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11.
Phytoplankton assemblage and seston composition of the San José's gulf (Argentine, 42° S) were studied during a period of two years. Cell counts, chlorophyll, particulate nitrogen and particulate carbon determination were made. Phytoplankton synecology was studied using principal component analysis. 相似文献
12.
It has been recently that particulate matter (PM) exposure increases the risk and exacerbation of allergic asthma. However, the underlying mechanisms and factors associated with increased allergic responses remain elusive. We evaluated IL‐23 and IL‐23R (receptor) expression, as well as changes in the asthmatic phenotype in mice administered PM and a low dose of house dust mite (HDM). Next, changes in the phenotype and immune responses were evaluated after intranasal administration of anti‐IL‐23 antibody during co‐exposure to PM and low‐dose HDM. We also performed in vitro experiments to investigate the effect of IL‐23. IL‐23 expression was significantly increased in Epcam+CD45− and CD11c+ cells, while that of IL‐23R was increased in Epcam+CD45− cells only in mice administered PM and low‐dose HDM. Administration of anti‐IL‐23 antibody led to decreased airway hyperresponsiveness, eosinophils, and activation of dendritic cells, reduced populations of Th2 Th17, ILC2, the level of IL‐33 and granulocyte‐macrophage colony‐stimulating factor (GM‐CSF). Inhibition of IL‐23 in PM and low‐dose HDM stimulated airway epithelial cell line resulted in decreased IL‐33, GM‐CSF and affected ILC2 and the activation of BMDCs. PM augmented the phenotypes and immunologic responses of asthma even at low doses of HDM. Interestingly, IL‐23 affected immunological changes in airway epithelial cells. 相似文献
13.
The effects of dissolved organic matter (DOM), water soluble organic matter derived from sewage sludge, on the sorption of atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-trazine) by soils were studied using a batch equilibrium technique. Six paddy soils, chosen so as to have different organic carbon contents, were experimented in this investigation. Atrazine sorption isotherms on soils were described by the linear equation, and the distribution coefficients without DOM (Kd) or with DOM (Kd*) were obtained. Generally, the values of Kd*/Kd initially insoil-solution system form. Critical concentrations of DOM (DOMnp) were obtained where the value of Kd* was equal to Kd. The presence of DOM with concentrations lower than DOMnp promoted atrazine sorption on soils (Kd* > Kd), whereas the presence of DOM with concentrations higher than DOMnp tended to inhibit atrazine sorption (Kd* < Kd). Interestingly, DOMnp for tested soils was negatively correlated to the soil organic carbon content, and the maximum of Kd*/Kd (i.e.Kmax) correlated positively with the maximum of DOM sorption on soil (Xmax). Further investigations showed that the presence of hydrophobic fraction of DOM evidently promoted the atrazine sorption on soils, whereas the presence of hydrophilic DOM fraction obviously tended to inhibit the atrazine sorption. Interactions of soil surfaces with DOM and its fractions were suggested to be the major processes determining atrazine sorption on soils. The results of this work provide a reference to the agricultural use of organic amendment such as sewage sludge for improving the availability of atrazine in soils. 相似文献
14.
Fungal laccases - occurrence and properties 总被引:8,自引:0,他引:8
Baldrian P 《FEMS microbiology reviews》2006,30(2):215-242
Laccases of fungi attract considerable attention due to their possible involvement in the transformation of a wide variety of phenolic compounds including the polymeric lignin and humic substances. So far, more than a 100 enzymes have been purified from fungal cultures and characterized in terms of their biochemical and catalytic properties. Most ligninolytic fungal species produce constitutively at least one laccase isoenzyme and laccases are also dominant among ligninolytic enzymes in the soil environment. The fact that they only require molecular oxygen for catalysis makes them suitable for biotechnological applications for the transformation or immobilization of xenobiotic compounds. 相似文献
15.
Leon P.M. Lamers G. Els Ten Dolle Serge T.G. Van Den Berg Sebastiaan P.J. Van Delft Jan G.M. Roelofs 《Biogeochemistry》2001,55(1):87-101
Sulphate (SO4
2-)reduction rates are generally low in freshwaterwetlands and are regulated by the scarceavailability of the ion. Increasedconcentrations of this electron acceptor due tosulphur (S) pollution of groundwater andsurface water may, however, lead to highSO4
2- reduction rates now regulatedby the availability of appropriate electrondonors. Due to variations in this availability,the response to S pollution (e.g. from surfacewater or groundwater) is expected to differbetween soils. This hypothesis was tested inlaboratory mesocosm experiments by comparingtwo wetland soil types with distinctlydifferent humus profiles: a Hydromoder and aRhizomull type. In the first type, expected tohave a higher availability of degradable soilorganic matter (SOM), SO4
2-availability appeared to be rate limiting forSO4
2- reduction. In the Rhizomullsoils, in contrast, the electron acceptor didnot limit SO4
2- reduction rates athigher concentrations. These differences inresponse could not, however, be attributed todifferences in the various SOM fractions or inSOM densities. Eutrophication and free sulphideaccumulation, two major biogeochemical problemscaused by SO4
2- pollution, occurredin both types. The absolute extent ofphosphorus mobilisation was determined by theconcentration of this element in the soil (C/Pratio), while the level of sulphideaccumulation was governed by the concentrationof dissolved iron in the pore water. It wastherefore concluded that neither the humusprofile nor the concentrations of different SOMfractions in the soils are reliable indicatorsfor the sensitivity of wetland types to Spollution. 相似文献
16.
