Effect Of Heavy Metals On The Environment Environmental Sciences Essay
|✅ Paper Type: Free Essay||✅ Subject: Environmental Sciences|
|✅ Wordcount: 4030 words||✅ Published: 1st Jan 2015|
Heavy metals are most abundant forms of pollution in Malaysia either in the forms of solid or liquid. With the vast industrialization and economic development in coastal region, heavy metals are continuing to be introduced to the estuarine and coastal environment which eventually end up into the river, runoffs and land based area (Yu et al., 2007). Metals diffuses into the aquatic environment will settle down and be incorporated into sediments together with organic matters, Fe/Mn oxides, sulfides, and clay (Wang and Chen, 2000). However, heavy metal mobility or availability in contaminated materials depends to large extent upon the different chemical and mineralogical forms that occurred (Song et al., 1999). Therefore, sediments seem to be an excellent medium in the assessment of the metals bound to the particulates. Nonetheless, sediments are known to act as a sink for heavy metals to be introduced into waters either from both natural and anthropogenic sources thus providing an excellent proof of man’s impact (Pempkowiase et al., 1999; Guevara et al., 2005). In addition, they may also act as traps for various types of pollutants including heavy metals (Poh and Mun, 1994). Indeed, changes in environmental conditions such as pH and redox potential should be monitored since it may results in remobilization of heavy metals. Unfortunately, due to the scarcity of information available to establish the heavy metal concentration in sediment using sequential extraction, no data is presented concerning the heavy metal pollution in the rivers except for one author Shazili et al., 2008 on Langat River Basin. Heavy metals element is particularly crucial because any slight changes in availability may cause these elements to become either toxic or deficient to plant (Krishnamurti et al., 1995). In fact, sequential extraction analysis is a technique which is used to investigate the geochemical partitioning of heavy metals amongst solid mineral and organic phases in sediment or other earth minerals (Howard and Vandenbrink, 1999). Sequential fractionation also frequently used in approaches to evaluate metals distribution into different chemical forms present in solid phases. Although direct methods provide an unambiguous identification of the heavy metal forms and ways why they occur, they might not be sufficiently sensitive where heavy metals occur at relatively low levels and they do not provide quantitative information on heavy metal mobility and availability (Song et al., 1999). However, sequential extraction approach is undoubtedly useful since few attempts have completed and few modification have been made based on Tessier et al., (1979); such as Silviera et al., (2006); Krishnamurti et al., (1995); Song et al., (1999); Forghani et al., (2009), Poh and Mun, (1994).
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2.0 Problem Statement
Langat river, Bernam River and Klang River basin is located in the state of Selangor in which known to be the most developing states in Malaysia other than Kuala Lumpur. All of these rivers are primarily important as water source not only limited to supplying water to consumer but also for other purposes such as aquaculture and agriculture activity, fishing, effluent discharge, irrigation and even sand mining. With the vast industrialization held in the river such as sand mining it generate the release of metal bound in sediment into the water promoting metals diffussion into the aquatic organisms and eventually ends up into human’s body. Moreover, each metals poses their own threat to human, particularly Cadmium (Cd) are known for causing adverse health effects, once ingest into our body it will cause lung cancer moreover it seldom important as a cause of phytotoxicity in paddy field (Chaney, 2010). On the other hand, Zinc (Zn) is a deficient and phytotoxic element in sediment which causes abdominal pain to humans, the latter due to industrial contamination (Chaney, 2010). Copper (Cu) in sediments strongly adsorbs to clay minerals, iron and manganese oxides and organic material. In addition, it tends to remain in horizons that have a greater organic content whereas sandy sediment with low pH poses the greatest potential for Cu leaching. On contrary, lead (Pb) is considered to be one of the major environmental pollutants and has been incriminated as a cause of accidental poisoning in domestic animals more than any other substance. In a nutshell, these metals are emboldened to be analyses since this metal endured high toxicity in the environment thus poses high potential threat and risk to humans and living organisms.
