ORIGINAL ARTICLE

Evaluation of elemental enrichments in surface sedimentsoff southwestern Taiwan

Chen-Tung Chen Æ Selvaraj Kandasamy

Received: 5 May 2007 / Accepted: 25 June 2007

� Springer-Verlag 2007

Abstract Surface slices of 20 sediment cores, off south-

western Taiwan, and bed sediment of River Kaoping were

measured for major and trace elements (Al, As, Ca, Cd, Cl,

Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P, Pb, S, Si, Ti, V, and Zn)

to evaluate the geochemical processes responsible for their

distribution, including elemental contamination. Major

element/Al ratio and mean grain size indicate quartz-

dominated, coarse grained sediments that likely derived

from sedimentary rocks of Taiwan and upper crust of

Yangtze Craton. Bi-plot of SiO2 versus Fe2O3T suggests the

possible iron enrichment in sediments of slag dumping

sites. Highest concentrations of Cr, Mn, P, S, and Zn found

in sediments of dumping sites support this. Correlation

analysis shows dual associations, detrital and organic car-

bon, for Cr, P, S, and V with the latter association typical

for sediments in dumping sites. Normalization of trace

elements to Al indicates high enrichment factors (>2) for

As, Cd, Pb, and Zn, revealing contamination. Factor

analysis extracted four geochemical associations with the

principal factor accounted for 25.1% of the total variance

and identifies the combined effects of dumped iron and

steel slag-induced C–S–Fe relationship owing to authigenic

precipitation of Fe–Mn oxyhydroxides and/or metal sul-

fides, and organic matter complexation of Fe, Mn, Ca, Cr,

P, and V. Factors 2, 3, and 4 reveal detrital association (Ti,

Al, Ni, Pb, Cu, and V), effect of sea salt (Cl, Mg, Na, and

K) and anthropogenic component (As and Zn)-carbonate

link, respectively, in the investigated sediments.

Keywords Geochemistry � Elemental contamination �Dumping � Surface sediments � Southwestern Taiwan

Introduction

Previous research on marine pollution is considered as

abundant; however, there is still a lack of global under-

standing on the impact of anthropogenic activities on the

marine environment owing to the lack of critical evalua-

tion of elemental contamination in many studies. Metals,

including metalloid, though they are natural components

of the Earth’s crust, have widely increased their distri-

bution in the environment as a consequence of modern

industrial and human activities (Grimalt et al. 2001). For

example, on the average, the anthropogenic emissions of

As, Cd, Cu, Ni, and Zn exceed the inputs of these ele-

ments from natural sources by about twofold or more; in

the case of lead, the same ratio is about 17 (Nriagu and

Pacyna 1988). Marine sediments, especially in coastal and

estuarine regions in the vicinity of urban and harbor areas,

are becoming increasingly polluted with heavy metals

(Loring and Rantala 1992; Szefer et al. 1995). Since the

sediments integrate the external environmental effects,

caused essentially by modernization, by the way of

accumulating elemental contaminants at the rate of

accurately detectable way, they become an ultimate res-

ervoir for metals and provide input records of metals to

the ecosystem (Zwolsman et al. 1996). In addition, a

knowledge of the concentration and distribution of trace

elements in sediments plays a key role in detecting

sources of pollution in aquatic systems (Forstner and

Wittmann 1981) and, for this reason, sediments can be

investigated as an important environmental parameter in

major marine monitoring programs.

C.-T. Chen � S. Kandasamy (&)

Institute of Marine Geology and Chemistry,

National Sun Yat-Sen University,

Kaohsiung 804, Taiwan

e-mail: kselva8@yahoo.com

123

Environ Geol

DOI 10.1007/s00254-007-0916-2

The island of Taiwan has a length of 385 km with a

maximum width of 143 km and has an area of 36,000 km2

(Fig. 1). Though the island is situated near a thermal

boundary, the southern tip of the island and many offshore

islands have well-developed fringing reefs (Fujiwara et al.

2000) with high biodiversity. For instance, Taiwan’s reefs

hold 300 species of Scleractinian corals and 1,200 species

of reef fish (Dai 1997). However, tremendous economic

development at the expense of environment has brought

prosperity to Taiwan thereby increasing the GNP from 12.3

million in 1951 to 9 trillion in 2004. As a result, severe

pollution has occurred in the coastal area adjacent to Tai-

wan due to industrialization and modernization of human

community (Lin and Wang 2004). Recent study of histor-

ical changes of trace metal pollution in sediments of

southwestern Taiwan has also indicated increased metal

pollution since 1970 (Hung and Hsu 2004). Previous

researchers have concentrated their efforts on river pollu-

tion rather than coastal sediments and very few investiga-

tions have previously been published on coastal sediments

and biota of Taiwan, especially on heavy metals (Chen

1977; Hung 1994, 1995; Chen and Wu 1995; Lee et al.

1998; Chen and Chen 2001; Chen 2002) but with a general

lack of major–trace element relationship. Thus, complete

evaluation of elemental contamination and major–trace

elements relationship of coastal sediments of this oceanic

island is still rudimentary. Therefore, we present here the

concentrations of 20 major, minor, and trace elements in

surface slices (0–2.5 cm) of 20 core sediments collected

during 1995 under the environmental monitoring program

of ocean dumping sites, off southwestern Taiwan. A

representative bed sediment of River Kaoping, a major

river discharging (water: 8.5 · 109 m3 year–1; sediment:

3.6 · 108 tonne year–1) into the study area, collected dur-

ing the program was also included in order to compare the

results. The main objectives of this study are (1) to delin-

eate natural and anthropogenic levels of trace elements and

their association with major elements to deduce the pos-

sible carrier phases as well as geochemical factors that

control the levels of trace metals in the study area and (2)

to provide first environmental assessment report from the

dumping sites as it is essential for Island’s future envi-

ronmental monitoring issues related to offshore dumping.

To execute our aims, we have used normalization and

statistical techniques.

