8261. 题目: Systematic optimization approach for the efficient management of the photo-Fenton treatment process
期刊: Science of The Total Environment
作者: Francesca Audino, Gerard Campanyà, Montserrat Pérez-Moya, Antonio Espuña, Moisès Graells
摘要: The photo-Fenton process is a photochemical process that has proved to be highly efficient in degrading new potentially harmful contaminants. Despite of this, scarce attention has been paid to the development of systematic procedures and optimisation strategies to efficiently operate such a process. The present work aims at investigating the effectiveness of a model-based approach in carrying out the dynamic optimisation of the recipe of a photo-Fenton process, performed in fed-batch mode (reactant dosage).
8262. 题目: Identification of sources and transformations of nitrate in the Xijiang River using nitrate isotopes and Bayesian model
期刊: Science of The Total Environment
作者: Cai Li, Si-Liang Li, Fu-Jun Yue, Jing Liu, Jun Zhong, Zhi-Feng Yan, Ruo-Chun Zhang, Zhong-Jun Wang, Sen Xu
摘要: Coupled nitrogen and oxygen isotopes of nitrate have proven useful in identifying nitrate sources and transformation in rivers. However, isotopic fractionation and low-resolution monitoring limit the accurate estimation of nitrate dynamics. In the present study, the spatio-temporal variations of nitrate isotopes (15N and 18O) and hydrochemical compositions (NO3− and Cl−) of river water were examined to understand nitrate sources in the Xijiang River, China. High-frequency sampling campaigns and isotopic analysis were performed at the mouth of the Xijiang River to capture temporal nitrate variabilities. The overall values of δ15N-NO3− and δ18O-NO3− ranged from +4.4‰ to +14.1‰ and from −0.3‰ to +6.8‰, respectively. The results of nitrate isotopes indicated that NO3− mainly originated from soil organic nitrogen (SON), chemical fertilizer (CF), and manure and sewage wastes (M&S). The negative correlation of nitrate isotopic values with NO3−/Cl− ratios suggested the importance of denitrification in NO3− loss. The results of Bayesian model with incorporation of isotopic fractionation during the denitrification showed that SON and CF contributed to the most (72–73%) nitrate in the wet season; whereas approximately 58% of nitrate was derived from anthropogenic inputs (M&S and CF) in the dry season. The nitrate flux was 2.08 × 105 tons N yr−1 during one hydrologic year between 2013 and 2014, with 86% occurring in the wet season. Long-term fluctuations in nitrate flux indicated that nitrate export increased significantly over the past 35 years, and was significantly correlated with nitrate concentrations. The seasonal pattern of nitrate dynamics indicated the mixing of nitrified NO3− and denitrified NO3− between surface flow and groundwater flow under different hydrological conditions. Overall, the present study quantitatively evaluates the spatio-temporal variations in nitrate sources in a subtropical watershed, and the high-frequency monitoring gives a better estimate of nitrate exports and proportional contributions of nitrate sources.
8263. 题目: Carbon emissions induced by land-use and land-cover change from 1970 to 2010 in Zhejiang, China
期刊: Science of The Total Environment
作者: Enyan Zhu, Jingsong Deng, Mengmeng Zhou, Muye Gan, Ruowei Jiang, Ke Wang, AmirReza Shahtahmassebi
摘要: Land-use and land-cover change (LUCC) is a crucial factor affecting carbon emissions. Zhejiang Province has witnessed unprecedented LUCC concomitant with rapid urbanization from 1970 to 2010. In this study, remote sensing, geographic information system (GIS) and the Intergovernmental Panel on Climate Change (IPCC) method were combined to quantify changes in both vegetation carbon storage and soil organic carbon (SOC) storage resulting from LUCC during 1970–1990 and 1990–2010. For both 1970–1990 and 1990–2010, the results showed successive decrease in farmlands (2.8 × 105 ha or −9.15% and 5.9 × 105 ha or −20.49%, respectively) and grasslands (3.4 × 104 ha or −10.73% and 1.5 × 105 ha or −54.1%, respectively), and continuous increase in forests (2.0 × 104 ha or 0.33% and 1.7 × 105 ha or 2.81%, respectively) and built-up lands (2.07 × 105 ha or 78.41% and 6.49 × 105 ha or 137.8%, respectively). From 1970 to 1990, approximately 8.3 Tg of the total carbon sink declined, including a 0.4 Tg reduction in vegetation carbon and a 7.9 Tg reduction in SOC. While from 1990 to 2010, approximately 17.5 Tg of carbon storage declined, comprising a 2.8 Tg of carbon accumulated by vegetation, and a 20.3 Tg reduction in SOC. Overall, LUCC has resulted in huge amount of carbon emissions in Zhejiang from 1970 to 2010. Efficient planning for LUCC and gradual mitigation of carbon emissions are indispensable for future urban development in China under increasing pressure from global warming.
