Int. J. Mol. Sci. 2014, 15, 9991-10004; doi:10.3390/ijms15069991
OPEN ACCESSInternational Journal of

Molecular Sciences
ISSN 1422-0067
www.mdpi.com/journal/ijms
ArticleConcentration of Antifouling Biocides and Metals in SedimentCore Samples in the Northern Part of Hiroshima Bay
Noritaka Tsunemasa 1,* and Hideo Yamazaki 2
1

2

Environmental Conservation Division of the Environment Bureau, Hiroshima City,
1-6-34 Kokutaiji-Machi, Naka-ku, Hiroshima 730-8586, Japan
School of Science and Engineering, Department of Life Science, Kinki University, 3-4-1 Kowakae,
Higashiosaka, Osaka 577-8502, Japan; E-Mail: yamazaki@life.kindai.ac.jp* Author to whom correspondence should be addressed; E-Mail: tunemasa-n@city.hiroshima.lg.jp;
Tel.: +81-82-504-2188; Fax: +81-82-504-2229.
Received: 3 March 2014; in revised form: 15 April 2014 / Accepted: 23 April 2014 /Published: 4 June 2014

Abstract: Accumulation of Ot alternative antifoulants in sediment is the focus of this research.
Much research had been done on surface sediment, but in this report, the accumulation in
the sediment core was studied. The Ot alternative antifoulants, Diuron, Sea-Nine211, andIrgarol 1051, and the latter’s degradation product, M1, were investigated in five samples
from the northern part of Hiroshima Bay. Ot compounds (tributyltin (TBT) and triphenyltin(TPT)) were also investigated for comparison. In addition, metal (Pb, Cu, Zn, Fe and Mn)levels and chronology were measured to better understand what happens after accumulationon the sea floor. It was discovered that Ot alternative antifoulant accumulation characteristics
in sediment were like Ot compounds, with the concentration in the sediment core being
much higher than surface sediment. The concentration in sediment seems to have been
affected by the regulation of Ot compounds in 1990, due to the concentration of Ot
alternative antifoulants and Ot compounds at the survey point in front of the dock, showing
an increase from almost the same layer after the regulation.
Keywords: Irgarol 1051; M1; Diuron; Sea-Nine 211; metal; sediment core; chronology

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1. Introduction
Organotin (Ot) compounds, used for many years as antifouling biocides on ships, marine structuresand fishing nets, became a problem, because of their toxicity and environmental accumulation [1].
The movement towards global regulation began in October 2001, when the International Maritime
Organization (IMO) adopted the International Convention on the Control of Harmful Antifouling
Systems (AFS Convention) [2]. The regulation took effect on the 17 September 2008, prohibiting theuse of Ots as active ingredients in antifouling agents on marine vessels. Therefore, instead of theprohibited Ot compounds, paint manufacturers had to develop many alternative products to be used
as antifouling coatings.
At first, it was thought that Ot alternative antifoulants would not accumulate as much in sea waterand sediment as organotin compounds, because the resolution speed of Ot alternative antifoulants
was faster [3]. However, Ot alternative antifoulants have subsequently been detected at higher levels
than initially expected in sea water and sediment, which has caused concern about the possible effects.
The presence of Ot alternative antifoulants in surface sediment had previously been researchedin areas, such as Hong Kong [4], India [5], Malaysia [6], Thailand [7], Vietnam [8], Greece [9],Denmark [10], etc. However, little was known about the accumulation of these compounds inthe sediment core. The detection of biocides in the sediment core in earlier studies in the
United Kingdom [11], Brazil [12], Korea [13], Japan [14], etc., were only of organotin compounds. In
Korea, Brazil and Japan, the highest concentration of tributyltin (TBT) was detected at 46,100, 6000
and 962 µg/kg, respectively.
In this report, the Ot alternative antifoulants, Diuron, Sea-nine211 and Irgarol 1051, and the latter’s
degradation product, M1, were investigated in five sediment core samples taken from the northern partof Hiroshima Bay. Ot compounds were also investigated for comparison with alternative antifoulants.
In addition, metal (Pb, Cu, Zn, Fe and Mn) levels and chronology were measured to better understandwhat occurs after metals accumulate in the sediment core.
2. Results
2.1. Alternative Biocides
In this study, all of the investigated compounds were detected in sediment core samples. The detected
ranges of the investigated compounds are shown in Table 1. Every depth’s detected concentration in
the sediment core samples is shown in Figure 1. Accumulation values of all investigated compounds
except M1 were obtained.
Previous data on Ot alternative antifoulants in sediment core samples could not be found, so theresults of this research were compared with that of previous reports on sea floor sediment samples
instead. The antifouling biocide and degradation product concentration levels in previous samples areshown in Table 2.
The residual of Irgarol 1051 in sediment samples was reported by many researchers. The highest levelsof Irgarol 1051 detected in sea floor sediment samples from harbors in the UK, Greece, the Baltic Sea,
Japan’s Otsuchi Bay, Spain, the North Sea and Japan’s Osaka Bay were 1011 µg/kg [15–19],690 µg/kg [20], 220 µg/kg [21], 100 µg/kg [22], 57 µg/kg [23], 14 µg/kg [21] and 8.2 µg/kg [24],Int. J. Mol. Sci. 2014, 15

