Aradhana Mehra

Impact of Fly Ash from Coal-Fired Power Stations in Delhi, with Particular Reference to Metal Contamination

Indraprastha Power Station (IPP Stn) and Rajghat Power House (RPH), owned by Delhi Electric Supply Undertaking, are both coal-fired power stations located on Ring Road in New Delhi. Ash content of the coal used ranges between 38–47%. The ash is collected in electrostatic precipitators which have an efficiency of 99.3% (IPP station), and 99.7% (RPH). There are instances of major dust pollution around the power stations from fly ash dispersal. The main method of disposal of fly ash from the power stations is by mixing with water, the resultant slurry is pumped through pipes to ash disposal ponds. The supernatant from these ponds is discharged into River Yamuna. Field studies have revealed large quantities of fly ash being deposited into the river. Local populations of Eichhornia crassipes have reduced dramatically between 1987–1995, with a marked reduction in the year 1994–1995. Field studies, conducted in January, 1995 have investigated the impact of fly ash dispersal in the Delhi region with particular reference to metal contamination. Elemental concentrations for a range of elements are determined by ICP-AES in fly ash and top soils along four transects from the power stations up to a distance of 8 km. The effects of fly ash leachates from the ash settling ponds on the river are determined by analyzing river overbank soils and vegetation for their elemental contents. It is concluded that fly ash dispersal from the stacks are a source of alkali, alkaline-earth and to some extent heavy metals in soils in the vicinity of the power stations, and enrichment of elements in river overbank soils are a result of discharge of fly ash leachates from ash disposal ponds. However, the impact from both these sources of metal contamination is not large enough to give cause for concern. Marked reduction in populations of Eichhornia crassipes downstream of the river where it receives leachates from the ash disposal ponds are attributed to turbidity of the ash pond leachates and metal toxicity. Elemental enrichment in the floodplain soils, as a result of fly ash particle deposition during monsoons, may enhance the horticultural value of these soils as is shown by a healthy cultivated crop of Brassica juncea.

Effects of osmotic pretreatments on oxidative stress, antioxidant profiles and cryopreservation of olive somatic embryos

A three-day pretreatment of olive somatic embryos (SE) with 0.75 M sucrose, combined with cryoprotection (0.5M DMSO, 1M sucrose, 0.5M glycerol and 0.009 M proline) and controlled rate cooling, supported regrowth (as 34.6% fresh weight gain) and resumption of embryo development after cryopreservation. Pretreatment with mannitol or sorbitol did not support regrowth. Profiles of sugars, proline, antioxidant enzymes, Reactive oxygen species (ROS), secondary oxidation products and ethylene were constructed for the most successful (0.75 M) pretreatment series. Sucrose was the optimal pretreatment for supporting recovery, it also elevated glutathione reductase (GR) activity compared to controls, whereas superoxide dismutase (SOD), catalase and guaiacol peroxidase activities remained relatively unchanged. Superoxide dismutase activity was higher in SE pretreated with sucrose, compared with those pretreated with polyols; H(2)O(2) was enhanced in SE pretreated with sorbitol and sucrose compared to mannitol. The overall trend for ethylene and OH production revealed their levels were highest in SE pretreated with polyols albeit, for individual treatments this was not always the case. Generally, pretreatments did not significantly change embryo secondary oxidation profiles of ThioBarbituric Acid Reactive Substances (TBARS) and Schiffs bases. In combination these studies suggest oxidative processes may influence regrowth of cryopreserved olive SE and that optimal pretreatments could, in part, increase tolerance by an overall enhancement of endogenous antioxidants (particularly GR), proline and sugars.

A study of Eichhornia crassipes growing in the overbank and floodplain soils of the River Yamuna in Delhi, India.

River Yamuna, like most of the major rivers of India, has become increasingly polluted over the years from both point and non-point sources, particularly in the urban sectors such as Delhi. Field studies, conducted in January, 1994 have investigated the impact of wastewater discharges from four major drains (Najafgarh, Power House, Barapula, Kalkaji) on the overbanks, floodplains and Eichhornia in River Yamuna in Delhi, with particular reference to elemental contamination. It is concluded that except for Cd and Co, overall mean soil concentrations along the full stretch of the river in Delhi are within the world background levels of uncontaminated soils. However, the wastewater discharges from the drains, with the exception of Barapula drain, generally increase the elemental concentrations of overbank soils downstream of the discharges. Eichhornia plants growing along the banks receiving wastewaters from the Najafgarh and Barapula drains are unhealthy and reduced in population which can be attributed to a combination of alkaline pH of the growth medium, metal toxicity and high BOD at the site receiving effluents from the Najafgarh drain, and alkaline pH, metal toxicity and the turbid conditions of water with fly ash particle deposition on the plant surfaces at the site receiving effluents from the Barapula drain. Generally, considering the entire stretch of the river in Delhi, the roots of these plants growing on the overbank soils are found to be accumulators of all elements except Co, Al and Fe, with Co uptake being minimal. There are marked differences in elemental uptake of the water hyacinths growing on the overbanks and floodplains of the river.

Mechanisms of Copper Tolerance By Armeria Maritima in Dolfrwynog Bog, North Wales – Initial Studies

Preliminary field studies were carried out at Dolfrwynog Bog in July 2000. Replicate samples of water, Armeria maritima plants and the soils adhering to its roots were collected and analysed for copper. Concentrations of up to 6486 mg kg−1 of copper in the soils were recorded. Accumulation of copper by the plant as expressed by concentration factors (CF) show that it is acting mainly as a copper excluder. Of the copper that is taken up, most of it is retained within the roots with very little being transported to the shoots of the plant. Moreover, a further possible mechanism of tolerance is exhibited by the excretion of copper through its decaying leaves. Towards the use of in vitro cultures to study the copper tolerance mechanisms in A. maritima a micropropagation protocol has been developed. The ex vitro plants have been rooted and established in compost.

