Oral Low-Molecular Weight Hyaluronic Acid in the Treatment of Atrophic Vaginitis

The aim of this study was to evaluate the effectiveness of low molecular weight hyaluronic acid oral tablets for the treatment of atrophic vaginitis. 12 women with atrophic vaginitis were recruited for this double blind, placebo-controlled study. Patients were randomized to receive either low molecular weight hyaluronic acid (HA) oral tablets or placebo for three months. Vaginal biopsies were taken at baseline and after three months of treatment, and vaginal epithelium was analysed using light microscopy. The evaluation of symptoms was self-assessed by the patients. Biopsies from HA group showed an epithelium thicker than in placebo group. The lamina propria from the HA group also showed a denser appearance compared to placebo group. Morphometric analysis showed significant differences between HA and baseline in the number of epithelial layers and in the thickness. The evaluation of symptoms also showed an effective improvement in the patients treated with HA, compared to baseline and to placebo group. In conclusion, oral administration of HA tablets improved the vaginal epithelium, decreasing atrophy. This can be an ideal option for patients with atrophic vaginitis who do not want to or can not take estrogen and show low compliance toward vaginal administration.

Exploring the relationship of hyaluronic acid molecular weight and active targeting efficiency for designing hyaluronic acid-modified nanoparticles

Although it is reported that the targeting ability of hyaluronic acid(HA)-based nanoparticles(NPs) is molecular weight(MW) dependent,the influence of HA MW on targeting efficiency of HA-functionalized NPs and the underlying mechanism remain elusive. In this study,we constituted three HA-functionalized Dox-loaded NPs(Dox/HCVs) different HA MWs(7,63,and 102 k Da) and attempted to illustrate the effects of HA MW on the targeting efficiency.The three Dox/HCVs had similar physiochemical and pharmaceutical characteristics,but showed different affinity to CD44 receptor. Furthermore,Dox/HCV-63 exerted the best targeting effect and the highest cytotoxicity compared with Dox/HCV-7 and Dox/HCV-102. It was interesting to found that both the HA-CD44 binding affinity and induced CD44 clustering by HA-based NPs were HA MW-dependent,the two of which determine the apparent targeting efficacy of Dox/HCV NPs in the conflicting directions. Those results laid a good foundation for rationally designing HA-based NPs in cancer therapy.

Characteristics and distribution of low molecular weight organic acids in the sediment porewaters in Bosten Lake, China

The composition and vertical profiles of low molecular-weight organic acids （LMWOAs） and the contribution of them to dissolved organic matter （DOM） in sediment porewaters in Bosten Lake, Xinjiang, China were investigated. The results showed that total concentration of LMWOAs was up to 94.5 μmol/L and their proportion in DOM was 5.6%, suggesting that LMWOAs were important chemical components in DOM in lake sediment porewaters. Among the seven LMWOAs, pyruvic and acetic acid had the highest concentrations with 26.30 and 8.31 μmol/L, accounting for 51.4% and 14.92% of LMWOAs, respectively. Trifluoroacetic and sorbic acid had the lowest concentrations, indicating that the compositions of LMWOAs in relative reducing environments were largely different from those reported in glacier, atmosphere and soils. The concentrations of lactic, acetic, formic, sorbic and oxalic acid decreased with increasing depth, probably relating to stronger microbial activities in the initial stage of early diagenesis. Trifluoroacetic acid was mainly anthropogenic with its concentration, showing a diusive trend from the surface to bottom sediments. The concentrations of lactic acid and nitrate generally showed a consistent profile. The increasing concentration of pyruvic acid in the vertical profile was just opposite to that of sulfate, revealing a significant negative relationship between them. Oxalic acid remained constant except for an obvious peak at 6 cm depth. The results indicated the diversities in sources and behaviors for various LMWOAs during early diagenesis in sediments.

