1. 题目: Contribution of extracellular polymeric substances and microbial community on the safety of drinking water quality: By mean of Cu/activated carbon biofiltration
作者: Zhihao Bi, Tong Li, Xueci Xing, Peng Qi, Zesong Li, Chun Hu, Xiaoran Xu, Zhimin Sun, Gang Xu, Chaoxiang Chen, Kunyu Ma
摘要: Change in water quality was investigated with laboratory-scale ozone-biological activated carbon filters using copper-modified granular activated carbon (Cu/GAC) and unmodified granular activated carbon (GAC). In the first seven days of the experimental period, Cu/GAC removed organic matter more efficiently owing to its enhanced adsorption capacity. As the running time increased, the amount of disinfection by-products (DBPs), dissolved organic carbon, and extracellular polymeric substances (EPS) increased sharply in the effluent of the Cu/GAC filter (CCW). More importantly, the EPS suspended in the CCW exhibited weaker flocculating efficiency and hydrophobicity, causing more active chemical reactions between chlorine and EPS substances. The copper species significantly limited the microbial biomass (0.01 nmol/L adenosine triphosphate) but stimulated the secretion of significant amounts of EPS by microorganisms for self-protection. Furthermore, the microbial community in the bulk water was successfully shaped by Cu/GAC, resulting in a continuous supply of EPS-derived DBP precursors and a sharp rise in chlorine consumption in the downstream drinking water distribution. Therefore, use of modified GAC materials, similar to Cu/GAC, as carrier materials for biological activated carbon (BAC) treatment remains controversial, despite enhanced pollutant adsorption capacity. This is the first study to reveal the mechanism of BAC-modified materials for water quality stability. The study potentially contributes to a comprehensive understanding of the effects of biofilm transformation and microbial community succession on drinking water quality. These results showed that tap water safety risks could be reduced by improving BAC pretreatment in drinking water treatment plants.
2. 题目: Impact of Spartina alterniflora invasion on soil bacterial community and associated greenhouse gas emission in the Jiuduansha wetland of China
期刊: Applied Soil Ecology
作者: Chiquan He, Xiaoxi Wang, Daoyuan Wang, Zhenzhen Zhao, Feifei Wang, Liyu Cheng, Haiyue Feng, Pu Zhang
摘要: Coastal wetlands are essential sources of greenhouse gases (GHGs) emission, and lots of them are invaded by Spartina alterniflora across different climate zones. We chose Jiuduansha wetland as a typical wetland ecosystem with minimal human activities to study the impacts and interactions between S. alterniflora invasion, soil functional microorganisms, and GHGs emission. Our findings indicated that in comparison to the mudflat and S. mariqueter habitat, the S. alterniflora invasion increased soil carbon dioxide (CO2) emission, which was highly positively related to aboveground biomass, soil organic carbon (SOC), and the ammonium‑nitrogen (NH4+-N) concentration, but negatively related to the nitrate‑nitrogen (NO3–-N) concentration. The relative abundances of soil C-decomposing bacteria increased in S. alterniflora habitat compared with S. mariqueter habitat. Compared with the P. australis habitat, S. alterniflora invasion reduced soil CO2 emission, which was negatively related to salinity. The relative abundances of soil C-fixing bacteria (phylum Chloroflexi) and functional genes (acsA-F and rbcL) decreased in S. alterniflora habitat. Moreover, the S. alterniflora invasion increased soil methane (CH4) emission compared with the S. mariqueter and P. australis habitats, which was positively related to aboveground biomass, SOC and NH4+-N concentration, and negatively related to the NO3–-N concentration. Besides, the relative abundances of CH4 oxidation functional genes were decreased in S. alterniflora habitat compared with the S. mariqueter and P. australis habitats. Meanwhile, the oxidation of CH4 to methanol was mainly regulated by mmoX gene at our study site. Thus, the soil CO2 and CH4 emissions after S. alterniflora invasion were regulated by soil environmental factors and soil C-fixing, C-decomposing, and CH4 oxidation functional microorganisms. Our results are helpful to better understand the mechanisms involved in the impacts of S. alterniflora invasions on GHG emissions in coastal wetlands.
