Solid-liquid Partition Research Articles

Unraveling Drug Delivery from Cyclodextrin Polymer-Coated Breast Implants: Integrating a Unidirectional Diffusion Mathematical Model with COMSOL Simulations.

Breast cancer ranks among the most commonly diagnosed cancers worldwide and bears the highest mortality rate. As an integral component of cancer treatment, mastectomy entails the complete removal of the affected breast. Typically, breast reconstruction, involving the use of silicone implants (augmentation mammaplasty), is employed to address the aftermath of mastectomy. To mitigate postoperative risks associated with mammaplasty, such as capsular contracture or bacterial infections, the functionalization of breast implants with coatings of cyclodextrin polymers as drug delivery systems represents an excellent alternative. In this context, our work focuses on the application of a mathematical model for simulating drug release from breast implants coated with cyclodextrin polymers. The proposed model considers a unidirectional diffusion process following Fick's second law, which was solved using the orthogonal collocation method, a numerical technique employed to approximate solutions for ordinary and partial differential equations. We conducted simulations to obtain release profiles for three therapeutic molecules: pirfenidone, used for preventing capsular contracture; rose Bengal, an anticancer agent; and the antimicrobial peptide KR-12. Furthermore, we calculated the diffusion profiles of these drugs through the cyclodextrin polymers, determining parameters related to diffusivity, solute solid-liquid partition coefficients, and the Sherwood number. Finally, integrating these parameters in COMSOL multiphysics simulations, the unidirectional diffusion mathematical model was validated.

Using the quantitative ion character-activity relationships (QICAR) model to predict the solid-liquid release of metals in soil

Dissolved metals in the soil’s liquid phase are more easily absorbed by biological tissues, thus posing potential risks to living organisms. Therefore, studying the solid-liquid partition coefficient (Kd) of metals in the soil helps understand their environmental risks. We collected 102 Kd data of metals in soil from the literature to build a quantitative ion character-activity relationship model (s-QICAR) based on the metals’ physicochemical properties. Correlation analysis showed ten elemental physicochemical properties related to Kd, including covalent bond index, atomic mass, and first hydrolysis constant, with R2 = 0.502–0.989. Through comparative screening, 39s-QICAR models were finally established, including covalent bond index and first hydrolysis constant. The established s-QICAR model predicted the Kd values of Mo, Sb, and La in the 39 soil samples, ranging from 21 to 19978. Finally, a coupling analysis was conducted between Kd-metal and soil physicochemical properties. The s-QICAR model with covalent bond index as the independent variable was mainly affected by soil pH and cation exchange capacity, while the s-QICAR model with first hydrolysis constant was influenced primarily by clay content. Therefore, this study established a predictive model for soil Kd, providing a basis for soil environmental risk assessment and management. Environmental ImplicationDissolved metals present in the soil liquid phase are more easily absorbed by biological tissues, thus posing potential risks to living organisms. Therefore, studying the solid-liquid partition coefficient (Kd) of metals in the soil helps understand their environmental risks. Common Kd values are obtained by measuring the content of soil solid and liquid phase metals. However, this method is time-material consuming. We study the relationship between element properties and their Kd, then establish a model that does not rely on measured data to predict Kd of soil elements, providing a basis for soil environmental risk assessment and management.

Large-scale arsenic mobilization from legacy sources in anoxic aquifers: Multiple methods and multi-decadal perspectives

