1. 题目: A synthesis framework using machine learning and spatial bivariate analysis to identify drivers and hotspots of heavy metal pollution of agricultural soils
期刊: Environmental Pollution
作者: Shiyan Yang, David Taylor, Dong Yang, Mingjiang He, Xingmei Liu, Jianming Xu
摘要: Source apportionment can be an effective tool in mitigating soil pollution but its efficacy is often limited by a lack of information on the factors that influence the accumulation of pollutants at a site. In response to this limitation and focusing on a suite of heavy metals identified as priorities for pollution control, the study established a comprehensive pollution control framework using factor identification coupled with spatial agglomeration for agricultural soils in an industrialized part of Zhejiang Province, China. In addition to elucidating the key role of industrial and traffic activities on heavy metal accumulation through implementing a receptor model, specific influencing factors were identified using a random forest model. The distance from the soil sample location to the nearest likely industrial source was the most important factor in determining cadmium and copper concentrations, while distance to the nearest road was more important for lead and zinc pollution. Soil parent materials, pH, organic matter, and clay particle size were the key factors influencing accumulation of arsenic, chromium, and nickel. Spatial auto-correlation between levels of soil metal pollution and industrial agglomeration can enable a more targeted approach to pollution control measures. Overall, the approach and results provide a basis for improved accuracy in source apportionment, and thus improved soil pollution control, at the regional scale.
2. 题目: Further reuse of phosphorus-laden biochar for lead sorption from aqueous solution: Isotherm, kinetics, and mechanism
期刊: Science of The Total Environment
作者: Lei Pei, Fan Yang, Xiaoyun Xu, Hongyan Nan, Xiangyang Gui, Ling Zhao, Xinde Cao
摘要: Biochar and engineered biochar have been used for phosphorous recovery from wastewater, but the resulted phosphorous-laden (P-laden) biochar needs further disposal. In this study, the feasibility of reusing P-laden biochar for Pb immobilization as well as the underlying mechanism was explored. Three types of engineered biochar, i.e., Ca modified biochar, Mg modified biochar, and Fe modified biochar, were selected to sorb P and then the exhausted biochar was further used for Pb sorption. Results showed that Mg and Ca modified biochar exhibited considerable Pb sorption capacity after P sorption with the maximum value of 3.36–4.03 mmol/g and 5.49–6.58 mmol/g, respectively, while P-laden Fe modified biochar failed to sorb Pb due to its acidic pH. The removal of Pb by P-laden Mg modified biochar involved more precipitation including PbHPO4, Pb5(PO4)3(OH), and Pb3(CO3)2(OH)2 because of its higher P sorption capacity and more -OH group on the surface. Cation exchange with CaCO3 to form PbCO3 was the main mechanism for Pb removal by P-laden Ca modified biochar despite the formation of Pb5(PO4)3(OH) precipitate. Our results demonstrate that waste P-laden biochar can be further used for the effective removal of Pb, which provides a potential approach for waste adsorbent disposal.
3. 题目: Evaluation of ultrasound as a preventative algae-controlling strategy: degradation behaviors and characteristic variations of algal organic matter components during sonication at different frequency ranges
期刊: Chemical Engineering Journal
作者: Yangrui Huang, Wenjun Zhang, Lei Li, Xinmin Wei, Huaizheng Li, Naiyun Gao, Juanjuan Yao
摘要: To date, the removal of harmful algae and specific algae metabolites (e.g., microcystins, odorous compounds and phycocyanin) by ultrasound has been confirmed. However, the effects of ultrasound on algal organic matter (AOM) variation have not been systematically investigated, which is of great necessity for the management of water safety and the practical application of ultrasound for algae control. This study investigated the effects of ultrasound at three typical frequencies on the degradation behaviors and characteristics of AOM, including their fluorescence properties, molecular weight and especially sample toxicity. The results showed effective growth inhibition of algae over 7 days after ultrasonic treatment at frequencies of 29.4, 470 and 780 kHz; however, extracellular AOM increased by 1.4%–147.2%, -2.1%–82.5% and 0.9%–90.8%, respectively. High-frequency ultrasound (470 and 780 kHz) had significantly better AOM degradation. The fluorescence pseudo first-order rate constant refers to the decrease in fluorescence and implicates AOM degradation. The rate constants of AOM components were 0.00178–0.00295, 0.00880–0.01763 and 0.00670–0.01319 for the 29.4, 470 and 780 kHz treatments (0.059 W/mL), respectively. Low-frequency sonication was dominated by limited pyrolysis and supercritical water oxidation (SCWO) and mainly caused non-fracture damage. In addition to pyrolysis and SCWO, high-frequency sonication included conspicuous hydroxyl radical oxidation that accounted for more than 60% of the degradation. During high-frequency sonication, some AOM (∼25.1 kDa) was degraded into smaller products (0.8–2.0 kDa), and the degradation of the humic-like components was greater than that of the protein-like components. Moreover, high-frequency sonication caused an evident decrease in the toxicity of AOM. This study indicates that high-frequency ultrasound was a promising algae-controlling strategy with respect to effectiveness and safety.
