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全氟和多氟化合物(per- and polyfluoroalkyl substances,PFASs)是一类氢原子完全或部分被氟取代的人工合成有机化合物[1]. 由于其独特的物理化学性质,PFASs在工业和消费品中具有多种用途,例如纺织品、食品包装、化妆品、和消防泡沫等[2]. 然而,接触PFASs可能会造成激素分泌、生殖、免疫、代谢以及胎儿生长发育等方面的毒理作用[3]. 根据全球许多研究,PFASs已在地表水、土壤、沉积物、动物、空气、灰尘等基质中被发现[4],它们在各环境介质中的普遍存在引起了越来越多的关注. PFASs的环境持久性和生物累积性导致其最终在动物、植物和人体内蓄积. 太湖作为长三角地区的重要水源地,其污染状况一直备受关注. 太湖流域包括江苏、浙江等几个人口密集、工业发达的地区,PFASs生产及纺织处理、金属电镀、消防、半导体等相关产业分布密集[5-6],PFASs生产使用量及其环境排放潜力较大. 目前已经有少量研究报道了太湖地表水和沉积物中PFASs的污染特征[7-10],但其关注的目标PFASs化合物种类较少,尤其是关于一些新型PFASs还鲜有报道. 目前,国内外持久性有机污染物(POPs)履约行动力度逐渐加强,对一些库存PFASs例如全氟辛基磺酸(PFOS)等使用、生产的限制管控和替代不断强化,世界范围内的许多区域出现了PFOS等管控目标污染水平的逐年降低,也伴随着各种新型短链以及杂原子取代型PFASs环境污染水平的逐渐升高. 因此在环境监测中将更多的新型PFASs纳入分析目标更有利于对PFASs污染的全面准确认识.
梅梁湾是太湖污染最严重的地区[9-10]. 因此,本研究选取靠近无锡市的太湖梅梁湾为研究区域,设置5个湖体采样点和3个河流入湖口采样点,采集地表水和沉积物样品,对其中的包括多种新型PFASs在内的32种PFASs目标物进行分析测定. 在此基础上研究PFASs组成特征和PFASs在地表水和沉积物两相之间的分配,并从生态和人体健康两方面对PFASs进行了风险评估,以期全面了解该区域PFASs的污染状况和风险,为污染预防管控和治理提供基础数据.
太湖梅梁湾水环境中全氟和多氟化合物的污染特征及风险评估
Pollution characteristics and risk assessment of per- and polyfluoroalkyl substances in waters of Meiliang Bay, Taihu Lake
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摘要: 以太湖梅梁湾为研究区域,采集地表水和沉积物样品,分析和比较了32种PFASs目标物的污染特征. ∑PFASs在地表水和沉积物中的浓度分别为162.82—187.62 ng·L−1(平均值171.34 ng·L−1)和1.04—4.81 ng·g−1干重(平均值3.06 ng·g−1干重). 地表水中以PFOA(平均值39.13 ng·L−1)、PFHxA(平均值31.71 ng·L−1)、PFBA(平均值28.80 ng·L−1)、PFBS(平均值16.93 ng·L−1)、PFOS(平均值14.49 ng·L−1)等中短链化合物为主,沉积物中则以PFOS(平均值0.69 ng·g−1干重)等中长链化合物为主. 另外,在地表水和沉积物中检出了3种新型PFASs:全氟丁基磺酰胺(FBSA),全氟壬烯氧基苯磺酸(OBS)和6:2氯代多氟醚磺酸(6:2 Cl-PFESA). PFASs在地表水和沉积物之间的分配与其疏水性及碳链长度有关. 生态风险评估结果表明,PFASs对水生生物风险较低;人体健康风险评估表明,通过饮用水估计的PFASs摄入量低于相关标准,不存在健康风险,但PFASs对太湖流域生态环境和周边居民的长期风险仍需引起关注.Abstract: Surface water and sediment samples were collected from Meiliang Bay, Taihu Lake, for investigating the pollution characteristics of 32 per- and polyfluoroalkyl substances (PFASs). The concentrations of ∑PFASs in water and sediment ranged from 162.82—187.62 ng·L−1 and 1.04—4.81 ng·g−1 dry weight (dw) with the mean value at 171.34 ng·L−1 and 3.06 ng·g−1 dw, respectively. Short- and medium-chain PFASs, such as PFOA, PFHxA, PFBA, PFBS, and PFOS, were predominant compounds in water with the mean concentration at 39.13 ng·L−1, 31.71 ng·L−1, 28.80 ng·L−1, 16.93 ng·L−1, and 14.49 ng·L−1, respectively, while medium- and long-chain compounds such as PFOS (mean concentration: 0.69 ng·g−1 dw) were dominant in sediment. Additionally, three emerging PFASs, perfluorobutylsulphonamide (FBSA), p-perfluorous nonenoxybenzene sulfonate (OBS), and 6:2 chlorinated polyfluoroalkyl ether sulfonic acid (6:2 Cl-PFESA), were also detectable in water and sediment. The distribution of PFASs between water and sediment was strongly related to their hydrophobicity and carbon chain length. The risk assessment showed that PFASs in water display low risk to aquatic organisms. The estimated intake value of PFASs via drinking water was lower than the relevant health standard, indicating that PFASs posed no health risk for the residents. However, the long-term risk of PFASs to the ecological environment of Taihu Lake basin and the surrounding residents still needs to be concerned.
