Enhanced real-time cyanobacterial fluorescence monitoring through chlorophyll-a interference compensation corrections.

In situ fluorometers can be used as a real-time cyanobacteria detection tool to maintain safe drinking and recreational water standards. However, previous studies into fluorometers have established issues arising mainly from measurement inaccuracies due to green algae interference. Therefore, this study focusses on developing correction factors from a systematic study on the impact of green algae as an interference source. This study brings a novel technique where the chlorophyll-a (Chl-a) and phycocyanin measurements are used to correct the fluorometer output for interference bias; four fluorometers were tested against three key cyanobacterial species and the relationship between phycocyanin output, green algae and cyanobacteria concentrations were investigated. Good correlation (R2 > 0.9, p-value < 0.05) was found between the fluorometer phycocyanin output and increasing green algae concentration. The optimal correction method was selected for each of the fluorometer and cyanobacteria species pairs by validating against data from the investigation of green algae as an interference source. The correction factors determined in this study reduced the measurement error for almost all the fluorometers and species tested by 21%-99% depending on the species and fluorometer, compared to previous published correction factors in which the measurement error was reduced by approximately 11%-81%. Field validation of the correction factors showed reduction in fluorometer measurement error at sites in which cyanobacterial blooms were dominated by a single species.

Integrated membrane systems incorporating coagulation, activated carbon and ultrafiltration for the removal of toxic cyanobacterial metabolites from Anabaena circinalis.

The use of integrated membrane systems (a train of treatment processes incorporating one or more membranes) is increasing globally as the technology is very effective for the production of high quality drinking water. In this investigation a laboratory scale integrated membrane system (IMS) featuring coagulation, powdered activated carbon (PAC) and ultrafiltration (UF) was investigated for the removal of an Australian strain of the cyanobacteria Anabaena circinalis and the cyanotoxin it produced. Three coagulants were compared, aluminium chlorohydrate (ACH), aluminium sulphate (alum) and an engineered aluminium coagulant referred to as high performance aluminium chlorohydrate (HPAC). PAC (Acticarb PS1000) was tested to determine adsorption of extracellular saxitoxin. Removal of A. circinalis cells was 100% by UF alone and the removal of cells prior to the membrane by coagulation reduced fouling attributed to algogenic organic material. Alum was the least efficient coagulant for removal of cells while ACH and HPAC were similar. Saxitoxin removal reached a maximum of 80% using ACH and PAC. The UF-IMS was challenged using a natural bloom of A. circinalis that occurred in the Myponga Reservoir in South Australia.

Spinal anaesthesia for ambulatory arthroscopic surgery of the knee: a comparison of low-dose prilocaine and fentanyl with bupivacaine and fentanyl.

BACKGROUND: Prospective data on the use of prilocaine for ambulatory spinal anaesthesia remain limited. We compared the behaviour and characteristics of subarachnoid block using prilocaine and fentanyl with that of bupivacaine and fentanyl. METHODS: In a prospective, double-blind, randomized controlled trial, 50 patients undergoing elective ambulatory arthroscopic knee surgery received subarachnoid anaesthesia, with either prilocaine 20 mg and fentanyl 20 µg (Group P) or plain bupivacaine 7.5 mg and fentanyl 20 µg (Group B). Primary endpoints included times for onset of maximum sensory block level and regression of sensory block to L4, and also motor block at 1 and 2 h, and levels of haemodynamic stability. Comparisons between the groups were made by χ² test for proportions and the Mann-Whitney test for ordinal data. Time-to-event data were analysed by the Mann-Whitney test for uncensored data or the logrank test for censored data. RESULTS: At 2 h, motor block in Group P had fully resolved in 86% of patients, compared with 27% in Group B (P<0.001). Median time to regression of sensory block to L4 was significantly shorter in Group P (97 min) than in Group B (280 min) (P<0.001). A clinically significant decrease in arterial pressure was more common in Group B (73%) than in Group P (32%) (P=0.004). Two patients in Group P required conversion to general anaesthesia, but for reasons unrelated to prilocaine itself. CONCLUSIONS: The combination of prilocaine and fentanyl is a better alternative to that of low-dose bupivacaine and fentanyl, for spinal anaesthesia in ambulatory arthroscopic knee surgery.

Nanofiltration for the removal of algal metabolites and the effects of fouling.

