polluted levels of metals which are in agreement with overall river quality previously classified as degraded but without reporting of the elemental data. Serious issues of pollution are related to the site near jetty which possibly serves as a point source for metal enrichment to the sediment. Sources of rare earth elements are natural and no significant environmental issue was observed owing to the low anthropogenic inputs (i.e. mining).
Most of the metals, TOC, fine grain size fraction and ƩREE concentration showed a trend of increasing values from upstream towards the river mouth. It is most likely due to the hydraulic conditions caused by intense tropical rain events that remove and transport fine sediment particles from upper catchments (dominantly sand) to the downstream locations (silty sand texture).
Chondrite-normalized rare-earth elements (REE) patterns showed higher LREE as compared to HREE. Fine particles, TOC and high pH-redox conditions favor enrichment of metals close to the estuary as compared to the upstream river waters. Longer contact time of metal ions in the water column under low flow rate (downstream locations) retains metals on surface sediments resulting in elevated levels. Fine sediment size has higher ratio of surface area to volume than the coarser sediments and therefore, provides larger area of binding site. This work contributed by documenting the current levels of 22 elements so that any changes in future can be monitored and managed considering the Penang River catchment areas undergoing rapid urban development.
Authors would like to thank the Oceanography and Biodiversity Laboratory, School of Marine and Environmental Science and Institute of Oceanography and Environment for providing the facilities to carry out the research work. Thanks also to our friends for their help in sampling and continued support during the laboratory work. We appreciate valuable time of Mr Yuzwan bin Mohammad spent in preparing maps using GIS.
M. C.Ong,F. M.Fok,K.Sultan,B.Joseph,11, (2016) Distribution of Heavy Metals and Rare Earth Elements in the Surface Sediments of Penang River Estuary, Malaysia. Open Journal of Marine Science,06,79-92. doi: 10.4236/ojms.2016.61008