Study area

The factors adversely impacting the coastal part of south-

western Taiwan include dense population, many electro-

chemical plants, large industrial complexes, harbors, waste

dumping grounds, ocean outfalls, coal and nuclear power

plants (Lee et al. 1998). Moreover, southwestern coast of

Taiwan is famous for harbor activity as Kaohsiung Harbor

(KH), one of the world’s busiest maritime activity places,

advantageously situated in the vital sea lanes connecting

North Pacific and the Indian Ocean. This harbor is, there-

fore, home to the world’s fifth largest container port. Off-

shore part of the study area has served as iron and steel slag

disposal sites. The two squared areas in Fig. 1 served as old

and new dumping sites between 1984 and 1988 and be-

tween 1988 and 1995, respectively. To study the impact of

disposed wastes on the chemistry of sediments, 12 gravity

cores were collected in and around old and new dumping

sites. Similarly, 8 core sediments were collected from the

Fig. 1 Study area and offshore

(open circles), coastal (opentriangles), and river (filledtriangle) sampling locations.

The two squared areas represent

new and old dumping (iron and

steel slag) sites

Environ Geol

123

coastal area adjoining KH to compare and delineate the

effect of dumped iron and steel slag on the sediment

chemistry.

Materials and methods

Sampling

A suite of 20 gravity cores was collected from water depths

varying up to 537 m in and around old and new dumping

sites, off southwestern Taiwan, and near coastal region

adjoining KH (Fig. 1) during 1995 using 2 m long gravity

corer onboard the R/V Ocean Researcher III (Cruise No.

274). Samples from the top 2.5 cm, representing age ranges

from ~18 to 22 years at the prevailing sedimentation rate

(0.13 cm year–1; Hung and Hsu 2004) were carefully taken

from the each core to evaluate the levels of natural and

enhanced concentrations of different major and trace ele-

ments. One representative sample collected from River

Kaoping (Fig. 1) using a Shipek grab during the program

was included in the evaluation.

Analyses

Upon collection, pH and Eh of offshore core top samples

were measured using pH meter (Model: PHM 85 Precision)

with appropriate electrodes. The collected cores were then

capped, sealed airtight and frozen before they were brought

to shore laboratory for further investigation. Prior to de-

tailed chemical analysis, the surface slices of all the col-

lected cores were freeze dried, homogenized (removal of

particles >1 mm), and mean sediment grain size (Mz) ob-

tained using a Coulter LS-100 particle size analyzer after

proper removal of carbonate with 1 N HCl and organic

matter by 30% H2O2. Other portion of the each homoge-

nized sample of bulk sediment was finely ground (<200

mesh) in an agate mortar and organic carbon (OC) was

determined with the help of elemental analyzer (LECO

CHN-932) at 950�C in the combustion chamber with a

precision of ±1.2% (Lou and Chen 1997). Calcium car-

bonate (CaCO3) was calculated from the wt.% of sediment

inorganic carbon determined with the same elemental

analyzer after OC removal with 30% H2O2. Totally, 20

major, minor, and trace elements (Al, As, Ca, Cd, Cl, Cr,

Cu, Fe, K, Mg, Mn, Na, Ni, P, Pb, S, Si, Ti, V, and Zn)

were determined using X-ray fluorescence (XRF) spec-

trometer (Model: Rigaku RIX 2000) equipped with an Rh

tube. Briefly, 2–3 g of each sample powder was compacted

into a round disc (30 mm diameter) under 20 ton pressures

for 20 min with cellulose as backing. These pellets were

X-rayed and the measurement was carried out at an

acceleration voltage of 50 kV and a current of 50 mA. The

accuracy of the analytical method was established with

standard reference materials (SRMs), BCSS-1, MESS-1,

PACS-1, SRM 2704, and NIES-2. Based on the analyses of

reference materials, accuracy of the measurements was

within ±5% for major and trace elements such as Al (range

0.44–3.74), Ca (0.11–0.57), Cl (0.21–4.84), Cr (0.26–2.82),

Fe (0.44–4.65), K (0.10–1.43), Mg (0.56–3.08), Ni (0.26–

3.60), Si (0.11–2.24), Ti (0.70–4.06), and Zn (0.40–2.72).

The same was ±10 for Cd (2.55–8.92), Cu (0.38–8.90), Mn

(0.70–8.70), Na (0.60–8.54), P (0.13–5.48), Pb (0.29–4.02),

S (0.37–8.96), and V (1.49–8.91). Arsenic however shows

higher error of ±25% (1.46–24.43) likely because of its

metalloid nature. Three replicates of one sample were run

and the following coefficient of variation obtained: Al,

0.44%; As, 2.04%; Ca, 0.76%; Cd, 7.02%; Cl, 0.38%; Cr,

5.97%; Cu, 0.95%; Fe, 0.43%; K, 0.58%; Mg, 0.84%; Mn,

0.60%; Na, 4.97%; Ni, 1.86%; P, 0.29%; Pb, 3.04%; S,

0.34%; Si, 0.58%; Ti, 0.39%; V, 6.13%, and Zn, 2.22%.

Moreover, mean grain size and OC were not carried out in

bed sediment of River Kaoping due to its coarse, sandy

nature.

Results and discussion

Major element geochemistry

Coastal and offshore sediments are, in general, mixtures of

aluminosilicates and carbonate debris. Therefore, evalua-

tion in terms of element/Al ratios would normally yield

better understanding of elemental behaviors because such

ratios can be interpreted in terms of the texture and min-

eralogy (Calvert et al. 1993). For the purpose of initial

appraisal of sediment composition and provenance, we

have used different reference materials such as the upper

continental crust (UCC; Taylor and McLennan 1985), up-

per crust of Yangtze Craton (UC-YC; Gao et al. 1998) and

different shale compositions. The mean Si/Al ratios of

offshore and coastal sediments (3.42 and 3.89; Table 1)

were close to this ratio in average shale (3.13; Turekian and

Wedepohl 1961) and the UCC (3.85). The entire Si/Al

range (2.89–4.48) of coastal and offshore sediments further

well corresponds to Si/Al ratios of different shale compo-

sitions such as average shale, Post-Archean Australian

Shale-PAAS (2.94; Taylor and McLennan 1985) and North

American Shale Composite-NASC (4.66; Gromet et al.