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表 1 PFASs的离子对和质谱参数
Table 1. Mass transitions and parameters of mass spectrometry
化合物
Compound名称
Name母离子Q1 子离子Q3 解簇电压/ V
DP入口电压/ V
EP碰撞入口
电压/ V
CEP碰撞能量/ eV
CE碰撞出口
电压/ V
CXPPFCAs 全氟烷基羧酸 PFBA 全氟丁酸 212.8 168.8 −15.5 −10.0 −15.0 −16.2 −4.7 PFPeA 全氟戊酸 262.8 218.9 −21.5 −10.0 −19.2 −15.5 −5.8 PFHxA 全氟己酸 312.8 269.0 −18.7 −10.0 −19.5 −15.6 −7.8 PFHpA 全氟庚酸 362.8 319.0 −23.0 −10.0 −20.0 −13.0 −9.0 PFOA 全氟辛酸 412.8 369.0* −16.5 −10.0 −21.7 −15.2 −10.4 412.8 168.8 −20.6 −10.0 −40.0 −24.5 −4.4 PFNA 全氟壬酸 462.8 419.1 −31.4 −10.0 −43.2 −19.1 −12.1 PFDA 全氟癸酸 512.8 469.1 −24.4 −10.0 −37.0 −24.0 −7.4 PFUnDA 全氟十一酸 562.8 519.1 −23.4 −10.0 −50.2 −30.0 −8.5 PFDoDA 全氟十二酸 612.8 569.0 −24.0 −10.0 −40.3 −25.6 −9.2 PFTrDA 全氟十三酸 662.8 619.0 −33.4 −10.0 −40.7 −24.0 −10.3 PFTeDA 全氟十四酸 712.8 669.0 −52.9 −10.0 −38.1 −21.1 −11.2 PFSAs 全氟烷基磺酸 PFBS 全氟丁基磺酸 298.8 79.9* −71.2 −10.0 −29.8 −51.2 −3.5 298.8 99.0 −70.2 −10.0 −31.0 −40.0 −5.1 PFPeS 全氟戊基磺酸 348.8 79.9* −72.0 −10.0 −26.4 −63.0 −3.4 348.8 99.0 −72.8 −10.0 −93.3 −42.5 −5.0 PFHxS 全氟己基磺酸 398.8 79.9* −75.3 −10.0 −44.2 −66.0 −3.1 398.8 99.0 −72.6 −10.0 −30.2 −51.4 −2.0 PFHpS 全氟庚基磺酸 448.8 79.9* −81.0 −10.0 −46.0 −75.0 −3.6 448.8 99.0 −85.0 −10.0 −40.0 −56.1 −2.0 PFOS 全氟辛基磺酸 498.8 79.9* −89.1 −10.0 −34.0 −86.1 −3.4 498.8 99.0 −82.0 −10.0 −56.1 −62.7 −2.0 PFNS 全氟壬基磺酸 548.8 79.9* −90.6 −10.0 −34.0 −92.1 −3.3 548.8 99.0 −94.6 −10.0 −31.5 −75.8 −2.0 PFDS 全氟癸基磺酸 599.3 79.9* −97.0 −10.0 −21.3 −76.0 −3.6 599.3 99.0 −98.2 −10.0 −36.1 −81.0 −2.0 Cl-PFESAs 氯代多氟醚磺酸 6:2 Cl-PFESA 6:2氯代多氟醚磺酸 530.6 351.0* −66.0 −10.0 −40.0 −41.6 −9.8 530.6 83.0 −56.0 −10.0 −38.0 −50.6 −1.6 8:2 Cl-PFESA 8:2氯代多氟醚磺酸 631.0 451.2* −31.0 −10.0 −35.5 −35.0 −7.0 631.0 83.2 −75.0 −10.0 −52.9 −53.0 −4.3 10:2 Cl-PFESA 10:2氯代多氟醚磺酸 731.1 551.1 −90.1 −10.0 −32.5 −33.6 −8.6 731.1 83.1 −91.5 −10.0 −64.6 −70.7 −1.5 FTSs 氟调聚磺酸 4:2 FTS 4:2氟调聚磺酸 326.8 81.0 −50.1 −10.0 −31.8 −46.4 −4.0 326.8 307.0 −51.5 −10.0 −22.5 −32.7 −8.9 6:2 FTS 6:2氟调聚磺酸 426.8 81.0 −54.4 −10.0 −35.2 −61.0 −4.0 426.8 407.0 −55.2 −10.0 −28.2 −39.0 −6.1 8:2 FTS 