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26001. 题目: Sorption of organic compounds to two diesel soot black carbons in water evaluated by liquid chromatography and polyparameter linear solvation energy relationship
文章编号: N18072702
期刊: Water Research
作者: Po-Hsin Su, Dave Ta Fu Kuo, Yang-hsin Shih, Chih-yu Chen
更新时间: 2018-07-27
摘要: Substantial variability in sorption capacity of black carbon (BC) has been a major challenge for accurate fate and risk assessment of organic pollutants in soils and sediments. 16 model organic sorbates (logK_OW = 0.38–4.21) encompassing diverse chemical functionalities were used to probe the sorption capacity of two diesel soot samples representative of graphitic BC (BC1, specific surface area (SSA) = 87 m²/g) and amorphous, oxygenated BC (BC2; SSA = 3.6 m²/g). The BC-water sorption coefficients (logK_BC) of the model sorbates were determined using reversed-phase liquid chromatography (RP-LC) on soot-filled columns. It was found that mass-based logK_BC's of BC1 (1.64–3.66 L/kg_BC) exceeded those of BC2 (0.68–3.48 L/kg_BC) consistently for all model sorbates. However, area-normalized logK_BC's of BC2 were larger than those of BC1, suggesting that the overall sorption was more favored on the oxygenated sorbent per area basis. Linear solvation energy relationships (LSERs) for sorption onto BC1 and BC2 were found to be logK_BC = (2.49 ± 0.65)E + (−2.71 ± 0.88)S + (1.17 ± 0.46)A + (2.52 ± 0.34)V and logK_BC = (1.12 ± 0.39)E + (−1.68 ± 0.32)S + (−3.70 ± 0.57)B + (4.37 ± 0.38)V + (−1.51 ± 0.22), respectively. The LSERs indicated that sorption onto soot was generally enhanced with increasing non-specific van der Waals and decreasing cavitation cost (i.e., eE, sS, and vV terms). The logK_BC difference between BC1 and BC2, ΔlogK_BC, appeared to be correlated with the H-bonding capacity of the sorbates but not logK_OW. Analysis of literature and experimental logK_BC's revealed that logK_BC and logSSA across different types of BC (i.e., soot, char, charcoal, activated carbon) were linearly correlated for benzene and toluene (r² = 0.88–0.91). This work illustrates the utility of RP-LC in determining the sorption coefficients of high-capacity sorbents and suggests the possibility of a unified sorption model for the continuum of black carbon.

26002. 题目: A simple approach to estimate daily loads of total, refractory, and labile organic carbon from their seasonal loads in a watershed
文章编号: N18072701
期刊: Environmental Science and Pollution Research
作者: Ying Ouyang, Johnny M. Grace, Wayne C. Zipperer, Jeff Hatten, Janet Dewey
更新时间: 2018-07-27
摘要: Loads of naturally occurring total organic carbons (TOC), refractory organic carbon (ROC), and labile organic carbon (LOC) in streams control the availability of nutrients and the solubility and toxicity of contaminants and affect biological activities through absorption of light and complex metals with production of carcinogenic compounds. Although computer models have become increasingly popular in understanding and management of TOC, ROC, and LOC loads in streams, the usefulness of these models hinges on the availability of daily data for model calibration and validation. Unfortunately, these daily data are usually insufficient and/or unavailable for most watersheds due to a variety of reasons, such as budget and time constraints. A simple approach was developed here to calculate daily loads of TOC, ROC, and LOC in streams based on their seasonal loads. We concluded that the predictions from our approach adequately match field measurements based on statistical comparisons between model calculations and field measurements. Our approach demonstrates that an increase in stream discharge results in increased stream TOC, ROC, and LOC concentrations and loads, although high peak discharge did not necessarily result in high peaks of TOC, ROC, and LOC concentrations and loads. The approach developed herein is a useful tool to convert seasonal loads of TOC, ROC, and LOC into daily loads in the absence of measured daily load data.

