Neutralizing Capacity (neutralizing + capacity)

Distribution by Scientific Domains

Selected Abstracts

Semiparametric M -quantile regression for estimating the proportion of acidic lakes in 8-digit HUCs of the Northeastern US

Monica Pratesi
Abstract Between 1991 and 1995, the Environmental Monitoring and Assessment Program of the US Environmental Protection Agency conducted a survey of lakes in the Northeastern states of the US to determine the ecological condition of these waters. Here, to this end, we want to obtain estimates of the proportion of lakes at (high) risk of acidification or acidified already for each 8-digit hydrologic unit code (HUC) within the region of interest. Sample sizes for the 113 HUCs are very small and 27 HUCs are not even observed. Therefore, small area estimation techniques should be invoked for the estimation of the distribution function of acid neutralizing capacity (ANC) for each HUC. The procedure is based on a semiparametric M -quantile regression model in which ANC depends on elevation and the year of the survey linearly, and on the geographical position of the lake through an unknown smooth bivariate function estimated by low-rank thin plate splines. Copyright 2008 John Wiley & Sons, Ltd. [source]

Constrained multivariate trend analysis applied to water quality variables

D. M. Cooper
Abstract Constrained multivariate regression analysis is used to model trends and seasonal effects in time series measurements of water quality variables. The constraint used ensures that when identifying trends the scientifically important charge balance of model-fitted concentrations is maintained, while accounting for between variable dependencies. The analysis is a special case of linear reduction of dimensionality which preserves the integrity of a subset of the original variables, while allowing the remainder to be identified as linear combinations of this subset. The technique is applied to water quality measurements made at the outflow from Loch Grannoch, an acid-sensitive loch in Scotland. A reduction in marine ion concentrations is observed in water samples collected four times a year over the period 1988,2000. This is identified with long term variability in the marine component in rainfall. Separation of the non-marine component of the solute load shows a reduction in non-marine sulphate and calcium concentrations, and an increase in the non-marine sodium concentration. There is no significant change in either alkalinity or acid neutralizing capacity over the period. The reduction in non-marine sulphate is consistent with reductions in atmospheric inputs of sulphate. However, the reduction in sulphate has not been accompanied by a reduction in the acidity of water samples from Loch Grannoch, but with a reduction in calcium concentration and an apparent increase in organic acids, as evidenced by increased dissolved organic carbon concentrations, with possible increases in nitrate and non-marine sodium concentrations. Copyright 2002 John Wiley & Sons, Ltd. [source]

Inhibition of HIV-1 IIIB and clinical isolates by human parotid, submandibular, sublingual and palatine saliva

Jan G. M. Bolscher
Human saliva is known to possess components that decrease the HIV-1 infectivity in vitro. The mechanism of how these components inhibit the infectivity is still not clear on the molecular level. The purpose of this study was to discriminate between serous and mucous components with respect to inhibitory capacity and site of action. We have used total saliva and saliva from the major (sero)mucous glands: submandibular gland, sublingual glands, and glands in the palate, in comparison with the serous parotid glands. HIV-1 IIIB and primary variants were incubated with saliva, and inhibition of HIV-1-infection was determined by analysing the cytopathic effect on MT-2 cells. Mucous saliva, as well as serous saliva, contained high molecular weight components that reduced HIV-1-infectivity, at least partially by entrapment of the virus particles. Lower molecular weight components in all types of saliva possessed strong HIV-1 neutralizing capacity. Using pro-viral DNA synthesis by reverse transcription as a discrimination point in the replication cycle, the results indicated that part of the saliva samples acted before, but others after, this point. In conclusion, saliva inhibits HIV-1-infection by the action of high molecular weight components in combination with low molecular weight components from serous as well as mucous saliva, affecting different stages of the infection cycle. [source]

