Photochemical production of dissolved inorganic carbon from suwannee river humic acid

The photochemical mineralization of dissolved organic carbon(DOC) to dissolved inorganic carbon(DIC) is a key process in carbon cycling.Using a Suntest CPS solar simulator,Suwannee River humic acid(SRHA) was photooxidated to examine the effects of O2 levels,the wavelength of incident light,and the concentration of Fe on the photoproduction of DIC.Increasing the O2 abundance enhanced photodegradation of SRHA.The rate of DIC photoproduction under air saturation in the first 24 h(4.40 μmol/(L h)) was increased by a factor of 1.56 under O2 saturation,but fell by only 36% under N2 saturation.To evaluate the relative importance of UV-B,UV-A,and visible radiation in the photodegradation,we examined the above process using Mylar-d films and UF-3 and UF-4 plexiglass filters.The results indicated that the UV-B,UV-A and visible wavelengths accounted for 31.8%,32.6% and 25.6%,respectively,of DIC production with simulated sunlight irradiation.The above results also indicated that photoproduction of DIC could take place in natural water at depths greater than those that UV light can reach.When 20 μmol/L desferrioxamine mesylate(DFOM,a strong Fe complexing ligand) was added,the rate of DIC photoproduction fell to 55.6% that of the original SRHA samples with 5.46 μmol/L Fe.

Soil organic carbon contents, aggregate stability,and humic acid composition in different alpine grasslands in Qinghai-Tibet Plateau

Alpine grassland soils on Qinghai-Tibet Plateau store approximately 33.5 Pg of organic carbon(C) at 0–0.75 m depth and play an important role in the global carbon cycle.We investigated soil organic C(SOC),water-soluble organic C(WSOC),easily oxidizable organic C(EOC),humic C fractions,aggregate-associated C,aggregate stability,and humic acid(HA) composition along an east-west transect across Qinghai-Tibet Plateau,and explored their spatial patterns and controlling factors.The contents of SOC,WSOC,EOC,humic C fractions and aggregate-associated C,the proportions of macroaggregates(2-0.25) and micro-aggregates(0.25-0.053 mm),and the aggregate stability indices all increased in the order alpine desert < alpine steppe < alpine meadow.The alkyl C,O-alkyl C,and aliphatic C/aromatic C ratio of HA increased as alpine desert < alpine meadow < alpine steppe,and the trends were reverse for the aromatic C and HB/HI ratio.Mean annual precipitation and aboveground biomass weresignificantly correlated with the contents of SOC and its fractions,the proportions of macro- and microaggregates,and the aggregate stability indices along this transect.Among all these C fractions,SOC content and aggregate stability were more closely associated with humic C and silt and clay sized C in comparison with WSOC,EOC,and macro- and microaggregate C.The results suggested that alpine meadow soils containing higher SOC exhibited high soil aggregation and aggregate stability.Mean annual precipitation should be the main climate factor controlling the spatial patterns of SOC,soil aggregation,and aggregate stability in this region.The resistant and stable C fractions rather than labile C fractions are the major determinant of SOC stocks and aggregate stability.

Effects of humic acid coatings on phenanthrene sorption to black carbon

Black carbon （BC） can strongly adsorb hydrophobic organic compounds （HOCs）. The HOC sorption to coated BC could be attenuated in soil and sediment compared with that of the parent BC. To study the potential causes of the sorption attenuation, humic acid （HA） and BC were isolated. Phenanthrene （PHE） was selected as the representative of HOCs. BC was coated with the precipitated HA. The PHE sorption to the HA-coated BC was determined. The HA coatings on BC could result in the significant sorption attenuation of PHE to BC. The attenuation varied in different HA origin and was positively correlated to the aromaticity of HA. The attenuation could be explained by the direct competition between HA and PHE for the available sorption sites on BC and the reduction of the available sorption sites as a result of the pore blockage of BC caused by the HA coatings. Therefore, the HA coatings on BC was one potential cause of the attenuation of HOC sorption to BC in soil and sediment.

