Pesticide residue level in tea ecosystems of Hill and Dooars regions of West Bengal, India

In the present study we quantified the residues of organophosphorus (e.g. ethion and chlorpyrifos), organochlorine (e.g. heptachlor, dicofol, alpha-endosulfan, beta-endosulfan, endosulfan sulfate) and synthetic pyrethroid (e.g. cypermethrin and deltamethrin) pesticides in made tea, fresh tea leaves, soils and water bodies from selected tea gardens in the Dooars and Hill regions of West Bengal, India during April and November, 2006. The organophosphorus (OP) pesticide residues were detected in 100% substrate samples of made tea, fresh tea leaves and soil in the Dooars region. In the Hill region, 20% to 40% of the substrate samples contained residues of organophosphorus (OP) pesticides. The organochlorine (OC) pesticide residues were detected in 33% to 100% of the substrate samples, excluding the water bodies in the Dooars region and 0% to 40% in the Hill region. The estimated mean totals of studied pesticides were higher in fresh tea leaves than in made tea and soils. The synthetic pyrethroid (SP) pesticide residues could not be detected in the soils of both the regions and in the water bodies of the Dooars. Sixteen percent and 20% of the made tea samples exceeded the MRL level of chlorpyrifos in Dooars and Hill regions respectively. The residues of heptachlor exceeded the MRL in 33% (April) and 100% (November) in the Dooars and 40% (April) and 20% (November) in the Hill region. Based on the study it was revealed that the residues of banned items like heptachlor and chlorpyrifos in made tea may pose health hazards to the consumers.     

Biodegradation of benzene, toluene, and xylene (BTX) in liquid culture and in soil by Bacillus subtilis and Pseudomonas aeruginosa strains and a formulated bacterial consortium

Purpose

The major aromatic constituents of petroleum products viz. benzene, toluene, and mixture of xylenes (BTX) are responsible for environmental pollution and inflict serious public concern. Therefore, BTX biodegradation potential of individual as well as formulated bacterial consortium was evaluated. This study highlighted the role of hydrogen peroxide (H₂O₂), nitrate, and phosphate in stimulating the biodegradation of BTX compounds under hypoxic condition.

Materials and methods

The individual bacterium viz. Bacillus subtilis DM-04 and Pseudomonas aeruginosa M and NM strains and a consortium comprising of the above bacteria were inoculated to BTX-containing liquid medium and in soil. The bioremediation experiment was carried out for 120?h in BTX-containing liquid culture and for 90?days in BTX-contaminated soil. The kinetics of BTX degradation either in presence or absence of H₂O₂, nitrate, and phosphate was analyzed using biochemical and gas chromatographic (GC) technique.

Results

Bacterial consortium was found to be superior in degrading BTX either in soil or in liquid medium as compared to degradation of same compounds by individual strains of the consortium. The rate of BTX biodegradation was further enhanced when the liquid medium/soil was exogenously supplemented with 0.01?% (v/v) H₂O₂, phosphate, and nitrate_. The GC analysis of BTX biodegradation (90?days post-inoculation) in soil by bacterial consortium confirmed the preferential degradation of benzene compared to m-xylene and toluene.

Conclusions

It may be concluded that the bacterial consortium in the present study can degrade BTX compounds at a significantly higher rate as compared to the degradation of the same compounds by individual members of the consortium. Further, addition of H₂O₂ in the culture medium as an additional source of oxygen, and nitrate and phosphate as an alternative electron acceptor and macronutrient, respectively, significantly enhanced the rate of BTX biodegradation under oxygen-limited condition.     

Time series analysis of coal mine accident experience

This study investigates several forecasting techniques that can be useful to mine safety managers for studying mine accident rate behavior. Three time series models were studied for extrapolation of accident rates. These models are applied to historical accident incidence data from a coal mine. Further, a method is presented for evaluating the three models for the selection of an appropriate model. For this particular mine application, it is concluded that the more complex Box-Jenkins ARMA model as well as first order autoregressive model do not give better results than the simple exponential smoothing model. However, when the random variations or autocorrelations in the accident experience rates between periods are different, the models may predict differently. As such, specific models must be developed for each mine on the basis of statistical analysis of the mine accident experience data over time. Moreover, the importance of incorporating human judgement to interpret the results of statistical forecasting cannot be overemphasized. Integration of policy or operating changes, which may impact mine safety performance, with statistical forecasting techniques is essential to arrive at a realistic prediction of future performance.     

