This study investigates alum-contaminated water in An Giang province within the Mekong Delta, emphasizing methodological approaches to assess its distribution and impacts. The research conducted from March to May 2021 involved surveys of residents, public sector employees, and provincial managers, complemented by expert interviews and extensive fieldwork. Surface water samples were collected during both rainy and dry seasons across three districts, with parameters such as turbidity, pH, and temperature measured onsite, and aluminum (Al), iron (Fe), and copper (Cu) concentrations analyzed in the laboratory using atomic absorption spectrometry. The data were further processed using QGIS software to create comprehensive maps illustrating seasonal variations in water quality. The findings revealed significant spatial and temporal variations in water quality, with pH levels fluctuating markedly between the dry and rainy seasons. Household surveys indicated a lack of awareness regarding effective water treatment methods, with most respondents relying on local authorities for solutions. The study highlights the need for community education and participation in addressing alum contamination, offering insights into the environmental and public health implications of water quality in the region. This research contributes valuable knowledge to the ongoing efforts in environmental conservation and water quality management in the Mekong Delta.

  • Distribution and impacts of natural alum-contaminated water in the Mekong Delta were assessed.

  • There is an urgent need for improving human health and environment from surveys and analyses.

  • Integrating geographic information systems for comprehensive water management and promoting community engagement are the key recommendations.

  • Future research should explore locally available biomaterials for environmental remediation, building on previous successes.

The Mekong Delta, located in the vast and fertile lower region of the Mekong River, has been distinguished as a UNESCO World Heritage Site since 2014 (Tuan et al. 2015). Enriched with mineral resources (Hung Anh & Schneider 2020), vast forests (Le & Le 2021), substantial oil and gas reserves (Khain & Polyakova 2008), and a web of rivers and canals, this region embodies a unique hydrological regime (Sasges & Ziegler 2023) characterized by distinct seasonal features: floodwaters laden with sediment, plankton, and larvae in the rainy season (Triet et al. 2020; Nyanga et al. 2021), saline intrusion along coastal zones during the dry season (Binh et al. 2020), and acidic water within alkaline soils (Ha et al. 2019; Le et al. 2023). Despite its inherent advantages, the Mekong Delta confronts complicated challenges, primarily stemming from upstream development and climate change-induced factors (Binh et al. 2020; Park et al. 2020; Triet et al. 2020). Freshwater scarcity persists in remote locales, hindered by inconsistent infrastructure and developmental disparities across the region (Boretti 2020; Pan 2020).

The impacts of alum-contaminated water spread across the environment and human health, prompting an exploration into innovative environmental remediation technologies (Tran et al. 2022). Particularly in the Long Xuyen Quadrangle, domestic water sources suffer from alum contamination, detrimentally impacting productivity and community well-being (Thanh et al. 2020). Emerging studies have begun to harness alum-contaminated water as an adsorbent in environmental contexts (Phu et al. 2021). Noteworthy research studies, such as those conducted by Thanh & Toan (2017); Tran et al. (2022), and Thanh (2016) demonstrate successful applications in synthesizing novel materials from alum-contaminated water, showing enhanced catalytic properties for environmental remediation.

The prevalence of alum-contaminated water across the Mekong Delta (Stoop et al. 2015; Nguyet 2022; Huong et al. 2023), especially in An Giang province, represents both an opportunity and a challenge in water resource management. However, the utilization of this resource remains constrained due to traditional management practices, including slow data processing and the limitations of paper-based centralized databases. To address these challenges, the integration of geographic information systems (GIS) emerges as a potential solution (Yuan 2021). Local administrations have effectively utilized GIS for environmental management (Anh et al. 2021; Minh et al. 2022; Rohani et al. 2022), emphasizing the need for its implementation to streamline alum-contaminated water management in the region. For instance, the provincial Department of Agriculture and Rural Development has implemented VDAPES software (https://vdapes.com) as part of its agricultural digital transformation. This GIS-integrated software covers areas such as cultivation, plant protection, and irrigation and has attracted significant attention with over 100,000 visitors in its first year. This aligns with the national digital transformation program, approved under Decision No. 749/QD-TTg by the Prime Minister, which sets goals for digitalization by 2025 and targets through 2030. Similar GIS tech is used in Ho Chi Minh City and An Giang for environmental management (flood management).

