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41.
Eutrophication of surface water is a worldwide concern. Sediments may play an important role in buffering phosphorus (P) concentration in the overlying water column. However, information on the spatial variation of sediment P availability as affected by agricultural water discharge and hydrological conditions is limited. In this study river sediments were sampled in spring, summer, fall and winter, respectively from seven locations along a main tributary (Ten Mile Creek, TMC), which receives surface runoff water from agricultural lands and discharges into the Indian River Lagoon, south Florida, USA, and analyzed for P availability. Simultaneously, hydrological variables were measured on the spot and river water samples were collected for analyses of water quality. The results demonstrated that available P in the sediments of TMC as measured by several commonly used extraction procedures had a large spatial variation. The downstream locations had a greater amount of available P in the sediments than the upstream locations, which is attributable to the settlement of finer particles due to slower water flow and increased influence from salt water in the downstream locations where the fresh river water gradually mixed with salt water from the Indian River Lagoon. Phosphorus availability in the sediments appeared to be related to P sorption by iron and aluminum oxides and the competition for adsorbing sites between SO42− and PO43−. This spatial variation of P availability agrees with the elevation of chlorophyll a (Chla) in overlying water body in the downstream locations of TMC, indicating that the internal P source plays an important role in triggering an algal boom in surface water systems. 相似文献
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Andosols are the dominant soils in the Valle de Bravo basin, the origin of a significant amount of Mexico City's drinking water. The main land use is agriculture and most of the existing surface water bodies are eutrophic. Nitrogen fertilizer is used extensively. There have been very few studies on nitrate (NO3−) fate in this type of soil and region. Comprehensive laboratory studies were conducted to determine the fate of NO3− in an Andosol profile from Valle de Bravo, in order to assess the risk of water resources contamination. Nitrate retention was analysed statically (using batch experiments) and dynamically (using intact and packed soil columns) at different soil depths and its competition with Cl− was evaluated. Complementary laboratory experiments were conducted to study water transport through the columns and nitrogen transformations in the soil. In batch and columns, NO3− adsorption was linear in the range of concentrations studied and higher in the deepest soil layer. Preferential flow pathways were found in the unaltered deeper soil layers, while tillage activity in the top layer destroyed the pore continuity. In spite of the deeper soil layer's greater capacity for NO3− retention, the presence of preferential flow pathways coupled with high rainfall intensities, makes the NO3− mobile below the root zone at 1 m depth and increases the risk of groundwater contamination. The results illustrate the complexity of nitrate fate in Andosols and can be used to improve agricultural practices in the central Mexico region. 相似文献
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D.E. Gomez L.G. Arroyo H.R. Stämpfli L.E. Cruz O.J. Oliver 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2013,27(3):548-553
Background
The quantitative effect of strong electrolytes, pCO2, and plasma protein concentration in determining plasma pH and bicarbonate concentrations can be demonstrated with the physicochemical approach. Plasma anion gap (AG) and strong ion gap (SIG) are used to assess the presence or absence of unmeasured anions.Hypotheses
The physicochemical approach is useful for detection and explanation of acid‐base disorders in horses with colitis. AG and SIG accurately predict hyperlactatemia in horses with colitis.Animals
Fifty‐four horses with acute colitis and diarrhea.Methods
Retrospective study . Physicochemical variables were calculated for each patient. ROC curves were generated to analyze sensitivity and specificity of AG and SIG for predicting hyperlactatemia.Results
Physicochemical interpretation of acid‐base events indicated that strong ion metabolic acidosis was present in 39 (72%) horses. Mixed strong ion acidosis and decreased weak acid (hypoproteinemia) alkalosis was concomitantly present in 17 (30%) patients. The sensitivity and specificity of AG and SIG to predict hyperlactatemia (L‐lactate > 5 mEq/L) were 100% (95% CI, 66.4–100; P < .0001) and 84.4% (95% CI, 70.5–93.5 P < .0001). Area under the ROC curve for AG and SIG for predicting hyperlactatemia was 0.95 (95% CI, 0.86–0.99) and 0.93 (95% CI, 0.83–0.99), respectively.Conclusion and Clinical relevance
These results emphasize the importance of strong ions and proteins in the maintenance of the acid‐base equilibria. AG and SIG were considered good predictors of clinically relevant hyperlactatemia. 相似文献46.
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《Communications in Soil Science and Plant Analysis》2012,43(22):3231-3234
Effects of different kinds of anion exchange membrane (AEM) on soil P extracted by AEM (AEM P) were investigated in three soils (Cumulic Andosol, Yellow soil, and Gray Lowland soil). There was no significant difference in AEM P among the AEMs tested (BDH-Prolabo 551642S, AGC Engineering Selemion AMT, and AGC Engineering Selemion AMV). The AEM P was greater than water-soluble P in all soils. Although AEM P was greater than Truog-extractable P in Cumulic Andosol, the reverse was true in the Yellow soil and Gray Lowland soil. 相似文献
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J. Bouda L. Núñez-Ochoa J. Doubek J. Aguilar-Bobadilla 《Research in veterinary science》2009,87(1):26-28
The effect of age and sex on blood acid-base and plasma electrolyte values was determined in venous blood samples from 45 clinically healthy ostriches (Struthio camelus) from 26 days to 6 years of age. Animals were divided by age into four groups and the group of adults was divided by sex into two subgroups. Blood samples were collected without sedation. There was a significant (P < 0.05) age difference in blood values of base excess (BE), plasma , total CO2 (TCO2), Na+, K+, Cl− and anion gap (AG). The highest plasma concentrations of Na+, Cl− and value of AG were found in adult ostriches with a steady decrease to chicks. A significant (P < 0.05) sex difference in adult animals with higher blood pH, lower blood values of pCO2, BE, plasma concentrations of , TCO2 and K+ was found in females. We concluded that blood acid-base values and plasma electrolyte concentrations in ostriches are affected by age and sex. 相似文献
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添加不同水平阴离子盐对人工瘤胃液理化指标的影响 总被引:2,自引:0,他引:2
本试验采用人工瘤胃模拟装置研究了添加不同水平阴离子盐0、-50mEq/kg、-100mEq/kg和-150mEq/kg的日粮对瘤胃消化代谢的影响。通过对瘤胃液pH值、NH3-N、VFA浓度的测定,结果表明,添加阴离子盐水平在-150mEq/kg内,对瘤胃pH值和氨氮浓度有一定影响,但差异不显著(p>0.05);当添加水平在-100mEq/kg和-150mEq/kg时,对乙酸浓度、丙酸浓度及乙酸/丙酸比例影响差异均为显著(P<0.05)。 相似文献