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稀土元素是指镧系元素以及与镧系元素性质相似的两个元素钪(Sc)和钇(Y)共17种元素[1],广泛应用于工农业生产和高新技术产业[2]。含稀土产品的生产与应用,导致其向环境中的迁移和富集急剧增加。已有研究证实稀土元素对生物体具有毒性作用,对包括植物、微生物、水生和陆生生物在内的多种生物产生急性和慢性生态毒性效应[3-5]。因此环境中稀土元素的含量及其风险评估也日益受到人们关注。
垃圾焚烧具有减容量大、可回收能源等特点,成为当今城市生活垃圾处理的主要技术之一[6-7]。作为最大的发展中国家,中国在2019年产生了24206.2万吨城市固体废物,约50.69%的垃圾通过焚烧进行处置。尽管大部分有机物在焚烧的过程中被完全氧化为二氧化碳和水,但重金属、二噁英等一些污染物在高温下吸附在焚烧尾气的细颗粒上,通过尾气排放由干湿沉降等途径进入垃圾焚烧厂周边环境。已有大量研究表明,垃圾焚烧会对周边居民和生态造成一定的风险[8-10]。我国大部分城市的生活垃圾在短期内还难以实现分类收集,因此含稀土制品的垃圾实际上已经长期进入焚烧系统,这使得稀土元素也会和其他污染物一样最终通过尾气排放进入周边环境。目前,国内有关于垃圾焚烧厂周边环境的研究主要集中在重金属、二噁英、多氯联苯等污染物的分布、污染特征等[11-15],而关于稀土元素的研究相对薄弱,对其潜在生态风险的研究则更为鲜少。
本文主要是对垃圾焚烧厂周边土壤中15种稀土元素的浓度进行调查分析,探讨焚烧厂周边土壤中稀土元素的空间分布差异,以评估焚烧排放的稀土元素对周围环境的影响。并结合潜在生态风险评价法评估垃圾焚烧厂周边土壤中稀土元素的风险程度,为垃圾焚烧厂的生态风险评估及管控提供理论依据。
浙江某垃圾焚烧厂周边土壤中稀土元素分布特征及潜在生态风险评价
Spatial distribution and potential ecological risk assessment of rare earth elements in soil surrounding a waste incineration plant in Zhejiang
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摘要: 采用电感耦合等离子体质谱仪测定了浙江某垃圾焚烧厂周边表层土壤样品中镧、铈、镨、钕、钇等15种稀土元素的浓度。利用统计学方法分析稀土元素分布特征,并评价土壤稀土元素的潜在生态风险水平。结果表明,该垃圾焚烧厂周边表层土壤中稀土元素平均浓度范围为0.49—84.51 mg·kg−1,总稀土元素浓度范围为231.21—259.47 mg·kg−1,均高于土壤背景值,而焚烧厂尾气中的稀土元素浓度达到385.73 mg·kg−1。稀土元素的浓度增量分析结果表明,稀土元素的浓度增量趋势与风频分布趋势相似,浓度增量越大的区域其风频越大,两者的相关性系数达到0.928。潜在生态风险指数显示,该垃圾焚烧厂周边土壤中稀土元素的潜在生态风险评价指数值范围为16.67—17.21,风频较小的上风向区域和平行风向1区域处于低生态风险水平,风频较大的下风向区域和平行风向2区域处于中等生态风险水平。垃圾焚烧厂周边土壤中稀土元素累积很可能受到了焚烧厂尾气排放的影响,随着焚烧尾气的持续排放,后期生态风险可能还会增加。Abstract: The concentrations of fifteen rare earth elements (La, Ce, Pr, Nd and Y, etc) in the surface soils surrounding a waste incineration plant in Zhejiang were determined using inductive coupled plasma spectrometer. The spatial distribution of the rare earth elements was studied by statistical methods, and their potential ecological risk was assessed. The results indicated that the rare earth elements were detected with mean concentrations ranging from 0.49 to 84.51 mg·kg−1. The total concentrations of the rare earth elements ranged from 231.21 to 259.47 mg·kg−1, which were higher than the local soil background values. It was found that the total concentrations of the rare earth elements in tail gas from the incineration stack reached 385.73 mg·kg−1. The analysis results showed that the area with the highest increment concentration of rare earth elements coincided with the highest wind frequency direction. The correlation coefficient between them reached 0.928. The potential ecological risk index values of the rare earth elements ranged from 16.67 to 17.21. The upwind area and parallel wind direction 1 area with low wind direction frequency were at low ecological risk level. In contrast, the downwind area and parallel wind direction 2 area with higher wind direction frequency were at medium ecological risk level. The accumulation of the rare earth elements in soil surrounding the waste incineration plant was likely to be affected by the tail gas exhausted from the waste incineration plant. The ecological risk may increase in the future as the continuous operation of waste incineration plant.
