61. 题目: Long-term effects of contrasting tillage systems on soil C and N pools and on main microbial groups differ by crop sequence
期刊: Soil and Tillage Research
作者: Giuseppe Badagliacca, Vito Armando Laudicina, Gaetano Amato, Luigi Badalucco, Alfonso Salvatore Frenda, Dario Giambalvo, Rosolino Ingraffia, Antonella Plaia, Paolo Ruisi
摘要: Determining the best conservation agriculture practices for increasing soil organic carbon (C) and hence soil quality is of paramount importance in the semi-arid Mediterranean environment, where soils are experiencing a continuous decline in organic matter. Therefore, the aim of this long-term study was to assess the combined effects of tillage system and crop sequence on soil organic C and biochemical properties of soil generally used as indicators of soil quality. After 23 years of continuous application of contrasting tillage systems (conventional tillage [CT], vs. no tillage [NT]) and crop sequences (wheat monoculture vs. wheat-faba bean rotation), soil samples were collected from topsoil (0–15 cm) and subsoil (15–30 cm) at three different times during a cropping year. Soil samples were analyzed for total and labile organic C pools, microbial biomass C (MBC) and microbial biomass N, basal respiration, and the abundance of main microbial groups by phospholipid fatty acids. Long-term NT increased total organic C (TOC) at a yearly rate of 0.17 g kg−1. This in turn stimulated microbial biomass, in particular Gram-negative bacteria. This suggests a higher soil quality in NT, as was confirmed by the increase in MBC/TOC and the decrease in stress indices. In contrast, no differences were observed with regard to fungal biomass. These findings suggest the need to reconsider the role of specific bacterial groups in organic C accumulation in soils of semiarid environments. It is interesting that the effects of long-term NT varied widely by crop sequence, whereas in CT changes in biochemical characteristics and in the main microbial groups due to crop sequence were modest. Thus, the interaction among various aspects of agronomic management modulates the effects of substrate quality on chemical and biological properties of soil.
62. 题目: Responses of nitrification and bacterial community in three size aggregates of paddy soil to both of initial fertility and biochar addition
期刊: Applied Soil Ecology
作者: Qiong Hou, Ting Zuo, Jian Wang, Shan Huang, Xiaojun Wang, Longren Yao, Wuzhong Ni
摘要: Biochar has been suggested to increase the soil nutrient retention capacity. The interaction of biochar addition and soil initial fertility through modifying soil aggregates on soil bacterial community and nitrogen transformation is still unclear. A 60-day incubation experiment was conducted to investigate the influences of biochar addition on soil nitrification and associated nitrifying microbial community in three size aggregates of different derived soils. The results indicated that potential nitrification rates (PNRs) in three size soil aggregates of biochar addition treatment were significantly (P < 0.05) higher than those of no biochar addition, especially in small size aggregates or in the soils collected from no fertilizer plots. The results of 16S rRNA gene profiling showed that biochar addition significantly (P < 0.05) increased community alpha-diversity. Nitrosomonas was relatively more abundant in microaggregates, whereas Nitrospira was more abundant in macroaggregates. Biochar addition could modify structure of soil microbial communities by changing soil properties, and consequently regulate the nitrification processes as suggested by canonical correlation analysis. Conclusively, biochar addition can promote the nitrification process with the higher community diversity and activity of nitrifying bacteria in soils, more strongly in fertile soils or in the small macroaggregates. The initial soil fertility should be fully considered in practical application of biochar.