4. 题目: Mercury accumulation in the sediment of the Western Mediterranean abyssal plain: A reliable archive of the late Holocene
期刊: Geochimica et Cosmochimica Acta
作者: D. Cossa, A Mucci, S. Guédron, M. Coquery, O. Radakovich, R. Escoube, S. Campillo, S. Heussner
摘要: Temporal reconstruction of Hg deposition from sediment archives is relatively straightforward in organic-rich or high sedimentation rate environments, such as lakes and ocean margins. To retrieve long-term records at regional or global scales, deep-sea sediments are more appropriate, but such records are scarce and their reliability has been questioned because of possible post-depositional Hg diagenetic remobilization. Here, we investigated the accumulation of Hg in the Balearic Abyssal Plain (2850 m deep) of the Western Mediterranean through a comprehensive characterization of the chemical and isotopic composition (organic carbon, nitrogen, sulfur, major and redox-sensitive elements) of sediment trap material and sediment cores. The analysis of material collected in the sediment traps, deployed at 250, 1440, and 2820 m, indicates that Hg is (i) partially re-emitted to the atmosphere and mobilized in the twilight zone and that (ii) the Hg downward flux depends on the primary production in surface waters, suggesting that organic matter (OM) acts as the main Hg-carrier phase. As the Hg concentrations of material collected in the traps vary little with depth but the Hg:Corg ratio of the settling particulate matter decreases with depth, Hg must be re-adsorbed onto the more refractory fraction of the settling OM. Results of selective chemical extractions of the sediment indicate that Hg is very weakly coupled to the iron cycle but strongly associated with sulfur, supporting the assumption that its vertical distribution was only weakly altered by diagenetic remobilization. In addition, the distributions of S and δ34S in the sedimentary column exclude the possibility that local volcanism impacted on Hg enrichment of the sediments. Accordingly, a reconstruction of Hg accumulation rates (Hg-AR) during the Late Holocene is readily achieved. Biological mixing and smoothing of the sediment record, as revealed by the distribution of radionuclides in surface sediments, was considered in the interpretation of the Hg-AR record. The first anthropogenic Hg signal recorded in the studied cores corresponds to the Iron Age and the Roman Empire period, as Hg-ARs rose from the baseline (0.7 ± 0.2 µg m-2 yr-1) to an average value of 2.2 ± 0.5 µg m-2 yr-1. The Hg-ARs return to baseline values at the decline of the Roman Empire, display a small increase during the Medieval Period (1.5 ± 0.5 µg m-2 yr-1), increase abruptly at the onset of the Industrial Era, leading to a ∼10-fold increase in Hg deposition in the last 120 years (8.9 ± 1.4 µg m-2 yr-1), and retreat progressively over the past 50 years.
