Yael Laor

Publications of Yael Laor

• A screening tool for selection of field odor assessors.

  Authors: Yael Laor, Pola Orenstein, Uzi Ravid, Rima Baybikov, Aviva Hanan, Ibrahim Saadi, Yael Abbou

  Journal of the Air & Waste Management Association (1995). 12/2011; 61(12):1353-60.

  Field odor assessors are required to rate or describe several odor parameters, such as intensity, duration, offensiveness, and character. Ideally, their assessments should reflect the average odorField odor assessors are required to rate or describe several odor parameters, such as intensity, duration, offensiveness, and character. Ideally, their assessments should reflect the average odor perception of a specific community. The authors developed a three-part screening test for recruiting odor assessors: (1) distinguishing between different odorants by means of a triangular forced-choice test; (2) evaluating odor intensity; and (3) describing hedonic tone and odor character. Grading was based on two criteria: correctly answering the relevant parts of the test, and evaluation of odor parameters relative to the entire tested population. The latter involved grading each tested individual according to the similarity of their score to the average result of 179 tested individuals, comprising 48% women and 52% men whose age and residence distributions were identical between women and men (except for the oldest group). To exclude relatively less sensitive individuals who showed poor ability to distinguish between different odorants and various odor intensities, and/or provided atypical description (or rating) of odor intensity, character, and offensiveness, it was suggested that only individuals whose final score was within the upper 75% (final score +/- 80.75) would be qualified as odor assessors. According to this criterion, 73.8% of men and 78.6% of women passed the test. Among urban and rural dwellers, 77.4% and 67.4%, respectively, were qualified. Pass rate clearly diminished with increasing age: from 89.3% at 21-30 years to 54.6% at 61-70 years. This screening tool is recommended by the Israel Ministry of Environmental Protection for selection of field odor assessors to serve the general community and regulatory authorities.

• Odorants and malodors associated with land application of biosolids stabilized with lime and coal fly ash.

  Authors: Yael Laor, Moshe Naor, Uzi Ravid, Pinchas Fine, Ilan Halachmi, Yona Chen, Rima Baybikov

  Journal of environmental quality. 09/2011; 40(5):1405-15.

  Malodor emissions limit public acceptance of using municipal biosolids as natural organic resources in agricultural production. We aimed to identify major odorants and to evaluate odor concentrationsMalodor emissions limit public acceptance of using municipal biosolids as natural organic resources in agricultural production. We aimed to identify major odorants and to evaluate odor concentrations associated with land application of anaerobically digested sewage sludges (Class B) and their alkaline (lime and coal fly ash)-stabilized products (Class A). These two types of biosolids were applied at 12.6 tonnes ha(-1) (dry weight) to microplots of very fine clayey Vertisol in the Jezreel Valley, northern Israel. The volatile organic compounds (VOCs) emitted from the biosolids before and during alkaline stabilization and after incorporation into the soil were analyzed by headspace solid-phase microextraction followed by gas chromatography-mass spectrometry. Odor concentrations at the plots were evaluated on site with a Nasal Ranger field olfactometer that sniffed over a defined land surface area through a static chamber. The odors emitted by anaerobically digested sewage sludges from three activated sludge water treatment plants had one characteristic chemical fingerprint. Alkaline stabilization emitted substantial odors associated with high concentrations of ammonia and release of nitrogen-containing VOCs and did not effectively reduce the potential odor annoyance. Odorous VOCs could be generated within the soil after biosolids incorporation, presumably because of anaerobic conditions within soil-biosolids aggregates. We propose that dimethyl disulfide and dimethyl trisulfide, which seem to be most related to the odor concentrations of biosolids-treated soil, be used as potential chemical markers for the odor annoyance associated with incorporation of anaerobically digested sewage sludges.

• Original and Residual Phytotoxicity of Olive Mill Wastewater Revealed by Fractionations before and after Incubation with Pleurotus ostreatus.