8:2氟调聚磺酸 526.9 81.0 −65.9 −10.0 −37.9 −73.2 −4.0 526.9 506.9 −71.0 −10.0 −33.9 −43.2 −15.0 FSAs 全氟磺酰胺 FBSA 全氟丁基磺酰胺 297.8 77.9 −46.7 −10.0 −23.9 −39.8 −3.8 FHxSA 全氟己基磺酰胺 397.8 77.9 −60.0 −10.0 −31.8 −47.2 −4.3 FOSA 全氟辛基磺酰胺 497.8 77.9 −74.1 −10.0 −33.9 −60.0 −4.5 N-MeFOSAA N-甲基全氟-1-辛烷磺酰胺基乙酸 569.7 419.2 −50.5 −10.0 −31.2 −31.9 −6.4 569.7 511.8 −42.1 −10.0 −29.1 −32.0 −7.9 N-EtFOSAA N-乙基全氟-1-辛烷磺酰胺基乙酸 583.8 419.2 −47.2 −10.0 −34.0 −33.0 −5.3 583.8 525.9 −44.0 −10.0 −31.2 −32.2 −8.3 NaDONA 4,8-二氧杂-3-氢-全氟壬酸 377.0 85.0* −25.0 −10.0 −27.0 −48.9 −4.9 377.0 251.0 −21.0 −10.0 −26.0 −18.8 −7.0 HFPO-DA 六氟环氧丙烷二聚体 329.0 285.0 −11.0 −10.0 −18.5 −11.8 −7.9 OBS 全氟壬烯氧基苯磺酸 603.1 172.0* −87.1 −10.0 −49.5 −52.6 −4.2 602.5 108.0 −82.2 −10.0 −41.5 −85.9 −2.5 602.5 465.0 −101.9 −10.0 −32.2 −49.0 −6.3 IS 内标 13C4−PFBA 13C标记全氟丁酸 216.9 171.9 −24.0 −10.0 −12.6 −13.5 −4.8 13C4−PFOA 13C标记全氟辛酸 416.8 372.1 −25.4 −10.0 −20.7 −13.5 −5.5 13C2−PFDA 13C标记全氟癸酸 515.0 470.0 −22.3 −7.0 −26.2 −18.2 −13.2 13C2−PFDoDA 13C标记全氟十二酸 614.8 570.0 −25.6 −10.0 −33.1 −22.0 −9.4 18O2−PFHxS 18O标记全氟己基磺酸 403.0 102.9 −81.2 −9.0 −40.9 −48.0 −2.5 13C4−PFOS 13C标记全氟辛基磺酸 502.8 79.9 −91.8 −10.0 −44.4 −78.3 −3.6 *定量离子quantification ion. 表 2 PFASs的加标回收率和检出限(LODs)
Table 2. The spike recoveries and limits of detection (LODs) of PFASs
化合物
Compound地表水
Water沉积物
Sediment回收率/%
Recovery相对标准偏差/%
RSD方法检出限/(ng·L−1)
LOD回收率/%
Recovery相对标准偏差/%
RSD方法检出限/ (ng·g−1)
LODPFBA 92.9±6.9 7.4 0.23 98.3±4.4 4.5 0.09 PFPeA 101.0±8.5 8.4 0.14 92.9±7.8 8.3 0.06 PFHxA 101.7±9.5 9.3 0.09 101.3±9.3 9.1 0.03 PFHpA 110.5±8.5 7.6 0.12 98.3±8.1 8.2 0.05 PFOA 104.7±10.5 9.9 0.36 92.0±7.3 7.0 0.14 PFNA 103.4±7.7 7.4 0.18 100.1±10 10.0 0.07 PFDA 102.9±9.5 9.3 0.17 109.9±6.6 6.0 0.07 PFUnDA 92.2±7.2 7.6 0.18 91.5±7.4 8.1 0.07 PFDoDA 95.2±12.3 12.8 0.20 92.3±4.1 4.4 0.08 PFTrDA 97.5±9.3 9.4 0.28 96.5±10.9 11.3 0.11 PFTeDA 102.7±10.9 9.5 0.68 102.9±12.1 11.8 0.27 PFBS 105.1±12.3 11.6 0.07 102.6±4.6 4.4 0.03 PFPeS 109.6±9.1 8.3 0.09 98.3±3.0 3.0 0.04 PFHxS 99.0±9.6 9.7 0.08 93.7±4.5 4.8 0.03 PFHpS 99.1±8.7 8.7 0.06 95.1±3.9 4.1 0.03 PFOS 99.2±8.7 7.3 