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respectively. In the survey Point 5 sediment core sample, the highest concentration level was measured
at 270 µg/kg, making it the third highest level behind the U.K. and Greek sea floor sediment samples.
Table 1. Minimum-maximum concentrations of investigated compounds in sediment coresamples from Hiroshima Bay, (Hiroshima, Japan).
Point Number
1
2
3
4
5

Irgarol 1051
2.4–27
7.1–24
0.4–64
2.1–3.5
9.1–270

M1
ND–0.80.2–0.5
0.1–2.1
0.1–0.3
0.4–13

Diuron1.4–13
3.9–10
2.5–11
3.0–7.7
11–220

Sea-Nine 211
ND
ND
ND–3.3
ND–0.8
7.6–140

ND: not detected; Unit: μg/kg·dry.

Figure 1. Concentrations of organotin alternative antifoulants in sediment core samples.
The survey Point 4 sediment year was not measured in sediment core samples from Hiroshima
Bay, (Hiroshima, Japan). Sediment years were calculated by the 210Pb concentration.
Survey point 1

Survey point 2
depth (cm)

May 2003
May 2003
May 2003
Jan 1999
Sep 1994
Sep 1988

0

Feb 1982

20

Jan 1976

25

10

M1

15

30

Apr 1962

5

Mar 2005
Mar 2005
Jan 2001

50

Mar 2004

15

Irgarol
1051

DiuronApr 1990

20

DiuronSea‐Nine211

Sep 1983

25

Sea‐Nine
211

Aug 1976

30
35

100

0

(μg/kg・ｄｒｙ)

Survey point 3

M1

Mar 199640
0

10Irgarol1051

35

Jan 19540

Mar 2005
Mar 2005

5

May 1969

depth (cm)

50

100

(μg/kg・ｄｒｙ)

Survey point 4

depth (cm)0

Feb 2002

5

M1

10

Irgarol
1051
Diurondepth (cm)0
5

Jan 2000
Jan 1998
Aug 1995

15

Apr 1993
20

Mar 1990

1015

Sea‐Nine
211

20
25

25
0

50
(μg/kg・ｄｒｙ)

100

0

50
(μg/kg・ｄｒｙ)

100

M1
Irgarol
1051
DiuronSea‐Nine
211

Int. J. Mol. Sci. 2014, 15

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Figure 1. Cont.
Survey point 5(year)

depth (cm)

Jul 2004
May 2003
Mar 2002
Feb 2001
Jan 2000
May 19980

Aug 1996
Jan 1995

20

5
10
15

25

Feb 1993

30

Jul 1990

35

May 1985
Apr 1980
Aug 1975

40

M1
Irgarol
1051
DiuronSea‐Nine
211

45
50
0

100

200

300

(µg/kg･dry)

