Arsenic contaminated groundwater and its potential health risk A case study in Long An and Tien Giang provinces of the Mekong Delta, Vietnam 1 23 Environmental Science and Pollution Research ISSN 0944[.]
Arsenic-contaminated groundwater and its potential health risk: A case study in Long An and Tien Giang provinces of the Mekong Delta, Vietnam Van-Truc Nguyen, Thi-Dieu-Hien Vo, Thanh-Dai Tran, Thi-Nhu-Khanh Nguyen, Thanh-Binh Nguyen, BaoTrong Dang & Xuan-Thanh Bui Environmental Science and Pollution Research ISSN 0944-1344 Environ Sci Pollut Res DOI 10.1007/s11356-020-10837-6 23 Your article is protected by copyright and all rights are held exclusively by SpringerVerlag GmbH Germany, part of Springer Nature This e-offprint is for personal use only and shall not be self-archived in electronic repositories If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website The link must be accompanied by the following text: "The final publication is available at link.springer.com” 23 Author's personal copy Environmental Science and Pollution Research https://doi.org/10.1007/s11356-020-10837-6 GREEN TECHNOLOGIES FOR SUSTAINABLE WATER Arsenic-contaminated groundwater and its potential health risk: A case study in Long An and Tien Giang provinces of the Mekong Delta, Vietnam Van-Truc Nguyen & Thi-Dieu-Hien Vo & Thanh-Dai Tran & Thi-Nhu-Khanh Nguyen & Thanh-Binh Nguyen & Bao-Trong Dang & Xuan-Thanh Bui 4,7 Received: April 2020 / Accepted: 13 September 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020 Abstract The occurrence of arsenic (As) in groundwater (drilled well water) that were used for drinking, cooking, and personal hygiene and its risks to human health in Long An and Tien Giang provinces (Mekong delta, Vietnam) were evaluated in this study The average As concentrations were 15.92 ± 11.4 μg/L (n = 24, Long An) and 4.95 ± 4.7 μg/L (n = 24, Tien Giang) The average concentrations of As in Long An had not reached the WHO and QCVN 01: 2009/BYT healthy drinking water standard (10 μg/L) When used as a source of water for drinking and daily activities, arsenic-contaminated groundwater may have a direct impact on human health The risk assessment from groundwater established by the US Environmental Protection Agency (USEPA) was conducted The risk assessment showed that the average cancer risk (CR) values were 8.68 × 10−4 (adults) and 2.39 × 10−3 (children) for Long An, and 2.70 × 10−4 (adults) and 7.43 × 10−4 (children) for Tien Giang These results were significantly higher than the CR (1 × 10−4) proposed by the USEPA The adverse health effect was therefore specifically warned by the use of arsenic-contaminated groundwater This research offers valuable knowledge for efficient water management approaches to guarantee local communities’ health protection Keywords Drinking water Heavy metal contamination Non-carcinogenic risk Carcinogenic risk Water management strategy Responsible Editor: Philippe Garrigues Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11356-020-10837-6) contains supplementary material, which is available to authorized users * Thi-Dieu-Hien Vo vtdhien@ntt.edu.vn Faculty of Applied Sciences–Health, Dong Nai Technology University, Bien Hoa, Dong Nai, Vietnam * Xuan-Thanh Bui bxthanh@hcmut.edu.vn Faculty of Environment and Natural Resources, Ho Chi Minh City University of Technology (HCMUT), Ho Chi Minh City 700000, Vietnam Department of Marine Environmental Engineering, National Kaohsiung University of Science and Technology, Kaohsiung, Taiwan Ho Chi Minh City University of Technology – HUTECH, 475 A Dien Bien Phu, Binh Thanh district, Ho Chi Minh City, Vietnam Key Laboratory of Advanced Waste Treatment Technology, Vietnam National University Ho Chi Minh (VNU-HCM), Linh Trung ward, Thu Duc district, Ho Chi Minh City 700000, Vietnam Van-Truc Nguyen truc1021006@gmail.com Thanh-Binh Nguyen ntbinh179@nkust.edu.tw Institute of Research and Development, Duy Tan University, Da Nang 550000, Vietnam Faculty of Environmental and Food Engineering, Nguyen Tat Thanh University, Ho Chi Minh City, Vietnam Author's personal copy Environ Sci Pollut Res Introduction Arsenic is the poisonous element that is odorless, colorless, and tasteless (Kuivenhoven and Mason 2019) People not realize they are absorbing invisible toxic Thus, it is called the “invisible killer.” The highest risk of arsenic exposure is through the digestive route Arsenic and its compounds have been attributed to high carcinogens (group 1) for humans (WHO 2010) Arsenic is wellknown to cause various diseases including bladder, skin, kidney, prostate, lung, and liver cancers (Fallahzadeh et al 2017) Too much exposure to excessive arsenic can cause all sorts of health problems, namely immediate sickness and even death Besides the As exposure associated with the consumption of fish, vegetables, and rice, the As exposure was considered using groundwater as the drinking water (Liang et al 2016) In developing countries, particularly in Southeast Asia, where surface water has been polluted and sanitized, groundwater is one of the critical fresh-water sources for drinking and living (Buschmann et al 2007) Natural As concentration in groundwater was at low levels (0.5–0.9 μg/L) However, the occurrence of high-level As in groundwater might be due to the release of arsenic from natural or anthropogenic sources (Gao et al 2019) Indeed, in