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Ammonium Sulphate (ammonium + sulphate)

Distribution by Scientific Domains
Life Sciences30%
Earth and Environmental Science30%
Chemistry23%

Terms modified by Ammonium Sulphate

  • ammonium sulphate precipitation
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    Selected Abstracts

    Captures of the olive fruit fly Bactrocera oleae on spheres of different colours

    ENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2001
    Byron I. Katsoyannos
    Abstract Alighting and capture of wild olive fruit flies, Bactrocera oleae (Rossi) (Diptera, Tephritidae), on spheres of seven different colours was studied on Chios island, Greece. The 70-mm-diam plastic spheres, coated with adhesive, were suspended on olive trees. Yellow and orange spheres trapped the greatest number of males while red and black spheres trapped the greatest number of females. White and blue spheres were the least effective for both sexes. Peak captures occurred in the late afternoon and especially around sunset. Since mating takes place in the last hours of the photophase, the increased captures during that period may be related to the sexual behaviour of the fly. When red spheres were assessed against glass McPhail traps baited with 2% ammonium sulphate, which consist a standard tool for monitoring the olive fruit fly in Greece, there were no significant differences in male captures. However, spheres trapped almost three times as many females as McPhail traps. The possible mechanisms underlying colour discrimination, the motivation of alighting flies and the possible use of red spheres for monitoring and controlling B. oleae are discussed. [source]

    Amino acid 15N in long-term bare fallow soils: influence of annual N fertilizer and manure applications

    EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 4 2008
    R. Bol
    Summary Long-term dynamics of amino acids (AAs), from a bare fallow soil experiment (established in 1928 at INRA-Versailles, France), were examined in unamended control (Con) plots and plots treated with ammonium sulphate (Amsul), ammonium nitrate (Amnit), sodium nitrate (Nanit) or with animal manure (Man). Topsoil (0,25 cm) from 1929, 1963 and 1997 was analysed for C, N and 15N content and distribution of 18 amino acids recovered after acid hydrolysis with 6 m HCl. With time, soil N, C and AA content were reduced in Con, Amsul, Amnit and Nanit, but increased in Man. However, the absolute N loss was 3,11 times larger in Man than Nanit, Amsul, Amnit and Con, due to the much higher N annual inputs applied to Man. From 1929 to 1997 in Con, Amsul, Amnit and Nanit the whole soil and non-hydrolysable-N pool ,15N increased associated with the loss of N (indicative of Rayleigh 15N/14N fractionation). No ,15N change from 1929 to 1997 was found in the hydrolysable AA-N (HAN) pool. Fertilizer N inputs aided stabilization of soil AA-N, as AA half-life in the mineral N fertilizer treatments increased from 34 years in 1963 to 50 years in 1997. The ,15N values of alanine and leucine reflected both source input and 15N/14N fractionation effects in soils. The ,15N increase of ornithine (,6,) was similar to the whole soil. The ,15N change of phenylalanine in Con (decrease of 7,) was related to its proportional loss since 1929, whereas for Amsul, Amnit, Nanit and Man it was associated with isotope effects caused by the fertilizer inputs. However, the soil ,15N value of most individual amino acids (IAAs) did not significantly change over nearly 70 years, even with mineral or organic N inputs. We conclude for these bare fallow systems that: (i) ,15N changes in the whole soil and non-hydrolysable AA pool were solely driven by microbial processes and not by the nature of fertilizer inputs, and (ii) without plant inputs, the ,15N of the HAN pool and (most) IAAs may reflect the influence of plant,soil interactions from the previous (arable cropping) rather than present (fallow) land use on these soil ,15N values. [source]

    Baseflow and peakflow chemical responses to experimental applications of ammonium sulphate to forested watersheds in north-central West Virginia, USA,

