Nataša Đurišić-Mladenović

Principal component analysis of indicator PCB profiles in breast milk from Poland

Principal component analysis (PCA) was applied to a data set containing the levels of indicator polychlorinated biphenyls (PCBs) in human milk of mothers living in the Wielkopolska region, Poland, in order to investigate the information captured in the PCB patterns and to elucidate the relationship between PCB concentrations in milk and donor characteristics. According to the obtained PCA results milk fat content was the most influential factor affecting the PCB levels in milk of the Wielkopolska cohort. The lifestyle data collected from the questionnaire completed by the donors appeared to have no influence on PCB concentrations in breast milk. The score plots revealed the PCB contents of milk were quite low and uniform with a few outliers, without discrimination observed either between the primipareous and secundipareous females or between donors from the urban and rural areas. Comparison of the PCB levels and profiles of human milk from the Wielkopolska region and from various European and Asian locations made by PCA reflected a generally low background exposure and indicated the possible reasons for the outlying of some samples. In order to enhance the chances of observing the relationship between donor habits and PCB levels in breast milk it was suggested that the questionnaire be redesigned to gather information about vegetable product consumption and indoor air exposure.

Chemometric assessment of the semivolatile organic contaminants content in the atmosphere of the selected sites in the Republic of Macedonia

Data obtained through a pilot study for the development of the monitoring network in the Central and Eastern Europe (MONET_CEEC) 2006, regarding the occurrence of 12 organochlorine pesticides (OCPs), seven indicator polychlorinated biphenyls (PCBs) and 28 polycyclic aromatic hydrocarbons (PAHs) in the air of six locations in the Republic of Macedonia have been interpreted by principal component (PCA) and cluster (CA) analysis. The data structures of three sets organized to contain the atmospheric concentrations of (a) PAHs, the so‐called PAHs set, (b) both classes of organochlorine compounds (PCBs and OCPs) grouped in the organochlorinated compounds (OCCs) set and (c) the overall data (the semivolatile organic compounds (SVOCs) set) were compared. The PCA results suggested mixed origin of PAHs, especially dominant in the urban zones of Skopje, the capital of the Republic of Macedonia. Furthermore, it was found that retene had a distinctive source that separated it from the rest of the PAHs, and it was linked to the incidents of biomass burning. The OCC atmospheric patterns differed among the sites more than it was the case with the PAH patterns, implying some site‐specific sources or conditions that influenced the OCC atmospheric concentrations. CA coupled with bootstraps confirmed the groupings of samples found by the PCA biplots. The influence of available meteorological parameters on the SVOC atmospheric concentrations has been evaluated by multiple regression analysis (MRA) indicating the positive impacts of temperature and wind speed for majority of analyzed SVOCs. Precipitation was found to be linked proportionally only with pentachlorobenzene and hexachlorobenzene. Copyright

Comparison of multianalyte proficiency test results by sum of ranking differences, principal component analysis, and hierarchical cluster analysis

AbstractSum of ranking differences (SRD) was applied for comparing multianalyte results obtained by several analytical methods used in one or in different laboratories, i.e., for ranking the overall performances of the methods (or laboratories) in simultaneous determination of the same set of analytes. The data sets for testing of the SRD applicability contained the results reported during one of the proficiency tests (PTs) organized by EU Reference Laboratory for Polycyclic Aromatic Hydrocarbons (EU-RL-PAH). In this way, the SRD was also tested as a discriminant method alternative to existing average performance scores used to compare mutlianalyte PT results. SRD should be used along with the z scores—the most commonly used PT performance statistics. SRD was further developed to handle the same rankings (ties) among laboratories. Two benchmark concentration series were selected as reference: (a) the assigned PAH concentrations (determined precisely beforehand by the EU-RL-PAH) and (b) the averages of all individual PAH concentrations determined by each laboratory. Ranking relative to the assigned values and also to the average (or median) values pointed to the laboratories with the most extreme results, as well as revealed groups of laboratories with similar overall performances. SRD reveals differences between methods or laboratories even if classical test(s) cannot. The ranking was validated using comparison of ranks by random numbers (a randomization test) and using seven folds cross-validation, which highlighted the similarities among the (methods used in) laboratories. Principal component analysis and hierarchical cluster analysis justified the findings based on SRD ranking/grouping. If the PAH-concentrations are row-scaled, (i.e., z scores are analyzed as input for ranking) SRD can still be used for checking the normality of errors. Moreover, cross-validation of SRD on z scores groups the laboratories similarly. The SRD technique is general in nature, i.e., it can be applied to any experimental problem in which multianalyte results obtained either by several analytical procedures, analysts, instruments, or laboratories need to be compared. FigureSum of ranking differences (SRD) order analytical methods or laboratories according to their overall (multianalyte) performances using either the average (or median) or the assigned values as the reference for the ranking

