Aging of Toughened Polylactic Acid Nanocomposites: Water Absorption,Hygrothermal Degradation and Soil Burial Analysis

The environmental aging behaviour of montmorillonite (MMT) filled polylactic acid (PLA) nanocomposites (PLA/MMT) and linear low density polyethylene (LLDPE)-toughened PLA (PLA/LLDPE ratio = 90/10) nanocomposites (PLA/LLDPE/MMT) were investigated in this study. The nanocomposites were subjected to water absorption, hygrothermal degradation and soil burial analysis. Both PLA/MMT and PLA/LLDPE/MMT nanocomposites were immersed in distilled water at three different temperatures (room temperature, 60, and 90 °C) and the weight difference before and after immersion was calculated. The kinetics of water absorption for both nanocomposites followed the Fick’s second law of diffusion, where a linear relationship exists between the initial moisture absorption at any time t and t ^1/2 (the square root of time), followed by a horizontal plateau (saturation). The equilibrium moisture content (M _m ) and diffusion coefficient (D) of PLA nanocomposites increased with the addition of MMT (2 phr) and LLDPE. However, the D values of both nanocomposites decreased by increasing MMT (4 phr). The M _m for PLA/MMT and PLA/LLDPE/MMT nanocomposites increased by increasing immersion temperature (60 °C) and prolonged immersion resulted in hygrothermal degradation of both nanocomposites. The hygrothermal degradation studies showed that PLA degrades much faster at 90 °C as compared to 60 °C in both the nanocomposites. The addition of MMT and LLDPE improved the hygrothermal stability of PLA in both nanocomposites. Soil burial test revealed deterioration of impact strength in all samples while the rate of biodegradation was retarded in the presence of MMT and LLDPE.     

Qualitative assessment on premature human mortality due to the emission of fine particulate matter from the Matarbari coal power plant

This study reports the probability of increased mortality of people within the political border of Bangladesh due to the emission of fine particulate matter with diameters of 2.5 microns or less (PM_2.5) from the Matarbari coal power plant (MCPP). A Gaussian plume dispersion model has been used for this estimation. The PM_2.5 emission rate data are unavailable as the construction of MCPP is still in its initial stage; therefore, the anticipated PM_2.5 emission rate has been estimated based on data from a number of coal‐fired power plants in India and China. To make this study more meaningful, two different emission rates have been considered representing the best‐case and worst‐case scenarios. In both cases, the intake fraction has been found to be 0.12×10^?2, and the value of relative risk varies between 1.134 and 1.374, respectively. Finally, it is estimated that approximately 11.5 million people inside Bangladesh will be exposed to the PM_2.5 emission from MCPP, and between 7,667 and 17,675 people will experience premature death every year.     

Removal of arsenic species from water by batch and column operations on bagasse fly ash

Bagasse fly ash (BFA, a sugar industrial waste) was used as low-cost adsorbent for the uptake of arsenate and arsenite species from water. The optimum conditions for the removal of both species of arsenic were as follows: pH 7.0, concentration 50.0 μg/L, contact time 50.0 min, adsorbent dose 3.0 g/L, and temperature 20.0 °C, with 95.0 and 89.5 % removal of arsenate and arsenite, respectively. The Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich adsorption isotherms were used to analyze the results. The results of these models indicated single-layer uniform adsorption on heterogeneous surface. Thermodynamic parameters, i.e., ΔG°, ΔH°, and ΔS°, were also calculated. At 20.0 to 30.0 °C, the values of ΔG° lie in the range of ?4,722.75 to ?4,878.82 and ?4,308.80 to ?4,451.73 while the values of ΔH° and ΔS° were ?149.90 and ?121.07, and 15.61 and 14.29 for arsenate and arsenite, respectively, indicating that adsorption is spontaneous and exothermic. Pseudo-first-order kinetics was followed. In column experiments, the adsorption decreased as the flow rate increased with the maximum removal of 98.9 and 95.6 % for arsenate and arsenite, respectively. The bed depth service time and Yoon and Nelson models were used to analyze the experimental data. The adsorption capacity (N _o) of BFA on column was 3.65 and 2.98 mg/cm³ for arsenate and arsenite, respectively. The developed system for the removal of arsenate and arsenite species is economic, rapid, and capable of working under natural conditions. It may be used for the removal of arsenic species from any contaminated water resources.     

Effect of PCM on temperature fluctuation during the door opening of a household refrigerator

Temperature fluctuation inside the cabinet of a household refrigerator significantly affects the quality of preserved food. Phase change material (PCM) is a latent heat storage system that can store and release the heat energy by changing its phase from liquid to solid and solid to liquid respectively. Therefore, use of PCM inside the refrigerator cabinet has the potential for minimizing the temperature fluctuation during the door opening and the power failure. However, very few studies in the literature were dedicated to investigating the role of PCM to reduce the temperature fluctuation. The aim of this work is to experimentally investigate the effects of PCM on temperature fluctuation inside the cabinet of a household refrigerator during the door opening and power failure. The results found that a significantly lower temperature fluctuation can be obtained using PCM. It was found that during the door opening condition the air temperature in the cabinet rose rapidly. However, when a PCM container was used, temperature variation was reduced to 3–5°C. During the power failure, the system with PCM maintained a lower temperature inside the storage chamber for a long period of time (about 2 hours). Moreover, the test results indicate that PCM maintains more stable temperature in the foodstuffs inside the refrigerator. This reduction of temperature fluctuation ultimately improves the quality of preserved food.     

