scholarly journals Seasonal photoreactivity of dissolved organic matter from lakes with contrasting humic content

2000 ◽  
Vol 57 (5) ◽  
pp. 875-885 ◽  
Author(s):  
Måns J Lindell ◽  
H Wilhelm Granéli ◽  
Stefan Bertilsson
Keyword(s):  
Organic Acids ◽  
Uv Radiation ◽  
Dissolved Inorganic Carbon ◽  
Sampling Period ◽  
Low Molecular Weight ◽  
Ultraviolet A ◽  
Surface Layers ◽  
Hydraulic Residence Time ◽  
Doc Concentration ◽  
Artificial Uv

We studied seasonal variability in photodegradation of dissolved organic carbon (DOC) resulting from artificial ultraviolet-A (UV-A) and UV-B irradiation. Water samples were taken approximately monthly from the surface layers of two oligotrophic lakes with contrasting humic content, situated in southern Sweden. Lake water was filter-sterilized (0.2 μm) and exposed to artificial UV radiation in quartz tubes. Potential DOC photodegradation, measured as a photoproduction of dissolved inorganic carbon (DIC) and oxalic, malonic, formic, and acetic acid in irradiated samples, was observed throughout the sampling period. In addition, exposure to UV radiation resulted in a decrease in DOC, absorbance, and humic substance fluorescence. The photoproduction of DIC and the low molecular weight (LMW) organic acids varied seasonally, being generally higher in winter and spring (December-May), while DOC appeared to become less photoreactive after the extensive exposure to solar radiation during summer. Production rates of both DIC and LMW organic acids were approximately eight times higher in the humic lake despite that the DOC concentration was only two times higher than in the clearwater lake. This is most probably due to the high input of allochthonous DOC and the resulting higher absorbance to DOC ratio in the humic system. Furthermore, the longer hydraulic residence time in the clearwater system could have resulted in an accumulation of residual DOC, recalcitrant to further photodegradation.

scholarly journals Ancient low–molecular-weight organic acids in permafrost fuel rapid carbon dioxide production upon thaw

2015 ◽  
Vol 112 (45) ◽  
pp. 13946-13951 ◽  
Author(s):  
Travis W. Drake ◽  
Kimberly P. Wickland ◽  
Robert G. M. Spencer ◽  
Diane M. McKnight ◽  
Robert G. Striegl
Keyword(s):  
Carbon Dioxide ◽  
Molecular Weight ◽  
Organic Carbon ◽  
Organic Acids ◽  
Dissolved Inorganic Carbon ◽  
Carbon Dioxide Production ◽  
High Temporal Resolution ◽  
Low Molecular Weight ◽  
Doc Concentration ◽  
Permafrost Soils

Northern permafrost soils store a vast reservoir of carbon, nearly twice that of the present atmosphere. Current and projected climate warming threatens widespread thaw of these frozen, organic carbon (OC)-rich soils. Upon thaw, mobilized permafrost OC in dissolved and particulate forms can enter streams and rivers, which are important processors of OC and conduits for carbon dioxide (CO2) to the atmosphere. Here, we demonstrate that ancient dissolved organic carbon (DOC) leached from 35,800 y B.P. permafrost soils is rapidly mineralized to CO2. During 200-h experiments in a novel high–temporal-resolution bioreactor, DOC concentration decreased by an average of 53%, fueling a more than sevenfold increase in dissolved inorganic carbon (DIC) concentration. Eighty-seven percent of the DOC loss to microbial uptake was derived from the low–molecular-weight (LMW) organic acids acetate and butyrate. To our knowledge, our study is the first to directly quantify high CO2production rates from permafrost-derived LMW DOC mineralization. The observed DOC loss rates are among the highest reported for permafrost carbon and demonstrate the potential importance of LMW DOC in driving the rapid metabolism of Pleistocene-age permafrost carbon upon thaw and the outgassing of CO2to the atmosphere by soils and nearby inland waters.

Influences on the Hydrophobicity of Concrete Surfaces Treated with Alkyl Trialkoxysilanes

2014 ◽  
Vol 20 (6) ◽  
pp. 405-412
Author(s):  
U. Antons ◽  
M. Raupach ◽  
O. Weichold
Keyword(s):  
Uv Radiation ◽  
Cement Hydration ◽  
Alkaline Media ◽  
Water Repellent ◽  
Portland Cement Concrete ◽  
Accelerated Carbonation ◽  
Surface Layers ◽  
Hydrophobic Layer ◽  
Furnace Slag

