Evaluation of Trace Metal Contamination in Ise Bay, Mie Prefecture, Central Japan, Based on Geochemical Analysis of Tidal Flat Sediments

Geochemical analysis of tidal flat sediments was conducted to evaluate the environment of Ise Bay, Mie, central Japan. The sediment samples were analyzed using XRF to determine the geochemical compositions of sediments in the Ise and Matsusaka estuaries and their foreshores. Enrichment Factor (EF) and the Anthropogenic Contribution (AC) parameters were used to examine the potential effect of human activity. Furthermore, the Coastal Ocean Sediment Database, lowest and severe effect levels and Canadian Sediment Quality Guidelines were applied as benchmarks to assess the sediment quality. The results show that the highest average concentrations of metals occur in the Ise estuary, mainly due to the presence of higher proportions of silt and clay in samples at that site. The EFs of Pb in the Matsusaka foreshore, and that of As in the Ise foreshore reflect minimal pollution. The average AC ranged from 1 to 30%, implying that the lithology is the primary control of any enrichment in trace metals within the bay. The sediment quality guidelines indicate that the metal levels in the study areas do not constitute a major threat to biota.


Introduction
Environmental pollution related to the release of trace metals from industries is a worldwide issue.Contamination of trace metals in the environment is of major concern, because these metals are regarded as severe inorganic pollutants due to their toxicity, persistence, and the problem of bioaccumulation (Tam & Wong, 2000).Although heavy metals may originate from various sources, early studies have correlated elevated concentrations of certain inorganic elements in sediments of rivers, estuaries, and coastal regions with increased anthropogenic activities, including agricultural operations, land use, and industrial expansion.The latter activity is potentially a major contributor of inorganic contaminants.prefecture closest to Nagoya, contains the cities of Yokkaichi with its large petrochemical complexes, Suzuka and the Honda Motor Co. factory, and Kameyama, the base of the Sharp Corporation plant that manufactures LCD TVs.The economic output of this area is one of the largest in Mie prefecture (Chubu Economic Federation, 2011).Ise Bay in Mie prefecture is also close to the Chubu industrial district of Japan, and hence could receive a relatively high pollutant loading (Smith & Yanagi, 1997).
In addition to the industries described above, central Japan is characterized by estuaries, and is noted for coastal ecosystems rich in seafood and fishery resources.Excellent fishing grounds are found among the rich marine resources of Ise Bay, including young shirasu sardines, Japanese littleneck clams and anago saltwater eels.The catch of tiger puffers from Ise Bay is the largest in Japan (Chubu Economic Federation, 2011).
The high level of industrial activity in central Japan has the potential to affect the quality of coastal and estuarine sediments in Ise Bay, and thereby negatively influencing the local seafood farms.Coastal and estuarine regions are important sinks for many persistent pollutants, which may accumulate in organisms and in bottom sediments (Szefer et al., 1995).The measurement of trace element concentrations and distributions in marine environments thus leads to better understanding of their behavior in the aquatic environment, and is of obvious importance for detecting sources of pollution (Förstner & Wittman, 1979).In addition, understanding the distribution of trace metal contamination in coastal and estuarine systems is essential to facilitate sustainable management of coastal zones, and to provide the scientific basis necessary to target regulatory actions.Therefore, geochemical analysis is required to determine the present status of Ise Bay.
Several studies have been carried out in Ise Bay in recent years (e.g., Furukawa, 1999;Sugimoto et al., 2005;Ohta et al., 2007;Shota et al., 2009).However, few geochemical analyses have been made to determine the geographical distribution of trace metals, and the factors that control their distribution.Consequently, this study aims to identify the geographical distribution of six selected trace metals (As, Pb, Zn, Cu, Ni, and Cr), to determine the factors that control their abundances, and to evaluate the sediment quality in Ise Bay with respect to established international sediment quality guidelines.

