In this study, equilibrium isotherms, kinetics and thermodynamics of ciprofloxacin on seven sediments in a batch sorption process were examined. The effects of contact time, initial ciprofloxacin ...concentration, temperature and ionic strength on the sorption process were studied. The
K
d
parameter from linear sorption model was determined by linear regression analysis, while the Freundlich and Dubinin–Radushkevich (D–R) sorption models were applied to describe the equilibrium isotherms by linear and nonlinear methods. The estimated
K
d
values varied from 171 to 37,347 mL/g. The obtained values of
E
(free energy estimated from D-R isotherm model) were between 3.51 and 8.64 kJ/mol, which indicated a physical nature of ciprofloxacin sorption on studied sediments. According to obtained
n
values as measure of intensity of sorption estimate from Freundlich isotherm model (from 0.69 to 1.442), ciprofloxacin sorption on sediments can be categorized from poor to moderately difficult sorption characteristics. Kinetics data were best fitted by the pseudo-second-order model (
R
2
> 0.999). Thermodynamic parameters including the Gibbs free energy (Δ
G
°), enthalpy (Δ
H
°) and entropy (
Δ
S°) were calculated to estimate the nature of ciprofloxacin sorption. Results suggested that sorption on sediments was a spontaneous exothermic process.
•Six PCB congeners and 12 PAH compounds were determined in bulk deposition samples.•Extraction on silica sorbent followed by GC-ECD and GC-MS/MS analysis.•The deposition rates of ∑12PAHs up to 1069 ...ng m−2 d−1 in cold period.•There weren't significant seasonal variations in the deposition fluxes of PCBs.•First study in Croatia to produce results for PAHs and PCBs in deposition matters.
A method based on solid phase extraction (SPE), gas chromatography tandem mass spectrometry (GC-MS/MS) and gas chromatography with electron capture detector (GC-ECD) was developed for the determination of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in atmospheric deposition samples. Six indicator PCB congeners were analysed by GC-ECD equipped with two micro electron-capture detectors and two gas chromatographic columns, while 12 PAH compounds were analysed by GC-MS/MS. Solid phase extraction on silica sorbent proved suitable for accumulation of PAHs and PCBs from deposited matters. The extraction procedure was based by passing the whole sample volume through a silica cartridge with dichloromethane and n-hexane as the eluting solvents. Two different performances of a bulk collector were compared. The method was validated using field total deposited samples collected monthly over a year by bulk method at an urban background station in Zagreb, Croatia. The levels and occurrence of PCBs corresponded to global environmental pollution, with the deposition rates of ∑6PCBs between 6 - 28 ng m−2 d−1. The deposition rates of ∑12PAHs varied between 132 and 714 ng m−2 d−1 during the warm period, whereas it achieved a significantly higher range of 171 to 1069 ng m−2 d−1 in the cold period.
Praćenje razina koncentracija PM2,5 frakcije lebdećih čestica kao i određivanje njihova kemijskog sastava od velike je važnosti s obzirom na to da su brojna istraživanja pokazala povezanost te ...frakcije čestica i štetnih učinaka na zdravlje ljudi i kvalitetu okoliša. Na mjernoj postaji smještenoj na području Nacionalnog parka Plitvička jezera sakupljani su 24-satni uzorci frakcije lebdećih čestica PM2,5 na filtrima od kvarcnih vlakana tijekom 2015. godine. Masene koncentracije frakcije lebdećih čestica PM2,5 gravimetrijski su određene, dok su masene koncentracije organskog (OC) i elementnog (EC) ugljika određene metodom termičko-optičke transmisije. Najviše masene koncentracije lebdećih čestica, OC-a i EC-a izmjerene su ljeti, dok su najniže izmjerene zimi.
Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna .
Narrow city streets surrounded by tall buildings are favorable to inducing a general effect of a “canyon” in which pollutants strongly accumulate in a relatively small area because of weak or ...inexistent ventilation. In this study, levels of nitrogen-oxide (NO2), elemental carbon (EC) and organic carbon (OC) mass concentrations in PM10 particles were determined to compare between seasons and different years. Daily samples were collected at one such street canyon location in the center of Zagreb in 2011, 2012 and 2013. By applying machine learning methods we showed seasonal and yearly variations of mass concentrations for carbon species in PM10 and NO2, as well as their covariations and relationships. Furthermore, we compared the predictive capabilities of five regressors (Lasso, Random Forest, AdaBoost, Support Vector Machine and Partials Least squares) with Lasso regression being the overall best performing algorithm. By showing the feature importance for each model, we revealed true predictors per target. These measurements and application of machine learning of pollutants were done for the first time at a street canyon site in the city of Zagreb, Croatia.