26003. 题目: Divergence of soil microarthropod (Hexapoda: Collembola) recovery patterns during natural regeneration and regeneration by planting of windthrown pine forests
文章编号: N18072614
期刊: Forest Ecology and Management
作者: Maria Sterzyńska, Jarosław Skłodowski
更新时间: 2018-07-26
摘要: Windthrows are natural disturbances that influence the functioning and structure of forest ecosystems and the belowground components of an ecosystem. Soil processes such as the recycling of organic matter, energy and nutrients are controlled by soil fauna. However, little is still known about the post-disturbance recovery of soil microarthropod communities in forest stands exposed to windthrow of various severity and post-windthrow forest management over time. This study assessed soil Collembola community recovery in pine forest stands over the long-term (between 9 and 14 years after the disturbance event). We predicted that (1) different severity of windthrow disturbance in a pine forest has different effects on the recovery of Collembola community composition and functional structure, even after 10 years; (2) The recovery of Collembola communities is similar during regeneration of a forest disturbed by windthrow and in a pine plantation planted after clearing of a windthrown forest and subsequent soil preparation; (3) The changes in the Collembola community during forest regeneration after windthrow disturbance can be explained by selected environmental variables, especially the leaf area index LAI. As expected, regeneration processes within forest stands shifted the species composition of collembolan communities and changed their functional structure. The surface dwelling collembolan species (epigeic and atmobiotic life form) responded to regeneration processes mainly in pine stands, especially in a pine plantation established after a clearing of broken pines and subsequent soil preparation. Our results suggest different sensitivity of collembolan communities to environmental changes induced by various degrees of opening of the tree canopy by windthrow and to those caused by the post disturbance treatment. These findings confirm that collembolan community composition recovery is slow and divergent during natural regeneration of pine stands and regeneration by planting but does not differ between moderately and severely successional trajectories. Our results also confirm the importance of canopy closure for the possibility of Collembola community regeneration. If canopies were more closed (higher leaf area index, LAI index), the possibility of regeneration increased, especially in the young pine plantations, as seen in the final years of our study.
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26004. 题目: Glomalin changes in urban-rural gradients and their possible associations with forest characteristics and soil properties in Harbin City, Northeastern China
文章编号: N18072613
期刊: Journal of Environmental Management
作者: Wenjie Wang, Qiong Wang, Wei Zhou, Lu Xiao, Huimei Wang, Xingyuan He
更新时间: 2018-07-26
摘要: Glomalin-related soil protein (GRSP) is a glycoprotein from the hyphae and spores of arbuscular mycorrhizal fungi. Despite urbanization being the leading cause of present-day land-use changes, there is limited information available on the effects of urbanization on GRSP. We sampled soil from 257 plots in Harbin City, China, and surveyed forest characteristics, soil properties, and urbanization gradients related to ring road development, urban history, and land use. Two glomalin components (easily extracted glomalin, EEG; and total glomalin, TG) and their relative contributions to soil organic carbon (SOC: EEG/SOC, TG/SOC) were measured in the laboratory. We found exponential increases in EEG/SOC and TG/SOC from the most urbanized to the most rural regions, indicating that urbanization sharply reduced glomalin-related SOC sequestration. In general, 1.3–1.4-fold higher glomalin levels were found in the newly urbanized, previously rural areas, while glomalin contribution to SOC sequestration was lower by 38–59% for EEG and 74–85% for TG in the most urbanized regions compared to rural regions. Accompanying these recorded changes in glomalin, linear decreases in soil pH and electrical conductance were observed in all three urban-rural gradients from the urban center to the rural area, and steep decreases in conifer ratio and shrub richness were seen in two of the gradients. The complex associations among glomalin and forest characteristics, soil properties, and urbanization gradients were decoupled and cross-checked using redundancy analysis variation partitioning and structural equation model analysis. Urbanization indirectly changed glomalin features by altering soil properties, with soil properties accounting for over 60% of the glomalin variation. Forest characteristics and urbanization gradients contributed to 10–15% of the glomalin variation. With rapid urbanization occurring in China and on a global scale, glomalin variation should be considered when evaluating soil carbon sequestration and in developing effective forest management strategies, with the aim of ameliorating soil degradation in urbanized regions by rehabilitating glomalin accumulation.

26005. 题目: Microbial and plant-derived compounds both contribute to persistent soil organic carbon in temperate soils
文章编号: N18072612
期刊: Biogeochemistry
作者: Pierre Barré, Katell Quénéa, Alix Vidal, Lauric Cécillon, Bent T. Christensen, Thomas Kätterer, Andy Macdonald, Léo Petit, Alain F. Plante, Folkert van Oort, Claire Chenu
更新时间: 2018-07-26
摘要: Our study tests the emerging paradigm that biochemical recalcitrance does not affect substantially long-term (50 years) SOC persistence. We analyzed the molecular composition of SOC in archived soils originating from four European long-term bare fallow experiments (Askov, Rothamsted, Versailles and Ultuna). The soils had been collected after various periods (up to 53 years) under bare fallow. With increasing duration of bare fallow without new organic inputs, the relative abundance of cutin- and suberin-derived compounds declined substantially, and the abundance of lignin-derived compounds was close to zero. Conversely, the relative abundance of plant-derived long-chain alkanes remained almost constant or increased during the bare fallow period. The relative abundance of N-containing compounds, considered to be abundant in SOC derived from microbial activity, increased consistently illustrating that microbial turnover of SOC continues even when plant inputs are stopped. The persistence of the different families of plant-derived compounds differed markedly over the scale of half a century, which may be ascribed to their contrasting chemical characteristics and recalcitrance, or to differences in their interactions with the soil mineral matrix, and likely some combination since chemical composition drives the degree of mineral association. Using soil from this unique set of long-term bare fallow experiments, we provide direct evidence that multi-decadal scale persistent SOC is enriched in microbe-derived compounds but also includes a substantial fraction of plant-derived compounds.

