Acid azo dye degradation by free and immobilized horseradish peroxidase (HRP) catalyzed process

Acid azo (Acid Black 10 BX) dye removal by plant based peroxidase catalyzed reaction was investigated. Horseradish peroxidase (HRP) was extracted from horseradish roots and its performance was evaluated in both free and immobilized form. HRP showed its ability to degrade the dye in aqueous phase. Studies are further carried out to understand the process parameters such as aqueous phase pH, H2O2 dose, dye and enzyme concentrations during enzyme-mediated dye degradation process. Experimental data revealed that dye (substrate) concentration, aqueous phase pH, enzyme and H2O2 dose play a significant role on the overall enzyme-mediated reaction. Acrylamide gel immobilized HRP showed effective performance compared to free HRP and alginate entrapped HRP. Alginate entrapped HRP showed inferior performance over the free enzyme due to the consequence of non-availability of the enzyme to the dye molecule due to polymeric immobilization. Standard plating studies performed with Pseudomonas putida showed enhanced degradation of HRP catalyzed dye compared to control.     

Heavy metal contaminations in the groundwater of Brahmaputra flood plain: an assessment of water quality in Barpeta District, Assam (India)

A study was conducted to evaluate the heavy metal contamination status of groundwater in Brahmaputra flood plain Barpeta District, Assam, India. The Brahmaputra River flows from the southern part of the district and its many tributaries flow from north to south. Cd, Fe, Mn, Pb, and Zn are estimated by using atomic absorption spectrometer, Perkin Elmer AA 200. The quantity of heavy metals in drinking water should be checked time to time; as heavy metal accumulation will cause numerous problems to living being. Forty groundwater samples were collected mainly from tube wells from the flood plain area. As there is very little information available about the heavy metal contamination status in the heavily populated study area, the present work will help to be acquainted with the suitability of groundwater for drinking applications as well as it will enhance the database. The concentration of iron exceeds the WHO recommended levels of 0.3 mg/L in about 80% of the samples, manganese values exceed 0.4 mg/L in about 22.5% of the samples, and lead values also exceed limit in 22.5% of the samples. Cd is reported in only four sampling locations and three of them exceed the WHO permissible limit (0.003 mg/L). Zinc concentrations were found to be within the prescribed WHO limits. Therefore, pressing awareness is needed for the betterment of water quality; for the sake of safe drinking water. Statistical analysis of the data was carried out using Special Package for Social Sciences (SPSS 16).     

Lead, arsenic, fluoride, and iron contamination of drinking water in the tea garden belt of Darrang district, Assam, India

Drinking water quality with respect to lead, iron, fluoride, and arsenic has been carried out in and around tea gardens of Darrang district of Assam, India. The district lies between 26°25^′ and 26°55^′ northern latitude and 91°45^′ and 91°20^′ east longitude and covers an area of 3,465.30 km². Twenty-five different sampling stations were selected for the study. Iron, lead, and arsenic were analyzed by using an atomic absorption spectrometer, Perkin Elmer AA 200, while fluoride was measured by the SPADNS method using a UV–VIS spectrometer, Shimadzu 1240 model. The study revealed that the water sources in the area are heavily polluted with lead. Statistical analysis of the data is presented to determine the distribution pattern, localization of data, and other related information. Statistical observations imply non-uniform distribution of the studied parameters with a long asymmetric tail either on the right or left side of the median.     

Fraction distribution and risk assessment of heavy metals and trace elements in sediments of Lake Uluabat

To examine the status and risk of heavy metal pollution, the distribution of As, Cd, Cr, Ni, and Pb in the sediment of Lake Uluabat was characterized. The present study used a four-stage method to assess the ecotoxicological effects of the heavy metal and trace elements fractions in the sediment of Lake Uluabat. Total Cr and Ni concentrations in the sediment were determined to have exceeded the severe effect level (SEL) limit values. The percentages of the variable fractions of Cr and Ni were below 10%. Because of this reason, they were not defined to have a high risk. The relationships among the physicochemical parameters, heavy metals and trace elements in water and sediment were determined statistically. Pb, Cd, and As in the water were found in relation with some of the fractions. Moreover, it was thought that the amounts of the elements of As releasing into the water might be increased due to their relations with the physicochemical parameters.     

