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22641. 题目: Structure-activity relationships of the papermill sludge-based flocculants in different dye wastewater treatment
文章编号: N20050604
期刊: Journal of Cleaner Production
作者: Kangying Guo, Yue Gao, Baoyu Gao, Qiyun Feng, Xue Shen, Caiyu Liu, Qinyan Yue, Xing Xu
更新时间: 2020-05-06
摘要:

The molecular structures of the flocculants determine their application performances, but seldom researches have focused on the structure-activity relationships (SAR) of the papermill sludge-based flocculants (PSBFs). Here, four flocculants with different charge densities (CD), molecular weights (Mw) and chain architectures were synthesized from papermill sludge. The characterization results of the PSBFs confirmed the success of chemical modification and the structural diversities of the four flocculants. The series of decolorization experiments showed that branched flocculants were more efficient and economical in dye removals than linear ones, the maximum color removal was above 95.0%. The flocs formed by branched flocculants were large, strong, loose and easy to settle, but those by linear ones were not. However, branched flocculants with high Mw levels were limited in decolorization efficiencies due to the steric hindrance effects. The abundant side chains of the high-Mw flocculants intertwined with each other, thereby impeding the contact between the contaminants and flocculants. Positively charged flocculants could remove contaminants mainly through charge neutralization and bridging action. Branched flocculants with abundant side chains were more pH-insensitive than linear ones due to the strong adsorption bridging effects. Also, the branched PSBFs were efficient even with the coexisting humic acid (HA) and kaolin particles in both disperse red and reactive blue dye removals. The flocculation mechanisms and SAR of the PSBFs were discussed in this manuscript.

22642. 题目: Optimization of biochemical oxygen demand to total nitrogen ratio for treating landfill leachate in a single-stage partial nitrification-denitrification system
文章编号: N20050603
期刊: Journal of Cleaner Production
作者: Jiayi Li, Qingping Du, Huangqiang Peng, Yanlong Zhang, Yunqian Bi, Ying Shi, Yanbing Xu, Tao Liu
更新时间: 2020-05-06
摘要:

In this study, a partial nitrification-denitrification (PND) system was established to treat landfill leachate with different influent biochemical oxygen demand to total nitrogen ratio (BOD/N = 0.73, 2.27 and 1.44). The long-term operation results showed the highest TN removal rate of 226 mg/(L·d) have been stably obtained under influent BOD/N of 1.44. Additionally, the influent BOD/N affected the composition and content of the extracellular polymeric substances (EPS) in the sludge, especially the humic acid-like matter in tightly bound EPS (TB-EPS), thus affecting the sludge sedimentation and the system performance. The higher the influent BOD/N, the better the sludge sedimentation. At the micro-level, the microbial community evolved markedly under different influent BOD/N and Ottowia was the dominant genus in the system. At an influent BOD/N of 1.44, the relative abundance of aerobic denitrifying bacteria and mixotrophic denitrifying bacteria was highest, which ensuring the system has a good PND performance of the system. Overall, the results of this study clarified the effects and mechanisms of different BOD/N on the PND system and provided theoretical basis and technical reference for practical engineering application.

22643. 题目: Improved method to apportion optical absorption by black and brown carbon under the influence of haze and fog at Lumbini, Nepal, on the Indo-Gangetic Plains
文章编号: N20050602
期刊: Environmental Pollution
作者: Saifi Izhar, Tarun Gupta, Arnico K. Panday
更新时间: 2020-05-06
摘要:

Estimates of the brown carbon (BrC) absorption and their contribution to light absorption in ambient aerosols are poorly understood. The existing approaches to apportion light absorption into black carbon (BC) and BrC mainly use the assumption of fixed angstrom absorption exponent (AAE) for BC (1.0), which is not always true for ambient aerosols. Besides, these estimates are seldom validated, leaving significant uncertainty with derived values. Also, BrC absorption studies are largely focused on aqueous extracts, which truly do not represent the aerosolized form, hence the relationship between aqueous extracts and aerosolized form is a subject of research. With this in mind, we collected ambient PM_2.5 filter samples at Lumbini, Nepal, at the northern edge of the Indo-Gangetic Plains (IGP) during winter 2017-18. These samples were analyzed for different compositions of carbonaceous aerosol and optical properties. BC and BrC absorptions were derived using a preexisting simplified two-component model but with improved conditions. Although BC dominated spectral absorption, BrC contribution for the carbonaceous aerosol absorption increased substantially at ultraviolet wavelengths (example 14.8–53.6% at 365 nm). Further water-soluble BrC absorption value in aerosol was found to be higher by 1.8 times to that obtained in aqueous extracts. Water-soluble OC contributed ∼65% to OC loading and 50% to BrC absorption at 365 nm, indicated the equally important role of water-insoluble organics. Mass absorption efficiency (MAE) of water-soluble BrC in aerosol was found to be 1.7 m²/g, lower to water-insoluble by 2.2 times. High BC MAE was observed which showed positive dependence on secondary coating. Sample collected during events with fog droplets showed a reduction in carbonaceous components loading and light absorption but enhancement in MAE for BrC and BC, signifying that aqueous processing can significantly modify the aerosol optical properties.