Nanofiltration (NF) has been shown to be an effective way of removing organic micropollutants from drinking water due to its size exclusion properties. A rapid bench scale membrane test unit was utilised to trial six NF membranes to remove the algal metabolites, microcystin, cylindrospermopsin, 2-methylisoborneol (MIB) and geosmin (GSM). Membrane fouling due to the algal metabolites was observed for both charged and neutral metabolites. MIB and GSM were removed effectively by low molecular weight cut-off (MWCO) membranes but less effectively by a higher MWCO membrane. Removal of MIB and GSM by the higher MWCO membrane was improved as the membrane fouled. Microcystin was initially removed to above 90% by tight NF membranes but fouling of several membranes caused decreased percent removals over time. Tight NF membranes afforded removals of 90-100% for cylindrospermopsin, while removal by the higher MWCO membrane was lower but improved with time due to fouling.

Comparison and modeling of the adsorption of two microcystin analogues onto powdered activated carbon.

The presence of cyanobacterial toxins, such as microcystins, in drinking water supplies is a major concern for water authorities worldwide due to possible adverse health effects associated with exposure to these compounds. Adsorption onto powdered activated carbon in the water treatment process offers an effective treatment option for the removal of these compounds. However, for the efficient use of powdered activated carbon, knowledge of the appropriate dose to apply is required. In this study the adsorption of two microcystin analogues, microcystin-LR and microcystin-LA, onto powdered activated carbon was studied for two waters. Analysis of batch kinetic and equilibrium adsorption data showed that the homogeneous surface diffusion model could successfully predict the adsorption kinetics of the two toxins. The application of the homogeneous surface diffusion model is extremely useful to water treatment plant operators as it can be used to predict the powdered activated carbon dose for the removal of algal toxins based on the analogue(s) present, influent toxin concentration and powdered activated carbon contact time. Adsorption was also found to be different for the two toxin analogues, and dependent on the water character. Microcystin-LR was much more easily removed than microcystin-LA in both waters, and adsorption of both analogues was lower in the water with a higher dissolved organic carbon concentration.

Cooperative biodegradation of geosmin by a consortium comprising three gram-negative bacteria isolated from the biofilm of a sand filter column.

AIMS: To isolate and identify bacteria from a sand filter column capable of degrading the taste and odour compound, geosmin. In doing so, to investigate if these organisms degrade geosmin either individually or if an alternative mechanism is utilized. METHODS AND RESULTS: Geosmin-degrading bacteria from a biologically active sand filter column were enriched by their growth in a minimal medium supplemented with geosmin as the sole carbon source. By day 51, 21.7 mg l(-1) of geosmin had been degraded as determined by solid-phase microextraction gas chromatography/mass spectrometry, and was accompanied by a 2.12 log(10) increase in active bacterial numbers as measured using the BacLight(TM) bacterial viability kit and flow cytometric enumeration. During the onset of geosmin degradation, the predominance of three bacteria, most similar to previously cultured species of Sphingopyxis alaskensis, Novosphingobium stygiae and Pseudomonas veronii based on 16S rRNA gene sequences was detected by denaturing gradient gel electrophoresis. Subsequent isolation of these organisms revealed that degradation of geosmin, when present as either the sole carbon source (ranging from 40 ng l(-1) to 20 mg l(-1)) or when spiked into sterile reservoir water (37 and 131 ng l(-1)), occurred only when all three isolates were present. None of the isolates was shown to be capable of degrading geosmin either individually or in any combination of two. CONCLUSIONS: This study has reported, for the first time, the cooperative degradation of geosmin by a consortium comprising three gram-negative bacteria isolated from a biologically active sand filter column. SIGNIFICANCE AND IMPACT OF THE STUDY: These results are important for researchers currently employing molecular-based approaches to further understand the biodegradation of geosmin by bacteria, as such studies may be complicated by the discovery of geosmin degradation occurring by a consortium. This study also advances the knowledge surrounding the types of bacteria capable of degrading the taste and odour compound, as investigations to date regarding this are limited.

The effect of water quality and NOM character on the ozonation of MIB and geosmin.

The ozonation of MIB and geosmin was studied in synthetic waters containing two natural organic material (NOM) fractions and sodium bicarbonate. The ozonation of both compounds was found to be affected by the character of the NOM fractions, with higher apparent rate constants observed in the fraction containing higher UV/visible absorbing properties. As the concentration of bicarbonate was increased, the destruction of both compounds decreased. MIB was found to be more resistant to ozonation than geosmin.

