Organophosphorous pesticide removal from water by graphene-based materials - only adsorption or something else as well?

The extensive use of pesticides requires innovative approaches to remediate these compounds from the environment. Carbon materials are traditionally used as adsorbents for removing pesticides, and the development of new families of carbon materials allows more advanced approaches in environmental applications. Using Density Functional Calculations, we have predicted chemical reaction between the S(O)=P moieties of organophosphates with point defects in graphene - single vacancies, Stone-Wales defects and epoxy-groups. The reaction was confirmed using Ultra High Performance Chromatography for two graphene oxide samples and dimethoate as a representative of organophosphates. The exact reaction mechanism is still elusive, but it is unambiguously confirmed that no selective oxidation of dimethoate to more toxic oxo-analog occurs. Presented results can help develop novel systems for irreversible conversion of organophosphates to non-toxic compounds without using aggressive chemical agents or external physical factors like UV radiation.

Monocrotophos induced histopathological and biochemical Changes in gills, stomach and intestine of Anabas testudineus (Cuvier)

Monocrotophos, an organophosphate pesticide is used frequently in paddy fields of India. Although its impact of toxicity has been reported in many organisms, its effect on digestive and respiratory organs in Anabas testudineus is scanty. The Present investigation was conducted to evaluate the impact of histopathological and biochemical indices on freshwater fish A.testudineus exposed to sub-lethal concentration (45 ppm) of an organophosphorous pesticide monocrotophos (MT). Severe histoarchitectural and biochemical changes were observed in fishes exposed to monocrotophos when compared to fishes of control group. Exposure of fishes to the pesticide resulted in induction of histological abnormalities in gills, stomach and intestine. This was accompanied with reduction in total protein content and an elevation in catalase activity in gills, stomach and intestine. These structural alterations of the gills, stomach and intestine could affect respiration, digestion and absorption of nutrients which in turn could adversely affect growth and survival of the freshwater fish A. testudineus. The result of this investigation serves as a biomonitoring tool for the effects of organophosphorous pesticide MT on the aquatic biota.

Contamination Levels of Organochlorine and Organophosphorous Pesticide Residues in Water and Sediment from River Owena, Nigeria

River Owena functions as the source of water for the Owena dam which supplies drinking water to the communities in the region, the river also plays an important economic role in irrigation and fish farming in the region. But there has been an indiscriminate used of pesticide because residents of the study area are not well orientated concerning the negative impact of pesticide in the environment. Analysis of organochlorine and organophosphorous pesticide residues was carried out in water and sediment from river Owena, the objective of the research is to determine the contamination levels of organochlorine and organophosphorous pesticide in the water and sediment of river Owena. Analysis was carried out using gas chromatography coupled with electron capture detector in order to identify and quantify the concentration of organochlorine and organophosphorous pesticide in the water and sediment samples from river Owena. Analysis revealed the contamination of water and sediment with organophosphorous pesticide residues at different contamination levels in both dry and rainy season, while a low levels of organochlorine pesticide residues only during the dry season. The TOPP for sediment samples ranges from 1.045mg/L during the dry season and 2.279mg/L during the rainy season, while the TOPP for water samples ranges from 7.163mg/L during the dry season to 7.83mg/L during the rainy season. The TOCP values ranges from 1.288mg/L to 0.015mg/L for sediment and water samples respectively during the dry season, while organochlorine pesticides were not detected during the rainy season. The occurrence and seasonal variation of organophosphorous pesticide residues in river Owena can be attributed to the intense agricultural and urban activities in the vicinity of river Owena.