Unbiased Measurement of Phosphate and Phosphorus Speciation in Surface Waters

Two-dimensional ion chromatography tandem-mass spectrometric (2D-IC-MS/MS) method for the analysis of phosphorus compounds in soil

Investigations into soil organic phosphorus (Po) dynamics are instrumental in understanding the transformations and processes responsible for ecosystem productivity. However, quantitative analysis of Po in a soil environment is extremely challenging due to low target analyte concentrations and matrix interferences with chromatography and analysis. Consequently, a two-dimensional ion chromatography-tandem mass spectrometric (2D-IC-MS/MS) method was developed to estimate soil Po concentrations. The first dimension diverted early eluting anions to waste while preconcentrating P compounds in a trap column, followed by chromatographic separation and detection in the second dimension. Detection was done using a mass spectrometer, and quantification was performed using the multiple reaction monitoring scan (MRM) method. The linear range of the studied P compounds, mostly nucleotides, was 0.05-50 ng/mL. Most P compounds were detected and quantified in calcareous subsoil samples in the concentration ranges 0.70-51.78 ng/g. The developed method achieved chromatographic separation that allowed unambiguous identification of isobars/isomers and isotopologues contributing to interferences in MS detection. However, improvements to the extraction method and post-clean-up procedures are required due to the complexity of soil extract composition, extreme matrix effect and/or loss of analyte during preconcentration. The method is ideal for simultaneously analyzing P compounds from environmental samples to elucidate key components of the soil P dynamics.

Limitations of the molybdenum blue method for phosphate quantification in the presence of organophosphonates

Organophosphonates (OPs) are widely used as chelating agents in domestic and industrial applications. While regarded as hardly biodegradable, OPs can undergo abiotic transformation with phosphate (PO43-) as a main transformation product. As some OPs are suspected precursors of glyphosate in surface waters, their environmental fate is of current interest. Due to analytical challenges posed by quantification of individual OPs, monitoring PO43- formation is a widely used proxy to monitor OP transformations. The molybdenum blue (MB) method, employing UV/Vis spectroscopy, is frequently used for PO43- quantification due to its sensitivity and operational simplicity. However, while interference of certain inorganic ions is well-documented, the effects of OPs on the accuracy of the MB method remain unexplored. This study investigated the effects of six OPs, namely N-(phosphonomethyl)glycine (glyphosate), 1-hydroxyethylidene(1,1-diphosphonic acid) (HEDP), iminodi(methylene phosphonate) (IDMP), aminotris(methylene phosphonate) (ATMP), ethylenediaminetetra(methylene phosphonate) (EDTMP), and diethylenetriaminepenta(methylene phosphonate) (DTPMP). Spectral analysis of pure PO43- standards using the MB method exhibits two characteristic absorption maxima (λmax) at 710 and 880 nm. In the presence of OPs, a new λmax appears around 760 nm. This is accompanied by an increase in absorbance values at both 710 and 880 nm, leading to significant over-quantification of PO43- concentrations. Among the evaluated OPs, DTPMP exhibits the most substantial interference (PO43- over-quantification by up to 240%), while glyphosate causes minimal interference (≤ 20%). The effects are most pronounced at OPs:PO43- ratios ≥1. A case study simulating DTPMP transformation confirms PO43- over-quantification of up to 350%, revealing limitations of the MB method. Therefore, careful data evaluation and complementary analytical techniques for accurate PO43- measurements are indispensable in OP transformation research.

Weak interaction strategy enables enhanced selectivity and reusability of arginine-functionalized imprinted aerogel for phosphate adsorption

Efficient phosphate adsorption from eutrophic waters remains challenging, fundamentally due to inherent trade-off in common adsorbents: high-binding energy between adsorbent and phosphate compromises reusability while low-binding energy suppresses selectivity. Herein, an innovative arginine-functionalized imprinted aerogel (AFIA-1:4) was fabricated by click chemistry and imprinting modification for overcoming this trade-off through synergistic weak interactions. Results shown that AFIA-1:4 exhibited high adsorption capacity (Qmax of 40.65 mg/g, 30.44 % higher than phoslock), rapid kinetics (15 min), and broad pH applicability (3-11) at 2 mg P/L solution. Moreover, its selectivity coefficient ranged from 10 to 90 even with 15- to 125-fold excess interfering anions, surpassing common adsorbents. After 10 cycles, AFIA-1:4 still maintained 98.15 % regeneration rate with 99.14 % phosphate desorption. Characterizations and calculations confirmed core roles of multiple hydrogen bonds and shape screening in maintaining selectivity and reusability. These findings advanced development of next-generation of phosphate adsorbents, which contributed to sustainable prevention and management of eutrophication.