26006. 题目: A farm-scale investigation of the organic matter composition and soil chemistry of Andisols as influenced by land use and management
文章编号: N18072611
期刊: Biogeochemistry
作者: Ritha Kov, Marta Camps-Arbestain, Roberto Calvelo Pereira, Manuel Suárez-Abelenda, Qinhua Shen, Stanislav Garbuz, Felipe Macías Vázquez
更新时间: 2018-07-26
摘要: Andisols are characterised by having abundant reactive Al in the form of short-range ordered (SRO) Al constituents and organo-Al complexes, which facilitates the accumulation of soil organic matter (OM). However, recent studies of New Zealand pastoral systems have reported loss of carbon (C) from Andisols when under intense management. This study compares the organic and inorganic chemistry of Andisols on two adjacent pasture sites under different pastoral management regimes (Paddock 2 being more intensively managed than Paddock 1), as well as under a nearby pine stand (Forest). Mean soil pH-H₂O in Forest (5.3) was significantly lower (P < 0.05) than that in Paddock 1 (5.7), which itself was significantly lower (P < 0.05) than in Paddock 2 (6.1). Soil C concentrations were significantly higher (P < 0.05) in the soils under pasture than under pine (63.8 g C/kg), and C in Paddock 1 (98.1 g C/kg) was significantly higher (P < 0.05) than in Paddock 2 (84.1 g C/kg). The ratio of Al in organo-Al complexes (as estimated with sodium pyrophosphate) to the sum of Al in both SRO and organo-Al complexes (Al_p/Al_o) was significantly smaller (P < 0.05) as the alkalinity of the soils increased (0.38, 0.23, 0.16 for Forest, Paddock 1 and Paddock 2, respectively). At the molecular level, soils under Forest had a larger relative contribution of degraded products of plant polysaccharides than those under pasture, while these had a larger contribution of fresh (e.g. cellulose and cutan/suberan aliphatic structures) and N-rich OM (e.g., microbial fingerprints, denoting a high microbial activity). Dissolved organic C content in the rhizosphere of pasture species was similar between paddocks, but Paddock 2 had a significantly (P < 0.05) greater contribution of organic acids of MW < 500 Da and higher pH (6.8 vs. 6.2). The results (1) confirm the common enrichment in organic C of New Zealand top soils under pasture compared to those under pine, and (2) reveal that the changes in the soil chemistry associated with pasture management may weaken the ability of these soils to preserve OM.

26007. 题目: A hard, high-carbon, lignomor with conchoidal fracture: Cunnite, from mature myrtle beech (Nothofagus cunninghamii (Hook. f.) Oerst.)
文章编号: N18072610
期刊: Geoderma
作者: Christopher Dean, Ernst Horn
更新时间: 2018-07-26
摘要: Introduced here is a newly discovered, hard, high‑carbon, macroscopically homogenous, solid lignomor that is part of the natural decomposition product of mature, rainforest hardwood trees of the species myrtle beech (Nothofagus cunninghamii (Hook. f.) Øerst.). The substance, named cunnite, exhibits conchoidal fracture (indicating isotropic bonding), whereas all other tree decomposition products noted were readily friable, with no evidence of strong bonding. It is a dehydrated form of lignomor and its pre-dehydrated form also has conchoidal fracture. Cunnite was examined by carbon assay, radiocarbon dating, scanning electron microscopy (SEM) and Fourier transform infra-red spectroscopy (FT-IR). All wood cell walls had decomposed but the FT-IR results suggested that cunnite is high in lignin, and therefore it is most likely formed by a brown-rot fungi. Cunnite appears to be unique in that it is a product of natural decomposition but has relatively strong bonding. This bonding may be either from re-polymerisation or hydrogen bonding. If original polymer segments remain then they are most likely often cross-linked. Although cunnite appears to be stable beyond the decomposition of the entire tree, the age determined from radiocarbon dating for our samples does not imply that it is particularly long-lived thereafter. Cunnite is part of the forest carbon cycle but forms only a small fraction of the soil organic carbon pool. If the composition of cunnite is determined accurately in future work, and a synthetic version made, then it may be useful on a commercial scale as an adsorbent of hydrogen (i.e. storage for renewable energy) or of toxic substances; or it may provide other products useful in materials science or chemical engineering.