Assessment of availability, ecological feature, and habitat preference of the medicinal herb Houttuynia cordata Thunb in the Brahmaputra Valley of Assam, India

Houttuynia cordata Thunb. is a rhizome-bearing aromatic medicinal herb and is restricted to specialized moist habitats. The plant is collected from natural habitats for local consumption and trade. The status of the species and its variations in physiological performance in different habitats were studied in selected sites of geographically different areas of Brahmaputra valley in eastern India. The surveys were conducted in two different growth stages of the plant during 2005–2007. The sites where the species was encountered were marked and a distribution map was prepared. The frequency and density of the plant was higher in the moist habitats with higher organic carbon (0.85 ± 0.05%). Generally, the density, biomass production and growth had significant (P < 0.05) positive relationship with the soil physicochemical properties (linear curve fit). Soil moisture was the most dependent factor for the plant growth and the optimum growth was recorded at 78 ± 5.6% (r²?= 0.9; P ≤ 0.01). The physiological performance of the plant in all the studied sites were significantly varied (P < 0.05). The growth and development of H. cordata were also different in the flowering and senescence stages. Clay loam soil, average soil pH of 5.9, and 78% soil moisture were the favorable soil characteristics for the better growth of H. cordata and, hence, these data may be considered for conservation of the species.     

Population growth of Euchlanis dilatata (Rotifera): combined effects of methyl parathion and food (Chlorella vulgaris)

In the present work, the combined impact of four concentrations (0, 0.0625, 0.125, and 0.25 mg/L) of methyl parathion and three densities (0.5 x 10(6), 1.0 x 10(6), and 2.0 x 10(6) cells/mL) of the green alga Chlorella vulgaris on the population growth of Euchlanis dilatata was studied. In general, regardless of the food level, an increase in the concentration of methyl parathion resulted in a significant reduction of the maximal population density and rate of population increase. The population growth rate in the controls ranged from 0.248 to 0.298; rates were lower in the presence of the pesticide. At any toxicant concentration, rotifers fed higher algal density showed significantly higher population growth compared with those at lower food levels. An interaction between toxicant and food level was evident on the population growth of E. dilatata. Results have been discussed in light of the protective role of algal density on the toxic effects of insecticides on rotifers and the differences in susceptibility to toxicants between planktonic and littoral rotifers.     

Studies on comparative population growth of some species of the rotifer Lecane (Rotifera)

We compared the population growth patterns of 5 species of the rotifer genus Lecane [(L. quadridentata (Ehrenberg, 1830), L. comuta (Muller, 1786), L. papuana (Murray, 1913), L. unguitata (Fadeev, 1925) and L. pyriformis (Daday, 1905)] ranging in adult average body size from 30 to 140 microm. All species were cultured under laboratory conditions for 25-30 days using the green alga Scenedesmus acutus as the exclusive diet, at a density of 1.0 x 10(6) cells ml(-1) at 24 degrees C. Regardless of the species, lecanids reached their peak population densities after 4 weeks. Peak population densities ranged from 15 to 320 ind. ml(-1), depending on body size. There was an inverse curvilinear relation between body lengths and peak population abundances (densities) of the Lecane species. Egg ratios (eggs per female) for the tested species were < 0.6 during the exponential phase but declined to 0.1 (or lower) as the population density increased. The rates of population increase for the lecanids were in general lower(0.10 to 0.21 day (-1)) than other well-studied rotifer species including members of Brachionidae.     

Heavy metal contamination of drinking water in Kamrup district, Assam, India

This study was undertaken to assess the heavy metal concentration of the drinking water with respect to zinc, copper, cadmium, manganese, lead and arsenic in Kamrup district of Assam, India. Ground water samples were collected from tube wells, deep tube wells and ring wells covering all the major hydrogeological environs. Heavy metals in groundwater are estimated by using Atomic Absorption Spectrometer, Perkin Elmer Analyst 200. Data were assessed statistically to find the distribution pattern and other related information for each metal. The study revealed that a good number of the drinking water sources were contaminated with cadmium, manganese and lead. Arsenic concentrations although did not exceeded WHO limits but was found to be slightly elevated. Copper and zinc concentrations were found to be within the prescribed WHO limits. An attempt has also been made to ascertain the possible source of origin of the metals. Positive and significant correlation existing between manganese with zinc and copper indicates towards their similar source of origin and mobility. In view of the present study and the level of heavy metal contamination, it could be suggested to test the potability of the water sources before using it for drinking purpose.     

A semi-coupled model for determining the distribution of two-dimensional coherent structures in open channel flow

Environmental Fluid Mechanics - Mixing layers and associated large-scale turbulent structures are some of the most common features of turbulent shallow water flow. Due to their...