22644. 题目: Ocean Color Algorithms for estimating chlorophyll a, CDOM absorption, and particle backscattering in the Arctic Ocean
文章编号: N20050601
期刊: Journal of Geophysical Research: Oceans
作者: K. M. Lewis, K. R. Arrigo
更新时间: 2020-05-06
摘要:

As the Arctic Ocean (AO) is increasingly altered by anthropogenic climate change, it is critical that we accurately assess ongoing changes in its capacity to support marine life. Ocean color remote sensing provides an effective tool to estimate phytoplankton biomass and net primary production in the remote and under‐sampled AO. However, standard algorithms have been parameterized using global datasets that severely underrepresent the AO. Because the optical properties of AO waters differ markedly from those of lower latitude waters, standard algorithms perform poorly in the AO. Here, we use the largest bio‐optical database ever assembled for AO waters to examine seasonal and regional patterns of AO optical properties and to quantify their impact on ocean color algorithms. We find that the standard algorithms fail to accurately retrieve the primary photosynthetic pigment chlorophyll a (Chl a) in the AO; it is overestimated at low phytoplankton biomass due to exceptionally high absorption of colored dissolved organic matter (CDOM), particularly on the interior shelves, and underestimated at high biomass due to the photoacclimation of phytoplankton growing in low‐light leading to high pigment packaging effect. Using this large bio‐optical database that includes in situ measurements from across the AO and through the entire growing season, we parameterize a new empirical (AOReg.emp) and semi‐analytical (AO.GSM) algorithm which represent the unique bio‐optical properties of the AO to successfully retrieve Chl a, CDOM absorption, and particle backscattering with better accuracy than any algorithm yet applied to the AO.

22645. 题目: Distribution and diagenesis of trace metals in marine sediments of a coastal Mediterranean area: St Georges Bay (Lebanon)
文章编号: N20050512
期刊: Marine Pollution Bulletin
作者: Amonda El Houssainy, Carine Abi-Ghanem, Duc Huy Dang, Céline Mahfouz, Dario Omanović, Gaby Khalaf, Stéphane Mounier, Cédric Garnier
更新时间: 2020-05-05
摘要:

St Georges Bay of Lebanon's coast is an open bay to the Mediterranean Sea. It is exposed to numerous anthropogenic activities such as industrial effluent, untreated wastewater discharge and maritime activities resulting in increasing chemical contamination, especially with trace metals. Contamination with trace metals (Cu, Cd, Co, Pb, As, Ag and Hg) and the influence of early diagenesis on their distribution were studied on both sediments and waters. For this purpose, sediment cores were collected, then treated under inert atmosphere to retrieve pore waters and solid fraction. The area appears to be seriously impacted by the materials transported by the Beirut River and/or by direct inputs, and recent land reclamation using dumpsite material. The sediments showed a significant level of contamination. Element mobility was studied by selective extraction on sediments. The mobility of trace elements from solid fraction to pore waters is controlled by the Fe/Mn cycle and organic matter.

