Experimental and molecular dynamic simulation study of perfluorooctane sulfonate adsorption on soil and sediment components

Soil and sediment play a crucial role in the fate and transport of perfluorooctane sulfonate (PFOS) in the environment. However, the molecular mechanisms of major soil/sediment components on PFOS adsorption remain unclear. This study experimentally isolated three major components in soil/sediment: humin/kerogen, humic/fulvic acid (HA/FA), and inorganic component after removing organics, and explored their contributions to PFOS adsorption using batch adsorption experiments and molecular dynamic simulations. The results suggest that the humin/kerogen component dominated the PFOS adsorption due to its aliphatic featureswhere hydrophobic effect and phase transfer are the primary adsorptionmechanism. Compared with the humin/kerogen, the HA/FA component contributed less to the PFOS adsorption because of its hydrophilic and polar characteristics. The electrostatic repulsion between the polar groups of HA/FA and PFOS anions was attributable to the reduced PFOS adsorption.When the soil organicmatterwas extracted, the inorganic component also plays a non-negligible role because PFOS molecules might form surface complexes on SiO₂ surface. The findings obtained in this study illustrate the contribution of organic matters in soils and sediments to PFOS adsorption and provided newperspective to understanding the adsorption process of PFOS on micro-interface in the environment.     

同源地人工湖水体和底泥中有机物组成及有机结构的分析研究

采用XAD-8大孔吸附树脂对水体和底泥中的有机物进行组分分离,并通过傅里叶变换红外光谱(FTIR)、紫外-可见光谱(UV-Vis)和三维荧光光谱(3DEEMs)对自然水体和底泥中的疏水酸(腐殖酸、富里酸)、疏水碱、疏水中性物质和亲水物质进行表征和对比.结果表明,水体中有机物含量:亲水物质富里酸腐殖酸疏水碱疏水中性物质,底泥中有机物的含量为:腐殖酸富里酸亲水物质疏水碱疏水中性物质.根据红外、紫外、三维荧光光谱可知底泥中有机物的芳香程度、不饱和程度及分子量大小略高于水体有机物.根据荧光指数(FI)和自生源指标(BIX)可知,底泥和水体的腐殖酸和富里酸主要来源于陆生动植物和土壤有机质,而其余物质主要源于细菌和藻类活动.     

湖泊沉积物有机质的连续提取与荧光光谱特征分析

采用化学连续提取与三维荧光光谱相结合的方法研究了蠡湖沉积物中可提取有机质的组成、结构和空间分布特征,并探讨了可提取态有机质组分与可交换态氮和弱吸附态磷之间的相关关系.结果表明,蠡湖沉积物中有机质含量为5.59~22.11 g·kg~(-1)(以C计),均值为12.28g·kg~(-1),其中水可提取态有机质(WSOM)、富里酸(FA)、胡敏酸(HA)和胡敏素(HM)的比例分别为5.14%、11.81%、9.63%和73.42%,空间上呈现由西向东逐渐递增,湖岸大于湖心的分布趋势.WSOM鉴别出3个荧光组分,以类氨基酸荧光峰(W-C1)占优势,占总荧光强度的比例为42.49%;FA鉴别出2个荧光组分,以富里酸荧光峰(F-C2)为主,比例为67.63%;HA的3个荧光峰中,以类胡敏酸荧光峰(H-C1和H-C3)为主,两者之和的比例为71.55%.多元回归统计表明,可提取有机质组分与游离态氮和易解析态磷含量之间均显著正相关,且与氮的相关性系数大于与磷,反映了可提取有机质与可交换态氮的关系更为密切,可用于指示沉积物生物可利用性氮磷的污染状况.     