Effects of Nano-carbon Humic Acid Water-retaining Fertilizer on Citrus Growth and the Soil Bacterial Community in Citrus Field

[Objective] In order to reveal the effects of reducing the amount of novel nano-carbon humic acid water-retaining fertilizer(CSF) on soil microbial community structure and citrus growth. [Method]In this study,conventional fertilization was as the control(KC1) in Wanzhou citrus orchard of Three Gorges Reservoir area. CSF reductions by 0%(KC2),10%(KC3),20%(KC4),30%(KC5) and 40%(KC6) were used to analyze the changes of soil bacterial community structure,citrus yield and quality. [Result]The results showed that the observed species,Shannon index,Chao1 index and PDwholetree of KC6 were higher than those of KC1,and were the same as KC2. The abundance of Xanthomonadaceae was the highest in KC5. Compared with KC1,the Xanthomonadaceae in KC3,KC4 and KC6 was significantly decreased,and the levels of Nitrosomonadaceae and Pseudomonasaceae were higher than that of KC1 after the treatment of KC6. Sphingomonas in different reduction treatments was lower than that of KC1,but Burkholderia and Pseudomonas were significantly higher than those of KC1. It was found that the similarity among treatments was small after bacterial community similarity clustering analysis,and citrus yield increased somewhat after CSF fertilization reduction.When CSF fertilization reduced by 30%,citrus yield increased by 4. 50%. When CSF fertilization reduced by 40%,citrus yield decreased by4. 14%. After CSF fertilization,citrus quality did not change significantly in CSF conventional fertilization and reduction of 10% and 40%,while significantly decreased in 20% and 30% of fertilization reduction. [Conclusion] CSF fertilization reduction changed the diversity of soil bacterial community structure and the yield and quality of citrus.

CuO-containing multi-walled carbon nanotubes:a novel catalyst for the catalytic ozonation of humic acid in water

CuO particles were attempted to fill in the channel of multi-walled carbon nanotubes (MWCNTs) as novel catalytic materials CuO@MWCNTs used for ozonation of humic acids (HA) in aqueous solution.Catalyst samples were characterized by transmission electron microscopy (TEM),X-ray diffraction (XRD),thermogravimetric analysis (TG) and X-ray photoelectron spectroscopy (XPS).The removal efficiency of HA was promoted in the presence of CuO@MWCNTs compared with that of Al2O3-supported CuO catalyst (CuO/Al2O3) and CuO-coating MWCNTs catalyst (CuO/MWCNTs).The strong synergetic effect in the confinement environment on CuO nanoparticles can attribute to the locally higher pressure due to the lower potential energy of reactants in the channels.Strong interaction happened between the catalyst and reactants,which promoted the decomposition of ozone and the generation of OH.The results of experimental and theoretical investigation confirmed that CuO@MWCNTs promotes the initiation and generation of OH,hence accelerating the degradation of organic pollutants.

Adsorptive removal of tetracycline from water using Fe(Ⅲ)-functionalized carbonized humic acid

Humic acid(HA)was carbonized at 300,400 and 500℃ and then functionalized with 1 wt%–12 wt%Fe(Ⅲ)respectively[CHA300/400/500-Fe(Ⅲ)].Adsorption of such Fe(III)-functionalized carbonized HA as adsorbents to aqueous tetracycline(TC:25 mg·L^-1)was studied.The adsorption equilibrium time for CHA400-Fe(Ⅲ)to TC was 6 h faster and the adsorption removal efficiency(Re)was two times higher than that of HA/CHA.The adsorption Reof CHA400-Fe(Ⅲ)loaded 10%iron[CHA400-(10%)Fe(Ⅲ)]to TC could reach 99.8%at 8 h and still kept80.6%after 8 cycles.The adsorption kinetics were well fitted to the pseudo-second-order equation and the adsorption isotherms could be well delineated via Langmuir equations(R^2N 0.99),indicating that the homogeneous chemical adsorption of TC occurred on the adsorbents.The main adsorption mechanisms of TC were complexation Fe(III)and hydrophobic distribution.Electropositive and electronegative repulsion between TC and CHA400-(10%)Fe(Ⅲ)at lowly p H(2)and highly p H(8–10)respectively,leaded to the relatively low adsorption capacity and more notable influence of ion concentration.When the p H was between 4 and 8,TC mainly existed in neutral molecules(TCH2),so the influence of ion concentration was not obvious.The dynamic adsorption results showed that the CHA400-(10%)Fe(Ⅲ)could continuously treat about 2.4 L TC(27 mg·L^-1)wastewater with the effluent concentration as low as 0.068 mg·L^-1.Our study suggested a broad application prospect of a new,effective,lowcost and environment-friendly adsorbent CHA400-(10%)Fe(Ⅲ)for treatment of low-concentration TC polluted wastewater.

Single-Ni-atoms on nitrogenated humic acid based porous carbon for CO_(2) electroreduction

tWe proposed a facile synthesis of single-Ni-atom catalysts on low-cost porous carbon using a calcina-tion method at the temperatures of 850-1000°C,which were used for CO_(2) electrochemical reduction to CO.The porous carbon was prepared by carbonizing cheap and abundant humic acid.The structural characterizations of the as-synthesized catalysts and their electrocatalytic performances were analyzed.The results showed that the single-Ni-atom catalyst activated at 950°C showed an optimum catalytic performance,and it reached a CO Faradaic efficiency of 91.9% with a CO partial current density of 6.9 mAcm^(-2)at-0.9 V vs.reversible hydrogen electrode(RHE).Additionally,the CO Faradaic efficiency and current density of the optimum catalyst changed slightly after 8 h of continuous operation,suggesting that it possessed an excellent stability.The structure-activity relations indicate that the variation in the CO_(2) electroche-mical reduction performance for the as-synthesized catalysts is ascribed to the combined effects of the increase in the content of pyrrolic N,the evaporation of Ni and N,the decrease in pore volume,and the change in graphitization degree.

Carbon Sequestration in Soil Humic Substances Under Long-Term Fertilization in a Wheat-Maize System from North China

The changes in humic substances （HS） is fundamental in detecting soil carbon sequestration mechanisms in natural and cultivated environments. Based on a long-term trial, the amounts of water dissolved substances （WSS）, humic acid （HA）, fulvic acid （FA） and humin （HU） were determined to explore the impact of long-term fertilization on HS. Increases in the amounts of WSS, HA, FA and HU were significant different among the treatments with manure. A significant correlation was found between the increased soil organic carbon （SOC） and HS （R^2=0.98, P〈0.01）. The change in the E4/E6 ratio was significantly correlated with the increased SOC （R2=0.88, P〈0.01）, HA （R^2=0.91, P〈0.01）, FA （R^2=0.91, P〈0.01） and HU （R^2=0.88, P〈0.01）. The cluster was mainly divided into two parts as manure fertilization and inorganic fertilization, based on the increases in HA, FA and HU. These results suggest that long term fertilization with manure favours carbon sequestration in HS and is mainly stabilized as HU, while the HA becomes more aliphatic. We conclude that increases in SOC can be linked to changes in the molecular characteristics of HS fractions under long term fertilization.

玉米秸秆还田下深松年限对土壤有机碳含量及胡敏酸结构特征的影响

为明确不同秸秆还田结合耕作措施下土壤有机碳组分的变化特征,基于6 a秸秆还田长期定位试验,利用三维荧光光谱技术,对CK(不深松+不秸秆还田)、NFG(不深松+每年秸秆还田)、EFG(隔一年深松+每年秸秆还田)、TFG(隔两年深松+每年秸秆还田)和SFG(连年深松+每年秸秆还田)处理下土壤有机碳(SOC)含量及胡敏酸(HA)结构特征进行分析。结果表明:与CK相比,EFG处理0~10 cm土层的SOC、HA含量和PQ值分别显著增加25.23%、16.19%和4.27%,FA含量降低4.55%。10~20 cm土层,EFG处理的SOC含量最高,较CK增加13.18%;SFG处理的HA和FA含量较CK提高最多,增幅分别为13.27%和32.74%。通过HA三维荧光图谱发现,与CK(Ex/Em=270/455,270/460)相比,EFG(Ex/Em=280/455,270/465)处理下0~10 cm和10~20 cm土层中的HA荧光峰波长均有红移现象。土壤胡敏酸中包含两个组分,C1(Ex/Em=270/280)和C2(Ex/Em=440/515)同为类腐殖酸物质,胡敏酸整体腐殖化程度较高,结构较为复杂;其中EFG和TFG处理的C2组分所占比例最高,分别为28.59%和31.38%。各处理的C1和C2组分F_(max)值均较CK有所增加,即腐殖化程度增加。综上所述,EFG处理(隔一年深松+每年秸秆还田)通过提升土壤有机碳及腐殖酸类物质含量,增加腐殖化程度,加强了土壤的供肥能力,为黑龙江黑土区较佳的耕作技术措施。