63. 题目: Mobilization of arsenic from coal fly ash in the presence of dissolved organic matter
期刊: Applied Geochemistry
作者: Amrika Deonarine, Allan Kolker, Michael W. Doughten, James T. Holland, Jeremy D. Bailoo
摘要: In this study, we examined the influence of dissolved organic matter (humic and fulvic acids) on arsenic (As) mobilization from two Class F coal fly ashes under oxic and anoxic conditions. Batch leaching experiments were conducted to examine As leaching behavior and changes in As aqueous and solid phase speciation after exposure to humic and fulvic acids for up to 4 weeks (ash: buffer ratio = 0.01 g/mL). Under oxic conditions, mobilized As concentrations increased compared to the organic-free controls and were positively correlated with percent aliphatic carbon and oxygen/carbon ratio of the humic and fulvic acids, suggesting both non-specific hydrophobic association of the organic matter with the surface of the fly ash particles and competitive desorption between negatively charged organic functional groups and As anions adsorbed to mineral surfaces. Under anoxic conditions, organic matter enhanced the reductive dissolution of As-bearing iron oxides such as hematite, resulting in increased As mobilization. X-ray absorption spectroscopy indicated that the majority of As in the leached and unleached fly ash was As(V) (≥ 90%), with As(V)-ferrihydrite precipitation occurring under all leaching conditions tested. Our results demonstrated that humic and fulvic acids are capable of mobilizing As from fly ash under both oxic and anoxic conditions, though redox appeared to be a larger driver of As mobilization compared to dissolved organic matter (DOM). DOM is a parameter which should be considered in risk assessment strategies for fly ash that is exposed to water (e.g., subsurface infiltration) or released to aquatic systems.
64. 题目: Arbuscular mycorrhizal trees cause a higher carbon to nitrogen ratio of soil organic matter decomposition via rhizosphere priming than ectomycorrhizal trees
期刊: Soil Biology and Biochemistry
作者: Liming Yin, Feike A. Dijkstra, Richard P. Phillips, Biao Zhu, Peng Wang, Weixin Cheng
摘要: Tree roots and their associated microbes can significantly influence soil organic matter (SOM) decomposition, i.e., the rhizosphere priming effect. This effect is expected to be greater in trees associated with arbuscular mycorrhizal (AM) fungi, which produce higher extracellular enzymes especially surrounding hyphae, than in trees associated with ectomycorrhizal (ECM) fungi. Here, we selected five tree species associated with AM (Juglans mandshurica Maxim. and Cunninghamia lanceolata (Lamb.) Hook.) or ECM (Picea koraiensis Nakai, Quercus mongolica Fischer ex Turcz. and Larix kaempferi (Lamb.) Carriere). We grew tree seedlings inside of cores lined with different mesh sizes to investigate how roots, hyphae and exudates influence soil carbon (C) and nitrogen (N) mineralization via the rhizosphere priming effect, using a 13C natural abundance approach and a 15N pool dilution method, concurrently. We found that compared to unplanted control pots, tree seedlings significantly accelerated soil C decomposition by on average 78%, i.e., positive priming. AM-associated trees induced 2.1 times greater soil C decomposition than ECM-associated trees across all mesh sizes. In contrast, gross N mineralization did not differ between tree-mycorrhizal associations. Compared to ECM counterparts, AM-associated trees produced higher C- and lower N-degrading enzyme activities. Consequently, AM-associated trees induced a significantly higher C:N ratio of SOM decomposition than their ECM counterparts, which could be associated with the differences in soil enzyme activities for C and N degradation. Further, for both AM- and ECM-associated trees, we found no significant influences of mesh size on soil C decomposition, suggesting that the rhizosphere priming effect of mycorrhizal symbiosis was predominantly driven by root exudates. We conclude that AM-associated trees may enhance SOM decomposition with a higher C:N ratio than their ECM counterparts mainly due to differences in microbial enzyme investment. Our findings imply that tree-mycorrhizal associations are capable of modulating soil biogeochemical cycling via the rhizosphere priming effect.
65. 题目: Coupled data-driven and process-based model for fluorescent dissolved organic matter prediction in a shallow subtropical reservoir
期刊: Environmental Modelling & Software
作者: Xinchen Wang, Hong Zhang, Edoardo Bertone, Rodney A. Stewart, Sara P. Hughes
摘要: Monitoring and understanding the dissolved organic matter (DOM) cycle in a drinking water reservoir is crucial to water authorities, since most water treatment practices aim to remove DOM to prevent the formation of potentially harmful disinfection by-products. A vertical profiling system (VPS) installed in reservoirs can continuously detect the fluorescent DOM (fDOM) and determine the fDOM transport process. Although the VPS can interprete fDOM concentrations, water treatment operators still collect and rely upon DOM datasets that are manually sampled throughout the year. A long-term historical database provides an opportunity to develop a three-dimensional fDOM prediction model. In the present study, we collected and analysed VPS and sampling data and developed and assessed an innovative coupled data-driven and process-based model. These models were able to forecast future fDOM in both temperate and extreme weather conditions. Modelling scenario analysis concluded that deeper layers of the reservoir as well as areas close to the riverine zone had higher fDOM concentrations than any other zones during storm events. Simulated fDOM can be a proxy for dissolved organic carbon concentration. The model also determined that inflow creeks were predominant fDOM sources during storm events and continuing winds transported the fDOM from bottom to surface water layers. This study has implications for reservoir and water treatment plant operators seeking to gain a better understanding of the DOM cycle in a reservoir and to more efficiently manage DOM removal.
