多环芳烃在长江口滨岸颗粒物-水相间的分配

利用长江口滨岸水环境中颗粒相与溶解相多环芳烃的实测浓度,获取了多环芳烃化合物在颗粒物-水相间的分配系数K_p.结果表明,分配系数K_p值在507～10 179 L/kg之间,枯季高于洪季,随多环芳烃环数的增加而增大;K_oc值与辛醇-水分配系数K_ow之间存在较好的线性自由能关系（枯季R²＝0.82,洪季R²＝0.68）,推断出长江口滨岸颗粒物亲脂性较差,对多环芳烃的吸收能力相对较弱.长江口滨岸各采样点多环芳烃化合物的lgK_oc值均超过了经典平衡分配模型的预测值上限,多环芳烃两相分配行为不受颗粒物浓度、粒径及上覆水盐度、溶解态有机碳的控制（R²<0.1）,表现出主要受POC及非均一性混合物PSC共同影响的特点;扩展后的含PSC相的颗粒物-水相分配模型较为准确地模拟了lgK_ow<6的多环芳烃化合物野外原位分配过程.     

Removal of polycyclic aromatic hydrocarbons from aqueous solution by raw and modified plant residue materials as biosorbents

Removal of polycyclic aromatic hydrocarbons （PAHs）, e.g., naphthalene, acenaphthene, phenanthrene and pyrene, from aqueous solution by raw and modified plant residues was investigated to develop low cost biosorbents for organic pollutant abatement. Bamboo wood, pine wood, pine needles and pine bark were selected as plant residues, and acid hydrolysis was used as an easily modification method. The raw and modified biosorbents were characterized by elemental analysis, Fourier transform infrared spectroscopy and scanning electron microscopy. The sorption isotherms of PAHs to raw biosorbents were apparently linear, and were dominated by a partitioning process. In comparison, the isotherms of the hydrolyzed biosorbents displayed nonlinearity, which was controlled by partitioning and the specific interaction mechanism. The sorpfion kinetic curves of PAHs to the raw and modified plant residues fit well with the pseudo second-order kinetics model. The sorption rates were faster for the raw biosorbents than the corresponding hydrolyzed biosorbents, which was attributed to the latter having more condensed domains （i.e., exposed aromatic core）. By the consumption of the amorphous cellulose component under acid hydrolysis, the sorption capability of the hydrolyzed biosorbents was notably enhanced, i.e., 6-18 fold for phenanthrene, 6-8 fold for naphthalene and pyrene and 5-8 fold for acenaphthene. The sorpfion coefficients （Kd） were negatively correlated with the polarity index [（O＋N）/C], and positively correlated with the aromaticity of the biosorbents. For a given biosorbent, a positive linear correlation between logKoc and logKow for different PAHs was observed. Interestingly, the linear plots of logKoc-logKow were parallel for different biosorbents. These observations suggest that the raw and modified plant residues have great potential as biosorbents to remove PAHs from wastewater.     

卤系阻燃剂在东江工业水体中的质量浓度及其分配特征

本研究分析了东江工业水体中卤系阻燃剂的浓度,组成分布以及分配特征.结果表明多溴联苯醚(PBDEs)是水体中的主要的卤系阻燃剂,占总卤系阻燃剂的41.0%,其质量浓度范围为1 102.3~3 666.9 pg·L~(-1),其中BDE209是颗粒相的主要成分.四溴双酚A(TBBPA)占总卤系阻燃剂的32.4%,其质量浓度范围为1 120.9~2 856.5 pg·L~(-1),其他卤系阻燃剂如十溴二苯乙烷(DBDPE)、德克隆(DP)和六溴环十二烷(HBCDs)分别占总卤系阻燃剂的16.3%、7.3%和3.0%,其质量浓度范围分别为397.7~1 736.8、235.7~778.1和9.5~266.8 pg·L~(-1).在对水体溶解相和颗粒相分配的研究中发现,PBDEs、DBDPE、DP和HBCDs主要存在于水体颗粒相中,而TBBPA由于其较大的水溶性,主要存在于溶解相中;卤系阻燃剂的lgK_(oc)与lgK_(ow)之间存在显著的相关性,但是lgK_(oc)实测值与其理论预测值有一定差异,这可能是受控于悬浮颗粒(SPM)含量和溶解有机碳(DOC)含量这两个因素,此外,颗粒相和溶解相之间分配是否达到平衡也是影响测量lg Koc值的因素.     

