Screening of inorganic and organic contaminants in

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concentrations of 277 organic micro-pollutants and ten ele- ments (As, Cu, Cd ...... Average concentration (detection frequency) of L-menthol in floodwater in Hue ...
Environ Sci Pollut Res DOI 10.1007/s11356-017-8433-7

RESEARCH ARTICLE

Screening of inorganic and organic contaminants in floodwater in paddy fields of Hue and Thanh Hoa in Vietnam Ha Thu Trinh 1,2 & Helle Marcussen 2 & Hans Christian B. Hansen 2 & Giang Truong Le 3 & Hanh Thi Duong 4 & Nguyen Thuy Ta 1 & Trung Quang Nguyen 4 & Soren Hansen 2 & Bjarne W. Strobel 2

Received: 15 September 2016 / Accepted: 9 January 2017 # Springer-Verlag Berlin Heidelberg 2017

Abstract In the rainy season, rice growing areas in Vietnam often become flooded by up to 1.5 m water. The floodwater brings contaminants from cultivated areas, farms and villages to the rice fields resulting in widespread contamination. In 2012 and 2013, the inorganic and organic contaminants in floodwater was investigated in Thanh Hoa and Hue. Water samples were taken at 16 locations in canals, paddy fields and rivers before and during the flood. In total, 940 organic micro-pollutants in the water samples were determined simultaneously by GC-MS method with automatic identification and quantification system (AIQS), while ICP-MS was used for determination of ten trace elements in the samples. The concentrations of 277 organic micro-pollutants and ten elements (As, Cu, Cd, Cr, Co, Pb, Zn, Fe, Mn, Al) ranged from 0.01 to 7.6 μg L−1 and 0.1 to 3170 μg L−1, respectively, in the floodwater. Contaminants originated from industrial sources (e.g. PAH) were detected at low concentrations, ranged from Responsible editor: Philippe Garrigues Electronic supplementary material The online version of this article (doi:10.1007/s11356-017-8433-7) contains supplementary material, which is available to authorized users. * Ha Thu Trinh [email protected]

1

Institute of Chemistry, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam

2

Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C, Denmark

3

Department of Planning and Finance, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam

4

Institute of Environmental Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam

0.01 to 0.18 μg L−1, while concentrations of pollutants originated from domestic sources (e.g. sterols, pharmaceuticals and personal care products and pesticides) were ranged from 0.01 to 2.12 μg L−1. Isoprocarb had the highest detection frequency of 90%, followed by isoprothiolane (88%) and fenobucarb (71%). The results indicated that contaminants in floodwater come from untreated wastewater from villages, and the agricultural activities are the major sources of increased pesticides resuspended in the floodwater in this study. Keywords AIQS-DB . Floodwater . Organic contaminant . Screening . Paddy field . Pesticide . Trace element

Introduction Vietnam is located in both a tropical and a temperature zone influenced strongly by monsoon and with increasing frequency of storms, floods, and droughts leading to a substantial variation in agricultural production (ADPC 2003). The hurricane season lasts from August to November with an annual average of four storms per year causing floods in the central Vietnam (ADPC 2003). Floodwater brings nutrients and sediments to the soil that generally enrich soil quality. However, the floodwater cause resuspension of contaminants present in the soil (e.g. As, Cd), nutrients (nitrate, phosphate) and agrochemicals (e.g. pesticides) (Maillard et al. 2011). The situation is aggravated by intensive use of agrochemicals that is not following prescriptions such as spraying at higher concentrations than recommended, use illegal pesticides or discard packing materials in the field (Berg 2001; Berg and Tam 2012; Thuy et al. 2012). Some soils and sediments in Vietnam were contaminated by the persistent pollutants dichlorodiphenyltrichloroethane (DDT) and polychlorinated

Environ Sci Pollut Res

biphenyl (PCB) from past use (Hoai et al. 2011), or even from illegal use (Nishina et al. 2010; Hoai et al. 2011). In some parts of Vietnam, the natural content of toxic elements is the soil, such as arsenic, released and dispersed with suspended sediments in high concentrations in the water (Gustafsson and Tin 1994; Polya et al. 2008). Releasing and spreading of pollutants is highly variable, and depending on the soil properties, cultivation history, characteristics and loads of contaminants, the hydrological regime and the water flow paths (Gustafsson 2006). In Vietnam, more than 80% of the population works in agriculture, and the land for rice production covers around 4.3 million ha or approximately 46% of the agricultural land. The average use of pesticides for rice is 3.34 kg ha−1 per cropping season (Anh 2002), and pesticides represent a potential major source of pollution to freshwaters (Nakano et al. 2004a, Nakano et al. 2004b; Comoretto et al. 2007; Son et al. 2006). Residential areas and small-scale farms are usually adjacent to agricultural lands, particularly in rice production areas. Wastewaters from residential areas is discharged directly to canals, ponds, rivers and paddy fields, and may be part of the irrigation water (Raschid-Sally et al. 2004). During flooding events, pathogens and contaminants from the residential discharges disperse into the floodwater. Moreover, redox potential will decrease and reduction of Mn(III/IV), Fe(III) and SO42− to Mn(II), Fe(II) and HS− takes place (Murase and Kimura 1997), and the release of some element will be enhanced causing higher concentrations in the floodwater (Amery et al. 2007; Koopmans and Groenenberg 2011; Yu et al. 2007). In this study, inductively coupled plasma mass spectrometry (ICP-MS) was utilized to simultaneously determine the major harmful metals, while semi-volatile organic compounds (SVOCs) in floodwater was screened by automatic identification and quantification system (AIQS) with a gas chromatograph-mass spectrometer (GC-MS) and database (DB) (Kadokami et al. 2005). This system consists of mass spectra, retention times and calibration curves of 940 SVOCs, which are essential for both identification and quantification of target substances. As long as the GC-MS conditions remain constant, the database system can be used to predict exact retention times and to obtain reliable quantification results without prior analysis of standards for all compounds (Kadokami et al. 2004, 2005). The AIQS-DB was successfully applied to evaluate pollutant profiles and risk caused for the ecological state of rivers and river sediments in Japan (Kadokami et al. 2009, 2013), Vietnam (Hanh et al. 2014a) and China (Kong et al. 2015). Polycyclic aromatic hydrocarbons (PAHs) that originated from industrial sources were detected in rivers of China (Kong et al. 2015) and Dokai Bay in Japan (Kadokami et al. 2013). A proper understanding of the contamination levels in floodwater and distribution of contaminants in the source