5. 题目: Quantitative source apportionment of dissolved organic matters in wet weather overflows of storm drainage systems based on degradation potential index and end member mixing model
期刊: Science of The Total Environment
作者: Zhen-liang Liao, Zhi-chao Zhao, Hao Chen, Jun Wu
摘要: Dissolved organic matter (DOM) in wet weather overflows (WWFs) of storm drainage systems mainly originates from anthropogenic sources, such as paved runoff, illegally discharged domestic sewage and the retained sediment. This study provides a promising method to quantitatively apportion the WWF DOM of storm drainage systems using degradation potential index (DPI) and end member mixing (EMM) model. DPI is derived from excitation-emission matrix parallel factor analysis (EEM-PARAFAC), which can endow the end members and itself of WWF DOM with numerical features, and thus help quantify the source contributions of WWF DOM in EMM model. Findings show that (1) DPI was a reliable tool in the quantitative source apportionment of WWF DOM, owing to its features of small variance within source and large variances between sources; (2) DPI combined with EMM model could help identify the factors that induce significant impacts on the source contributions of WWF DOM, such as the storm pumping discharge and antecedent dry days in our case study; (3) the identified factors could guide the development of effective strategies for WWF DOM control, e.g. sediment management in our case.
6. 题目: Adsorption and removal of seven antibiotic compounds present in water with the use of biochar derived from the pyrolysis of organic waste feedstocks
期刊: Journal of Environmental Chemical Engineering
作者: Marinos Stylianou, Anastasis Christou, Costas Michael, Agapios Agapiou, Panos Papanastasiou, Despo Fatta-Kassinos
摘要: Biochar produced from organic waste feedstocks have lately been utilized as adsorbents for the decontamination of antibiotics-contaminated environmental matrices. The aim of the present study is a) the assessment of the adsorption capacity of three distinct derived biochars [biosolids (BDΒ), cattle manure (MDB) and spent coffee grounds (SCGDB)], applied either at a low (1gL-1) or high (10gL-1) dose on seven antibiotics (tetracycline, TET; erythromycin, ERY; clarithromycin, CLA; ampicillin, AMP; ofloxacin, OFL; sulfamethoxazole, SMX; trimethoprim, TMP) spiked as mixture in environmentally relevant concentration (100μgL-1) of an aqueous solution (8.27 < pH <10.48) and b) the understanding of the relative adsorption mechanisms. Batch sorption experiments showed that all biochars applied at the low dose efficiently removed more than 70%, reaching even 100% of TET, ERY, CLA, whereas MDB also removed AMP. Biochars applied at the high dose (10gL-1) exhibited enhanced adsorption capacity, resulting in the quick (within 5min of incubation) and complete removal of TET, ERY, CLA, as well as increased removal (>85%) of AMP and TMP. However, the studied biochar failed to remove OFL and SMX. The adsorption results were best fitted to the Freundlich model with the sole exception of SMX. The main responsible mechanisms for the adsorption of antibiotics included surface complexation, H-bonding, π-π electron-donor-acceptor (EDA) interactions, pore-filling effects or the simultaneous occurrence of several of these mechanisms. Overall, the results highlighted the potential utilization of BDB, MDB and SCGDB for the decontamination of antibiotics-contaminated water bodies, while promoting the circular economy strategy.
7. 题目: Vertical migration of microplastics in porous media: Multiple controlling factors under wet-dry cycling
期刊: Journal of Hazardous Materials
作者: Jing Gao, Shizhen Pan, Pengfei Li, Liuwei Wang, Renjie Hou, Wei-Min Wu, Jian Luo, Deyi Hou
摘要: Terrestrial soils are not only a large reservoir for Microplastics (MPs), but also a possible entrance to the subsurface environment, posing potential risks to the subterranean habitats and groundwater. In this study, we examined the vertical transport of MPs of four polymers, i.e., polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP) and polyamide (PA), in porous sand media driven by wet-dry cycling. The effects of polymer properties, MP size, sand particle size, wet-dry cycles, and dissolved organic matter (DOM) on their migration behavior were investigated. Surface hydrophobicity showed a strong positive correlation with MP mobility, with PA exhibiting the greatest movement potential, followed by PE, PET, and PP. The penetration depth of MP particles increased with decreasing MP particle size (dMP) and increasing sand diameter (dsand). MP particles migrated deeper in sand media when dMP/dsand < 0.11. Furthermore, frequent wet-dry cycles and the presence of DOM promoted the vertical migration of MPs in the sand. The results revealed multiple factors influencing the vertical migration of MPs in sand, which is instructive for understanding the ecological risk of MPs in potentially contaminated soil (e.g., farmland with long-term mulching) to the subsurface environment and potential negative impact to public health.
