Search

The capacity of an artificial recharge field to alter organic matter and the bacterial flora of surface water was assessed by following changes in bacterial communities and composition of natural organic matter (NOM) over the first meter of infiltration depth. The sampling strategy applied in this study ensured that water samples consisted only of infiltrated water, excluding natural groundwater. Water was sampled at 50 and 100 cm below the surface of an infiltration basin divided into two halves; one side was dried and frozen and one was infiltrating water during the winter period prior to the sampling period. Bacterial cell counts, proportions of intact cells and community fingerprints were determined by flow cytometry, and NOM was characterized using total organic carbon (TOC), UV254 nm-absorbance (UVA) and fluorescence spectroscopy. Around 40% of the NOM was removed after only 50 cm. Protein-like components were reduced to a larger extent (45–50%) than the humic-like components (25%), suggesting removal of mostly biodegradable fractions of NOM. After only 50 cm of infiltration, about 99% total cell count (TCC) was removed. The flow cytometric data revealed that the bacterial communities collected after infiltration from the basin area that had been dried and frozen were more similar to those in the raw water. This suggests that drying and freezing the basin negatively impacted its treatment capacity. The results from this study highlight the importance of a well-developed biofilm and unsaturated zone for artificial recharge.

Despite our growing understanding of the global carbon cycle, scientific consensus on the drivers and mechanisms that control dissolved organic carbon (DOC) turnover in aquatic systems is lacking, hampered by the mismatch between research that approaches DOC reactivity from either intrinsic (inherent chemical properties) or extrinsic (environmental context) perspectives. Here we propose a conceptual view of DOC reactivity in which the combination of intrinsic and extrinsic factors controls turnover rates and determines which reactions will occur. We review three major types of reactions (biological, photochemical, and flocculation) from an intrinsic chemical perspective and further define the environmental features that modulate the expression of chemically inherent reactivity potential. Finally, we propose hypotheses of how extrinsic and intrinsic factors together shape patterns in DOC turnover across the land-to-ocean continuum, underscoring that there is no intrinsic DOC reactivity without environmental context. By acknowledging the intrinsic–extrinsic control duality, our framework intends to foster improved modeling of DOC reactivity and its impact on ecosystem services.

Seasonal variability in the removal of dissolved organic matter (DOM) by drinking water biological activated carbon (BAC) filters is often attributed to temperature changes. However, it can be rather difficult to directly relate temperature to treatment efficiency at full scale due to seasonal variations in other influential parameters like DOM concentration and character, and microbial activity. Furthermore, processes in BAC filters include adsorption, desorption and biodegradation within biofilms while each respond differently to temperature. This study aimed to decouple these processes by studying the removal of various DOM fractions from coagulated and settled drinking water when in contact with aged (>3 years) BAC filter material at different water temperatures. DOM removal was measured as changes in dissolved organic carbon (DOC), ultraviolet absorbance at 254 nm (UV254) and fluorescence. Under the particular experimental conditions there was little evidence of biological removal; instead, removal of DOM fractions emitting at longer wavelengths (“humic-like”, >430 nm) was consistent with chemisorption, removal of DOM emitting at intermediate wavelengths (“humic-like”, 390–420 nm) was consistent with physisorption, and multiple mechanisms were indicated for “protein-like” (

Samples from fifty-five surface water resources and twenty-five drinking water treatment plants in Europe, Africa, Asia, and USA were used to analyse the fluorescence composition of global surface waters and predict aromaticity and treatability from fluorescence excitation emission matrices. Nine underlying fluorescence components were identified in the dataset using parallel factor analysis (PARAFAC) and differences in aromaticity and treatability could be predicted from ratios between components H

Advancing our understanding of the behaviour of dissolved organic matter (DOM) in aquatic environments necessitates efforts to combine complementary analytical data sets. However, some analytical measurements require sample pre-treatment, while others are carried out on bulk water samples, and it remains unclear if the resulting data sets can be compared. Here, we investigated the impact of solid-phase extraction with PPL resins on DOM optical properties. In samples from contrasting Arctic fjords, extraction efficiencies based on optical properties varied spectrally with averages between 31 ± 13% at 411 nm and 40 ± 12% at 363 nm for chromophoric DOM. Similarly, the extraction efficiency for specific fluorescence components varied between 37 ± 16% and 58 ± 18%. Solid-phase extraction also decreased S275–295, fluorescence index, and the freshness index, but increased S350–400, and apparent fluorescence quantum yields, indicating that the extraction process was qualitatively selective. Six fluorescence components identified independently in bulk water samples and extracted DOM using parallel factor analysis exhibited different behaviours. Three had identical spectral properties before and after extraction, although their extraction efficiencies varied with water mass characteristics and DOM composition, whereas three other components appeared to change after extraction. With the exception of one fluorescence component, the dynamics of optical properties in bulk water samples were not accurately reflected by DOM extracts. These results indicate that solid-phase extraction imparts a qualitative selectivity that leads to the homogenization of DOM extracts relative to their original samples. Efforts to integrate chemical information from different analytical methods should prioritize comparisons of measurements obtained on the same samples.

