Bulk Organic Content Research Articles

Evaluation of plasmon-enhanced catalytic ozonation for the abatement of micropollutants in environmental matrices

Advanced oxidation processes (AOPs) have been widely investigated for the treatment of recalcitrant organic pollutants. Here we report the first study on the performance evaluation in different environmental matrices of a newly-developed AOP, plasmon-enhanced catalytic ozonation with silver doped spinel ferrite (0.5wt%Ag/MnFe2O4) as the catalyst, for the degradation of representative micropollutants (e.g. atrazine and atenolol). The real matrices include surface water (SW, pH 6.82), secondary effluent (SE, pH 7.22), and reverse osmosis/RO concentrate (ROC, pH 7.90) generated during water reuse. A kinetic model combining the Rct concept (the ratio of the total •OH-exposure to the total O3-exposure) and expressions of transient steady state hydroxyl radical (•OH) concentrations has been successfully developed to predict the treatment performance, where the effects of major influencing factors (e.g. solution chemistry such as pH and water constituents, and operating conditions) were explicitly quantified. Bulk organic contents, carbonate/bicarbonate, and phosphate were found to be the major chemical species that influenced the target compound removal, through interactions with reactive species (e.g. •OH) and/or the solid catalysts. Lower bromate formation was observed in the plasmon-enhanced catalytic ozonation process, compared with ozonation and catalytic ozonation processes. Low energy consumption (electrical energy per order/EEO 0.011–0.086 kWh/m3 for different matrices) together with low byproduct formation has demonstrated that plasmon-enhanced catalytic ozonation is a novel promising AOP for various water treatment and reuse applications.

Southern California Vegetation, Wildfire, and Erosion Had Nonlinear Responses to Climatic Forcing During Marine Isotope Stages 5–2 (120–15 ka)

AbstractA multiproxy record from Baldwin Lake, San Bernardino Mountains, allowed us to examine variation and relationships between erosion, wildfire, vegetation, and climate in subalpine Southern California from 120 to 15 ka. Bulk organics, biogenic silica, and molar C:N data were generally antiphased with magnetic and trace element data and displayed long‐term (105 year) shifts between autochthonous and allocthonous deposition. This was most pronounced during Marine Isotope Stage (MIS) 5, and we hypothesize that local summer insolation was the primary driver for Baldwin Lake's productive and unproductive lake state alternations. Wildfire history was inferred from charcoal concentrations and vegetation change from pollen. Relationships between these ecological processes, basin deposition, and summer insolation were often nonlinear. Sagebrush expansion, wildfire, and weak basin weathering characterized MIS 4, while during MIS 2, the basin was highly erosive, rarely burned, and the forest was impacted by shifts in Southern Californian hydroclimate. Despite coniferous forest cover throughout MIS 3, submillennial oscillations in charcoal, pollen, and bulk organic content occurred, consistent with pollen records from Eurasia's Mediterranean biome that span multiple glacial‐interglacial cycles. Highly resolved global CO2 records and sea surface temperatures in key regions of the Pacific show no apparent relationship to these landscape conditions, and we suggest submillennial hydroclimatic variability as a potential driver. Highly resolved long pollen records from Southern California are an urgent research need to better understand the finer‐scale (≤103 year) interactions between past vegetation, wildfire, and erosion, given the current natural disaster risks that 21st century climate change poses to both human and ecological communities.

Ultraviolet/persulfate pre-treatment for organic fouling mitigation of forward osmosis membrane: Possible application in nutrient mining from dairy wastewater

The forward osmosis (FO) membrane process has recently established its potential as an alternative option to traditional membrane processes for producing clean water and recovering nutrients from anaerobically treated wastewater streams. However, organic fouling of membrane leads to reduced flux, and, thus, reduced amount of the extractable resources. In this study, the impact of ultraviolet/persulfate (UV/PS)oxidation pre-treatment for the mitigation of organic fouling in the FO process during processing of anaerobically treated dairy effluent (ATDE) was determined using a multi-cycle filtration method. The UV/PS performance was compared with control pre-treatments such as stand-alone ultraviolet (UV) irradiation and potassium persulfate (PS) oxidation. Size exclusion chromatography confirmed that flux reduction over successive filtration cycles was due mainly to the humic substances and building blocks i.e., sub-units of humic substances in the feedwater. Although all investigated pre-treatment options mitigated membrane fouling, UV/PS achieved a greater enhancement in flux and decrease in both reversible and irreversible foulant deposition than stand-alone UV and PS pre-treatments. This was because UV/PS could generate sulfate andhydroxyl radicals, which were effective for decreasing the bulk organic content and fluorescent organic content, and particularly for breaking down the large molecular weight (MW) hydrophobic compounds to small MW hydrophilic components, resulting in less organics adhesion to the membrane. This research shows the applicability of UV/PS pre-treatment for the organic fouling mitigation of FO membrane during processing of ATDE for applications such as nutrient mining from ATDE.