  Authors: Ido Aviani, Michael Raviv, Yitzhak Hadar, Ibrahim Saadi, Yael Laor

  Journal of agricultural and food chemistry. 11/2009;

  Concentrations of dissolved organic carbon (DOC) and total phenols (TP), and the phytotoxicity to cress (Lepidium sativum L.) were determined for three molecular-sized fractions of olive millConcentrations of dissolved organic carbon (DOC) and total phenols (TP), and the phytotoxicity to cress (Lepidium sativum L.) were determined for three molecular-sized fractions of olive mill wastewater (OMW), <1000, 1000-5000, and >5000 Da, before and after incubation with Pleurotus ostreatus. The <1000-Da fraction contained 82% of the total DOC and 48% of the TP, and was the most phytotoxic. Ethyl acetate separation of aqueous and solvent fractions showed that the aqueous fraction contained 93% of the total DOC, 83% of the TP, and was most phytotoxic, indicating low importance of monomeric phenols. Incubation of whole OMW and of the separate size fractions with P. ostreatus mycelia reduced TP by factors of 4.3-5.3, but exerted diverse impact on phytotoxicity; overall, P. ostreatus efficacy in organic load removal and OMW detoxification was limited. Additional size fractionation of the incubated fractions revealed that most residual phytotoxicity was associated with low-molecular weight (MW) compounds originated from the <1000 Da fraction and not with low-MW byproducts from the degradation of higher-MW fractions and that polymerized metabolites were nonphytotoxic. Total phenols should not be used as sole indicators of the successful remediation of OMW.

• Spatial and seasonal patterns of fluorescent organic matter in Lake Kinneret (Sea of Galilee) and its catchment basin.

  Authors: Mikhail Borisover, Yael Laor, Arkady Parparov, Nadezhda Bukhanovsky, Marcos Lado

  Water research. 08/2009; 43(12):3104-16.

  Lake Kinneret (Sea of Galilee) is one of the major water resources in Israel. The origin and characteristics of natural organic matter (NOM) in the lake and its tributary rivers were studied usingLake Kinneret (Sea of Galilee) is one of the major water resources in Israel. The origin and characteristics of natural organic matter (NOM) in the lake and its tributary rivers were studied using fluorescence excitation emission matrices (EEM) and parallel factor analysis. Two humic-like and one proteinous components were sufficient to describe EEM variability among 167 water samples collected between 2/2005 and 9/2006. The two humic-like components showed different relations in lake and riverine samples. Their vertical distribution in the lake was affected by seasonal stratification and distance from water surface, presumably reflecting the release of humic-like matter from sediments, its production via NOM transformation in the bottom layers, and its photodegradation in the upper layers. Vertical distribution of the proteinous component, indicating biological activity at upper water layers, did not correlate with that of the humic-like components. Dissolved organic carbon concentrations did not show any vertical stratification, emphasizing the power of EEM to explore NOM dynamics.

• Methodological aspects of microcalorimetry used to assess the dynamics of microbial activity during composting.

  Authors: Shlomit Medina, Michael Raviv, Ibrahim Saadi, Yael Laor

  Bioresource technology. 07/2009;

  Isothermal microcalorimetry is a sensitive non-invasive analytical tool that can become useful in research on compost and other biosolids. The aim of the present study was to address severalIsothermal microcalorimetry is a sensitive non-invasive analytical tool that can become useful in research on compost and other biosolids. The aim of the present study was to address several methodological aspects that are critical to the use of microcalorimetry to assess the dynamics of microbial activity in such systems. The results show that: (1) The calorimetric baseline is strongly influenced by the run temperature in the range relevant to composting systems (20-60 degrees C), and is also affected by addition of the water that is required to maintain or optimize microbial activity, presumably because some water evaporates through ampoule gaskets. (2) Amending mature compost with readily available substrates requires additional careful baseline treatment. (3) Sample heterogeneity can be successfully minimized by passing through a 2-mm sieve. Additional size separation can be useful to enable focusing on the more active fractions. (4) Oxygen depletion is a key feature in batch calorimetric analysis; for samples of highly active composts or manure, the total amount of heat released relative to the oxygen available in the ampoule may indicate the co-existence of anaerobic and aerobic metabolic pathways. Finally, practical recommendations for microcalorimetry analyses of pre-mature and mature composts are outlined.

• Dynamics of offensive gas-phase odorants in fresh and aged feces throughout the development of beef cattle.