A study was conductedat a water treatment plant to optimize parallelrapid gravity biofilters for dissolved organic matter (DOM) removal.The biofilters treat urban and agriculturally impacted river water using a commercial non-adsorptive, expanded-clay filter medium. The study aimed to locate the optimal operating conditions via experimental manipulation of the biofilter empty bed contact time (EBCT) during full-scale operation at the plant. During a two-month experiment, contact times in four parallel biofilters were switched to and maintained at 15, 30, 50, and 80 min by manipulating the hydraulic loading on each filter. The removal efficiency of organic matter fractions increased with EBCT for dissolved organic carbon (DOC) and microbial humic-like (F290/420) and protein-like (F280/340) fluorescent organic matter. Other DOM fractions were largely unaffected by biofiltration,or at slightly higher concentrations in the effluent. Protein-like fluorescence is associated with labile organic matter fractions, which are known to be removed poorly by drinking water treatment barriers apart from biological filters. The results suggest that long contact times (>30 min) have advantages for the operation of some biological filters, especially if placed ahead of barriers that are sensitive to biofouling, e.g., membranes.

Despite the numerous studies that have investigated the occurrence and fate of plastic particles in the environment, only a limited effort has been devoted toward exploring the characteristics of dissolved organic matter (DOM) leached from microplastics. In this study, using excitation emission matrix-parallel factor analysis (EEM-PARAFAC), we explored the fluorescence signatures of plastic-derived DOM from commonly used plastic materials, which included two polymers (polyvinyl chloride (PVC) and polystyrene (PS)), two additives (diethylhexyl phthalate (DEHP) and bisphenol A (BPA)), and two commercial plastics. The exposure of the selected plastics to UV light facilitated the leaching of DOM measured in terms of dissolved organic carbon and fluorescence intensity. Four fluorescent components were identified, which included three protein/phenol-like components (C1, C3, and C4) and one humic-like component (C2). The C1 and C4 components were highly correlated with the amounts of DOM leached from DEHP and BPA, respectively, under both leaching conditions, while both C2 and C4 presented good correlations with the DOM leached from polymers under UV light. The C4 may serve as a good fluorescence proxy for DOM leached from BPA or BPA-containing plastics. This study highlights the overlooked issue of plastic-derived DOM leaching into the aquatic environment through optical characterization.

Dissolved organic matter (DOM) in aquatic environments forms a vast reservoir of carbon present as a complex super-mixture of compounds. An efficient approach to tracking the production and removal of specific DOM fractions is needed across disciplines, for purposes that range from improving global carbon budgets to optimising water treatment in engineered systems. Although widely used to study DOM, fluorescence spectroscopy has yet to deliver specific fractions with known spectral properties and predictable distributions. Here, we mathematically isolate four visible-wavelength fluorescent fractions in samples from contrasting lake, river, and ocean environments. Using parallel factor analysis (PARAFAC), we show that most measured fluorescence in environmental samples can be explained by ubiquitous spectra with nearly stable optical properties and semi-labile photodegradation rate constants over environmental pH gradients. Sample extraction changed bulk fluorescence spectra but not the number or shape of underlying PARAFAC components, while photobleaching preferentially removed the two longest-wavelength components. New approaches to analysing fluorescence datasets incorporating these findings should improve the interpretation of DOM fluorescence and increase its utility for tracing organic matter biogeochemistry in aquatic systems.

There is a trend of increasing natural organic matter (NOM) in raw drinking waters of Nordic countries due to climate change. Seasonal deterioration in NOM quality imparts challenges for delivering a consistently high drinking water quality. In this study, a simple and cost effective operational strategy was investigated that improved short-term NOM removal in a full-scale treatment plant. Three granular activated carbon (GAC) media biofilters were modified by replacing a small fraction of saturated filter media with new media. Relative to replacing the entire biofilter media, this approach required lower capital cost and shorter downtime, and maintained conditions for biological filter functioning. NOM removal efficiencies were compared in modified versus unmodified (reference) filters using online UV absorbance, and offline fluorescence and dissolved organic carbon measurements. The modified biofilters showed improved organic matter removal lasting for at least four weeks. Partial replenishment of GAC in full-scale biofilters may be a useful and sustainable operational strategy for coping with temporarily high NOM loads in raw waters that might otherwise cause water quality problems.

The spectra responsible for natural dissolved organic matter (DOM) fluorescence in 90 peer-reviewed studies have been compared using new similarity metrics. Numerous spectra cluster in specific wavelength regions. The emerging patterns suggest that most fluorescence spectra are not tied to biogeochemical origin, but exist across a wide range of different environments.

Investigating the biogeochemistry of dissolved organic matter (DOM) requires the synthesis of data from several complementary analytical techniques. The traditional approach to data synthesis is to search for correlations between measurements made on the same sample using different instruments. In contrast, data fusion simultaneously decomposes data from multiple instruments into the underlying shared and unshared components. Here, Advanced Coupled Matrix and Tensor Factorization (ACMTF) was used to identify the molecular fingerprint of DOM fluorescence fractions in Arctic fjords. ACMTF explained 99.84% of the variability with six fully shared components. Individual molecular formulas were linked to multiple fluorescence components and vice versa. Molecular fingerprints differed in diversity and oceanographic patterns, suggesting a link to the biogeochemical sources and diagenetic state of DOM. The fingerprints obtained through ACMTF were more specific compared to traditional correlation analysis and yielded greater compositional insight. Multivariate data fusion aligns extremely complex, heterogeneous DOM data sets and thus facilitates a more holistic understanding of DOM biogeochemistry.