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•Applying Machine Learning Methods of traffic-related pollutants at a street canyon site, Croatia.•Selection of features and ability to explain model were improved with permutation importance.•The predictivity of pollutants by regression models increases in order PM10 < NO2 < EC < OC.•Test predictivity of pollutants are important for future urban planning and air quality.
Cilj: Prikazati specifičnu komplikaciju kroničnog pankreatitisa, odnosno perforaciju tankog crijeva uslijed kompresivnog učinka pseudociste te različite načine dijagnostike i liječenja. Prikaz ...slučaja: Pacijent u dobi od 60 godina zaprimljen je na hitni prijam zbog difuznih bolova u abdomenu, najviše lokaliziranih u žličici te je naveo da obilno povraća tamnosmeđi sadržaj nakon svakog unosa vode i hrane. Fizikalnim pregledom ustanovljena je palpatorna bolnost stijenke abdomena i defans stijenke. Prilikom hospitalizacije napravljen je CT abdomena koji je ukazao na egzacerbaciju kroničnog pankreatitisa. U prilog egzacerbaciji kroničnog pankreatitisa govorila je velika cistična tvorba (195 × 109 × 158 mm). U pseudocistu je postavljen dren radi kontinuiranog pražnjenja. Nakon perkutane drenaže i dalje je perzistirala pseudocista veličine 21 × 18 mm te je ostvarila komunikaciju s manjom cističnom tvorbom iz burse omentalis. Sljedećeg dana ERCP tehnikom postavile su se dvije pankreatične proteze zbog stenoziranog ductusa pancreaticusa na prijelazu između glave i repa gušterače. Pred otpust pacijenta UTZ abdomena pokazao je reziduu pseudociste veličine 30 × 30 mm. Tjedan dana nakon otpusta pacijent dolazi na hitni prijam radi povraćanja, smanjenog apetita, anergije i mršavljenja. Daljnjim pretragama ustanovila se perforacija tankog crijeva kao posljedica adhezivnog ileusa i peritonitis. Stanje se pacijenta tijekom dva dana pogoršavalo – bio je anergičan, usporen, smanjenog stanja svijesti te je preminuo na odjelu intenzivnog liječenja. Zaključak: Ileus i perforacija tankog crijeva vrlo su rijetke komplikacije pseudociste gušterače, te je do danas ovo drugi opisan slučaj perforacije tankog crijeva uslijed kompresivnog učinka pseudociste. Simptomi ileusa kod egzacerbacije kroničnog pankreatitisa trebali bi pobuditi sumnju na kompresivne smetnje cistične tvorbe u abdomenu.
Aim: To present a specific complication of chronic pancreatitis which is perforation of the small intestine due to the compressive effect of pseudocysts, and different ways of diagnosis and treatment of the same. Case report: A 60-year-old man was admitted to the emergency room due to diffuse abdominal pain and profuse vomiting of dark brown contents. Physical examination revealed palpatory abdominal wall pain and abdominal defanse. During hospitalization, a CT of the abdomen was made, which indicated an exacerbation of chronic pancreatitis.As a support of the exacerbation of chronic pancreatitis, s a large cystic formation (195x109x158mm) well limited was found, filled with denser content in gravity-dependent parts. A drain was placed in the pseudocyst for continuous emptying. After percutaneous drainage, a pseudocyst measuring 21x18mm persisted and made communication with a smaller cystic formation from the bursa omentalis. The next day, two pancreatic prosthesis were placed by ERCP technique due to stenosed ductus pancreaticus at the junction between the head and tail of the pancreas. Prior to the patient’s discharge, US of the abdomen showed a residual pseudocyst measuring 30x30mm. One week after discharge, the pacient came back to emergency room because of the vomiting, decressed appetite and energy, and weight loss. Further examinations revealed a perforation of the small intestine as the resault of adhesive ileus and peritonitis. The patient’s condition worsened in two days and he was described as anergic with decreased state of consciousness and he died that day in the intensive care unit. Conclusion: A pseudocyst that grows despite therapeutic procedures, and the symptoms and signs of ileus in the exacerbation of chronic pancreatitis should raise suspicion of compression disorders of cystic formation in the abdomen.
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•First application of microwave-assisted extraction (MAE) of organic pollutants from human milk samples.•Sample pretreatment maximizes MAE efficiency for PBDE extraction.•MAE has a ...potential with liquid samples.•First data on PBDE burden in Croatian mothers.