松花江水中天然有机物的提取分离与特性表征

将反渗透与XAD大孔树脂吸附技术相结合,对松花江水中天然有机物(NOM)进行了浓缩和分离,并采用紫外光谱、红外光谱、液相凝胶色谱、官能团滴定1、HNMR核磁共振等分析手段,对松花江水中NOM及其各分离组分和一种商用腐殖酸CHA的特性进行了比较和表征.结果表明,利用反渗透进行NOM浓缩对水中有机物具有很高的回收率;松花江水中NOM组成为:富里酸>腐殖酸>亲水部分;各组分芳香性为:腐殖酸>憎水部分>富里酸>亲水部分,E₄/E₆与芳香性之间缺乏必然的联系;腐殖酸和商用腐殖酸具有较高的不饱和性,NOM和亲水部分次之,憎水部分和富里酸中饱和烃含量较多;紫外吸收较弱的有机成分对NOM分子量的贡献较大;NOM及其分离组分的总酸度为9.84～12.15meq/g,羧酸含量为CHA>亲水>憎水>NOM>富里酸>腐殖酸;NOM及其各分离组分的溶解性有机物构成以脂肪烃为主.     

多环芳烃在岩溶地下河表层沉积物-水相的分配

利用实测老龙洞地下河水中和沉积物中多环芳烃(polycyclic aromatic hydrocarbons,PAHs)的实际浓度,获取了溶解相-沉积物中PAHs的分配系数Kp值.研究了老龙洞地下河PAHs在水相和沉积物中的质量浓度变化及其在水相和沉积物间的分配.研究结果表明水相和沉积物中PAHs质量浓度分别为81.5~8 089 ng·L-1,平均值(1 439±2 248)ng·L-1和58.2~1 051 ng·g-1,平均值(367.9±342.6)ng·g-1;PAHs组成均以2~3环为主,但沉积物中明显富集高环PAHs.沉积物-水相Kp值分布在55.74~46 067 L·kg-1范围内,随PAHs环数的增加而增大.沉积物-水相中实测的有机碳分配系数(lg Koc)大部分高于预测值上限,PAHs强烈吸附在沉积物上.lg Koc与正辛醇-水分配系数(lg Kow)呈较好的线性自由能关系(R2=0.75),但其斜率小于1,推测地下河沉积物对PAHs化合物的吸收能力较差.     

南水北调丹江口水库原水有机物分子组成规律及其强化混凝处理的效能对比

以取自南水北调中线工程的丹江口水库原水作为研究对象,考察了丹江口水库原水中有机物的分子量大小和亲疏水性分子组成规律,并确定了其所适用的强化混凝工艺条件.分离试验表明,丹江口原水中有机物主要以小分子量形式存在.其中,1 000组分的溶解性有机碳(DOC)和UV254所占比例最大,分别为39.98%和39.10%,且此区间还具有最高的三卤甲烷生成潜能(THMFP)和含氮消毒副产物生成潜能(N-DBPFP).亲疏水性方面,原水中弱疏水性组分含量最高,疏水性有机物的比例用DOC表征时超过80%.强疏水性组分含量最低但是强疏水性组分的THMFP最大,占总量的57.31%,而各组分的NDBPFP则相差不大.混凝试验表明,当采用聚合硫酸铁(PFS,4 mg·L-1)和聚丙烯酰胺(PAM,0.4 mg·L-1)处理丹江口原水时,强化混凝效果最好,可实现较为有效的去除浊度(76.33%)、DOC(25.57%)、UV254(37.78%)及THMFP(23.16%).本研究成果可为南水北调河南受水区既有水厂升级改造与工艺的优化运行提供有效的理论和技术支持.     