Dissolved organic matter (DOM) is a complex pool of compounds with a key role in the global carbon cycle. To understand its role in natural and engineered systems, efficient approaches are necessary for tracking DOM quality and quantity. Fluorescence spectroscopy combined with parallel factor analysis (PARAFAC) is very widely used to identify and quantify different fractions of DOM as proxies of DOM source, concentration and biogeochemical processing. A major limitation of the PARAFAC approach is the requirement for a large data set containing many variable samples in which the fractions vary independently. This severely curtails the possibilities to study fluorescence composition and behavior in small or unique datasets. Herein, we present a simple and inexpensive experimental procedure that makes it possible to mathematically decompose a small dataset containing only highly-correlated fluorescent fractions. The approach, which uses widely-available commercial extraction sorbents and previously established protocols to expand the original dataset and inject the missing chemical variability, can be widely implemented at low cost. A demonstration of the procedure shows how a robust six-component PARAFAC model can be extracted from even a river-water dataset with only five bulk samples. Widespread adoption of the procedure for analyzing small fluorescence datasets is needed to confirm the suspected ubiquity of certain DOM fluorescence fractions and to create a shared inventory of ubiquitous components. Such an inventory could greatly simplify and improve the use of fluorescence as a tool to investigate biogeochemical processing of DOM in diverse water sources.

Drinking water lakes are threatened globally and therefore in need of protection. To date, few studies have been carried out to investigate how the composition and dynamics of chromophoric dissolved organic matter (CDOM) in drinking water lakes are influenced by inflow rate. Such CDOM can lead to unpleasant taste and odor of the water and produce undesirable disinfection byproducts during drinking water treatment. We studied the drinking water Lake Qiandao, China, and found that the concentrations of suspended particulate matter (SPM) in the lake increased significantly with inflow rate (p 0.001). Similarly, close relationships between inflow rate and the CDOM absorption coefficient at 350 nm a(350) and with terrestrial humic-like fluorescence C3 and a negative relationship between inflow rate and the first principal component (PC1) scores, which, in turn, were negatively related to the concentrations and relative molecular size of CDOM (p 0.001), i.e. the concentration and molecular size of CDOM entering the lake increased proportionately with inflow rate. Furthermore, stable isotopes (δD and δ(18)O) were depleted in the upstream river mouth relative to downstream remaining lake regions, substantiating that riverine CDOM entering the lake was probably driven by inflow rate. This was further underpinned by remarkably higher mean chlorophyll-a and in situ measured terrestrial CDOM fluorescence (365/480 nm) and apparent oxygen utilization (AOU), and notably lower mean PC1 and CDOM spectral slope (S275-295) recorded in the upstream river mouth than in the downstream main lake area. Strong negative correlations between inflow rate and a(250):a(365), S275-295, and the spectral slope ratio (SR) implied that CDOM input to the lake in rainy period was dominated by larger organic molecules with a more humic-like character. Rainy period, especially rainstorm events, therefore poses a risk to drinking water safety and requires higher removal efficiency of CDOM during drinking water treatment processes.

The roles of dissolved organic matter (DOM) in microbial processes and nutrient cycles depend on its composition, which requires detailed measurements and analyses. We introduce a package for R, called staRdom (&ldquo, spectroscopic analysis of DOM in R&rdquo, ), to analyze DOM spectroscopic data (absorbance and fluorescence), which is key to deliver fast insight into DOM composition of many samples. staRdom provides functions that standardize data preparation and analysis of spectroscopic data and are inspired by practical work. The user can perform blank subtraction, dilution correction, Raman normalization, scatter removal and interpolation, and fluorescence normalization. The software performs parallel factor analysis (PARAFAC) of excitation&ndash, emission matrices (EEMs), including peak picking of EEMs, and calculates fluorescence indices, absorbance indices, and absorbance slope indices from EEMs and absorbance spectra. A comparison between PARAFAC solutions by staRdom in R compared with drEEM in MATLAB showed nearly identical solutions for most datasets, although different convergence criteria are needed to obtain similar results and interpolation of missing data is important when working with staRdom. In conclusion, staRdom offers the opportunity for standardized multivariate decomposition of spectroscopic data without requiring software licensing fees and presuming only basic R knowledge.

Molecular size plays an important role in dissolved organic matter (DOM) biogeochemistry, but its relationship with the fluorescent fraction of DOM (FDOM) remains poorly resolved. Here high-performance size exclusion chromatography (HPSEC) was coupled to fluorescence emission-excitation (EEM) spectroscopy in full spectral (60 emission and 34 excitation wavelengths) and chromatographic resolution (

Treated drinking water may become contaminated while travelling in the distribution system on the way to consumers. Elevated dissolved organic matter (DOM) at the tap relative to the water leaving the treatment plant is a potential indicator of contamination, and can be measured sensitively, inexpensively and potentially on-line via fluorescence and absorbance spectroscopy. Detecting elevated DOM requires potential contamination events to be distinguished from natural fluctuations in the system, but how much natural variation to expect in a stable distribution system is unknown. In this study, relationships between DOM optical properties, microbial indicator organisms and trace elements were investigated for households connected to a biologically-stable drinking water distribution system. Across the network, humic-like fluorescence intensities showed limited variation (RSD = 3.5-4.4%), with half of measured variation explained by interactions with copper. After accounting for quenching by copper, fluorescence provided a very stable background signal (RSD

