摘要
为建立适用于酸性富硒土壤有效硒提取的方法,从湖北省恩施土家族苗族自治州建始县天然富硒区采集了40份土壤样品进行水稻盆栽试验,采用连续浸提法和10种常用的单步浸提法对土壤硒形态和有效硒进行了提取、测定,并分析了不同浸提方法提取的有效硒含量与植物硒的相关性。结果显示:建始县酸性富硒土壤中水溶态和交换态硒的含量较低,分别为0.12~46.0、0.58~197.35 μg/kg;硒主要以有机结合态和残渣态等难以被植物利用的形态存在,铁锰氧化物结合态、有机结合态及残渣态硒含量分别为0.01~0.34、0.05~0.88、0.04~2.72 mg/kg;在10种单一浸提剂中,0.5 mol/L NaHCO3和0.1 mol/L KH2PO4溶液对土壤有效硒的提取效率较高;在不同土壤硒形态中,交换态硒与植物硒的相关性最高(r= 0.80,P<0.01),其余形态硒与植物硒含量的相关性均低于交换态硒。在单一浸提法中,0.1 mol/L KH2PO4溶液和0.5 mol/L NaHCO3溶液提取的土壤有效硒含量较高,但前者与植物硒含量的相关性更为显著(r= 0.83,P<0.01)。因此,综合考虑提取效率及与植物硒的相关性,0.1 mol/L KH2PO4浸提法是提取弱酸性富硒土壤中生物有效硒的最适方法。
硒(Se)是人体必需的微量营养元
研究表明,土壤总硒作为评估土壤硒含量的指标,可在一定程度反映土壤硒的有效性,但评估效果有
单一浸提法常用来提取土壤有效硒。浸提剂可分为水浸提剂、中性盐浸提剂、有机络合剂、其他酸性或碱性溶液等,主要有去离子水、K2SO4溶液、KCl溶液、NaHCO3溶液、KH2PO4溶液、HCl溶液、NaOH溶液、DTPA溶液和EDTA溶液等。水常用于水溶态硒的提取,主要依靠水的溶解作用提取水溶性硒,但其提取能力相对较
本研究以恩施天然富硒土壤为研究对象,采用连续浸提法和常见的10种单一浸提法对土壤硒形态及有效硒进行提取、测定,并通过分析水稻对不同富硒土壤样品中硒的吸收,结合连续浸提法及单一浸提法测得的土壤有效硒含量与植物硒含量的相关性分析结果,筛选出结果准确、操作简便的有效硒的提取方法,为准确评价富硒土壤中硒的生物有效性及富硒土壤资源的利用提供科学依据。
土壤样品采集于湖北省恩施土家族苗族自治州建始县。共计采集40份耕层(0~20 cm)土壤样品,采样点位置信息见

图1 采样位点分布
Fig. 1 Soil sampling points in Jianshi County of Enshi
样品编号 Sample No. | pH | 有机质含量/(g/kg) Content of organic matter | 总铁含量/(g/kg) Content of total Fe | 总铝含量/(g/kg) Content oftotal Al | 总锰含量/(g/kg) Content of total Mn |
---|---|---|---|---|---|
1 | 5.32 | 44.66 | 35.99 | 57.50 | 1.23 |
2 | 6.78 | 79.66 | 37.38 | 53.26 | 0.87 |
3 | 5.21 | 36.33 | 26.33 | 42.98 | 0.79 |
4 | 5.72 | 25.56 | 34.15 | 58.86 | 1.08 |
5 | 7.46 | 21.43 | 31.05 | 53.44 | 1.05 |
6 | 6.32 | 28.34 | 40.02 | 63.17 | 1.72 |
7 | 6.53 | 54.51 | 40.55 | 69.27 | 0.78 |
8 | 5.71 | 30.25 | 23.52 | 50.86 | 0.19 |
9 | 6.04 | 32.02 | 23.15 | 40.25 | 0.57 |
10 | 5.78 | 15.82 | 30.75 | 53.02 | 0.74 |
11 | 7.72 | 34.33 | 27.11 | 48.07 | 0.76 |
12 | 6.52 | 26.63 | 28.68 | 56.28 | 0.22 |
13 | 6.65 | 27.19 | 28.38 | 47.37 | 1.08 |
14 | 7.84 | 43.31 | 28.00 | 49.43 | 1.08 |
15 | 6.84 | 38.7 | 32.17 | 48.70 | 0.68 |
16 | 5.84 | 16.34 | 27.64 | 49.49 | 0.98 |
17 | 6.15 | 32.35 | 24.05 | 39.21 | 0.82 |
18 | 6.16 | 18.96 | 33.50 | 64.58 | 0.63 |
19 | 6.32 | 29.32 | 29.13 | 44.55 | 1.15 |
20 | 6.18 | 32.42 | 36.95 | 58.21 | 1.58 |
21 | 6.54 | 26.79 | 38.81 | 60.46 | 0.97 |
22 | 6.91 | 28.40 | 31.60 | 55.22 | 0.91 |
