Amount Of Total Organic Carbon Research Articles

Characteristics and origin of low-organic-matter carbonate source rocks in the Middle–Upper Ordovician, Tarim Basin, northwestern China

The continually-discovered large volumes of marine hydrocarbons indicate a huge exploration potential within the carbonate rocks of Ordovician in the Tarim Basin, northwestern China. The Middle–Upper Ordovician (O2+3) carbonate source rocks are at a highly mature stage. These rocks presently contain a low amount of total organic carbon (TOCpd ≤0.5%) (TOCpd means the present-day TOC). A mass balance approach is used to identify the source rocks that have expelled hydrocarbons. The characteristics and origin of hydrocarbon expulsion from low-TOCpd source rocks are studied, which are significant for oil exploration in the basin. The results showed that a low-TOCpd O2+3 source rock having expelled hydrocarbons was type I and had a very narrow oil window. With a high rock maturity and a high original TOC (TOCo) value exceeding 1%, nearly 80% of the generated hydrocarbons were expelled. The content of gammacerane and C28 steranes in the oil and source rock extracts were relatively lean, with a V-shaped distribution of regular steranes, suggesting a possible genetic relation between the low-TOCpd source rocks and the marine oil in the Tabei area. Hydrogen-rich planktonic algae or acritarchs were the main hydrocarbon parent materials, distributed in the subsiding platform-slope facies. Organic matter was preserved under reducing conditions, and source rocks were formed with a favorable kerogen type and a moderate hydrocarbon generation potential. This study illustrates the hydrocarbon expulsion of low TOCpd source rocks in northern Tarim Basin, which is greatly significant for analyzing the genesis of marine crude oil in Tarim Basin, and evaluating the distribution of marine source rocks. This research method is theoretically significant for oil and gas exploration in the same type of highly-mature carbonate paleobasins.

Soils of xerophytic meadows of the Middle Podesen’ya: on the issues of accumulation of organic substances and biochemical activity

Relevance. Natural meadow communities, belonging to the dry meadows group, in the conditions of a decrease in floodplain of the leading water artery in the Bryansk region — the Desna River are characterized by significant changes in the mode of economic use. However, a significant part of dry meadows is used as pasture lands, so the regime of intensive exploitation of these lands significantly changes the ecological regimes of phytocenoses, reducing the carbon-depositing functions. For xerophytic (dry) meadows of natural origin, the establishment of soil carbon reserves, the identification of biochemical and microbiological activity is especially important in the light of the low stability of these communities under pasture load and wide distribution throughout the territory of the Middle Podesen’ya.Methods. The research provided for field route studies and in-house data processing using the methods of trial sites, the method of ecological and floral classification, the method of ecological scales (according to G. Ellenberg), ecological and chemical methods — determination of organic carbon, the weight method, biochemical and microbiological methods for the study of the biocompatible body.Results. For the soils of xerophytic (dry) meadows, for the first time, carbon-absorbing capacity, enzymatic activity for urease, catalase, cellulase, depending on the phytocenotic complex, has been established for the Middle Podesen’ya. A positive strong correlation has been established with organic carbon and average monthly precipitation in June, July and August. Over a two-year observation period, the amount of total organic carbon in the soil changed in a number of associations communities: Festuco ovinae-Koelerium delavignei > control > Agrimonio eupatoriae-Poetum angustifoliae > Caro carvi-Deschampsietum > Anthoxantho-Agrostietum tenuis > Hieracio pilosellae-Agrostietum tenuis > Koelerio delavignei-Festucetum rubrae > Anthyllidi-Trifolietum montani > Polygalo vulgaris-Anthoxanthoetum.

Occurrence and ecological risk of PAHs in urban road runoff in Beijing.