paddy fields are required to provide risk information for the public and environmental authorities as well as to carry out proper water treatment to ensure healthy water supply for people living in the flooded areas. Therefore, we have carried out a comprehensive study on water quality in canals, paddy fields and rivers before, during and after flooding in the north (Thanh Hoa) and centre (Hue) of Vietnam. The aims were the following: (i) to clarify the pollution characteristics of contaminants in floodwater, (ii) to relate contamination levels during flooding to possible sources, (iii) to map the changes in water quality before and after a flooding event and (iv) to look for specific processes causing contaminant release.

Materials and analysis Study sites and sample collection Two locations in the centre of Vietnam, Thang Long (19° 35′ 24″ N, 105° 38′ 22″ E) and Huong Toan (16° 30′ 52″ N, 107° 32′ 12″ E) in Thanh Hoa and Thua Thien Hue province, respectively (Fig. 1), were selected for this study. Thanh Hoa and Hue have a tropical monsoon climate with annual average temperature and annual precipitation of ca 24 °C and 1700 mm, and 25 °C and 2600 mm, respectively. Both locations are low land areas that often experience flooding in the rainy season. Rice is the main crop with two annual cultivation cycles, the spring crop from January to June, and the summer crop from June to October; in between soil is left uncultivated. Water samples were collected in the canals, paddy field and in the river that drain off water from the studied paddy field (Fig. 1, Table S1.1) in 2012 and 2013 before flooding and thereafter in the flooded paddy fields. Sampling before flooding in Thanh Hoa in 2012 and 2013 was carried out in June during sowing of a new crop of rice. Some herbicides were in use at that time, and water level in the field was 5– 10 cm. In Hue, the rice was flowering and had been sprayed at least twice with pesticides; the water level in the paddy field was 5–10 cm at the sampling time in June (Table S1.2). Sampling of floodwater was done twice in 2012 and 2013. In Thanh Hoa in 2012, an area of about 200 ha was flooded with 0.5–1.5 m water, and floodwater was sampled on September 4, 2012, 3 days after the flooding reached maximum. During flooding, the rice was flowering and had been sprayed with pesticides at least two times. In 2013, floodwater was sampled in the field after the flooding reached its maximum (0.5–1 m), and on September 1, 3 days after flooding. In Hue, flooding of 0.25–1 and 0.5–1.5 m were the maximum flooding on November 25, 2012 and September 8, 2013, respectively, when the rice was harvested and the soil bare (Table S1.2). Water samples for determination of trace elements and anions were kept in 1 L polyethylene (PE) bottles, while 1 L

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Fig. 1 Location of 17 sampling sites in Thanh Hoa (TR: Muc River; TL1, TL2. TL3, TL4, TL5 and TL6: canals surrounding the study field; TC1, TC2, TC3 and TC4: canals in the paddy field; T1, T2, T3, T4, T5,

T6 and T7: paddy fields) and 16 sampling sites in Hue (HR1, HR2: Bo River; HC1, HC2, HC3, HC4, HC5, HC6, HC7: canals in the field; H1, H2, H3, H4, H5, H6, H7: paddy fields)

amber glass bottles were used for organic micro-pollutant analysis. The bottles containing water samples were stored in an icebox and then transported to a laboratory where they were stored at 4 °C until processed. For trace element analysis, the 1 L water sample was filtered through a 0.45 μm cellulose nitrate filter (Whatman) and acidified with 5 mL HNO3 (98%) then analysed by ICP-MS.

performed by blank analysis and the analysis of a River Water Certified Reference Material for Trace Metals and other Constituents (SLRS-6, the National Research Council Canada, NRC). Good recoveries (mean, 80–120%) were obtained for Al, As, Cd, Co, Cr, Cu, Fe, Mn, Pb and Zn.

Chemical analysis

SVOCs (Table S2) in the water were extracted using the method of Kadokami et al. (2009). Briefly, after addition of 38 surrogates (1 μg) (Table S3) and 20 g NaCl to 1 L water samples, the samples were liquid–liquid extracted (LLE) three times with 100, 50 and 50 mL of dichloromethane (10 min in each). The extracts were then dehydrated using anhydrous sodium sulphate and concentrated to about 5 mL by rotary evaporation. Hexane (20 mL) was added to the concentrate and re-concentrated to 5 mL using rotary evaporator; this step was done twice. The extract was finally concentrated under a gentle nitrogen stream to approximately 1 ml and spiked with 100 μL of a mixture of eight internal standard solution (10 μg mL −1) (Hayashi Pure Chemical, Osaka, Japan) (Table S4) prior to analysis.

