To what extent does the pollution of heavy metals in a freshwater habitat affect asian clams (corbicula javanica) species

Research Question

How Does the Concentration of Heavy Metals (mg/kg) Present in the Penang River Basin Affect the Concentrations Present in Corbicula Javanica?

The aim of this paper is to investigate the concentration of heavy metals present in the Sungai Pinang River Basin from 2020 through the use of secondary data. This study will analyze the effects of the amount of heavy metal present in the Penang River on the water systems and the heavy metal concentrations found in Corbicula Javanica clam species. This allows a prediction of possible sources of pollution and health risks to the consumption of shellfish species.

On some occasions in Penang when my family ordered shellfish dishes they would not be available at any of the restaurants due to the risk of heavy metal poisoning. This led me to become aware of heavy metal pollution as an issue in Malaysia.

The Sungai Pinang River Basin is located in George Town, Penang, Malaysia where heavy metals have polluted soils from anthropogenic activities. (Mohd Saad et al., 2006 ). In 1999, the Drainage and Irrigation Department (DID) categorized Sungai Pinang as class IV based on the Interim National Water Quality Standards (alleh Sabdul Hakim et al 2020).

Heavy metals describe metalloid elements that are pollutants in the environment even at low concentrations (Lenntech, n.d. ). It poses a threat to the environment as it is a persistent pollutant in the ecosystem it is present in the environment (Ilahi et al., 2019). Heavy metals are released by anthropogenic activities such as rapid urbanization, pesticide production etc; it is non-biodegradable allowing them to persist in the environment for over an extended period.

Corbicula Javanica species are commonly found around the Sungai River Basin. The Corbicula Javanica clams feeding on the planktonic organisms would be exposed to biomagnification as it uptakes the toxins from the lower trophic levels and continues to pass on to upper trophic levels when ingested. “Bivalve molluscs depend on sediment size due to filter-feeding behavior, bioavailability would be increased if the particles were covered in heavy metals.” (Tutu, 2017)

I decided to investigate the concentration of heavy metals in the Sungai River Basin in correlation to the heavy metal concentrations found in Corbicula Javanica to study the risks of heavy metal pollution effects. A positive correlation between the concentration of heavy metals and the adverse effects it has on human or animal health. (Tchounwou et al., 2012) The Corbicula Javanica species is a bivalve mollusc allowing it to uptake heavy metals through food sources in the polluted environment. Therefore the study aims to indicate a correlation between the concentrations of heavy metals from the Sungai River Basin and the number of heavy metals found in the Corbicula Javanica.

Null hypothesis (H₀) -

• The concentration of heavy metals in the sediment of the Sungai Pinang Basin does not affect the concentration of heavy metals concentrations in the soft tissues of Corbicula Javanica

Alternative hypothesis (H₁) -

• The concentration of heavy metals in the sediment of the Sungai Pinang Basin affects the concentration of heavy metals concentration in the soft tissues of Corbicula Javanica

• Decide on an area to study in Malaysia that has a risk of heavy metal pollution (Sungai Pinang Basin, Malaysia) This was done by researching the potential areas that are mostly affected by heavy metal pollution in the waterways and also had a high population of shellfish (Corbicula Javanica) that was widely consumed.
• Obtain secondary statistical data of the concentration of heavy metals in (Corbicula Javanica) from another study of the same area in Sungai Pinang Basin. To ensure the two data are influenced by the same factor, the data of the number of heavy metals in the sediments are collected from Sungai Pinang, the concentration found in Corbicula Javanica is at the end of Sungai Pinang; therefore the concentration of heavy metals found in Corbicula Javanica would be affected by the same factors affecting the Sungai Pinang.
• Data was chosen from the assessment of heavy metals contamination in Sungai Pinang Basin published in the IOP Conference Series: Earth and Environmental Science, 2020 done by students from the University of Science Malaysia and the Nanyang Environmental Water Institute. The concentration of heavy metals present in (Corbicula Javanica) is from the International Journal of Environmental Research and Public Health.

The student decided to acquire secondary data based in Malaysia as there is no available fieldwork regarding the topic of study. A lab experiment was not chosen as a method of data collection as it violates ethical guidelines for animal testing. The data featured is obtained from “Assessment of Heavy Metal Contamination in Sediments in Sungai Pinang River Basin '' featured on the IOP Conference Series Earth and Environmental Science (EES) and ResearchGate website. This study was conducted by the Universiti of Sains Malaysia (USM) and Nanyang Environmental Water Research Institute (NEWRI). The data on Corbicula Javanica clam species is obtained from “Human Health Risk Assessments of Trace Metals on the Clam Corbicula Javanica in the Sungai Pinang Basin Malaysia '' from the National Library of Medicine. The student will compare the concentration of heavy metals in the rivers to standard water ranges by WHO, National Water Quality Index and Malaysian Food Act Regulations 1983 to assess correlation of heavy metals present against concentrations in Corbicula Javanica.

There are no health and safety implications in this study due to all data used were derived from sources of publication on the internet.

