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30601. 题目: Optimization process of organic matter removal from wastewater by using Eichhornia crassipes
文章编号: N18081608
期刊: Environmental Science and Pollution Research
作者: Sènandémi Edwige Reine Mahunon, Martin Pépin Aina, Akuemaho Virgile Onésime Akowanou, Edmond Konan Kouassi, Benjamin Kouassi Yao, Kopoin Adouby, Patrick Drogui
更新时间: 2018-08-16
摘要: This study aimed to determine the optimal conditions for organic matter removal from wastewater by Eichhornia crassipes (E.C). As a matter of fact, a complete factorial design was used to determine the effect of residence time (X1), plant density (X2) and initial chemical oxygen demand (COD) concentration (X3) on the phytoremediation process. The process’s performance was measured on COD (Y1), NH4+ (Y2) and PO43− (Y3), with the results indicating a reduction of 8.59–81.71% of COD (Y1); 22.53–95.81% of NH4+ (Y2) and 0.54–99.35% of PO43− (Y3). Then, the first-order models obtained for COD, NH4+ and PO43− removal were validated using different statistical approaches such as statistical and experimental validation. Moreover, multi-response optimization was carried out through different scenarios. On the whole, the results obtained indicated that two serial ponds are required for an optimum organic matter removal by Eichhornia crassipes. Indeed, for the first pond, a residence time of 15 days is needed with a plant density of 60 ft/m2 and an initial concentration of about 944 mg/L. The second was the same residence time as the first with similar plant density of 60 ft/m2 and an initial load 192 mg/L (> 200 mg/L). Optimal organic matter removal from wastewater using Eichhornia crassipes requires two ponds arranged in chain.
30602. 题目: Impact of land cover types on soil aggregate stability and erodibility
文章编号: N18081607
期刊: Environmental Monitoring and Assessment
作者: Remzi İlay, Yasemin Kavdir
更新时间: 2018-08-16
摘要: Gökçeada is the biggest island, and it is also known as the organic island of Turkey. Approximately 65% of the Gökçeada lands have slope > 12%. Climate, topography, land cover, and soil characteristics are considered to be the main natural factors affecting soil erosion severity in the Gökçeada. Prevention of soil degradation, hence the preservation or improvement of the overall quality of the soil, is directly related to the presence of stable soil aggregates. In addition, the resistance to weathering and replacement of soil particles are also relevant aspects in terms of sustainability. Aggregate stability (AS) and erodibility of land (Kfac) are related to soil properties. However, this relationship can vary under different circumstances. In this study, 248 surface soil samples have been taken from forest and semi-natural areas (FSNA) and agricultural areas (AGRA) according to CORINE 2006. Eleven selected soil properties were measured, and their impacts on AS and Kfac (RUSLE-K) were determined by using the CRT (classification and regression tree) in Gökçeada. Results showed that the relations among soil characteristics changed according to the land cover classes. Total organic carbon is much more associated with AS in AGRA, while total carbon is associated with AS in FSNA. The effect of calcium carbonate on Kfac was higher than other soil properties when the land cover type was ignored. On the other hand, in AGRA, the effect of between clay content on Kfac was greater than those of FSNA.
30603. 题目: Non-Singlet Oxygen Kinetic Solvent Isotope Effects in Aquatic Photochemistry
文章编号: N18081606
期刊: Environmental Science & Technology
作者: Caroline A. Davis, Kristopher McNeill, Elisabeth M.-L. Janssen
更新时间: 2018-08-16
摘要: The kinetic solvent isotope effect (KSIE) is typically utilized in environmental photochemistry to elucidate whether a compound is susceptible to photooxidation by singlet oxygen (1O2), due to its known difference in lifetime in water (H2O) versus heavy water (D2O). Here, the overall indirect photodegradation rates of diarylamines in the presence of dissolved organic matter (DOM) were enhanced in D2O to a greater extent than expected based on their reactivity with 1O2. For each diarylamine, the relative contribution of reaction with 1O2 to the observed KSIE was determined from high resolution data of 1O2 lifetimes by time-resolved infrared luminescence spectroscopy. The additional enhancement in D2O beyond reaction with 1O2 contributed significantly to the observed KSIE for diarylamines (8–65%) and diclofenac (100%). The enhancement was ascribed to slower reduction of transient radical species of the diarylamines due to H/D exchange at DOM’s phenolic antioxidant moieties. A slower second-order reaction rate constant with a model antioxidant was verified for mefenamic acid radicals using transient absorption spectroscopy. Changes in lifetime and reactivity with triplet sensitizers were not responsible for the additional KSIE. Other pollutants with quenchable radical intermediates may also be susceptible to such an additional KSIE, which has to be considered when using the KSIE as a diagnostic tool.