1984). This suggests that the sediments are chemically

similar to shales, especially offshore sediments which are

all composed of fine to very fine silts (Mz range 6.47–

15.08 lm). However, the bed sediment of River Kaoping

shows very high Si/Al ratio (5.16), even higher than the

UCC and UC-YC (4.17), which was attributed most likely

to sandstone mineralogy, a dominant rock type in the

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123

drainage basin of this river. The obtained Si/Al variations

appear to be produced by variations in the quartz and K-

feldspar (Si/Al = 3.1) contents rather than illite (1.7) and

kaolinite (1.2). According to Turekian and Wedepohl

(1961), the Si/Al ratio of 3 in sediments is taken as an

index of the presence of detrital clay minerals. The higher

Si/Al ratios (>3) obtained in all our samples (except one

sample, CS6; Table 1) further indicate the dominance of

sand and silt grains with higher amount of quartz and

feldspars rather than clays due to Island’s highest erosion

but moderate chemical weathering rates (Selvaraj and Chen

2006). Our size analysis also showed quite similar infer-

ences: mean sediment grain sizes (6.47–15.08 lm; Ta-

ble 2) of offshore sediments show their fine and very fine

silty nature in contrast to coarser (65–452 lm) coastal

sediments which all fall under medium, fine and very fine

sand classes of siliclastic sediments of Shipboard Scientific

Party (2003) modified after Wentworth (1922). Calvert

et al. (1993) have also found highly variable ratios of Si/Al

in the coarse-grained, shallower surface sediments of South

China and Sulu Seas due essentially to variable proportions

of quartz and feldspars relative to clays.

Aluminum is believed to be an index element for the

terrigenous source (e.g., Nath et al. 1989) and both Ti and

Al are refractory elements which are extremely immobile

in the marine environment (Bischoff et al. 1979). The mean

ratios of Ti/Al in offshore and coastal sediments are 0.054

and 0.049 (Table 1), respectively, and these ratios are more

close to this ratio in UC-YC (0.053) and average compo-

sition of sedimentary rocks of Taiwan (ACST; 0.049;

Selvaraj and Chen 2006), suggesting that offshore and

coastal sediments were likely derived from upper crust of

Yangtze Craton and sedimentary rocks (metapelite, phyl-

lite, sandstone, and shale) of Taiwan, respectively. This

inference is further supported by the Ti/Al ratio (0.049) of

bed sediment of River Kaoping which was very similar to

the mean Ti/Al of coastal sediments. The mean Fe/Al ratios

of offshore and coastal sediments (0.49 and 0.47) closely

resemble the Fe/Al of UC-YC (0.50) and ACST (0.44;

Table 1), suggesting the absence of authigenic iron min-

erals in sediments. In other words, the iron presents in the

sediment was mostly in structural position of aluminosili-

cates. The mean, higher Ca/Al ratios of 0.22 and 0.21 for

offshore and coastal sediments were probably attributed to

shell materials and lower ratio of 0.18 found in the bed

sediment of River Kaoping supports this. The ratios are,

however, slightly lower than UC-YC (0.26), revealing the

initial loss of Ca from Ca-silicates during chemical

weathering process. Similarly, the mean ratios of Mg/Al,

K/Al, and P/Al of offshore and coastal sediments show

close association with these ratios in UC-YC and ACST.

Exceptionally, the Na/Al ratios in most of the sediments

were low when compared to crustal materials and ACST

indicating significant loss of Na, similar to Ca, because

both elements are, in general, dissolved easily during initial

stages of weathering processes.

Table 1 Mean major element/Al ratios in surface sediments, off southwestern Taiwan, and bed sediment of River Kaoping, compared with

major element/Al ratios of UCC, UC-YC, ACST, and average shale

Si/Al Ti/Al Fe/Al Ca/Al Mg/Al Na/Al K/Al P/Al

Offshore sediments (water depths: 105–537 m)

Minimum 2.89 0.052 0.42 0.064 0.13 0.077 0.25 0.005

Maximum 3.85 0.057 0.77 0.40 0.21 0.13 0.29 0.012

Mean 3.42 0.054 0.49 0.22 0.15 0.10 0.28 0.007

SD (N = 12) 0.28 0.001 0.09 0.11 0.03 0.01 0.01 0.002

Coastal sediments (water depths: <100 m)

Minimum 3.23 0.041 0.39 0.14 0.11 0.076 0.24 0.003

Maximum 4.48 0.056 0.57 0.34 0.28 0.25 0.39 0.007

Mean 3.89 0.049 0.47 0.21 0.16 0.14 0.30 0.005

SD (N = 8) 0.48 0.004 0.07 0.07 0.07 0.07 0.06 0.002

Bed sediment, River Kaoping 5.16 0.049 0.51 0.18 0.12 0.15 0.26 0.006

UCCa 3.85 0.038 0.44 0.38 0.16 0.36 0.35 0.008

UC-YCb 4.17 0.053 0.50 0.26 0.19 0.29 0.29 0.018

ACSTc 4.66 0.049 0.44 0.13 0.14 0.18 0.32 0.005

Average Shaled 3.13 0.052 0.54 0.18 0.17 0.07 0.30 0.008

a Taylor and McLennan (1985)b Gao et al. (1998)c Selvaraj and Chen (2006)d Turekian and Wedepohl (1961)

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Major elements such as Mg (–0.86), K (–0.84) Fe

(–0.75), Ca (–0.53), and Na (–0.53) show significant neg-

ative correlations with Si (Table 3) indicating the presence

of quartz-rich sand and silt. The negative correlations of Si

with almost all the major and trace elements as well as Cl,

OC, and S (Table 3) indicate dilution of particulate trace

elements by sandy, detrital sediments. The contrast in

composition between quartz-rich sand and heavy mineral-

rich sand has been clearly depicted by the negative corre-

lation between SiO2 and Al2O3, Fe2O3, and MgO in shelf

sediments of the Gulf of the Farallones (Dean and Gardner

1995). A plot between SiO2 and Fe2O3T (Fig. 2a) shows a

deviation (marked with a dashed line) from its original

negative trend due to iron enrichment which is attributable

to dumped slag materials. It is also evident that because of

iron enrichment, SiO2 value was reduced around 5%

(detrital dilution) in the sample CS12 collected from the

new dumping site when compared to the surrounding

samples. This inference is further substantiated by the Fe/

Al ratio of sample CS12 which shows 0.77 (Table 1). This

ratio is higher than 0.69, the value indicating the presence

of Fe held in structural position of aluminosilicates (Cal-

vert 1976), and suggestive of incorporation of iron into

sediment from slag materials. All other samples showing

Fe/Al ratio lower than 0.69 reveals that Fe in all the sed-

iments was associated with aluminosilicate. The linear

relationship between Al and K (r = 0.45; Table 3) suggests

the presence of illite, a product of moderate chemical

weathering, which is well in accordance with the X-ray

diffraction (XRD) patterns of these samples (Chen 1997).

