Investigation of groundwater and soil quality near to a municipal waste disposal site in Silchar, Assam, India

Unscientific management of municipal solid waste is one of the direct sources of contamination in developing countries, such as India. The present investigation carried out during Oct–Dec 2019 attempts to assess the parameters, such as quality of groundwater and soil along three depths (0–5, 5–15 and 15–30 cm), in proximity to a dumping site in Silchar, a rapidly evolving city of North-East India. Standard protocols of soil and water quality assessments were carried out. The pH values of the surface soils were found to be slightly acidic. Decrease in acidity with increasing depth was observed in the study site. The relative abundance of the analyzed elements at all soil depths was Zn > Fe > Ni > Cu > Cr. Weak correlation between the concentration of Cu, Fe and Zn, and the bulk density of the soil highlighted the micronutrient status of the soil. The impact of the nearby dumpsite on trace element contamination is indicated by the ‘extremely contaminated’ status of the soils with respect to geo-accumulation index. Majority of the groundwater samples exhibited pH levels below the desired limits, making it unfit for consumption by local communities. While Fe, Cu and Ni levels in groundwater samples exceeded the guideline values, Cr and Zn concentrations were found to be within limits except one sample. Principal Component Analysis of the observed data was carried out to ascertain the predominant sources of contamination. The observations indicate the negative impacts of nearby dumpsite on environmental parameters, such as groundwater and soil quality, as highlighted in this research.

Oil exploration activities: assessment of hazardous impacts on 'Golden silk' cultivation

Aliphatic-aromatic hydrocarbons and heavy metals (Cd, Cu, Co, Cr, Ni, Pb and Zn) were estimated in soil and leaf samples of Machilus bombycina (host plant of Antheraea assama silkworm) plantation along with atmospheric benzene, toluene and xylene (BTX) concentration near the oil exploration region of upper Assam, India, during the pre-monsoon and post-monsoon periods in six different sites. The results revealed higher aliphatic-aromatic hydrocarbons (ranging from 26.55 to 59.42 mg kg^-1) and heavy metal contaminations in all the six soil sampling sites during the pre-monsoon period while the trend was the opposite for the plant leaves. Polyaromatic hydrocarbons (9.85 mg kg^-1) were found in one soil sampling site near an abandoned oil well. The lead concentration in the soil showed values from 14.36 ± 1.5 to 96.5 ± 5.6 mg kg^-1 and found to be higher than the WHO limit in most of the samples. The aliphatic-aromatic hydrocarbon m-xylene was also found in M. bombycina plant leaves which could be traced due to crude oil. Cd and Pb concentrations in leave samples were found to be higher than the maximum allowable limit of 0.3 and 5.3 mg kg^-1, respectively. Principal component analysis of hydrocarbons in soil and leaves showed different clusters during the pre-monsoon and post-monsoon periods. The crude protein and total carbohydrate contents in the leaves were lower than those of uncontaminated samples which are an indication of a major disturbance to overall growth of plants. BTX concentration was found in the range of 119-198 μg m^-3 which indicates that atmospheric contamination in the studied area is causing the death of A. assama larvae.

Utilization of Euryale ferox Salisbury seed shell for removal of basic fuchsin dye from water: equilibrium and kinetics investigation

Euryale ferox Salisbury (E. ferox) is an environmentally and economically important wetland macrophyte.

Using coal fly ash as a support for Mn(II), Co(II) and Ni(II) and utilizing the materials as novel oxidation catalysts for 4-chlorophenol mineralization

In this work, Mn(II), Co(II) and Ni(II) were incorporated into waste coal fly ash used as a catalyst support by refluxing with the appropriate aqueous salt solution. The materials were calcined at 773-873 K for 5 h and the amount of divalent cations entering into the fly ash was determined by AAS measurements. Further characterization included estimation of oxides by XRF, structural properties by XRD, topographical features by SEM, surface functional groups by FT-IR, surface area and pore dimensions by BET N2-adsorption isotherms. The efficiency of the materials as environmental oxidation catalysts were tested with respect to destruction of 4-chlorophenol (4-CP) in water in the presence of hydrogen peroxide. Considered as one of the most persistent, toxic and largely applied organic compound, 4-CP enters water from the effluents of petrochemical, plastic, pesticide, kraft mill and other organochemical industries and research centers. Wet oxidation of 4-CP was tested by varying the mole ratio of 4-CP and H2O2, catalyst load, temperature, reaction time, 4-CP concentration and pH. Oxidation of 4-CP (5 × 10(-3) M or 643 mg L(-1)) was 51.1% for Mn(II)-fly ash, 58.3% for Co(II)-fly ash and 61.0% for Ni(II)-fly ash after 180 min at 323 K with 4-CP: H2O2 mole ratio of 1:1. COD load of the reaction mixture (4-CP: 5 × 10(-3) M, H2O2: 5 × 10(-3) M, catalyst load: 1.0 g L(-1), temperature 323 K, reaction time 0-240 min) decreased from 1480 to 620, 380, and 140 mg L(-1) respectively after oxidation with Mn(II)-fly ash, Co(II)-fly ash and Ni(II)-fly ash (overall COD reduction was 58.0, 74.3 and 90.5% respectively). The oxidation followed second order kinetics with the average rate coefficient of 7.9, 1.3 and 1.2 L mol(-1) min(-1) for Mn(II)-, Co(II)- and Ni(II)-fly ash. Increase in H2O2: 4-CP mole ratio from 1:1 to 20:1 (reaction time 300 min, catalyst load 1.0 g L(-1)) enhanced destruction from 52.1 to 95.6% for Mn(II)-fly ash, 58.3-95.6% for Co(II)-fly ash and from 60.4 to 94.8% for Ni(II)-fly ash. The oxidation increased with catalyst load but very high loads were not effective. Low pH favored the oxidation, but the catalysts performed well at the pH of aqueous 4-CP solution. A mechanism for the reactions is suggested based on the analysis of the products of oxidation.

Production of a non-cytotoxic bioflocculant by a bacterium utilizing a petroleum hydrocarbon source and its application in heavy metal removal

A bacterium isolated from the activated sludge of an oil refinery of Assam, India retained efficient bioflocculating activity through production of the bioflocculant when it was grown on a crude oil amended medium void of any other carbon source.