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30604. 题目: Graphene Modified Electro-Fenton Catalytic Membrane for in Situ Degradation of Antibiotic Florfenicol
文章编号: N18081605
期刊: Environmental Science & Technology
作者: Wen-Li Jiang, Xue Xia, Jing-Long Han, Yang-Cheng Ding, Muhammad Rizwan Haider, Ai-Jie Wang
更新时间: 2018-08-16
摘要: The removal of low-concentration antibiotics from water to alleviate the potential threat of antibiotic-resistant bacteria and genes calls for the development of advanced treatment technologies with high efficiency. In this study, a novel graphene modified electro-Fenton (e-Fenton) catalytic membrane (EFCM) was fabricated for in situ degradation of low-concentration antibiotic florfenicol. The removal efficiency was 90%, much higher than that of electrochemical filtration (50%) and single filtration process (27%). This demonstrated that EFCM acted not only as a cathode for e-Fenton oxidation process in a continuous mode but also as a membrane barrier to concentrate and enhance the mass transfer of florfenicol, which increased its oxidation chances. The removal rate of florfenicol by EFCM was much higher (10.2 ± 0.1 mg m–2 h–1) than single filtration (2.5 ± 0.1 mg m–2 h–1) or batch e-Fenton processes (4.3 ± 0.05 mg m–2 h–1). Long-term operation and fouling experiment further demonstrated the durability and antifouling property of EFCM. Four main degradation pathways of florfenicol were proposed by tracking the degradation byproducts. The above results highlighted the feasibility of this integrated membrane catalysis process for advanced water purification.
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30605. 题目: The remineralization of sedimentary organic carbon in different sedimentary regimes of the Yellow and East China Seas
文章编号: N18081604
期刊: Chemical Geology
作者: Bin Zhao, Peng Yao, Thomas S. Bianchi, Ana R. Arellano, Xuchen Wang, Jianbin Yang, Rongguo Su, Jinpeng Wang, Yahong Xu, Xinying Huang, Lin Chen, Jun Ye, Zhigang Yu
更新时间: 2018-08-16
摘要: We investigated the remineralization of sedimentary organic carbon (SOC) at 12 sites in East China Sea mobile-muds (ECSMMs) and South Yellow Sea central mud deposits (SYSMDs) - using a time-sequence sediment incubation experiment. We examined pore-water dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), fluorescent dissolved organic matter (FDOM), dissolved inorganic nitrogen (DIN) nutrients (NH4+, NO3−, and NO2−), redox sensitive elements (Fe2+ and Mn2+), and major anions (SO42− and Cl−) in incubated sediments, to better constrain controlling mechanisms of SOC remineralization under different sedimentary regimes. Lower DIC production rates in SYSMDs (2.36–3.13 mmol m−2 d−1) than those in ECSMMs (2.94–13.5 mmol m−2 d−1), were mainly attributed to cold bottom water masses and a relatively stable sedimentary environment in SYS. Higher DIC production rates were observed mostly at offshore sites of ECSMMs that had relatively enriched 13C of SOC - which indicated preferential degradation of labile SOC of marine origin. When compared with tropical mobile-muds, higher bottom-water temperatures, thicker mobile-muds, and large inputs of reactive terrestrial OC resulted in more intense remineralization of SOC in Amazon mobile-muds than in ECSMMs. Lower ratios of DOC/DIC production rates in ECSMMs (0.11–0.72) were likely indicative of efficient transformation of OC, and largely due to sulfate reduction. A rapid increase in marine protein-like FDOM components during the incubation indicated that less stable marine SOC was preferentially converted to DOC - and then to DIC. Our SOC budget indicates that 16.8% of SOC was decomposed in sediments of ECSMMs, but only about 5.4% of SOC was decomposed in SYSMDs, suggesting lower SOC preservation efficiency in mobile-muds than distal muds.
