Environmental concentrations as ratios of random variables

Human-induced environmental change increasingly threatens the stability of socio-ecological systems. Careful statistical characterization of environmental concentrations is critical to quantify and predict the consequences of such changes on human and ecosystems conditions. However, while concentrations are naturally defined as the ratio between solute mass and solvent volume, they have rarely been treated as such, typically limiting the analysis to familiar distributions generically used for any other environmental variable. To address this gap, we propose a more general framework that leverages their definition explicitly as ratios of random variables. We show that the resulting models accurately describe the behavior of nitrate plus nitrite in US rivers and salt concentration in estuaries in the Everglades by accounting for heavy tails potentially emerging when the water volume fluctuates around low values. Models that preclude the presence of heavy tails and the related high probability of extreme concentrations could significantly undermine the accuracy of diagnostic frameworks and the effectiveness of mitigation interventions, especially for soil contamination characterized by a water volume (i.e., soil moisture) frequently approaching zero.

Kajian pengaruh kondisi dekomposisi analisis logam tembaga dalam sedimen di pelabuhan ikan Sendang Biru secara SSA

Cu that is absorbed in marine sediments can accumulate in the food chain even in small concentrations. Cu analysis in these sediments can be used to analyze water pollution due to human activities. The purpose of this study was to determine the level of Cu in decomposed sediments with variation of solvent concentration, variation of decomposition time, and variation of solvent volume and then compare the result of Cu analysis decomposed using HNO3 solvent under effective condition with aqua regia solvent. The method of analysis used is decomposition technique of sediment sample by using reflux and then analyzed with AAS.. Cu yang terserap dalam sedimen laut dapat berakumulasi dalam rantai makanan meskipun dalam konsentrasi kecil. Analisis Cu dalam sedimen ini dapat digunakan untuk menganalisis pencemaran perairan akibat aktivitas manusia. Tujuan penelitian ini adalah menentukan kadar Cu dalam sedimen yang didekomposisi dengan variasi konsentrasi pelarut, variasi waktu dekomposisi, dan variasi volume pelarut dan membandingkan hasil analisis Cu yang didekomposisi menggunakan pelarut HNO3 pada kondisi efektif dengan pelarut akuaregia. Metode analisis yang digunakan yaitu teknik dekomposisi sampel sedimen dengan menggunakan refluks dan dianalisis dengan SSA.

Highly Stable Thin Films Based on Novel Hybrid 1D (PRSH)PbX3 Pseudo-Perovskites

In this study, the structure and morphology, as well as time, ultraviolet radiation, and humidity stability of thin films based on newly developed 1D (PRSH)PbX3 (X = Br, I) pseudo-perovskite materials, containing 1D chains of face-sharing haloplumbate octahedra, are investigated. All films are strongly crystalline already at room temperature, and annealing does not promote further crystallization or film reorganization. The film microstructure is found to be strongly influenced by the anion type and, to a lesser extent, by the DMF/DMSO solvent volume ratio used during film deposition by spin-coating. Comparison of specular X-ray diffraction and complementary grazing incidence X-ray diffraction analysis indicates that the use of DMF/DMSO mixed solvents promotes the strengthening of a dominant 100 or 210 texturing, as compared the case of pure DMF, and that the haloplumbate chains always lie in a plane parallel to the substrate. Under specific DMF/DMSO solvent volume ratios, the prepared films are found to be highly stable in time (up to seven months under fluxing N2 and in the dark) and to highly moist conditions (up to 25 days at 78% relative humidity). Furthermore, for representative (PRSH)PbX3 films, resistance against ultraviolet exposure (λ = 380 nm) is investigated, showing complete stability after irradiation for up to 15 h at a power density of 600 mW/cm2. These results make such thin films interesting for highly stable perovskite-based (opto)electronic devices.

Optimasi Penggunaan High Shear Mixer pada Pembuatan Fraksi Alkaloid dari Daun Awar-awar (Ficus septica) dengan Desain Faktorial

Awar-awar (Ficus septica) is an Indonesian anticancer plant that contains alkaloids as the active compound. The n-hexane insoluble fraction (FTLH) is alkaloid-containing fraction obtained from the ethanolic extract of F. septica leaves (EEDFS) by fractionation using n-hexane. High shear mixer (HSM) can be used to optimize the separation processes, including fractionation. The application of HSM in the fractionation of EEDFS is affected by fractionation duration, amount of solvent per gram extract, and strirring strength. Thus, these parameters must be optimized to obtain the optimum condition for the production of FTLH with the highest alkaloid content. This study aimed to optimize the production of FTLH using HSM with factorial designs. The single factor experimental design was employed to determine the influence of the individual variable on the alkaloid content and to define the optimum range value of each variable. A full factorial design was used to determine the presence of interaction among the factors and to determine the optimal fractionation condition. The results showed that all investigated factors independently affected alkaloid contents. The solvent volume of 14-18 mL per gram extract, the fractionation duration of 2.5-5.0 minutes, and the stirring strength of 3000 rpm are the optimal range value of each factor. The optimal conditions were solvent volume of 14.0-14.4 mL/gram extract, fractionation duration of 2.5-2.7 minutes, and strirring strength at 3000 rpm. At the optimal condition, the total alkaloid content in the FTLH reached 0.1466% or 1.3 times higher than the extract (0.1128%).