Table 2. Previous Irgarol 1051, M1, Diuron and Sea-Nine 211 research data.
Location
Hiroshima Bay, Japan (2004, 2005)
Hiroshima Bay, Japan (2002–2005)
Otsuchi Bay, Japan (2005)
Osaka Bay, Japan (2003)
Piraeus-Elefsina, Greece (1999, 2000)
Southampton Water, UK (2000)
Barcelona, Spain
Southampton Water, UK (1998)
Baltic Sea (1997, 1998)
North Sea (1997, 1998)
Orwell Estuary, UK (1998)
The Solent, UK (1998)
Blackwater Estuary, UK (1998, 1999)
Hamble Estuary, UK

Irgarol 1051
0.4–270<1–28<0.05–100<0.08–8.2<LOD–690
0.3–3.5
3–57<LOD–110<4–220<LOD–14<10–1011<LOD
3.3–222
12–190Concentrations (µg/kg)
M1
Diuron<0.1–13
1.4–220<1–9<4–73<0.18–0.47<0.08–530<0.18–2.9<0.64–1350******<LOD–0.3
0.4–6.2
0.2–3.3******<LOD–1420
***
***
***
***
***
<12–395<LOD–5.7
<LOD
***
***
***
***

Sea-Nine 211<1.0–140***<0.04–150<0.04–2.4<LOD–49
***
***
***
***
***
***
***
***
***

Reference
this research
[25]
[22]
[24]
[20]
[15]
[23]
[16]
[21]
[21]
[17]
[26]
[18]
[19]

LOD: limit of detection; ***: not measured.

The highest concentration of the Irgarol 1051 degradation product, M1, in sediment was detected
at 5.7 µg/kg in the UK harbors, the Solent, (Isle of Wight, UK) [15,26], 2.9 µg/kg in Osaka Bay [24]and 0.47 µg/kg in Otsuchi Bay (Iwate Pref., Japan) [22]. In comparison, the highest level ofconcentration in survey Point 5 sediment was significantly higher at 13 µg/kg.
The highest concentration of Diuron in sediment detected in the U.K. was 1420 µg/kg in Southampton
water (Hampshire, UK) [15–17]. In Japan, Osaka Bay measured at 1350 µg/kg [24] and 530 µg/kg in
Otsuchi Bay [22]. The Hiroshima Bay results indicated that the highest concentration level was insurvey Point 5 sediment at 220 µg/kg, making it lower than the sea floor sediment samples of otherreported data.

Int. J. Mol. Sci. 2014, 15

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Surprisingly, the concentration of Sea-Nine 211 in sediment had only been reported in a few
publications. From the few articles that do list it, the highest concentration of Sea-Nine 211 in sediment
was reported at 150 µg/kg in Otsuchi Bay [22], 49 µg/kg in Piraeus-Elefsina, (Athens, Greece) [20],and 2.4 µg/kg in Osaka Bay [24]. The highest concentration level in survey Point 5 sediment was
140 µg/kg, approximately the same as in Otsuchi Bay.
2.2. Organotin Compounds
Ot compounds (TBT and triphenyltin (TPT)) were only investigated at survey Point 5, where theOt compound’s value had been high in previous research. TBT and TPT were detected from 48 to
1400 µg/kg and from 75 to 550 µg/kg, respectively. The analytical results of survey Point 5 are also shownin Figure 2.
In Korea, the highest concentration of TBT in the sediment core sample, which was gathered in
Ulsan Bay nearby a maintenance shipyard and in Okpa Bay nearby a shipyard, were 46,100 µg/kg
and 9000 µg/kg, respectively [13]. In Brazil, the highest concentration of TBT in the sediment coresample gathered from Guanabara Bay, home of the second most important trading harbor in Brazil,
was 6000 µg/kg [12]. The highest concentration level of TBT, which was detected at 962 µg/kg [14] insurvey Point 5 was considerably lower than in the Korean and Brazilian samples. The large numbers ofvessels and the lack of regulation on the use of TBT in Korea and Brazil could explain the much higher
levels of TBT recorded in these areas.
Figure 2. Concentrations of organotin compounds in survey Point 5 sediment core samples.
The sediment years were calculated by the 210Pb concentration. TBT, tributyltin;
TPT, triphenyltin.
Survey point 5(year)