30606. 题目: Cork wastewater purification in a cooperative flocculation/adsorption process with microwave-regenerated activated carbon
文章编号: N18081603
期刊: Journal of Hazardous Materials
作者: Xinyu Ge, Zhilin Wu, Giancarlo Cravotto, Maela Manzoli, Pedro Cintas, Zhansheng Wu
更新时间: 2018-08-16
摘要: The aim of this work is to investigate a novel cork wastewater (CW) purification method that combines flocculation/adsorption with the microwave assisted regeneration of coconut powder activated carbon (CPAC). The flocculation treatment made use of FeSO4·7H2O/NaOH and provided high removal efficiency, as shown by the observed values of UV254 (90%), chemical oxygen demand (COD, 86%), polyphenols (PP, 81%),total solid (TS, 40%), total suspended solid (TSS, 62%), and total dissolved solid (TDS, 18%). After the flocculation and filtration, CPAC was used to further remove left TSS, TDS and dissolved organics. The effects of CPAC amount, pH value and adsorption time have been studied. It was found that 250 mg is the optimum CPAC amount for the treatment of 50 mL CW at pH 3.5 for 10 min. Overall process effectiveness can be summarised as follows: UV254 (100%), COD (98%), PP (100%), TS (58%), TSS (93%), and TDS (24%), while the characteristic colour of the CW completely disappeared. The microwave regenerated CPAC can undergo five runs without appreciable losses in removal efficiency. Predictably, this simple and scalable process could afford a promising treatment method for other industrial wastewaters with high content of organic matters such as PP, phenolic acids and tannins.
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30607. 题目: The treatment of flowback water in a sequencing batch reactor with aerobic granular sludge: Performance and microbial community structure
文章编号: N18081602
期刊: Chemosphere
作者: Xiaoting Zhang, Aoxiang Chen, Daijun Zhang, Shuangwu Kou, Peili Lu
更新时间: 2018-08-16
摘要: The extensive application of hydraulic fracturing technology has significantly promoted the large-scale development of shale gas. However, it is a great challenge for shale gas extraction to effectively manage large-volume flowback water (FW) with high salinity and complex organic substances. Here, we report an aerobic granular sludge (AGS) tolerable to high salinity, and suited to the treatment of FW. The performance of a sequencing batch reactor (SBR) with the AGS for the treatment of the synthetic FW and the microbial community structure at different salinity levels were investigated. The AGS fed with synthetic FW possessed a larger average particle size and a higher settling rate (50 m h−1). When NaCl concentration increased to 50.0 g L−1, the removal efficiency of total organic carbon (TOC) increased to 79 ± 1%, and the removal rate of polyacrylamide (PAM) raised up to 42.7 ± 0.7 g m−3 d−1. Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, and Sphingobacteriia dominated in the microbial community of AGS. Cellvibrionaceae, Rhodocyclaceae, Enterobacteriaceae, Moraxellaceae, Pseudomonadaceae, and Halomonadaceae belonging to Betaproteobacteria and Gammaproteobacteria played important role in degrading PAM, polycyclic aromatic hydrocarbons (PAH), and some other organics in FW at high salinity. These results suggest that an AGS-based SBR is a promising technology for the treatment of FW.
