Occurrence of perfluorinated chemicals (PFCs) in leachate, surface water and sediment collected from Tay Mo landfill and surrounding areas

Cite this paper: Vietnam J. Chem., 2021, 59(2), 239-246 Article DOI: 10.1002/vjch.202000157 239 Wiley Online Library © 2021 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH GmbH Occurrence of perfluorinated chemicals (PFCs) in leachate, surface water and sediment collected from Tay Mo landfill and surrounding areas Nguyen Thuy Ngoc, Phung Thi Vi, Pham Hung Viet, Duong Hong Anh * Research Centre for Environmental Technology and Sustainable Development (CETASD), VNU University of Science, Vietnam National University, Hanoi 10000, Viet Nam Key Laboratory of Analytical Technology for Environmental Quality and Food Safety Control (KLATEFOS), VNU University of Science, Vietnam National University, Hanoi 10000, Viet Nam Submitted September 11, 2020; Accepted February 19, 2021 Abstract The municipal landfill is considered to be a potential source of different environmental contaminants derived from consumer goods, including perfluorinated chemicals (PFCs). Twenty-four leachate, surface water samples and twenty- four sediment samples collected at Tay Mo landfill (Hanoi, Vietnam) and surrounding areas were analysed for sixteen PFCs. Total concentrations of PFCs in leachate and surface water ranged from 103 to 328 ng/L (mean: 161 ng/L) at Tay Mo landfill, 19.1-22.4 ng/L (mean: 20.7 ng/L) in ponds nearby the landfill, 5.19-6.96 ng/L (mean: 5.96 ng/L) in Nhue River around the landfill, 5.57-12.7 ng/L (mean: 9.00 ng/L) in the upstream and 3.81-11.5 ng/L (mean: 7.14 ng/L) in the downstream. The total concentrations of PFCs in landfill sediment which ranged from 3.52 to 6.70 ng/g (mean: 5 ng/g) was 3-4 times higher than those in sediment taken from Nhue River and the ponds around the landfill. The dominating detected compounds were short-chain perfluorinated alkyl substances like PFOA, PFHxA, PFHpA in water, and PFOS, PFBS in sediment. Keywords. PFCs, leachate, Tay Mo municipal landfill. 1. INTRODUCTION In 2009, a number of perfluorinated chemicals (PFCs) were included in the list of persistent organic pollutants (POPs) that need to be monitored, restricted, and even banned under the Stockholm Convention. Due to their both lipophilic and hydrophilic properties, PFCs have been used since the 1950s [1,2] for the surface treatment of furniture. There are numerous applications of PFCs in domestic and industrial activities such as impregnation or coating agents on the surface of carpets, leather, being used in textile and garment products, paper and wrapping paper, metal surface, cleaning products, and some types of plastic, insecticides, etc. [3] After being used, along with waste, the PFCs will be discharged into the surrounding environment and found in most environmental objects like water, soil, biota and the food chain. [1,2,4] To date, the data on PFCs in Vietnam environment is still limited, focusing on surface water, sediment and freshwater fish, etc. [1,4,5] The municipal dumping site is a waste collection site of consumer goods being potential contamination sources of PFCs such as carpets, upholstery, garments, leather products, wrapping paper, etc. The landfill technology, which is widely applied in Vietnam, is the decomposition method of waste material with the least energy consumption. During the decomposition process, consequently undesirable pollutants such as PFCs can be released into leachate owning the risk of contamination for the surrounding environment, especially surface water and groundwater. [6] While a considerable number of studies on the occurrence of PFCs have been conducted in landfills in many countries [7] , investigations in Vietnam are still minimal. Joo Woo Kim et al. reported the occurrence of PFCs in one leachate and nine river water samples around Nam Son landfill since 2011 [8] and N.H. Lam investigated levels of PFCs in samples around landfills in Ho Chi Minh City (HCMC) in 2017. [4] Studies on municipal dumping sites in the USA, Europe indicated that PFCs were detected in the leachate at concentrations ranging from hundreds to thousands of ng/L at sites where have been closed for 2-4 decades. [7] The Tay Mo landfill has been one of domestic waste sites in Hanoi operating for 3 years from 1997 to 2000. At that time, the leachate treatment system was not worked effectively, even not used. At present, Vietnam Journal of Chemistry Duong Hong Anh et al. © 2021 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH GmbH www.vjc.wiley-vch.de 240 residual household waste has been still piled up to become open-air huge garbage piles in few areas. Accordingly, this site can be a potential source which releases pollutants into the surrounding environment. In this study, leachate, surface water and sediment samples were collected at the Tay Mo landfill, nearby ponds, Nhue River at the positions in the front, near and the back of the site to elucidate the occurrence and level contamination of PFCs in the environment around this garbage dump that has closed for 20 years. 