66. 题目: Records of iodine isotopes (129I, 127I) in the Barkol peat bog from northwest China and their sources, transport and preservation
作者: Xue Zhao, Xiaolin Hou, Dongliang Zhang, Yunpeng Yang, Zhao Huang, Qi Liu
摘要: The research on geochemical behaviors of iodine is significant for deep understanding of the source and distribution of iodine on the earth. However, as one of the most important sources, the ocean emissions and relative transport pathways of iodine, as well as the preservation after deposition are still not well known, especially in the arid areas of central Asia. A peat sediment core collected nearby Barkol Lake from northwest China was analyzed for iodine isotopes (127I and 129I). The observed high 127I concentration in the top 2 cm indicated a significant accumulation of iodine in the surface oxic conditions due to the continuous sources of incompletely decomposed organic matter. Dissociation of iodine into pore waters occurred once the anoxic conditions established beneath the surface by a serial reduction reaction during the degradation of organic matter. The temporal variation of anthropogenic 129I in the peat sediment recorded its sources and transport pathways. Besides the global fallout 129I during late 1950s and early 1960s, the significantly increased air releases from the European nuclear fuel reprocessing plants during 1975 to 1997 and the increased marine discharges since 1990’s contributed the major portion of 129I in the peat core. The major transport pathway of 129I from the Europe was through Westerlies following the re-emission of the marine discharged 129I to the atmosphere, indicating a clearly ocean emitted iodine in the concerned Central Asia.
67. 题目: Biochar heavy metal removal in aqueous solution depends on feedstock type and pyrolysis purging gas
期刊: Environmental Pollution
作者: Md. Shahinoor Islam, Jin-Hyeob Kwak, Christopher Nzediegwu, Siyuan Wang, Kumuduni Palansuriya, Eilhann E. Kwon, M. Anne Naeth, Mohamed Gamal El-Din, Yong Sik Ok, Scott X. Chang
摘要: The effectiveness of biochar as a sorptive material to remove contaminants, particularly heavy metals, from water is dependent on biomass type and pyrolysis condition. Biochars were produced from pulp mill sludge (PMS) and rice straw (RS) with nitrogen (N2) or carbon dioxide (CO2) as the purging gas. The sorptive capacity of the biochars for cadmium(II), copper(II), nickel(II) and lead(II) was studied. The heavy metal adsorption capacity was mainly affected by biomass type, with biochars adsorption capacities higher for lead(II) (109.9-256.4 mg g-1) than for nickel(II) (40.2-64.1 mg g-1), cadmium(II) (29.5-42.7 mg g-1) and copper(II) (18.5-39.4 mg g-1) based on the Langmuir adsorption model. The highest lead(II) adsorption capacities for PMS and RS biochars were 256.4 and 133.3 mg g-1, respectively, when generated using N2 as the purging gas. The corresponding lead(II) adsorption capacities were 250.0 and 109.9 mg g-1, respectively, when generated using CO2 as the purging gas. According to the intraparticle diffusion model, 30-62% of heavy metal adsorption was achieved in 1 h; film diffusion was the rate-dominating step, whereas pore diffusion was a rate-limiting step. Ion exchange and complexation between heavy metals and biochar surface functional groups such as carbonyl and hydroxyl groups were effective mechanisms for heavy metal sorption from the aqueous solution. We conclude that proper selection of both the feedstock type and the purging gas is important in designing biochars for the effective removal of potentially toxic metals from wastewater.
