Protein-like Fluorescence Intensities Research Articles

The sediment fluorescence–trophic level relationship: using water-extractable organic matter to assess past lake water quality in New Zealand

ABSTRACT Lake sediments are the physical remnants of past allochthonous and autochthonous carbon and mineral inputs and therefore have the potential to illuminate both past terrestrial carbon cycling and within-lake biological productivity. However, there are currently no robust, rapid, and inexpensive methods to chemically characterise the organic matter (OM) components in lake sediments, which limits their utility for reconstructing past soil carbon export trends or trophic status. This study explores the use of 3D excitation–emission matrix (EEM) fluorescence spectroscopy of water extractable dissolved organic matter (WEDOM) from lake sediments as a method for reconstructing past soil dissolved organic matter (DOM) export and past lake water quality. Using contemporary lake sediments from 11 New Zealand lakes, we demonstrate that both overall WEDOM fluorescence and protein-like fluorescence intensity are strong functions of trophic status across lakes. We also demonstrate that protein-like fluorescence is a function of sedimentary total nitrogen concentrations in palaeo-sediments from a pristine, high-altitude lake (Adelaide Tarn). This approach has applications in the evaluation of the trophic status of infrequently monitored lakes and in palaeolimnology.

Characterization of released metabolic organics during AOC analyses by P17 and NOX strains using 3-D fluorescent signals

Assimilable organic carbon (AOC) serves as an indicator of the biostability of drinking water distribution systems; however, the properties of the released organic metabolites by Pseudomonas fluorescens (P17) and Spirillum (NOX) used in AOC bioassays are seldom discussed. In this study, fluorescence excitation emission matrix (FEEM) was selected to characterize organic metabolites after substrate biotransformation and their divergences at different growth stages of both strains in AOC bioassay. Excellent correlation between ATP and colony-forming units (CFUs) was observed for both strains. The concentration of ATP per colony was six times higher in the P17 strain than in the NOX strain. A retarding phenomenon was observed for the NOX strain in the presence of high acetate-C content (100–150 μg acetate-C/L). The fluorescence wavelength peaks were wider for the protein-like substance released by the P17 strain than for those released by the NOX strain. However, fluorescent fulvic-like substances only existed in the NOX strain. Relative humus accumulation (RHA), the ratio of protein-like fluorescence intensity to humus-like fluorescence intensity, decreased in the P17 strain but substantially increased in the NOX strain in the logarithmic growth phase. RHA showed a descending trend for the P17 strain as compared to that of the NOX strain during the progress from logarithmic to stationary growth phase at three different acetate-C concentrations; however, the opposite was observed at 100 μg acetate-C/L, indicating that high acetate-C content may affect the properties of released organic matter from both strains.

Effects of acidification on the optical properties of dissolved organic matter from high and low arsenic groundwater and surface water

The optical properties of bulk dissolved organic matter (DOM) at ambient pH and upon acidification (pH ~2) by hydrochloric acid (HCl) or nitric acid (HNO3) were examined in groundwater and surface water samples from the Bengal Basin. Samples of shallow high arsenic (As) and deep low As groundwaters and surface waters from the same geographic area were collected and preserved with HCl and HNO3. The optical properties of groundwater samples responded to acidification differently than those of the surface water samples. The intensity of humic-like and protein-like fluorescence decreased by 47% and 80%, respectively, upon acidification with HCl in groundwater but remained unchanged in surface water samples. Similarly, the humification index (HIX) decreased only in surface waters (from 6.6 to 3.7) and remain unchanged in groundwaters upon HCl acidification. The absorbance at 254 nm (Abs254) was not affected by HCl acidification; however, HNO3 acidification increased Abs254 in groundwater (by 9-fold) as well as in surface water samples (by 3-fold), possibly due to inherent absorbance of HNO3 at 254 nm. Humic- and protein-like fluorescence intensities decreased by HNO3 acidification by 49% and 78% respectively, which may be attributed to aggregation losses and changes in the protonation states of amines, hydroxyls and carboxylic functional groups. Parallel factor (PARAFAC) analysis revealed a unique component that resulted from the acidification of samples with HNO3. The other fluorescence indices such as fluorescence index (FI) and freshness index (β:α) remained unchanged upon either type of acidification of surface water as well as groundwater samples. These results reflect the effects of pH perturbation in groundwater environments where DOC concentrations may be lower as compared to surface water environments and provide insights into the structural, molecular and reactive properties of DOM in these environments.

