181. 题目: Interpreting ramped combustion thermograms using 13C NMR spectroscopy to characterize soil organic matter composition
While many advanced analytical methods have been applied to soil organic matter (SOM), its highly complex and heterogeneous chemical composition still eludes complete characterization. Analytical thermal analysis has been proposed as a relatively rapid, inexpensive method for SOM characterization that requires no pre-treatment, but is challenging due to a lack of direct information about chemical composition. The goal of this study was to inform the interpretation of coupled differential scanning calorimetry and evolved gas analyses (DSC, CO2-EGA) using spectral correlations with solid phase 13C NMR data. We used a subset of soils collected as part of the Australian National Soil Carbon Research Program (SCaRP), which were physically fractionated and characterized using conventional analytical methods. Correlating the well-understood NMR spectra with the less-understood DSC and CO2-EGA thermograms provided some indications of which chemical compounds combust at which temperatures. Overall, the EGA data generated stronger correlations compared to correlations with DSC data, which was attributable to greater variability in DSC data due thermal reactions associated with minerals. Direct comparison of NMR and thermal data for the mineral associated organic matter in the fine (<50 µm) fraction was not possible due to the need to demineralize samples prior to NMR analyses. Thermal analyses showed substantial differences in samples pre- and post-HF pretreatment, and the NMR data for HF treated samples showed scattered and weak correlation patterns with DSC and EGA data for untreated samples. While precise chemical compositions cannot be gleaned directly from thermal analyses results, thermal approaches provide an avenue of investigation into SOM reactivity based on bioenergetics that may be a quantitative representation of SOM persistence.
182. 题目: The effect of silica-magnetite nanoparticles on the ecotoxicity of the antibiotic ciprofloxacin
The increase in the production and application of engineered nanomaterials, including nanoparticles (NPs), leads to their discharge into the environment, where they can interact with coexisting antibiotics from wastewater, causing a complicated joint effect on organisms that need to be studied. Herein, a typical engineered nanomaterial, silica-magnetite NPs modified with tetraethoxysilane and 3-aminopropyltriethoxysilane (MTA-NPs, 1–2 g/L), and common antibiotic ciprofloxacin (CIP, 0–5 mg/L) were selected as the analytes. Their joint toxicity to a model of ciliates infusoria, Paramecium caudatum was specifically investigated. The impact of CIP, MTA-NPs, and humic acids (HA) was tracked for 24 h, individually and collectively, on the mortality of infusoria. The addition of MTA-NPs and HA at the studied concentrations leads to 40% mortality of organisms. The combined presence of the MTA-NPs at a concentration of 1.5–2 mg/L and HA at a concentration of 20–45 mg/L has a multiplier effect and allows to reduce the mortality rate of ciliates > 30% due to the enhanced removal of CIP. That finding demonstrated a clearly detoxifying role of dissolved organic matter (here, humic substances) in case of complex water pollution where pharmaceuticals and nanomaterials are presented.
183. 题目: Effects of Fe(II) and organic carbon on nitrate reduction in surficial sediments of a large shallow freshwater lake
Nitrate-reducing ferrous [Fe(II)]-oxidizing (NRFO) has been reported from lake sediments as a natural reduction pathway. However, the effects of the contents of Fe(II) and sediment organic carbon (SOC) on the NRFO process still remain unclear. In this study, the influences of Fe(II) and organic carbon on nitrate reduction were analyzed quantitatively at two typical seasonal temperatures (25 °C representing summers and 5 °C for winters) by conducting a series of batch incubation experiments, using surficial sediments at the western zone of Lake Taihu (Eastern China). Results showed that Fe(II) greatly promoted NO3‾-N reduction by denitrification (DNF) and dissimilatory nitrate reduction to ammonium (DNRA) processes at high-temperature (25 °C, representing summer season). As Fe (II) increased (e.g., Fe(II)/NO3‾ = 4), the promotion effect on NO3‾-N reduction was weakened, but on the other side, the DNRA process was enhanced. In comparison, the NO3‾-N reduction rate obviously decreased at low-temperature (5 °C, representing the winter season). NRFO in sediments mainly belongs to biological rather than abiotic processes. A relatively high SOC content apparently increased the rate of NO3‾-N reduction (r = 0.023–0.053 mM/d), particularly on the heterotrophic NRFO. It is interesting that the Fe(II) consistently remained active in the nitrate reduction processes no matter whether SOC was sufficient in the sediment, particularly at high-temperature. Overall, the combining effects of both Fe(II) and SOC in surficial sediments made a great contribution towards NO3‾-N reduction and N removal in a lake system. These results provide a better understanding and estimation of N transformation in sediments of the aquatic ecosystem under different environmental conditions.