Analysis of matrix parameters The pH and total dissolved solid (TDS) in the waters were determined by Hach Sension 156 portable multiparameter water quality meter with Sension platinum electrodes for pH (p/n 51910), and conductivity (p/n 51975-00). The chemical oxygen demand (COD), the concentrations of nitrite (NO2−), nitrate (NO3−) and ammonium (NH4+) were determined according to Standard Methods for the Examination of Water and Wastewater (Method 2005). The open reflux method was used for COD determination (Aqualytic, Germany) and titration with ferrous ammonium sulphate. Nitrate in water was determined through difference of concentrations of nitrite in the original sample, and nitrite in the sample after reduction of the sample was carried through a column packed with the treated copper–cadmium granules. Nitrite was determined by diazotizing with sulfanilamide to form a reddish-purple coloured azodye, which was measured at 540 nm by a 25UV/VIS Spectrometer (Perkin Elmer). The ammonium was determined by the indophenol blue method. Analysis of elements Elements in the water were determined by ICP-MS (Agilent 7500CX, Agilent Technologies, UK). Quality controls were

Extraction of semi-volatile organic compounds

Comprehensive analysis of SVOCs Determination of SVOCs was carried out using GC-MS (QP2010 Plus, Shimadzu, Kyoto, Japan) with scanning and selected ion monitoring (SIM-Scan). The measurement conditions of GC-MS (Table S5) were similar to that described by Kadokami et al. (2009). Total ion current chromatograms obtained by GC-MS scan were processed by an identification and quantification system in a GC-MS database (AIQS-DB) (Kadokami et al. 2005) that was able to determine the concentrations of the 940 SVOCs. Substances targeted by SIM were quantified by the internal standard method as reported by

Environ Sci Pollut Res

(Hanh et al. 2014b). If samples were measured by multiple methods (scan, SIM), we preferentially used the results from SIM followed by scan. The method detection limits (MDL) of PAHs, OCPs, sterols and PCBs measured by SIM were 1, 2, 8–3201 and 0.4–1.6 ng L−1, respectively. The MDL of the remaining compounds measured by TIM were 5 to 500 ng L−1. Quality control To ensure the precision and accuracy of analytical procedures, procedure blanks and overall recoveries were conducted for each set of the samples analysed. The accuracy of individual sample analysis and matrix effects were verified by examining the recoveries of 38 surrogates (deuterium-labelled internal standards) which were chosen as being representative of the 940 compounds based on their physico–chemical properties. Laboratory blank samples were carried out for every ten samples for cross-verification; prior to extraction, water and blank samples (1 L of purified water previously washed with 50 ml dichloromethane 3 times) were spiked 38 surrogate compounds. Twenty-eight out of 38 surrogates were recovered from 65 to 125% except for polar chemicals, such as phenols and amines, which are difficult to extract with dichloromethane. Relative standard deviations (RSDs) of 38 surrogates were below 22% (Tables S3). These results confirmed that all the sample analyses were acceptably precise. When reporting data, blank concentrations were subtracted from sample concentrations; the reported concentrations were not adjusted for recovery values.

Results and discussion Basic water characteristics, trace elements, and matrix parameters Concentrations of investigated elements and matrix compounds (As, Cu, Cd, Cr, Co, Pb, Zn, Fe, Mn, Al, pH, TDS, COD, NO3− and NH4+) (Table 1 and Table S7, S8) were lower than the current technical regulation on surface water quality (QCVN 08:2008/BTNMT/B1 2008), issued by Ministry of Natural Resources Environment of Vietnam. There were no significant difference in concentrations of trace elements and water matrix compounds between canals and fields in Thanh Hoa and Hue in floodwater. However, the concentrations of the investigated parameters were different between the two sites and the 2 years. The TDS values in floodwaters in the field in Thanh Hoa in 2012 was 17.6 mg L−1, which was lower than those in 2013 (24.8 mg L−1), while this value was similar in the 2 years in Hue. In general, the concentrations of NO3−, NO2− and NH4+ were low, with the highest concentration of

NO3− (0.72 mg L−1) which was seven times lower than the QCVN 08/2008 (5.0 mg L−1), while the highest concentration of NO2− (0.14 mg L−1) was seven times higher than the QCVN 08/2008 (0.02 mg L−1). COD in the floodwater in the field in 2012 was higher than those in 2013 at both sites studied. COD in the field in Hue was 3.65 mg L−1 and 2.0 mg L−1 in 2012 and 2013, respectively, while the values of 2.31 mg L−1 and 1.97 mg L−1 were observed in Thanh Hoa in 2012 and 2013, respectively. The concentrations of all elements in floodwater in Thanh Hoa in 2012 is lower than in 2013, while in contrast to the floodwaters in Hue (Table 1, S7, S8). The mean concentrations of elements in floodwater are higher than those before flooding in Hue in 2 years; meanwhile in Thanh Hoa, this trend was seen in 2013 only. This probably is due to the following: (1) the difference in floodwater levels that caused differences in dilution and redox conditions and (2) the characteristics of the soils causing differences in release of particulates and trace elements to the water. The floodwater levels at Thanh Hoa were higher in 2012 (1.5 m) than in 2013 (1.0 m), and, additionally, flooding happened between two crops, which means that the soil surface was not disordered; and consequently, there were little suspended particulates and TDS in the floodwater. Meanwhile, in Hue in both years, the flooding occurred about 1 month after the harvest season when the soil surface was still disturbed after harvest practices. Afterwards, the field was inundated by rainwater that was kept in the fields until the time of flooding. As a result, there was a higher concentration of suspended particles and TDS in the floodwater, and the concentrations of Cu, Pb, Zn, Cr, Co, Cd and As in floodwaters in Hue were higher than in Thanh Hoa. This observation is consistent with findings for floodwater in the Dese River (Zonta et al. 2005), where these elements are associated with the suspended particles and thus moved during flood conditions. The highest concentrations of Fe (2739 mg L−1) and Mn (32.8 mg L−1) were found in Hue in 2012, under flooding condition (1.5 m) when redox reactions may take place and reduction of Mn(III/IV) to Mn(II), and Fe(III) to Fe(II) results in increased dissolution of Fe(II)- and Mn(III/ IV)-(hydr)oxides (Patrick and Jugsujinda 1992; Guo et al. 1997, Murase and Kimura 1997; Donahoe and Liu 1998; Miao et al. 2006,). When these metal oxides dissolve, other trace elements like Cd, Cu, Co, Cr and Pb may be released as these trace elements were sorbed to the metal oxides. In addition, organic matter may release and increase the concentration of dissolved organic matter that keeps metal ions complexed and in solution (Tack et al. 2006; Grybos et al. 2009). The highest arsenic levels were found in the floodwater in Hue 2012, i.e. higher than in the water before flooding. When the soil was flooded and the reduction potential becomes sufficiently low, As(V) may have been reduced to As(III), which in turn has a lower sorption affinity for soil particles (Wilson et al. 2010) resulting in partial release to the water.