The occurrence and ecological risks of 16 polycyclic aromatic hydrocarbons (PAHs) in different types of urban road runoff in Beijing during two typical rainfall events were studied. The average concentration of PAHs in road runoff particulate was in the order of Guanyuanqiao Road (ring road, 15,175 ng/L) > Huayuanqiao Road (primary road, 4,792 ng/L) > Dongcheng Alley (alley, 4,774 ng/L) > Nansihuan Viaduct (viaduct, 770 ng/L), much higher than dissolved PAHs. The total concentration of ∑16PAHs decreased with runoff scouring. Rainfall conditions and the accumulation of PAHs in the early rainfall period show a significant impact on PAHs pollution. The event mean concentration range of PAHs is 674-21,596 ng/L, following in the order of ring road > primary road > alley > viaduct. The proportion of four-ring PAHs was the highest. The first flush effect of PAHs is found in both rainfall events, and the effect of different ring PAHs is relatively similar. The content of PAHs is positively correlated with the amount of total organic carbon and suspended substance in runoff (r2> 0.72). The ecological risk assessment indicated that PAHs in road runoff except viaduct road corresponded to high risk.

Combining methane clumped and bulk isotopes, temporal variations in molecular and isotopic composition, and hydrochemical and geological proxies to understand methane's origin in the Ronda peridotite massifs (Spain)

In serpentinised peridotite and ultramafic rock systems, methane (CH4) origin is frequently considered abiotic, but variable microbial and thermogenic components can also exist. Typically, the origin of CH4 is studied using bulk, 13C/12C and 2H/H isotopic composition, molecular gas composition, occasionally radiocarbon (14C), microbiology and geological context. Recent advances in CH4-clumped isotope methods have yielded novel insights into the formation of CH4: nonetheless, their interpretation in natural gas samples is often uncertain and requires additional research. Here, we study the origin of the gas released in hyperalkaline (pH > 10) springs in the Ronda Peridotite Massifs (southern Spain), combining bulk and clumped CH4 isotopes with molecular gas composition, hydrochemical (Total Organic Carbon and Platinum Group Elements in water), geothermal and geo-structural data. Five springs analysed in 2014 have been re-examined for changes in gas chemistry over time, and three newly discovered gas-bearing springs are analysed for the first time. Regardless of whether springs have microbial or abiotic isotopic fingerprints, we find that bulk CH4 isotopes are fairly stable over a seven-year period. This suggests that the CH4 source(s) or postgenetic processes (such as oxidation and diffusion) have not undergone significant temporal changes. Major variations in H2 and CH4 concentrations in certain springs may be the result of changes in gas pressure and migration intensity. Paired CH4 clumped isotopes (Δ12CH2D2 - Δ13CH3D) were analysed in two bubbling springs, where the presence of CH4 can be interpreted as non-microbial based on 13C enrichment, absence of 14C, and the presence of ethane and propane. However, these isotopes are in disequilibrium, which prevents the quantification of the gas formation temperature. Within the Δ12CH2D2 - Δ13CH3D diagram, the data lie within both the microbialgenic zone, suggested by previous authors, and the abiotic zone that results combining data from laboratory gas synthesis and other natural gas samples. Therefore, attributing a microbial origin to CH4 based only on clumped isotopes is less definite than previously assumed. The amount of Total Organic Carbon appears to be correlated with the origin of CH4, as it is higher in 13C-depleted CH4 samples and lower in 13C-enriched samples. Palladium (Pd) and Rhodium (Rh) dissolved in water (the more soluble Platinum Group Elements) can be a proxy for the chromitite ore deposits contained in plagioclase tectonite layers throughout the investigated area, which may act as catalysts for abiotic CO2 hydrogenation. Clumped isotope disequilibrium and the reported absence of diffuse CH4-bearing fluid inclusions in the peridotites appear to rule out high temperature gas genesis in post-magmatic inclusions. These observations, along with the moderate temperatures at the base of the peridotite massifs and the consistent occurrence of gas along tectonic contacts between serpentinised (H2-bearing) peridotite and carbon-bearing rocks, are compatible with the theory of low-temperature CO2 hydrogenation.