NOM and MIB, who wins in the competition for activated carbon adsorption sites?

The adsorption of an odour compound common in drinking water, 2-methylisoborneol (MIB), was studied on two activated carbons in the presence of 13 well-characterised natural organic matter (NOM) solutions. It was found that, although the carbons and the NOM solutions had a wide range of characteristics, the major competitive mechanism was the same in all cases. The low molecular weight NOM compounds were the most competitive, participating in a direct competition with the MIB molecule for adsorption sites. Equivalent background concentration (EBC) calculations indicated a relatively low concentration of directly competing compounds in the NOM. Some evidence of pore restriction was also seen, with microporous carbons most affected by low molecular weight NOM, and mesoporous carbons impacted by the higher molecular weight compounds.

First Report of Powdery Mildew Caused by Erysiphe cichoracearum on Creeping Thistle (Cirsium arvense) in North America.

Creeping or Canada thistle (Cirsium arvense (L.) Scop.) is a perennial weed of Eurasian origin that arrived in North America as early as the 1700s (3). Spreading by seeds and rhizomes, it is now widely distributed in Canada, Alaska, and 40 other states. It is apparently absent from Texas, Oklahoma, Louisiana, Mississippi, Alabama, Georgia, Florida, and South Carolina (1). Powdery mildew is common on C. arvense in Europe, but it has never been observed in North America (4). In Europe and Asia, powdery mildew of C. arvense is caused by any one of the following fungi: Leveillula taurica, two species of Sphaerotheca, and varieties of Erysiphe cichoracearum and E. mayorii. Specimens of C. arvense infected with powdery mildew (deposited in the U.S. National Fungus Collections as BPI 843471) were collected in the fall of 2003 near Moscow, ID and in two areas in Oregon (the canyon of the Grande Ronde River and near the base of the Wallowa Mountains). Mycelium and cleistothecia were observed on stems and upper and lower surfaces of leaves. The mean diameter of the cleistothecia was 122 (±11.6) µm. Basally inserted, mycelioid appendages were hyaline or brown and varied considerably in length, but most were in the range of 80 to 120 µm. Asci averaged 58 (±5.5) µm × 35 (±4.1) µm in length and width, respectively. Each ascus bore two ascospores averaging 23 (±1.4) µm × 14 (±1.7) µm. Conidia averaged 30 (±3.0) µm × 14 (±0.8) µm. The specimens fit the description of E. cichoracearum DC. (2). Because the length/breadth ratio of conidia is greater than 2, the specimens could be further diagnosed as E. cichoracearum var. cichoracearum (2). Also noteworthy was the presence of the hyperparasitic Ampelomyces quisqualis Ces. ex Schlechtend. E. cichoracearum is thought to be a cosmopolitan powdery mildew of broad host range, but this concept is difficult to reconcile with the absence of mildew on North American populations of C. arvense for more than 200 years. References: (1) Anonymous. USDA Natural Resources Conservation Service Plants Profile for Cirsium arvense. On-line publication, 2003. (2) U. Braun. A monograph of the Erysiphales (powdery mildews), J. Cramer, Berlin-Stuttgart, 1987. (3) G. Cox. Alien Species in North America and Hawaii, Island Press, Washington, D.C., 1999. (4) D. F. Farr et al. Fungal Databases, Systematic Botany and Mycology Laboratory, ARS, USDA. On-line publication, 2003.

Treatment options for microcystin toxins: similarities and differences between variants.

Over sixty variants of the blue-green algal toxin microcystin have been identified. The two microcystin variants LR and LA vary in only one amino group ie. arginine for microcystin LR and alanine for microcystin LA. In the literature to date, the general consensus has been that m-LR and m-LA should respond similarly to a range of water treatment processes. This is the case for ozonation and biodegradation by organisms colonising granular activated carbon filters; there is negligible difference in the response to these processes between the two variants. However, the adsorption of m-LR onto activated carbon is significantly higher than that of m-LA. This result is surprising as m-LA has a lower molecular weight, and is more hydrophobic, factors that would be expected to favour the adsorption of this compound over m-LR. This trend is also seen for the variants RR and YR. The effect is seen on both negatively and positively charged carbons, indicating that the difference between the variants is not caused by electrostatic interactions with the carbon surface. Electrostatic shielding experiments suggest that electrostatic repulsion between the adsorbed m-LA molecules, with a net charge of -2, may be responsible for the low adsorption. The other variants tested have a lower net charge and therefor experience lower intermolecular repulsion in the adsorbed state.