Utilizing Water Treatment Residuals for Phosphorus Removal:Batch Trials,Column Trials and Effects of Three Low-Molecular-Weight Organic Acids

Phosphorus( P) has been recognized as a major limited nutrient responsible for the eutrophication of surface waters. Water treatment residuals( WTRs) are safe by-products of water treatment plants and are cost-efficient adsorbents. In this study, batch experiments and column experiments based on WTRs were employed to study the characteristics of P adsorption and the effects of lowmolecular-weight organic acids( LMWOAs)( citric acid, oxalic acid,and tartaric acid) on P adsorption. Different models of adsorption were used to describe equilibrium and kinetic data. The adsorption data were fitted well by a pseudo-second order kinetic model. The adsorption process was determined to be controlled by three steps of diffusion mechanisms through the intra-particle model.The adsorption equilibrium was well described by the Langmuir,Freundlich,Redlich-Peterson,and Sips isotherm models. Batch and continuous flow experiments indicated that the LMWOAs exhibited inhibitory action,and as pH increased,the inhibitory action became weaker for all the three acids. The effect of LMWOAs concentration was not significant on inhibition. The effects of LMWOAs were closely related to reaction time.

Preparation and Characterization of AlginateHyaluronic Acid-chitosan based Composite Gel Beads

The aim of this study was to fabricate composite gel beads based on natural polysaccharides. Hyaluronic acid（HA） and Chitosan（CS） were successfully admixed with Ca^2＋/alginate（SA） gel system to produce SA/HA/CS gel beads by dual crosslinking： the ionic gelation and the polyelectrolyte complexation. The preparation procedure was that the weight ratio of SA（2%, m/v） to HA（2%, m/v） was kept at 2：1, then the mixture was dripped into the Ca^2＋ solution for ion-crosslinking, and finally polyelectrolyte crosslinked with 2% low molecular weight CS（LMW-CS） for 1.5 hours. The optimal formulation was achieved by adjusting the concentration and the weight ratio of SA, HA and LMW-CS. Due to the incorporation of HA and LMWCS, the swelling ratio of the beads at pH 7.4 was increased up to 120, and the time for the maximum swelling degree was prolonged to 7.5 h. The swelling behavior was obviously improved compared to the pure SA/Ca^2＋ system. The preliminary results clearly suggest that the SA/HA/CS gel beads may be a potential candidate for biomedical delivery vehicles.

低分子量有机酸对亚热带地区典型土壤磷吸附的影响

为探索低分子量有机酸对亚热带地区典型土壤磷吸附的影响,采用批处理法研究了柠檬酸和草酸对旱地土、水稻土磷素吸附特征的作用,重点探讨了不同浓度有机酸和柠檬酸钠、有机酸加入顺序等对土壤磷吸附的影响。结果表明:柠檬酸和草酸显著降低了土壤磷吸附动力学的颗粒内扩散模型拟合度,减弱了磷素在土壤颗粒内部扩散过程。Langmuir和Freundlich方程对有机酸存在下土壤磷吸附等温数据均有较好的拟合效果(R2=0.863~0.996)。有机酸降低了土壤磷素最大理论吸附量。土壤磷吸附量与有机酸浓度呈指数函数关系,0.1~5 mmol/L有机酸对土壤磷吸附的影响最大。有机酸浓度小于1 mmol/L时,柠檬酸对土壤磷素吸附的抑制程度大于草酸;而当浓度大于5 mmol/L时,草酸的抑制程度更大。在相同浓度时,0.1~5 mmol/L的柠檬酸钠比柠檬酸对土壤磷吸附能力抑制程度更大,先加入有机酸进一步降低了土壤对磷素吸附量,说明阴离子竞争吸附是低浓度柠檬酸降低土壤磷吸附能力的主要原因,而柠檬酸浓度为5~50 mmol/L时,有机酸与土壤铁铝等金属离子的络合作用占主导。