23 | 6.96 | 64.15 | 36.33 | 53.93 | 0.98 |
24 | 5.36 | 22.39 | 30.85 | 50.78 | 1.04 |
25 | 6.06 | 16.55 | 31.99 | 52.23 | 0.83 |
26 | 5.11 | 15.54 | 20.18 | 38.18 | 0.36 |
27 | 5.65 | 28.05 | 26.76 | 46.28 | 0.82 |
28 | 5.93 | 39.28 | 31.90 | 53.19 | 1.61 |
29 | 6.28 | 20.99 | 28.26 | 47.47 | 1.29 |
30 | 7.78 | 36.84 | 36.68 | 64.75 | 0.67 |
31 | 5.50 | 26.89 | 29.79 | 46.77 | 0.90 |
32 | 6.23 | 35.40 | 33.12 | 59.83 | 0.42 |
33 | 5.23 | 33.40 | 24.88 | 41.06 | 0.72 |
34 | 5.4 | 20.08 | 35.08 | 64.24 | 0.62 |
35 | 5.03 | 29.77 | 25.92 | 46.74 | 0.72 |
36 | 7.16 | 36.73 | 32.20 | 55.50 | 0.30 |
37 | 6.67 | 24.99 | 27.39 | 46.98 | 0.95 |
38 | 7.43 | 67.35 | 33.04 | 56.93 | 0.65 |
39 | 4.9 | 14.30 | 23.60 | 37.62 | 0.37 |
40 | 6.17 | 33.58 | 31.08 | 55.57 | 0.49 |
为探究不同硒生物有效性的土壤对水稻硒吸收的影响,在华中农业大学玻璃温室中进行了水稻盆栽试验。具体操作如下:将0.5 kg风干土壤装入塑料盆中,以尿素、过磷酸钙和K2SO4作为基肥,分别以N 0.2 g/kg、 P2O5 0.15 g/kg和 K2O 0.2 g/kg的用量施入土壤。水稻品种为“闽丰优3301”,将水稻幼苗移栽到塑料盆中,每个处理重复3次。在种植期间保持2 cm的上覆水高度,移栽后30 d收获水稻地上部分,用去离子水仔细清洗、于60 ℃烘干至恒质量,然后研磨过孔径0.15 mm筛,储存待测。
植物样品用HNO3–HClO4(4∶1,V/V)消解,在消化过程中温度保持在180 ℃。消煮至消化液清亮并冒白烟,取出、冷却后加入6 mol/L的HCl,再次加热至溶液变为清亮并伴有白烟出现时取出,随后定容并过滤。硒含量测定采用原子荧光光谱法(HG–AFS–8220),仪器检测限为0.01 μg/L。土壤总硒的测定除了用HNO3–HClO4(3∶2,V/V)代替HNO3–HClO4(4∶1,V/V)之外,其他测定步骤同植物硒含量的测定。同时以小麦籽粒标准样品(GBW-10011, GSB-2)和土壤标准样品(GBW-07404, GSS-4)作为质控样品,硒回收率分别为96.8%±1.7%和97.3%±1.6%。
分别采用超纯水、0.25 mol/L KCl溶液、0.2 mol/L K2SO4溶液、0.5 mol/L NaHCO3溶液、0.1 mol/L KH2PO4溶液、DTPA溶液、0.05 mol/L EDTA溶液、0.1 mol/L HCl溶液和0.4 mol/L HNO3溶液作为提取剂对供试土壤有效硒含量进行提取、测
提取剂 Extractants | 浓度/(mol/L) Concentration | 土液比(m∶V) Soil∶Solution | 提取方法 Extraction methods |
---|---|---|---|
超纯水 Ultrapure water | 1∶10 | 25 ℃,200 r/min振荡2 h | |
KCl | 0.25 | 1∶10 | 25 ℃,200 r/min振荡2 h |
K2SO4 | 0.2 | 1∶10 | 25 ℃,200 r/min振荡2 h |
NaHCO3 | 0.5 | 1∶5 | 25 ℃,200 r/min振荡2 h |
NaHCO3 | 0.5 | 1∶10 | 25 ℃,200 r/min振荡2 h |
KH2PO4 | 0.1 | 1∶10 | 25 ℃,200 r/min振荡2 h |
DTPA | / | 1∶10 | 25 ℃,200 r/min振荡1 h |
EDTA | 0.05 | 1∶10 | 25 ℃,200 r/min振荡2 h |
HCl | 0.1 | 1∶10 | 25 ℃,200 r/min振荡1.5 h |
HNO3 | 0.4 | 1∶10 | 25 ℃,200 r/min振荡1.5 h |
注: DTPA浸提剂由0.005 mol/L的二乙烯三胺五乙酸、0.01 mol/L的CaCl2和0.1 mol/L的三乙醇胺组成。Note:DTPA was composed of 0.005 mol/L DTPA, 0.01 mol/L CaCl2, and 0.1 mol/L TEA.
