Uptake and Accumulation of Zinc by Grey Mangrove at Wonorejo Mangrove Forest, Surabaya, Indonesia

. Heavy metals have non-biodegradable, toxic and accumulative properties in the environment. Heavy metals that enter water bodies will be carried by the flow towards the coast. Zinc (Zn) is one of the metals found polluting the waters in the city of Surabaya, Indonesia. One of the efforts to overcome this problem is the use of mangroves as phytoremediation agents. The purpose of the study was to determine the ability of Avicennia marina (Forssk.) Vierh in the Wonorejo Ecoforest to accumulate Zn by determining the bioconcentration factor (BCF) and the translocation factor (TF). Determination of the sampling points of this study using the transect method. Samples were taken in the form roots, stems, and leaves of mangrove plants and those were analyzed for Zn concentration using an atomic absorption spectrophotometer (AAS). Based on the result, A. marina showed the immobilized of Zn in root due to the BCF value was higher than 1. In conclusion, A. marina have potential to be phytoremediation plants in coastal area.


Introduction
The increasing of industries has both positive and negative impacts.The positive impact resulting from industrial activities is the creation of many jobs, while the negative impact is a decreasing of environmental quality due to waste disposal.Industrial waste is a serious problem in the era of industrial industrialization [1].Every industrial activity will produce various kinds of waste.The type of waste varies depend on the type of activity.According to Nasir and Saputro [2], industrial waste treatment must start from the beginning of the process untill the end, because if it is not conducted properly, it will have a fatal impact on the environment and human survival.According to Yudo [3], industrial waste is generally disposed of into rivers without any treatment, so that it can cause a decreasing in the quality of water bodies.
The coastal zone has a high potential for heavy metal accumulation because it is directly adjacent to land and sea [1].Heavy metal pollution in coastal areas is caused by agricultural runoff, industrial and domestic waste, chemical spills, ship fuel, WWTP effluent, mining and domestic waste [4].According to Tchounwou et al., heavy metals such as mercury (Hg), lead (Pb), arsenic (As), cadmium (Cd), chromium (Cr), zinc (Zn) and nickel (Ni) are inorganic materials that often cause serious water problems.The heavy metal waste enters water bodies and then settles in river estuary sediments [6].The continuous deposition of heavy metals will cause environmental pollution because of the accumulative and toxic properties of metals [6].One of the efforts to overcome heavy metal pollution in estuary dan coastal areas is phytoremediation using mangrove plants.Mangroves are plants that can live in areas with high salinity [7].Several studies have proven that mangrove plants can accumulate heavy metals that pollute the environment [8].The estuary of the Wonorejo river has the potential to accumulate heavy metals due to this location is passed by industries and domestic areas [9].The aim of this study was to determine the ability of Avicennia marina (Forssk.)Vierh that grown at Wonorejo Mangrove Forest to uptake and accumulate of Zn.

Location sampling
The location of the study was at the Wonorejo Mangrove Ecoforest area, in Surabaya, Indonesia.Based on the consideration of mangrove thickness, the determination of sampling stations was observed visually, using the google earth application, with easy road access and safety to reach the study location.

Determination of BCF (bioconcentration factor) and TF (translocation factor)
The results of the analysis of the concentrations contained in the environment and mangrove plants, were used to calculate the values of BCF (bioconcentration factor) and TF (translocation factor).The BCF and TF were used to determine the heavy metals' accumulation and translocation abilities, in parts of the mangroves.The Bio-concentration factor (BCF) or biological accumulation coefficient (BAC) calculation [10] was used to determine the plants' ability to extract metal from the substrate [11].Equation (1) shows BAC determination The BCF determination results were used to classify plants that are in as shown in Table 1 based on Bini et al. [10].

