scholarly journals Complex interactions of in-stream dissolved organic matter and nutrient spiralling unravelled by Bayesian regression analysis

2021 ◽  
Vol 18 (10) ◽  
pp. 3103-3122
Author(s):  
Matthias Pucher ◽  
Peter Flödl ◽  
Daniel Graeber ◽  
Klaus Felsenstein ◽  
Thomas Hein ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Transport Processes ◽  
Bayesian Regression ◽  
Positive Interactions ◽  
Cow Dung ◽  
Complex Interactions ◽  
Fluorescence Measurements ◽  
Non Linear ◽  
Nutrient Spiralling

Abstract. Uptake and release patterns of dissolved organic matter (DOM) compounds and co-transported nutrients are entangled, and the current literature does not provide a consistent picture of the interactions between the retention processes of DOM fractions. We performed plateau addition experiments with five different complex DOM leachates in a small experimental stream impacted by diffuse agricultural pollution. The study used a wide range of DOM qualities by including leachates of cow dung, pig dung, corn leaves, leaves from trees, and whole nettle plants. We measured changes in nutrient and dissolved organic carbon (DOC) concentrations along the stream course and determined DOM fractions by fluorescence measurements and parallel factor (PARAFAC) decomposition. To assess the influences of hydrological transport processes, we used a 1D hydrodynamic model. We developed a non-linear Bayesian approach based on the nutrient spiralling concept, which we named the “interactions in nutrient spirals using Bayesian regression” (INSBIRE) approach. This approach can disentangle complex interactions of biotic and abiotic drivers of reactive solutes' uptake in multi-component DOM sources. It can show the variability of the uptake velocities and quantify their uncertainty distributions. Furthermore, previous knowledge of nutrient spiralling can be included in the model using prior probability distributions. We used INSBIRE to assess interactions of compound-specific DOM and nutrient spiralling metrics in our experiment. Bulk DOC uptake varied among sources, showing decreasing uptake velocities in the following order: corn > pig dung > leaves > nettles > cow dung. We found no correlations between bulk DOC uptake and the amounts of protein-like compounds or co-leached soluble reactive phosphorus (SRP). The fastest uptake was observed for SRP and the tryptophan-like component, while the other DOM components' uptake velocities more or less resembled that of the bulk DOC. Almost all DOM components showed a negative relationship between uptake and concentration, known as efficiency loss. Furthermore, we observed a few negative and (weak) positive interactions between the uptake and the concentration of different components, such as a decreased uptake of protein-like compounds at high concentrations of a high-molecular-weight humic-like compound. We also found an influence of the wetted width on the uptake of SRP and a microbially derived humic substance, which indicates the importance of the sediment–water interface for P and humic C cycling in the studied stream. Overall, we show that bulk DOC is a weak predictor of DOC uptake behaviour for complex DOM leachates. Individual DOM compound uptake, including co-leached nutrients, is controlled by both internal (quality-related) and external (environmental) factors within the same aquatic ecosystem. We conclude that the cycling of different C fractions and their mutual interaction with N and P uptake in streams is a complex, non-linear problem, which can only be assessed with advanced non-linear approaches, such as the presented INSBIRE approach.

scholarly journals Complex interactions of in-stream DOM and nutrient spiralling unravelled by Bayesian regression analysis

2020 ◽  
Author(s):  
Matthias Pucher ◽  
Peter Flödl ◽  
Daniel Graeber ◽  
Klaus Felsenstein ◽  
Thomas Hein ◽  
...  
Keyword(s):  
Nitrate Uptake ◽  
Soluble Reactive Phosphorus ◽  
Transport Processes ◽  
Bayesian Regression ◽  
Nutrient Concentrations ◽  
Small Stream ◽  
Fluorescence Measurements ◽  
Wide Range ◽  
Non Linear ◽  
Nutrient Spiralling

