Effect of environmental factors on the complexation of iron and humic acid

A method of size exclusion chromatography coupled with ultraviolet spectrophotometry and off-line graphite furnace atomic absorption spectrometry was developed to assess the complexation properties of iron(Fe) and humic acid(HA) in a water environment. The factors affecting the complexation of Fe and HA, such as ionic strength, p H, temperature and UV radiation, were investigated. The Fe–HA complex residence time was also studied. Experimental results showed that p H could influence the deprotonation of HA and hydrolysis of Fe, and thus affected the complexation of Fe and HA. The complexation was greatly disrupted by the presence of Na Cl. Temperature had some influence on the complexation. The yield of Fe–HA complexes showed a small decrease at high levels of UV radiation, but the effect of UV radiation on Fe–HA complex formation at natural levels could be neglected. It took about 10 hr for the complexation to reach equilibrium, and the Fe–HA complex residence time was about 20 hr.Complexation of Fe and HA reached a maximum level under the conditions of p H 6, very low ionic strength, in the dark and at a water temperature of about 25°C, for 10 hr. It was suggested that the Fe–HA complex could form mainly in freshwater bodies and reach high levels in the warm season with mild sunlight radiation. With changing environmental parameters, such as at lower temperature in winter or higher p H and ionic strength in an estuary, the concentration of the Fe–HA complex would decrease.     

石墨炉原子吸收法测定水与废水中硒

采用石墨炉原子吸收法测定水与废水中硒,以镍盐为基体改进剂,提高了灰化温度,消除了基体干扰。方法的最低检出浓度为1.4ppb,废水测定的变异系数为2.9％～7.5％,加标回收率为95.0％～105.4％     

微波消解-石墨炉原子吸收光谱法测定环境空气中的镉

建立了过氯乙烯滤膜采集环境空气中镉,微波消解滤膜、硝酸镁溶液作为基体改进剂,石墨炉原子吸收光谱法测定镉的方法。本方法前处理操作过程简单、省时、酸用量少、环境污染小,方法的灵敏度和准确度都有很大的提高。当采样体积为6000L,镉的最低检出质量浓度为0．0008mg／m^3。     

石墨炉原子吸收光谱法测定土壤中痕量钻

建立了硝酸－氢氟酸－盐酸混酸体系微波消解土壤样品,石墨炉原子吸收分光光谱法测定土壤中痕量钴的方法。通过对标准土样的测定结果表明,该方法容易操作、准确、可靠。     

石墨炉原子吸收法测定大气中锡的研究

研究了１０种基体改进剂和不同石墨管对石墨炉法测定锡的影响，结果表明，使用热解涂层石墨管并采用铁－抗坏血酸作基体改进剂，可获得最高的灵敏度和最好的回收率，用此法对锡标准样品进行测定，所得结果与定值吻合，相对误差为３．０％￣４．０％，相对标准偏差为２．０％￣４．８％，检出限为０．４０μｇ／Ｌ。     

Sorption of tylosin and sulfamethazine on solid humic acid

Tylosin(TYL) and sulfamethazine(SMT) are ionizable and polar antimicrobial compounds,which have seeped into the environment in substantial amounts via fertilizing land with manure or sewage. Sorption of TYL and SMT onto humic acid(HA) may affect their environmental fate. In this study, the sorption of TYL and SMT on HA at different conditions(pH, ionic strength) was investigated. All sorption isotherms fitted well to the Henry and Freundlich models and they were highly nonlinear with values of n between 0.5 and 0.8, which suggested that the HA had high heterogeneity. The sorption of TYL and SMT on HA decreased with increasing p H(2.0–7.5), implying that the primary sorption mechanism could be due to cation exchange interactions between TYL~+/SMT~+ species and the functional groups of HA.Increasing ionic strength resulted in a considerable reduction in the K_d values of TYL and SMT,hinting that interactions between H bonds and π–π EDA might be an important factor in the sorption of TYL and SMT on HA. Results of Fourier transform infrared(FT-IR) and ~13C-nuclear magnetic resonance(NMR) analysis further demonstrated that carboxyl groups and O-alkyl structures in the HA could interact with TYL and SMT via ionic interactions and H bonds,respectively. Overall, this work gives new insights into the mechanisms of sorption of TYL and SMT on HA and hence aids us in assessing the environmental risk of TYL and SMT under diverse conditions.     