  Authors: Ariel Shabtay, Uzi Ravid, Arieh Brosh, Rima Baybikov, Harel Eitam, Yael Laor

  Journal of animal science. 02/2009;

  Livestock odors are largely caused by several groups of volatile organic compounds (VOCs), including sulfur containing compounds, volatile fatty acids (VFAs), phenols and indoles. Throughout theLivestock odors are largely caused by several groups of volatile organic compounds (VOCs), including sulfur containing compounds, volatile fatty acids (VFAs), phenols and indoles. Throughout the growth stages of cattle in nursery and feedlot, distinctly different diets are formulated to meet the animal's changing requirements. Because diet compositions as well as manure management are two major factors affecting odor emissions, it was assumed that changes in diet composition along calves' development would impact VOCs emissions from fresh and stored manure. In this study the dynamic of gas phase VOCs in feces from six Holstein-Friesian bull calves was followed at five ages: 1-5 weeks (stage-I), 6-8 weeks (stage-II, before weaning), 9-14 weeks (stage-III, after weaning) and 15-36 weeks (stage-IV and V). The crude protein (CP) content of the formulated diet decreased from 23.0% to 13.9%. Fresh feces samples were incubated either under aerobic or anaerobic conditions for 21 days. VOCs were analyzed from feces headspace using solid phase microextraction followed by GC-MS. Distinct changes in gas-phase VOCs were observed in fresh and aged feces from different ages of calves. Semi-quantitatively (based on comparative peak area counts), the following trends were observed: 1. S-compounds were the least dominant in fresh feces at the age of 2 weeks (stage-I) whereas VFA-esters were the most dominant. 2. At age of 7 weeks (stage-II), a week before calves weaning, feces seemed to be the most offensive presumably due of the difficulty to synchronize between animal's requirements and diet formulation during this stage of rapid development. 3. VOCs decreased during feces storage under aerobic conditions but significantly increased at all five life stages during storage under anaerobic conditions. This study demonstrates that life stage in combination with manure management affect odor emissions from beef fattening operations. Incorporation of calves' age and diet in odor modeling could improve annoyance predictions.

• Chemical-sensory characterization of dairy manure odor using headspace solid-phase microextraction and multidimensional gas chromatography mass spectrometry-olfactometry.

  Authors: Yael Laor, Jacek A Koziel, Lingshuang Cai, Uzi Ravid

  Journal of the Air & Waste Management Association (1995). 10/2008; 58(9):1187-97.

  Livestock operations are associated with emissions of odor, gases, and particulate matter. The majority of previous livestock odor studies focused on swine operations whereas relatively few relate toLivestock operations are associated with emissions of odor, gases, and particulate matter. The majority of previous livestock odor studies focused on swine operations whereas relatively few relate to dairy cattle. Identifying the compounds responsible for the primary odor impact is a demanding analytical challenge because many critical odor components are frequently present at very low concentrations within a complex matrix of numerous insignificant volatiles. The objective of this study was to describe a chemical-sensory profile of dairy manure odor using headspace solid-phase microextraction (HS-SPME) and multidimensional gas chromatography-mass spectrometry-olfactometry (MDGC-MS-O). Two analytical approaches were used: (1) HS-SPME time-series extractions (from seconds up to 20 hr) followed by gas chromatography-mass spectrometry-olfactometry (GC-MS-O) analyses, and (2) relatively short HS-SPME extractions (30 min) followed by MDGC-MS-O analyses on selected chromatogram heart-cuts. Dairy manure was collected at research dairy farms in the United States and Israel. Volatile organic compounds (VOCs) resolved from multiple analyses included sulfur-containing compounds, volatile fatty acids, ketones, esters, and phenol/indole derivatives. A total of 86 potential odorants were identified. Of them, 17 compounds were detected by the human nose only. A greater number of VOCs and odorous compounds were detected, as well as higher mass loading, on solid-phase microextraction (SPME) fibers observed for longer extractions with SPME. However, besides sulfur-containing compounds, other selected compounds showed no apparent competition and displacement on the SPME fiber. The use of MDGC-MS-O increased chromatographic resolution even at relatively short extractions and revealed 22 additional odorants in one of the regions of the chromatogram. The two analytical approaches were found to be parallel to some extent whereas MDGC-MS-O can also be considered as a complementary approach by resolving more detailed chemical-sensory odor profiles.

• Land spreading of olive mill wastewater: effects on soil microbial activity and potential phytotoxicity.