Odour is an important aspect of systems for human and agricultural waste management and many technologies are developed with the sole purpose of reducing odour. Compared with greenhouse gas assessment and the assessment of toxicity, odour assessment has received little attention in the life cycle assessment (LCA) community. This article aims to redress this. Firstly, a framework for the assessment of odour impacts in LCA was developed considering the classical LCA framework of emissions, midpoint and endpoint indicators. This suggested that an odour footprint midpoint indicator was worth striving for. An approach to calculating an areal indicator we call “odour footprint”, which considers the odour detection threshold, the diffusion rate and the kinetics of degradation of odourants, was implemented in MATLAB. We demonstrated the use of the characterisation factors we calculated in a case study based on odour removal technology applied to a pig barn. We produced a list of 33 linear characterisation factors based on hydrogen sulphide equivalents, analogous to the linear carbon dioxide equivalency factors in use in carbon footprinting, or the dichlorobenzene equivalency factors developed for assessment of toxic impacts in LCA. Like the latter, this odour footprint method does not take local populations and exposure pathway analysis into account—its intent is not to assess regulatory compliance or detailed design. The case study showed that despite the need for materials and energy, large factor reductions in odour footprint and eutrophication potential were achieved at the cost of a smaller factor increase in greenhouse emissions. The odour footprint method is proposed as an improvement on the established midpoint method for odour assessment in LCA. Unlike it, the method presented here considers the persistence of odourants. Over time, we hope to increase the number of characterised odourants, enabling analysts to perform simple site-generic LCA on systems with odourant emissions.

Non-methane volatile organic compounds (NMVOCs) emitted from mechanically ventilated poultry sheds in similar stages (32-36d) of broiler production were measured by thermal desorption-gas chromatography/mass spectrometry (TD-GC/MS), then identified using parallel factor analysis (PARAFAC2) and the NIST11 database. Calibration models predicting odor measured by dilution olfactometry from NMVOC concentrations via orthogonal projection to latent structures (O-PLS) made good predictions (Rp2=0.83-0.87, RMSEp=137-175OU) using one to eight NMVOCs with either one or two latent variables representing odor concentration and character, respectively. Similar changes in odorant composition were observed in each sampling campaign, with samples collected early in the day more odorous and more sulfurous than samples collected later in the day. High litter moisture favored sulfur-containing odorants over alcohols, aldehydes and ketones but had little bearing on perceived odor, whereas high bird density favored alcohols, aldehydes and ketones over sulfur-containing odorants. Eight VOCs that were important predictors of odor across all sheds in order of decreasing importance were dimethyl sulfide (DMS), dimethyl trisulfide (DMTS), 2-3 butanedione, 3-methyl-butanal, 1-butanol, 3-methyl-1-butanol, acetoin, and 2-butanone. Four additional NMVOCs also influenced perceived odor although less predictably; these were n-hexane, 2-butanol, dimethyl disulfide (DMDS), and 1-octen-3-ol. All of the odorants are associated with microbial or fungal activity in the litter and manure, except n-hexane, which may originate from hexane-extracted soybean meal in the chicken feed. The organosulfides measured in this study may have arisen from the field sites as well as from the degradation of thiols captured on sorbent tubes during analysis by TD-GC/MS. © 2013 Elsevier Ltd.

The fluorescence of dissolved organic matter (DOM) is suppressed by a phenomenon of self-quenching known as the inner filter effect (IFE). Despite widespread use of fluorescence to characterize DOM in surface waters, the advantages and constraints of IFE correction are poorly defined. We assessed the effectiveness of a commonly used absorbance-based approach (ABA), and a recently proposed controlled dilution approach (CDA) to correct for IFE. Linearity between corrected fluorescence and total absorbance (ATotal; the sum of absorbance at excitation and emission wavelengths) across the full excitation-emission matrix (EEM) in dilution series of four samples indicated both ABA and CDA were effective to an absorbance of at least 1.5 in a 1 cm cell, regardless of wavelength positioning. In regions of the EEMs where signal to background noise (S/N) was low, CDA correction resulted in more variability than ABA correction. From the ABA algorithm, the onset of significant IFE (>5%) occurs when absorbance exceeds 0.042. In these cases, IFE correction is required, which was the case for the vast majority (97%) of lakes in a nationwide survey (n= 554). For highly absorbing samples, undesirably large dilution factors would be necessary to reduce absorbance below 0.042. For rare EEMs with ATotal > 1.5 (3.0% of the lakes in the Swedish survey), a 2-fold dilution is recommended followed by ABA or CDA correction. This study shows that for the vast majority of natural DOM samples the most commonly applied ABA algorithm provides adequate correction without prior dilution. © 2013, by the American Society of Limnology and Oceanography, Inc.

To minimize the risk of biological invasions associated with commercial shipping, vessels are required to conduct ballast water exchange (BWE)≤200 nautical miles offshore when arriving in the US from foreign ports, and some states require coastal BWE≤50 miles offshore along domestic routes. Previous research suggests that the intensity of fluorescent dissolved organic matter (fDOM) can be used to verify whether BWE was implemented. This study examined seasonal and spatial variability of fDOM in Pacific rim ports and the adjacent seas, using the North American coast as a model system to test whether regional fluorescence intensity thresholds consistently distinguish port sites from coastal and oceanic sites at increasing distances from shore. Over 2000 samples from major port systems on the US Pacific coast and along offshore (perpendicular) and alongshore (parallel) transects were analyzed. Overall, humic fDOM fluorescence intensity (C3*=370/494nm) effectively discriminated port versus oceanic sites located further than 100. miles from shore, but discriminated only a subset of coastal versus oceanic sources within the northeastern Pacific. Data from additional global ports are needed to predict the frequency of false positive or false negative ballast source determinations using fDOM for foreign vessel traffic. © 2012 Elsevier B.V.