22646. 题目: The role of the understory in litter DOC and nutrient leaching in boreal forests
文章编号: N20050511
期刊: Biogeochemistry
作者: Geert Hensgens, Hjalmar Laudon, Matthias Peichl, Itziar Aguinaga Gil, Quan Zhou, Martin Berggren
更新时间: 2020-05-05
摘要: Dissolved organic carbon (DOC) derived from plant litter plays an important role in the ecosystem carbon balance and soil biogeochemistry. However, in boreal coniferous forests no integrated understanding exists of how understory vegetation contributes to litter leaching of DOC, nitrogen (N) and phosphorus (P) with different bioavailability at the forest stand level. We characterized water extractable leachates from fresh and decayed litter of dominant canopy and understory sources in a boreal coniferous forest, in order to explore the contribution of understory vegetation as a source of both total and bioavailable forms of DOC, N and P. Recently produced litter from deciduous species (including Vaccinium myrtillus) yielded the highest amounts of DOC. However, this leaching potential decreased exponentially with mass loss through litter decay. The DOC lability generally showed little interspecific variation, although wood derived DOC was more recalcitrant. Lability decreased progressively with litter aging. Water extractable nutrients increased proportionally with DOC, and roughly a quarter (N) or half (P) had directly bioavailable inorganic forms. Scaled to annual litterfall at the forest stand, understory vegetation contributed ~ 80% of the water extractable DOC and nutrients from fresh litter, with > 60% coming from Vaccinium myrtillus alone. However, as litter decomposes, the data suggest a lower leaching potential is maintained with a larger contribution from needle, wood and moss litter. Our study shows that understory vegetation, especially V. myrtillus, is a key driver of litter DOC and nutrient leaching in boreal coniferous forests.

22647. 题目: Enhanced Heavy Metal Removal from Synthetic Stormwater Using Nanoscale Zerovalent Iron–Modified Biochar
文章编号: N20050510
期刊: Water, Air, and Soil Pollution
作者: Md Sazadul Hasan, Mengistu Geza, Raul Vasquez, Govinda Chilkoor, Venkataramana Gadhamshetty
更新时间: 2020-05-05
摘要: The use of biochar for removal of heavy metals from stormwater is limited due to large area requirements and inadequate removal of nutrients and heavy metals at higher initial concentrations. In this study, biochar-supported nanoscale zerovalent iron (BC-nZVI) was effectively utilized for removing heavy metals from synthetic stormwater. We performed batch adsorption and laboratory-scale column experiments to demonstrate the exceptional ability of BC-nZVI to remove heavy metals (Cu, Cd, and Zn) at varying higher initial concentration range (2.5 to 60 mg L⁻¹) compared with typical urban stormwater runoff. The batch experiment results suggested that the metal removal efficiency of BC-nZVI compared with biochar was enhanced by 43% and 57% in individual metal solution and 50% and 42% in the mixed metal solution for Cd and Zn, respectively. The maximum adsorption capacities of BC-nZVI for individual metal ions increased by 97% and 40% for Cd²⁺ and Zn²⁺, respectively, compared with original biochar. A series of characterization studies based on scanning electron microscopy, Fourier transform infrared spectroscopy, and Brunauer–Emmett–Teller revealed the chemical and morphological features of BC-nZVI, which are responsible for the enhanced metal removal. A laboratory-scale column study mimicking the field scale revealed the metal removal efficiencies of BC-nZVI increased by 115% and 123% for Cd²⁺ and Zn²⁺, respectively, compared with unmodified biochar. The higher removal efficiencies and adsorption capacities demonstrate the potential use of BC-nZVI as a media for attenuating heavy metals in current stormwater management practices.

22648. 题目: Biochar Adsorption of Antibiotics and its Implications to Remediation of Contaminated Soil
文章编号: N20050509
期刊: Water, Air, and Soil Pollution
作者: Min PAN
更新时间: 2020-05-05
摘要: Antibiotic contamination in water and soil has been widely investigated. However, there is still no effective removal method for antibiotics from water or soil environments. Therefore, the single and competitive sorption dynamics of ionizable tetracycline (TC), sulfamethazine (SMZ), norfloxacin (NOR), erythromycin (ERY), and chloramphenicol (CAP) adsorbed by NaOH-activated and hematite-modified biochars were investigated. NaOH-activated biochar (NAB) showed much better antibiotic sorption than the hematite-modified biochar (HMB). The affinity coefficient of NAB for TC, NOR, and ERY were at least 100 times higher than that of the HMB. The sorption rate of the five target antibiotics was faster in the single-solute systems than in the ternary-solute systems. Sorption capacity was inhibited in the competitive system for all five antibiotics adsorbed by either the NaOH-activated or hematite-modified biochars. Antibiotic sorption by the biochars was governed by electrostatic interactions, π-π electron donor-acceptor (EDA) interactions, and hydrogen bonding. All five antibiotics showed similar adsorption trends in pH treatments of both biochars. However, the sorption capacity slightly increased from pH 7 to pH 9 in HMB compared with those in NAB, as the metal ions from the hematite modification provided cation bridging combinations to negatively charged antibiotics at a high pH value. These observations are useful for producing NaOH-activated biochar as an engineered sorbent to reduce the bioavailability of antibiotics in water and soil. The results are important for the application of biochars to use as soil amendments in the remediation of antibiotic co-pollution in agricultural water or soils.

