【作者】 赵涛；

【导师】 孙荣国； 张玉涛；

【作者基本信息】 贵州师范大学 ， 分析化学， 2022， 硕士

【摘要】 汞（Hg）是一种持久性有毒的全球公认的污染物。在大气中主要以气态元素汞（GEM）存在,占总气态汞的95%以上。GEM主要来源于人为和自然释放。尽管已有大量研究致力于估算人为汞释放,但关于自然来源的汞释放的估算不足。此外,土壤中储存的Hg占陆地生态系统的90%以上,全球表层土壤Hg（0-40 cm）估计大于300000Mg,导致Hg从自然基质（即水、蔬菜、土壤和岩石）中释放是GEM的一个重要来源,占全球GEM输入的三分之二。此外,GEM在密闭的大棚环境下可以发生累积作用,导致叶片植物吸收更多的GEM。通常,在大棚生产中常常施加肥料促进农作物生长和提高农产品质量;与此同时,肥料中含有大量的有机质、矿物质和阳离子交换量,可通过螯合、吸附和氧化等作用影响土壤中Hg的化学性质。据此,本研究以模拟大棚为基础,未被Hg污染的土壤为研究对象,探讨施加腐殖酸肥、酵素和有机肥对大棚土壤中土壤-大气Hg（0）释放通量、不同价态汞（Hg（0）、Hg（I）和Hg（II））、土壤总汞（THg）、土壤理化性质（SOM、CEC、Eh和pH）和环境因素（光照强度、土壤湿度和温度）的影响,根据这些指标的相互关系分析土壤Hg（0）释放及价态转变的机制。主要结论如下:（1）在大棚环境下,空白土壤（CK）的土壤-大气Hg（0）释放通量随着时间的延长而逐渐降低,其变化范围和平均值为:104.97-42.32(73.017±25.80 ng·（m²·h）^-1),高于农田的土壤-大气Hg（0）释放通量(高粱:35.38 ng·（m²·h）^-1;玉米:28.76 ng·（m²·h）^-1)。大棚内的GEM主要来源于土壤-大气Hg（0）释放通量,并在大棚内累积,变化范围和平均值为:3.72-102.04（68.75±44.70 ng/m³）,远高于农田上空的GEM浓度（3.26-10.8 ng/m³）。当施加腐殖酸肥、酵素和有机肥后,土壤-大气Hg（0）释放通量和GEM均随着肥料剂量的增加而降低,其土壤-大气Hg（0）释放通量的平均值分别为:22.99 ng·（m²·h）^-1（有机肥）>20.51ng·（m²·h）^-1（腐殖酸肥）>14.77 ng·（m²·h）^-1（酵素）;GEM的平均值分别为:27.99 ng/m³（有机肥）>15.83 ng/m³（腐殖酸肥）>11.66 ng/m³（酵素）,并且施加酵素对土壤-大气Hg（0）释放通量和GEM的降低效果最好。（2）施加腐殖酸肥、酵素和有机肥均能促进土壤Hg的Hg（0）/Hg（I）和Hg（I）/Hg（II）氧化过程,并且随着肥料剂量的增加而增加,导致土壤Hg（0）和Hg（I）随着肥料剂量的增加而降低,其土壤Hg（0）含量的平均值分别为:0.86 ng/g（CK）>0.48 ng/g（有机肥）>0.43 ng/g（腐殖酸肥）>0.25 ng/g（酵素）;土壤Hg（I）含量的平均值分别为:18.69 ng/g（CK）>13.56 ng/g（有机肥）>9.96 ng/g（腐殖酸肥）>7.54 ng/g（酵素）,从而抑制土壤Hg（0）释放。此外,施加酵素能更好的促进土壤Hg的Hg（0）/Hg（I）和Hg（I）/Hg（II）氧化过程。肥料自身携带的Hg（330.87 ng/g（有机肥）>302.34 ng/g（腐殖酸肥）>263.87 ng/g（酵素））和促进Hg的氧化过程导致土壤Hg（II）和THg随着肥料剂量的增加而增加（土壤Hg（II）含量的平均值分别为:137.03 ng/g（腐殖酸肥）>124.38 ng/g（酵素）>121.67 ng/g（有机肥）>75.34 ng/g（CK）;THg含量的平均值分别:147.42 ng/g（腐殖酸肥）>135.71 ng/g（有机肥）>132.17 ng/g（酵素）>94.89 ng/g（CK））。通过相关性分析表明,土壤-大气Hg（0）释放通量主要来源于土壤Hg（0）释放。土壤体系中Hg（0）的产生主要经历Hg（II）/Hg（I）和Hg（I）/Hg（0）的还原过程,而不是直接由Hg（II）还原产生。土壤Hg（II）是土壤Hg的主要形态。（3）在0-120 d,总体上所有处理组的光照强度和温度逐渐升高,土壤湿度没明显的变化。对于CK、腐殖酸肥、酵素和有机肥处理组的土壤理化性质平均值变化范围分别为SOM:66.79 g/kg（酵素）>60.90 g/kg（腐殖酸肥）>55.87 g/kg（有机肥）>49.39 g/kg（CK）;Eh:622.04 m V（酵素）>622.00 m V（腐殖酸肥）>621.54 m V（有机肥）>607.00 m V（CK）;pH:6.70（酵素）>6.45（CK）>6.13（有机肥）>6.04（腐殖酸肥）;CEC:22.75 cmol/kg（腐殖酸肥）>19.11 cmol/kg（有机肥）>17.90 cmol/kg（CK）>17.10 cmol/kg（酵素）。施加腐殖酸肥和有机肥可以提高SOM、土壤Eh和土壤CEC,降低土壤pH;在0-120 d,SOM和土壤CEC没明显的变化,土壤pH逐渐降低;在0-30 d,土壤Eh降低,之后逐渐升高,在60 d达到平衡。施加酵素后可以提高SOM、土壤Eh和土壤pH;在0-120 d,SOM和土壤CEC没有显著变化,土壤pH逐渐降低;1%-酵素在0-30 d的土壤Eh降低,之后升高,而3%-酵素和5%-酵素的土壤Eh在0-120 d升高,并在60 d时达到平衡。（4）腐殖酸肥和有机肥的表面比CK的粗糙,含有更多的微孔,能促进Hg（0）从微孔进入肥料或土壤表面。CK、腐殖酸（100%-HA）、有机肥（100%-OF）和施加等比例酵素的土壤（100%-酵素-Hg（0））中主要含有-COOH、-C-O和-C=O官能团,而100%-HA和100%-OF还含有-OH官能团、Cl和S元素,此外,100%-酵素-Hg（0）中也含有Cl元素。红外光谱分析表明,-OH、-COOH、-C-O和-C=O官能团均能和Hg（0）作用。其他研究表明,Cl元素可以促进Hg（0）的氧化。因此,施加腐殖酸肥、酵素和有机肥能促进土壤Hg（0）的吸附和氧化。（5）在大棚环境下,施加三种肥料后土壤理化性质是影响土壤-大气Hg（0）释放通量的主要因素,而环境因素没有影响。总体上,施加腐殖酸肥、酵素和有机肥后首先通过改变土壤Eh来控制土壤的氧化还原状态,即施加三种肥料均可提高土壤Eh使土壤处于氧化状态,促进土壤Hg（0）经Hg（0）/Hg（I）和Hg（I）/Hg（II）的氧化过程,抑制土壤Hg（0）的释放,从而降低土壤-大气Hg（0）释放通量,随后肥料可以改变其他土壤理化性质去影响不同价态汞（Hg（0）、Hg（I）和Hg（II））之间的转变,从而影响土壤Hg的活性和氧化还原性,最终影响土壤-大气Hg（0）释放通量。更多还原