As a method, microwave-assisted extraction (MAE) has a number of advantages over other extraction methods, such as lower solvent consumption and analyte loss, shorter processing time, and higher sample throughput. So far, however, MAE has mostly been applied with solid samples like sediments and soil. This paper describes the first MAE of organic pollutants from human milk samples, the influence of sample preparation and pretreatment, and how extraction conditions (type and volume of solvent, extraction temperature) were optimized. The most efficient way to extract polybrominated diphenyl ethers (PBDEs) from human milk using MAE was dissolving a freeze-dried sample in ultrapure water and applying a solvent mixture of n-hexane and acetone (1:1, v/v) with formic acid and 2-propanol as denaturing agents at 105 °C for 20 min. Extracts were cleaned up with concentrated sulfuric acid and on SPE column containing neutral and acidified silica with n-hexane and dichloromethane (4:1, v/v) as elution solvent. The method was validated at two concentration levels through parallel analysis by gas chromatography with two detection techniques and application in real samples and a baby formula (similar matrix). It has shown great potential for the analysis of organic pollutants in important biological matrices such as human milk. Further optimization could extend its application to other classes of persistent organic pollutants (POPs).
First data on polycyclic aromatic hydrocarbons (PAHs) and nitro-aromatic compounds (NACs) in aerosols as well as of PAHs, polychlorinated biphenyls (PCBs) and NACs in bulk and wet atmospheric ...deposition samples were simultaneously obtained during 6-month-long field campaign at the costal central Adriatic area. Special attention was given to open-fire biomass burning episodes as extreme events common for the overall Mediterranean coastal area in order to gain a better understanding of the atmospheric variabilities and potential sources of trace organic pollutants in coastal environments. Diesel and gasoline combustion related to land and maritime traffic as well as occasional open-fire episodes (forest fires) were found to be the dominant pollution sources of PAHs in PM10 particles. NACs were determined almost exclusively in samples affected by biomass burning episodes. Open-fire episodes had a strong contribution to the overall NACs atmospheric deposition fluxes. Several chlorinated congeners of PCBs were predominantly contributed in deposition samples.
•First data of organic contents in aerosols and deposition samples at the Adriatic area•Data obtained during biomass burning events as extreme events for the Adriatic area•Strong influence of biomass burning on deposition fluxes of organic contents
In this paper, the authors investigated changes in mass concentrations of particulate matter (PM) during the Coronavirus Disease of 2019 (COVID-19) lockdown. Daily samples of PM
, PM
and PM
fractions ...were measured at an urban background sampling site in Zagreb, Croatia from 2009 to late 2020. For the purpose of meteorological normalization, the mass concentrations were fed alongside meteorological and temporal data to Random Forest (RF) and LightGBM (LGB) models tuned by Bayesian optimization. The models' predictions were subsequently de-weathered by meteorological normalization using repeated random resampling of all predictive variables except the trend variable. Three pollution periods in 2020 were examined in detail: January and February, as pre-lockdown, the month of April as the lockdown period, as well as June and July as the "new normal". An evaluation using normalized mass concentrations of particulate matter and Analysis of variance (ANOVA) was conducted. The results showed that no significant differences were observed for PM
, PM
and PM
in April 2020-compared to the same period in 2018 and 2019. No significant changes were observed for the "new normal" as well. The results thus indicate that a reduction in mobility during COVID-19 lockdown in Zagreb, Croatia, did not significantly affect particulate matter concentration in the long-term..
Tomato waste was studied as a low-cost biosorbent for the removal of five pharmaceuticals (dexamethasone, febantel, procaine, praziquantel, and tylosin) from water. Tomato waste was characterized ...chemically and microstructurally before and after simulated sorption. Sorption performance was interpreted as a function of the initial pharmaceuticals concentration, temperature, and physicochemical properties of the tomato waste. The linear, Freundlich, and Dubinin–Radushkevich (D-R) isotherms were used to describe the experimental results at different temperatures (298, 303, and 308 K). Thermodynamic parameters such as standard free energy (ΔG°), enthalpy change (ΔH°), and entropy change (ΔS°) were determined. Negative values of ΔG° in the temperature range of 298–308 K strongly indicate the spontaneous nature of the biosorption process. In addition, the values of ΔH° for the biosorption of dexamethasone, procaine, praziquantel, and tylosin on tomato waste were negative, indicating exothermic processes, while the positive value for febantel indicated an endothermic process. The kinetic data were analyzed using (i) kinetic models to determine the kinetic parameters (Lagergren’s pseudo-first order and Ho’s pseudo-second order) and (ii) adsorption–diffusion models to the describe transport mechanisms of pharmaceuticals from aqueous solution onto tomato waste as adsorbent (Weber–Morris intraparticle diffusion and Boyd film diffusion models).
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