Environ Sci Pollut Res Table 1 Parameter

Mean concentrations of heavy metals and matrix parameters in water samples before flood (BF) and flood (F) in Thanh Hoa and Hue Unit

Cu Pb Zn Cr Co Cd As Fe Mn Al pH

μg L−1 μg L−1 μg L−1 μg L−1 μg L−1 μg L−1 μg L−1 μg L−1 μg L−1 μg L−1 −

TDS COD NH4+ NO2− NO3−

mg L−1 mg L−1 mgN L−1 mgN L−1 mgN L−1

Hue

Thanh Hoa

2012

2013

2012

BF

F

BF

F

BF

F

BF

F

1.32 ± 0.23 1.18 ± 0.29 28.1 ± 5.7 1.41 ± 0.14 0.02 ± 0.00 0.02 ± 0.02 0.74 ± 0.10 184 ± 21 0.53 ± 0.23 26.2 ± 9.2

46.9 ± 24.4 56.6 ± 13.8 429 ± 125 51.6 ± 8.0 17.4 ± 6.0 1.05 ± 0.29 23.1 ± 6.8 2739 ± 815 32.8 ± 5.6 294 ± 117

22.1 ± 15.3 3.83 ± 1.40 49.3 ± 21.0 3.04 ± 0.75 0.26 ± 0.11 0.09 ± 0.05 3.43 ± 0.67 58.3 ± 8.8 16.6 ± 7.01 49.7 ± 24.5

37.6 ± 5.4 4.23 ± 0.37 280 ± 85 5.08 ± 2.75 0.55 ± 0.44 0.15 ± 0.02 13.3 ± 3.3 470 ± 41 1.24 ± 2.00 44.5 ± 3.5

4.53 ± 1.69 3.77 ± 1.26 27.2 ± 7.36 5.83 ± 1.35 0.46 ± 0.65 0.09 ± 0.05 4.24 ± 2.63 335 ± 186 4.86 ± 2.67 260 ± 136

6.31 ± 1.63 1.43 ± 0.71 120 ± 43 2.28 ± 0.35 0.04 ± 0.01 0.09 ± 0.11 0.41 ± 0.11 63.9 ± 38.6 5.35 ± 3.20 30.9 ± 11.0

29.1 ± 11.5 4.46 ± 1.63 72.1 ± 27.1 4.36 ± 1.72 0.59 ± 0.17 0.15 ± 0.14 2.51 ± 0.52 92.5 ± 25.2 9.44 ± 1.84 24.5 ± 7.96

11.3 ± 6.5 4.46 ± 1.62 412 ± 251 8.46 ± 1.69 0.64 ± 0.30 0.31 ± 0.27 7.45 ± 0.62 470 ± 194 3.62 ± 1.96 233 ± 139



7.00 ± 0.18

6.86 ± 0.21

6.83 ± 0.02



6.71 ± 0.12

5.26 ± 1.09

6.98 ± 0.20

− − − − −

32.4 ± 12.4 3.65 ± 2.74 0.26 ± 0.18 0.03 ± 0.02 0.16 ± 0.03

97.1 ± 24.5 6.02 ± 2.65 0.74 ± 0.87 0.41 ± 0.01 0.41 ± 0.01

30.0 ± 4.70 2.00 ± 0.23 0.14 ± 0.04 0.01 ± 0.00 0.08 ± 0.04

− − − − −

17.8 ± 4.99 2.31 ± 0.75 0.11 ± 0.05 0.14 ± 0.25 0.43 ± 0.12

123 ± 53 15.1 ± 4.0 1.95 ± 2.73 2.02 ± 2.43 1.87 ± 0.76

24.8 ± 3.6 1.97 ± 0.53 0.05 ± 0.05 0.04 ± 0.01 0.31 ± 0.16

Organic contaminants in floodwater Two hundred and seventy-seven compounds out of 940 chemicals were detected (Table S6). The compounds were classified into 22 groups based on their usage or origin (Fig. 2 and Table 2). The chemicals detected in this study are similar to those observed in river waters and sediments by Hanh et al. (2014a, 2014b). The compounds were also classified into three main sources (agriculture, household and industry) based on their origin (Table S6, Fig. 3). Compounds within the agricultural and household groups showed the highest concentrations with variable levels between years and sites, while compounds originating mainly from industry showed low concentrations. The compounds originating from agricultural sources (pesticides) were detected at all sampling points in Thanh Hoa and Hue. Previous studies (Nakano et al. 2004a, 2004b; Comoretto et al. 2007, 2008; Karpouzas and Miao 2007; Lamers et al. 2011; Anyusheva et al. 2012) indicated that the pesticides used in the rice fields were the main origin of nonpoint-source pollution of surface water in rice growing regions. This study indicated that both pesticides and household chemicals are the main contaminants in floodwater and higher levels observed in 2012 (Fig. 2). Distribution of contaminants in floodwater of two study sites The agriculture, household and industry chemical groupings at the two sites are shown in Fig. 3c, d. The industry and