some regions, drinking waterbased on groundwater extracted by pumping wells can be polluted by natural inorganic arsenic with the concentrations more than the permission limit (10 μg/L) of the WHO (WHO 2001) Some regions facing with serious arsenic contamination were West Bengal of India (Rahman et al 2015), Taiwan (Liang et al 2016), Chile (Marshall et al 2007), Mexico (Pacheco et al 2018), and Bangladesh (Wasserman et al 2004), Cambodia (Buschmann et al 2007), China (Li et al 2018), Vietnam (Berg et al 2001) Many studies about arsenic pollution of groundwater were conducted in Red River’s Delta, for example, the average As concentration of 159 μg/L in Hanoi (Berg et al 2001) and 294.66 μg/L in Ha Nam province (Van et al 2009) Studies in Mekong River’s Delta reported the As concentration in Dong Thap province (666 μg/L), An Giang province (1351 μg/L), and Kien Giang (16 μg/L) (Hoang et al 2010); in Vinh Long province (16.9 μg/L) and Tra Vinh province (1.0 μg/L) (Nguyen and Itoi 2009) The characteristics of wells as well as groundwater quality parameters also significantly affected the concentration of As Berg et al (2008) evaluated the correlation between As concentration and Fe, ammonium, DOC, redox potential in the well water of Vinh Phuc province The results showed that positive correlations of As/ NH4+-N (r2 = 0.41) and As/DOC (r2 = 0.6) were recorded Meanwhile, Fe and redox potential had weak correlations with As concentration Gong et al (2014) also found a negative correlation between As and the well depth in some areas of Texas, USA Machado et al (2019) found the correlation between As concentration and pH, Fe, Mn, F − , SO 2− in the well water of Medical Geology in Uruguay The positive correlations were recorded such as As/pH (r = 0.44), As/F − (r = 0.59), and As/SO 42− (r2 = 0.30) The weak negative correlations were found for As/Fe and As/Mn Most recently, Machado et al (2020) also found the positive correlation of As/Cl − (r2 = 0.39), As/F− (r2 = 0.52), As/Na (r2 = 0.55), and As/ V (r2 = 0.62) From the review data, the physicochemical factors are also significantly correlated with the concentration of As There is still a severe shortage of drinking water in certain areas of the developing world In rural areas of Vietnam, groundwater is considered the main source of water when surface water is limited and polluted Most of the households use sand filters to remove iron and odors in groundwater before drinking (Huy et al 2014) Thereby, health risk assessment attributed to arsenic-contaminated groundwater is critical for protecting human health The health risks were evaluated based on the hazard quotient (HQ) and target risk (TR) established by USEPA Many studies have applied these risk assessment methods in many different countries such as Chile (Marshall et al 2007), China (Li et al 2018), Mexico (Pacheco et al 2018), Pakistan (Shah et al 2020), Taiwan (Vu et al 2017), Thailand (Wongsasuluk et al 2018), Turkey (Kavcar et al 2009), and Vietnam (Phan and Nguyen 2018) Indeed, arsenic-contaminated groundwater caused significant human health influences in many areas of the world, e.g., bladder cancer in the USA (Steinmaus et al 2003), neurobehavioral disorders in Taiwan (Tsai et al 2003), and miscarriages in Bangladesh (Rahman et al 2009) (details information was described in Van et al (2009) In general, the results of the evaluation were intended to enhance the awareness of the residents and provide insight into the water management strategy According to the simulated data of Erban et al (2013), As concentrations in Long An and Tien Giang provinces were up to 100 μg/L However, no studies have conducted surveys of As concentration in groundwater, its correlation with physicochemical parameters, as well as an assessment of human health risks in these two provinces The research results contribute to a better understanding of the health risks assessment of As in groundwater and fill the information gap about heavy metal pollution in groundwater from Mekong delta, Vietnam, where there is a lack of information on heavy metals in groundwater Thus, it is necessary to investigate arsenic contamination in Long An and Tien Giang provinces to (i) identify the status of arsenic and create arsenic contamination maps; (ii) find correlation factors, equations, and types between arsenic and groundwater parameters comprising alkalinity, ammonia, manganese, well depth; and (iii) assess human health risk due to As concentration Author's personal copy Environ Sci Pollut Res Materials and methods Study area The Mekong Delta is located in the southern part of Vietnam (Fig 1) and is known as the largest rice warehouse in Vietnam with the total land area of approximately 1.7 million hectares There are thirteen provinces such as An Giang, Bac Lieu, Ben Tre, Ca Mau, Dong Thap, Hau Giang, Kien Giang, Long An, Tien Giang, Vinh Long, the province-level municipality of Can Tho, Soc Trang, and Tra Vinh Long An is located between 106° 10′ E longitude and 10° 40′ N latitude The area of this province is 4495.5 km2 and has a population of 2,002,767 inhabitants Tien Giang is located between 106° 10′ E longitude and 10° 25′ N latitude It covers about 2510.5 km2 area and has a population of 1,764,185 These areas are characterized by a dense and complex network of rivers, lakes, and channels The characteristics of