depth (cm)0

Jul 2004
May 2003
Mar 2002
Feb 2001
Jan 200051015May 1998
Aug 1996

20

Jan 1995

25

Feb 1993

30

Jul 1990

TBT
TPT

35

May 1985
Apr 1980

40

Aug 1975

45

0

500

1,000

1,500

50
2,000

(µg/kg・dry)

2.3. Metals
The detected ranges of metals are shown in Table 3. Every depth’s detected concentrations of
sediment core samples are shown in Figure 3. This analysis was performed to gather data on theconcentrations of metals along with how they reacted to oxidation and the reduction of sediment.
Generally, accumulation is shown by measuring Mn, Fe and Cu.

Int. J. Mol. Sci. 2014, 15

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Table 3. Minimum-maximum concentrations of metals.
Point Number
1
2
3
4
5

Pb
17–45
14–41
62–140
25–47
25–160Cu
78–160
74–110150–3300
67–82
50–1200Zn
190–450
190–320
420–710
230–450
170–700

Fe
36,000–50,000
37,000–46,000
60,000–82,000
48,000–60,000
41,000–45,000Mn
380–590
430–620
500–640
370–520560–670

Unit: mg/kg·dry.

Figure 3. Concentrations of metals in sediment core samples.
depth (cm)Survey point 1

depth (cm)0Survey point 2

0

5

5

10

10

15

Mn

20

Zn

25

Cu

20

Pb

25

30

Mn

15

Zn
Cu
Pb

30

35
40
0

500

1,000

35

1,500

0

500

1,000

(mg/kg・ｄｒｙ)

depth (cm)1,500

(mg/kg・ｄｒｙ)

Survey point 3

Surver point 4

depth (cm)

0

0

5

5
Mn

10

Mn

10

Zn

Zn
15

Cu
Pb

20
25
0

1,000

2,000

3,000

15

Cu
Pb

20
25

4,000

0

500

(mg/kg･dry)

1,000

1,500

(mg/kg・ｄｒｙ)

depth (cｍ)Survey point 5

0
5
10
15
20

Mn

25

Zｎ

30

Cu

35

Pb

40
45
50
0

500

1,000

1,500

（ｍｇ/ｋｇ・ｄｒｙ）

In this research, it was only Cu that showed signs of accumulation. At Point 3, in the 12–15 cm
layer, Cu was detected at 3300 mg/kg. At Point 5 in the 3–6 cm layer, 1200 mg/kg was detected.
Furthermore, at Point 5, Cu was detected in the 12–15 cm layer at 600 mg/kg and Zn was detected in
the same layer at 750 mg/kg.

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3. Discussion
In general, chemical compounds are often attached to the smaller particles. The grain distributionof the sediment core’s surface is shown in Table 4.
Survey Points 1 and 2 were located in the same fishery harbor. Point 2 is nearer than Point 1 withrespect to its entrance, so the specific surface area, below 67 µm (%), of Point 2 is lower than Point 1.
However, their concentration level was almost the same. It was thought that many leisure boats
anchored in the fishery harbor long term.
Though the specific surface area, below 67 µm (%), of Point 4 was relatively high, the concentrationof Ot alternative antifoulants was much lower, due to the boats only passing through the survey point.
Survey Point 5 was mostly high in specific surface area and below 67 µm (%) in all samples.
The Ot alternative antifoulants were thought to have come from the nearby dock, so it is believed thatthe accumulation speed was high.
Table 4. Grain distribution of the sediment core’s surface.
Survey
Point
1
2
3
4
5

Specific Surface Area
(cm2/cm3)
33,92624,89033,37437,22940,214

Median Particle Size(µm)
10.1930
14.430710.1875
8.96907.6898Arithmetic Mean
Particle Size (µm)
15.011933.687919.3025
15.4780
12.1456

Below 67 µm
(%)
97.5
86.0
93.4
95.7
98.1

Grain distribution was mesured by HORIBA LA-920 (HORIBA K.K., Kyoto, Japan).