8264. 题目: Estimation of unsaturated shear strength parameters using easily-available soil properties
期刊: Soil and Tillage Research
作者: Elham Amiri Khaboushan, Hojat Emami, Mohammad Reza Mosaddeghi, Ali Rrza Astaraei
摘要: Unsaturated soil shear strength is an important parameter in soil erosion and management. Measurement of unsaturated shear strength at field scale is difficult, time-consuming, and very costly. This study was conducted to investigate the relationship between unsaturated shear strength parameters and soil properties, and to predict the unsaturated shear strength parameters (effective cohesion, c', angle of effective internal friction, φ' and angle of internal friction related to matric suction, φb) using multiple-linear regression (MLR). Direct shear tests were performed at combinations of three normal stresses of 25, 50 and 100 kPa, and four matric suctions of 0, 10, 30 and 50 kPa (i.e., 12 tests per each soil) to determine the shear strength parameters in 14 soils. Soil properties including particle size distribution (sand, silt, and clay percentages or geometric mean diameter, dg and geometric standard deviation, σg), organic matter content (OM), calcium carbonate content (CaCO3), compactness indices (bulk density, ρb and, relative bulk density, ρb-rel), and mean weight diameter of aggregates (MWDdry, MWDwet), structural stability indices (aggregate stability, AS, stability index, SI and index of crusting, Ic) were determined and used as predictors in MLR models. Strong negative correlations were found between c' and φ'. The c' positively correlated with clay content. Significant negative correlation was observed between c' and sand fractions and dg. Significant positive correlation was obtained between φ' and fractions of sand and dg. The φ' negatively correlated with clay, fine silt content (FSi), MWDdry, and AS. The φb had no significant correlation with soil properties, indicating that φb is independent of soil properties and basically is affected by matric suction. Clay, coarse sand (CS) and very fine sand (VFS) were applied in the model for predicting c'. Clay had a positive and, CS and VFS had negative effects on c'. Pedotransfer functions (PTFs) using the fine sand (FS) and VFS as predictor could estimate the φ' accurately, so that they entered to PTFs with positive signs. In addition, the φb was predicted by parameter Ic only, so that it had negative effect on φb. Overall, better prediction models were developed for φ' than for c' and φb.