2013

household chemicals showed the highest concentrations in the canals in Thanh Hoa (TL2 and TC2) and probably originated in wastewaters from villages. Sites TL1, TL4 and TC1, which were far away from the villages, contaminated with agriculture chemicals, with fewer household chemical in the sites far from the canal and field (T1, T4-T6). Downstream in Thanh Hoa, concentrations of all chemical groupings were low in the water supply canals (TL3, TL5), but increased after passing the village (TC1), and then again declined in the fields (T1, T4-T6) and finally reduced in the river (TR) due to dilution. For Hue, HC6 showed high concentrations of agricultural and household chemicals, which is remarkably different from the 16 other sampling sites (Fig. 3d). These high concentrations were attributed to disposal of pesticide residues (empty pesticide containers such as bottles and bags) at the edge of the water supply canal leading into the field; as well as pesticides sprayed onto the edges of canals and ditches represent an important source. Similar observation of pesticide contaminant sources have been seen in the Red River Delta (Thuy et al. 2012) and the Mekong Delta (Toan et al. 2013). A different contamination trend was seen in Thanh Hoa, where water supply for the fields (Bo River, HR1, HC1 and HC2) showed low contaminant levels. However, during passthrough, the fields the concentrations of agricultural chemicals increased (HC8). Finally, the concentrations drop when pumped into the Bo River (HR2) due to dilution. Overall, the different sampling stations along with the water flow clearly demonstrated that water was contaminated with household

Environ Sci Pollut Res 48 42

2.0

3 24 a) Thanh Hoa-2012

1.5

Field

Canal

1.0 0.5 0.0 1

Concentration (µg/L)

Fig. 2 Pollution profile of floodwater in the fields and canals in Thanh Hoa (a, b) and Hue (c, d) in 2012 and 2013 (1: insecticides, 2: herbicides, 3: fungicides, 4: other pesticides, 5: antioxidants, 6. fire retardants, 7: disinfectants and insecticidal fumigants, 8: fatty acid methyl ester, 9: metabolites of detergents, 10: fragrances and cosmetics, 11: leaching from tires, 12: petroleum, 13: plant or animal steroids, 14: plasticizers, 15: PPCPs, 16: other substances of household origin, 17: intermediate for resins production, 18: intermediate in organic synthesis, 19: PAHs, 20: solvent, 21: explosives, 22: other substances of industry origin)

2.0

2

3

4

5

6

7

8

9

10 11 12 13 14 15 16 17 18 19 20 21 22 6 10

24

6 15 b) Thanh Hoa-2013

1.5

Field

Canal

1.0 0.5 0.0 1

2

3

4

5

6

7

8

9

10 11 12 13 14 15 16 17 18 19 20 21 22 1714

2.0

3 c) Hue-2012

1.5

Field

Canal

1.0 0.5 0.0 1

2

3

4

5

6

7

8

9

10 11 12 13 14 15 16 17 18 19 20 21 22 34

2.0

3 d) Hue-2013

1.5

Field

Canal

1.0 0.5 0.0 1

2

3

4

5

6

7

8

9

10 11 12 13 14 15 16 17 18 19 20 21 22

Pollutant compounds

chemicals during passing-through the village and polluted with agricultural chemicals when passing through the paddy fields. Contaminant levels at the two locations The average concentration of total agriculture chemicals in floodwaters in the fields and canals in Thanh Hoa were lower in 2012 (1.64 and 2.85 μg L−1, respectively) than in 2013 (3.0 and 5.2 μg L−1, respectively) (Fig. 3a). The average total concentrations of chemicals originated from household observed in the rice fields (55 μg L−1) and canals (67 μg L−1) in 2012 were two to four times higher than those observed in 2013. The difference between the 2 years is probably due to the small flood observed in 2013 where only the rice fields were flooded. In contrasts, high water levels recorded for the 2012 flood and floodwater entered into villages thus transporting organic pollutants from the households into rice

fields and canals. In addition, before the flooding, the average concentrations of household chemicals in 2012 were four to ten times higher than in 2013 (Fig. 4a), which indicated that there was an accumulation of chemicals building up in or around the households before the flooding in 2012. In Hue, average total concentrations of agriculture (3.4 μg L−1) and household chemicals (18.7 μg L−1) in the canals in 2012 were about two times and five times higher than those in 2013 (Fig. 3b). For both years, the floods were small, and only rice fields were flooded, with the lowest water levels recorded in 2012. This suggests that the lower levels of contamination in Hue in 2013 were due to dilution. Dilution is clearly seen by comparison of concentrations of household chemicals before and during flooding (Fig. 4b). Overall, the results obtained from this screening showed that the total concentrations of detected contaminants in floodwaters in Thanh Hoa were higher than in Hue (Fig. 4a, b), which probably is due to the geographical differences and floodwater levels at