While geogenic arsenic (As) contamination of aquifers have been intensively investigated across the world, the mobilization and transport of As from anthropogenic sources have received less scientific attention, despite emerging evidence of poor performance of widely used risk assessment models. In this study we hypothesize that such poor model performance is largely due to insufficient attention to heterogeneous subsurface properties, including the hydraulic conductivity K and the solid-liquid partition (Kd), as well as neglect of laboratory-to-field scaling effects. Our multi-method investigation includes i) inverse transport modelling, ii) in-situ measurements of As concentrations in paired samples of soil and groundwater, and iii) batch equilibrium experiments combined with (iv) geochemical modelling. As case study we use a unique 20-year series of spatially distributed monitoring data, capturing an expanding As plume in a Chromated Copper Arsenate (CCA)-contaminated anoxic aquifer in southern Sweden. The in-situ results showed a high variability in local Kd values of As (1 to 107 L kg−1), implying that over-reliance of data from only one or few locations can lead to interpretations that are inconsistent with field-scale As transport. However, the geometric mean of the local Kd values (14.4 L kg−1) showed high consistency with the independently estimated field-scale “effective Kd” derived from inverse transport modelling (13.6 L kg−1). This provides empirical evidence for the relevance of using geometric averaging when estimating large-scale “effective Kd” values from local measurements within highly heterogenous, isotropic aquifers. Overall, the considered As plume is prolonged by about 0.7 m year−1, now starting to extend beyond the borders of the industrial source area, a problem likely shared with many of the world's As-polluted sites. In this context, geochemical modelling assessments, as presented here, provided a unique understanding of the processes governing As retention, including local variability in, e.g., Fe/Al-(hydr)oxides contents, redox potential and pH.

Chemical composition and cytotoxic activity from n-hexane extract of Homalomena pendula

Background and objectives: The genus Homalomena belongings to the Araceae family. Secondary metabolites afforded from this genus show various bioactivities. This study aimed to determine the chemical composition and cytotoxicl activities of compounds isolated from n-hexane extract of rhizomes of Homalomena pendula. Materials and methods: The rhizomes of Homalomena pendula were collected from Lam Dong, Vietnam in January 2021. Extraction methods included maceration, liquid-liquid and solidliquid partition. Isolation of pure compounds was carried out by a combination of various chromatographic methods. Chemical structures were determined by extensive spectroscopic methods. Evaluation of cytotoxic activity was performed by Skehan’s method. Results: 3 sesquiterpenoids (α-cadinol, homalomenol C, taiwaninone A) and 1 steroid (sitoindoside I) were isolated. α-cadinol inhibited SK-LU-1 and HEK-293A with IC50 of 97.75 ± 4.38 μM and 92.52 ± 2.80 μM, respectively. Sitoindoside I inhibited SK-LU-1, MCF7, Hep G2, 8505c and HEK-293A with IC50 of 44.05 ± 1.91 μM; 48.97 ± 3.93 μM; 60.64 ± 2.18 μM; 48.15 ± 5.51 μM and 57.22 ± 5.20 μM, respectively. Conclusion: This is the first report on the cytotoxic activity of compounds isolated from Homalomena pendula. Key words: Homalomena pendula, cytotoxic, α-cadinol, sitoindoside I.

A methodological framework to study the behavior and kinetic influence of V, Mn, Co, Ni, Cu, Zn, As, Se and Mo during pyrite formation via the polysulfide pathway at ambient temperature