68. 题目: Sewage sludge and solid residues from biogas production derived biochar as an effective bio-waste adsorbent of fulvic acids from water or wastewater
作者: Magdalena Kończak, Anna Siatecka, Michael A. Nazarkovsky, Bożena Czech, Patryk Oleszczuk
摘要: Due to environmental concern, direct utilization of sewage sludge or residues from biogas production is restricted. Conversion of problematic bio-wastes into biochars can be a very effective solution. In the presented study, the adsorption of fulvic acids onto series of biochars produced from bio-wastes such as sewage sludge, residues from biogas production, and plant (Miscanthus sp.) were performed to examine the behavior of biochars in the environment and interactions with fulvic acids as the representatives of dissolved organic matter. The results clearly indicate that the highest excess of fulvic acids, 93-96 mg g-1, was chemisorbed onto biochar obtained specifically from sewage sludge. The mechanism of the adsorption was independent from applied biochar feedstock. Monolayer coverage was dominant onto all biochars. Generally, adsorption was assumed to be controlled by polar interactions between fulvic acids and the biochars or pre-adsorbed and residual fulvic acids molecules (which were dominant) and the strong π-π interactions. The obtained high values of the adsorption capacity of sewage sludge derived biochars confirmed that thermal treatment is a very effective tool of bio-waste management.
69. 题目: Evaluation of Temperature on the Biological Activities and Fertility Potential During Vermicomposting of Pig Manure Employing Eisenia fetida
期刊: Journal of Cleaner Production
作者: Yong Zhou, Dan Zhang, Yunfeng Zhang, Jingshi Ke, Deli Chen, Minggang Cai
摘要: In this laboratory-scale study, the biological activities and vermicomposting potential of Eisenia fetida in pig manure were investigated to evaluate the influence of temperature (10°C-50°C) on vermicomposting effect. The enzyme activities of catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), and the content of malondialdehyde (MDA) in earthworm, macro-nutrients (N, P, K), total organic carbon (TOC), humification index (HIX) and C/N ratio in pig manure have been investigated simultaneously. Results revealed that CAT activity elevated initially and then declined with the increased temperature. The increased POD, SOD activity and MDA content indicated the antioxidant stress response of earthworm and the optimum temperature was found at 30°C. After vermicomposting the pig manure for 60 d under temperature range of 10°C-50°C, the vermicompost exhibited a significant increase in macro-nutrients, whereas a reduction was observed in TOC, C/N ratio and HIX, reflecting the efficient decomposition of organic waste driven by earthworms and microorganisms synergistically. The result of total microbial population showed the increase of actinomycetes and bacterial population. The enhancement percentage was in the order: 30°C > 40°C > 50°C > 20°C > 10°C, revealing the impact of temperature. The results indicated the advantage of vermicomposting with Eisenia fetida and the regulation mechanism of temperature on the vermicomposting effect of pig manure. The present study will benefit to the utilization of agricultural wastes and achieving environmental sustainability.
70. 题目: Effects of microorganism-mediated inoculants on humification processes and phosphorus dynamics during the aerobic composting of swine manure
期刊: Journal of Hazardous Materials
作者: Tao Zhang, Xiaosha Wu, Sabry M. Shaheen, Jörg Rinklebe, Nanthi S. Bolan, Esmat F. Ali, Guoxue Li, Daniel C.W. Tsang
摘要: There is significant interest in the treatment of swine manure, which is a hazardous biowaste and a source of pathogenic contamination. This work investigated the effects of microorganism-mediated inoculants (MMIs) on nutrient flows related to humification or phosphorus (P) dynamics during the aerobic composting of swine manure. The impact of MMIs on microbe succession was also evaluated. The addition of MMIs had positive effects associated with nutrient flows, including thermal activation, decreases in certain fluorescence emissions, lower mass loss and variations in levels of certain elements and functional groups. MMIs altered the maturation behavior and kinetics of organic matter while improving microbial activity. Phosphorus was found in the compost in the forms of MgNH4PO4·6H2O crystals and Poly-P as the IP species, and Mono-P as the OP species in compost generated from the dissolution or inter-transformation among P pools. These nutrient flows are attributed to changes in the structure of microbial communities as a consequence of introducing MMIs. Diverse microbial compositions were identified in different composting phases, although Bacillus appeared in each phase. This work provides support for the aerobic composting of hazardous biowaste as well as an improved understanding of nutrient flows, as a means of producing higher quality compost.