  Authors: Ibrahim Saadi, Yael Laor, Michael Raviv, Shlomit Medina

  Chemosphere. 02/2007; 66(1):75-83.

  Extremely high organic load and the toxic nature of olive mill wastewater (OMW) prevent their direct discharge into domestic wastewater treatment systems. In addition to the various treatment schemesExtremely high organic load and the toxic nature of olive mill wastewater (OMW) prevent their direct discharge into domestic wastewater treatment systems. In addition to the various treatment schemes designed for such wastewater, controlled land spreading of untreated OMW has been suggested as an alternative mean of disposal. A field study was conducted between October 2004 and September 2005 to assess possible effects of OMW on soil microbial activity and potential phytotoxicity. The experiment was carried out in an organic orchard located on a Vertisol-type soil (Jezre'el Valley, Israel) and included two application levels of OMW (36 and 72m(3)ha(-1)). Total microbial counts, and to less extent the hydrolytic activity and soil respiration were increased following the high OMW application level. A bench-scale lab experiment showed that the rate of OMW mineralization was mainly dependent on the general status of soil activity and was not related to previous acclimatization of the soil microflora to OMW. Soil phytotoxicity (% germination and root elongation) was assessed in soil extracts of samples collected before and after each OMW application, using germinating cress (Lepidium sativum L.) seeds. We found direct short-term effect of OMW application on soil phytotoxicity. However, the soil was partly or completely recovered between successive applications. No further phytotoxicity was observed in treated soils as compared with control soil, 3 months after OMW application. Such short-term phytotoxicity was not in correlation with measured EC and total polyphenols in the soil extracts. Overall, the results of this study further support a safe controlled OMW spreading on lands that are not associated with sensitive aquifers.

• Fluorescence-based evidence for adsorptive binding of pyrene to effluent dissolved organic matter.

  Authors: Mikhail Borisover, Yael Laor, Nadezhda Bukhanovsky, Ibrahim Saadi

  Chemosphere. 01/2007; 65(11):1925-34.

  Using fluorescence intensity measurements, pyrene interactions with different types of effluent dissolved organic matter (EDOM) originated from treated municipal wastewater are examined. MultipleUsing fluorescence intensity measurements, pyrene interactions with different types of effluent dissolved organic matter (EDOM) originated from treated municipal wastewater are examined. Multiple observations show that fluorescence intensity of pyrene-EDOM solutions is non-linearly related to pyrene concentration, with distinct concave-up dependence. Testing the effect of pyrene concentration on fluorescence intensity of pyrene-EDOM solutions provides a tool to examine whether binding of an organic compound to EDOM follows linear or non-linear isotherm. Possible coupling between static and dynamic quenching effects was addressed while analyzing fluorescence data. Limited number of EDOM binding sites results in a non-linear binding isotherm such that the concept of pyrene "partitioning" between aqueous phase and "bulky" EDOM organic phase is hardly relevant. Maximal EDOM capacity for pyrene binding is estimated approximately as 0.1% ww(-1). Examination of the differences between the total fluorescence intensity of pyrene-EDOM solution and the fluorescence intensities of separated constituents (pyrene and EDOM) was used to illustrate the accumulation of pyrene-EDOM complexes and saturation of some EDOM binding sites. Strong interactions between pyrene and EDOM binding sites may result in pyrene distribution coefficients differing at least by a factor 3.5-7 at varying pyrene concentrations.

• Monitoring of effluent DOM biodegradation using fluorescence, UV and DOC measurements.

  Authors: Ibrahim Saadi, Mikhail Borisover, Robert Armon, Yael Laor

  Chemosphere. 05/2006; 63(3):530-9.

