Similar Physical-chemical Properties Research Articles

Ultrafast-adsorption-kinetics molecular sieving of propylene from propane

The separation of propylene (C3H6) and propane (C3H8) is very costly due to similar physical-chemical properties and has been listed as one of the seven chemical separations to change the world. High-purity C3H6 is an important raw material to produce polypropylene and acrylonitrile. However, C3H8 is produced as a by-product in the production process of C3H6, which has a similar structure and boiling point as those of C3H6. Traditionally, the separation of C3H6 and C3H8 by distillation has high energy consumption and an unremarkable separation effect. Therefore, there is an urgent need to develop more energy-saving and efficient methods for the separation of C3H6 and C3H8.

Deep Eutectic Solvents: Green Applications

Recently, ionic liquids (ILs) have attracted considerable attention in scientific research as greensolvents. Owing to their low vapor pressure, ILs were qualified as green solvents. However, the ”greenaffiliation” of ILs is now contested by many research groups. The hazardous toxicity and the very poorbiodegradability of many ILs have been reported in the literature. Additionally, their synthesis generallyrequires a large amount of salts and solvents. These drawbacks and the high price of common ILs delayedtheir industrial applications. To overcome these drawbacks, a new generation of solvents, named DeepEutectic Solvents (DESs), has emerged. DESs can be formed by mixing, at moderate temperature, two ormore components that can be chosen to be cheap, renewable and biodegradable. These compounds arecapable of forming a eutectic mixture with a melting point lower than that of the individual component.DESs are generally liquid at temperatures lower than 100 C.Many DESs have similar physical-chemical properties to those of ILs, while being much cheaper andenvironmentally friendlier. Owing to these advantages, there is growing interest in DESs in many fields ofresearch. DESs are chemically tailorable solvents since they can be designed by properly combining variousquaternary ammonium or phosphonium salts with different hydrogen bond donors (HBD) or complexingagents. Hence, task-specific DESs with different physical-chemical properties can be prepared.In this work, we discuss the important contributions of DESs in diverse applications, e.g. electrochemicalprocesses, catalysis, synthesis, absorption of CO2, desulfurization of fuels, separation, and dissolution andextraction processes.

Bioinformatics Approach on Bioisosterism Softwares to be Used in Drug Discovery and Development

Background:In the rational drug development field, bioisosterism is a tool that improves lead compounds' performance, referring to molecular fragment substitution that has similar physical-chemical properties. Thus, it is possible to modulate drug properties such as absorption, toxicity, and half-life increase. This modulation is of pivotal importance in the discovery, development, identification, and interpretation of the mode of action of biologically active compounds.Objective:Our purpose here is to review the development and application of bioisosterism in drug discovery. In this study history, applications, and use of bioisosteric molecules to create new drugs with high binding affinity in the protein-ligand complexes are described.Method:It is an approach for molecular modification of a prototype based on the replacement of molecular fragments with similar physicochemical properties, being related to the pharmacokinetic and pharmacodynamic phase, aiming at the optimization of the molecules.Results:Discovery, development, identification, and interpretation of the mode of action of biologically active compounds are the most important factors for drug design. The strategy adopted for the improvement of leading compounds is bioisosterism.Conclusion:Bioisosterism methodology is a great advance for obtaining new analogs to existing drugs, enabling the development of new drugs with reduced toxicity, in a comparative analysis with existing drugs. Bioisosterism has a wide spectrum to assist in several research areas.

Geochemical signatures and natural background values of rare earth elements in soils of Brazilian Amazon.