71. 题目: Constructing N, P-dually doped biochar materials from biomass wastes for high-performance bifunctional oxygen electrocatalysts
作者: Lin-Lin Ma, Xiao Hu, Wu-Jun Liu, Hong-Chao Li, Paul K.S. Lam, Jianxiong Raymond Zeng, Han-Qing Yu
摘要: The large scale lignocellulosic biomass wastes could also be regarded as abundantly-available renewable resources, and how to convert them into value-added products via sustainable approaches is still a big challenge. In this work, we demonstrated a facile pyrolysis method to construct N, P-dually doped biochar materials from the lignocellulosic biomass wastes. The as-synthesized N, P-dually doped biochar samples could act as electrocatalysts for oxygen reduction and evolution reactions (ORR/OER), showing excellent catalytic performance and long-term durability, as well as robust tolerance to CO and methanol. The unique hierarchical porous structure, favorable electronic structure modified by the N and P doping, as well as a variety of defect sites induced by the N and P doping into the carbon framework were identified as the main contributions to the prominent catalytic activity of the as-synthesized N, P-dually doped biochar materials. We expect this work would spur more efforts into developing advanced materials from the large scale lignocellulosic biomass wastes.
72. 题目: Quantification of blue carbon in seagrass ecosystems of Southeast Asia and their potential for climate change mitigation
期刊: Science of The Total Environment
作者: Milica Stankovic, Rohani Ambo-Rappe, Filipo Carly, Floredel Dangan-Galon, Miguel D. Fortes, Mohammad Shawkat Hossain, Wawan Kiswara, Cao Van Luong, Phan Minh-Thu, Amrit Kumar Mishra, Thidarat Noiraksar, Nurjannah Nurdin, Janmanee Panyawai, Ekkalak Rattanachot, Mohammad Rozaimi, U. Soe Htun, Anchana Prathep
摘要: Seagrasses have the ability to contribute towards climate change mitigation, through large organic carbon (Corg) sinks within their ecosystems. Although the importance of blue carbon within these ecosystems has been addressed in some countries of Southeast Asia, the regional and national inventories with the application of nature-based solutions are lacking. In this study, we aim to estimate national coastal blue carbon stocks in the seagrass ecosystems in the countries of Southeast Asia including the Andaman and Nicobar Islands of India. This study further assesses the potential of conservation and restoration practices and highlights the seagrass meadows as nature-based solution for climate change mitigation. The average value of the total carbon storage within seagrass meadows of this region is 121.95 ± 76.11 Mg ha−1 (average ± SD) and the total Corg stock of the seagrass meadows of this region was 429.11 ± 111.88 Tg, with the highest Corg stock in the Philippines (78%). The seagrass meadows of this region have the capacity to accumulate 5.85–6.80 Tg C yr−1, which accounts for $214.6–249.4 million USD. Under the current rate of decline of 2.82%, the seagrass meadows are emitting 1.65–2.08 Tg of CO2 yr−1 and the economic value of these losses accounts for $21.42–24.96 million USD. The potential of the seagrass meadows to the offset current CO2 emissions varies across the region, with the highest contribution to offset is in the seagrass meadows of the Philippines (11.71%). Current national policies and commitments of nationally determined contributions do not include blue carbon ecosystems as climate mitigation measures, even though these ecosystems can contribute up to 7.03% of the countries' reduction goal of CO2 emissions by 2030. The results of this study highlight and promote the potential of the southeast Asian seagrass meadows to national and international agencies as a practical scheme for nature-based solutions for climate change mitigation.