delta sediments were similar to the Ganges Delta (Hoang et al 2010) The Mekong Delta had about 60% of the low flooded lowland areas with highsulfate acid soil The characteristic of the weather here is tropical monsoon with an average annual temperature of 27 °C and precipitation of 1660 mm There are two distinct seasons including sunny (November–April) and rainy (May–October) seasons (Pham et al 2017) Main water resources for residents in Long An and Tien Giang provinces consist of surface water, rainfall, and groundwater The groundwater wells in suburban areas of these provinces where a water supply system was not available were randomly selected for this study Most of these wells serve as the main sources of drinking water, cooking, and hygiene for residents The well water is directly used and is only treated by a simple sand filtration unit before using it Therefore, the quality of groundwater must be controlled here because it has the potential to adversely affect human health As contamination sources are mainly from natural sources which are caused by the washing of As-rich sediments from natural soils (Jessen 2009) Furthermore, herbicides used in agriculture are also a source of As emissions However, these herbicides have been banned in Vietnam since 1997 (VMARD 1997) Another source is industrial activity but it is not significant Sampling, pretreatment, and analysis A total of 48 groundwater samples were collected from 24 wells in rural areas or urban fringe of Long An and 24 wells in those of Tien Giang province (detailed information of the sampling locations shown in Table S1) All wells in this study were operated by high-pressure water pumps Wells were categorized into two types including shallow wells with less than 60 m depth and deep wells with more than 60 m depth The surveyed wells of Long An were deep wells In Tien Giang, 18 deep wells and shallow wells were sampled In this study, the sampling time was during March and April (dry season, less influence of rainwater) The sampling process followed the TCVN6663-11 (2011) A record was made for every sample collected and a tag or label was used to identify the information of groundwater samples Information to provide Fig Location map of the studied area and sampling sites in Long An and Tien Giang Author's personal copy Environ Sci Pollut Res accurate sample identification, including the specific sample identification number, the sample collector name, sampling time (hour, day, month, and year), and the exact location was determined using global positioning systems (GPS), and other data such as weather conditions, water level, and water temperature was also performed Before sample collection, groundwater was left to flow for about Sampling bottles were washed with DI water and 5% HNO3 solution to ensure their purity After passing through a 0.45-μm Whatman filter, samples were added with mL of 69% HNO3, then stored at °C, and transported directly to the laboratory Groundwater samples were analyzed within weeks Field measurements included pH, TDS, and turbidity Alkalinity, ammonia, phosphate, and sulfate were tested in the laboratory The pH value was determined with a pH meter (Mi 150, Milwaukee, Rumania) TDS was measured by Greisinger G1410 conductivity tester TDS, conductivity, salinity (G1410, Greisinger, Germany), and turbidity was measured onsite using a HI-93703 portable turbidity meter (HI93703, Hanna, Rumania) Total alkalinity was determined by titration using methyl orange and bromocresol green indicators in the laboratory The DR/2010 spectrophotometer (DR/ 2010, Hach, USA) was used for the ammonia, phosphorus, and sulfate All laboratory analyses were carried according to standard methods (APHA 1998) Heavy metals were determined by an inductively coupled plasma mass spectrometryICPMS (ICP-MS, model 7700x, Agilent, USA) using an ICPMS-grade standard in Gwangju Institute of Science and Technology, South of Korea The metals were measured in triplicate for each sample and a reagent blank was analyzed for every 10 samples Reagent blanks were prepared and analyzed for metals using the same procedure, and the results showed that all concentrations of metals were lower than the detection limits (MDL of As (0.01 μg/L); Ba (0.008 μg/L); Fe (0.081 μg/L); Mn (0.27 μg/L)) To ensure analytical accuracy, certified reference standards were used (SRM-1648a) The recoveries were 90–120% for all metals Risk assessment In this study, the risk assessment for human health of As is according to USEPA (2005) The average daily dose (ADD) of As was determined as follows: ADD ¼ ðC IR E F EDÞ=ðAT BW Þ ð1Þ where ADD is average daily dose from ingestion (mg/kg day), C is arsenic concentration in water (mg/L), IR is water ingestion rate (L/day), EF is exposure frequency (day/year), ED is exposure duration (year), AT is averaging time (day), and BW is body weight (kg) In this study, IR is L/day for adults and L/day for children (Phan and Nguyen 2018) ED is 70 years for adults and 10 years for children (Radfard et al 2019) EF is 365 days/year for both adults and children (Muhammad et al 2010) AT is 25,550 days for adults and 3650 days for children (Rasool et al 2016; Radfard et al 2019) BW is 55 kg for adults and 10 kg for children (Van et al 2009; Phan and Nguyen 2018) The hazard quotient (HQ) was determined as follows: HQ ẳ ADD=R f D 2ị Where HQ is hazard quotient (cases with HQ > are attributed to human health risks), RfD is a reference dose (mg/kg day) In this study, the RfD of As is 0.0003 mg/kg day (USEPA 2005; Radfard et al 2019) The carcinogenic risk (CR) was determined as follows: CR ¼ CS F ADD ð3Þ where CSF is the cancer slope factor for As In this study, CSF is 1.5 (mg/kg day)−1 (Rasool et al 2016; Radfard et al 2019) The total carcinogenic risk less than and equal to × 10−4 was proposed as the maximum acceptable risk level (USEPA 2005; Alidadi et al 2019) Statistical analysis Descriptive statistics including average and standard deviation were performed Pearson’s correlation was employed to reveal the relationship between the As concentration and physicochemical parameters Statistical Package for Social Sciences software (SPSS) version 16.0 was used for all statistical analyses Results and discussion Arsenic concentration in groundwater Arsenic forms in aqueous media consist of arsenious acid (H3AsO30, H2AsO3−, As (III)) and arsenic acid (H2AsO4−, HAsO42−, As (V)) The toxicity of As (III) is stronger than that of As (V) (Corsini et al 2018) Average As concentration of both provinces were shown in Fig 2a (detailed information on the sampling locations shown in Table S2) As concentration in Long An was significantly higher than in Tien Giang The occurrence of As in groundwater was attributed to the geological origin Soils in Long An have a sulfuric horizon that can adsorb As (Husson et al 2000) Nevertheless, sulfuric acid may be extracted from soils under reduced conditions, resulting in the release of arsenic (Nguyen and Itoi 2009) These might explain why As concentrations in Long An were higher than in Tien Giang As shown in Fig 2a, two outliers (L7 and L8 with high As concentrations) were also observed in Long An According to the survey during the sampling process, the current potential sources of As emissions were Author's personal copy Environ Sci Pollut Res Fig Boxplot of arsenic contamination (a), the concentration of arsenic in groundwater (b), and the map of arsenic contamination level (c) in Long An and Tien Giang Author's personal copy Environ Sci Pollut Res virtually absent in these sites This high As pollution may, therefore, be attributable to the natural geological characteristics as well as the anthropogenic activities that have taken place in the past, as described above in the definition of the study area Figure 2b shows the As concentration of all samples in the Long An and Tien Giang provinces As concentration ranged from 0.03 to 46.88 μg/L and 0.05 to 13.33 μg/L in Long An and Tien Giang, respectively The highest (46.88 μg/L) in sampling point L7 and the lowest As concentration (0.03 μg/L) in sampling point L23 was detected in Long An The average As concentrations were 15.92 ± 11.4 μg/L (Long An) and 4.95 ± 4.7 μg/L (Tien Giang) Figure 2c presented that was 18 sampling points (75% of samples) in Long An, and sampling points (25% of samples) in Tien Giang exceeded the safe limit of WHO as well as QCVN 01: 2009/ BYT (10 μg/L) Therefore, these results provided useful information that gives warnings to the residents to get the most appropriate treatment and usage plan Table shows that As concentration in northern Vietnam is much higher than in southern Vietnam The mean As concentration observed in this work was significantly lower than the one found in the samples collected in the northern part of Vietnam (Berg et al 2001; Van et al 2009) and Dong Thap and An Giang (Van et al 2009; Hoang et al 2010), but higher than in the southern part of Vietnam such as Vinh Long, Tra Vinh and Kien Giang (Nguyen and Itoi 2009; Hoang et al 2010) This study also showed the As concentration was much lower than the one detected in Pakistan (Shakoor et al 2015; Rasool et al 2016), Cambodia (Buschmann et al 2007), Bangladesh (Wasserman et al 2004), India (Rahman et al 2015; Chakraborti et al 2016), Taiwan (Liang et al 2016), and China (Li et al 2018) In general, the presence of arsenic in groundwater fluctuated significantly This might be related to the geochemical characteristics of the sampling area The soluble products of weathering and decomposition of rock also greatly affect the mineral concentration in groundwater samples (Chenini et al 2010) The accumulation of ions in groundwater might vary according to the geological frame of the geographic location In this case, an important factor might be the different types of aquifers encountered in the different study areas Physicochemical characteristics of groundwater The pH was slightly acidic in the range of 5.50–7.08 in Long An and alkaline in the range of 6–8.59 in Tien Giang The average pH in groundwater samples of both provinces was 6.59 and 7.85, respectively pH is one of the most important indicators of water quality because it affects the dissolution of minerals, resulting in to change in As concentration (Sracek et al 2004) Indeed, the pH in Long An was lower than in Tien Giang It might be the cause of significantly higher As concentration in Long An than that of Tien Giang At low pH (less than pH 6.9), under oxidizing condition, H2AsO4− is dominant, whilst at higher pH, HAsO42− becomes dominant Under reducing condition at pH less than about pH 9.2, the most abundant were the uncharged arsenic species H3AsO30, which was more toxic than other forms of As (Corsini