3.0 Significance of Study
This study is prominent since in Malaysia there is only few attempted study using sequential extraction as medium in determining the fate of metals in environment. Particularly, this study will be useful as a baseline data for goverment bodies to be more sensitive on the issues related to heavy metals. On the other hand, this study will provide a delineation on the sources of metals which contribute the most anthropogenically or naturally to the environment since the major contributor on the environment deteroriation is a non point source. Therefore, identifying the potential sources is crucial in maintaining the environment. Nonetheless, by conducting this study it ables to generate a profound understanding on the sources and parent materials of which heavy metals are highly introduce to the estuary. Thus, contribute to the discovery of metals strength and percentage of binding to organic or inorganic pollutants. Hence, providing an illustration on the status of pollution in the selected rivers based on screening of the forms of metals associated in the river. In addition, the attempted method will utter a method development in assesing the metal in the environment. This study is beneficiary especially by the Department of Irrigation on the overview of the river status thus able to mitigate a scheme on reducing the metal accumulation into the river by identifying the source of pollution.
4.0 Research Objective
To ascertain the chemical and mineralogical forms of Pb, Cu, Cd and Zn in selected polluted river.
To profile the metal speciation (Pb, Cd, Cu, Zn) in the sediment at selected polluted river in Selangor.
To determine the heavy metals affinity for specific geochemical phases in the recently deposited sediments in the river.
To identify the pollution sources and active component of heavy metals accumulate into the surficial sediment and its chemical behavior in the aquatic environment.
5.0 Literature Review
A river is component of water cycle. Mostly rainfall on land will passes through a river on its way to the ocean and smaller side streams will joins the river forming a tributaries (DID, 2010). In Malaysia, the water within a river generally originates from precipitation through surface runoff, groundwater recharge (as seen at base flow conditions / during periods of lack of precipitation) and release of stored water in natural or man-made reservoirs, such as wetlands, ponds or lakes (DID, 2010). Therefore, the rainfall will generate the surface runoff and flows into the river. While the runoff will collect all the suspended particulates on the land surface into the river. This is why source of metal is very hard to trace since it is a non point sources elements which diffuse into the river Basin. Therefore, in this case sediments play an important role in identication of the metals since it acts as transport and storage of potentially hazardous metals (Yu et al., 2008).
Bernam River is approximately about 3335 km2 and it forms a boundary between States of Perak in the north and Selangor in the south. The undulating hills of Bernam River merge into an undeveloped peat swamp area where the downstream of the peat swamp is a densely populated coastal strip along the Bernam River. Rice is cultivated in the lower areas ad- jacent to peat swamps and rubber, oil palm, coconuts and cocoa are cultivated in estates and smallholder schemes. Agrochemicals (fertilizers and herbicides) used on agricultural lands suggest a potential non-point source of pollution and toxicity affecting the aquatic ecosystems (Yap and Ong, 1990). Logging generates pollution through soil erosion, siltation and sedimentation in the streams. On the other hand, Langat River basin covered an area of 1300 km2 in the south of Kuala Lumpur and the length of Langat River is approximately about 120 km long (Sarmani, 1989). Langat river known as an important water source not only limited to supplying water to consumer but also for other purposes such as recreation, fishing, effluent discharge, irrigation and even sand mining (Juahir, 2009). Whereas, Klang River is notable as a highly polluted river in Selangor which flows through Kuala Lumpur and suburban area of the densely populated and highly industrialized Klang Valley (Tan, 1995). The upper reaches of the Klang River serve as an important source of water supply to an estimated population of two million people in this region, together with its growing industrial activities (Tan, 1995). According to the Environmental Quality Report (Department of Environment, 2007), the Klang River is regarded as one of the rivers which have been seriously affected by pollution. Discharges of wastewater from industrial activities in the Klang River basin have also contributed to increasing levels of organic chemical pollutants in the waterways.