2. MATERIALS AND METHODS 2.1. Studied area and sampling location The Tay Mo landfill with an area of 4.9 ha which located about 10 km west of the center of Hanoi was operated from 1997 to 2000 and received about 1,400 tons of waste per day. [9] In the 1990s, the primary treatment and disposal method for the city's domestic waste was landfills. At those landfills, leachate was hardly treated or only treated by old and inefficient technologies. Because leachate from the landfill can be washed away with rainwater, it is unavoidable that a lot of toxic substances from leachate can be dispersed into the surrounding environment. Currently, the Tay Mo landfill has stopped working, but the amount of garbage in the past is still piled up. At present, next to this closed landfill, the Phu Dien composting plant, which specializes in the treatment of faecal sludge from toilets, is managed by the Hanoi Urban Environmental Company (URENCO). Leachates, surface water and sediment samples were collected at the following locations: (i) At the landfill: 04 points (TM1, TM2, TM3, TM4) - drainage from the landfill; (ii) ponds next to landfill: 02 points (TM5, TM6); (iii) Nhue River around the landfill (NS01, NS02, NS03, NS04); (iv) the upstream of Nhue River (NU01, NU02, NU03, NU04); (v) the downstream of Nhue River (ND01 to ND10). Sampling locations are shown in figure 1. Total collected samples were 24 water samples and 24 sediment samples. Figure 1: Sampling areas: Tay Mo landfill and surrounding area, Nhue River upstream, Nhue River downstream Figure 2: Sampling locations: Tay Mo landfill (TM1 to TM4) and surrounding area (the pond: TM5, TM6; Nhue River: NS01 to NS04) 2.2. Analysis The analytical procedure of PFCs in water and sediment was optimized by the laboratory [10] based on the method provided in ISO 25101:2009. [11] The steps of sample preparation and analysis of PFCs by liquid chromatography-tandem mass spectrometry (LC-MS/MS) are briefly summarized below. Preparation of surface water samples: The water sample was filtered through a glass filter GF/F (Whatman) to remove suspended solids, then spiked with the surrogate solution containing MPFAC - MXA (Wellington, Canada). An Oasis-WAX cartridge (225 mg, Water, USA) was conditioned before the sample was passed through the cartridge. The extraction column was eluted with 4 mL of methanol and 4 mL of 0.1 % ammonium acetate solution in methanol (m/v). The eluate was Vietnam Journal of Chemistry Occurrence of perfluorinated chemicals © 2021 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH GmbH www.vjc.wiley-vch.de 241 concentrated to 1 mL under a gentle nitrogen stream, filtered through a 0.2 µm nylon filter and put into an injection vial. Preparation of sediment samples: Approximately 5.0 g of the wet sample was weighed and stored in a 50 mL PP tube, then spiked with the surrogate standards containing MPFAC - MXA (Wellington, Canada). The sample was added with 20 mL of methanol, vortexed and subjected to an ultrasonic extraction for 15 minutes. Next, the mixture was centrifuged to collect the extract. This procedure was repeated three times, and all supernatant was combined and concentrated to 5 mL in a rotary evaporator. The final 5 mL was mixed with distilled water to obtain a solution containing 20 % (v/v) methanol. The SPE procedure for the solution of sediment extract was the same as that described for the water sample. Instrumental analysis of PFCs by LC-MS/MS: Sixteen PFCs including 12 perfluoroalkyl carboxylic acids (PFCAs, C5-14, C16 and C18), 4 perfluoroalkyl sulfonates (PFASs, C4, C6, C8 and C10), and 9 isotope-labelled surrogate standards of PFCAs and PFASs were analyzed on LC-MS/MS 8040 (Shimadzu, Japan). The chromatographic separation was achieved with a Poroshell 120 EC- C18 analytical column (150 mm  2.1 mm  2.7 µm) with the mobile phase A containing 2 mM ammonium acetate and methanol (9:1, v/v) and methanol as solvent B. Solvent gradient program was set up as following steps. The mobile phase was initially 30 % B and 70 % A for 2 min and then changed to 95 % B and 5 % A in 16 min and held for 4 min. At the end of the analysis, the mobile phase was changed to the initial composition (30 % B) for 3 min; flow rate was 0.3 mL/min. The PFCs were quantified and qualified using tandem mass spectrometry where the precursor ions were fragmented into product ions. The target compounds were ionized by the Electrospray Ionization (ESI) technique with DL temperature of 250 o C and the nitrogen