The Effect of Biochar Applied Alone and in Combination with Mineral and Organic Fertilisers on the Yield of White Cabbage and Soil Properties

The study aimed to investigate the effectiveness of biochar application on fertile soils in a temperate climate during the first year of application. The field trial was conducted on a nutrient-rich silt loam soil at two experimental sites in north-eastern Slovenia (Biš and Skorba). The effect of biochar applied alone or in combination with compost or mineral fertiliser on soil properties and yield of white cabbage was studied. In addition to the control (C), the soil received five treatments including biochar (B; 1.5 t/ha), compost (CO; 1.5 t/ha), biochar-mixed compost (BCO; 3.0 t/ha), standard mineral fertilisers (NPK; NPK 0.35 t/ha, potassium sulphate 0.25 t/ha and calcium ammonium nitrate 0.25 t/ha) and combined application of half the amountof NPK and BCO (NPK+BCO). The results showed that the applied treatments had no significant influence on the measured soil chemical parameters, except for the amount of total organic carbon, electrical conductivity and pH in Biš and total carbon in Skorba. All investigated parameters (cabbage head weight, head circumference, total and market yield) were higher at the experimental site Skorba. Statistically significant differences were found only at the experimental site Biš, where the treatment influenced all parameters (p < 0.01), except for the head circumference of the cabbage. The NPK and NPK+BCO treatments produced significantly higher total yields (66.7 t/ha and 65.8 t/ha, respectively) and marketable yields (53.2 t/ha and 51.8 t/ha, respectively) compared to the other treatments (41.3-52.6 t/ha and 30.5-42.4 t/ha, respectively). Although the differences between the other treatments were insignificant, a trend of decreasing cabbage yields towards CO > BCO > B was observed. Similar results were also obtained when analysing the average data of the two experimental sites.

A critical review of methods, principles and progress for estimating the gross primary productivity of terrestrial ecosystems

The gross primary productivity (GPP) of terrestrial ecosystems reflects the total amount of organic carbon assimilated by vegetation through photosynthesis per given unit of time and area, which represents the largest carbon flux in carbon budget and plays a fundamental part in the carbon cycle. However, challenges such as determining how to select appropriate methods to improve GPP estimation accuracy at the regional/global scale remain. Therefore, it is of great importance to comprehensively review the research progress on the methods for estimating the GPP of terrestrial ecosystems and to summarize their flaws, merits and application fields. In this study, we reviewed studies of GPP estimation at different spatiotemporal scales, and systematically reviewed the principles, formulas, representative methods (Ground observations, Model simulations, SIF based GPP, and NIRv based GPP) at different scales and models (Statistical/Ecological process/Machine learning/Light use efficiency models), as well as the advantages and limitations of each research method/models. A comprehensive comparison of GPP research methods was performed. We expect that this work will provide some straightforward references for researchers to further understand and to choose appropriate models for assessing forest ecosystem GPP according to the research objectives and area. Thus, critical and effective GPP estimation methods can be established for the terrestrial carbon cycle, carbon neutralization accounting and local carbon emission reduction policy formulation and implementation.

Experimental result of a shipwreck influence on the surrounding soft sediment communities in the vicinity of Bushehr port, Persian Gulf

Unplanned artificial reefs like old shipwrecks provide a hard substratum for the colonization of organisms, contributing to increasing local productivity and environmental carrying capacity especially when they are lies in soft sediment-dominated areas. Also, these structures can change the local current regime, sedimentation processes and composition of benthic species in the adjacent sediment. The present study aimed to evaluate the spatial effect of a shipwreck on its surroundings. Experimentally have been examined the relationship between sediment characteristics, abundance and macroinvertebrates richness in distance gradient (20, 50, 100 and 400 m) from a shipwreck that sank in 1983 on a soft bottom floor in the north of the Persian Gulf. Around the shipwreck, a total of 74 taxa were identified. The result indicated that macrobenthic density and richness varied significantly between distances with higher values at 20 and 50 m away from the wreck. Likewise, spatial variations in grain size were observed. A high concentration of gravel (63%) was recorded at about 20 m away from the wreck. Although, the amount of total organic carbon did not differ significantly among distances and does not explain the observed variations in density, richness and diversity of macrobenthos. In consequence, it is suggested that the proximity of the wreck modified the community structure of macrobenthos and sediment characteristics up to a distance of 50 m.