非交联透明质酸分子质量降解的机制及影响因素

背景:不同分子质量的透明质酸其结构、理化性质(如流变性质)与生物活性有较大差异,当非交联透明质酸降解程度过大,由高分子质量透明质酸降解为低分子质量透明质酸时,产品的性质与生物功能也会随之改变,从而对产品使用造成影响。目的:综述非交联透明质酸分子质量降解机制以及分子质量降解对非交联透明质酸结构、流变性质、生物活性和应用的影响。方法:由第一作者检索PubMed、中国知网数据库和其他数据库中收录的与透明质酸分子质量相关的文献,根据纳入与排除标准筛选相关度高的优质文献后。检索时间为2017年1月至2022年12月,英文检索词为“hyaluronic acid,non-cross-linked hyaluronic acid,molecular weight,degradation,structure,rheological properties,biological activity”,中文检索词为“透明质酸,非交联透明质酸,分子量,降解,结构,流变性质,生物活性”,最终纳入47篇文献进入综述分析。结果与结论:①非交联透明质酸主要通过特异性酶解作用和非特异性自由基降解作用两种途径实现体内分子质量降解。②非交联透明质酸分子质量降解会改变其结构与流变性质,造成聚合物网络结构解开,黏性、黏弹性等流变性质降低,机械性能下降,从而影响产品的实际应用效果。③非交联透明质酸的生物活性具有分子质量依赖性,不同分子质量透明质酸的生物活性不同,甚至高分子质量透明质酸和低分子质量透明质酸与同一受体结合会表现出完全相反的生物效应。④非交联透明质酸分子质量降解会降低产品的安全性和有效性,影响产品的使用寿命与应用性能,最终影响临床应用效果。⑤非交联透明质酸作为可降解生物材料在伤口愈合、组织工程及美容医学等领域具有极高的应用潜力,深入研究与理解非交联透明质酸分子质量降解特性与生物活性之间的关联也是更好地开发伤口敷料、药物递送系统与组织工程支架等领域应用的前提。⑥但目前针对非交联透明质酸分子质量降解的相关研究较少,对于如何有效避免在临床应用时非交联透明质酸分子质量降解带来的潜在风险尚不明确。⑦因此,对于非交联透明质酸在应用过程中分子质量降解引发的一系列潜在风险,包括对于其结构、性质及生物活性的影响以及由此对机体造成的改变是今后需密切关注的方向之一。

低分子量酶解灵芝硒多糖对小鼠肠道菌群的影响

目的研究低分子量灵芝硒多糖对肠道菌群紊乱小鼠的改善调节作用。方法利用生物发酵法培养富集灵芝硒多糖,采用热水浸提法提取灵芝硒多糖,并进一步酶解为低分子量多糖,以水解率为响应值,在单因素基础上,用响应面法优化酶解工艺条件。随后使用超滤膜截取10 kDa以下多糖,以头孢克肟诱导建立肠道紊乱小鼠模型,灌胃低分子量灵芝硒多糖,并测定小鼠体重及肠道内容物短链脂肪酸含量,利用16S rRNA高通量测序分析小鼠肠道菌群变化。结果灵芝硒多糖的富硒量为(327±26)mg/g,多糖含量为(6.14±0.18)%,低分子量多糖的酶解最优工艺为温度50℃、pH 5.5、时间121 min,该条件下的水解率为62.8%。研究表明低分子量多糖对小鼠体重无影响,高通量测序结果显示低分子量灵芝硒多糖能有效改善肠道菌群失调症状,调节肠道菌群的物种组成,显著上调厚壁菌门(Firmicutes)丰度,降低拟杆菌门(Bacteroidetes)丰度,上调产酸菌乳杆菌属(Lactobacillus)、布劳特氏菌属(Blautia)、链球菌(Streptococcus)、样棒菌属(Allobaculum)、颤螺菌属(Oscillospira)等丰度,增加乙酸、丁酸含量,下调普雷沃氏菌(Prevotella)、拟杆菌属(Bacteroides)、梭菌属(Clostridium)、粪球菌属(Coprococcus)、瘤胃球菌属(Ruminococcus)丰度,抑制丙酸分泌。结论低分子量灵芝硒多糖具有改善小鼠肠道菌群失调作用,可能是通过调整菌群组成来影响短链脂肪酸分泌达到保护肠道健康的目的。

透明质酸的制备、功能特性及其调节肠道健康的研究进展

透明质酸(HA)是一种非硫酸化糖胺聚糖,2021年获批为新食品原料后,引起食品科研人员与产业界的广泛兴趣。近年来,越来越多的研究显示,HA的生物活性根据其分子质量的不同,发挥促炎或抗炎、促细胞增殖或抗增殖作用。为了高效、精准地提高HA在食品中的应用价值,有必要根据分子质量的差异性,全面归纳总结HA在食品相关领域的研究进展。本文概述HA的应用开发进展,重点分析不同分子质量HA的制备方法、细胞功能、消化吸收特性,从维持稳态、缓解炎症两个维度分析HA对肠道的调节作用,以期促进HA在营养与健康产业的精准开发及应用。

