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[.]
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Environmental Science and Pollution
Research
ISSN 0944-1344
Environ Sci Pollut Res
DOI 10.1007/s11356-020-10837-6
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
Trang 21 23
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Trang 3GREEN 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 Nguyen1&Thi-Dieu-Hien Vo2&Thanh-Dai Tran3&Thi-Nhu-Khanh Nguyen4&Thanh-Binh Nguyen5&
Bao-Trong Dang6&Xuan-Thanh Bui4,7
Received: 1 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
* Xuan-Thanh Bui
bxthanh@hcmut.edu.vn
Van-Truc Nguyen
truc1021006@gmail.com
Thanh-Binh Nguyen
ntbinh179@nkust.edu.tw
1 Institute of Research and Development, Duy Tan University, Da
Nang 550000, Vietnam
2 Faculty of Environmental and Food Engineering, Nguyen Tat Thanh
University, Ho Chi Minh City, Vietnam
3 Faculty of Applied Sciences–Health, Dong Nai Technology University, Bien Hoa, Dong Nai, Vietnam
4 Faculty of Environment and Natural Resources, Ho Chi Minh City University of Technology (HCMUT), Ho Chi Minh City 700000, Vietnam
5 Department of Marine Environmental Engineering, National Kaohsiung University of Science and Technology, Kaohsiung, Taiwan
6
Ho Chi Minh City University of Technology – HUTECH, 475 A Dien Bien Phu, Binh Thanh district, Ho Chi Minh City, Vietnam
7 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
https://doi.org/10.1007/s11356-020-10837-6
Trang 4Arsenic is the poisonous element that is odorless,
color-less, and tasteless (Kuivenhoven and Mason 2019)
People do 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
carcino-gens (group 1) for humans (WHO2010) Arsenic is
well-known 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
liv-ing (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
water-based 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
contamina-tion 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
concen-tration of As Berg et al (2008) evaluated the correlation
between As concentration and Fe, ammonium, DOC,
re-dox 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−, SO4 2− in the well water of Medical Geology in Uruguay The positive correlations were recorded such
as As/pH (r2= 0.44), As/F− (r2= 0.59), and As/SO4 2−
(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 concen-tration 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 be-fore drinking (Huy et al.2014) Thereby, health risk assess-ment attributed to arsenic-contaminated groundwater is criti-cal for protecting human health The health risks were evalu-ated 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 aware-ness of the residents and provide insight into the water man-agement 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 physico-chemical parameters, as well as an assessment of human health risks in these two provinces The research results con-tribute 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 con-tamination in Long An and Tien Giang provinces to (i) iden-tify the status of arsenic and create arsenic contamination maps; (ii) find correlation factors, equations, and types be-tween arsenic and groundwater parameters comprising alka-linity, ammonia, manganese, well depth; and (iii) assess hu-man health risk due to As concentration
Trang 5Materials 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
be-tween 106° 10′ E longitude and 10° 40′ N latitude The area of
this province is 4495.5 km2and has a population of 2,002,767
inhabitants Tien Giang is located between 106° 10′ E
longi-tude and 10° 25′ N latilongi-tude It covers about 2510.5 km2area
and has a population of 1,764,185 These areas are
character-ized 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
high-sulfate acid soil The characteristic of the weather here is
trop-ical 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
ground-water The groundwater wells in suburban areas of these
prov-inces 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
treat-ed 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 contam-ination sources are mainly from natural sources which are caused by the washing of As-rich sediments from natural soils (Jessen2009) 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 TableS1) All wells in this study were operated by high-pressure water pumps Wells were cat-egorized 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 6 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 sam-ple collected and a tag or label was used to identify the infor-mation of groundwater samples Inforinfor-mation to provide
Fig 1 Location map of the studied area and sampling sites in Long An and Tien Giang
Trang 6accurate 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 5 min Sampling
bot-tles were washed with DI water and 5% HNO3solution to
ensure their purity After passing through a 0.45-μm
Whatman filter, samples were added with 3 mL of 69%
HNO3, then stored at 4 °C, and transported directly to the
laboratory Groundwater samples were analyzed within
2 weeks Field measurements included pH, TDS, and
turbid-ity 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,
sa-linity (G1410, Greisinger, Germany), and turbidity was
mea-sured onsite using a HI-93703 portable turbidity meter
(HI-93703, Hanna, Rumania) Total alkalinity was determined by
titration using methyl orange and bromocresol green
indica-tors 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
deter-mined by an inductively coupled plasma mass
spectrometry-ICPMS (MS, model 7700x, Agilent, USA) using an