Overall, the major element/Al ratios suggest that the

sediments are coarse-grained (sand and silt sizes), quartz-

dominated, authigenic Fe-free and moderately weathered

products of sedimentary rocks of Taiwan and UC-YC,

especially the latter source for offshore sediments. The

above interpretations are well consistent with their mean

values of weathering indices such as Chemical Index of

Alteration (CIA; 74, 73, and 63 for offshore, coastal, and

river sediments) and Plagioclase Index of Alteration (PIA;

84, 83, and 66); both show moderate chemical weathering

condition in Taiwan (Selvaraj and Chen 2006). Further-

more, the above inferences are well corroborated with

Table 2 Data of major elements, mean grain size (Mz), calcium carbonate (CaCO3) and organic carbon (OC) in surface sediments off

southwestern Taiwan

Sample Major elements (%)

Si Ti Al FeT Mg Ca Na K P Cl S Mz (lm) CaCO3 (%) OC (%)

Offshore sediments (water depth: 105–537 m)

CS4 30.1 0.43 7.81 3.30 1.08 1.50 0.73 2.10 0.05 0.03 0.04 9.36 2.41 0.57

CS5 29.3 0.46 8.16 3.60 1.13 1.60 0.74 2.30 0.05 0.04 0.03 9.71 4.74 1.05

CS6 26.9 0.53 9.32 5.00 1.28 0.60 0.72 2.70 0.05 0.14 0.11 6.47 4.74 1.01

CS8 29.9 0.42 7.92 3.60 1.05 1.40 0.82 2.00 0.07 0.18 0.05 10.7 5.97 0.76

CS10 27.5 0.44 8.01 3.90 1.14 1.80 1.06 2.20 0.06 0.63 0.11 13.9 4.74 1.42

CS12 25.4 0.43 7.83 6.00 1.55 3.10 0.82 2.30 0.09 0.33 0.13 7.67 6.34 1.60

CS13 28.0 0.48 9.00 4.20 1.16 1.10 1.04 2.60 0.05 0.39 0.04 8.28 4.74 0.82

CS14 29.1 0.47 8.49 3.90 1.09 1.30 0.86 2.30 0.06 0.07 0.04 15.1 4.74 0.90

CS15 27.5 0.43 8.23 3.90 1.41 3.30 0.87 2.20 0.06 0.21 0.06 8.26 4.74 1.24

CS17 28.2 0.48 8.64 4.00 1.21 1.40 0.88 2.50 0.05 0.20 0.06 8.09 4.66 0.90

CS19 28.3 0.41 7.73 3.60 1.66 2.80 0.89 2.00 0.07 0.24 0.09 13.4 2.26 1.36

CS21 28.8 0.43 8.25 3.60 1.07 1.30 0.91 2.30 0.06 0.21 0.05 9.25 6.71 0.92

Coastal sediments (water depth <100 m)

HB005 24.1 0.38 7.47 4.26 2.09 2.56 1.76 2.92 0.04 0.85 0.06 102.6 6.68 0.30

HBT01 29.0 0.49 8.77 4.00 1.13 1.40 0.67 2.34 0.06 0.03 0.06 64.7 5.44 0.44

K1 25.3 0.32 7.25 4.08 2.01 2.28 1.82 2.84 0.03 0.81 0.01 451.7 4.10 0.12

KN2 31.2 0.35 7.58 3.32 0.96 1.38 0.78 2.07 0.05 0.02 0.02 380.0 4.54 0.08

KN12 31.4 0.38 7.50 3.43 1.01 1.35 0.77 2.00 0.05 0.02 0.04 197.0 3.74 0.29

KS2 31.5 0.39 7.47 3.28 1.00 1.27 0.75 2.01 0.05 0.02 0.03 145.7 4.56 0.16

KS11 31.7 0.36 7.70 3.20 0.95 1.09 0.77 2.13 0.04 0.01 0.02 330.0 4.32 0.13

S1 34.0 0.31 7.59 2.98 0.82 1.51 0.94 1.80 0.03 0.02 0.03 239.0 4.77 0.22

Bed sediment, River Kaoping

RK 33.8 0.32 6.56 3.32 0.78 1.19 0.97 1.72 0.04 0.04 0.03 ND ND ND

ND not determined, FeT total Fe, OC organic carbon

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XRD patterns of these samples which all, except for bed

sediment of River Kaoping that was not analyzed for

minerals, show quartz–feldspars–calcite–illite–chlorite–

kaolinite assemblage (Chen 1997).

Trace element geochemistry

Table 4 compares the range and mean concentrations of

total trace metals, including Fe, for the sediments studied

with those obtained for other areas of Taiwan, East China

Sea, the UCC, UC-YC, ACST and average shale as well as

fresh and recovered iron and steel slag. Cadmium values of

coastal and offshore surface sediments are within the range

of reported concentrations of Cd in sediments of other

areas of Taiwan coast. However, our Cd values (maximum

1.2 lg g–1), including bed sediment of River Kaoping

(RK), are lower than those in sediments from Kaohsiung

River (KR; maximum 1.91 lg g–1; Chen and Wu 1995)

and KH (maximum 6.6 lg g–1; EPA 1992; Chen and Wu

1995). Table 4 demonstrates, in general, the high concen-

trations of Cr in offshore than coastal sediments (Table 5),

possibly attributed by dumped iron and steel slag which

contains considerable amount of Cr, the metal used to

harden steel to manufacture stainless steel alloys. Bed

sediment of RK shows low concentrations of Cr than

coastal and offshore sediments and the value is low against

the reported Cr in sediments of KH (EPA 1992; Hung

1994) and ACST, but higher with respect to coastal sedi-

ments of other parts of Taiwan and East China Sea. Sim-

ilarly, our Cu values are comparable to other coastal

sediments of Taiwan and the values are low with respect to

harbor sediments. We also obtained very low concentration

of Cu (14 lg g–1; Table 4) from bed sediment of River

Kaoping, which is suggestive of uncontaminated condition

especially with this metal; the situation is contrary to

abnormal Cu concentrations (200–5,000 lg g–1) observed

in sediment and oyster samples of the northwestern Taiwan

(Lin and Hsieh 1999).