The concentration of antifouling biocides in sediment core samples from Hiroshima Bay was muchhigher than the corresponding sea floor sample concentrations [25]. In particular, the survey Point 5
sample had the highest observed concentration of the alternative biocides.
As shown in Figures 1 and 2, the concentration of Ot alternative antifoulants and Ot compounds
at survey Point 5 began to increase from almost the same point. In the case of Ot alternative antifoulants, it
was thought that the rise in the concentration was caused by the increase of the consumption after the
regulation of Ot compounds in 1990. On the other hand, in the case of Ot compounds, the cause wasmainly due to the way the dock replaced the Ot compound paints with the Ot alternative antifoulants.
When the regulation became effective in Japan, the Ot compounds were stripped from ships before theOt alternative antifoulants were painted on to the ships. In the case of this dock, the stripped pieces ofOt compound paint were not cleared from the dry dock, so when the ships were relaunched, thestripped paint chips on the ground were washed into the sea water. Obviously, this would have had an
impact on the Ot compound concentration levels shown in Figure 2.
The sediment core’s layers were thought to indicate the chronology of the biocide’s accumulation.
At first, it was thought that the concentration of biocides would be higher in the layers closest to thesurface, with a gradual decrease in the deeper layers. In fact, the results indicated differently, as thehighest concentration levels were detected at deeper points. Metals in the sediment, especially Mn, Fe
and Cu, are known to go through a process of dissolution as the sediment conditions cycle throughoxidation and reduction, as new layers of sediment form [27].

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Metal concentrations in every core section were measured to elucidate the distribution in every layer
and their relationship to the concentrations of biocides analyzed. In this study, only the concentrationsof Cu, which were obtained at survey Points 3 and 5 showed signs of accumulation. However, it wasthought that this accumulation was not as a result of oxidation and reduction, due to accumulation of
Mn or Fe not being detected. Both Mn and Fe generally react more to oxidation and reduction than Cu,
making it unlikely that oxidation and reduction were the cause of accumulation. Furthermore, theincrease of Zn in the same layer with a similar pattern to Cu support this theory. The more likely causeof Cu accumulation is that Cu was present in the paint fragments of the antifouling biocides.
Therefore, from this research, it is inconclusive whether or not alternative antifouling biocides areaffected by the change in conditions due to oxidation and reduction.
According to Jacobson et al. [3], the half-life of Sea-Nine 211 and TBT in sea water is one hourand six to nine months, respectively. It was thought that Sea-Nine 211 did not accumulate in sediment.
However, high concentrations were measured in sediment cores. Therefore, it is clear that the binding
to sediment protects molecules from breakdown.
Furthermore, according to Tsunemasa et al. [28,29], the toxicity (LC50) of Sea-Nine 211 and TBT
on oyster embryos is 28 and 16 µg/L, respectively. The highest value of Sea-Nine 211 and TBT in thesurvey Point 5 sediment core is five and 87 times more compared with the toxicity values on oyster
embryos, respectively. If these compounds dissolve in sea water, it is clear that they have an effect on
the marine organisms (for example, oyster and sea urchin embryos).
As the consumption of these biocides increases, it will have a negative impact through the retardationof the development of eggs and embryos, leading to an increased mortality rate. Therefore, it is thoughtthat the antifouling biocide resolution speed in sea water and sediment should be improved.
4. Experimental Section
4.1. Sampling Description
A map of the sampling stations is shown in Figure 4. Three fishery harbors, one environmental
standard point and one dock around the Otagawa River mouth were investigated. Five sediment
samples were collected in December 2004 and March 2005. At Points 1 and 2 in the fishery harbor,there were many more leisure boats than commercial fishing boats anchored. At Point 3 in the fisheryharbor, the ratio of commercial fishing boats to leisure boats was about the same. The environmental
standard Point 4 was located in a recess of Hiroshima Bay. Point 5 was located at the entrance tothe dock, and it was at this point where high concentrations of organotin compounds had beenpreviously reported.
4.1.1. Sampling
The sediment from the sea floor was collected with a sediment core sampler, divided into 3–5 cm-thicksections, centrifuged at 3000 rpm for 10 min and stored at −20 °C until analysis. Survey Points 1 and 2
were collected on 19 December 2004, other points were collected on 1 March 2005. The collected
depths were 39, 33, 23, 23 and 46 cm, respectively.

