Prediction of sediment quality based on the concentration of heavy metals Cu, Zn, and Ni in Jakarta Bay using the index analysis approach

The purpose of this study was to predict the concentration of heavy metals Cu, Zn, and Ni in sediments and to predict the sediment quality based on an index analysis approach (contamination factors, geo accumulation index, pollution load index, ecological risk index, and potential ecological risks index). The sediment sample taken by using a sediment grab in Jakarta Bay. Heavy metal content measured by using Atomic Absorption Spectrophotometer (AAS). The results showed that the Cu range from 14.79 to 55.36 µg.g−1 with an average of 33.178 µg.g−1, Zn range from 82.05 to 441.91 µg.g−1 with an average of 197.484 µg.g−1 and Ni range from 16.47 to 22.09 µg.g−1 with an average of 19.328 µg.g−1. The mean levels of Zn and Cu were still lower than the threshold value of sediment quality, i.e., 108 µg.g−1 for Cu, 271 µg.g−1 for Zn, while for Ni is higher, ie, 16 µg.g−1. The results of the index analysis showed that the average value of contamination factor (CF) of Cu, Zn, and Ni were 1.614, 2.018, Ni -0.138 respectively (1 < CF < 3, moderate contamination), the average of geo accumulation index values of Cu, Zn, and Ni were -0.136, -1.010, -0.138 ((Igeo < 0, unpolluted) respectively. The average Pollution Load Index value (PLI) is 1.637 (PLI > 1); based on the PLI index, sediments are categorized as polluted by Cu, Zn, and Ni. Based on ecological risk index (Er) and potential ecological risk index (RI), sediment includes low risk ecology (Er < 40) and low potential risk ecology (RI<150).


Introduction
Jakarta Bay is a densely populated area with various activities, and this is where pollutants from the land transported directly or indirectly through 13 river systems that flow in the DKI Jakarta area. These pollutants come from high anthropogenic activities such as industrial waste, ports, fisheries, and garbage. The waste contains materials that are toxic and dangerous. Subsequently, toxic materials and harmful materials such as heavy metals have been accumulating in sediment in Jakarta Bay.
Heavy metals considered a vital contaminant of the environment if they are present in more than their natural concentration [1] [2]. Heavy metals are a natural component of rocks. As a result of rocks weathering, they are transferred to soil and bottom sediments, where they are supplemented with metals originating from anthropogenic activity such as urbanization, industrialization, transportation, and energy production [3] [4]. Due to their toxicity, persistence, and potential to bioaccumulate, heavy metals present severe environmental pollution [5] [6]. Heavy metals, both essential and non-essential, have essential meanings in ecotoxicology because both are persistent and toxic to living organisms. Heavy metals are chemical elements naturally found in marine waters, and aquatic organisms need low levels, but in high levels are toxic when exceeding their threshold values [7]. Heavy metals can come from industrial, agricultural, urban, and mining activities [8]. Heavy metals in marine sediments mainly come from nature (input from rivers) and anthropogenic sources (coastal human settlements). If they enter to seawaters, their distribution strongly influenced by physical-chemical factors (sedimentation process, mineral decomposition, hydrodynamic transport, redox conditions, and biological extraction) and considered as contaminants if the levels exceed the safe threshold values for environmental protection [9].
The levels of heavy metals Cu, Zn, and Ni in sediments in the western part of Jakarta Bay are higher than in the central and eastern parts of Jakarta Bay [10]. The high levels of heavy metals in the sediments in the western part of the Jakarta Bay area due to ship activity, the number of industries, and the higher population density than Jakarta's central and western parts. According to Wahyunningsih (2014) [11], the high levels of heavy metals in Jakarta Bay are caused by the rivers' high pollution level coming to Jakarta Bay. Permanawati et al. (2013) [12] reported that the levels of heavy metals Cu and Zn from surface sediments in Jakarta Bay in October-November 2010 were relatively low and were still below the criteria set by sediment quality standards. According to Kusuma et al., (2016) [13], the source of heavy metals lead (Pb), copper (Cu), and zinc (Zn) comes from land, while cadmium (Cd) and (Ni) come from the sea. Most of the heavy metal sources in Jakarta Bay's waters come from lands, such as port and industrial activities. Most of the heavy metal sources originating from the mainland are from port activities such as ship painting, ballast water disposal, ship docking, and refueling, which can contribute heavy metals to the waters and various industries in coastal areas chemical, paint, textile factories. Furthermore, battery rock, which discharges its waste through rivers or drains to Jakarta Bay.
This study aimed to assess the quality of sediments of Jakarta Bay using the index analysis approach.