8265. 题目: Improving understanding of soil organic matter dynamics by triangulating theories, measurements, and models
作者: Joseph C. Blankinship, Asmeret Asefaw Berhe, Susan E. Crow, Jennifer L. Druhan, Katherine A. Heckman, Marco Keiluweit, Corey R. Lawrence, Erika Marín-Spiotta, Alain F. Plante, Craig Rasmussen, Christina Schädel, Joshua P. Schimel, Carlos A. Sierra, Aaron Thompson, Rota Wagai, William R. Wieder
摘要: Soil organic matter (SOM) turnover increasingly is conceptualized as a tension between accessibility to microorganisms and protection from decomposition via physical and chemical association with minerals in emerging soil biogeochemical theory. Yet, these components are missing from the original mathematical models of belowground carbon dynamics and remain underrepresented in more recent compartmental models that separate SOM into discrete pools with differing turnover times. Thus, a gap currently exists between the emergent understanding of SOM dynamics and our ability to improve terrestrial biogeochemical projections that rely on the existing models. In this opinion paper, we portray the SOM paradigm as a triangle composed of three nodes: conceptual theory, analytical measurement, and numerical models. In successful approaches, we contend that the nodes are connected—models capture the essential features of dominant theories while measurement tools generate data adequate to parameterize and evaluate the models—and balanced—models can inspire new theories via emergent behaviors, pushing empiricists to devise new measurements. Many exciting advances recently pushed the boundaries on one or more nodes. However, newly integrated triangles have yet to coalesce. We conclude that our ability to incorporate mechanisms of microbial decomposition and physicochemical protection into predictions of SOM change is limited by current disconnections and imbalances among theory, measurement, and modeling. Opportunities to reintegrate the three components of the SOM paradigm exist by carefully considering their linkages and feedbacks at specific scales of observation.
8266. 题目: Manure amendment reduced plant uptake and enhanced rhizodegradation of 2,2′,4, 4′-tetrabrominated diphenyl ether in soil
期刊: Biology and Fertility of Soils
作者: Leilei Xiang, Yang Song, Yongrong Bian, Guangxia Liu, Anna Herzberger, Chenggang Gu, Xin Jiang, Fang Wang
摘要: To test whether manure amendment in soil reduces plant uptake of persistent organic pollutants, carrot (Daucus carota L.) was used as a model plant and 2,2′,4,4′-tetrabrominated diphenyl ether (BDE-47) was selected as a model persistent organic pollutant to conduct a pot experiment with contaminated soil amended by composted pig manure. The results showed that the concentration and bioconcentration factors (BCFs) of BDE-47 in the edible part of carrot significantly decreased from 229.7 ± 28.2 to 43.4 ± 20.4 ng g−1 and from 1.86 ± 0.5 to 0.15 ± 0.03, respectively, with increasing composted pig manure dose from 0 to 4%. Organic matter (OM) derived from composted pig manure played a dominant role in reducing persistent organic pollutant bioavailability in soil. Composted pig manure amendment and carrot cultivation jointly altered the bacterial community composition in soil, especially the rhizosphere. Rhizodegradation of BDE-47 was enhanced from 8.6 to 28.5% with increasing composted pig manure dose from 0 to 4%, corresponding to increased soil microbe diversity and polybrominated diphenyl ether-degrading bacteria (Sphingomonas, etc.) abundance in the rhizosphere. This study is the first, to the best of our knowledge, to provide an effective agronomic strategy of manure amendment to reduce plant uptake and simultaneously enhance rhizodegradation of persistent organic pollutants in soil, and thus potentially reduce human health risks through dietary intake.
8267. 题目: Pretreatment of macroalgal Laminaria japonica by combined microwave-acid method for biohydrogen production
期刊: Bioresource Technology
作者: Yanan Yin, Jianlong Wang
摘要: Suitable pretreatment can effectively enhance the fermentative hydrogen production from algae biomass. In this study, combined microwave-acid pretreatment was applied to disintegrate the biomass of macroalgae L. japonica, and dark fermentation in batch mode was conducted for hydrogen production. The results showed that combining microwave pretreatment at 140°C and 2450 MHz with 1% H2SO4 for 15 min could effectively disrupt macroalgal cells and release the organic matters, and soluble chemical oxygen demand (SCOD) concentration increased by 1.92-fold and achieved 5.12 g/L. During the fermentation process, both polysaccharides and proteins were consumed. Hydrogen production process was dominated by acetate-type fermentation, and the dominance of genus Clostridium contributed to more efficient hydrogen production. After the pretreatment, hydrogen yield increased from 15 mL/g TSadded to 28 mL/g TSadded, and energy conversion efficiency increased from 9.5% to 23.8%. Combined microwave-acid pretreatment is potential in enhancing hydrogen production from the biomass of L. japonica.