Fluorescence by naturally occurring dissolved organic matter (FDOM) is a sensitive indicator of ballast water source, with high FDOM in coastal ballast water decreasing typically dramatically when replaced by oceanic seawater during ballast water exchange. In this study, FDOM was measured in 92 ships arriving at Pacific ports on the US west coast and in New Zealand, and used to assess their compliance with ballast water regulations that required 95% replacement of port water to minimize invasive species risks. Fluorescence in many ships that reported ballast water exchange was significantly higher than is usual for oceanic seawater, and in several cases, significantly higher than in other ships with similar provenance and ballast water management. Pre-exchange source port conditions represented the largest source of uncertainty in the analysis, because residual coastal FDOM when highly fluorescent can significantly influence the fluorescence signature of exchanged ballast water. A meta-analysis comparing the intensities of FDOM in un-exchanged ballast tanks with calculated pre-exchange intensities assuming that ships all correctly implemented and reported ballast water exchange revealed notable discrepancies. Thus, the incidence of high-FDOM port waters was seven times lower in reality than would be expected on the basis of these calculations. The results suggest that a significant rate of reporting errors occur due to a combination of factors that may include inadequate ballast water exchange and unintentional or deliberate misreporting of ballast water management.

The task of identifying individual compounds within complex gas chromatography - mass spectrometry (GC-MS) chromatograms is made more difficult by interferences between peaks with similar mass spectra eluting at the same time, typically against a background of chemical and electronic noise. Although chemometric techniques like parallel factor analysis and multivariate curve resolution can help to purify spectra and improve correlations with reference compounds, file incompatibilities between GC-MS acquisition software and modeling software prevent the modeled spectra from being easily compared to spectra in reference libraries. In this paper we present an enhancement to OpenChrom, an open-source software for chromatography and mass spectrometry, which implements the automated cross-matching of modeled spectra to NIST08 and NIST11 mass spectral databases. The benefits of this approach are demonstrated using a complex environmental dataset consisting of non-methane volatile organic compound emissions sampled on an Australian poultry farm. © 2012 Elsevier B.V.

Membrane fouling remains an operational challenge in the ultrafiltration (UF) membrane treatment of wastewater effluent and research is on-going to improve understanding of the organic character of foulants. Two advanced organic characterisation techniques that have potential to lend insight into membrane fouling are size exclusion chromatography with organic carbon, UV254 and nitrogen detection (LC-OCD) and fluorescence excitation-emission matrix (EEM) spectroscopy. In this study, UF treatment was undertaken for five tertiary wastewater effluents. The total hydraulic resistance was determined as well as that contributed by foulant layers fractionated by rinsing, backwashing and chemically desorbing. Organic characterisation for UF feed samples, permeates and each foulant layer was then performed using LC-OCD and FEEM spectroscopy with the aim of improving understanding of the character of foulants present in effluent organic matter (EfOM) and to determine the potential for the use of FEEM spectroscopy as a foulant indicator in such systems. It was determined that the biopolymer fraction was most significantly reduced on UF treatment, as anticipated due to its high molecular size. This was supported by the observation that the majority of the foulant layer comprised predominantly protein-enriched biopolymers (38-60% of total foulant layer DOC) that could be removed by rinsing. The resistance attributed to rinsing was directly related to the combined DOC concentration associated with proteins and low molecular weight neutral compounds as defined by LC-OCD analysis. Furthermore, tyrosine-like fluorescence intensity (λex/em=250/304nm) of both the rinsing solutions and UF feed samples showed good correlation with associated hydraulic resistance for EfOM originating from domestic wastewater, suggesting that fluorescence has potential to be used as a foulant indicator for these systems. © 2011 Elsevier B.V.

A method is proposed for automatically determining the upper and lower boundaries of the Raman scatter peak in fluorescence spectroscopy from empirical data. Accurate peak boundaries are needed to calculate accurate Raman peak areas, used for normalizing fluorescence signals to produce data in units that are comparable between instruments. Comparisons of Raman peak boundaries across nine individual instruments (FluoroMax 3 (FM3) fluorometers from HORIBA Jobin Yvon and Cary Eclipse (CE) fluorometers from Varian Inc.) at the excitation wavelength λex = 350 nm reveal consistent results. At 350 nm excitation, the Raman peak was confined by the emission wavelengths of 382–418 nm, with boundaries determined for the FM3 fluorometers deviating by no more than 0.5 nm and 1.5 nm with respect to the start and end of the peak, and CE fluorometers deviating by up to 1.5 nm and 2 nm, respectively. Peak width was a function of fluorometer type and excitation wavelength. For the FM3 instruments, widths increased from approximately 30 nm at λex = 300 nm to 40 nm at λex = 380 nm, while for the CE instruments, peaks were approximately 5–8 nm narrower. Code for implementing the procedure in MATLAB, which allows for the adjustment of input parameters to compensate for noisy data, is provided in the Supplemental Material (available online).

