Soil adsorption studies of a rice herbicide,cyhalofop-butyl,in two texturally different soils of India

The ability of herbicides to be adsorbed by the soil and sediment and their tendency to be desorbed are some of the most important factors affecting soil and water contamination. Therefore, a sorption study was conducted to evaluate the adsorption of cyhalofop-butyl, butyl (2R)-2-[4-(4-cyano-2-fluorophenoxy) phenoxy] propanoate, in the sandy clay loam and clayey soils using a batch equilibrium method. The adsorption of cyhalofop-butyl was found positively related with the clay and organic carbon content. Freundlich constants (K _f) of cyhalofop-butyl in the clayey and sandy clay loam were found to be 13.39 and 2.21, respectively. Sorption coefficients (K _oc) and distribution coefficients (K _d) were found to be 265.38 and 2,092.79, and 1.38 and 11.48, for sandy clay loam and clayey soils, respectively. The adsorption isotherm suggested a relatively higher affinity of cyhalofop-butyl to the adsorption sites at low equilibrium concentrations. The low value of the soil organic carbon partition coefficient (K _oc) of cyhalofop-butyl in the sandy loam soil suggested its weaker adsorption in soil and thus increased its risk of mobility into water sources; hence, it should be used judiciously to prevent groundwater contamination     

Outdoor 220Rn, 222Rn and terrestrial gamma radiation levels: investigation study in the thorium rich Fen Complex, Norway

The present study was done in the Fen Complex, a Norwegian area rich in naturally occurring radionuclides, especially in thorium ((232)Th). Measurement of radioactivity levels was conducted at the decommissioned iron (Fe) and niobium (Nb) mining sites (TENORM) as well as at the undisturbed wooded sites (NORM), all open for free public access. The soil activity concentrations of (232)Th (3280-8395 Bq kg(-1)) were significantly higher than the world and the Norwegian average values and exceeded the Norwegian screening level (1000 Bq kg(-1)) for radioactive waste, while radium ((226)Ra) was present at slightly elevated levels (89-171 Bq kg(-1)). Terrestrial gamma dose rates were also elevated, ranging 2.6-4.4 μGy h(-1). Based on long-term surveys, the air concentrations of thoron ((220)Rn) and radon ((222)Rn) reached 1786 and 82 Bq m(-3), respectively. Seasonal variation in the outdoor gamma dose rates and Rn concentrations was confirmed. Correlation analyses showed a linear relationship between air radiation levels and the abundance of (232)Th in soil. The annual outdoor effective radiation doses for humans (occupancy 5 h day(-1)) were estimated to be in the range of 3.0-7.7 mSv, comparable or higher than the total average (summarized indoor and outdoor) exposure dose for the Norwegian population (2.9 mSv year(-1)). On the basis of all obtained results, this Norwegian area should be considered as enhanced natural radiation area (ENRA).     

210-Polonium studies in some environmental and biological matrices of Domiasiat uranium deposit area, West Khasi Hills, Meghalaya, India

The study was performed using a silicon surface barrier alpha spectrometer at Bhabha Atomic Research Centre, Mumbai, India. Through the study, the observed ²¹⁰Po activity in water sample from different locations in the Domiasiat area ranges from 0.04 to 0.69 Bq/l. The daily and annual intake of ²¹⁰Po through water was also estimated and the mean value of 0.72 and 263.61 Bq, respectively, were observed. It is observed that the effective doses through water were higher than the World Health Organization recommended dose of 0.05 mSv/year. The total annual effective doses through terrestrial ingestion for all the locations was studied and the mean annual effective dose was observed to be 0.315 mSv, which, when compared to the worldwide and the Indian values, was observed to be slightly higher. The mean activity in soil is found to be 124.8 ±5.7 Bq/kg and in meat the activity is 0.43 ±0.05 Bq/kg. In fishes, an activity of 0.48 ±0.07 Bq/kg in Garra lamta, 0.29 ±0.02 Bq/kg in Neolissocheilus hexaganolepis, and 3.3 ±0.1 Bq/kg in Macrobrachium sp. is observed. Activity concentration in plant samples was analyzed and the activity ranges from 0.020 ±0.002 to 9.69 ±0.35 Bq/kg. Committed effective dose by the adult population of the Domiasiat area through intake of ²¹⁰Po through these food items was also determined and compared with the Indian average value and the worldwide average value.     