0.07 99.6±7.1 6.3 0.03 PFNS 89.1±7.7 8.4 0.07 98.4±4.8 4.9 0.03 PFDS 80.7±4.1 5.1 1.36 94.2±5.5 5.7 0.55 6:2 Cl-PFESA 86.9±6.1 7.0 0.20 96.8±4.5 4.5 0.08 8:2 Cl-PFESA 75.4±6.1 8.0 0.12 84.1±8.8 10.5 0.05 10:2 Cl-PFESA 78.3±7.5 9.5 0.27 77.3±4.6 5.6 0.11 4:2 FTS 154.3±11 6.9 0.79 94.1±8.5 7.3 0.32 6:2 FTS 124.7±15 11.7 0.50 119.9±8.5 6.9 0.20 8:2 FTS 115.3±3.4 2.9 0.28 112.6±6.0 5.1 0.11 FBSA 90.8±6.9 7.6 0.05 82.2±3.4 4.2 0.02 FHxSA 78.4±2.1 2.7 0.03 72.6±5.1 7.1 0.01 FOSA 97.0±8.5 8.8 0.03 78.7±3.1 3.9 0.01 NaDONA 104.6±7.5 7.2 0.19 96.0±4.3 4.5 0.08 HFPO-DA 107.9±7.8 7.3 1.58 70.9±3.7 4.4 0.63 N-MeFOSAA 92.0±9.0 9.8 0.68 108.8±7 6.4 0.27 N-EtFOSAA 100.3±10.6 10.5 0.71 104.8±2.0 1.9 0.29 OBS 100.9±4.5 4.4 0.36 131.0±4.9 3.7 0.14 -
[1] RAHMAN M F, PELDSZUS S, ANDERSON W B. Behaviour and fate of perfluoroalkyl and polyfluoroalkyl substances (PFASs) in drinking water treatment: A review [J]. Water Research, 2014, 50: 318-340. [2] TEYMOURIAN T, TEYMOORIAN T, KOWSARI E, et al. A review of emerging PFAS contaminants: Sources, fate, health risks, and a comprehensive assortment of recent sorbents for PFAS treatment by evaluating their mechanism [J]. Research on Chemical Intermediates, 2021, 47(12): 4879-4914. doi: 10.1007/s11164-021-04603-7 [3] SUNDERLAND E M, HU X C, DASSUNCAO C, et al. A review of the pathways of human exposure to poly- and perfluoroalkyl substances (PFASs) and present understanding of health effects [J]. Journal of Exposure Science & Environmental Epidemiology, 2019, 29(2): 131-147. [4] CHENG B, ALAPATY K, ZARTARIAN V, et al. Per- and polyfluoroalkyl substances exposure science: Current knowledge, information needs, future directions [J]. International Journal of Environmental Science and Technology, 2021, 3: 1-16. [5] LI L, ZHAI Z H, LIU J G, et al. Estimating industrial and domestic environmental releases of perfluorooctanoic acid and its salts in China from 2004 to 2012 [J]. Chemosphere, 2015, 129: 100-109. doi: 10.1016/j.chemosphere.2014.11.049 [6] XIE S W, WANG T Y, LIU S J, et al. Industrial source identification and emission