Metabolic, neurotoxic and immunotoxic effects of PFAAs and their mixtures on the proteome of the head kidney and plasma from rainbow trout (Oncorhynchus mykiss)

PFAAs (Perfluoroalkyl acids) are a class of bioaccumulative, persistent and ubiquitous environmental contaminants which primarily occupy the hydrosphere and its sediments. Currently, a paucity of toxicological information exists for short chain PFAAs and complex mixtures. In order to address these knowledge gaps, we performed a 3-week, aqueous exposure of rainbow trout to 3 different concentrations of a PFAA mixture (50, 100 and 500 ng/L) modeled after the composition determined in Lake Ontario. We conducted an additional set of exposures to individual PFAAs (25 nM each of PFOS (12,500 ng/L), PFOA (10,300 ng/L), PFBS (7500 ng/L) or PFBA (5300 ng/L) to evaluate differences in biological response across PFAA congeners. Untargeted proteomics and phosphorylated metabolomics were conducted on the blood plasma and head kidney tissue to evaluate biological response. Plasma proteomic responses to the mixtures revealed several unexpected outcomes including Similar proteomic profiles and biological processes as the PFOS exposure regime while being orders of magnitude lower in concentration and an atypical dose response in terms of the number of significantly altered proteins (FDR < 0.1). Biological pathway analysis revealed the low mixture, medium mixture and PFOS to significantly alter (FDR < 0.05) a number of processes including those involved in lipid metabolism, oxidative stress and the nervous system. We implicate plasma increases in PPARD and PPARG as being directly related to these biological processes as they are known to be important regulators in all 3 processes. In contrast to the blood plasma, the high mixture and PFOA exposure regimes caused the greatest change to the head kidney proteome, altering many proteins being involved in lipid metabolism, oxidative stress and inflammation. Our findings support the pleiotropic effect PFAAs have on aquatic organisms at environmentally relevant doses including those on PPAR signaling, metabolic dysregulation, immunotoxicity and neurotoxicity.

Measurements and analysis of nitrogen and phosphorus in oceans: Practice, frontiers, and insights

Nitrogen and phosphorus concentrations in oceans have been extensively studied, and advancements in associated disciplines have rapidly progressed, enabling the exploration of novel and previously challenging questions. A keyword analysis was conducted using the Scopus database to examine chronological trends and hotspots, offering comprehensive insights into the evolution of marine nitrogen and phosphorus research. For this purpose, author keyword networks were developed for the periods before 1990, 1990 to 2000, 2001 to 2011, and 2012 to 2022. Furthermore, analytical techniques employed in the recent decade to determine nitrogen and phosphorus concentrations in seawater were assessed for their applicability and limitations through a critical review of more than 50 journal articles. Taxonomy and nitrogen biogeochemistry were the prominent research interests for the first two periods, respectively, while stable isotopic tracking of nitrogen and phosphorus processes emerged as the dominant research focus for the last two decades. The integration of macroeconomic factors in research development and the chronological rise of interdisciplinary research were identified. Conventional analytical techniques such as spectrophotometry, colorimetry, fluorometry, and elemental analysis were noted, along with emerging techniques like remote sensing and microfluidic sensors.

Analysis of environmental pollutants using ion chromatography coupled with mass spectrometry: A review

The rise of emerging pollutants in the current environment and requirements of trace analysis in complex substrates pose challenges to modern analytical techniques. Ion chromatography coupled with mass spectrometry (IC-MS) is the preferred tool for analyzing emerging pollutants due to its excellent separation ability for polar and ionic compounds with small molecular weight and high detection sensitivity and selectivity. This paper reviews the progress of sample preparation and ion-exchange IC-MS methods in the analysis of several major categories of environmental polar and ionic pollutants including perchlorate, inorganic and organic phosphorus compounds, metalloids and heavy metals, polar pesticides, and disinfection by-products in past two decades. The comparison of various methods to reduce the influence of matrix effect and improve the accuracy and sensitivity of analysis are emphasized throughout the process from sample preparation to instrumental analysis. Furthermore, the human health risks of these pollutants in the environment with natural concentration levels in different environmental medias are also briefly discussed to raise public attention. Finally, the future challenges of IC-MS for analysis of environmental pollutants are briefly discussed.

Temporal Trends of Phosphorus in Urban Atmospheric Aerosols

Air particulate samples collected from a Canadian urban area station showed seasonal trend of the phosphorus with peak levels observed for April-June periods and levels not significantly changed between 2007 and 2015. The phosphorus measured as total phosphorus (TP) in digested aqueous extracts showed an exponential increase with daily temperature (R2=0.544, N=474), with the best correlation observed for the 2010 subset (R2=0.727, N=55). The temperature correlation was not observed with the total suspended particles (TSP). Longer dry periods during spring-summer months favored higher P level on aerosols. The temperature and precipitation pattern dependence indicate a possible climate change influence on the aerosol P levels. The unchanged yearly aerosol TP content does not directly reflect the dropping trend observed in surface water after 1990s from the same area during spring-summer periods.