22649. 题目: Increased litter input significantly changed the total and active microbial communities in degraded grassland soils
文章编号: N20050508
期刊: Journal of Soils and Sediments
作者: Rongxiao Che, Dong Liu, Jinling Qin, Fang Wang, Weijin Wang, Zhihong Xu, Linfeng Li, Jinming Hu, Iman Tahmasbian, Xiaoyong Cui
更新时间: 2020-05-05
摘要: Purpose Increasing organic matter input and phosphorus fertilization are employed extensively to restore degraded grasslands. Nevertheless, little is known about their effects on microbes, especially on active microbial populations. Therefore, this study is aimed at examining the short-term influences of litter and phosphorus addition on microbes in degraded grassland soils. Materials and methods A microcosm experiment was established using soils sampled from a heavily degraded Tibetan alpine meadow. The experiment used a two-way factorial design with grass litter and phosphorus addition as the main factors. Microbial abundance and rDNA transcriptional activity were assessed through quantitative PCR. Total and active microbial community profiles were measured using DNA- and RNA-based MiSeq sequencing, respectively. Results and discussion As shown in this study, litter addition significantly increased microbial rDNA transcriptional activity and fungal abundance, but it decreased microbial α-diversity. However, prokaryote abundance was unaffected by the litter addition. Total and active soil microbial community profiles and interaction patterns were also significantly altered by litter addition. The relative abundance of copiotrophic and oligotrophic microbial lineages significantly increased and decreased, respectively, in the soils with litter addition. Functional predictions suggested that litter addition might significantly increase the abundance of pathogens, as well as microbes related to nitrogen fixation, denitrification, and chitinolysis, while decreasing nitrifier abundance. In contrast, no significant effects of the phosphorus addition on soil microbes were observed. Conclusions These findings highlight the significant effects of increasing litter input on total and active soil microbial communities and suggest that microbial responses should be considered when restoring degraded grasslands by increasing organic matter input.

22650. 题目: Octanol–Water Partition Coefficients of Aristolochic Acids and Implications to the Etiology of Balkan Endemic Nephropathy
文章编号: N20050507
期刊: Aquatic Geochemistry
作者: Thomas C. Voice
更新时间: 2020-05-05
摘要: The octanol–water partition coefficients (K_ow) of the aristolochic acids, AA I and AA II, were determined using the traditional shake-flask method as a function of pH and ionic strength. These compounds have been implicated in the etiology of Balkan endemic nephropathy, but evidence of a plausible exposure pathway remains elusive, and research is constrained by the absence of critical physical–chemical parameters on these compounds. Apparent K_ow values were determined across a range of pH and ionic strength conditions. The results show that the apparent K_ow decreased by approximately four orders of magnitude as pH increased from 2 to 9. The pH dependence was well described by a simple model that calculated the apparent K_ow based on the ionization fractions and intrinsic K_ow values for the neutral and ionized species. Higher ionic strength solutions resulted in higher K_ow values at high pH, but had no effect at low pH. These results suggest that transport of aristolochic acids will be highly dependent on pH and ionic strength, with significant aqueous-phase transport at neutral to slightly alkaline conditions, with the highest mobility occurring under low ionic strength conditions, and the possibility of significant partitioning to nonpolar phases, such as soil organic matter or plant material, at low pH. Much of the region where BEN is prevalent is a karst environment, and pH values are generally above 8, thus leaching and groundwater transport are favored, which can suggest possible exposure routes.