Study Area
Ise Bay is located in Mie prefecture, on the island of Honshu, in central Japan (Figure 1).Ise Bay has a surface area of 1738 km 2 , an average depth of 19.5m, and a water volume of 33.9 km 3 , (Oceanographical Society of Japan, 1985).Its catchment area is approximately 18,153 km 2 , which contains a population of about 10.65 million (Xueqiang & Matsumoto, 2005).The Pacific Ocean and Ise Bay exchange water through Irago Strait.The Kiso, Nagara, and Ibi Rivers, collectively known as the Kiso Rivers, flow into the head of the bay in the north.This flow contributes 85% of the total freshwater discharge into the bay (Fujiwara et al., 1996).The bay is also fed by the Miyagawa River in the south and by the Kushida and Kumozu Rivers in the southwest.The speed of tidal currents in the bay is 0.1 m s -1 , while tidal flow converges at Irago Strait, where current speeds exceed 0.8 m s -1 during spring tides (Fujiwara et al., 2002).
The geology of the study areas is characterized by Sanbagawa metamorphic rocks, both mafic and felsic plutonic rocks, marine and non-marine Miocene sediments, terrace deposits, and marine and non-marine Holocene sediments.The basement rocks in the study area are mainly metamorphic rocks of accretionary complex origin, and granitic rocks.The Median Tectonic Line (MTL) runs through the study area, and forms the boundary between two geologically contrasting metamorphic belts, the Sanbagawa and Ryoke Belts (Yamamoto, 1994).

Sediment Sample Collection and Preparation
Thirty-eight tidal flat sediment samples were collected from the Matsusaka and Ise areas of Ise Bay.The samples were collected at low tides, between April and July 2012.Ten estuary and twelve foreshore sediment samples were collected from Matsusaka, and eight estuary and eight foreshore sediment samples from Ise (Figure 1).The sedimentation rate in Ise Bay ranges from 0.06 to 0.76 g cm -2 y -1 (Lu & Matsumoto, 2005).The uppermost two cm of surface sediment were collected at each sampling site, using a plastic spatula.The collected samples were composite, containing both sandy and muddy sediments.About 200 g of sediment was collected at each site.

Analytical Procedures
The samples were first homogenized, and then approximately 50g of each were then dried in an oven at 110 o C for 48 hours to eliminate free water and volatile organic matter.The dried samples were then ground for 20 minutes in an automatic agate mortar and pestle grinder.The powdered samples were compressed into briquettes using a force of 200 kN for 60s.Selected major and trace element (TiO 2 , Fe 2 O 3 , MnO, CaO, P 2 O 5, As, Pb, Zn, Cu, Ni, and Cr) and total sulfur (TS) concentrations were determined at Shimane University, using a Rigaku RIX 2000 X-ray fluorescence spectrometer equipped with a Rh-anode X-ray tube.Analytical methods, instrumental conditions, and calibration followed those described by Ogasawara (1987).Average errors for the elements analyzed are less than ±10% of the amount present.Analytical results for U.S. Geological Survey standard SCo-1 (Cody Shale) were acceptable compared with the proposed values of Potts et al. (1992).

Grain Size Analysis
Prior to grain size analysis, separate splits of the sediment samples were oven dried at 110˚C for 24 hours.The dried subsamples were then sieved to isolate the < 2000 µm fraction for the sandy sediments, and the <300µm fraction for the muddy sediments.From these retained fractions, the organic matter in 1g splits of the sandy and 0.5g splits of the muddy sediments was decomposed using hydrogen peroxide (H 2 O 2 ) at concentrations of 8% and 36%, respectively.After 24 hours digestion, the samples were again dried for 24 hours.Grain size analysis of the muddy sediments (n=16) was performed using a Shimadzu Laser Diffraction Particle Size Analyzer (Model SALD-3000S), whereas that of the sandy sediments samples (n=22) was measured by the settling tube method (Gibbs, 1974;Tucker, 1988).The Wentworth (1922) grain size classification was used to categorize the sediment samples.