【Abstract】 Mercury（Hg）is a persistent,toxic and well-established global contaminant.In the atmosphere,the Hg mainly exists as the gaseous elemental Hg（GEM）,which accounts for more than 95%of total gaseous mercury.The GEM mainly comes from both anthropogenic and natural sources.Although extensive studies have been devoted to estimating anthropogenic Hg emissions,studies on Hg estimation from natural sources are insufficient.Furthermore,soils account for more than90%of Hg stored in terrestrial ecosystems,with global topsoil Hg pools（0-40 cm）estimated as being>300 000 Mg,induced the release of Hg from natural substrates（i.e.,water,vegetables,soils and rocks）are a significant source of GEM,and accounts for up to two-thirds of the global Hg input to the atmosphere.In addition,the GEM is accumulated in closed circumstance of greenhouse,resulted in the leaf Hg was more uptaked the GEM in greenhouse.Generally,the fertilizers are often applied in order to promoted crop growth and improved the quality of agricultural products for greenhouse production.At the same time,fertilizers contain a wealth of organic matter,minerals and cation exchange capacity,which can affect the chemical properties of Hg in soil through chelation,adsorption and oxidation.Based on this conclusion,this study is based on the simulated greenhouse,and unpolluted soil with Hg is the research object,which to investigate the influence of the soil-air Hg（0）release fluxes,the valence states of Hg（Hg（0）,Hg（I）and Hg（II））,the soil total mercury（THg）,the soil properties（SOM,CEC,Eh and pH）and environmental factors（light intensity,soil moisture and temperature）in greenhouse soil after amended with humic acid fertilizer,enzyme and organic fertilizer.Hereby,the mechanism of soil Hg（0）release and valence transformation were analyzed based on the correlation of these indexes.The main conclusions are as follows:（1）In the greenhouse environment,the soil-air Hg（0）release flux of blank soil（CK）showing a decreasing tendency over time,which ranged from and mean were 104.97-42.32(73.01±25.80 ng·（m²·h）^-1),they were much higher than that of agricultural fields(broomcorn of 35.38ng·（m²·h）^-1,corn of 28.76 ng·（m²·h）^-1).The GEM in greenhouse is predominantly come from soil-air Hg（0）release fluxes,and is accumulated in greenhouses,with the ranged from and mean 3.72-102.04（68.75±44.70 ng/m³）,which is much higher than that of farmland（3.26-10.8 ng/m³）.After the soil amended with humic acid fertilizer,enzyme and organic fertilizer,the soil-air Hg（0）release fluxes showed a decreasing