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30608. 题目: Enhanced removal of bio-refractory dissolved organic matter from cassava distillery wastewater by powdered activated carbon-ballasted coagulation: Detailed study of separation characteristics and mechanisms
文章编号: N18081601
期刊: Chemosphere
作者: Ming Zhang, Yu Chen, Li Xie, Qi Zhou
更新时间: 2018-08-16
摘要: Efficient removal of bio-refractory dissolved organic matter (DOM) and colorants is essential for discharging or reusing the distillery wastewater. An important part of recalcitrant DOM still exists in the effluent of regular coagulation though the ferric coagulant has been found to be effective in decoloration. The present work adopted powdered activated carbon (PAC) as ballasting agent to achieve robust separation effect and efficiency of bio-refractory DOM from the bio-chemically treated cassava distillery wastewater (BTDWW). More than 90% of DOC could be removed at the PAC and Fe(III)-coagulant dosage of 1.40 g/L and 0.84 g/L as Fe when the BTDWW was neutral. PAC should be dosed before coagulant in order to mix well with the DOM in the BTDWW. The analyses of DOM in effluent reveal that PAC facilitated the removal of lignin breakdown products which could not be well eliminated by regular coagulation; the removal of DOM with MW < 5 kDa was mostly enhanced. The characteristics of flocs demonstrate that PAC reinforced the interaction between Fe(III) species and DOM by providing more reaction sites. The sedimentation could be completed within the initial 5 min, and the highest settling velocity was almost 8 times higher than that of the only Fe(III)-involved flocs. The large size and favorable robustness of PAC-involved flocs enabled decent sedimentation even though their stretched structure might not be desirable in regular coagulation. The PAC-ballasted coagulation is recommended as tertiary treatment of BTDWW considering its high efficiency and sound economic feasibility.
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30609. 题目: Long-term afforestation significantly improves the fertility of abandoned farmland along soil clay gradient on the Chinese Loess Plateau
文章编号: N18081516
期刊: Land Degradation & Development
作者: Yan Zhang, Liyun Wei, Xiaorong Wei, Xuetong Liu, Mingan Shao
更新时间: 2018-08-15
摘要: In China, almost half of the total land area is degraded, mainly due to the unreasonable use of land for agricultural production. During the past half‐century, afforestation has become a popular management option to remedy degraded soils. In this paper, we studied the long‐term effects of afforestation on the major properties of soils with different textures. We measured the changes in soil physical, chemical and fertility properties after 10, 20 and 30 years of afforestation with black locust (Robinia pseudoacacia) on abandoned farmland at 5 sites on the Loess Plateau, China, which is characterized by a temperate monsoon climate. The soil clay contents varied significantly among sites. The objectives were to understand how long‐term afforestation affects soil properties and whether such effects depend on the soil texture. Averaged across the 5 sites and the depths of 0‐10 and 10‐20 cm, afforestation resulted in significant increases in the proportion of macroaggregates (+22.5%), saturated hydraulic conductivity (+185.4%), organic matter content (+110.5%) and total nitrogen content (+110.5%) but significant decreases in the proportion of microaggregates (‐21.9%) and bulk density (‐10.8%). The silt+clay fraction, soil pH and nitrate content were minimally affected by afforestation. The effects of afforestation were greater at 0‐10 cm than at 10‐20 cm, but they varied between sites. Furthermore, most soil metrics linearly responded to the time of afforestation, and such responses were dependent on the soil clay content. Our results suggest that long‐term afforestation improves soil fertility better in soils with a clay content of approximately 20%.
30610. 题目: Organic carbon aging during across-shelf transport
文章编号: N18081515
期刊: Geophysical Research Letters
作者: Rui Bao, Masao Uchida, Meixun Zhao, Negar Haghipour, Daniel Montlucon, Ann McNichol, Lukas Wacker, John M. Hayes, Timothy I. Eglinton
更新时间: 2018-08-15
摘要: Compound‐specific radiocarbon analysis (CSRA) was performed on different grain‐size fractions of surficial sediments to examine and compare lateral transport times (LTTs) of organic carbon. 14C aging of long‐chain leaf wax fatty acids along two dispersal pathways of fluvially‐derived material on adjacent continental margins implies LTTs over distances of ~30 to 500 km that range from hundreds to thousands of years. The magnitude of aging differs among grain size fractions. Our finding suggests that LTTs vary both temporally and spatially as a function of the specific properties of different continental shelf settings. Observations suggest that 14C aging is widespread during lateral transport over continental shelves, with hydrodynamic particle sorting inducing age variations among organic components residing in different grain sizes. Consideration of these phenomena is of importance for understanding carbon cycle processes and interpretation on sedimentary records on continental margins.