负载腐植酸生物炭对矿区土壤淋溶液中Mn^(2+)吸附性能的影响

利用玉米秸秆基生物炭(CSB)负载腐植酸制备腐植酸改性生物炭(CSB-HA),用于吸附矿区土壤淋溶液中Mn^(2+)并分析其吸附特性。借助SEM、BET、XRD、XPS和FT-IR等方法对制备得到的样品进行表征分析,CSB-HA比表面积为7.911 m^(2)/g,孔隙以介孔居多。优良的孔隙结构提供大量吸附点位,并促进与污染物的接触,使吸附性能提升。CSB-HA表面富含C=O、O=C—O和—COOH等含氧官能团,其中氧原子能与重金属离子进行络合配位形成配位键,从而去除Mn^(2+)。CSB-HA对Mn^(2+)的最大吸附量为21.493 mg/g,准一级动力学模型、准二级动力学模型、Langmuir等温式和Temkin等温式能较好拟合吸附过程,Temkin常数b<1 kJ/mol,能证明吸附过程存在物理吸附。准二级动力学模型和Langmuir等温式拟合度更高且更接近实际检测值,故吸附过程为单分子层吸附,受物理吸附和化学吸附共同作用,且化学吸附占主导地位。因此含氧官能团种类和质量分数对CSB-HA吸附Mn^(2+)产生重要影响。由液膜扩散模型和颗粒内扩散模型分析扩散过程,液膜扩散模型拟合线与纵轴截距较小,因此该过程不是控速阶段。颗粒内扩散模型可拟合为膜扩散阶段(0~60 min)和颗粒内扩散阶段(60~240 min),后者吸附速率明显降低(k_(id1)=1.159>k_(id2)=0.287),且拟合线均不通过原点,故颗粒内扩散阶段是吸附过程的控速关键阶段。热力学模拟中,分离系数R_(L)均在0.4~0.6,ΔH=15.41 kJ/mol>0,且ΔG均为负数并随温度升高而减小,表明吸附过程是可逆且自发吸热的,升温能促进吸附反应进行。ΔS=49.90 J/(mol·K)>0,证明吸附过程中固液界面随机性增加。模拟淋溶液吸附实验表明CSB-HA吸附Mn^(2+)效果较好且对淋溶液pH有调节作用。

不同pH值对牛粪-小麦秸秆好氧堆肥过程中碳转化特征及腐熟度的影响

为探究不同pH对牛粪-小麦秸秆好氧堆肥过程中碳素转化规律以及堆肥产品腐熟度的影响,以牛粪和小麦秸秆为主要原料,采用密闭式强制通风系统进行好氧堆肥试验,设置4个不同pH处理。T1:CK(常规堆肥),pH=8.74;T2:pH=8.5;T3:pH=7.5;T4:pH=6.5,研究不同pH值对牛粪牛粪-小麦秸秆好氧堆肥过程中堆肥总有机碳、可溶性有机碳、腐殖酸及其组分含量和腐殖化参数的影响。结果发现:pH的不同导致了堆体温度的不同,堆体初始pH=6.61时将延迟堆体进入高温期,进而影响堆肥进程;在整个堆肥过程中,T1~T4处理TOC含量分别减少了29.36%、28.58%、27.36%和28.64%,堆体的初始pH较高易造成好氧堆肥中碳素的损失,降低堆体pH有利于堆肥腐熟期堆体内微生物对纤维素、半纤维素和木质素等物质分解、促进可溶性有机碳和胡敏酸的生成与积累、提高腐殖酸类物质含量以及堆肥产品的腐殖聚合度和腐殖化系数。当堆体初始pH=7.73时,更有利于堆肥过程中可溶性碳与腐殖酸类物质的生成与积累以及胡敏酸与富里酸之间的转化,并且堆肥产品的腐熟度最高,堆肥品质最佳。因此,建议以畜禽粪便为堆肥原料的堆肥配料制作中应添加酸式添加剂或碱式添加剂调节堆体pH,将堆体pH调至7.73左右最佳。试验结果可为更好地研究好氧堆肥过程中碳素的转化规律和高效利用以及改良堆肥工艺参数提供参考。