Category

20 21 22

19

18 Industry

Intermediate in organic synthesis PAH Solvent Other substances of industry origin

0–1.08 (0.19)

0–0.01 (0)

0–0.51 (0.16)

0 (0)

0–0.94 (0.20)

0–0.01 (0)

0 (0)

0–0.31 (0.09) 0.01–0.56 (0.13) 0.02–0.10 (0.04) 0.02–0.38 (0.06) 0–0.18 (0.05) 0.00–0.38 (0.07) 0.02–0.37 (0.12) 0.02–0.17 (0.07) 0–0.26 (0.09) 0–0.26 (0.09) 0–0.28 (0.12) 0–0.31 (0.04)

0–0.69 (0.12)

0–0.21 (0.02)

0–0.03 (0.01)

Other substances of domestic origin Intermediate for resin

17

0–1.00 (0.33)

0–2.58 (0.40) 0–1.14 (0.28) 0–0.16 (0.05) 0–0.41 (0.08) 4.6–146 (62.8) 14.2–86.3 (41.6) 1.62–12.6 (3.88) 2.95–29.7 (8.50) 0 (0) 0–0.87 (0.33) 0 (0) 0 (0) 0.02–118 (38.8) 0.23–6.18 (3.18) 1.07–4.64 (2.07) 2.90–25.7 (10.8) 0–0.66 (0.18) 0–0.66 (0.18) 0.01–0.58 (0.15) 0–0.18 (0.05) 0.07–0.52 (0.23) 0 (0) 0.01–0.15 (0.07) 0.02–0.20 (0.08)

Leaching from tire n-Alkanes/petroleum Steroid Plasticizer PPCPs Reagent

11 12 13 14 15 16 0–0.07 (0.01)

0.02–0.33 (0.11) 0–0.04 (0.02) 0 (0)

0.05–1.52 (0.42) 0.04–3.13 (0.87) 0.01–1.20 (0.30) 0.05–3.31 (1.42) 0–0.27 (0.04) 0–2.02 (0.37) 0–0.03 (0) 0–0.41 (0.04) 0 (0) 0–6.10 (1.74) 0 (0) 0 (0)

F

F

0–2.37 (0.67) 0–1.05 (0.25) 0–2.25 (0.79)

0–1.97 (0.38) 0–0.03 (0.01) 0–0.01 (0)

0–1.24 (0.47) 0.01–2.06 (0.64) 0–2.11 (0.26) 0–0.01 (0) 0 (0) 0 (0)

0–0.73 (0.10) 0.09–0.28 (0.17) 0–0.30 (0.05) 0–0.01 (0.0) 0 (0) 0 (0)

0–4.10 (1.21) 0.44–5.69 (1.81) 0.42–2.74 (1.13) 0–0.87 (0.34) 0–2.08 (0.63) 0–0.34 (0.13) 0–3.25 (0.91) 0.01–28.3 (8.38) 0.07–0.78 (0.29) 0–0.71 (0.06) 0–0.57 (0.14) 0–0.21 (0.06)

BF

2013

0–1.29 (0.26)

0–0.21 (0.05)

0–1.78 (0.47)

(0) 0–1.39 (0.58)

0

0–0.12 (0.01)

(0)

(0)

0–0.54 (0.18)

0

0

0.01–0.09 (0.04) 0.01–1.99 (0.25) 0.01–0.13 (0.05) 0.02–0.20 (0.06) 0 (0) 0–0.66 (0.11) 0–0.16 (0.04) 0.05–0.21 (0.10) 0–0.09 (0.01) 0–0.17 (0.02) 0–0.06 (0.01) 0–0.33 (0.07)

0–0.04 (0.01)

0 (0)

0–0.02 (0.01)

0–0.07 (0.02) 0–1.95 (0.46) 0–0.41 (0.08) 0–0.21 (0.05) 30.9–122 (73.4) 3.70–46.2 (16.0) 2.11–14.7 (8.42) 1.49–8.07 (3.11) 0 (0) 0–4.27 (0.88) 0 (0) 0 (0) 6.05–136 (44.7) 0–8.06 (1.90) 1.01–20.9 (8.59) 0.17–4.36 (2.19) 0.01–0.07 (0.03) 0–0.19 (0.04) 0–0.17 (0.03) 0–0.16 (0.05) 0–0.19 (0.11) 0 (0) 0–0.12 (0.03) 0.02–0.18 (0.08)

0–0.39 (0.15) 0 (0) 0 (0)

0.21–14.1 (3.03) 0.21–0.37 (0.27) 0.02–21.3 (4.63) 0–2.05 (0.74)

0–0.64 (0.18) 0.03–0.24 (0.09) 0.06–0.69 (0.25) 0–0.48 (0.13) 0–0.01 (0) 0–0.25 (0.02) 0 (0) 0 (0) 0 (0)

0–0.74 (0.21) 0–0.27 (0.05) 0 (0)

0.01–7.27 (1.89) 0.01–1.28 (0.50) 0.50–3.65 (1.64) 0.68–8.18 (3.10) 0.14–1.54 (0.47) 0.04–0.49 (0.22) 0–0.36 (0.13) 0.01–0.44 (0.18) 0.01–4.02 (0.81) 0.06–2.76 (0.70) 0.04–2.67 (0.92) 0.03–2.54 (0.69) 0–0.82 (0.24) 0–1.40 (0.36) 0–0.23 (0.05) 0–0.48 (0.17)