8268. 题目: Performance and toxicity assessment of nanoscale zero valent iron particles in the remediation of contaminated soil: A review
作者: Wenjing Xue, Danlian Huang, Guangming Zeng, Jia Wan, Min Cheng, Chen Zhang, Chanjuan Hu, Jing Li
摘要: Nanoscale zero valent iron (nZVI) particles have been studied in recent years as a promising technology for the remediation of contaminated soil. Although the potential benefits of nZVI are considerable, there is a distinct need to identify possible risks after environmental exposure to nZVI. This work firstly introduced the remediation of nZVI for heavy metals and chlorinated organic compounds in contaminated soil. And the corresponding stabilization mechanisms were discussed. We also highlighted the factors affecting nZVI reactivity, including nZVI surface area, nZVI stabilizers, soil pH, soil organic matter and soil types. In addition, this review shows a critical overview of the current understanding of toxicity of nZVI particles to soil bacteria and fungi. The toxicity mechanisms, cellular defenses behaviors and the factors affecting the toxicity of nZVI were summarized. Finally, the remaining barriers to be overcome in materials development for environment application are also discussed.
8269. 题目: Tryptophan-like fluorescence as a measure of microbial contamination risk in groundwater
期刊: Science of The Total Environment
作者: Saskia Nowicki, Dan J. Lapworth, Jade S.T. Ward, Patrick Thomson, Katrina Charles
摘要: Microbial water quality is frequently assessed with a risk indicator approach that relies on Escherichia coli. Relying exclusively on E. coli is limiting, particularly in low-resource settings, and we argue that risk assessments could be improved by a complementary parameter, tryptophan-like fluorescence (TLF). Over two campaigns (June 2016 and March 2017) we sampled 37 water points in rural Kwale County, Kenya for TLF, E. coli and thermotolerant coliforms (total n = 1082). Using three World Health Organization defined classes (very high, high, and low/intermediate), risk indicated by TLF was not significantly different from risk indicated by E. coli (p = 0.85). However, the TLF and E. coli risk classifications did show disagreement, with TLF indicating higher risk for 14% of samples and lower risk for 13% of samples. Comparisons of duplicate/replicate results demonstrated that precision is higher for TLF (average relative percent difference of duplicates = 14%) compared to culture-based methods (average RPD of duplicates ≥ 26%). Additionally, TLF sampling is more practical because it requires less time and resources. Precision and practicality make TLF well-suited to high-frequency sampling in low resource contexts. Interpretation and interference challenges are minimised when TLF is measured in groundwaters, which typically have low dissolved organic carbon, relatively consistent temperature, negligible turbidity and pH between 5 and 8. TLF cannot be used as a proxy for E. coli on an individual sample basis, but it can add value to groundwater risk assessments by improving prioritization of sampling and by increasing understanding of spatiotemporal variability.
8270. 题目: Photocatalytic degradation of bisphenol A over a ZnFe2O4/TiO2 nanocomposite under visible light
期刊: Science of The Total Environment
作者: Thanh Binh Nguyen, C.P. Huang, Ruey-an Doong
摘要: A ZnFe2O4-TiO2 nanocomposite combining p-type ZnFe2O4 and n-type TiO2 was successfully fabricated. The ZnFe2O4-TiO2 nanocomposite greatly enhanced the bisphenol A (BPA) photodegradation under visible light irradiation at 465 ± 40 nm. Loading TiO2 with 1 wt% of ZnFe2O4 produced high photocurrent and low charge transfer resistance. The photodegradation rate of BPA by ZnFe2O4-TiO2, which was highly dependent on the water chemistry including pH, anions, and humic acid, was 20.8–21.4 times higher than that of commercial TiO2 photocatalysts. Chloride and sulfate ions enhanced BPA photodegradation mostly due to the production of more radical species; whereas nitrate, dihydrogen phosphate, and bicarbonate ions decreased the photodegradation rate of BPA due to the scavenge of hydroxyl radicals. The photoactivity and recyclability of ZnFe2O4-TiO2 in lake water was also assessed. A near complete BPA removal from lake water was observed under visible light irradiation. Furthermore, >90% of photocatalytic activity toward BPA degradation was achieved in 5 cycles of continuous addition of BPA to the lake water. The BPA degradation intermediates were identified by HPLC/MS/MS and possible reaction pathways were proposed. Results clearly demonstrate the excellent visible-light-sensitive photocatalytic degradation of BPA over ZnFe2O4-TiO2 composite which has a great application potential for the decomposition of emerging contaminants in impaired waters.