Analysis of Samples from Wastewater Treatment Plant and Receiving Waters Using EEM Fluorescence Spectroscopy

The samples from several treatment units in wastewater treatment plant (WWTP) and different sample sites of receiving waters were characterized using excitation-emission matrix (EEM) fluorescence spectroscopy. After analyzed by parallel factor analysis (PARAFAC) method, the EEM fluorescence spectra of the principal components and fluorescence intensity scores matrix were acquired. Results showed that protein-like and fulvic-like substances were the main components of the samples from the WWTP and the receiving water body. The intensity of protein-like fluorescence in the influent samples was rather strong, and those of the following samples decreased significantly. The protein-like fluorescence intensity of the samples was relatively weak from the upstream of receiving water body, while those of the samples increased significantly from the water body near the urban area. The protein-like fluorescence intensity of upstream samples of the WWTP disposal outlet was stronger than that of downstream in the receiving waters. The fluorescence intensity scores of protein-like substance could be correlated with the COD concentration of the samples and the correlation curves were established. The correlation coefficient of the WWTP samples was 0. 930 and that of receiving water body samples was 0.913. The protein-like fluorescence could be used to evaluate the organic pollution of the samples. This study will provide a new method to investigate the operation status of WWTP and corresponding effect on the receiving water body.

Study on DOM Fluorescence Characteristics and Coagulation Mechanism of Secondary Effluent in Wastewater Treatment Plant

In order to study the differences of dissolved organic matter (DOM) characteristics between the secondary effluent and the surface water, ultrafiltration (UF) was combined with three-dimensional excitation-emission matrix (EEM) spectroscopy to investigate the fluorescence characteristics of total DOM and different molecular weight fractions of them. Moreover, the DOM removal characteristics by coagulation were analyzed also under the respective optimal dosage of coagulant (PAC). The results showed that: DOM of secondary effluent contained four notable fluorescence peaks: humic acid-, fulvic acid-, aromatic protein- and soluble microbial product-like fluorophores, which were more than surface water. Coagulation was easy to remove macromolecules as humus, but the removal efficiency was not high enough for the relative small molecules as protein and microbial products. Fluorescence index (FI) indicated that secondary effluent after biotreatment were mainly from microbial sources. The correlation relationship between the humus-, protein-like fluorescence intensity and UV254 are strong in secondary effluent.

Molecular fluorescence analysis of rainwater: Effects of sample preservation

Very different filtration and preservation procedures may be found in the literature on the study of the rainwater dissolved organic fraction. Thus, the influence of sample filtration and preservation procedures on the fluorescence of rainwater dissolved organic matter (DOM) was studied in this work. Rainwater was filtered through different filters (quartz 0.22 μm or PVDF 0.45 μm) and excitation ( λ em = 415 nm) and synchronous (Δ λ = 70 nm) fluorescence spectra were obtained at the same day of collection, or after preservation by refrigeration (1–7 days) or by freezing (1–4 weeks). The excitation–emission matrix (EEM) spectra of rainwater showed six types of fluorescent bands: two corresponding to humic-like bands, and four resembling proteins. Then, the excitation and synchronous spectra were chosen in order to monitor changes in the humic-like and protein-like bands, respectively. The filtration procedures adopted in this work did not affect the fluorescence properties of the rainwater samples. However, these properties were differently preserved by refrigeration or freezing: after refrigeration, filtered rainwater maintained the original fluorescent properties for at least 4 days, while after freezing fluorescent properties were not always preserved since it occurred a decrease of protein-like fluorescence intensity.

