Analysis and Estimation of Trace Metals in Seawater and
Prof. Dr. Trinh Xuan Gian
Institute of Chemistry, Vietnam National Center for Natural Science and Technology.
Hoang Quoc Viet Road, Caugiay District, Hanoi, Vietnam
ABSTRACT
Water samples from off shore of Vietnam from latitude 6oN to 21oN and longitude 103oC to 112oE were collected on 30 April 1999 to 29 May 1999 and analyzed for copper (Cu), lead (Pb), cadmium (Cd), zinc (Zn), nickel (Ni), chromium (Cr), arsenic (As) and mercury (Hg). The concentration of metals Cu, Pb, Cd, Zn, Ni and Cr was measure using flameless atomic absorption spectroscopy.
The total concentration of all eight metals was in concentration ranges of unpolluted coastal water. The results indicated that the concentration of metals in bottom layer higher than in surface layer. Also, trace metal contents in the surface sediment were studied in off shore of Vietnam during this cruise. Total metals content were measured. The range of concentration of metals were 10.3 - 71.0 mg.g-1 for Cu, 12.9 - 33.7 mg.g-1 for Pb, 1.29 - 18.72 mg.g-1 for Cd, 45.8 - 164.8 mg.g-1 for Zn, 21.2 - 93.6 mg.g-
1 for Cr, 5.7 - 45.8 mg.g-1 for Ni, 1.64 - 3.80 mg.g-1 for As, and 0.104 - 0.493 mg.g-1 for Hg. The levels found in the present study are similar to data from other marine.
Key words: Trace metals, Seawater, Surface sediment, South China Sea, Off shore of Vietnam
Aquatic systems such as the seawater, inland water etc. are important stages in the biogeochemical cycle. Although dissolved levels are usually in the trace range of 10-6-10-9 Ml-1 they remain significant, because they entry into the food chain and interactions with suspended particulate and sediments largely occur via the dissolve state.
The various heavy metals as Cd, Ni, As, Hg, etc. in seawater become toxic if present in excessive quantities and pose a potential threat to the ecosystem. Therefore, there has been constant effort to measure the impact of these metals on fauna [De Silva].
In environmental research and protection toxic metal, particularly Cd, Pb, Hg, As, Ni, Cr, etc.
are becoming increasingly signification owing their biological nondergradability and chromic toxicity resulting from their accumulation in vital organs of man. As part of the SEAFDEC Cooperative Program in the Study of Fisheries Oceanography of the South China Sea, a Research on trace heavy metals in seawater was made.
The first analyses of seawater were performed just prior the beginning to the 19th century in
Sediment in the South China Sea, Area IV: Vietnamese Waters
Introduction
General comparative considerations suggest atomic absorption spectroscopy and modern voltametric methods, particularly differential pulse stripping voltammetry with high sensitivity, precision, and accuracy also a simple sample preparation and treatment to be the most promising chose for the determination and characterization of toxic heavy metal traces in seawater.
Material and Methods Analytical methods
The concentrations of metals: Cu, Pb, Cd, Zn, Ni, Cr, As and Hg in Vietnamese waters were studied in the SEAFDEC interdepartmental collaborative research survey. The samples were analyzed in laboratory of the Department for Analytical Science and Technique of the Institute of Chemistry, National Center for Natural Science and Technology of Vietnam, NCST.
All bottles, filter membranes and lab wares that would be contact with samples were carefully pre-washed by 10% suprapure HNO3acid and Mili-Q water. Merck standard solutions diluted by Mili-Q water was use as standard.
The concentrations of metals Cu, Pb, Cd, Zn, Cr, Ni were measured using graphite furnace atomic absorption spectrometer PE AAS 3300, USA and As by using hydride AAS technique with MHS-10, Hg by using coldvapour method with MHS-10, and 746 VA Trace Analyzer Metrohm, Switzerland. Polyethylene containers, which have been previously cleaned with nitric acid then rinse with water, shall be used for sampling.