    HYDROLOGICAL PROCESSES, Issue 12 2002
    Pamela J. Edwards
    Abstract Stream water was analysed to determine how induced watershed acidification changed the chemistry of peakflow and baseflow and to compare the relative timing of these changes. Two watersheds in north-central West Virginia, WS3 and WS9, were subjected to three applications of ammonium sulphate fertilizer per year to induce acidification. A third watershed, WS4, was the control. Samples were collected for 8 years from WS9 and for 9 years from WS3. Prior to analyses, concentration data were flow adjusted, and the influence of natural background changes was removed by accounting for the chemical responses measured from WS4. This yielded residual values that were evaluated using robust locally weighted regression and Mann,Kendall tests. On WS3, analyte responses during baseflow and peakflow were similar, although peakflow responses occurred soon after the first treatment whereas baseflow responses lagged 1,2 years. This lag in baseflow responses corresponded well with the mean transit time of baseflow on WS3. Anion adsorption on WS3 apparently delayed increases in SO4 leaching, but resulted in enhanced early leaching losses of Cl and NO3. Leaching of Ca and Mg was strongly tied, both by timing and stoichiometrically, to NO3 and SO4 leaching. F -factors for WS3 baseflow and peakflow indicated that the catchment was insensitive to acid neutralizing capacity reductions both before and during treatment, although NO3 played a large role in reducing the treatment period F -factor. By contrast, the addition of fertilizer to WS9 created an acid sensitive system in both baseflow and peakflow. On WS9, baseflow and peakflow responses also were similar to each other, but there was no time lag after treatment for baseflow. Changes in concentrations generally were not as great on WS9 as on WS3, and several ions showed no significant changes, particularly for peakflow. The lesser response to treatment on WS9 is attributed to the past abusive farming and site preparation before larch planting that resulted in poor soil fertility, erosion, and consequently, physical and chemical similarities between upper and lower soil layers. Even with fertilizer-induced NO3 and SO4 leaching increases, base cations were in low supplies and, therefore, unavailable to leach via charge pairing. The absence of a time lag in treatment responses for WS9 baseflow indicates that it has substantially different flow paths than WS3. The different hydrologies on these nearby watersheds illustrates the importance of understanding watershed hydrology when establishing a monitoring programme to detect ecosystem change. Published in 2002 by John Wiley & Sons, Ltd. [source]

    Partial purification and characterisation of banana [Musa (AAA Group) ,Gros Michel'] polyphenol oxidase

    INTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 4 2009
    Chitsuda Chaisakdanugull
    Summary Polyphenol oxidase (PPO) from pulp of banana [Musa (AAA Group) ,Gros Michel'] was extracted and precipitated with 80% saturated ammonium sulphate followed by conventional column chromatography on Sephacryl S-200 HR and fast protein liquid chromatography on Mono Q column. The lyophilised PPO obtained from Sephacryl S-200 HR column was used for characterisation and inhibition studies. The partially purified PPO obtained from the Mono Q column exhibited at least three isoenzymes. The banana PPO had optimum pH for activity at 7 and it was stable around the same pH. Only 48% of initial enzyme activity was lost after heating at 70 °C for 30 min. The enzyme was completely inhibited by 2 mm sodium metabisulphite, 2 mm l -cysteine, 4 mm ascorbic acid, and 100 mm 4-hexylresorcinol. The Km and Vmax of banana PPO for dopamine were 2.08 mm and 0.124 mm min,1 respectively. [source]

    Strategies to Improve the Use Efficiency of Mineral Fertilizer Nitrogen Applied to Winter Wheat

    JOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 3 2002
    K. Blankenau
    Recovery of fertilizer nitrogen (N) applied to winter wheat crops at tillering in spring is lower than that of N applied at later growth stages because of higher losses and immobilization of N. Two strategies to reduce early N losses and N immobilization and to increase N availability for winter wheat, which should result in an improved N use efficiency (= higher N uptake and/or increased yield per unit fertilizer N), were evaluated. First, 16 winter wheat trials (eight sites in each of 1996 and 1997) were conducted to investigate the effects of reduced and increased N application rates at tillering and stem elongation, respectively, on yield and N uptake of grain. In treatment 90-70-60 (90 kg N ha,1 at tillering, 70 kg N ha,1 at stem elongation and 60 kg N ha,1 at ear emergence), the average values for grain yield and grain N removal were up to 3.1 and 5.0 % higher than in treatment 120-40-60, reflecting conventional fertilizer practice. Higher grain N removal for the treatment with reduced N rates at tillering, 90-70-60, was attributed to lower N immobilization (and N losses), which increased fertilizer N availability. Secondly, as microorganisms prefer NH4+ to NO3, for N immobilization, higher net N immobilization would be expected after application of the ammonium-N form. In a pot experiment, net N immobilization was higher and dry matter yields and crop N contents at harvest were lower with ammonium (ammonium sulphate + nitrification inhibitor Dicyandiamide) than with nitrate (calcium nitrate) nutrition. Five field trials were then conducted to compare calcium nitrate (CN) and calcium ammonium nitrate (CAN) nutrition at tillering, followed by two CAN applications for both treatments. At harvest, crop N and grain yield were higher in the CN than in the CAN treatment at each N supply level. In conclusion, fertilizer N use efficiency in winter wheat can be improved if N availability to the crops is increased as a result of reduced N immobilization (and N losses) early in the growth period. N application systems could be modified towards strategies with lower N applications at tillering compensated by higher N dressing applications later. An additional advantage is expected to result from use of nitrate-N fertilizers at tillering. Strategien zur Verbesserung der Effizienz von Düngerstickstoff in Winterweizen Aus früheren Versuchen mit Winterweizen ist bekannt, daß zur Ernte die Wiederfindung von im Frühjahr zur Bestokkung gedüngtem Stickstoff (N) geringer ist, als die von N aus Spätgaben. Die Ursachen liegen in einer höheren mikrobiell-bedingten Netto-N-Immobilisation, aber auch N-Verlusten zwischen Bestockung und Schoßbeginn im Vergleich zu späteren Wachstumstadien begründet. In den vorliegenden Versuchen wurden zwei Strategien getestet, um insbesondere die früh in der Vegetation auftretende Netto-N-Immobilisation zu vermindern. Die dadurch erwartete erhöhte N-Verfügbarkeit sollte zu einer erhöhten N-Effizienz (höherer N-Entzug/Ertrag bezogen auf die N-Düngung) führen. 1996 und 1997 wurden jeweils 8 Feldversuche mit Winterweizen durchgeführt, um den Einfluß einer reduzierten Andüngung bei gleichzeitig erhöhter Schossergabe im Vergleich zur konventionellen N-Düngung zu untersuchen. Tatsächlich wurden in dem Prüfglied 90-70-60 (N-Sollwertdüngung: 90 kg N ha,1, Schossergabe: 70 kg N ha,1, Ährengabe: 60 kg N ha,1) im Mittel bis zu 3.1 % höhere Erträge und 5.0 % höhere N-Abfuhren mit dem Korn im Vergleich zur konventionellen Variante 120-40-60 (N-Sollwertdüngung: 120 kg N ha,1, Schossergabe: 40 kg N ha,1 und Ährengabe: 60 kg N ha,1) erzielt. Die höhere N-Abfuhr kann auf eine erhöhte N-Verfügbarkeit infolge geringerer mikrobieller N-Festlegung zurückgeführt werden. Da die vornehmlich heterotrophen Bodenmikroorganismen bevorzugt NH4+ gegenüber NO3, immobilisieren, kann eine höhere N-Immobilisation bei Ammonium-Düngung erwartet werden. Tatsächlich wurden in einem Gefäßversuch nach Düngung von Ammoniumsulfat (+ Nitrifikationshemmer Dicyandiamid) geringere Trokkenmasseerträge und N-Aufnahmen von Weizenpflanzen erzielt als mit Calciumnitrat. Für die Ammoniumsulfatvariante ergab sich eine höhere Netto-N-Immobilisation. Danach wurde in fünf Feldversuchen mit Winterweizen der Einfluß einer Andüngung mit Nitrat (Calciumnitrat) im Vergleich zur Verwendung des ammoniumhaltigen Kalkammonsalpeters (KAS) auf die N-Aufnahme und den Kornertrag untersucht (beide Varianten erhielten KAS als Spätgaben). In der nitratangedüngten Variante wurden zum Teil signifikant höhere Ertäge und N-Aufnahmen in Korn und Stroh ermittelt. Aus den dargestellten Versuchen kann gefolgert werden, daß die Düngerstickstoff-Effizienz verbessert werden kann, wenn vor allem die N-Immobilisation (und eventuell auch N-Verluste) in frühen Wachstumsstadien zwischen Bestockung und Schoßbeginn verringert und so die N-Verfügbarkeit erhöht wird. Es kann empfohlen werden Winterweizenbestände mit geringeren N-Mengen , als nach N-Sollwert 120 kg N ha,1 vorgesehen , anzudüngen und die Schossergabe entsprechend zu erhöhen. Die Verwendung von nitrathaltigen Düngern bei der Andüngung ist von Vorteil. [source]

    The effect of environmental factors on the distribution of Neoparamoeba pemaquidensis in Tasmania