Pyritization links the biogeochemical cycles of Fe, S and C to those of trace elements (TE) such as As, Ni, Cu, Co, Mn, Zn, Se and Mo in reducing environments. The scavenging modes of such impurities in pyrite are parameters of importance for evaluating to which extent pyrite can immobilize TE under diverse (sub)surface conditions. Furthermore, determining the fate of TE during pyritization is a prerequisite to evaluate the ability of pyrite to record the chemical signature of surrounding waters at the time of precipitation. Here, we provide a methodological framework to study the incorporation of TE during a reaction sequence leading to pyrite formation via the polysulfide pathway. Laboratory syntheses were conducted by reacting a FeS precursor with elemental sulfur – both readily obtained by reducing FeCl3 with Na2S in solution under strict anoxia – at ambient temperature and in the presence of aqueous V, Mn, Co, Ni, Cu, Zn, As, Se and Mo in a TE/Fe molar ratio of 0.5 mol%. Within this simplified framework, our experiments aimed at reproducing the early formation of pyrite in water column aggregates/bottom sediments before the late diagenetic aging phases. Solids and liquids were sampled over time during the reaction sequence leading to pyrite formation, up to 3100 h, and further analyzed by ICP-OES, XRD, XRF and STEM-EDXS to obtain information on (1) the kinetics of pyrite formation and (2) the extent of TE incorporation in the solid phase, during and after the complete conversion of FeS to FeS2. Pyrite formation kinetic is observed to be strongly influenced by the identity of the added TE, with the delay before nucleation decreasing in the order Ni >> Mn, Co > Cu, Zn, Se > Control, V >> As, Mo. During the full reaction sequence, i.e. FeS plus S(0) conversion to FeS2, Mn remains in the liquid phase, Ni, Co, V, Cu, and Se quickly precipitate and remain sequestered overtime, Zn and Mo precipitate and are further released into solution, and As is partially incorporated in the solid. Elemental mapping at the microscale using STEM-EDXS show that, except for Mn, the TE are associated with pyrite. Moreover, while TE are homogeneously distributed at the particle scale for Co, Cu, Zn, As, and Se, Ni-pyrite exhibited an enriched core. The solid-liquid partition coefficients of each TE during our pyritization experiments in our simplified model system are calculated and ranks as follows: Cu ≥ Ni ≥ Co > Se > V > Mo >> As > Zn >> Mn. These partitions are discussed in the light of values reported in the literature from natural settings. The important differences observed exemplify the complexity to predict TE pyrite-water partition in sedimentary environments, in particular when considering additional multifactorial processes such as the local biogeochemistry of micro-environments, as well as the partial sequestration of TE by non-sulfide minerals such as authigenic clays and carbonates.

Modeling and simulation of trifluralin herbicide movement due to its application on soils by chemigation

The Trifluralin (TFN) is a pre-emergent herbicide which is widely used in agriculture. Usually, this pesticide is directly applied to the soil, where it can remain for long periods or can be transported. In this sense, knowing the dynamics of an herbicide soil transport is essential to avoid environmental contamination problems and risks to human health. Thus, this study aims to model and simulate TFN movement on soils with two different textures, a sandy loam and clay loam soil. It was considered that the herbicide was applied via chemigation trough a subsurface drip irrigation system, under a non-steady regime. Therefore, the transport parameters of TFN in these soils and physical-hydric characteristics of these were used, while the physical environment modeling were conducted using the Hydrus 2D software. The results showed that both in sandy and clayey soils, the TFN tends to be retained by the soil, close to where it was applied, not exceeding a layer greater than 2.5 mm outside the dripper radius, even in more favorable conditions such as the presence of irrigation. Finally, it could be concluded that this herbicide movement in the soil is of low potential, due to this product high solid-liquid partition coefficient (Kd), even in sandy soil, which has low cation exchange capacity (CEC).

ZnO Nanomaterials and Ionic Zn Partition within Wastewater Sludge Investigated by Isotopic Labeling.

The increasing commercial use of engineered zinc oxide nanomaterials necessitates a thorough understanding of their behavior following their release into wastewater. Herein, the fates of zinc oxide nanoparticles (ZnO NPs) and ionic Zn in a real primary sludge collected from a municipal wastewater system are studied via stable isotope tracing at an environmentally relevant spiking concentration of 15.2 µg g−1. Due to rapid dissolution, nanoparticulate ZnO does not impart particle‐specific effects, and the Zn ions from NP dissolution and ionic Zn display indistinguishable behavior as they partition equally between the solid, liquid, and ultrafiltrate phases of the sludge over a 4‐h incubation period. This work provides important constraints on the behavior of engineered ZnO nanomaterials in primary sludge—the first barrier in a wastewater treatment plant—at low, realistic concentrations. As the calculated solid–liquid partition coefficients are significantly lower than those reported in prior studies that employ unreasonably high spiking concentrations, this work highlights the importance of using low, environmentally relevant doses of engineered nanomaterials in experiments to obtain accurate risk assessments.