Table 1. Category of BCF value
The TF value was determined using Equation 2 [11,12].
3 Results and discussions

The concentration of Zn in sediments
The results of the analysis of Zn in sediments was shown in Figure 2. The concentration of Zn were 56.7 mg kg -1 , 45.8 mg kg -1 , 62.5 mg kg -1 and 59.6 mg kg -1 at code location of SBP3 A. marina, SCP1 A. marina, SCP2 A. marina and SCP3 A. marina, respective.Indonesia does not have quality stones for sediments in coastal areas, so the sediment quality standards used in this study refer to the Environmental Protection Agency (EPA) Sediment Quality, Australian and New Zealand Environment and Conservation Council (Anzecc/Armcanz Guidelines) and the Canadian Council of Ministers. of Environment (CCME).The quality standards used in this study for Zn sediments came from America, Australia and Canada.The American quality standard for Zn sediment is > 2 mg kg -1 , Australia 410 mg kg -1 and Canada 315 mg kg -1 .Based on Figure 2, all sediments in this study have exceeded the quality standard threshold according to the sediment quality reference from America due to concentrations of Zn in the sediment were greater than 2 mg kg -1 .However, based on the Australian and Canadian quality standards, concentration of Zn in the sediment in the estuary were still below the quality standard.

Mangrove ability to remediate heavy metal Zn by determining BCF and TF
Mangrove plants were used as phytoremediation agents, due to being able to accumulate heavy metals around them naturally, which was also referred to as biosorption.Mangroves also filter, catch, and bind pollution within the environment, in the form of excess sediment, garbage, and other household wastes, which contributed greatly to improving water quality [14].Figure 2 showed concentration of Zn in mangrove roots, stems and leaves of A. marina at B and C Station.The Zn concentration in the roots of A. marina at B Station was high (82.3mg kg -1 ).The results showed that Zn in mangrove roots at station of C had a range of 52.2 mg kg -1 to 93.3 mg kg -1 .The highest average Zn concentration in the mangrove roots of station C was found in the mangrove type of A. marina.A. marina was able to absorb the highest Zn metal compared to other types of mangroves.Concentration of Zn in stems of A. marina were 51.2 mg kg -1 till 101.3 mg kg -1 at B dan C Station.Concentration of Zn in leaves of A. marina were 37.6 mg kg -1 till 138.3 mg kg -1 .According to research by Amin [7], Avicennia mangroves have a higher accumulation capacity than other mangrove species.A. marina prevents the entry of heavy metals into other tissues so that the concentration of heavy metals in the roots is higher.The BCF value were calculated using equation 1.The BCF value in A. marina were 1.14 till 1.49.Figure 4 showed the BCF value of A. marina.Based on the classify which plants [10], A. marina showed potential as a hyperaccumulator for Zn.This result indicates that A. marina was taken up Zn from sediment and A. marina was included as a hyperaccumulator plant for Zn.It considered that A. marina was an efficient hyperaccumulator plants.However, according to Meeinkuirt et al. [15], A. marina was a phytoremediator plants for Zn, Cr, and Pb; and Rhizophora mucronata Lam. for Cu and Zn. A. marina showed the immobilized of Zn in root due to the BCF value was higher than 1.
Figure 5 showed the TF value of A. marina.The TF showed the all of value did not excess 1, it indicated that the process of phytoremediation was phytostabilization.Some species accumulated metals in shoots; however, they cannot be classified as hyperaccumulators since metal concentrations were not sufficiently high to fit the criteria for plants in a phytoextraction strategy, even those with TF > 1 and BCF > 1.

Conclusions
The Zn accumulation by roots of A. marina reached 52.2 mg kg -1 till 93.0 mg kg -1 .The BCF value in A. marina were 1.14 till 1.49 with the concentration Zn in sediment were 52.2 mg kg -1 to 93.3 mg kg -1 .A. marina showed potential as a hyperaccumulator for Zn.However, the TF showed the most of value did not excess 1, it indicated that the process of

Fig. 3 . 4 E3S
Fig. 3. Concentration of Zn in mangrove roots, stems and leaves of A. marina

Fig. 5 .
Fig. 5. TF value or translocation factor on A. marina