多次低剂量应用草酸促进芹菜减磷生产

针对蔬菜作物生长期一次性低剂量应用草酸土壤磷素活化作用时效短和一次性高剂量应用草酸风险较大的缺点,选用多次低剂量灌溉应用草酸的方法,以期持续、安全地活化设施菜地土壤盈余磷素,推动设施蔬菜减磷生产。选用速效磷含量分别为88.6和46.1mg·kg^(−1)的两个设施菜地土壤(分别简称土壤A和土壤B)开展室内浅层土壤(深度为1 cm)培养试验、无植物和种植芹菜的盆栽土壤(深度17 cm)温室试验,探究多次低剂量应用草酸活化土壤磷素及促进芹菜生产效果。土壤培养试验揭示多次低剂量灌溉应用草酸(每次草酸应用0.36 g·kg^(−1),共5次,每次间隔10 d)均可以持续、平稳地提高土壤A和土壤B的水溶性无机磷(DIP)的含量。无植物的盆栽土壤试验则显示在土壤A中多次低剂量灌溉应用草酸的土壤磷素活化作用集中在0~10 cm土层,特别是0~5 cm土层。盆栽芹菜试验多次应用草酸(芹菜定植30 d应用草酸4次,每次0、0.18或者0.36 g·kg^(−1),每次间隔10 d)的结果显示,土壤A和土壤B施磷分别减量70%和54%的前提下,两个草酸应用剂量均提高芹菜收获时两个土壤0~5 cm土层的DIP含量,在土壤A中增幅显著(分别为92.0%和165%),在土壤B中仅较高草酸剂量下显著增加64.5%;较高草酸剂量的芹菜增产效果不明显,较低草酸剂量的增产效果显著(20.0%~33.6%,P<0.05),在土壤B中更为明显。多次低剂量灌溉应用草酸在其它土壤-蔬菜系统中的效果及风险有待研究。

柠檬酸改性低分子量减水剂的合成、性能及机理

以柠檬酸(CA)和聚乙二醇聚丙二醇单甲醚(MPEPPG)为主要反应原料,通过酯化反应合成一种柠檬酸改性低分子量减水剂(LMWS)。通过红外光谱、核磁氢谱和凝胶色谱测试获得合成减水剂的结构参数信息。同时通过动态光散射(DLS)、水泥净浆Zeta电位、减水剂对水泥的吸附性能、水泥净浆凝结时间、水泥水化热、水泥净浆塑性粘度、水泥净浆流动度及混凝土性能等研究对比了相同酸醚比(n(CA)∶n(MPEPPG)=1∶1)时不同分子量LMWS的综合性能。结果表明:相同掺量条件下,分子量适中的LMWS-3显著降低水泥净浆的塑性粘度并延缓水泥的水化进程,具有优异的初始分散和分散保持性能。

离子色谱法同时测定低分子量肝素钠注射液中的有机酸和无机阴离子

目的建立同时测定低分子量肝素钠注射液中醋酸根离子、氯离子、亚硫酸根离子、硫酸根离子和草酸根离子含量的离子色谱法。方法色谱柱为Dionex IonPac AS11(250 mm×4 mm),保护柱为Dionex IonPac AG11(50 mm×4 mm),用淋洗液自动发生器,采用氢氧化钾梯度洗脱,流速为1.0 mL·min^(-1),检测器为配有化学抑制器的电导检测器。结果醋酸根离子、氯离子、亚硫酸根离子、硫酸根离子和草酸根离子分别在0.12~24μg·mL^(-1)、0.24~48μg·mL^(-1)、0.4~80μg·mL^(-1)、0.04~8μg·mL^(-1)、0.3~60μg·mL^(-1)与测定值线性关系良好,r分别为0.9991、0.9999、0.9999、0.9995、0.9995;加样回收率分别为105.3%、101.0%、102.3%、96.8%和108.3%(n=6),RSD分别为2.2%、1.8%、1.6%、2.6%和1.6%。结论该方法操作简便,灵敏,高效,可用于同时测定低分子量肝素钠注射液中醋酸根、亚硫酸根、硫酸根、草酸根和氯离子的含量,为其质量提供保证。