Evaluation of semi-mechanistic models to predict soil to grass transfer factor of 137Cs based on long term observations in French pastures

The aim of this study was to evaluate and improve the accuracy of the semi-mechanistic models used in regulatory exposure assessment tools, to describe the transfer factors of 137Cs from pasture soils to grass observed in different grazing areas of France between 2004 and 2017. This involved a preliminary parameterization step of the dynamic factor describing the ageing of radiocesium in the root zone using a Bayesian approach. A data set with mid-term (10 years about) and long term (more than 20 years) field and literature data from 4 European countries was used. A double kinetics of the bioavailability decay was evidenced with two half-life periods equal to 0.46 ± 0.11 yr and 9.57 ± 1.12 yr for the fast and slow declining rates respectively. We, then, tested a few existing alternative models proposed in literature. The comparison with field data showed that these models always underestimated the observations by one to two orders of magnitude, suggesting that the solid-liquid partition coefficient (Kd) was overestimated by models. The results suggest that semi mechanistic models might fail in the long-term prediction of the radionuclide transfer from soil-to-plant in the food chain. They highlight the need to calculate Kd using easily exchangeable 137Cs (i.e. labile fraction) rather than total soil 137Cs.

Anaerobic digestibility of resin acids in primary sludge: Effect of ozone pretreatment

Resin acids in pulp and paper mills wastewater are potentially partitioned in the solids in post–primary clarification due to higher hydrophobicity with log Kow ∼1.74–5.80. They are known to adversely affect anaerobic digestion (AD) process, although the effect has not been quantified deterministically in control studies. The objective of the present work was to determine the effect of untreated and ozonated spiked resin acids on AD of primary sludge. Batch adsorption tests were conducted to determine the solid-liquid partition coefficient (Kd) of resin acids on the primary sludge. Higher Kd was obtained at pH 4; however, it was decreased by 78–98% at pH 8. Thereafter, batch AD of model resin acids in primary sludge using food to microorganism ratio (S0/X) of 0.5gtCOD/gVSSindicated only 15–20% removal of resin acids in the liquid phase anaerobically. While, ozonation in pure water using 0.74–1.48 mg O3/mg tCOD showed >90% reduction of the test resin acids, an ozone dose of 0.52 mg O3/mg tCOD reduced 50–70% spiked resin acids’ load to the digester. However, no further removal of resin acids occurred during AD over 30 days. About 42% reduction in methane production compared to the control digestor occurred in the presence of 150 mg/L of resin acids. When treated with 0.52 mg O3/mg tCOD, methane production improved and was comparable to the control digestor, indicating that resin acids may not be detrimental to AD at a concentration range of 45–75 mg/L.

A rapid and practical prediction method for the Arizona solvent system family used in high speed countercurrent chromatography.

Selecting the appropriate solvent system is the key to the successful separation of samples by using countercurrent chromatography. Although high-speed countercurrent chromatography has been widely used in the separation and preparation of natural products, the selection of a solvent system has always been a stumbling block to the application of high-speed countercurrent chromatography. In order to explore a rapid and practical prediction method to select countercurrent chromatography solvent system, five linear prediction models of the Arizona solvent system family (HEMW) was established by using fourteen compounds with different structures and five HPLC columns of different brands. And two different solvent system selection methods (The partition coefficient K of the target compound in the solvent system was in the range of 0.25<K<2.5) were proposed for targeted separation of compounds and multi-component separation in a complex sample respectively. The appropriate HSCCC solvent system of five known compounds was determined by a HPLC analysis and a shake flask test and the appropriate HSCCC solvent system of two Chinese herbal extracts was determined by a HPLC analysis to verify the prediction method. In this study, solid-liquid partition chromatography (HPLC) and liquid-liquid partition chromatography (HSCCC) were linked by polarity to simplify the screening process of solvent system. This method reduced the difficulty and workload of solvent system selection, which provided methods and ideas for more solvent system prediction models.