To streamline and map the distribution of alum-contaminated water in An Giang province, this article conducts an assessment of the current scenario, aiming to establish a comprehensive database and formulate an accurate map delineating the distribution of alum-contaminated water sources.

Methods and approaches

Investigating the interplay between social practices and contexts, the study adopted a social practice approach (Herndl & Nahrwold 2000), employing Gideon (2012)'s survey methodology to delve into alum-contaminated water as a social practice. It sought to unravel opinions, treatment attitudes, and water usage demands through formal interview formats similar to surveys. Conducted between March 1 and May 20, 2021, the survey targeted residents, public sector employees, and provincial managers in An Giang province. Complemented by expert interviews, the collected data underwent analysis via SPSS 22.0 and Microsoft Excel 2020, supplemented by information obtained from related documents and studies (AGDONRE 2021b).

Ethical considerations were paramount in our research involving human participants. Approval was obtained from the Scientific and Academic Council of An Giang University by Decision No. 2208/QD-DHAG on 29/12/2020, with strict adherence to the guidelines and regulations stipulated by Nature Scientific Reports. Informed consent was diligently acquired from all participants and/or their legal guardians, ensuring compliance with ethical standards for human research.

Fieldwork included random surface water sampling during both rainy and dry seasons in three districts (Figure 1). Onsite assessments encompassed turbidity, pH, and temperature measurements, while laboratory analysis, utilizing an atomic absorption spectrometer (AAS) (Figure 2), gauged Al, Fe, and Cu levels. This process adhered to established guidelines for environmental sample collection and analysis, ensuring data reliability.
Figure 1

Images of alum-contaminated surface water in the study area.

Figure 1

Images of alum-contaminated surface water in the study area.

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Figure 2

Field-collected sample of alum-contaminated water and AAS instrument in laboratory analysis.

Figure 2

Field-collected sample of alum-contaminated water and AAS instrument in laboratory analysis.

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QGIS software facilitated the creation of eight comprehensive maps in 2021, illustrating the varying quality of alum-contaminated water in An Giang province. These detailed maps, based on pH, turbidity, Fe, and Al concentrations, offer a digital representation of water quality affected by alum contamination across different seasons. The process of mapping the distribution of alum-contaminated water involved a systematic utilization of QGIS software, as illustrated in Figure 3. It commenced by accessing geographical data from Vietnam OpenStreetMap, leveraging provincial administrative boundaries as the base framework. These maps visually articulate the dynamic variations in water quality resulting from alum contamination, clearly delineating the differences between dry and rainy seasons in An Giang province.
Figure 3

The implementation process for mapping the distribution of alum-contaminated water.

Figure 3

The implementation process for mapping the distribution of alum-contaminated water.

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The methodology adhered to the guidelines of scientific reports, ensuring ethical conduct, transparency in data collection and analysis, and compliance with best practices in environmental sampling and mapping techniques. The documentation and reporting of our study follow the stringent requirements outlined in the relevant guidelines to ensure the reliability and credibility of our research.

Study area: An Giang province

The study focuses on the Mekong Delta, a key driver of Vietnam's economy, contributing significantly to national food and aquatic production (Boretti 2020). Encompassing 12 provinces and Ho Chi Minh City across about 3.9 million hectares, it hosts nearly 17 million people, making up 12% of the country's land area and 20% of its population (GSO 2022). An Giang province (Figure 4), part of this delta, positioned along the Mekong River's right bank at the Hau River within the Long Xuyen Quadrangle, spans 353,682.95 hectares, housing 11 administrative units (GSO 2020).
Figure 4

Location of An Giang province. Reprinted from An Giang official portal website (AGDONRE 2016).

Figure 4

Location of An Giang province. Reprinted from An Giang official portal website (AGDONRE 2016).

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An environmental report for An Giang Province in 2021 focused on the Tien River, Hau River, Phu Hoi River, and Chau Doc River. Water quality varied, mainly medium in sections of the Hau River, Phu Hoi River, and Chau Doc River used for irrigation. In contrast, the Tien River had poor water quality, designated for navigation. The water quality index (WQI) revealed a spectrum of inland canal water quality, demanding specific treatment measures (AGDONRE 2021a). Monitoring 25 sites showed fluctuations, with some sites improving from poor to moderate quality in September, while others declined from good to average. These findings emphasize the need for urgent action to address deteriorating water quality trends in the region.

