1.Introduction

The owner of marine facility shall make a report on such facility to the Minister of Oceans and Fisheries under the provisions of Article 33 of Marine Environment Management Act of Korea. The shipyard means a workplace or facility where ships are built, repaired or broken up, and is designated as a marine facility of item Da of subsection 1 by the table 1 attached to the Enforcement Ordinance of the Marine Environment Management Act.

Total 178 shipyards were reported to be distributed across the country and to account for 26.5 % of all marine facilities, and 45 % of total shipyards were concentrated around southeastern area of Korea, as of the end of the year 2009(Kim, 2010a; Kim, 2010b). Marine environment is, therefore, likely to be deteriorated in this area(Kim and Han, 2014).

Major shipyards took passive attitudes and evaded reporting their facilities to the Minister of Oceans and Fisheries by reason that shipbuilding facility or shipbuilding yard is clearly stipulated in the type of marine facilities but not expressly stated in the scope of marine facilities of item Da of subsection 1 by the table 1 attached to the Enforcement Ordinance of Marine Environment Management Act(MLTM, 2010).

In process of shipbuilding, the potential for the discharge of various metals such as copper(Cu), zinc(Zn) and iron(Fe) from shipbuilding yards to their surrounding waters always exists. It is, therefore, necessary to investigate the current state of pollution of heavy metals in seawater around major shipyards of Korea(Kim and Han, 2014).

In Korea, most of studies and researches for heavy metals in coastal area focused on sediments(Kim et al., 2008a; Kim et al., 2008b; Kim et al., 2012a; Kim et al., 2012b; Kim and Um, 2013; Kim and Jang, 2014) and the concentrations of trace metals in the organs of minke whale were measured by Jeon et al.(2012). Some studies on the vertical distribution and behavior of trace metals in the Pacific, Atlantic and Indian Oceans were conducted by Bruland(1980), Yeats and Campell(1983) and Saager et al.(1992), and a few researches for heavy metals in seawater around Korea were performed by Lee et al.(1984), Kim et al.(2007) and Kim et al.(2008b). It is, however, difficult to find any research for heavy metals in seawater around major shipyards in Korea.

In this study, for the purpose of elucidating the current state of marine pollution of heavy metals around major shipyards in Korea, seawater samples were collected at eleven sampling stations and four control stations around 4 major shipyards which are located in southeastern area of Korea, and six kinds of metals in seawater were analyzed.

The outcomes of this study are expected to be used as a basic reference to establish local or national plans for the prevention of marine pollution around nationwide shipyards of Korea.

2.Reviews of metal-related literatures

2.1.Groups of metals

Metals are natural constituents of seawater. Metals of biological concern may be divided into three groups, namely, light, transitional and heavy metals. Light metals such as sodium, potassium, calcium, etc. are normally transported as mobile cations in aqueous solutions. Transitional metals, for example, iron, copper, cobalt and manganese are essential in low concentrations but may be toxic in high concentrations. Heavy metals such as mercury, lead, tin, selenium and arsenic are generally not required for metabolic activity and are toxic to the cell at quite low concentrations(Clark, 1986).

2.2.Characteristics of metals

Absorption of heavy metals from solutions is dependent on active transport systems in some microorganisms and sea urchin larvae, but generally in plants and animals it is by passive diffusion across gradients created by adsorption at the surface, and by binding by constituents of the surface cells, body fluids, etc.. An alternative and important pathway for animals is when metals are adsorbed onto or are present in food, and by the collection of particulate or colloidal metal by a food-collecting mechanism such as the bivalve gill. There are considerable variation in the extent of which plants and animals can regulate the concentrations of metals in the body. Plants and bivalve mollusca are poor regulators of heavy metals. Decapod crustaceans and fish are generally able to regulate essential metals such as zinc and copper, but nonessentials such as mercury and cadmium are less well regulated(Clark, 1986).

Usually, trace metals exist infinitesimally in natural water such as seawater and fresh water(Bruland et al., 1991), and many are essential for living organisms. Trace metals may, however, be classified as persistent pollutants, because they are hardly degraded in the environment. They have a tendency to accumulate in organisms and to magnify accumulation concentrations higher and higher in organs or tissues of organisms through food chains in ecosystem(Kim et al., 2008b). Heavy metals which flowed into the sea can turn into particulate through biogeochemical cycle, deposit and accumulate on the sediments after all, and may cause biological effect on marine organisms such as benthos which inhabits the sediments(Salomons and Forstner, 1984).