30611. 题目: Drivers of Dissolved Organic Matter in the Vent and Major Conduits of the World's Largest Freshwater Spring
文章编号: N18081514
期刊: Journal of Geophysical Research: Biogeosciences
作者: Casey Luzius, Francois Guillemette, David C. Podgorski, Anne M. Kellerman, Robert G. M. Spencer
更新时间: 2018-08-15
摘要: Wakulla Springs is the largest and deepest freshwater spring on Earth and has exhibited increased chromophoric dissolved organic matter (CDOM) inputs (i.e. browning) in recent decades. To examine the drivers of changing dissolved organic matter (DOM) at the spring vent we examined dissolved organic carbon (DOC) concentrations and DOM composition via optical parameters (i.e. absorbance and fluorescence) in the major conduits and a connecting spring over the course of one year. Sample sites separated clearly based on DOC concentration, CDOM absorbance, and optical parameters indicative of autochthonous (clear groundwater) versus allochthonous (terrestrial) DOM. Seasonality was apparent in the allochthonous dominated sites with increasing terrestrial contribution particularly with large precipitation events post dry periods. Principle component analysis highlights the ability of optical parameters to show the dominance of sample sites draining from the southwest (i.e. Apalachicola National Forest) as responsible for the CDOM rich water at the vent, whereas water draining from the north was comparatively clear. Increasing CDOM rich waters at the vent suggests that either input from conduits draining from the southwest have increased, or the relative dilution with clear groundwater has decreased in the conduit system prior to discharge from the vent. Sea‐level rise impacts in the region have been suggested to result in more blackwaters delivered to the vent, and ongoing extraction of clear groundwater reduces the dilution capacity on CDOM rich waters. Thus, anthropogenic impacts in the region need to be addressed if the trend of increased CDOM inputs at Wakulla Springs is to be reversed.
30612. 题目: Mixing State of Carbonaceous Aerosols of Primary Emissions from “Improved” African Cookstoves
文章编号: N18081513
期刊: Environmental Science & Technology
作者: Yuchieh Ting, Edward J. S. Mitchell, James D. Allan, Dantong Liu, Dominick V. Spracklen, Alan Williams, Jenny M. Jones, Amanda R. Lea-Langton, Gordon McFiggans, Hugh Coe
更新时间: 2018-08-15
摘要: Designs of “improved” stoves are introduced recently to benefit the solid fuel consumption of cooking activities in developing countries, but the uncertainties concerning the combustion processes and particulate emissions remain poorly characterized. To help understand this, combustion in three examples of “improved” African cookstoves was investigated in the laboratory. A typical European heating stove was included for comparison purpose. Detailed aerosol emissions were studied in real-time with an Aerosol Mass Spectrometer and Single Particle Soot Photometer, to explore interactions between black carbon (BC) and organic carbon aerosols, which were parametrized according to modified combustion efficiency (MCE), a common metric used within the atmospheric emission community. Greater than 50% of the total organic matter (OM) was found in BC-containing particles when MCE was >0.95 for dry oak and coal fuels, whereas at lower MCE, over 80% of the total OM for most of the fuels existed in particles without detectable BC. When the OM mass fraction of total particulate matter (PM1) > 0.9, the mass ratio of OM to refractory BC in BC-containing particles was about 2–3, but only ∼0.8 when OM mass fraction
30613. 题目: Estimating CDOM concentration in highly turbid estuarine coastal waters
文章编号: N18081512
期刊: Journal of Geophysical Research: Oceans
作者: Jun Zhao, Wenxi Cao, Zhantang Xu, Bin Ai, Yuezhong Yang, Guangzhen Jin, Guifen Wang, Wen Zhou, Yong Chen, Haiyun Chen, Zhaohua Sun
更新时间: 2018-08-15
摘要: We proposed a support vector machine (SVM) algorithm to retrieve colored dissolved organic matter (CDOM) concentration (using ag(443) as a proxy) in the highly turbid Pearl River estuary (PRE). Two band ratios, namely Rrs(443)/Rrs(547) and Rrs(488)/Rrs(547), were used as inputs. Comparisons between the estimated and measured ag(443) illustrated high accuracy of the SVM algorithm, yielding R2s of 0.98 and 0.89, mean absolute percentage errors (MAPEs) of 5.18% and 13.1%, and root mean square deviations (RMSDs) of 0.012 and 0.034 m‐1 for the training and validation datasets, respectively. The SVM algorithm was also evaluated against existing ones for the study area and gave the best accuracy with a R2 of 0.9, a MAPE of 10.23%, and a RMSD of 0.025 m‐1. The diurnal dynamics of CDOM in the PRE was revealed showing complicated variations and influenced by the combined effects of wind, tide, circulation, and river discharge. As for remote sensing applications, the SVM‐based CDOM product exhibited great potential to trace the Pearl River plume and the satellite‐derived plume area agreed well with the FVCOM model simulation result. SVM is an accurate and fast tool for retrieving CDOM concentration, especially in highly turbid estuarine coastal waters, and thus, river plume dynamics can be traced.