Household survey analysis: alum-contaminated water perceptions and demographics in Thoai Son, Tri Ton, and Tinh Bien districts

Conducting a comprehensive survey across the Thoai Son, Tri Ton, and Tinh Bien districts involved studying 300 households to understand demographic patterns. The survey revealed a predominantly male presence of 67.7%, compared to 32.3% females, with an average respondent age of 47 years, ranging from 25 to 96 years. Agricultural households constituted the majority at 71%, while the remaining 29% represented various professions like small businesses, government services, teaching, freelancing, or homemaking (Figure 5).
Figure 5

Distribution of respondents' occupational characteristics in 300 households.

Figure 5

Distribution of respondents' occupational characteristics in 300 households.

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The dependency on water supply sources for drinking (86.4%) and domestic use (68%) was substantial, although a minority used a combination of water supply and rainwater (9.3%) or solely relied on rainwater or river and canal water (2.0%) for their needs. Moreover, water use for production and irrigation showed a division, with 35.3% utilizing treated water sources and a larger percentage (58%) directly extracting untreated river and canal water, indicating a variance in water source preferences among households.

The survey uncovered diverse perceptions of water quality across seasons, with 42.3% believing water quality improved during the rainy season and 34% during the dry season. Notably, 18% noted fluctuations in water quality irrespective of the season, anticipating heightened alum concentration in the rainy season. Alum-contaminated water posed various challenges, affecting health (34%), affecting production activities (19.3%), and causing material damage (8%). A mere 4% associated with serious health risks like intestinal tract issues or cancer with alum contamination. However, households displayed limited knowledge of effective water treatment methods, with over 60% relying on external authorities for solutions.

The household survey (Figure 6) highlighted a significant lack of knowledge among over 60% of respondents regarding alum-contaminated water treatment, primarily attributing this gap to the belief that local authorities are responsible for such measures.
Figure 6

Household survey on alum-contaminated water treatment methods and challenges in implementation.

Figure 6

Household survey on alum-contaminated water treatment methods and challenges in implementation.

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In addition, an insufficient understanding of treatment methods and theoretical propaganda that lacks practical applications further contributed to this issue. Of those aware, 18% employed filter columns, facing challenges in maintenance, resulting in over 80% of filters remaining unchanged for 9 months. Lime treatment, chosen by 11%, was considered somewhat effective but suitable solely for specific water sources to prevent digestive issues. Alternative methods like chloramine B, potassium permanganate, and aerator with sand and gravel filters were less favored (3.7%) due to perceived high costs, supply unavailability, and insufficient understanding of their usage. Approximately 18% of households installed filter columns, facing challenges related to high installation costs, maintenance, and replacement difficulties. Moreover, around 14.3% practiced a method using lime and ash, considering it somewhat effective but restricting its use to specific water sources to prevent health risks. Only a small percentage employed alternative methods due to concerns about costs, supply availability, and a lack of understanding of maintenance and replacement, hindering broader adoption of these treatments for alum-contaminated water in the study area. Despite these limitations, 68% of households expressed a keen interest in environmental treatment knowledge through training sessions, emphasizing the urgency to educate communities and empower them in combating alum contamination and promoting environmental conservation efforts.

The household survey outlined the multifaceted impacts of alum-contaminated water, with 34% of respondents reporting skin-related issues, 19.3% indicating adverse effects on production activities, and 8% citing damage to utensils. In addition, 4% associated this water with severe health concerns such as intestinal tract issues or cancer. Notably, 32.7% acknowledged experiencing multiple adverse effects, while a minimal fraction (2%) perceived no impact on health or production. Regarding water treatment, 64% lacked knowledge and relied on local authorities. The survey also highlighted a strong interest (68%) among households for environmental treatment knowledge training, with 17% expressing full agreement and 15% showing partial interest. The study concludes by recommending comprehensive training programs to educate households about effective treatment methods and encourage community participation in environmental conservation efforts in An Giang province.