腐殖酸极性与有机农药吸附行为的关系

用不同的方法对腐殖酸(HA)进行了结构改性处理,并用元素分析仪、红外光谱仪和电位滴定仪对改性前后的HA进行了表征;通过振荡平衡法,研究了HA改性前后对有机农药甲基对硫磷、西维因、克百威的吸附行为.结果表明,水解处理使得HA的碳水化合物结构减少,肟化处理使得HA的C=N结构增加,氧化处理使HA的芳香环发生开环反应、-COOH基团增加,肟化和氧化处理均使得HA极性增强;有机农药甲基对硫磷、西维因、克百威通过分配作用吸附于HA,分配系数Kd与HA有的机碳含量成正比,HA的极性越强,吸附量越小.     

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.     

土壤中钼的形态分析方法研究

本文对土壤中有效钼的浸取条件进行最佳化，并利用提高灰化温度达到消除浸取剂对石墨炉原子吸收测定钼的影响，方法用于国标样品和武汉市区土壤样品中钼的形态分析，获得满意的分析结果。     

氢氧化铁和腐殖酸结合态镉在文蛤体内的富集

氢氧化铁和腐殖酸是沉积物中重金属的重要储存库,在一定程度上均可以控制重金属在底栖生物体内的富集.本文在3个浓度梯度(70、140、280mg·kg-1)下,通过颗粒物悬浮系统,研究了氢氧化铁和腐殖酸颗粒上附着的Cd在文蛤体内富集规律.实验结果表明,氢氧化铁和腐殖酸结合态Cd对文蛤的生物有效性存在显著差异.在Cd浓度为7...     

Pahokee泥炭腐殖酸的相对分子量分布特征及其对菲的吸附影响

使用切面流超滤方法,将Pahokee泥炭中分离出的腐殖酸分为具有不同相对分子质量的8个级分(UF1:<1k;UF2:1～3k;UF3:3～5k;UF4:5～10k;UF5:10～30k;UF6:30～50k;UF7:50～100k:UF8:>300k),表明该泥炭中的腐殖酸主要分布于几个高相对分子量级分中(UF5,UF6和UF8),可占所提取的腐殖酸质量的83 5%.体积排阻色谱的流出曲线说明可以通过超滤手段将腐殖酸这种复杂的、非均匀性的大分子物质分成相对均一的、窄相对分子量分布的分子.而两种方法所测相对分子量的差异可能与两个操作系统间不同的操作条件有关.各超滤级分的腐殖酸对菲的吸附实验说明相对分子量是影响腐殖酸吸附的一个重要参数;随相对分子量的增加,腐殖酸对菲的吸附及其非线性特征均增强.     

Towards a better hydraulic cleaning strategy for ultrafiltration membrane fouling by humic acid: Effect of backwash water composition

As a routine measurement to alleviate membrane fouling, hydraulic cleaning is of great significance for the steady operation of ultrafiltration (UF) systems in water treatment processes. In this work, a comparative study was performed to investigate the effects of the composition of backwash water on the hydraulic cleaning performance of UF membranes fouled by humic acid (HA). Various types of backwash water, including UF permeate, Milli-Q water, NaCl solution, CaCl₂ solution and HA solution, were compared in terms of hydraulically irreversible fouling index, total surface tension and residual HA. The results indicated that Milli-Q water backwash was superior to UF permeate backwash in cleaning HA-fouled membranes, and the backwash water containing Na⁺ or HA outperformed Milli-Q water in alleviating HA fouling. On the contrary, the presence of Ca^2 + in backwash water significantly decreased the backwash efficiency. Moreover, Ca^2 + played an important role in foulant removal, and the residual HA content closely related to the residual Ca^2 + content. Mechanism analysis suggested that the backwash process may involve fouling layer swelling, ion exchange, electric double layer release and competitive complexation. Ion exchange and competitive complexation played significant roles in the efficient hydraulic cleaning associated with Na⁺ and HA, respectively.     

