Application of first-order and Monte Carlo analysis in watershed water quality models

To achieve effective environmental control, it is important to develop methodologies for dealing with uncertainties in model simulation of pollution behaviour and effects. Several procedures have been proposed to quantify uncertainties in modelling studies. This paper utilizes the two methods that are widely applied, i.e. functional analysis and Monte Carlo Simulation.The first-order part of the functional analysis method provides a measure of uncertainties in dependent variables in terms of uncertainties in independent variables. The procedure is based on first-order terms in the Taylor series expansion of the dependent variable about its mean value with respect to one or more independent variables. The major assumption in this procedure is that all independent and dependent variables are the second moment variables (SMV), which means that the behaviour of any SMV is completely described by its mean and standard deviation. The mathematical simplicity of the procedure allows application by simple input-output models. Consequently, it has been applied to many environmental simulators, e.g. hydrological models, stream water quality models, lake water quality models and ground water pollution models.The Monte Carlo Simulation (MCS) method uses a large number of repeated trials or simulations with the values for stochastic inputs or uncertain variables selected at random from their assumed parent probability distributions to establish an expected range of model uncertainty.     

Why is sodium cocoyl isethionate (SCI) mild to the skin barrier?–An in vitro investigation based on the relative sizes of the SCI micelles and the skin aqueous pores

Sodium cocoyl isethionate (SCI) is an important surfactant ingredient in mild, syndet (synthetic detergent) cleansing bars. In vitro and in vivo studies have demonstrated that SCI is mild and less damaging to the skin barrier than soaps and surfactants such as sodium dodecyl sulfate (SDS). We have recently shown that SDS forms small micelles in aqueous solutions contacting the skin relative to the aqueous pores in the stratum corneum (SC), and as a result, the SDS micelles can contribute to SDS skin penetration and induce skin barrier perturbation. In this paper, we attempt to explain the well-documented skin mildness of SCI by examining the size of the SCI micelles relative to that of the aqueous pores in the SC. For this purpose, we have conducted in vitro mannitol skin permeability and average skin electrical resistivity measurements upon exposure of the skin to an aqueous SCI contacting solution in the context of a hindered-transport aqueous porous pathway model of the SC. These in vitro studies demonstrate that an SCI micelle of radius 33.5 ± 1 Å (as determined using dynamic light-scattering measurements) experiences significant steric hindrance and cannot penetrate into the SC through aqueous pores that have an average radius of 29 ± 5 Å.We believe that this inability of the SCI micelles to contribute to SCI skin penetration and associated skin barrier perturbation is responsible for the observed skin mildness of SCI. Through in vitro quantitative skin radioactivity assays using ¹⁴C-radiolabeled SCI and pig full-thickness skin (p-FTS), we also show conclusively that SCI skin penetration is dose-independent, an important finding that provides additional evidence that the larger SCI micelles cannot penetrate into the SC through the smaller aqueous pores that exist in the SC, and therefore, cannot induce skin barrier perturbation.     

Fatty acids of boal fish oil by urea fractionation and gas-liquid chromatography.

The fatty acid composition of body and liver fats of boal, Wallago attu (Schn.), a cat fish, belonging to the family Siluridae and commonly known as fresh-water shark has been determined by urea fractionation and gas–liquid chromatography (g.l.c.). The percentages of major component acids were found to be, 16:0, 10.5; 16:1 ω9, 7.6; 18:0, 7.2; 18:1 ω9, 17.4; 18:2ω9, 8.4; 18:3ω3, 6.1; 20:4ω3, 3.7 and 22:6ω3, 4.4. In addition, a number of minor component acids have been detected and estimated. The liver oil fatty acids have also been determined without fractionation and the percentages of major component acids found were 16:0, 23.5; 18:0, 12.7; 18:1ω9, 7.0; 20:4ω3, 13.7; 22:6ω3, 11.2. The oil has been studied for the first time for its fatty acid composition.     

Green, Blue and Grey Water Footprints of Primary Crops Production in Nepal

This study aims to estimate the green, blue and grey water footprints (WFs) of nine primary crops production in 75 districts, 5 developmental regions and 3 physiographic divisions of Nepal using local meteorological, agronomical and irrigation data at high spatial resolution. The estimates are based on the framework prescribed by the guideline of the Water Footprint Network. The green and blue WFs are calculated using a water balance model whereas the grey WF is estimated as the volume of freshwater needed to dilute nitrate pollution to an acceptable level. WF varies across different crops considered, different districts, development regions and physiographic divisions. WF of potato and wheat in Nepal is comparable to the world average; but paddy, barley and pulses have higher while sugarcane and maize have lower values compared to the world average. WFs of paddy, maize, potato and wheat are lower in Terai than the Hills and Mountains due to the accessibility of irrigation system and higher crop yield. Millet, pulses, oilseeds and barley have lower WFs and are suitable for Mountains. Similarly, sugarcane is suitable for both Terai and Mountain divisions because of its lower WF. Crops in Far Western Development Region generally have higher WFs due to the low crop productivity, and higher fertilizer use.