et al 2018) Besides, pH affected some of the water quality parameters such as ionic solubility and pathogen survival, which will impact human health eventually Too high pH made the water tastes bitter, whereas too low pH caused the sour taste (Muhammad et al 2010) The pH value in the aquifer in this study was within the recommended range (6.5– 8.5) recommended by WHO, except that in Long An Alkalinity in groundwater fluctuated from 27 to 230 mg/L and 60 to 644 mg/L in Long An and Tien Giang, respectively The alkalinity of water in the study area may be due to the presence of HCO3− that was formed from the weathering of carbonate rock (Langman et al 2019) The average concentrations of phosphate in both provinces were low, ranging from 0.028 ± 0.03 to 0.29 ± 0.75 mg/L The highest concentration of phosphate was 3.8 mg/L for groundwater of Tien Giang and the lowest concentration (0.003 mg/L) was found in Long An Similarly, low phosphate was also found in the well water in Turkey (Ağca et al 2014) The occurrence of phosphate in groundwater might be caused by leakage from runoff and/or soil However, phosphorus is highly immobile in the soil since most of the total phosphorus in the soil consists of calcium phosphate and magnesium phosphate Some phosphorus had been contained in the soil by clay When anthropogenic deposits were therefore overlooked, the phosphate leakage into groundwater was very small (Ağca et al 2014) This might explain for relatively low phosphate levels that were found in some aquifers The average concentration of ammonium in groundwater range from 0.734 ± 1.12 to 4.72 ± 2.01 mg/L The lowest ammonium nitrogen concentration in Long An was 0.19 mg/L and 51.27 times lower than the concentration detected in Tien Giang Ammonium nitrogen in groundwater was also primarily derived from anthropogenic activities The ammonium nitrogen concentration in this study was significantly lower than that (0.11–63.72 mg/L) found by Ağca et al (2014) The average TDS in groundwater samples from Long An and Tien Giang was 282 mg/L and 349 mg/L, respectively The lowest observed value for TDS was 140 mg/L for Long An and the highest TDS (1150 mg/L) was found in the Tien Giang sampling sites In groundwater samples, most solutes, including inorganic salts, small amounts of organic matter, and dissolved gases will contribute to TDS (Prakash and Somashekar 2006) High levels of TDS in groundwater might mainly due to the presence of iron, sulfate, and occasionally arsenic The high TDS concentration at Cho Moi station, An Giang province (Mekong Delta) was 4516 ± 2768 mg/L in groundwater recorded by (Phan and Nguyen 2018) Author's personal copy Environ Sci Pollut Res Table Concentration of As (μg/L) in groundwater from this study and other sites reported in the literature Site Country Mean As conc.(μg/L) References Long An (Southern of Vietnam) Tien Giang (Southern of Vietnam) Dong Anh (Northern of Vietnam) Vietnam Vietnam Vietnam 15.9 4.95 220 This study This study Berg et al (2001) Tu Liem (Northern of Vietnam) Vietnam 230 Berg et al (2001) Gia Lam (Northern of Vietnam) Vietnam 3050 Berg et al (2001) Thanh Tri (Northern of Vietnam) Vietnam 3010 Berg et al (2001) Ha Nam (Northern of Vietnam) Vietnam 348 Van et al (2009) Dong Thap (Southern of Vietnam) Vietnam 666 Van et al (2009) An Giang (Southern of Vietnam) Vietnam 1351 Hoang et al (2010) Kien Giang (Southern of Vietnam) Vietnam 16.0 Hoang et al (2010) Vinh Long (Southern of Vietnam) Tra Vinh (Southern of Vietnam) Mashhad Vietnam Vietnam Iran 16.9 1.00 0.18 Nguyen and Itoi (2009) Nguyen and Itoi (2009) Alidadi et al (2019) Jinghui irrigation China 0.54 Zhang et al (2019) Jinghuiqu China 1.89 Zhang et al (2019) Ubon Ratchathani Thailand 1.06 Wongsasuluk et al (2014) Ubon Ratchathani Thailand 2.19 Wongsasuluk et al (2018) Sungai Petani, Kedah Malaysia 2.51 Ahmad et al (2015) Brisbane River estuary Australia 3.90 Duodu et al (2017) Sumatra Indonesia 5.18 Winkel et al (2008) I’Zmir Turkey 6.47 Kavcar et al (2009) Mexico Mexico > 10.0 Pacheco et al (2018) Uruguay Uruguay 15.7 Machado et al (2019) Rahim Yar Khan of Punjab Pakistan 31.0 Shakoor et al (2015) Kandal, Takeo, and Prey Vêng Cambodia 81.7 Buschmann et al (2007) Araihazar Bangladesh 118 Wasserman et al (2004) Mailsi, Pụnab Pakistan 156 Rasool et al (2016) West Bengal India 255 Rahman et al (2015) Pingtung Plain Taiwan 348 Liang et al (2016) Jianghan Plain China 1081 Li et al (2018) Patna India 1466 Chakraborti et al (2016) Rainwater runoff, agricultural runoff, leakage from industrial activities, and solid waste deposit could contribute greatly to turbidity in groundwater It is essential to encapsulate pathogenic organisms in particles that cause turbidity resulting in health hazards (Prakash and Somashekar 2006) In this study, turbidity varied from 0.5 to 280 NTU and to 68 NTU in Long An and Tien Giang, respectively These results were noticeably lower than those (0–316 NTU) in the study of Prakash and Somashekar (2006) Sulfate was present in almost all samples The highest (26.73 mg/L) and lowest (1.06 mg/L) sulfate (SO42−) concentrations were detected in Tien Giang The average concentration of sulfate in groundwater samples from two sites Long An and Tien Giang was 12.81 ± 7.18 mg/L and 5.09 ± 5.54 mg/L, respectively High sulfate concentration may be due to both pyrite oxidation and gypsum