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26008. 题目: The importance of bioconcentration into the pelagic food web base for methylmercury biomagnification: A meta-analysis
文章编号: N18072609
期刊: Science of The Total Environment
作者: Pianpian Wu, Martin J. Kainz, Andrea G. Bravo, Staffan Åkerblom, Lars Sonesten, Kevin Bishop
更新时间: 2018-07-26
摘要: Methylmercury (MeHg) transfer from water into the base of the food web (bioconcentration) and subsequent biomagnification in the aquatic food web leads to most of the MeHg in fish. But how important is bioconcentration compared to biomagnification in predicting MeHg in fish To answer this question we reviewed articles in which MeHg concentrations in water, plankton (seston and/or zooplankton), as well as fish (planktivorous and small omnivorous fish) were reported. This yielded 32 journal articles with data from 59 aquatic ecosystems at 22 sites around the world. Although there are many case studies of particular aquatic habitats and specific geographic areas that have examined MeHg bioconcentration and biomagnification, we performed a meta-analysis of such studies. Aqueous MeHg was not a significant predictor of MeHg in fish, but MeHg in seston i.e., the base of the aquatic food web, predicted 63% of the variability in fish MeHg. The MeHg bioconcentration factors (i.e., transfer of MeHg from water to seston; BCF_w-s) varied from 3 to 7 orders of magnitude across sites and correlated significantly with MeHg in fish. The MeHg biomagnification factors from zooplankton to fish varied much less (logBMF_z-f, 0.75 ± 0.31), and did not significantly correlate with fish MeHg, suggesting that zooplanktivory is not as important as bioconcentration in the biomagnification of fish MeHg across the range of ecosystems represented in our meta-analysis. Partial least square (PLS) and linear regression analyses identified several environmental factors associated with increased BCF, including low dissolved organic carbon, low pH, and oligotrophy. Our study reveals the widespread importance of MeHg bioconcentration into the base of the aquatic food web for MeHg at higher trophic levels in aquatic food webs, as well as the major influences on the variability in this bioconcentration.
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26009. 题目: Sorption reduces the biodegradation rates of multivalent organic acids in volcanic soils rich in short-range order minerals
文章编号: N18072608
期刊: Geoderma
作者: Kazumichi Fujii, Chie Hayakawa, Yoshiyuki Inagaki, Kenji Ono
更新时间: 2018-07-26
摘要: Sorption can limit biodegradation of low-molecular-weight organic acids (LMWOAs), while this validity needs to be accessed in volcanic soils rich in short range order (SRO) Al/Fe minerals and organic matter. We tested whether both sorption and microbial mineralization of LMWOAs are controlled by the amounts of SRO minerals and organo-Al/Fe complex in volcanic soils. We analyzed the soil solution concentrations, sorption isotherms, and mineralization kinetics of ¹⁴C-radiolabeled acetate, oxalate, malate, citrate, and glucose. The sorption of LMWOAs increased with increasing amount of SRO minerals and organo-Al/Fe complex, irrespective of indigenously adsorbed organic matter levels. Mineralization of multivalent LMWOAs (oxalate, malate, and citrate) displays a contrary pattern to sorption and decreased with increasing amount of SRO minerals and organo-Al/Fe complex. Sorption consistently reduces microbial mineralization rates through removal of LMWOAs from soil solution, but it can also suppress microbial activity of multivalent LMWOA mineralization. Both sorption and microbial mineralization of multivalent LMWOAs are more strongly controlled by the amounts of SRO minerals and organo-Al/Fe complex than acetate. Sorption-induced retardation of multivalent LMWOA mineralization contributes to preservation of organic matter in volcanic soils.

26010. 题目: Investigation of the treatability of molasses and industrial oily wastewater mixture by an anaerobic membrane hybrid system
文章编号: N18072607
期刊: Journal of Environmental Management
作者: Meltem Sarioglu Cebeci, Öznur Begüm Gökçek
更新时间: 2018-07-26
摘要: In this study, the anaerobic treatability of automotive industry wastewater and its treatment in the subsequent membrane system were examined by using molasses, which is a waste of the sugar industry, as a co-substrate. Organic loadings of 3-3, 5-4, and 5gCOD/L/day were applied to a UASB reactor made of steel with a working volume of 7 L. The hydraulic retention time (HRT) was kept constant at 2 days. Temperature, pH, COD, alkalinity, Volatile Fatty acid (VFA) and biogas were monitored. The best COD removal was achieved at the value of 4 gCOD/L/day. The average COD removal rate was 77%. The effluent from the UASB reactor was transferred to the membrane system. The flux reductions of the PW10 kDa UF membrane at different concentrations were 1.717 gCOD/L, 1.934 gCOD/L, 2.257 gCOD/L, 4 gCOD/L, and 8 gCOD/L, and they were 90.78%, 42.69%, 45.88%, 51.00%, and 56.60%, respectively, at the input concentrations. The flux reductions of the UE50 100 kDa UF membrane at the input concentrations of 4 gCOD/L and 8 gCOD/L were 76.00% and 66.25%, respectively. It was determined that the UE50 100 kDa membrane caused more fouling compared to the PW 10 kDa UF membrane. Pore fouling models were determined for the flux reduction in the membranes and the mechanism behind it. Heavy metal and organic matter removals were examined in the effluent obtained from the membrane experiments.