Iron shows higher values in offshore sediments and the

values are higher than previously reported values except

shelf sediments of East China Sea, where this element

shows comparatively higher values (Table 4); however, all

our values are lower than the UCC, except two samples,

CS6 and CS12, which show very high values of 5 and 6%,

respectively; both fall in the new dumping site (Fig. 1).

Strikingly, the highest values of Cr (158 lg g–1), Mn

(2,773 lg g–1), P (907 lg g–1), S (1,267 lg g–1), and Zn

(219 lg g–1) are associated with CS12 (Table 5), revealing

the influence of dumped iron and steel slag materials on the

chemistry of sediments. It is well known that steel contains

significant amount of impurities like phosphorous and

sulfur. The other alloying elements such as Cr, Co, Cu, Mo,

Ni, Ti, and V are added to improve corrosive strength,

high temperature, and mechanical properties of steel. In

Table 3 Correlation coefficients (r) between different pairs of variable (N = 21)

Si Ti Al Fe Mg Ca Na K P S As Cd Cr Cu Mn Ni Pb V Zn Mz

Al 0.90

Fe –0.75 0.47

Mg –0.86 0.52

Ca –0.53 0.68

Na –0.53 0.74

K –0.84 0.45 0.58 0.72 0.59

P 0.56 0.54

Cl –0.77 0.81 0.48 0.89 0.69

S –0.51 0.50 0.71 0.69

Cr –0.59 0.52 0.79 0.53 0.83 0.78

Cu –0.66 0.63 0.53 0.44 0.56 0.46 0.45

Mn 0.55 0.68 0.70 0.68 0.81

Ni 0.78 0.60 0.57

Pb 0.54 0.49 0.69 0.59 0.55 0.70

V –0.47 0.81 0.78 0.66 0.63 0.67 0.71 0.44 0.46

Zn 0.48 0.62

Mz –0.81 –0.62 –0.71 –0.60 0.45 –0.61 –0.59 –0.55 –0.74

CaCO3 0.46 0.45

OC –0.49 0.62 0.48 0.57 0.76 0.78 –0.50 –0.50 0.79 0.70 0.79 –0.78

Bold values are significance at the 0.01 level and others are at the 0.05 level

Mz mean grain size, CaCO3 calcium carbonate, OC organic carbon

Environ Geol

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addition, the significant amount of Mn acts as an important

components of steel (Fe: 80–98%; Mn: 0.2–16%; C: 0.03–

1.25%; P: maximum 0.05%; S: maximum 0.05%). Steel

slag or scrap also consist significant amount of metals such

as Cr, Ni, V, and Mo. Coastal and river sediments show

lower concentrations of Mn with respect to UC-YC and

this element has not been reported previously from our

coast except one report (Lee et al. 2000) which shows a

consistent range (Table 4). It is interesting to note, how-

ever, that many offshore samples have higher concentra-

tions of Mn. Abnormal Mn values (2,773 and 2,475 lg g–1)

associated with new and old dumping sites clearly indicate

the influence of dumped materials and further supported by

very high concentrations of Mn obtained from fresh

(11,000 lg g–1) and recovered slag (14,347 lg g–1) (Chen

and Hungspreugs 1996; Table 4). Relatively low value of

Mn in old dumping site suggests dilution of contaminants

probably by recent sediments through natural attenuation

processes as observed in historical dumping site in Baltic

Sea (Leipe et al. 2005). Table 4 also shows, when com-

pared to the previously reported values, lower concentra-

tions of Ni and the values are lower than the average shale.

In contrast, the highest concentrations of offshore and

coastal sediments (46 and 40 lg g–1) appear to be higher

than Ni values in source materials, ACST and UC-YC as

well as UCC, suggesting Ni enrichment in few locations.

Lead and zinc are mostly higher than reference and source

compositions, UCC, UC-YC, and ACST, as well as other

coastal sediments of Taiwan, which likely reveal contam-

ination, although the values of these elements in our study

are fivefold lower than the reported values in sediments of

KH (EPA 1992; Hung 1994).

The entire geochemical data set including mean grain

size and OC of current study was subjected to correlation

analysis in order to explore the possible associations

existing between different variables. Table 3 shows a

correlation matrix for the parameters studied where tita-

nium, a detrital indicator, is positively correlated with Al

(0.90), V (0.81), Ni (0.78), Cu (0.63), and P (0.56). It re-

veals the association of V, Ni, and Cu in lattices of alu-

minosilicate minerals of continental origin and thereby

suggests the natural variability of these metals in the sed-

iments. This is further supported by the positive relation of

Al with V (0.78) and Ni (0.60). Iron exhibits positive

covariance with Cr, S, and V and this association probably

was induced by dumped materials because all these ele-

ments are important ingredients in the process of manu-

facturing different grades of steel. It is clear from Table 3

that the positive correlations among P, Cr, OC, Mn, Pb, S,

and V are mainly related to anthropogenic inputs and re-

flect the complexing nature of OC/matter. Note (Table 3)

that Cr, V, S, and P show dual associations, detrital (Ti and

Al) and OC, and these associations are conveniently

interpreted as normal and dumped material induced con-

ditions, respectively, in the study area. Recent study on

coastal sediments of southwestern Taiwan has also sug-

gested the relative enrichment of metals in areas of high

mud and OC contents (Hung and Hsu 2004). Mean grain

size, however, invariably exhibits negative or insignificant

Fig. 2 Plots of a SiO2 versus Fe2O3T, b OC versus S, and c OC versus

S/Fe total. Dashed line in top panel represents the iron enrichment in

sediments (CS12 and CS6) of new dumping site. Also note the

enrichment of sulfur (middle panel) and S/Fe ratio (lower panel) in

sediments (CS6, CS10, CS12, and CS19) of dumping sites

Environ Geol

123

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Environ Geol

123

correlations with almost all the elements studied here, ex-

cept Cd (r = 0.45; Table 3), suggesting weak granular

affinity of elements.

Normalization and enrichment factors

Normalization is a technique used to separate the metals of

natural variability from the metal fraction that is associated

with sediments due to modern activities. Normalization of

estuarine and coastal sediment trace elements data has been

achieved, in specific, by using Al (Windom et al. 1989), Fe

(Morse et al. 1993), Li (Loring 1991), Yb (Szefer et al.

