STATEMENT OF THE PROBLEM
Heavy metal pollution is one of the most topical environmental problems
Communities are increasingly concerned about heavy metal pollution affecting their daily lives, as industrial, agricultural, and domestic wastes continuously release heavy metals into water bodies Promoting the reuse of wastewater in agriculture offers significant economic and environmental advantages, including water conservation and nutrient utilization However, the use of untreated wastewater carries environmental and health risks for both users and consumers of agricultural products derived from such water sources (Venditti et al., 2000).
Sediment forms through the deposition of solid materials in water bodies, where suspended solids settle under specific hydrodynamic conditions These sediments can both source and trap heavy metals and contaminants, accumulating them over time (Rickert et al., 1977) Research by Forstner and Muller (1981) indicates that sediments in coastal areas near industrial and urban zones often contain heavy metal pollution at levels significantly higher than natural background concentrations The buildup of these heavy metals is primarily due to biogenic and lithogenic processes Contaminated sediments, which consist of soils, sand, organic matter, or minerals, pose a risk to human health as they can introduce toxic materials into the food chain (Klank et al., 2006).
Over the past three decades, research has focused on the association of heavy metals with suspended solids and bed sediments due to the dynamic nature of stream environments (Yousef et al., 1994) Heavy metals often attach to suspended particulate matter, which can settle into sediments through flocculation and sedimentation processes Sediments, while integral to aquatic systems, present complexities at the sediment-water interface, particularly within the oxide zone, where mineralization processes are intensified These microbial-catalyzed reactions can alter the minerals binding heavy metals and their speciation, impacting their mobility (Mark et al., 1982) Additionally, sediments serve as a vital substrate for organisms and interact with overlying water, significantly contributing to the aquatic ecosystem while accumulating high concentrations of heavy metals (Rickert et al., 1977; Klank et al., 2006).
Heavy metal pollution in soils has gained significant global attention over recent decades, stemming from both natural and human activities Anthropogenic sources of soil contamination include urban and industrial waste, mining, smelting of non-ferrous metals, and metallurgical processes While regulatory authorities have traditionally focused on water quality, there is now a growing recognition of soil's critical role as a reservoir for pollutants, a conduit for harmful substances to groundwater, and a source of contaminants for crops.
There is an increasing concern regarding the accumulation of toxic metals in soils across Japan and Central Europe, which may soon reach critical levels due to ongoing anthropogenic activities.
Heavy metals, while naturally present in the earth’s crust, can accumulate in soil to toxic levels due to factors such as the application of sewage sludge, industrial contamination, rapid population growth, urbanization, and inadequate wastewater treatment facilities These metals are highly persistent in soil, remaining for thousands of years Their retention in soil occurs through mechanisms like adsorption, ion exchange, precipitation, co-precipitation, and organic binding.
Heavy metals introduced to soil can migrate through the soil layers, becoming either more soluble or leached away by water This mobility can lead to excessive accumulation, which negatively impacts soil fertility, disrupts ecosystem functions, and poses health risks to both animals and humans.
Plants play a crucial role in ecosystems by facilitating the transfer of heavy metals from abiotic to biotic environments In areas affected by pollution, the impact of industrial effluents on soil and the use of municipal and industrial wastewater for irrigation is well documented, raising concerns about the transfer of toxic heavy metals from soil to plants One significant pathway for dietary uptake of these metals is through crops irrigated with contaminated wastewater The primary sources of heavy metals in plants include air, water, and soil Wastewater-irrigated soils tend to accumulate heavy metals in the surface layers, and when the soil's capacity to retain these metals diminishes due to repeated wastewater use, they can leach into groundwater and soil solutions, making them available for plant uptake.
Research indicates that soil composition plays a crucial role in the absorption of heavy metals by various plant species across different locations The levels of heavy metals found in plants are closely linked to the overall concentrations of these metals present in the soil.