氨甲环酸分别联合阿司匹林、低分子肝素钙在全膝关节置换术血液管理中的效果分析

目的探讨氨甲环酸分别联合阿司匹林、低分子肝素钙调控炎症介质、血栓弹力图(TEG)在全膝关节置换术(TKA)血液管理中的价值。方法2020年1月~2022年10我院拟行TKA老年病人120例,电脑随机数字法分为A组(60例)和B组(60例),分别给予氨甲环酸+阿司匹林、氨甲环酸+低分子肝素钙,均治疗2周。比较两组围术期指标、并发症[下肢深静脉血栓(DVT)、肌间静脉血栓(MCVT)、切口感染]、输血率、不良反应(胃肠不适、皮下瘀斑)及TEG参数[凝血反应时间(R)、血液凝固时间(K)、最大振幅(MA)、凝固角(α角)]、炎症介质[可溶性CD40配体(sCD40L)、Toll样受体4(TLR4)、肿瘤坏死因子(TNF)-α]、血管内皮损伤因子[可溶性血栓调节蛋白(sTM)、血管内皮细胞生长因子(VEGF)、E-选择素]。结果两组术后24小时引流量、隐性失血量、总失血量、术中出血量、术后72小时Hb及HCT水平比较,差异无统计学意义(P>0.05);两组组间、不同时间点及组间·不同时间点交互TEG参数比较,差异无统计学意义(P>0.05);术后2周A组血清TLR4、sCD40L、TNF-α水平较B组降低,血浆sTM及血清VEGF、E-选择素水平较B组降低,差异有统计学意义(P<0.05);A组DVT、MCVT、切口感染发生率、输血率与B组比较,差异无统计学意义(P>0.05);A组不良反应总发生率与B组比较,差异无统计学意义(P>0.05)。结论与联合低分子肝素钙比较,氨甲环酸联合阿司匹林能保护血管内皮,抑制炎症反应,但两者均可维持病人凝血功能,避免大量失血或血栓形成,在安全性与有效性方面无显著差异。

不同分子量透明质酸对牙周膜细胞成骨分化的影响

目的:比较人牙周膜细胞(PDLCs)对4种不同分子量透明质酸(HA)的生物学反应。方法:将人牙周膜细胞(PDLCs)在培养基中单独培养21d(对照组)或添加成骨诱导(OS组)。其余4个实验组分别在OS培养基中添加不同分子量的HA:超低分子量透明质酸组(ULMWHA)、低分子量透明质酸组(LMWHA)、中分子量透明质酸组(MMWHA)和高分子量透明质酸组(HMWHA)。每天检查细胞形态。VonKossa染色和钙沉积法定性及定量分析不同分子量HA刺激下PDLCs的成骨分化和矿化。结果:随着时间的推移,单独使用OS或添加HA刺激的细胞显微镜下显示典型的成骨分化的外观。刺激21d后,各组均出现矿物沉积和钙沉积,其中LMWHA组表现出最显著的钙沉积。结论:透明质酸可以促进PDLCs的矿化,其中LMWHA作用较大。

