Heavy metal content in estuaries water and sediment of Banten Bay, Indonesia

The primary economic activity in the estuaries of Banten Bay is fisheries. To maintain their productivity, it is essential to ensure good water quality, which requires monitoring of heavy metal content in both water and sediment. Therefore, this research aimed to investigate heavy metal content in estuaries’ water and sediment of Banten Bay. A survey was conducted in four estuaries, namely Karangantu, Wadas, Cengkok, and Pamong. Heavy metal content in estuaries water was analyzed in April and October 2021, while heavy metal content in estuaries sediment was analyzed in October 2021. Other parameters were analyzed in the laboratory or in situ. The analysis showed that the lead (Pb) content in the estuaries’ water exceeded the standard in April but met the standard in October, while the iron (Fe) and cadmium (Cd) content in the water fulfilled the standard in both months. The Pb, Fe, and Cd content in the estuaries’ sediment also met the standard. The Principal Component Analysis (PCA) indicated that the Pb content in the water was influenced by organic carbon (C organic), while the Cd content was affected by total suspended solids (TSS), oxidation-reduction potential (ORP), salinity, and water depth. Furthermore, the Pb and Fe content in the sediment was influenced by pH, while the Cd content was affected by C organic.


Introduction
Banten Bay is home to numerous estuaries that serve as primary fishing grounds.However, to sustain fishing productivity, it is crucial to maintain good water quality.However, to maintain the productivity of the fisheries, it is crucial to ensure good water quality.This is because human activities in these estuaries could have a detrimental impact on water and sediment conditions, which could ultimately reduce the catch of fish.Estuaries are unique landscapes where the freshwater of rivers meets the saltwater of the sea.This makes them important ecosystems that are heavily influenced by the interactions between land, rivers, and oceans [1].
Metals can penetrate natural water and become part of the water and sediment through absorption, precipitation, and ion exchange processes [2].The distribution of metals is controlled by dynamic balance and physical-chemical interactions, which are commonly affected by factors such as pH, concentration, type of compound, conditions of reduction-oxidation reactions, and metal valency.[3].
Furthermore, metals are one of the types of pollutants that can contaminate water bodies such as estuaries, and they can be toxic and harmful to biota when their content exceeds the standard.Although the presence of heavy metals in water is a natural occurrence that is limited to certain amounts in the water column, sediment, and biota fat, the amount of these heavy metals can increase due to the input of waste from industry and other activities [2].
According to [4], the concentration of nutrients and metals in Banten Bay is lower than that in Jakarta Bay.The content of lead (Pb), copper (Cu), and cadmium (Cd) in the coastal area of Banten Bay still meets the standard [5].
Monitoring the heavy metal content resulting from estuarine activities is essential for maintaining good conditions.Therefore, this research aims to investigate the heavy metal content in the water and sediment of Banten Bay's estuaries, located in Indonesia.

Research time and place
This research was conducted at four estuaries in Banten Bay, namely Karangantu, Wadas, Cengkok, and Pamong.These estuaries were selected as sampling stations 1, 2, 3, and 4, respectively, as shown in Figure 1.Each of these sampling stations represents a fishing area with various characteristics of environmental conditions around the estuaries.For example, Wadas is an area that includes iron processing, sugar production, fish auctions, and residential areas.Karangantu, on the other hand, is an area that features fishing ports, residential areas, and tourist attractions.Cengkok is an area that encompasses aquaculture, agriculture, and fishing settlements, while Pamong is an agricultural and residential area.Sampling for heavy metal content in the estuaries' water was carried out in April and October 2021, while sampling for heavy metal content in the sediment was carried out in October 2021.

Sampling and analysis of water and sediment
To determine the physical and chemical parameters of the water in the estuaries of Banten Bay, composite water samples were taken from the water surface, the Secchi depth, and the bottom using a water sampler.Several physical and chemical parameters were determined in situ using calibrated Water Quality Checker (WQC) from YSI, a Secchi disk, and a current meter.The measured parameters included pH, dissolved oxygen, Oxidative Reductive Potential (ORP), water temperature, salinity, turbidity, conductivity, Total Dissolved Solids (TDS), water current, depth, and Secchi depth.Other parameters, such as Total Suspended Solids (TSS), metal content in water and sediment, type of sediment substrate, and organic carbon content in sediment, were analyzed in the laboratory.
The samples collected for the analysis of heavy metal content in the water of the estuaries were preserved using HNO3.For the analysis of Total Suspended Solids (TSS), samples were taken from 250 mL of water and filtered using a GF/A filter.For the analysis of organic carbon and metal content in the sediment, sediment samples were stored at 4°C.The analysis of the parameters was conducted in the laboratory following the procedures described in [6].