8271. 题目: Bioactivity of humic substances and water extracts from compost made by ligno-cellulose wastes from biorefinery
期刊: Science of The Total Environment
作者: R. Spaccini, V. Cozzolino, V. Di Meo, D. Savy, M. Drosos, A. Piccolo
摘要: The ligno-cellulose residues from biorefinery production of bio-ethanol were used as woody structuring material within an on-farm composting system, with the aim to obtain bioactive water soluble and humic fractions from composted materials. The molecular characterization of initial biomasses and final products revealed a transformation towards more stable compounds during composting and showed the selective incorporation of specific phenolic derivatives of ligno-cellulose in both bulk samples and corresponding extracts. While the use of the stable bulk composts as organic fertilizer resulted in a decrease of nitrogen and phosphorous assimilation in maize tissues, a bio-stimulation was shown by water soluble organic compounds and humic substances in germination tests and pot experiments, respectively. The differential responses obtained in maize seedlings and plants were related to the molecular composition and concentration of the applied water extracts and humic substances, thus suggesting a role of phenols and lignin derivatives in the stimulation of maize roots and shoots and the enhancement of P uptake. The results confirm that ligno-cellulose residues may be effectively recycled as composting additives in order to enrich mature compost in aromatic and lignin compounds. A preliminary knowledge on the molecular characteristics and biological properties of composted materials is an essential requirement to select the most suitable derivatives from composted ligno-cellulose wastes in sustainable agricultural practices.
8272. 题目: Fluorescence Quenching and Energy Transfer Phenomena Associated with the Interactions of Terbium Ion and Humic Acid
期刊: Aquatic Geochemistry
作者: Mingquan Yan, Gregory V. Korshin, Marc F. Benedetti, Chi-Wang Li
摘要: Fluorescence of the hydrophobic acid fraction (HPOA) of Suwannee River natural organic matter and Tb3+ excitation spectra were measured in tandem using the instantaneous and time-resolved emission modes. The intensity of HPOA fluorescence decreased in the presence of Tb3+, while the intensity of the emission from Tb3+ cations bound by HPOA increased by up to several orders of magnitude due to energy transfer (ET) from HPOA to Tb3+ ions. To determine intrinsic ET and fluorescence quenching (FQ) coefficients, NICA–Donnan modeling was carried. It showed that phenolic groups in HPOA dominated both the ET and FQ processes and that the binding of Tb3+ by HPOA could be described using the non-ideality parameter nTb, median binding constant log KTb for the phenolic sites and intrinsic ET and FQ coefficients (denoted as ηTbΦ and αTbΦ), and were 0.48, 8.5, 1385 and 0.12, respectively. The high value of the energy transfer coefficient of Tb3+ ions bound by the phenolic groups in HPOA is indicative of both the match between the electronic levels of the donor and acceptor, and the short distance between them. The deviation of the data of Nica–Donnan modeling of the ET and FQ dependence of versus [Tb]total for a 1.0 M ionic strength highlights the need to quantify the distribution of donor–acceptor distances in HPOA molecules in more detail.