Calculation of Enrichment Factors and Anthropogenic Contribution
The enrichment factor (EF) of elements proposed by Simex & Helz (1981) was used to determine the lithogenic and anthropogenic influence in the sediments of the study areas.The EF is expressed as: where "X" is the element under consideration,"TiO 2 " the chosen reference element, and the subscripts "sample" and "crust" indicate concentrations in the sample and an appropriate crustal material.
The anthropogenic contribution was also computed using the equation developed by N'guessan et al. (2009): (2)

Statistical Analysis
For determining the relationships among the elements, Excel 2010 was used to compute Pearson's coefficient of correlation.In addition, the two-tailed Mann-Whitney U test in the SPSS 10.0 statistical package was used to compare the concentrations of As, Pb, Zn, Cu, Ni, and Cr between the estuary and foreshore at both Matsusaka and Ise.Significant differences between the estuary and the foreshore of these sites were established by the least significant difference test (p <0.05).

Sediment Characteristics
Grain size distributions (weight % sand, silt, and clay) of the Matsusaka and Ise estuary and foreshore surface sediments are illustrated in Figure 2.
In the Matsusaka estuary, except for sample sites M6 and M22, both of which contain more than 50% of silt, almost all samples are dominated by sand, ranging approximately from 70% for M5 to 100% for M21.Likewise, in the Matsusaka foreshore, all sample sites are dominated by sand, ranging nearly from 56 % in M7 to 100% in M25.
Silt forms more than 50% of all the samples in the Ise estuary, except for those at sites I24 and I31, which contain approximately 50% and 33% sand respectively.In this same area, clay is present in all the sampling sites, with the maximum value of 24% observed at site I23.This is also the highest value among all samples in the two study areas.In contrast, in the Ise foreshore all samples except one consist mainly of sand, with values ranging from 76% to 100%.The exception is the sample at site I28, which is composed of almost 90% silt.
Overall, sand dominates the grain size distributions in the Matsusaka area, including estuary and foreshore, and in the Ise foreshore, whereas silt is the most dominant fraction in the Ise estuary.Clay (~15-25%) is also a significant component in the Ise estuary samples.Ise Bay sediment characteristics are similar to those of the adjacent Mikawa Bay, in which the sediments are predominantly composed of sand, with lesser silt and clay (Lu and Matsumoto, 2009).

Concentrations of Elements in the Sediments
Elemental concentrations in the Matsusaka and Ise estuary and foreshore surface sediments and their minimum, maximum, mean, and Mann-Whitney U test values are shown in Table 1.For comparison, this table includes values for average Japan upper crust (JUC) from Togashi et al. (2000) and upper continental crust (UCC) from Taylor & McLennan (1985).

Matsusaka
The average concentrations of trace metals and total sulfur in the Matsusaka estuary were 5, 16, 46, 17, 14, 40 and 1375 mg/kg for As, Pb, Zn, Cu, Ni, Cr and TS, respectively.In this same area, the average abundances of the major oxides were 0.58 wt% for TiO 2 , 4.99% for Fe 2 O 3 , 0.09% for MnO, 2.16% for CaO, and 0.11% for P 2 O 5 .In the Matsusaka foreshore, the mean concentrations of the trace metals and total sulfur were 4, 14, 35,9,11, 38, and 1173 (Taylor & McLennan, 1985), the average concentrations of As are almost double in the Matsusaka area (both estuary and foreshore), and nearly three and five times greater in the Ise foreshore and estuary, respectively.In addition, in the Ise estuary, compared to UCC values, the average concentrations of Ni and Cr are almost three times greater, those of Cu nearly two times greater, those of Pb slightly above, and those of Zn lower.Furthermore, average abundances of Cu in the Ise estuary and those of Cr in the Ise foreshore are double those of UCC.
Overall, among the study areas, the maximum concentrations and the highest average concentrations of As, Pb, Zn, Cu, Ni, and Cr were observed in the Ise estuary.Furthermore, for the comparison of the concentrations of these trace metals in the Matsusaka area, the two-tailed Mann-Whitney U test showed that the differences between the Matsusaka estuary and foreshore were statistically insignificant (Table 1).In contrast, the same test applied to the Ise area indicated that the differences in As, Pb, Zn, Cu, Ni, and Cr observed between the estuary and foreshore are statistically significant.A graphical statistical summary of the concentrations of trace metals in the Matsusaka and Ise datasets (Figure 3 a-f)) highlights the contrasts between the Ise estuary and foreshore sediments, and the similarity of the two environments at Matsusaka.