estimation of perfluorooctane sulfonate in China [J]. Environment International, 2013, 52: 1-8. doi: 10.1016/j.envint.2012.11.004 [7] CHEN M, WANG Q, SHAN G Q, et al. Occurrence, partitioning and bioaccumulation of emerging and legacy per- and polyfluoroalkyl substances in Taihu Lake, China [J]. Science of the Total Environment, 2018, 634: 251-259. doi: 10.1016/j.scitotenv.2018.03.301 [8] GUO C S, ZHANG Y, ZHAO X, et al. Distribution, source characterization and inventory of perfluoroalkyl substances in Taihu Lake, China [J]. Chemosphere, 2015, 127: 201-207. doi: 10.1016/j.chemosphere.2015.01.053 [9] MA X X, SHAN G Q, CHEN M, et al. Riverine inputs and source tracing of perfluoroalkyl substances (PFASs) in Taihu Lake, China [J]. Science of the Total Environment, 2018, 612: 18-25. doi: 10.1016/j.scitotenv.2017.08.235 [10] PAN G, ZHOU Q, LUAN X, et al. Distribution of perfluorinated compounds in Lake Taihu (China): Impact to human health and water standards [J]. Science of the Total Environment, 2014, 487: 778-784. doi: 10.1016/j.scitotenv.2013.11.100 [11] MENG L Y, SONG B Y, ZHONG H F, et al. Legacy and emerging per- and polyfluoroalkyl substances (PFAS) in the Bohai Sea and its inflow rivers [J]. Environment International, 2021, 156: 106735. doi: 10.1016/j.envint.2021.106735 [12] LENG Y F, XIAO H L, LI Z, et al. Occurrence and ecotoxicological risk assessment of perfluoroalkyl substances in water of lakes along the middle reach of Yangtze River, China [J]. Science of the Total Environment, 2021, 788: 147765. doi: 10.1016/j.scitotenv.2021.147765 [13] WANG Y, SHI Y L, CAI Y Q. Spatial distribution, seasonal variation and risks of legacy and emerging per- and polyfluoroalkyl substances in urban surface water in Beijing, China [J]. Science of the Total Environment, 2019, 673: 177-183. doi: 10.1016/j.scitotenv.2019.04.067 [14] 环境保护部. 中国人群暴露参数手册(成人卷/儿童卷)[M]. 北京: 中国环境出版社, 2013/2016. Ministry of Environmental Protection. Exposure factors handbook of Chinese population (adults/children)[M]. Beijing: China Environmental Press, 2013/2016(in Chinese).