An Integrated Approach to Reservoir Characterization for Evaluating Shale Productivity of Duvernary Shale: Insights from Multiple Linear Regression

In the development of unconventional shale resources, production forecasts are fraught with uncertainty, especially in the absence of a full, multi-data study of reservoir characterization. To forecast Duvernay shale gas production in the vicinity of Fox Creek, Alberta, the multi-scale experimental findings are thoroughly evaluated. The relationship between shale gas production and reservoir parameters is assessed using multiple linear regression (MLR). Three hundred and five core samples from fifteen wells were later examined using the MLR technique to discover the fundamental controlling characteristics of shale potential. Quartz, clay, and calcite were found to comprise the bulk of the Duvernay shale. The average values for the effective porosity and permeability were 3.96% and 137.2 nD, respectively, whereas the average amount of total organic carbon (TOC) was 3.86%. The examined Duvernay shale was predominantly deposited in a gas-generating timeframe. As input parameters, the MLR method calculated the components governing shale productivity, including the production index (PI), gas saturation (Sg), clay content (Vcl), effective porosity (F), total organic carbon (TOC), brittleness index (BI), and brittle mineral content (BMC) (BMC). Shale gas output was accurately predicted using the MLR-based prediction model. This research may be extended to other shale reservoirs to aid in the selection of optimal well sites, resulting in the effective development of shale resources.

Geographic imprint and ecological functions of the abiotic component of periphytic biofilms

Geographic imprint and ecological functions of the abiotic component of periphytic biofilms

Shift in Microbial Community Structure with Temperature in Deulajhari Hot Spring Cluster, Odisha, India

Hot springs are the reservoirs of novel hyperthermophilic and often mesophilic bacteria that provide information about the prevailing community structure. Here we analyzed the metagenome profile based 16S rRNA amplicon sequencing of the three different springs from Deulajhari hot spring cluster, S1, S2 and S3, having a range of temperature (43°C to 65°C), pH (7.14 – 8.10) and variation in N, P, K, TOC, Salinity, COD and TDS. These thermal spring clusters are covered with the dense vegetation of Pandanus and continuously enriched by plant leaf debris, thus resulting in a high amount of total organic carbon (TOC). The number of phyla varied among the springs: 20 in S1 (43°C), 18 in S2 (55°C) and 24 in S3 (65°C) from the 16S rRNA data. Out of the reported phyla in each spring, the most abundant were Chloroflexi, Proteobacteria, Chlorobi and Acidobacteria, which correlated with the temperature gradient. Various metabolic pathways such as ABC transporters, Two-component system, Purine metabolism were most abundantly present in the S2 sample compared to the other two. The CCA analysis revealed the correlation between physiochemical parameters and their functional annotation. The present study establishes the relation between the physiological parameters and the structural distribution of microbiota along the temperature gradient.

Sodium Percarbonate Activation by Plasma-Generated Ozone for Catalytic Degradation of Dye Wastewater: Role of Active Species and Degradation Process

In this paper, sodium percarbonate (SPC) was activated by ozone (O3) from plasma for catalytic treatment of dye wastewater. Methyl blue (MB), a typical industrial dye, was selected as the target dye contaminant. Results showed that enhancing O3 dosage and reducing MB concentration were beneficial to MB degradation. Compared to acid condition, a higher removal efficiency of MB was obtained in alkaline condition. With an increase of SPC dosage, the removal efficiency of MB first was raised, and then it declined. Under the optimal dosage of 50 mg/L, the removal efficiency of MB reached 85.7% with 30 min treatment time. The energy efficiency was improved from 5.21 g/kWh to 5.71 g/kWh. A synergetic effect can be established between O3 and SPC. Radical capture experiments verified that ·OH, ·O2−, 1O2, and ·CO3− played important parts in MB degradation. With increasing reaction time, the amount of total organic carbon (TOC) declined and the amount of ammonia nitrogen (NH3-N) increased. The addition of SPC enhanced the solution’s pH value and conductivity. The degradation pathway was proposed based on density functional theory (DFT) analysis and relevant literatures. The toxicity of MB was alleviated after O3/SPC treatment. The O3/SPC process was also suitable for the treatment of other dyes and actual wastewater.