8. 题目: Additive-free hydrothermal leaching method with low environmental burden for screening of strontium in soil
期刊: Environmental Science and Pollution Research
作者: Takuma Kato, Mika Nagaoka, Haixin Guo, Hiroki Fujita, Taku Michael Aida, Richard Lee Smith
摘要: In this work, hydrothermal leaching was applied to simulated soils (clay minerals vermiculite, montmorillonite, and kaolinite) and actual soils (Terunuma, Japan) to generate organic acids with the objective to develop an additive-free screening method for determination of Sr in soil. Stable strontium (SrCl2) was adsorbed onto soils for the study, and ten organic acids (citric, L(+)-tartaric, succinic, oxalic, pyruvic, formic, glycolic, lactic, acetic, and propionic) were evaluated for leaching Sr from simulated soils under hydrothermal conditions (120 °C to 200 °C) at concentrations up to 0.3 M. For strontium-adsorbed vermiculite (Sr-V), 0.1 M citric acid was found to be effective for leaching Sr at 150 °C and 1 h treatment time. Based on these results, the formation of organic acids from organic matter in Terunuma soil was studied. Hydrothermal treatment of Terunuma soil produced a maximum amount of organic acids at 200 °C and 0.5 h reaction time. To confirm the possibility for leaching of Sr from Terunuma soil, strontium-adsorbed Terunuma soil (Sr-S) was studied. For Sr-S, hydrothermal treatment at 200 °C for 0.5 h reaction time allowed 40% of the Sr to be leached at room temperature, thus demonstrating an additive-free method for screening of Sr in soil. The additive-free hydrothermal leaching method avoids calcination of solids in the first step of chemical analysis and has application to both routine monitoring of metals in soils and to emergency situations. Graphical abstract
9. 题目: Response of soil enzyme activity and soil bacterial community to PCB dissipation across different soils
作者: Junjie Du, Fen Hou, Qixing Zhou
摘要: Soils are a repository for polychlorinated biphenyls (PCBs). A pot incubation experiment was performed with four soils (black soil, paddy soil, oasis soil, and fluvo-aquic soil) treated with Aroclor 1242 to achieve PCB concentrations of 5 mg kg−1. The soil enzyme activities of protease, phosphatase, catalase, dehydrogenase, and laccase were determined by spectrophotometry. The soil bacterial communities were investigated using Illumina sequencing analysis. The results showed that the characteristics of the test soils varied among the soil types. The fluvo-aquic soil had the greatest PCB dissipation rate (86.41%), followed by the oasis (79.31%), paddy (56.09%), and black (50.65%) soils. The soil pH, cation exchange capacity, soil organic matter content, and particle diameter played significant roles in PCB dissipation from soils. The soil type had a greater influence than PCB contamination on the soil enzyme activities and bacterial communities (alpha diversity, community structure, and composition). Among the four soils, the bacterial communities of the fluvo-aquic soil were the most susceptible to PCB contamination. However, the bacterial communities of the black soil were not changed by PCB contamination.
10. 题目: Sources and compositional characterization of chromophoric dissolved organic matter in a Hainan tropical mangrove-estuary
期刊: Journal of Hydrology
作者: Lu Yan, Xianjun Xie, Kang Peng, Ningdi Wang, Yuyao Zhang, Yamin Deng, Yiqun Gan, Qinghua Li, Yanpeng Zhang
摘要: Chromophoric dissolved organic matter (CDOM) is a major optically active component of DOM in estuaries that plays a significant part in maintaining the ecosystem sustainability of mangrove forests via affecting nutrient and micronutrient ((micro)nutrient) biogeochemical processes and pathways. This study was conducted in Hainan Dongzhai Harbor to better understand the sources, composition, and behaviors of CDOM in a tropical mangrove estuary. Water samples were collected from the upper fluvial mangrove zones to the lower marine endmember along the estuarine salinity gradient and analyzed by absorption and fluorescence spectroscopy combined with parallel factor analysis (PARAFAC). DOC, TDN, TDSi, Mn, Ba, and optical characteristics, i.e., a254, SUVA, HIX, and the abundance of humic-like CDOM, are negatively correlated with salinity. Terrestrial/anthropogenic inputs, riverine runoff, and mangrove porewater exchange are sources of (micro)nutrients and aromatic CDOM into the estuary. In contrast, pH, DO, TDP, SR, BIX, and tryptophan-like CDOM are positively correlated with salinity. This indicates saltwater dilution, tidal mixing, photo-oxidation, and microbial degradation processes promote the enrichment of low MW autochthonous CDOM and TDP, together with the removal of humic-like substances and other (micro)nutrients in the lower estuary. Overall, these findings have important implications for biogeochemical cycling processes driven by CDOM composition and sources in mangrove estuaries.