伊敏褐煤腐植酸结构特征及其分子模型构建

从褐煤中提取腐植酸对于实现褐煤的清洁高效利用具有重要的意义,而探究蒙东地区褐煤腐植酸结构并构建相应的分子模型对于该地区褐煤应用具有广泛的指导作用。采用碱溶酸析法提取蒙东伊敏褐煤的腐植酸,通过采用X射线衍射、^(13)C核磁共振以及X射线光电子能谱等方法对腐植酸的结构特征进行全面表征。结果表明:伊敏褐煤腐植酸中的芳香结构是基础,而脂肪结构主要以交联键以及侧链形式存在;褐煤腐植酸中的芳香团簇尺寸较小,芳香层间距相对较大,且呈现无序排列。根据结构表征相关参数,重构了具有代表性的中国蒙东伊敏褐煤腐植酸分子模型。所构建的伊敏褐煤腐植酸分子结构模型计算数据与实验数据大体吻合,能够充分反映伊敏褐煤腐植酸的化学结构特点。模型中芳香碳结构主要以苯、萘环的形式呈现,少量以菲环形式的存在;脂肪碳主要以较短的侧链和脂肪环形式存在,起到连接芳香基本结构单元的作用。氧元素主要以羧基和酯等O—C=O形式存在,同时还包括一定量的酮、醛、醌、酚、醇以及醚氧,其中羰基C O和醚氧具有交联作用。氮元素则主要以吡咯环的形式存在,并伴有少量的吡啶环和季氮。与西南地区云南褐煤腐植酸结构相比,伊敏褐煤中的芳香碳含量更高且吡咯含氮官能团所占比例也更大,并呈现出一定的地区差异性。

腐植酸基炭材料的制备及其应用研究进展

腐植酸基炭材料是一种以腐植酸为主要原料制备而成的新型碳材料,近年来在农业、环保、能源等领域中发挥了重要作用。其制备方法多种多样,包括热解、碱活化、物理混合等。综述了腐植酸基炭材料的制备方法,评估了不同制备方法的优势及局限性,并分析了各种方法对特定应用场景的适用性,同时总结了腐植酸基炭材料的应用实例,对其发展方向进行了展望,以期为腐植酸基炭材料的深入研究与发展提供参考。

基于生物滤池的炼化企业反渗透浓水处理研究

在炼化企业进行侧线试验考察反硝化生物滤池和碳基曝气生物滤池(CBAF)组合工艺对炼化企业污水回用过程中产生的反渗透浓水中总氮和有机物的去除效果,并分析处理过程中的有机物变化情况。结果表明:组合工艺可以有效去除反渗透浓水中的总氮(平均去除率为51.25%),降低化学需氧量(降低幅度为59.44%);反渗透浓水中主要污染物为腐殖酸类物质和溶解性微生物代谢产物,通过CBAF工艺处理后的污水中主要污染物的荧光强度显著降低;经过CBAF处理后,小分子酸类物质、构造块、小分子中性类物质、腐殖酸类物质和生物聚合物等亲水性有机碳的浓度分别可以降低81.65%,68.58%,63.85%,60.83%,49.30%;同时,由于载体的吸附作用,CBAF反应器对亲水性、疏水性有机碳都有较高的去除率(分别为64.20%和74.58%)。

Rapid, Semi-Automated Fractionation of Freshwater Dissolved Organic Carbon Using DAX 8 (XAD 8) and XAD 4 Resins in Tandem