To limit the spread of non-indigenous marine species, ships can be legally required to conduct ballast water exchange (BWE) prior to discharging ballast water. It has been proposed to verify BWE by measuring concentrations of coastal tracers in ballast tanks, which should track their removal. Using 3 Australian ports as case studies (Port Botany, Port Curtis and Port Phillip Bay), each representing a different BWE verification difficulty level, the spatial and temporal variability of chromophoric dissolved organic matter (CDOM) and 3 trace elements (manganese [Mn], barium [Ba] and phosphorus [P]), were measured to assess their utility as tracers of coastal (unexchanged) ballast water. CDOM fluorescence at λex/λem = 320/414 nm (C2*) and 370/494 nm (C3*) and Mn concentrations were significantly higher in ports than in the adjacent Tasman Sea, except near port entrances and at a few sites in Port Botany. Ba concentrations demonstrated the least power to discriminate coastal sources, but P easily discriminated water from mesotrophic Port Phillip Bay. In general, tracers showed greater variation between and within ports, rather than between seasons. Conservative BWE thresholds were calculated to be 1.6 quinine sulphate equivalents for C2*, 0.9 quinine sulphate equivalents for C3*, 1.4 μg l-1 for Mn and 6.9 μg l -1 for Ba. Overall, these thresholds would allow water sourced from eastern Australian ports to be identified as coastal at 92%, 69% and 74% of sites examined using C3*, Mn and Ba, respectively, requiring 71 ± 26%, 54 ± 40% and 59 ± 38% replacement with mid-ocean water to be within ocean baseline concentration ranges. © Inter-Research 2010 · www.int-res.com.

The transfer of organisms in ballast water of commercial ships is a leading cause of bio- logical invasions in coastal ecosystems. Ships arriving in New Zealand are now required to treat their ballast water to reduce the risk of transferring invasive aquatic organisms between ports. Most of these ships conduct mid-ocean ballast water exchange (BWE), replacing coastal water with open ocean water, but methods to verify BWE have been lacking. Samples were collected from ballast tanks and the ambient ocean on ships trading between southeastern Australia and New Zealand, to test the use of chemical (chromophoric dissolved organic matter or CDOM, Ba, Mn and P) concentra- tions to discriminate ballast water sources. Australian ballast water provides a difficult and valuable test case for BWE verification due to its high salinity and low chemical tracer concentrations resulting from Australia's low rainfall and nutrient-poor soils. Our results indicate that elevated CDOM, Ba and Mn were robust tracers of port waters, whereas elevated P was not a diagnostic tracer except of bal- last water originating from Port Phillip Bay. Exchanged ballast tanks were diagnosed by CDOM flu- orescence below 2.1 (for wavelength pair C2*, Ex/Em = 320/414 nm) and 1.2 (for wavelength pair C3*, Ex/Em = 370/494 nm) (quinine sulfate equivalents, QSE), and Ba and Mn concentrations below 5.7 and 3.5 μg l -1 respectively. These results are consistent with recent studies in the northern hemi- sphere, indicating that elevated concentrations of these tracers are robust indicators of unexchanged ballast water. Whereas clear differences existed between port and oceanic signatures, coastal and oceanic samples could not always be distinguished due to precipitously declining tracer concentra- tions within short distances from land.

A rapid, highly sensitive and selective detector is urgently required to detect contamination events in recycled water systems - for example, cross-connection events in dual reticulation pipes that recycle advanced treated sewage effluent - as existing technologies, including total organic carbon and conductivity monitoring, cannot always provide the sensitivity required. Fluorescence spectroscopy has been suggested as a potential monitoring tool given its high sensitivity and selectivity. A review of recent literature demonstrates that by monitoring the fluorescence of dissolved organic matter (DOM), the ratios of humic-like (Peak C) and protein-like (Peak T) fluorescence peaks can be used to identify trace sewage contamination in river waters and estuaries, a situation analogous to contamination detection in recycled water systems. Additionally, strong correlations have been shown between Peak T and biochemical oxygen demand (BOD) in rivers, which is indicative of water impacted by microbial activity and therefore of sewage impacted systems. Hence, this review concludes that the sensitive detection of contamination events in recycled water systems may be achieved by monitoring Peak T and/or Peak C fluorescence. However, in such systems, effluent is treated to a high standard resulting in much lower DOM concentrations and the impact of these advanced treatment processes on Peaks T and C fluorescence is largely unknown and requires investigation. This review has highlighted that further work is also required to determine (a) the stability and distinctiveness of recycled water fluorescence in relation to the treatment processes utilised, (b) the impact of matrix effects, particularly the impact of oxidation, (c) calibration issues for online monitoring, and (d) the advanced data analytical techniques required, if any, to improve detection of contamination events.

Recent regulation mandates that ships conduct mid-ocean ballast water exchange (BWE) prior to discharging foreign ballast in U.S. territorial waters. We investigated the utility of dissolved concentration measurements for 6 elements (Ba, P, Mn, U, V and Mo) in the ballast tanks of ships operating in the North Pacific and Atlantic oceans as tracers of mid-ocean BWE. Relatively conservative elements Mo, U and V provided little additional information beyond that obtained from salinity, whereas nonconservative Ba, P and Mn offered greater resolution. The utility of Ba, P and Mn was further examined in the context of three criteria: (1) stability, or whether tracers maintain stable concentrations in ballast tanks over time; (2) fidelity, or the degree to which tracer concentrations in ballast tanks faithfully reflect concentrations at their ocean source; and (3) predictability, or the degree to which ballast tanks have a predictable and restricted range of tracer concentrations following BWE. We found that in water held in ballast tanks over time, average stability increased for MnPBa, as reflected by decreasing coefficients of variation (30%21%3%) and fidelity increased in the same direction. While Ba and P usually increased discrimination at high salinities, Mn was typically the most sensitive indicator of BWE and the presence of residual port water in partially exchanged tanks. Ba, P and Mn in tanks exchanged in the Atlantic exhibited different concentration ranges compared to tanks exchanged in the Pacific, suggesting that if trace elements are to be used to verify BWE, criteria for discriminating between exchanged and unexchanged ballast tanks may need to be basin-specific.