First Report of Powdery Mildew (Sawadaea bicornis) on Norway Maple (Acer platanoides) in North America.

Norway maple (Acer platanoides L.) was introduced into the continental United States around 1756 as a street tree (2). It is a widely planted shade tree in the northern United States and Canada due to its fast growth rate when young and its tolerance of pavement and dry soils. Powdery mildew is common on Norway maple in Europe with records from at least 22 countries according to the databases of the U.S. National Fungus Collections. However, there are no North American records. In September 2002, powdery mildew was observed on young Norway maple trees along the Idaho-Washington border in Moscow and Pullman, respectively. Mildew was not observed on older Norway maple trees. The mildew occurred mainly on the upper leaf surface as patches of dense, white mycelium with scattered or gregarious cleistothecia. Mean diameter of the cleistothecia was 146 (± 13.4) µm. Short stalked and subsessile asci averaged 69 (± 4.1) µm × 48 (± 5.4) µm. Ascospores averaged 27 (± 3.2) µm × 12 (±0.9) µm. Appendages were deeply cleft, simple, or one to three times dichotomously branched. This mildew fits the description of the European species Sawadaea bicornis (Wallr:Fr.) Homma (1). Also, conforming to S. bicornis were chains of macroconidia (21 (± 2.7) × 14 (± 1.5) µm) and microconida. Fibrosin bodies were seen in both. Infection of only some young trees and its absence in previous years lead us to believe that the introduction is recent in the Pacific Northwest. The susceptibility of native maples to the Norway maple mildew remains to be determined. Specimens have been deposited in the U.S. National Fungus Collections (BPI 842088). References: (1) U. Braun. A monograph of the Erysiphales (powdery mildews) J. Cramer, Berlin-Stuttgart, 1987. (2) D. J. Nowak and R. A. Rowntree. J. Arboric. 16:291, 1990.

First Report of Powdery Mildew (Microsphaera palczewskii) on Siberian Pea Tree (Caragana arborescens) in North America.

Caragana arborescens Lam. is an exotic ornamental that can also be somewhat invasive. In July 2002, powdery mildew was observed on C. arborescens along the Idaho-Washington border in Moscow and Pullman, respectively. Leaves were colonized as soon as they emerged, and entire plants were affected. The fungus covered both leaf surfaces, but cleistothecia were more abundant on abaxial surfaces. The mean diameter of the cleistothecia was 91 (± 9.8) µm. Short-stalked asci averaged 67 (± 7.1) µm × 37 (± 5.2) µm, and the ascospores were 21 (± 2.0) µm × 13 (± 0.8) µm. There are records of four species of Microsphaera on C. arborescens in Europe and Asia. The measurements fit the description of Microsphaera palczewskii Jacz. (1), and the identification was confirmed by comparison with specimens of this fungus on C. arborescens from Sweden (U.S. National Fungus Collections: BPI 749057 and 749058). Specimens of M. grossulariae (Wallr. ex Fr.) Lev. on Ribes divaricatum Dougl. from California (BPI 558266) were also examined, but the cleistothecial appendages were distinctly different from those of the Idaho specimens. To our knowledge, this is the first reported occurrence in North America of powdery mildew on C. arborescens and the first report of M. palczewskii. The latter may have been introduced recently into North America because there are areas in southern Canada and the northern United States in which C. arborescens is unaffected by powdery mildew. Interestingly, it is only in recent decades that M. palczewskii has spread from Asia into Europe (2). Now, host and parasite have been reunited in North America as well. Specimens have been deposited in the U.S. National Fungus Collections (BPI). References: (1) U. Braun. A monograph of the Erysiphales (powdery mildews) J. Cramer, Berlin-Stuttgarg, 1987. (2) S. Huhtinen et al. Karstenia 41:31, 2001.

The application of powdered activated carbon for MIB and geosmin removal: predicting PAC doses in four raw waters.