Urban nonpoint source pollution buildup and washoff models for simulating storm runoff quality in the Los Angeles County

Many urban nonpoint source pollution models utilize pollutant buildup and washoff functions to simulate storm runoff quality of urban catchments. In this paper, two urban pollutant washoff load models are derived using pollutant buildup and washoff functions. The first model assumes that there is no residual pollutant after a storm event while the second one assumes that there is always residual pollutant after each storm event. The developed models are calibrated and verified with observed data from an urban catchment in the Los Angeles County. The application results show that the developed model with consideration of residual pollutant is more capable of simulating nonpoint source pollution from urban storm runoff than that without consideration of residual pollutant. For the study area, residual pollutant should be considered in pollutant buildup and washoff functions for simulating urban nonpoint source pollution when the total runoff volume is less than 30 mm.     

Preconcentration and determination of lead and cadmium levels in blood samples of adolescent workers consuming smokeless tobacco products in Pakistan

The present study was aimed to evaluate the cadmium (Cd) and lead (Pb) levels in the blood samples of adolescent boys, chewing different smokeless tobacco (SLT) products in Pakistan. For comparative purpose, boys of the same age group (12–15 years), not consumed any SLT products were selected as referents. To determine trace levels of Cd and Pb in blood samples, a preconcentration method, vortex-assisted liquid–liquid microextraction (VLLME) has been developed, prior to analysis by flame atomic absorption spectrometry. The hydrophobic chelates of Cd and Pb with ammonium pyrrolidinedithiocarbamate were extracted into the fine droplets of ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate, while nonionic surfactant, Triton X-114 was used as a dispersing medium. The main factors affecting the recoveries of Cd and Pb, such as concentration of APDC, centrifugation time, volume of IL and TX-114, were investigated in detail. It was also observed that adolescent boys who consumed different SLT products have 2- to 3-fold higher levels of Cd and Pb in their blood samples as compared to referent boys (p?<?0.001).     

Assessment of phenanthrene bioavailability in aged and unaged soils by mild extraction

It has become apparent that the threat of an organic pollutant in soil is directly related to its bioavailable fraction and that the use of total contaminant concentrations as a measure of potential contaminant exposure to plants or soil organisms is inappropriate. In light of this, non-exhaustive extraction techniques are being investigated to assess their appropriateness in determining bioavailability. To find a suitable and rapid extraction method to predict phenanthrene bioavailability, multiple extraction techniques (i.e., mild hydroxypropyl-β-cyclodextrin (HPCD) and organic solvents extraction) were investigated in soil spiked to a range of phenanthrene levels (i.e., 1.12, 8.52, 73, 136, and 335 μg g^− 1 dry soil). The bioaccumulation of phenanthrene in earthworm (Eisenia fetida) was used as the reference system for bioavailability. Correlation results for phenanthrene suggested that mild HPCD extraction was a better method to predict bioavailability of phenanthrene in soil compared with organic solvents extraction. Aged (i.e., 150 days) and fresh (i.e., 0 day) soil samples were used to evaluate the extraction efficiency and the effect of soil contact time on the availability of phenanthrene. The percentage of phenanthrene accumulated by earthworms and percent recoveries by mild extractants changed significantly with aging time. Thus, aging significantly reduced the earthworm uptake and chemical extractability of phenanthrene. In general, among organic extractants, methanol showed recoveries comparable to those of mild HPCD for both aged and unaged soil matrices. Hence, this extractant can be suitable after HPCD to evaluate risk of contaminated soils.     

Monitoring of Coliforms and chlorine residual in water distribution network of Rawalpindi, Pakistan

The present study was undertaken to examine the drinking water quality of Rawal Treatment Plant, Rawalpindi and its distribution network by collecting samples from eight different locations. The aim was to determine potential relationship between the presence of microorganisms and chlorine residual in the distribution network. Quantification of chlorine residual, turbidity, standard plate count (SPC), fecal and total coliforms by Most Probable Number (MPN) was performed. Three different forms of chlorine were measured at each sampling station such as free chlorine, residual chlorine, chloramines and total chlorine residual. A critical evaluation of data presented indicated that pH generally ranged from 7.02–7.30; turbidity varied from 0.34–2.79 NTU; conductivity fluctuated from 359–374 μS/cm; and TDS values were found to be ranging between 180–187 mg/l. Station # 7 was found to be most contaminated. The value of total chlorine was found to be 0.86 to1.7 mg/l at Station # 3 and 6, respectively. Highest standard plate count was 62 CFU/ml at Station # 7. Total coliforms were less than 1.1 MPN/100 ml at almost most of the stations except at Station # 3 where it was found to be greater than 23.0 MPN /100 ml. Overall aim of this study is to create awareness about contamination of drinking water in the water distribution networks and to make recommendations to provincial agencies such as EPA, CDA and WASA that regular monitoring should be carried out to ensure that the chlorine residual is available at consumer end.     

Health risk assessment of drinking arsenic-containing groundwater in Hasilpur,Pakistan: effect of sampling area,depth, and source

Environmental Science and Pollution Research - Currently, several news channels and research publications have highlighted the dilemma of arsenic (As)-contaminated groundwater in Pakistan. However,...     

A comparison study of the potential risks induced in arable land and forest soils by carcass-derived pollutants

Environmental Geochemistry and Health - Improper decisions concerning animal carcass disposal sites pose grave threats to environmental biosecurity. However, only a few studies have focused on the...