Rare earth elements (REEs) are generally defined as a homogenous group of elements with similar physical-chemical properties, encompassing Y and Sc and the lanthanides elements series. Natural REEs contents in soils depend on the parent material, the soil genesis processes and can be gradually added to the soil by anthropogenic activities. The REEs have been considered emerging pollutants in several countries, so the establishment of regulatory guidelines is necessary to avoid environmental contamination. In Brazil, REE soils data are restricted to some regions, and knowledge about them in the Amazon soils is scarce, although this biome covers more than 40% of the Brazilian territory. Thus, the objectives of this study were to determine the REE content in soils of two hydrographic basins (Solimões and Rio Negro) of the Amazon biome, establish their Quality Reference Values (QRV) and to investigate the existence of enrichment of REEs in urban soils. The ΣREE(Y+Sc) content of Solimões surface samples was 109.28mgkg-1 and the ΣREE(Y+Sc) content in the subsurface samples was 94.11mgkg-1. In soils of Rio Negro basin, the ΣREE(Y+Sc) was 43.95 15mgkg-1 surface samples and 38.40mgkg-1 in subsurface samples. The ΣREE(Y+Sc) in urban topsoils samples was 38.62mgkg-1. The REEs contents pattern in three studied areas are influenced in different amplitude by natural soil properties. The REEs content in urban topsoils were slightly higher than the Rio Negro pristine soils, but the ecological risk was low. QRVs recommend for Solimões soils ranged from 0.01 (Lu) to 145.6mgkg-1 (Ce) and for Rio Negro soils ranged from 0.05 (Lu) to 15.8mgkg-1 (Ce).

Cadmium Fractions in Two Calcareous Soils Affected by Incubation Time, Zinc and Moisture Regime

ABSTRACTThis study has been performed to determine the impact of zinc (Zn) on cadmium (Cd) fractions in two types of calcareous soils of the Fars province in Iran at the waterlogged condition. High-reduced conditions in soil reduce Cd solubility because of the development of Cd Sulfide. Cadmium and Zn have similar physical-chemical properties; they are maintained in soil’s exchangeable sites as a divalent ion. Since such few studies have been conducted in calcareous soils of Iran, we examined the effect of Zn on Cd fractions due to their similar characteristics. Treatments were three levels of Cd (0, 30 and 60 mg kg−1 of soil as CdSO4.8H2O), three levels of Zn (0, 5 and 10 mg kg−1 of soil as ZnSO4 .7 H2O), three levels of incubation times (2, 4 and 8 weeks), and two types of soils (clay and sandy clay loam). The randomized completed block design (RCBD) was used for this experiment. After 2, 4, and 8 weeks of treatments, the sequential extraction technique was used to determine the Cd concentration in (WsEx), (Fe-MnOx), (Car), (OM) and (Res.) fractions. The data indicated that based on the soil texture 64% to 70% of the Cd was extracted in the WsEx and Fe-MnOx fractions. The waterlogged condition decreased the Cd concentration in the WsEx fraction and increased the Fe-MnOx, Car and OM fractions. Cd concentration in Res. fraction was higher in the clay soil while WsEx, Car and OM fractions were higher in the sandy clay loam soil. Adding Zn as zinc sulfate reduced the concentration of Cd in Fe-MnOx, Car and OM fractions but had no significant effect on the WsEx and Res. fractions. It can be concluded that the change in the Cd concentration in its chemical fractions caused by Zn addition might be from the competitive transport and adsorption interaction between these two ions. The presence of Zn reduces the concentration of Cd in those forms that are easily released into the soil solution from where they can be absorbed by plants.Abbreviation: WsEx: Water Soluble and Exchangeable; Car: Carbonate; Fe-MnOx: Iron-Manganese Oxides; OM: Organic Matter; Res: Residual

Molecular modelling methods in food safety: Bisphenols as case study

Bisphenol A (BPA), a synthetic compound widely used as a building block for polycarbonate plastics, has been declared in the European Union (EU) as a substance of very high concern (SVHC). A series of BPA alternatives and derivatives (bisphenols/BPs) with similar physical-chemical properties have been produced and used by companies for substituting it. To evaluate the estrogenic and androgenic binding activity of 26 BPs, a non-statistical in silico approach has been applied. The results of molecular docking analyses applied on six different nuclear receptors (NRs) have revealed that: i) some BPA metabolites could lower the harmful effects of BPA exposure; ii) BPS is a lower interactor for all NRs, but it does not appear safer at all for androgen receptor (AR), for which its binding activity is found similar to a pharmacological anti-androgen; iii) only a BP has been found as a safer compound for all NRs considered. Moreover, molecular dynamic simulation of three BPs on ERα have revealed that the presence of negative hydrophobic interactions could induce a decrease in receptor activity. Overall, the present results demonstrate that in silico methods could be a valid approach to screen estrogenic and androgenic activity of food contact materials (FCMs).