The figure above indicates Jalan Air Itam, Taman Sri Pinang and Fishery Area have exceeded the arsenic concentration limits of the NWQS and the WHO Index. Arsenic concentrations in Corbicula Javanica from all sampling points exceed permissible levels of the Malaysian Food Act 1983. The river is highly polluted due to residents unregulated dumping and commercial dumping of pig feces from pig farms. (Kaur, 2019) Long-term exposure to arsenic may cause health complications such as cancer, diabetes, and cardiovascular diseases. (Cherney, 2018) 

Figure 5 indicates Lorong Kulit, Jalan Perak, Jalan Patani, Taman Lembah, Masjid Maqbul Jelutong and Fishery Area exceed the cadmium concentration water quality limits of WHO index and NWQS. Cadmium concentration found in soft tissues of Corbicula Javanica does not exceed the permissible levels by the Malaysian Food Act 1983. The pollution is due to resident's rubbish disposal into the river and unregulated toxic waste disposal from several factories. (Jelutong and Juru Rivers Badly Polluted, 2014)

Figure 6 indicates all points except for Jalan Air Itam and Jalan Patani exceed lead concentration standards by NWQS and WHO. Lead concentrations found in soft tissues of Corbicula Javanica from all sampling sites exceeded the range of the Malaysian Food Act 1983. Possible pollution sources in Taman Lembah may come from upstreams of other locations. Long-term exposure may cause neurological disorders and behavioral difficulties. (U.S. Food and Drug Administration, 2023)

Figure 7 indicates chromium concentration that exceeds NWQS and WHO standards at all points except for Taman Lembah. Chromium concentrations found in soft tissues of Corbicula Javanica from all sampling sites exceeded the levels by the Malaysian Food Act 1983. Habits of disposing of rubbish into the drains slowing into the waterways to Sungai Pinang around the Jalan Patani area. (Xian, 2020) Long-term exposure to the high concentration of chromium through a food diet may lead to liver abnormalities. (What Are the Physiologic Effects of Chromium Exposure, 2013)

Figure 8 indicates Taman Sri Pinang exceeds the zinc concentration standards of NWQS and WHO at 5.8392 mg/kg. Zinc concentrations found in soft tissues of Corbicula Javanica from all sampling sites exceeded the levels of the Malaysian Food Act 1983. Anthropogenic sources of zinc may come from fertilizers or pesticides given that there are agricultural farms from upstream of Sungai Pinang Basin Long-term exposure to zinc may lead to nervous system disorders, and anemia and cause damage to the pancreas. (Zinc Fact Sheet, nd)

• The r-value¹ calculated is 0.890. A strong positive correlation between the amount of heavy metals in Corbicula Javanica and in the water sediments of Air Itam; both Arsenic and chromium levels exceed the permissible levels.

The r-value calculated is 0.706. It shows a strong positive correlation between the amount of heavy metals in Corbicula Javanica and in the water sediments of Jalan Patani; both Chromium and zinc levels exceeded the permissible levels.

• The r-value calculated is 0.934. It shows a strong positive correlation between the amount of heavy metals in Corbicula Javanica and in the water sediments of Sungai Jelutong. Chromium and lead levels exceeded the permissible levels.

• The r-value calculated is 0.815. It shows a strong positive correlation between the number of heavy metals in Corbicula Javanica and in the water sediments of Sungai Tengah. Arsenic, chromium, and lead levels exceeded the permissible levels.

All sampling points indicated a positive correlation between the heavy metal concentrations of Sungai Pinang water sediments and concentrations of the Corbicula Javanica soft tissues. This indicates that the concentration of heavy metals found in water sediments increases the concentration of heavy metals that accumulates in the bivalve organism.

The concentrations of heavy metal concentrations present in the Sungai Pinang Basin have positive correlation concentrations present in the soft tissues of Corbicula Javanica. Therefore the alternative hypothesis is accepted, the concentration in water sediments affects the bioaccumulation of heavy metals in organisms living in the region. The anthropogenic source is a major contributor to heavy metal concentrations in sediments of water. The Sungai Pinang Basin is surrounded by commercial areas and residences, pollution caused by these areas includes illegal disposal of waste and littering of rubbish into the waterways. The Straits Times reported that the Air Itam River which flows into Sungai Pinang has been highly polluted due to the dumping of pig feces. Pig feces contain high amounts of chromium, arsenic, zinc, and lead which contribute to the accumulation of heavy metals in river sediments.

• The student could have overcome the lack of data by setting a specific research question on a specific anthropogenic activity to study. Selecting a specific activity can reduce the potential anomalies found in the data.

The possible solution to reduce the number of heavy metal levels in Sungai Pinang in order to reduce the risk of heavy metal pollution in Corbicula Javanica species is implementing rhizofiltration. Rhizofiltration uses plants that are able to absorb high levels of toxic metals to decontaminate groundwater. (Hawaii Education, n.d.)

The optimal plant to resolve this issue is water hyacinth. Water hyacinths have a fast-growing root system allowing them to consistently absorb heavy metals from the water over a long period of time. This species can absorb cadmium, arsenic, lead, zinc and copper metals effectively which has been studied in this paper. Hyacinths are found all over Malaysia allowing them to be easily obtained and cost-effective to plant in Malaysia. The fast-growing characteristic of this species may reduce the cost to plant a large number of hyacinths, it can also quickly spread and clean up more concentrations of heavy metals from the water. The flowers of water hyacinths can serve as an aesthetically pleasing view replacing the murky polluted water, increasing chances of cooperation from local residents.

However there is a risk of eutrophication with this method. The rapid growing characteristic of the water hyacinth may rapidly spread over the surface of the water, decreasing light showing into the water and consequently decreasing other photosynthesis activities of indigenous plant species. The dead-off water hyacinths will be broken down by bacteria, bacteria decomposition consumes oxygen in the process, thereby decreasing oxygen levels in the water. This may result in unfavorable conditions for aquatic organisms killing off the organisms, and disrupting the aquatic ecosystem balance.

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