and dry air at the flow rate of 3 and 15 L/min, respectively. The calibration curve for each congener was constructed at concentrations of 0.1; 0.5; 2.0; 5.0; 10; 20 ppb. The correlation coefficient of the calibration curve (R 2 ) was over 0.997. QA/QC: The mixture of surrogate standards was added to each sample prior to sample pre-treatment for the purpose of determining the recovery efficiency of PFCs in each run. A blank- and a matrix-spiked samples were always analysed performed in the same batch. The recovery efficiency of PFCs in water samples and sediment samples ranged from 67 to 114 % and from 60 to 116 %, respectively. The limit of detection (LOD) and limit of quantitation (LOQ) was calculated as the concentrations that had signal-to- noise (S/N) ratios of 3 and 10, respectively. LOQ of PFCs in water samples ranged from 0.1-0.4 ng/L, and LOQ in sediment samples was in the range of 0.1-0.2 ng/g. 3. RESULTS AND DISCUSSION 3.1. Total concentration of PFCs in leachate and sediment from Tay Mo landfill At studied sites in Tay Mo landfill, the total concentrations of 16 PFCs ranged from 103-328 ng/L in leachate and 3.52-6.70 ng/g d.w in dry sediment. Total concentrations of PFCs in sampling sites TM2, TM3, and TM4 locating on the water runoff from the landfill to the surrounding area were detected at similar levels in both leachate and sediment samples. The point TM1 which was collected at open-air waste piles, reached a very high level of total PFCs in leachate (328 ng/L). There is a similarity in the total PFCs concentration of leachate samples between Tay Mo closed landfill (in this study) and Nam Son active landfill (363 ng/L in the study of J. W. Kim [8] ). By contrast, the total concentrations of PFCs in the sediment at TM1 were lower than other points. At present, information on the occurrence of PFCs in sediment samples in landfills has been limited in Vietnam. N. H. Lam reported that concentrations of the target PFCs in sediments obtained from the discharge drain at a landfill in HCMC ranged from 1.31 to 1.75 ng/g d.w, [4] only equal to one-third of these levels found in this study. In leachate, perfluoroalkyl carboxylic acids (PFCAs) were found at higher concentrations than perfluoroalkyl sulfonates (PFCASs) (p < 0.05) due to the better solubility in water of the former. Short- chain PFCAs (C5-C8) were detected at much higher frequencies than long-chain PFCAs (p < 0.05), and long-chain PFAAs with more than 11 carbon atoms were hardly found. Among sixteen PFCs, PFOA, PFHxA, and PFHpA were the most common compounds, with the contribution to total PFCs in the leachate of 31.7 %, 28.2 % and 16.3 %, respectively. PFOA which had concentrations in the range of 28.9 and 110 ng/L in wastewater at Tay Mo landfill were significantly higher than other PFCs, it is notable that this compound was always detected in surface water in Vietnam. [4,12] The most significant predominance of PFOA in leachate in this work is consistent with other studies in the world. [6] Of the Vietnam Journal of Chemistry Duong Hong Anh et al. © 2021 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH GmbH www.vjc.wiley-vch.de 242 PFASs, PFOS was found at the highest concentration in a range of 6.66-45.9 ng/L, accounting for 11.9 % of total PFCs. In comparison with other congeners, long-chain PFASs like PFDS had the lowest concentration, approximately 0.2 ng/L. The obtained results were similar to various studies, suggesting that PFAAs are the most dominant components of PFCs, and mainly short- chain substances were released from domestic waste. [7] Table 1: Concentrations of PFCs in leachate and sediment collected from Tay Mo landfill, Hanoi Compounds Concentrations in leachate (ng/L) Concentrations in sediment (ng/g d.w) TM1 TM2 TM3 TM4 TM1 TM2 TM3 TM4 Perfluorooctanonic acid (PFOA) 110.8 33.53 28.90 31.29 0.39 0.34 0.51 0.48 Perfluorooctansulfonate (PFOS) 45.91 12.38 6.66 11.58 0.94 2.08 0.26 2.54 Total 16 PFCs 328 103 104 108 3.52 5.74 4.06 6.70 Average concentration of total PFCs 161 5.00 3.2. Composition of PFCs in leachate and sediment at Tay Mo landfill The composition of all target PFCs in leachate and sediment samples at Tay Mo landfill is shown in figures 3 and 4. Unlike the trend of leachate samples, in sediments, PFASs were major congeners contributing to the total content of PFCs. For instance, PFOS and PFBS were found with the highest proportion in all samples, accounting for 28.3 and 14.6 % of total PFCs; meanwhile, no long- chain PFASs like PFDS was detected. For the PFAAs group, the short-chain acids such as PFHxA, PFHpA and PFOA were observed in all samples where PFOA was still the most dominant component. Compared with the results in leachate, the detection frequencies of long-chain acids with more than 11 carbon atoms in