Abstract: Ba Vi National Park, one of 28 Vietnamese National Parks, is currently preserved and exploited for a variety of purposes, including the preservation of intact natural forest ecosystems and genetic resources of rare plants and animals. This paper presents the monitoring results of microbial contamination in surface water environment of the Ba Vi National Park (Ha Noi) in the period 2013-2014 and 2018. The results showed that total coliform (TC) density varied from 23 to 11,000 MPN/100ml in bimonthly observation in 2013-2014 which was lower than that one of sampling campaign in 2018, from 900 MPN/100ml to 8,100 MPN/ml. Fecal coliform (FC) densities varied from 0 to 110 MPN/100ml in 2013-2014, lower than in 2018, when it varied from 0 MPN/100ml to 600 MPN/100ml. At several observation times, both TC and FC were higher than the allowable values of the Vietnam national technical regulation QCVN 08-MT: 2015/BTNMT column A1 for surface water quality. The exceeded values of TC and FC than the allowable values and the increase trend from the 2013 to 2018 periods indicated the potential risks to the public health in this region when people use water for domestic and agricultural purposes. Our results provide dataset for environmental management in the Ba Vi National Park in order to protect the eco-environment in parallel with social-economic development. Vườn Quốc gia Ba Vì, một trong 28 vườn quốc gia của Việt Nam hiện đang được bảo tồn và khai thác cho nhiều mục đích, trong đó có bảo tồn nguyên vẹn các hệ sinh thái rừng tự nhiên, các nguồn gen động, thực vật quý hiếm, các đặc sản rừng và các di tích lịch sử, cảnh quan tự nhiên trong vùng. Bài báo trình bày kết quả quan trắc, đánh giá mức độ ô nhiễm vi sinh vật trong môi trường nước mặt tại Vườn Quốc Gia Ba Vì, Hà Nội giai đoạn 2013-2014 và 2018. Kết quả cho thấy mật độ coliform tổng số (TC) biến đổi trong khoảng từ 23 – 11.000 MPN/100ml trong các đợt quan trắc định kỳ 2 tháng/lần trong hai năm 2013 - 2014 và trong khoảng từ 900 – 8.100 MPN/100ml trong một đợt quan trắc năm 2018. Mật độ fecal coliform (FC) biến đổi trong khoảng từ 0 - 110 MPN/100ml năm 2013 -2014 và từ 0 - 600 MPN/100ml vào năm 2018. Vào một số thời điểm quan trắc, mật độ FC và TC vượt giá trị cho phép của quy chuẩn kỹ thuật Quốc Gia QCVN 08-MT:2015/BTNMT cột A1 về chất lượng nước mặt. Các giá trị TC và FC vượt quá giá trị cho phép và xu hướng gia tăng TC và FC từ 2013 -2018 cho thấy nguy cơ tiềm tàng khi người dân sử dụng nguồn nước này cho các mục đích sinh hoạt và nông nghiệp. Như vậy, kết quả của nghiên cứu này nhấn mạnh nhu cầu giám sát thường xuyên chất lượng nước và cần thực hiện các giải pháp hiệu quả để xử lý và quản lý nguồn gây ô nhiễm trong khu vực nhằm bảo vệ môi trường sinh thái song song với phát triển kinh tế - xã hội của khu vực.