Natural deep eutectic solvents and aqueous solutions as an alternative extraction media for propolis.

Ethanolic extracts of propolis are consumed for their health benefits even though direct consumption of alcoholic extracts is not always ideal. Natural Deep Eutectic Solvents (NADES) can potentially extract similar compounds as alcoholic extracts while being better for direct consumption. Therefore, in this work alternative solvents for the extraction of green propolis including its biomarker artepillin C were examined. Sixteen NADES made from low toxicity chemicals, including the essential amino acid l-lysine, were explored along with twelve individual NADES components and honey, which showed similar physical-chemical properties to NADES. At 50 °C NADES made from choline chloride-propylene glycol or lactic acid proved to be equal or better than the benchmark EtOH:Water 7:3 (v/v). Alternatively, aqueous l-lysine appeared as a potential solvent for the preparation of aqueous propolis extracts. From these findings NADES, honey and aqueous l-lysine solutions all demonstrated the potential to replace ethanol or water for extracting green propolis.

Purification of phenolic compounds from genipap (<i>Genipa americana</i> L.) extract by the ultrasound assisted ultrafiltration process

The aim of this study was to evaluate the potential of an integrated membrane process for purification of polyphenol and genipin components from genipap fruit extract. Optimal conditions for aqueous extraction of polyphenols from genipap fruit pulp were at 71°C for 49 min using a fruit pulp:water ratio of 1:3 (w w-1). Microfiltration with membranes of different pore sizes (0.22, 0.3 and 0.8 µm) resulted in a clarified permeate with similar physical-chemical properties, but the permeate flux through the 0.8 µm membrane was higher than through the other membranes. The sequential ultrafiltration process reduced even more total and soluble solids of the microfiltered extract. Purities of polyphenols and genipin were, respectively, 2.5 and 1.2 times greater in the permeate than in the feed stream. Application of ultrasound during the ultrafiltration increased the steady state permeate flux and the purities of polyphenols and genipin in the permeate stream. Results suggest application of microfiltration as a clarification step followed by the ultrasound assisted ultrafiltration to produce a purified genipap extract with high contents of polyphenols and genipin.

Variability of release rate of flame retardants in wastewater treatment plants

Information on variability is important in the assessment of the releases and potential risks of brominated flame retardants (BRFs) in the environment, but related data are limited. In this study, two release-characterizing parameters, release fraction to final effluent and influent-biosolids transfer coefficient, were used to quantify releases of five BFRs from eight secondary wastewater treatment plants (WWTPs). The five BFRs are recalcitrant, hydrophobic, and low in volatility. The two parameters for these BFRs were found to vary from day to day and season to season within individual WWTPs as well as from one WWTP to another. These temporal and spatial variations were, however, comparable to each other and both within a factor of 3 above or below the parameter averages. Averages for release fraction were in the range of 0.02–0.29 and those for influent-biosolids transfer coefficient in the range of 3–26 L/g, depending upon a given BFR at a given WWTP. These ranges and the observed factor-3 variability are not only useful for estimating releases of the five BFRs, but more importantly provide read-across data for the assessment of substances with similar physical-chemical properties.

<b>Evaluation of the density, volatility and anti-knock rating physical-chemical properties of alternative butanol/gasoline fuel blends

Butanol, popularly known as butyl alcohol, has been recently recognized by researchers from around the world as a promising component for use in blends with gasoline, because of its very similar physical-chemical properties. In this study, butan-1-ol ( n -butanol) and 2-methylpropan-1-ol (isobutanol) were blended with pure gasoline in proportions of up to 30% mass. The blends density, volatility and anti-knock rating were experimentally determined and compared with Brazilian commercial gasoline specifications. The results showed that the blends properties kept a strong dependency on the linear or branched butanol molecular structure and with the interaction effects of its hydroxyl groups. In the blends, a polynomial increase in density was observed, with a consequent volatility reduction, affecting the vapor pressure and distillation curve, especially for specified 50 and 90% evaporated temperatures (T50 and T90). Minor effects were observed at the T10 and FBP curve extremes. Octane rating and anti-knock index gains were observed, with noted increase of MON for 2-methylpropan-1-ol based blends. At the tested butanol content range, blends characteristics presented satisfactory compatibility with Brazilian gasoline specifications.