The physicochemical properties of soils, including pH, organic matter content, and cation exchange capacity, significantly influence the accumulation of heavy metals and their availability for plant uptake.
(Mandaokar et al., 1994; Alloway, 1995) Moreover, the uptake and accumulation of heavy metal by plants are dominantly dependent on the available rather total heavy metal in the soil
Consuming contaminated plants is a significant route for heavy metals to enter the human body, leading to serious systemic health issues due to the excessive accumulation of these dietary heavy metals.
Heavy metals, such as cadmium (Cd), are highly persistent in the environment due to their nonbiodegradable and nonthermo-degradable nature, leading to toxic accumulation (Olive, 1997; Brigden and Santillo, 2004) Their toxicity poses significant risks to human health, with cadmium specifically targeting the kidneys and contributing to various diseases, including skeletal disorders like osteoporosis and osteomalacia, as well as increasing the likelihood of hypertension and heart disease.
Santillo, 2004) Lead (Pb) is one of the most toxic elements naturally occurring on
High levels of lead exposure can lead to severe health issues, including irreversible brain damage, seizures, coma, and even death if not treated promptly Lead toxicity also adversely affects the kidneys, particularly at moderate to high concentrations Additional symptoms of lead poisoning may include gastrointestinal disturbances such as abdominal pain, cramps, constipation, and anorexia, as well as weight loss and immunosuppression (Brigden and Santillo, 2004).
Hanoi City, located in the Red River Delta of Vietnam, is bordered by the hilly provinces of Vinh Phu and Bac Thai to the north, Ha Bac and Hai Hung to the east, and Ha Tay to the south.
Hanoi, located between latitudes 20°25' to 21°2' north and longitudes 105°15' to 106°3' east, is a tropical city significantly influenced by monsoons The city experiences all four seasons: spring, summer, autumn, and winter, with its climate divided into two main periods The dry season, from October to April, is marked by cold winds and light drizzles, while the rainy season, lasting from May to September, brings heavy rainfall and intense sunshine.
Currently, Vietnam is going through a period of industrialization and modernization and according to the economic development strategy up to 2020, and
SCOPE OF OBJECTIVES
Numerous studies have been made on the heavy metal pollution of water and sediment in different river systems in over the world (Ricker et al., 1977; Forstner and
Muller, 1981; Mark et al., 1982; Yousef et al., 1994; Birch et al., 1996; Fukue et al.,
2006) However, there are very few empirical data for heavy metal contamination of water and river sediment in Hanoi City, Vietnam (Ho and Egashira, 2000) Ho and
Egashira (2000) focused solely on the heavy metal pollution of river sediments, neglecting to address the impact of heavy metal contamination in water and its effects on soil quality and crop health when using polluted irrigation water.
This study aims to assess heavy metal pollution in the water and sediment of the To Lich and Kim Nguu Rivers, as well as its impact on soil and crop quality in Hanoi, Vietnam The research focuses on evaluating the extent of contamination and its implications for agricultural practices in the region.
(i) To assess the water quality of the To Lich and Kim Nguu Rivers in Hanoi City and its suitability for irrigation water
(ii) To evaluate the heavy metal pollution of sediment in the To Lich and Kim
The Nguu River is closely associated with the Thuy Loi University, which specializes in water resources and hydrology This institution plays a crucial role in educating students about water management and environmental sustainability Through its programs, Thuy Loi University emphasizes the importance of understanding river systems and their impact on ecosystems The university's commitment to research and innovation in hydrology contributes significantly to the advancement of water resource management in the region.
(iii) To evaluate the effects of using polluted irrigation water on the quality of soils and crops in Hanoi, City
(iv) To find out the suitable chemical leaching solutions to eliminate heavy metals from contaminated sediments and soils
RESEARCH CONTRIBUTIONS
The following list identifies some benefits from research:
Heavy metal pollution in the water and sediments of the To Lich and Kim Nguu Rivers poses significant environmental concerns Based on the findings, we recommend that the Vietnamese government implement policies aimed at reducing wastewater discharge from factories through effective wastewater treatment solutions.
