Abstract：To explore a simple, economic and reliable method for separation and extraction of microplastics from soil, eleven mixed solutions comprising saturated NaCl and NaI solutions with progressively changing volume ratios (F1~F11) were prepared. These mixed solutions were used as the flotation liquid to extract four types of microplastics including polyethylene (PE), polystyrene (PS), polyvinyl chloride (PVC), and polyethylene terephthalate (PET) absorbed by soil with an improved protocol for flotation separation. The results showed that the total extraction rate of microplastics was only 55.83% when used purely NaCl saturated solution, while this extraction rate increased with an growing volume ratio of NaI in the mixture. The total extraction rate exceeded 90% when the volume ratio of saturated NaCl solution to NaI solution was 1:1and reached as high as 96.67% when using purely NaI solution. For all the eleven mixed solutions used, the extraction rates of PE and PS exceeded 86.67%, relatively higher than that of the other two types of microplastics. When using saturated NaCl solution alone, the extraction rates of PVC and PET were extremely low compared with that of 93.33% and 90% respectively in case the volume ratio of NaCl to NaI solution was 1:1, which were close to those obtained using NaI solution alone. Sum of the extraction rates of lower-density microplastics PE and PS was constantly higher than that of higher-density microplastics PVC and PET for all the eleven mixed solutions. However, the difference between extraction rates was neglectable among the mixed solutions F6 to F11. Based on the abovementioned results and considering factors such as economic cost, it is recommended that the mixture of saturated NaCl to NaI solution with a volume ratio of of 1:1 could be the optimal to extract microplastics in soil samples.
林婧, 李振国, 余光辉, 张勇, 宋焱, 王广怀, 姜晓倩. 密度分离法提取土壤中微塑料的优化[J]. 中国环境科学, 2022, 42(7): 3285-3294.
LIN Jing, LI Zhen-guo, YU Guang-hui, ZHANG Yong, SONG Yan, WANG Guang-huai, JIANG Xiao-qian. Optimization of microplastics extraction from soil by density separation. CHINA ENVIRONMENTAL SCIENCECE, 2022, 42(7): 3285-3294.
Thompson R C, Olsen Y, Mitchell R P, et al. Lost at Sea:where is all the plastic?[J]. Science, 2004,304(5672):838-838.
[2]
Claessens M, De Meester S, Van Landuyt L, et al. Occurrence and distribution of microplastics in marine sediments along the Belgian coast[J]. Marine pollution bulletin, 2011,62(10):2199-2204.
[3]
Andrady A L. Microplastics in the marine environment[J]. Marine Pollution Bulletin, 2011,62(8):1596-1605.
[4]
Alimi O S, Farner Budarz J, Hernandez L M, et al. Microplastics and nanoplastics in aquatic environments:aggregation, deposition, and enhanced contaminant transport[J]. Environmental Science&Technology, 2018,52(4):1704-1724.
[5]
田媛,涂晨,周倩,等.环渤海海岸大气微塑料污染时空分布特征与表面形貌[J].环境科学学报, 2020,40(4):1401-1409. Tian Y, Tu C, Zhou Q, et al. The temporal and spatial distribution and surface morphology of atmospheric microplastics around the Bohai Sea[J]. Acta Scientiae Circumstantiae, 2020,40(4):1401-1409.
[6]
Nizzetto L, Langaas S, Futter M. Pollution:Do microplastics spill on to farm soils?[J]. Nature, 2016,537(7621):488-488.
[7]
EFSA Panel on Contaminants in the Food Chain (CONTAM). Presence of microplastics and nanoplastics in food, with particular focus on seafood[J]. Efsa Journal, 2016,14(6):e04501.
[8]
Kosuth M, Mason S A, Wattenberg E V. Anthropogenic contamination of tap water, beer, and sea salt[J]. PloS one, 2018,13(4):e0194970.
[9]
Schymanski D, Goldbeck C, Humpf H U, et al. Analysis of microplastics in water by micro-Raman spectroscopy:release of plastic particles from different packaging into mineral water[J]. Water Research, 2018,129:154-162.
[10]
Wright S L, Kelly F J. Plastic and human health:a micro issue?[J]. Environmental science&technology, 2017,51(12):6634-6647.
[11]
Antunes J C, Frias J G L, Micaelo A C, et al. Resin pellets from beaches of the Portuguese coast and adsorbed persistent organic pollutants[J]. Estuarine, Coastal and Shelf Science, 2013,130:62-69.