Abstract: Wastewater, especially non-treated wastewater from different sources is one of causes for surface and ground water pollution. However, the monitoring of wastewater quality has not been regularly implemented. This paper presents the preliminary observation results of the wastewater quality of different sources such as domestic, fishery processing, husbandry, agricultural runoff and irrigation canals in some coastal communes of Giao Thuy district, Nam Dinh province in 2017 - 2018. The results showed variation values of some variables as following: pH: 3.4 to 8.7; DO: 1.1 – 7.6 mg/l; conductivity: 0.01 – 〉 99.9 S/m; Suspended solids: 7 – 599 mg.L-1; nitrate (NO3-): 0.01-1.74 mgL-1; ammonium (NH4+): 0.01 - 3.99 mgNL-1, phosphate (PO43-): 〈 0.01– 3.05 mgPL-1, total phosphorus: 0.01 – 5.03 mgPL-1. The values of some variables such as DO, pH, nitrite, ammonium, suspended solids and phosphate at some observation time exceeded the allowed values of the Vietnamese standards for domestic wastewater quality, for industrial wastewater quality and for surface water quality. Among these different wastewaters observed, the higher contents of nutrients were found for domestic wastewater. The results provide a dataset for environmental managers in order to control of wastewater quality, especially for the coastal communes where coastal aquacultural areas are large like Giao Thuy district, Nam Dinh province. Nước thải, đặc biệt là nước thải chưa qua xử lý từ nhiều nguồn thải khác nhau là một trong những nguyên nhân gây ô nhiễm nguồn nước mặt và nước ngầm. Tuy nhiên việc giám sát chất lượng nước, lại chưa được thường xuyên thực hiện. Bài báo trình bày kết quả khảo sát bước đầu về chất lượng nước thải sinh hoạt, chế biến thủy sản, chăn nuôi, nông nghiệp, kênh dẫn tưới tiêu tại một số xã ven biển thuộc huyện Giao Thủy, tỉnh Nam Định trong năm 2017 - 2018. Kết quả khảo sát cho thấy khoảng giá trị của một số thông số như sau: pH 3,4 – 8,7; DO: 1,1 – 7,6 mgL-1; độ dẫn điện: 0,01 – 99,9 S/m; chất rắn lơ lửng: 7 – 599 mg.L-1; nitrat (NO3-): 0.01-1.74 mgL-1; amoni (NH4+): 0.01 - 3.99 mgNL-1; phốtphat (PO43-): 〈 0,01 - 3,05 mgPL-1 và phốtpho tổng số: 0,01 – 5,03 mgL-1. Hàm lượng một số chỉ tiêu như NO2, NH4+, PO43-, SS tại một số thời điểm đã vượt quá giá trị cho phép theo các quy chuẩn nước thải sinh hoạt, nước thải công nghiệp và nước tưới tiêu. Trong các loại nước thải đã quan trắc, nước thải sinh hoạt có hàm lượng các chỉ tiêu dinh dưỡng cao hơn. Các kết quả nghiên cứu nhằm cung cấp cơ sở dữ liệu cho các nhà quản lý về việc kiểm soát chất lượng nước thải, đặc biệt là các xã ven biển có diện tích nuôi trồng thủy sản khá lớn như huyện Giao Thủy, tỉnh Nam Định.

Abstract: Abstract. The Red River (Vietnam) is representative of a south-east Asian river system, strongly affected by climate and human activities. This study aims to quantify the spatial and seasonal variability of CO2 partial pressure and CO2 emissions of the lower Red River system. Water quality monitoring and riverine pCO2 measurements were carried out for 24 h at five stations distributed along the lower Red River system during the dry and the wet seasons. The riverine pCO2 was supersaturated relative to the atmospheric equilibrium (400 ppm), averaging about 1589±43 ppm and resulting in a water–air CO2 flux of 530.3±16.9 mmol m−2 d−1 for the lower Red River. pCO2 and CO2 outgassing rates were characterized by significant spatial variation along this system, with the highest values measured at Hoa Binh station, located downstream of the Hoa Binh Dam, on the Da River. Seasonal pCO2 and CO2 outgassing rate variations were also observed, with higher values measured during the wet season at almost all sites. The higher river discharges, enhanced external inputs of organic matter from watersheds and direct inputs of CO2 from soils or wetland were responsible for higher pCO2 and CO2 outgassing rates. The difference in pCO2 between the daytime and the night-time was not significant, suggesting weak photosynthesis processes in the water column of the Red River due to its high sediment load.