Economic Estimation of Various Membranes and Distillation for Propylene and Propane Separation

The separation of propylene and propane is very costly due to similar physical-chemical properties. In this study, the effect of various membranes on the economic performance of the olefin unit was evaluated. The Robeson’s line cannot judge the economic performance of membrane separation systems. A precise model of cocurrent and counter-current hollow fiber membrane was developed and implemented in a commercial chemical engineering software to estimate the economics of the best inorganic (ZIF-8) and polymeric (6FDA-TrMPD) membranes compared with the existing distillation unit. At the same area, the cocurrent flows have higher recovery and the counter-current flows have higher purity. The use of the alternative polymer membrane results in a drastic increase in costs. The ZIF-8 membrane performance leads to a 30% increase in the total capital costs, while the annual cost considerably decreased by 46%. When the membrane performance is appropriate in terms of selectivity and permeability, the use of membrane ...

Green solvents: Applications in petroleum refinery

In the last two decades, Ionic Liquids (ILs) have attracted considerable attention in many fields of scientific research. ILs have drawn an increasing interest due to their unique physical and chemical properties that showed a great potential as an alternative media in many potential applications. ILs are defined as low melting point, lower than 100 °C, salts consisting of organic cations and organic/inorganic anions both of which are large ions and held together by electrostatic interactions. ILs has very low vapor pressure, non-flammable, tunable and can dissolve both polar and non-polar compounds. Owing to their low vapor pressure ILs were qualified as green solvents. However, the green affiliation of ILs is now contested by many research groups. The conventional technology used for oil extraction from oilseeds is by solvent extraction. In solvent extraction, n-hexane is used as a solvent for its attributes such as simple recovery, non-polar nature, low latent heat of vaporization (330 kJ/kg) and high selectivity to solvents. However, usage of hexane as a solvent has lead to several repercussions such as air pollution, toxicity and harmfulness that prompted to look for alternative options.The hazardous toxicity and the very poor biodegradability of many ILs have been reported in the literature. ILs with high purity is also required since impurities, even in trace amounts, affect their physical properties. These drawbacks together with the high price of common ILs delayed their industrial applications and new concepts were strongly needed in order to utilize these systems in a more rational way. To overcome these drawbacks, a new generation of solvents, named Deep Eutectic Solvents (DES), has emerged as alternative to ILs in many applications. Formation of these DESs can be obtained by simply mixing together two or more components that can be chosen to be cheap, renewable and biodegradable. These compounds are capable of forming a eutectic mixture with a melting point lower than that of each individual component. DESs are generally liquid at temperatures lower than 100 °C. Many DESs have similar physical-chemical properties to those of ILs, while being much cheaper and environmentally friendlier. Owing to these advantages, there is now of growing interest in DESs in many fields of research. DESs are chemically tailorable solvents since they can be designed by properly combining various quaternary ammonium or phosphonium salts with different Hydrogen Bond Donors (HBD) or complexing agents. Hence, task-specific DESs with different physical-chemical properties can be prepared. It should also be noted that although components of DESs are potentially reactive chemicals, their auto-association by a hydrogen bond drastically limits their reactivity, allowing their use in many fields of research. In this work, we discuss the application of both ILs and DESs in petroleum refining and petrochemical processes. Examples include, but are not limited to, separation of aromatics, de-sulfurization, de-nitrification and carbon dioxide capture.

Characterization of Phase Separation Propensity for Amorphous Spray Dried Dispersions.