不同有机酸对石灰性土壤磷的活化效应及机理

【目的】添加低分子量有机酸是活化土壤难溶性磷有效途径。比较研究几种低分子量有机酸及其组合对土壤磷的活化性能,为土壤磷的高效利用提供依据。【方法】低磷和高磷石灰性土壤选自新疆石河子,设置5个低分子有机酸添加处理:草酸、柠檬酸、黄腐酸、柠檬酸+草酸、草酸+柠檬酸+黄腐酸处理,和一个0.01mmol/L KCl对照。采用吸附平衡实验法测定土壤磷的吸附量;采用土壤吸附动力学实验法测定土壤磷的解吸动力学。采用常规和灭菌土壤培养方法,通过连续浸提法研究低分子有机酸及其组合对磷组分动态转化的影响和pH对磷的活化效应。【结果】Langmuir与Elovich模型均可较好地拟合土壤对磷的吸附热力学(R^(2)=0.852~0.994)与吸附动力学过程(R^(2)=0.882~0.975)。低磷土壤的最大吸附量(Q_(max))、最大缓冲容量(MBC)、吸附力常数(K_L)和吸附速率(b)均高于高磷土壤,表明低磷土壤对磷的吸附更强。低分子量有机酸添加均降低了Q_(max)、MBC和b。草酸对Q_(max)和MBC的降幅最大,低磷土壤降幅分别为28.5%和74.9%,高磷土壤分别为14.7%和73.3%。柠檬酸对低磷土壤的b值降幅最大(80.9%),草酸对高磷土壤的b值降幅最大(22.0%)。与CK相比,草酸添加显著提高了Olsen-P含量,草酸+柠檬酸效果次之,黄腐酸对磷的活化效果最差。不灭菌培养条件下,草酸和草酸+柠檬酸处理低磷土壤的Olsen-P含量分别增加了42.6%和18.5%,高磷土壤分别增加了27.3%和1.01%;草酸和草酸+柠檬酸处理的活性磷组分Resin-P在低磷土壤中分别增加了80.9%和77.4%,在高磷土壤中分别增加了79.5%和72.8%;非活性磷组分Di HCl-P在低磷土壤中分别降低了8.87%和5.89%,在高磷土壤中分别降低了8.83%和5.54%;Con HCl-P在低磷土壤中分别降低了25.1%和12.9%,在高磷土壤中分别降低了16.9%和5.30%。柠檬酸处理的Resin-P在低磷和高磷土壤中分别增加了70.2%和79.5%,而NaOH-P则分别降低了14.8%、26.3%,说明草酸、草酸+柠檬酸促进了非活性磷向活性磷组分的转化,柠檬酸则促进了中活性磷向活性磷组分的转化。土壤灭菌培养各处理磷组分含量与不灭菌培养无显著差异,说明微生物对有机酸活化土壤磷的效应无显著影响。不论是否灭菌,土壤Olsen-P含量的增加与pH降低呈负相关,因此致酸效应不是小分子有机酸活化土壤难溶性磷的主要机制。【结论】小分子有机酸通过与磷竞争吸附位点或进行螯合反应活化土壤磷,而不是通过致酸效应或激发磷活化相关的微生物。3种小分子有机酸相比,草酸活化磷的效果最大,其次是柠檬酸、黄腐酸,单一有机酸的活化效果大于有机酸组合。

A review of environmental characteristics and effects of low-molecular weight organic acids in the surface ecosystem

Low molecular weight organic acids （LMWOAs） are prevalent on the earth＇s surface. They are vital intermediate products during metabolic pathways of organic matter and participate in the tricarboxylic acid cycle during life activities. Photochemical reactions are pivotal for LMWOAs＇ origination and play a large role in determining their diversity and their ultimate fate. Within the long time that organic matter is preserved in sediments, it can be decomposed and converted to release organic and inorganic pollutants as well as C, N, and P nutrients, which are of potential ecological risk in causing secondary pollution to lake water. The sediment pool is a comprehensive and complex compartment closely associated with overlying water by various biochemical processes, during which LMWOAs play critical roles to transport and transform elements. This article elucidates geochemical behaviors of LMWOAs in the surface environment in details, taking natural water, soil, and aerosol as examples, focusing on reviewing research developments on sources and characteristics, migration and mineralization of LMWOAs and relevant environmental effects. Simultaneously, this review article depicts the categories and contents of LMWOAs or their contribution to DOC in environmental media, and evaluates their importance during organic matter early diagenesis. Through concluding and discussing the conversion mechanisms and influencing factors, the next research orientations on LMWOAs in lake ecosystems are determined, mainly concerning relationships with hydrochemical parameters and microorganisms, and interactions with pollutants. This will enrich the knowledge on organic matter degradation and related environmental effects, and help reconstruct a theoretical framework for organic compound succession and influencing factors, providing basic data for lake eutrophication and ecological risk assessment, conducive to better control over water pollution and proper management of water quality.

Effects of low molecular weight organic acids on aggregation behavior of biochar colloids at acid and neutral conditions