Insight into the carbonaceous fraction of three cultural layers of different age from the area of Verona (NE Italy)

Cultural layers are deposits resulting from settlement and human activity on natural soil in the past. Materials from past domestic activities that become buried into the soil can be used to reconstruct human impact in a specific area in the past. For instance, humans have used fire for millennia, and charcoal in soils and sediments is applied as evidence of anthropic activity. In this context, assessing the abundance and degradation level of charcoal fragments can clarify anthropic activities in cultural deposits. In European towns, cultural layers with similar characteristics, have been defined as urban “Dark Earth” (UDE) but their age, formation and composition often differ significantly across sites.This study examined three archaeological sites in Verona, Italy, where UDE layers with similar characteristics have been identified. The primary aim of this research is to understand the anthropogenic influence on the development of UDE layers, by characterizing their geochemistry and the carbonaceous materials. To pursue this goal, we provide a micromorphological description of the sites, evaluate UDE features and the abundance of charred material andcharacterize the amorphous/crystalline degreethrough µ-Raman spectroscopy. Bulk material was described in terms of amounts of total organic carbon (TOC), recalcitrant organic carbon (ROC), total inorganic carbon (TIC), and trace element concentration. Radiocarbon dating of charred and humin fractions was performed to clarify the dynamics underlying UDE origin. We investigate the relationship between the different variables analyzed in the UDE layers at each site. Results show that a diverse array of human activities including metal tool and/or ceramic manufacturing were related to the formation of UDE layers. The investigation of carbonaceous fractions highlight differences in soil organic carbon and charred material, both of which are correlated with human influence.

A New Setup for the Measurement of Total Organic Carbon in Ultrapure Water Systems.

With the increasing demand for ultrapure water in the pharmaceutical and semiconductor industry, the need for precise measuring instruments for those applications is also growing. One critical parameter of water quality is the amount of total organic carbon (TOC). This work presents a system that uses the advantage of the increased oxidation power achieved with UV/O3 advanced oxidation process (AOP) for TOC measurement in combination with a significant miniaturization compared to the state of the art. The miniaturization is achieved by using polymer-electrolyte membrane (PEM) electrolysis cells for ozone generation in combination with UV-LEDs for irradiation of the measuring solution, as both components are significantly smaller than standard equipment. Conductivity measurement after oxidation is the measuring principle and measurements were carried out in the TOC range between 10 and 1000 ppb TOC. The suitability of the system for TOC measurement is demonstrated using the oxidation by ozonation combined with UV irradiation of defined concentrations of isopropyl alcohol (IPA).

Geochemistry and organofacies characteristics of organic-rich chalky marl deposits, northern Jordan: Insights into Type II-S source rock

This study deals with organic matter in chalky marls of the Wadi Shallala Formation in northern Jordan. We report geochemical analyses (Total organic carbon, programmed pyrolysis, bitumen extraction, and pyrolysis–gas chromatography) for the chalky marls from 17 samples to provide information on the quantity, quality, the thermal maturity of the organic matter, their potential as petroleum source rocks. The chalky marl samples contain a significant amount of total organic carbon (TOC, max = 6.53%) and hydrogen index (HI) ranging from 300 to 702 mg HC/g TOC. The organic facies are mainly Types-II and -I kerogen with a potential to generate high amounts of oil. The dominance of such kerogen is consistent with significant amounts of fluorescent alginite macerals, observed under ultraviolet light microscopy. These organic facies are also confirmed by the Py-GC investigation, showing sulfur-rich Type II-S kerogen. The presence of weak carbon–sulfur (C-S) bounds in the kerogen molecules, however, suggests the generation of sulfur-rich oil at the early stages during the oil-generation window as reported by earlier works. Both geochemical maturity indicators (i.e., Tmax and PI) and the fluorescence color of the liptinite macerals indicate that the studied chalky marls in the outcropped section of the study area are still thermally immature, and maturity did not alter the organic-rich intervals to generate suitable oil for commercial production. Therefore, these organic-rich sediments in the locations having relatively deeper stratigraphic sections are likely to be promising source rocks and recommend for petroleum exploration and production in northern Jordan.