A generalized screening approach, applying isothermal calorimetry at 37 °C 100% RH, to formulations of spray dried dispersions (SDDs) for two active pharmaceutical ingredients (APIs) (BMS-903452 and BMS-986034) is demonstrated. APIs 452 and 034, with similar chemotypes, were synthesized and promoted during development for oral dosing. Both APIs were formulated as SDDs for animal exposure studies using the polymer hydroxypropylmethlycellulose acetyl succinate M grade (HPMCAS-M). 452 formulated at 30% (wt/wt %) was an extremely robust SDD that was able to withstand 40 °C 75% RH open storage conditions for 6 months with no physical evidence of crystallization or loss of dissolution performance. Though 034 was a chemical analogue with similar physical chemical properties to 452, a physically stable SDD of 034 could not be formulated in HPMCAS-M at any of the drug loads attempted. This study was used to develop experience with specific physical characterization laboratory techniques to evaluate the physical stability of SDDs and to characterize the propensity of SDDs to phase separate and possibly crystallize. The screening strategy adopted was to stress the formulated SDDs with a temperature humidity screen, within the calorimeter, and to apply orthogonal analytical techniques to gain a more informed understanding of why these SDDs formulated with HPMCAS-M demonstrated such different physical stability. Isothermal calorimetry (thermal activity monitor, TAM) was employed as a primary stress screen wherein the SDD formulations were monitored for 3 days at 37 °C 100% RH for signs of phase separation and possible crystallization of API. Powder X-ray diffraction (pXRD), modulated differential scanning calorimetry (mDSC), Fourier transform infrared spectroscopy (FTIR), and solid state nuclear magnetic resonance (ssNMR) were all used to examine formulated SDDs and neat amorphous drug. 452 SDDs formulated at 30% (wt/wt %) or less did not show phase separation behavior upon exposure to 37 °C 100% RH for 3 days. 034 SDD formulations from 10 through 50% (wt/wt %) all demonstrated thermal traces consistent with exothermic phase separation events over 3 days at 37 °C 100% RH in the TAM. However, only the 15, 30, and 50% containing 034 samples showed pXRD patterns consistent with crystalline material in post-TAM samples. Isothermal calorimetry is a useful screening tool to probe robust SDD physical performance and help investigate the level of drug polymer miscibility under a humid stress. Orthogonal analytical techniques such as pXRD, ssNMR, and FTIR were key in this SDD formulation screening to gain physical understanding and confirm or refute whether physical changes occur during the observed thermal events characterized by the calorimetric screening experiments.

Light-Assisted Detection of Methanol in Contaminated Spirits

The growing market of artisanal alcoholic beverages have faced challenges to assess the quality of the commercialized products. Contaminated beverages, resulting not only from an uncontrolled production process but also from deliberate adulteration, may contain nonsafe amounts of methanol leading to risks for consumers. Ethanol and methanol share similar physical-chemical properties. Both are colorless, soluble in water, and they have very close values of density. Although analytical laboratorial methods can precisely determine the alcoholic composition, rapid distinction between them is a conundrum. This paper proposes and compares two methods that can be used to fast detect the contamination of alcoholic beverages with methanol. Despite the proximity between densities of methanol and ethanol, as well as the close refractive indexes of methanol and water, it is shown that these macroscopic parameters can be used together to analyze the beverage composition. Additionally, using the fingerprinting molecular analysis provided by Raman spectroscopy and a statistical procedure based on principal component analysis, it is shown a rapid method for the detection of methanol presence in beverages above a pre-established level, without the need for addition of any standard to the sample. The performances of both methods were tested and validated with samples containing different amounts of water, ethanol, and methanol and beverages deliberately contaminated with methanol.

Evolution of chemical composition of fogwater in winter in Chengdu, China

Two sampling sites representing the urban and suburban area of Chengdu, China were sampled and analyzed for selected chemicals to characterize the evolution of the chemical composition of fogwater. A trend of total organic carbon (TOC) > total nitrogen (TN) > total inorganic carbon (TIC) was observed for both sites. Variation of inorganic ions indicated that inorganic pollutants were not accumulated in the fog. Concentrations of n-alkanes (C11–C37) at the urban site ranged from 7.58 to 27.75 ng/mL while at the suburban site concentrations were 2.57–21.55 ng/mL. The highest concentration of n-alkanes was observed in the mature period of fog (393.12 ng/mL) which was more than ten times that in the fog formation period (27.83 ng/mL) and the fog dissipation period (14.87 ng/mL). Concentrations of Σ15PAHs were in the range of 7.27–38.52 ng/mL at the urban site and 2.59–22.69 ng/mL at the suburban site. Contents of PAHs in the mature period of fog (27.15 ng/mL) > fog dissipation period (11.59 ng/mL) > fog formation period (6.42 ng/mL). Concentrations of dicarboxylic acids (C5–C9) ranged from 10.92 to 40.78 ng/mL, with glutaric acid (C5) as the dominant dicarboxylic acid. These data provide strong indications of the accumulation of certain organic chemicals of environmental concern in fog and fog water, and provide additional insights about processes in urban and suburban air acting on organic chemicals with similar physical chemical properties.