11. 题目: Latitudinal variability of preserved sedimentary organic matter along the Peruvian continental margin as inferred from petrographic and geochemical properties
期刊: Marine Chemistry
作者: Maricarmen Igarza, Mohammed Boussafir, Michelle Graco, Abdelfettah Sifeddine, Jorge Valdés, Dimitri Gutiérrez
摘要: Processes controlling preservation and accumulation of organic matter (OM) in marine sediments are highly sensitive towards both natural and anthropogenic impacts. Thus, the sedimentary OM is considered a key proxy for the characterization of recent and past sedimentary environments. Along the Peruvian continental margin (PCM), high primary production and an intense oxygen minimum zone (OMZ) favor the accumulation and preservation of OM in sediments. Spatial variations in oceanographic conditions impact on both productivity and the redox conditions, in particular the OMZ intensity. These factors in turn lead to spatial differences in depositional conditions and OM accumulation and preservation. Therefore, this study aims at characterizing nature and types of recent sedimentary OM along the PCM covering a wide latitudinal and bathymetric range. With this purpose, a total of 29 surface sediment samples were collected from Tumbes (3°S) to San Juan (15°S) and analyzed by means of organic petrography (palynofacies analysis) and Rock-Eval pyrolysis. Results allowed characterizing the OM from recent sediments. Along the PCM, the sedimentary OM is predominantly amorphous, revealing its overwhelming marine origin. The highest abundances of gelified amorphous OM, total organic carbon, S1 and S2 Rock-Eval fractions occurred towards the southern part of the study area, especially off Callao (12°S) and Pisco (14°S), considered important upwelling and primary productivity centers. A principal component analysis performed allowed the description of main OM depositional environments. In the outer continental shelf of Callao (12°S) and OMZ of Pisco (14°S), accumulation of well-preserved OM occurs whereas in the inner shelf of Callao redox oscillations lead to less OM accumulation and pyrite formation in sediments. North of Callao, from Tumbes (3°S) to Huacho (11°S), a mixed signal of OM accumulation was observed. Finally, along the slope, transportation processes seem to play a key role in OM accumulation. This study also allowed the evaluation of certain proxies (e.g. Rock-Eval hydrogen index and oxygen index) routinely used in palaeoceanographic studies.
12. 题目: Intensive vegetable production results in high nitrate accumulation in deep soil profiles in China
期刊: Environmental Pollution
作者: Xinlu Bai, Yun Jiang, Hongzhi Miao, Shaoqi Xue, Zhujun Chen, Jianbin Zhou
摘要: A comprehensive understanding of the patterns and controlling factors of nitrate accumulation in intensive vegetable production is essential to solve this problem. For the first time, the national patterns and controlling factors of nitrate accumulation in soil of vegetable systems in China were analysed by compiling 1262 observations from 117 published articles. The results revealed that the nitrate accumulation at 0–100 cm, 100–200 cm, 200–300 cm, and >300 cm were 504, 390, 349, and 244 kg N ha−1, with accumulation rates of 62, 54, 19, and 16 kg N ha−1 yr−1 for plastic greenhouse vegetables (PG); for open field vegetables (OF), they were 264, 217, 228, and 242 kg N ha−1 with accumulation rates of 26, 24, 18, and 10 kg N ha−1 yr−1, respectively. Nitrate accumulation at 0–100 cm, 0–200 cm, and 0–400 cm accounted for 5%, 11%, and 17% of accumulated nitrogen (N) inputs for PG, and represented 4%, 9%, and 13% of accumulated N inputs for OF. Nitrogen input rates and soil pH had positive effects and soil organic carbon, water input rate, and carbon to nitrogen ratio (C/N) had negative effects on nitrate accumulation in root zone (0–100 cm soil). Nitrate accumulation in deep vadose zone (>100 cm soil) was positively correlated with N and water input rates, and was negatively correlated with soil organic carbon, C/N, and the clay content. Thus, for a given vegetable soil with relatively stable soil pH and soil clay content, reducing N and water inputs, and increasing soil organic carbon and C/N are effective measures to control nitrate accumulation.