Sampling
Fifty-eight stations from offshore of Vietnam from latitude 6oN to 21oN and longitude 103oE to 112oE were established in this study (Fig.1)
TH AILA ND
C AM BO DIA VIE T NA M
C HIN A
Gul f o f Th a il an d
S outh
C hina
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H a i P h o n g
D a N a n g
N h a T ra n g
V u n g T a o
2 2
2 0
1 8
1 6
1 4
1 2
1 0
8 H ai N a n Ta o
1
3 2
4 5
7 6
8 9 10
1 3 1 2 11
1 4 15 16
2 0 1 9 1 8 1 7 2 1 2 2 23 2 4 2 8 2 7 2 6 2 5 2 9 3 0 3 1 3 2 3 7 3 6 35 3 4 3 3 3 9 4 0 41
4 8 3 8 5 4 5 3 5 5 5 6 5 7 58
> 2 7/4 (08 0 0) 2 9/4 (1 00 0)>
> 4 /5 (1 70 0 ) 5 /5 (1 7 00 )>
> 1 5/5 (10 0 0) 1 7/5 (0 80 0)>
> 3 0/5 (10 0 0) 1 /6 (10 0 0)>
4 9
Paracels Is lan ds
> 2 0/5 (08 :30 ) 2 0/5 (1 0 :0 0)>
MV SEAFDEC collected the water samples on 30 April 1999 to 29 May 1999. The water was collected at each station during cruise at least two depth (surface and bottom) by water sampler attached to a rosette system. The water samples were transferred into acidic washed PE bottles and acidified to pH 1 with suprapure nitric acid for determination of Cu, Pb, Cd, Zn, Ni, Cr and As and with 1ml 10%
K2Cr2O7 solution to 1 liter for determination of Hg. Glass or other inert materials should be used if there is a risk of interaction of the sample with the container.
Determination of Cu, Pb, Cd, Zn, Ni and Cr
This method describes the determination of soluble copper, lead, cadmium, zinc, chromium and nickel in seawater and other saline waters by the simultaneous extraction of their complexes with ammonium pyrirolidine dithiocarbanate in to methyl isobutyl ketone and by the atomic absorption spectrophotometer with the graphite tube technique. Place 750ml aliquot of the sample, acidified seawater and each of the calibration solutions into series of 1 liter separating funnels fitted with polytetrafluoroethylene (PTFE) taps.
Add 35 ml of MIBK followed by 7ml of 1% APDC. Shake vigorously for 30 min. separate the organic layer in a polypropylene bottle and store for analysis. Allow the mixture to settle for at least 1h away from light or heat in the stoppered funnel. The settling time shall be strictly the same for all the solutions. Collect the organic layer taking care to avoid any trace of the aqueous phase (centrifuge if necessary) carry out a blank test in parallel with the determination by the same procedure, using the same quantities of all the reagents as in the sampling and chelation and extraction, but replacing the test portion by water.
Proceed as follows for each metal being determined. Before carrying out the spectrometric measurement, set up spectrometer according to the manufacturer’s instructions by aspirating the organic extract of calibration solution of the metal being determined and using information in Table1.
Optimize the aspiration and conditions. Adjust the response of the instrument to zero absorbance with MIBK. For each metal being determined, aspirate the set of organic extracts of the calibration solutions. Plot a graph having the metal contents, in micrograms per liter, of the calibration solutions as abscissas and the corresponding values of absorbance as ordinates for example by measuring the absorbance of a calibration solution every five samples. Aspirate the organic extract of the test portion.
Measure the absorbance of the metal being determined and after each measurement aspirate MIBK in order to rinse the nebulizer system.
Table 1. Wavelength (nm) used to determine metal element.
E le m e nt to be deter m in ed W a v eleng th (n m )
N ic kel 2 32 .0
C op p er 3 24 .7
Z inc 2 13 .8
Determination of Mercury
Mercury ions are reduced to metallic mercury by NaBH4, entrancement of the mercury in a current of inert gas at ambient temperature and determination of the mercury, by flameless atomic absorption spectrometry at a wavelength of 253.7nm
Take a test portion of 100 ml from the previously mixed sample containing not more than 0.5 mg of mercury. Prepare, just before use, using the standard mercury solutions at least five calibration solutions, covering the range of concentrations which can be measured with the apparatus to be used.
Treat each of these solutions immediately after their preparation in exactly the same way as the test portion on which the determination is to carry out. Also, proceed in exactly the same way on a solution in which the standard mercury solution is replaced with water.