30614. 题目: Joint effects of extrinsic biophysical fluxes and intrinsic hydrodynamics on the formation of hypoxia west off the Pearl River Estuary
文章编号: N18081511
期刊: Journal of Geophysical Research: Oceans
作者: Zhongming Lu, Jianping Gan, Minhan Dai, Hongbin Liu, Xiaozheng Zhao
更新时间: 2018-08-15
摘要: Using field measurements and a process‐oriented three‐dimensional coupled physical‐biogeochemical numerical model, we investigated the physical and biogeochemical processes governing the bottom hypoxic zone on the western shelf off the Pearl River Estuary. The intensity and area of the hypoxia grew with increasing total nutrient input from the Pearl River that has increased continuously in recent decades. The hypoxic zone was formed and maintained largely associated with the stable water column where the stability was provided simultaneously by wind stress and freshwater discharge, favourable local hydrodynamics for flow convergence, and westward organic matter transport. Wind stress altered the stratification, while freshwater discharge changed the stratification and baroclinic velocity shear simultaneously. Two‐layered flow with a cyclonically‐rotating current around a salient edge of the western shelf off the estuary hydrodynamically enhanced the local convergence, allowing sufficient residence time for the remineralization of organic matter produced in the hypoxic zone and organic matter transported into the region. Our results suggest that a combination of unique local hydrodynamic feature and decomposition of organic matter in water column and sediment are the cause of the formation and maintenance of the bottom hypoxia on the western shelf of the estuary during summer.
30615. 题目: The frequent effects of hydroxyl radicals on the oxidation of crude oil in soil
文章编号: N18081510
期刊: CLEAN - Soil, Air, Water
作者: Jinlan Xu, Qianqian Cao, Miaojia Zhang, Fan Wang, Tinglin Huang, Junhao Ren
更新时间: 2018-08-15
摘要: The characteristics of the hydroxyl radicals (•OH) frequently produced in the Fenton process and the effects of these radicals on the oxidation of hydrophobic total petroleum hydrocarbons (TPH) in soil were investigated. Twelve groups of Fenton oxidation experiments were conducted using two kinds of crude oil‐contaminated soil samples (S1 and S2) with different soil organic matter (SOM) contents. The results showed that the decrease of TPH increased by 6774 mg/kg (S1) and 5875 mg/kg (S2) by using the frequent •OH (•OHf). These results were two times the results obtained by using the single •OH (•OHs) (S1: 3410 mg/kg, S2: 2918 mg/kg). The decrease of hydrophobic long‐chain alkanes C21–C30 was greatly improved by using the •OHf, i.e., oxidation of 1557–3011 mg/kg in soil S1 and 1371–2532 mg/kg in soil S2. Moreover, the C21–C30 alkanes in soil S1 with low SOM (3.89%) were more degraded after oxidation. The residual non‐aqueous phase liquid (NAPL) TPH content by using the •OHf (266–1200 mg/kg) was much lower than that by using the •OHs (2519–4070 mg/kg). The residual of the NAPL TPH by using the •OHf was 11–29% of the residual by using the •OHs. This result indicated that residual NAPL TPH was reduced by using the •OHf, and the TPH contents in the two soil samples were efficiently oxidized.