184. 题目: Seasonality of downward carbon export in the Pacific Southern Ocean revealed by multi-year robotic observations
At high latitudes, the biological carbon pump, which exports organic matter from the surface ocean to the interior, has been attributed to the gravitational sinking of particulate organic carbon. Conspicuous deficits in ocean carbon budgets challenge this as a sole particle export pathway. Recent model estimates revealed that particle injection pumps have a comparable downward flux of particulate organic carbon to the biological gravitational pump, but with different seasonality. To date, logistical constraints have prevented concomitant and extensive observations of these mechanisms. Here, using year-round robotic observations and recent advances in bio-optical signal analysis, we concurrently investigated the functioning of two particle injection pumps, the mixed layer and eddy subduction pumps, and the gravitational pump in Southern Ocean waters. By comparing three annual cycles in contrasting physical and biogeochemical environments, we show how physical forcing, phytoplankton phenology and particle characteristics influence the magnitude and seasonality of these export pathways, with implications for carbon sequestration efficiency over the annual cycle.
185. 题目: Application of biogas-slurry and biochar improves soil multifunctionality in a poplar plantation during afforestation processes
Management can largely influence the sustainability and functionality of forest plantations. However, the role of biogas-slurry and biochar application in supporting soil’s multifunctionality during afforestation remains poorly understood.
We conducted a six-year field experiment to examine the responses of soil ecosystem multifunctionality (EMF) to the application of biogas-slurry applied annually as four treatments, and a single initial application of four treatments of biochar in a new poplar plantation based on a reclaimed coastal area. The EMF was calculated as the standardized average of multiple soil surrogates of soil functions linked with C, N, and P cycles.
Both biogas-slurry and biochar had significantly positive effects on EMF and individual functions, with biogas-slurry having the strongest positive effect, thus promoting carbon stocks and nutrient availability. Furthermore, interactions between biochar and biogas-slurry produced a substantial synergistic effect on soil multifunctionality. The application of biogas-slurry significantly and directly increased the C, N, and P cycle multifunctionality (CCMF, NCMF, and PCMF, respectively). In contrast, a single application of biochar profoundly increased the CCMF but decreased the NCMF, thus requiring a trade-off of multiple elements of soil multifunctionality.
We show that organic management has the potential to boost multiple ecosystem functions during afforestation. These findings further highlight the importance of rational fertilization strategies for long-term forest management.
186. 题目: Bacterial reworking of particulate organic matter in a dynamic marginal sea: implications for carbon sequestration
Concentrations of particulate organic carbon (POC) and total hydrolyzable amino sugars (THAS) were measured along a transect of the dynamic South Yellow Sea (SYS) to investigate the bioreactivity and bacterial reworking of particulate organic matter (POM). Results showed that POM bioavailability was linked with primary production, as revealed by the significant correlation between chlorophyll-a concentrations and the diagenetic indicator glucosamine/galactosamine (GlcN/GalN). Production of bioavailable POM could rapidly stimulate microbial activity, generating hot spots of heterotrophic alteration. Lower GlcN/GalN ratios (< 3) observed in the entire SYS indicate that POM underwent extensive microbial alteration. In particular, extremely low GlcN/GalN ratios (∼0.7) were found in the Yellow Sea Cold Water Mass, reflecting high bacterial alteration of POM. Estimates based on the bacterial biomarker muramic acid showed that on average ∼13% of POM in the SYS was of bacterial origin. Elevated bacterial contributions were found in both nearshore and offshore areas. Strong mixing in the nearshore and the presence of cyclonic eddies in offshore waters may increase the residence time of POM in the water column and thus promote bacterial transformation of POM. Overall, our findings indicate that bacterial reworking of POM varies with productivity and that the extensive bacterial transformation of the remaining POM observed in the water column probably enhances long-term carbon sequestration.