Int. J. Mol. Sci. 2014, 159999

4.1.2. Chemicals
The investigated materials were Diuron (3-(3,4-dichlorophenyl)-1,1-dimethylurea), Sea-Nine211®
(4,5-dichloro-2-n-octyl-3(2H)isothiazolone) (Rhom and Hass, Philadelphia, PA, USA), Irgarol 1051®
(2-methylthio-4-tert-butylamino-6-cyclopropylamino-s-triazine) (Chiba Speciality Chemicals K.K.,
Basel, Switzerland) and the latter’s degradation product, M1 (2-methylthio-4-tert-butylamino-6amino-s-triazine), which were thought to be commonly used in Japan as biocides. The Ot compounds(TBT and TPT) were also investigated for comparison with the alternative antifoulants. In addition, metals(Pb, Cu, Zn, Fe and Mn) in the core samples were measured in order to detect the behavior that wascaused by the change in the condition of oxidation and reduction.
Figure 4. Survey points.

4.2. Chemical Analysis
4.2.1. Alternative Biocides
The method used for the determination of alternative compounds in sediment was based on thatused by Harino et al. [24], with some modification. In a centrifuge tube, 5 g of wet sediment weremixed with 10 mL of acetonitrile for 10 min with a mechanical shaker. After removing thesupernatant, the analytes were re-extracted with 10 mL of acetonitrile for 10 min, and then the mixture
was centrifuged. The combined supernatants were concentrated to about 1 mL on a rotary evaporator,
and then, up to 45 mL of distilled water was added. The analytes were then extracted three times with

Int. J. Mol. Sci. 2014, 15

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10 mL of dichloromethane, and the organic layer was dried with anhydrous Na2SO4. After 10 mL of
methanol and 100 µL of atrazine-13C3 (1 mg/L) were added to the organic layer, which was thenconcentrated to 2 mL by rotary evaporation. The analytes were detected by LC/MS-MS. The analyticalcondition is shown in Table 5. The detection limits of Sea-Nine 211, Diuron, Irgarol 1051 and M1 inthe sediment samples were set at 1.0, 1.0, 0.1 and 0.1 µg/kg dry weight, respectively.
4.2.2. Organotin Compounds
The method used to determine the Ots in sediment samples was based on that of Midorikawa et al. [30]with some modification. The analytes underwent extraction, centrifugation, elution, cleaning
and concentration.
Tributyltin monochloride (TBTCl)-d27 and triphenyltin monochloride (TPTCl)-d15 were used asa surrogate standard. Tetrabutyltin (TeBT)-d36 and tetraphenyltin (TePT)-d20 were used as an internal
standard. The final solution was concentrated to 0.5 mL. The analytes were detected by GC/MS. The
analytical condition is shown in Table 6. The Ot’s detection limits in the sediment samples were set
at 0.1 µg/kg dry weight.
Table 5. LC/MS/MS conditions (Irgarol 1051, Diuron, Sea-Nine 211, M1).

