The equipment for time-resolved measurements of excitation-emission matrix of seawater fluorescence in natural conditions

摘要

Excitation-emission matrix (EEM) technique is widely used to study the properties of organic matter in seawater. Additional variations of the exciting radiation parameters (in addition to the wavelengths), such as duration and intensity, allow to get more spectral information about the object of research, and allow to identify some individual components or to study the dynamics of the molecular changes in the sample of analyzed liquid. One of the main limitations of the EEM is that usually necessary to carry out research in the laboratory on the specialized equipment. The paper describes the hardware system allowing carry out measurements in the field studies. The hardware system includes a set of light-emitted diodes (LEDs) working in the range from 245 to 600 ran, which produce sequential excitation fluorescence of the sample liquid, which is detected using a 32-channel photomultiplier tube (PMT). Number of LEDs can vary from 7 to 16. Through the use of multi-channel photomultiplier reached the required measurement sensitivity and efficiency measurement is less than 1 minute for full cycle. Minimum 4 channel in excitation range of 350-600 nm support the work of variable duration excitation pulses from microseconds to seconds. It makes possible to measure the fluorescence of the chlorophyll-a with closed or open reaction centers of phytoplankton cells. The use of multiple excitation radiation allows to activate various mechanisms of energy transfer in the photosynthetic apparatus of phytoplankton cells, improves measurement accuracy, reduces dependence on the variation in species composition and functional state of phytoplankton.