(ii) Provide a complete evaluation on the effects of using polluted irrigation water from the To Lich and Kim Nguu Rivers on the quality of soil and crops
(iii) Using the suitable chemical leaching solutions to eliminate heavy metals from contaminated sediments and soils.
ORGANIZATION OF THESIS
The thesis consists of six chapters, all of them under the form of scientific papers have already published or submitted
Chapter 1: Presents the scope and objectives of research
Chapter 2: Presents the results from research program to assessment the water quality of two rivers in Hanoi City and its suitability for irrigation water
Chapter 3 presents the findings of a research program focused on assessing heavy metal pollution in contaminated river sediment within Hanoi City The study highlights the extent of pollution and its potential impact on the environment and public health By analyzing sediment samples, the research aims to provide critical insights into the sources and levels of heavy metals, contributing to the understanding of environmental degradation in urban waterways.
Chapter 4: Presents the results from the research program to evaluate the impacts of river pollution on the quality of agricultural soil and vegetables
Chapter 5: Presents the results from research program to evaluate the impacts of wastewater-irrigated on the quality of paddy soil and rice grain
Chapter 6: Presents the conclusions, research contributions and recommendations for the future work.
INTRODUCTION
For decades, industrial activities have led to the release of heavy metals from chemical compounds into water bodies, raising significant concerns about their levels in the aquatic environment These metals pose serious risks to living organisms within food chains and can adversely affect human health.
The To Lich and Kim Nguu Rivers in Hanoi, Vietnam, serve as vital sources of irrigation for suburban agriculture and fishing farms, primarily producing rice and various vegetables such as water morning glory, water dropwort, and spinach Despite existing regulations aimed at controlling industrial pollutants, enforcement remains inadequate, leading to untreated industrial wastewater being discharged into these rivers This pollution significantly impacts water quality, raising serious concerns among local farmers Unfortunately, there has been limited research on how this water contamination affects agricultural land and crop health through irrigation, highlighting a critical gap in understanding the implications of river pollution on farming practices.
Water pollution poses significant threats to aquatic life, agricultural productivity, and public health in nearby communities Among the various pollutants, heavy metals are particularly concerning as they can enter the food chain, posing serious health risks These metals are non-biodegradable and accumulate in waterway sediments, often bound with organic and inorganic materials This study focuses on analyzing the chemical properties of stream waters to evaluate heavy metal contamination and its implications for irrigation water quality.
METHODOLOGY
In December 2005, eight surface water samples were collected from eight different locations in Hanoi, Vietnam, during the dry season, characterized by lower river water levels compared to the rainy season.
Figure 2.1 illustrates the locations of sampling sites and factories associated with Dai Hoc Thuy Loi This map highlights the distribution of various research and industrial facilities, emphasizing their significance in the study The proximity of these sites plays a crucial role in understanding the environmental impact and resource management in the region By analyzing data from these locations, we can gain insights into the operational practices and their effects on local ecosystems.
The pH of water was measured with a pH meter (HM 30 G Horiba) Electric conductivity (EC) was determined using conductivity meter (CM 20S TOA)
Dissolved oxygen (DO) levels were assessed using the Yellow Spring YS1 58, while chemical oxygen demand (COD) was measured through the Kali Manganese method (KMnO4) Total suspended solids (TSS) were evaluated by filtering original water samples with glass filtering paper, followed by drying the collected solids at 100°C to determine their mass.
Cation and anion concentrations in filtered water samples were analyzed using an ion chromatograph (DIONEX DX-100), while both water-soluble and total heavy metal concentrations were assessed in filtered and non-filtered samples, respectively Heavy metals were measured with an atomic absorption spectrophotometer (AAS – Solar S2 Thermo electronic cooperation) All determinations were performed in duplicate, with relative deviations typically under 5%.
