Dynamics of traffic noise in a tropical city Varanasi and its abatement through vegetation

Noise level monitoring and its reduction with different width and height of vegetation belt were studied in the Varanasi city. Noise level monitoring of the Varanasi city revealed the fact that area category A (without vegetation) was highly polluted as compare to area category B (with vegetation) having less fluctuation of traffic load. Four plant species Putranjeva roxburghi, Cestrum nocturnum, Hibiscus rosasinensis and Murraya peniculata were tested for noise reduction study at different frequencies. Experiment revealed the fact that H. rosasinensis reduced noise highest at both low and high frequencies (100-500 Hz, 22 dB and 2.5-6.3 KHz 26 dB), followed by M. peniculata (100-500 Hz, 18 dB and 2.5-6.3 KHz 20 dB), P. roxburghi (100-500 Hz 15 dB and 2.5-6.3 KHz 17 dB) and C. nocturnum (100-500 Hz 9 dB and 2.5-6.3 KHz 14 dB). Significance of vegetation belt in noise reduction was established with multiple regression models.     

Long-term effect of rice-based farming systems on soil health

Integrated rice–fish culture, an age-old farming system, is a technology which could produce rice and fish sustainably at a time by optimizing scarce resource use through complementary use of land and water. An understanding of microbial processes is important for the management of farming systems as soil microbes are the living part of soil organic matter and play critical roles in soil C and N cycling and ecosystem functioning of farming system. Rice-based integrated farming system model for small and marginal farmers was established in 2001 at Central Rice Research Institute, Cuttack, Odisha. The different enterprises of farming system were rice–fish, fish–fingerlings, fruits, vegetables, rice–fish refuge, and agroforestry. This study was conducted with the objective to assess the soil physicochemical properties, microbial population, carbon and nitrogen fractions, soil enzymatic activity, and productivity of different enterprises. The effect of enterprises induced significant changes in the chemical composition and organic matter which in turn influenced the activities of enzymes (urease, acid, and alkaline phosphatase) involved in the C, N, and P cycles. The different enterprises of long-term rice-based farming system caused significant variations in nutrient content of soil, which was higher in rice–fish refuge followed by rice–fish enterprise. Highest microbial populations and enzymatic properties were recorded in rice–fish refuge system because of waterlogging and reduced condition prolonged in this system leading to less decomposition of organic matter. The maximum alkaline phosphatase, urease, and FDA were observed in rice–fish enterprise. However, highest acid phosphatase and dehydrogenase activity were obtained in vegetable enterprise and fish–fingerlings enterprise, respectively.     

Habitat-associated changes in some metabolic dehydrogenases and proteins of tropical earthworms

Impacts of different habitats on specific activities of LDH, cMDH, mMDH, cytoplasmic and mitochondrial proteins of M. posthuma, P. sansibaricus, L. mauritii were studied. Maximum specific activity of LDH of the earthworm M. posthuma and L. mauritii was observed in garden. In case of P. sansibaricus, maximum LDH specific activity was found in sewage. Minimum specific activity of LDH of the earthworm M. posthuma was found in non-cultivated field. However, P. sansibaricus and L. mauritii exhibited minimum activity in orchard and cultivated pedoecosystem, respectively. The maximum specific activity of cMDH and mMDH in earthworms from sewage and minimum from non-cultivated field (in case of M. posthuma), garden (in P. sansibaricus) and cultivated land (in L. mauritii) may be due to availability of more organic matter and nitrogen content in the former than in the later cases. Variations in specific activities of these metabolic enzymes due to changes in their pedoecological habitats clearly demonstrate the impact of pedoecosystem on respiratory capacity of the earthworms. Earthworms from pedoecosystem richer in organic matter and nitrogen showed elevated levels of cytoplasmic and mitochondrial protein. The changes in enzyme-specific activity and protein profiles were habitat specific.     

Alterations in aerobic and anaerobic dehydrogenases and protein levels of three tropical earthworm species with respect to different seasons

The specific activities of cMDH, mMDH and LDH of earthworms (M. posthuma, P. sansibaricus, L. mauritii) started increasing with the onset of favorable seasonal conditions from July to August. A lower temperature and moisture favor the increase in specific activities of enzymes during post-rainy (September–October) and winter (November–January) seasons. The maximum specific activities of enzymes from December to January indicate greater aerobic and anaerobic energy production to cope up with the cold condition. However, the enzyme activities decreased in summer (February–April) with the increase in the ambient temperature. The specific activities were minimum in summer (May–June) as earthworms would be entering quiescent phase to avoid extreme heat and thus showed least energy requirement in this period. Similar seasonal variations were found in the cytoplasmic and mitochondrial proteins. The maximum and minimum seasonal effects were on the epigeic (P. sansibaricus) and endo-anecic (M. posthuma) earthworms, respectively. The differences in the profile of dehydrogenases and proteins may be assigned to the differences in the ecological categories of earthworms.     

Biomonitoring seasonal variation of urban air polycyclic aromatic hydrocarbons (PAHs) using Ficus benghalensis leaves

Temporal and seasonal variations of polycyclic aromatic hydrocarbons (PAHs) concentrations in leaves of Ficus benghalensis were investigated in Varanasi city (India). Leaf samples were collected from six sites from urban area of Varanasi and from a control site. PAH extraction was done by sonication in dichloromethane-acetone and quantification by GC-MS. In January total leaf PAHs concentrations at all the urban sites were twice higher as compared to other season's viz. summer and rainy. In contrast, at the control site leaf PAHs concentrations showed lower values than urban sites. The maximum concentrations of total PAHs in winter were due to the medium molecular weight PAHs which increases with respect to both low and high molecular weight PAHs. The temporal variation of medium molecular weight PAHs was similar both at the urban and remote sites. These results support biomonitoring ability of Ficus benghalensis leaves to temporal variations in PAHs contamination.     