187. 题目: A synthesis of the effect of regenerative agriculture on soil carbon sequestration in Southeast Asian croplands
Policymakers and businesses in Southeast Asia are increasingly interested in using carbon markets to encourage adoption of regenerative agriculture practices by farmers. These practices are thought to mitigate climate change by reducing soil carbon loss and enhancing soil carbon sequestration. However, there is uncertainty in the ability of regenerative agriculture practices to increase soil organic carbon (SOC) stocks of croplands. We reviewed 92 empirical studies that investigated the effects of 17 regenerative farming practices across 11 broad categories of crops on SOC stock or content in Southeast Asia. Our synthesis found supporting evidence for the use of organic amendments like biochar, compost, and manure, as well as cover cropping, crop rotation, and conservation tillage to increase SOC. However, studies for practices like addition of compost and manure reported increases in greenhouse gas emissions like methane (CH4) and nitrous oxide (N2O), demonstrating that increases in SOC may be offset by increases in greenhouse gas emissions. Only a few studies measured both the changes in SOC stocks and greenhouse gas emissions and none of the studies completed full greenhouse gas inventories. Estimating the net impact of SOC gains and increase of greenhouse gas emissions will be necessary to understand the overall effect of practices like compost, manure and crop residue incorporation on net atmospheric greenhouse gas concentrations. If these practices are implemented for soil carbon projects, practitioners should anticipate increases in greenhouse gas emissions from soils and implement additional practices, such as alternate wetting and drying, to optimize the climate change mitigation effects of regenerative agriculture. We encourage future research on practices, such as agroforestry and changes in crop residue management, where there are few studies and little variation in experimental design and environmental conditions. Given the interest in scaling up regenerative agriculture through voluntary carbon markets to boost SOC stocks in croplands, policymakers and businesses can support research in this area by making field-collected data from their projects accessible to researchers to further the study of the impact of these practices across different abiotic conditions and soil managements. This data sharing would alleviate the paucity and improve the quality of empirical data on regenerative agricultural practices in Southeast Asian croplands, facilitate practice-specific meta-analyses, and help to optimize climate change mitigation effects of regenerative agriculture.
188. 题目: Composition and molecular structure analysis of hydrophilic/hydrophobic extracellular polymeric substances (EPS) with impacts on sludge dewaterability
Extracellular polymeric substances (EPS) have a significant effect on the dewaterability of waste-activated sludge (WAS); however, the role of polarity distribution (hydrophilic/hydrophobic characteristics) of EPS in sludge dewatering remains unclear. In this study, the relationship between the characteristics of EPS hydrophilic/hydrophobic fractions (composition and molecular structure) and sludge physicochemical properties of 8 different sludge samples was investigated, and a structural equation model was constructed to describe the potential mechanisms of key EPS parameters on sludge dewatering. Experimental results showed that the variation in sludge EPS polarity led to significant changes in the surface hydrophilicity/hydrophobicity and structure compactness, which affected the sludge dewaterability. Specifically, the increase in the content of tyrosine-like proteins, especially those related to hydrophobic acid fraction (HPO-A), played a key role in increasing the surface hydrophobicity of sludge and promoting its dewaterability. In contrast, humic acids in hydrophilic EPS (HPI) could interact with hydrophobic proteins to form dense biopolymers (characterized by high nonprotonated nitrogen (Nnonpr) content), resulting in a more stable and compact structure of the EPS matrix (characterized by low random coil content) and deterioration of sludge dewaterability. This study provides a new perspective for the exploration of the relationship between hydrophilic/hydrophobic biopolymers and sludge dewaterability.
