以離心及自動攝像技術量測地面水中可被Alcian blue染色之物質

Abstract

Transparent exopolymer particles (TEP) are defined as transparent particles that are composed mainly of acid polysaccharides and are stainable with Alcian blue. These particles are particularly abundance in diverse aqueous environments, participate in a wide range of important processes in environmental science, and currently regarded as an important contributor to biofilm forming and membrane biofouling. However, TEP actually only reflect a small fraction from the whole spectrum of the materials stainable with Alcian blue (AB) in aquatic environment. Significant larger amounts of these materials have been found in colloidal and dissolved fractions. This study developed a centrifugation-based approach to analyze Alcian blue-stainable matter (ABSM), which are not confined to TEP, but also all particle and soluble matters stainable with AB in freshwater. Separation efficiency of insoluble complexes between AB and its stainable materials were measured with a wide range of relative centrifugal forces (RCF) (1089 to 34957 ×G) using particle size distribution. The changes in particle size distribution at various RCF provides us an insight of fates of these complexes, which was not addressed in all published methods. Accordingly, centrifugation at high RCF (from 12096 ×G) was an effective alternative to filter-based approach in separation of the complexes while lower RCF as suggested from the literatures could not totally separate them. Next, the optimal conditions were defined in the standard procedure (pH 2.5 and RCF at 12096 ×G) which was then applied to measure various fractions of these materials in freshwater samples. Comparing the results from our method with TEP measured by reference methods revealed a significant correlation for the particle fraction of these materials. Remarkable amounts of ABSM were found in the filtrates of all samples, raising the significance of the small size fractions, especially in membrane fouling. A standard protocol using FlowCAM for on-line observation and quantification of Alcian blue-stainable particles in freshwater was first time established. Samples from three reservoirs with a wide range of TEP (27 – 1679 mg.GX.L-1) were directly used for method development and factors which potentially affect the measurement were tested. The results showed a wide variety of morphological forms of AB stainable particles from the water samples. Remarkably, characteristics of the particles measured instantaneously differed significantly from those measured at the steady state, as a result of particle aggregation. Compared to traditional microscopic methods, this on-line method provided a simple, rapid and less labour-intensive analysis with particle morphological conservation and a large number of particle attributes. By overcoming the limitations from the formers, this FlowCAM based method would offer routine monitoring of these transparent particles from various freshwater sources. We then report the fate of different fractions of ABSM in Pao-Shan reservoir, Taiwan, in a one-year study (2013 to 2014) and an intensive study during phytoplankton bloom (2014). The interactions between the fractions, including AB stainable particles, particle and colloidal TEP (pTEP and cTEP), dissolved ABSM, and their relationship to other water quality parameters were analyzed. The results of the one-year study likely showed relationships of pTEP concentration to phytoplankton count and chl a, while in the intensive study, AB stainable particles abundance and pTEP concentration were correlated neither phytoplankton count nor chl a, but strongly positively correlated with some species’ abundance. The difference indicates that sampling frequency and phytoplankton composition should be addressed for studying the links between AB stained fractions and phytoplankton. The interaction between different fractions further suggests that the majority of AB stainable particles and pTEP would be directly generated by some phytoplankton species, whereas their abiotic generation by cTEP or dissolved ABSM may only have contributed partly to their formation. This differs from previous studies which generally posited that pTEP are mainly formed abiotically from dissolved precursors.

Transparent exopolymer particles (TEP) are defined as transparent particles that are composed mainly of acid polysaccharides and are stainable with Alcian blue. These particles are particularly abundance in diverse aqueous environments, participate in a wide range of important processes in environmental science, and currently regarded as an important contributor to biofilm forming and membrane biofouling. However, TEP actually only reflect a small fraction from the whole spectrum of the materials stainable with Alcian blue (AB) in aquatic environment. Significant larger amounts of these materials have been found in colloidal and dissolved fractions. This study developed a centrifugation-based approach to analyze Alcian blue-stainable matter (ABSM), which are not confined to TEP, but also all particle and soluble matters stainable with AB in freshwater. Separation efficiency of insoluble complexes between AB and its stainable materials were measured with a wide range of relative centrifugal forces (RCF) (1089 to 34957 ×G) using particle size distribution. The changes in particle size distribution at various RCF provides us an insight of fates of these complexes, which was not addressed in all published methods. Accordingly, centrifugation at high RCF (from 12096 ×G) was an effective alternative to filter-based approach in separation of the complexes while lower RCF as suggested from the literatures could not totally separate them. Next, the optimal conditions were defined in the standard procedure (pH 2.5 and RCF at 12096 ×G) which was then applied to measure various fractions of these materials in freshwater samples. Comparing the results from our method with TEP measured by reference methods revealed a significant correlation for the particle fraction of these materials. Remarkable amounts of ABSM were found in the filtrates of all samples, raising the significance of the small size fractions, especially in membrane fouling. A standard protocol using FlowCAM for on-line observation and quantification of Alcian blue-stainable particles in freshwater was first time established. Samples from three reservoirs with a wide range of TEP (27 – 1679 mg.GX.L-1) were directly used for method development and factors which potentially affect the measurement were tested. The results showed a wide variety of morphological forms of AB stainable particles from the water samples. Remarkably, characteristics of the particles measured instantaneously differed significantly from those measured at the steady state, as a result of particle aggregation. Compared to traditional microscopic methods, this on-line method provided a simple, rapid and less labour-intensive analysis with particle morphological conservation and a large number of particle attributes. By overcoming the limitations from the formers, this FlowCAM based method would offer routine monitoring of these transparent particles from various freshwater sources. We then report the fate of different fractions of ABSM in Pao-Shan reservoir, Taiwan, in a one-year study (2013 to 2014) and an intensive study during phytoplankton bloom (2014). The interactions between the fractions, including AB stainable particles, particle and colloidal TEP (pTEP and cTEP), dissolved ABSM, and their relationship to other water quality parameters were analyzed. The results of the one-year study likely showed relationships of pTEP concentration to phytoplankton count and chl a, while in the intensive study, AB stainable particles abundance and pTEP concentration were correlated neither phytoplankton count nor chl a, but strongly positively correlated with some species’ abundance. The difference indicates that sampling frequency and phytoplankton composition should be addressed for studying the links between AB stained fractions and phytoplankton. The interaction between different fractions further suggests that the majority of AB stainable particles and pTEP would be directly generated by some phytoplankton species, whereas their abiotic generation by cTEP or dissolved ABSM may only have contributed partly to their formation. This differs from previous studies which generally posited that pTEP are mainly formed abiotically from dissolved precursors.