Portable, stable, and sensitive assay to detect phosphate in water with gold nanoparticles (AuNPs) and dextran tablet

A novel and highly sensitive tablet-based colorimetric sensor is developed for the detection of phosphate (Pi) in drinking and surface water using mercaptoacetic acid-capped gold nanoparticles (MA-AuNPs). Characterization of AuNPs and MA-AuNPs was achieved by ultraviolet-visible (UV-Vis) spectroscopy, Fourier transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM) and Dynamic light scattering (DLS). The principle of this sensor is based on the aggregation and disaggregation mechanisms of AuNPs that result in a color change from blue to red due to the surface plasmon resonance effect, where europium ions (Eu³⁺) act as the aggregating agent. Herein, dextran is used to encapsulate the Eu³⁺ ions into a tablet format to make the detection system user friendly. Hence, the sensor only requires dissolving a Eu³⁺-dextran tablet into the water sample and subsequently adding MA-AuNPs for the colorimetric quantification of phosphate. This assay is very sensitive with a calculated detection limit of 0.3 μg L^-1 and an upper detection limit of 26 μg L^-1, while 10 μg L^-1 is the allowable limit of Pi in drinking water. A comparative study with a conventional Hach kit confirmed the accuracy of our sensor. Also, real water samples from river, lake, and tap sources were tested to examine the sensor's applicability towards commercialization. The assay did not interfere with common ions in water, thus being Pi-specific, and the performance of the assay was stable for up to at least three weeks. Overall, our new approach provides a simple, stable, rapid, low-cost and promising device for Pi detection in water.

Phosphorus-based metabolic pathway tracers in surface waters

Trophic status in surface waters has been mostly monitored by measuring soluble reactive phosphorus (SRP) and total phosphorus (TP). Additional to these common parameters, a two-dimensional ion chromatography mass spectrometry (2D-IC-MS) method was used to simultaneously measure soluble phosphate (Pi), pyrophosphate (PPi), and eleven phosphate-containing metabolites (P-metabolites) in Lake Ontario and its tributaries. From the additional P species, PPi, adenosine 5'-monophosphate (AMP), glucose 6-phosphate (G-P), D-fructose 6-phosphate (F-P), D-fructose 1,6-biphosphate (F-2P), D-ribulose 5-phosphate (R-P), D-ribulose 1,5-bisphosphate (R-2P), and D-(-)-3-phosphoglyceric acid (PGA) were detected and quantified in the lake and river samples. The additional multivariate statistical analysis identified similarities between samples collected at different locations. The presence of R-P, R-2P, and F-2P in Lake Ontario tributaries seems to be mainly related to the Calvin cycle, while the lack of all these three P-metabolites and higher PGA levels than G-P in Toronto Harbour samples seems to be the result of depleted Calvin cycle, pentose phosphate, and glycolysis metabolic pathways.

Effects of decabromodiphenyl ether on activity, abundance, and community composition of phosphorus mineralizing bacteria in eutrophic lake sediments

Polybrominated diphenyl ethers (PBDEs) are typical persistent organic pollutants (POPs) in the environment. However, little is known about their effects on phosphorus mineralizing bacteria (PMB) in eutrophic lake sediments, despite the critical role of PMB in phosphorus (P) biogeochemical cycling. In this study, we carried out a 60-day microcosm experiment to understand the effects of 2 and 20 mg kg^-1 dry weight decabromodiphenyl ether (BDE-209) on the activity, abundance, diversity, and community composition of PMB in the sediment of Taihu Lake, a typical eutrophic lake in China. The results showed that BDE-209 contamination, regardless of the contamination levels, significantly increased the orthophosphate concentration in overlying water and available phosphorus concentration in sediments on day 60. Such increases may be explained by the stimulatory effects of BDE-209 on alkaline phosphatase (ALP) activity and PMB abundance. Moreover, based on Miseq sequencing of the phoD gene encoding ALP, Actinobacteria was the dominant PMB phylum in all treatments, and BDE-209 significantly increased the diversity of PMB and altered their community composition. In particular, the relative abundances of some PMB genera such as Bradyrhizobium were increased significantly after 60 days of the High treatment. A co-occurrence network analysis further revealed that the high level of BDE-209 contamination strengthened the connectivity and interspecific co-operative relationships in the PMB community. These results will help us to understand the effects of POPs on P biogeochemical cycling in eutrophic lakes and the associated microbial mechanisms.