BF

BF

BF

F

2012

2013

2012 F

Hue

Thanh Hoa

5 Household Antioxidant 6 Fire retardant 7 Disinfectants and insecticidal fumigants 8 Fatty acid methylester 9 Metabolites of detergents 10 Fragrances and cosmetics

1 Agriculture Total insecticides 2 Total herbicides 3 Total fungicides 4 Total other pesticides

Origin

Table 2 Concentrations (μg L−1) of chemicals belonging to different chemical categories and origins in water samples before flood (BF) and flood (F) in Thanh Hoa and Hue (values in parentheses are the mean concentrations)

Environ Sci Pollut Res

Environ Sci Pollut Res a)Thanh Hoa 30

55

b) Hue

67

2012:field 2012:canal 2013: field 2013:canal

25 20

Concentration (

Fig. 3 Total concentration of compounds originated from agriculture, household and industry in floodwater in Thanh Hoa (a) and Hue (b). c and d represented the concentrations from different emission sources at each site in Thanh Hoa and Hue, respectively, in 2013

15 10 5 0 Agriculture

Industry

c) Thanh Hoa 2013

TR

Sampling site

Household

Agriculture

HR1

TL5

HC8

TL3

HC7

TL4

HC6

TL2

HC5

TL1

HC4

TC3

HC3

TC2

HC2

TC1

HC1

T7

H7

T6

H6

T5

H5

T4

H4

T3

H3

T2

H2

Industry d) Hue 2013

HR2

TL6

T1

Agriculture Household Industry

H1 0

10

the two locations studied. The sampling sites in Thanh Hoa are located at a lower altitude, close to the villages and Fig. 4 Average concentration (μg L−1) of compounds originated from agriculture, household, and industry in 2012 and 2013 in Thanh Hoa (a) and Hue (b). Pesticides concentrations in floodwater in the canals and fields in 2012 and 2013 in Thanh Hoa (c) and Hue (d)

Household

20

30

40 50 Concentration (

0

4

8

12

16

20

affected by wastewaters discharged from the villages. In addition, the villages and fields in Thanh Hoa were flooded with

Environ Sci Pollut Res

high water levels (1–2 m) in 2012 where spreading of contaminants was most intensive. In Hue however, the study sites are located far from the villages, and flooding only occurred in the fields with floodwater levels of 0.25–1 and 0.5–1.5 m in 2012 and 2013, respectively, which were lower than that in Thanh Hoa.

Pesticides One hundred and seven pesticides (46 insecticides, 32 herbicides and 29 fungicides) were detected at over 10% detection frequencies with concentrations in the floodwaters ranging from 0.01 to 6.13 μg L−1. The most frequently detected pesticides were isoprocarb (70–90%), followed by isoprothiolane (10–88%), metalaxyl (35–71%) and fenobucarb (24–71%). Fenobucarb was detected at high frequency probably because it has been using in large amounts in Vietnam for paddy field cropping (Lamers et al. 2011; Anyusheva et al. 2012). The differences in pesticide concentrations between the 2 years and between canals and fields are shown in Fig. 4c, d. The variation in pesticide concentrations between 2012 and 2013 is attributed to the differences in floodwater levels as well as the quantity and the kinds of pesticides applied. Insecticide concentrations in Thanh Hoa in 2012 were lower than in 2013, which is in contrast to fungicide concentrations. For instance, in 2013, the rice paddy fields at Thanh Hoa were infected with rice blast disease, with the associated intense fungicide spraying explaining the subsequent high concentrations of the fungicides in the floodwaters. In Hue, farmers used herbicides in fields and at edges and banks of canals for cultivation of chilli plants before arrival of the flood in 2013, which may help explain the high herbicide concentrations recorded later in the floodwaters for this site (Fig. 4d). The most frequently detected insecticides in Thanh Hoa and Hue were carbamates. Fenobucarb and isoprocarb are widely used in the paddy fields in Vietnam (Berg and Tam 2012; Thuy et al. 2012). Isoprocarb and fenobucarb were detected at high frequencies (88 and 71%, respectively) and concentrations (0.68 and 0.07 μg L−1, respectively) in floodwaters in Thanh Hoa in 2013, while these values were lower (0.09 and 0.01 μg L −1, respectively) in 2012. In Hue, isoprocarb was the most frequently detected insecticide (100% in 2013) with detected concentrations of lower than 0.04 μg L−1. Fenobucarb was detected in 29% sampling site with the highest concentration value of 0.54 μg L−1 in 2013. The herbicide oxabetripnil was also detected in Thanh Hoa and Hue in 2013 with average concentrations of 0.06 μg L−1. Fungicides are used both for pretreatment of rice seeds before sowing, and later in the paddy fields, and hence fungicides are expected to be detected in the floodwater. Propamocarb was the most frequently detected fungicide (82% in 2013) with the highest concentration (1.31 μg L−1).