土壤硒形态测定采用经过优化的传统连续浸提
土壤总硒含量和硒形态测定结果(

图2 土壤样品总硒含量(A)和硒形态分布特征(B)
Fig. 2 Total concentration(A) and fractions distribution(B) of Se in natural seleniferous soil
本研究分别采用10种常用方法对土壤有效硒进行了提取、测定。

图3 不同浸提方法测定的土壤有效硒含量
Fig. 3 Content of soil available Se measured by various single extraction method
分别将土壤总硒、传统的连续浸提法测定的5种土壤硒形态和10种单一浸提剂提取的土壤有效硒与植物硒含量进行相关性分析(

图4 土壤中不同形态硒与植物硒含量的相关性分析(n=40)
Fig. 4 Correlation analyses between various soil Se fractions and Se in plants (n=40)
A:水溶态硒 SOL-Se ;B:交换态硒EXC-Se;C:铁锰氧化物结合态硒 FMO-Se;D:有机结合态硒 OM-Se;E:残渣态硒 RES-Se;F:土壤总硒 Total Se;r代表Pearson相关系数,**代表在0.01的水平上达到显著差异。下同。r values mean Pearson’s correlation coefficients, ** indicates significant difference at 0.01 level.The same as follows.
在本研究中,采用不同浸提剂提取的土壤有效硒与植物硒含量之间的相关性差异较大(

图5 不同浸提方法提取的有效硒含量与植物硒的关系(n=40)
Fig. 5 Relationships between Se extracted by various extractants and Se in plants (n=40)
A:0.25 mol/L KCl(1∶10,soil∶solution); B:0.2 mol/L K2SO4 (1∶10,soil∶solution); C:0.5 mol/L NaHCO3 (1∶5,soil∶solution); D:0.5 mol/L NaHCO3(1∶10,soil∶solution); E:0.1 mol/L KH2 PO4((1∶10,soil∶solution); F:0.1 mol/L HCl (1∶10,soil∶solution); G:0.4 mol/L HNO3 (1∶10,soil∶solution); H:0.05 mol/L EDTA(1∶10,soil∶solution).