  The potential of effluent DOM to undergo microbial degradation was assessed in batch experiments. Effluent samples from Haifa wastewater treatment plant and Qishon reservoir (Greater Haifa wastewaterThe potential of effluent DOM to undergo microbial degradation was assessed in batch experiments. Effluent samples from Haifa wastewater treatment plant and Qishon reservoir (Greater Haifa wastewater reclamation complex, Israel) were incubated either with effluent or soil microorganisms for a period of 2-4 months and were characterized by dissolved organic carbon contents (DOC), UV(254) absorbance and by fluorescence excitation-emission matrices. Three main fluorescence peaks were identified that can be attributed to humic/fulvic components and "protein-like" structures. During biodegradation, specific fluorescences (F/DOC) of the three peaks were increased at various extents, suggesting selective degradation of non-fluorescing constituents. In some cases increase in the effluent fluorescence (F) was observed thus proposing (i) the formation of new fluorescing material associated with DOM biodegradation and/or (ii) degradation of certain organic components capable of quenching DOM fluorescence. Based on the ratio between fluorescence intensity and UV(254), different biodegradation dynamics for fluorescent DOM constituents as compared with other UV-absorbing molecules was delineated. Overall, about 50% of the total DOM was found to be readily degradable such that residual resistant DOC levels were between 8 and 10 mg l(-1). Enhanced levels of residual DOM in effluent-irrigated soils may contribute to the DOM pool capable of carrying pollutants to groundwater.

• Using a passive multilayer sampler for measuring detailed profiles of gas-phase VOCs in the unsaturated zone.

  Authors: Yael Laor, Daniel Ronen, Ellen R Graber

  Environmental science & technology. 02/2003; 37(2):352-60.

  The purpose of this study was to test in the laboratory the performance of a passive multilayer sampler (MLS) for obtaining detailed profiles of gas-phase volatile organic compounds (VOCs) inThe purpose of this study was to test in the laboratory the performance of a passive multilayer sampler (MLS) for obtaining detailed profiles of gas-phase volatile organic compounds (VOCs) in unsaturated sediments. The MLS is essentially a chain of isolated, cylindrical stainless steel dialysis cells filled with distilled water and closed with membranes at both ends. The sampling principle is based on passive equilibration of the unsaturated zone gas phase with water in the cells. Using trichloroethene (TCE) as a model VOC, and after testing the required equilibration time in the laboratory (about 50 h), results of a large container (210 L) experiment show that TCE concentrations obtained by the MLS deployed inside a well screen corresponded very well to the profile obtained by dialysis cells buried in the sediment. A field profile taken at the saturated-unsaturated interface region of a VOC-contaminated area using the MLS shows steep TCE concentration gradients (1119 microg TCE/L-air/cm) in the gas phase of the unsaturated zone just above the water table.

• Evidence for nonlinear binding of PAHs to dissolved humic acids.

  Authors: Yael Laor, Menahem Rebhun

  Environmental science & technology. 04/2002; 36(5):955-61.

  Binding of pyrene, fluoranthene, and phenanthrene to dissolved humic acids (HA) was determined by the fluorescence quenching (FQ) and complexation-flocculation (CF) methods. Determinations by the CFBinding of pyrene, fluoranthene, and phenanthrene to dissolved humic acids (HA) was determined by the fluorescence quenching (FQ) and complexation-flocculation (CF) methods. Determinations by the CF method, using varying contaminant concentrations and a constant HA concentration, yielded nonlinear Freundlich-type isotherms (n = 0.65-0.84). Experiments using both the CF and the FQ methods with varying HA concentrations and a constant contaminant concentration yielded curved "Stern-Volmer"-type plots that also indicate nonlinear binding. These findings suggest that linear partitioning or site complexation in the presence of excess available sites cannot fully describe the interactions of hydrophobic compounds with dissolved humic material. Site-specific hydrophobic interactions at limited interior or external molecular surfaces may be considered.

• Methodological aspects of microcalorimetry used to assess the dynamics of microbial activity during composting

  Authors: Shlomit Medina, Michael Raviv, Ibrahim Saadi, Yael Laor

  Bioresource Technology.

  Isothermal microcalorimetry is a sensitive non-invasive analytical tool that can become useful in research on compost and other biosolids. The aim of the present study was to address severalIsothermal microcalorimetry is a sensitive non-invasive analytical tool that can become useful in research on compost and other biosolids. The aim of the present study was to address several methodological aspects that are critical to the use of microcalorimetry to assess the dynamics of microbial activity in such systems. The results show that: (1) The calorimetric baseline is strongly influenced by the run temperature in the range relevant to composting systems (20–60 °C), and is also affected by addition of the water that is required to maintain or optimize microbial activity, presumably because some water evaporates through ampoule gaskets. (2) Amending mature compost with readily available substrates requires additional careful baseline treatment. (3) Sample heterogeneity can be successfully minimized by passing through a 2-mm sieve. Additional size separation can be useful to enable focusing on the more active fractions. (4) Oxygen depletion is a key feature in batch calorimetric analysis; for samples of highly active composts or manure, the total amount of heat released relative to the oxygen available in the ampoule may indicate the co-existence of anaerobic and aerobic metabolic pathways. Finally, practical recommendations for microcalorimetry analyses of pre-mature and mature composts are outlined.