dissolution (Nguyen and Itoi 2009) Samples with high concentrations of sulfate were found in wells near the rivers and seas Therefore, the interaction between groundwater and marine deposits or disturbance between freshwater and seawater has led to high sulfate levels Similar results were found in the study of Nguyen and Itoi (2009) The sulfate concentrations in this study were significantly lower than the sulfate concentrations (average 53 mg/L, max 773 mg/L) found in other areas along the Mekong River (Nguyen and Itoi 2009) Total Fe in groundwater fluctuated from 0.27 to 9.45 mg/L and 0.03 to 9.02 mg/L in Long An and Tien Author's personal copy Environ Sci Pollut Res Giang, respectively The highest observed values for total Fe was 9.45 mg/L in Long An and the lowest total Fe (0.03 mg/L) was found in Tien Giang The average of total Fe values in groundwater samples from two sites Long An and Tien Giang was 3.78 ± 2.99 mg/L and 1.23 ± 2.62 mg/L, respectively Compared with the study of Machado et al (2019) in Uruguay (2.0 to 242.7 μg/L), the concentration of Fe in the aquifer in this study was much higher As concentration in Uruguay was slightly lower than in Long An but much higher than in Tien Giang Iron had little effect on health, but caused unpleasant odors and affected the quality of food cooked or laundered The presence of iron in groundwater was related to the rock formation The high concentration of Fe in groundwater may be due to the casing pipe corrosion, not using the well for a long time, permeating iron pollutants, solid waste disposal, industrial activities, etc (Prakash and Somashekar 2006) The Ba concentration in groundwater ranged from 67.55 to 420 μg/L and 2.25 to 728.3 μg/L in Long An and Tien Giang, respectively The highest (728.3 μg/L) and the lowest Ba concentration (2.25 μg/L) was observed in Tien Giang The average Ba concentrations in Long An and Tien Giang were 202.35 ± 94.72 μg/L and 143.51 ± 154.79 μg/L, respectively It can be seen that Ba concentration increases with an increase in As concentration A similar trend was found by Hoang et al (2010) when studying in An Giang and Dong Thap, Vietnam Concentrations of Ba as well as As in this study were also significantly lower than in An Giang and Dong Thap The Mn concentration in groundwater ranged from to 489.1 μg/L and 0.02 to 3745 μg/L in Long An and Tien Giang, respectively The highest (3745 μg/L) and the lowest Mn concentrations (0.02 μg/L) were measured in Tien Giang The average Mn concentrations in Long An and Tien Giang were 115.02 μg/L and 561.03 μg/L, respectively Compared with the study of Hoang et al (2010), Mn concentration in this study was 5–14 times lower for Long An and 1.9–3 times for Tien Giang In general, the pH, sulfate, and Ba values in all samples were within the safety limits (5.5–8.5 for pH, 250 mg/L for sulfate, 0.7 mg/L for Ba) The ammonium, total Fe, and turbidity in both provinces exceeded the safety limits for drinking water of the QCVN 01: 2009/BYT (VMOH 2009) Approximately 8% of samples in Long An and 79% samples of Tien Giang exceeded the allowed limit for ammonium (3 mg/L) The TDS and Mn concentration in the sample from Long An was within the safety limits of the QCVN 01: 2009/BYT (1000 mg/L for TDS, 300 μg/L for Mn), except in Tien Giang Compared to USEPA standards (USEPA 2001), about 50% and 91% of samples in Long An and 37% and 23% of samples in Tien Giang exceeded the allowed limit for Mn (50 μg/L) and Fe (0.3 mg/L) Correlation of arsenic and other parameters Pearson’s correlation coefficient is set to quantify the relationship between two quantitative variables In this study, the correlation analysis at p < 0.01 was conducted between arsenic and other parameters (Table 2) As mentioned in the discussion of arsenic concentration results in groundwater, the distribution of As concentration depends on various factors such as physicochemical properties of groundwater, geological characteristics, and anthropogenic activities Therefore, the correlations between the parameters for each province were assessed in this study The result shows that strong correlations were found between the elemental pairs of As/alkalinity (r2 = 0.606), As/ammonium (r2 = − 0.611) and As/Ba (r2 = 0.560) for Long An; while strong correlation was noted by As/TDS (r2 = −0.513) and As/Mn (r2 = − 0.509) for Tien Giang Similar to the research results of Bundschuh et al (2004) and Machado et al (2019), a positive correlation recorded for As/sulfate in Long An As and pH had a positive correlation for all samples in the studied areas As negatively correlated to Fe and Mn This might be because hydroxyl ions competed for adsorption sites on Fe and Mn oxides and clay minerals at higher pH, resulting in the release of As into groundwater These findings were in line with the previous studies (Bundschuh et al 2004; Machado et al 2019) Based on Table 2, positive correlations were obtained for As and the depth of the well for both provinces, particularly a strong correlation (r = 0.583) that occurred in Tien Giang This was similar to the predicted results for Long An and Tien Giang by Erban et al (2013) For linear or non-linear regression analysis, arsenic correlated with manganese as compound, growth, exponential curves (medium correlation factor, confidence interval 99%) in Long An and Tien Giang provinces Thus, it is concluded