RESULTS AND DISCUSSION
Table 2.1 summarizes the water quality characteristics, revealing a pH range of 6.8 to 11 Notably, the pH levels for WS 2, 3, and 6 significantly exceed the Vietnamese standard for surface water, which is set between 5.5 and 9 (TCVN 5942-1995; MOSTE of Vietnam, 2002).
The EC ranged from 0.66 to 0.78 mS/cm The DO exhibited extremely low values of
The surface water quality in Vietnam is not meeting the required standards, with dissolved oxygen levels recorded at 0.1-0.7 mg/L, significantly below the minimum of 2 mg/L Additionally, the chemical oxygen demand (COD) and total suspended solids (TSS) levels ranged from 106-184 mg/L and 200-350 mg/L, respectively, both exceeding the TCVN (5942-1995) standards set by the Ministry of Science, Technology, and Environment (MOSTE).
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Table 2.1 Chemical properties in the waters of the To Lich and Kim Nguu Rivers
(mS/cm) DO** COD** TSS**
Ca Mg K Na F Cl Br NO3 SO4 PO4
* pH was measured on site
** TCVN 5942-1995 B (MOSTE of Vietnam, 2002): Category B: applied to the surface water used for the purpose other than domestic water supply, including irrigation water
Table 2.2 Correlation coefficient between chemical properties of waters
EC DO COD TSS pH
The significance of the findings at the 1% level highlights the importance of research conducted at Dai Hoc Thuy Loi This institution, known for its focus on water resources and engineering studies, plays a crucial role in advancing knowledge in these fields The repeated emphasis on "Dai Hoc Thuy Loi" underscores its reputation as a leading university, contributing to innovative solutions and academic excellence in water-related disciplines.
Cation concentrations were consistent across the samples, whereas anion concentrations varied significantly Notably, fluorine was present only in WS 6, 7, and 8, with its levels, along with the elevated NO3 concentrations in WS 1 and WS 2, surpassing surface water quality standards.
Table 2.2 shows the correlation coefficients between the chemical properties of the water samples The correlation coefficient was significant between DO and
COD at 1 % level, but was not significant for other combinations of the chemical properties
Table 2.3 presents the concentrations of water-soluble and total heavy metals in the analyzed water samples The average concentrations of water-soluble metals, after filtering to eliminate suspended solids, were found to be in the following order: chromium (Cr) levels were higher than copper (Cu) levels.
> Pb > Zn > Ni > Cd The average total metal concentrations of the samples containing suspended solids were in the order Cr > Pb > Cu > Zn > Ni > Cd
The total heavy metal concentrations for Cd, Cr and Pb exceeded the permissible level of the surface water standard (TCVN 5942-1995B: MOSTE of
In 2002, a study in Vietnam revealed that the copper (Cu) concentrations in water samples WS 2, 3, 5, and 7 exceeded the acceptable standards, while the levels of nickel (Ni) and zinc (Zn) remained within permissible limits.
The analysis of total and water-soluble metal concentrations reveals that, except for cadmium (Cd), total metal concentrations exceed water-soluble concentrations This discrepancy indicates that the mass of heavy metals, represented by the difference between these two concentrations, is primarily retained by suspended solids.
Table 2.3 Heavy metal concentrations in waters from the To Lich and Kim Nguu Rivers
Water soluble heavy metal concentration (mg/L) Total heavy metal concentration (mg/L)
Cd Cr Cu Ni Pb Zn Cd Cr Cu Ni Pb Zn
* pH was measured at lab
** TCVN 5942-1995 B (MOSTE of Vietnam, 2002): Category B: applied to surface water used for purpose other than domestic water supply, including irrigation water
Figure 2.2 Relationships among total, water-soluble concentrations and metal retained by suspended solid
M e ta ls r et ian ed b y sus pe nde d s o li d ( m g /k g)
Total heavy metal concentration (mg/kg)
T o ta l h eav y m et al c o n c en tr at io n ( m g /L )
Water soluble heavy metal concentration (mg/L)
M et al s r et ai n ed b y sus pe nde d s ol id ( m g/ k g)
Water soluble heavy metal concentration (mg/L)
The analysis of heavy metals retained by suspended solids in the samples revealed the following concentrations: Copper (Cu) at 2.61 g/kg, Zinc (Zn) at 2.87 g/kg, Lead (Pb) at 2.49 g/kg, Cadmium (Cd) at 0.03 g/kg, Chromium (Cr) at 4.13 g/kg, and Nickel (Ni) at 0.22 g/kg.