26011. 题目: Lipid biomarkers in suspended particulate matter and surface sediments in the Pearl River Estuary, a subtropical estuary in southern China
文章编号: N18072606
期刊: Science of The Total Environment
作者: Wei Guo, Guodong Jia, Feng Ye, Huayun Xiao, Zhongyi Zhang
更新时间: 2018-07-26
摘要: Lipid biomarkers in sediments in the Pearl River Estuary (PRE) have been studied in several previous studies, but little is known about their occurrence in the overlying water. Here, we determined the concentrations of lipids (n-alkanes, n-alkanols, sterols and fatty acids) in suspended particulate matter (SPM) in surface water and in sediments from the PRE. The data will improve our understanding of the sources, transport and sedimentation of lipids in estuarine environments. Our results showed that short-chain (C_14–20) n-alkyl lipids contributed more than long-chain (C_21–34) n-alkyl lipids to the total lipid concentrations in both SPM and sediments, suggesting aquatic plants and bacteria were the main contributors, whereas terrestrial organic matter (OM) were the minor contributors of n-alkyl lipids. It suggested that phytoplankton and bacteria contributing >65% to the n-alkyl lipids of SPM based on the three end-member mixing models. The concentrations of most lipids, except n-alkanes, decreased quickly in the low-salinity mixing zone and slowly decreased thereafter, with a transient slight increased when the salinity was 20–25, which would have been caused by variations of primary production in the aquatic system. In May, when rainfall was highest, lipids were characterized by a substantial contribution of terrestrial n-alkanes in the upstream SPM. Microbial activity and lipid degradation were found to occur in the water, and were most intense in the low–salinity mixing zone. Terrigenous lipids contributed more to the total lipid concentrations in sediments than in SPM, which demonstrated that terrigenous OM is relatively recalcitrant, and aquatic phytoplankton-derived OM is labile.
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26012. 题目: Contamination of polybrominated diphenyl ethers (PBDEs) in urban mangroves of Southern China
文章编号: N18072605
期刊: Science of The Total Environment
作者: Minwei Chai, Ruili Li, Cong Shi, Xiaoxue Shen, Rongyu Li, Qijie Zan
更新时间: 2018-07-26
摘要: Mangroves are threatened due to urban development and human activities in coastal regions. Four urban mangroves in Shenzhen (rapidly developing city of China) were selected according to urban functional zoning, namely, Shajing mangrove (SJM) and Xixiang mangrove (XXM) featured with industry district, Futian mangrove (FTM) and Baguang mangrove (BGM) featured with central business district and ecological preserve. Eight BDE congeners (BDE-28, -47, -99, -100, -153, -154, -183, and -209) in mangrove sediments and leaves were determined. The highest level of BDE-209 in SJM was proximate to areas of point-source discharges of Dongbao River in Pearl River Estuary, China. Total organic carbon (TOC) was influential in BDE-209 accumulations in SJM, XXM, and FTM. Multiple variate analysis implied that PBDEs in SJM, XXM and FTM mainly composed of penta-, octa-, and deca-BDEs, with surface runoff to be the main contamination sources; while BGM was contaminated by penta- and octa-BDEs. Ecological risk of BDE-209 was high in SJM, with medium/negligible risk in the other urban mangroves. The transfers of BDE-209 from sediment to leaf were weak (BGM and FTM), improved (XXM), and restricted (SJM), respectively. This is the first reports of spatial distribution and bioaccumulation of PBDEs in urban mangroves featured with different urban functional zonings. More attention is required to reduce emission of PBDEs into the environment and manage PBDEs contamination in urban mangroves.