22651. 题目: Multicompartment occurrence and partitioning of alternative and legacy per- and polyfluoroalkyl substances in an impacted river in China
文章编号: N20050506
期刊: Science of the Total Environment
作者: Lijuan Gao, Jingling Liu, Kun Bao, Nannan Chen, Bo Meng
更新时间: 2020-05-05
摘要:

Per- and polyfluoroalkyl substances (PFASs) are emerging global environmental contaminants. Exploring the occurrence and environmental behavior of PFASs in the aquatic environment is a key step in solving global fluorine chemical pollution problems. In this study, surface water, pore water, and sediment were collected from the main tributary and the middle and lower reaches of the Daling River, adjacent to the Fuxin fluorochemical manufacturing facilities in Liaoning Province in China, to elucidate the occurrence and partition behavior of PFASs. The total concentrations of PFASs ranged from 48.4 to 4578 ng/L in the overlying water, from 173 to 9952 ng/L in the pore water, and from 2.16 to 40.3 ng/g dw in the sediment fraction. Generally, perfluorobutanoic acid (PFBA) and perfluorobutane sulfonate (PFBS) were the predominant congeners in the samples, with the mean relative content fractions being almost consistently >40% in the dissolved phase and >25% in the sediment. Hexafluoropropylene oxide dimer acid (HFPO-DA) and chlorinated polyfluorinated ether sulfonic acid (6:2 Cl-PFESA) were detected, albeit at low levels. In addition, the detection frequency and the contribution of legacy long-chain PFASs in sediment were higher than those in the overlying water and pore water. Except for perfluorohexane sulfonate (PFHxS), the concentrations of the alternative PFASs in the pore water were higher than in the overlying water. The organic carbon fraction was a more important controlling factor for PFAS sediment levels than cations content. As with legacy long-chain PFASs, HFPO-DA and 6:2 Cl-PFESA tended to partition into the solid phase, whereas short-chain PFASs were readily distributed in the aqueous phase. Such research results will be helpful in modeling the transport and fate of PFASs released by point sources into coastal waters through rivers and in developing effective risk assessment and management strategies for the control of PFAS pollution.

22652. 题目: Efficient removal of U(VI) from aqueous solutions using the magnetic biochar derived from the biomass of a bloom-forming cyanobacterium (Microcystis aeruginosa)
文章编号: N20050505
期刊: Chemosphere
作者: Binliang Wang, Yingying Li, Junli Zheng, Yiwei Hu, Xiaojun Wang, Baowei Hu
更新时间: 2020-05-05
摘要:

The utilization of Microcystis biomass is an urgent issue in the mitigation of cyanobacterial bloom. In this study, Microcystis-derived biochar (MB) and Fe₃O₄-modified biochar (Fe₃O₄/MB) were fabricated for the U(VI) elimination. The results showed that U(VI) sorption process by either MB or Fe₃O₄/MB was pH-dependent and ionic strength-independent. The maximum sorption capacity of MB was higher than that of Fe₃O₄/MB. According to the analysis of X-ray photoelectron spectroscopy, U(VI) sorption on both MB and Fe₃O₄/MB was mainly ascribed to the surface complexation between U(VI) and oxygen-containing functional groups on the surface of MB. Fe₃O₄ particles on the surface of MB didn't provide extra active sites for the sorption of U(VI), but it enabled the adsorbent to be magnetically separated. Five consecutive sorption/desorption cycles verified the good reusability of Fe₃O₄/MB in this study. Therefore, the investigation is not only meaningful for the utilization of nuisance biomass from cyanobacterial blooms, but also provides novel adsorbents for the U(VI) removal from aqueous solutions.

22653. 题目: Treatment of digestate residues for energy recovery and biochar production: From lab to pilot-scale verification
文章编号: N20050504
期刊: Journal of Cleaner Production
作者: Chunxing Li, Jie Li, Lanjia Pan, Xinyu Zhu, Shengyu Xie, Guangwei Yu, Yin Wang, Xiaofang Pan, Gefu Zhu, Irini Angelidaki
更新时间: 2020-05-05
摘要:

Hydrothermal pretreatment was used for dewatering food waste digestate residue, and biochar/biogas were generated from the separated solid and liquid phases via pyrolysis and anaerobic digestion, respectively. Increasing hydrothermal pretreatment temperature (110–200 °C) clearly improved dewaterability, whereas enhancing treatment duration (30–90 min) had little impact. The optimal condition of 160 °C/30 min gave the best dewatering performance with relative lower energy consumption and was chosen for pilot-scale verification achieving 61.7 wt% dry weight content after mechanical squeezing. Moreover, the filtrate and filter cake obtained at optimal condition were applied for biogas and biochar production in lab scale. The methane yield of the filtrate was 335 mL/g COD. Pyrolysis temperature of 500 °C gave better biochar performance and was verified in a pilot scale test. Additionally, the heavy metals in digestate were effectively immobilized during hydrothermal dewatering and pyrolysis processes. In the end, mass/energy balance calculated using pilot-scale data presented the combined systems provided a promising strategy for accomplishing energy recovery and resource reuse of digestate residue.