Inter-Element Relationships
Excel 2010 was used to compute Pearson's coefficient of correlation, to examine the relationships among the elements.and P 2 O 5 in the Matsusaka estuary.In the Matsusaka foreshore, Fe 2 O 3 concentrations are strongly associated with As, Zn, Cu, Cr, and TiO 2 and TS with Zn, Cu, and P 2 O 5 and finally TiO 2 with As, Zn, Cu, Cr, and MnO.
In the Ise estuary, the concentrations of Fe 2 O 3 showed strong correlations with As, Cu, Ni, Cr, and TiO 2 , the latter also being strongly associated with As, Cu, and Ni.Significant associations of TiO 2 , Fe 2 O 3 , MnO, and P 2 O 5 with As, Pb, Zn , Cu, Ni, and Cr also occur in the Ise foreshore, where TS also showed strong positive relationships with Zn, Cu, Cr, TiO 2 , Fe 2 O 3, MnO, and P 2 O 5 .In contrast, CaO showed negative correlations with all trace metals in the study areas, except for Pb in the Matsusaka foreshore, and Zn in the Ise estuary, where these two trace metals exhibit strong positive correlations with CaO.
The interrelationships between As, Pb, Zn, Cu, Ni, and Cr, particularly in the Matsusaka estuary and in the Ise foreshore, indicate strong internal positive correlations, suggesting a common source of these metals and a similar enrichment process in the surface sediments.The significant correlations between TS and As, Pb, Zn, Cu, and Ni in the Matsusaka estuary, between TS and Zn, and Cu in the Matsusaka estuary, between TS and Zn in the Ise estuary, and also between TS and Zn, Cu, and Cr, indicate that their concentrations may in part be related to pyritization (Ahmed et al., 2010).The strong positive associations of Fe 2 O 3 and some metallic elements in the estuary and foreshore sediments of the study areas (Table 2) suggest that iron may influence their enrichment mechanism.
Al 2 O 3 , Fe 2 O 3 and TiO 2 contents have been often used as proxies to define elemental sources and to evaluate grain size effects (Ishiga et al., 1999;Roser, 2000;Ortiz & Roser 2006a).Titanium is generally regarded as a conservative lithogenic element that is abundant in clays.In soils and sediments linear correlations exist between TiO 2 and other lithogenic elements.Elements that show strong correlations with TiO 2 should only reflect natural detrital inputs.In contrast, if no correlations exist between TiO 2 and a given metallic element, then this may suggest that additional natural or anthropogenic processes have contributed to elemental enrichment (Dalai & Ishiga, 2013).
In the study areas, Zn and Cr are strongly correlated with TiO 2 in the Matsusaka estuary (Figures 4c and f), as are As, Zn, Cu, and Cr in the Matsusaka foreshore (Figures 4a, c, d and f), As, Cu, and Ni in the Ise estuary (Figures 4a, d and e), and As, Pb, Zn , Cu, Ni, and Cr in the Ise foreshore (Figures 4a-f), indicating that these elements are mainly of natural origin, and are mainly concentrated in clay minerals (Roser, 2000).However, the concentrations of As, Pb, Cu, and Ni in the Matsusaka estuary (Figs.4a, b, d, and e), those of Pb and Ni in the Matsusaka foreshore (Figures 4b and e), and those of Pb, Zn, and Cr in the Ise estuary show some scatter to higher values, suggesting that part of the load of these elements could be derived from anthropogenic sources.
A significant feature of the TiO 2 plots is that the foreshore and estuary sediments at both Ise and Matsusaka combine to form single trends at each locality (Figure 4).For As, Pb and Zn the trends for both localities are similar and overlap, suggesting detrital control from a common source material.A few estuary samples from both localities show slight enrichment for Pb and Zn at high TiO 2 , suggesting some anthropogenic contribution is possible.In the Matsusaka area (estuary and foreshore), the concentrations of As are at least four times greater than those from Kumozu and Hannai rivers, which feed the estuary.However, the concentrations of Ni for the Matsusaka estuary and foreshore, and those of Zn for the Matsusaka foreshore are almost one third of the values observed from the Kumozu River.Similarly, the Matsusaka estuary and foreshore show Zn concentrations which are below those of the Hannai River (Table 3).
Two elements (Cu and Cr) show differing trends from the two localities, with distinctly higher concentrations at given TiO 2 in the Ise samples, especially those in the estuary.The higher contents in the Ise estuary are partly driven by grain size, as these samples contain the highest silt and mud fractions (see below).However, differing provenance may also be a factor.AIST data (Table 3) for a stream sediment from the lower reaches of the Miya River, which feeds the Ise estuary, shows marked enrichment in Cr (142 mg/kg) and Cu (46 mg/kg) compared to the Kumozu and Hannai Rivers (37-95 and 15-17 mg/kg, respectively).The Miya River value is similar to the maximum observed in the Ise estuary, suggesting that the latter sediments contain a mafic component contributed from Sanbagawa schists in the Miya catchment.Nickel also shows a linear trend in the Ise samples overall and higher value (71 mg/kg) in the Miya River, but scatter and lower values in the Matsusaka suite (all <20 mg/kg), comparable with lower values in the Kumozu and Hannai Rivers (38 and 12 mg/kg respectively).The higher values in the Ise suite further suggest the presence of a small mafic component that is less significant at Matsusaka.These features suggest that the compositions of the sediments in these proximal estuary and foreshore settings in Ise Bay are strongly influenced by the rivers that fed them.Mixing by circulation within the bay may therefore be limited to deeper water zones.
Among the study areas, the Ise estuary shows the highest average concentrations of As, Pb, Zn, Cu, Ni, and Cr (Table 1).The variety of grain size observed in this location explains these elevated concentrations.In all the sampling sites in the Matsusaka estuary (except M6 and M22), in the Matsusaka foreshore (except M7), and in the Ise foreshore (except I28), the sediment content are mainly characterized by sand, which account for more than 63% of the total composition.In contrast, almost all the sample sites in the Ise estuary contain more silt and clay compared to the other areas (Figures 2a-d).The combined silt and clay content at each sampling site in the Ise estuary (except I24 and I31) accounts for at least 75% of the bulk composition.It is well established that fine-grained sediments adsorb contaminants more readily than coarse-grained sediment.More specifically, clay-sized material represents the fraction with the greatest adsorbing capacity, owing to larger surface area and greater cation exchange capacity, and because clay material can serve as a host for contaminant scavengers, such as Mn/Fe oxides and organic matter (Horowitz, 1991).Therefore, the high trace metal concentrations in the Ise estuary are closely associated with the abundance of fine-grained sediment in the samples, as well as the mafic component delivered by the Miya River.