Using Synchronous Fluorescence Technique as a Water Quality Monitoring Tool for an Urban River

The development of a monitoring tool for predicting water quality and tracing pollution sources are important for the management of sustainable aquatic ecosystems in urban areas. In this study, synchronous fluorescence technique was applied to 18 sampling sites of a typical urban watershed in Korea, some of which are directly affected by the effluent from a wastewater treatment plant (WWTP), to investigate the capability of the technique for biochemical oxygen demand (BOD) prediction and source discrimination. Sampling was conducted three times at the same sites during the low flow period between October and November, 2005. Protein-like fluorescence intensities of the samples showed a positive linear relationship with the BOD values (Spearman’s rho = 0.90, p < 0.0001). The BOD prediction capability was superior to other monitoring tools such as UV absorption and conductivity measurements particularly for the upstream sites from the WWTP, which ranged from 0.0 to 5.0 mg/l as BOD. The protein-like fluorescence and a ratio of protein-like/fulvic-like fluorescence were suggested as good fluorescence signatures to discriminate different sources of dissolved organic matter (DOM). The samples collected from four different DOM source regions including upstream sites from the WWTP, downstream sites, discharge from a reservoir, and headwater were distinguished from one another by varying ranges of the two selected fluorescence signatures. Our results suggest that the synchronous fluorescence technique has the potential to be developed into a real-time water quality management tool for the comprehensive monitoring of urban rivers.

Fluorescence characterization of dissolved organic matter in an urban river and its complexation with Hg(II)

Dissolved organic matter (DOM) in the Nanming River, an urban river in Guiyang City in SW China, and its complexation behavior with Hg(II) were investigated using fluorescence spectroscopy and the quenching titration technique. Three major fluorophores, two humic-like and one protein-like fluorescence, were observed in most of the DOM samples. Significant correlations were observed between the humic-like and protein-like fluorescence intensities, as well as, between them and other water quality parameters such as dissolved organic carbon, PO 4 3 - , chemical oxygen demand and NH 4 + concentrations, suggesting that agricultural and municipal wastewaters may be the source for both protein-like and humic-like fluorescence materials in the river. The fluorescence quenching titration resulted in similar values for the conditional stability constants for Hg(II) complexes with the humic-like and protein-like fluorophores, likely due to the dominance of Hg binding with O-containing function groups at the high Hg(II) concentrations used in the titration. Effects of Cl −, Ca 2+, Mg 2+ and Cu 2+ ions on the binding between Hg(II) and three different fluorophores were also studied. The fluorescence index from the Nanming River was further found to be controlled by pH and Hg(II), cautioning its use in discriminating the sources of DOM.

Protein‐like fluorescence intensity as a possible tool for determining river water quality

AbstractThe results of a comparison between chemical water quality determinants and river water fluorescence on the River Tyne, NE England, demonstrate that tryptophan‐like fluorescence intensity shows statistically significant relationships between nitrate, phosphate, ammonia, biochemical oxygen demand (BOD) and dissolved oxygen. Tryptophan‐like fluorescence intensity at the 280 nm excitation/350 nm emission wavelength fluorescence centre correlates with both phosphate (r = 0·80) and nitrate (r = 0·87), whereas tryptophan‐like fluorescence intensity at the 220 nm excitation/350 nm emission wavelength centre correlates with BOD (r = 0·85), ammonia (r = 0·70) and dissolved oxygen (r = −0·65). The strongest correlations are between tryptophan‐like fluorescence intensity and nitrate and phosphate, which in the Tyne catchment derive predominantly from point and diffuse source sewage inputs. The correlation between BOD and the tryptophan‐like fluorescence intensity suggests that this fluorescence centre is related to the bioavailable or labile dissolved organic matter pool. The weakest correlations are observed between tryptophan‐like fluorescence intensity and ammonia concentration and dissolved oxygen. The weaker correlation with ammonia is due to removal of the ammonia signal by wastewater treatment, and that with dissolved oxygen due to the natural aeration of the river such that this is not a good indicator of water quality. The observed correlations only hold true when treated sewage, sewerage overflows or cross connections, or agricultural organic pollutants dominate the water quality—this is not true for two sites where airport deicer (propylene glycol, which is non‐fluorescent) or landfill leachate (which contains high concentrations of humic and fulvic‐like fluorescent DOM) dominate the dissolved organic matter in the river. Mean annual tryptophan‐like fluorescence intensity agrees well with the General Water Quality Assessment as determined by the England and Wales environmental regulators, the Environment Agency. Copyright © 2004 John Wiley &amp; Sons, Ltd.

