Dissolution of Aluminum in Variably Charged Soils as Affected by Low-Molecular-Weight Organic Acids

Low-molecular-weight (LMW) organic acids exist widely in soils and play an important role in soil processes such as mineral weathering, nutrient mobilization and Al detoxification. In this research, a batch experiment was conducted to examine the effects of LMW organic acids on dissolution of aluminum in two variably charged soils, an Ultisol and an Oxisol. The results showed that the LMW organic acids enhanced the dissolution of Al in the two investigated soils in the following order: citric > oxalic > malonic > malic > tartaric > salicylic > lactic > maleic. This was generally in agreement with the magnitude of the stability constants for the Al-organic complexes. The effects of LMW organic acids on Al dissolution were greater in the Ultisol than in the Oxisol as compared to their controls. Also, the accelerating effects of citric and oxalic acids on dissolution of Al increased with an increase in pH, while the effects of lactic and salicylic acids decreased. Additionally, when the organic acid concentration was less than 0.2 mmol L-1, the dissolution of Al changed little with increase in acid concentration. However, when the organic acid concentration was greater than 0.2 mmol L-1, the dissolution of Al increased with increase in acid concentration. In addition to the acid first dissociation constant and stability constant of Al-organic complexes, the promoting effects of LMW organic acids on dissolution of Al were also related to their sorption-desorption equilibrium in the soils.

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.

Determination of Organic Acids in Root Exudates byHigh Performance Liquid Chromatography: III. Effectsof Interfering Factors

INTRODUCTIONCollectionofrootexudateswasakeysteptodeterminethecomponentsandamountsofrootexudates.Asfordifferelltmediaofplaotgrowth,themethodsforcollectingrootexudateswerealsodifferent.Undersolutionculture,rootexudateswerefrequentlyobtainedbysubmerging...

Spatial Distribution Characteristics of Organic Acids in Two Late-blooming Rhododendron Species

[Objectives]The spatial distribution characteristics of organic acids in two late-blooming Rhododendron species(Rhododendron decorum and Rhododendron stamineum)in Guizhou Baili Rhododendron National Forest Park were explored,in order to provide reference for exploring the plant-soil relationship of subtropical forest.[Methods]The fresh leaf,stem,root,litter,humus and soil samples of R.decorum and R.stamineum were collected.The contents of eight low molecular weight organic acids including oxalic acid,tartaric acid,malic acid,citric acid,acetic acid,lactic acid,succinic acid and formic acid were determined by high performance liquid chromatography(HPLC).[Results]Oxalic acid is the main organic acid in the two species of Rhododendron.Among different samples,the content of organic acids was in the following order:root>fresh leaf>humus>litter>stem>soil.[Conclusions]The content of organic acids in the root was significantly higher than that in other parts.The types of organic acids in stems were the least.

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.

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.

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。

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.

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.

白酒厂污泥与生活污泥有机组分的差异性及其淋溶迁移风险评估

通过对白酒厂污泥和生活污泥中腐植酸、低分子有机酸的含量对比分析,探讨两种污泥中有机组分的差异性及其淋溶迁移的环境风险。结果表明,酒厂污泥中有机质和腐植酸(NaOH浸提)平均含量分别为428.2,342.47 g/kg,平均比生活污泥中的含量高47.7%,62.6%。从污泥浸提(H 3PO 4浸提)的低分子有机酸含量,白酒厂污泥中柠檬酸和苹果酸含量分别达3.90,0.88 g/kg,分别是生活污泥的10.00倍和1.83倍;而生活污泥中的草酸含量达3.74 g/kg,是白酒厂污泥的2.94倍。两种污泥的腐植酸均含有丰富的羟基、酚羟基,而白酒厂污泥的腐植酸还含有丰富的羧基。两种污泥的6次连续淋溶的实验表明,生活污泥的淋溶液中,COD、NH_(4)^(+)-N含量范围分别为121.5~380.5,1.83~10.67 mg/L,平均比酒厂污泥高出55.8%,27.2%;而白酒厂污泥的淋溶液中,TP含量范围为0.84~1.90 mg/L,平均比生活污泥淋溶液中的含量高28.1%,白酒厂污泥有机组分淋溶迁移对水环境的影响小于生活污泥。综上所述,白酒厂污泥的有机组分及腐植酸的资源化利用优于生活污泥。

