研究目的
To investigate the absorption properties of phytoplankton, non-algal particles, and chromophoric dissolved organic matter in Lake Qiandaohu, characterize their seasonal and spatial variability, and compare them with oceanic and shallow inland waters to support bio-optical modeling and remote sensing applications.
研究成果
CDOM absorption is a major contributor to total absorption in Lake Qiandaohu, with seasonal variations showing higher values in summer due to allochthonous inputs. Phytoplankton absorption peaks in spring, indicating seasonal growth cycles. NAP absorption is higher in summer and autumn, influenced by external sources. The water column exhibits vertical inhomogeneity, less pronounced in winter. The study provides foundational data for bio-optical model parameterization and remote sensing algorithms, highlighting the lake's mesotrophic status and the influence of human activities and natural factors on optical properties.
研究不足
The study is limited to one artificial lake (Lake Qiandaohu), which may not represent all inland waters. Seasonal variability was captured but interannual variations were not addressed. The use of specific instruments and methods (e.g., spectrophotometers, filters) may introduce measurement errors, and the spatial coverage, while extensive, might miss some micro-variabilities. The reliance on laboratory measurements for absorption coefficients could be affected by sample degradation if not processed promptly.
1：Experimental Design and Method Selection:
The study involved field campaigns in four seasons (summer, autumn, winter, spring) at 90 sites in Lake Qiandaohu. Optical measurements and water sampling were conducted to measure absorption coefficients using spectrophotometry and quantitative filter techniques. Theoretical models included exponential fitting for CDOM and NAP absorption spectra.
2：Sample Selection and Data Sources:
Water samples were collected from surface and multiple depths at fixed and varying sites across different regions of the lake. Samples were filtered and stored for laboratory analysis of CDOM, particle absorption, and chlorophyll-a concentration.
3：List of Experimental Equipment and Materials:
Equipment included Perkin Elmer lambda-35 and lambda-950 spectrophotometers, Whatman GF/F filters, Millipore polycarbonate filters, quartz cuvettes, Turner fluoroprobe, Secchi disc, HACH NPW-160 analyzer. Materials included methanol for bleaching, Milli-Q water, and ethanol for chlorophyll extraction.
4：Experimental Procedures and Operational Workflow:
For CDOM absorption, samples were filtered through GF/F and 0.22-μm filters, measured with a spectrophotometer using a 10-cm cuvette. For particle absorption, quantitative filter technique was used with methanol extraction to separate phytoplankton and NAP absorption. Chlorophyll-a was measured using fluoroprobe after ethanol extraction. Data were analyzed statistically with OriginPro software.
5：22-μm filters, measured with a spectrophotometer using a 10-cm cuvette. For particle absorption, quantitative filter technique was used with methanol extraction to separate phytoplankton and NAP absorption. Chlorophyll-a was measured using fluoroprobe after ethanol extraction. Data were analyzed statistically with OriginPro software.
Data Analysis Methods:
5. Data Analysis Methods: Statistical analyses included mean, standard deviation, ANOVA, t-tests, regression, and correlation analyses. Absorption coefficients were calculated using specific equations for CDOM and particles, with corrections for path length amplification.
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