189. 题目: Amendments of waste ochre from former coal mines can potentially be used to increase soil carbon persistence
There is an increasingly urgent need to remove CO2 from the atmosphere. Increasing C storage in soils has been discussed as a possible method of achieving this. Regardless of whether increasing soil C would result in reduced atmospheric C or not, increasing the amount of organic carbon (OC) stored as organic matter in soils is widely regarded as leading to agronomic benefits such as increased water retention and resistance to erosion. Fe oxides adsorb OC in soil, protecting it from degradation. In this study we investigated the use of waste ochre (Fe oxy-hydroxide) that precipitates from the drainage of former coal mines as a soil amendment to increase C storage in soils via reduced C lability. In preliminary batch experiments, ochres reduced the release of OC from soils into solution. In plant growth experiments with wheat (var. Skyfall, RAGT) 5 wt% amendments of ochre to soils significantly reduced the concentration of hot water extractable OC by approximately 16% and OC lost from the soils in leachate by approximately 43%. Above ground plant biomass was significantly reduced by approximately 50% in the amended soils. There was no evidence for increased uptake of potentially toxic elements in the plants from the ochre-amended soils compared to the study controls but Olsen P extractable phosphate was decreased by the ochre amendments. In subsequent experiments with agronomically realistic additions of KH2PO4 there was no difference in plant biomass between the study controls and the ochre-treated soils suggesting that reduced plant growth was due to reduced P availability; C lability was still significantly reduced. Furthermore, the ochre amendments helped retain th added phosphate in the soil. These results indicate that Fe oxide amendments to soil may be a viable way of changing soil chemistry in order to increase the amount of OC retained in soils. Further experiments investigating the impacts of the ochre amendments on greenhouse gas emissions and soil biology are required followed by field trials where the impact of more variable soil moisture and temperature effects can be assessed and crops grown to harvest. A full Life Cycle Analysis could then be performed. Given the relatively limited quantities of former coal mine ochres available in the UK and the carbon footprint of transporting materials prior to adding them to soils, similar experiments to those reported here, taking into account chemical and mineralogical variations, are warranted to determine the global stock pile of Fe-rich wastes that could potentially be used to reduce C lability in soils.
190. 题目: Oxygenation of the Earth aided by mineral–organic carbon preservation
Photosynthesis produces molecular oxygen, but it is the burial of organic carbon in sediments that has allowed this O2 to accumulate in Earth’s atmosphere. Yet many direct controls on the preservation and burial of organic carbon have not been explored in detail. For modern Earth, it is known that reactive iron phases are important for organic carbon preservation, suggesting that the availability of particulate iron could be an important factor for the oxygenation of the oceans and atmosphere over Earth history. Here we develop a theoretical model to investigate the effect of mineral–organic preservation on the oxygenation of the Earth, supported by a proxy compilation for terrigenous inputs and the burial of reactive iron phases, and find that changes to the rate of iron input to the global ocean constitute an independent control on atmosphere–ocean O2 and marine sulfate levels. We therefore suggest that increasing continental exposure and denudation may have helped fuel the rise in atmospheric O2 and other oxidants over Earth history. Finally, we show that inclusion of mineral–organic preservation makes the global marine O2 reservoir more resilient to changes in nutrient levels by breaking the link between productivity and organic carbon burial. We conclude that mineral–organic preservation is an important missing process in current assessments of Earth’s long-term carbon cycle.
191. 题目: Sources and fates of particulate organic matter in inland waters with complex land use patterns
Elucidating the sources of particulate organic matter (POM) is the foundation for understanding their fates and the seasonal variation of their movement from the land-to-ocean aquatic continuum (LOAC). The POM from different sources has different reactivity, which determines their fates. However, the key link between the sources and fates of POM, especially in the complex land use watersheds in bays is still unclear. Stable isotopes and contents of organic carbon and nitrogen were applied to reveal them in a complex land use watershed with different gross domestic production (GDP) in a typical Bay, China. Our results showed that the POMs preserved in suspended particulate organic matter (SPM) were weakly controlled by assimilation and decomposition in the main channels. Source apportionments of SPM in the rural area were controlled by soil (46 % ~ 80 %), especially inert soils eroded from land to water due to precipitation. The contribution of phytoplankton resulted from slower water velocity and longer residence time in the rural area. The soil (47 % ~ 78 %) and manure and sewage (10 % ~ 34 %) were the two major contributors to SOMs in the developed and developing urban areas. The manure and sewage were important sources of active POM in the urbanization of different LUI, which showed discrepancies in the three urban areas (10 % ~ 34 %). Due to soil erosion and the most intensive industry supported by GDP, the soil (45 % ~ 47 %) and industrial wastewater (24 % ~ 43 %) were the two major contributors to SOMs in the industrial urban area. This study demonstrated the close relationship between the sources and fates of POM with complex land use patterns, which could reduce uncertainties in future estimates of the LOAC fluxes and secure ecological and environmental barriers in a bay area.
