On-field monitoring is an important way to obtain data in marine environmental research. The ocean environmental conditions are harsh and complex, and there are many difficulties in seawater sample collecting, storing, and transporting. Therefore, the on-field and in-situ detections of chemical parameters have always been pursued by oceanographers and have become a research hot point in the seawater analysis field. In this review, the recent research progress of detection methods with molecular spectroscopy techniques for trace nutrients and metals in seawater was summarized. From the view of sensitivity and detection range, we discussed analytical techniques of trace nutrients (phosphate, nitrate, nitrate, and ammonium) and metals (iron, manganese, copper, and aluminum). It focused on methods of on-field and in-situ measures and development of optical methods such as spectrophotometry, fluorescence, and chemiluminescence, as well as the corresponding instruments that are most suitable in marine field observation. Examples of the application of these methods and relative instruments in land-and ship-based laboratories, ship-board underway monitoring, and long-term in-situ observation were presented. The key problems and possible solutions were analyzed, and the future development of the research field was proposed.
Keywords: metals; molecular spectroscopy; nutrients; seawaters; trace analysis.