Visible-light-driven photocatalytic inactivation of bacteriophage f2 by Cu-TiO2 nanofibers in the presence of humic acid

Pathogenic viruses in drinking water are great threats to public health. Visible-light-driven photocatalysis is a promising technology for virus inactivation. However, the existing photocatalytic antiviral research studies have mostly been carried out in single-component systems, neglecting the effect of natural organic matter, which exists widely in actual water bodies. In this paper, electrospun Cu-TiO₂ nanofibers were prepared as photocatalysts, and their photocatalytic antiviral performance in the presence of humic acid (HA) was comprehensively studied for the first time. The properties of the reaction mixture were measured during the reaction. In addition, the safety, reliability and stability of photocatalytic disinfection in the mixed system were evaluated. The results showed that the virus removal efficiency decreased with the increase of the HA concentration. The type of reaction solution, such as PBS buffer solution or water, did not affect the removal efficiency noticeably. Under acidic conditions, the electrostatic forces between photocatalysts and viruses were strengthened, leading to higher virus removal efficiency. As the reaction time went on, the pH value in the solution increased first and then tended to be stable, the conductivity remained stable, and the dissolved oxygen increased first and then decreased. The safety test showed that the concentration of Cu ions released into the solution was lower than specified by the international standards. No photoreactivation was observed, and the addition of HA significantly reduced the reutilization efficiency of the photocatalysts.     

皂角苷及腐殖酸对微生物降解蒽的影响

研究了皂角苷(1种生物表面活性剂)和腐殖酸(1种类表面活性物质)对微生物降解蒽的影响,并与Tween-80(1种化学表面活性剂)对蒽的增溶及促进微生物降解的作用进行了对比.结果表明,在不加任何表面活性物质时,微生物需要7d产生足够的糖脂使葸溶解,并发生微生物降解.皂角苷、腐殖酸和Tween-80均能较大程度的加速葸的降解,而且在相同条件下皂角苷及腐殖酸的效果明显优于Tween-80.腐殖酸及皂角苷大大缩短了微生物降解葸的时间,在2～4d内蒽的降解率可达到98%.同时,发现腐殖酸的浓度、葸的初始浓度均影响着蒽的微生物降解速率.     

Fe(II)、Fe(III)对砷与不同分子量腐植酸络合性能的影响

以腐植酸（HA）代表天然有机质,采用平衡透析和超滤的方法研究铁离子（Fe （II）、Fe （III））对不同分子量HA与砷离子（As （V）、As （III））络合作用的影响,并利用红外光谱（FT-IR）表征其络合特征.结果发现,Fe （II）和Fe （III）均能增强HA络合As能力,且对As （V）络合能力的增强作用大于As （III）;pH值显著影响HA络合As能力;溶解性有机碳（DOC）浓度由5mg/L增大到200mg/L,As络合百分比随之增加,此时HA-Fe （III）络合As （III）百分比最大,为24.55%;初始As浓度由10μg/L增加1000μg/L,As络合百分比随之降低,其中HA-Fe （III）络合As （III）百分比最低,为3.11%.相同环境条件下,分子量>100kDa络合As百分比最大,其中HA-Fe （II）络合As （III）的百分比最高为26.43%;分子量小于10kDa的HA络合As百分比明显高于其他分子量的HA.Fe的增强作用主要源于Fe与羧基形成桥梁再与As络合形成三元络合物.     

Efficient capture of aqueous humic acid using a functionalized stereoscopic porous activated carbon based on poly(acrylic acid)/food-waste hydrogel

Stereoscopic porous carbons have shown good potential in humic acid (HA) removal. In this work, a novel stereoscopic porous activated carbon (SPAC) was designed and synthesized via the self-assembly of a hydrogel based on food waste during in-situ polymerization, vacuum drying, carbonization, and activation. Then, the SPAC was functionalized with 3-aminopropyltriethoxysilane (APTES) and the adsorption behavior of the modified SPAC (SPAC-NH₂) was studied systematically. The effects of pH, contact time, initial concentration of HA, and adsorbent dose were investigated, showing that optimal HA removal efficiency (> 98.0%) could be achieved at an initial HA concentration of 100?mg/L. The experimental adsorption isotherm data was fitted to the Langmuir model with a maximum adsorption capacity of 156.0?mg?HA/g SPAC-NH₂. Analysis of the mechanism indicated that the removal of HA was mainly realized through the amidization reaction between the COOH groups of HA and the NH₂ groups of APTES. All of the above results showed that SPAC-NH₂ powder is an efficient, eco-friendly, and reusable adsorbent which is suitable for the removal of HA from wastewater.     