3.Sampling and analysis

3.1.Collection of seawater samples

Seawater samples were collected at three sampling stations(A1, A2 and A3) and one control station(AC) around A-shipyard in Ulsan, at two sampling stations(B1 and B2) and one control station(BC) around B-shipyard in Busan, at three sampling stations(C1, C2 and C3) and one control station(CC) around C-shipyard, and at three sampling stations(D1, D2 and D3) and one control station(DC) around D-shipyard in Geojedo for 5 days from August 2 to August 6, 2010, using specialized online pump with filter for collection of metals on board the ship(Fig. 1).

3.2.Method of analysis

Seawater samples were added by undiluted solution of nitric acid(HNO₃) and pre-treated, and analyzed for copper(Cu), zinc(Zn), iron(Fe), cadmium(Cd) and lead(Pb) by Inductively Coupled Plasma Mass Spectrometer(ICP-MS, Perkin Elmer: Elan 6000). Mercury(Hg) was analyzed by Automatic Mercury Analyzer (AMA-254, Milestone). Analytical results of metal concentration in the SRM(CASS-4, MESS-2) showed the recovery rates to be 97 % (Cu), 98 %(Zn), 99 %(Cd), 95 %(Pb) and 99 %(Hg), respectively.

4.Results and discussion

The results of seawater analyses were shown in Table 1 and the average concentrations of six kinds of metals around four major shipyards were illustrated in Table 2.

4.1.Copper(Cu)

The concentrations of copper at eleven sampling stations and four control stations around 4 major shipyards were compared one another, as shown in Fig. 2.

The average Cu concentration at three sampling stations A1, A2 and A3 around A-shipyard in Ulsan was 1.249 ㎍/L and was 2.75 times higher than 0.455 ㎍/L at control station AC. The average Cu concentration at two sampling stations B1 and B2 around B-shipyard in Busan was 1.638 ㎍/L and was 2.73 times higher than 0.600 ㎍/L at control station BC. The average Cu concentration at three sampling stations C1, C2 and C3 around C-shipyard in Geojedo was 0.817 ㎍/L and was 2.75 times higher than 0.297 ㎍/L at control station CC. The average Cu concentration at three sampling stations D1, D2 and D3 around D-shipyard in Geojedo was 1.101 ㎍/L and was 1.64 times higher than 0.673 ㎍/L at control station DC.

With regard to average Cu concentrations at sampling stations around shipyards, B-shipyard ranked the first by 1.638 ㎍/L, A-shipyard the second by 1.249 ㎍/L, D-shipyard the third by 1.101 ㎍/L, and C-shipyard the fourth by 0.817 ㎍/L.

The average Cu concentrations at sampling stations around A-shipyard, B-shipyard and C-shipyard were 2.73~2.75 times higher than those at control stations and were very similar to one another, while the average Cu concentration at sampling stations around D-shipyard was 1.64 times higher than that at control station. This implies that lots of copper was used in anti-fouling paint for ships' hulls and this use inevitably resulted in copper being transferred to the marine environment from shipyards.

Despite the existence of a number of detoxifying and storage systems for copper, it is the most toxic metal, after mercury and silver, to a wide spectrum of marine life, hence its value in anti-fouling preparations(Clark, 1986). There is no danger to humans of copper poisoning from seafood. Copper in the sea is not regarded as a health hazard(Clark, 1986).

Around four major shipyards, the Cu concentrations at all sampling stations were 0.551~2.022 ㎍/L and those at all control stations were 0.297~0.673 ㎍/L as shown in Table 1. The Cu concentrations at all sampling and control stations were higher than 0.060~0.319 ㎍-Cu/L in the seawater of the East Sea(Kim et al., 2007), 0.220~0.590 ㎍-Cu/L in the seawater of Gaduk Channel, Korea(Kim et al., 2008b) and 0.034~0.334 ㎍-Cu/L in the North Pacific Ocean(Bruland, 1980), and were lower than Korean environmental standards of 20 ㎍-Cu/L for the protection of human health and of 3.0 ㎍-Cu/L for short-term protection of marine ecosystem as provided in the table attached to Article 2 of the Enforcement Decree of the Framework Act on Environmental Policy, as shown in Table 2.