22654. 题目: Sedimentary organic matter and early Toarcian environmental changes in the Lusitanian Basin (Portugal)
文章编号: N20050503
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Bruno Rodrigues, Luís V. Duarte, Ricardo L. Silva, João Graciano Mendonça Filho
更新时间: 2020-05-05
摘要:

The objective of this study is to investigate the relationship between early Toarcian climatic events and the composition of kerogen assemblages in the Lusitanian Basin (Portugal). In particular, we aim to understand how the Pliensbachian–Toarcian Event (Pl–Toa Event) and Toarcian Oceanic Anoxic Event (TOAE) affected the continental areas of the western Iberian margin and how possible variations in continental sources of organic matter (OM) were expressed in marginal-marine and hemipelagic depositional environments during the early Toarcian.

We present here a characterisation [total organic carbon (TOC), total sulphur (TS), δ¹³C in kerogen concentrate (δ¹³C_Kerogen), and palynofacies] of kerogen assemblages from several uppermost Pliensbachian (emaciatum ammonite Zone)–lower Toarcian sections in the Lusitanian Basin (western Iberian margin), including the Peniche section, which contains the Toarcian GSSP. In all sections, TOC concentration is low (average 0.4 wt%), with the highest values reaching up to 2.1 wt% in a discrete level located approximately 10.5 m above the base of the levisoni Zone at Peniche. The TOAE negative carbon isotope excursion is observed in kerogen concentrate at the base of the levisoni Zone throughout the basin. Palynofacies analysis demonstrates that the kerogen assemblages are mostly of terrestrial affinity, with the dominance of the Phytoclast Group and terrestrial palynomorphs, and with punctual increases in amorphous organic matter, freshwater (e.g. Botryococcus sp.) and marine microplankton (dinoflagellate cysts, acritarchs, and prasinophyte algae) in specific stratigraphic intervals. A change in palynofacies assemblages associated with the TOAE is observed around the base of levisoni Zone. Although with slight differences between sections, the TOAE interval records an increase in non-opaque, translucent, phytoclasts (NOP) and cuticle fragments, and is also associated with an increased contribution of terrestrial palynomorphs (increase in sporomorphs and Classopollis in tetrads and agglomerates) and decrease in marine palynomorphs. The increases in NOP and terrestrial palynomorphs support the postulated enhancement of the hydrological cycle and increased export of terrestrial OM into marine environments during the early Toarcian, especially during the TOAE, in the western Iberian margin. Understanding the impact of the early Toarcian climatic events on land-based ecosystems may provide important insights into current climate change.

22655. 题目: Insights into the removal efficiencies of aged polycyclic aromatic hydrocarbons in humic acids of different soil aggregate fractions by various oxidants
文章编号: N20050502
期刊: Environmental Pollution
作者: Wenbing Tan, Niankai Liu, Qiuling Dang, Dongyu Cui, Beidou Xi, Hong Yu
更新时间: 2020-05-05
摘要:

Chemically oxidative removal of polycyclic aromatic hydrocarbons (PAHs) in soil is related to their occurrence state. Whether the heterogeneity of natural organic matter has an effect on the occurrence of PAHs in soil and, if there is an effect, on the oxidative removal efficiency of PAHs remains unknown. In this study, the removal efficiencies of 16 priority PAHs aged in humic acids (HAs) of different soil aggregate fractions by various oxidants were investigated by combining soil fractionation and microreaction experiments. Results showed that the accumulations of PAHs in particulate HA (P-HA) and microaggregate occluded HA (MO-HA) mainly occurred in the early period of the aging time frame. In contrast, PAH accumulation in non-aggregated silt and clay associated HA (NASCA-HA) was relatively slow and tended to saturate in the late period of the aging time frame. The cumulative contents of PAHs throughout the entire aging period in MO-HA and NASCA-HA were significantly greater than that in P-HA. The aged PAHs in P-HA and NASCA-HA exhibited the highest and lowest removal efficiencies, respectively. This ranking was mainly governed by the molecular size and polarity of HAs. Sodium persulfate and potassium permanganate had the highest removal efficiencies in total PAHs in HAs, with average efficiencies of 85.8% and 79.1%, respectively, in P-HA. Hydrogen peroxide had the lowest degradation efficiency in PAHs. In particular, the degradation efficiency of total PAHs in NASCA-HA was lowered to 31.0%. PAH congeners in HAs showed a large difference in oxidative removal efficiency. Low-ring PAH was more easily degraded than medium- and high-ring PAHs, and in most treatments, fluoranthene and pyrene in the medium ring and benzo[a]pyrene in the high ring demonstrated higher efficiencies than other PAHs with the same number of rings. Our findings are useful in promoting the accurate and green remediation of PAH-contaminated soils.