The retention of heavy metals by suspended solids is primarily attributed to the complexation of these metals with both organic and inorganic ligands Key mechanisms for immobilizing metals through organic matter include enhanced metal adsorption due to increased surface charge, the formation of organic and inorganic metal complexes, metal precipitation, and the reduction of metals from more mobile higher valence forms to less mobile lower valence forms (Bolan and Duraisamy, 2003).
This article evaluates the impact of industrial effluents on the water quality of the To Lich and Kim Nguu Rivers, referencing data from Table 2.5, which details the industrial plants in the sampling areas, alongside heavy metal concentrations from Table 2.3 Notably, an alarming cadmium (Cd) concentration of 1.1 mg/L was recorded at sampling site WS 3, likely resulting from discharges from plastic and machine manufacturing plants in the Thuong Dinh industrial zone Additionally, chromium (Cr) levels were elevated across all samples, with the highest concentration of 5.96 mg/L detected at WS 7, primarily attributed to effluents from a machine plant in Hai Ba.
The high concentration of chromium (Cr) in WS 1 within Trung industrial zone is likely attributed to wastewater discharge from a nearby leather factory, as chromium is a key component in leather production (Brigden and Santillo, 2004).
The high concentrations of Cu and Pb were found in WS 2 (Cu = 1.66 mg/L) and WS 7 (Cu = 1.07 mg/L and Pb = 1.74 mg/L) Wastewater from the plants in
The Thuong Dinh and Hai Ba Trung industrial zones are experiencing significant inflow of pollutants, primarily from the textile and footwear industries Research by Marcussen et al (2006) indicates that the sediment accumulation in these areas is largely attributed to these sectors Addressing the environmental impact of industrial activities in these zones is crucial for sustainable development and pollution management.
Table 2.4 Heavy metal concentrations in suspended solids (g/kg)
No Cu Pb Zn Cd Cr Ni
The elevated levels of copper (Cu) in WS 2 and WS 7 can be attributed to wastewater discharges from the footwear factory in Thuong Dinh industrial zone, as well as leather and textile facilities in Hai Ba Trung industrial zone.
Lead (Pb) contamination in various sites primarily originates from pollutants linked to transportation and manufacturing activities In Hanoi City, the main source of Pb remains emissions from motor vehicles, despite a significant reduction following the elimination of tetra-ethyl lead as a fuel additive Additionally, the predominant contributor to Pb levels in stream water is the aerosol emissions from gasoline-powered vehicles (Turer et al.).
INTRODUCTION
Analyzing bottom sediments is essential for identifying the sources and extent of trace metal contamination in aquatic environments Sediments can effectively retain trace metals and other pollutants over time, making them valuable for assessing historical contamination levels in water bodies (Mark et al., 1982).
Yousel et al (1994) indicated that the transport of heavy metals through sediments is a very slow process since the sediments possess a high metal retaining capacity
Heavy metal contamination in sediment remains a significant environmental challenge, with growing recognition of the critical role suspended sediment plays in transporting various pollutants, including metals and organic matter Contaminants primarily adhere to suspended particles through flocculation and sedimentation, as noted by Gibbs (1977) Research by Sato et al (2006) indicates that suspended particles can effectively accumulate metals from water, similar to biogenic particles Following particle deposition, a reduction process leads to the dissolution of these metals Comparisons show that metal concentrations in suspended solids from surface water are lower than those in settled particles near the bottom To ensure the hydraulic and technical functionality of rivers, canals, reservoirs, and harbors, regular removal of settled sediment is essential.