4.2.Zinc(Zn)

The concentrations of zinc at eleven sampling stations and four control stations around 4 major shipyards were compared one another, as shown in Fig. 3.

The average Zn concentration at three sampling stations A1, A2 and A3 was 0.550 ㎍/L and was 5.24 times higher than 0.105 ㎍/L at control station AC. The average Zn concentration at two sampling stations B1 and B2 was 0.567 ㎍/L and was 1.62 times higher than 0.349 ㎍/L at control station BC. The average Zn concentration at three sampling stations C1, C2 and C3 was 0.228 ㎍/L and was 5.56 times higher than 0.041 ㎍/L at control station CC. The average Zn concentration at three sampling stations D1, D2 and D3 was 0.384 ㎍/L and was 5.91 times higher than 0.065 ㎍/L at control station DC.

With regard to average Zn concentrations at sampling stations around shipyards, B-shipyard ranked the first by 0.567 ㎍/L, A-shipyard the second by 0.550 ㎍/L, D-shipyard the third by 0.384 ㎍/L, and C-shipyard the fourth by 0.224 ㎍/L.

The average Zn concentrations at sampling stations around A-shipyard, C-shipyard and D-shipyard were 5.24~5.91 times higher than those at control stations and were very similar to one another, while the average Zn concentration at sampling stations around B-shipyard was 1.62 times higher than that at control station. This implies that lots of zinc was used in galvanized coatings of metals for ships' hulls(Clark, 1986) and zinc wastes were likely to be discharged to sea from shipyards.

Around four major shipyards, the Zn concentrations at all sampling stations were 0.136~1.040 ㎍/L and those at all control stations were 0.041~0.349 ㎍/L as shown in Table 1. The Zn concentrations at all sampling and control stations were similar to 0.016~1.563 ㎍-Zn/L in the seawater of the East Sea(Kim et al., 2007), 0.16~1.29 ㎍-Zn/L in the seawater of Gaduk Channel, Korea(Kim et al., 2008b) and 0.006~0.602 ㎍-Zn/L in the North Pacific Ocean(Bruland, 1980), and were lower than Korean environmental standards of 100 ㎍-Zn/L for the protection of human health and of 34 ㎍-Zn/L for short-term protection of marine ecosystem as shown in Table 2.

4.3.Iron(Fe)

The concentrations of iron at eleven sampling stations and four control stations around 4 major shipyards were compared one another, as shown in Fig. 4.

The average Fe concentration at three sampling stations A1, A2 and A3 was 7.410 ㎍/L and was 6.75 times higher than 1.098 ㎍/L at control station AC. The average Fe concentration at two sampling stations B1 and B2 was 5.884 ㎍/L and was 1.44 times higher than 4.100 ㎍/L at control station BC. The average Fe concentration at three sampling stations C1, C2 and C3 was 3.332 ㎍/L and was much lower than 16.235 ㎍/L at control station CC.

It was unusual that the Fe concentration at control station CC was 16.235 ㎍/L and was much higher than those at the other control stations AC, BC and DC. The average Fe concentration at three sampling stations D1, D2 and D3 was 5.451 ㎍/L and was 1.30 times higher than 4.201 ㎍/L at control station DC.

With regard to average Fe concentrations at sampling stations around shipyards, A-shipyard ranked the first by 7.410 ㎍/L, B-shipyard the second by 5.884 ㎍/L, D-shipyard the third by 5.451 ㎍/L, and C-shipyard the fourth by 3.332 ㎍/L.

The average Fe concentration at sampling stations around A-shipyard was 6.75 times higher than that at control station and ranked the first, and the average Fe concentrations at sampling stations around B-shipyard and D-shipyard were 1.30~1.44 times higher than those at control stations and were very similar to each other. This implies that plenty of iron was used in iron plates of ships' hulls, and lots of iron dust and welding slag were likely to be transferred to the marine environment from shipyards. It was, however, unusual that the average Fe concentration at sampling stations around C-shipyard was much lower than that at control station.

Around four major shipyards, the Fe concentrations at all sampling stations were 1.116~13.880 ㎍/L and those at all control stations were 1.098~16.235 ㎍/L as shown in Table 1.

Iron is not usually a significant contaminant of the sea, but it has come to prominence over sea dumping of ‘red mud’ from the extraction of alumina from bauxite, and ‘acid iron waste’ from the production of titanium dioxide. Both wastes contain a large amount of iron(Clark, 1986).