[12]
Frias J, Sobral P, Ferreira A M. Organic pollutants in microplastics from two beaches of the Portuguese coast[J]. Marine Pollution Bulletin, 2010,60(11):1988-1992.
[13]
Oliveira M, Ribeiro A, Hylland K, et al. Single and combined effects of microplastics and pyrene on juveniles (0+group) of the common goby Pomatoschistus microps (Teleostei, Gobiidae)[J]. Ecological Indicators, 2013,34:641-647.
[14]
Ashton K, Holmes L, Turner A. Association of metals with plastic production pellets in the marine environment[J]. Marine Pollution Bulletin, 2010,60(11):2050-2055.
[15]
范秀磊,常卓恒,邹晔锋,等.可降解微塑料对铜和锌离子的吸附解吸特性[J].中国环境科学, 2021,41(5):2141-2150. Fan X L, Chang Z H, Zou Y F, et al. Adsorption and desorption properties of degradable microplastic for Cu2+ and Zn2+[J]. China Environmental Science, 2021,41(5):2141-2150.
[16]
Brennecke D, Duarte B, Paiva F, et al. Microplastics as vector for heavy metal contamination from the marine environment[J]. Estuarine, Coastal and Shelf Science, 2016,178:189-195.
[17]
La Daana K K, Gårdfeldt K, Lyashevska O, et al. Microplastics in sub-surface waters of the Arctic Central Basin[J]. Marine Pollution Bulletin, 2018,130:8-18.
[18]
Zhao S, Zhu L, Wang T, et al. Suspended microplastics in the surface water of the Yangtze Estuary System, China:first observations on occurrence, distribution[J]. Marine Pollution Bulletin, 2014,86(1/2):562-568.
[19]
Eriksen M, Mason S, Wilson S, et al. Microplastic pollution in the surface waters of the Laurentian Great Lakes[J]. Marine Pollution Bulletin, 2013,77(1/2):177-182.
[20]
Anderson P J, Warrack S, Langen V, et al. Microplastic contamination in lake Winnipeg, Canada[J]. Environmental Pollution, 2017,225:223-231.
[21]
王志超,窦雅娇,周鑫,等.岱海冰封期微塑料与环境因子的关系及风险评价[J].中国环境科学, 2022,42(2):889-896. Wang Z C, Dou Y J, Zhou X, et al. Relationship between microplastics occurrence and environmental factors and risk assessment during ice-covered period of the Daihai Lake. China Environmental Science, 2022,42(2):889-896.
[22]
He B, Goonetilleke A, Ayoko G A, et al. Abundance, distribution patterns, and identification of microplastics in Brisbane River sediments, Australia[J]. Science of the Total Environment, 2020, 700:134467.
[23]
Rillig M C. Microplastic in terrestrial ecosystems and the soil?[J]. Environmental Science&Technology, 2012,46(12):6453-6454.
[24]
Li J, Liu H, Chen J P. Microplastics in freshwater systems:A review on occurrence, environmental effects, and methods for microplastics detection[J]. Water research, 2018,137:362-374.
[25]
Lots F A E, Behrens P, Vijver M G, et al. A large-scale investigation of microplastic contamination:abundance and characteristics of microplastics in European beach sediment[J]. Marine Pollution Bulletin, 2017,123(1/2):219-226.
[26]
Zhao J, Ran W, Teng J, et al. Microplastic pollution in sediments from the Bohai Sea and the Yellow Sea, China[J]. Science of the Total Environment, 2018,640:637-645.
[27]
Phuong N N, Poirier L, Lagarde F, et al. Microplastic abundance and characteristics in French Atlantic coastal sediments using a new extraction method[J]. Environmental Pollution, 2018,243:228-237.
[28]
Liebezeit G, Dubaish F. Microplastics in beaches of the East Frisian islands Spiekeroog and Kachelotplate[J]. Bulletin of environmental contamination and toxicology, 2012,89(1):213-217.
[29]
韩丽花,李巧玲,徐笠,等.大辽河沉积物中微塑料的污染特征[J].中国环境科学, 2020,40(4):1649-1658. Han L H, Li Q L, Xu L, et al. The pollution characteristics of microplastics in Daliao River sediments[J]. China Environmental Science, 2020,40(4):1649-1658.
[30]
Wang J, Wang M, Ru S, et al. High levels of microplastic pollution in the sediments and benthic organisms of the South Yellow Sea, China[J]. Science of the Total Environment, 2019,651:1661-1669.
[31]
Van Cauwenberghe L, Vanreusel A, Mees J, et al. Microplastic pollution in deep-sea sediments[J]. Environmental Pollution, 2013,182:495-499.