Low molecular weight organic acids(LMWOAs),as active components in the rhizosphere carbon cycling,may influence the environmental behaviors of biochar colloids.This study selected the pine-wood and wheat-straw biochars(PB and WB)as two typical biochars.The effects of typical LMWOAs(oxalic acid,citric acid,and malic acid)on aggregation kinetics of PB and WB colloids were investigated under pH 4 and 6 conditions.Critical coagulation concentrations(CCCs)of both PB and WB colloids were decreased with the LMWOAs regardless of the types of biochar and the solution pH,and the most significant effect occurred in pH 4 due to more LMWOAs sorption on the biochar colloids.The different types of LMWOAs caused various CCCs changes.For example,the CCC values of PB colloids decreased from 75 mM to 56,52,and 47 mM in the pH 4 NaCl solutions when 1 mM oxalic acid,citric acid,and malic acid were present in the suspensions,respectively.The chemical structure(functional groups)and molecular weight of LMWOAs,solution pH,and the electrophoretic mobility(EPM)of biochar co-influence the interactions between biochar colloids and LMWOAs,thus affecting the stability of biochar colloids in the presence of LMWOAs.The presence of LMWOAs accelerated the aggregation of colloidal biochar by increasing the interaction of surface bridging bonds(hydrogen bonding)and decreasing the repulsive force between colloidal biochar particles.This study showed that LMWOAs could accelerate the aggregation of biochar colloids in acidic or neutral environments and reduce the mobility of biochar colloids in soil rhizosphere.

Temporal and spatial variations of low-molecular-weight organic acids in Dianchi Lake, China

Low-molecular-weight organic acids （LMWOAs） in eutrophic lake water of Dianchi, Southwestern China Plateau were investigated diurnally and vertically using ion chromatography. Two profiles （P1 and P2） were studied due to the difference of hydrochemical features. Lactic, formic, pyruvic and oxalic acid were detected as major components at P1 and P2 which were on average 7.98 and 6.53 ~tmol/L, respectively, corresponding to their proportions of 2.68% and 2.48% relative to DOC. Pyruvic acid was regarded as the uppermost species at P1 and P2, reaching up to 3.82 and 3.35 μmol/L and accounting for 47.9% and 51.3%, respectively, in individual TOA. Although humus were of biogenetic production at both sites, the significant negative correlation between diurnal variations of TOAs, fluorescence intensity （FI） of protein-like components and humic-like components at P1 indicated LMWOAs were greatly originated from bacterioplankton excretion and degradation. However, correlations between diurnal variations of humic-like FI and physicochemical parameters demonstrated algal origination of LMWOAs at P2. Although content of humus was high, TOA at P2 was 1.45 ~tmol/L lower than that at P1, due to the co-influence of more intense photo-oxidation and aggregation at P2. Therefore, TOAs exhibited quite opposite diurnal variation trends of increasing-decreasing and decreasing-increasing at P1 and P2, respectively. Except for impact of solar radiation, bacterial decomposition and assimilation rendered shifts of maximal LMWOAs along water column at P1. Covering with massive algae, UV rays penetrated shallower depth that LMWOAs assembled in surface layer water before 18：00 at P2 and represented decreasing profiles.

Investigation of low-molecular weight organic acids and their spatiotemporal variation characteristics in Hongfeng Lake,China

The identities and concentrations of low-molecular-weight organic acids （LMWOAs） were determined by ion chromatography throughout a 20-m water column in Hongfeng Lake, China. The spatiotemporal variations of LMWOAs and their contributions to dissolved organic matter （DOM） in a research period of 24 hr were also investigated. The results demonstrated that five LMWOAs （lactic, acetic, pyruvic, sorbic, oxalic acid） were detected, and their total concentration and proportion in DOC were 6.55 μmol/L and 7.47%. Their average levels were 2.50, 0.65, 2.35, 0.96 and 0.09 μmol/L, respectively. LMWOAs were higher during daytime （10：00-18：00 on Jun 13, 2008） than nighttime （21：00-6：00 the next morning）, in particular 4.99 μmol/L high in the epilimnion （ 1 m water depth）, reflecting the fact that direct import from terrigenous sources and photochemical production from humic materials were dominant during LMWOAs＇ origin and accumulation. The same factors caused LMWOAs to be 0.63 μmol/L in the epilimnion higher than in the hypolimnion. The rapid decrease of total organic acid （TOA） up until 18：00 mainly resulted from bio-uptake and mineralization in the hypolimnion （〉1 m water depth）. Pyruvic acid increased with time in the epilimnion and decreased in the hypolimnion, largely related to the two contrary processes of continuous degradation and synthesis of macromolecular organic matter during life materials＇ cycle mediated by organisms. Simultaneously, plankton behavior and thermal stratification played a pivotal role in LMWOAs＇ behavior in the water column, causing decreasing and increasing profiles. The distribution of LMWOAs represents an interesting resource for biogeochemical research of DOM in aquatic ecosystems.