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Zhang Y.-B.,Nanjing Normal University | Zhang Y.-B.,CAS Nanjing Institute of Geography and Limnology | Zhang Y.-L.,CAS Nanjing Institute of Geography and Limnology | Zha Y.,Nanjing Normal University | And 4 more authors.
Huanjing Kexue/Environmental Science

Photosynthetically active radiation (PAR) is defined as the wavelength band of 400 to 700 nm, representing most of the visible solar radiation that could be used for photosynthesis. PAR is attenuated by the absorption and scattering of nonpigment suspended matter, chromophoric dissolved organic matter and phytoplankton, and it plays an important role in determining the density and distribution of aquatic organisms. This study developed an empirical model and presented the spatial-temporal distribution of PAR diffuse attenuation coefficient [Kd(PAR)] for the slightly turbid Xin'anjiang Reservoir based on the in situ ground data and the matching Landsat 8 data. The results showed that the three-band combinational model of Kd(PAR) using Band 2, Band 3 and Band 8 could give a reasonable and acceptable estimation accuracy with a determination coefficient of 0.87. Independent dataset was used to validate the model with a mean relative error of 9.16% and a root mean square error of 0.06 m-1. Therefore, the three-band combination using Landsat 8 data could be used to accurately estimate Kd(PAR) in the slightly turbid Xin'anjiang Reservoir. Kd(PAR) exhibited significant seasonal and spatial differences. Kd(PAR) was higher in autumn (September-November) and summer (June-August) with the average Kd(PAR) of (0.82±0.60) m-1and (0.77±0.41) m-1, but lower in winter (December-February) and spring (March-May) with the average Kd(PAR) of (0.56±0.50) m-1 and (0.40±0.45) m-1, respectively. Spatially, Kd(PAR) ranged from 0.002 to 13.86 m-1 with an average of (0.64±0.49) m-1. The temporal heterogeneity of Kd(PAR) was mainly caused by the seasonal rainfall and seasonal growth of phytoplankton. The spatial heterogeneity was mainly caused by suspended matter concentration derived from watershed inputs and human dredging activity. © 2015, Science Press. All right reserved. Source

Yin Y.,Hangzhou Institute of Environmental Science | Wu Z.-X.,Chunan Environmental Monitoring Station | Zhang Y.-L.,CAS Nanjing Institute of Geography and Limnology | Liu M.-L.,Hangzhou Institute of Environmental Science | And 4 more authors.
Zhongguo Huanjing Kexue/China Environmental Science

To investigate the spectral absorption characteristics, spatial distribution and source of colored dissolved organic matter (CDOM), 53 surface water samples were collected from Xin'anjiang Reservoir in July, 2013.The spatial distribution of CDOM absorption coefficient at 350 nm[a(350)], carbon-specific CDOM absorption coefficient [a*(350)], the spectral slope (S), as well as the relationships between CDOM and water quality parameters were studied. Using hierarchical cluster analysis, we divided a(350) into three districts (A, B, and C districts). a(350) decreased from north western area (A district) to the central reservoir and the north eastern area (B district), and to the south western area and the south eastern area (C district). The distribution pattern of a (350) was similar to the distribution of a*(350) but different from that of S. Significantly positive linear correlations between a (350) and chlorophyll a concentration, phytoplankton absorption coefficient and suspended solids indicated a critical contribution of phytoplankton metabolism and degradation products of CDOM. ©, 2014, Chinese Society for Environmental Sciences. All right reserved. Source

Yin Y.,Hangzhou Institute of Environmental Science | Wu Z.-X.,Chunan Environmental Monitoring Station | Liu M.-L.,Hangzhou Institute of Environmental Science | He J.-B.,Hangzhou Institute of Environmental Science | Yu Z.-M.,Hangzhou Institute of Environmental Science
Huanjing Kexue/Environmental Science

Based on monthly in situ data collected at six sampling sites in Qiandaohu Lake between 2011 and 2012, the dynamic distributions of dissolved oxygen (DO) were analyzed and the relationships between DO and the environmental factors were investigated. The results showed that there were obviously vertical and temporal variations in the distributions of DO. In winter, the average values of DO were generally higher than those in other seasons, but no significant vertical distribution variation was found except Dabaqian. However, the vertical differences of DO in summer were larger than those in spring and autumn. Moreover, the maximum values of DO found in euphotic zone at the sites of Xiaojinshan, Santandao, Dabaqian in summer were 11.59, 12.52, 10.96 mg·L-1, respectively. The maximum DO at surface layer was found in spring while the minimum value appeared in autumn. Seasonal differences in relationships between dissolved oxygen and water temperature, pH, and Chla concentration were discussed. In summer, highly significant linear correlation between DO and water temperature was found indicating that the temperature thermal stratification was the key factor to influence the vertical distribution of DO. The relative higher correlation coefficients between DO and pH, Chla concentration in spring and summer were due to the phytoplankton photosynthesis. Source

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