3. 题目: Understanding the influence of pre-ozonation on the formation of disinfection byproducts and cytotoxicity during post-chlorination of natural organic matter: UV absorbance and electron-donating-moiety of molecular weight fractions
期刊: Environment International
作者: Wen-Long Wang, Min-Yong Lee, Ye Du, Tian-Hui Zhou, Zheng-Wei Yang, Qian-Yuan Wu, Hong-Ying Hu
摘要: Pre-ozonation can reduce the formation of disinfection byproducts (DBPs) and related adverse effects during subsequent chlorination, but the change of each molecular weight (MW) fraction during each step of combined pre-ozonation and post-chlorination has not been well illustrated. In this study, it was investigated in terms of electron-donating-moieties (EDMs) and UVA254 for a representative natural organic matter from Suwanee river (SRNOM). Pre-ozonation suppressed the post-chlorination of SRNOM through oxidation of almost all EDMs (>85%) and UVA254 (>90%) in high MW fractions (HMW, >3.2 kDa) and moderate EDMs (43%) and UVA254 (72%) in medium MW fractions (MMW, 1.0–3.2 kDa). Furthermore, pre-ozonation led to comparable abatements of EDMs and UVA254 for HMW fractions, but lower abatement of EDMs than UVA254 for MMW fractions. However, when t-BuOH was used as an •OH-quencher, pre-ozonation led to a few instances in which there were higher abatements of EDMs than UVA254 for the MMW fraction. These findings suggested that the HMW fraction dominantly underwent ring-cleavage of phenols via O3– or •OH-oxidation. Differently, the MMW fraction underwent ring-cleavage of phenols and quinones-formation via O3-oxidation, but occasionally underwent hydroxylation and hydro-phenol formation via •OH-oxidation. Because of forehand elimination of reactive moieties (e.g. EDMs), pre-ozonation obviously inhibited the formation of representative DBPs (67%–84% inhibition), total organic chloride (51% inhibition) and cytotoxicity (31% inhibition), but may have promoted the formation of carbonyl-DBPs (trichloroacetone and chloral hydrate). When compared with UVA254, EDMs would better for surrogate of DBPs formation. EDM abatement surrogated the formation of total organic chlorine (TOCl) and cytotoxicity following a two-stage phase, possibly because the speciation of DBPs and transformation products varied with the abatement of EDMs.
4. 题目: Predicting Rock-Eval® thermal analysis parameters of a soil layer based on samples from its sublayers; an experimental study on forest soils
期刊: Organic Geochemistry
作者: Eva Kanari, Pierre Barré, François Baudin, Alain Berthelot, Nicolas Bouton, Frédéric Gosselin, Laure Soucémarianadin, Florence Savignac, Lauric Cécillon
摘要: Soil sampling depths strongly vary across soil studies. Stocks of elements (such as C, N) or organic matter in a soil layer can be simply calculated from stocks measured in its sublayers. This calculation is less obvious for other soil characteristics, such as soil organic carbon (SOC) persistence, complicating the comparison of results from different studies. Here, we tested whether Rock-Eval® parameters of a soil layer, characterizing soil organic matter and its biogeochemical stability, can be determined using Rock-Eval® data measured on its sublayers. Soil samples collected in 10 plots located in eight French forest sites, taken up at two different depths (0–30 cm, 30–50 cm), and their mixtures were analysed with Rock-Eval®. Expected values for the Rock-Eval® parameters of the soil mixtures were calculated either: (1) as the weighted mean of Rock-Eval® parameters measured on the two sublayers, or (2) based on a signal reconstructed as the weighted mean of Rock-Eval® thermograms recorded on the two sublayers. Our results showed a good agreement between measured and expected Rock-Eval® parameter values. However, when the clay content strongly differed between the two soil sublayers, the amount of pyrolyzed hydrocarbons measured on the soil mixtures was slightly lower than expected. We conclude that it is reasonable to calculate Rock-Eval® parameters of a soil layer, from the Rock-Eval® signature of its sublayers. Our findings facilitate the harmonization of Rock-Eval® data from large scale soil studies using different sampling depths.
5. 题目: Online Liquid Chromatography and FT-ICR MS Enable Advanced Separation and Profiling of Organosulfates in Dissolved Organic Matter
期刊: ACS ES&T Water
作者: Yulin Qi, Chao Ma, Shuang Chen, Jinfeng Ge, Qiaozhuan Hu, Si-Liang Li, Dietrich A. Volmer, Pingqing Fu
摘要: Dissolved organic matter (DOM) is an ultracomplex mixture of organic compounds in the land/ocean–atmosphere interface. Normally, polar compounds from DOM are hardly retained by liquid chromatography (LC) columns for further analytical purposes. Here, we utilized Fourier transform ion cyclotron resonance mass spectrometry with LC for online analysis of DOM in river water and rainwater. With sophisticated instrumental optimization, different portions of metal salts, carboxyl-rich alicyclic molecules, organosulfates (OSs), and lignin-like compounds could be fully fractionated within one LC cycle (20 min). The complexity of the analyte was greatly reduced by LC separation, which therefore allows much better MS performance. Moreover, the compounds’ structures were characterized by tandem mass spectrometry (MSn). The protocol presented herein offers a novel insight into the conventional LC-MS method, that it has the potential to investigate OSs and other components in DOM according to specific functional groups and heteroatoms and to explore their potential sources and reaction mechanisms.