Abstract: Background and aims – Biomonitoring is an important tool for assessing river water quality, but is not routinely applied in tropical rivers. Marked hydrological changes can occur between wet and dry season conditions in the tropics. Thus, a prerequisite for ecological assessment is that the influence of ‘natural’ hydrological change on biota can be distinguished from variability driven by water quality parameters of interest. Here we aimed to (a) assess seasonal changes in water quality, diatoms and algal assemblages from river phytoplankton and artificial substrates through the dry-wet season transition (February–July 2018) in the Red River close to Hanoi and (b) evaluate the potential for microscopic counts and high-performance liquid chromatography (HPLC) analysis of chlorophyll and carotenoid pigments for biomonitoring in large tropical rivers. Methods – River water (phytoplankton) and biofilms grown on artificial glass substrates were sampled monthly through the dry (February–April) to wet (May–August) season transition and analysed via microscopic and HPLC techniques. Key results – All phototrophic communities shifted markedly between the dry and wet seasons. Phytoplankton concentrations were low (c. thousands of cells/mL) and declined as the wet season progressed. The dominant phytoplankton taxa were centric diatoms (Aulacoseira granulata and Aulacoseira distans) and chlorophytes (Scenedesmus and Pediastrum spp.), with chlorophytes becoming more dominant in the wet season. Biofilm diatoms were dominated by Melosira varians, and areal densities declined in the wet season when fast-growing pioneer diatom taxa (e.g. Achnanthidium minutissimum, Planothidium lanceolatum) and non-degraded Chlorophyll a concentrations increased, suggesting active phytobenthos growth in response to scour damage. Otherwise, a-phorbins were very abundant in river seston and biofilms indicating in situ Chlorophyll a degradation which may be typical of tropical river environments. The very large range of total suspended solids (reaching 〉 120 mg/L) and turbidity appears to be a key driver of photoautotrophs through control of light availability. Conclusions – Hydrological change and associated turbidity conditions exceed nutrient influences on photoautotrophs at inter-seasonal scales in this part of the Red River. Inter-seasonal differences might be a useful measure for biomonitoring to help track how changes in suspended solids, a major water quality issue in tropical rivers, interact with other variables of interest.

Abstract: Due to utilization increase of chemical fertilizers and manures and of a large water volume for irrigation, agricultural runoff has significantly accelerated water pollution. The Red River locates in Vietnam where agriculture plays an important role in the country’s economy. This paper presented the observation results of organic matters concentrations in agricultural runoff from different plant fields (vegetable, flower and rice) in the Red River Delta in 2013 -2014. The results showed that DOC concentrations varied in a high range from 1.0 mg.L-1 to 37.1 mg.L-1, averaging 10.2 ± 6.2 mg.L-1 whereas POC concentrations varied from 0.5 to 4.5 mg.L-1, averaging 1.7 ± 0.7 mg.L-1 for a total 104 samples observed. TOC concentrations in water from the vegetable and flower fields (11.7 ± 7.3 mg.L-1 and 12.6 ± 6.0 mg.L-1 respectively) were higher than the one from the rice field (8.5 ± 6.6 mg.L-1). Lower organic matters concentrations were found in the rainy season than in the dry season due to dilution process. The results suggest the needs for regularly monitoring and efforts to control organic matter pollution from agricultural runoff in the Red River basin or other river basins in developing countries. Do sử dụng phân bón và thể tích nước tưới lớn, canh tác nông nghiệp đã và đang góp phần đáng kể gây ô nhiễm nguồn nước. Sông Hồng nằm ở Việt Nam, nơi ngành nông nghiệp đóng vai trò quan trọng trong nền kinh tế. Bài báo trình bày kết quả quan trắc hàm lượng cacbon hữu cơ (TOC) bao gồm dạng hòa tan (DOC) và không tan (POC), trong nước chảy tràn từ đất canh tác (rau, hoa, lúa) ở đồng bằng sông Hồng năm 2013 -2014. Kết quả cho thấy DOC thay đổi rất rộng từ 1,0 mg.L-1 đến 37,1 mg.L-1, trung bình đạt 10,2 ± 6,2 mg.L-1 trong khi POC thay đổi từ 0,5 mg. L-1 đến 4,5 mg.L-1, trung bình đạt 1,7 ± 0,7 mg.L-1 đối với 104 mẫu nước. TOC từ trồng rau và hoa (11,7 ± 7,3 mg. L-1 và 12,6 ± 6,0 mg.L-1) cao hơn so với trồng lúa (8,5 ± 6,6 mg. L-1). TOC trong mùa mưa thấp hơn so với mùa khô. Cần thường xuyên giám sát và nỗ lực kiểm soát ô nhiễm chất hữu cơ do nước chảy tràn từ đất canh tác ở lưu vực sông Hồng.