Assessment and mapping of seasonal changes in water quality parameters in alum-contaminated areas in An Giang province

The study area encompassing An Giang province exhibits a notable prevalence of alkaline soils, particularly evident in the vicinity neighboring Kien Giang province, predominantly within Tri Ton and Tinh Bien districts, with a minor presence in the Thoai Son district. To comprehensively assess the quality of surface water in these specific districts, extensive sampling was conducted by the author to analyze distinct parameters. The selected parameters for analysis within the alum-contaminated water encompassed Fe and Al. In addition, the study focused on examining other relevant parameters, including Cu, and conducted in situ measurements such as pH and turbidity to gain a comprehensive understanding of surface water quality. However, the fluctuations are minimal in Cu content (ranging from ‘not detected’ to 0.01 mg/L) across all study areas during both dry and rainy seasons, conforming to the permissible limit (1 mg/L) outlined in QCVN 01-1:2018/BYT, signifying an absence of Cu metal pollution in the water source within the study area.

Analysis of pH parameters

pH levels in water are a critical indicator of its acidity or alkalinity, influencing the solubility and biological availability of chemical compounds, including nutrients and heavy metals. The analysis of pH fluctuations across various regions during dry and rainy seasons (Figure 7) shows significant variations. While some areas exhibit minor pH changes, others demonstrate substantial disparities, emphasizing the dynamic nature of these levels throughout the year.
Figure 7

Distribution map of water quality contaminated with alum in the (a) dry and (b) rainy seasons according to the pH parameter in 2021.

Figure 7

Distribution map of water quality contaminated with alum in the (a) dry and (b) rainy seasons according to the pH parameter in 2021.

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Figure 7(a) illustrates the spatial variability in pH distribution across the region during the dry season, revealing notable differences among various communes. The most acidic zones, with pH levels between 3.0 and 5.69, are concentrated primarily in the northwestern parts of the region, particularly in Tinh Bien and sections of Tri Ton. These low pH levels are concerning due to their potential to adversely impact aquatic ecosystems and overall water quality. As one moves from Vinh Phuoc toward Vong Dong, pH levels gradually increase, indicating less acidic conditions, though still below optimal levels. The difference in pH levels between the dry and rainy seasons is primarily due to the dilution effect during the rainy season. During the dry season, the pH levels are notably low, especially in northwestern regions such as Tinh Bien and Tri Ton, where values range between 3.0 and 5.69. This acidity is likely exacerbated by lower water volumes and concentrated contaminants, including alum. Such acidity can disrupt aquatic ecosystems by affecting the survival of aquatic organisms, reducing biodiversity, and altering food web dynamics. Acidic water can also corrode infrastructure, increase the leaching of harmful metals from soils and sediments, and pose health risks when used for drinking or irrigation.

Figure 7(b) shows that during the rainy season, the pH distribution shifts markedly toward higher values, predominantly ranging from 5.5 to 7.6. This shift is attributable to the increased water volumes that dilute acidic substances, leading to higher pH levels across the region. For example, areas such as Chau Phu and Tan Lap in the central and eastern regions exhibit pH levels exceeding 7.0, suggesting near-neutral conditions more favorable for sustaining aquatic life. However, the western regions, including Tinh Bien and Tri Ton, continue to display relatively lower pH levels, albeit with reduced severity compared to the dry season. A more granular analysis reveals variability within specific communes. In Van Giao commune of Tinh Bien district, pH levels during the dry season fluctuate between 6.36 and 7.04, increasing to a range of 7.29 to 7.64 during the rainy season, reflecting a low difference ratio of approximately 1.09–1.15. In contrast, Tan Loi commune experiences a more pronounced seasonal shift, with pH levels ranging from 3.0 to 3.67 during the dry season and increasing to 6.57–6.93 in the rainy season, reflecting a higher difference ratio of 1.89–2.19. Similar trends are observed in other communes, including Tan Lap, Vinh Phuoc, Co To, and Tan Tuyen, with varying degrees of acidity and seasonal fluctuations.

The pH levels in Van Giao, Vong The, Vong Dong, and Tan Lap communes (at a relative level) during both seasons remain within the permissible range of 6.0–8.5, as stipulated by QCVN 01-1:2018/BYT – National Technical Regulation on Clean Water Quality for Domestic Use. However, in Tan Loi and Tan Tuyen communes, pH levels fall below the allowable limit during the dry season, while in Vinh Phuoc and Co To communes, the pH remains below the permissible level throughout both seasons.