施用生物质炭对土壤腐殖质组成和胡敏酸结构特征影响

为研究玉米秸秆生物质炭施用后土壤腐殖质组成和土壤胡敏酸结构的变化,选择腐殖质组成修改法和国际腐殖质协会推荐的方法进行土壤腐殖质组分提取和HA样品纯化,采用重铬酸钾外加热法和TOC分析仪测定土壤、水溶性物质(WSS)、富里酸(FA)、胡敏酸(HA)和胡敏素(Hu)有机碳含量,采用元素组成和红外光谱分析HA的结构变化.研究结果表明:施入玉米秸秆生物质炭后,表层和亚表层土壤及其腐殖质组分有机碳含量均有不同程度的提高,表层土壤、WSS、FA、HA和Hu有机碳含量增加幅度较大,分别增加了83.61%、112.50%、89.63%、91.78%和89.82%,说明玉米秸秆生物质炭的施用更有助于表层土壤有机碳的积累;PQ值(HA在腐殖酸中的比例)略有增加;土壤HA的缩合程度和芳香性增强,氧化度降低.此外,施用玉米秸秆生物质炭后,土壤及其腐殖质组分有机碳含量随土层深度的增加而降低,与表层相比,亚表层土壤、WSS、FA、HA和Hu有机碳含量分别下降了62.84%、52.94%、62.38%、66.62%和61.61%;土壤PQ值略有降低;土壤HA的缩合程度和芳香性降低,氧化度增加.     

DOM不同相对分子质量组分在无机矿物上的吸附及其对卡马西平吸附的影响实验

为探究溶解性有机质(DOM)不同相对分子质量组分在矿物质上的吸附特征及其与药物和个人护理品(PPCPs)类污染物的结合作用对两者吸附过程的影响,以卡马西平作为目标污染物,用商用腐殖酸制备DOM,以石英砂代表无机矿物,开展吸附实验,并采用透析实验和红外光谱表征等手段,探讨了不同相对分子质量腐殖酸(HA)的结构特征及其与卡马西平(CBZ)的结合作用对HA或CBZ在固相介质上吸附作用的差异及产生机制.结果表明,大分子量HA有更多的羟基、芳香烃和脂肪烃,以疏水物质为主;而小分子量HA有更多的醇和羧基,以亲水物质为主.HA与CBZ的结合主要通过CBZ的氨基与小分子量HA中极性官能团的结合,以及CBZ疏水基团与大分子量HA中脂肪族与芳香族的疏水作用.CBZ与HA之间的相互作用对腐殖酸或卡马西平的吸附产生明显差异.当CBZ不存在时,石英砂主要通过疏水作用结合HA中疏水性大分子或与HA的羟基、羧基等发生交换配位反应,且石英砂更倾向于吸附HA中的脂肪性及疏水性大分子组分.当CBZ存在时,石英砂转而吸附HA中的小分子量部分,且HA在石英砂上的最大吸附量减小.当HA不存在时,CBZ可通过疏水作用,范德华力和极性相互作用使其在石英砂上有一定量的吸附.加入HA后,石英砂吸附增加的CBZ归因于部分HA分子与CBZ结合后共吸附或累积吸附于石英砂上.     

A comparison of the compositional differences between humic fractions isolated by the IHSS and exhaustive extraction procedures