Abstract: The Red river system is a typical example of Southeast Asian rivers that is strongly impacted by human and climatic conditions, especially in the recent period. In this paper, we aim to investigate the longitudinal variation of the water quality of the Red river, in the section from Hanoi city to the Ba Lat estuary. The sampling campaigns were conducted in the dry seasons in 2017 and 2018. The monitoring results showed that the average concentrations of nutrients (NO2-, NO3-, NH4+, PO43-) were still lower than the allowed values of the Vietnamese standard limits for surface water quality (QCVN 08:2015/BTNMT, column A1) whereas the average concentrations of Cl- and TSS exceeded the allowed values of the QCVN 08:2015/BTNMT, column A1 4.6 and 2.3 times, respectively. NO3- and dissolved silica (DSi) concentrations showed a significant variation from the Hanoi site to the Ba Lat site (6.62 mg/l to 1.19 mg/l for NO3- and 5.21 mg/l to 2.14 mg/l for DSi) whereas SO42-, NO2- and Cl- increased markedly in this longitudinal section, especially from the point SH6 where the salinity started to increase. Based on the three different methods for classification of trophic levels and on the different variables observed during the dry seasons in 2017–2018, the nutrient concentrations of the Red river water tended to slightly increase from the site Hanoi (SH1) to the site SH5 at Nam Dinh, indicating the increase of nutrient external input along the river whereas it tended to decrease from the site SH6 (at mesotrophic/eutrophic level) to the last observed site SH9 (at oligotrophic/mesotrophic level) at the sea due to the dilution of seawater. Seawater in dry season could affect directly the river downstream about 35 km far from the sea. The results may be a guide for planning of water use including agricultural irrigation in the Red river estuary.

Abstract: Concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) were determined in settled house dust and road dust samples collected from a core urban area of Hanoi. Levels of PAHs ranged from 830 to 3500 (median 2000) ng/g in house dust, and from 1400 to 4700 (median 1700) ng/g in road dust. Concentrations of PAHs in dust samples of this study were within the moderate range as compared with those from other countries in the world. Toxic equivalents to benzo[a]pyrene (BaP-EQs) in our samples ranged from 81 to 850 (median 330) ng BaP-EQ/g with principal contributors as BaP and dibenz[a,h] anthracene, which accounted for 69% to 93% of BaP-EQs. In almost all the samples, proportions of high-molecular-weight PAHs (HMW-PAHs with 4–6 rings) were higher than those of low-molecular-weight PAHs (LMW-PAHs with 2–3 rings), suggesting emission sources from combustion processes rather than direct contamination by petrogenic sources. Traffic activities were estimated as important sources of PAHs in the studied areas, for example, vehicular exhaust and tire debris. Keywords: PAHs, house dust, road dust, traffic emission, urbanization. References [1] K. Srogi, Monitoring of environmental exposure to polycyclic aromatic hydrocarbons: a review, Environ. Chem. Let. 5 (2007) 169-195. https://doi. org/10.1007/s10311-007-0095-0.[2] K.H. Kim, S.A. Jahan, E. Kabir, R.J.C. Brown, A review of airborne polycyclic aromatic hydrocarbons (PAHs) and their human health effects. Environ. Int. 60 (2013) 71–80. https://doi. org/10.1016/j.envint.2013.07.019.