Comparison with other studies
In order to appreciate the level of trace metal concentrations in Ise Bay relative to those in other geographical areas, the average concentrations of Pb, Zn, Cu, Ni, and Cr from the study areas in Ise Bay, were compared to those from Tokyo Bay, Osaka Bay, Shantou Bay, Mansan Bay, and San Francisco Bay (Table 3).The average concentrations of Pb and Zn reported by Nagaoka et al. (2004) for Osaka Bay and by Terashima et al. (2007) for Tokyo Bay, central Japan, are all greater than those of all the study areas from Ise Bay.Particularly, the concentrations of Pb (58 mg/kg) and Zn (242 mg/kg) in Osaka Bay are almost three and four times, respectively, higher than those of the Ise estuary.In addition, Pb (35 mg/kg) and Zn (222 mg/kg) for Tokyo Bay are greater than those in the Ise estuary, with Zn being almost four times higher.However, the average concentration of Cr in the Ise estuary is slightly above that of Tokyo Bay (Cr; 87mg/kg), and is almost double that seen in Osaka Bay (Cr; 49 mg/kg).
The concentrations of Pb, Zn, and Cu in Shantou Bay (China) are enriched with respect to all the study areas from Ise Bay, as are the concentrations of Pb and Zn from Mansan Bay in South Korea.In addition, the concentrations of Pb, Zn and Cu from San Francisco Bay (USA) are enriched relative to the Matsusaka estuary and foreshore, and Ise foreshore, but depleted with respect to the Ise estuary.Finally, the concentrations of Ni and Cr from Shantou and Mansan Bays are greater than those of the Matsusaka estuary and foreshore, but are below of those from the Ise estuary.Overall, the low levels of Pb, Zn, and Cu, and Ni and Cr (in some cases) observed in Ise Bay imply that the bay is relatively pristine compared to these other studies.

