Application of sequential leaching, risk indices and multivariate statistics to evaluate heavy metal contamination of estuarine sediments: Dhamara Estuary, East Coast of India

In the present study, concentration of some selected trace metals (Fe, Mn, Ni, Co, Pb, Zn, Cu, Cr and Cd) are measured in Brahmani, Baitarani river complex along with Dhamara estuary and its near shore. Chemical partitioning has been made to establish association of metals into different geochemical phases. The exchangeable fraction is having high environmental risk among non-lithogeneous phases due to greater potential for mobility into pore water. The metals with highest bio-availability being Cd, Zn and Cr. The metals like Mn, Zn, Cd and Cu represent an appreciable portion in carbonate phase. Fe–Mn oxides act as efficient scavenger for most of the metals playing a prime role in controlling their fate and transport. Among non-lithogeneous phases apart from reducible, Cr showed a significant enrichment in organic phase. Risk assessment code values indicate that all metals except Fe fall under medium-risk zone. In estuarine zone Cd, Zn, Pb and Cr are released to 32.43, 26.10, 21.81 and 20 %, respectively, indicating their significant bio-availability pose high ecological risk. A quantitative approach has been made through the use of different risk indices like enrichment factor, geo-accumulation index and pollution load index. Factor analysis indicates that in riverine zone, Fe–Mn oxides/hydroxides seem to play an important role in scavenging metals, in estuarine zone, organic precipitation and adsorption to the fine silt and clay particles while in coastal zone, co-precipitation with Fe could be the mechanism for the same. Canonical discriminant function indicates that it is highly successful in discriminating the groups as predicted.     

Biodegradation of Pro-oxidant Filled Polypropylene Films and Evaluation of the Ecotoxicological Impact

The biodegradability of calcium stearate (CaSt) and cobalt stearate (CoSt) filled polypropylene (PP) films were investigated in this work. The PP films were prepared using melt blending technique followed by hot press moulding. On the basis of their tensile properties, the optimum amount of pro-oxidants was taken as 0.2 phr. Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used for the characterization of optimized films. Presence of pro-oxidant in the PP was confirmed by the FTIR studies. Addition of pro-oxidants in the films decreased the thermal stability as revealed by TGA analysis. Crystallinity of the pro-oxidant filled PP decreased with addition of pro-oxidants as showen by DSC. The maximum biodegradation of CaSt and CoSt containing PP films was showen 7.65 and 8.34%, respectively with 0.2 phr. Both the microbial test and plant growth test (on corn and tomato) indicated that biodegradation intermediates were non toxic.     

Mycoremediation of heavy metals: processes,mechanisms, and affecting factors

Environmental Science and Pollution Research - Industrial processes and mining of coal and metal ores are generating a number of threats by polluting natural water bodies. Contamination of heavy...     

Experimental investigation of solar-powered desiccant cooling system by using composite desiccant “CaCl<Subscript>2</Subscript>/jute”

A solar-powered composite desiccant cooling system has been experimentally investigated. It consists of evacuated tube solar water heater, composite desiccant bed heat exchanger (CDBHE), direct evaporative cooling unit and cooling tower. The composite desiccant material has been synthesized by using iron mesh and jute layer impregnated with calcium chloride solution, and this composite desiccant is placed in shell- and tube-type heat exchanger to make CDBHE. In this desiccant cooling system, the evacuated tube solar water heater is used to produce required hot water for regeneration of composite desiccant material. A cooling tower is used to produce cooling water which is pumped into CDBHE during dehumidification process to remove heat of adsorption. Direct evaporative cooling unit is used to cool the outlet process air of CDBHE. It has been found that the average dehumidification rate increases by 54.1 % when using circulating cooling water. The COP_th of desiccant cooling system has been found to be 0.46 with a cooling capacity of 353.8 W.     