Humic substances (HSs), consisting, on the basis of solubilities in aqueous acid and basic media, of humic acids (HAs), fulvic acids (FAs), and humin (Hu), are the major components of soil organic matter (SOM). Most studies of soil/natural organic matter (SOM/NOM) have been carried out on extracts of soils in dilute sodium hydroxide solutions, the solvent used to extract the Standards of the International Humic Substances Society (IHSS). However, Hu, the major component in the classical definition of HSs, is insoluble in aqueous base and is not isolated by the traditional IHSS method. Recently, a sequential exhaustive extraction (SEE) process has been shown to be capable of isolating and separating the major components of the classically defined HSs from the soils of the temperate and tropical regions. The SEE system was used in the present study to isolate the HA/FA and Hu fractions from a subtropical volcanic Taiwanese soil. Chemical and compositional properties of these extracts were then compared with similarly obtained isolates from soils from the different climatic regions. Increases in the aliphatic relative to aromatic carbon contents were observed for both the HA and FA fractions when the pH values of the extraction media were increased. HAs and FAs isolated using the SEE method have spectroscopic profiles similar to those from the IHSS isolate; however, the cumulative extraction efficiency (%) of the SEE method (65 %) for the volcanic soil was much higher than for the traditional IHSS method (33 %). When the residual volcanic soil, following extractions once, three, and eight times with 0.1 M NaOH were then extracted with dimethyl sulphoxide (DMSO) plus concentrated sulphuric acid (the final solvent in the SEE sequence) it was seen that the content of crystalline polymethylene hydrocarbon (33 ppm ¹³C-NMR resonance in the Hu (or DMSO/acid)) extract increased relative to the amorphous methylene (30 ppm). That highlights the difficulty in dissolving the more highly ordered hydrocarbon structures that would be expected to have closer associations with the mineral colloids. Although the SEE procedure isolated all of the HAs and FAs from the Yangmingshan soil, extractability of the Hu from the volcanic soil in the DMSO/acid solvent was low (21 %), and contrasted with the much higher yields from temperate and tropical regions. The decreased Hu extraction may arise from its associations with the extensive iron and aluminium hydroxide mineral colloids in the soil. The Hu from this sub-tropical soil was different from the Hus isolated from other soil types, indicating the need to isolate and characterise these recalcitrant organic material in order to understand the organic carbon components in soils in greater detail. Such results would indicate that more attention should be given to mineral colloids in soils, and to the organo/mineral associations that will have an important role in the stabilities of OM in the soil environment.     

多方法研究呼伦湖表层沉积物有机质的赋存特征及来源

湖泊沉积物有机质是全球碳循环的重要组成部分之一.寒旱区湖泊由于地理位置和气候条件的特殊性,其沉积物有机质的赋存和迁移转化特征更容易受到气候变化的影响.以我国寒旱区典型代表湖泊——呼伦湖为例,采用连续提取法、C/N（碳氮比值）、δ13C（碳稳定同位素）、三维荧光光谱技术对呼伦湖表层沉积物有机质的含量和组分的时空分布特征、污染来源及稳定性进行了研究.结果表明:①2018年10月（秋季）、2019年3月（冬季）、2019年5月（春季）、2019年7月（夏季）,呼伦湖表层沉积物中w（TOC）的平均值分别为（25.05±9.73）（26.92±11.60）（24.68±10.19）（24.36±10.01）g/kg,呈冬季高、夏季低,由西北部向东南部递减的时空分布趋势.②w（WEOM）（WEOM为水提态有机质）、w（FA）（FA为富里酸）、w（HA）（HA为胡敏酸）和w（HM）（HM为胡敏素）的年均值分别为（0.63±0.33）（2.31±1.26）（3.42±1.49）（19.21±7.83）g/kg,w（WEOM）:w（FA）:w（HA）:w（HM）为1.0:3.7:5.5:30.7,其中HM为有机质的优势组分.③WEOM包括类富里酸组分C1,类腐殖酸组分C2和C3,以及类色氨酸组分C4共4个荧光组分,其中,类腐殖质组分（C1+C2+C3）贡献了总荧光强度的79.2%,为优势荧光组分.④沉积物有机质主要来自于陆源,陆源有机质的平均贡献率在80%左右.⑤沉积物PQ值（胡敏酸占腐殖酸的比例）和WEOM的HIX（腐殖化指数）年均值分别为0.55和6.39,表明现阶段呼伦湖表层沉积物有机质腐殖化程度较高且相对稳定.研究显示:呼伦湖表层沉积物有机质含量较高,表现出季节和空间分布差异性;有机质主要来自陆源,以类腐殖质为主,具有腐殖化程度高和相对稳定的特点.      