The comparative analysis between the dry and rainy seasons reveals substantial differences in pH levels, underscoring the significant impact of seasonal variations on water chemistry in alum-contaminated areas. The increased pH levels in the rainy season are attributed to the dilution of acids by rainwater, which reduces the severity of acidity observed in the dry season. Despite these seasonal improvements, certain communes such as Tan Loi and Tan Tuyen continue to have pH levels below permissible limits during the dry season, while Vinh Phuoc and Co To remain below acceptable levels throughout both seasons. This highlights the ongoing challenges in managing water quality and underscores the need for continued monitoring and intervention.

Turbidity parameters in alum-contaminated water

Turbidity, a measure of water clarity, is influenced by suspended particles such as silt, organic matter, and microorganisms. High turbidity levels can reduce light penetration, disrupting photosynthesis in aquatic plants and leading to decreased oxygen levels in water bodies. This can harm aquatic life and exacerbate the growth of harmful algal blooms. For local residents, high turbidity water is aesthetically unpleasing, can carry pathogens, and is more challenging and costly to treat for drinking purposes. Turbidity also affects the efficiency of water treatment processes, requiring more extensive filtration and disinfection. The examination of turbidity levels in various regions during dry and rainy seasons (Figure 8) exposes significant disparities.
Figure 8

Distribution map of water quality contaminated with alum in the (a) dry and (b) rainy seasons according to the turbidity parameter 2021.

Figure 8

Distribution map of water quality contaminated with alum in the (a) dry and (b) rainy seasons according to the turbidity parameter 2021.

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During the dry season (Figure 8(a)), Van Giao commune shows turbidity levels ranging from 22 to 27 FAU and Tan Loi from 32 to 37 FAU, while Vinh Phuoc has lower levels, from 7 to 12 FAU. These differences suggest that localized factors such as land use and sediment dynamics impact water quality. In the rainy season, turbidity generally increases (Figure 8(b)). Van Giao's levels decrease to 2–7 FAU, showing a high seasonal ratio of 3.9–11 times. Tan Loi's levels are stable, ranging from 27 to 32 FAU, with a low seasonal ratio of 1.16–1.19 times. Vinh Phuoc's turbidity rises significantly to 37–49 FAU, with a seasonal ratio of 4.08–5.23 times, while Co To and Vong Dong maintain consistent levels of 2–7 FAU. Tan Tuyen and Vong The show significant seasonal variations, with turbidity decreasing from 32–37 FAU to 2–7 FAU and from 17–22 FAU to 2–7 FAU, respectively.

The results revealed significant seasonal variations in turbidity levels across the area, with notable increases at the onset of the dry season and decreases toward the end of the rainy season. Vinh Phuoc commune shows a distinct pattern, where turbidity decreases during the dry season and increases in the rainy season, illustrating the complex interplay between environmental factors and water quality. The observed seasonal differences are largely due to changes in hydrological conditions. During the dry season, reduced water flow and higher evaporation concentrate sediments, leading to higher turbidity. In contrast, the rainy season brings increased runoff and sediment transport, which typically raises turbidity levels, although the extent varies by location.

Analysis shows that turbidity frequently exceeds the permissible limits set by QCVN 01-1:2018/BYT throughout the year. During the dry season, turbidity levels exceed regulatory limits by 3.5 to 18.5 times, while in the rainy season, they surpass allowable limits by up to 24.5 times in some areas. This persistent exceedance indicates a concerning trend of water quality deterioration, particularly in areas such as Vong The, Vong Dong, Tan Tuyen, Co To, and Van Giao communes. These findings underscore the need for effective sediment management and sustainable land use practices to address the significant water quality issues exacerbated by anthropogenic activities.

Iron (Fe) parameters in alum-contaminated water

Iron is a naturally occurring element in water, but elevated levels can lead to several environmental and health issues. In An Giang province, iron concentrations were particularly high during the dry season in certain regions. Excessive iron can discolor water, stain plumbing fixtures, and laundry, and give water an unpleasant metallic taste. Environmentally, high iron concentrations can lead to the precipitation of iron oxides, which can smother aquatic habitats and affect the respiratory functions of fish and other aquatic organisms. Moreover, iron can react with other elements, potentially forming harmful compounds that pose additional risks to human health. The comparison of iron (Fe) content in various study areas during dry and rainy seasons (Figure 9) reveals significant fluctuations.
Figure 9

Distribution map of water quality contaminated with alum in the (a) dry and (b) rainy seasons according to the iron (Fe) parameter 2021.