Probability distributions and statistical inference for axial data

Observations on axes which lack information on the direction of propagation are referred to as axial data. Such data are often encountered in enviromental sciences, e.g. observations on propagations of cracks or on faults in mining walls. Even though such observations are recorded as angles, circular probability models are inappropriate for such data since the constraint that observations lie only in [0, π) needs to be enforced. Probability models for such axial data are argued here to have a general structure stemming from that of wrapping a circular distribution on a semi-circle. In particular, we consider the most popular circular model, the von Mises or circular normal distribution, and derive the corresponding axial normal distribution. Certain properties of this distribution are established. Maximum likelihood estimation of its parameters are shown to be surprisingly, in contrast to trigonometric moment estimation, numerically quite appealing. Finally we illustrate our results by several real life axial data sets. Received: September 2004/ Revised: December 2004     

Metal contents in the groundwater of Sahebgunj district, Jharkhand, India, with special reference to arsenic

A detailed study has been presented on groundwater metal contents of Sahebgunj district in the state of Jharkhand, India with special reference to arsenic. Both tubewell and well waters have been studied separately with greater emphasis on tubewell waters. Groundwaters of all the nine blocks of Sahebgunj district have been surveyed for iron, manganese, calcium, magnesium, copper and zinc in addition to arsenic. Normal distribution statistic, exploratory data analysis and robust Z-score analysis have been employed to find out the distribution pattern, localisation of data, outliers and other related information. Groundwaters of three blocks of Sahebgunj, namely, Sahebgunj, Rajmahal and Udhawa have been found to be alarmingly contaminated with arsenic present at or above 10 ppb. Arsenic distribution patterns in these blocks are highly asymmetric in nature with the common feature of increasing width from first to fourth quartile. A very broad fourth quartile in each case represents a long asymmetric tail on the right of the median. Tubewell waters of at least two more blocks require regular monitoring to identify the outbreak of arsenic at the onset. Groundwaters of Sahebgunj district in general contain high iron and manganese. It is by and large soft in nature. Well waters have been found to be better with regard to arsenic but iron and manganese contents do not vary significantly. Normal distribution analysis (NDA), box and whisker (BW) plot and Z-score analysis together can provide a reasonably complete statistical picture of metal contents in Sahebgunj district groundwaters.     

Experimental study of solar energy–based water purifier of single-slope type by incorporating a number of similar evacuated tubular collectors

Environmental Science and Pollution Research - This research paper deals with the experimental investigation of solar energy–based water purifier (SEBWP) of single-slope type by incorporating...     

Heavy metals alter photosynthetic pigment profiles as well as activities of chlorophyllase and 5-aminolevulinic acid dehydratase (ALAD) in Amaranthus lividus seedlings

Varied concentrations of PbCl2 and CdCl2 in the germinating media reduced the total chlorophyll and carotenoid contents in primary leaves of Amaranthus lividus seedlings (168 h old). When chlorophyll a and chlorophyll b contents were measured separately, greater loss of chl b than chl a under the identical conditions of heavy metal treatment was observed In addition, the loss of total chlorophyll was more than carotenoids under the same magnitude of heavy metal treatment. The effect of heavy metal treatment at germination stage was further studied on chlorophyll accumulation in primary leaves in relation to the activities of 5-aminolevulinic acid dehydratase (ALAD) and chlorophyllase. The activities of ALAD gradually diminished in response to both the heavy metals in a concentration-guided manner, while the activities of chlorophyllase did not exhibit any significant change.     

Evaluation and standardisation of a simple HG-AAS method for rapid speciation of As(III) and As(V) in some contaminated groundwater samples of West Bengal, India

A simple HG-AAS technique has been evaluated and standardised for rapid speciation of As(III) and As(V) in a number of contaminated groundwater samples of West Bengal, India. Citric acid has been used for selective hydride formation of As(III). The sensitivity of the evaluated HG-AAS method is 7.91 mg(-1)l, standard deviation, 0.001 and detection limit, 0.4 microg l(-1). As(III) sensitivity remains constant in the sample pH range of 2.3-10.6. Concomitant mineral matrix of the water samples did not interfere with arsenic determination. Eight out of ten groundwater samples analysed for As(IlI)and As(V) contain more As(III), which lies in the range of 54-350 ppb. As(III) estimation in drinking water along with total arsenic should be invoked as a policy for a realistic risk assessment of the contaminated water.