Soil exchangeable base cations along a chronosequence of Caragana microphylla plantation in a semi-arid sandy land, China

As a pioneer leguminous shrub species for vegetation re-establishment, Caragana microphylla is widely distributed in the semi-fixed and fixed sandy lands of the Horqin region, North China. C. microphylla plantations modify organic carbon (SOC), nitrogen (N) and phosphorus dynamics, bulk density and water-holding capacity, and biological activities in soils, but little is known with regard to soil exchange properties. Variation in soil exchangeable base cations was examined under C. microphylla plantations with an age sequence of 0, 5, 10, and 22 years in the Horqin Sandy Land, and at the depth of 0–10, 10–20, and 20–30 cm, respectively. C. microphylla has been planted on the non-vegetated sand dunes with similar physical-chemical soil properties. The results showed that exchangeable calcium (Ca), magnesium (Mg), and potassium (K), and cation exchange capacity (CEC) were significantly increased, and Ca saturation tended to decrease, while Mg and K saturations were increased with the plantation years. No difference was observed for exchangeable sodium (Na) neither with plantation years nor at soil depths. Of all the base cations and soil layers, exchangeable K at the depth of 0–10 cm accumulated most quickly, and it increased by 1.76, 3.16, and 4.25 times, respectively after C. microphylla was planted for 5, 10, and 22 years. Exchangeable Ca, Mg, and K, and CEC were significantly (P<0.001) and positively correlated with SOC, total N, pH, and electrical conductivity (EC). Soil pH and SOC are regarded as the main factors influencing the variation in exchangeable cations, and the preferential absorption of cations by plants and different leaching rates of base cations that modify cation saturations under C. microphylla plantation. It is concluded that as a nitrogen-fixation species, C. microphylla plantation is beneficial to increasing exchangeable base cations and CEC in soils, and therefore can improve soil fertility and create favorable microenvironments for plants and creatures in the semi-arid sandy land ecosystems.

Effects of particle characteristics on flame propagation behavior during organic dust explosions in a half-closed chamber

To reveal the effects of particle characteristics on the mechanisms of flame propagation during organic dust explosions clearly, three long chain monobasic alcohols which are solids at room temperature and have similar physical–chemical properties were chosen to carry out experiments in a half-closed small chamber. A high-speed video camera was used to record the flame propagation process and to obtain the direct light emission photographs. Flame temperature was detected by a fine thermocouple. Based on the experimental results above, analysis was conducted on flame propagation characteristics and temperature profiles of organic particle cloud. As a result, it was found that the particle materials, especially volatility, strongly affected the flame propagation behavior. Particle concentration also affects the combustion zone propagation process significantly. With increasing the particle concentration, the maximum temperature of the combustion zone increases at the lower concentration, reaches a maximum value, and then decreases at the higher concentration. The propagation velocity of the combustion zone has a linear relationship with the maximum temperature, which implies conductive heat transfer is dominant in the flame propagation process of the three different volatile dusts.

Decabromodiphenyl ethane and decabromodiphenyl ether in Swedish background air

Decabromodiphenyl ethane (DPDPE) is a flame retardant that has been on the market for more than 20 years and is used as a replacement for decabromodiphenyl ether (BDE-209). Environmental data on DPDPE are scarce but for BDE-209, studies have shown that long-range transport in the atmosphere leads to contamination of remote regions. Given their similar physical–chemical properties, we hypothesized that this is also true for DPDPE. In this study we explored the European continent as a source for DBDPE by collecting air samples at a back-ground location in southern Sweden. Twelve samples with stable air mass back trajectories over the 24 h sampling period were analysed. BDE-209 and 5 polycyclic aromatic hydrocarbons (PAHs) were also included in the study. The concentration ranges of DBDPE and BDE-209 were similar, 0.077–7.9 and 0.093–1.8 pg m −3 air, respectively. The highest concentrations were detected when the air originated from the European continent and the lowest during periods with rather stagnant air over southern Scandinavia. The concentrations of DBDPE and BDE-209 did not co-vary, indicating that there are different major sources of the two compounds. In air, the compounds measured in this study are predominantly associated with particles. PAHs in the atmosphere are known to originate primarily from combustion processes and their concentrations were highly correlated with several measures of atmospheric particle concentration, i.e. PM 10, PM 2.5, soot, and N 450 (number of particles in the size range approximately 420–450 nm). No clear correlations were found between the concentrations of DBDPE or BDE-209 and any of the measures of particle concentrations, indicating that the emissions of these are not related to the major sources of emissions of soot or small particles.

