硒镉高背景区茶叶中硒和砷、汞、镉的积累与浸出特征研究
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摘要
为阐明地质高背景区微量元素的生物地球化学循环,以及其在农作物中的积累和潜在健康风险,探讨了硒镉高背景区茶叶中硒、砷、汞、镉4种微量元素的积累特征,分析了采集时间、叶片成熟度、炒制温度对微量元素含量的影响;以硒的最大浸出量为参考,研究了富硒茶最佳的冲泡条件,并对4种微量元素的浸出特征和健康风险进行了评价。结果表明,所有茶园土壤均达到高硒水平,其中46.67%的土壤硒过量。镉的含量远超土壤风险筛选值,且57.31%为可交换态。所有茶叶均达到富硒茶标准,而砷、汞、镉未出现超标。土壤硒对茶叶中重金属的积累没有明显的拮抗作用,反而会促进汞的积累。高温炒制导致茶叶中63.51%的硒损失,而采集时间和叶片成熟度对茶叶中砷、汞、镉的含量有显著影响。硒的浸出主要受冲泡温度和次数影响,最高仅有26.06%的硒能进入茶汤;砷主要受冲泡次数和时间影响,而汞主要受冲泡温度影响。茶汤中硒、砷、汞、镉的浸出量很低,目标危害系数远小于1,没有明显的健康风险。研究表明,地质高背景区微量元素在茶叶中的积累特征及相关的健康风险与人为污染区存在较大差异。
It is very important to highlight the biogeochemical cycle of trace elements and their accumulation in crops and potential health risks in high geological background areas. The accumulation of selenium(Se), arsenic(As), mercury(Hg)and cadmium(Cd)in tea leaves was investigated and the impacts of harvest season, leaf maturity and drying temperature on the concentrations of these trace elements were analyzed. The optimal tea making conditions were obtained based on the maximum leaching of Se in the infusion, and the leaching characteristics of 4 trace elements and associated health risks were evaluated. The results showed that soil Se ranged from high to excessive(46.67%)according to the landscape ecological background value of Se in China. The concentration of Cd in the soil was much higher than the risk screening value and the proportion of acid exchangeable Cd species was 57.31%. Tea samples were recognized as Se-rich tea and contained normal amounts of As, Hg and Cd, according to the national standards of China. Soil Se did not have any antagonistic effect on the accumulation of toxic metals. On the contrary, it was positively correlated with Hg concentration in the tea leaves. A high-temperature for drying resulted in a 63.51% loss of foliar Se, while harvest season and leaf maturity exhibited significant effects on the concentrations of As, Hg and Cd. The leaching of Se was mainly controlled by temperature and brewing times and only 26.06% of Se was leached into the infusion under the optimal conditions. In contrast, As and Hg in the infusion were mainly subjected to brewing times, duration and temperature. There was no obvious health risk in the consumption of Se-rich tea in this study because all the target hazard quotients(THQ)were less than 1. The results indicated that the accumulation of trace elements in tea leaves and the associated health risks in a high geological background area were different from those in polluted areas.
It is very important to highlight the biogeochemical cycle of trace elements and their accumulation in crops and potential health risks in high geological background areas. The accumulation of selenium(Se), arsenic(As), mercury(Hg)and cadmium(Cd)in tea leaves was investigated and the impacts of harvest season, leaf maturity and drying temperature on the concentrations of these trace elements were analyzed. The optimal tea making conditions were obtained based on the maximum leaching of Se in the infusion, and the leaching characteristics of 4 trace elements and associated health risks were evaluated. The results showed that soil Se ranged from high to excessive(46.67%)according to the landscape ecological background value of Se in China. The concentration of Cd in the soil was much higher than the risk screening value and the proportion of acid exchangeable Cd species was 57.31%. Tea samples were recognized as Se-rich tea and contained normal amounts of As, Hg and Cd, according to the national standards of China. Soil Se did not have any antagonistic effect on the accumulation of toxic metals. On the contrary, it was positively correlated with Hg concentration in the tea leaves. A high-temperature for drying resulted in a 63.51% loss of foliar Se, while harvest season and leaf maturity exhibited significant effects on the concentrations of As, Hg and Cd. The leaching of Se was mainly controlled by temperature and brewing times and only 26.06% of Se was leached into the infusion under the optimal conditions. In contrast, As and Hg in the infusion were mainly subjected to brewing times, duration and temperature. There was no obvious health risk in the consumption of Se-rich tea in this study because all the target hazard quotients(THQ)were less than 1. The results indicated that the accumulation of trace elements in tea leaves and the associated health risks in a high geological background area were different from those in polluted areas.
引文
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[28]叶宏萌,李国平,郑茂钟,等.武夷山茶园土壤汞、镉和砷形态及茶叶有效性特征[J].热带作物学报,2016,37(11):2094-2099.YE Hong-meng,LI Guo-ping,ZHENG Mao-zhong,et al.Fraction distribution and tea bioavailability of Hg,Cd,Se in soil from Wuyishan tea garden[J].Chinese Journal of Tropical Grops,2016,37(11):2094-2099.