Inorganic sulphate extraction from SO2 -impacted Andosols

T. Delfosse
Summary Sulphate sorption on to the surface of short-range ordered minerals and precipitation of Al-hydroxy sulphate contribute to the acid neutralizing capacity of soils. The correct measurement of total inorganic sulphate is thus essential in soils that are accumulating SO42, anions. We extracted SO42, by various solutions, namely 0.005 m Ca(NO3)2, 0.016 m KH2PO4, 0.5 m NH4F and 0.2 m acidic NH4 -oxalate (pH 3), from Vitric and Eutric Andosols exposed to prolonged deposition of acid and SO2 from an active volcano (Masaya, Nicaragua). We attributed sulphate extractable by KH2PO4 (20,3030 mg kg,1) to anion-exchangeable SO42,, which was much smaller than NH4F- and oxalate-extractable SO42, (400,9680 and 410,10 480 mg kg,1, respectively). Our results suggest the occurrence of a sparingly soluble Al-hydroxy-mineral phase extractable by both NH4F and oxalate. The formation of Al-hydroxy minerals would result from the combination of enhanced weathering caused by strong acid loading and simultaneous occurrence of large SO42, concentrations in soil solution. Oxalate extracted slightly more inorganic SO42, than did NH4F, this additional amount of SO42, correlating strongly with oxalate-extractable Si and Fe contents. Preferential occlusion of SO42, by short-range ordered minerals, especially ferrihydrite, explains this behaviour. If we exclude the contribution of occluded sulphate then oxalate and NH4F mobilize similar amounts of SO42, and are believed to mobilize all of the inorganic SO42, pool. [source]

Surface podzolization in Cambisols under deciduous forest in the Belgian loess belt

V. Brahy
Summary Surface podzolization involves the migration of metal,humus complexes to a depth of a few centimetres. In acid soils derived from loess, this process has been diagnosed mainly by morphological observation. We investigated this process in a toposequence of Luvisols and Cambisols on loess using selective extraction and mineralogical data as well as characteristics of the leaf litter. The humus type (O and OAh horizons) is a moder in the three Luvisols and one of the Cambisols, whereas it is a fibrimor in the two other Cambisols. The contents in total alkaline and alkaline-earth cations range from 35 to 60 cmolc kg,1 in the fibrimor and from 40 to 90 cmolc kg,1 in the moder humus. In the two Cambisols with fibrimor smectite occurs in the clay fraction of the Ah horizon; Fe,humus complexes seem to have moved, but no more than 9 cm, from the Ah to the AB horizon beneath. Relative to the Ah horizon, the upper part of the AB has larger tetraborate-extractable Fe/Al ratio and optical density of the oxalate extract. Such features converge to diagnose surface podzolization in the Cambisols with fibrimor. However, they were not detected in the Cambisol and Luvisols with moder. In the two Cambisols with fibrimor, surface podzolization is consistent with (i) their smaller iron content, (ii) their more advanced weathering stage and (iii) their lower acid neutralizing capacity. [source]

Inhibition of hepatitis C virus infection by anti-claudin-1 antibodies is mediated by neutralization of E2,CD81,Claudin-1 associations,

HEPATOLOGY, Issue 4 2010
Sophie E. Krieger
The tight junction protein claudin-1 (CLDN1) has been shown to be essential for hepatitis C virus (HCV) entry,the first step of viral infection. Due to the lack of neutralizing anti-CLDN1 antibodies, the role of CLDN1 in the viral entry process is poorly understood. In this study, we produced antibodies directed against the human CLDN1 extracellular loops by genetic immunization and used these antibodies to investigate the mechanistic role of CLDN1 for HCV entry in an infectious HCV cell culture system and human hepatocytes. Antibodies specific for cell surface,expressed CLDN1 specifically inhibit HCV infection in a dose-dependent manner. Antibodies specific for CLDN1, scavenger receptor B1, and CD81 show an additive neutralizing capacity compared with either agent used alone. Kinetic studies with anti-CLDN1 and anti-CD81 antibodies demonstrate that HCV interactions with both entry factors occur at a similar time in the internalization process. Anti-CLDN1 antibodies inhibit the binding of envelope glycoprotein E2 to HCV permissive cell lines in the absence of detectable CLDN1-E2 interaction. Using fluorescent-labeled entry factors and fluorescence resonance energy transfer methodology, we demonstrate that anti-CLDN1 antibodies inhibit CD81-CLDN1 association. In contrast, CLDN1-CLDN1 and CD81-CD81 associations were not modulated. Taken together, our results demonstrate that antibodies targeting CLDN1 neutralize HCV infectivity by reducing E2 association with the cell surface and disrupting CD81-CLDN1 interactions. Conclusion: These results further define the function of CLDN1 in the HCV entry process and highlight new antiviral strategies targeting E2-CD81-CLDN1 interactions. (HEPATOLOGY 2010.) [source]

Controls on surface water chemistry in two lake-watersheds in the Adirondack region of New York: differences in nitrogen solute sources and sinks