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26013. 题目: Variations in cropland soil organic carbon fractions in the black soil region of China
文章编号: N18072604
期刊: Soil and Tillage Research
作者: Xiyang Wang, Dongsheng Yu, Chong Wang, Yue Pan, Jianjun Pan, Xuezheng Shi
更新时间: 2018-07-26
摘要: The use of three discrete soil organic carbon (SOC) pools proposed by the CENTURY model to study the SOC dynamics helps to understand the changes in cropland SOC pool and its stability. This study focuses on a typical black soil (mollisol) region in Northeast China. Based on historical soil data from samples that were collected in the 1980s, we selected 44 sampling points and collected 88 soil samples from the surface (0–20 cm) and subsurface (20–40 cm) layers in 2010. A 100-day laboratory incubation for each sample was conducted to measure the decomposition rates of SOC at different times, and data from the incubation experiment were fitted to a three-pool first-order model that divided the total SOC into active (C_a), slow (C_s) and resistant (C_r) SOC fractions. A method for predicting the concentrations of the three SOC fractions was developed and used to obtain the concentrations of SOC fractions in the 1980s at each sampling point. The results showed that a power function model (D_soct = a × t^b) could be used as the universal SOC decomposition curve model. Using the universal model, the predictive method accurately estimated the concentrations of C_a, C_s and C_r of upland soils in this black soil region, which effectively solved the problem of a lack of soil samples and SOC fractions data in previous studies of the spatial-temporal variations of SOC fractions in regional soils. From 1980 to 2010, the estimated variations of the C_a, C_s and C_r in the surface upland soil were +0.37, −5.53 and −6.32 g kg⁻¹, and the corresponding contributions to the loss of the total SOC were -3.2%, +48.2% and +55.1%, respectively, while the variations of the C_a, C_s and C_r in the subsurface soil were +0.19, −0.43 and −2.45 g kg⁻¹, and the corresponding contributions to the loss of the total SOC were −7.1%, +16.0% and +91.1%, respectively. The decrease in the total SOC is primarily attributed to the decrease of the C_s and C_r fractions in the region, although the C_a fraction has significantly increased. The overall variations in the SOC fractions suggest a declining stability of the SOC pool in the black soil region of Northeast China.

26014. 题目: Enhanced removal of Cr(VI) by biochar with Fe as electron shuttles
文章编号: N18072603
期刊: Journal of Environmental Sciences
作者: Jingwen Xu, Yongguang Yin, Zhiqiang Tan, Bowen Wang, Xiaoru Guo, Xia Li, Jingfu Liu
更新时间: 2018-07-26
摘要: Biochar is extensively used as an effective soil amendment for environmental remediation. In addition to its strong contaminant sorption capability, biochar also plays an important role in chemical transformation of contaminant due to its inherent redox-active moieties. However, the transformation efficiency of inorganic contaminants is generally very limited when the direct adsorption of contaminants on biochar is inefficient. The present study demonstrates the role of Fe ion as an electron shuttle to enhance Cr(VI) reduction by biochars. Batch experiments were conducted to examine the effects of Fe(III) levels, pyrolysis temperature of biochar, initial solution pH, and biochar dosage on the efficiency of Cr(VI) removal. Results showed a significant enhancement in Cr(VI) reduction with an increase in Fe(III) concentration and a decrease of initial pH. Biochar produced at higher pyrolysis temperatures (e.g., 700°C) favored Cr(VI) removal, especially in the presence of Fe(III), while a higher biochar dosage proved unfavorable likely due to the agglomeration or precipitation of biochar. Speciation analysis of Fe and Cr elements on the surface of biochar and in the solution further confirmed the role of Fe ion as an electron shuttle between biochar and Cr(VI). The present findings provide a potential strategy for the advanced treatment of Cr(VI) at low concentrations as well as an insight into the environmental fate of Cr(VI) and other micro-pollutants in soil or aqueous compartments containing Fe and natural or engineered carbonaceous materials.
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26015. 题目: Active iron bound to SOM catalyzes H2O2 to oxidize alkanes in soil
文章编号: N18072602
期刊: Environmental Science: Processes Impacts
作者: Jinlan Xu, Qianqian Cao, Miaojia Zhang, Chengwei Yang
更新时间: 2018-07-26
摘要: To explore the oxidation effects and mechanisms for the oxidation of alkanes in the Fenton system by two types of iron bound to soil organic matter (Fe-SOM) catalyzing H2O2 in crude oil contaminated soil, the oxidation experiment was performed in active Fe-SOM and Fe-SOM systems. The results showed that the TPH removal ability of active Fe-SOM (average 0.36 g TPH/g Fe-SOM) was 2.25-fold of the corresponding value of Fe-SOM. Active Fe-SOM contained both -NH2 and -OH functional group, and had higher content of iron with high binding energy, while Fe-SOM only contained -NH2 group. Thus, the large yield of hydroxyl radicals (·OH) was generated (8.92 a.u.) by active Fe-SOM catalyzing H2O2, while the corresponding yield of ·OH in Fe-SOM system was only 4.81 a.u. In addition, the removal efficiency of C17-C23 (70%) were comparable to C24-C30 (69%), not restricted by the hydrophobicity of different alkanes. The alkanes removal in active Fe-SOM was higher than that in Fe-SOM although the content of Fe-SOM was double of active Fe-SOM. In summary, the active Fe-SOM formed by the soil sample containing humic acid-like and hydrophobic acids derivate could catalyze H2O2 to improve the removal efficiency of crude oil in contaminated soil.