Blooms of blue-green algae in reservoirs often produce the musty-earthy taste and odour algal metabolites 2-methylisoborneol (MIB) and geosmin. MIB and geosmin are not removed by conventional water treatment and their presence in the distribution system, even at low ng L-1 levels, can result in consumer complaints. Powdered activated carbon (PAC) can effectively remove MIB and geosmin when the correct dose is applied. The homogeneous surface diffusion model (HSDM) was used to predict PAC doses required to reduce MIB and geosmin concentrations to below 10 ng L-1 at four water treatment plants in Adelaide, South Australia. In jar tests, undertaken under treatment plant conditions, the predicted doses were found to produce water of the desired quality in three of the four waters. The poor predictions found in the fourth water, which had a considerably higher turbidity, were attributed to the incorporation of PAC in a larger, denser floc, leading to a reduced effective contact time of the adsorbent. It was found that higher doses of PAC were required for both compounds to produce acceptable quality water when turbidities rose above 26 NTU.

Ozonation of NOM and algal toxins in four treated waters.

The occurrence of cyanobacteria (blue-green algae) blooms and the possibility of production of cyanotoxins (algal toxins) have become major concerns for drinking water providers worldwide. Ozone has been shown to be effective for the destruction of some classes of toxins under specific conditions, although most researchers agree that the dose and contact time required will depend on water quality. The clarification of the relative effects of water quality parameters such as dissolved organic carbon concentration and character, and alkalinity, has not been previously attempted. In this study the cyanotoxins microcystin LR and LA and anatoxin-a were ozonated at a range of ozone doses in four treated waters with very different water quality. For both the toxins, 100% destruction was related to a residual ozone concentration present after 5 min. This was, in turn, related to the water quality and indicated that a direct reaction with molecular ozone could be responsible for the destruction. The results confirmed that both the toxins would be destroyed under conditions usually utilised for ozonation prior to granular activated carbon (GAC) filtration. This will apply under a range of water quality conditions but not necessarily a range of temperatures. The saxitoxin class of compounds was very resistant to oxidation by ozone and would require further treatment such as GAC filtration.

Recessive resistance to septoria stem canker of hybrid poplar.

ABSTRACT Stem canker, caused by Septoria musiva, is the most serious disease limiting intensive hybrid poplar culture in eastern North America. Populus deltoides (D) is itself resistant, but the susceptibility of western black cottonwood, P. trichocarpa (T) is apparently dominant in the F(1) generation. To test a hypothesis of recessive inheritance of canker resistance, a three-generation T x D pedigree was deployed in the field in Iowa and Minnesota. In both sites and in keeping with expectations, P. trichocarpa and its F(1) hybrids were susceptible to canker, whereas the P. deltoides parent was resistant. In Iowa, 10 of 70 F(2) (TD x TD) individuals were free of canker, suggesting that a single recessive gene might control resistance. In the third year in Minnesota, more resistant individuals than expected were seen in the F(2) generation and in TD x D and T x TD backcross progenies due to disease escape. By the fifth year, this was no longer an issue, but winter injury may have eliminated many clones. Qualitatively, however, evidence for recessive inheritance of resistance was still obtained. The only canker-free clones were in the TD x D backcross and the F(2) generation, the two progenies in which they were expected. However, conclusive evidence that recessive canker resistance is conferred by a single gene was not obtained in this field study.

Abundant Pathogenic Variation in the New Hybrid Rust Melampsora xcolumbiana on Hybrid Poplar.

ABSTRACT The recently described rust hybrid Melampsora xcolumbiana was discovered as a result of its novel pathogenic variation on Populus trichocarpa x P. deltoides (TxD) hybrid poplar. To characterize this pathogenic variation, 10 commercial TxD clones, all F(1) clones, were chosen as host differentials. Fourteen mononuredinial isolates of Pacific Northwestern field collections of M. xcolumbiana, from 1996 to 1998 inclusive, were determined to be 13 distinct pathotypes. In contrast, four Southeastern isolates of M. medusae could not be distinguished on the same TxD host differentials, although they can be distinguished as pathotypes using P. deltoides differentials. The first three pathotypes of M. xcolumbiana (Mxc1, Mxc2, and Mxc3) and a Mississippi isolate of M. medusae were inoculated onto a three-generation TxD pedigree, formerly used to characterize the Mmd1 gene for resistance to M. medusae. Resistance to the Mxc3 pathotype mapped to the same linkage group (group Q) as the Mmd1 gene. In contrast, linked genes for resistance to Mxc1 and to Mxc2 were located on linkage group O, and were unlike Mmd1 and Mxc3 in that they were inherited from P. deltoides. The latter two genes resembled Mmd1 and Mxc3 in that infection type was correlated with quantitative traits such as uredinial density and latent period. Pathogenic variation in M. xcolumbiana matches resistance genes from both P. trichocarpa and P. deltoides and reveals the vulnerability to hybrid rust of commercial TxD hybrid poplar clones.