that correlation curves of arsenic with manganese were compound, growth, exponential forms Arsenic correlated with ammonia as a cubic curve in Long An and Tien Giang provinces However, this relationship was S curve in Long An With high regression coefficients (above 0.8) and 99% confidence intervals, alkalinity and ammonia were the two parameters used to predict the concentration of arsenic in groundwater (Table 3) The correlation equations are as follows: As ẳ e4:316 246:294=Alkalinityị 4ị As ẳ 1:142 Ammonium 1:924Þ ð5Þ Author's personal copy Environ Sci Pollut Res Table Correlation analysis between arsenic and other physicochemical parameters for Long An and Tien Giang As pH Long An and Tien Giang (n = 48) Long An (n = 24) Tien Giang (n = 24) TDS Turbidity Alkalinity Ammonium Sulfate Phosphate Fe As − 0.291* − 0.316* − 0.198 0.024 − 0.601** 0.278 As As 0.165 0.397 0.606** 0.264 − 0.611** − 0.196 0.101 − 0.452* − 0.348 − 0.114 − 0.242 − 0.338 − 0.513* − 0.332 − 0.180 0.023 Ba Mn Well’s depth 0.304* − 0.351* 0.149 − 0.279 0.560** − 0.489* 0.011 − 0.290 − 0.155 − 0.509* 0.583** **Correlation is significant at the 0.01 level (2-tailed) *Correlation is significant at the 0.05 level (2-tailed) The values of Pearson analysis in the range of 0.0–0.29 for poor, 0.3–0.49 for moderate, and 0.5–1.0 for strong correlation (Bundschuh et al 2004; SS 2020) Human health risk assessment The average daily dose (ADD), hazard quotient (HQ), and carcinogenic risk (CR) can be used for risk assessment (Rasool et al 2016; Radfard et al 2019) The results indicate that the average CR for adults and children in Long An province was 8.68 × 10 −4 and 2.39 × 10−3 , respectively while the average CR for adults and children in Tien Giang was 2.70 × 10−4 and 7.43 × 10−4, respectively The average CR was higher than the CR value of × 10−4 which provided by the USEPA (2005) and Zhang et al (2019) Figure indicated that in Long An province, 83% CR for adults and 83% CR for children were (avg 8–24 times) higher than CR of × 10−4 while in Tien Giang province, 58% CR for adults children and 75% CR for children were Table higher (avg 3–7 times) than CR of USEPA High CR values were observed at L7 and L8 Table reveals that the mean CR for children was higher than that for adults The results show that for every 10,000 people, 24 children and adults for Long An and children and adults for Tien Giang would be at risk of cancer The WHO standard limit was 10 μg/L for As This level could lead to adults and 15 children who are likely to face cancer risk in ten thousand people Risk levels in the present study were more serious than those mentioned by Huy et al (2014) Namely, the average risk of CR for adults in Chuyen Ngoai Commune, Hanam Province, Vietnam, was estimated at 2.53 × 10−4 The results show that for every 10,000 adults in Chuyen Ngoai commune, about people will have cancer due to the consumption of filtered groundwater Phan and Nguyen (2018) evaluated health risk for the residents who were using groundwater contaminating As in An Correlation analysis between arsenic and parameters in groundwater in Long An and Tien Giang provinces Long An and Tien Giang n = 48 Long An n = 24 Tien Giang n = 24 Pearson factor Linear and non-linear regression Value (r2) Remarks Curve type R2 Equations As vs ammonium − 0.601** Strong Cubic negative 0.514 As = 21.783–11.509 × ammonium + 2.298 × ammonium2 – 0.138 × ammonium3 As vs ammonium As vs manganese (Mn) As vs alkalinity As vs manganese (Mn) As vs Well’s depth (WD) − 0.611** Strong Power negative − 0.489* Moderate Compound, negative growth, exponential 0.606** Strong S positive − 0.509* Strong Compound, negative growth, exponential 0.583** Strong Cubic positive 0.844 As = 1.142 × ammonium (−1.924) 0.685 Compound: As = 27.781 × 0.988Mn Growth: As = e(3.324–0.012 × Mn) Exponential: As = 27.781 × e(−0.012 × Mn) 0.845 As = e(4.316–246.294/alkalinity) 0.513 Compound: As = 3.835 × 0.999Mn Growth: As = e(1.344–0.001 × Mn) Exponential: As = 3.835 × e(−0.001 × Mn) 0.529 As = 21.783–11.509 × WD + 2.298 × WD2–0.138 × WD3 **Correlation is significant at the 0.01 level (2-tailed) *Correlation is significant at the 0.05 level (2-tailed) The values of Pearson analysis in the range of 0.0–0.29 for poor, 0.3–0.49 for moderate, and 0.5–1.0 for strong correlation (Bundschuh et al 2004; SS 2020) Author's personal copy 4.01 × 10−6–7.03 × 10−3 2.39 × 10−3 1.71 × 10−3 8.15 × 10−6–2 × 10−3 7.43 × 10−4 7.03 × 10−4 1.48 × 10−6–2.56 × 10−3 8.68 × 10−4 6.22 × 10−4 2.96 × 10−6–7.27 × 10−4 2.70 × 10−4 2.56 × 10−4 0.01–15.63 5.31 3.8 0.02–4.44 1.65 1.57 ADD, average daily dose; HQ, hazard quotient; CR, cancer risk 2.72 × 10−6–4.69 × 10−3 1.59 × 10−3 1.14 × 10−3 5.43 × 10−6–1.33 × 10−3 4.95 × 10−4 4.1693 × 10−4 Long An (n = 24) Range Mean Std Tien Giang (n = 24) Range Mean Std 0.03–46.88 15.92 11.40 0.05–13.33 4.95 4.7 9.87 × 10−7–1.7 × 10−3 5.79 × 10−4 4.15 × 10−4 1.97 × 10−6–4.84 × 10−4 1.80 × 10−4 1.71 × 10−4 0.003–5.68 1.93 1.38 0.01–1.63 0.6 0.57 Children Adults Children Adults Children Adults Statistics Arsenic concentration (μg/L) Average daily dose from ingestion (ADD) Province Table Risk assessment summary for Long An and Tien Giang provinces Hazard quotient of As (HQ) Carcinogenic risk of As (CR) Environ Sci Pollut Res Giang province The results show that higher CR ranged from 8.66 × 10−4 to 8.26 × 10−2 for