13. 题目: The influence of a static magnetic field on a Chlorella vulgaris - Bacillus licheniformis consortium and its sewage treatment effect
期刊: Journal of Environmental Management
作者: Xin Luo, Hao Zhang, Jibiao Zhang
摘要: In this study, the influence of a static magnetic field (SMF) on a Chlorella vulgaris-Bacillus licheniformis consortium and the subsequent effect of this algal-bacterial consortium on sewage treatment were explored. Accordingly, the algal density, Fv/Fm, algal aggregation percentage, extracellular polymeric substances (EPS) content, dissolved organic matter distribution, enzymatic activity, metabolites, microbial community diversity and nutrient removal were investigated. For the treatment group exposed to an SMF of 150 mT, the total phosphorus removal rate reached 82.21%, which was 19.10% higher than the control group. On the last day, the algal density of the 150 mT group was the highest, being 56.01% greater than the control group. The high intensity SMF promoted the anti-oxidative stress response in C. vulgaris. It also affected EPS secretion, subsequently influencing the algal aggregation percentage and bacterial growth. Bacillus accounted for the largest proportion of the overall microbial community in the 150 mT group, which was conducive to rapid formation of the C. vulgaris-B. licheniformis consortium. In short, the SMF was conducive to the rapid formation of a C. vulgaris-B. licheniformis consortium. The use of an SMF can promote the efficiency of the algal-bacterial consortium, thereby shortening the processing time.
14. 题目: Nickel in soil and water: Sources, biogeochemistry, and remediation using biochar
期刊: Journal of Hazardous Materials
作者: Ali El-Naggar, Naveed Ahmed, Ahmed Mosa, Nabeel Khan Niazi, Balal Yousaf, Anket Sharma, Binoy Sarkar, Yanjiang Cai, Scott X. Chang
摘要: Nickel (Ni) is a potentially toxic element that contaminates soil and water, threatens food and water security, and hinders sustainable development globally. Biochar has emerged as a promising novel material for remediating Ni-contaminated environments. However, the potential for pristine and functionalized biochars to immobilize/adsorb Ni in soil and water, and the mechanisms involved have not been systematically reviewed. Here, we critically review the different dimensions of Ni contamination and remediation in soil and water, including its occurrence and biogeochemical behavior under different environmental conditions and ecotoxicological hazards, and its remediation using biochar. Biochar is effective in immobilizing Ni in soil and water via ion exchange, electrostatic attraction, surface complexation, (co)precipitation, physical adsorption, and reduction due to the biogeochemistry of Ni and the interaction of Ni with surface functional groups and organic/inorganic compounds contained in biochar. The efficiency for Ni removal is consistently greater with functionalized than pristine biochars. Physical (e.g., ball milling) and chemical (e.g., alkali/acidic treatment) activation achieve higher surface area, porosity, and active surface groups on biochar that enhance Ni immobilization. This review highlights possible risks and challenges of biochar application in Ni remediation, suggests future research directions, and discusses implications for environmental agencies and decision-makers.