Abstract. Uptake and release patterns of dissolved organic matter (DOM) compounds and nutrients are entangled, and the current literature does not provide a consistent picture of the link between DOM composition, nutrient concentrations, and effects on their cycling. We performed two plateau addition experiments for each of five different, realistic, complex DOM leachates in a small stream, heavily enriched in nitrate but not phosphate or DOM due to diffuse agricultural pollution. By including cow and pig dung as well as corn, leaves and nettles leachates, the study used a wide range of different DOM qualities. We measured changes in nutrient concentrations and determined DOM fractions by fluorescence measurements and parallel factor (PARAFAC) decomposition. To assess influences from hydrological transport processes, we used a 1-D hydrodynamic model. We propose a non-linear Bayesian approach to the nutrient spiralling concept, the Interactions in Nutrient Spirals using BayesIan REgression (INSBIRE) approach. This approach can disentangle complex and interacting biotic and abiotic drivers in nutrient uptake metrics, show their variability and quantify their error distribution. Furthermore, previous knowledge on nutrient spiralling can be included in the model using prior probability distributions. We used INSBIRE to assess interactions of compound-specific DOM and nutrient spiralling metrics the data of our experiment. The uptake processes of different DOM fractions were linked to each other. We observed stimulating and dampening effects of DOM fractions on each other and the overall DOM uptake. We found saturation effects for dissolved organic carbon (concentration of C, DOC) uptake, as rising concentrations of a DOM fraction dampened its uptake. The degradation of a humic DOM component of terrestrial origin was stimulated by other DOM fractions, pointing to priming effects. We also found an influence of the wetted width on the uptake of soluble reactive phosphorus (SRP) and a microbially derived humic substance, which indicates the importance of the sediment-water interface for P and humic C cycling in the studied stream. Interestingly, we found no interactions between DOM uptake and nitrate or SRP concentrations, or any effect of the added DOM leachates on nitrate uptake, indicating that the increase in DOC concentrations and SRP concentrations were not sufficient to affect the relatively steady nitrate uptake during the experiments. Overall, we show that bulk DOC is a weak predictor of DOC uptake behaviour for complex DOM leachates and that individual DOM compound uptake, nitrate uptake and SRP uptake are controlled very differently within the same aquatic ecosystem. We also found effects of hydromorphology on the uptake of one humic fluorophore and SRP. We conclude that cycling of different C fractions, their interaction and interactions with N and P uptake in streams is a complex, non-linear problem, which can only be assessed with advanced non-linear approaches, such as we present with INSBIRE.

Complex interactions of in-stream DOM and nutrient spiralling unravelled by Bayesian regression analysis

2021 ◽  
Author(s):  
Matthias Pucher ◽  
Peter Flödl ◽  
Daniel Graeber ◽  
Klaus Felsenstein ◽  
Thomas Hein ◽  
...  
Keyword(s):  
Nutrient Uptake ◽  
Nutrient Dynamics ◽  
Gas Production ◽  
Transport Processes ◽  
Bayesian Regression ◽  
Nutrient Concentrations ◽  
Cow Dung ◽  
Small Stream ◽  
Fluorescence Measurements ◽  
Nutrient Spiralling

