Acetylcholinesterase-polyaniline biosensor investigation of organophosphate pesticides in selected organic solvents

The behavior of an amperometric organic-phase biosensor consisting of a gold electrode modified first with a mercaptobenzothiazole self-assembled monolayer, followed by electropolymerization of polyaniline in which acetylcholinesterase as enzyme was immobilized, has been developed and evaluated for organophosphorous pesticide detection. The voltammetric results have shown that the formal potential shifts anodically as the Au/MBT/PANI/AChE/PVAc thick-film biosensor responded to acetylthiocholine substrate addition under anaerobic conditions in selected organic solvent media containing 2% v/v 0.05 M phosphate buffer, 0.1 M KCl (pH 7.2) solution. Detection limits in the order of 0.147 ppb for diazinon and 0.172 ppb for fenthion in acetone-saline phosphate buffer solution, and 0.180 ppb for diazinon and 0.194 ppb for fenthion in ethanol-saline phosphate buffer solution has been achieved.     

Mercury concentrations at a historically mercury-contaminated site in KwaZulu-Natal (South Africa)

Introduction  

A mercury (Hg) processing plant previously operating in KwaZulu-Natal Province (South Africa) discharged Hg waste into a nearby river system causing widespread contamination since the 1980s. Although the processing plant ceased operation in the 1990s, Hg contamination (due to residual Hg) remains significant. Previous studies in the area since the plant’s closure have found elevated Hg concentrations in fish, and that these concentrations were as a direct consequence of widespread contamination of the Hg processing plant operations conducted between the 1980s and 1990s.     

Alkaline hydrothermal conversion of fly ash precipitates into zeolites 3: the removal of mercury and lead ions from wastewater

In this paper, the utilisation of zeolites synthesised from fly ash (FA) and related co-disposal filtrates as low-cost adsorbent material were investigated. When raw FA and co-disposal filtrates were subjected to alkaline hydrothermal zeolite synthesis, the zeolites faujasite, sodalite and zeolite A were formed. The synthesised zeolites were explored to establish its ability to remove lead and mercury ions from aqueous solution in batch experiments, to which various dosages of the synthesised zeolites were added. The test results indicated that when increasing synthesised zeolite dosages of 5-20 g/L were added to the acid mine drainage (AMD) wastewater, the concentrations of lead and mercury in the wastewater were reduced accordingly. The lead concentrations were reduced from 3.23 to 0.38 and 0.17 microg/kg, respectively, at an average pH of 4.5, after the addition of raw FA zeolite and co-disposal filtrate zeolite to the AMD wastewater. On the other hand, the mercury concentration was reduced from 0.47 to 0.17 microg/kg at pH=4.5 when increasing amounts of co-disposal filtrate zeolite were added to the wastewater. The experimental results had shown that the zeolites synthesised from the co-disposal filtrates were effective in reducing the lead and mercury concentrations in the AMD wastewater by 95% and 30%, respectively.     

Aggregation and dissolution of silver nanoparticles in a laboratory-based freshwater microcosm under simulated environmental conditions

Silver nanoparticles (NP) are used in several applications, including their use as antimicrobial agents in textiles, personal care, and other domestic products. As such, there is a high potential for the release of silver nanoparticles (AgNP) in the aquatic environment. In aquatic ecosystems, nanomaterials are affected by abiotic factors, such as temperature, that alter their chemistry and influence their fate in the environment. Preliminary studies indicate that NP tend to form aggregates which are potentially more recalcitrant than unaggregated NP. These and other fate processes are largely dependent on both the characteristics of the NP and that of the environment. In this study, lab experiments were conducted to investigate the physicochemical properties and temperature solubility of AgNP (<100 nm) that may potentially influence the fate and behavior of AgNP in the aqueous environment. Results indicated that, under these tested conditions, AgNP may be transformed in size and thereby affect fate, bioavailability, and toxicity. In this study, a novel method was used to determine whether AgNP would form agglomerates, or behave as isolated particles, or dissolve when in aqueous media and under different environmental conditions. The new aspects evaluated in this study demonstrated that AgNP are transformed in both size and state under variable environmental conditions.     