Enrichment factor and anthropogenic contribution
Enrichment factors (EF) and anthropogenic (AC) contribution are both practical tools used to identify elemental sources in sediments.Consequently, the selection of an adequate normalizer and suitable background values in evaluating the EF and AC is crucial for the interpretation of geochemical data.
Normalizers such as Al, Ti, and Fe are often used (Chester & Stoner, 1973).More specifically, Fe has been extensively used in many geochemical studies (Ackerman, 1980;Emmerson et al., 1997;Lee et al., 1998).A potential difficulty with using Fe, however, is that in certain circumstances this element can be mobile during diagenesis (Finney & Huh, 1989), and Fe hydroxide precipitates occur in estuarine and coastal sea sediments.Iron can also be contributed from anthropogenic sources.As Al was not determined in this study, Ti was used as the normalizer in Equations ( 1) and ( 2) for computing the EF and anthropogenic contribution (%AC), respectively, because of its relatively low mobility during various sedimentary processes (Johnsson, 1993;Roser, 2000).
Average values for the upper continental crust (e.g.Taylor & McLennan, 1985;Wedepohl, 1995) are also often used to provide background metals levels.However, these crustal values tend to be very general, and may mislead in a specific coastal area (Gibbs, 1993).For instance, the values provided by Taylor & McLennan (1985) for the upper continental crust (UCC) and those by Togashi et al. (2000) for the Japan upper crust (JUC) show large differences for the concentrations of As and Cr ( Table1).The JUC concentrations of Cr and As are two and three times, respectively, greater than those of UCC.As a result, using UCC values for these elements would impact the interpretation of the geochemical data.For this reason, the values provided by Togashi et al. (2000) were used in this study.As these values are also more likely to reflect contributions from the local geology, they are more specific, and thus will provide more accurate results for the EF and the AC.
The interpretation of EF values is performed based on defined scales.According to Zhang & Liu (2002), EF values between 0.5 and 1.5 indicate that the metal is entirely derived from crustal materials or natural processes, whereas EF values greater than 1.5 suggest anthropogenic sources.
Figure 5 shows the average EF values for the Matsusaka and Ise estuary and foreshore sediments.In the Matsusaka area, the EF of As in the foreshore, and those of Pb both in the estuary and foreshore are all greater than 1, as is the EF of Cu in the Ise estuary.Similarly, the EF of As, Pb, Ni, and Cr in the Ise foreshore are also above 1.However, among the above-mentioned elements, only the EF of Pb (1.67) in the Matsusaka foreshore, and that of As (1.56) in the Ise foreshore exceed 1.5, suggesting minimal enrichment, as stated by Sutherland (2000) for EF values ranging from 1 to 2.
The anthropogenic contribution of the selected metals is shown in Table 4, which includes the mean and range for the AC of the metals in the study areas.The mean AC of Pb in the Matsusaka estuary and foreshore are 1% and 13%, respectively.These percentages suggest that lithogenic or natural processes account for 99% of the Pb in the Matsusaka estuary, and 87% in the Matsusaka foreshore.In the Ise estuary, the mean AC of Cu is 22%, indicating that 78% of this metal is also derives from lithogenic sources.In addition, the AC values for As, Pb,Ni and Cr are 30,11,2,and 20%,respectively.Overall, the average contributions from lithogenic or natural processes in the study areas range from 70 to 99%, implying that anthropogenic sources account only for a minor part of the enrichment of the trace metals in these areas.This observation is consistent with the EF values (Figure 5), which show that even the most elevated average values of the trace metals are rated only in the category of minimal enrichment.These minimal enrichments do not pose a major environmental threat to the biota living in the study areas.However, regular monitoring is necessary to evaluate concentrations of these trace metals over time, particularly Pb in the Matsusaka foreshore and As in the Ise foreshore.