73. 题目: Trametes versicolor laccase-assisted oxidative coupling of estrogens: Conversion kinetics, linking mechanisms, and practical applications in water purification
期刊: Science of The Total Environment
作者: Kai Sun, Dan Hong, Jie Liu, Abdul Latif, Shunyao Li, Gang Chu, Wenxiu Qin, Youbin Si
摘要: The potential application of fungal laccase-assisted bioremediation for estrogen elimination has caused tremendous attention. Herein, naturally-occurring Trametes versicolor laccase (Tvlac) was capable of significantly removing 17β-estradiol (E2) and 17α-ethynylestradiol (EE2) at pH 5. A lower (or higher) pH caused decline in the velocity constants (kprcs) by obstructing the single-electron oxidation of estrogen at Tvlac T1-Cu site (or intercepting the intramolecular-electron transfer between Tvlac T1-Cu and T2/T3-Cu sites). Humic acid (HA) and natural phenolic compounds (PCs) are omnipresent in water and can influence the conversion kinetics of estrogen in Tvlac-triggered reactions. Compared with HA-free, the kprcs values of E2 and EE2 in presence of HA respectively reduced 58.61%–83.72% and 69.72%–95.62% at different pH levels. Additionally, the kprcs values for estrogen were also hampered obviously by O-dihydroxyphenol structure of model PCs, owning to the created monomeric/polymeric O-quinones inverted estrogen phenoxy radicals. The generated carbon-carbon/oxygen self-linking aggregates during Tvlac-mediated estrogen oxidative coupling were characterized, and the polymerization mechanisms were speculated. A fluid-bed reactor with cross-linked-entrapped Tvlac in Ca-alginate beads was established to treat E2 and EE2, respectively. Compared with free Tvlac, immobilized Tvlac prominently exhibited a higher pH and temperature stability. Especially, the fluid-bed reactor with immobilized Tvlac could be reused, keeping its high conversion efficiencies of E2 and EE2 in natural water, only changing from 99.2% to 73.6% and from 98.5% to 70.9% after 1 to 5 cycles, respectively. These findings present an alternative immobilized fungal laccase-based clean biotechnology for continuously handling estrogen-contaminated waterbodies at a large-scale.
74. 题目: Removal of humic acid and Cr(Ⅵ) from water using ZnO-30N-zeolite
作者: Lingling Wang, Dionysios D. Dionysiou, Jianming Lin, Yuxian Huang, Xiaolan Xie
摘要: The mutual influence of humic acid and Cr(Ⅵ) on water purification using ZnO-30N-zeolite was investigated in the laboratory. The removal of humic acid by ZnO-30N-zeolite with both pollutants present reached 90% in 5 minutes. With humic acid alone, more than one day was required to reach the same level of removal. Synergy between humic acid and chromium was thus demonstrated in their removal process by ZnO-30N-zeolite. However, the presence of humic acid showed no obvious effect on the removal capacity of Cr(Ⅵ) by ZnO-30N-zeolite. X-ray photoelectron spectra showed that Cr(VI) was reduced to Cr(Ⅲ) in the process by both humic acid and ZnO-30N-zeolite. The kinetic mechanism of synergistic removal of humic acid and Cr(Ⅵ) by ZnO-30N-zeolite in binary pollutant system was also proposed.
75. 题目: Hot-water extractable C and N as indicators for 4p1000 goals in a temperate-climate long-term field experiment: A case study from Hungary
期刊: Ecological Indicators
作者: László Bankó, Gergely Tóth, Csaba L. Marton, Sándor Hoffmann
摘要: Soil organic matter (SOM) consists of various labile and stable fractions, which are differently influenced by agricultural activities and land-use change. This study, aimed at investigating the feasibility of achieving 4p1000 goals on conventionally tilled plough-land, was carried out in a 42 years-old long-term field experiment (LTE), in which the effect of three farmyard manure (FYM) doses and the FYM equivalent NPK mineral fertiliser rates can be examined, together with that of mineral fertiliser with and without ploughed-in plant residues. The soil total organic carbon (SOC) and nitrogen (SN) and the labile hot-water soluble C (HWC) and N (HWN) fractions were determined (0–0.3 m) and used as indicators. The parameters of the tilled area were compared with those of a grassland area with similar characteristics. The suitability of these parameters for use as soil quality indicators (SQI) was also examined in terms of soil fertility. The results showed that the most sensitive fraction for the detection of treatment effects were HWC and HWN. Increases in these labile organic fractions were significantly related to the gains of SOC stocks. Based on the close correlation between these factors and both SOC and crop yield it is recommended that they should be used as indicators for the prediction of changes in SOC and in studies on soil fertility or soil quality. The initial C stock of 40.46 Mg ha−1 became 40.27–47.05 Mg ha−1 on the tilled soil after four decades, while on the grassland it rose to 69.31 Mg ha−1. The carbon sequestration rate (CSR) in the various fertilisation systems exhibited the following order: plant residue incorporation >FYM addition > mineral fertilisation (0.147–0.156, 0.101–148 and –0.021–0.065 Mg ha−1 yr−1, respectively), while an outstandingly high value of 0.687 Mg ha−1 yr−1 was recorded for the grassland. Despite the fact that the carbon sequestration potential (CSP) remained high (55.36–62.48%), the achievement of 4 per 1000 aims can only be ensured in treatments involving high rates of organic matter and only in the short term.