Set up the instrument in accordance with the manufacturer’s introductions. Transfer a volume of sample solution into aeration flask in accordance with the manufacturer’s introductions with on the entrainment gas supply and let the developed mercury vapour flow through the absorption cell and measure the absorption of atoms in the beam of the PE - AAS - 3300 by using of MHS - 10 carry out a blank test with each batch of samples, but replacing the test portion with water and using the same volume of reagents as for the determination prefer.
Determination of Arsenic
The method is based on the atomic absorption measurement of arsenic generated by the thermal decomposition of arsenic (III) hydride. As (III) is reduced to gaseous arsenic (III) hydride (AsH3) by reaction with sodium tetrahydroborate in a hydrochloric acid medium.
The absorbance is determined at a wavelength of 193.7nm. Set all instrumental parameters of the atomic absorption spectrometer in accordance with the manufacturer’s operating manual and optimize the position of the absorption cell in order to obtain maximum transmission of the light beam.
Pass a stream of argon through the system and set the instrument to zero. Measure the absorption given by the solutions in the following order:
· Blank solution,
· Calibration solutions,
· Samples, prepared as follows,
Depending on the hydride system used, transfer an appropriate volume of the sample solution to the reaction vessel (MHS - 10). Connect the reaction vessel to the hydride system pass argon through the solution until the absorption signal of atomic absorption spectrometer returns to zero. For 20 ml of the sample solution add 5ml ± 0.1ml of sodium tetrahydroborate solution to the solution and record the signal. Repeat the procedure using separate portions of each solution. Use the mean of these results. Establish the calibration curve using means of values obtained with the blank and calibration solutions.
accuracy of the results. The percentage recovery of copper was 102.5%, lead was 116.6%, cadmium was 116,6%, zinc was 108.9%, nickel was 104.1% and chromium was 109.8%. The result of analysis indicated good recoveries of all determined metals (Table 2).
Table 2. Analytical performance based on Reference Seawater. (µg/l).