Comparison of Metal Concentrations with Sediment Quality Guidelines
To evaluate the contamination levels of As, Pb, Zn, Cu, Ni and Cr in the study areas, the Coastal Ocean Sediment Database (COSED), the lowest effect level (LEL) and the severe effect level (SEL), and the Canadian Sediment Quality Guidelines (CSedQGs), including the interim sediment quality guideline (ISQG) and the probable effect level (PEL), were applied as benchmarks (Table 5).
The COSED values are indicative of metal contamination, and are used to quantify degradation of sediment quality in estuarine and marine ecosystems (Ruiz-Fernández et al., 2003).The New York State Department of Environmental Conservation (NYSDEC, 1999) points out that if both the LEL and SEL criteria are exceeded, the metal concerned may severely impact biota health, whereas if only the LEL criterion is exceeded, impact on biota health may be moderate.The CSedQGs present values for individual chemicals or elements in both freshwater and marine (including estuarine) sediments for the protection of aquatic life, and were developed from available scientific information on the biological effects of chemicals associated with sediments (SAIC, 2002).The CSedQGs present two numerical limits: (1) the lesser limit is termed the interim sediment quality guideline (ISQG) value, and (2) the greater limit is called the probable effect level (PEL;CSMWG, 2003).Sediment chemical concentrations below the ISQG values are unlikely to be associated with adverse biological effects, whereas concentrations above the PEL are expected to be frequently associated with adverse biological effects.Adverse effects are occasionally observed in sediments which contain metal concentrations between the two threshold values (CSMWG, 2003).The average concentrations of Cu and Ni from Ise estuary (Table 5), representing the highest values compared to the other study areas, are almost identical to the COSED values.With respect to the LEL and SEL, Ni and Cr in the Ise estuary are classed as moderately contaminated, whereas Cr in the Matsusaka estuary and foreshore, as well as As and Cu in the Ise estuary, and finally Ni and Cr in the Ise foreshore show slight contamination in these areas.Relative to the ISQG and PEL values, the Ise estuary is slightly contaminated with As, Cu, and Cr, as is Ise foreshore with Cr.However, the enrichment factor values of these metals from the above locations are less than 1.5 (Fig. 5), suggesting that these metals are entirely derived from crustal materials or natural processes (Zhang & Liu, 2002).