不同有机物料对黑土腐殖质元素组成及结构的影响

 利用元素分析仪及红外光谱仪研究施用不同有机物料对黑土腐殖质元素组成及结构影响的差异性.结果表明:与对照(CK)相比,有机物料施用5a后,黑土胡敏酸(HA)中C、H含量均显著降低,并以木本处理作用最显著.除动物粪便处理HA中N含量与CK相等外,其余有机处理N含量均显著高于CK,施用动物残体则使HA中O含量显著降低.施用草本残体可以提高富里酸(FA)中N含量.动物残体使FA中H含量显著降低.施用草本残体、木本残体使FA中C含量升高,O含量影响降低.有机物的施用使铁结合胡敏素(HMi)中C、H含量下降而使O含量上升,并以草本处理作用最显著,同时草本处理也使HMi中N含量降低.与CK相比,施用动物粪便、木本残体提高了粘粒结合胡敏素(HMc)中C、N含量而降低了O含量,有机物料施用5a后均使黑土HMc中H含量降低,且各处理之间差异显著.与CK相比,有机物料施用五年后均使HA及FA脂族性减弱,并以草本残体处理影响最明显.对于HMc,施用有机物料有利于提高其脂族性,同时使芳香C=C振动减弱,并且以木本处理影响最明显.有机物料施用5a后使HMi的羟基含量及碳水化合物减少,而使其脂族性提高.试验结果证实,不同有机物料处理对黑土腐殖质各组分特征的影响有明显差异.     

狐尾藻在不同营养底泥腐解过程中胡敏酸的变化

采用平行因子分析方法,结合紫外吸收光谱、三维荧光光谱以及傅里叶变换红外光谱技术,研究了沉水植物狐尾藻在低、中、高营养底泥腐解过程中胡敏酸（HA）的变化,进一步揭示了不同营养底泥对沉水植物腐解的影响机制.结果表明,底泥营养水平越高,狐尾藻腐解得越快（P<0.05）,释放出更多的溶解性有机碳（DOC）、溶解性总氮（DTN）、溶解性总磷（DTP）和腐殖质;底泥营养程度与HA的疏水性、分子复杂性、分子量大小呈正相关（P<0.05）;荧光鉴别出不同营养底泥HA都含有1种类蛋白质组分C2和2种类富里酸组分C1、C3,且类富里酸组分和类蛋白质组分在不同腐解条件下具有相似的组分特征;不同营养底泥不同时间提取的HA红外图谱较为相似,表明不同腐解条件不同时间提取的HA含有相似的官能团,狐尾藻腐烂高营养底泥组提取的HA含有更多的芳香性物质和有机磷.采用光谱分析法对狐尾藻腐烂分解HA成分的化学结构特征进行系统的研究,可深入了解不同营养底泥对沉水植物腐解的影响机制,为湖泊水环境生态治理和修复提供理论参考.     

Effects of fulvic acid and humic acid from different sources on Hg methylation in soil and accumulation in rice

Humus is often used as an organic modifier to reduce the bioaccumulation of heavy metals in plants, but the effects of different humus components from different sources on the fate of mercury (Hg) in paddy fields are still unclear. Here, fulvic acid (FA) and humic acid (HA) extracted from composted straw (CS), composted cow dung (CCD), peat soil (PM) and lignite coal (LC) were used to understand their effects on the methylation and bioaccumulation of Hg in paddy soil by pot experiments. Amendments of both FA and HA largely increased the abundance of Hg-methylating microbes and low-molecular-weight organic matters (e.g, cysteine) in paddy soil. They were also found to change the aromaticity, molecular size and Chromophoric DOM concentration of DOM, and resulted in heterogeneous effects on migration and transformation of Hg. All the FA-amended treatments increased the mobility and methylation of Hg in soil and its absorption in roots. Nevertheless, FA from different sources have heterogeneous effects on transport of Hg between rice tissues. FA-CCD and FA-PM promoted the translocation of MeHg from roots to rice grains by 32.95% and 41.12%, while FA-CS and FA-LC significantly inhibited the translocation of inorganic Hg (IHg) by 52.65% and 66.06% and of MeHg by 46.65% and 36.23%, respectively. In contrast, all HA-amended treatments reduced the mobility of soil Hg, but promoted Hg methylation in soil. Among which, HA-CCD and HA-PM promoted the translocation of MeHg in rice tissues by 88.95% and 64.10%, while its accumulation in rice grains by 28.43% and 28.69%, respectively. In general, the application of some FA and HA as organic modifiers to reduce Hg bioaccumulation in rice is not feasible.     