6. 题目: Reverse osmosis concentrate treatment by microbubble ozonation-biological activated carbon process: Organics removal performance and environmental impact assessment
期刊: Science of The Total Environment
作者: W.H. Loh, Q.Q. Cai, R. Li, L. Jothinathan, B.C.Y. Lee, O.H. Ng, J. Guo, S.L. Ong, J.Y. Hu
摘要: Reverse osmosis (RO) is being used in many water reclamation facilities to produce high quality water that can be reused for different purposes. As a part of the RO process, a reject stream is produced as the reverse osmosis concentrate (ROC), which contains elevated levels of contaminants compared to the source water. Effective treatment and safe disposal of ROC via cost-effective means is very challenging. This study aims to develop a robust microbubble ozonation–biological process for industrial ROC treatment with a target effluent chemical oxygen demand (COD) lower than 60 mg/L. As compared to macrobubble ozonation, microbubble ozonation exhibited better ozone dissolution and 29% higher COD removal efficiency with the same ozone dosage. Under the optimum operating conditions with ozone dosage of 30 mg/L, ROC natural pH of 8.67 and ozonation duration of 1 h, microbubble ozonation achieved 42% COD removal efficiency while increasing the BOD5/COD ratio (ratio of biological oxygen demand over 5 days to the corresponding chemical oxygen demand) in ROC from 0.042 to 0.216. A biological activated carbon (BAC) column with an empty bed contact time (EBCT) of 120 min was combined with microbubble ozonation for continuous ROC treatment. Over the 100-day operation, the combined system performed consistent organics removal with an average effluent COD of 45 mg/L. Both LC-OCD data and fluorescence EEM spectra confirmed humic substances were the dominant organic species in ROC. Ozone pre-treatment could achieve significant removal of humic substances in raw ROC. ATP analysis found that ozone pre-treatment enhanced BAC biofilm activity by around 5 folds. 5 min acute toxicity assessment with Aliivibrio fischeri showed 4 times reduction of bioluminescence inhibition in ozone treated ROC. From the environmental point of view, Life cycle assessment (LCA) results demonstrated that Ozone-BAC system had significant environmental burdens on climate change and human toxicity due to the electricity production process. These environmental impacts can be mitigated by optimizing the ozonation process with reduced ozone dosage or utilizing renewable energy sources for electricity generation.
7. 题目: Fatty acids as indicators of sediment organic matter dynamics in a monsoon-influenced tropical estuary
期刊: Ecological Indicators
作者: Laxman Gardade, Lidita Khandeparker, Dattesh V. Desai, P. Atchuthan, Arga Chandrashekar Anil
摘要: Sedimentary organic matter (OM) composition serves as a biomarker and helps in hindcast analysis of the events in the habitat. The present study was carried out on a monthly basis to evaluate the contribution of different biological communities to the surface sediment in a monsoon-influenced tropical Zuari estuary, west coast of India, using source-specific fatty acid (FA) biomarkers and total organic carbon to nitrogen ratio (TOC/TN). Our observations revealed spatio-temporal variation in the OM composition in this estuary, which is influenced by in situ production, bacterial re-working, riverine inputs, and hydrodynamics. The content of TOC, TN, and total FAs in the sediment ranged from 0.13 to 4.27%, 0.01 to 0.31%, and 29 to 122 µg g−1 sediment dry weight, respectively. High content of TOC, TN, total FAs, terrestrial plants-specific FAs, and detrital derived FAs at the lower mid-estuarine (inner) stations when compared to the mouth of the estuary, points out lower mid-estuarine region as the major depositional site for the OM. Low amount of OM at the mouth of the estuary is attributed to high bacterial contribution, which seems to be maintained by repetitive cycles of resuspension-deposition of organic materials. Thus, it seems that the estuarine morphology influences the deposition of OM and plays an important role in the functioning of the estuarine ecosystem. The contribution of phytoplankton-specific FAs was high at the banks of the estuary, which form a suitable habitat for benthic organisms including artisanal fisheries. Diatom, dinoflagellate, and zooplankton-specific FAs were high during the post-monsoon season and decreased from the pre-monsoon to monsoon season. Terrestrial plants and bacteria-derived FAs were high during the monsoon suggesting the role of bacteria in the assimilation of terrestrial material. Elucidating the degradation pattern of in situ produced and terrestrial-derived organic matter through the laboratory designed microcosm experiments is a way forward.