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表 1 垃圾焚烧厂周边表层土壤中稀土元素浓度(mg·kg−1)1)
Table 1. REEs concentration of surface soil around the waste incineration plant(mg·kg−1)
元素
Elements最大值
Maximum最小值
Minimum平均值
AverageK-S检验
Asymp.Sig
(2-tailed)背景点
Background site背景值[19]
Background values中国
China浙江
ZhejiangLa 49.59 40.19 43.34 0.424 39.30 39.70 33.80 Ce 93.94 81.31 84.51 0.227 76.60 68.40 62.00 Pr 10.94 9.09 9.98 0.877 8.89 7.17 6.30 Nd 40.66 36.29 38.04 0.725 33.10 26.40 20.90 Sm 8.59 6.67 7.63 0.764 6.58 5.22 3.99 Eu 1.73 1.41 1.55 0.801 1.24 1.03 0.70 Gd 7.10 5.82 6.30 0.467 5.74 4.60 3.18 Tb 1.22 0.98 1.08 0.979 0.96 0.63 0.41 Dy 6.17 4.99 5.56 0.891 4.95 4.13 3.29 Ho 1.33 1.12 1.22 0.968 1.10 0.87 0.65 Er 3.49 2.76 3.12 0.397 2.95 2.54 2.05 Tm 0.55 0.48 0.50 0.072 0.47 0.37 0.28 Yb 3.28 2.86 3.09 0.374 2.85 2.44 2.07 Lu 0.51 0.45 0.49 0.728 0.43 0.36 0.31 Y 35.96 30.82 33.22 0.932 28.80 22.90 18.60 ∑REEs 259.47 231.21 239.62 0.566 213.90 186.76 158.53 ∑LREE 201.47 179.30 184.04 0.192 165.70 147.92 127.69 ∑HREE 58.00 50.33 54.57 0.989 48.20 38.84 30.84 ∑LREE/∑HREE 3.61 3.16 3.39 0.961 3.44 3.81 4.14 ∑LREE/∑REEs 0.78 0.76 0.77 0.985 0.77 0.79 0.81 1)∑REEs为总稀土浓度;∑LREE为轻稀土(La-Eu)浓度;∑HREE为重稀土(Gd-Y)浓度
1)∑REEs is total concentrations of REEs;∑LREE is total concentrations of LREE;∑HREE is total concentrations of HREE表 2 不同风向土壤中稀土元素浓度(mg·kg−1)
Table 2. REEs concentration in different wind direction(mg·kg−1)
元素
Elements上风向
Upwind direction下风向
Downwind direction平行风向1
Parallel wind direction平行风向2
Parallel wind direction背景值
Background values最大值
Maximum最小值
Minimum平均值
Average最大值
Maximum最小值
Minimum平均值
Average最大值
Maximum最小值
Minimum平均值
Average最大值
Maximum最小值
Minimum平均值
AverageLa 43.94 42.20 43.00 49.59 42.25 45.69 43.41 40.19 42.26 44.37 41.00 42.43 39.30 Ce 85.94 82.35 83.69 93.94 81.31 87.42 84.49 82.15 83.21 85.13 82.12 83.73 76.60 Pr 10.26 9.49 9.89 10.18 9.49 9.96 10.93 9.09 9.81 10.94 9.74 10.27 8.89 Nd 39.51 36.80 37.92 40.66 37.26 38.56 38.59 37.03 37.65 39.26 36.29 38.03 33.10 Sm 7.92 7.04 7.35 8.10 7.42 7.84 7.63 6.67 7.22 8.59 7.74 8.09 6.58 Eu 1.73 1.41 1.56 1.65 1.52 1.59 1.48 1.45 1.47 1.67 1.48 1.57 1.24 Gd 7.10 5.84 6.34 6.52 6.09 6.30 6.36 5.82 6.16 6.75 5.99 6.38 5.74 Tb 1.22 0.98 1.06 1.14 1.01 1.09 1.09 1.04 1.06 1.13 1.04 1.09 0.96 Dy 6.17 4.99 5.48 5.88 5.17 5.52 5.82 5.19 5.52 5.88 5.47 5.71 4.95 Ho 1.33 1.12 1.19 1.29 1.18 1.25 1.28 1.18 1.22 1.29 1.20 1.24 1.10 Er 3.49 2.76 3.03 3.38 2.99 3.19 3.23 3.12 3.17 3.22 2.80 3.07 2.95 Tm 0.55 0.48 0.50 0.53 0.51 0.52 0.51 0.49 0.50 0.53 0.49 0.50 0.47 Yb 3.28 2.86 3.05 3.27 2.94 3.13 3.19 2.93 3.10 3.14 3.04 3.10 2.85 Lu 0.50 0.45 0.47 0.51 0.48 0.49 0.49 0.46 0.48 0.51 0.49 0.50 0.43 Y 33.91 30.82 31.97 35.96 31.99 33.99 35.53 32.35 33.20 35.48 32.85 33.72 28.80 ∑REEs 231.21 244.86 236.48 235.67 259.47 246.53 233.48 237.66 236.02 236.72 242.59 239.44 213.90 表 3 不同物质中稀土元素的相对丰度值