Abstract The paper focuses on how alkaline media, UV radiation, and carbonation as well as on-going cement hydration affects hydrophobic treatments of concrete and influences the properties of these water-repellent layers. Single-sided nuclear magnetic resonance measurements show that layers formed by impregnating samples with alkyl trialkoxysilanes are stable even under long-term exposure to alkaline solution and UV radiation, with the damage of the latter being limited to the topmost surface layers. Microstructural changes during accelerated carbonation of blast furnace slag cement based concrete have a major impact on the hydrophobic layer properties, while the carbonation of Portland cement concrete has no influence. On-going hydration additionally influences the hydrophobic layer properties.

scholarly journals INFLUENCE OF VARIOUS FEED ADDITIVES ON THE ACTIVITY OF CHYME AND BLOOD PLASMA ENZYMES OF YOUNG MEAT CHICKEN OF ORIGINAL LINE

THE BULLETIN ◽  
2021 ◽  
Vol 2 (390) ◽  
pp. 12-17
Author(s):  
A. Grozina
Keyword(s):  
Molecular Weight ◽  
Organic Acids ◽  
Blood Plasma ◽  
Digestive Enzymes ◽  
Feed Additives ◽  
Pancreatic Enzymes ◽  
Control Group ◽  
Physiological Status ◽  
Low Molecular Weight ◽  
Original Line

The research aimed to determine the effect of a mixture of low molecular weight organic acids and complex phytobiotics when replacing a feed antibiotic with them on the activity of digestive enzymes in the duode-nal chyme and the activity of pancreatic enzymes in the blood plasma of young stock B5 and B9 meat chicken lines. The experiments were carried out on the original lines of meat poultry lines B5 (Cornish) and B9 (Plymouth rock). There was an operation to insert a cannula into the duodenum at the age of 6 weeks. The enzymatic activity of the duodenum chyme and the content of pancreatic enzymes in the blood plasma in the groups of chickens receiving antibiotics, low molecular weight organic acids, and phytobiotics with the diet. The data showed that the influence of feed additives on the physiological status of poultry was different. The use of low molecular weight organic acids of the B5 and B9 chicken lines had a significant effect on the production of digestive enzymes due to an increase in the activity of chyme lipase (by 98.3%) and blood plasma lipase (by 26.6%) in B9 chickens and an increase in chyme proteases (by 30.9%) in B5 chickens compared with the control group, where the antibiotic was used. The introduction of complex phytobiotics into the diet had a negative effect on chickens of the B5 line (Cornish), reducing the activity of amylase and lipase of the duodenal chyme (by 29.2 and 26.9%) compared with the control group. In B9 (Plymouth rock) chickens, only the chyme amylase activity increased by 30.8% that indicates an improvement in the availability of feed carbohydrates. These data confirm the need to take into account the different effects of feed additives on the digestion processes in different poultry crosses.

scholarly journals Short-term effects of phosphate fertilizer enriched with low molecular weight organic acids on phosphorus release kinetic and availability under calcareous conditions in arid region

2018 ◽  
Vol 2 ◽  
pp. 66
Author(s):  
Adil Mihoub ◽  
Mustapha Daddi Bouhoun ◽  
Asif Naeem
Keyword(s):  
Molecular Weight ◽  
Acid Solution ◽  
Organic Acids ◽  
Phosphorus Release ◽  
Favorable Effect ◽  
Available Phosphorus ◽  
Low Molecular Weight ◽  
Release Kinetic ◽  
P Availability ◽  
Phosphate Fertilizers

Phosphate reactions and retention in the soil are of paramount importance from the perspective of plant nutrition and fertilizer use efficiency. The objective of this work was to investigate the effect of some low molecular weight organic acids (LMWOAs) on phosphorus release kinetic and its availability in calcareous soil. Experiments were conducted in laboratory. Soil-limestone mixtures were prepared to achieve highly calcareous samples (i.e. 50% CaCO3). The prepared samples were mixed thoroughly with phosphate fertilizers i.e. Triple super phosphate (TSP) and Monoammonium Phosphate (MAP) and watered with distilled water only (CK), with citric acid solution (CA) and with oxalic acid solution (OA). The treatments were arranged in a CRD with three replications and incubated at 25 ± 2°C and 80% soil moisture for a period of 960 h. The parabolic model was used for describing the decrease in P with time. As a result, all treatments showed a significant decrease in available P with time. Using LMWOAs showed important results and combination of phosphate fertilizers with both LMWOAs solutions exerted a very favorable effect on P availability in soil. The parabolic diffusion equation used was fitted well to experimental data. Addition of LMWOAs decreased loss in extractability of P with increasing soil available phosphorus fraction. Moreover, treatments irrigated by LMWOAs solutions released a lot of phosphorus compared to untreated treatments.

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