26016. 题目: Soil organic carbon depletion and degradation in surface soil after long-term non-growing season warming in High Arctic Svalbard
文章编号: N18072601
期刊: Science of The Total Environment
作者: Philipp R. Semenchuk, Eveline J. Krab, Mattias Hedenström, Carly A. Phillips, Francisco J. Ancin-Murguzur, Elisabeth J. Cooper
更新时间: 2018-07-26
摘要: Arctic tundra active-layer soils are at risk of soil organic carbon (SOC) depletion and degradation upon global climate warming because they are in a stage of relatively early decomposition. Non-growing season (NGS) warming is particularly pronounced, and observed increases of CO₂ emissions during experimentally warmed NGSs give concern for great SOC losses to the atmosphere. Here, we used snow fences in Arctic Spitsbergen dwarf shrub tundra to simulate 1.86 °C NGS warming for 9 consecutive years, while growing season temperatures remained unchanged. In the snow fence treatment, the 4-11 cm thick A-horizon had a 2% lower SOC concentration and a 0.48 kg C m⁻² smaller pool size than the controls, indicating SOC pool depletion. The snow fence treatment's A-horizon's alkyl/O-alkyl ratio was also significantly increased, indicating an advance of SOC degradation. The underlying 5 cm of B/C-horizon did not show these effects. Our results support the hypothesis that SOC depletion and degradation are connected to the long-term transience of observed ecosystem respiration (ER) increases upon soil warming. We suggest that the bulk of warming induced ER increases may originate from surface and not deep active layer or permafrost horizons. The observed losses of SOC might be significant for the ecosystem in question, but are in magnitude comparatively small relative to anthropogenic greenhouse gas enrichment of the atmosphere. We conclude that a positive feedback of carbon losses from surface soils of Arctic dwarf shrub tundra to anthropogenic forcing will be minor, but not negligible.
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26017. 题目: Order from disorder: do soil organic matter composition and turnover co-vary with iron phase crystallinity?
文章编号: N18072507
期刊: Biogeochemistry
作者: Steven J. Hall, Asmeret A. Berhe, Aaron Thompson
更新时间: 2018-07-25
摘要: Soil organic matter (SOM) often increases with the abundance of short-range-ordered iron (SRO Fe) mineral phases at local to global scales, implying a protective role for SRO Fe. However, less is known about how Fe phase composition and crystal order relate to SOM composition and turnover, which could be linked to redox alteration of Fe phases. We tested the hypothesis that the composition and turnover of mineral-associated SOM co-varied with Fe phase crystallinity and abundance across a well-characterized catena in the Luquillo Experimental Forest, Puerto Rico, using dense fractions from 30 A and B horizon soil samples. The δ¹³C and δ¹⁵N values of dense fractions were strongly and positively correlated (R² = 0.75), indicating microbial transformation of plant residues with lower δ¹³C and δ¹⁵N values. However, comparisons of dense fraction isotope ratios with roots and particulate matter suggested a greater contribution of plant versus microbial biomass to dense fraction SOM in valleys than ridges. Similarly, diffuse reflectance infrared Fourier transform spectroscopy indicated that SOM functional groups varied significantly along the catena. These trends in dense fraction SOM composition, as well as ¹⁴C values indicative of turnover rates, were significantly related to Fe phase crystallinity and abundance quantified with selective extractions. M ssbauer spectroscopy conducted on independent bulk soil samples indicated that nanoscale ordered Fe oxyhydroxide phases (nano-goethite, ferrihydrite, and/or very-SRO Fe with high substitutions) dominated (66–94%) total Fe at all positions and depths, with minor additional contributions from hematite, silicate and adsorbed Fe^II, and ilmenite. An additional phase that could represent organic-Fe^III complexes or aluminosilicate-bearing Fe^III was most abundant in valley soils (17–26% of total Fe). Overall, dense fraction samples with increasingly disordered Fe phases were significantly associated with increasingly plant-derived and faster-cycling SOM, while samples with relatively more-crystalline Fe phases tended towards slower-cycling SOM with a greater microbial component. Our data suggest that counter to prevailing thought, increased SRO Fe phase abundance in dynamic redox environments could facilitate transient accumulation of litter derivatives while not necessarily promoting long-term C stabilization.