Characterization of dissolved organic matter from source to sea using fluorescence and absorbance spectroscopy

Dissolved organic matter fluorescence, absorbance and dissolved organic carbon were measured from source to sea in the River Tyne catchment, of ∼2935 km 2 and encompassing areas of contrasting land use. The catchment has three major tributaries: the North Tyne which has good water quality, high dissolved organic carbon concentrations and visible water colour from the high proportion of peat in its upper catchment; the South Tyne which has good water quality with typical riverine dissolved organic carbon concentrations and drains from limestone uplands; and the Derwent, a more urbanized catchment which is increasingly impacted by treated sewage effluent discharges towards its mouth. Thirty sample sites, 23 along the three main tributaries and seven within the estuary, were sampled on six occasions over the period 2002–2003. High absorbance at 340 nm and dissolved organic carbon concentration identify N Tyne waters due to the peaty headwaters, but no downstream trends in these parameters are observed in any of the tributaries, in contrast to the estuary where a rapid decrease is observed in both. Fluorescence in contrast demonstrated downstream trends in both intensity and wavelength, especially in the Derwent as it is increasingly impacted by anthropogenic dissolved organic matter. Elevated protein-like fluorescence intensity also fingerprints sewage effluent within the estuary. The absorbance coefficient at 340 nm was found to have the strongest correlation to dissolved organic carbon concentration, greater than all fluorescence intensity parameters measured. However, fluorescence analysis permits the source of the dissolved organic matter to be determined, and therefore has implications for understanding its fate in estuaries and the ocean.

Measurement of protein-like fluorescence in river and waste water using a handheld spectrophotometer

Protein-like fluorescence intensity in rivers increases with increasing anthropogenic DOM inputs from sewerage and farm wastes. Here, a portable luminescence spectrophotometer was used to investigate if this technology could be used to provide both field scientists with a rapid pollution monitoring tool and process control engineers with a portable waste water monitoring device, through the measurement of river and waste water tryptophan-like fluorescence from a range of rivers in NE England and from effluents from within two waste water treatment plants. The portable spectrophotometer determined that waste waters and sewerage effluents had the highest tryptophan-like fluorescence intensity, urban streams had an intermediate tryptophan-like fluorescence intensity, and the upstream river samples of good water quality the lowest tryptophan-like fluorescence intensity. Replicate samples demonstrated that fluorescence intensity is reproducible to ±20% for low fluorescence, ‘clean’ river water samples and ±5% for urban water and waste waters. Correlations between fluorescence measured by the portable spectrophotometer with a conventional bench machine were 0.91; (Spearman's rho, n=143), demonstrating that the portable spectrophotometer does correlate with tryptophan-like fluorescence intensity measured using the bench spectrophotometer.

Chemical characterization of protein-like fluorophores in DOM in relation to aromatic amino acids

A systematic survey of the protein-like fluorescence intensities was conducted at 11 stations along the 137°E transect from bay to oceanic areas in the northwestern Pacific using three-dimensional excitation emission matrix (3DEEM) spectroscopy and the concentrations of aromatic amino acids obtained by high-performance liquid chromatography (HPLC) in dissolved organic matter (DOM). The 3DEEM patterns of tyrosine-like and tryptophan-like peaks in protein-like fluorophores were variable across different marine environments. The tyrosine-like peak was observed at all stations and depths, while the tryptophan-like peak was only distinguishable as a clear peak in bay and coastal surface waters. These distribution patterns were similar to those of actual concentrations of tyrosine and tryptophan in total hydrolyzable amino acids (THAA) in DOM. Consequently, the tyrosine- and tryptophan-like fluorescence intensities were interpreted to be correlated to the concentrations of tyrosine and tryptophan, respectively, indicating that tyrosine and tryptophan were responsible for the protein-like fluorescence intensities of DOM. The protein-like fluorescence intensities were also correlated to the concentrations of THAA, suggesting that the dynamics of aromatic amino acids were similar to those of THAA. In addition, protein-like fluorescence intensities may be useful indicators as to the dynamics of not only aromatic amino acids but of THAA in bulk DOM as well. Comparison of the tyrosine- and tryptophan-like fluorescence intensities with the concentrations of aromatic amino acids and THAA suggests that the dissolved amino acids were components of relatively small peptides and not protein molecules.