192. 题目: Deep tillage enhanced soil organic carbon sequestration in China: A meta-analysis
The increasing atmospheric carbon dioxide (CO2) causes serious environmental problems, soil organic carbon (SOC) sequestration is suggested as an efficient strategy to offset global CO2 emissions. Deep tillage (DT) can change soil properties and the input and loss of OC, and then influence SOC sequestration across the whole soil profile. However, the effect of DT on SOC sequestration relative to conventional tillage (CT) under different environmental factors and management practices is unclear in China. In this study, we evaluated the response of SOC stock to DT based on collected field data (447 observations) with a meta-analysis. DT significantly increased SOC stock by 7.36% over CT, with a greater increase for subsoiling (8.76%) than for deep ploughing (DP) (5.85%). Subsoiling enhanced SOC across the 0–40 cm soil layer and the greatest increase occurred at 0–10 cm layer (11.41%); DP enhanced SOC stock at 10–40 cm layer, but had no effect on SOC of 0–10 cm layer. DP and subsoiling did not affect SOC storage below 40 cm depth. According to subgroup analysis, the high rainfall, fine soil texture, residue retained, double cropping, and high rate of N fertilization greatly promoted SOC stock compared with the low rainfall, sandy texture, residue removal, monoculture, and low N fertilizer input under DT. DT significantly enhanced SOC storage under low initial SOC (<15 g kg−1), but did not affect SOC when the initial SOC exceeded 15 g kg−1 compared with CT. However, the experiment duration, initial SOC and bulk density (BD) did not significantly affect the response of SOC to DT. Overall, this study has supplied a reference for SOC management in mitigating climate change, and the specific environmental factors and management practice should be considered when utilizing DT to enhance SOC sequestration in different regions of China.
193. 题目: The characteristic evolution and formation mechanism of hybrid microalgae biofilm and its application in mariculture wastewater treatment
Microalgae biofilm had important applications in both energy and environmental fields. However, the current research on the formation mechanism of microalgae biofilm was vague. And the treatment of mariculture wastewater by microalgae biofilm was rare. Herein, a kind of natural hybrid microalgae was applied in this study to investigate the mechanism of microalgae biofilm formation and the treatment of mariculture wastewater under different ammonia nitrogen loads (13 mg/L, 25 mg/L, 37 mg/L). The results indicated that filamentous algae were first to attach to the carrier and then formed a web-like structure. Later, more non-filamentous algae and bacteria involved in the formation of biofilm. Protein in extracellular polymeric substances (EPS) was the key substance for the initial colonization. The NN functional group, tryptophan, high molecular weight of EPS promoted microalgae biofilm formation. When the ammonia nitrogen concentration was 25 mg/L, the microalgae biofilm reached the maximum biomass (1.79 mg/cm2) and the highest nitrogen and phosphorus removal efficiency (98% of NH4+-N, 84% of TN, 68% of PO4--P). The study provides a theoretical basis for understanding the mechanism of natural hybrid microalgae biofilm formation and its application for mariculture wastewater treatment.
194. 题目: Simple adsorptive removal of crystal violet, a triarylmethane dye, from synthetic wastewater using Fe (III)-treated pine needle biochar
Untreated and Fe (III)-treated pine needle biochar (PNB) were evaluated at different pH for the removal of toxic crystal violet (CV) dye from synthetic wastewaters. Adsorption kinetics followed the pseudo-first-order kinetics involving intra-particle diffusion process. The adsorption rate constant increased with Fe treatment of PNB especially at pH 7.0. Adsorption data of CV conformed well to Freundlich adsorption isotherms and both adsorption capacity (ln K) and order of adsorption (1/n) of CV were nearly doubled with Fe (III) treatment of PNB at pH 7.0. Desorption of adsorbed CV from both untreated and Fe (III)-treated PNB could be accounted satisfactorily by third-degree polynomial equations. An increase in ionic strength and temperature enhanced dye adsorption onto untreated and Fe (III)-treated PNB. Adsorption of CV was an endothermic and spontaneous reaction with an increase in entropy of the system. FTIR spectra revealed that C = O of carboxylic acid aryls and C = O and C–O–C in lignin residues of PNB reacted with Fe (III) besides the formation of some iron oxyhydroxide minerals. The changes in FTIR confirmed the possible bonding of positively charged moiety of CV with the untreated and Fe-treated PNB. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) revealed the porous surfaces of PNB with clear accumulation of Fe (III) after treatment and deposition of CV dye on surfaces and pores of PNB. Iron (III)-treated PNB at pH 7.0 can serve as an ecofriendly and cost-effective adsorbent for the efficient removal of CV dye from wastewaters.