Natural dissolved organic carbon (DOC) consists of different bio-molecular classes of compounds that are currently very difficult and time-consuming to isolate as individual compounds. However, it is possible to separate natural DOC into hydrophobic and hydrophilic fractions. Such characterisation approaches are becoming increasingly important because, over the past 20 years natural DOC concentrations have been rising rapidly in many parts of the world, most likely influenced by climate change. Higher DOC concentrations in drinking water catchments present a serious problem for the water industry because DOC can form disinfection by-products DBPs during water treatment (e.g. chlorination). Hence, there is an urgent need to better characterise natural DOC before, during and after water treatment. However, current DOC fractionation procedures are extremely laborious requiring days and continual manual monitoring to separate sufficient quantities of DOC for subsequent analysis. This seriously limits sample throughput and the parameter space which can be studied. In this paper, we propose a much more rapid semi-automated method (12.5 hours/litre/sample) which utilises readily available equipment, i.e., HPLC pump or similar and sequential columns of Amberlite DAX 8 and XAD 4 resins. The method reduces the manual input from continual attention to minutes. This paper describes the development of the method and its application in the fractionation of natural DOC from reservoir and lake samples fed from upland peat-land catchments. Recoveries are found to be comparable to those using the manual technique, with the dominant component being hydrophobic acid accounting for 35% - 40% of the natural DOC with the second largest, being hydrophilic acid at 20% - 27%.

Different Carbon Fractions in Soils and Their Relationship with Trace Elements Content

Luvisols, Stagnogleys and Cambisols, although less fertile, are used intensively for mixed farming, grazing and as forestland. Therefore we aimed our study at determination of total organic carbon （TOC） content, humic substances （HS） content, humic acids （HA） content, fulvic acids （FA）, hot water extractable carbon （Chw） content and content total and labile trace elements content. Humic substances quality was assessed by HA/FA ratio and by coloured indexes measured in ultraviolet and visible UV-VIS spectral range. The total and labile contents of Zn, Cd, Cu, Co, Pb, Mo and Se were determined by flame or electro-thermal atomic absorption spectrometry after extraction of the soil samples in the aqua regia （total content） and in the solution of 0.01 M CaCI2. Total and labile trace elements content was correlated with determined carbon fractions and soil reaction. Results showed that studied soils content low amount of TOC and had low quality of humic substances. HA/FA ratio was less than 1 and colour indexes were higher than 4. All determined carbon fractions correlated with labile form of Zn and Cd. Correlation between soil reaction and total zinc content was found. Significant effect of humic substances content on to water-soluble forms of heavy metals was detected.

化肥减量配施腐植酸对玉米碳氮代谢及干物质量的影响

本研究设置CF(常规化肥+150 kg/hm^(2)硫酸钾)、0.85 CF(85%常规化肥配施50 kg/hm^(2)硫酸钾和400 kg/hm^(2)腐植酸钾)和0.70CF(70%常规化肥配施600 kg/hm^(2)腐植酸钾)3个处理,于2019—2020年连续两年在黑龙江大庆进行玉米盆栽试验,分析化肥减量配施腐植酸对玉米碳氮代谢相关指标及生物量的影响。结果表明,与CF相比,0.85CF和0.70CF处理叶片蔗糖磷酸合成酶(SPS)活性显著提高22.7%~84.4%和26.6%~131.3%,蔗糖合成酶(SS)活性显著提高17.8%~135.7%和68.1%~139.8%,转化酶(INV)活性分别提高13.7%~28.7%和16.7%~23.4%,还原糖、可溶性糖和淀粉含量分别显著提高12.4%~29.1%、25.4%~72.8%和52.9%~144.8%。0.85CF处理叶片硝酸还原酶(NR)活性较CF处理显著提高45.0%~49.8%;施用腐植酸处理的叶片谷氨酰胺合成酶(GS)和谷氨酸合成酶(GOGAT)活性较CF处理分别显著提高10.4%~48.3%和27.1%~55.5%,加速氮素同化转化过程;0.85CF和0.70CF处理叶片可溶性蛋白含量较CF处理分别显著提高15.0%~24.2%和26.9%~52.5%。0.85CF和0.70CF处理两年间单株干物质量较CF处理分别显著提高112.3%、88.8%和106.2%、120.8%。本研究中,化肥减量配施腐植酸增强玉米碳氮代谢活性,增加玉米植株地上部干物质量,且85%常规化肥施用量配施400 kg/hm^(2)腐植酸钾(0.85CF)效果更优,可作为东北黑土区玉米绿色高效栽培的推荐施肥量。