The concentration of the determined metals in seawater of survey cruise at surface and bottom layer of sampling are presented in the Tables 3, 4, 5, 6, 7, 8, 9, and 10 in nM and Tables11, 12, 13, 14, 15, 16, 17 and 18 in µg/l
Table 3. Cu-Concentration in seawater.
S t a t i o n S a m p l e s C u ( n M ) S t a t i o n S a m p l e s C u ( n M ) S t a t i o n S a m p l e s C u ( n M )
1 S 7 6 . 6 4 2 1 S 6 5 . 1 6 4 1 S 5 9 . 4 9
1
1 B 9 0 . 3 4 2 1
2 1 B 8 0 . 1 1 4 1
4 1 B 7 9 . 1 6
2 S 7 3 . 8 1 2 2 S 7 5 . 2 3 4 2 S 5 8 . 0 7
2 2 B 8 7 . 1 9 2 2
2 2 B 7 2 . 7 1 4 2
4 2 B 7 8 . 0 6
3 S 7 4 . 5 9 2 3 S 7 2 . 7 1 4 3 S 6 4 . 9 9
3 3 B 7 5 . 3 8 2 3
2 3 B 6 7 . 8 3 4 3
4 3 B 7 5 . 8 6
4 S 7 9 . 0 0 2 4 S 7 8 . 8 5 4 4 S 6 0 . 1 2
4 4 B 7 6 . 4 8 2 4
2 4 B 7 9 . 1 6 4 4
4 4 B 8 3 . 5 7
5 S 6 2 . 3 2 2 5 S 7 5 . 0 7 4 5 S 6 4 . 0 5
5
5 B 8 0 . 5 8 2 5
2 5 B 7 6 . 4 8 4 5
4 5 B 7 9 . 4 8
6 S 6 7 . 9 9 2 6 S 6 7 . 8 3 4 6 S 5 8 . 0 7
6 6 B 6 7 . 2 0 2 6
2 6 B 8 0 . 5 8 4 6
4 6 B 7 8 . 2 2
7 S 6 5 . 7 8 2 7 S 7 6 . 0 1 4 7 S 6 0 . 9 1
7 7 B 6 7 . 8 3 2 7
2 7 B 7 8 . 0 6 4 7
4 7 B 7 6 . 0 2
8 S 5 8 . 8 6 2 8 S 7 2 . 7 1 4 8 S 6 4 . 9 9
8 8 B 7 4 . 5 9 2 8
2 8 B 7 9 . 1 6 4 8
4 8 B 5 8 . 5 4
9 S 6 0 . 4 3 2 9 S 7 5 . 0 7 4 9 S 6 7 . 0 4
9 9 B 6 7 . 0 4 2 9
2 9 B 9 2 . 2 2 4 9
4 9 B 6 4 . 0 5
1 0 S 6 0 . 7 5 3 0 S 7 2 . 7 1 5 0 S 6 1 . 8 5
1 0 1 0 B 7 2 . 2 3 3 0
3 0 B 8 5 . 3 0 5 0
5 0 B 8 1 . 5 2
1 1 S 5 8 . 3 9 3 1 S 6 2 . 0 1 5 1 S 6 4 . 2 1
1 1 1 1 B 7 2 . 5 5 3 1
3 1 B 7 7 . 7 5 5 1
5 1 B 7 6 . 1 7
1 2 S 5 1 . 9 3 3 2 S 6 2 . 6 4 5 2 S 7 8 . 8 5
1 2
1 2 B 6 1 . 8 5 3 2
3 2 B 8 1 . 0 5 5 2
5 2 B 7 9 . 1 6
1 3 S 6 7 . 0 4 3 3 S 6 7 . 9 9 5 3 S 6 0 . 1 2
1 3 1 3 B 7 2 . 7 1 3 3
3 3 B 7 5 . 8 6 5 3
5 3 B 7 3 . 8 1
1 4 S 6 1 . 8 5 3 4 S 5 8 . 8 6 5 4 S 5 8 . 0 7
1 4 1 4 B 7 5 . 7 0 3 4
3 4 B 7 4 . 9 1 5 4
5 4 B 6 0 . 9 0
1 5 S 6 4 . 8 4 3 5 S 6 4 . 8 4 5 5 S 6 4 . 9 9
1 5 1 5 B 8 0 . 5 8 3 5
3 5 B 6 6 . 2 6 5 5
5 5 B 8 0 . 7 4
1 6 S 6 0 . 4 3 3 6 S 5 9 . 1 7 5 6 B 6 3 . 7 4
1 6
1 6 B 6 2 . 4 8 3 6
3 6 B 6 1 . 0 6 5 6
5 6 B 8 0 . 8 9
1 7 S 6 4 . 0 5 3 7 S 6 7 . 8 3 5 7 S 6 1 . 6 9
1 7 1 7 B 7 4 . 1 3 3 7
3 7 B 7 7 . 4 3 5 7
5 7 B 7 8 . 3 7
Cu Pb Cd Zn Ni Cr
CASS-3 0.517 0.012 0.030 1.24 0.386 0.092
Our result 0.530 0.014 0.035 1.35 0.402 0.101
Table 4. Pb-Concentration in seawater.