Absorbance and fluorescence spectroscopy are economical tools for tracing the supply, turnover and fate of dissolved organic matter (DOM). The colored and fluorescent fractions of DOM (CDOM and FDOM, respectively) are linked by the apparent fluorescence quantum yield (AQY) of DOM, which reflects the likelihood that chromophores emit fluorescence after absorbing light. Compared to the number of studies investigating CDOM and FDOM, few studies have systematically investigated AQY spectra for DOM, and linked them to fluorescence quantum yields (Ф) of organic compounds. To offer a standardized approach, a MATLAB toolbox for the determination of apparent quantum yields of DOM (aquaDOM), featuring two calculation approaches, was developed and used to derive AQYs for samples from the Norwegian Sea. Ф of the organic compounds varied between 0.00079 and 0.35, whereas the average AQY for DOM samples at 350 nm was 0.011 ± 0.003. The AQY at 350 nm increased with depth, while the AQY at 250 nm showed no trend. Laboratory tests indicated that Ф of compound mixtures are additive and represent an intermediate of the constituents. Additionally, the presence of non-fluorescent chromophores greatly suppressed calculated AQYs. Similar trends in the DOM AQY at 350 nm were observed in natural samples. We therefore hypothesize that fluorescence AQYs can indicate changes in the relative abundances of CDOM and FDOM. Additionally, the optical properties of 15 potential DOM constituents were determined and compared to more than 200 modelled spectra (PARAFAC components) in the OpenFluor database. Apparent matches, based on spectral similarity, were subsequently evaluated using molar fluorescence and absorbance. Five organic compounds were potential matches with PARAFAC components from 16 studies; however, the ability to confirm matches was limited due to multiple compounds exhibiting very similar spectra. This reiterates the fact that spectral similarity alone is insufficient evidence of the presence of particular compounds, and additional evidence is required.

Mid-ocean ballast water exchange is mandatory for ships discharging foreign ballast in US territorial waters in order to reduce the risk of biological invasions. However, a reliable tool for determining whether the procedure took place is lacking. We investigated chromophoric dissolved organic matter (CDOM) fluorescence as a tracer of mid-ocean exchange on nine research cruises out of Asia, Europe, and the USA, focusing on challenging source conditions (high salinity, low CDOM). Using parallel factor analysis, we identified nine independent fluorescent components present in varying concentrations in the ocean and in ballast water. One component was sufficient for predicting the coastal vs oceanic source of most ballast water samples. Across nine cruises, thresholds (1.7 and 0.7 ppb quinine sulfate equivalent units) at two fixed wavelength pairs (lambda(ex)/lambda(em) = 320/414 and 370/496 nm, respectively) discriminated coastal from oceanic ballast water in95% of samples (N = 514). Our results suggest that single- and dual-channel fluorometers could be optimized for verifying ballast water exchange.

We examined methods for verifying whether or not ships have performed mid-ocean ballast water exchange (BWE) on four commercial vessels operating in the Pacific and Atlantic Oceans. During BWE, a ship replaces the coastal water in its ballast tanks with water drawn from the open ocean, which is considered to harbor fewer organisms capable of establishing in coastal environments. We measured concentrations of several naturally occurring chemical tracers (salinity, six trace elements, colored dissolved organic matter fluorescence and radium isotopes) along ocean transects and in ballast tanks subjected to varying degrees of BWE (0-99%). Many coastal tracers showed significant concentration changes due to BWE, and our ability to detect differences between exchanged and unexchanged ballast tanks was greatest under multivariate analysis. An expanded dataset, which includes additional geographic regions, is now needed to test the generality of our results.

An online repository of published organic fluorescence spectra has been developed, which can be searched for quantitative matches with any set of unknown spectra. It fills a critical gap by increasing access to measured and modelled (PARAFAC) spectra, and linking across studies and systems to reveal "global" fluorescence trends.

Organic matter (OM) is a ubiquitous constituent of natural waters quantifiable at very low levels using fluorescence spectroscopy. This technique has recognized potential in a range of applications where the ability to monitor water quality in real time is desirable, such as in water treatment systems. This study used PARAFAC to characterize a large (n=1479) and diverse excitation emission matrix (EEM) data set from six recycled water treatment plants in Australia, for which sources of variability included geography, season, treatment processes, pH and fluorometer settings. Five components were identified independently in four or more plants, none of which were generated during the treatment process nor were typically entirely removed. PARAFAC scores could be obtained from EEMs by simple regression. The results have important implications for online monitoring of OM fluorescence in treatment plants, affecting choices regarding experimental design, instrumentation and the optimal wavelengths for tracking fluorescent organic matter through the treatment process. While the multimodel comparisons provide a compelling demonstration of PARAFAC's ability to distill chemical information from EEMs, deficiencies identified through this process have broad implications for interpreting and reusing (D)OM-PARAFAC models.