However, metals in sediment comes in various forms of elements. Therefore, each metals may give beneficiary and may also cause a potential threat to human. Once consumable in our body it might cause a significant imbalance thus causing deformities and poor health (Birungi et al., 2008). Sediment are an important features in the river any activities occured related to sediment such deepen or mining may cause the release of heavy metals into the river. This is because heavy metals may enter into natural water and become a part of the water sediment system and their distribution processes are controlled by a dynamic set of physical-chemical interactions and equilibrium (Jain, 2003). Therefore, the metals may bind to the aquatic organisms. Since these river is an essential water source in the state of Selangor, any aquaculture activity held in the river may have a significant potential of heavy metals accumulate into the fish or prawns. On the other hand, the deposition of metals in sediments usually occurs through an interaction between sediment and water (Piron et al., 1990), whereby changes of metal contents of sediments and water depend on changes of water chemistry, such as, temperature, pH and solute concentration. That is why such study is prominent since metals interactions between bed sediment and water in aquatic environment play an important role on water quality and the fate and transport of metals.
There are series of modification of sequential extraction technique have been made upon the suitability of the study. The recent modification are introduce by Silviera et al., 2006 which proposed to the studies specifically on the tropical soil. This method listed out seven fractionation steps which each illustrates the metal bound particulate in the sediments. The first three fractionation steps explains the geochemical condition of the sediment whereas the fourth to the seventh steps refers to the anthropogenic conditions. This method is an alternative way to determine the source of metals, because the anthropogenically sourced metals preferentially partition to the non-residual phase of the sediment while the residual phase generally reflects background geochemical conditions (Forghani et al., 2009). Moreover, this method were chosen since it selectively extracts metal bound by specific sediment fractions with minimal effect on the other sediment components (Silviera et al., 2006). In addition, this method are an important tool for predicting the potential effects of environmental changes and land application of metals on the redistribution of chemical forms in tropical sediments (Silviera et al., 2006).
6.0 Research Methodology
Thirty representative surficial sediments (0-20cm depth) will be taken from selected polluted river in Selangor from upstream to downstream of the river. Surface sediments samples will be collected in triplicates and homogenised in a zip lock polyethylene bags. The sampling will be conducted during low tide to enable the source of pollution from the mainland to be determined without the influence of input from seawater compared to sampling during high tide. Sediment samples will be collected using plastic scoops, Eckman Grab or core sampler and place into acid-washed double zip-lock polyethylene bag. All samples will be stored in cool box at 4°C during transportation to the laboratory prior to analysis.
The laboratory apparatus are also acid washed and rinsed thoroughly first with distilled water to ensure any contaminants and traces of cleaning reagent were removed before the analysis. Pre-clean polycarbonate centrifuge tube with soaked overnight in 5 % (v/v) nitric acid rinsed with distilled water after 24 hours prior to analysis. It is performed in clean laboratory to minimize the potential risk of contamination.
Physicochemical parameters such as pH, redox potential, salinity and conductivity will be measured using the 1:2 ratio of sediment and double deionized water (DDW). In addition, cations exchange capacity (CEC) and loss on ignition (LOI) will also be determined in the study.
The sediment physicochemical analyses will be determined by mixing 10 g of air dried sample (<2 mm) with 20 mL of double deionised water (DDW) in a long form beaker (Pyrex or centrifuge bottle). The long form beakers will be used because its narrow shape can help to immerse the electrode in the supernatant without introducing the tip into the sediment. The mixture of sediment sample and DDW is later stirred intermittently for 30 minutes. Then, the sample will be let stand for 1 hour before the pH, conductivity, redox potential and salinity was measured by immersing the electrodes into the supernatant. The readings for the four parameters were recorded once the reading has stabilized. All the samples were tested in triplicate as quality control.