8. 题目: Investigation of carbonaceous materials electrosorption attributes and its performance for capacitive deionization process within the presence of humic acid
期刊: Environmental Science and Pollution Research
作者: Annadurai Thamilselvan, Kadarkarai Govindan, A. Samson Nesaraj, Subramanian Uma Maheshwari, Michael Noel
摘要: This present investigation emphasizes on pros and cons of humic acid (HA) on electrosorption behaviour and performance efficiency of capacitive deionization (CDI) process. Electrosorptive removal of HA was examined by lab scale CDI flow cell under 100 ppm Na2SO4 as a supporting electrolyte. In addition, the electrosorption capacitance and desalination performances were also evaluated through cyclic voltammetry studies. In this perspective, we employed the carbon-based electrodes such as chemically treated activated carbon cloth (ACC), carbon aerogel electrodes grade-I (CA-I) and carbon aerogel electrode grade-II (CA-II) with active surface area for 1 cm2 and 24 cm2 respectively. The specific capacitance values of 30, 23 and 10 F g-1 were achieved for ACC, CA-1 and CA-II with 100 ppm Na2SO4 and 10 ppm HA electrolyte solution. The experimental results substantiated that ACC electrode exhibited higher removal efficiency compared to other two carbon electrodes (CA-I and CA-II). Eventually, the electrosorption removal of natural organic matter HA was observed as 15% for CA-I, 30% for CA-II and 58% for ACC electrodes in a CDI flow cell.
9. 题目: Removal of ciprofloxacin from water by millimeter-sized sodium alginate/H3PO4 activated corncob-based biochar composite beads
期刊: Separation and Purification Technology
作者: Jian Chen, Jinbo Ouyang, Xionghui Cai, Xiaohong Xing, Limin Zhou, Zhirong Liu, Di Cai
摘要: The removal of ciprofloxacin (CIP) from aqueous system is of great significance for water treatment. Here, millimeter-sized sodium alginate/H3PO4 activated corncob-based biochar composite beads (SA-PB) were prepared by a facile phase inversion method. These beads were characterized with SEM, EDS, FTIR, XRD and Raman. Results showed that SA-PB beads were successfully prepared and endowed the merits from alginate and biochar. SA-PB containing 80 wt% PB (SA-PB80) exhibited excellent CIP sorption capacity, which is much higher than pure SA and those containing 20 wt% and 50 wt% PB. Kinetic results showed that the sorption process could be fitted to pseudo-second-order model. The isotherm data indicated that sorption behavior conformed to the Langmuir model. Furthermore, SA-PB exhibited high tolerance to ionic strength and favorable reusability, and SA-PB also has plentiful desirable advantages such as biodegradability, economy and easily separable for solid-liquid system as well as its efficient CIP capture performance.
10. 题目: Photochemical (UV–vis/H2O2) degradation of carotenoids: Kinetics and molecular end products
作者: Sofia Semitsoglou-Tsiapou, Travis B. Meador, Bo Peng, Lihini Aluwihare
摘要: Constraining the formation mechanisms of organic matter that persists in aquatic reservoirs is important for determining the reactivity and fate of carbon and nutrients in these environments. Recent studies have linked dissolved organic matter (DOM) accumulating in the ocean to linear terpenoid structures, and carotenoid degradation products have been proposed as potential precursors. The prevalence of reactive oxygen species in aquatic environments and their potential to be quenched by carotenoids led us to examine radical-assisted photochemical degradation of carotenoids as a potential mechanism for DOM formation and transformation. Experiments were conducted with aggregates of β-carotene, astaxanthin, fucoxanthin and meso-zeaxanthin in THF:H2O under solar light irradiation assisted by hydrogen peroxide (UV–Vis/H2O2). Based on the fine structure of UV–Vis spectra, it was determined that β-carotene and meso-zeaxanthin formed J-type aggregates in experimental solutions, while astaxanthin and fucoxanthin formed H2-type aggregates, consistent with their structural characteristics. All carotenoids degraded under the combined influence of photolysis and ￼OH scavenging, with fucoxanthin exhibiting the fastest degradation kinetics (kPO = 3.69 10−3 s−1) and meso-zeaxanthin the slowest (kPO = 4.37 10−4 s−1). The major degradation products detected by electrospray ionization (ESI) tandem mass spectrometry (MS/MS) were apo-aldehydes and apo-ketones, with the latter tending to accumulate, but epoxidation of the carotenoids also took place, and longer irradiation times resulted in lower molecular weight products. Reaction kinetics and accumulating carotenoid oxidation products identified in this study provide potential formation mechanisms and biomarkers for examining DOM cycling.