Release behavior and bioefficacy of imazethapyr formulations based on biopolymeric hydrogels

Controlled release formulations of imazethapyr herbicide have been developed employing guar gum-g-cl-polyacrylate/bentonite clay hydrogel composite (GG-HG) and guar gum-g-cl-PNIPAm nano hydrogel (GG-NHG) as carriers, to assess the suitability of biopolymeric hydrogels as controlled herbicide release devices. The kinetics of imazethapyr release from the developed formulations was studied in water and it revealed that the developed formulations of imazethapyr behaved as slow release formulations as compared to commercial formulation. The calculated diffusion exponent (n) values showed that Fickian diffusion was the predominant mechanism of imazethapyr release from the developed formulations. Time for release of half of the loaded imazethapyr (t_1/2) ranged between 0.06 and 4.8 days in case of GG-NHG and 4.4 and 12.6 days for the GG-HG formulations. Weed control index (WCI) of GG-HG and GG-NHG formulations was similar to that of the commercial formulation and the herbicidal effect was observed for relatively longer period. Guar gum-based biopolymeric hydrogels in both macro and nano particle size range can serve as potential carriers in developing slow release herbicide formulations.     

Tracing the factors responsible for arsenic enrichment in groundwater of the middle Gangetic Plain,India: a source identification perspective

Arsenic contamination in groundwater is of increasing concern because of its high toxicity and widespread occurrence. This study is an effort to trace the factors responsible for arsenic enrichment in groundwater of the middle Gangetic Plain of India through major ion chemistry, arsenic speciation, sediment grain-size analyses, and multivariate statistical techniques. The study focuses on the distinction between the contributions of natural weathering and anthropogenic inputs of arsenic with its spatial distribution and seasonal variations in the plain of the state Bihar of India. Thirty-six groundwater and one sediment core samples were collected in the pre-monsoon and post-monsoon seasons. Various graphical plots and statistical analysis were carried out using chemical data to enable hydrochemical evaluation of the aquifer system based on the ionic constituents, water types, hydrochemical facies, and factors controlling groundwater quality. Results suggest that the groundwater is characterized by slightly alkaline pH with moderate to strong reducing nature. The general trend of various ions was found to be Ca²⁺ > Na⁺ > Mg²⁺ > K⁺ > NH₄ ⁺; and HCO₃ ⁻ > Cl⁻ > SO₄ ²⁻ > NO₃ ⁻ > PO₄ ³⁻ > F⁻ in both seasons. Spatial and temporal variations showed a slightly higher arsenic concentration in the pre-monsoon period (118 μg/L) than in the post-monsoon period (114 μg/L). Results of correlation analyses indicate that arsenic contamination is strongly associated with high concentrations of Fe, PO₄ ³⁻, and NH₄ ⁺ but relatively low Mn concentrations. Further, the enrichment of arsenic is more prevalent in the proximity of the Ganges River, indicating that fluvial input is the main source of arsenic. Grain size analyses of sediment core samples revealed clay (fine-grained) strata between 4.5 and 7.5 m deep that govern the vertical distribution of arsenic. The weathering of carbonate and silicate minerals along with surface-groundwater interactions, ion exchange, and anthropogenic activities seem to be the processes governing groundwater contamination, including with arsenic. Although the percentage of wells exceeding the permissible limit (50 μg/L) was less (47%) than that reported in Bangladesh and West Bengal, the percentage contribution of toxic As(III) to total arsenic concentration is quite high (66%). This study is vital considering that groundwater is the exclusive source of drinking water in the region and not only makes situation alarming but also calls for immediate attention.     

The promise of Beijing: Evaluating the impact of the 2008 Olympic Games on air quality

To prepare for the 2008 Olympic Games, China adopted a number of radical measures to improve air quality. Using the officially reported air pollution index (API) from 2000 to 2009, we show that these measures improved the API of Beijing during and a little after the Games, but a significant proportion of the effect faded away by October 2009. For comparison, we also analyze an objective and indirect measure of air quality at a high spatial resolution – aerosol optimal depth (AOD), derived using the data from NASA satellites. The AOD analysis confirms the real but temporary improvement in air quality, it also shows a significant correlation between air quality improvement and the timing and location of plant closure and traffic control. These results suggest that it is possible to achieve real environmental improvement via stringent policy interventions, but for how long the effects of these interventions will last will largely depend on the continuation of the interventions.