30616. 题目: The changing faces of soil organic matter research
文章编号: N18081509
期刊: European Journal of Soil Science
作者: P. Smith, S. Lutfalla, W. J. Riley, M. S. Torn, M. W. I. Schmidt, J.-F. Soussana
更新时间: 2018-08-15
摘要: Summary For the 70th Anniversary of the establishment of the British Society of Soil Science, this short paper explores the idea that research on soil organic matter has remained a central theme within soil science over the past 70 years, albeit with changing emphasis and application. The number of publications on soil organic matter has increased greatly in recent decades; for example, there were almost 35 000 journal papers with this theme in the decade 2007–2016. Several topics in research on soil organic matter, such as soil fertility, have endured for a number of decades, with publications found on soil organic matter and fertility in the decade 1947–1956. A search with other keywords occurring with soil, such as climate change, biodiversity, fertility, quality, health and security, showed that several topics did not appear before the 1970s and 1980s, but since then the sub‐topics and applications have diversified. Carbon is a keyword that has become more associated with publications on soil organic matter; carbon is in over half of soil organic matter publications of the last decade. A closer examination of research on agricultural soil carbon sequestration since 1990 reveals that the focus of papers in the literature has changed over this period. A closer examination of papers on modelling shows that the next generation of soil organic matter models is developing from pseudo first‐order decay models using conceptual pools and prescribed controls of turnover time to vertically resolved, microbially explicit models representing mineral surface and plant interactions. Given its higher policy profile during the last 2 years, research on soil organic matter and soil carbon sequestration is predicted to have a bright future.
30617. 题目: Limited effect of organic matter on soil available water capacity
文章编号: N18081508
期刊: European Journal of Soil Science
作者: B. Minasny, A. B. McBratney
更新时间: 2018-08-15
摘要: Summary Soil water‐holding capacity is an important component of the water and energy balances of the terrestrial biosphere. It controls the rate of evapotranspiration, and is a key to crop production. It is widely accepted that the available water capacity in soil can be improved by increasing organic matter content. However, the increase in amount of water that is available to plants with an increase in organic matter is still uncertain and may be overestimated. To clarify this issue, we carried out a meta‐analysis from 60 published studies and analysed large databases (more than 50 000 measurements globally) to seek relations between organic carbon (OC) and water content at saturation, field capacity, wilting point and available water capacity. We show that the increase in organic carbon in soil has a small effect on soil water content. A 1% mass increase in soil OC (or 10 g C kg−1 soil mineral), on average, increases water content at saturation, field capacity, wilting point and available water capacity by: 2.95, 1.61, 0.17 and 1.16 mm H2O 100 mm soil−1, respectively. The increase is larger in sandy soils, followed by loams and is least in clays. Overall the increase in available water capacity is very small; 75% of the studies reported had values between 0.7 and 2 mm 100 mm−1 with an increase of 10 g C kg−1 soil. Compared with reported annual rates of carbon sequestration after the adoption of conservation agricultural systems, the effect on soil available water is negligible. Thus, arguments for sequestering carbon to increase water storage are questionable. Conversely, global warming may cause losses in soil carbon, but the effects on soil water storage and its consequent impact on hydrological cycling might be less than thought previously.