Station Samples Pb (nM) Station Samples Pb (nM) Station Samples Pb (nM)
1S 9.56 21S 8.73 41S 9.75
1 1B 10.52 21
21B 9.85 41
41B 8.49
2S 9.79 22S 8.40 42S 8.11
2 2B 13.18 22
22B 9.03 42
42B 8.59
3S 8.40 23S 8.16 43S 9.22
3 3B 9.51 23
23B 9.27 43
43B 11.29
4S 10.23 24S 7.63 44S 8.59
4 4B 11.15 24
24B 10.33 44
44B 9.75
5S 8.49 25S 9.80 45S 7.58
5 5B 10.81 25
25B 9.07 45
45B 15.01
6S 9.07 26S 9.51 46S 7.82
6 6B 8.97 26
26B 11.29 46
46B 11.87
7S 8.49 27S 10.23 47S 9.80
7 7B 11.25 27
27B 13.61 47
47B 9.56
8S 8.30 28S 10.52 48S 8.78
8 8B 8.83 28
28B 14.38 48
48B 11.25
9S 7.58 29S 9.75 49S 9.46
9 9B 9.85 29
29B 10.62 49
49B 8.83
10S 8.83 30S 8.49 50S 8.25
10 10B 10.96 30
30B 11.25 50
50B 9.70
11S 9.27 31S 7.14 51S 8.16
11 11B 11.82 31
31B 11.63 51
51B 9.46
12S 9.70 32S 8.40 52S 8.69
12 12B 9.60 32
32B 11.29 52
52B 11.92
13S 8.54 33S 7.82 53S 7.34
13 13B 10.28 33
33B 11.97 53
53B 14.07
14S 8.11 34S 9.22 54S 7.14
14 14B 7.78 34
34B 8.64 54
54B 9.27
15S 8.88 35S 8.78 55S 8.56
15 15B 7.82 35
35B 11.48 55
55B 7.87
16S 7.58 36S 9.70 56B 7.53
16 16B 6.95 36
36B 10.23 56
56B 9.60
17S 9.75 37S 8.40 57S 8.40
17 17B 6.66 37
37B 6.47 57
57B 8.45
18S 6.37 38S 8.11 58S 10.52
18 18B 7.53 38
38B 10.81 58
58B 10.52
19S 7.05 39S 8.74
19 19B 8.78 39
39B 9.51
20S 9.70 40S 8.30
20 40
Note:
• S: Surface layer, 2m
• B: Bottom layer, ≥≥ 100m
Table 5. Cd-Concentration in seawater.
Station Samples Cd (nM) Station Samples Cd (nM) Station Samples Cd (nM)
1S 1.86 21S 2.05 41S 1.25
1
1B 2.14 21
21B 1.33 41
41B 2.31
2S 1.95 22S 1.60 42S 1.42
2 2B 2.31 22
22B 2.05 42
42B 2.40
3S 1.69 23S 1.42 43S 1.07
3 3B 2.05 23
23B 1.60 43
43B 2.58
4S 1.51 24S 1.33 44S 1.16
4
4B 1.42 24
24B 1.42 44
44B 2.14
5S 1.78 25S 1.86 45S 0.98
5 5B 1.51 25
25B 1.69 45
45B 2.22
6S 1.60 26S 1.69 46S 2.67
6 6B 1.96 26
26B 1.95 46
46B 2.40
7S 1.51 27S 1.51 47S 2.49
7
7B 1.16 27
27B 2.31 47
47B 2.58
8S 1.42 28S 1.60 48S 1.25
8 8B 1.33 28
28B 2.76 48
48B 2.67
9S 1.60 29S 2.31 49S 1.86
9 9B 1.33 29
29B 2.85 49
49B 1.60
10S 1.33 30S 1.51 50S 2.31
10
10B 2.05 30
30B 2.76 50
50B 2.05
11S 1.07 31S 1.69 51S 1.78
11 11B 2.14 31
31B 2.49 51
51B 2.31
12S 0.98 32S 1.95 52S 1.51
12 12B 2.40 32
32B 2.14 52
52B 3.38
13S 1.16 33S 1.25 53S 1.42
13 13B 2.76 33
33B 2.31 53
53B 3.91
14S 1.60 34S 1.16 54S 1.25
14 14B 1.25 34
34B 1.07 54
54B 3.11
15S 1.07 35S 1.33 55S 1.07
15 15B 1.42 35
35B 1.51 55
55B 2.14
16S 1.25 36S 1.51 56B 2.55
16
16B 1.25 36
36B 2.14 56
56B 2.49
17S 1.69 37S 1.80 57S 0.98
17 17B 1.86 37
37B 2.67 57
57B 2.85
18S 1.42 38S 1.95 58S 2.05
18 18B 1.95 38
38B 1.69 58
58B 5.05
19S 1.86 39S 2.67
19
19B 1.16 39
39B 3.39
20S 2.67 40S 1.51
20 20B 1.07 40
40B 2.14
Note:
• S: Surface layer, 2m
• B: Bottom layer, ≥≥ 100m
Table 6. Zn-Concentration in seawater.