Field work
The sediment samples collected from five sampling locations along coastal of Jakarta Bay during July 2015 ( Figure 1). Thirty-one sediment samples collected from Jakarta Bay using a Smith-McIntyre grab mud sampler in July 2015. The sampling locations represent areas with increasing distances from the shoreline, which are estuary (river mouth) (code M), 5 km (code D), 10 km (code C), 15 km (code B), and 20 km (code A) away from the coastline. Triplicate sampling performed on each site. In the field, the sediment samples from each site homogenized to obtain a composite sediment sample, immediately stored in sample bottles, kept in a cooled icebox, and transported to the laboratory [14].

Sample treatment
The concentration of heavy metals Cu, Zn, and Ni in the sediment sample determined using a Flame Atomic Absorption Spectrophotometer (Varian Spectro AA 20) following the USEPA method [15]. A reference material, PACS-2, was used to ensure the accuracy of the data. The typical recovery ranges between 95-100%, and the percent difference for the reference material is <5%. The concentration of heavy metals expressed in mg of metals per kg of sediment (dry weight).

Data Analysis 2.3.1 Contamination Factor (CF) and
Degree of Contamination (DC).The contamination factor (CF) used to determine the contamination status of the study area. The formula and terminology for describing the contamination factor (CF) shown as follows [16,17].
Where Cmetal = the concentration of a given metal in the sediment, and Cbackground is a metal concentration of a control sample. The CF value for describing the contamination levels. The range are low (CF<1), moderate (1≤CF<3), considerable (3≤CF<6), and very high (CF≥6).

Potential Ecological Risk Index Method (RI).
The Assessment of ecological risks of heavy metals in sediment samples done using the Ecological Risk Assessment (Er), and Risks Index (RI) proposed by [16] and reported in [18]. The potential ecological risk index method RI used to evaluate heavy metals' harm in the sediment samples. RI was calculated by using the following formula [16,19]: Where RI is the potential ecological risks index; Er is the ecological risk index for single heavy metal pollution and can be calculated as: Er = CF x Tr (4) Tr is the response coefficient for the toxicity of the single metal. CF is the contamination factor and defined as: Where Cm is the concentration of heavy metal in the sediment, and C background is the reference [20,21]. Table 1. Shows the concentration of heavy metal in the controlled sample: CF and the response coefficient for single metal (Tr). The background values of the upper limits of heavy metals in Jakarta Bay in 1995, used as reference values to evaluate the pollution in the paper. The usage of local background as the background has been done [21] in Bohai Bay China. Table 1. Environmental background of heavy metals in sediments from Jakarta Bay waters (Cbackground) [22] and toxicity coefficient of heavy metals (Tr) [21].. Based on the calculated Er and RI, the grading standards of the elected heavy metals' potential ecological risk obtained. Table 2 shows the potential ecological risk index's value range and the potential toxicity index along with the ecological risk level. Considerable risk 300≤RI<600 Considerable ecological risk 160≤Er<320

Element
High risk RI≥600 Very high ecological risk Er≥320 Very high risk

Geo Accumulation
Index. The geo accumulation index (Igeo) used to assess the contamination level of metal in sediments. It is a quantitative measure of the degree of pollution in aquatic sediments. The geo accumulation index is generally used to determine the anthropogenic contamination in sediments, as introduced by [23,24,25]. This index evaluates the contamination levels by comparing present concentrations with background levels. The Igeo expressed using the following Muller equation: Where: Cn = measured concentration of element n in the sediments. Bn = geochemical background for the element n, 1.5 is incorporated in the relationship to account for possible variation in background data (the background matrix correction factor) owing to lithogenic effects. The geo accumulation index consists of seven grades (0 to 6) based on the increasing numerical value of the index and ranges from unpolluted to extremely polluted. The standard Igeo values are presented as follows; Igeo<0, class 0 (uncontaminated), 0<Igeo<1, class 1 (unpolluted to moderately), 1<Igeo<2, class 2 (moderately polluted), 2<Igeo<3, class 3 (moderately to heavy polluted), 3<Igeo<4, class 4 (heavily polluted), 4<Igeo<5, class 5 (heavily to extreme polluted) and Igeo>5, class 6 (extremely polluted)

Result And Discussion
The results of this research presented in Table 3. From that table can be seen the highest concentration of Cu was found at location M (estuary area about 0.5 km from the coastal line), and then following by D, C, B, and A, for Zn, the highest concentration was also found at M location and following by D, C, B, and A, for Ni, the highest concentration was found at D location, and then following C, M, A, and B.