76. 题目: Distribution and factors influencing organic and inorganic carbon in surface sediments of tidal flats in northern Jiangsu, China
期刊: Ecological Indicators
作者: Peipei Yang, Qiang Shu, Qing Liu, Zhou Hu, Shunjie Zhang, Yanyu Ma
摘要: Large amounts of organic carbon (OC) and inorganic carbon (IC) are stored in coastal sediments. These carbon compounds play an important role in coping with global climate change. In this study, the surface sediments of four tidal flat sections in northern Jiangsu were analysed for their OC and IC contents, as well as changes in the physical and chemical properties of the sediments (particle size, pH, salinity (SAL), and N, P, and S contents). A partial least squares regression (PLSR) was conducted to explore the factors affecting OC and IC variations. According to the results, the OC and IC contents exhibited increasing trends when moving from the seaward to landward parts of the sections. The OC variations were large and IC variations were small in all four sections and the vegetation coverage contributes to the carbon content of tidal flat sediments. The PLSR analysis indicates that the main factors influencing OC and IC contents in the tidal flat system were particle size (sand, silt, and clay) and N content, while SAL had the least influence on OC and IC contents. The IC and OC contents are positively coupled, which may indicate that the nearshore vegetation has a greater contribution to OC, affects the coastal hydrodynamic conditions, and enhances the retention of IC. Additionally, the transformation of OC to IC also positively contributed to the coupling of their contents.
77. 题目: Evidence linking calcium to increased organo-mineral association in soils
作者: Mike C. Rowley, Stephanie Grand, Jorge E. Spangenberg, Eric P. Verrecchia
摘要: Geochemical indicators are emerging as important predictors of soil organic carbon (SOC) dynamics, but evidence concerning the role of calcium (Ca) is scarce. This study investigates the role of Ca prevalence in SOC accumulation by comparing otherwise similar sites with (CaCO 3 -bearing) or without carbonates (CaCO 3 -free). We measured the SOC content and indicators of organic matter quality (C stable isotope composition, expressed as δ 13 C values, and thermal stability) in bulk soil samples. We then used sequential sonication and density fractionation (DF) to separate two occluded pools from free and mineral-associated SOC. The SOC content, mass, and δ 13 C values were determined in all the fractions. X-ray photoelectron spectroscopy was used to investigate the surface chemistry of selected fractions. Our hypothesis was that occlusion would be more prevalent at the CaCO 3 -bearing site due to the influence of Ca on aggregation, inhibiting oxidative transformation, and preserving lower δ 13 C values. Bulk SOC content was twice as high in the CaCO 3 -bearing profiles, which also had lower bulk δ 13 C values, and more occluded SOC. Yet, contrary to our hypothesis, occlusion only accounted for a small proportion of total SOC (< 10%). Instead, it was the heavy fraction (HF), containing mineral-associated organic C, which accounted for the majority of total SOC and for the lower bulk δ 13 C values. Overall, an increased Ca prevalence was associated with a near-doubling of mineral-associated SOC content. Future investigations should now aim to isolate Ca-mediated complexation processes that increase organo-mineral association and preserve organic matter with lower δ 13 C values.