[15] CHU S G, LETCHER R J, MCGOLDRICK D J, et al. A new fluorinated surfactant contaminant in biota: Perfluorobutane sulfonamide in several fish species [J]. Environmental Science & Technology, 2016, 50(2): 669-675. [16] XU L, SHI Y L, LI C X, et al. Discovery of a novel polyfluoroalkyl benzenesulfonic acid around oilfields in Northern China [J]. Environmental Science & Technology, 2017, 51(24): 14173-14181. [17] SHI Y L, SONG X W, JIN Q, et al. Tissue distribution and bioaccumulation of a novel polyfluoroalkyl benzenesulfonate in crucian carp [J]. Environment International, 2020, 135: 105418. doi: 10.1016/j.envint.2019.105418 [18] SHI Y L, VESTERGREN R, XU L, et al. Human exposure and elimination kinetics of chlorinated polyfluoroalkyl ether sulfonic acids (Cl-PFESAs) [J]. Environmental Science & Technology, 2016, 50(5): 2396-2404. [19] LIU W X, HE W, QIN N, et al. Temporal-spatial distributions and ecological risks of perfluoroalkyl acids (PFAAs) in the surface water from the fifth-largest freshwater lake in China (Lake Chaohu) [J]. Environmental Pollution, 2015, 200: 24-34. doi: 10.1016/j.envpol.2015.01.028 [20] GEWURTZ S B, BRADLEY L E, BACKUS S, et al. Perfluoroalkyl acids in great lakes precipitation and surface water (2006-2018) indicate response to phase-outs, regulatory action, and variability in fate and transport processes [J]. Environmental Science & Technology, 2019, 53(15): 8543-8552. [21] ZHOU Z, LIANG Y, SHI Y L, et al. Occurrence and transport of perfluoroalkyl acids (PFAAs), including short-chain PFAAs in Tangxun Lake, China [J]. Environmental Science & Technology, 2013, 47(16): 9249-9257. [22] ZHOU Y Q, WANG T Y, LI Q F, et al. Spatial and vertical variations of perfluoroalkyl acids (PFAAs) in the Bohai and Yellow Seas: Bridging the gap between riverine sources and marine sinks [J]. Environmental Pollution, 2018, 238: 111-120. doi: 10.1016/j.envpol.2018.03.027 [23] YU N Y, SHI W, ZHANG B B, et al. Occurrence of perfluoroalkyl acids including perfluorooctane sulfonate isomers in Huai River Basin and Taihu Lake in Jiangsu Province, China [J]. Environmental Science & Technology, 2013, 47(2): 710-717. [24] AHRENS L, TANIYASU S, YEUNG L W Y, et al. Distribution of polyfluoroalkyl compounds in water, suspended particulate matter and sediment from Tokyo Bay, Japan [J]. Chemosphere, 2010, 79(3): 266-272. doi: 10.1016/j.chemosphere.2010.01.045 [25] SHI Y L, VESTERGREN R, ZHOU Z, et al. Tissue distribution and whole body burden of the chlorinated polyfluoroalkyl ether sulfonic acid F-53B in crucian carp (Carassius carassius): Evidence for a highly bioaccumulative contaminant of emerging concern [J]. Environmental Science & Technology, 2015, 49(24): 14156-14165. [26] HIGGINS C P, LUTHY R G. Sorption of perfluorinated surfactants on sediments [J]. Environmental Science & Technology, 2006, 40(23): 7251-7256. [27] YANG S W, XU F F, WU F C, et al. Development of PFOS and PFOA criteria for the protection of freshwater aquatic life in China [J]. Science of the Total Environment, 2014, 470/471: 677-683. doi: 10.1016/j.scitotenv.2013.09.094 [28] ZHANG S Y, KANG Q Y, PENG H, et al. Relationship between perfluorooctanoate and perfluorooctane sulfonate blood concentrations in the general population and routine drinking water exposure [J]. Environment International, 2019, 126: 54-60. doi: 10.1016/j.envint.2019.02.009 [29] 国家市场监督管理总局, 国家标准化管理委员会. 生活饮用水卫生标准: GB 5749—2022[S]. 北京: 中国标准出版社, 2022. State Administration for Market Regulation, Standardization Administration of the People's Republic of China. Standards for drinking water quality: GB 5749—2022[S]. Beijing: Standards Press of China, 2022(in Chinese).
[30] MENG J, LIU S F, ZHOU Y Q, et al. Are perfluoroalkyl substances in water and fish from drinking water source the major pathways towards human health risk? [J]. Ecotoxicology and Environmental Safety, 2019, 181: 194-201. doi: 10.1016/j.ecoenv.2019.06.010 [31] LI J, AI Y F, HU J R, et al. Polyfluoroalkyl substances in Danjiangkou Reservoir, China: Occurrence, composition, and source appointment [J]. Science of the Total Environment, 2020, 725: 138352. doi: 10.1016/j.scitotenv.2020.138352 [32] CHEN M, ZHU L Y, WANG Q, et al. Tissue distribution and bioaccumulation of legacy and emerging per-and polyfluoroalkyl substances (PFASs) in edible fishes from Taihu Lake, China [J]. Environmental Pollution, 2021, 268: 115887. doi: 10.1016/j.envpol.2020.115887 [33] European Food Safety Authority (EFSA). Perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA) and their salts Scientific Opinion of the Panel on Contaminants in the Food chain [J]. EFSA Journal, 2008, 6(7): 653.