Study And Application Of An Analyzer For 2-D Fe(?)Distribution In Sediment Pore Water Based On Ferrozine Coloration And CCD Sensor

As one of the important biogenic elements,iron(Fe)is involved in a variety of biogeochemical reactions.Iron exists in various chemical states in sediment pore waters.Therefore,the research on speciation,content and distribution of iron in the pore water of sediments is of great significance.The dominant species of iron in sediment pore water are dissolved Fe(?)and Fe(?).The current methods for determination of two-dimensional Fe(?)distribution in sediment pore water can in-situ collect samples,but the samples are still needed to be sent back to the laboratory for processing and analysis.During the processes of sample shipping and handling,Fe(?)could be easily oxidized or polluted to a certain extent.To solve the problems remained in the existing methods,a convenient,fast,high-resolution and in-situ method with the relative homemade analyzer for determination of two-dimensional Fe(?)distributions in sediment pore water was developed in this research.A gel technique similar to Diffusive Gradients in Thin-films Technique-like was used to concentrate and produce color compound with Fe(?)in pore water,and a small integrated digital imaging instrument was adapted to in-situ capture and store gel color images.In the laboratory the gel image was analyzed to obtain the Fe(?)data.The main research contents and results are summarized as follows:(1)A profiler,which could be inserted into sediment was constructed.A small handheld scanner was selected as the imaging instrument,driven by the synchronous belt structure with reciprocating linear motion.The gel was scanned every 75 seconds by the scanner,which was controlled by a control module with STM32F103C8T6 microcontroller as the core.The image was obtained and saved.Finally,a overall waterproof housing was designed and produced to hold the profiler.(2)Agarose cross-linked polyacrylamide gels and polyacrylamide gels impregnated C18 and ferrozine were used as diffusive phase and concentrating phase,respectively,which could in-situ accumulate Fe(?)and produce color Fe(?)compound.1 h was selected as the optimal time for the chromogenic reaction to obtain the gel image corresponding to various Fe(?)concentrations in pore water.The grayscale intensities of the gel images were acquired with Image-J software,and the calibration curves of Fe(?)concentration versus the grayscale intensities of gel image was established.(3)On the basis of previous research,by increasing the thickness of concentrating gel for holding more ferrozine,the up limit of measurement range had been increased from 100?mol/L to 200 ?mol/L.The preparation process of the gel was optimized.The relative standard deviation of grayscale intensities of different batch of gels was 9.4%.The recoveries of spiked Fe(?)standard at 10-75 ?mol/L level from pore water were in the range of 91%-110%.The salinity effect was examined and the results showed that the salinity had no significant influence on the determination results.The gel-imaging profiler integrated system and the method were successfully applied in the lotus pond in Tan Kah Kee College of Xiamen University,the beach at Jimei district,Xiamen City and the reservoir of Xiang'an campus of Xiamen University.The two-dimensional Fe(?)distributions in sediment pore water of the two places were obtained.