化肥减量条件下秸秆还田配施腐植酸对玉米碳氮代谢的影响

【目的】秸秆直接全量还田技术在东北黑土区农业生产中被广泛应用,但关于还田秸秆腐解过程对当季作物的直接影响及其配套技术研究较少。对秸秆与腐植酸互作效应的研究可为完善东北黑土区秸秆还田技术提供参考。【方法】在减少15%化肥常规施用量的基础上,以化肥常量施肥(CF)为对照,设置化肥减量15%增施腐植酸(HA)、化肥减量15%增施秸秆(SR)、化肥减量15%增施腐植酸和秸秆(SRH)处理,研究玉米秸秆还田配施腐植酸对当季玉米植株碳氮代谢的影响,以期明确秸秆还田及腐植酸对化肥减量情况下玉米生长的生理效应。【结果】秸秆还田提高了玉米叶片磷酸烯醇式丙酮酸羧化酶(PEPC)活性,腐植酸提高了玉米叶片1,5-二磷酸核酮糖羧化酶(Rubisco)和PEPC活性,秸秆还田配施腐植酸在PEPC活性上具有互作效应。虽然秸秆还田降低了蔗糖磷酸合成酶(SPS)活性,但腐植酸提高了SPS活性,两者均提高了蔗糖合成酶活性,且两者互作下同步提高了酸性转化酶(AI)和中性转化酶(NI)活性,促进了还原糖(RS)合成,进而提高了总可溶性糖(TSS)含量,加强了淀粉合成。秸秆还田对玉米植株氮代谢无直接影响,腐植酸对氮代谢关键酶活性具有正效应。【结论】秸秆还田配施腐植酸提高了化肥减量条件下玉米叶片光合效率和光合产物的贮存能力,植株氮代谢水平不低于常规施肥对照。

黑龙江省半干旱区秸秆还田方式对土壤胡敏酸碳含量及胡敏酸荧光结构特征的影响

为促进黑龙江省西部半干旱区地力提升和秸秆综合利用,以黑龙江省农业科学院齐齐哈尔分院秸秆长期定位试验田为研究对象,对CK(常规种植)、FM(秸秆翻埋还田)和FG(秸秆覆盖还田)3种处理下胡敏酸碳(HAGC)含量和荧光结构进行分析.结果表明,FM和FG处理下土壤胡敏酸碳含量和胡富比(HA/FA)均表现为随着土层加深呈下降趋势,而富里酸碳(FAGC)变化无明显规律.各处理土壤胡敏酸三维荧光光谱具有类似指纹图谱特征,均出现1个主要荧光特征峰.与CK相比,FG和FM处理HA荧光峰波长均有红移现象(激发/发射波长变大).C1和C2组分包含的物质均为类腐殖酸物质.比较各处理C1组分和C2组分类腐殖酸物质的Fmax值可知,FM>FG>CK.其中FM处理下的类腐殖酸组分Fmax值最大,但不同处理间无显著差异.综上所述,秸秆翻埋还田和覆盖还田均可通过提升土壤胡敏酸碳含量,提升腐殖酸类物质含量增强土壤的保肥能力,其中以秸秆翻埋处理效果最佳.

GO/PDA/CNT双层低压膜去除腐殖酸及抗污染性能

腐殖酸(Humic acid,HA)是水体中常见的膜污染物质和消毒副产物前驱体.通过真空抽滤将碳纳米管(Carbon nanotubes,CNTs)和氧化石墨烯(Graphene oxide,GO)负载于基膜表面,结合聚多巴胺(Polydopamine,PDA)的交联黏合功能,制备了GO/PDA/CNT双层低压膜.采用ATR-FTIR分析证实了PDA在GO膜表面的聚合,通过超声破碎验证了双层膜的稳定性.结果表明,GO/PDA/CNT双层膜性能稳定,渗透通量达到1238 L/(m^(2)·h·MPa),高于GO膜的279 L/(m^(2)·h·MPa).该膜对HA的去除率达到88.5%,均高于GO膜(85.8%)和CNT膜(38.9%).GO膜和CNT膜的比通量在过滤HA过程中分别降至0.314和0.697,GO/PDA/CNT双层膜的比通量下降幅度最小(0.753).提高搅拌速率有利于双层膜对HA的去除并进一步缓解膜污染,但搅拌速率过高会加剧膜污染;酸性条件下双层膜对HA去除率最高(94.5%),膜污染相较于中性和碱性条件更为严重.GO/PDA/CNT双层膜的制备,有助于提高膜滤效率和强化腐殖质类有机物的去除,减少消毒副产物的产生.