[3] E. Stogiannidis, R. Laane, Source characterization of polycyclic aromatic hydrocarbons by using their molecular indices: an overview of possibilities. Rev. Environ. Contam. Toxicol. 234 (2015) 49–133. https://doi.org/10.1007/978-3-319-10638-0_2.[4] H.I. Abdel-Shafy, M.S.M. Mansour, A review on polycyclic aromatic hydrocarbons: source, environmental impacts, effect on human health and remediation. Egypt. J. Pet. 25 (2016) 107–123. https://doi.org/10.1016/j.ejpe.2015.03.011.[5] ATSDR, 1995. Toxicological profile for polycyclic aromatic hydrocarbons. https://www.atsdr.cdc. gov/toxprofiles/tp69.pdf.[6] M.T. Anh, L.M. Triet, J.J. Sauvain, J. Tarradellas, PAH contamination levels in air particles and sediments of Ho Chi Minh City, Vietnam. Bull. Environ. Contam. Toxicol. 63 (1999) 728–735. https://doi.org/10.1007/s00128 9901040.[7] T.T. Hien, L.T. Thanh, T. Kameda, N. Takenaka, H. Bandow, Distribution characteristics of polycyclic aromatic hydrocarbons with particle size in urban aerosols at the roadside in Ho Chi Minh City, Vietnam. Atmos. Environ. 41 (2007) 1575–1586. https://doi.org/10.1016/j.atmosenv. 2006.10.045.[8] M. Kishida, K. Imamura, N. Takenaka, Y. Maeda, P.H. Viet, H. Bandow, Concentrations of atmospheric polycyclic aromatic hydrocarbons in particulate matter and the gaseous phase at roadside sites in Hanoi, Vietnam. Bull. Environ. Contam. Toxicol. 81 (2008) 174–179. https://doi. org/10.1007/s00128-008-9450-5. [9] H.Q. Anh, K. Tomioka, N.M. Tue, L.H. Tuyen, N.K. Chi, T.B. Minh, P.H. Viet, S. Takahashi, A preliminary investigation of 942 organic micro-pollutants in the atmosphere in waste processing and urban areas, northern Vietnam: levels, potential sources, and risk assessment. Ecotoxicol. Environ. Saf. 167 (2019) 354–364. https://doi.org/10.1016/j.ecoenv.2018.10.026.[10] C.V. Hung, B.D. Cam, P.T.N Mai, B.Q. Dzung, Heavy metals and polycyclic aromatic hydrocarbons in municipal sewage sludge from a river in highly urbanized metropolitan area in Hanoi, Vietnam: levels, accumulation pattern and assessment of land application. Environ. Geochem. Health 37 (2015) 133–146. https:// doi.org/10.1007/s10653-014-9635-2.[11] C.T. Pham, N. Tang, A. Toriba, K. Hayakawa, Polycyclic aromatic hydrocarbons and nitropolycyclic aromatic hydrocarbons in atmospheric particles and soil at a traffic site in Hanoi, Vietnam. Polycycl. Aromat. Comp. 35 (2015) 355–371. https://doi.org/10.1080/10406 638.2014.903284.[12] H.Q. Anh, K. Tomioka, N.M. Tue, G. Suzuki, T.B. Minh, P.H. Viet, S. Takahashi, Comprehensive analysis of 942 organic micro-pollutants in settled dusts from northern Vietnam: pollution status and implications for human exposure. J. Mater. Cycles Waste Manag. 21 (2019) 57–66. https://doi.org/10.1007/s101 63-018-0745-2.[13] L.H. Tuyen, N.M. Tue, G. Suzuki, K. Misaki, P.H. Viet, S. Takahashi, S. Tanabe, Aryl hydrocarbon receptor mediated activities in road dust from a metropolitan area, Hanoi-Vietnam: contribution of polycyclic aromatic hydrocarbons (PAHs) and human risk assessment. Sci. Total Environ. 491-492 (2014) 246–254. https://doi.org/10.1016/j.scitotenv.2014. 01.086.[14] L.H. Tuyen, N.M. Tue, S. Takahashi, G. Suzuki, P.H. Viet, A. Subramanian, K.A. Bulbule, P. Parthasarathy, A. Ramanathan, S. Tanabe, Methylated and unsubstituted polycyclic aromatic hydrocarbons in street dust from Vietnam and India: occurrence, distribution and in vitro toxicity evaluation. Environ. Pollut. 