11. 题目: Seasonal variations in molecular size of chromophoric dissolved organic matter from the lower Changjiang (Yangtze) River
期刊: Journal of Geophysical Research: Biogeosciences
作者: Lingbin Zhao, Lei Gao, Laodong Guo
摘要: Large world rivers and their DOM fluxes could regulate ecosystem function and biogeochemical processes in coastal marine environments. Knowledge about the seasonal variations in composition and molecular size of DOM remains scarce but is important to a better understanding of the role of river fluxes. Monthly time-series (July 2018 to June 2019) surface water samples were collected from the lower Changjiang (Yangtze) River, one of the largest world rivers, for the measurements of both dissolved organic carbon (DOC) and chromophoric dissolved organic matter (CDOM) to elucidate seasonal changes in their abundance, optical properties, and molecular size distributions among the < 1 kDa, 1–3 kDa, 3–10 kDa, and 10 kDa–0.7 μm size-fractions. On average, the < 1 kDa low-molecular-weight DOM made up about two thirds of the bulk CDOM, leaving the other one third in the 1 kDa–0.7 μm size-fraction. Optical properties and molecular size of DOM transported by the Changjiang River had an evident seasonality. In general, DOM exported from the Changjiang River can be characterized as lower DOC, lower aromaticity, and lower colloidal abundance compared to other world rivers. Together with available literature data, our results show that world rivers with higher/lower DOC concentrations and higher/lower aromaticity also contain more/less colloidal (> 1 kDa) DOM. Our year-long time-series study provides additional valuable baseline data for a better understanding of seasonal changes in the abundance, composition, and molecular weight distribution of DOM from the lower Changjiang River and the potential impacts on the biogeochemical cycling of DOM in the adjacent estuarine, coastal, and shelf areas.
12. 题目: Soil organic matter and biological activity under long-term contamination with copper
期刊: Environmental Geochemistry and Health
作者: Inna V. Zamulina, Andrey V. Gorovtsov, Tatiana M. Minkina, Saglara S. Mandzhieva, Marina V. Burachevskaya, Tatiana V. Bauer
摘要: Organic matter (OM) and enzymes activity can act as indicators of the time and level of soil contamination with heavy metal. The goal of this study is evaluation of the effect of chronic long-term soil contamination with Cu on OM and biological activity in Spolic Technosols. The monitoring plot is located in the zone of industrial wastewater storage and sludge reservoirs in the Seversky Donets River flood plain. The total amount of Cu in the investigated soils varied greatly from 52 to 437 mg/kg. The results of Cu sequential fractionation the contaminated soil have shown that the chemical fraction composition of metal changed when the soil contamination level increased. The amount of Cu compounds associated with OM and Fe and Mn oxides was also higher. Fractions of OM from the humic and fulvic acids groups were studied. Soil was subjected to extraction with cold and hot water, and the content of water-soluble OM (WSOM) was determined. An increased solubility of humic and fulvic acids as well as elevated content of cold and hot extraction WSOM was established. The cold-extracted amount of WSOM increased with an enhance in the Cu content. The long-term contamination of soil with Cu leads to an adaptation of microorganisms to this adverse environmental factor, and this adaptation is manifested in the WSOM content increase. The effect of Cu contamination on microbiological activity was assessed by plate-counting culturable microorganisms and determining urease and dehydrogenase enzymatic activity. A high level of soil contamination with Cu showed a noticeable negative effect on the number of soil bacteria; however, active and potentially active bacteria were observed even in the highly contaminated soils. The changes in soil OM and microbial communities caused by Cu pollution can lead to disruption of ecosystem functioning.
13. 题目: Rethinking application of animal manure for wheat production in China
期刊: Journal of Cleaner Production
作者: Yonghua Li, Nan Bai, Zhenkui Tao, Xiaotian Mi, Gang He, Zhaohui Wang
摘要: The application of animal manure contributes greatly to improving soil fertility and maintaining/increasing wheat yield; however, it is rarely used in China's wheat production. This distortion emphasizes the importance of comprehensive analysis of manure use from theoretical and practical perspectives. A meta-analysis on China's wheat production was therefore conducted to quantify the effects of animal manure applications (SNM: substituting chemical N fertilizer by manure under the same total N input; AMCF: additional manure based on the same chemical fertilizer) on wheat productivity, environmental costs, and economic profits, and a large-scale farmer survey was performed to explore the reasons for the low manure-use rate. Overall, soil organic carbon (SOC) content in SNM and AMCF increased by 21% and 32%, respectively, relative to using chemical fertilizer alone (control). For SNM, yield increased by 5–8% when chemical N fertilizer was substituted with manure at <15% and 15–30%. For AMCF, yield increased by 14% with a 69% increase in total N input. NH3 volatilization and NO3− residual at wheat harvest in SNM reduced by 24% and 21%, respectively, but N2O emissions and estimated GHG emissions increased by 41% and 14%, respectively. NH3 volatilization, N2O emissions, NO3− residue, and estimated GHG emissions in AMCF increased by 12–50%. There was no impact to net ecosystem economic benefit (NEEB) when using pig manure and chicken manure, while the NEEB associated with SNM and AMCF reduced by 13–74% when using cow manure and commercial manure. Although applying manure has the capability to increase SOC and yield, only 1% of N comes from manure in wheat production, which mainly results from low economic profits. Policies and investment incentives that increase economic profits and minimize environmental costs will be crucial to facilitating the widespread use of manure.