Tree species diversity and composition in logged and unlogged rainforest of Kudremukh National Park, South India

Species composition and diversity in logged and unlogged forests were assesed to understand the regeneration of the residual stand twenty years after logging in Kudremukh National Park, South India. Relative density, frequency and basal area were measured by Point Centered Quarter method to calculate the diversity and stand quality. The logged forest harbored lower stem density of mature trees (508 ha(-1)) than unlogged ones (630 ha(-1)). Indeed, logging operations increased the species diversity in the regenerative phase (seedling phase) due to the creation of larger canopy gaps. The extra radiation reaching the ground, facilitated the colonization of early and late secondary species. Ramakrishanan Index of Stand Quality (RISQ) values in logged forest was higher in comparison with unlogged forest, indicating the dominance of early and late secondary species, especially at sapling phase. The light demanding secondary forest species contribute higher percentage to the overall tree population in logged forest. It is observed from the study that a sufficient period of felling cycle should be practiced to reinstate the same set of species prevailed before logging.     

Cyhalofop‐p‐butyl mobility and distribution of residues in soil at various depths

This study was conducted to evaluate cyhalofop‐p‐butyl mobility in a sandy loam soil and subsequent distribution of residues at various depths under field conditions. Soil samples were taken from 0 to 150 cm depths at 3–90 d after rains in lysemeter of 1 and 2 m depths. Cyhalofop‐p‐butyl application at two rates and subsequent precipitation had a significant impact on soil, physico‐chemical properties and herbicide mobility. Precipitation caused substantial mobility of cyhalofop‐p‐butyl in the soil and 1.1–7.6 μg L^?1 of cyhalofop‐p‐butyl was found in leachates. Cyhalofop‐p‐butyl residues in the leachates were probably due to preferential flow through the soil. Cyhalofop‐p‐butyl residues were detected in significant amounts from the soil up to 10 d, later, residues were found below the detection limit but its three transformation products viz., cyhalofop acid, diacid, and phenol were detected.     

Synthesis and application of graphene-based sensors in biology: a review

Environmental Chemistry Letters - Biosensors are gaining interest in biomedical and environmental sciences. In particular, graphene-based biosensors are promising due to the unique properties of...     

Targeting natural products against SARS-CoV-2

Environmental Science and Pollution Research - The human coronavirus disease (COVID-19) pandemic is caused by a novel coronavirus; the Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV-2)....     

Phytoremediation of radiostrontium ((90)Sr) and radiocesium ((137)Cs) using giant milky weed (Calotropis gigantea R.Br.) plants

Potential of plants to remove radionuclides/toxic elements from soils and solutions can be successfully applied for removal of important radionuclides such as strontium-90 (⁹⁰Sr) and cesium-137 (¹³⁷Cs). When uptake of ¹³⁷Cs and ⁹⁰Sr by Calotropis gigantea plants incubated in distilled water spiked with the radionuclides either alone or in combination was studied, it was found to have a high efficiency for the removal of ⁹⁰Sr, with 90% being removed from solutions (5 × 10³ kBq l⁻¹) within 24 h of incubation. However, in case of ¹³⁷Cs, about 44% could be removed from solutions (5 × 10³ kBq l⁻¹) at the end of 168 h of incubation. Accumulation of ⁹⁰Sr and ¹³⁷Cs was higher in roots compared to shoots. The plants could remediate both ⁹⁰Sr and ¹³⁷Cs when they were added together to the solution. When two months old plants were incubated in low level nuclear waste, 99% of activity disappeared at the end of 15 days. The present study suggests that C. gigantea could be used as a potential candidate plant for phytoremediation of ⁹⁰Sr and ¹³⁷Cs.     

Determination of total arsenic content in water by atomic absorption spectroscopy (AAS) using vapour generation assembly (VGA)

Analysis of arsenic in water is important in view of contamination of ground water with arsenic in some parts of the world including West Bengal in India and neighboring country Bangladesh. WHO has fixed the threshold for arsenic in drinking water to 10ppb (microg/l) level, hence the methodology for determination of arsenic is required to be sensitive at ppb level. Atomic absorption spectrophotometry with vapour generation assembly (AAS-VGA) is well known technique for the trace analysis of arsenic. However, total arsenic analysis [As(III)+As(V)] is very crucial and it requires reduction of As(V) to As(III) for correct analysis. As(III) is reduced to AsH3 vapours and finally to free As atoms, which are responsible for absorption signal in AAS. To accomplish this the vapour generation assembly attached to AAS has acid channel filled with 10 M HCl and the reduction channel with sodium borohydride. Further sample can be reduced either before aspiration for analysis, using potassium iodide (KI) or the sample can be introduced in the instrument directly and KI can be added in the reduction channel along with the sodium borohydride. The present work shows that samples prepared in 3 M HCl can be reduced with KI for 30 min before introduction in the instrument. Alternatively samples can be prepared in 6 M HCl and directly aspirated in AAS using KI in VGA reduction channel. The latter methodology is more useful when the sample size is large and time cycle is difficult to maintain. It is observed that the acid concentration of the sample in both the situations plays an important role. Further reduction in acid concentration and analysis time is achieved for the arsenic analysis by using modified method. Analysis in both the methods is sensitive at ppb level.