Mari Ito
Abstract The southwestern Adirondack region of New York receives among the highest rates of atmospheric nitrogen (N) deposition in the USA. Atmospheric N deposition to sensitive ecosystems, like the Adirondacks, may increase the acidification of soils through losses of exchangeable nutrient cations, and the acidification of surface waters associated with enhanced mobility of nitrate (NO3,). However, watershed attributes, including surficial terrestrial characteristics, in-lake processing, and geological settings, have been found to complicate the relationships between atmospheric N deposition and N drainage losses. We studied two lake-watersheds in the southwestern Adirondacks, Grass Pond and Constable Pond, which are located in close proximity (,26 km) and receive similarly high N deposition, but have contrasting watershed attributes (e.g. wetland area, geological settings). Since the difference in the influence of N deposition was minimal, we were able to examine both within- and between-watershed influences of land cover, the contribution of glacial till groundwater inputs, and in-lake processes on surface water chemistry with particular emphasis on N solutes and dissolved organic carbon (DOC). Monthly samples at seven inlets and one outlet of each lake were collected from May to October in 1999 and 2000. The concentrations of NO3, were high at the Grass Pond inlets, especially at two inlets, and NO3, was the major N solute at the Grass Pond inlets. The concentrations of likely weathering products (i.e. dissolved Si, Ca2+, Mg2+, Na+) as well as acid neutralizing capacity and pH values, were also particularly high at those two Grass Pond inlets, suggesting a large contribution of groundwater inputs. Dissolved organic N (DON) was the major N solute at the Constable Pond inlets. The higher concentrations of DON and DOC at the Constable Pond inlets were attributed to a large wetland area in the watershed. The DOC/DON ratios were also higher at the Constable Pond inlets, possibly due to a larger proportion of coniferous forest area. Although DON and DOC were strongly related, the stronger relationship of the proportion of wetland area with DOC suggests that additional factors regulate DON. The aggregated representation of watershed physical features (i.e. elevation, watershed area, mean topographic index, hypsometric-analysis index) was not clearly related to the lake N and DOC chemistry. Despite distinctive differences in inlet N chemistry, NO3, and DON concentrations at the outlets of the two lakes were similar. The lower DOC/DON ratios at the lake outlets and at the inlets having upstream ponds suggest the importance of N processing and organic N sources within the lakes. Although an inverse relationship between NO3, and DOC/DON has been suggested to be indicative of a N deposition gradient, the existence of this relationship for sites that receive similar atmospheric N deposition suggest that the relationship between NO3, and the DOC/DON ratio is derived from environmental and physical factors. Our results suggest that, despite similar wet N deposition at the two watershed sites, N solutes entering lakes were strongly affected by hydrology associated with groundwater contribution and the presence of wetlands, whereas N solutes leaving lakes were strongly influenced by in-lake processing. Copyright 2006 John Wiley & Sons, Ltd. [source]

Littoral macroinvertebrates as indicators of lake acidification within the UK

Ben McFarland
Abstract 1.The Water Framework Directive (WFD) requires the assessment of acidification in sensitive water bodies. Chemical and littoral macroinvertebrate samples were collected to assess acidification of clear and humic lakes in the UK. 2.Of three acid-sensitive metrics that were regressed against acid neutralizing capacity (ANC) and pH, highly significant responses were detected using the Lake Acidification Macroinvertebrate Metric (LAMM). This metric was used to assign high, good, moderate, poor and bad status classes, as required by the WFD. 3.In clear-water lakes, macroinvertebrate changes with increasing acidification did not indicate any discontinuities, so a chemical model was used to define boundaries. In humic lakes, biological data were able to indicate a distinct, good,moderate boundary between classes. 4.Humic lakes had significantly lower pH than clear lakes in the same class, not only at the good,moderate boundary where different methods were used to set boundaries, but also at the high,good boundary, where the same chemical modelling was used for both lake types. These findings support the hypothesis that toxic effects are reduced on waters rich in dissolved organic carbon (DOC). 5.A typology is needed that splits humic and clear lakes to avoid naturally acidic lakes from being inappropriately labelled as acidified. 6.Validation using data from independent lakes demonstrated that the LAMM is transportable, with predicted environmental quality ratios (EQRs) derived from mean observed ANC, accurately reflecting the observed EQR and final status class. 7.Detecting and quantifying acidification is important for conservation, in the context of appropriate restoration, for example, by ensuring that naturally acid lakes are not treated as anthropogenically acidified. Copyright 2009 John Wiley & Sons, Ltd and Crown Copyright 2009 [source]