Physicochemical and time factors affecting 137Cs transfer through a paddy soil–rice system

ABSTRACT To clarify the factors affecting 137Cs transfer from soil to brown rice in comparison with 133Cs transfer and also to determine the key parameters of the solid-liquid partition coefficient (K d), concentration factor from soil solution to brown rice (CF), and transfer factor from soil to brown rice (TF), we analyzed the results of our previous paper in which a rice pot-culture experiment under different fertilization treatments using three paddy soils in Fukushima 3 years after the Fukushima Daiichi Nuclear Power Station accident was conducted. The TF values for 137Cs were the same as or smaller than the literature values obtained within 2 years of the accident, 2–17 times higher than those for global fallout 137Cs from atmospheric nuclear tests, and 2–20 times higher than those for natural 133Cs. The CF values for 137Cs were negatively correlated with the soil solution K+ concentration. A theoretical approach, under the assumption that 137Cs in soil is mainly adsorbed at the frayed edge site (FES) and ion exchange of 137Cs with K+ and NH4 + ions is in equilibrium, partly explained the variability in the soil solution 137Cs concentrations under different soil and fertilization conditions and suggested that the major portion of 137Cs in soil would be adsorbed in FES under lower K+ and NH4 + concentrations but fixed in the collapsed interlayer sites under higher K+ and NH4 + concentrations, the ranges of which are typically observed in agricultural soils. Our results indicate that the major factors affecting 137Cs transfer from soil to brown rice would be the 137Cs, K+, and NH4 + concentrations in the soil solution and the time elapsed from the deposition of 137Cs, and emphasize the necessity of including the dynamic 137Cs adsorption and fixation process in soil into the TF prediction models applicable to agricultural soils received with periodical fertilizations.

Combining thermophilic aerobic reactor (TAR) with mesophilic anaerobic digestion (MAD) improves the degradation of pharmaceutical compounds

The removal efficiency of nine pharmaceutical compounds from primary sludge was evaluated in two different operating conditions: (i) in conventional Mesophilic Anaerobic Digestion (MAD) alone and (ii) in a co-treatment process combining Mesophilic Anaerobic Digestion and a Thermophilic Aerobic Reactor (MAD-TAR). The pilot scale reactors were fed with primary sludge obtained after decantation of urban wastewater. Concerning the biodegradation of organic matter, thermophilic aeration increased solubilization and hydrolysis yields of digestion, resulting in a further 26% supplementary removal of chemical oxygen demand (COD) in MAD-TAR process compared to the conventional mesophilic anaerobic digestion. The highest removal rate of target micropollutants were observed for caffeine (CAF) and sulfamethoxazole (SMX) (>89%) with no substantial differences between both processes. Furthermore, MAD-TAR process showed a significant increase of removal efficiency for oxazepam (OXA) (73%), propranolol (PRO) (61%) and ofloxacine (OFL) (41%) and a slight increase for diclofenac (DIC) (4%) and 2 hydroxy-ibuprofen (2OH-IBP) (5%). However, ibuprofen (IBP) and carbamazepine (CBZ) were not degraded during both processes. Anaerobic digestion affected the liquid-solid partition of most target compounds. Sorbed fraction of pharmaceutical compounds on the sludge tend to decrease after digestion, this tendency being more pronounced in the case of the MAD-TAR process due to much lower concentration of solids.