Metalaxyl was also detected in both sites at low concentration of less than 0.05 μg L−1. Although dichlorodiphenyltrichloroethane (DDT) has been banned in Vietnam for two decades (Hung and Thiemann 2002), metabolites were still detected in floodwater samples at both studied locations. p,p’-DDD and o,p’-DDT were detected in 20–30% of the samples in Thanh Hoa and at a concentration of 0.05 μg L−1 in both years. However, in Hue, detection frequency was higher (50%) with a concentration of 0.2 μg L−1 in 2012, and ten times lower concentrations 2013. These concentrations exceed the threshold values issued by the Vietnam national technical regulation on surface water quality (QCVN 08:2008/BTNMT/B1 2008). Household chemicals Fatty acid methyl ester, petroleum, plant or animal steroids and plasticizers were detected at high concentrations (Table S6, Fig. 2a–d). In Thanh Hoa, average of total concentrations of fatty acid methyl ester in floodwater in the field and canals were 0.57 and 0.97 μg L−1, respectively, in 2012, while these values were 1.64 and 1.39 μg L−1, respectively, in 2013. In Hue, these concentrations were 0.46 and 0.88 μg L−1, in the field and canal, respectively, in 2012, and 0.46 and 0.95 μg L−1 in the field and canal, respectively, in 2013. Average total concentrations of n-alkanes in the field and canals in Thanh Hoa were 48.3 and 42.3 μg L−1, respectively, in 2012. These values were seven and five times lower than those of 2013. In Hue, n-alkanes concentrations were 17.8 and 14.3 μg L−1 in the field and canal, respectively, in 2012 (Fig. 2) where the high levels were observed at canals HC5 (28.1 μg L−1), HC6 (9.73 μg L−1) and HC3 (3.7 μg L−1). The leakage of oil and petroleum products from mini pumps, very commonly used throughout the year for irrigation in these areas, might be one of the sources among others of nalkanes detected in these sites. Six (α-sterol, β-sitosterol, cholestanol, cholestane, coprostanol, cholesterol) out of ten sterols analysed were the most abundant, being observed in some water samples in Hue and Thanh Hoa in 2012. In Hue, sum of sterols concentrations ranged from 0.01 μg L−1 (H5) to 4.77 μg L−1 (H7) with a mean value of 0.94 μg L−1, while in Thanh Hoa these values were from 0.01 μg L−1 (T7) to 0.87 μg L−1 (T1) (0.37 μg L−1). Coprostanol was suggested as an indicator of faecal pollution already in the late 1960s (Murtaugh and Bunch 1967) and has been used as a powerful molecular marker for faecal pollution monitoring in several environmental matrices (Eganhouse et al. 1988). The coprostanol concentrations were from 0.21 to 3.53 μg L−1 and from 0.04 to 0.87 μg L−1 in Hue and Thanh Hoa, respectively. The ratio of copostanol to cholesterol can be used to indicate sewage (>0.2) (Grimalt et al. 1990) or human faeces (>0.3) contamination (Glassmeyer et al. 2005). In this study, the values of over one were observed

Environ Sci Pollut Res

in four out of 14 sites in Hue and the values of over eight were observed in three out of ten sites in Thanh Hoa, which demonstrated that these studied sites were seriously contaminated by untreated sewage. The group of plasticizers (mainly phthalates) was detected at 17 to 100% samples with concentrations ranged from 0.03 to 5.1 μg L−1. Similar concentration levels were found for Thanh Hoa and Hue with average total phthalate concentrations ranged from 1.5–3.2 μg L−1 for both years except for Thanh Hoa in 2013 where concentrations were five times higher. This was probably due to less floodwater. The source of the plasticizers is probably from the plastic covers used in rice-seedling nurseries during the winter-spring crop. PPCPs used for human, veterinary medicine in agriculture and aquaculture (Laville et al. 2004) have been found in surface, drink, ground water and coastal environments as well as in soil and sediment (Nakada et al. 2008; Kim et al. 2009). Three PPCPs (L-menthol, aspirin, diethyltoluamide) out of 14 PPCPs in the database were detected in the floodwaters. Average concentration (detection frequency) of L-menthol in floodwater in Hue was 0.08 μg L−1 (27%) and 0.01 μg L−1 (94%) in 2012 and 2013, respectively. While in Thanh Hoa, this values were 0.02 μg L−1 (33%) and 0.07 μg L−1 (82%), respectively. Average concentration (detection frequency) of diethyltoluamide in floodwater in Thanh Hoa was 0.01 μg L−1 (33%) and 0.01 μg L−1 (82%) in 2012 and 2013, respectively. The detection levels of L-methol and diethyltoluamide were similar to those reported by Hanh et al. (2014a, 2014b). These results indicate contaminated of floodwater by untreated wastewater from villages.

Conclusions This paper presents the first comprehensive study on a wide spectrum of micro-pollutants in floodwater in the north and centre of Vietnam. A large number of trace organic chemicals were detected (277 of 940 screened). Here of, pesticides and household chemicals were the main group of chemical compounds identified. Concentrations of elements and matrix parameters were generally lower than regulation values proposed by Ministry of Natural Resources Environment of Vietnam (QCVN 08:2008/BTNMT 2008). Released elements from soil, pesticides in the rice field and household chemicals from untreated wastewater when passing through villages contaminated the floodwater. After flooding events, higher levels of pollutants were observed, which probably was due to the release of contaminants from suspended field sediments or the release from wastewater around villages under flood conditions. The content of contaminants depends on the level of floodwater and time of the flooding in relation to the growth state of the paddy rice in the field. The comprehensive data obtained in this study provide the first baseline data on

contaminants as heavy metals and organic micro-pollutants in floodwater in the countryside in Vietnam. This data provides valuable information for refining chemical inventories and technical support for the purification of floodwater in order to remove contaminants from the water to provide clean drinking water for people both before and during flooding periods. Acknowledgements We acknowledge our colleagues at the Institute of Chemistry, Vietnam Academy of Science and Technology, and Department of Plant and Environmental Sciences at University of Copenhagen for helpful assistance with sampling and analyses. This study was financially supported by the Danish Ministry of Foreign Affairs’ program Danida for Innovative Cleaning Technology for production of drinking water during flooding episodes in the A-water project, a co-operation between University of Copenhagen and Vietnam Academy of Science and Technology.

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