Electrocoagulation coupled with electrooxidation for the simultaneous treatment of multiple pollutants in contaminated sediments

In situ and simultaneous remediation of a variety of pollutants in sediments remains a challenge. In this study, we report that the combination of electrocoagulation (EC) and electrooxidation (EO) is efficient in the immobilization of phosphorus and heavy metals and in the oxidation of ammonium and toxic organic matter. The integrated mixed metal oxide (MMO)/Fe anode system allowed the facile removal of ammonium and phosphorus in the overlying water (99% of 10 mg/L NH4+-N and 95% of 10 mg/L P disappeared in 15 and 30 min, respectively). Compared with the controls of the single Fe anode and single MMO anode systems, the dual MMO/Fe anode system significantly improved the removal of phenanthrene and promoted the transition of Pb and Cu from the mobile species to the immobile species. The concentrations of Pb and Cu in the toxicity characteristic leaching procedure extracts were reduced by 99% and 97% after an 8 hr operation. Further tests with four real polluted samples indicated that substantial proportions of acid-soluble fraction Pb and Cu were reduced (30%–31% for Pb and 16%–23% for Cu), and the amounts of total organic carbon and NH4+-N decreased by 56%–71% and 32%–63%, respectively. It was proposed that the in situ electrogenerated Fe(II) at the Fe anode and the active oxygen/chlorine species at the MMO anode are conducive to outstanding performance in the co-treatment of multiple pollutants. The results suggest that the EC/EO method is a powerful technology for the in situ remediation of sediments contaminated with different pollutants.

A new submerged photocatalytic membrane reactor based on membrane distillation for ketoprofen removal from various aqueous matrices

The removal of ketoprofen from simulated sea, brackish and surface water as well as secondary effluent of a municipal wastewater treatment plant in a submerged photocatalytic membrane reactor (SPMR) coupling photocatalysis and direct contact membrane distillation was investigated. TiO2 photocatalyst was suspended in a feed. The investigations revealed almost complete photooxidation of ketoprofen (initial concentration of 10 mg·L−1) after 5 h, regardless of the matrix, and mineralization ranging from 19 to 56%. For comparison, ketoprofen mineralization in deionized water reached about 86%. No ketoprofen was found in distillate, however, the type of the feed affected the amount of total organic carbon (TOC) and total inorganic carbon (TIC). The highest TOC content in distillate was observed for the secondary effluent. The type of the aqueous matrix affected the concentration of dissolved oxygen in feed, which decreased to the highest extent in the case of surface water (61% after 5 h). The analysis of toxicity towards Aliivibrio fischeri revealed that regardless of the feed type the distillate was non-toxic. A slight increase of permeate flux was observed during the process compared to pure water flux which was explained in terms of thermal conductivity of the TiO2 layer on a membrane surface.

Using Fe–Cu/HGF composite cathodes for the degradation of Diuron by electro-activated peroxydisulfate

An iron-copper graphite felt (Fe–Cu/HGF) electrode was successfully prepared by heat treatment and impregnation of graphite felt as the support followed by calcination, and an electro-activated peroxydisulfate (E-PDS) system with Fe–Cu/HGF as the cathode was constructed to degrade Diuron. This system synergistically activated PDS through electrochemical processes and transition metal catalysis. High-valence metal ions could be converted into low-valence metal ions by reduction at the cathode, and low-valence metal ions continuously activated PDS to generate more sulfate radicals (SO4-) and hydroxyl radicals (OH) to accelerate Diuron degradation. The Fe–Cu/HGF composite cathode exhibited a performance superior to graphite felt (RGF) obtained using pretreatment only, including increased hydrophilicity, significantly increased number of defect sites and larger electroactive surface area. Under optimized experimental degradation conditions, Diuron could be completely removed in 35 min, at which time copper ion leaching was not detected in the solution, while the total iron ion concentration was 0.27 mg L−1. Extending the reaction time to 6 h, the amount of total organic carbon was reduced to 32.2%. In addition, the free radicals that degraded Diuron were identified as mainly SO4- and OH with a slightly higher contribution of SO4-. The mechanism and pathways of Diuron degradation in the E-PDS system were determined. The E-PDS system was successfully applied to the degradation of other pollutants and the degradation of Diuron in different simulated water environments. In summary, the E-PDS system using Fe–Cu/HGF as the cathode is a promising treatment method for Diuron-containing wastewater.