tendency with the increasing fertilizer dosage,and the mean of soil-air Hg（0）release fluxes respectively were 22.99 ng·（m²·h）^-1（organic fertilizer）>20.51 ng·（m²·h）^-1（humic acid fertilizer）>14.77 ng·（m²·h）^-1（enzyme）,which the mean of GEM respectively were 27.99 ng/m³（organic fertilizer）>15.83 ng/m³（humic acid fertilizer）>11.66 ng/m³（enzyme）,and had best influence effect of the soil-air Hg（0）release fluxe and GEM for applying with enzyme in soil.（2）The oxidation process of soil Hg via Hg（0）/Hg（I）and Hg（I）/Hg（II）can be promoted in greenhouse soil after amended with humic acid fertilizer,enzyme and organic fertilizer,and showing a increasing tendency with the increasing fertilizer dosages,which caused the soil Hg（0）and Hg（I）decreased with the increasing fertilizer dosages.The mean concentration of soil Hg（0）respectively were 0.86 ng/g（CK）>0.48 ng/g（organic fertilizer）>0.43 ng/g（humic acid fertilizer）>0.25ng/g（enzyme）,and the mean concentration of soil Hg（I）respectively were 18.69 ng/g（CK）>13.56 ng/g（organic fertilizer）>9.96 ng/g（humic acid fertilizer）>7.54 ng/g（enzyme）,lead to the soil Hg（0）release was inhibited.In addition,the oxidation process of soil Hg by Hg（0）/Hg（I）and Hg（I）/Hg（II）can be better stimulated with applying the enzyme.The soil Hg（II）and THg increased were increasing with fertilizer dosage due to the Hg carried with the fertilizer（330.87 ng/g（organic fertilizer）>302.34 ng/g（humic acid fertilizer）>263.87 ng/g（enzyme））and the oxidation process of soil Hg was promoted（the mean concentration of soil Hg（II）respectively were 137.03 ng/g（humic acid fertilizer）>124.38ng/g（enzyme）>121.67 ng/g（organic fertilizer）>75.34 ng/g（CK）;the soil THg mean concentration respectively were 147.42 ng/g（humic acid fertilizer）>135.71 ng/g（organic fertilizer）>132.17 ng/g（enzyme）>94.89ng/g（CK））.The correlation analysis indicated that the soil-air Hg（0）release fluxes were mainly from soil Hg（0）release.These result shown that the generation of soil Hg（0）was underwent the reduction process of Hg（II）/Hg（I）and Hg（I）/Hg（0）,but not come from the direct reduction of Hg（II）/Hg（0）.The soil Hg（II）is the main form of soil Hg.（3）During 0-120 d,the light intensity and temperature of all treatments gradually increased,and soil moisture did not significantly variation.For CK,humic acid fertilizer,enzyme and organic fertilizer treatments group,the soil propertie mean contents were SOM:66.79 g/kg（enzyme）>0.90 g/kg（humic acid fertilizer）>55.87 g/kg（organic fertilizer）>49.39 g/kg（CK）;Eh:622.04 m V（enzyme）>622.00 m V（humic acid fertilizer）>621.54 m V（organic fertilizer）>607.00 m V（CK）;PH:6.70（enzyme）>6.45（CK）>6.13（organic fertilizer）>6.04（humic acid fertilizer）;CEC:22.75 cmol/kg（humic acid fertilizer）>19.11 cmol/kg（organic