195. 题目: Interaction between MIL-101(Cr) and natural organic matter in an integrated MOF-UF system
As an emerging metal organic framework (MOF) material, MIL-101(Cr) has a large specific surface area and good hydraulic stability, making it ideal in applications before ultrafiltration (UF). However, the unclear interaction between MIL-101(Cr) and natural organic matter (NOM) was identified as the main limitation to understand membrane fouling. To reveal the working mechanisms of NOM removal using MIL-101(Cr), an integrated system of MOF and UF was constructed and operated in separation mode (SM) and coating mode (CM). Based on the results, MIL-101(Cr) had a high NOM adsorption capacity of 68.454 mg/g for HA and 174.725 mg/g for BSA at saturation. Permeate quality improvement occurred in both modes over a 37.7% UV254 removal rate and a 15% fluorescence intensity decrease, and permeation performance of the hybrid system was simultaneously enhanced. We found that MIL-101(Cr) influenced membrane fouling behaviors and models because of the foulant transformation in SM and dispersed NOM in the MIL-101(Cr) layer in CM. Furthermore, MIL-101(Cr) played a dual role in the integrated system. It could remove NOM by adsorption, leading to membrane fouling reduction, but also caused additional filtration resistance. Notably, MIL-101(Cr) showed the overall positive effects due to its open hollow structure and good hydrophilicity. The π-π interactions and salt-bridges between MIL-101(Cr) and NOM played a dominant role in adsorption. Whilst SM was more efficient in membrane fouling mitigation due to reduced membrane fouling resistance and a normalized flux increase above 15%, CM could achieve the same permeate quality with less MIL-101(Cr) usage and reaction time. This study reveals the interaction between MIL-101(Cr) and NOM and their effects on UF, providing a scientific basis for the widespread application of MOFs.
196. 题目: Impacts and mechanism of total organic sulfur in extracellular polymeric substances on fouling of the anaerobic self-forming dynamic membrane bioreactor
A side-stream cross-flow anaerobic self-forming dynamic membrane bioreactor (AnSFDMBR) connected with an up-flow anaerobic sludge blanket (UASB) reactor was used to replace the UASB and middle settling tank in sulfate reduction, autotrophic denitrification, and nitrification integrated (SANI) process. To reduce the water and energy consumption for AnSFDMBR backwashing, the optimum condition of trans-membrane pressure (TMP)-based backwashing were investigated under sequential batch operations. Based on the optimum condition, a lab-scale AnSFDMBR was operated continuously for 243 days without a drop in flux, with good effluent quality. In the sequential batch operation study, AnSFDMBR showed no significant accumulation of total extracellular polymeric substances (EPSs) during 40 days of operation without backwashing. Polysaccharides slightly accumulated in the dynamic layer regardless of the final TMP and operation duration, indicating that TMP-based backwashing is suitable for the studied AnSFDMBR system. In long-term operation with TMP-based backwashing, total EPSs in dynamic layer to sludge ratio dramatically dropped during the fouling phase. According to the evaluation of total organic sulfur (TOS) in dynamic layer and mesh EPSs, it was found that TOS, mainly poly-sulfur generated in UASB reactor, played a critical role in fouling in saline wastewater treatment. TOS deposited on the mesh over 40% by weight of the total EPS in the fouling phase clearly led to system fouling. Additional sequential batch operations with different seawater percentages (%V/V) (control, 10%, 20%, 30% and 50%) demonstrated that the TOS accumulation on the mesh increased with time and salinity which also aligned with the long-term operation.
197. 题目: Characteristics, sources and driving factors of riverine CDOM in a severe erosion basin on the Loess Plateau, China
Chromophoric dissolved organic matter (CDOM) plays a crucial role in aquatic ecosystems and biogeochemical processes. The characteristics, sources and influencing factors of riverine CDOM were determined with 56 samples collected in the Wuding River (WDR) Basin in spring and summer. The CDOM optical characteristics varied greatly during different seasons. The mean S275-295 was higher in spring than in summer, while SUVA254 exhibited the opposite result. The mean biological source index (BIX) was lower in summer than in spring, while the mean humification index (HIX) was higher in summer than in spring (p < 0.01). C1 and C3 (humic-like components) and C2 (tryptophan-like component) were extracted by parallel factor analysis (PARAFAC). C1 and C3 were prominent in summer, while C2 was prominent in spring. The effects of environmental factors on CDOM showed great differences. Chlorophyll a (Chla), dissolved organic carbon (DOC), electrical conductivity (EC) and dissolved oxygen (DO) had significant effects on the CDOM concentration (p < 0.05) in spring, while only DOC exerted significant effects on the CDOM concentration in summer. However, water quality parameters played important roles in evaluating the CDOM fluorescence components in summer. Total suspended matter (TSM) and turbidity (Tur) exerted significant effects on the humic-like fluorescence peaks (p < 0.05), while pH, Chla, DO, and EC had significant influences on tryptophan-like substances during this period. Based on redundancy analysis, precipitation, water erosion area and human activity intensity greatly affected the CDOM concentration, C1 and C3, while human activity intensity significantly affected C2 in the sub-basins in summer. CDOM was not significantly influenced by the surrounding environmental factors in spring except for the human activity intensity, which greatly influenced C1 and C3.