14. 题目: Application of dimensional analysis in sorption modeling of the styryl pyridinium cationic dyes on reusable iron based humic acid coated magnetic nanoparticles
作者: Anahita Esmaeilian, Kevin E. O'Shea
摘要: Cationic dyes exist in various industrial wastewaters and removal prior to discharge is necessary due to their carcinogenic behavior which poses a serious threat to human health. Iron based humic acid coated magnetic nanoparticles (HA-MNPs) were evaluated for the removal of 2-[4-(dimethylamino) styryl]-1-methylpyridinium iodide (2-ASP) as a model compound for cationic styryl pyridinium dyes from aqueous media. HA-MNPs were prepared by co-precipitation and characterized. The adsorption of 2-ASP, measured by fluorescence, demonstrates HA-MNPs are efficient for the 2-ASP removal with a maximum adsorption capacity of ∼8 mg/g. Kinetic behavior and equilibrium studies showed the adsorption process fits with pseudo 2nd order and Langmuir isotherm models. The adsorption is relatively fast with ∼70% of the adsorption complete within 30 min. The overall removal increases by increasing solution pH. The observed increase in adsorption can be assigned to an enhanced electrostatic attraction between the positively charged 2-ASP and the increase in the negative charge on the HA-MNPs surface as a function of increasing solution pH. Effective and repetitive regeneration of the HA-MNPs was achieved using NaOH treatment of saturated sorbent. Regeneration of HA-MNPs showed that removal efficiency remains consistently high after five consecutive cycles. Dimensional analysis suggested that initial concentration/sorbent dose ratio should be considered for accurate sorption modeling confirmed by experimental data. Then generalized empirical models for isothermal study and removal efficiency prediction were accurately deduced. This finding will help researchers in sorption studies to design their experiments more efficiently and to develop improved empirical models in removal prediction.
15. 题目: A slight increase in soil pH benefits soil organic carbon and nitrogen storage in a semi-arid grassland
期刊: Ecological Indicators
作者: Jinwei Zhang, Xuefeng Wu, Yujie Shi, Chengji Jin, Yuheng Yang, Xiaowei Wei, Chunsheng Mu, Junfeng Wang
摘要: Grassland soil organic carbon and nitrogen storage (SOC storage and SNC storage) have been regarded as indicators to evaluate impacts of global climate change on ecosystem functions due to their significant impact on atmospheric carbon (C) concentration. The variations in vegetation and soil properties in diverse vegetation patch types may change soil C and nitrogen (N) sequestration capacity. However, the quantities of SOC and SNC stored and the mechanisms behind the variation in this storage under diverse vegetation patches in grassland ecosystems are still unclear. Here we conducted a field experiment to measure the variations in vegetation composition, soil properties and SOC storage and SNC storage among five common vegetation patch types in the Eastern Eurasian steppe. Then we investigated the link between vegetation variation and the SOC and SNC storage. The results showed that (1) the combined effects of competitive ability and physiological stress drove the unimodal relationship between species diversity and soil pH. (2) Biomass production did not reach its maximum in patch types with the greatest plant diversity due to saline-alkaline stress, but the live vegetation N storage reached its maximum in these highly diverse patches due to complementary resource utilization effects. (3) Although biomass production of patches with the greatest biodiversity did not reach a maximum due to a slight increase in soil pH, the largest SOC and SNC storage values were found in the highly diverse patches. Our study implies that in natural grassland, high levels of species diversity may accelerate the decomposition rate, resulting in more recalcitrant organic C and N are released into the soil. At the same time, our observation that reductions in the area of the originally dominant patch type due to the expansion of other species during grassland degradation suggests that comprehensive measurements of SOC and SNC storage in different vegetation patches should be undertaken for accurate evaluation of the C and N sequestering capacity of grasslands. Our results can also help policy makers determine how to achieve sustainable development of grasslands based on C and N sequestration.