Cation Exchange Capacity (CEC)
Sediment samples for CEC determination will be prepare in two 10 g portions, one for treatment with a 1 M NaCl solution and other with a 1 M NH4Cl solution. Approximately about 10 ml of 95% ethanol will be carefully poured on sediment sample and drawn through the sediment by suction. The ethanol remaining in the sediment will later be removed by overnight evaporation. Then, the sediment will be transferred to small 50 ml Polycarbonate centrifuge tubes. Hence, about 30 ml of 1M NaCl was applied to one set of sub samples and 1 M NH4Cl solution was added to other set. The centrifuge tubes contains with the sediment pre-treated with NaCl and NH4Cl then will be shaken end over end for about 10-20 minutes and subsequently centrifuged at 3000 rpm for 30 minutes in order to settle the fines. After the samples are centrifuged, the supernatant will be removed with syringe and filter through a 0.45 µm filter. About 15 ml of sample will be used for the analysis of Ca, Mg, and K from the NaCl supernatant solution and preserved with 1% 7M HNO3. Meanwhile, the solution from NH4Cl supernatant will be used for determination of Na and also preserved with 1% 7M HNO3. Sample analysis for Ca, Mg, Na and K adopted similar procedure as in the case of major cations determination.
The exchangeable cation concentration are converted from meq/100g to equivalent fractions (Î²T) as (Apello & Postma, 2005)
Î²T = meqI-Xz_____
âˆ‘I, Jâ€¦.. meqI-Xz
Where I, J,â€¦â€¦. are exchangeable cations, meqI-Xi is normally given in meq/100 g dry sediment and âˆ‘ meqI-Xz is essential equal to CEC, ignoring minor amounts of Fe, Mn, etc.
Loss of Ignition (LOI)
Dry a sample in an oven at 105°C to constant weight. Accurately weigh 1g of this dried sample and pour into a preweighed dry crucible. Optionally, a few drops of H2O2 may be added at this stage to promote oxidation. The samples will be transfered into muffle furnace and gradually increase the temperature to 500°C. Leave inside the oven at this temperature for at least 4h or overnight if convenient. Cool, transfer to a dessicator and allow it to cool to room temperature. Weigh and calculate loss on ignition in % as:
LOI (%) = 100 x (M1 – M2)
Where M1 is the initial weight (g) and M2 is the weight after ignition (g).
Sequential Extraction Procedure
The methods that will be used in this study are based on modification methods from (Silviera et al., 2006). The fractionation of heavy metals in sediments will be carried out in triplicate, using 1 g of air-dried sediment. Then, sediment samples will be placed in 50 ml polycarbonate centrifuge tubes, mixed in a stepwise fashion with various reagents as shown in figure 1, and the suspensions equilibrated. By following equilibration, the solution and solid phases will then be separated by centrifugation at 1225 g for 10 min. In between each successive extraction, the solid residues are suspended in 5 ml of 0.1 M NaCl, shaken by hand, and centrifuged to displace extracting solution remaining from the previous step. The supernatant will be added to the former extractant. The steps are intended to reduce sample dispersion and to minimize read sorption of the metal. The supernatants will be filtered through a 0.45 µm membrane, and the solid residues are preserved for the subsequent extractions. The concentrations of Cu, Zn, Pb and Cd in the various extracts will be determined by Inductive Couple Plasma-Mass Spectrometry (ICP-MS). Mass balances, calculated by summing individual Pb, Cd, Cu and Zn masses recovered from fractions, were compared with the independently determined total metal masses.
Further data analysis will be conducted using the raw data obtained from the sample analysis. Descriptive analysis, cluster analysis, factor Analysis will be conducted using few softwares such as SPSS version 17 and Multivariate Statistical Package (MVSP) and AQUACHEM. Enrichment factors (EF) will be calculated to determine the level of trace metal contamination of the sediments.
7.0 Project Benefit
2 research journal with impact factor
Output expected from the project
It is expected that several publication can be produced from the data obtained in this study which useful as a reference for future research.
It will provide the latest information on the level of metal pollution in Selangor which useable for relevant authority to make the future planning and management purposes.
Economic contribution of the project
By using the information gathered in this research, the relevant government bodies can make better planning and take preventive measures to avoid further contamination of the river as it is crucial source for the nation fisheries and aquaculture activity. Moreover, important because a lot of the population which resides near the mangrove area depend on it for their livelihood. Since, the destruction or contamination of this area will affect their source of income. The reduction in fisheries produce from the mangrove area due to metal pollution will results in higher imports of fish products which in turn increase the outflow of money from the country.
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