1999; Szefer 2002), OC (Daskalakis and O’Connor 1995),

and grain size (Palanques and Diaz 1994). Among these

proxies, Al is a conservative element and has been widely

used objectively to compensate for variations in both grain

size and composition. Besides, anthropogenic input of Al is

a very rare phenomenon. The characteristic advantages of

Al normalization over other proxies have been mentioned

elsewhere (Loring and Rantala 1992; Rubio et al. 2000;

Selvaraj et al. 2004). Normalization can also be applied to

determine enrichment factors (EFs) which provide a tool to

evaluate sediment quality. EFs close to unity point to

crustal origin and >10 are considered as non-crustal sour-

ces (Nolting et al. 1999). Since our major element/Al ratio

(see major element geochemistry section) indicates the

upper crust of Yangtze Craton (Gao et al. 1998) and

average composition of sedimentary rocks of Taiwan

(Selvaraj and Chen 2006) as the sources for offshore and

coastal sediments, respectively, we have chosen these two

reference materials to calculate EFs employing the equa-

tion: EF = (Metal/Al)Sediment/(Metal/Al)UC-YC/ACST.

The calculated EFs for the elements As, Cd, Cr, Cu, Mn,

Ni, Pb, V, and Zn in the studied sediments are presented in

Table 6. Enrichment factors calculated with respect to UC-

YC show higher mean values for Pb (2.65) and Cd (2.46),

well-established metals of anthropogenic origin, in off-

shore sediments. Metals such as Zn, Cr, As, and Mn are

also have EFs >1 thereby suggest their enrichments in

offshore sediments likely due to dumped iron and steel

slag. Similarly, mean EFs calculated with respect to ACST

were higher unity for Pb, Ni, Cu, Mn, V, and Zn, indicating

Table 5 Data of trace elements and physicochemcial parameters (Eh and pH) in surface sediments off southwestern Taiwan

Sample Trace elements (lg/g)

As Cd Cr Cu Mn Ni Pb V Zn pH Eh (mV)

Offshore sediments (water depth: 105–537 m)

CS4 5.0 0.20 78 31 393 38 41 100 92 7.88 113

CS5 1.0 0.25 81 33 356 40 47 114 99 7.31 155

CS6 6.2 0.20 105 40 573 46 53 141 118 7.36 146

CS8 3.2 0.22 85 44 655 42 57 92 109 7.06 149

CS10 5.7 0.18 83 41 647 40 47 109 113 7.97 200

CS12 10.5 0.15 158 31 2,773 36 61 134 219 8.61 88

CS13 3.0 0.24 82 37 439 42 50 109 106 7.43 110

CS14 5.9 0.27 81 37 711 40 51 118 105 7.52 112

CS15 7.9 0.22 111 42 1,162 36 41 106 95 7.95 102

CS17 2.9 0.19 87 36 482 40 45 102 102 7.73 120

CS19 3.5 0.21 108 36 2,475 37 44 100 91 8.12 96

CS21 7.4 0.24 105 45 660 42 67 102 119 7.52 240

Coastal sediments (water depth <100 m)

HB005 14.5 0.60 84 57 371 37 45 81 198 ND ND

HBT01 19.9 0.29 96 49 379 40 53 101 244 ND ND

K1 7.2 0.22 64 26 357 36 42 68 163 ND ND

KN2 BDL 0.88 69 26 369 35 47 84 132 ND ND

KN12 17.8 1.20 76 30 368 37 53 74 143 ND ND

KS2 23.9 0.28 72 31 365 36 46 87 162 ND ND

KS11 BDL 0.43 67 27 356 36 42 70 140 ND ND

S1 BDL 0.33 56 14 390 26 21 87 85 ND ND

Bed sediment, River Kaoping

RK 15.2 0.23 58 14 320 38 40 54 94 ND ND

ND not determined, BDL below detectable limit (<0.1 ppm)

Environ Geol

123

sediment contamination, despite the EFs of studied metals

vary significantly based on the reference materials used.

Coastal sediments also exhibit higher mean EFs for Cd

(6.98), As (2.77), Pb (2.48), and Zn (2.17) with respect to

UC-YC, which further supports the above inference. It has

been previously shown (Selvaraj and Chen 2006) that

coastal sediments of Taiwan were mainly derived from the

sedimentary rocks in Taiwan, and our EF calculation over

ACST further reveals contaminated condition of coastal

sediments by metals such as Pb, Zn, Ni, and Cu (Table 6).

Bed sediment of River Kaoping reveals more or less sim-

ilar results that also shows higher enrichment factors for As

(4.76), Cd (3.34), and Pb (2.65) against UC-YC but Pb

(2.16), Ni (1.86), and Zn (1.28) against ACST, indicating

considerable input of contaminated sediment through river

into the coastal zone.

It is worth mentioning here that our calculation of EFs

with respect to the UCC (not shown in Table 6) shows

polluted nature of coastal sediments in terms of As (EFs

range 5.33–17.06; mean 8.21) but contaminated condition

for offshore sediments (EFs range 1.78–7.15; mean 3.18).

Although very high EF values obtained especially for As

and Cd in offshore and coastal sediments with respect to

the UC-YC indicate contaminated nature of sediments

(Table 6), lower EF values of these elements with respect

to real sources, UC-YC and ACST as revealed by element/

Al ratios, when compared to UCC, suggestive of two

points: (1) the UCC cannot be used as a reference material

to calculate EFs and, in turn, to study anthropogenic impact

on sediments derived from this small island (0.024%) of

the earth’s surface as we normally do for sediments that

integrate weathered materials from the larger continental

Table 6 Summary statistics of enrichment factors (EFs) with respect to upper crust of Yangtze Craton (UC-YC) and average composition of

sedimentary rocks of Taiwan (ACST) in sediments, off southwestern Taiwan, compared with EFs from other areas of Taiwan