194 (2014) 272–280. https://doi.org/10.1016/j.envpol. 2014.07.029.[15] H.Q. Anh, T.M. Tran, N.T.T. Thuy, T.B. Minh, S. Takahashi, Screening analysis of organic micro-pollutants in road dusts from some areas in northern Vietnam: a preliminary investigation on contamination status, potential sources, human exposures, and ecological risk. Chemosphere 224 (2019) 428–436. https://doi.org/10.1016/j. chemosphere.2019.02.177.[16] H.T.T. Thuy, T.T.C. Loan, T.H. Phuong, The potential accumulation of polycyclic aromatic hydrocarbons in phytoplankton and bivalves in Can Gio coastal wetland, Vietnam. Environ. Sci. Pollut. Res. 25 (2018) 17240–17249. https://doi. org/10.1007/s11356-018-2249-y.[17] P.C. Van Metre, B.J. Mahler, J.T. Wilson, PAHs underfoot: contaminated dust from coal-tar sealcoated pavement is widespread in the United States. Environ. Sci. Technol. 43 (2009) 20–25. https://doi.org/10.1021/es802119h.[18] L. Liu, A. Liu, Y. Li, L. Zhang, G. Zhang, Y. Guan, Polycyclic aromatic hydrocarbons associated with road deposited solid and their ecological risk: Implications for road stormwater reuse. Sci. Total Environ. 563–564 (2016) 190–198. https://doi.org/10.1016/j.scitotenv.2016.04.114.[19] X. Zheng, Y. Yang, M. Liu, Y. Yu, J.L. Zhou, D. Li, PAH determination based on a rapid and novel gas purge-microsyringe extraction (GP-MSE) technique in road dust of Shanghai, China: Characterization, source apportionment, and health risk assessment. Sci. Total Environ. 557–558 (2016) 688–696. https://doi.org/10.1016/j. scitotenv.2016.03.124.[20] T.T. Dong, B.K. Lee, Characteristics, toxicity, and source apportionment of polycyclic aromatic hydrocarbons (PAHs) in road dust of Ulsan, Korea. Chemosphere 74 (2009) 1245–1253. https: //doi.org/10.1016/j.chemosphere.2008.11.035.[21] R. Khanal, H. Furumai, F. Nakajima, C. Yoshimura, Carcinogenic profile, toxicity and source apportionment of polycyclic aromatic hydrocarbons accumulated from urban road dust in Tokyo, Japan. Ecotoxicol. Environ. Saf. 165 (2018) 440–449. https://doi.org/10.1016/j. ecoenv.2018.08.095.[22] N. Soltani, B. Keshavarzi, F. Moore, T. Tavakol, A.R. Lahijanzadeh, N. Jaafarzadeh, M. Kermani, Ecological and human health hazards of heavy metals and polycyclic aromatic hydrocarbons (PAHs) in road dust of Isfahan metropolis, Iran. Sci. Total Environ. 505 (2015) 712–723. https://doi.org/10.1016/j.scitotenv.2014.09.097.[23] B.A.M. Bandowe, M.A. Nkansah, Occurrence, distribution and health risk from polycyclic aromatic compounds (PAHs, oxygenated-PAHs and azaarenes) in street dust from a major West African Metropolis. Sci. Total Environ. 553 (2016) 439-449. https://doi.org/10.1016/j. scitotenv.2016.02.142.[24] T.C. Nguyen, P. Loganathan, T.V. Nguyen, S. Vigneswaran, J. Kandasamy, D. Slee, G. Stevenson, R. Naidu, Polycyclic aromatic hydrocarbons in road-deposited sediments, water sediments, and soils in Sydney, Australia: Comparisons of concentration distribution, sources and potential toxicity. Ecotoxicol. Environ. Saf. 104 (2014) 339–348. https://doi.org/10.1016/j.ecoenv.2014.03.010. [25] C. Y. Kuo, H.C. Chen, F.C. Cheng, L.R. Huang, P.S. Chien, J.Y. Wang, Polycyclic aromatic hydrocarbons in household dust near diesel transport routes. Environ. Geochem. Health 34 (2012) 77–87. https://doi.org/10.1007/s10653-011-9392-4.