The spectroscopic studies of humic acid extracted from sediment collected at different seasons

Goczałkowice Reservoir is the biggest water reservoir in the south of Poland. For our studies bottom sediments were collected from eight different places of the reservoir at various seasons of the year.EPR spectroscopy was applied to analyse both quantitatively and qualitatively the humic acids (HA) present in the samples. EPR spectra of the extracted HA exhibited broad lines from the paramagnetic metal ions and narrow lines from free radicals. The values of the free radical concentration obtained for HA amounted to 1.14–13.6×1016sping−1 depending on the season and the place of sample collection. The values of the g factor obtained for HA were of the range 2.0027–2.0035.The EPR studies show that HA extracted from bottom sediment collected at various points of the Goczałkowice Reservoir exhibit similar physical–chemical properties. It was also observed that the depth of the reservoir affects the content of the oxygen functional groups as well as the free radical concentration in HA.The identification of the functional groups was done by means of IR. UV/VIS spectroscopy was used to estimate the maturity of the HA.

Endosulfan, a global pesticide: A review of its fate in the environment and occurrence in the Arctic

This review investigates the fate and behaviour of endosulfan, a current-use organochlorine pesticide, in temperate environments and the Arctic. Usage data and patterns, physical–chemical properties, environmental partitioning and degradation, environmental levels, global distribution and temporal trends are evaluated and discussed in the context of criteria that designate a substance as a persistent organic pollutant. Endosulfan is one of the most abundant OC pesticides in the global atmosphere and is capable of undergoing long range transport to remote locations such as the Arctic. Degradation of the two isomers, α- and β-endosulfan, does occur in temperate/tropical soil and aquatic systems, both by abiotic and biotic processes, although this is highly dependent on the prevailing environmental conditions. Endosulfan sulfate is the major metabolite and this recalcitrant compound has been detected in air and is present in remote mountain lake sediments, although in comparison to α-endosulfan, data for this compound in the wider environment are lacking. Temporal trends from ice/snow cores as well as mountain lake sediments reveal a marked increase in endosulfan accumulation from the 1980s onwards. Furthermore, unlike other ‘legacy’ OC pesticides, levels of α-endosulfan do not show a decline in atmospheric monitoring data, reflecting ongoing use of this pesticide in the northern hemisphere. Endosulfan is present at low concentrations (relative to the pesticide, lindane) in surface Arctic Ocean waters, with the atmosphere likely to be the major contemporary source. Residues of endosulfan have been detected in marine biota for different geographical regions of the Arctic, with higher bioaccumulation factors (> 10 3–10 7) for zooplankton and various species of fish, compared to studies in warmer/temperate systems. Endosulfan is present in marine mammals, although there is uncertainty in the various Arctic biota datasets due to differences in analytical techniques. For some biota, biomagnification factors for α-endosulfan are > 1, notably from fish to seal, although there is a wide variability in values between the same species for different regions of the Arctic. There is little if any evidence of trophic magnification of α-endosulfan in well-defined marine foodwebs, with some evidence of bio-dilution at higher trophic levels, presumably due to increased metabolism. Endosulfan does fulfil several of the criteria under the UNEP Stockholm Convention for designation as a persistent organic pollutant. The α- and β-isomer have similar physical–chemical properties and environmental behaviour to some of the obsolete organochlorine pesticides, although an assessment of their persistence and toxicity should be viewed alongside endosulfan sulfate, as ‘Σendosulfan’. Persistence of ‘Σendosulfan’ coupled to ongoing use of endosulfan pesticides, will ensure continued long-range transport and contamination of remote environments.