26018. 题目: ZrO₂ nanoparticles confined in metal organic frameworks for highly effective adsorption of phosphate
文章编号: N18072506
期刊: Chemosphere
作者: Tao Liu, Jiankang Feng, Yuqiu Wan, Shourong Zheng, Liuyan Yang
更新时间: 2018-07-25
摘要: Highly dispersed ZrO₂ particles confined in the MIL-101 (denoted as MIL-101@Zr(DS)) with varied ZrO₂ loading amounts were prepared by the double solvents method. For comparison, ZrO₂ loaded MIL-101 samples were synthesized by the conventional impregnation method (denoted as MIL-101@Zr(I)) and the deposition method (denoted as MIL-101@Zr(D)). The characterization results indicated that for MIL-101@Zr(DS), ZrO₂ particles were dominantly confined in MIL-101 with a much higher dispersion as compared with MIL-101@Zr(I) and MIL-101@Zr(D). The maximum phosphate adsorption capacity and ZrO₂ content normalized phosphate adsorption capacity of the MIL-101@Zr(DS) were 21.28 mg P·g^-1 and 1120.0 mg P·g^-1, respectively. Additionally, the ZrO₂ content normalized phosphate adsorption capacity was significantly larger than that for MIL-101@Zr(I) and MIL-101@Zr(D) as well as the reported values for other Zr-based adsorbents. The effects of solution chemistry on phosphate adsorption to MIL-101@Zr(DS), MIL-101@Zr(I) and MIL-101@Zr(D) were also examined. Compared with MIL-101@Zr(I) and MIL-101@Zr(D), the adsorption of phosphate on MIL-101@Zr(DS) was less affected by the coexistence of anions and dissolved humic acid. Increasing pH from 3 to 12 led to decreased phosphate adsorption capacity of MIL-101@Zr(DS) from 10.38 mg P·g^-1 to 2.03 mg P·g^-1. Accordingly, used MIL-101@Zr(DS) could be effectively regenerated under alkaline conditions and exhibited stable adsorption-desorption performance.
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26019. 题目: Pre-purification by membrane filtration of paralytic shellfish toxins from Alexandrium minutum dinoflagellate
文章编号: N18072505
期刊: Separation and Purification Technology
作者: Rafik Balti, Nicolas Brodu, Jiaxuan Zhang, Zouher Amzil, Delphine Drouin, Véronique Séchet, Anthony Massé
更新时间: 2018-07-25
摘要: The Paralytic shellfish neurotoxins (PST) are of increasing interest for biomedical applications. The chemical synthesis is often complex and expensive that’s why the purification by membrane filtration of PST from Alexandrium minutum dinoflagellate was investigated. Disrupted micro-alga cells by ultrasonic treatment were diafiltred to let pass toxins through an ultrafiltration membrane. Then, the mean permeate was concentrated and diafiltrated by nanofiltration. Mean permeate fluxes equal to 187, 135 and 135 L.h^–1.m^-2 were obtained during the first diafiltration, the concentration step and the final diafiltration respectively. Up to 57 % (mol/mol) and 78 % (mol/mol) of organic matters and salts were removed respectively. Divalent ions were sparsely removed contrary to monovalent ones. C1 and C2 toxins were successfully purified since more than 75 % (mol/mol) were recovered. However, only 27 to 50 % (mol/mol) of GTX2, GTX3 and STX were recovered.

26020. 题目: Long-chain n-alkane and n-fatty acid characteristics in plants and soil - potential to separate plant growth forms, primary and secondary grasslands?
文章编号: N18072504
期刊: Science of The Total Environment
作者: Xiaoqing Li, Barbara J. Anderson, Iris Vogeler, Luitgard Schwendenmann
更新时间: 2018-07-25
摘要: Plant-derived lipid molecular proxies can provide insight into present-day soil carbon input and to what extent organic carbon is degraded within soil. To explore whether soil characteristics of ‘primary’ (i.e., native grasslands above the historic treeline) and ‘secondary’ (i.e., human-modified grasslands below the historic treeline) grasslands reflect recent and/or past vegetation input we compared lipid characteristics in modern vegetation and soil from 30 locations around the historic treeline (1150 m) in Central Otago, New Zealand. At each location the dominant plant species and the mineral topsoil (0–10 cm) were analyzed for a range of n-alkane and n-fatty acid proxies. Grass/herbs and trees differed in their total n-alkane concentration (88.9 vs 232.6 μg/g plant dry weight), even-over-odd predominance (EOP, 10.2 vs 18.3) and n-C₂₀/n-C₂₄ ratio (2.2 vs 6.4). Soil samples under all plant growth forms had considerably lower n-alkane and n-fatty concentrations than the corresponding plant samples. Soil under grass/herbs had lower (4.1) odd-over-even predominance (OEP) values compared to soil under trees (10.1) indicating that lipid degradation under grass/herbs cover was higher. Principle component analysis demonstrated that soil lipid characteristics reflected the current vegetation cover. Principal component analysis also revealed a separation between ‘primary’ and ‘secondary’ grasslands. However, further evaluations are required to confirm the validity of lipid proxies in reconstructing the vegetation history of secondary grasslands.
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