氯苯类化合物在沉积物上的非线性吸附行为

以5种自然沉积物为对象,采用批量平衡法,测定了氯苯、1,4-二氯苯、1,2,4-三氯苯和1,2,4,5-四氯苯在这5种沉积物样品上的吸附等温线,以研究沉积物自然有机质（NOM）的性质对氯苯类化合物（chlorobenzenes, CBs）吸附行为的影响.结果表明,1,2,4-三氯苯在虎门、黄沙、雅岗、三水、长洲5种沉积物中的等温吸附线性因子n都小于1,分别为0.956、 0.858、 0.872、 0.947和0.915,说明所有吸附等温线均为非线性;同时,非线性的程度n与极性指数（O+N）/C呈负相关关系,相关系数R²达0.994 7,表明NOM的聚合度（以极性指数为表征）直接影响着吸附非线性程度;5种沉积物对1,2,4-三氯苯的吸附亲和力（K_oc）随沉积物极性指数的增大而减弱,说明NOM聚合度较高的沉积物对1,2,4-三氯苯的吸附亲和力更强;氯苯、1,4-二氯苯、1,2,4-三氯苯、1,2,4,5-四氯苯在同一种沉积物（黄沙）上吸附等温线的线性因子n分别0.755、 0.788、 0.858、 0.949,非线性程度按溶质分子由小到大的顺序依次减弱,说明溶质分子本身的性质也影响着CBs在沉积物上的吸附性能.     

Removal of polycyclic aromatic hydrocarbons and phenols from coking wastewater by simultaneously synthesized organobentonite in a one-step process

The optimal condition for a one-step process removing organic compounds from coking wastewater by simultaneously synthesized organobentonite as a pretreatment was investigated. Results showed that sorption of organic compounds by organobentonite was positively correlated to the cation surfactant exchange on the bentonite and the octanol-water partition coefficient (K_ow) of the solutes. With 0.75 g/L bentonite and 180 mg/L (60% of bentonite cation exchange capacity) cetyltrimethylammonium bromide, the removal efficiencies of the 16 polycyclic aromatic hydrocarbon (PAHs) specified by the US Environmental Protection Agency in coking wastewater except naphthalene were more than 90%, and that of benzo(a)pyrene was 99.5%. At the same time, the removal efficiencies of COD_Cr, NH₃-N, volatile phenols, colour and turbidity were 28.6%, 13.2%, 8.9%, 55% and 84.3%, respectively, and the ratio of BOD₅/COD_Cr increased from 0.31 to 0.41. These results indicated that the one-step process had high removal efficiency for toxic and refractory hydrophobic organic compounds, and could improve the biodegradability of the coking wastewater. Therefore it could be a promising technology for the pretreatment of toxic and refractory organic wastewater.     

深圳湾生态系统多环芳烃（PAHs）特征及其生态危害

2004年在深圳湾海域采集海水、悬浮物、表层沉积物和柱状沉积物样品,并分析其中15种多环芳烃的含量及其相关参数,同时采用210Pb法测定柱状沉积物的年龄.结果表明,海水、悬浮物、表层沉积物和柱状沉积物中总的PAHs含量分别为(69.4±24.7)ng·L-1、(429.1±231.8)ng·g-1、(353.8±128.1)ng·g-1和(321.1±134.6)ng·g-1,各介质优势组分均为菲、荧蒽和芘;1948～2004年期间,深圳湾柱状沉积物中PAH各单体的浓度总体上一直在增加,PAHs的平均沉积通量为89.9ng/(cm2·a);PAH各单体在沉积物/海水中的分配系数(Koc)与其相应的辛醇/水比(Kow)存在明显的正相关性,即可用PAH的Kow值来预测深圳湾海域PAH的Koc.目前,水体与沉积物中PAH含量对该海域的水生生物尚未构成威胁.     

水稻秸秆主要组分的提取及其对芘的吸附作用

从水稻秸秆中提取主要组分--木质素、纤维素、半纤维素,利用元素分析和红外光谱对其性质进行了表征,并研究了芘在秸秆及其3种组分上的吸附行为.结果表明,各组分性质差异很大,木质素具有较高的芳香性和较低的极性,而纤维素和半纤维素具有较高的极性和脂肪性.不同组分对芘的吸附等温线均符合Freundlich方程,但吸附能力因其结构的差异而不同,木质素对芘的吸附能力最强, 吸附容量KF为5.04×104,比纤维素高100倍左右,而芘在半纤维素上的吸附能力略低于纤维素.低浓度(水相平衡浓度ce=0.01 Sw)下,秸秆对芘的吸附主要受木质素的控制,而且分配系数Kd略低于按照木质素质量分数计算的预测值,可能是由于木质素的烷基和芳香结构被周围的极性结构所覆盖.但在高浓度(ce = 0.5 Sw)时,秸秆对芘的吸附高于各组分的加和,芘向秸秆其他组分的分配作用不能忽略.芘在木质素上的吸附表现为非线性(非线性指数,n = 0.89),而其它3种吸附剂对芘的吸附更趋向于线性(n > 0.96).n值与芳香性呈负相关关系,而与极性呈正相关关系,表明芳香性导致的特殊作用力是造成吸附非线性的主要原因.有机碳标化分配系数Koc随吸附剂芳香性的增强而增大,但随极性的增强而减小.     