Conclusions
Geochemical analysis was carried out for Matsusaka and Ise estuary and foreshore sediments.Average concentrations of trace metals and major oxides (except for CaO) were higher in the estuaries than in the foreshore sediments.Among the study areas, the Ise estuary presents the highest average concentrations of As, Pb Zn Cu, Ni, and Cr, and also the greatest weight percent of the fine-grained sediments.
The concentrations of Zn and Cr in the Matsusaka estuary, those of As, Zn, Cu, and Cr in the Matsusaka foreshore, those of As, Cu, and Ni in the Ise estuary, and finally those of As, Pb, Zn, Cu, Ni, and Cr in the Ise foreshore show strong correlations with TiO 2 , suggesting that these elements are mainly of lithogenic origin.In contrast, the concentrations of As, Pb, Cu, and Ni in the Matsusaka estuary, those of Pb and Ni in the Matsusaka foreshore, and those of Pb, Zn, and Cr in the Ise estuary show weaker correlations with TiO 2 , suggesting that part of the load of these elements in a few samples had a different enrichment process with respect to TiO 2. Contribution of a small amount of mafic material derived from the Miya River may account for the higher Cr, Cu and Ni observed in the Ise estuary and foreshore.
The metals do not constitute a major potential impact on biota health in any of the study areas, based on comparison with COSED, LEL, SEL, ISQG and PEL values.In addition, enrichment factor values for the study areas indicate that only Pb in the Matsusaka foreshore, and As in the Ise foreshore show minimal enrichment, suggesting that these areas are only slightly polluted with respect to these two trace metals.The low anthropogenic contributions (AC) show that anthropogenic activities account for a minor contribution for the enrichment of the trace metals in the study areas, implying that the lithology, source and natural processes exert the most influence on elemental concentrations in the study areas.However, continuous monitoring of Pb in the Matsusaka foreshore is necessary, as is that of As in the Ise foreshore, as the EFs of these two elements reflect minimal pollution.
mg/kg for As, Pb, Zn, Cu, Ni, Cr, and TS, respectively, whereas the concentrations of the major oxides averaged 0.45 wt% TiO 2 , 3.84% Fe 2 O 3 , 0.08% MnO, 2.25% CaO, and 0.08% P 2 O 5 .The highest concentrations of Ni and TS occurred in the Matsusaka estuary, where the highest values of As, Pb, Zn, and Cu (all of which are outliers) were also observed.In contrast, the highest values of Cr occurred in the Matsusaka foreshore.
4.2.2IseOnaverage, the Ise estuary surface sediments contain 9 mg/kg As, 23 mg/kg Pb, 63 mg/kg Zn, 47 mg/kg Cu, 52 mg/kg Ni, 112 mg/kg Cr, and 1890 mg/kg TS.In the Ise foreshore, the average concentrations ofAs, Pb, Zn, Cu,  Ni, Cr, and TS are 6, 11, 34, 12, 23, 61, and 923 mg/kg, respectively.The highest values of these elements, as well as their highest average concentrations thus occurred in the Ise estuary.In addition, average concentrations of the major elements for the Ise estuary were 0.84 wt% TiO 2 , 6.61% Fe 2 O 3 , 0.16% MnO, 1.15% CaO, and 0.16% P 2 O 5 , whereas for the foreshore, the mean concentrations of TiO 2 , Fe 2 O 3 , MnO, CaO, P 2 O 5 were 0.36, 3.62, 0.08, 1.95, and 0.07%, respectively.Average concentrations of Cu In the Ise estuary are almost double those of the Japan upper crust (JUC) value, whereas As, Pb, Ni, and Cr show slightly elevated values, and Zn displays lower values, as do all the trace elements in the Matsusaka area ( estuary and foreshore) and in the Ise foreshore.Compared to upper continental crust (UCC) values

Table 1
Elemental concentrations in the Matsusaka and Ise estuary and foreshore surface sediments Table 2 displays correlation matrices for elements in the Matsusaka and Ise estuary and foreshore sediments.Strong positive relationships were observed between the concentrations of Fe 2 O 3 and As, Zn, Cu, Cr, TiO 2 , MnO, and P 2 O 5 , between TS and As, Pb, Zn, Cu, Ni, and P 2 O 5 , and also between TiO 2 and Zn, Cr, MnO,

Table 2
Correlations between the elements in the Matsusaka and Ise estuary and foreshore

Table 4
Anthropogenic contribution (%AC) values for the surface sediments from the Matsusaka and Ise areas of Ise Bay, Japan

Table 5
Sediment quality criteria and average metal concentrations (mg/kg) in the Ise Bay sediment samples Interim Sediment Quality Guideline (ISQG;SAIC, 2002) 4