我国的富硒土壤硒含量标准为≥0.4 mg/kg,本研究中的土壤硒含量均值为0.80 mg/kg,55%的土壤样品硒含量超过了富硒土壤标准,35%的土壤硒含量达到中硒水平(0.175~0.4 mg/kg)。总之,建始县的土壤硒资源分布较为丰富。水溶态硒和交换态硒被认为是生物有效性较高的硒形态,然而本研究中土壤中水溶态和交换态硒的含量较低,硒主要以有机结合态和残渣态等难以被植物利用的形态存在,这与前人对紫阳富硒土壤的研究结果类
不同浸提方法提取的土壤有效硒含量差异很大,这主要受到浸提剂的性质和其提取机制的影响。DTPA溶液属于碱性浸提剂,可提取土壤中的水溶态和部分腐殖酸结合态的硒,还能够溶解部分含硒化合物,因此,DTPA溶液对土壤有效硒的提取能力较
不同形态的硒和不同提取方法提取的土壤有效硒与植物硒含量的相关性差异较大。Peng
参考文献 References
RAYMAN M P.Selenium and human health[J].The lancet,2012,379(9822):1256-1268. [百度学术]
MA Y Z,ZHANG N C,LI Y N,et al.Differences in selenium concentration and bioavailability between paddy and dryland soils of China:a study based on literature collection and field sampling[J/OL].Journal of hazardous materials,2023,445:130467[2023-07-09].https://doi.org/10.1016/j.jhazmat.2022.130467. [百度学术]
LYU C H,CHEN J W,LI L,et al.Characteristics of Se in water-soil-plant system and threshold of soil Se in seleniferous areas in Enshi,China[J/OL].The science of the total environment,2022,827:154372[2023-07-09].https://doi.org/10.1016/j.scitotenv.2022.154372. [百度学术]
DINH Q T,CUI Z W,HUANG J,et al.Selenium distribution in the Chinese environment and its relationship with human health:a review[J].Environment international,2018,112:294-309. [百度学术]
LYU C H,QIN Y J,ZHAO Z Q,et al.Characteristics of selenium enrichment and assessment of selenium bioavailability using the diffusive gradients in thin-films technique in seleniferous soils in Enshi,Central China[J/OL].Environmental pollution,2021,273:116507[2023-07-09].https://doi.org/10.1016/j.envpol.2021.116507. [百度学术]
WANG M K,CUI Z W,XUE M Y,et al.Assessing the uptake of selenium from naturally enriched soils by maize (Zea mays L.) using diffusive gradients in thin-films technique (DGT) and traditional extractions[J/OL].The science of the total environment,2019,689[2023-07-09].https://doi.org/10.1016/j.scitotenv.2019.06.346. [百度学术]
BASSIL J,NAVEAU A,BUENO M,et al.Determination of the distribution and speciation of selenium in an argillaceous sample using chemical extractions and post-extractions analyses:application to the hydrogeological experimental site of Poitiers[J].Environmental science and pollution research,2016,23(10):9598-9613. [百度学术]
WANG S S,LIANG D L,WANG D,et al.Selenium fractionation and speciation in agriculture soils and accumulation in corn (Zea mays L.) under field conditions in Shaanxi Province,China[J].Science of the total environment,2012,427/428:159-164. [百度学术]
FORDYCE F M. Selenium deficiency and toxicity in the environment[M]//SELINUS O,ALLOWAY B,CENTENO J A,et al.Essentials of medical geology.New York:Springer,2013:375-416. [百度学术]
WANG J,LI H R,LI Y H,et al.Speciation,distribution,and bioavailability of soil selenium in the Tibetan Plateau Kashin-beck disease area:a case study in Songpan County,Sichuan Province,China[J].Biological trace element research,2013,156(1/2/3):367-375. [百度学术]
LI J,LIANG D L,QIN S Y,et al.Effects of selenite and selenate application on growth and shoot selenium accumulation of pak choi (Brassica chinensis L.) during successive planting conditions[J].Environmental science and pollution research,2015,22(14):11076-11086. [百度学术]
DINH Q T,LI Z,TRAN T A T,et al.Role of organic acids on the bioavailability of selenium in soil:a review[J].Chemosphere,2017,184:618-635. [百度学术]
WANG D,ZHOU F,YANG W X,et al.Selenate redistribution during aging in different Chinese soils and the dominant influential factors[J].Chemosphere,2017,182:284-292. [百度学术]
侯军宁,李继云.土壤硒的形态及有效硒的提取[J].土壤学报,1990,27(4):405-410.HOU J N,LI J Y.Forms of selenium in soil and extraction of available selenium[J].Acta pedologica sinica,1990,27(4):405-410 (in Chinese with English abstract). [百度学术]
李辉勇,刘鹏,刘军鸽,等.酸性水稻土有效硒提取剂的比较研究[J].生态环境,2003,12(1):12-14.LI H Y,LIU P,LIU J G,et al.Comparative studies on available Se extractants for acid paddy soils[J].Ecology and environmental sciences,2003,12(1):12-14 (in Chinese with English abstract). [百度学术]