Table 3. Relative abundance value of rare earth elements in different substances
元素
Elements本地土壤
Local soil中国土壤[19]
China soil世界土壤[20]
World soil沉积物[20]
Sediment地壳[21]
Crust火成岩[22]
Igneousrock植物[23]
Plant国际水域[22]
International water世界淡水[20]
World freshwater$\displaystyle{ {\Sigma }_{i=1}^{8} }$ 相对丰度值
Relative abundance
valueLa 1.95 2.16 1.25 2.02 1.10 2.52 1.36 0.35 2.00 12.20 1.53 Ce 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 8.00 1.00 Pr 8.61 8.62 7.14 8.56 7.54 8.34 8.82 1.88 18.69 59.51 7.44 Nd 2.31 2.03 1.43 2.59 1.65 1.93 1.65 0.43 1.00 12.43 1.55 Y 2.66 4.15 1.25 2.08 1.79 1.64 5.00 0.09 15.38 18.66 2.33 表 4 稀土元素的毒性系数
Table 4. Toxicity coefficient value of rare earth elements
元素
Elements本地水体/(mg·L−1)
Local water背景值/(mg·kg−1)
Background value释放系数(×10−3)
Release coefficient相对丰度值
Relative abundance
value毒性系数初始值
Initial value of toxicity coefficient毒性系数
Toxicity coefficientLa 0.0982 39.30 2.50 1.53 3.82 2 Ce 0.3063 76.60 4.00 1.00 4.00 2 Pr 0.0136 8.89 1.53 7.44 11.38 5 Nd 0.1893 33.10 5.71 1.55 8.85 5 Y 0.0093 28.80 0.33 2.33 0.77 1 表 5 稀土元素的潜在生态风险指数分级标准
Table 5. Classification of potential ecological risk corresponding to
and RI$ {E}_{r}^{i} $ $ {E}_{r}^{i} $ 风险程度 Risk degree RI 风险程度 Risk degree <5$ {E}_{r}^{i} $ 低风险 RI<17 低风险 5≤ <10$ {E}_{r}^{i} $ 中等风险 17≤RI<34 中等风险 10≤ <20$ {E}_{r}^{i} $ 较高风险 34≤RI<68 较高风险 20≤ <40$ {E}_{r}^{i} $ 高风险 RI≥68 高风险 -
[1] DINALI G S, ROOT R A, AMISTADI M K, et al. Rare earth elements (REY) sorption on soils of contrasting mineralogy and texture [J]. Environment International, 2019, 128: 279-291. doi: 10.1016/j.envint.2019.04.022 [2] GOODENOUGH K M, WALL F, MERRIMAN D. The rare earth elements: Demand, global resources, and challenges for resourcing future generations [J]. Natural Resources Research, 2018, 27(2): 201-216. doi: 10.1007/s11053-017-9336-5 [3] BLINOVA I, MUNA M, HEINLAAN M, et al. Potential hazard of lanthanides and lanthanide-based nanoparticles to aquatic ecosystems: Data gaps, challenges and future research needs derived from bibliometric analysis [J]. Nanomaterials, 2020, 10(2): 1-19. [4] GWENZI W, MANGORI L, DANHA C, et al. Sources, behaviour, and environmental and human health risks of high-technology rare earth elements as emerging contaminants [J]. Science of the Total Environment, 2018, 636: 299-313. doi: 10.1016/j.scitotenv.2018.04.235 [5] SQUADRONE S, BRIZIO P, STELLA C, et al. Rare earth elements in marine and terrestrial matrices of Northwestern Italy: Implications for food safety and human health [J]. Science of the Total Environment, 2019, 660: 1383-1391. doi: 10.1016/j.scitotenv.2019.01.112 [6] 李崇, 任国玉, 高庆先, 等. 固体废物焚烧处置及其清洁发展机制 [J]. 环境科学研究, 2011, 24(7): 819-827. LI C, REN G Y, GAO Q X, et al. Solid waste incineration disposal and associated CDM in China [J]. Research of Environmental Sciences, 2011, 24(7): 819-827(in Chinese).