Sequential extraction of lutein and β‐carotene from wet microalgal biomass

AbstractBACKGROUNDMicroalgae are a promising resource to produce carotenoids for food/feed applications. However, energy‐intensive pre‐treatments such as drying and cell destruction can hinder the sustainability of the process. Direct extraction from wet biomass may reduce energy consumption, but the residual water can reduce the effectiveness of the organic solvents used for the extraction. In this work, the extraction of lutein and β‐carotene from wet untreated microalgal biomass is investigated. The process includes a sequence of successive extraction stages with methanol.RESULTSWe show that the sequential extraction can effectively overcome the reduced extraction efficiency induced by the residual water in the biomass. The biomass was dehydrated during the first extraction stage, which increased the efficiency starting from the second stage. This allowed an extraction yield of &gt;95% to be attained for both lutein and β‐carotene after five extraction stages. A mathematical model was developed by coupling mass balances with a linear equilibrium model, satisfactorily describing the partition of the two carotenoids between the solid and the solvent phase. By fitting the model to the data obtained by the first extraction stage, liquid–solid partition coefficients (Kd) equal to 2.0 × 10−3 and 1.1 × 10−4 were estimated for lutein and β‐carotene, respectively. The Kd of both carotenoids increased to ≈10−2 during the six subsequent extraction stages without water.CONCLUSIONSDirect solvent extraction from wet untreated microalgal biomass is a promising strategy to produce carotenoids. The described model can provide guidelines to design industrial processes. © 2020 Society of Chemical Industry

On the Effect of Filling Rate on Positive Macrosegregation Patterns in Large Size Cast Steel Ingots

The effect of filling velocity on positive macrosegregation in large size steel ingots was studied. Macrosegregation and macro/microstructures were characterized on the hot-tops and a portion of the upper section of two ingots. The measurements revealed that segregation features in the two ingots varied as a function of the alloying elements, and that the severity of positive macrosegregation in the casting body was reduced when the filling rate was increased. It was also found that at the higher filling rate, grain morphologies in the first solidified zones of the ingot changed from columnar to equiaxe, and secondary dendrite arm spacing (SDAS) became slightly smaller in the intermediate and final solidified zones. The experimental findings were analyzed in the framework of diffusion and convection-controlled solidification, as well as liquid metal flow theories. The solute dependence of segregation features was related to the difference in the solid-liquid partition coefficient and diffusion capability of each element in the liquid iron. Calculation of Reynolds numbers (Re) during the filling process, for both ingots, showed that higher filling velocity caused more instable movement of the liquid metal in the initial solidification stage, resulting in the modification of grain morphology, as well as accelerated solidification rate.

Characteristics of Copper Sorption by Various Agricultural Soils in China and the Effect of Exogenic Dissolved Organic Matter on the Sorption

ABSTRACTTo explore the effect of exogenic dissolved organic matter (DOM) on Cu(II) sorption in agricultural soils, 26 agricultural soils were collected across China. Exogenic dissolved organic matter, extracting from wheat straw (DOMW) and swine manure (DOMS), respectively, were added to the soils to conduct a series of batch sorption and characterization experiments. The solid-liquid partition coefficient (Kd) ranged from 0.02 to 76.46 L g−1, suggesting different Cu(II) sorption on various soils. PCA analysis indicated that pH, free Fe/Al oxides, carbon, and total Cu content had a significant positive relationship with the Cu(II) sorption, respectively. And the contribution rate of pH was the highest (38.15%). Moreover, DOM markedly inhibited the Cu(II) sorption in alkaline soils while promoted the Cu(II) sorption in acidic soils, which were interacted by the soil properties and DOM characteristics. The effect of DOMS on Cu(II) sorption were more obvious than DOMW, which were further confirmed by Fourier transform infrared (FTIR) spectroscopy. FTIR also showed Cu(II) was primarily adsorbed on the specific functional groups, such as CO, OH, and CO, providing direct evidences for the binding of Cu(II) with DOM. This study can guide the rational use of organic fertilizers, and also provide baseline knowledge for the prevention and control of soil pollution.