<p>The carbon cycle in aquatic environments is of high interest because of its effects on water quality and greenhouse gas production as well as its alteration through anthropogenic activities with unknown outcomes. Uptake and release of dissolved organic matter (DOM) compounds is depending on the molecular structure and is strongly linked to N and P dynamics. Current research has not fully revealed the complex patterns behind.</p><p>To investigate the interactions between DOM components, we performed ten plateau addition experiments with different, realistic, complex DOM leachates (cow dung, pig dung, corn, leaves and nettles) in a small stream. The DOM quality was determined by fluorescence measurements and parallel factor (PARAFAC) decomposition and the nutrient concentrations were measured at eleven consecutive points in the stream at plateau conditions. The hydrological transport processes were incorporated by using the results of a 1-D hydrodynamic model.</p><p>The nutrient spiralling concept and its application in nutrient dynamics is a valuable basis for the analysis of our data. However, we could not find a data analysis approach, that suited the nature of our questions and data. Based on previously observed nutrient uptake models, we extended the nutrient spiralling concept by additional non-linear terms to analyse interactions between different DOM components.</p><p>We developed the “Interactions in Nutrient Spirals using BayesIan REgression (INSBIRE)” approach to analyse DOM uptake and retention mechanism. This approach can disentangle complex and interacting biotic and abiotic drivers in nutrient uptake metrics, show their variability and quantify their error distribution. We successfully used INSBIRE to show DOM-compound-specific interactions and draw conclusions from the data of our experiment. The applicability of INSBIRE has still to be tested in other studies, but we see a high potential not only in DOM dynamics but any kind of solute dynamics where interactions are crucial.</p>

scholarly journals Impact of forest harvesting on water quality and fluorescence characteristics of dissolved organic matter in eastern Canadian Boreal Shield lakes in summer

2015 ◽  
Vol 12 (23) ◽  
pp. 6999-7011 ◽  
Author(s):  
P. Glaz ◽  
J.-P. Gagné ◽  
P. Archambault ◽  
P. Sirois ◽  
C. Nozais
Keyword(s):  
Water Quality ◽  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Forest Harvesting ◽  
Spectroscopic Techniques ◽  
Clear Cutting ◽  
Fluorescence Measurements ◽  
Fluorescence Characteristics ◽  
Boreal Shield ◽  
Shield Lakes

Abstract. Forestry activities in the Canadian Boreal region have increased in the last decades, raising concerns about their potential impact on aquatic ecosystems. Water quality and fluorescence characteristics of dissolved organic matter (DOM) were measured over a 3-year period in eight eastern Boreal Shield lakes: four lakes were studied before, 1 and 2 years after forest harvesting (perturbed lakes) and compared with four undisturbed reference lakes (unperturbed lakes) sampled at the same time. ANOVAs showed a significant increase in total phosphorus (TP) in perturbed lakes when the three sampling dates were considered and in DOC concentrations when considering 1 year before and 1 year after the perturbation only. At 1 year post-clear cutting DOC concentrations were about 15 % greater in the perturbed lakes at ~ 15 mgC L−1 compared to 12.5 mgC L−1 in the unperturbed lakes. In contrast, absorbance and fluorescence measurements showed that all metrics remained within narrow ranges compared to the range observed in natural waters, indicating that forest harvesting did not affect the nature of DOM characterized with spectroscopic techniques. These results confirm an impact of forestry activities 1 year after the perturbation. However, this effect seems to be mitigated 2 years after, indicating that the system shows high resilience and may be able to return to its original condition in terms of water quality parameters assessed in this study.

scholarly journals Technical note: Effects of iron(II) on fluorescence properties of dissolved organic matter at circumneutral pH

2020 ◽  
Author(s):  
Kun Jia ◽  
Cara C. Manning ◽  
Ashlee Jollymore ◽  
Roger D. Beckie
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Redox Status ◽  
Technical Note ◽  
Component Distribution ◽  
Quenching Effect ◽  
Parafac Model ◽  
Groundwater Samples ◽  
Non Linear ◽  
Parallel Factor