Distribution of heavy metal in sediment
The concentration of Cu, Zn, and Ni in the surface sediments in Jakarta Bay waters' five sites are listed in Table 1 [27] found that the average concentration of Cu in sediment in Jakarta Bay in May and June was 46.90 mg kg -1 and 49.80 mg kg -1 . The data above showed that the concentration of Cu is varied; this may be caused by the research's different station positions and time. The Canadian Council of Ministers for the Environment (2002) [28] states that the threshold value of Cu in sediments for marine organisms protection is 35.7 mg kg -1 . The Sediment Quality Guidelines (SQG) determine the uncontaminated sediment with Cu is <25 mg kg -1 [29]. KLH (2010) [30] define threshold values of Cu in the sediments to marine organisms is 108 mg kg -1 , and the average concentration of Cu in the earth's surface is 45 ppm [25]. The Cu range from 14.79-55.36 mg kg -1 with an average of 33.178 mg kg -1 , which did not exceed the background value 45 mg kg -1 . The highest concentration of Cu was found in Station M and the lowest in Station A. It indicates that M station receives more input of waste containing Cu. Thus, when referring to the [28] and [30] above, the sediments in these waters are still suitable for the marine organism exception M and D.
The The average Zn level is higher than Zn's background levels, which is 90 mg kg -1 [29]. The Canadian Council of Ministers for the Environment [27] states that Zn's threshold value in sediment for marine organisms protection is 123 mg kg -1 . KLH (2010) [30] sets Zn's threshold value in sediments for 271 mg kg -1 for marine organisms. Sediment Quality Guidelines (SQG) stated that Zn does not pollute sediment has a Zn concentration of less than 90 ppm [31]. The background level of Zn on the earth's surface is 95 mg kg -1 . Thus, when referring to KLH showed that Zn concentration in sediments in these waters is still good for marine organisms protection.
Ni  [32] states that Ni lowest value in sediments that can harm marine organisms is 16 mg kg -1 . Based on that BCMWLAP [32], Ni concentration is not suitable for marine organisms protection. Fig 12 shows that Ni concentrations in all stations have higher than the background value and the threshold value. The normal concentration of Ni in the background is 68 mg kg -1 [29]. Sediment Quality Guidelines (SQG) stated that the Ni concentration in non-polluted sediments is less than 20 mg/kg and in moderately polluted sediments range from 20-50 mg kg -1 [29].
Based on the average values, the metals follow the decreasing concentration in the order of Zn>Cu>Ni. The data shows that Zn and Cu are the dominant metals found in the study area's surface sediment.