作物耐低磷机制研究进展

磷是作物生长发育必需的营养元素之一,在作物的生命过程中发挥重要作用。作物在长期进化过程中形成了一系列低磷适应机制,主要涉及土壤磷的活化、吸收、转运和内部磷的循环、再利用等过程。从作物低磷胁迫下的根系形态、根系分泌物、与微生物共生体系、分子机制4个方面综述了作物耐低磷机制的最新研究进展,旨在为作物栽培调控及耐低磷作物品种的改良与选育提供借鉴。

低密度有机-无机互穿网络堵漏体系研究

采用常规可固化堵漏剂解决低压地层裂缝性漏失时会产生密度过大或承压不足的技术难题,因此研究低密度高抗压的堵漏体系具有重要意义。通过合成聚丙烯酰胺(polyacrylamide,HPAM)交联形成有机网络,并优选水泥材料形成无机网络,构建低密度有机-无机互穿网络堵漏体系;采用模拟水驱实验、X射线衍射、扫描电子显微镜(scanning electron microscope,SEM)、高温高压(high temprature and high pressure,HTHP)堵漏模拟实验、抗压实验等分析了堵漏体系的性能和堵漏机理。结果表明,聚丙烯酰胺交联反应形成的有机网络与水泥水化形成的无机网络通过静电力和范德华力等作用可形成互穿网络体系,体系抗压达6.3 MPa,密度为1.28 g/cm^(3),固化时间实现2~5 h可控,固化前后的酸溶率分别为87.8%和63.4%,堵漏及解堵性良好。

基于超低温诱导的风味咖啡滋味及抗氧化活性分析

以卡蒂姆咖啡鲜果为研究对象,分析超低温(-40℃)、低温(-20℃)、软冻温度(-7℃)、冰温(-2℃)、冷藏温度(4℃)、常温(25℃)处理咖啡鲜果后咖啡熟豆的生物碱、有机酸含量及抗氧化活性,利用系统聚类对结果进行分类分析,最后通过感官评定进行验证。结果显示:不同温度处理咖啡后酸味相关化合物苹果酸含量由低到高为-40℃<25℃<-20℃<4℃<-7℃<-2℃,苦涩味相关化合物奎宁酸含量由低到高为-40℃<25℃<4℃<-20℃<-7℃<-2℃,葫芦巴碱含量由低到高为-40℃<25℃<4℃<-20℃<-2℃<-7℃。-40℃处理咖啡鲜果,其苹果酸、奎宁酸、葫芦巴碱含量均为最低,分别为3.83、531.91、9.31 mg/g。-40℃处理感官评分最高,能得到诸如热带水果、牛奶巧克力、黑莓等风味。不同温度处理咖啡鲜果后咖啡熟豆中多酚、黄酮含量差异显著,1,1-二苯基-2-三硝基苯肼(1,1-diphenyl-2-picrylhydrazyl radical,DPPH)、2,2’-联氮-二(3-乙基-苯并噻唑-6-磺酸)二铵盐[2,2’-azinobis-(3-ethylbenzthiazoline-6-sulphonate),ABTS]阳离子自由基清除能力差异显著。系统聚类(平方欧式距离为15)获得的分类结果与滋味呈味物质含量、抗氧化性结果一致。综上可得,超低温(-40℃)诱导处理咖啡鲜果可获得风味独特的咖啡。