15. 题目: Adaptive monitoring approach to assess dissolved organic matter dynamics during rainfall events
期刊: Environmental Monitoring and Assessment
作者: Caroline Kozak, Juliana Leithold, Luciane Lemos do Prado, Heloise Garcia Knapik, Júlio César de Rodrigues Azevedo, Sérgio Michelotto Braga, Cristovão Vicente Scapulatempo Fernandes
摘要: Rainfall events induce water quality transformation in river systems influenced by the watershed land use and hydrology dynamics. In this context, an adaptive monitoring approach (AMA) is used to assess non-point sources (NPS) of pollution events, through dissolved organic matter (DOM) contribution. The case study is a monitoring site in a semi-urban watershed characterized by NPS contribution. An integrated quali-quantitative method for DOM based on dissolved organic carbon (DOC) content, spectroscopic techniques of excitation-emission fluorescence (EEF), and UV–visible absorbance is proposed. The results indicate a mix of allochthonous and autochthonous DOM characteristics from NPS sources associated to vegetation area influence (A285/DOC of 15.43 L (g cm)−1 and SUVA254 of 2.11 L (mg m)−1). The EEF signals showed more humic-like than protein-like characteristics with peaks A and C (approximately 5.72 r.u.) more intense than peaks B, T1, and T2 (approximately 4.33 r.u.), indicating NPS from the soil leachate. The absorbance ratio values indicate a mix of organic compounds with greater proportion of refractory characteristics with high aromaticity and molecular weight (approximately A300/A400 of 4.15 and A250/A365 of 4.48), associated with the surface wash-off of accumulated residual and subsurface soil erosion, which contribute to complex organic matter structures. The fluorescence indexes, overall, indicated allochthonous sources with intermediate humic characteristics (FI ≈ 1.43, BIX ≈ 0.65, and HIX ≈ 7.98). The proposed integrated optical property strategy represents an opportunity for better understanding of DOM dynamic assessment for identifying potential mitigation techniques for organic pollution control and improving water quality conditions.
16. 题目: Effects of nitrogen-enriched biochar on rice growth and yield, iron dynamics, and soil carbon storage and emissions: A tool to improve sustainable rice cultivation
期刊: Environmental Pollution
作者: Xiaolei Yin, Josep Peñuelas, Jordi Sardans, Xuping Xu, Youyang Chen, Yunying Fang, Liangquan Wu, Bhupinder Pal Singh, Ehsan Tavakkoli, Weiqi Wang
摘要: Biochar is often applied to paddy soils as a soil improver, as it retains nutrients and increases C sequestration; as such, it is a tool in the move towards C-neutral agriculture. Nitrogen (N) fertilizers have been excessively applied to rice paddies, particularly in small farms in China, because N is the major limiting factor for rice production. In paddy soils, dynamic changes in iron (Fe) continuously affect soil emissions of methane (CH4) and carbon dioxide (CO2); however, the links between Fe dynamics and greenhouse gas emissions, dissolved organic carbon (DOC), and rice yields following application of biochar remain unclear. The aims of this study were to examine the effects of two rates of nitrogen (N)-enriched biochar (4 and 8 t ha−1 y−1) on paddy soil C emissions and storage, rice yields, and Fe dynamics in subtropical early and late rice growing seasons. Field application of N-enriched biochar at 4 and 8 t ha−1 increased C emissions in early and late rice, whereas application at 4 t ha−1 significantly increased rice yields. The results of a culture experiment and a field experiment showed that the application of N-enriched biochar increased soil Fe2+ concentration. There were positive correlations between Fe2+ concentrations and soil CO2, CH4, and total C emissions, and with soil DOC concentrations. On the other way around, these correlations were negative for soil Fe3+ concentrations. In the soil culture experiment, under the exclusion of plant growth, N-enriched biochar reduced cumulative soil emissions of CH4 and CO2. We conclude that moderate inputs of N-rich biochar (4 t ha−1) increase rice crop yield and biomass, and soil DOC concentrations, while moderating soil cumulative C emissions, in part, by the impacts of biochar on soil Fe dynamics. We suggest that water management strategies, such as dry-wet cycles, should be employed in rice cultivation to increase Fe2+ oxidation for the inhibition of soil CH4 and CO2 production. Overall, we showed that application of 4 t ha−1 of N-enriched biochar may represent a potential tool to improve sustainable food production and security, while minimizing negative environmental impacts.
17. 题目: Exploring the drivers controlling the priming effect and its magnitude in aquatic systems
期刊: Journal of Geophysical Research: Biogeosciences
作者: Lúcia Fernandes Sanches, Bertrand Guenet, Nicholas dos Anjos Cristiano Marino, Francisco Assis Esteves
摘要: Changes in mineralization rates of stable or persistent organic matter induced by inputs of labile organic matter can alter the organic carbon (C) balance along the terrestrial-aquatic ecosystem continuum. This phenomenon, also known as the priming effect, is well-established in terrestrial ecosystems, but has only recently been explored in the domain of aquatic ecology– with widely contrasting responses of stable carbon to the priming effect reported across the literature. Here, we compiled data from experimental studies on C mineralization in aquatic systems that directly or indirectly tested for the priming effect, and used a meta-analytic approach to investigate the physical and chemical drivers behind the differing outcomes reported across studies. We found that the reported heterogeneity could be explained by two main factors: how the priming effect is measured and whether the study was performed in the laboratory or under field conditions. These findings suggest that how the priming effect is tested and measured has strong implications for its detection and magnitude.
