Progress in in-situ monitoring of low-cost phosphorus forms in lakes and their geochemical characteristics

China Instrument Network Instrument Development Phosphorus is widely recognized as a limiting nutrient that plays a critical role in determining the productivity of aquatic ecosystems and influencing the growth of algae. Understanding the biogeochemical behavior of phosphorus and its impact on ecological responses is essential for improving water quality and restoring ecosystems. However, most existing studies focus primarily on pentavalent phosphate (HPO₄²⁻), while neglecting the presence of other phosphorus species such as trivalent (P³⁺), monovalent (P⁺), and even negatively charged forms like P⁻. In recent years, an increasing number of studies have highlighted that these low-cost phosphorus forms are actually widespread in natural environments, and their redox processes may play a more significant role in maintaining ecosystem balance and elemental cycles than previously thought.

In-situ analysis technical process of low-cost phosphorus in the environment

The frequent occurrence of eutrophication in Chinese lakes often leads to large-scale hypoxia, which significantly alters the form and environmental behavior of phosphorus in water systems. Due to the low concentration, instability, and susceptibility to interference of these low-cost phosphorus species, traditional analytical methods struggle to accurately detect and characterize them. As a result, our current understanding of phosphorus speciation and its geochemical behavior—especially in eutrophic lakes—remains limited.

Recently, researchers led by Han Chao from the Nanjing Institute of Geography and Lakes, Chinese Academy of Sciences, have pioneered a new approach that combines in-situ sampling with advanced two-dimensional capillary trace analysis technology. This innovative method enables the simultaneous separation and online monitoring of various phosphorus forms in complex environmental matrices. It allows for the efficient purification and enrichment of ultra-trace phosphorus species and interfering substances, significantly enhancing detection sensitivity. This breakthrough enables more accurate reconstruction of low-cost phosphorus information in natural environments. Based on this technique, the team conducted detailed studies on the distribution and migration mechanisms of low-cost phosphorus in the anoxic zones of Lake Taihu, one of China's most eutrophic lakes. Through both laboratory simulations and field monitoring, they explored the geochemical characteristics and transformation dynamics of these phosphorus forms.

The findings were published in *Water Research* under the title "In situ sampling and speciation method for measuring dissolved phosphite at ultratrace concentrations in the natural environment." The research was supported by the National Natural Science Foundation of China, the Natural Science Foundation of Jiangsu Province, and the National Key Laboratory of Pollution Control and Resource Research.

(Original title: In-situ monitoring of low-temperature phosphorus forms in lakes and research on their geochemical characteristics)