30618. 题目: Electrochemical advanced oxidation processes (EAOPs) as alternative treatment techniques for carwash wastewater reclamation
文章编号: N18081507
期刊: Chemosphere
作者: Soliu O. Ganiyu, Elisama Vieira dos Santos, Emily Cintia Tossi de Araújo Costa, Carlos A. Martínez-Huitle
更新时间: 2018-08-15
摘要: Electrochemical advanced oxidation processes such as electrooxidation (EO), electrooxidation with hydrogen peroxide generation (EO-H2O2) and electro-Fenton process (EF) have been investigated as alternative treatment techniques for complete removal of anionic surfactants and organic matters from real carwash wastewater. The electrochemical processes were performed with acidified real carwash wastewater using boron doped anode and carbon felt cathode. In all cases, the chemical oxygen demand (COD) removal efficiency was always increased with rise in applied current and complete organic matter decay was achieved at applied current of 500 mA or above after 6 h of electrolysis. Faster and higher COD decay was observed with EF compared to either EO or EO-H2O2 treatment, at all currents and electrolysis time. Besides, complete degradation of anionic surfactants – the major organic content of the wastewater could be achieved at all applied currents studied irrespective of the process used, indicating the efficacy of processes for total remediation of real carwash wastewater. The short-chain carboxylic acids formed as the final organic byproducts were identified and quantified by ion-exclusion chromatography. More so, lower energy consumption and higher current efficiency were achieved with EF compared to EO-H2O2. Electrochemical treatment was found to be a powerful technology for the complete abatement of organic matter in carwash wastewater for possible reuse.
30619. 题目: Stoichiometry of decomposing Spathodea campanulata leaves in novel puertorrican forests
文章编号: N18081506
期刊: Forest Ecology and Management
作者: Ariel E. Lugo, Oscar L. Abelleira Martínez
更新时间: 2018-08-15
摘要: One of the challenges in the restoration of degraded lands is the re-establishment of soil structure and fertility. Novel forests that regenerate on recently abandoned and degraded agricultural lands are among the first biotic systems that begin the process of soil rehabilitation. The rate of litter decomposition and associated element mobility is one of many processes that contribute to the understanding of how ecosystem-level processes restore eroded soils. We studied the stoichiometry of Spathodea campanulata leaves decomposing in novel subtropical moist forests. We found that the speed of leaf decomposition was high (annual decomposition constant of 5.0 to 2.6 or half-life of 51 to 98 days). Spathodea leaf mass loss was particularly fast during the first 16 days of decomposition (half-life of 33 days). Leaf litter was characterized by high chemical quality with low C/N, C/P, and N/P. During the leaf decomposition process, macroelements (N, P, K, Ca, and Mg) were more mobile than microelements (Al, Mn, Fe, and Na). As leaf litter decomposed, nitrogen increased in concentration, the quantity of all macroelements decreased, and microelements tended to increase in both concentration and quantity. Because of the rapid rate of decomposition and high chemical quality of Spathodea leaf litter, it appears that the potential for yielding residual soil organic matter from its leaves is reduced, but this is a tradeoff with the rapid release of elements, which contributes to the high juvenile tree density and primary productivity observed in novel Spathodea forests.
30620. 题目: Dominant Fraction of EPFRs from Nonsolvent-Extractable Organic Matter in Fine Particulates over Xi’an, China
文章编号: N18081505
期刊: Environmental Science & Technology
作者: Qingcai Chen, Haoyao Sun, Mamin Wang, Zhen Mu, Yuqin Wang, Yanguang Li, Yansong Wang, Lixin Zhang, Zimeng Zhang
更新时间: 2018-08-15
摘要: To understand the nature and possible sources of environmentally persistent free radicals (EPFRs) in atmospheric aerosols, the present study used a solvent extraction method to fractionate aerosol components with different polarities and solvent resistance in fine particulate matter (PM2.5) from Xi’an, China. The characteristics of EPFRs, that is., their concentration, type and lifetime, were obtained based on their electron paramagnetic resonance spectra. The results showed that the EPFRs in the PM2.5 samples were carbon-centered with a nearby heteroatom (g = 2.0031) and had a long half-life of more than 3 years. Nearly all of the extractable EPFRs were detected in the water-insoluble organic fraction and showed characteristics indicating that may contain oxygen-centered radical (g = 2.0038). Most of the total EPFRs in the PM2.5 were derived from solvent-resistant organic matter (88%), which likely consisted of graphene oxide analogues. The results suggest that previous studies may have missed the major proportion of EPFRs in atmospheric particulates if they only focused on solvent-extractable or metallic oxide-formed EPFRs. Our results showed that the EPFR concentration was significantly and positively correlated with the elemental carbon and NO2 concentrations, suggesting that traffic emissions may be an important source of EPFRs in PM2.5 over Xi’an.
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