When dredged sediment comes into contact with air, chemical and microbial oxidation leads to dissolution, and the material poses an environmental risk
Organic matter in sediments is a crucial factor influencing the control and transport of heavy metal concentrations (Gaiero et al., 1995) It exists in both dissolved and suspended forms, as well as within bottom sediments, where its functional groups interact with heavy metals (Mulligan and Yong, 2005) Research by Cart et al (2006) indicates that organic fractions play a significant role in the absorption of metals by sediment Furthermore, the concentrations and speciation of sediment-associated metals show considerable temporal variation, which reflects the accumulation of metals and organic matter in riverbeds during periods of low flow.
Heavy metals in sediment are found in various chemical forms and particle-binding phases, including complexation with organic compounds and adsorption onto carbonates and oxide minerals Understanding these forms is crucial for assessing the mobility, availability, and toxicity of trace metals in environmental studies Various methods, particularly those focusing on metal adsorption and desorption, have been developed to determine these forms, with extraction procedures being widely utilized in soil science.
Hanoi has undergone significant economic growth and urban development in recent decades However, inadequate city planning and ineffective wastewater management for both industrial and residential areas have led to severe environmental issues, including heavy metal contamination in surface water and sediment in rivers and lakes.
This chapter presents the chemical properties of river sediment, focusing on heavy metal concentrations and the impact of industrial activities on sediment contamination It assesses the mobility of heavy metals through selective sequential extraction and leaching tests, highlighting the significant role of organic matter in the sediment's behavior.
MATERIALS AND METHODS
Surface sediment samples were collected from the top 20 cm at six submerged sites, along with two core samples taken from depths of 0 to 90 cm at two sites where the sediment was exposed to air.
December 3 to 6 of 2005 (Fig 3.1 and Table 3.1) They were air-dried, ground, and passed through a 1-mm sieve, and preserved in plastic bottles at room temperature
3.2.2.1 Chemical and Physical Properties of Sediment
SD11 SD19 SD13 SD14 SD15
FACTORY SEDIMENT SAMPLING Fl ow Dir ect ion
Figure 3.1 illustrates the locations of various sampling sites and factories associated with Dai Hoc Thuy Loi The map highlights the distribution of these sites, emphasizing their significance in the context of the study Each location plays a crucial role in the research, facilitating the collection of data essential for understanding the environmental and industrial impacts in the region This visual representation aids in comprehending the geographical relationships between the sampling sites and the respective factories, contributing to a more comprehensive analysis of the findings.
The pH was measured using soil suspension with soil: water ratio of 1:2.5
The organic carbon content was assessed using the Tyurin method, while the organic matter content was calculated by multiplying the organic carbon value by a coefficient of 1.724, as outlined by the Committee of Soil Standard Methods for Analyses and Measurement (1986) Additionally, cation exchange capacity (CEC) was measured following the method established by Muramoto et al (1992).
In the particle-size analysis, 10 g of an air-dried sample were treated with hot
To effectively remove organic matter, a 7% hydrogen peroxide (H2O2) solution is used in conjunction with ultrasonic vibration at 38 kHz The process involves deflocculating the mixture by adjusting the pH to 10 with the addition of 1M sodium hydroxide (NaOH) Following a designated sedimentation period, the clay fraction, which is less than 2 micrometers, is siphoned off for further analysis.
The entire clay fraction was isolated through a process of sonification, sedimentation, and siphoning, accompanied by intermittent pH adjustments The silt fraction, ranging from 2 to 20 µm, was obtained via repeated sedimentation and siphoning Additionally, the fine sand (20-200 µm) and coarse sand (200-1,000 µm) fractions were separated using wet sieving After drying in an oven at 105 °C, the mass of each fraction was measured to determine the particle size distribution of the soil.