• Compost suppressiveness against Fusarium oxysporum was not reduced after one-year storage under various moisture and temperature conditions

  Authors: Ibrahim Saadi, Yael Laor, Shlomit Medina, Arkady Krassnovsky, Michael Raviv

  Soil Biology and Biochemistry.

  The effect of storage conditions on compost suppressiveness against fusarium wilt of melon, caused by Fusarium oxysporum f. sp. melonis (FOM) was studied in relation to the dynamics of compostThe effect of storage conditions on compost suppressiveness against fusarium wilt of melon, caused by Fusarium oxysporum f. sp. melonis (FOM) was studied in relation to the dynamics of compost microbial activity and biodegradability. For this purpose, mature suppressive compost, prepared from tomato plants and separated cow manure, was divided into four portions and stored for one year under cool/warm (12 or 28 °C) or dry/wet (15–35 or 55–65% moisture content) conditions, in four different combinations: cool-dry, warm-dry, cool-wet and warm-wet. All composts retained and even enhanced their suppressive capacity during storage, with no significant differences among them by the end of the storage period. However, significant differences were found in the dynamics of some of the measured chemical and microbial properties. The microbial activity of composts stored under wet conditions was higher than that of those stored under dry condition, which resulted in a substantial decrease in dissolved organic matter content (expressed as dissolved organic carbon; DOC) and increase in its recalcitrance to biological degradation, decrease in basal heat emission, slower response to added glucose or citric acid, and higher NO3 concentration, indicating increased nitrification under wet conditions. The DOC significantly correlated with several microbial properties as well as with compost suppressiveness of fusarium wilt of melon seedlings, and may be regarded as a most suitable general index for compost maturity. A best-subset multiple linear regression analysis revealed that the three best predictors, namely dissolved organic carbon (DOC), basal heat, and mesophilic bacterial counts, could explain as much as 83% of the total variance in compost suppressiveness. The generally agreed association between compost maturity and suppressiveness was verified in this case. It appears that compost microbial populations might compete and interfere with the saprophytic stage of FOM conidia, between germination and host invasion. In conclusion, it was demonstrated that compost suppressiveness against fusarium wilt of melon can be maintained for at least one year under a wide range of storage conditions, without any loss of suppressive capacity. This fact has positive logistical implications for the use of suppressive composts against FOM.

• Fluorescence-based evidence for adsorptive binding of pyrene to effluent dissolved organic matter

  Authors: Mikhail Borisover, Yael Laor, Nadezhda Bukhanovsky, Ibrahim Saadi

  Chemosphere.

  Using fluorescence intensity measurements, pyrene interactions with different types of effluent dissolved organic matter (EDOM) originated from treated municipal wastewater are examined. MultipleUsing fluorescence intensity measurements, pyrene interactions with different types of effluent dissolved organic matter (EDOM) originated from treated municipal wastewater are examined. Multiple observations show that fluorescence intensity of pyrene–EDOM solutions is non-linearly related to pyrene concentration, with distinct concave-up dependence. Testing the effect of pyrene concentration on fluorescence intensity of pyrene–EDOM solutions provides a tool to examine whether binding of an organic compound to EDOM follows linear or non-linear isotherm. Possible coupling between static and dynamic quenching effects was addressed while analyzing fluorescence data. Limited number of EDOM binding sites results in a non-linear binding isotherm such that the concept of pyrene “partitioning” between aqueous phase and “bulky” EDOM organic phase is hardly relevant. Maximal EDOM capacity for pyrene binding is estimated approximately as 0.1% w w−1. Examination of the differences between the total fluorescence intensity of pyrene–EDOM solution and the fluorescence intensities of separated constituents (pyrene and EDOM) was used to illustrate the accumulation of pyrene–EDOM complexes and saturation of some EDOM binding sites. Strong interactions between pyrene and EDOM binding sites may result in pyrene distribution coefficients differing at least by a factor 3.5–7 at varying pyrene concentrations.