16. 题目: Effects of horticulture on soil organic matter properties in highly weathered tropical soils
期刊: Soil and Tillage Research
作者: Matheus Sampaio C. Barreto, Judith Schellekens, Marlon Ramlogan, Ashaki A. Rouff, Evert J. Elzinga, Pablo Vidal-Torrado, Luis Reynaldo F. Alleoni
摘要: Soil organic matter (SOM) plays an important role not only for agriculture but also in the global carbon (C) balance with a potential to mitigate climate change. Land-use changes from native vegetation to intensive agricultural use enhance mineralization of SOM and thereby cause decreases in the amount of soil C. Association of SOM on soil minerals is highlighted as key stabilization mechanism of SOM. To examine the contribution of land-use change and soil mineralogy on soil C losses, soils with different soil mineralogy assemblage were studied from four areas in Brazil, all having sites with agriculture and nearby soils under native vegetation. We assessed SOM stability by thermogravimetric (TGA) and differential scanning calorimetry (DSC) and the molecular composition of functional soil C pools by pyrolysis gas chromatography/mass spectrometry (Py–GC/MS). On average, 33 % of soil C was lost in three sites after land-use change. Py-GC/MS indicates a dominance of reworked and/or microbial material (58–99 % N-containing products and carbohydrates), and low contribution from plant-derived products such as lignin phenols (from 0.1 to 7.7 %), and striking similarities in molecular composition between native vegetation and corresponding sites under agriculture. Thermal data indicate lower energy content in soils under native vegetation than agriculture, confirming microbial-derived SOM. The gibbsite content was positively correlated to N-containing products in both SOM extracted by alkaline solution (r2 = 0.60) and SOM residual after alkaline extraction (r2 = 0.82), while the kaolinite content showed a negative correlation with N-containing compounds (r2 = 0.72) and a positive one with carbohydrates (r2 = 0.48). Thus although SOM content highly decreased upon horticulture, both Py-GC/MS and thermal analyses indicate that SOM composition is mainly controlled by site instead of land-use, and the strong correlations with clay minerals suggest a mineralogical control on SOM composition.
17. 题目: UV-induced activation of organic chloramine: Radicals generation, transformation pathway and DBP formation
期刊: Journal of Hazardous Materials
作者: Yangtao Wu, Weiqiu Zhang, Lingjun Bu, Shumin Zhu, Wang Jue, Shiqing Zhou
摘要: Organic chloramines of little disinfection efficacy commonly exist in disinfection process (chlor(am)ination) due to the wide presence of organic amines in water, of which N-chlorodimethylamine (CDMA) is a typical one. For the first time, UV photolysis for the activation of CDMA was investigated. UV photolysis caused the cleavage of N-Cl bond in CDMA to form Cl• and subsequently HO•, both of which are dominant contributors to the destruction of model contaminant bisphenol A (BPA). Typical spectra of HO• were detected by electron paramagnetic resonance (EPR) experiments, while spectra of reactive nitrogen species (RNS) were not detected during UV photolysis of CDMA. The increase of pH (6.0-8.0), HCO3−/CO32−, Cl− and nature organic matter inhibited the degradation of BPA. We proposed pathways of CDMA and BPA degradation based on the identified transformation products. UV photolysis of CDMA and BPA reduced the formation of N-nitrosodimethylamine (NDMA) at pH 8.0, but increased the formation of trichloronitromethane (TCNM) at pH 7.0 and 8.0. The increasing toxicity and the formation of TCNM and NDMA gave us a hint that formation of organic chloramines should be concerned.
18. 题目: Suwannee River Natural Organic Matter concentrations affect the size and phosphate uptake of colloids formed by iron oxidation
期刊: Geochimica et Cosmochimica Acta
作者: Claudia Moens, Erik Smolders
摘要: Iron (Fe) oxyhydroxide colloids facilitate the transport of organic matter, oxyanions and trace metals in the environment. This study was set up to compare the sizes of Fe-OC colloids formed by oxidation of Fe(II) in the presence of different concentrations of Suwannee River NOM and to evaluate how variable DOC/Fe ratios impact the binding of phosphate. The molar dissolved organic carbon (DOC) to Fe ratio in test solutions was varied to cover the range of environmental freshwaters. Low levels of phosphate (3.2 µM PO4, molar P/Fe 0.036) were either present during coprecipitation together with the NOM or were equilibrated with the colloids post-synthesis. The suspended colloids were analysed with Flow Field Flow Fractionation (FlFFF-UV-ICP-MS) and radiolabeled orthophosphate 32PO4 was used to facilitate the detection of P. Decreasing NOM concentrations consistently increased the colloid size both in absence and presence of PO4 during colloid formation. Over a wide molar DOC/Fe range (10–1400), the Fe-OC colloid size was very small (< 10 nm). Further decreasing the DOC/Fe ratio yielded larger colloids until the limit for colloid stability was reached (DOC/Fe ≤ 1). The molar PO4/Fe ratio in the colloids varied by a factor 2–3 among the Fe-OC colloids. Within the 1–20 nm colloids formed at high DOC/Fe ratio, the measured OC/Fe ratio decreased by a factor 100 with increasing size, suggesting a surface area controlled sorption of NOM. By contrast, the PO4/Fe ratio increased by a factor 2–3 with decreasing DOC/Fe ratio and increasing size, suggesting a high size dependent PO4/NOM competition on the surfaces that can be explained by steric interactions. Thus, NOM enhances the mobility of PO4 by formation of small OM-Fe-PO4 complexes but the highest proportion of PO4 was adsorbed on the largest and, likely, least mobile particles.