Station Samples Zn (nM) Station Samples Zn (nM) Station Samples Zn (nM)
1S 156.52 21S 156.68 41S 136.96
1
1B 188.38 21
21B 118.45 41
41B 147.73
2S 149.36 22S 134.38 42S 146.97
2 2B 180.65 22
22B 155.31 42
42B 133.17
3S 133.32 23S 120.43 43S 134.08
3 3B 181.11 23
23B 134.38 43
43B 154.86
4S 145.91 24S 158.95 44S 133.17
4 4B 162.90 24
24B 138.63 44
44B 168.06
5S 152.13 25S 132.56 45S 172.00
5
5B 150.46 25
25B 135.59 45
45B 158.05
6S 150.46 26S 145.91 46S 161.83
6 6B 147.27 26
26B 157.14 46
46B 147.73
7S 127.10 27S 152.73 47S 163.96
7 7B 132.87 27
27B 170.02 47
47B 146.82
8S 127.71 28S 150.00 48S 132.56
8 8B 137.57 28
28B 188.38 48
48B 150.76
9S 133.59 29S 151.22 49S 131.65
9
9B 149.85 29
29B 174.27 49
49B 156.53
10S 162.75 30S 156.37 50S 136.96
10
10B 156.38 30
30B 182.92 50
50B 167.91
11S 133.47 31S 146.06 51S 133.17
11 11B 158.05 31
31B 198.99 51
51B 203.55
12S 141.36 32S 147.43 52S 140.45
12 12B 135.59 32
32B 173.82 52
52B 161.99
13S 115.42 33S 134.53 53S 150.16
13 13B 138.63 33
33B 164.11 53
53B 150.46
14S 133.47 34S 142.42 54S 126.04
14
14B 131.50 34
34B 176.24 54
54B 134.08
15S 141.97 35S 140.15 55S 150.46
15 15B 131.05 35
35B 148.49 55
55B 156.53
16S 133.32 36S 157.44 56B 150.64
16 16B 139.81 36
36B 172.00 56
56B 167.75
17S 123.31 37S 134.54 57S 152.13
17 17B 140.45 37
37B 148.95 57
57B 173.82
18S 154.86 38S 150.61 58S 102.53
18 18B 163.50 38
38B 146.97 58
58B 187.17
19S 150.15 39S 139.08
19
19B 155.01 39
39B 156.53
20S 167.14 40S 133.32
20 20B 138.21 40
40B 161.98
Note:
• S: Surface layer, 2m
• B: Bottom layer, ≥≥ 100m
Table 7. Ni-Concentration in seawater.
Station Samples Ni (nM) Station Samples Ni (nM) Station Samples Ni (nM)
1S 20.61 21S 17.54 41S 13.29
1
1B 36.62 21
21B 25.89 41
41B 29.47
2S 27.59 22S 28.62 42S 27.93
2
2B 33.73 22
22B 24.87 42
42B 21.80
3S 25.21 23S 22.82 43S 29.64
3 3B 39.35 23
23B 27.59 43
43B 24.19
4S 23.34 24S 21.63 44S 22.14
4 4B 34.41 24
24B 28.96 44
44B 22.65
5S 19.08 25S 19.76 45S 21.46
5 5B 29.47 25
25B 32.19 45
45B 36.45
6S 17.20 26S 25.21 46S 22.31
6 6B 29.98 26
26B 27.59 46
46B 34.41
7S 33.73 27S 34.24 47S 20.09
7 7B 24.53 27
27B 27.93 47
47B 33.38
8S 19.07 28S 24.18 48S 19.08
8 8B 25.21 28
28B 25.89 48
48B 32.02
9S 14.82 29S 27.59 49S 17.20
9
9B 27.59 29
29B 28.96 49
49B 29.64
10S 16.01 30S 25.04 50S 30.83
10
10B 30.83 30
30B 41.05 50
50B 35.09
11S 21.46 31S 23.51 51S 29.13
11 11B 30.49 31
31B 39.69 51
51B 36.28
12S 23.51 32S 21.97 52S 17.54
12 12B 22.82 32
32B 42.24 52
52B 37.13
13S 22.82 33S 24.02 53S 16.86
13 13B 21.46 33
33B 36.96 53
53B 39.86
14S 24.19 34S 29.47 54S 31.68
14 14B 21.80 34
34B 39.86 54
54B 33.72
15S 15.33 35S 27.59 55S 22.31
15 15B 34.58 35
35B 30.99 55
55B 32.70
16S 18.90 36S 22.82 56B 26.92
16 16B 18.90 36
36B 29.98 56
56B 31.85
17S 18.39 37S 15.67 57S 21.12
17
17B 19.42 37
37B 30.83 57
57B 34.41
18S 20.27 38S 16.52 58S 19.25
18
18B 20.10 38
38B 34.58 58
58B 31.34
19S 20.44 39S 23.80
19 19B 23.34 39
39B 29.97
20S 19.25 40S 16.86
20
20B 24.87 40
40B 39.86
Note:
• S: Surface layer, 2m
• B: Bottom layer, ≥≥ 100m
Table 8. Cr-Concentration in seawater.