fertilizer）>17.90 cmol/kg（CK）>17.10 cmol/kg（enzyme）,respectively.Applying humic acid and organic fertilizer can be increased soil SOM,soil Eh and soil CEC,and decreased soil pH.During 0-120 d,the soil SOM and CEC did not significantly variation,and soil pH gradually decreased.Moreover,the soil Eh showed a decreasing tendency during the 0-30,then reached the equilibrium on the 60 d amended with humic acid and organic fertilizer.The soil SOM,soil Eh,and soil pH can be enhanced with the enzyme.During 0-120 d,soil SOM and CEC did not significantly variation,and soil pH decreased gradually.On the 0-30 d,the Eh showed a decreasing tendency,then to be enhanced for amended with 1%-enzyme,For 3%and 5%enzyme,the soil showed a increasing tendency during 0-120 d,and reached the equilibrium on the 60 d.（4）The surface of humic acid fertilizer and organic fertilizer are rough and contains more micropores than the CK,which can promote Hg（0）enter the surface of fertilizer or soil from micropores.For CK,humic acid fertilizer（100%-HA）,organic fertilizer（100%-OF）and soil with applying equal proportion of enzyme（100%-enzyme-Hg（0））were involved-COOH,-C-O and-C=O functional groups,which the100%-HA and 100%-OF also contained-OH functional group,Cl and S elements.Furthermore,100%-enzyme-Hg（0）also contained Cl element.The Fourier Transform Infrared Spectrum（FTIR）demonstrated that the Hg（0）was combined with-OH,-COOH,-C-O and-C=O functional groups.Other studies showed that the Cl element can be promoted the oxidation of Hg（0）.Thus the adsorption and oxidation of Hg（0）were enhanced for soil amended humic acid fertilizer,organic fertilizer and enzyme.（5）After the soil amending with humic acid fertilizer,enzyme and organic fertilizer,ambient environment conditions are no longer the key factors,and the soil properties are the dominant factors,involved in the soil-air Hg（0）release process in the greenhouse environment.In general,first,the redox state of soil was controlled by the variation of soil Eh applying the humic acid fertilizer,enzyme and organic fertilizer,which the soil Eh was enhanced after amending with humic acid fertilizer,enzyme and organic fertilizer,resulting in the soil environment was in oxidation state,then the oxidation process of Hg（0）through Hg（0）/Hg（I）and Hg（I）/Hg（II）were promoted,leading to the release of soil Hg（0）was inhibited,and the soil-air Hg（0）release fluxes was reduced.Subsequently,the activity and reducibility of soil Hg were influenced according the variation of other soil properties to be influenced the transformation of the soil Hg valence states（Hg（0）,Hg（I）and Hg（II））amending with humic acid fertilizer,enzyme and organic fertilizer,which the soil-air Hg（0）release fluxes were impacted.更多还原