Cuantificación voltamétrica de carbofurano en papa (Solanum tuberosum L., Solanaceae)

&lt;p&gt;El exceso en la aplicación de plaguicidas puede&lt;br /&gt;generar acumulaciones en los tubérculos de papa&lt;br /&gt;que sobrepasen el límite máximo residual (LMR)&lt;br /&gt;presentado por el Codex Alimentarius, lo cual&lt;br /&gt;representa riesgos para la salud de los consumidores.&lt;br /&gt;La cuantificación de plaguicidas es un proceso&lt;br /&gt;costoso y de difícil acceso para los cultivadores y&lt;br /&gt;entes de salud y de vigilancia. En este artículo se&lt;br /&gt;presenta una metodología sencilla, económica y&lt;br /&gt;asequible para la cuantificación de carbofurano en&lt;br /&gt;tubérculos. El método de voltametría diferencial&lt;br /&gt;de pulso (DPV) para carbofurano fue validado para&lt;br /&gt;su cuantificación en papa. El estudio fue realizado&lt;br /&gt;usando como electrolito de soporte la solución buffer&lt;br /&gt;Britton-Robinson, un electrodo de trabajo de carbón&lt;br /&gt;vítreo, Ag/AgCl como electrodo de referencia y&lt;br /&gt;platino como electrodo auxiliar. El insecticida&lt;br /&gt;en papa fue extraído por reparto sólido-líquido y&lt;br /&gt;los resultados obtenidos fueron contrastados por&lt;br /&gt;espectroscopía UV-Vis, lo cual permitió deducir que el&lt;br /&gt;método voltamétrico genera resultados satisfactorios,&lt;br /&gt;precisos y confiables para la cuantificación de carbofurano&lt;br /&gt;en muestras de este tubérculo. Estos resultados&lt;br /&gt;son una evidencia del uso de carbofurano en el&lt;br /&gt;municipio de Ventaquemada (Boyacá). Este método&lt;br /&gt;de detección de carbofurano puede utilizarse como&lt;br /&gt;una herramienta para monitorear el uso de estos&lt;br /&gt;compuestos químicos en la papa.&lt;/p&gt;

Análise de resíduos de agrotóxicos organoclorados em morango usando o método QuEChERS com CG- µECD

Due their physical end chemical properties, organochlorine pesticides (OCPs) have been occured the contamination the environment and food chain. The consume of this products at low concentration dose represent a potential hazards to human health. The QuEChERS method was adjusted and used for the determination of 12 organochlorine pesticides (α- BHC, β - BHC, heptachlor, dicofol, endosulfan lacton, OP DDD, α - endosulfan, OP DDE, PP DDE, β - endosulfan, PP DDD, endosulfan sulfate) residues in 36 strawberries samples from three markets of the Piracicaba/ Sao Paulo – Brazil, during the period of October 2010 until September 2011. The method involved extraction with ethyl acetate, solid–liquid partition with MgSO4 and CH3COONa followed by dSPE clean up with PSA sorbent. Analyses were carried out with GC–µECD equipment. A HP-5 30 m x 0.32mm x 0.25 µm column was used. The method was validated using a strawberry sample without pesticides residues (blank), spiked at 0.01 and 0.1 mg kg-1; the average recovery by the method varied between 72.9 to 120% with RSD% < 9.6%. The method showed linearity r2 ≥ 0.99 and the LOQ ranged from 0,001 to 0.01 mg kg-1. It could be concluded that QuEChERS method used with GC-µECD is an alternative to determine organochlorine pesticides in strawberries. The results obtained indicate that this method sensitive and has no matrix effect. The method showed six of the samples analyzed have contamination by endosulfan sulfate at the concentrations of 0.003 to 0.02 mg kg-1.

Adsorption Characteristics and the Effect of Dissolved Organic Matter on Mercury(II) Adsorption of Various Soils in China

ABSTRACTTo evaluate the adsorption characteristics and effects of dissolved organic matter (DOM) from wheat straw (DOMW) and swine manure (DOMS) on mercury [Hg(II)] adsorption by soils, a series of experiments was conducted on 26 soils with different soil properties.Results showed that the values of Kd (a solid–liquid partition coefficient) of soils varied within a range of 0.768–14.386 L g−1. Kd values were mainly controlled by soil organic matter (SOM), cation exchange capacity (CEC), soil nitrogen (N), and soil sulfur (S). When DOMW and DOMS were added to the soil samples, the amount of Hg(II) adsorbed by the soils decreased significantly. Furthermore, based on the decreased percentage of adsorption of Hg(II) by soil upon adding DOMW (PDOMW) or DOMS (PDOMS), about 73.08% soils, the values of PDOMS were smaller than those of PDOMW. The PDOMW values were related to SOM, pH, free Fe oxide content, and CEC, whereas PDOMS values were related to soil free Fe/Al oxide contents. Therefore, we should pay more attention about mercury risk caused by the addition of exogenous organic matter in soils, especially for the soils with low or high pH, less SOM, low CEC, and less free Fe/Al oxide.