22656. 题目: Effect of Darcy flux on the release of dissolved organic matter and nitrogen from coal gangue in a coal mine underground reservoir: Column experiments
文章编号: N20050501
期刊: Chemical Geology
作者: Qing Zhang, Shaohe Luo, Li Zhao, Panqun Zhang, Shidong Wang, Chao Sun, Lei Zhang
更新时间: 2020-05-05
摘要:

Underground reservoirs packed with coal gangue have been widely used to store and purify mine water in the coal mine areas of China; however, minimal information is available about the effects of pollutants released from the packed matrix on the quality of stored water. Column experiments were performed at 25 °C and Darcy fluxes of 0.39, 0.73, and 1.56 cm/h to investigate the effect of Darcy flux on the dynamic changes of dissolved organic matter (DOM) and nitrogen released from the packed coal gangue. Results showed that the values of dissolved organic carbon (DOC), UV₂₅₄, organic nitrogen (ORG-N), nitrate, and total dissolved solids (TDS) in the effluent decreased rapidly within 3.7 pore volumes (PV) at the three Darcy fluxes and then decreased slowly and tended to become stable during the column experiments. However, the effluent concentrations of NH₄⁺–N, which is the major nitrogen released from the packed matrix, and total nitrogen (TN) decreased and increased alternately, which can be relative to the lithology, mineral, and chemical composition of the studied matrix. The quantities of DOC, NH₄⁺–N, ORG-N, and TN released from the studied matrix decreased with Darcy flux, suggesting a positive effect of hydraulic retention time (HRT) on the resolution of pollutants from the studied matrix. Moreover, the microbial environment got weakened with an increase in Darcy flux, as confirmed by the variation trends of the biological/autochthonous index (BIX) and the fluorescence index (FI). Thus, the evident accumulation of NO₂⁻ –N and the highest content of NO₃⁻−N were observed due to incomplete nitrate reduction with a low efficiency at 1.56 cm/h. The findings will be helpful in estimating the variation of water quality during the storage of mine water in a coal mine underground reservoir in China.

22657. 题目: Phosphorus Sorption and Desorption in Soils Treated by Thermal Desorption
文章编号: N20050402
期刊: Water, Air, and Soil Pollution
作者: T. M. DeSutter
更新时间: 2020-05-04
摘要: Thermal desorption (TD) is an effective way to remove hydrocarbons from soil. Soil exposure to temperatures between 100 and 400 °C to volatilize hydrocarbons can alter soil chemical properties that have potential to change phosphorus (P) dynamics. A series of laboratory soil sorption and desorption experiments were conducted on native and thermal desorption (TD)-treated soils to determine behavior of P with respect to availability for plant uptake and risk for runoff. The average relative increase in P sorption after TD treatment was between 14 and 26% as shown by S_max values. This increase in soil P sorption capacity is likely due to the potential creation of biochar materials and mineral transformations of Fe and Al oxides during TD treatment. Dissolved organic carbon association with P did not influence sorption. Desorption of P was least in TD-treated soils, indicating that the interaction between P and binding sites was strong. The amount of P retained by these soils (S_max values) may be of agronomic concern and should be considered when developing fertility plans. Based on these results, TD-treated soils pose no apparent threat to nearby surface waters.