18. 题目: Promoting anaerobic co-digestion of sewage sludge and food waste with different types of conductive materials: Performance, stability, and underlying mechanism
期刊: Bioresource Technology
作者: Jialin Liang, Liwen Luo, Dongyi Li, Sunita Varjani, Yunjie Xu, Jonathan W.C. Wong
摘要: In this research, we investigated and compared the effects of three widely used conductive materials, e.g., zero-valent iron (Fe0), magnetite (Fe3O4), and biochar on the performance, stability, and in-depth mechanism during the anaerobic co-digestion process of sewage sludge and food waste. Among the three conductive materials, Fe0 could achieve the highest cumulative methane production of 394.0 mL/g volatile solids (VS) added, which was 1.24-fold and 1.17-fold higher than that receiving Fe3O4 and biochar. The mechanistic studies indicated that compared to the Fe3O4 and biochar groups, Fe0 could significantly enhance the release of soluble protein, polysaccharide, and dissolved organic matters, the degradation of volatile fatty acids and VS, and the activities of key enzymes and direct interspecies electron transfer (DIET). Consequently, the methane yield and digestate dewaterability were notably improved. Collectively, these findings will offer suggestions of the preferable conductive materials in the anaerobic co-digestion process for decision makers.
19. 题目: Processes in submerged soils – linking redox potential, soil organic matter turnover and plants to nutrient cycling
期刊: Plant and Soil
作者: Petra Marschner
摘要: Background Submerged soils are globally important both in natural and agricultural ecosystems and cover 5–7% of the global land surface. Therefore, processes in submerged soils are important for global biogeochemical cycles. These processes are strongly influenced by oxygen availability, i.e. redox potential. Scope This review aims to provide an overview of the role of redox potential in nutrient cycling, soil organic matter turnover and the effect of plants on nutrient cycling processes in submerged soil. Conclusion In submerged soils, the active terminal electron acceptor for reduction processes follows the sequence O2, NO3−, MnO2, Fe3+, SO42− and CO2 where, in most cases organic matter, is the electron donor. Depletion of available organic matter during this sequence can limit the subsequent processes. Drying and rewetting of previously submerged soils have complex effects on nutrient cycling. Submerged soils often have higher organic matter content than aerobic soils which is due to chemical, metabolic and physical mechanisms. Plants have complex effects on processes in wetland soils resulting from release of oxygen from roots which can induce iron and methane oxidation around roots. However, plants can also increase methane release due to transport of methane via aerenchyma to the shoots. For a better understanding of processes in submerged soils, future investigations across scales, ranging from microscale to macroscale, are needed.
20. 题目: Sulfurization of dissolved organic matter in the anoxic water column of the Black Sea
期刊: Science Advances
作者: Gonzalo V. Gomez-Saez, Thorsten Dittmar, Moritz Holtappels, Anika M. Pohlabeln, Anna Lichtschlag, Bernhard Schnetger, Antje Boetius, Jutta Niggemann
摘要: Today’s oceans store as much dissolved organic carbon (DOC) in the water column as there is CO 2 in the atmosphere, and as such dissolved organic matter (DOM) is an important component of the global carbon cycle. It was shown that in anoxic marine sediments, reduced sulfur species (e.g., H 2 S) abiotically react with organic matter, contributing to carbon preservation. It is not known whether such processes also contribute to preserving DOM in ocean waters. Here, we show DOM sulfurization within the sulfidic waters of the Black Sea, by combining elemental, isotopic, and molecular analyses. Dissolved organic sulfur (DOS) is formed largely in the water column and not derived from sediments or allochthonous nonmarine sources. Our findings suggest that during large-scale anoxic events, DOM may accumulate through abiotic reactions with reduced sulfur species, having long-lasting effects on global climate by enhancing organic carbon sequestration.