Station Samples Cr (nM) Station Samples Cr (nM) Station Samples Cr (nM)
1S 23.08 21S 16.54 41S 16.73
1
1B 22.12 21
21B 13.08 41
41B 27.31
2S 19.80 22S 15.19 42S 17.69
2
2B 24.23 22
22B 14.23 42
42B 16.73
3S 18.85 23S 14.23 43S 24.42
3
3B 18.85 23
23B 15.19 43
43B 26.35
4S 18.46 24S 21.73 44S 16.54
4
4B 16.15 24
24B 21.35 44
44B 27.30
5S 15.96 25S 20.00 45S 34.81
5
5B 25.38 25
25B 19.04 45
45B 24.23
6S 18.65 26S 22.31 46S 25.00
6
6B 27.12 26
26B 23.66 46
46B 22.69
7S 19.42 27S 18.85 47S 24.23
7
7B 20.77 27
27B 20.77 47
47B 25.38
8S 16.35 28S 14.62 48S 21.15
8
8B 30.77 28
28B 21.54 48
48B 23.65
9S 21.54 29S 25.39 49S 14.82
9
9B 15.77 29
29B 24.23 49
49B 24.04
10S 14.62 30S 17.31 50S 15.19
10
10B 23.46 30
30B 25.00 50
50B 35.00
11S 17.69 31S 16.54 51S 16.54
11
11B 18.08 31
31B 21.35 51
51B 26.73
12S 16.73 32S 13.85 52S 15.38
12
12B 26.16 32
32B 16.92 52
52B 23.37
13S 21.35 33S 16.15 53S 20.58
13 13B 23.85 33
33B 19.04 53
53B 28.46
14S 18.46 34S 15.77 54S 21.54
14 14B 25.19 34
34B 25.58 54
54B 25.00
15S 26.54 35S 15.19 55S 18.85
15
15B 20.96 35
35B 23.85 55
55B 33.85
16S 14.23 36S 25.77 56B 15.92
16 16B 22.18 36
36B 16.73 56
56B 30.39
17S 14.82 37S 22.31 57S 15.00
17 17B 16.73 37
37B 17.69 57
57B 37.31
18S 23.27 38S 17.31 58S 20.38
18 18B 15.19 38
38B 25.58 58
58B 25.38
19S 25.00 39S 25.19
19 19B 16.92 39
39B 24.23
20S 17.69 40S 25.77
20
20B 18.08 40
40B 25.19
Note:
• S: Surface layer, 2m
• B: Bottom layer, ≥≥ 100m
Table 9. As-Concentration in seawater.