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。

四川盆地简阳地区二叠系火山碎屑岩储层特征与成岩演化

火山碎屑岩油气藏作为重要的非常规油气藏,对油气增储上产具有重要的意义。通过岩心观察,综合薄片鉴定、QEMSCAN扫描、X射线衍射、物性分析、包裹体测温及碳氧同位素分析等资料,系统分析了四川盆地简阳地区二叠系火山碎屑岩储层特征及其成岩演化过程。研究结果表明:(1)简阳地区二叠系火山碎屑岩储层岩石类型主要包括火山角砾熔岩、凝灰熔岩和熔结火山角砾岩,整体物性都较好,孔隙度为0.78%~32.00%,平均为16.67%,渗透率为0.001~2.680 mD,平均为0.125 mD,属于高孔低渗储层,储集空间以次生孔隙和裂缝为主,包括脱玻化孔、基质溶蚀孔及溶蚀缝等类型。(2)研究区发育多种成岩作用,主要有熔结、压实、脱玻化、胶结及溶蚀作用等。(3)研究区经历了同生成岩、表生成岩与埋藏成岩3个阶段,成岩演化受深部热液、大气淡水及有机酸流体的共同影响,一方面流体活动造成热液矿物或碳酸盐胶结物的沉淀对储层物性起破坏性作用;另一方面热液流体促进油气运移,酸性流体的溶蚀改造作用对储层孔隙发育起建设性作用。

Fine-tuned mesoporous covalent organic frameworks for highly efficient low molecular-weight proteins separation

Covalent organic frameworks(COFs)are prominent porous materials for molecules separation due to their desirable structures.However,very few COFs are reported for the separation of macromolecules such as low molecular-weight(MW)proteins.Here,two stable mesoporous COFs(Azo-COF and Tp-COF)with highly crystallized frameworks are synthesized,and their pore sizes are slightly-regulated via elaborate selection of pyrene knots and amino linkages.Benefiting from the pore size difference less than 4 ?,the tandem utilization of these two COFs exhibits efficiently size-selective separation ability towards low MW proteins cytochrome c and myoglobin with small MW difference of 2 kDa,in which protein adsorption possibilities are verified by computational calculations together with confocal laser scanning microscopy(CLSM).Furthermore,a simple COF-based separation device is designed and prepared to achieve effective and low-consumption proteins separation.This work has offered an optimized synthetic strategy for fine-tuned mesoporous COFs and expanded their applications on macromolecules separation.

Prediction of Polycyclic Aromatic Hydrocarbon Bioaccessibility to Earthworms in Spiked Soils by Composite Extraction with Hydroxypropyl-β-Cyclodextrin and Organic Acids

Traditional exhaustive extraction methods often overestimate the risk of polycyclic aromatic hydrocarbon(PAH) bioaccessibility to biota. Therefore, reliable assessment methods need to be established. In this study, a composite extraction with hydroxypropyl-β-cyclodextrin(HPCD) and three low-molecular-weight organic acids, oxalic acid(OA), malic acid(MA), and citric acid(CA), was used to predict the PAH bioaccessibility to earthworms, subjecting to two soils(red soil and yellow soil) spiked with selected PAHs,phenanthrene, pyrene, chrysene, benzo(a)anthracene, benzo(b)fluoranthene, benzo(k)fluoranthene, and benzo(a)pyrene. For both soils,concentrations of PAHs by composite extraction using HPCD-OA(R^2= 0.89–0.92, slope = 1.89–2.03; n = 35), HPCD-MA(R^2=0.92–0.96, slope = 1.43–1.67; n = 35), and HPCD-CA(R^2= 0.92–0.96, slope = 1.26–1.56; n = 35) were significantly correlated with PAH accumulation in the Eisenia fetida earthworms. Moreover, the HPCD-CA-and HPCD-MA-extracted PAH concentrations were closer to the earthworm-accumulated PAH concentration than the extraction using just HPCD. The results indicated that the composite extraction could improve the prediction of PAH bioaccessibility, and therefore can serve as a reliable chemical method to predict PAH bioaccessibility to earthworms in contaminated soils.