[7] 张倩, 徐海云. 生活垃圾焚烧处理技术现状及发展建议 [J]. 环境工程, 2012, 30(2): 79-81,89. ZHANG Q, XU H Y. Status and development suggestion of incineration technology of domestic garbages [J]. Environmental Engineering, 2012, 30(2): 79-81,89(in Chinese).
[8] 王宇珊, 钟昌琴, 刘成坚, 等. 垃圾焚烧厂的环境空气、飞灰和土壤二噁英水平研究及风险评价 [J]. 华南师范大学学报(自然科学版), 2020, 52(5): 49-56. WANG Y S, ZHONG C Q, LIU C J, et al. PCDD/Fs concentration in air, fly ash and soil around a municipal solid waste incinerator and its risk assessment [J]. Journal of South China Normal University (Natural Science Edition), 2020, 52(5): 49-56(in Chinese).
[9] LI J, ZHANG Y, SUN T, et al. The health risk levels of different age groups of residents living in the vicinity of municipal solid waste incinerator posed by PCDD/Fs in atmosphere and soil [J]. Science of the Total Environment, 2018, 631-632: 81-91. doi: 10.1016/j.scitotenv.2018.03.009 [10] 王宇珊, 刘成坚, 陈晓燕, 等. 垃圾焚烧厂周边土壤的重金属污染风险评价 [J]. 华南师范大学学报(自然科学版), 2020, 52(5): 57-64. WANG Y S, ZHONG C Q, CHEN X Y, et al. Pollution risk assessments of heavy metals in soils around a municipal solid waste incinerator [J]. Journal of South China Normal University (Natural Science Edition), 2020, 52(5): 57-64(in Chinese).
[11] 冯经昆, 钟山, 孙立文, 等. 重庆某垃圾焚烧厂周边土壤重金属污染分布特征及来源解析 [J]. 环境化学, 2014, 33(6): 969-975. doi: 10.7524/j.issn.0254-6108.2014.06.005 FENG J K, ZHONG S, SUN L W, et al. Spatial distribution and source analysis of heavy metal contamination in soil surrounding a municipal solid waste incineration plant in Chongqing [J]. Environmental Chemistry, 2014, 33(6): 969-975(in Chinese). doi: 10.7524/j.issn.0254-6108.2014.06.005
[12] 郭彦海, 孙许超, 张士兵, 等. 上海某生活垃圾焚烧厂周边土壤重金属污染特征、来源分析及潜在生态风险评价 [J]. 环境科学, 2017, 38(12): 5262-5271. GUO Y H, SUN X C, ZHANG S B, et al. Pollution characteristics, source analysis and potential ecological risk assessment of heavy metals in soils surrounding a municipal solid waste incineration plant in Shanghai [J]. Environmental Chemistry, 2017, 38(12): 5262-5271(in Chinese).
[13] 赵曦, 李娟, 陆克定, 等. 华南某垃圾焚烧厂排放PCBs和PCNs的固气分布、同系物分布及毒性当量特征 [J]. 环境化学, 2015, 34(7): 1268-1274. doi: 10.7524/j.issn.0254-6108.2015.07.2015020401 ZHAO X, LI J, LU K D, et al. Characterization of particle / gas partition, congener patterns, and TEQ of PCBs and PCNs released from a municipal solid waste incinerator( MSWI) in South China [J]. Environmental Chemistry, 2015, 34(7): 1268-1274(in Chinese). doi: 10.7524/j.issn.0254-6108.2015.07.2015020401
[14] 黄慧敏, 刘强, 刘晓一, 等. 生活垃圾焚烧厂周边大气汞浓度分布及其健康风险评估 [J]. 环境污染与防治, 2016, 38(7): 66-70. HUANG H M, LIU Q, LIU X Y, et al. Concentration distribution and health risk assessment of mercury emitted from municipal solid waste incineration plant [J]. Environmental Pollution & Control, 2016, 38(7): 66-70(in Chinese).