LC
ColumnMobile phase
Flow rate
Oven temp.
Injection vol.
MS
Analytical mode
Ionization
Nitrogen curten gas
Ion spray voltage
Ion source gas 1
Ion source gas 2
Collision gas
Monitor ions

Conditions
Agilent model 1100 series HPLC
(Agilent; Yokogawa Analytical System, Tokyo, Japan)
narrow bore C18 silica column(2.1 mm i.d. × 150 mm, 5 μm)
TSKgel ODS-80T (TOSOH)(A):(B) 50:50 → (20 min) → 100:0 (10 min)
(A): methanol; (B): water
20 µL/min
40 °C
10 µL
PE-Sciex API2000 (Sciex; Applied Biosystems, Framingham, MA, USA)
ESI-MS-MS
positive ion mode
40 µL/min
4800 V
40 µL/min
70 µL/min
4 µL/min
Sea-Nine 211: 282/170(43) Diuron: 233/46(160)
Irgarol 1051: 254/198(83) M1: 214/158(43)Int. J. Mol. Sci. 2014, 15

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Table 6. GC/MS conditions (TBT, TPT).

GC
ColumnOven temp.

Flow rate
Injector temp.
Injection vol.
MS
Interface temp.
Source temp.
Ionization energy
Source temp.
Ionization energy
Analytical mode
Monitor ions

Conditions
Hewlett-Packard 6890 Series GC System
DB-5ms(0.25mm i.d. × 30m, 0.25 μm) (J&W Scientific Co., Folsom, CA, USA)
60 °C (2 min)—raised by 20 °C/min—130 °C—raised by
10 °C/min—210 °C—raised by 5 °C/min—260 °C—raised by
10 °C/min—300 °C (2 min)He, 1 mL/min
Splitless (purge time 1 min)
250 °C
2 µL(5973N)
280 °C
230 °C
280 °C
230 °C
70 eV
SIM
TBT: 263 (261) TPT: 351 (349)

4.2.3. Metals
In a 200-mL beaker, 2 g of wet sediment core sample were mixed with 10 mL of nitric acid and
20 mL of hydrochloric acid while being heated on a hotplate. When the volume had reduced by half,
the beaker was removed from the heat. Then, 20 mL of nitric acid was added to the mixture andreheated. When the mixture value had reduced by 20 mL, it was cooled to room temperature. Next,
50 mL of water were added to the mixture, and it was warmed on low heat. After the deposits had
settled to the bottom of the beaker, the solution was filtered with filter paper. The resulting solution
was used for the analysis of metals, performed on a Thermo electron corporation m series
AA Spectrometer with flame. The detection limits of lead, copper, zinc, iron and manganese in thesediment samples were set at 0.5, 0.5, 5.0, 5.0 and 5.0 mg/kg dry weight, respectively.
4.2.4. Chronology
210

Pb chronology was applied to the cores using the model of Matsumoto [31], in which core depth
was corrected for the sediment compaction [32]. Geochronology was also employed based upon
the fallout of the fission product, 137Cs, from the stratosphere, introduced by nuclear weapons testing.
The 137Cs profile was adjusted for decay (half-life: 30 y) during the time between the measurement andthe sediment deposition, only for the period after 1950, because the 137Cs should theoretically not be
detected before then. The 137Cs maxima (1963 fallout maximum) corroborated the 210Pb ages as
being reliable.

Int. J. Mol. Sci. 2014, 15

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5. Conclusions
1. Irgarol 1051 clearly had the highest concentration measured in four of the five survey points,
with survey Point 4 being the exception.
2. Higher concentrations of antifouling biocides in the sediment core samples than the surface sediment
samples indicated that this is where accumulation occurs.
3. Oxidation and reduction were not the causes of the high concentration levels of Cu in survey
Points 3 and 5, due to the accumulation of Mn or Fe not being detected.
4. The 1990 regulation led to higher concentrations of Ot alternative antifoulants and Ot compounds
in survey Point 5. The former was due to increased consumption; the latter due to paint chips
containing Ot compounds that were stripped being washed into the sea.
5. After metals have accumulated in the sediment core, they tend not to shift.
Acknowledgments
This work was partly supported by the Mitsui & Co., Ltd. Environmental Fund (2007).
Conflicts of Interest
The authors declare no conflict of interest.
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Cleary, J.J.; Stebbing, A.R.D. Organotin on surface microlayer and subsurface water of southwest
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