    JOURNAL OF FISH DISEASES, Issue 10 2005
    M Douglas-Helders
    Abstract Aquaculture in Tasmania is mostly carried out in estuaries. These estuarine habitats show a great variety and form unique environments in which Neoparamoeba pemaquidensis, the amoebic gill disease (AGD)-causing protozoan, may or may not survive. Tasmania is divided into two zones, one where AGD is present and one where AGD is absent, but any ecological data to rationalize this distribution is lacking. In in vitro trials N. pemaquidensis strains were exposed to different concentrations of ammonium sulphate, copper sulphate, copper sulphate and tannin, and different Neoparamoeba densities, salinities and temperatures. A trial using field water samples investigated the survival of N. pemaquidensis in waters sourced from AGD-free and AGD-positive zones, and water analysis was performed to determine any differences. Significantly decreased protozoan survival was found with exposure to increasing copper sulphate concentrations from 10 to 100 000,m (P < 0.001), salinity of 15, (P < 0.001), low Neoparamoeba densities of 625 and 1250 cells mL,1 (P = 0.0005), and water sourced from Macquarie Harbour (P < 0.001). The water chemistry of this AGD-free zone showed significantly lower dissolved calcium and magnesium concentrations which may contribute to this area being AGD-free. Understanding of the ecology of N. pemaquidensis will enable better control and prevention strategies for Tasmanian salmon growers. [source]

    Response surface methodology for optimizing the fermentation medium of Clostridium butyricum

    LETTERS IN APPLIED MICROBIOLOGY, Issue 4 2004
    G.Q. He
    Abstract Aims:, Strains of Clostridium butyricum have been increasingly used as probiotics for both animals and humans. The aim of this study was to develop a growth medium for cultivating C. butyricum ZJUCB using a statistical methodology. Methods and Results:, Response surface methodology (RSM) was used to evaluate the effects of variables, namely the concentrations of the glucose, pectin, soyabean cake extract, casein, corn steep flour, ammonium sulphate, sodium bicarbonate and the medium initial pH. A fractional factorial design was applied to study the main factors that affected the growth of a probiotic strain of C. butyricum currently preserved in our lab and the central composite experimental design was adopted to derive a statistical model for optimizing the composition of the fermentation medium. The experimental results showed that the optimum fermentation medium for the growth of C. butyricum was composed of 2% glucose (w/v), 0·5% pectin (w/v), 0·2% casein (w/v), 3·98% soyabean cake extract, 0·1% (NH4)2SO4 (w/v), 0·124% NaHCO3 (w/v), 0·37% corn steep flour (w/v), 0·02% MnSO4 H2O (w/v), 0·02% MgSO4 7H2O (w/v) and 0·002% CaCl2 (w/v) at pH 7·5. Conclusions:, After incubating 24 h in the optimum fermentation medium, the populations of the viable organisms were estimated to be 109 CFU ml,1. In the present study, we report the optimization of a growth medium that produced increased yields using statistical approach. Significance and Impact of the Study:, The use of bacteria as a probiotic is showing increasing potential. The development of a growth medium that has a high yield is an obvious need, and the approach to optimizing a growth medium is innovative. [source]

    Effect of the nitrogen source on caffeine degradation by Aspergillus tamarii

    LETTERS IN APPLIED MICROBIOLOGY, Issue 1 2004
    G. Gutiérrez-Sánchez
    Abstract Aims:, To evaluate caffeine degradation and nitrogen requirements during Aspergillus tamarii growth in submerged culture. Methods and Results:,Aspergillus tamarii spores produced on a coffee infusion agar medium added with sucrose were used. Several caffeine and ammonium sulphate concentrations (0,1 and 0,1·36 g l,1, respectively) were tested simultaneously on fungal biomass production and caffeine degradation. An additional caffeine pulse (4 g l,1) was added for all experiments after 48 h of fermentation. Results revealed that when using 0·90 g l,1 of caffeine and 0·14 g l,1 of ammonium sulphate, biomass production and caffeine degradation were enhanced. Highest biomass production (Xmax = 9·87 g l,1) with a specific growth rate (,) of 0·073 h,1 and caffeine degradation rate of 0·033 g l,1 h,1, was observed under these conditions. Conclusions:, Caffeine degradation as well as biomass production were characterized. Significance and Impact of the Study:, These studies set the stage for future characterization studies of intracellular enzymes involved in caffeine degradation. Moreover, results observed may help in the biotreatment of residues from the coffee agroindustry. [source]