Figure 9

Distribution map of water quality contaminated with alum in the (a) dry and (b) rainy seasons according to the iron (Fe) parameter 2021.

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Figure 9(a) shows the regional disparities in iron concentrations during the dry season. In Van Giao and Vong The communes, iron levels range from 5.6 to 7.6 mg/L, compared to 1.8 to –3.7 mg/L in the rainy season, indicating a seasonal variation of 2–3.1 times. Similarly, in Tan Loi commune, levels drop from 13.4 to 15.3 mg/L in the dry season to 9.5 to 11.4 mg/L in the rainy season, with a difference ratio of 1.3 to 1.4 times. Meanwhile, Tan Lap commune shows little seasonal change, with consistent iron levels of 5.6–7.6 mg/L across both seasons.

Figure 9(b) highlights the impact of hydrological changes on iron levels, with the most notable fluctuation in Vinh Phuoc commune, where concentrations jump from 3.7 to 5.6 mg/L in the dry season to 108 to 123 mg/L in the rainy season – a 22- to 29.2-fold increase. This suggests significant iron mobilization due to runoff and soil erosion. Tan Tuyen commune also shows a marked seasonal difference, with iron levels dropping from 13.4 to 15.3 mg/L in the dry season to 1.8 to 3.7 mg/L in the rainy season, a 4.1 to 7.4 times difference. In contrast, Co To commune maintains stable iron concentrations of 1.8–3.7 mg/L across both seasons, indicating relative geochemical stability.

These findings reveal that iron concentrations in the study area are subject to considerable temporal variability, typically increasing at the onset of the dry season and declining toward the end of the rainy season. This pattern likely results from the combined effects of reduced water flow, increased evaporation during the dry season, and the enhanced mobilization of iron via surface runoff during the rainy season. Notably, the inverse trend observed in Vinh Phuoc commune, where iron levels decrease during the dry season and increase sharply during the rainy season, highlights the complex interactions between local hydrology and geochemistry.

Importantly, the iron concentrations recorded across all study sites during both the dry and rainy seasons significantly exceed the permissible limit of 0.3 mg/L, as stipulated by QCVN 01-1:2018/BYT – Vietnam's National Technical Regulation on Clean Water Quality for domestic use. The magnitude of exceedance, ranging from 6 to 410 times above the allowable threshold, underscores the severity of iron alum contamination in the region, particularly in Vinh Phuoc, Tan Loi, and Tan Tuyen communes. These findings call for immediate and targeted interventions to mitigate the risks posed by high iron concentrations to public health and the environment.

Aluminum parameters in alum-contaminated water

The presence of aluminum (Al) in water, particularly in its dissolved form, is a concern due to its toxicity to aquatic life and potential health risks to humans. Analysis from Figure 10 demonstrates significant differences in Al content between dry and rainy seasons across multiple study areas.
Figure 10

Distribution map of water quality contaminated with alum in the (a) dry and (b) rainy seasons according to the aluminum (Al) parameter 2021.

Figure 10

Distribution map of water quality contaminated with alum in the (a) dry and (b) rainy seasons according to the aluminum (Al) parameter 2021.

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In Figure 10(a), the distribution of aluminum concentrations during the dry season demonstrates substantial spatial and temporal variability. In communes such as Van Giao, Tan Loi, Tan Lap, and other areas within Tinh Bien and Thoai Son districts, aluminum levels range from 0.9 to 6.8 mg/L. However, Vinh Phuoc commune in Tri Ton district exhibits markedly higher concentrations, ranging from 36.4 to 42.3 mg/L. This marked increase is attributed to reduced water volumes and intensified evaporation, which concentrate aluminum in remaining water bodies.