3.2.2.2 Semi-quantitative estimates of mineralogical composition
The relative mineral content in the clay fraction was estimated semi-quantitatively based on XRD peak intensities This estimation involved using peak height as a measure of peak intensity, with the assumption that the mineral proportions in a sample are normalized to 100% This approach maintains a consistent proportionality between peak intensity and the content of each mineral (Nguyen and Egashira, 2005).
The reflection of Mg-saturated and glycerol-solvated specimens is essential for calculating the peak intensities of various minerals Mica and smectite contents are determined from the intensities of the 1.00 nm and 1.80 nm peaks, respectively To assess chlorite content, the intensity of the K-saturated peak at 1.42-1.44 nm is utilized.
Table 3.1 Sediment sample location and relationship between the types of industry and metal concentration in the sediment
( cm ) Location Name of companies Number in Fig 1 Type of industry Volume of waster (m 3/ day)
Heavy metal concentration in sediment (mg/kg)
SD 3 60-90 Trang An Food and Candy Factory 3
Gold Star Rubber Company 5 Construction 54
Hanoi Soap Company 6 Textile and shoes 1,015
Thang Long Tobacco Factoy 7 Foodstuff and tobacco 22,114
Rong Dong Buld and Thermos Company 8 other 95
Thuong Dinh Footwear Factory 9 Total 28,165
Kim Dai Kim Plastic Factory 10 Cd (40)
Van Dien Phosphates Factory 12 Mechanical 100
Van Dien Battery Factory 13 Construction 329
Van Dien Mechanical Factory 14 Office 1,003
Hai Ba Trung industry zone
Hai Chau Candy Factory 17 Mechanical 296
Dong Nam A Beer Factory 18 Construction
Huu Nghi Food Factory 19 Textile Garment 18,243
Minh Khai Lock Factory 22 Mai Dong Mechanical Engineering Factory 23
The Environmental Information Office (2001) highlights the importance of sustainable practices in water management and environmental conservation It emphasizes the role of educational institutions, such as Dai Hoc Thuy Loi, in promoting awareness and fostering research in these critical areas By integrating environmental studies into their curriculum, these universities aim to equip future leaders with the knowledge necessary to address pressing ecological challenges The ongoing commitment to environmental stewardship is essential for ensuring a sustainable future for our planet.
The kaolinite content was calculated by normalizing the intensity of the heated specimen, using the intensity ratio of 0.425 nm peaks from both Mg-saturated, glycerol-solvated specimens and K-saturated, 550 °C-heated specimens This normalized intensity was subtracted from the intensity of the 0.715 nm peak of the Mg-saturated, glycerol-solvated specimen Additionally, the vermiculite content was determined by subtracting the normalized intensity of the 1.42 nm peak from the relevant measurements.
1.44 nm peak of the K-saturated and air dried specimen from the 1.42-1.44 nm peak intensity of the Mg-saturated and glycerol-solvated specimen The intensity of chlorite-vermiculite intergraded was estimated from the difference between the normalized 1.42-1.44 nm peak intensities of the K-saturated and air-drying specimen and of the K-saturated and 550 o C-heated specimen The content of the mica/vermiculite/smectite ~ mica/smectite mixed- layer mineral was estimated from the normalized intensity of the 1.00 nm peak of the K-saturated and 550 o C-heated specimen after subtracting the intensities due to mica, vermiculite, smectite and chlorite-vermiculite integrated The intensity of the 1.20 nm peak of the Mg-saturated and glycerol-solvated specimen was used to calculate the content of the mica/chlorite or mica/vermiculite mixed-layer mineral The contents of geothilite, gibbsite, and lepidocrolite were calculated from the intensities of the peak at 0.416-0.417, 0.484, and 0.627 nm, respectively The 0.425 peak intensity was used to calculate the quart content after multiplication by the coefficient 3, and sum of the intensities around
0.32 nm peak was used to estimate the feldspars content
To determine total heavy metal concentration, one gram of air-dried sediment sample was digested with 5 ml of concentrated HNO3 The mixture was slowly boiled using a hot plate until it reduced to about 20 ml, at which point an additional 5 ml of concentrated HNO3 was added A reflux cap was then placed on the flask, and the mixture was boiled for approximately 2 hours After cooling, the solution was transferred to a 50 ml volumetric flask and diluted to the mark with distilled water.