[15] 段振亚, 苏海涛, 王凤阳, 等. 重庆市垃圾焚烧厂汞的分布特征与大气汞排放因子研究 [J]. 环境科学, 2016, 37(2): 459-465. DUAN Z Y, SU H T, WANG F Y, et al. Mercury distribution characteristics and atmospheric mercury emission factors of typical Waste incineration plants in Chongqing [J]. Environmental Science, 2016, 37(2): 459-465(in Chinese).
[16] CHEN H, CHEN Z, CHEN Z, et al. Calculation of toxicity coefficient of potential ecological risk assessment of rare earth elements [J]. Bulletin of Environmental Contamination and Toxicology, 2020, 104(5): 582-587. doi: 10.1007/s00128-020-02840-x [17] 丁友超, 刘国庆, 王晓蓉. 稀土元素在土壤中的环境化学行为及其生物效应 [J]. 农业环境科学学报, 2002(6): 567-569,576. doi: 10.3321/j.issn:1672-2043.2002.06.027 DING Y C, LIU G Q, WANG X R. Environmental chemical behaviors of rare earth elements in soil and their biological effects [J]. Journal of Agro-Environment Science, 2002(6): 567-569,576(in Chinese). doi: 10.3321/j.issn:1672-2043.2002.06.027
[18] 黄圣彪, 王子健, 彭安. 稀土元素在土壤中吸持和迁移的研究 [J]. 农业环境科学学报, 2002(3): 269-271. doi: 10.3321/j.issn:1672-2043.2002.03.023 HUANG S B, WANG Z J, PENG A. Adsorption / desorption, transfer of rare earth elements (REEs) in soil [J]. Journal of Agro-Environment Science, 2002(3): 269-271(in Chinese). doi: 10.3321/j.issn:1672-2043.2002.03.023
[19] 中国环境监测总站. 中国土壤元素背景值[M]. 北京: 中国环境出版社, 1990: 88-89. CHINA NATIONAL ENVIRONMENTAL MONITORING CENTRE. Background value of soil elements in China [M]. Beijing: China Environmental Press, 1990: 88-89 (in Chinese).
[20] BOWEN H J M. Environmental chemistry of the elements[M]. New York: Academic Press, 1979: 24-28. [21] 黎彤, 倪守斌. 地球和地壳的化学元素丰度[M]. 北京: 地质出版社, 1990: 8-20. LI T, NI S B. The chemical element abundance of the earth and the earth’s crust [M]. Beijing: Geological Publishing House, 1990: 8-20 (in Chinese).
[22] 王中刚, 于学元, 赵振华, 等. 稀土元素地球化学[M]. 北京: 科学出版社, 1989. WANG Z G, YU X Y, ZHAO Z H, et al. Rare earth element geochemistry [M]. Beijing: Science Press, 1989 (in Chinese).
[23] TYLER G, OLSSON T. Plant uptake of major and minor mineral elements as influenced by soil acidity and liming [J]. Plant and Soil, 2001, 230(2): 307-321. doi: 10.1023/A:1010314400976 [24] 范明毅, 杨皓, 黄先飞, 等. 典型山区燃煤型电厂周边土壤重金属形态特征及污染评价 [J]. 中国环境科学, 2016, 36(8): 2425-2436. doi: 10.3969/j.issn.1000-6923.2016.08.024 FANG M Y, YANG H, HUANG X F, et al. Chemical forms and risk assessment of heavy metals in soils around a typical coal-fired power plant located in the mountainous area [J]. China Environmental Science, 2016, 36(8): 2425-2436(in Chinese). doi: 10.3969/j.issn.1000-6923.2016.08.024
[25] 李一蒙, 马建华, 刘德新, 等. 开封城市土壤重金属污染及潜在生态风险评价 [J]. 环境科学, 2015, 36(3): 1037-1044. LI Y M, MA J H, LIU D X, et al. Assessment of heavy metal pollution and potential ecological risks of urban soils in Kaifeng city, China [J]. Environmental Science, 2015, 36(3): 1037-1044(in Chinese).