The significant seasonal fluctuations are further illustrated in Figure 10(b), where aluminum concentrations during the rainy season range from 0.32 to 1.05 mg/L in most communes, with Tan Tuyen commune showing slightly higher levels of 4.72–5.45 mg/L. The ratio of concentrations between the dry and rainy seasons varies considerably, from approximately 2.8–114 times, reflecting the effect of increased runoff and dilution during the rainy season. Tan Tuyen commune, in particular, exhibits relatively large fluctuations in aluminum content between seasons. The dry season concentrations contribute to a higher relative increase in aluminum levels during the rainy season in certain areas. This is likely due to the accumulation of aluminum during the dry season, which, when diluted in the rainy season, still remains elevated compared to other regions.

The observed increase in aluminum levels during the dry season can be attributed to several factors. Reduced water volumes and increased evaporation lead to higher concentrations as the same amount of aluminum is concentrated in a smaller volume of water. In contrast, during the rainy season, increased precipitation and runoff dilute aluminum concentrations, leading to lower levels. The high fluctuation ratios observed, especially in areas such as Vinh Phuoc, suggest that these regions are particularly susceptible to variations in surface water conditions. In addition, the consistently high concentrations of aluminum in Vinh Phuoc, even during the rainy season, imply potential ongoing sources of contamination or more persistent environmental factors contributing to the elevated levels. This could be linked to industrial discharges, natural mineral deposits, or inadequate waste management practices.

Overall, Al content in both dry and rainy seasons surpasses permissible limits (0.2 mg/L) by 1.6–212 times according to QCVN 01-1:2018/BYT standards. This necessitates stringent management measures and prompt technical interventions to improve water resources and safeguard the well-being of households in these areas. The study observed considerable aluminum levels in alum-contaminated areas, which can become more bioavailable and toxic under low pH conditions. For aquatic organisms, elevated aluminum levels can impair gill function in fish, leading to respiratory distress and increased mortality rates. For local residents, prolonged exposure to aluminum in drinking water has been associated with neurological effects and potential links to diseases like Alzheimer's. High aluminum concentrations can also complicate water treatment processes, requiring more advanced and costly techniques to remove this contaminant effectively.

This study meticulously examined the interplay between social practices, alum contamination, and water quality in An Giang province, employing a comprehensive social practice approach alongside rigorous field and laboratory analyses. By surveying a diverse group of residents, public sector employees, and provincial managers, the study provided valuable insights into the perceptions, attitudes, and treatment practices surrounding alum-contaminated water. The findings revealed a significant dependency on untreated water sources, a lack of awareness regarding effective treatment methods, and an overreliance on local authorities for solutions. Despite the limited understanding, there was a strong interest in acquiring environmental treatment knowledge, underscoring the need for targeted educational programs.

This study conducted a comprehensive assessment and mapping of seasonal changes in water quality parameters in alum-contaminated areas of An Giang province, focusing on pH, turbidity, iron (Fe), and aluminum (Al). The findings revealed significant fluctuations across dry and rainy seasons, with some areas exhibiting drastic variations that exceed permissible limits, particularly in Fe and Al content. These results underscore the urgent need for targeted interventions and continuous monitoring to mitigate the adverse effects of alum contamination on surface water sources. The use of GIS in this study provided a digital representation of dynamic water quality changes across seasons, highlighting the areas most at risk.

Future research should focus on leveraging locally available biomaterials for environmental remediation, offering an eco-friendly and cost-effective solution for contaminants like Fe and Al. However, challenges such as substantial investment in research, overcoming technical barriers, and ensuring scalability must be addressed. Success depends on multidisciplinary collaboration among scientists, local authorities, and communities, with a need for specialized technical expertise and continuous financial support. In addition, comprehensive training programs are essential to educate communities and drive conservation efforts, particularly in regions with severe water quality issues.

This research was funded by Vietnam National University – Ho Chi Minh City (Grant Number A2020-16-01).

T.T.N. conceived of the idea, designed the experiments, got the funding, and supervised the study. S.D.H.C., T.T.L., Q.A.N.T., P.T.P., and L.B.T. did the survey, took water samples, analyzed the parameters, and processed data. Q.T.T., T.N.T., and S.P. drafted the manuscript. N.H.N. revised the manuscript.

We conducted the survey among 300 households and public sector experts in the Thoai Son, Tri Ton, and Tinh Bien districts (An Giang Province, Vietnam). Ethical considerations were diligently observed throughout the study, including obtaining informed consent from all participants and ensuring confidentiality.

All relevant data are included in the paper or its Supplementary Information.

The authors declare there is no conflict.

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