both children and adults In 1999, from the epidemiology studies, the National Research Council (NRC, USA) shows that there was enough evidence to conclude that the ingestion of As in drinking water leads to lung cancer A high concentration of As in drinking water would increase the risk of lung cancer (Celik et al 2008) In Bangladesh, As concentration (above 100 μg/L) in groundwater was associated with lung cancer (lung squamous cell carcinoma) in males CR of lung cancer was 159 males and 23 females per 100,000 population (Mostafa et al 2008) In Northern Chile, Marshall et al (2007) presented lung cancer mortality in region II where As concentration in groundwater was above 90 μg/L, compared with region V, which was otherwise similar to region II but not exposed to arsenic in groundwater The results showed that lung cancer mortality rates of 153 per 100,000 men and 50 per 100,000 women in region II were higher than that in region V with 54 per 100,000 men and 19 per 100,000 women Otherwise, Baastrup et al (2008) revealed no significant association between exposure to drinking water containing low arsenic concentration (0.05–25.3 μg/L) and lung cancer mortality in Denmark The risk assessment summary for Long An and Tien Giang is presented in Table The average HQ of adults and children in Long An province was 1.93 and 5.31, respectively while the average HQ of adults and children in Tien Giang was 0.6 and 1.65, respectively The highest HQ for adults (5.68) and children (15.63) was found in the groundwater samples collected in sampling point L7 of Long An The result shows that in Long An, 75% cases for adults and 83% of cases for children had HQ > In Tien Giang, 29% of cases for adults and 54% of cases for children had HQ > These results reveal that As concentration in groundwater samples of Long An and Tien Giang posed an adverse health risk to residents through using of As-contaminated groundwater (USEPA 2005; Wongsasuluk et al 2014) Conclusions and future perspectives In this study, As concentration in groundwater samples was determined The results show that As levels were ranging from 0.03 to 46.88 μg/L and 0.05 to 13.33 μg/L in Long An and Tien Giang, respectively As concentration could be found highly significant with alkalinity, ammonium nitrogen, manganese concentration, and well’s depth Erban et al (2013) indicated that contamination of As was not only influenced by the vertical movements of As due to pumping or the intrusion of dissolved organic matter from surface water sources but also the long-term pumping process that promoted soil compaction resulting in the release of As-containing solutes from deep clay Therefore, in order to have more insight, Author's personal copy Environ Sci Pollut Res Fig Risk assessment summary for Long An and Tien Giang provinces a Carcinogenic risk b Hazard quotient it is recommended to investigate the impact of nearby surface water sources, the operating time of the wells, and the effect of the geological conditions of the sites in future studies The health risk assessment of arsenic showed that the maximum carcinogenic risk (CR) for adults and children in Long An (2.56 × 10−3 and 7.03 × 10−3, respectively) was higher than those in Tien Giang (0.73 × 10−3 and × 10−3, respectively) The average CRs for children were potentially higher than those for adults Exposure to arsenic through drinking water is a public health concern; therefore, preventing arsenic exposure will reduce the incidence of cancer In the study area, awareness-raising activities on water use should be conducted for the residents Thus, pretreatment technologies for arsenic removal from groundwater should be applied before use for drinking purposes Also, a long-term groundwater quality monitoring program should be considered Furthermore, researching and developing appropriate groundwater treatment technologies is essential for the residents Acknowledgments The authors would like to thank for laboratory support and sampling of Ms Thi-Kim-Yen Nguyen, Dr Sunbeak Bang, and Ms Quy-Hao Nguyen Thanks for the English elaboration of Dr Mary Ellen Chavez Camarillo (University of San Carlos) This study has been conducted under the framework of CARE-RESCIF initiative Author contributions Investigation, software, writing—original draft, writing—review and editing: Van-Truc Nguyen; Investigation, software, writing—original draft: Thi-Nhu-Khanh Nguyen; Data curation, conceptualization, methodology: Thanh-Dai Tran and Thanh-Binh Nguyen; Author's personal copy Environ Sci Pollut Res Investigation, software, writing— original draft: Bao-Trong Dang; Funding acquisition, supervision, conceived, designed the methodology, writing—review and editing: Thi-Dieu-Hien Vo and Xuan-Thanh Bui Funding This research is funded by Nguyen Tat Thanh University, Ho Chi Minh City, Vietnam (No 2020.01.064) Data availability The data that support the findings of this study are openly available at DOI Compliance with ethical standards Conflict 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al 2009; Hoang et al 2010), but higher than in the southern part of Vietnam such as Vinh Long, Tra Vinh and Kien Giang (Nguyen and. .. water) that were used for drinking, cooking, and personal hygiene and its risks to human health in Long An and Tien Giang provinces (Mekong delta, Vietnam) were evaluated in this study The average