Data analysis
To evaluate the quality of the water and sediment in the estuaries of Banten Bay, the results of the analysis were compared to the standard for sea aquatic biota [7] and the guidelines for sediment quality [8].The correlation between the metal content in the water of the estuaries and other parameters was performed using Pearson's correlation method.To identify the physical and chemical parameters that affect the content of metals in the water and sediment of the estuaries, Principal Component Analysis (PCA) was used.All data analyses were conducted following the procedures described in [9] and [10].

Heavy metal content in estuaries water
The results of the analysis of the heavy metal content in the water and sediment of the estuaries of Banten Bay are presented in Table 1.To ensure representation across different seasons, sampling was conducted twice, in April and October.In April and October, the levels of Fe and Cd in the estuaries' water met the standard requirements, while the Pb content in April exceeded the standard, although it decreased in October.It is worth noting that there was a significant amount of rainfall at the four sampling stations in October, and the water depth was higher in October than in April, as shown in Table 1.This suggests that the rainwater may have contributed to the decrease in the metal content in the water [11].
Pb is a metal with low solubility and is commonly found in water in solution form or suspended form.According to Table 2, there is a correlation between Pb and turbidity in the estuaries water of Banten Bay, suggesting that Pb may be present in a suspended form.The low solubility of Pb results in its low concentration in water.The source of Pb in the aquatic area could be from ship fuel, which contains Pb and contributes to water pollution.In inland water, Pb can react with anions such as hydroxide, carbonate, sulfide, and sulfate, forming a complex compound [12].Table 1.Heavy metal content and other parameter results in estuaries water of Banten Bay.

Note: nd = not detected
In April, the highest Fe content in the estuaries water was found at station 1, while in October, the highest Fe content was found at station 2. It is worth noting that Wadas (station 2) is an area for iron processing, sugar, fish auctions, and residential areas, which may explain the higher Fe content observed in October.The Fe in water could be from industrial waste that entered the water column and sediment segment.

Heavy metal content in estuaries sediment
The analysis of heavy metal content in the estuaries sediment revealed that the levels of metal were higher than those found in water, as shown in Table 3.This is in line with the characteristics of metal, which can easily precipitate in sediment.When the flow rate is low, metal can easily deposit in sediment in the form of clay and silt [13].The analysis of heavy metal content in the sediment of the estuaries in Banten Bay revealed that the levels of metal met the recommended sediment quality guidelines [8].It is important to note that the content of metal in the water can affect the content of metal in the water column, highlighting the interconnectedness of the different components of the aquatic ecosystem [11].The highest Pb content in the sediment was found at station 1, which is an area for sea transportation.This suggests that ship fuel may be a significant source of Pb pollution in the region.The highest Cd content was found at station 2, which is an area for industrial activities, further highlighting the potential impact of human activities on the quality of the aquatic ecosystem.Interestingly, the lower content of metal in sediment was found at station 4, an area for agriculture and settlement (Pamong).

PCA result
The analysis revealed that the Pb content in the estuaries' water was influenced by the amount of C organic in the sediment.On the other hand, the Cd content in the water was influenced by several factors, including TSS, ORP, salinity, and water depth.Regarding the sediment, the analysis showed that the Pb and Fe content were influenced by the pH level, while the Cd content was influenced by the amount of C organic present in the sediment.The Pb content in the estuaries' water was found to be influenced by the amount of C organic in the sediment.This is because Pb can react with organic material in diluted phases and then precipitate in the sediment column [12].In contrast, the Cd content in the water was affected by factors such as ORP and salinity, which can exist in ionic form.Regarding the sediment, the analysis revealed that the Pb and Fe content were influenced by the pH level, as they could form hydroxide, oxide, or carbonate forms that precipitate in the sediment column.Conversely, the Cd content in the sediment was influenced by the C organic content in the sediment, which could be present in the form of hydroxide, oxide, or carbonate in anaerobic conditions with high organic content.
In general, this research reports that heavy metal content in the estuaries' water and sediment of Banten Bay was not affected aquatic biota, but monitoring should be carried out to support fisheries activity in these estuaries.

Conclusion
In April 2021, the Pb content in estuaries water of Banten Bay (Karangantu, Wadas, Cengkok, and Pamong) exceeded the standard for aquatic biota.However, in October 2021, it met the standard.The Fe and Cd content in estuaries water of Banten Bay in April and October 2021 met the standard.The Pb, Fe, and Cd in estuaries sediment met the recommended sediment quality guideline standard.The Pb content in estuaries water was affected by C organic, while Cd content in estuaries water was affected by TSS, ORP, salinity, and water depth.Similarly, the Pb and Fe content in estuaries sediment was affected by pH, while Cd content in estuaries sediment was affected by C organic.Although the heavy metal content in the estuaries water and sediment of Banten Bay were not found to be affecting aquatic biota, it is still essential to monitor them regularly to support fisheries activities in these estuaries.

Figure 2 .
Figure 2. PCA results between metal content and other water parameters.

Table 2 .
Result of correlation analysis between metal and other parameters in estuaries water.

Table 3 .
Result of metal content and C organic analysis in estuaries sediment of Banten Bay.