sediment samples were higher than those in leachate samples. The PFOS and PFOA concentrations found in sediment samples ranged from 0.26-2.54 and from 0.34-0.51 ng/g, respectively. Figure 3: PFC composition profiles in leachate from Tay Mo landfill Figure 4: PFC composition profiles in sediment from Tay Mo landfill 3.3. Occurrence of PFCs in Nhue river and surrounding area As described in the sampling locations, in addition to the Tay Mo landfill, water and sediment samples from the surrounding areas were collected, including two ponds next to the landfill, the Nhue River (the upstream (n = 4), downstream (n = 10), and the part Vietnam Journal of Chemistry Occurrence of perfluorinated chemicals © 2021 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH GmbH www.vjc.wiley-vch.de 243 flowing through the landfill (n = 4)). Total concentrations of PFCs and two considerable substances, including PFOS and PFOA in water and sediment, are listed in table 2. The total concentrations PFCs which varied from 19.1-328 ng/L (n = 6) in water samples at the Tay Mo landfill and two ponds next to the landfill were much higher than those in Nhue River (n = 18, the concentration range of 12.7-3.81 ng/L). Besides, there was no difference (p > 0.05) in the total concentration of PFCs in surface water samples from the different parts of the Nhue River. These phenomena may be due to different effects caused by the water flowing from the PFCs source (leachate in the landfill) to the receiving water bodies (the two ponds and Nhue River). The small ponds are closed water bodies which only receive rainwater and leachate from the landfill; consequently, the effect of substances in the leachate is significant. For the Nhue River, although the leachate from the landfill had high concentrations of PFCs, the flow of the drainage from this closed landfill was negligible compared to the large and continuous flow of the river. Therefore, the influence of the leachate in Tay Mo landfill on the presence of PFCs in water samples taken in Nhue River at the time of sampling (dry season) was not observed. At the landfill and two ponds next to there, PFOA and PFOS were detected with the detection frequency of 100 %. For surface water samples collected from Nhue River, while PFOS was found at a lower frequency (61 %), PFOA was observed in all samples and had the highest concentration among PFCs. The PFCs concentrations in Nhue River water were similar to the results obtained in our previous studies on the wastewater in the drainage system in central Hanoi (Kim Nguu River, To Lich River, Yen So Lake) with the total concentration of PFCs ranging from 4 to 10 ng/L in the dry season and there was no difference between upstream and downstream. [13] Although there are seven municipal wastewater treatment plants which have currently worked in Hanoi, it is the fact that approximately three fourth of wastewater amount from domestic activities and production has been discharged directly into this river and lake systems without sufficient treatment. Figure 5: Total concentration of PFCs in leachate, surface water and sediment at Tay Mo landfill compared to other investigated areas At the Tay Mo landfill, the average total concentrations of PFCs found in sediment (5 ng/g) were three- to four-fold greater than those in Nhue river (1.57 ng/g) and the ponds surrounding the landfill (1.34 ng/g), respectively. However, the comparison within result sets showed no statistically meaningful difference between samples collected at the landfill and other investigation areas. Analysis results indicated that, despite being closed, the Tay Mo landfill might be a potential source of PFCs that pre-existed or emerged by the decomposition of residual waste, probably affecting closed water bodies (like ponds) next to there. 3.4. Comparison of PFCs concentrations in wastewater and sediment from different dumping sites A variety of data on PFCs at landfill obtained in this study and other publications are summarized in table 2. The presence of PFCs in the wastewater and leachate is of great concern in many countries around the world, but in Vietnam, the data of PFCs in wastewater and leachate is still limited. The first literature published by J. W. Kim et al. in 2012 [8] showed that the total concentration of PFCs, PFOA and PFOS in leachate in Nam Son landfill in Hanoi were 360, 100 and 11 ng/L, respectively. The Nam Son landfill was put into operation after the Tay Mo Vietnam Journal of Chemistry Duong Hong Anh et al. © 2021 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH GmbH www.vjc.wiley-vch.de 244 landfill was full and had to stop working. Despite being closed for nearly 20 years, total concentrations of PFCs, PFOA and PFOS in leachate at Tay Mo landfill were similar to those at the operating