水体腐殖酸及其络合物Ⅰ.蓟运河腐殖酸的提取和表征

提取和研究了华北蓟运河的腐殖酸,并从实验中得到了一些结论。国产吸附树脂GDX-102对分离河水中的腐殖酸比较有效,黄腐酸在树脂吸附前后的红外光谱没有明显的区别。氨—乙醇混合液作为解吸液效果较好,而且不引进金属离子。水体黄腐酸(FA)和棕腐酸(HA)的分子量低于煤炭和土壤中的FA和HA,其趋势为河水FA<河泥FA<河泥HA。水生腐殖酸具有明显的荧光特性,其酸性基高于土壤和煤炭腐殖酸,且—COOH基含量一般低于土壤和煤炭腐殖酸,—OH基是总酸性基的主要部分。水体腐殖酸的碳含量较低,氧、硫、氮含量较高,因此可能有各种取代基,这在络合作用中必须予以考虑。     

不同组成有机质对土壤中砷迁移行为的影响

本研究选择腐植酸(HA)、黄腐酸(FA)和鸡粪提取的可溶性有机质(DOM)三种天然有机质,加入供试土壤,以溴离子作为示踪剂,通过四组模拟土柱实验,获得不同有机质组成的土壤中As (V)的穿透曲线,并用CXTFIT 2.1软件拟合,计算阻滞系数R_d值,同时测定流出液中As (V)的形态变化。结果表明:HA抑制了As (V)的迁移,而加入FA和DOM后As (V)在土壤中的移动性显著增强。四种处理(CK、土壤+HA、土壤+FA、土壤+DOM)中As (V)的阻滞系数R_d值分别为17.82、19.53、10.13和12.2,土柱中残留的As分别占As总量的27.4%、31.7%、19.2%和18.2%。腐植酸以芳香族含量为主,分子量较大,吸附固定As的能力较强;黄腐酸和提取的可溶性有机质主要结构为烷基碳和氧烷基碳,H/C和O/C值较高,与As存在竞争吸附,促进As的迁移。     

盐度和压力对沉积物逐级分离样品吸附毒性有机物的影响

用化学逐级分离法对大连近海沉积物中有机组分和无机组分进行分离,考察了盐度和压力对沉积物中有机组分和无机组分附几种毒性有机物的影响。结果表明,有机组分几种毒性有机物的吸附能力随盐度的升高线性递增;而无机组分的吸附能力随盐度的升高线减。升高压了沉积物中２组分对毒性有机物的吸附能力。但随压力的升高,吸附能力增加的幅度降低。吸附系数与压力之间的关系可用指数方程描述。     

水体底泥及岸边土壤有机无机复合体对磷吸附特征对比

以长春市新立城水库底泥及岸边土壤为研究对象,利用平衡吸附法研究底泥、土壤及二者有机无机复合体(砂粒、粉粒和粘粒)对磷的吸附热力学和动力学特征,并探讨底泥和土壤各级复合体对磷的吸附贡献,以期探明底泥和土壤对磷的富集规律.结果表明,底泥和土壤对磷的吸附热力学均符合Langmuir方程和Freundlich方程,且底泥对磷的理论最大吸附量约是土壤的3倍.底泥及土壤粘粒复合体对磷的吸附热力学符合Langmuir方程和Freundlich方程,粉粒及砂粒复合体对磷的吸附符合Henry方程.粘粒复合体对磷的吸附量均大于粉粒复合体,而粉粒复合体均大于砂粒复合体.底泥及土壤粘粒复合体对磷的吸附贡献约为60%,粉粒复合体对磷的吸附贡献稍大于砂粒复合体的吸附贡献.底泥、土壤及二者有机无机复合体对磷的吸附动力学符合一级动力学方程、Elovich方程和双常数方程,且均在24 h以内达到吸附平衡.研究结果表明,底泥与岸边土壤对磷的吸附具有相似的规律,且底泥及其复合体对磷的吸附能力均大于土壤,说明若磷素由于地表径流等因素由土壤进入到水体中,底泥对磷会有较强的吸附净化作用,即某种意义上底泥为河流磷素有效的"汇".     