ICP-MS-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:
ADD¼ C IR E F EDð Þ= AT BWð Þ ð1Þ
where ADD is average daily dose from ingestion (mg/kg day),
C is arsenic concentration in water (mg/L), IR is water
inges-tion 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 2 L/day for adults and
1 L/day for children (Phan and Nguyen2018) 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 chil-dren (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 Nguyen2018)
The hazard quotient (HQ) was determined as follows:
Where HQ is hazard quotient (cases with HQ > 1 are
attribut-ed to human health risks), RfD is a reference dose ( m g / k g d a y ) I n t h i s s t u d y , t h e R f D o f A s i s 0.0003 mg/kg day (USEPA2005; Radfard et al.2019) The carcinogenic risk (CR) was determined as follows:
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 1 × 10−4was 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 physico-chemical 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 (H3AsO3, H2AsO3−, As (III)) and arsenic acid (H2AsO4−, HAsO4 2−, 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 TableS2) As concentra-tion 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
Trang 7Fig 2 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
Trang 8virtually absent in these sites This high As pollution may,
therefore, be attributable to the natural geological
characteris-tics as well as the anthropogenic activities that have taken
place in the past, as described above in the definition of the
study area
Figure2bshows 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) Figure2cpresented
that was 18 sampling points (75% of samples) in Long An,
and 6 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
in-formation that gives warnings to the residents to get the most
appropriate treatment and usage plan
Table1shows that As concentration in northern Vietnam is
much higher than in southern Vietnam The mean As
concen-tration 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 Itoi2009; 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, HAsO4 2−becomes domi-nant Under reducing condition at pH less than about
pH 9.2, the most abundant were the uncharged arsenic species
H3AsO3, 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 sur-vival, 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 concen-trations of phosphate in both provinces were low, ranging from 0.028 ± 0.03 to 0.29 ± 0.75 mg/L The highest concen-tration 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 con-sists of calcium phosphate and magnesium phosphate Some phosphorus had been contained in the soil by clay When anthropogenic deposits were therefore overlooked, the phos-phate 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 concentra-tion in Long An was 0.19 mg/L and 51.27 times lower than the concentration detected in Tien Giang Ammonium nitro-gen in groundwater was also primarily derived from anthro-pogenic 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 Somashekar2006) 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)
Trang 9Rainwater runoff, agricultural runoff, leakage from industrial
activities, and solid waste deposit could contribute greatly to
turbidity in groundwater It is essential to encapsulate
patho-genic organisms in particles that cause turbidity resulting in
health hazards (Prakash and Somashekar2006) In this study,
turbidity varied from 0.5 to 280 NTU and 1 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 (SO4 2−)
centrations were detected in Tien Giang The average
con-centration 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 concen-tration 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 (aver-age 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
Table 1 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) Vietnam 15.9 This study
Tien Giang (Southern of Vietnam) Vietnam 4.95 This study
Dong Anh (Northern of Vietnam) Vietnam 220 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) Vietnam 16.9 Nguyen and Itoi ( 2009 ) Tra Vinh (Southern of Vietnam) Vietnam 1.00 Nguyen and Itoi ( 2009 ) Mashhad Iran 0.18 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 )
Trang 10Giang, 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
unpleas-ant odors and affected the quality of food cooked or
laun-dered 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
pol-lutants, solid waste disposal, industrial activities, etc
(Prakash and Somashekar2006)
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
ob-served 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
concentra-tion 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 1 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
low-est 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,
respec-tively 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 re-lationship between two quantitative variables In this study, the correlation analysis at p < 0.01 was conducted between arsenic and other parameters (Table 2) As men-tioned 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
anthropogen-ic activities Therefore, the correlations between the pa-rameters for each province were assessed in this study The result shows that strong correlations were found be-tween 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 (r2= 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, expo-nential curves (medium correlation factor, confidence in-terval 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 rela-tionship 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 ¼ eð4:316 246:294=AlkalinityÞ ð4Þ
As ¼ 1:142 Ammoniumð 1:924Þ ð5Þ