4.4.Cadmium(Cd)

The concentrations of cadmium at eleven sampling stations and four control stations around 4 major shipyards were compared one another, as shown in Fig. 5.

The average Cd concentration at three sampling stations A1, A2 and A3 was 0.028 ㎍/L and was 2.33 times higher than 0.012 ㎍/L at control station AC. The average Cd concentration at two sampling stations B1 and B2 was 0.020 ㎍/L which was 1.18 times higher than 0.017 ㎍/L at control station BC. The average Cd concentration at three sampling stations C1, C2 and C3 was 0.013 ㎍/L and was 1.30 times higher than 0.010 ㎍/L at control station CC. The average Cd concentration at three sampling stations D1, D2 and D3 was 0.016 ㎍/L and was 1.33 times higher than 0.012 ㎍/L at control station DC.

With regard to average Cd concentrations at sampling stations around shipyards, A-shipyard ranked the first by 0.028 ㎍/L, B-shipyard the second by 0.020 ㎍/L, D-shipyard the third by 0.016 ㎍/L, and C-shipyard the fourth by 0.013 ㎍/L.

While the average Cd concentration at sampling stations around A-shipyard was 2.33 times higher than those at control stations and ranked the first, the average Cd concentrations at sampling stations around B-shipyard, C-shipyard and D-shipyard were 1.18~1.33 times higher than those at control stations and were very similar to one another. This implies that some cadmium was likely to be released to the marine environment from shipyards.

Around four major shipyards, the Cd concentrations at all sampling stations were 0.007~0.031 ㎍/L and those at all control stations were 0.010~0.017 ㎍/L as shown in Table 1. The Cd concentrations at all sampling and control stations were similar to 0.011~0.058 -㎍-Cd/L in the seawater of the East Sea(Kim et al., 2007), 0.011~0.029 -㎍-Cd/L in the seawater of Gaduk Channel, Korea(Kim et al., 2008b) and 0.0003~0.127 -㎍-Cd/L in the North Pacific Ocean(Bruland, 1980), and were lower than Korean environmental standards of 10 -㎍-Cd/L for the protection of human health and of 19 -㎍-Cd/L for short-term protection of marine ecosystem as shown in Table 2.

Cadmium is widely distributed in the Earth's crust, but is particularly associated with zinc and it is produced commercially only as a by-product of zinc smelting. The iron, steel, and non-ferrous metal industries produce dust, fumes, waste water, and sludge containing cadmium. Zinc used in galvanized coatings of metals contains about 0.2 % cadmium as an impurity. It is estimated that all this cadmium is lost to the environment through corrosion within four to twelve years. Cadmium was suspected of being responsible for an outbreak of itai-itai disease in a Japanese village on the Jintsu river. It was attributed to contamination of rice by cadmium from the effluent from a zinc smelter(Clark, 1986).

4.5.Lead(Pb)

The concentrations of lead at eleven sampling stations and four control stations around 4 major shipyards were compared one another, as shown in Fig. 6.

The average Pb concentration at three sampling stations A1, A2 and A3 was 0.007 ㎍/L and was much lower than 0.026 ㎍/L at control station AC. The average Pb concentration at two sampling stations B1 and B2 was 0.016 ㎍/L and was much lower than 0.072 ㎍/L at control station BC. The average Pb concentration at three sampling stations C1, C2 and C3 was 0.033 ㎍/L and was lower than 0.052 ㎍/L at control station CC. The average Pb concentration at three sampling stations D1, D2 and D3 was 0.126 ㎍/L and was 10.50 times higher than 0.012 ㎍/L at control station DC.

With regard to average Pb concentrations at sampling stations around shipyards, D-shipyard ranked the first by 0.126 ㎍/L, C-shipyard the second by 0.033 ㎍/L, B-shipyard the third by 0.016 ㎍/L, and A-shipyard the fourth by 0.007 ㎍/L.

While the average Pb concentration at sampling stations around D-shipyard was 10.50 times higher than that at control station, the average Pb concentrations at sampling stations around A-shipyard, B-shipyard and C-shipyard were 0.007~0.033 ㎍/L, were lower than those at control stations, and were similar to one another.