The solution was analyzed for heavy metals including cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) using atomic absorption spectrometry (SOLAAR m, Nippon Jarrel-ash Co., Ltd., Japan) Each determination was performed in duplicate, with the relative deviation between duplicate values typically being less than 5%.
Selective sequential extraction (SSE) effectively utilizes specific reagents to extract various heavy metal fractions from sediment solids This method is essential for studying the distribution of particulate trace metals and assessing their potential mobility The extraction techniques employed are based on the framework established by Tessier et al (1979).
+ Water soluble fraction: One g of air dried sediment sample is extracted with 8 ml of distilled water at room temperature for 1 h with continuous agitation, shaking 1 h
+ Exchangeable fraction: The residual from water soluble fraction is extracted with 8 ml of 1M KNO3 for 1 h at room temperature with continuous agitation
+ Carbonate-bound fraction: The residual from exchangeable fraction is extracted with 8 ml of 1M CH 3 COONa adjusted to pH 5.0 with CH 3 COOH for 4 h with continuous agitation
+ Oxide-bound fraction: The residual from carbonate-bound fraction is extracted with
20 ml of 0.04M hydroxylamine hydrochloride NH 3 OH∙HCl in 25% (v/v) CH3COOH heated to 96 ± 3 o C with occasional agitation for 6 h
The organic-bound fraction is extracted from the residual oxide-bound fraction using 3 ml of 0.02M HNO3 and 5 ml of 30% H2O2, with the pH adjusted to 2 using HNO3 This mixture is then heated to 85 ± 2 °C for 2 hours, with occasional agitation to ensure thorough extraction.
To prepare the solution, add H2O2 (pH 2 with HNO3) and heat the mixture to 85°C for 3 hours with intermittent agitation After cooling, incorporate 5 ml of 3.2M CH3OONH4 in 20% (v/v) HNO3, then dilute the mixture to a total volume of 20 ml and agitate continuously for 30 minutes.
+ Residual fraction: The residual from organic-bound fraction is digested with 5 ml of concentrated HNO3 The mixed is heated to 96 ± 3 o C for 1 h with occasional agitation
An additional 5 ml of concentrated HNO 3 was added and the mixture is heated again
96 ± 3 o C to for more 2 h with intermittent agitation
Residues were separated from the supernatant by 30 min centrifugation at
RESULTS AND DISCUSSION
The chemical and physical properties of the sediment samples are shown in
The pH levels measured between 7.10 and 7.80, while organic matter content varied from 3.4% to 8.0% Notably, the highest organic matter content was observed in SD 12, indicating significant inflow of organic waste from local food, candy, and beer factories, as well as open markets and residential areas Additionally, the cation exchange capacity (CEC) ranged from 9.3, highlighting the soil's nutrient retention capabilities.
20.3 cmol c /kg The highest value of CEC in SD 12 could be attributed to the high organic matter content All the sediment samples have relatively low clay content, ranging between 3.3 and 10.3% The predominant fraction was silt for the samples,
SD 6, 7, 8, and 9 while it was fine sand for other samples
The XRD patterns of the Pb The leachability tends to decrease with increasing organic matter for those heavy metals other than Cr, Cd and Zn
To effectively reduce pollutants released from industrial plants, it is essential to implement government countermeasures and enhance wastewater treatment technologies Utilizing EDTA can play a crucial role in removing heavy metals from contaminated sediments, thereby improving environmental safety and compliance with regulatory standards.