Adsorption and partition of benzo(a)pyrene on sediments with different particle sizes from the Yellow River

Experiments have been carried out to study the sorption of Benzo(a)pyrene(Bap) on sediment particles from the Yellow River using a batch equilibration technique. Effects of particle size on the adsorption and partition of Bap were investigated with the particle content of 3 g/L. Several significant results were obtained from the study. (1) Isotherms of Bap could be fitted with the dual adsorption-partition model under different particle sizes, and the measured value of the adsorption and partition was in agreement with the theoretical value of the dual adsorption-partition model. (2) When the particle diameter was d ⩾ 0.025 mm, the adsorption was predominant in the sorption of Bap, which accounted for 68.7%–82.4% of the sorption. For the particles with the size of 0.007 mm⩽d<0.025 mm, the adsorption was predominant when the equilibrium concentration of Bap was 0–8.87 μg/L in the water phase; and the partition was predominant when the equilibrium concentration of Bap was higher than 8.87 μg/L in the water phase. When the particle diameter was d<0.007 mm, the partition was predominant. (3) On the point of particle size, the contribution of adsorption to sorption followed the order: “d⩾0.025 mm”>“0.007 mm ⩽d<0.025 mm” >“d<0.007 mm”. (4) The partition coefficients of Bap in solids with different particle sizes were linearly correlated with the organic content, and the K _oc of Bap was about 1.26 × 10⁵ (L/kg). Translated from Acta Scientiae Circumstantiae, 2006, 26(2): 269–274 [译自: 环境科学学报]     

天然有机物在氧化铝表面的吸附机理研究

考察了天然有机物(NOM)的2种分离组份(憎水部分HyO,亲水部分HyI)和一种商用腐殖酸(CHA)在氧化铝表面的吸附-解吸行为规律,从芳香性、分子量、极性的角度探讨了NOM自身特性对吸附性能的影响,并通过改变溶液性质(pH值、离子强度、二价阳离子Ca2 ),进一步论证了NOM在金属氧化物表面的吸附机理.结果表明,芳香性高、弱极性的有机物吸附性能较强;降低溶液的pH值,有助于增加吸附剂的吸附容量;离子强度和Ca2 对吸附行为的影响,与NOM自身和内部组分的性质有关.NOM吸附于金属氧化物表面的机理,可以归结为配位体交换、静电作用、憎水作用、阳离子架桥等多个因素共同作用的结果.采用原子力显微成像技术,进一步从微观角度证实了憎水作用和阳离子架桥作用的存在.     

臭氧氧化对天然有机物在氧化铝表面吸附行为的影响

为进一步明确臭氧预氧化对颗粒的脱稳作用,选用氧化铝（α-Al₂O₃）作为悬浮颗粒,考察了臭氧氧化后天然有机物（natural organic matters,NOM）特性及吸附行为的变化.结果表明,臭氧氧化能够破坏NOM的芳香结构,SUVA值降低25%～35%,氧化后酸性官能团含量增多,总酸度增加0.3～1.4 mmol·g^-1,分子量和极性的变化与NOM的性质有关;有机物初始浓度相对于臭氧投量较低时,NOM的溶解性增强,与其酸性官能团增加产生的吸附促进作用相抵消,因而吸附性能出现不变甚至降低的现象;有机物初始浓度较高时,臭氧能够起到强化NOM吸附的作用.采用2.5　mg·L^-1臭氧进行氧化后,以商用腐殖酸为代表的NOM的吸附形貌,由密集分布的球形对称聚集结构向网状结构过渡,分子之间的交联作用十分明显,吸附高度低于其氧化处理前,云母的表面覆盖率较氧化前略有提高.     