[29]Yang B B,Yang C,Shao Z Y,et al.Selenium(Se)does not reduce cadmium(Cd)uptake and translocation in rice(Oryza sativa L.)in naturally occurred Se-rich paddy fields with a high geological background of Cd[J].Bulletin of Environmental Contamination and Toxicology,2019,103(1):127-132.
[30]Wan Y N,Yu Y,Wang Q,et al.Cadmium uptake dynamics and trans-389location in rice seedlings:Influence of different forms of selenium[J].Ecotoxicology and Environmental Safety,2016,133:127-134.
[31]Sun S X,Lu X A,Williams P N,et al.Distribution and translocation of selenium from soil to grain and its speciation in paddy rice(Oryza sativa L.)[J].Environmental Sciences and Technology,2010,44(17):6706-6711.
[32]Chen S Z,Zhu S P,Lu D B.Solidified floating organic drop microextraction for speciation of selenium and its distribution in seleniumrich tea leaves and tea infusion by electrothermal vapourisation inductively coupled plasma mass spectrometry[J].Food Chemistry,2015,169:156-161.
[33]Schmite B D P,Bitobrovec A,Hacke A C M,et al.In vitro bioaccessibility of Al,Cu,Cd,and Pb following simulated gastro-intestinal digestion and total content of these metals in different Brazilian brands of yerba mate tea[J].Food Chemistry,2019,281:285-293.
[2]Xing L J,Zhang H,Qi R L,et al.Recent advances in the understanding of the health benefits and molecular mechanisms associated with green tea polyphenols[J].Journal of Agricultural and Food Chemistry,2019,67(4):1029-1043.
[3]de Oliveira L M,Das S,Da Silva E B,et al.Metal concentrations in traditional and herbal teas and their potential risks to human health[J].Science of the Total Environment,2018,633:649-657.
[4]Miri M,Bhatnagar A,Mahdavi Y,et al.Probabilistic risk assessment of exposure to fluoride in most consumed brands of tea in the Middle East[J].Food and Chemical Toxicology,2018,115:267-272.
[5]Zachara A,Galkowska D,Juszczak L.Contamination of tea and tea infusion with polycyclic aromatic hydrocarbons[J].International Journal of Environmental Research and Public Health,2018,15(1):45.
[6]Tong M M,Gao W J,Jiao M T,et al.Uptake,translocation,metabolism,and distribution of glyphosate in nontarget tea plant(Camellia sinensis L.)[J].Journal of Agricultural and Food Chemistry,2017,65(35):7638-7646.
[7]Winkel L H E,Johnson C A,Lenz M,et al.Environmental selenium research:From microscopic processes to global understanding[J].Environmental Science and Technology,2012,46(2):571-579.
[8]Hu Q H,Xu J,Pang G X.Effect of selenium on the yield and quality of green tea leaves harvested in early spring[J].Journal of Agricultural and Food Chemistry,2003,51(11):3379-3381.
[9]Molan A L.Antioxidant and prebiotic activities of selenium-containing green tea[J].Nutrition,2013,29(2):476-477.
[10]He N W,Shi X L,Zhao Y,et al.Inhibitory effects and molecular mechanisms of selenium-containing tea polysaccharides on human breast cancer MCF-7 cells[J].Journal of Agricultural and Food Chemistry,2013,61(3):579-588.
[11]Yu J,Yang J,Li M Z,et al.Protective effects of Chinese Fenggang zinc selenium tea on metabolic syndrome in high-sucrose-high-fat diet-induced obese rats[J].Scientific Reports,2018,8:3528.
[12]Kumar A,Singh R P,Singh P K,et al.Selenium ameliorates arsenic induced oxidative stress through modulation of antioxidant enzymes and thiols in rice(Oryza sativa L.)[J].Ecotoxicology,2014,23(7):1153-1163.
[13]Wang Y J,Dang F,Evans R D,et al.Mechanistic understanding of MeHg-Se antagonism in soil-rice systems:The key role of antagonism in soil[J].Scientific Reports,2016,6:19477.
[14]Wan Y N,Yu Y,Wang Q,et al.Cadmium uptake dynamics and translocation in rice seedling:Influence of different forms of selenium[J].Ecotoxicology and Environmental Safety,2016,133:127-134.
[15]Ding Y Z,Wang R G,Guo J K,et al.The effect of selenium on the subcellular distribution of antimony to regulate the toxicity of antimony in paddy soil[J].Environmental Science and Pollution Research,2015,22(7):5111-5123.
[16]An Z Z,Suo L N,Zhao L P,et al.Effects of selenium on uptake and distribution of trace elements and heavy metals in millet[J].Fresenius Environmental Bulletin,2017,26(8):5037-5040.