Effect of temperature on the sorption and desorption of perfluorooctane sulfonate on humic acid

Sorption and desorption of perfluorooctane sulfonate (PFOS) on humic acid at different temperatures were studied. It was found that the sorption process could be modeled with power kinetic equation very well, suggesting that diflusion predominated the sorption of PFOS on the humic acid. The sorption capacity was doubled when the temperature increased from 5 to 35°C, and thermodynamics parameters △G0 was calculated to be -7.11 to -5.04 kJ/mol, △H0 was 14.2 kJ/mol, and △S 0 was 69.5 J/(mol·K), indicating that the sorption was a spontaneous, endothermic, and entropy driven process. Desorption hysteresis occurred at all studied temperatures which suggested that humic acid may be an important sink of PFOS in the environment.     

Simultaneous size characterization and mass quantification of the in vivo core-biocorona structure and dissolved species of silver nanoparticles

Size characterization of silver nanoparticles with biomolecule corona(AgNP@BCs) and mass quantification of various silver species in organisms are essential for understanding the in vivo transformation of Ag NPs. Herein, we report a versatile method that allows simultaneous determination of the size of AgNP@BCs and mass concentration of various silver species in rat liver. Both particulate and ionic silver were extracted in their original forms from the organs by alkaline digestion, and analyzed by size exclusion chromatography combined with inductively coupled plasma mass spectrometry(SEC-ICP-MS). While the silver mass concentrations were quantified by ICP-MS with a detection limit of 0.1 μg/g, the effective diameter of AgNP@BCs was determined based on the retention time in SEC separation with size discrimination of 0.6-3.3 nm. More importantly, we found that the BC thickness of AgNP@BCs is core size independent, and a linear correlation was found between the effective diameter and core diameter of AgNP@BCs in extracted tissues, which was used to calibrate the core diameter with standard deviations in the range of 0.2-1.1 nm. The utility of this strategy was demonstrated through application to rat livers in vivo. Our method is powerful for investigating the transformation mechanism of Ag NPs in vivo.     

铬酸钡分光光度法和间接原子吸收法测定水中硫酸盐的比较

目的比较铬酸钡分光光度法和间接原子吸收法测定水中硫酸盐的异同。方法比较两种方法的标准曲线和回收率,并对12份地下水和地表水（硫酸盐浓度大于10.0 mg.L-1）分别用两种方法分析。同时进行两种方法精密度和准确度比较。结果两种方法的相关系数均大于0.999,回收率均满足分析要求。进行12份水样测定结果的配对t检验,t=0.13,P﹥0.05。对于10.0 mg.L-1的合成水样,铬酸钡法分光光度法测定相对误差为9.0%,而间接原子吸收法测定相对误差为0.4%。结论铬酸钡分光光度法在测定低浓度硫酸盐时,准确度和灵敏度较间接原子吸收法低,而大于10 mg/L时,两种方法都能得到较好的准确度和灵敏度。     

环境因子对胡敏酸介导下SDZ光解行为的影响

研究了在纯水条件及两种不同来源胡敏酸（HA）介导下,磺胺嘧啶（SDZ）和水稻土胡敏酸（SDHA）、泥炭土胡敏酸（NTHA）的不同浓度、pH值、光敏离子（NO₃^-和Fe³⁺）、离子强度（NaCl）以及金属离子（Ca²⁺、Mg²⁺和K⁺）等环境因子对SDZ紫外光降解的影响.结果表明：光照下,pH=7.1对两种体系的SDZ光降解有促进作用且效果最好.低SDZ浓度（2mg/L）以及低HA浓度（15mg/L）条件下使SDZ光解速率较快.光敏离子中NO₃^-通过光生·OH,促进了纯水中SDZ的光解,但在HA体系中,HA具有猝灭·OH的效应造成SDZ的光解速率低于纯水;Fe³⁺在HA体系下均表现为抑制作用,且抑制强度为NTHA>SDHA.在纯水中SDZ的光解速率随NaCl浓度增加而增加,HA介导下,较低浓度NaCl（C_NaCl=50mmol/L）抑制作用较强.金属离子（K⁺、Ca²⁺和Mg²⁺）在纯水中对SDZ的光解影响程度较弱,但在HA体系中均表现为抑制作用,抑制强度为K⁺ > Ca²⁺ > Mg²⁺,单价阳离子对SDZ光降解影响较为明显.