Behaviour of radiocaesium in coastal rivers of the Fukushima Prefecture (Japan) during conditions of low flow and low turbidity – Insight on the possible role of small particles and detrital organic compounds

To investigate riverine transfers from contaminated soils of the Fukushima Prefecture in Japan to the marine environment, suspended sediments, filtered water, sediments and detrital organic macro debris deposited onto river beds were collected in November 2013 within small coastal rivers during conditions of low flow rates and low turbidity. River waters were directly filtered on the field and high efficiency well-type Ge detectors were used to analyse radiocaesium concentrations in very small quantities of suspended particles and filtered water (a few mg to a few g). For such base-flow conditions, our results show that the watersheds studied present similar hydro-sedimentary behaviours at their outlets and that the exports of dissolved and particulate radiocaesium are comparable. Moreover, the contribution of these rivers to the instantaneous export of radiocaesium to the ocean is similar to that of the Abukuma River. Our preliminary results indicate that, in the estuaries, radiocaesium concentrations in suspended sediments would be reduced by more than 80%, while radiocaesium concentration in filtered waters would be maintained. Significant correlations between radiocaesium concentrations and radiocaesium inventories in the soils of the catchments indicate that there was at that time little intra and inter-watershed variability in the transfer processes of radiocaesium from lands to rivers at this regional scale. The apparent liquid–solid partition coefficient (KD) values acquired for the lowest loads/finest particles complement the values acquired by using sediment traps and highlight the strong capacity of the smallest particles to transfer radiocaesium. Finally, but not least, our observations suggest that there could be a significant transfer of highly contaminated detrital biomass from forest litter to the downstream rivers in a rather conservative way.

Celluclast and Cellic® CTec2: Saccharification/fermentation of wheat straw, solid–liquid partition and potential of enzyme recycling by alkaline washing

The hydrolysis/fermentation of wheat straw and the adsorption/desorption/deactivation of cellulases were studied using Cellic® CTec2 (Cellic) and Celluclast mixed with Novozyme 188. The distribution of enzymes – cellobiohydrolase I (Cel7A), endoglucanase I (Cel7B) and β-glucosidase – of the two formulations between the residual substrate and supernatant during the course of enzymatic hydrolysis and fermentation was investigated. The potential of recyclability using alkaline wash was also studied. The efficiency of hydrolysis with an enzyme load of 10FPU/g cellulose reached >98% using Cellic® CTec2, while for Celluclast a conversion of 52% and 81%, was observed without and with β-glucosidase supplementation, respectively. The decrease of Cellic® CTec2 activity observed along the process was related to deactivation of Cel7A rather than of Cel7B and β-glucosidase. The adsorption/desorption profiles during hydrolysis/fermentation revealed that a large fraction of active enzymes remained adsorbed to the solid residue throughout the process. Surprisingly, this was the case of Cel7A and β-glucosidase from Cellic, which remained adsorbed to the solid fraction along the entire process.Alkaline washing was used to recover the enzymes from the solid residue. This method allowed efficient recovery of Celluclast enzymes; however, this may be achieved only when minor amounts of cellulose remain present. Regarding the Cellic formulation, neither the presence of cellulose nor lignin restricted an efficient desorption of the enzymes at alkaline pH. This work shows that the recycling strategy must be customized for each particular formulation, since the enzymes found e.g. in Cellic and Celluclast bear quite different behaviour regarding the solid–liquid distribution, stability and cellulose and lignin affinity.