19. 题目: Spatial non-stationarity effects of driving factors on soil respiration in an arid desert region
作者: Jinlong Wang, Dexiong Teng, Xuemin He, Lu Qin, Xiaodong Yang, Guanghui Lv
摘要: Soil respiration (Rs) has significant spatial changes in terrestrial ecosystems, especially in arid areas where ecological factors and vegetation distribution have obvious patches. Despite growing interest regarding the variation of Rs and its driving factors, most studies have ignored the spatial heterogeneity in the relationship between Rs and driving factors. Sampling plots (100 m × 100 m) were arranged along a vertical transect from the river including the three habitat types of river bank (RB), transitional zone (TZ), and desert margin (DM) in arid area of northwest China. The Rs, soil microclimate (soil temperature and soil water content), and soil nutrients of different habitats were synchronously monitored. Geostatistics and geographically weighted regression (GWR) methods were used to evaluate the spatial variability of Rs and its relationship with driving factors. The mean value of Rs in RB (0.29 ± 0.25 μmol m−2 s−1) was significantly higher than that in TZ (0.18 ± 0.10 μmol m−2 s−1) and DM (0.12 ± 0.11 μmol m−2 s−1). The degree of spatial dependence of Rs in RB was higher than that in TZ, and the spatial structure of Rs was not detected in DM. The GWR model can clearly reflect significant spatial differences in the effects of driving factors on Rs. Soil microclimate, total nitrogen, and soil pH had a strong influence on the spatial variation of Rs in RB. Soil microclimate, ammonium nitrogen, nitrate nitrogen, available phosphorus, and organic matter had strong effects on the spatial variation of Rs in TZ, and soil microclimate, total phosphorus, and organic matter had stronger effects on the spatial variation of Rs in DM. The results indicate that the GWR model can reveal the complex spatial relationship between Rs and driving factors in detail, and provide a new direction for exploring the spatial heterogeneity of Rs.
20. 题目: Dynamic relationship between dissolved organic matter and soluble microbial products during wastewater treatment
期刊: Journal of Cleaner Production
作者: Gang Tang, Xiaolin Li, Zi Wang, Kai Wang, Binrui Li, Chongxuan Liu, Xing Zheng
摘要: Dynamics of the dissolved organic matter (DOM) and soluble microbial products (SMP) significantly affected the sustainability of wastewater treatment plants and effluent qualities. In this study, the origin, transformation, and seasonal variation of DOM components in the anaerobic/anoxic/oxic (A2O) units were illustrated with fluorescence analysis. Results show that the anaerobic process transformed humic acid-like substances (HA) and SMP into fulvic acid-like substances (FA) and aromatic proteins (AP), which indicated the decomposition of macromolecules. In cold seasons, the anoxic process turned AP to HA, SMP, and FA; but the oxic process reversed the transformation. In warm seasons, 6% of AP decreased while 3.1% of HA, 1.8% of SMP, and 1.0% of FA increased during the oxic process. Proteobacteria strains were isolated from the activated sludge to stimulate the SMP generation, it was found higher temperature facilitated the transformation of FA and HA (humics) to SMP and AP (proteins), which resulted more proteins presented in the wastewater DOM. These findings indicated that the treatment efficiency and DOM quality in A2O processes were influenced by influent quality and/or temperature conditions, and highlighted the generation of SMP by sludge microorganisms, based on which the corresponding strategies considering the seasonal DOM/SMP dynamics were recommended for the stringent regulation of effluents and the sustainability of the receiving water bodies. Besides, the overall fluorescence intensity was positively correlated with the quantified biopolymer contents in SMP, implying the potential of using the fluorescence-derived information to indicate more quantified DOM properties.