Isolation and Characterization of Antagonistic Bacillus Strains Capable to Degrade Ethylenethiourea

In this study, more than 150 bacteria showing antagonistic properties against bacterial and fungal pathogens of the tomato plant were isolated and characterized. The most efficient agents against these phytopathogenic microorganisms belong to the genus Bacillus: the best biocontrol isolates were representatives of Bacillus subtilis, B. mojavensis and B. amyloliquefaciens species. They intensively produced fengycin or/and surfactin depsipeptide antibiotics and also proved to be excellent protease secretors. It was proved, that the selected strains were able to use ethylenethiourea (ETU) as sole nitrogen source. These antagonistic and ETU-degrading Bacillus strains can be applied as biocontrol and also as bioremediation agents.

Esterification of sludge palm oil as a pretreatment step for biodiesel production.

Acid esterification of sludge palm oil, having 50 mas.% free fatty acids, i.e. 50 g of dominant free fatty acid per 100 g of oil, was investigated with the objective of determining conditions for the efficient reduction of free fatty acids. The influences of sulphuric acid dosage and molar ratio of methanol to oil were studied, with the final intention to obtain feedstock with a free fatty acids content acceptable for biodiesel production by alkali-transesterification. Esterification was performed using different molar ratios of methanol to oil (3:1, 6:1 and 9:1) and varying the amount of H2SO4 catalyst (0.92 mas.%, 1.84 mas.% and 4.60 mas.%). Under the applied conditions, the sulphuric acid dosage of 4.60 mas.% resulted in the satisfactory decrease of the feedstock’s free fatty acids for 6:1 and 9:1 molar ratios of methanol to oil. Thus, taking into account the economic reasoning, it can be concluded that approximately 5 mas.% of H2SO4 with 6:1 molar ratio of methanol to oily feedstock, might be regarded as the dosage necessary for satisfactory pretreatment of the feedstock to be further subjected to the alkaline transesterification. Finally, the effort to consolidate the information on acid esterification available in literature was made, contributing to knowledge on sustainable biodiesel production using the low-grade and low-cost sources.

POLYCYCLIC AROMATIC HYDROCARBONS IN PRODUCTS OF A BEET SUGAR FACTORY IN VOJVODINA: LEVELS AND INTAKES

The levels of 16 EPA polycyclic aromatic hydrocarbons (PAHs) were investigated in samples of sugar beets and their products representative for a beet sugar factory located in the central part of Vojvodina, the main agricultural region in Serbia. The sum of the detected PAHs ranged from 51 pg g −1 ww for molasses to 391 pg g −1 ww for dried sugar beet pulp. The concentration of benzo(a)pyrene (BaP) for all sample types was about or less than 100 pg g −1 ww, which is far less than the existing Serbian and EU tolerances set for some foodstuffs. The Serbian intake of BaP via total sugar consumption that ranged from 70–85 g per capita day −1 , was assessed to be from 0.029 to 0.035 ng kg −1 b.w. day −1 . Furthermore, the toxic equivalency factor (TEF) approach was used to estimate the carcinogenicity of PAH mixture found in analyzed samples.

Seasonal occurrence and cancer risk assessment of polycyclic aromatic hydrocarbons in street dust from the Novi Sad city, Serbia

This is the first investigation that identified seasonal occurrence, distribution and sources of 16 polycyclic aromatic hydrocarbons (PAHs) in 60 street dust samples collected within urban zone of Novi Sad, the second largest city in Serbia. The obtained results were further used for comprehensive assessment of carcinogenic risk of Serbian inhabitants exposed to PAHs present in street dust by the incremental lifetime cancer risk method. The total level of 16 PAHs ranged between 35 μg kg-1 and 2422 μg kg-1 in samples taken in summer and between 35 μg kg-1 and 587 μg kg-1 in samples taken in winter. In both seasons, 4-ring PAHs were the most dominant compounds and high molecular weight (HMW) PAHs had similar contribution (55% in summer and 65% in winter). The highest content was determined for fluoranthene (Fly) in both seasons (597 μg kg-1 in winter, 301 μg kg-1 in summer). The PAHs source apportionment was analyzed by principal component analysis (PCA) and diagnostic ratios, and combustion of petroleum seemed to be the main sources of the PAHs in street dust. The cancer risk level for children and adult were comparable for dermal contact and by ingestion, and ranged from 10-6 to 10-4 indicating a potential risk. Additionally, the total incremental life time cancer risk (ILCR) was assessed for children and adult population taking into account three possible exposure routs and the median total cancer risk was ˃10-5, with 7% of the samples having the risk ˃10-4 that should be considered of high concern with potential health problem. These results are the first of this kind for the whole Serbia and the Western Balkan region and can be considered as the base line for future research.