[26] W. Wang, F.Y. Wu, J.S. Zheng, M.H. Wong, Risk assessments of PAHs and Hg exposure via settled house dust and street dust, linking with their correlations in human hair. J. Hazard. Mater. 263 (2013) 627–637. https://doi.org/10.1016/j.jhazmat. 2013.10.023.[27] N. Ali, I.M.I. Ismail, M. Khoder, M. Shamy, M. Alghamdi, M. Costa, L.N. Ali, W. Wang, S.A.M.A.S. Eqani, Polycyclic aromatic hydrocarbons (PAHs) in indoor dust samples from cities of Jeddah and Kuwait: levels, sources and non-dietary human exposure. Sci. Total Environ. 573 (2016) 1607–1614. https://doi.org/10.1016/j. scitotenv.2016.09.134.[28] M.Y. Civan, U.M. Kara, Risk assessment of PBDEs and PAHs in house dust in Kocaeli, Turkey: levels and sources. Environ. Sci. Pollut. Res. 23 (2016) 23369–23384. https://doi.org/10. 1007/s11356-016-7512-5.[29] A. Maragkidou, S. Arar, A. Al-Hunaiti, Y. Ma, S. Harrad, O. Jaghbeir, D. Faouri, K. Hämeri, T. Hussein, Occupational health risk assessment and exposure to floor dust PAHs inside an educational building. Sci. Total Environ. 579 (2017) 1050–1056. https://doi.org/10.1016/j.scitotenv.2016. 11.055. [30] I.C. Yadav, N.L. Devi, J. Li, G. Zhang, Polycyclic aromatic hydrocarbons in house dust and surface soil in major urban regions of Nepal: implication on source apportionment and toxicological effect. Sci. Total Environ. 616–617 (2018) 223–235. https://doi.org/10.1016/j.scitotenv.2017.10.313.[31] R. Boonyatumanond, M. Murakami, G. Wattayakorn, A. Togo, H. Takada, Sources of polycyclic aromatic hydrocarbons (PAHs) in street dust in a tropical Asian mega-city, Bangkok, Thailand. Sci. Total Environ. 384 (2007) 420−432. https://doi.org/10.1016/j.scitotenv. 2007.06.046.[32] I. Sadiktsis, C. Bergvall, C. Johansson, R. Westerholm, Automobile tire–a potential source of highly carcinogenic dibenzopyrenes to the environment. Environ. Sci. Technol. 46 (2012) 3326−3334. https://doi.org/10.1021/es204257d.[33] M. Howsam, K.C. Jones, Sources of PAHs in the environment. In: Neilson, A.H. (Ed.), The Handbook of Environmental Chemistry Vol. 3 Part I PAHs and Related Compounds. Springer-Verlag, Berlin, Heidelberg (1998) 137–174. https://doi.org/10.1007/978-3-540-49697-7_4.[34] I.C.T. Nisbet, P.K. Lagoy, Toxic equivalency factors (TEFs) for polycyclic aromatic hydrocarbons (PAHs). Regul. Toxicol. Pharmacol. 16 (1992) 290–300. https://doi.org/10. 1016/0273-2300(92)90009-X.[35] B. Pieterse, E. Felzel, R. Winter, B. van der Burg, A. Brouwer, PAH-CALUX, an optimized bioassay for AhR-mediated hazard identification of polycyclic aromatic hydrocarbons (PAHs) as individual compounds and in complex mixtures. Environ. Sci. Technol 47 (2013) 11651–11659. https://doi.org/10.1021/es403810w.[36] M.B. Yunker, R.W. Macdonald, R. Vingarzan, R. H. Mitchell, D. Goyette, S. Sylvestre, PAHs in the Fraser River basin: a critical appraisal of PAH ratios as indicators of PAH source and composition. Org. Geochem. 33 (2002) 489–515. https://doi.org/10.1016/S0146-6380(02)00002-5.[37] M. Saha, A. Togo, K. Mizukawa, M. Murakami, H. Takada, M.P. Zakaria, N.H. Chiem, B.C. Tuyen, M. Prudente, R. Boonyatumanond, S.K. Sarkar, B. Bhattacharya, P. Mishra, T.S. Tana, Sources of sedimentary PAHs in tropical Asian waters: differentiation between pyrogenic and petrogenic sources by alkyl homolog abundance. Mar. Pollut. Bull. 58 (2009) 189–200. https://doi.org/10.1016/j.marpolbul.2008.04.049.