刘军鸽,刘鹏,葛旦之,等.淹水土壤有效态硒提取剂的比较研究[J].湖南农业大学学报,2000,26(1):5-8.LIU J G,LIU P,GE D Z,et al.Comparative studies of available Se extracts in flooding soil[J].Journal of Hunan Agricultural University,2000,26(1):5-8 (in Chinese with English abstract). [百度学术]
吴雄平,鲍俊丹,伊田,等.石灰性土壤有效硒浸提剂和浸提条件研究[J].农业环境科学学报,2009,28(5):931-936.WU X P,BAO J D,YI T,et al.Extractants and optimum extracting conditions of soil available selenium in calcareous soil[J].Journal of agro-environment science,2009,28(5):931-936 (in Chinese with English abstract). [百度学术]
周菲,彭琴,王敏,等.土壤-植物体系中硒生物有效性评价研究进展[J].科学通报,2022,67(6):461-472.ZHOU F,PENG Q,WANG M,et al.Advances in the evaluation of selenium bioavailability in soil-plant system[J].Chinese science bulletin,2022,67(6):461-472 (in Chinese with English abstract). [百度学术]
谢薇,杨耀栋,菅桂芹,等.四种浸提剂对果园与菜地土壤有效硒浸提效果的对比研究[J].岩矿测试,2020,39(3):434-441.XIE W,YANG Y D,JIAN G Q,et al.A comparative study of four extractants on the extraction of available selenium in vegetable and orchard soils[J].Rock and mineral analysis,2020,39(3):434-441 (in Chinese with English abstract). [百度学术]
周越,吴文良,孟凡乔,等.土壤中硒含量、形态及有效性分析[J].农业资源与环境学报,2014,31(6):527-532.ZHOU Y,WU W L,MENG F Q,et al.Review on the content,specification of selenium and its availability in soils[J].Journal of agricultural resources and environment,2014,31(6):527-532 (in Chinese with English abstract). [百度学术]
LIU X W,ZHAO Z Q,DUAN B H,et al.Effect of applied sulphur on the uptake by wheat of selenium applied as selenite[J].Plant and soil,2015,386(1/2):35-45. [百度学术]
汤丽玲,范辉,马生明,等.AB-DTPA通用提取剂法测定土壤地球化学样品元素有效性的可行性研究[J].物探化探计算技术,2007,29(S1):238-242,1.TANG L L,FAN H,MA S M,et al.A feasibility study of determining elemets in geochemical soil samples by using general extractant AB-DTPA[J].Computing techniques for geophysical and geochemical exploration,2007,29(S1):238-242(in Chinese with English abstract). [百度学术]
KESKINEN R,EKHOLM P,YLI-HALLA M,et al.Efficiency of different methods in extracting selenium from agricultural soils of Finland[J].Geoderma,2009,153(1/2):87-93. [百度学术]
PENG Q,WANG M K,CUI Z W,et al.Assessment of bioavailability of selenium in different plant-soil systems by diffusive gradients in thin-films (DGT)[J].Environmental pollution,2017,225:637-643. [百度学术]
CHANG C Y,YIN R S,WANG X,et al.Selenium translocation in the soil-rice system in the Enshi Seleniferous Area,Central China[J].Science of the total environment,2019,669:83-90. [百度学术]
LI J,PENG Q,LIANG D L,et al.Effects of aging on the fraction distribution and bioavailability of selenium in three different soils[J].Chemosphere,2016,144:2351-2359. [百度学术]
PENG Q,LI J,WANG D,et al.Effects of ageing on bioavailability of selenium in soils assessed by diffusive gradients in thin-films and sequential extraction[J].Plant and soil,2019,436(1/2):159-171. [百度学术]
SHARMASARKAR S,VANCE G F.Fractional partitioning for assessing solid-phase speciation and geochemical transformations of soil selenium[J].Soil science,1995,160(1):43-55. [百度学术]
朱建明,秦海波,李璐,等.湖北恩施渔塘坝高硒土壤中硒的结合态[J].环境科学学报,2008,28(4):772-777.ZHU J M,QIN H B,LI L,et al.Fractionation of selenium in high-Se soils from Yutangba,Enshi,Hubei[J].Acta scientiae circumstantiae,2008,28(4):772-777 (in Chinese with English abstract). [百度学术]
宋晓珂,王金贵,李宗仁,等.富硒土壤中有效硒浸提剂和浸提条件研究[J].中国农学通报,2018,34(3):152-157.SONG X K,WANG J G,LI Z R,et al.Extractants and extraction conditions of soil available selenium in selenium-enriched soil[J].Chinese agricultural science bulletin,2018,34(3):152-157 (in Chinese with English abstract). [百度学术]
温国灿,黄艳,郭永玲,等.酸性土壤有效硒提取条件优化的研究[J].农业环境科学学报,2007,26(5):1996-2000.WEN G C,HUANG Y,GUO Y L,et al.Optimal conditions of extraction method for available selenium in acid soils[J].Journal of agro-environment science,2007,26(5):1996-2000 (in Chinese with English abstract). [百度学术]