[32]
Corcoran P L, Biesinger M C, Grifi M. Plastics and beaches:A degrading relationship[J]. Marine pollution bulletin, 2009,58(1):80-84.
[33]
Ballent A, Corcoran P L, Madden O, et al. Sources and sinks of microplastics in Canadian Lake Ontario nearshore, tributary and beach sediments[J]. Marine Pollution Bulletin, 2016,110(1):383-395.
[34]
Zhang K, Xiong X, Hu H, et al. Occurrence and characteristics of microplastic pollution in Xiangxi Bay of Three Gorges Reservoir, China[J]. Environmental Science&Technology, 2017,51(7):3794-3801.
[35]
Zhang K, Su J, Xiong X, et al. Microplastic pollution of lakeshore sediments from remote lakes in Tibet plateau, China[J]. Environmental Pollution, 2016,219:450-455.
[36]
Claessens M, Van Cauwenberghe L, Vandegehuchte M B, et al. New techniques for the detection of microplastics in sediments and field collected organisms[J]. Marine Pollution Bulletin, 2013,70(1/2):227-233.
[37]
Nuelle M T, Dekiff J H, Remy D, et al. A new analytical approach for monitoring microplastics in marine sediments[J]. Environmental Pollution, 2014,184:161-169.
[38]
Liu M, Lu S, Song Y, et al. Microplastic and mesoplastic pollution in farmland soils in suburbs of Shanghai, China[J]. Environmental Pollution, 2018,242:855-862.
[39]
Lv W, Zhou W, Lu S, et al. Microplastic pollution in rice-fish co-culture system:A report of three farmland stations in Shanghai, China[J]. Science of the Total Environment, 2019,652:1209-1218.
[40]
Fries E, Dekiff J H, Willmeyer J, et al. Identification of polymer types and additives in marine microplastic particles using pyrolysis-GC/MS and scanning electron microscopy[J]. Environmental science:Processes&Impacts, 2013,15(10):1949-1956.
[41]
Shim W J, Song Y K, Hong S H, et al. Identification and quantification of microplastics using Nile Red staining[J]. Marine Pollution Bulletin, 2016,113(1/2):469-476.
[42]
Li Q, Wu J, Zhao X, et al. Separation and identification of microplastics from soil and sewage sludge[J]. Environmental Pollution, 2019,254:113076.
[43]
Bläsing M, Amelung W. Plastics in soil:Analytical methods and possible sources[J]. Science of the Total Environment, 2018,612:422-435.
[44]
Scheurer M, Bigalke M. Microplastics in Swiss floodplain soils[J]. Environmental science&technology, 2018,52(6):3591-3598.
[45]
Zhang K, Shi H, Peng J, et al. Microplastic pollution in China's inland water systems:a review of findings, methods, characteristics, effects, and management[J]. Science of the Total Environment, 2018,630:1641-1653.
[46]
Liebezeit G, Dubaish F. Microplastics in beaches of the East Frisian islands Spiekeroog and Kachelotplate[J]. Bulletin of Environmental Contamination and Toxicology, 2012,89(1):213-217.
[47]
Avio C G, Gorbi S, Regoli F. Experimental development of a new protocol for extraction and characterization of microplastics in fish tissues:first observations in commercial species from Adriatic Sea[J]. Marine environmental research, 2015,111:18-26.
[48]
顾伟康,杨国峰,刘艺,等.环境介质中微塑料的处理与检测方法研究进展[J].土木与环境工程学报(中英文), 2020,42(1):135-143. Gu W K, Yang G F, Liu Y, et al. Treatment and detection methods of microplastics from environmental media:A review[J]. Journal of Civil And Environmental Engineering (Chinese and English), 2020,42(1):135-143.
[49]
Hidalgo-Ruz V, Gutow L, Thompson R C, et al. Microplastics in the marine environment:a review of the methods used for identification and quantification[J]. Environmental Science&Technology, 2012, 46(6):3060-3075.
[50]
李昇昇,李良忠,李敏,等.环境样品中微塑料及其结合污染物鉴别分析研究进展[J].环境化学, 2020,39(4):960-974. Li S S, Li L Z, Li M, et al. Study on identification of microplastics and the combined pollutants in environmental samples[J]. Environmental Chemistry, 2020,39(4):960-974.
[51]
Imhof H K, Laforsch C, Wiesheu A C, et al. Pigments and plastic in limnetic ecosystems:A qualitative and quantitative study on microparticles of different size classes[J]. Water Research, 2016,98:64-74.