Controlling various contaminants in wastewater effluent through membranes and engineered wetland

For effective wastewater reclamation and water recovery, the treatment of natural and effluent organic matters (NOM and EfOM), toxic anions, and micropollutants was considered in this work. Two different NOM (humic acid of the Suwannee River, and NOM of US and Youngsan River, Korea), and one EfOM from the Damyang wastewater treatment plant, Korea, were selected for investigating the removal efficiencies of tight nanofiltration (NF) and ultrafiltration (UF) membranes with different properties. Nitrate, bromate, and perchlorate were selected as target toxic anions due to their well known high toxicities. Tri-(2-chloroethyl)-phosphate (TCEP), oxybenzone, and caffeine, due to their different K _ow and pK _a values, were selected as target micropollutants. As expected, the NF membranes provided high removal efficiencies in terms of all the tested contaminants, and the UF membrane provided fairly high removal efficiencies for anions (except for nitrate) and the relatively hydrophobic micropollutant, oxybenzon. Through the wetlands, nitrate was successfully removed. Therefore, a fair process of combining membranes with an engineered wetland could be proposed for sustainable wastewater reclamation and optimum control of contaminats.     

Sorption of chlorophenols onto fruit cuticles and potato periderm

To better understand the interaction mechanisms of plant surfaces with polar organic compounds, sorption of 4-chlorophenol, 2,4- dichlorophenol, and 2,4,6-trichlorophenol by fruit cuticles (i.e., tomato, apple, and pepper), and potato tuber periderm were investigated. The roles of cuticular components (waxes, cutin, cutan and sugar) on sorption of chlorophenols are quantitatively compared. Cutin and waxes govern the sorption capacity of bulk apple cuticle by hydrophobic interactions. Potato periderm with highest sugar content exhibits the lowest sorption capability for the chlorophenols. With the increase of hydrophobicity (i.e., K_ow ) of sorbate, the relative contribution of lipophilic components (wax, cutin and cutan) on total sorption increases, however, the ratios of K_oc to K_ow decreases due to increasing ionization degree of sorbates.     

水溶性有机碳对菲吸附系数测定的影响

以菲为代表性化合物,利用摇瓶吸附实验研究土壤水分配体系中溶解态有机碳(DOC)对有机碳归一化吸附系数测定结果的影响.研究结果表明,在吸附系数测定过程中土壤溶出的DOC会导致水相中菲的浓度显著增加,很大程度上改变了菲在土水两相中的分配平衡,从而导致吸附系数的测定误差.根据文献报道的菲与DOC相互作用常数(K_doc)以及实测体系中DOC浓度可以对实验数据进行校正,以获得更为可靠的结果,本文对线性吸附系数和Freundlich吸附系数分别进行了校正,得到有机碳归一化的吸附系数lgKoc为4.35 ,lgK_Foc为7.01.校正前后的lgK_oc与文献数据的对比从侧面反映出在水土体系的吸附研究中可能普遍包含因不同浓度DOC影响所造成的偏差,考虑这种影响对于准确比较不同研究得到的吸附参数具有重要意义.     

Effect of bioflocculants on the coagulation activity of alum for removal of trihalomethane precursors from low turbid water

Reactivity of chlorine towards hydrophobic groups present in natural organic matter(NOM)provokes the formation of carcinogenic disinfection byproducts such as trihalomethanes in chlorinated water. The present study aimed to investigate the variations in coagulant activity of alum using two different bioflocculants(coagulant aid) namely, Moringa oleifera and Cyamopsis tetragonoloba for the removal of hydrophobic fractions of NOM and subsequent chlorine consumption by treated water. Effect of dual coagulants on trihalomethane surrogate parameters such as total organic carbon, dissolved organic carbon, UV absorbing materials and prominent hydrophobic species such as phenolic groups along with aromatic chromophores, polyhydroxy aromatic moiety have also been studied. The concept of differential spectroscopy and absorbance slope index has been employed to understand the combined effects of alum-bioflocculants on the reactivity of NOM with chlorine. Our result shows that the combination of alum and C. tetragonoloba is more efficient for reducing trihalomethane surrogates from chlorinated water as compared to M. oleifera. C. tetragonoloba elicited synchronized effects of sweep coagulation and particle bridging-adsorption which eventually facilitated efficient removal of hydrophobic fractions of NOM. The variation in the mechanistic approach of bioflocculants was due to the presence of cationic charge on M. oleifera and adhesive property of C. tetragonoloba.     