In this paper, we propose a structure for organo-mineral associations in soils based on recent insights concerning the molecular
structure of soil organic matter (SOM), and on extensive published evidence from empirical studies of organo-mineral interfaces.
Our conceptual model assumes that SOM consists of a heterogeneous mixture of compounds that display a range of amphiphilic
or surfactant-like properties, and are capable of self-organization in aqueous solution. An extension of this self-organizational
behavior in solution, we suggest that SOM sorbs to mineral surfaces in a discrete zonal sequence. In the contact zone, the formation of particularly strong organo-mineral associations appears to be favored by situations where either (i) polar
organic functional groups of amphiphiles interact via ligand exchange with singly coordinated mineral hydroxyls, forming stable
inner-sphere complexes, or (ii) proteinaceous materials unfold upon adsorption, thus increasing adhesive strength by adding
hydrophobic interactions to electrostatic binding. Entropic considerations dictate that exposed hydrophobic portions of amphiphilic
molecules adsorbed directly to mineral surfaces be shielded from the polar aqueous phase through association with hydrophobic
moieties of other amphiphilic molecules. This process can create a membrane-like bilayer containing a hydrophobic zone, whose components may exchange more easily with the surrounding soil solution than those in the contact zone, but which are
still retained with considerable force. Sorbed to the hydrophilic exterior of hemimicellar coatings, or to adsorbed proteins,
are organic molecules forming an outer region, or kinetic zone, that is loosely retained by cation bridging, hydrogen bonding, and other interactions. Organic material in the kinetic zone
may experience high exchange rates with the surrounding soil solution, leading to short residence times for individual molecular
fragments. The thickness of this outer region would depend more on input than on the availability of binding sites, and would
largely be controlled by exchange kinetics. Movement of organics into and out of this outer region can thus be viewed as similar
to a phase-partitioning process. The zonal concept of organo-mineral interactions presented here offers a new basis for understanding
and predicting the retention of organic compounds, including contaminants, in soils and sediments. 相似文献
17.
Stuart G. Fisher 《International Review of Hydrobiology》1977,62(6):701-727
An annual organic matter budget for a 1700 m segment of Fort River (Massachusetts, USA) is presented. Primary production in this fourth order stream exceeds litter input annually, however ecosystem P/R is 0.5. Respiration in excess of gross primary production is supported by allochthonous organic matter imported from upstream reaches. The relative contribution of organic matter size fractions to stream consumers depends upon biologic lability, rate of input, and residence time in the ecosystem. Particles of seston size (1 μm to 1 mm) are most heavily used by consumers, however dissolved organic matter represents the largest input component. Microorganisms are the predominant consumers in this soft-water, nutrient-poor stream ecosystem. A conceptual model for assessing the processing efficiency of stream ecosystems is presented and discussed in terms of several headwater to estuary gradients. 相似文献
18.
19.
Liesje De Schamphelaire Korneel Rabaey Nico Boon Willy Verstraete Pascal Boeckx 《Geomicrobiology journal》2013,30(7-8):547-558
Both natural and anthropogenic processes are responsible for excessive organic loading of submerged soils, with detrimental environmental consequences. The often insufficient natural attenuation can be enhanced by exploiting microbial manganese cycles. This review describes how an anoxic oxidation of organic matter with concomitant reduction of MnO 2 can link up with a reoxidation of the resulting, soluble Mn(II) in oxic layers. The potentially attainable oxidation rates through these natural cycles are of the same order as the organic carbon accumulation rates. The microbiology and physiology of the responsible organisms are discussed, as well as examples of naturally occurring manganese cycles and the possibility to engineer this natural phenomenon. 相似文献
20.
Susanne Gauggel-Lewandowski Alexandra H. Heussner Pablo Steinberg Bart Pieterse Bart van der Burg Daniel R. Dietrich 《Chemico-biological interactions》2013
Due to increasing energy demand and limited fossil fuels, renewable energy sources have gained in importance. Particulate matter (PM) in general, but also PM from the combustion of wood is known to exert adverse health effects in human. These are often related to specific toxic compounds adsorbed to the PM surface, such as polycyclic aromatic hydrocarbons (PAH), of which some are known human carcinogens. This study focused on the bioavailability of PAHs and on the tumor initiation potential of wood combustion PM, using the PAH CALUX® reporter gene assay and the BALB/c 3T3 cell transformation assay, respectively. For this, both cell assays were exposed to PM and their respective organic extracts from varying degrees of combustion. The PAH CALUX® experiments demonstrated a concentration–response relationship matching the PAHs detected in the samples. Contrary to expectations, PM samples from complete (CC) and incomplete combustion (IC) provided for a stronger and weaker response, respectively, suggesting that PAH were more readily bioavailable in PM from CC. These findings were corroborated via PAH spiking experiments indicating that IC PM contains organic components that strongly adsorb PAH thereby reducing their bioavailability. The results obtained with organic extracts in the cell transformation assay presented the highest potential for carcinogenicity in samples with high PAH contents, albeit PM from CC also demonstrated a carcinogenic potential. In conclusion, the in vitro assays employed emphasize that CC produces PM with low PAH content however with a general higher bioavailability and thus with a nearly similar carcinogenic potential than IC PM. 相似文献