Correlation between heavy metals concentration with the station distance from coastal.
This Table 4 below shows the correlation between heavy metals and heavy metals with the station's distance. There is a correlation between Cu with Zn (r 0.915) but no correlation between Cu, Zn, and Ni (r 0.781, r 0.490). Asamuddin et al. (2011) [33] in their research in Sulu and Sulawesi Seas, found the correlation between Cu and Ni. Ra et al. (2013) [34] in their research in Korea, did not find the correlation between Ni with Cu and Zn. Gaspic et al. (2008) [35] in their research in Soline Bay, Croatia, reported there is no correlation between Cu, Zn, and Ni. Based on this correlation is predicted, Cu and Zn come from the same waste sources, while Cu and Ni, Zn, and Ni are predicted to come from different waste sources. For distance, there were correlations between Cu, Zn with distance (r = -0.974, r = -0.908), where the concentration of Cu and Zn is increased to a station near to the coastline, while Ni no correlation with the distance (r = 0.677). Li et al. (2012) [36] in their research in Jinzhou Bay (China), also found a correlation between the station's distance from the coastline to the levels of Cu, Zn, and Ni, where the stations farther from the coast have lower levels than those near the coast. Additionally, levels of heavy metals are also variations at each station, and this variation is due to the different characteristics of each location as the physical and chemical properties of water. Li et al. (2013) [37] stated that the level of acidity (pH), temperature, dissolved oxygen, and current velocity affected variation in heavy metal levels in sediments. Hagan et al. (2011) [38] stated that dissolved or deposited metals in sediments are influenced by the waters' physical and chemical properties such as pH, salinity, conductivity, and organic matter. The distribution of Cu and Zn in the research location is high on the coast and lower towards the sea. This was showed that the source of heavy metals for Cu and Zn comes from land, while the distribution of Ni is relatively varied; this data shows that the source of heavy metal Ni can come from the land and from the sea, such as from the activities of massive ships that do not load and unload in the coastal areas but loading and unloading in the middle of the sea. .005 .033 .209 N 5 5 5 5 *. Correlation is significant at the 0.05 level (2-tailed) **. Correlation is significant at the 0.01 level (2-tailed).
In general, this study shows that heavy metals' distribution patterns in sediments indicate the source; this is because the sea surface is dynamic. There is an influence from the complex physicchemical properties of the waters such as addiction-diffusion, adsorption-desorption, and depositiondissolution sediment. Most of the potential sources of heavy metals come from lands, such as port and industrial activities. Port activities such as ship painting, ballast water disposal, ship docking, and refueling can contribute heavy metals to the waters. Besides, various industries in coastal areas such as chemical, paint, textile, and battery stone factories estimated to dispose of their waste through rivers or drainage through the estuary to Jakarta Bay.

Estimating metals pollution impact 3.3.1. Contamination factor and Geo accumulation indexes.
The average value of the Cu contamination factor is 1.614, and this value is higher than 1 (1<CF <31), which means that sediment is in category moderate contamination. The average Igeo value is -0.136; this value is smaller than 0 (Igeo <0), which means that sediment is categorized as unpolluted (Table 5).  Table 6 shows the average of Zn contamination factor is 2.215, and this value is higher than 1 (1<CF <3), which means that sediment is including moderate contamination. The average of Igeo value is -1.010 is lower than zero (<0), which means that sediment is categorized as unpolluted (Igeo <0).  Table 7 shows the average Ni contamination factor is 1.368, and this value is more significant than one and smaller than 3 (1 <CF <3), which means that the sediment is categorized as moderate contaminated. The average Igeo value is -0.138; this value is smaller than 0, which means that sediment is categorized as unpolluted (Igeo <0).  Table 8 showed the PLI values at each station. PLI value ranges from 0.926-2,635 with an average of 1.637, and this value is higher than 1 (PLI >1), which means that overall sediment in the waters of Jakarta Bay is categorized as polluted by metals Cu, Zn, and Ni. The levels of Cu, Zn, and Ni in sediments relatively varied at each station. Differences in each station position can cause this variation.

Potential Ecological Risk Index (RI).
The ecological risk assessment in sediments was carried out by the potential ecological risk index (RI) proposed by [16]. The ecological risk factor Er and potential ecological risk index (RI) presented in Tables 9 and 10.  Table 9 showed that the average of risk indices (Er) of all heavy metals indicated that Cu (8.071), Zn (2.214), and Ni (6.843) were within low risk ecological (<40).
The potential ecological risk factor is known as the Risk Index (RI) in each location is lower than 150 (<150), and this is including low potential ecological risk (Table 10).  Table 11 shows the comparison of metals in sediments in Jakarta Bay with geochemical background and toxicological reference values (mg kg -1 ). 10 In the table above shows that the mean levels of Cu were higher than LEL, MET, CB TEC, EC TEL, and SQAV TEL. Zn is higher than TEL, ERL, LEL, MET, CB TEC, EC TEL, NOAA ERL, SQAV TEL, and SQO Netherland target. Ni is higher than TEL, LEL, and EC TEL.

Conclusion
The total levels of heavy metals detected in surface sediments Jakarta Bay waters corresponded to the order: Zn>Cu>Ni. Some of the levels of heavy metals in sediments in Jakarta Bay are still following the sediment quality standards, but some of them have passed the sediment quality standard. When referring to PLI values, sediments in these waters are generally categorized as polluted (PLI >1); when referring to potential ecological risk, sediment in the waters include low ecological risk and low potential ecological risk.