22658. 题目: Study of the dissolved organic matter (DOM) of the Auzon cut-off meander (Allier River, France) by spectral and photoreactivity approaches
文章编号: N20050401
期刊: Environmental Science and Pollution Research
作者: Davide Palma, Mohamad Sleiman, Olivier Voldoire, Aude Beauger, Edith Parlanti, Claire Richard
更新时间: 2020-05-04
摘要: Wetlands are recognized for the importance of their hydrological function and biodiversity, and there is now a consensus to protect and restore them as well as to complete the knowledge on their functioning. Here, we studied the dissolved organic matter (DOM) of a wetland composed of the Auzon cut-off meander, the Allier River, the alluvial fluvial flow, and watershed aquifer. Water was sampled at different locations, in spring, summer, and autumn. For each sample, DOM was characterized for its chemical and optical properties and its photooxidant capacity through its ability to generate DOM triplet excited states (³DOM*) and singlet oxygen upon simulated solar light exposure. UV-visible and fluorescence indices revealed that DOM was mainly microbial-derived whatever the sampling sites with spatial and temporal variations in terms of aromaticity (5.5–22%), specific UV absorbance at 254 nm (0.28–2.82 L m⁻¹mgC⁻¹), ratio of the absorbance at 254 and 365 nm (4.6–10.8), fluorescence index (1.35–166), and biological index (0.812–2.25). All the samples generated ³DOM* and singlet oxygen, rates of formation of which showed parallel variations. Using principal component analysis (PCA), we found positive correlations between the sensitizing properties of DOM samples and parameters associated to the abundance of low molecular weight and low absorbing chromophores. Moreover, the parameter variation across the wetland reinforced the hydrological movements observed in a previous study, suggesting that these parameters could be used as water connection tracers.

22659. 题目: Dissolved organic matter dominating the photodegradation of free DNA bases in aquatic environments
文章编号: N20050307
期刊: Water Research
作者: Jing Li, Xin Zhang, Wen-Yuan Fan, Mu-Cen Yao, Guo-Ping Sheng
更新时间: 2020-05-03
摘要:

Free DNA bases are widely present in the environments, and can be utilized by bacteria for their nucleic acids synthesis or as nutrition sources. In sunlit natural waters, these free bases probably undergo photodegradation which would change the bioavailable bases contents. Though the photodegradation of DNA has been investigated, the photodegradation behaviors of free bases may be quite different from DNA-confined bases in consideration of their different chemical environments. Herein, the photodegradation of four free bases (guanine, adenine, thymine and cytosine) was investigated. Results show that direct photodegradation of free bases in phosphate buffer caused by UV was slow. However, the photodegradation of these free bases were greatly enhanced in dissolved organic matter (DOM) solution. In the presence of 10–50 mg/L DOM, the photodegradation rates of free bases were increased by 1.85–14.6 times compared to the controls without DOM. DOM could result in indirect photodegradation by producing hydroxyl radical (•OH) and singlet oxygen (¹O₂) under irradiation, and this indirect photodegradation enhanced and dominated the free bases photodegradation. The •OH was involved in all four bases photodegradation, while the ¹O₂ only participated in guanine photodegradation. In phosphate buffer, the fastest photodegradation bases were pyrimidine, however, guanine became the fastest photodegradation base in DOM solution due to the selective oxidation of guanine by ¹O₂. In summary, DOM may be a determinant for free bases photodegradation in natural waters and thereby deeply influence their fates in aquatic environments.

22660. 题目: Revealing the 2D scale‐location specific variations of soil properties in the coal mining area of Changhe watershed, China
文章编号: N20050306
期刊: Land Degradation and Development
作者: Hongfen Zhu, Rutian Bi, Ruipeng Sun, Zhanjun Xu, Chunjuan Lv, Jason Yang
更新时间: 2020-05-03
摘要:

Many researches have been conducted to understand the scale‐location specific variations of soil properties in one‐dimensional soil samples. However, these results were not properly to understand the two‐dimensional distributions of soil characteristics, especially in the coal mining areas. Therefore, the objective of this study is to reveal the scale‐location dependent variation of two‐dimensional patterns for soil properties and to achieve soil organic matter (SOM) prediction based on its scale‐location effects in the coal mining area. To this end, SOM, porosity, and silt were measured at top (0–20 cm), middle (20–40 cm), and bottom layer (40–60 cm) in Changhe watershed, China. The scale‐specific spatial patterns of soil properties were extracted using two‐dimensional empirical mode decomposition (2DEMD), and SOM was predicted using stepwise multiple linear regression (SMLR) and 2DEMD_GS. It was found that the spatial distributions of SOM residue (>24 km) at middle layer, and porosity residue at top and bottom layers could reveal the differentiation between coal mining and non‐coal mining areas. The scale‐effects on the relationships between SOM and its covariates was stronger than that of land uses, and the relationships of SOM with the covariates in different land use types were distinctive at top layer, and were similar at bottom layer. 2DEMD_GS performed better than SMLR on SOM prediction for its involvement of scale and location effects. Therefore, the relationships between SOM and influencing factors were a function of scale, location, and land uses activities, and the scale‐ and location‐dependent method should be considered for SOM prediction.

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