猪粪堆肥过程中腐殖酸电子转移机制及光谱演化特征

3D-EEM),探究了猪粪堆肥过程中HA和FA的化学结构变化以及对ETC的影响。结果表明:HA的ETC由堆肥初期10.06 μmol e-/g C增长至末期40.07 μmol e-/g C,FA的ETC由堆肥初期的15.36 μmol e-/g C增长至末期的69.73 μmol e-/g C,二者均随时间变化呈波动上升趋势,且EDC在电子转移中占主要地位。光谱分析表明,堆肥中的木质素类物质经堆肥化后会转变为聚合度高的腐殖质类物质,相比于堆肥初期,腐熟期时有机质的腐殖化程度和芳香化程度增大,相对分子质量也增高。类蛋白物质(组分C4)在堆肥过程中逐渐减少,易被微生物作为碳源利用从而转化为类腐殖质物质(组分C2),且C2是堆肥中较为稳定的组分。相关性分析表明:类蛋白质物质减少、腐殖化程度增加会使HA和FA的ETC增强,FA的电子转移能力更容易受到腐殖化程度的影响。     

Comparative sorption and desorption behaviors of PFHxS and PFOS on sequentially extracted humic substances

The sorption and desorption behaviors of two perfluoroalkane sulfonates（PFSAs）, including perfluorohexane sulfonate（PFHx S） and perfluorooctane sulfonate（PFOS） on two humic acids（HAs） and humin（HM）, which were extracted from a peat soil, were investigated. The sorption kinetics and isotherms showed that the sorption of PFOS on the humic substances（HSs） was much higher than PFHx S. For the same PFSA compound, the sorption on HSs followed the order of HM 〉 HA2 〉 HA1. These suggest that hydrophobic interaction plays a key role in the sorption of PFSAs on HSs. The sorption capacities of PFSAs on HSs were significantly related to their aliphaticity, but negatively correlated to aromatic carbons,indicating the importance of aliphatic groups in the sorption of PFSAs. Compared to PFOS,PFHx S displayed distinct desorption hysteresis, probably due to irreversible pore deformation after sorption of PFHx S. The sorption of the two PFSAs on HSs decreased with an increase in p H in the solution. This is ascribed to the electrostatic interaction and hydrogen bonding at lower p H. Hydrophobic interaction might also be stronger at lower p H due to the aggregation of HSs.     

天然土壤有机质中菲的分配行为

天然土壤吸附不同初始浓度的菲后,提取胡敏酸组分(包括胡敏酸和富里酸),通过计算得到胡敏素组份所吸附的菲,用以研究菲在2种组份中的动态吸附/分配行为,以及初始浓度的影响,并利用Freundlich式进行拟合.结果表明:天然土壤中菲的吸附/分配过程表现出分阶段特征:从最初的快吸附至48 h左右达到转折点,然后进入慢吸附过程.在快吸附至转折点阶段,胡敏酸组分中菲的吸附比例(吸附量与初始量之比)出现先升后降的波动,可归因于初始时段矿物表面吸附、胡敏素竞争吸附的影响.在慢吸附阶段,胡敏酸中菲的吸附比例变化很小,菲初始浓度的影响也不大;而对于胡敏素组份,低初始浓度条件下菲的吸附比例明显大于高初始浓度条件,并呈现逐步增加的趋势,表明胡敏素组份是慢吸附的主要发生域.模型参数拟合结果显示:胡敏酸、全土、胡敏素吸附的非线性程度依次增加,并随时间逐渐加强.在吸附/分配的动力学过程中,胡敏酸和胡敏素分阶段不同的变化特征反映出土壤有机质组分异质性对非线性吸附行为的影响.     