[17]He P P,Lv X Z,Wang G Y.Effects of Se and Zn supplementation on the antagonism against Pb and Cd in vegetables[J].Environmental International,2004,30(2):167-172.
[18]Zhang H X,Rui Y K.Determination of heavy metals and trace elements in selenium-enriched cherry fruit by ICP-MS[J].Asian Journal of Chemistry,2013,25(16):9413-9414.
[19]Yuan L X,Zhu Y Y,Lin Z Q,et al.A novel selenocystine-accumulating plant in selenium-mine drainage area in Enshi,China[J].PLoSOne,2013,8:e65615.
[20]鲍士旦.土壤农化分析[M].北京：中国农业出版社,2000:373-375.BAO Shi-dan.Method of soil chemistry analysis[M].Beijing:Chinese Agriculture Science and Technology Publishers,2000:373-375.
[21]Olsen S R,Sommers L E.Phosphorus[M]//Page A L,Miller R H,Keeney D R(Eds.).Methods of soil analysis:Chemical and microbiological properties.2nd ed.American Society of Agronomy,Inc.,Wisconsin,1982:1159.
[22]Pérez-Moreno S M,Gázquez M J,Pérez-López R,et al.Validation of the BCR sequential extraction procedure for natural radionuclides[J].Chemosphere,2018,198:397-408.
[23]Peng C Y,Zhu X H,Hou R Y,et al.Aluminum and heavy metal accumulation in tea leaves:An interplay of environmental and plant factors and an assessment of exposure risks to consumers[J].Journal of Food Science,2018,83(4):1165-1172.
[24]谭见安.环境生命元素与克山病：生态化学地理研究[M].北京：中国医药科技出版社,1996.TAN Jian-an.Environmental life elements and Keshan disease:Astudy on ecological chemicogeography[M].Beijing:Chinese Medicine Science and Technology Press,1996.
[25]赵妍,宗良纲,曹丹,等.江苏省典型茶园土壤硒分布特性及其有效性研究[J].农业环境科学学报,2011,30(12):2467-2474.ZHAO Yan,ZONG Liang-gang,CAO Dan,et al.Distribution and availability of selenium in typical tea garden of Jiangsu Province,China[J].Journal of Agro-Environment Science,2011,30(12):2467-2474.
[26]宋明义.浙西地区下寒武统黑色岩系中硒与重金属的表生地球化学及环境效应[D].合肥：合肥工业大学，2009.SONG Ming-yi.Environmental effects of selenium and heavy metals in the lower Cambrian black series of western Zhejiang Province,China[D].Hefei:Hefei University of Technology,2009.
[27]刘意章,肖唐付,熊燕,等.西南高镉地质背景区农田土壤与农作物的重金属富集特征[J].环境科学,2019,40(6):2877-2884.LIU Yi-Zhang,XIAO Tang-fu,XIONG Yan,et al.Accumulation of heavy metals in agricultural soils and crops from an area with high geochemical background of cadmium,southwestern China[J].Environmental Science,2019,40(6):2877-2884.
[28]叶宏萌,李国平,郑茂钟,等.武夷山茶园土壤汞、镉和砷形态及茶叶有效性特征[J].热带作物学报,2016,37(11):2094-2099.YE Hong-meng,LI Guo-ping,ZHENG Mao-zhong,et al.Fraction distribution and tea bioavailability of Hg,Cd,Se in soil from Wuyishan tea garden[J].Chinese Journal of Tropical Grops,2016,37(11):2094-2099.
[29]Yang B B,Yang C,Shao Z Y,et al.Selenium(Se)does not reduce cadmium(Cd)uptake and translocation in rice(Oryza sativa L.)in naturally occurred Se-rich paddy fields with a high geological background of Cd[J].Bulletin of Environmental Contamination and Toxicology,2019,103(1):127-132.
[30]Wan Y N,Yu Y,Wang Q,et al.Cadmium uptake dynamics and trans-389location in rice seedlings:Influence of different forms of selenium[J].Ecotoxicology and Environmental Safety,2016,133:127-134.
[31]Sun S X,Lu X A,Williams P N,et al.Distribution and translocation of selenium from soil to grain and its speciation in paddy rice(Oryza sativa L.)[J].Environmental Sciences and Technology,2010,44(17):6706-6711.
[32]Chen S Z,Zhu S P,Lu D B.Solidified floating organic drop microextraction for speciation of selenium and its distribution in seleniumrich tea leaves and tea infusion by electrothermal vapourisation inductively coupled plasma mass spectrometry[J].Food Chemistry,2015,169:156-161.
[33]Schmite B D P,Bitobrovec A,Hacke A C M,et al.In vitro bioaccessibility of Al,Cu,Cd,and Pb following simulated gastro-intestinal digestion and total content of these metals in different Brazilian brands of yerba mate tea[J].Food Chemistry,2019,281:285-293.