Feeding ethology and surface sediment reworking by the ampharetid polychaete Melinna palmata Grube, 1870: Effects on sediment characteristics and aerobic bacterial community composition

The present study was aiming at describing the feeding ethology and assessing surface sediment reworking together with associated effects on sediment characteristics and aerobic bacterial community composition by the ampharetid polychaete Melinna palmata, which exhibits very dense populations in the Arcachon Bay (French Atlantic coast). There was a plasticity in the main aspects (i.e., positioning of the tube at the sediment-water interface, stretching of the worms outside their tubes while feeding, location and mechanism of faeces production) constitutive of the current knowledge regarding feeding ethology in ampharetids. On average, worms dedicated 84.6% of their time to the prospection of surface sediments and produced faeces exclusively at the water sediment interface, which resulted in surface sediment reworking and induced the zonation of surface sediment in three distinct areas, namely: undisturbed sediment, prospected and faecal mound areas. Average individual surface prospected area and surface sediment reworking rate were 28 cm2 and 6.8 mm3.h−1, respectively. Surface sediments were coarser and their bulk organic contents were lower in prospected areas, intermediate in faecal mound areas and higher in undisturbed sediments. Oxygen penetrated deeper in the sediment column in faecal mound areas. Aerobic bacterial community composition associated with surface oxygenated sediments within these three areas also significantly differed, which suggests that sediment reworking per se (i.e., irrespective of changes in redox conditions) do have an effect on those compositions. These results are discussed in terms of potential food limitation in the very dense populations of M. palmata present in the Arcachon Bay. It is suggested that the high densities of these populations result from both hydrosedimentary fluxes due to tidal currents and from the enhancement of particle sedimentation in Zostera noltei meadows.

Contact metamorphism and thermogenic gas generation in the Vøring and Møre basins, offshore Norway, during the Paleocene–Eocene thermal maximum

Voluminous volcanic intrusive activity took place in the Vøring and Møre basins at the Paleocene–Eocene boundary at about 56 Ma. This event caused thermal maturation of Cretaceous sedimentary rocks in the basins. We have estimated the resulting thermogenic gas generation potential from contact metamorphism using numerical simulations calibrated using borehole data. The borehole 6607/5-2 from the Utgard sill complex in the Vøring Basin contains two c . 100 m thick sills and is used as a case study. We present both new and compiled data showing that (1) the bulk organic content is reduced towards the sill intrusions, (2) a c . 1 km thick stratigraphic interval is thermally affected, based on vitrinite reflectance data, (3) relative emplacement timing can affect the gas yield by up to 25%, and (4) some of the thermogenic methane is still present in the aureoles. The numerical model is calibrated using data from 11 wells. We estimate that the total gas generation potential for the two Utgard sills equals that of the Troll field ( c . 10 Gt CH 4 ), the largest producing gas field offshore Norway. We show that in the Vøring and Møre basins, the total gas generation potential is up to 1500 Gt CH 4 ( c . 1100 Gt C), even from the relatively organic-poor Cretaceous source rocks with c . 1 wt% organic carbon, with implications for the carbon cycle at the Paleocene–Eocene boundary.

Micro-polluted surface water treatment and trace-organics removal pathway in a PAC-MBR system

Trace-organic contaminants elimination effectiveness and their removal pathways in a powder-activated carbon-membrane bioreactor (PAC-MBR) used for micro-polluted surface water treatment were investigated in this study. The results showed that PAC-MBR was capable of consolidating DOM elimination, enhancing trace-organic contaminants (2,4,6-trichlorophenol, nitrobenzene and trichloroethylene) removal efficiency, improving permeate biostability, and decreasing bulk organic content and specific fractional components, which was beneficial for membrane fouling mitigation. By series of well-designed batch-tests and estimation, trace-organics removal pathways were analyzed. The primary way of TCE removal was aeration volatilization, while that of NB and 2,4,6-TCP elimination was biodegradation which was greatly affected by biomass content within bulk. PAC addition was a positive way for effective trace-organics removal by increasing mixed solid adsorption capability, especially in start-up phase, and offering beneficial circumstances for biomass enrichment and functional bacteria accumulation. Thus, PAC addition into MBR is a simple and effective strategy to treat micro-polluted water resources.