Abstract. Modern fluorescence spectroscopy methods, including excitation-emission matrix (EEMs) spectra parsed using parallel factor analysis (PARAFAC) statistical approaches, are widely used to characterize dissolved organic matter (DOM) pools. The effect of soluble reduced iron, Fe(II), on EEM spectra can be significant, but is difficult to quantitatively assign. In this study, we examine the effects of Fe(II) on the EEM spectra of groundwater samples from an anaerobic deltaic aquifer containing up to 300 mg/L Fe(II), located a few kilometers from the ocean, adjacent to the Fraser River in Richmond, British Columbia, Canada. We added varying quantities of Fe(II) into groundwater samples to evaluate Fe(II)-DOM interactions. Both the overall fluorescence intensity and the intensity of the primary peak, a humic-like substance at excitation/emission wavelengths 239/441–450 nm (Peak A), decreased by approximately 60 % as Fe(II) concentration increased from 1 to 306 mg/L. Furthermore, the quenching effect was non-linear and proportionally stronger at Fe(II) concentrations below 100 mg/L. This non-linear relationship suggests a static quenching mechanism. In addition, DOM fluorescence indices are substantially influenced by the Fe(II) concentration. With increasing Fe(II), the fluorescence index (FI) tends to shift to a more microbial-derived origin, and both the humidification index (HIX) and freshness index (FrI) indicate more freshly produced DOM. Nevertheless, the 13-component PARAFAC model showed that the component distribution was relatively insensitive to Fe(II) concentration, and thus, PARAFAC may be a reliable method for obtaining information about the DOM composition and its redox status in Fe(II)-rich waters. By characterizing the impacts of up to 300 mg/L Fe(II) on EEMs using groundwater from an aquifer which contains similar Fe(II) concentrations, we advance previous works which characterized impacts of lower Fe(II) concentrations (less than 2 mg/L) on EEMs.

scholarly journals In situ fluorescence measurements of dissolved organic matter: A review

2020 ◽  
Vol 699 ◽  
pp. 134361 ◽  
Author(s):  
Elfrida M. Carstea ◽  
Cristina L. Popa ◽  
Andy Baker ◽  
John Bridgeman
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Fluorescence Measurements

scholarly journals The optical characteristics and sources of chromophoric dissolved organic matter (CDOM) in seasonal snow of northwestern China

2018 ◽  
Author(s):  
Yue Zhou ◽  
Hui Wen ◽  
Jun Liu ◽  
Wei Pu ◽  
Qingcai Chen ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Chemical Species ◽  
Anthropogenic Pollution ◽  
Northwestern China ◽  
Chromophoric Dissolved Organic Matter ◽  
Seasonal Snow ◽  
The North ◽  
Fluorescence Measurements ◽  
Potential Sources

Abstract. Chromophoric dissolved organic matter (CDOM) plays an important role in the global carbon cycle and energy budget. A field campaign was conducted across northwestern China from January to February 2012, and surface seasonal snow samples were collected at 39 sites in Xinjiang and Qinghai provinces. Light-absorption measurements, fluorescence measurements and chemical analysis were conducted to investigate the optical properties and potential sources of CDOM in seasonal snow. The abundance of CDOM (the absorption coefficient at 280 nm, a280) and the spectral slope from 275 to 295 nm (S275–295) ranged from 0.15–10.57 m−1 and 0.0129–0.0389 nm−1, respectively. The highest average a280 (2.30±0.52 m−1) and lowest average S275–295 (0.0188±0.0015 nm−1) in Qinghai indicated that the snow CDOM in this region had strongly terrestrial characteristic. Relatively low regional average a280 values were found in sites located to the north of the Tianshan Mountains and northwestern Xinjiang along the border of China (0.93±0.68 m−1 and 0.80±0.62 m−1, respectively). Parallel factor analysis (PARAFAC) identified three types of chromophores that were attributed to two humic-like substances (HULIS, C1 and C2) and one protein-like material (C3). C1 was mainly from soil HULIS, while the potential sources of C2 were complex and included soil, microbial activities, anthropogenic pollution and biomass burning. The good relationship between a280 and the intensity of C1 (R2 = 0.938, p<0.001) indicated that the CDOM abundance in the surface snow across northwestern China was mainly controlled by terrestrial sources. In addition, the regional variations of sources for CDOM in snow were further assessed by the analysis of chemical species (e.g., soluble ions) and air mass backward trajectories combined with satellite fire locations.

Sign in / Sign up

Export Citation Format

Share Document