Biological treatment of wastewater by selected aquatic plants

Pollutant-removal efficiency of certain macrophytes and algae, such as Eichhornia crassipes, Microcystis aeruginosa, Scenedesmus falcatus, Chlorella vulgaris and Chlamydomonas mirabilis, has been tested in laboratory conditions to evaluate their potential role in wastewater treatment. Sewage of Varanasi city, mixed with the effluents of about 1200 small-scale industries, was used for the tests. The investigation was performed in three stages i.e. a water hyacinth culture followed by an algal culture, and finally a second water hyacinth culture. For the first water hyacinth culture, 10 water hyacinth plants were grown in a tank of wastewater with 15 days' retention time. In the second stage, algal species were cultured in the treated wastewater for 5 days, whilst in the third stage, water hyacinth plants were again grown for further treatment of the wastewater for 9 days. This three-stage aquaculture resulted in very high reductions of BOD (96.9%), suspended solids (78.1%), total alkalinity (74.6%), PO(4)-P (89.2%), NO(3)-N (81.7%), acidity (73.3%), NH(4)-N (95.1%), COD (77.9%), hardness (68.6%) and coliform bacteria (99.2%). An increase in the concentration of dissolved oxygen (70%) was also observed.     

Effect of lead on growth and nitrate assimilation of Vigna radiata (L.) Wilczek seedlings in a salt affected environment

The inhibition of seedling growth and nitrate reductase activity in 5 d old Vigna radiata (L.) Wilczek cv. Pusa Baisakhi in the presence of 1.0 mM lead acetate increased drastically, if NaCl (6 and 12 EC) was also present in the nutrient media along with the metal salt. Correspondingly higher endogenous Na+ levels were accumulated in the roots and leaves of seedlings in presence of the two stresses. On the other hand, the levels of endogenous lead get reduced in presence of NaCl in both the roots and leaves. Roots accumulated more Pb2+ and Na+ than the leaves. The two stresses affect more drastically in the additive or even synergistic manner during the early growth phase of the seedlings.     

Intake of Chromium by the Adult Population of Mumbai City

Electro Thermal Atomic Absorption Spectrophotometry (ET-AAS), is used for the determination of chromium (Cr) in a variety of environmental matrices. The detection limit for the estimation of Cr is 2 pg absolute for a volume injection of 20 l. The precision of the method is established by analysing Cr from a synthetic mixture containing various elements in different qualities (0.5–10 ppm) and is found to be within ± 8%. The reliability of estimation is further assessed through the analysis of Standard Reference Materials (SRMs) of soil, hay, milk powder and lake sediment obtained from IAEA.The total intake of Cr through air, water and food works out to be 54 g/day for the adult population of Mumbai city. The dietary intake through food is the major contributor to the total intake of Cr. The concentration of Cr in atmospheric air and drinking water collected from different suburbs showed geometric mean concentrations of 0.09 g/m³ and 0.3 g/l, respectively. The daily intake of Cr, though lower, is closer to the lower bound of the recommended value of 50–200 g/day.     

Lead detoxification by coontail (Ceratophyllum demersum L.) involves induction of phytochelatins and antioxidant system in response to its accumulation

Coontail (Ceratophyllum demersum L.) plants when exposed to various concentrations of Pb (1-100microM) for 1-7days, exhibited both phytotoxic and tolerance responses. The specific responses were function of concentration and duration. Plants accumulated 1748mugPbg(-1) dw after 7d which reflected its metal accumulation ability, however most of the metal (1222microgg(-1) dw, 70%) was accumulated after 1d exposure only. The toxic effect and oxidative stress caused by Pb were evident by the reduction in biomass and photosynthetic pigments and increase in malondialddehyde (MDA) content and electrical conductivity with increase in metal concentration and exposure duration. Morphological symptoms of senescence phenomena such as chlorosis and fragmentation of leaves were observed after 7d. The metal tolerance and detoxification strategy adopted by the plant was investigated with reference to antioxidant system and synthesis of phytochelatins. Protein and antioxidant enzymes viz., superoxide dismutase (SOD, EC 1.15.1.1), guaiacol peroxidase (GPX, EC 1.11.1.7) ascorbate peroxidase (APX, EC 1.11.1.11), catalase (CAT, EC 1.11.1.6) and glutathione reductase (GR, EC 1.6.4.2) showed induction at lower concentration and duration followed by decline. All enzymes except GPX showed maximum activity after 1d. An increase in cysteine, non-protein thiols (NP-SH) and glutathione (GSH) content was observed at moderate exposure conditions followed by decline. Phytochelatins (PC(2) and PC(3)) were synthesized to significant levels at 10 and 50microM Pb with concomitant decrease in GSH levels. Thus production of PCs seems important for the detoxification of metal, however it may lead to depletion of GSH and consequently oxidative stress. Results suggest that plants responded positively to moderate Pb concentrations and accumulated high amount of metal. Due to metal accumulation coupled with detoxification potential, the plant appears to have potential for its use as phytoremediator species in aquatic environments having moderate pollution of Pb.