源自腐殖土的溶解性有机质组分对棕壤和黑土吸附苯并三唑的影响

溶解性有机质(DOM)影响着有机污染物在土壤中的吸附行为.将从腐殖土中提取的DOM(DOMbulk)用XAD-8树脂和阴/阳离子交换树脂进行分级,用红外光谱、元素分析、紫外分光光度计和电位滴定的方法对DOM不同组分特征进行分析.用吸附批次实验方法研究了DOM不同组分对棕壤和黑土吸附苯并三唑(BTA)的影响.结果表明,DOMbulk中疏水酸性(HOA)、疏水中性(HON)、亲水酸性(HIA)、亲水碱性(HIB)和亲水中性(HIN)组分比例分别为61%、17%、6%、2%和14%.由于黑土有机碳(OC)含量高于棕壤,黑土对BTA和DOM组分的吸附能力均大于棕壤.相对于黑土,棕壤吸附DOM的标化分配系数Koc较高,其原因是棕壤中含有较多的对吸附DOM起重要作用的黏粒和粉砂.由于水分子占据DOM结合点位,DOM组分与BTA在溶液中结合较弱.DOMbulk中HIN在土壤上吸附最强.HIN的吸附增加了土壤吸附BTA的点位,增加点位的促进吸附作用大于HIN与BTA的竞争吸附作用,最终表现为促进吸附.疏水组分在土壤上的吸附较弱,产生的新吸附点位较少,主要通过竞争吸附作用抑制土壤对BTA的吸附.DOMbulk由78%的疏水组分构成,对土壤吸附BTA的影响与疏水组分相似.     

甾体激素在污水处理厂中的赋存特征和行为归趋

污水处理厂是控制甾体激素环境排放的重要屏障之一,研究不同种类甾体激素在不同工艺污水处理厂中的赋存特征和行为归趋是提高污水处理厂对甾体激素处理效能的重要基础.对无锡市两个污水处理厂各工艺段中22种甾体激素的赋存情况进行8个月的监测,比较了厌氧-缺氧-好氧工艺(A²/O)和倒置A²/O工艺的处理效果.结果表明,甾体激素的进出水总浓度分别为27.7~256.8 ng ·L^-1和5.7~211.0 ng ·L^-1,剩余污泥中激素总含量为36.3~123.6 ng ·g^-1,主要检出雄酮、雄烯二酮、雌酚酮、雌三醇和孕酮.进出水中大多数激素的浓度随降雨量和温度的升高而略有降低的趋势,而冬夏的季节差异未对甾体激素的去除率产生显著影响.污水厂的二、三级处理工艺对激素的去除效果优于一级处理,倒置A²/O和传统A²/O相比对甾体激素的去除并未表现出明显的优势.甾体激素在污水和污泥间的分配系数lg Koc为2~4.5,在厂A中的lg Koc略高于厂B,激素的泥水分配可能影响其处理效果.     

Organic matter produced by algae and cyanobacteria: Quantitative and qualitative characterization

This work aims at characterizing organic matter produced by an alga Euglena gracilis and a cyanobacteria Microcystis aeruginosa and assessing the evolution of its characteristics during growth. A culture medium was optimized. The species growth phases were monitored using both visible spectrophotometry and flow cytometry cell counting. Organic matter fractionation according to hydrophobicity and specific UV absorbance (SUVA) index were used to specifically characterize the produced algal organic matter (AOM). The AOM characteristics were both growth phase and species dependent. However, a similar evolution was observed. The hydrophilic fraction (HPI) was the major fraction whatever the growth phases and was almost the only one produced during lag and exponential phases. It represented around 75% of AOM during exponential phase and then decreased when the stationary phase appeared. It represented 46% and 60% of the AOM during late decline phase for the cyanobacteria and the alga respectively. The hydrophobic (HPO) and transphilic (TPH) fractions started to appear from the beginning of the stationary phase with more hydrophobic compounds coming from intracellular organic material of dying cells. HPO and TPH percentages still increased during the decline phase probably because of two additional processes: photo-dissolution and leaching of particulate organic matter from cells fragments. A comparison of AOM during late decline phase and natural organic matter (NOM) from Glane River (France) underlined that AOM was more hydrophilic and presented a lower SUVA for each fractions than NOM. However, the difference between NOM and AOM hydrophobicity narrowed during decline phase.