The fluorescent properties of dissolved organic matter (DOM) are often studied in order to infer DOM characteristics in aquatic environments, including source, quantity, composition, and behavior. While a potentially powerful technique, a single widely implemented standard method for correcting and presenting fluorescence measurements is lacking, leading to difficulties when comparing data collected by different research groups. This paper reports on a large-scale interlaboratory comparison in which natural samples and well-characterized fluorophores were analyzed in 20 laboratories in the U.S., Europe, and Australia. Shortcomings were evident in several areas, including data quality-assurance, the accuracy of spectral correction factors used to correct EEMs, and the treatment of optically dense samples. Data corrected by participants according to individual laboratory procedures were more variable than when corrected under a standard protocol. Wavelength dependency in measurement precision and accuracy were observed within and between instruments, even in corrected data. In an effort to reduce future occurrences of similar problems, algorithms for correcting and calibrating EEMs are described in detail, and MATLAB scripts for implementing the study's protocol are provided. Combined with the recent expansion of spectral fluorescence standards, this approach will serve to increase the intercomparability of DOM fluorescence studies.

The optical properties of chromophoric dissolved organic matter (CDOM) are frequently used as tracers of water masses in bays and estuaries but present unique challenges in the ocean due to the small quantities of organic matter present and the similarities between spectra from coastal and offshore environments. Samples collected on trans-oceanic cruises in the Pacific and Atlantic oceans were used to investigate the optical characteristics of dissolved organic matter in waters with limited freshwater influence (salinity > 30). Parallel Factor Analysis (PARAFAC) of fluorescence spectra revealed that coastal and oceanic dissolved organic matter (DOM) fluorescence could be separated into at least eight separate components: 4–5 humic-like and 3–5 protein-like signals. Two of the humic components were identified as representing terrestrial organic matter and their signals could be traced in the open ocean (Pacific and Atlantic) at levels of approximately 1.5% of riverine concentrations. An additional humic component, traditionally identified as the “marine” or “M” peak, was found to be both sourced from land and produced in the ocean. These results demonstrate that the supply, mixing and removal of terrestrial organic matter in oceanic waters can be observed with relatively simple measurement techniques, suggesting that fluorescence spectroscopy could play a useful role in future studies of the origin and fate of DOM in oceanic environments.

The observed rates and deleterious impacts of biological invasions have caused significant alarm in recent years, driving efforts to reduce the risk (establishment) of new introductions. Characterizing the supply of propagules is key to understanding invasion risk and developing effective management strategies. In coastal ecosystems, ships' ballast water is an important transfer mechanism (vector) for marine and freshwater species. Commercial ships exhibit a high degree of variation in ballast water operations that affect both the quantity and quality of propagule supply, and thereby invasion risk. The per-ship inoculation size from ballast water depends upon both the volume discharged and the organism density. Moreover, propagule quality will vary among source regions (ports) and voyage routes, due to differences in species composition and transport conditions, respectively. We show that significant differences exist in (i) the frequency and volume of ballast water discharge among vessel types, (ii) the frequency of vessel types and routes (source regions) among recipient ports, and (iii) the transit success (survivorship) of zooplankton in ballast tanks among voyage routes. Thus, propagule supply is not a simple function of total ship arrivals. For ships, as well as other vectors, variation in propagule quantity and quality must be explicitly considered to estimate invasion risk and advance predictive ability.

PARAllel FACtor analysis (PARAFAC) is increasingly used to decompose fluorescence excitation emission matrices (EEMs) into their underlying chemical components. In the ideal case where fluorescence conforms to Beers Law, this process can lead to the mathematical identification and quantification of independently varying fluorophores. However, many practical and analytical hurdles stand between EEM datasets and their chemical interpretation. This article provides a tutorial in the practical application of PARAFAC to fluorescence datasets, demonstrated using a dissolved organic matter (DOM) fluorescence dataset. A new toolbox for MATLAB is presented to support improved visualisation and sensitivity analyses of PARAFAC models in fluorescence spectroscopy. © 2013 The Royal Society of Chemistry.

A rapid high-throughput method is presented for the determination of trace elements (P, V, Mn, As, Mo, Ba and U) in seawater with application to tracing ballast water exchange in ocean-going vessels. By employing direct flow injection and methane addition the method is capable of >700 continuous determinations of ten-fold diluted seawater samples in less than 30 h. The utility and resolution of elemental tracers are enhanced when accuracy and precision are sufficient to provide determination errors that are negligible relative to oceanic variations. Here we demonstrate long-term precision

Correction for ‘Supply-side invasion ecology: characterizing propagule pressure in coastal ecosystems’ by Emma Verling, Gregory M. Ruiz, L. David Smith, Bella Galil, A. Whitman Miller and Kathleen R. Murphy (Proc. R. Soc. B 272 , 1249–1256. (doi: 10.1098/rspb.2005.3090 )). A reference was omitted from the print version of this paper; the missing reference is as follows: Simberloff, D. 1989 Which insect introductions succeed and which fail? In Biological Invasions: a global perspective (ed. J. A. Drake, F. Di Castri, R. H. Groves, F. J. Kruger, H. A. Mooney, M. Rejmanek & M. H. Williamson), pp. 61–75. Chichester, UK: Wiley & Sons Ltd.

An experimental study was conducted to compare the effectiveness of audio-visual and written presentations in self-instructed learning. Subjects examined showed in one instance that listening with a visual component was as effective as reading, and under the other condition, listening with a visual component was superior to reading. The findings and implications are discussed.