78. 题目: Formation and influence factors of halonitromethanes in chlorination of nitro-aromatic compounds
作者: Junjie Wang, Zhigang Li, Shaoyang Hu, Jian Ma, Tingting Gong, Qiming Xian
摘要: Halonitromethanes (HNMs), typical nitrogenous disinfection byproducts during disinfection of chlorination and chloramination, are widely detected in drinking water. This study investigated the formation of two dominant HNMs, trichloronitromethane (TCNM) and dichloronitromethane (DCNM) during chlorination/chloramination of ten nitro-aromatic compounds (NACs), including six aromatic mono-nitro compounds, three aromatic di-nitro compounds and one aromatic tri-nitro compound. The results showed that 2-nitrophenol and 3-nitrophenol could be the main precursors of TCNM and DCNM, and the yields of TCNM were one order of magnitude higher than that of DCNM. HNMs formation in chlorination was much higher than that in chloramination. However, HNMs were hardly produced during chlorination and chloramination of the other eight NACs. In chlorination of 2-nitrophenol, a pH range of 5.0–7.0 facilitated the TCNM formation. Besides, the concentration of ferric and manganese ions had different influences on TCNM formation. While the concentration ranges were 0–2 mg/L, ferric ion significantly decreased TCNM formation but manganese ion had not any influence on TCNM formation. Contrary to a previous finding, nitrite significantly reduced TCNM formation, which implied that nitrite has different effects on TCNM formation from various precursors. Moreover, dissolved organic matter (DOM, 0–5 mg/L as C) significantly influenced the formation of TCNM in chlorination of 2-nitrophenol despite the low TCNM formation in chlorination of DOM. Several chlorinated intermediates were detected and identified as mono/di/tri-chloro-2-nitrophenol during chlorination of 2-nitrophenol. It is effectively to reduce the production of TCNM and DCNM formation from chlorination of 2-nitrophenol by controlling disinfection conditions in drinking water.
79. 题目: Stimulated biodegradation of all alkanes in soil
作者: Jinlan Xu, Lu Xu, Xue Qiao, Yuanyuan Zheng, Youlin Xie, Zhengli Yang
摘要: This study aim to investigate the biodegradation of all alkanes in soil by adding stimulater and indigenous bacteria. The experiments were carried out by adding native bacteria and the stimulater to the soil S1 (total petroleum hydrocarbon (TPH) = 22745 mg/kg) and soil S2 (TPH = 13833 mg/kg) to explored the effect and mechanism of the stimulated biodegradation of all alkanes in soil. The results showed that most alkanes were used as the main carbon source of TPH in the late stimulation stage, so that all alkanes could be biodegraded by stimulating. The biodegradation of C10 - C19 (4527 mg/kg) and C20 - C30 (8530 mg/kg) were much higher than the stimulated biodegradation of partial alkanes, which indicated that the biodegradation effect of TPH was greatly improved. In addition, for the stimulated biodegradation of all alkanes group, the relative activity of TPH (TPH biodegradation/DOC consumption) was nearly 5 times that of the stimulated biodegradation of partial alkanes group in the late stimulation stage. The amount of ammonia allocated to TPH in the late stimulation stage was nearly 10 times that of DOC, and the organic matter components changed greatly in the early stimulation stage, but there was basically no change in the later stage. It showed that the hydrocarbon degraders in the stimulated biodegradation of all alkanes group used DOC as the main carbon source in the early stimulation stage and mainly degrade TPH in the later stage, which improved the biodegradation efficiency of petroleum hydrocarbons.
80. 题目: Dissolved organic matter modulates the impact of herbicides on a freshwater alga: a laboratory study of a three-way interaction
期刊: Science of The Total Environment
作者: Soizic Morin, Nathalie Coquillé, Mélissa Éon, Hélène Budzinski, Édith Parlanti, Sabine Stachowski-Haberkorn
摘要: In freshwater environments, microorganisms such as microalgae are influenced by the concentrations of dissolved chemicals but can modify the fate of these substances by biosorption, accumulation and even metabolization. In this laboratory study, we assessed the growth and physiology of non-axenic cultures of the chlorophyte Sphaerellopsis sp. exposed to environmental concentrations of diuron, irgarol and S-metolachlor (0.5, 0.5 and 5 μg.L-1, respectively) singly and in mixture, in the presence or absence of natural dissolved organic matter (DOM). The growth, photosynthetic efficiency and relative intracellular lipid content of Sphaerellopsis sp., as were measured after 14 days of exposure, as were the concentrations of bacteria in the cultures. DOM absorbance and fluorescence, and concentrations of the herbicides and their metabolites in the culture medium were also recorded. The growth of Sphaerellopsis sp. was very low in the absence of DOM but dramatically enhanced in treatments where DOM was added. As a result, the toxicity of the herbicides observed in treatments without DOM was overcome in those where DOM was added. The chemical characteristics of DOM were modified by the microalgae, and the fate of the herbicides was affected by the interaction between microorganisms (both bacteria and algae) and the DOM. Herbicide concentrations decreased over time, with a simultaneous increase in some of their metabolites, suggesting a biological degradation in the presence of DOM.