Heavy metal accumulation in Brussels sprouts after irrigation with treated municipal waste water

Abstract This study aims at investigating the effects of the treated municipal wastewater (TMWW) on the essential and heavy metal interactions, and on the accumulation of these metals in the sprouts (edible plant part) of Brassica oleracea var gemmifera (Brussels sprouts). The statistical design included two variables: (a) TMWW, and (b) fresh irrigation water (control), in six replications, with a total of 12 experimental plots of 2.5×1.8 m = 4.5 m2 size. The following were found: a large number of interactions were identified in the sprouts (182), but only 74 of them were statistically significant. Also among them, the following interactions, i.e., Mn×N, Mn×Fe, Fe×Mn, Fe×N, N×Zn occurred not only in the sprouts, but according to our previous work, in the heads of Brassica olevacea var. Italica (Brocolli) as well, suggesting a consistency of occurrence of these interactions. However, the comparative effect of TMWW, on the interactions studied, in very few cases was found to be statistically significant, in comparison to that of the control. The elements N, P, Zn, Co, Ni and Cd accumulated mainly in the sprouts, while K, Ca, Mn, and B were concentrated in the leaves, the differences in the accumulation between the respective effects of TMWW and control, being statistically non-significant.

Towards an understanding of the effect of road pollution on adjacent food crops: Zea mays as an example

This work is a preliminary study to test the hypothesis that major roads can have an adverse effect on the heavy metal composition of soil and food crops. Surface and subsurface soil samples were collected at increasing distances from the major road in the Araxos area and they were analysed for organic C, Al, Pb, Cd, Zn, Cu, Ni, Fe, Mn, Cr, Co, P, Ca, Mg and Na by inductively coupled plasma emission spectroscopy. Levels of Ca, Al, Mg and Fe were significantly increased in the surface and subsurface soils in the vicinity of the roadside. This increase was due to dust released from lorries carrying building materials originating from limestone quarries existing in the area. The impact of traffic on adjacent soils was also evidenced by a sharp increase in Pb, Mn, Fe and Al concentrations in the leaves and roots of Zea mays L.

Trace Elements in Tea ( Camellia sinensis ) and their Bioavailability

In the context used by most consumers, tea is a beverage consisting of an infusion of processed and dried tea leaves. Human exposure to trace elements from tea consumption depends upon the trace element content of commercially produced teas, the transfer of these elements into the tea infusion, and the bioavailability of the elements in the human system. The transfer of trace elements into a tea infusion can be highly variable. As tea is a source of both essential and toxic elements, the intake of tea in the human diet can be beneficial or harmful. Bioavailability studies have shown that tea can be a useful source of some essential elements in the human diet and that moderate amounts of tea consumption is unlikely to have any harmful effect on healthy individuals. However, excessive consumption of tea can result in a person exceeding the allowable elemental intake for some elements.

Bioavailability of iodine in the UK-Peak District environment and its human bioaccessibility: an assessment of the causes of historical goitre in this area

Iodine is an essential micronutrient for human health. Its deficiency causes a number of functional and developmental abnormalities such as goitre. The limestone region of Derbyshire, UK was goitre-endemic until it declined from the 1930s and the reason for this has escaped a conclusive explanation. The present study investigates the cause(s) of goitre in the UK-Peak District area through an assessment of iodine in terms of its environmental mobility, bioavailability, uptake into the food chain and human bioaccessibility. The goitre-endemic limestone area is compared with the background millstone grit area of the UK-Peak District. The findings of this study show that ‘total’ environmental iodine is not linked to goitre in the limestone area, but the governing factors include iodine mobility, bioavailability and bioaccessibility. Compared with the millstone grit area, higher soil pH and calcium content of the limestone area restrict iodine mobility in this area, also soil organic carbon in the limestone area is influential in binding the iodine to the soil. Higher calcium content in the limestone area is an important factor in terms of strongly fixing the iodine to the soil. Higher iodine bioaccessibility in the millstone grit than the limestone area suggests that its oral bioaccessibility is restricted in the limestone area. Iodine taken up by plant roots is transported freely into the aerial plant parts in the millstone grit area unlike the limestone area, thus providing higher iodine into the human food chain in the millstone grit area through grazing animals unlike the goitre-prevalent limestone area.

Bioavailability of copper within Dolfrwynog Bog soils, North Wales, UK

Abstract Many studies have been reported in literature on the copper impregnated Dolfrwynog Bog and its flora, in particular the Cu-tolerant Armeria maritima. This paper investigates the bioavailability of Cu from the Bog soils using single and sequential extraction techniques for a number of specific sites. The Bog is enriched with Cu (concentrations in excess of 6,000 mg/kg). However, comparing with earlier studies on the Bog, Cu concentrations appear to have decreased markedly over time. This may be attributed to a decrease in the organic matter content of soils and subsequent loss of Cu by leaching into stream waters. Single extractions with deionised water show that the Cu is not readily bioavailable, however, EDTA and acetic acid extracted in excess of 50% of the total Cu showing that that there is potential for Cu to be bioavailable. Cu is predominantly associated with the organic fraction of soils as shown by EDTA and sequential extractions. Although the average percentage bioavailabilty of Cu in the Bog has not altered over time, the amount of Cu present in the Bog has decreased substantially, hence the amount of Cu available for uptake by vegetation has also decreased and this may alter the nature of the Bog in the future. Results also show that the Bog is not homogenous in nature and that Cu concentrations and bioavailability vary spatially.