RESUMEN
This paper explored the drought propagation phenomenon based on meteorological, hydrological, and agricultural aspects in the Yangtze River basin (YRB), China. To evaluate meteorological, hydrological, and agricultural droughts, this paper used three drought indices, standardized precipitation evapotranspiration index (SPEI), standardized runoff index (SRI), and standardized soil moisture index (SSMI), respectively. The community land model (CLM) in the YRB to generate the monthly evapotranspiration, soil moisture, runoff data, which are required for the estimation of drought index, were applied. Different mean durations (6-and 12-month) were used for drought estimation, and propagations of meteorological to hydrological and meteorological and agricultural droughts were investigated for different durations as SPEI6-SRI6, SPEI6-SSMI6, SPEI12-SRI12, SPEI12-SSMI12. The average drought propagation between 1950 and 2010 presented the highest autocorrelation and correlation with one-month lags in four combinations of drought indices in SPEI6-SRI6, SPEI6-SSMI6, SPEI12-SRI12, and SPEI12-SSMI12. Additionally, this paper estimated the optimal lags of SPEI-SRI and SPEI-SSMI drought propagations using mean 6-and 12-month lag times for six representative drought periods. Therefore, the propagation phenomenon of meteorological to hydrological and to agricultural droughts were confirmed in the YRB.
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Sequías , Ríos , Hidrología , Meteorología , SueloRESUMEN
The quality of water has deteriorated due to urbanization and the occurrence of urban stormwater runoff. To solve this problem, this study investigated the pollutant reduction effects from the geometric and hydrological factors of green infrastructures (GIs) to more accurately design GI models, and evaluated the factors that are required for such a design. Among several GIs, detention basins and retention ponds were evaluated. This study chose the inflow, outflow, total suspended solids (TSS), total phosphorus (TP), watershed area, GI area (bottom area in detention basins and permanent pool surface area in retention ponds), and GI volume (in both detention basins and retention ponds) for analysis and applied both ordinary least squares (OLS) regression and multiple linear regression (MLR). The geometric factors do not vary within each GI, but there may be a bias due to the number of stormwater events. To solve this problem, three methods that involved randomly extracting data with a certain range and excluding outliers were applied to the models. The accuracies of these OLS and MLR models were analyzed through the percentage bias (PBIAS), Nash-Sutcliffe efficiency (NSE), and RMSE-observations standard deviation ratio (RSR). The results of this study suggest that models which consider the influent concentration combined with the hydrological and GI geometric parameters have better correlations than models that consider only a single parameter.
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Contaminantes Ambientales , Contaminantes Químicos del Agua , Hidrología , Fósforo/análisis , Estanques , Lluvia , Movimientos del Agua , Contaminantes Químicos del Agua/análisisRESUMEN
The present study is aimed at examining whether potential evapotranspiration (PET), which is important for drought assessment, influences a drought index (standardized precipitation evapotranspiration index; SPEI) for different regions and climate zones. The study regions were East Asia, Europe, the United States (US), and West Africa, and the climate zones considered were the arid, semiarid, subhumid, and humid zones. We examined the pattern of water deficits, spatial trend of the SPEI, area ratio of spatial extent, and temporal trend to provide an understanding of drought characteristics. Two datasets, Climate Research Unit (CRU) and National Centers for Environmental Prediction (NCEP), were used for assessing the drought phenomena. Two types of evapotranspiration obtained using Thornthwaite and Penman-Monteith equations were used to estimate the PET. Negative water deficit values were clearly observed in the arid and semiarid zones of the majority of regions, whereas positive water deficit values were observed in the subhumid and humid zones of the regions. The SPEI spatial trend largely presented a decreasing trend in East Asia and West Africa, a neutral or decreasing trend in Europe, and a neutral or increasing trend in the US. The area ratio of the spatial extent showed large values of a neutral or decreasing trend in East Asia and Europe, a neutral or increasing trend in the US, and a decreasing trend in West Africa. The temporal trend of the spatial extent primarily exhibited no trend or an increasing trend in the aforementioned regions, except in the case of the majority of West Africa. Although the results obtained from the two datasets appear to be slightly different, they show that the PET is predominant in regions, especially in the US. The PET trends are identified through comparisons and used to understand the drought phenomena while considering various geographic regions and climatic zones.
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Monitoreo del Ambiente/métodos , Cambio Climático , SequíasRESUMEN
An extracellular 104 kDa exo-beta-d-glucosaminidase was purified and characterized from the culture supernatant of Aspergillus fumigatus S-26, which showed exceptionally strong chitosanolytic enzyme activity. The purified enzyme showed optimum pH of 3.0-6.0 and optimum temperature of 50-60 degrees C, and was stable between pH 2.0 and 10.0 and under 35 degrees C. The Km, Vmax, and kcat were determined to be 1.0 mg chitosan/ml, 7.8x10(-8) mol/s/mg protein, and 28.3 s-1, respectively. The exo-beta-D-glucosaminidase was severely inactivated by Cu2+ and Hg2+ at 10 mM. 2-Hydroxy-5-nitrobenzyl bromide, N-bromosuccinimide, and p-chloromercuribenzoic acid inhibited the enzyme. The enzyme did not degrade chitin, cellulose, and starch. The exo-beta-D-glucosaminidase did not reduce the viscosity of chitosan solutions at early stage of reaction, suggesting the exo-type of cleavage in polymeric chitosan chains. The exo-beta-D-glucosaminidase liberated only GlcN from chitosan, and GlcN plus the one-residue shortened oligomers from (GlcN)2-7. The exo-beta-D-glucosaminidase exhibited transglycosylation activity, resulting in the one-residue elongated oligomers.