Station Samples As (nM) Station Samples As (nM) Station Samples As (nM)
1S 21.22 21S 20.82 41S 23.62
1 1B 17.22 21
21B 18.55 41
41B 21.49
2S 22.29 22S 19.22 42S 22.02
2 2B 20.15 22
22B 16.68 42
42B 23.89
3S 17.48 23S 20.28 43S 21.76
3 3B 21.49 23
23B 19.35 43
43B 23.62
4S 27.76 24S 24.56 44S 23.22
4 4B 21.75 24
24B 22.82 44
44B 26.83
5S 23.89 25S 18.15 45S 21.36
5
5B 17.61 25
25B 19.22 45
45B 21.36
6S 20.55 26S 22.56 46S 24.16
6
6B 20.55 26
26B 20.02 46
46B 28.83
7S 32.70 27S 20.83 47S 27.76
7
7B 21.88 27
27B 18.15 47
47B 19.09
8S 21.22 28S 19.75 48S 25.09
8
8B 21.49 28
28B 18.01 48
48B 22.02
9S 30.96 29S 23.09 49S 23.49
9
9B 21.62 29
29B 20.82 49
49B 29.09
10S 26.29 30S 21.22 50S 23.22
10
10B 18.82 30
30B 20.42 50
50B 22.96
11S 33.37 31S 17.75 51S 26.96
11
11B 19.09 31
31B 78.95 51
51B 20.28
12S 21.16 32S 21.22 52S 21.89
12
12B 20.95 32
32B 24.16 52
52B 23.22
13S 21.22 33S 22.69 53S 20.42
13 13B 20.15 33
33B 19.22 53
53B 24.69
14S 21.49 34S 23.09 54S 19.62
14 14B 20.28 34
34B 19.75 54
54B 24.96
15S 19.62 35S 20.42 55S 21.89
15 15B 21.36 35
35B 23.49 55
55B 24.16
16S 19.22 36S 26.03 56B 23.36
16 16B 18.68 36
36B 38.03 56
56B 19.35
17S 23.89 37S 19.88 57S 19.89
17 17B 16.82 37
37B 19.49 57
57B 26.43
18S 17.88 38S 16.42 58S 20.55
18 18B 19.62 38
38B 19.49 58
58B 18.82
19S 23.49 39S 21.22
19 19B 19.62 39
39B 20.55
20S 21.76 40S 19.62
20 20B 20.82 40
40B 21.08
Note:
• S: Surface layer, 2m
• B: Bottom layer, ≥≥ 100m
Table 10. Hg-Concentration in seawater.
Station Samples Hg (nM) Station Samples Hg (nM) Station Samples Hg (nM)
1S 0.60 21S 0.85 41S 0.79
1 1B 0.55 21
21B 0.35 41
41B 0.89
2S 0.55 22S 0.45 42S 0.85
2 2B 0.69 22
22B 0.35 42
42B 0.89
3S 0.59 23S 0.45 43S 0.85
3 3B 0.69 23
23B 1.24 43
43B 0.89
4S 0.40 24S 0.49 44S 0.85
4 4B 0.40 24
24B 0.49 44
44B 0.80
5S 0.59 25S 0.45 45S 0.49
5 5B 0.85 25
25B 0.41 45
45B 0.82
6S 0.75 26S 0.49 46S 0.60
6 6B 0.55 26
26B 0.45 46
46B 0.45
7S 0.75 27S 0.45 47S 0.49
7 7B 0.55 27
27B 0.35 47
47B 0.60
8S 6.48 28S 0.35 48S 0.60
8 8B 0.49 28
28B 0.49 48
48B 3.60
9S 1.54 29S 0.99 49S 0.70
9 9B 0.89 29
29B 0.89 49
49B 1.05
10S 0.59 30S 0.45 50S 2.09
10 10B 0.60 30
30B 0.75 50
50B 1.45
11S 0.70 31S 0.65 51S 0.60
11 11B 0.70 31
31B 0.65 51
51B 0.55
12S 0.75 32S 0.89 52S 0.55
12 12B 0.45 32
32B 0.60 52
52B 0.55
13S 0.55 33S 0.80 53S 0.65
13 13B 0.45 33
33B 3.09 53
53B 0.65
14S 0.40 34S 1.69 54S 0.60
14
14B 0.80 34
34B 0.85 54
54B 0.49
15S 0.41 35S 0.60 55S 0.80
15
15B 0.65 35
35B 0.70 55
55B 0.49
16S 0.35 36S 0.75 56B 0.60
16
16B 0.49 36
36B 089 56
56B 7.13
17S 0.35 37S 0.45 57S 1.20
17
17B 0.41 37
37B 0.75 57
57B 0.89
18S 0.55 38S 0.60 58S 0.60
18
18B 0.89 38
38B 0.75 58
58B 2.46
19S 0.45 39S 0.70
19
19B 0.41 39
39B 0.95
20S 0.55 40S 0.60
20
20B 0.90 40
40B 2.59
Note:
• S: Surface layer, 2m
• B: Bottom layer, ≥≥ 100m