Enhanced bioremediation of sediment contaminated with polycyclic aromatic hydrocarbons by combined stimulation with sodium acetate/phthalic acid

In this study, four groups of laboratory scale experiments were performed by adding sodium acetate (SA), phthalic acid (PA), and SA-PA to river sediment to observe the microbial response and biodegradation efficiency of polycyclic aromatic hydrocarbons (PAHs). The results showed that the amount of total organic carbon consumed and the amount of sulfate reduction were both positively correlated (p < 0.01) with the biodegradation efficiency of the sum (∑) PAHs (∼40.5%). The lower the number of rings, the more PAHs were biodegraded, with an efficiency of 63.0% for ∑ (2 + 3) ring PAHs. Based on high-throughput sequencing and molecular ecological network analysis, it was found that the combined stimulation of SA and PA not only increased the relative abundance of PAHs-degrading bacterial (eg., Proteobacteria, Desulfobacterota, Campilobacterota and Firmicutes), but also had a strengthening effect on microbes in sediments. The altered microbial structure caused a variation in metabolic functions, which increased the amino acid metabolism to 12.2%, thus increasing the positive correlations among genera and improving the connectivity of the microbial network (p < 0.01). These changes may be responsible for the enhanced biodegradation of PAHs under SA-PA dosing in comparison to SA or PA dosing alone. This study revealed that the microbial community was stimulated by the combined addition of SA and PA, and indicated its role in enhancing biodegradation of PAHs in contaminated river sediments.

Research on the Monitoring Methods of VOCs Leak of Open Circulating Water System in Refineries

Open circulating water heat exchangers are widely used in refineries. According to the current emission standards, whether a circulating water system is leaking is determined by total organic carbon (TOC) concentration at the inlets and outlets of circulating water heat exchangers. However, this method is rough with low compatibility, making it hard to judge the actual leak of a circulating water heat exchanger. Taking a typical refinery with a yearly output of five million tons of oil as an example, we established a ledger of an open circulating water system and optimized the method to judge whether the system is leaking in this paper. The results show that there are 63% of the circulating water heat exchangers can be decided by monitoring the quality of circulating water. Among all, the leak of only 18.81% of the circulating water heat exchangers can be decided by monitoring the amount of TOC.

Interactive effects of soil water content and nutrients on root exudation in two Mediterranean tree species

Root exudation is affected by the soil water content (SWC) and availability of nutrients, but the impact of the interaction between these abiotic factors is unclear. Understanding the combined effect of these factors is vital for all ecosystems, including Mediterranean forests, where droughts are increasing. A greenhouse experiment was established with a drought treatment (control versus drought) and the subsequent recovery, factorially combined with four nutrient treatments (control, nitrogen (N) addition, phosphorus (P) addition, and both N and P addition). N was added as ammonium nitrate at a rate of 50 kg N ha−1 and P was added as calcium phosphate at a rate of 25 kg P ha−1. Exudation of total organic carbon (TOC) was measured from the roots of 64 saplings of each of two important tree species that coexist in montane Mediterranean regions, Pinus sylvestris (Scots pine) and Quercus ilex (holm oak). The amount of TOC released from individual roots of the saplings was measured to estimate root exudation per gram of root mass. Chlorophyll fluorescence (Fv/Fm) was also monitored to check for treatment effects on leaf performance. Chlorophyll fluorescence was not affected by SWC or nutrient addition in either species, but root exudation was, and varied between the two species. SWC was positively correlated with the amount of TOC released during the drought period for Q. ilex but had no effect on P. sylvestris. The addition of P increased root exudation in Q. ilex. The amount of TOC released in the recovery period for both species with no added nutrients was weakly negatively correlated with SWC during the drought period, potentially indicating a delayed positive effect of the earlier water stress. During recovery, SWC positively affected the amount of TOC collected from the roots when P was added for both species and when N was added for P. sylvestris. Our results indicate that the impacts of drought on root exudation will likely vary between species and will depend on the availability of soil nutrients.