First Report of Pestalotiopsis populi-nigrae on Poplar in North America.

Black acervuli were observed on abaxial surfaces of leaves of hybrid poplar (Populus trichocarpa Torr. & A. Gray × P. deltoides Marsh.) collected during fall 1998 in western Washington. Melampsora uredinia also were present but may be coincidental. When incubated in a moist petri dish, leaves became necrotic, and acervuli produced black masses of fivecelled, appendage-bearing conidia. Average conidia length was 25 µm. Three median versicolorous cells averaged 17.5 µm long and 6 µm wide; the upper two were darker than the lower one. There were typically three apical setulae, averaging 20 µm long. The average basal pedicel was 5 µm long. The fungus fits the description of Pestalotiopsis populi-nigrae (Sawada et Ito) Morelet. Originally described as an opportunistic pathogen on poplar in Japan (1), P. populi-nigrae was subsequently found on poplar in Europe (2). It is also the cause of cane blight of Rosa spp. in Japan (2), but it has never been reported in North America. A specimen has been deposited in the U.S. National Fungus Collections (BPI 746460). I did not observe P. populi-nigrae in 1997 to 1999 collections of rusted poplar leaves from the Southeast, western Kentucky, Minnesota, and Iowa nor in other Pacific Northwest collections. This was not a comprehensive survey for P. populi-nigrae but may indicate that the fungus is rare in North America. It also is possible that BPI 746460 represents an undescribed, uncommon species native to North America that is morphologically indistinguishable from P. populi-nigrae. Further research is required to test this hypothesis. References: (1) K. Ito. Bull. Gov. For. Exp. Stn. 45:135, 1950. (2) E. Kimishima et al. Ann. Phytopathol. Soc. Jpn. 62:502, 1996.

Inheritance of Carboxin Resistance in a European Field Isolate of Ustilago nuda.

ABSTRACT Two carboxin-resistant field isolates of Ustilago nuda from Europe were crossed with a carboxin-sensitive field isolate from North America. Meiotic tetrads isolated from germinating F(1) teliospores of one of the hybrids were tested for carboxin resistance and mating type. Carboxin resistance was shown to be controlled by a single gene (CBX1R), because a 1:1 segregation of carboxin resistance was observed in all 27 tetrads. Tetrad analysis indicated that the loci for carboxin resistance (Cbx1) and mating type (MAT1) segregate independently but may be located on the same chromosome. Tetrad analysis was not possible with the F(1) hybrid of he other field isolate, and its resistance cannot yet be attributed to CBX1R. Carboxin resistance was qualitatively dominant to sensitivity in vitro, as demonstrated by triad analysis of germinating F(1) teliospores. Quantitative in planta infection percents supported the conclusion that CBX1R is dominant, although incompletely, in the F(1) hybrid of one of the field isolates. Also, fewer than expected carboxin-sensitive F(2) individuals were observed in planta. However, inoculations of host plants with U. nuda have resulted in similar, unexpected variation in the past.

Adsorption of NOM onto Activated Carbon: Effect of Surface Charge, Ionic Strength, and Pore Volume Distribution.

Adsorption of natural organic matter (NOM) onto seven activated carbons with a wide range of surface properties was studied at high and low ionic strength over a range of pH values. From adsorption isotherm studies it was found that, for six of seven carbons, at low surface concentrations, increased ionic strength decreased NOM adsorption. As the surface concentration increased, the adsorption isotherms converged and intersected, after which the addition of salt resulted in increased adsorption. This "crossover point" marked a change in the adsorption mechanism from the "screening reduced" to the "screening enhanced" adsorption regimes. The adsorption mechanisms are extremely complicated and appear attributable to various factors, including electrostatic forces, pore volume distribution, and chemical interactions between the NOM and the surface functionalities on the carbon surfaces. Copyright 1999 Academic Press.