As Cd Cr Cu Mn Ni Pb V Zn

Offshore sediments—EFs with respect to UC-YCa

Minimum 0.25 1.82 1.02 0.83 0.42 0.87 2.17 0.90 1.22

Maximum 2.76 3.03 2.26 1.17 3.39 1.06 3.54 1.33 2.96

Mean 1.29 2.46 1.32 0.97 1.12 0.96 2.65 1.04 1.46

SD 0.68 0.37 0.35 0.13 1.02 0.05 0.45 0.12 0.48

EFs with respect to ACSTb

Minimum – – 0.69 1.22 0.47 1.41 1.76 1.10 1.03

Maximum – – 1.54 1.71 3.81 1.71 2.87 1.62 2.51

Mean – – 0.90 1.41 1.26 1.55 2.16 1.26 1.24

SD – – 0.23 0.18 1.14 0.08 0.37 0.15 0.41

Coastal sediments—EFs with respect to UC-YC

Minimum 2.05 2.89 0.82 0.39 0.41 0.69 1.20 0.71 1.18

Maximum 6.58 15.24 1.27 1.62 0.49 0.99 3.09 0.91 2.94

Mean 2.77 6.98 1.06 0.89 0.46 0.92 2.48 0.83 2.17

SD 2.61 4.33 0.15 0.37 0.02 0.10 0.56 0.08 0.56

EFs with respect to ACST

Minimum – – 0.56 0.57 0.46 1.10 0.98 0.86 1.00

Maximum – – 0.86 2.36 0.55 1.60 2.52 1.10 2.49

Mean – – 0.72 1.30 0.52 1.48 2.02 1.00 1.84

SD – – 0.10 0.54 0.03 0.16 0.45 0.09 0.48

Bed sediment, River Kaoping

EFs with respect to UC-YC 4.76 3.34 0.99 0.45 0.47 1.16 2.65 0.64 1.51

EFs with respect to ACST – – 0.97 0.66 0.52 1.86 2.16 0.78 1.28

Kaoping coastal sediments – 0.16 0.85 – – 0.53 1.20 – 1.18

Southwestern Taiwanc – 1.65 2.92 – – 2.38 4.94 – 3.50

Kaohsiung coast, Southwestern Taiwand – 1.20 0.60 0.90 – 1.50 4.50 – 3.40

a Gao et al. (1998)b Selvaraj and Chen (2006)c Hung and Hsu (2004)d Lee et al. (1998)

Environ Geol

123

landmass and (2) very high EF values of As and Cd might

also be related to the method of analysis applied in this

study which showed wider error limits for these elements

(see Materials and Methods Section) rather than real situ-

ation of sediments. Nonetheless, the decreasing order of

mean EFs in sediments of offshore with respect to UC-YC

(Pb > Cd > Zn > Cr > As > Mn > V > Cu > Ni) and the

coastal (Pb > Zn > Ni > Cu > V > Cr > Mn) and river

(Pb > Ni > Zn > Cr > V > Cu > Mn) environments with

respect to ACST clearly suggest that the offshore and

costal sediments are burdened with metals such as Cd, As,

Pb, and Zn with EFs >2.

Factor analysis

Geochemical factor analyses are highly suitable for deter-

mining the factors that control the trace metal distribution

than measurement of absolute metal concentrations in

specific size grains or the use of metal/normalizing element

ratios (Loring 1991; Winters and Buckley 1992). This is

because such studies can provide information about the

association of metal-inorganic or metal-organic phases.

Therefore, to decipher significant grouping of factors and

related possible geochemical controlling processes, the

whole sediment geochemical data including mean grain

size, CaCO3 and OC were subjected to factor analysis

using SPSS software (Version 7.5). The factors were ex-

tracted using Varimax rotation scheme with Kaiser Nor-

malization.

The results show that four factors account for 80.9% of

total variance (Table 7). Factor 1 account for 25.1% of

variance and Mn, Cr, P, S, OC, Ca, Fe, and V are loaded in

this factor. Association of OC, S, and P with redox sensi-

tive elements (Mn, Fe, and V) suggests the oxygen

depletion condition; it might be a temporary, local phe-

nomenon, and active oxidation-reduction processes near

the sediment-water interface. Further, the above associa-

tion is very characteristic feature of only two samples,

CS12 and CS19, which fall in the new and old dumping

sites (Fig. 1). The oxygen depletion is also supported by

high concentrations of S (1,267 and 940 lg g–1) in these

samples. Metals associated with sediments behave differ-

ently in anoxic/suboxic and oxic conditions which essen-

tially depend on physicochemical characteristics (pH, Eh,

and O2) of the depositional environment. For instance, oxic

depositional environment always have high Eh when

compared to suboxic environment where the Eh is often

low. Very high values of pH (8.61 and 8.12) and low values

of Eh (96 and 88) measured in the sediments of new and old

dumping sites were possibly as a result of production of

hydroxide ions during the dissolution of slag according to

equation: H2O + FeS M Fe2+ + HS– + OH–. Such disso-

lution was possible due to the relative solubility of

iron sulfides like pyrrhotite (Fe1–xS) and/or mackinawite

(FeS1–x) present in the slag when it sinks few cm below the

sediment-water interface due to its higher density to the

zone of low concentration of oxygen as also experimentally

demonstrated by Vdovic et al. (2006). Librated Fe2+ along

with Mn2+ which migrated upward in the sediment column

pore-water as dissolved species and oxidized as Fe3+ and

Mn4+ and get precipitated either as Fe–Mn oxyhydroxides

in the presence of free hydroxyl ions (OH–) or metal sul-

fides because of HS–. Increase of phosphate values around

100–400 lg g–1 in samples of dumping sites (Table 2)

suggests an adsorption of phosphate on iron hydroxides as

indicated by their statistically significant correlation

(r = 0.54; Table 3). Among the 12 samples collected in

and around the old and new dumping areas, CS12 exhibits

highest OC (1.60%) and pH (8.61) as well as lowest Eh

(88 mV), authenticating the presence of low oxygen con-

centration compared to the oxygen levels in coastal sedi-

ments studied. Sample CS12 therefore invariably shows

highest enrichment factors calculated with respect to UC-

YC for the elements such as As (2.76), Cd (3.03), Cr (2.26),

Mn (3.39), Pb (3.54), and Zn (2.96). This condition can

most likely be attributed to dumping of slag materials

Table 7 Varimax rotated factor matrix (N = 21)