    Bifunctional indole-3-acetyl transferase catalyses synthesis and hydrolysis of indole-3-acetyl- myo -inositol in immature endosperm of Zea mays

    PHYSIOLOGIA PLANTARUM, Issue 2 2003
    Stanislaw Kowalczyk
    1- O -(indole-3-acetyl)- , - d -glucose: myo -inositol indoleacetyl transferase (IA- myo -inositol synthase) is an important enzyme in IAA metabolism. This enzyme catalyses the transfer of the indole acetyl (IA) moiety from 1- O -(indole-3-acetyl)- , - d -glucose to myo -inositol to form IA- myo- inositol and glucose. IA- myo -inositol synthase was purified to an electrophoretically homogenous state from maize liquid endosperm by fractionation with ammonium sulphate, anion-exchange, adsorption on hydroxylapatite, affinity chromatography on ConA-Sepharose, preparative PAGE and isoelectric focusing. We thus obtained two enzyme preparations which differ in their Rf on 8% polyacrylamide gel. The preparation of Rf 0.36 contained a single 56.4 kDa polypeptide, whereas the preparation of Rf 0.39 consisted of two polypeptides of 56.4 and 53.5 kDa. Both purified preparations of IAInos synthase also exhibited the activity of an IAInos hydrolase, showing that the dual activity was associated with a single protein. Results of gel filtration and analytical SDS-PAGE suggest that the native enzyme exists as both a monomeric (65 kDa) and homo- or heterodimeric form (110,130 kDa). Analysis of peptide maps and amino acid sequences of two 21 amino-acid peptides showed that polypeptides of 56.4 and 53.5 kDa have the same primary structure and that the 3 kDa difference in molecular mass is probably caused by different glycosylation levels. Comparison of this partial and internal amino acid sequence with sequences of other plant acyltransferases indicated similarity to several proteins which belonged to the serine carboxypeptidase-like (SCPL) acyltransferase family. [source]

    Barley polyamine oxidase: characterisation and analysis of the cofactor and the N-terminal amino acid sequence

    PHYTOCHEMICAL ANALYSIS, Issue 3 2001
    Anna Radová
    Abstract This paper reports the first purification method developed for the isolation of an homogeneous polyamine oxidase (PAO) from etiolated barley seedlings. The crude enzyme preparation was obtained after initial precipitation of the extract with protamine sulphate and ammonium sulphate. The enzyme was further purified to a final homogeneity (by the criteria of isoelectric focusing and SDS,PAGE) using techniques of low pressure chromatography followed by two FPLC steps. The purified yellow enzyme showed visible absorption maxima of a flavoprotein at 380 and 450,nm: the presence of FAD as the cofactor was further confirmed by measuring the fluorescence spectra. Barley PAO is an acidic protein (pI 5.4) containing 3% of neutral sugars: its molecular mass determined by SDS,PAGE was 56,kDa, whilst gel permeation chromatography revealed the higher value of 76 kDa. The N-terminal amino acid sequence of barley PAO shows a high degree of similarity to that of maize PAO and to several other flavoprotein oxidases. The polyamines spermine and spermidine were the only two substrates of the enzyme with Km values 4,×,10,5 and 3,×,10,5,M and pH optima of 5.0 and 6.0, respectively. Barley polyamine oxidase is markedly inhibited by acridine dyes and hydrazines. Weak inhibition was observed with substrate analogues, aminoaldehydes, metal chelating agents and several other compounds. Copyright © 2001 John Wiley & Sons, Ltd. [source]

    Contribution of nitrification and denitrification to nitrous oxide emissions from soils after application of biogas waste and other fertilizers,

    RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 16 2009
    Mehmet Senbayram
    The attribution of nitrous oxide (N2O) emission to organic and inorganic N fertilizers requires understanding of how these inputs affect the two biological processes, i.e. denitrification and nitrification. Contradictory findings have been reported when the effects of organic and inorganic fertilizers on nitrous oxide emission were compared. Here we aimed to contribute to the understanding of such variation using 15N-labelling techniques. We determined the processes producing N2O, and tested the effects of soil moisture, N rates, and the availability of organic matter. In a pot experiment, we compared soil treated with biogas waste (BGW) and mineral ammonium sulphate (Min-N) applied at four rates under two soil moisture regimes. We also tested biogas waste, conventional cattle slurry and mineral N fertilizer in a grassland field experiment. During the first 37 days after application we observed N2O emissions of 5.6,kg N2O-N,ha,1 from soils supplied with biogas waste at a rate of 360,kg,N,ha,1. Fluxes were ca. 5-fold higher at 85% than at 65% water holding capacity (WHC). The effects of fertilizer types and N rates on N2O emission were significant only when the soil moisture was high. Organic fertilizer treated soils showed much higher N2O emissions than those receiving mineral fertilizer in both, pot and field experiment. Over all the treatments the percentage of the applied N emitted as N2O was 2.56% in BGW but only 0.68% in Min-N. In the pot experiment isotope labelling indicated that 65,95% of the N2O was derived from denitrification for all fertilizer types. However, the ratio of denitrification/nitrification derived N2O was lower at 65% than at 85% WHC. We speculate that the application of organic matter in conjunction with ammonium nitrogen first leads to a decrease in denitrification-derived N2O emission compared with soil receiving mineral fertilizer. However, at later stages when denitrification becomes C-limited, higher N2O emissions are induced when the soil moisture is high. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Bacteriocin production by Shigella sonnei isolated from faeces of children with acute diarrhoea

    APMIS, Issue 2 2010
    MIREILLE ÂNGELA BERNARDES SOUSA
    Sousa MÂB, Mendes EN, Apolônio ACM, Farias LM, Magalhães PP. Bacteriocin production by Shigella sonnei isolated from faeces of children with acute diarrhoea. APMIS 2010; 118: 125,35. Shigella is a common agent of diarrhoea, a worldwide major health problem. The bacterium produces bacteriocins; however, the role of these substances as a virulence factor is completely unknown. With the aim to search for colicin production by Shigella sonnei, to evaluate the influence of culture conditions on bacteriocin expression, and to characterize the substance partially, 16 S. sonnei strains isolated from children with diarrhoea were tested for antagonism against members of the intestinal microbiota or agents of diarrhoea. Nine strains exhibited isoantagonism and heteroantagonism against S. flexneri and diarrhoeagenic Escherichia coli. Autoantagonism and antagonism against the intestinal microbiota were not detected. Culture medium and incubation conditions influenced antagonism expression. Antagonism resulting from bacteriophages, low pH, fatty acids, hydrogen peroxide, and chloroform was excluded. The activity of the intracellular fraction obtained with 75% ammonium sulphate was preserved at pH 1.0,11.0, and was found to be reduced by organic solvents and affected by high temperatures and proteases. The antagonistic spectrum and the in vitro conditions for better antagonism expression suggest that the role of colicin in S. sonnei virulence, if any, would be expressed prior to infection, and may regulate population density of enteropathogens by helping in organism transmission. [source]

    Aerosol growth and activation in polluted air masses over a tropical metropolis in the Indian sub-continent

    ATMOSPHERIC SCIENCE LETTERS, Issue 2 2009
    S. Varun Raj
    Abstract Air pollution can affect cloud formation in more than one way. When the pollutant gases are condensable (e.g. oxides of sulphur), then the process of aerosol activation is eased to a certain extent aiding cloud formation. However, polluted days are often characterised by low updraught speeds which inhibit aerosol growth. In this study, we have critically examined the aerosol activation process in a polluted coastal environment where both effects are present. We have concentrated on the Chennai region (one of the largest cities in the world) of the Indian sub-continent because its pace of industrialisation is increasing rapidly, adding to increasing SO2 pollution over the years. Air masses over Chennai contain a mixture of aerosol particles including NaCl, because of its proximity to the Bay of Bengal, along with ammonium sulphate. We have used observational data along with a detailed microphysical chemical parcel model to study cloud activation effects. We find that over Chennai, often the presence of the condensable pollutant vapour (SO2) more than compensates for the low updraught speeds by lowering the level of maximum super saturation significantly. This latter effect favours the activation of ammonium sulphate as well as NaCl aerosol particles. We have undertaken a systematic analysis to quantify the relative strengths of these two competing effects and find that even with low updraught speeds, oxides of sulphur can perturb the activation domain comprising a mixture of aerosol particles to such an extent that aerosol particles in polluted environments often grow efficiently. This effect is non-intuitive in the sense that one associates smaller cloud droplet sizes with polluted air masses. This is the first microphysical modelling study for the Indian sub-continent where National Environmental Engineering Research Institute (NEERI) observations have been applied to cloud microphysical processes. Copyright © 2009 Royal Meteorological Society [source]