Colorimetric Chemical Differentiation and Detection of Phosphorus in Eutrophic and High Particulate Waters: Advantages of a New Monitoring Approach

Abstract

Phosphorus (P) is a key factor forcing eutrophication in limnic and marine systems, and all monitoring programs for water quality accordingly include P determinations. However, traditional monitoring does not allow an analysis of the different components involved in the P cycle taking place in the water column. Nonetheless, the implementation of measures addressing eutrophication requires a full understanding of the processes involved in the transformation and transport of P, in all its chemical forms. In this study, the P categories present in a river and its estuary in northern Germany, which discharge into the Baltic Sea, were characterized. Using the molybdenum blue method we found that the classification of P into the traditional fractions (DIP, DOP, POP) applied in the ocean cannot be applied to turbid waters such as rivers because interferences between the fractions seems to occur. Therefore a new nomenclature has been introduced. In addition to total phosphorus (TP) and dissolved molybdate-reactive phosphorus (DRP; previously referred to as inorganic phosphorus), dissolved non-molybdate-reactive phosphorus (DNP), particulate molybdatereactive phosphorus (PRP), and particulate non-molybdate-reactive phosphorus (PNP) were distinguished. The high spatial and temporal variations in the proportions of these forms with respect to the TP concentration well-demonstrate the complexity of the P cycle and the involved P fractions and emphasize the need for expanded monitoring approach. The potential of eutrophication could be underestimated if not all P categories were considered. With the new operational nomenclature the common and standardized molybdenum blue reaction could be used to implement the analysis of various P components into regular monitoring programs.

Turning Image Sensors into Position and Time Sensitive Quantitative Colorimetric Data Sources with the Aid of Novel Image Processing/Analysis Software

“…Colorimetric quantification and dynamic analysis of various properties of matter, including chemical properties such as pH value, can be done through image sensor arrays. Wise use of image sensors is necessary, as machine vision will allow advances in many different fields [ 12 , 13 , 14 , 15 , 16 , 17 , 18 ]. The image information can be used as inputs for machine learning, internet of things (IoT), and artificial intelligence (AI).…”

Bioavailability of Various Phosphorus Fractions and Their Seasonality in a Eutrophic Estuary in the Southern Baltic Sea – A Laboratory Approach

“…In addition to TP, four P fractions (DRP, DNP, PRP, and PNP) were measured. The reason for the extension of the P analysis from the traditionally monitored TP and DRP was the large difference between these fractions due to the higher amount of particulate matter in shallow eutrophic waters (Felgentreu et al, 2018). The P fractions were categorized using the adapted nomenclature based on their reactivity with molybdenum blue.…”

“…The dissolved and particulate P were differentiated via filtration (GF/F-filter, retention range 0.7 µm) of the water samples, and an analysis was performed for the original sample and the filtrate (for dissolved fractions). The particulate fractions were calculated as the difference between the sample and the filtrate (Felgentreu et al, 2018).…”

“…Consistent with the negative correlation between the total particulate C and DNP in the "1.2 µm" treatment (Spearman: 0.38; p ≤ 0.005), the transformation of DNP indicates that DNP is mostly taken up by bacteria, likely heterotrophic bacteria (Figure 4), which transform DNP into PNP or DRP. Based on the low concentrations of PRP (Supplementary Material 2), which are often close to the detection limit (0.07 µM according to Felgentreu et al, 2018), approximately 100% of PRP was used (Supplementary Material 6). The exceptions are in the "1.2 µm" treatment in March and September.…”

“…DIP as well as a small but unknown amount of labile organic P is measured (Jarvie et al, 2002). To prevent overestimation, the traditional terms for the P fractions, namely, DIP, dissolved organic P (DOP), particulate inorganic P (PIP), and particulate organic P (POP), were changed based on their analytical behavior (Felgentreu et al, 2018) into dissolved molybdate-reactive P (DRP; similar to DIP), dissolved non-molybdate-reactive P (DNP; similar to DOP), particulate molybdate-reactive P (PRP; similar to PIP), and particulate nonmolybdate-reactive P (PNP; similar to POP). The determination of these fractions and their respective bioavailability allow a more effective estimation of the eutrophication potential.…”