Chromophoric dissolved organic matter influence correction of algal concentration measurements using three-dimensional fluorescence spectra

The characteristics of H6 against Microcystis aeruginosa

Algal bloom caused by Microcystis aeruginosa has always been the focus of attention; microbial algal control has the advantages of significant effect, low investment cost, and environmental friendliness; the use of microbial technology to inhibit the bloom has a broad prospect for development. In this study, a strain of Enterobacterium algicidal bacteria screened from a river was used to study the algicidal characteristics against Microcystis aeruginosa using SEM, 3-D EEM and zeta potential. The results showed that the optimal dosage (v/v) of the strain was 5% and the removal rate of algal cells was 70% after 7 days. When the algal density was OD680nm = 0.3, the removal rate of algal cells reached 83% after 7 days. In the pH range of 5 ~ 11, the removal rate of algal cells was 70 ~ 80% after 7 days. Algicidal bacteria H6 is mainly indirect algae lysis and is supplemented by direct algae lysis. Algicidal bacteria H6 removes algicidal substances by secreting high temperature resistant algicidal substances and algicidal products are humic acids. Algicidal bacterium H6 was a strain of Enterobacterium with good algicidal effect in a wide pH range, which enriched the bacterial resources in the control of cyanobacteria bloom in water. The high temperature resistance of the algae-soluble substance secreted by the algae-soluble substance provided convenience for the subsequent preparation and application of bacterial powder.

Simultaneous Absorbance and Fluorescence Measurements Using an Inlaid Microfluidic Approach

A novel microfluidic optical cell is presented that enables simultaneous measurement of both light absorbance and fluorescence on microlitre volumes of fluid. The chip design is based on an inlaid fabrication technique using clear and opaque poly(methyl methacrylate) or PMMA to create a 20.2 mm long optical cell. The inlaid approach allows fluid interrogation with minimal interference from external light over centimeter long path lengths. The performance of the optical cell is evaluated using a stable fluorescent dye: rhodamine B. Excellent linear relationships (R² > 0.99) are found for both absorbance and fluorescence over a 0.1-10 µM concentration range. Furthermore, the molar attenuation spectrum is accurately measured over the range 460-550 nm. The approach presented here is applicable to numerous colorimetric- or fluorescence-based assays and presents an important step in the development of multipurpose lab-on-chip sensors.

Evaluation of aliphatic/aromatic compounds and fluorophores in dissolved organic matter of contrasting natural waters by SEC-HPLC with multi-wavelength absorbance and fluorescence detections

The analytical high performance size exclusion liquid chromatography (SEC-HPLC) with multi-wavelength absorbance and fluorescence detections and fluorescence 3D-excitation/emission matrix (EEM) were used for the analysis of average molecular size (MS), molecular size distribution of aliphatic/aromatic compounds and fluorophores in dissolved organic matter (DOM) from Suwannee River (SRDOM) and two Karelian lakes (Vodoprovodnoe Lake - L1DOM and Onego Lake - L2DOM). The average MS of DOM samples varied in the order SRDOM > L1DOM > L2DOM. The absorbance ratios A250/A365 and A210/A254 have been used for the DOM samples characterization. The absorbance ratio A250/A365 provided significant information about average MS of the bulk aquatic DOMs but was not exactly correlated with the results of SEC-HPLC data. The absorbance ratio A210/A254 in combination with SEC was well correlated with the content of DOM aliphatic/aromatic compounds and could be used as an important water quality index to estimate the level of protein-like material in the aquatic DOM. Regardless of the origin (river or lakes), different geographical locations and different average MS of DOM, several similar types of humic-like SEC-separated fluorophores were found within the samples. In all DOM samples the decrease of the fluorophores emission maxima paralleled the decrease of their relative MS. The combination of SEC-HPLC with multi-wavelength fluorescence and absorbance detection and EEM analyses appears very useful for DOM characterization and for tracking of microbial activity resulting from anthropogenic and/or eutrophic impact in aquatic environments.