Design of control strategies for nutrient removal in a biological wastewater treatment process

Wastewater treatment plants (WWTP) are highly non-linear operations concerned with huge disturbances in flow rate and concentration of pollutants with uncertainties in the composition of influent wastewater. In this work, the activated sludge process model with seven reactor configuration in the ASM3bioP framework is used to achieve simultaneous removal of nitrogen and phosphorus. A total of 8 control approaches are designed and implemented in the advanced simulation framework for assessment of the performance. The performance of the WWTP (effluent quality index and global plant performance) and the operational costs are also evaluated to compare the control approaches. Additionally, this paper reports a comparison among proportional integral (PI) control, fuzzy logic control, and model-based predictive control (MPC) configurations framework. The simulation outcomes indicated that all three control approaches were able to enhance the performance of WWTP when compared with open loop operation.

     

Prenatal Diagnosis of congenital disorder of glycosylation type Ia (CDG-Ia) by cordocentesis and transferrin isoelectric focussing of serum of a 27-week fetus with non-immune hydrops

Blood was obtained by cordocentesis from a fetus with non-immune hydrops demonstrated by ultrasound scanning at 27 weeks' gestation. Abnormalities of serum transferrin isoelectric focussing (IEF) were identified, characteristic of a congenital disorder of glycosylation type I (CDG-Ia). A diagnosis of CDG-Ia was confirmed by enzyme analysis of cultured amniocytes. This is the first report of CDG-Ia diagnosed by serum analysis in a fetus. Previous reports have warned that diagnostic abnormalities do not appear in serum until several weeks after birth. The sensitivity of cordocentesis transferrin IEF is unknown but is less than 100% effective because cases have been diagnosed postnatally after normal prenatal or neonatal studies. Enzyme analysis or mutation analysis is required for diagnosis of congenital disorder of glycosylation (CDGs) regardless of whether a diagnostic transferrin pattern is identified prenatally. The analysis of a small sample of serum, from cordocentesis, performed to check for fetal anemia, simplified the investigation, diagnosis, and genetic counselling of a case of non-immune hydrops detected at 27 weeks' gestation. This might be a useful test for other cases in these circumstances, as fetal blood is usually collected to check for anemia. Copyright © 2006 John Wiley & Sons, Ltd.     

Mercaptobenzothiazole-on-gold organic phase biosensor systems: 1. Enhanced organosphosphate pesticide determination

This paper reports the construction of the gold/mercaptobenzothiazole/polyaniline/acetylcholinesterase/polyvinylacetate (Au/ MBT/PANI/AChE/PVAc) thick-film biosensor for the determination of certain organophosphate pesticide solutions in selected aqueous organic solvent solutions. The Au/MBT/PANI/AChE/PVAc electrocatalytic biosensor device was constructed by encapsulating acetylcholinesterase (AChE) enzyme in the PANI polymer composite, followed by the coating of poly(vinyl acetate) (PVAc) on top to secure the biosensor film from disintegration in the organic solvents evaluated. The electroactive substrate called acetylthiocholine (ATCh) was employed to provide the movement of electrons in the amperometric biosensor. The voltammetric results have shown that the current shifts more anodically as the Au/MBT/PANI/AChE/PVAc biosensor responded to successive acetylthiocholine (ATCh) substrate addition under anaerobic conditions in 0.1 M phosphate buffer, KCl (pH 7.2) solution and aqueous organic solvent solutions. For the Au/MBT/PANI/AChE/PVAc biosensor, various performance and stability parameters were evaluated. These factors include the optimal enzyme loading, effect of pH, long-term stability of the biosensor, temperature stability of the biosensor, the effect of polar organic solvents, and the effect of non-polar organic solvents on the amperometric behavior of the biosensor. The biosensor was then applied to detect a series of 5 organophosphorous pesticides in aqueous organic solvents and the pesticides studied were parathion-methyl, malathion and chlorpyrifos. The results obtained have shown that the detection limit values for the individual pesticides were 1.332 nM (parathion-methyl), 0.189 nM (malathion), 0.018 nM (chlorpyrifos).