EKSTRAKSI MINYAK KACANG TANAH (PEANUT OIL) DENGAN PELARUT ETANOL DAN N-HEKSAN

Peanut is one of the sources of vegetable oil, the oil content is very high, less than 65% compared to copra which contains more or less 45% oil (Sari, 2006). This study aims to analyze the value of oil yield, density, viscosity, water content, and acid number of peanut oil produced from groundnut seeds. Based on the research that has been used, the variable solvent volume varies from 400 to 600 mL, the extraction temperature variable used is 75oCand 80oC, and the time variable varies from 2- 4 hours. The resulting extraction is distilled using 80oC and 85oC temperatures to separate the oil from the solvent. This research was carried out by extracting sohklets using different solvents, ethanol and n-hexane. From the results of this study, the highest percentage of oil was 58.29% with n-hexane solvent, density of 1.122 gr / mL, viscosity of 0.1029 cP, moisture content of 6%, and acidity rate of 2 mg NaOH / gr of oil . Based on the research that has been done, it can be concluded that the volume of the solvent and the extraction time greatly affect the yield value of the oil produced, density, viscosity, moisture content, and acid number.

Study on Phase Transfer Catalyst Used in the Synthesis of Sodium Isobutyl Xanthate

Xanthates are by far the most widely used collectors in the froth flotation beneficiation of sulfide ores. However, the xanthate production process suffers from low yield, low productivity, long reaction time and environmental pollution. To address these issues, an effective method was developed for the synthesis of xanthates using phase transfer catalyst. Sodium isobutyl xanthate was synthesized from isobutyl alcohol ((CH3)2CHCH2OH), sodium hydroxide (NaOH) and carbon disulfide (CS2) with dichloromethane (CH2Cl2) as solvent and cetyltrimethylammonium bromide (CTAB), cetyltrimethylammonium chloride (CTAC), tetrabutylammonium bromide (TBAB) and tetrabutylammonium chloride (TBAC) as phase transfer catalyst. The compound was characterized by elemental analysis, infrared spectrum, 1H NMR and 13C NMR. The influencing factors on the content and yield of sodium isobutyl xanthate including phase transfer catalyst type, phase transfer catalyst dosage and reaction time were studied by single-factor experiments. The influencing factors on the product purity and yield including reaction temperature, solvent volume, material ratio and rotating speed were studied by orthogonal experiments. The results showed that when the amount of TBAC was 3.0%malcohol, the reaction temperature was 35 °C, the solvent volume was 3.5 Valcohol, the rotating speed was 180 rpm, the reaction time was 4 h and the material ratio was n[(CH3)2CHCH2OH]:n(NaOH):n(CS2) = 1:1:1.10, the product yield could be up to 86.66% and the product purity reached 82.56%.

Simultaneous Determination of C4-C9 Alkylphenols and Bisphenol a in Environmental Water Using Gas Chromatography-Mass Spectrometry Technique

A liquid-liquid extraction combined with derivatization and gas chromatography-mass spectrometry (GC-MS) method was developed for the determination of C4-C9 alkylphenols (APs, included 4-tert-butylphenol, 4-n-butylphenol, 4-n-pentylphenol, 4-n-hexylphenol, 4-n-heptylphenol, 4-n-octylphenol, 4-tert-octylphenol, 4-n-nonylphenol and 4-nonylphenol) and bisphenol A (BPA) in environmental water. The extraction solvent, extraction number, extraction time, extraction solvent volume, pH value, salt content, concentration degree and derivatization time were optimized. The target compounds were quantified by internal standard method. Results showed that the optimal extraction number, time, solvent volume, pH value and salt content were 2, 5 min, 30 ml, about 2 and 5 g, respectively, and derivatization time was 1 h at room temperature. Dichloromethane was selected as the extraction solvent and was concentrated to 0.5 mL in the process of concentration. The developed method was validated and showed good linearity (R2 > 0.995), low limit of detection (LOD, 0.002 µg/L–0.006 µg/L), and excellent recovery (68.0 %–122 %) and low relative standard deviation (0.67 %–13.7 %). The developed method was finally applied to groundwater, surface water, seawater and sewage samples in Dongying City located at Yellow River Estuary and some of these target compounds were detected. The measured values of 4-nonylphenol and BPA in these water samples were below their restrictive values of relevant directives at home and abroad.