Variable Factor 1 Factor 2 Factor 3 Factor 4

Si –0.39 –0.36 –0.83 0.00

Ti 0.29 0.92 0.00 0.00

Al 0.12 0.87 0.00 –0.16

Fe 0.61 0.37 0.44 0.22

Mg 0.28 0.00 0.91 0.00

Ca 0.67 –0.41 0.49 0.00

Na –0.23 –0.28 0.90 0.00

K 0.00 0.47 0.82 0.00

P 0.83 0.37 –0.16 0.26

Cl 0.00 0.00 0.93 0.00

S 0.79 0.31 0.13 0.00

As –0.11 –0.29 –0.16 0.79

Cd –0.31 –0.27 –0.14 0.48

Cr 0.89 0.32 0.13 0.17

Cu 0.20 0.64 0.40 0.27

Mn 0.94 –0.15 0.00 0.00

Ni 0.00 0.87 0.00 0.00

Pb 0.33 0.61 0.00 0.49

V 0.58 0.67 0.00 –0.19

Zn 0.17 0.00 0.31 0.84

Mz –0.54 –0.66 0.00 0.23

CaCO3 0.00 0.29 0.24 0.53

OC 0.80 0.41 0.00 –0.34

Eigen values 8.91 4.49 2.84 2.34

Percent explained 25.1 24.1 20.7 11.0

Environ Geol

123

where the top 10 cm of our sediment core shows slag-

dominated sediments. Dumping-induced precipitation of

authigenic Fe–Mn oxyhydroxide and complexation of or-

ganic matter with Fe, Mn, and Cr observed here are in good

agreement with earlier observations of the association of

organic matter with Fe, Mn (Krom and Sholkovitz 1978)

and Cr (Selvaraj et al. 2004).

Furthermore, Table 3 demonstrates that the variables

associated with factor 1 are controlled essentially by four

components, i.e. OC–Fe–P–S. Among these, C–S–Fe

relationships in marine sediments have been used to

determine palaeoredox conditions in the environment of

deposition (e.g., Berner 1970, 1984; Raiswell and Berner

1985; Passier et al. 1996). Since the above association is

typical for sediments of dumping sites, we speculate that

the dumped iron and steel slag likely facilitate the above

association. A cross-plot of OC versus sulfur (Fig. 2b)

shows that the dumping site sediments (CS6, CS10, CS12,

and CS19) are relatively enriched in sulfur (940–

1,267 lg g–1) with low OC/S ratios of 9–14 when com-

pared to the surrounding sediments (OC/S: 16–40). Al-

though our OC/S range of sediments in dumping sites is

well consistent with established TOC/S ratios (range 3–13;

average 2.8) of normal modern marine sediments (Berner

and Raiswell 1984), their sulfur and iron enrichments

support strong C-S-Fe relationship, a characteristic feature

of redox condition which facilitates normally the formation

of pyrite. Our speculation is further supported by the sig-

nificant positive relationship between OC and S/FeT

(Fig. 2c), a measure of the degree of pyritization of the iron

(Gibson 1985), in sediments of dumping sites.

Factor 2 explains about 24.1% of variance and is char-

acterized by high loading for Ti, Al, Ni, Pb, Cu as well as V.

Correlation between Al and Ti is very high (0.90; Table 3)

and both Ti and Al are refractory elements which are ex-

tremely immobile in the marine environment (Bischoff et al.

1979). Therefore, Ti and Al in these sediments are consid-

ered to be of detrital origin. The association of Ni, Pb, Cu,

and V with detrital elements indicates the considerable ter-

rigenous input of these elements in the study area. This

inference, however, contrasts with the EFs of these elements

which all show the mean EF > 1, which further suggests

dual, including anthropogenic, sources for these metals.

Variables such as Cl, Na, Mg, and K are loaded in factor

3 which accounts for 20.7% of variance. This factor can

explain the effect of sea salt; the samples were not washed

free of salts. The presence of Mg2+ in this factor could be

due to the fact that it replaces Na2+ (Nath et al. 1989).

Association of K in this factor further suggests the presence

of sea salt mostly on illite, the dominant clay mineral in the

analyzed sediments (Chen 1997). Factor 4 accounting for

11.0% of total variance is characterized by high loading

of trace metals As and Zn, less likely Pb and Cd, along

with carbonate. This factor, without significant positive

emphasis on metal variables such as grain size, OC, Al, Fe

or Mn, strongly suggests anthropogenic source for these

metals and association with carbonate. Very high EF values

for these elements, especially As and Cd with respect to

UC-YC (Table 6), further authenticate the industrially

influenced As and Cd in the analyzed sediments and also

consistent with the high bioconcentration factors of these

elements in terrestrial biota of Taiwan (Hsu et al. 2006).

Conclusion

Concentrations of major elements and their ratios with Al

as well as mean grain size demonstrate that silty offshore

and sandy coastal sediments off southwestern Taiwan are

weathered products of upper crust of Yangtze Craton and

sedimentary rocks of Taiwan, respectively. Comparative

study of trace elements with published results indicates

higher Mn and Fe levels in sediments of dumping sites.

Correlation analysis differentiates the metals (V, Ni, and

Cu) of natural variability from elements (P, Cr, Mn, Pb,

and S) that are influenced by dumped iron and steel slag-

induced redox processes. Normalization of total trace

metals to Al and their ratios with reference materials

(UCC, UC-YC, and ACST) demonstrated the higher mean

enrichment factors (>2) for As, Cd, Pb, and Zn, reveal

contamination of sediments by these metals from anthro-

pogenic sources. Factor analysis reveals four dominant

geochemical associations: (1) dumped iron and steel slag-

induced association of Mn, Cr, P, S, OC, Ca, Fe, and V due

to authigenic Fe–Mn oxyhydroxides and/or metal sulfides

precipitation; (2) terrigenous association of Ni, Pb, Cu, and

V; (3) sea salt association of Cl, Mg, Na, and K; and (4)

anthropogenic association of As, Zn, and Cd. The data

presented here suggest that metal contamination, especially

by As, Cd, Pb, and Zn, is a significant factor in sediments

of southwestern Taiwan and justify the need for further

studies to ascertain long-term effects of contaminants as

well as dumped iron and steel slag on the sediment

chemistry.

Acknowledgments Financial supports from the China Steel

Corporation (84-Y93-003), the ROC National Science Council (NSC

86-2611-M110-007W, 93-2621Z-110-004, 95-2621-Z110-005, and

95-2611-M-110-001) and Aim for the Top University Plan (95C0312)

are greatly appreciated. Anonymous reviewer(s) are thanked for their

comments on an earlier draft of this manuscript.

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