Stable nitrogen isotope analysis of the Upper Devonian palynomorph, Tasmanites

Abstract Bulk samples are commonly used in stable (N) isotope studies to infer climate changes. However, due to uncertainties in the composition of bulk samples, the inconsistency of diagenetic alteration and the variation of dominant oceanic features, such as N-fixation and denitrification, the isolation of specific sedimentary N fractions has become a crucial step to understanding the nitrogen cycle. This paper describes the extraction techniques and the stable nitrogen isotope analysis (on a nano-EA-IRMS) of the palynomorph, Tasmanites spp. (80–200 μm) found in Upper Devonian (Famennian) black shales from Kentucky, USA. Tasmanites is a widely occurring and long-ranging prasinophyte (unicellular green algae) genus. Palynomorphs, such as Tasmanites, are highly resistant to most forms of decay. It is therefore suggested that the δ15N signature of this palynomorph may be a useful, unaltered indicator of baseline isotopic change in future palaeoclimate studies. The greatly reduced sample size accepted by the nano-EA-IRMS makes this technique a viable complement to bulk sediment analyses. The results, using the nano-EA-IRMS, demonstrate that the δ15N signature of the bulk organic samples differ significantly from that of the isolated Tasmanites spp. Three distinct isotopic relationships were observed from the three different sample localities. These include parallel changes in the δ15N values of bulk samples and extracted Tasmanites spp., variation in the δ15N of bulk samples, with no corresponding change recorded in Tasmanites spp., and opposing δ15N changes recorded between the bulk samples and the extracted Tasmanites spp. This inconsistent isotopic variation further emphasises the complexity of the nitrogen cycle. Possible explanations for the observed variation include changes in the rate of N-fixation and denitrification due to climate change, incomplete nitrification, and variation in the bulk organic content.

Decontamination industrial pharmaceutical wastewater by combining solar photo-Fenton and biological treatment

Characterization and treatment of a real pharmaceutical wastewater containing 775 mg dissolved organic carbon per liter by a solar photo-Fenton/biotreatment were studied. There were also many inorganic compounds present in the matrix. The most important chemical in this wastewater was nalidixic acid (45 mg/L), an antibiotic pertaining to the quinolone group. A Zahn–Wellens test demonstrated that the real bulk organic content of the wastewater was biodegradable, but only after long biomass adaptation; however, the nalidixic acid concentration remained constant, showing that it cannot be biodegraded. An alternative is chemical oxidation (photo-Fenton process) first to enhance biodegradability, followed by a biological treatment (Immobilized Biomass Reactor – IBR). In this case, two studies of photo-Fenton treatment of the real wastewater were performed, one with an excess of H 2O 2 (kinetic study) and another with controlled H 2O 2 dosing (biodegradability and toxicity studies). In the kinetic study, nalidixic acid completely disappeared after 190 min. In the other experiment with controlled H 2O 2, nalidixic acid degradation was complete at 66 mM of H 2O 2 consumed. Biodegradability and toxicity bioassays showed that photo-Fenton should be performed until total degradation of nalidixic acid before coupling a biological treatment. Analysis of the average oxidation state (AOS) demonstrated the formation of more oxidized intermediates. With this information, the photo-Fenton treatment time (190 min) and H 2O 2 dose (66 mM) necessary for adequate biodegradability of the wastewater could be determined. An IBR operated in batch mode was able to reduce the remaining DOC to less than 35 mg/L. Ammonium consumption and NO 3 − generation demonstrated that nitrification was also attained in the IBR. Overall DOC degradation efficiency of the combined photo-Fenton and biological treatment was over 95%, of which 33% correspond to the solar photochemical process and 62% to the biological treatment.

Surface analysis of soil material by X‐ray photoelectron spectroscopy

SummaryThe surface composition of particles present in the fine earth (< 2 mm) of 50 soil horizons differing in composition and pedogenetic origin (13 soil profiles) was analysed by X‐ray photoelectron spectroscopy (XPS) to assess the capability and limitations of this technique and to gain better knowledge of the soil samples. The surfaces were systematically enriched in carbon, sometimes up to 1000 times, indicating that the soil particle surfaces are coated with organic substances, even in horizons where the bulk organic content is less than 0.1 g kg−1. The distribution of carbon in the various oxidation states was 0.569 ± 0.008 C[0], 0.275 ± 0.004 C[+1], 0.089 ± 0.003 C[+2] and 0.066 ± 0.002 C[+3] for most horizons (mean ± standard error, 69 data). Only Andosol surface horizons systematically had surface organic matter in a more oxidized state. After correcting the results for the presence of organic coatings, we found that Si was generally depleted and Al enriched at the surface of soil particles, while Fe was either depleted or enriched depending on the sample considered. However, the coating of the coarser soil particles by the finer ones and their differential composition explained this observation and limits the interest of XPS for characterizing the surface enrichment of inorganic elements in crude soil samples. These limitations should be considered when interpreting XPS results in future work. Nevertheless, XPS can analyse the adsorbed organic matter and its functional composition of carbon without the need for any chemical or physical extraction that might alter the structure and composition of the organic molecules.