198. 题目: Photoaging process and mechanism of four commonly commercial microplastics
Microplastics (MPs) are the widespread emerging pollutants in the terrestrial systems, and photo-oxidation is an effective process for aging MPs on land. Here, four common commercial MPs were exposed to ultraviolet (UV) light to simulate the photo-aging of MPs on soil, and the changes in surface properties and eluates of photoaging MPs were studied. Results revealed that polyvinyl chloride (PVC) and polystyrene (PS) exhibited more pronounced physicochemical changes than polypropylene (PP) and polyethylene (PE) during photoaging on the simulated topsoil, due to the dechlorination of PVC and the debenzene ring of PS. Oxygenated groups accumulated in aged MPs were strongly correlated with dissolved organic matters (DOMs) leaching. Through analysis of the eluate, we found that photoaging altered the molecular weight and aromaticity of DOMs. PS-DOMs showed the greatest increase in humic-like substances after aging, whereas PVC-DOMs exhibited the highest amount of additive leaching. The chemical properties of additives explained their differences in photodegradation responses, which also accounted for the greater importance of chemical structure of MPs to their structural stability. These findings demonstrate that the extensive presence of cracks in aged MPs facilitates DOMs formation and the complexity of DOMs composition poses a potential threat to soil and groundwater safety.
199. 题目: Efficient removal of Tris(2-chloroethyl) phosphate by biochar derived from shrimp shell: Adsorption performance and mechanism study
Tris(2-chloroethyl) phosphate (TCEP) has been detected all over the world as a typical refractory organic phosphate, especially in groundwater. This work applied a calcium-rich biochar derived from shrimp shell as a low-cost adsorbent for TCEP removal. Based on the kinetics and isotherm studies, the adsorption of TCEP on biochar was monolayer adsorbed on a uniform surface, with SS1000 (the biochar was prepared at the carbonization temperature of 1000 °C) achieving the maximum adsorption capacity of 264.11 mg·g−1. The prepared biochar demonstrated stable TCEP removal ability throughout a wide pH range, in the presence of co-existing anions, and in diverse water bodies. A rapid removal rate of TCEP was observed during the adsorption process. When the dosage of SS1000 was 0.2 g·L−1, 95% of TCEP could be removed within the first 30 min. The mechanism analysis indicated that the calcium species and basic functional groups on the SS1000 surface were highly involved in the TCEP adsorption process.
200. 题目: Evaluation of phytoplankton-stimulating potency of effluent nitrogen depending on its chemical forms: A comparison between inorganic and organic nitrogen
Wastewater-originated nitrogen (N) is considered a primary N source in urban waters. In order to mitigate eutrophication in such waters, decreasing N discharges from wastewater treatment plants (WWTPs) is necessary. Upgrading WWTPs from conventional activated sludge (CAS) to biological nutrient removal (BNR) is the most common measure to lower levels of effluent N. However, in spite of successful N reduction through such upgrades, eutrophication persists in numerous urban waters. In this study, we investigated why decreased N discharge resulting from upgrading CAS to BNR, particularly predenitrification BNR, cannot necessarily alleviate eutrophication. Our laboratory reactor study demonstrated that compared to CAS effluent N, predenitrification BNR effluent N contains less dissolved inorganic N (DIN) but more dissolved organic N (DON), especially low molecular weight DON (LMW-DON). Bioassay-based experimental and numerical analyses found that effluent N has dissimilar phytoplankton-stimulating potency depending on its chemical forms. In particular, effluent LMW-DON showed significantly greater potency than effluent DIN. This difference in potency makes predenitrification BNR effluent N more productive for causing primary production than CAS effluent N. These results indicate that the impact of effluent N on eutrophication should be evaluated based on not only the total quantity but also the qualitative aspect of N.