Around four major shipyards, the Pb concentrations at all sampling stations were 0.004~0.334 ㎍/L and those at all control stations were 0.012~0.072 ㎍/L as shown in Table 1. The Pb concentrations at all sampling and control stations were higher than 0.002~0.160 ㎍-Pb/L in the seawater of the East Sea(Kim et al., 2007) and 0.004~0.332 ㎍-Pb/L in the seawater of Gaduk Channel, Korea(Kim et al., 2008b), and were lower than Korean environmental standards of 50 ㎍-Pb/L for the protection of human health and of 7.6 ㎍-Pb/L for short-term protection of marine ecosystem as shown in Table 2.

Much lead in metallic form, in battery casings and plates, in sheet and pipes, etc. is recovered and recycled, but most lead used in compound form is lost to the environment. Lead aerosols are carried to Earth in rain and snow and are widely scattered. Local high concentrations of lead may be caused by special circumstances. Compared with other metals, lead in the sea is not particularly toxic and at concentrations up to 0.8 ppm, lead nitrate even enhances the growth of the diatom Phaeodactylum presumably through the nutrient effect of the nitrate. High concentrations of lead can be accumulated by some animals without apparent harm. Although lead is held responsible for serious damage to health on land, such contamination of the sea and marine products as occurs does not appear to be a matter for concern(Clark, 1986).

4.6.Mercury(Hg)

The concentrations of mercury at eleven sampling stations and four control stations around 4 major shipyards were compared one another, as shown in Fig. 7.

The average Hg concentration at three sampling stations A1, A2 and A3 was 0.004 ㎍/L and was a little higher than or nearly equal to 0.002 ㎍/L at control station AC. The average Hg concentration at two sampling stations B1 and B2 was 0.002 ㎍/L and was a little higher or nearly equal to 0.001 ㎍/L at control station BC. The average Hg concentration at three sampling stations C1, C2 and C3 was 0.002 ㎍/L and was equal to 0.002 ㎍/L at control station CC. The average Hg concentration at three sampling stations D1, D2 and D3 was 0.002 ㎍/L and was equal to 0.002 ㎍/L at control station DC.

With regard to average Hg concentrations at sampling stations around shipyards, A-shipyard ranked the first by 0.004 ㎍/L, and B-shipyard, C-shipyard and D-shipyard ranked the second by 0.002 ㎍/L. However, the average Hg concentrations at all sampling stations around four major shipyards were 0.002~0.004 ㎍/L, were similar to one another, and were a little higher than or nearly equal to 0.001~0.002 ㎍/L at all control stations.

Around four major shipyards, the Hg concentrations at all sampling stations were 0.002~0.008 ㎍/L and those at all control stations were 0.001~0.002 ㎍/L as shown in Table 1. The Hg concentrations at all sampling and control stations were similar to 0.0017~0.0183 ㎍-Hg/L in Gaduk Channel of Korea(Kim et al., 2008b) and 0.001~0.050 ㎍-Hg/L in the open oceans(Clark, 1986), and were lower than Korean environmental standards of 0.5 ㎍-Hg/L for the protection of human health and of 1.8 ㎍-Hg/L for short-term protection of marine ecosystem as shown in Table 2.

Mercury is lost to the atmosphere and in waste waters from the chlor-alkali industry, and mercurial compounds are inevitably dispersed into the environment by the uses such as ‘slimicides’ used in the lumber and paper pulp industries to prevent fungal growth, anti-fouling paints for ship hulls, pesticides and seed dressings in agriculture, and in pharmaceuticals. Following the discovery in the early 1960s of the dangers to human health of mercury in the sea, there has been a marked reduction in inputs from some major sources in some areas. Major sources of mercury in coastal waters are rivers, marine outfalls, and wastes dumped directly into the sea. The fact that mercury is toxic to humans has been known for centuries. In the 20th century, mercury has been the only contaminant introduced by man into the sea that has certainly been responsible for human death. Mercury poisoning resulting from pollution of the sea occurred at the small Japanese coastal town of Minamata in 1953. This mercury poisoning was called as Minamata disease(Clark, 1986).

5.Conclusion

Seawater samples were collected at eleven sampling stations and four control stations around 4 major shipyards located in the southeastern coast of Korea in summer 2010, and 6 kinds of heavy metals in seawater samples were analyzed. The concentrations of heavy metals in seawater around major shipyards in Korea was summarized as follows.