Relationship between heavy metals and dissolved organic matter released from sediment by bioturbation/bioirrigation

Organic matter (OM) is an important component of sediment. Bioturbation/bioirrigation can remobilize OM and heavy metals that were previously buried in the sediment. The remobilization of buried organic matter, thallium (Tl), cadmium (Cd), copper (Cu) and zinc (Zn) from sediment was studied in a laboratory experiment with three organisms: tubificid, chironomid larvae and loach. Results showed that bioturbation/bioirrigation promoted the release of dissolved organic matter (DOM) and dissolved Tl, Cd, Cu and Zn, but only dissolved Zn concentrations decreased with exposure time in overlying water. The presence of organisms altered the compositions of DOM released from sediment, considerably increasing the percentage of fulvic acid-like materials (FA) and humic acid-like materials (HA). In addition, bioturbation/bioirrigation accelerated the growth and reproduction of bacteria to enhance the proportion of soluble microbial byproduct-like materials (SMP). The DOM was divided into five regions in the three-dimensional excitation emission matrix (3D-EEM), and each part had different correlation with the dissolved heavy metal concentrations. Dissolved Cu had the best correlation with each of the DOM compositions, indicating that Cu in the sediment was in the organic-bound form. Furthermore, the organism type and heavy metal characteristics both played a role in influencing the remobilization of heavy metal.     

某冶炼厂周边土壤碳组分与铜形态的相关性

研究了浙江某冶炼污染区农田土壤有机碳组分与铜(Cu)形态的相关关系.结果表明,研究区土壤Cu形态含量为铁锰氧化物结合态残渣态碳酸盐结合态有机质结合态可交换态,其中铁锰氧化物结合态Cu和残渣态Cu含量分别占全量的39.55%和39.19%.土壤p H值和碳组分对不同形态Cu含量存在一定程度的影响,其中p H值与碳酸盐结合态Cu和铁锰氧化物结合态Cu均呈显著正相关;溶解性有机碳(DOC)含量与可交换态Cu呈极显著正相关;富里酸(FA)含量与可交换态Cu呈极显著正相关,与有机结合态Cu呈显著正相关;胡敏酸(HA)含量分别与可交换态Cu和有机结合态Cu呈极显著正相关.土壤DOC、FA、HA的动态变化对这些在移动性上存在差异的Cu形态间的相互转化会带来一定程度的影响,从而改变土壤Cu的迁移能力和生物有效性.     

长期石油污染土壤腐殖质组成的研究

选择1口开采约20a的废弃油井,在距离井口0.5、1.5、2.5、3.5、4.5、5.5、6.5、7.5和10.5 m处进行多点采样,应用腐殖质组成修改法和Simon-Kumada法,分别研究了上述长期不同程度石油污染土壤的全土及不同结合形态腐殖质组成.结果表明,土壤石油含量随距井口距离加大而降低,最远处(10.5 m)和最近处(0.5 m)分别为0.08 g/kg和153.3 g/kg.随石油含量增加,土壤有机碳和水溶性有机碳含量增加;全土腐殖质中,可提取腐殖质(HE)含量和胡敏酸(HA)含量下降而胡敏素(HM)含量增加, HA/HE的百分比(PQ 72.0%～8.05%)下降而HM/HE(31.4～76.7)增加;不同结合形态腐殖质中,松、稳结合态腐殖质(HⅠ、HⅡ)的含量呈下降趋势而紧结合态腐殖质(HⅢ)的含量增加, HⅠ/HⅡ(0.19～0.39)呈增加趋势,而HⅠ/HⅢ(0.032～0.003)和HⅡ/HⅢ(0.096～0.009)下降, HⅠ、HⅡ的PQ(3.21%～1.42%、58.1%～35.5%)也下降,并且HⅠ的PQ变化幅度小于HⅡ;水溶性有机质(WSOM)的色调系数(△logk)下降而HA则变化不大.以上结果说明,随石油污染程度增加,土壤HM的形成增强而HA形成减弱,对HA形成的影响主要表现为对稳结合态HA形成的抑制作用, WSOM分子结构趋于复杂而HA没有明显变化.