8273. 题目: Effects of altered dry-season length and plant inputs on soluble soil carbon
作者: Peter M Homyak, Joseph C Blankinship, Eric W Slessarev, Sean M Schaeffer, Stefano Manzoni, Joshua P Schimel
摘要: Soil moisture controls microbial activity and soil carbon cycling. Because microbial activity decreases as soils dry, decomposition of soil organic matter (SOM) is thought to decrease with increasing drought length. Yet, microbial biomass and a pool of water‐extractable organic carbon (WEOC) can increase as soils dry, perhaps implying microbes may continue to break down SOM even if drought stressed. Here, we test the hypothesis that WEOC increases as soils dry because exoenzymes continue to break down litter, while their products accumulate because they cannot diffuse to microbes. To test this hypothesis we manipulated field plots by cutting‐off litter inputs and by irrigating and excluding precipitation inputs to extend or shorten the length of the dry season. We expected that the longer the soils would remain dry, the more WEOC would accumulate in the presence of litter, whereas shortening the length of the dry season, or cutting off litter inputs, would reduce WEOC accumulation. Lastly, we incubated grass roots in the laboratory and measured the concentration of reducing sugars and potential hydrolytic enzyme activities, strictly to understand the mechanisms whereby exoenzymes break down litter over the dry season. As expected, extending dry season length increased WEOC concentrations by 30% above the 108 μg C g−1 measured in untreated plots, whereas keeping soils moist prevented WEOC from accumulating. Contrary to our hypothesis, excluding plant litter inputs actually increased WEOC concentrations by 40% above the 105 μg C g−1 measured in plots with plants. Reducing sugars did not accumulate in dry senesced roots in our laboratory incubation. Potential rates of reducing sugar production by hydrolytic enzymes ranged from 0.7 to 10 μmol g−1 hr−1 and far exceeded the rates of reducing sugar accumulation (~0.001 μmol g−1 hr−1). Our observations do not support the hypothesis that exoenzymes continue to break down litter to produce WEOC in dry soils. Instead, we develop the argument that physical processes are more likely to govern short‐term WEOC dynamics via slaking of microaggregates that stabilize SOM and through WEOC redistribution when soils wet up, as well as through less understood effects of drought on the soil mineral matrix.
8274. 题目: Rapid oxidation of iodide and hypoiodous acid with ferrate and no formation of iodoform and monoiodoacetic acid in the ferrate/I−/HA system
期刊: Water Research
作者: Xianshi Wang, Yulei Liu, Zhuangsong Huang, Lu Wang, Yicheng Wang, Yanting Li, Juan Li, Jingyao Qi, Jun Ma
摘要: Toxic and odorous iodinated disinfection byproducts (I-DBPs) could form in the chemical oxidation of iodine-containing water. A critical step for controlling the hazardous I-DBPs is to convert the iodine species into stable and harmless iodate (IO3−) while inhibiting the accumulation of highly reactive hypoiodous acid (HOI). Herein, the oxidation of I− and HOI with ferrate was investigated, and the formation profile of HOI during the oxidation of I− was determined based on 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) coloring method through a stopped-flow spectrophotometer. The second-order rate constants (kapp) of ferrate with HOI decreased from 1.6 × 105 M−1s−1 to 8.3 × 102 M−1s−1 as the solution pH varied from 5.3 to 10.3, which were 7.5, 7.2 and 13.8 times higher than that of ferrate with I− at pH 6.0, 7.0 and 8.0, respectively. Compared with other oxidants such as ozone, hypochlorous acid, chloramine and potassium permanganate, ferrate would swiftly oxidize HOI formed in the I− oxidation process. For the ferrate oxidation of I-containing water, HOI was swiftly oxidized to IO3− from pH 5.0 to 9.0. Phosphate buffer promoted the oxidation of I− while inhibited the oxidation of HOI with ferrate. When 5 mgC/L of humic acids (HA) existed in the solution, no formation of iodoform and monoiodoacetic acid (MIAA) was observed in the oxidation of iodide (20 μM) with ferrate (from 10 μM to 80 μM). These results have important implications for the control of I-DBPs in water treatment.
8275. 题目: A Neolithic palaeo-catena for the Xagħra Upper Coralline Limestone plateau of Gozo, Malta, and its implications for past soil development and land use
作者: Charles French, Sean Taylor, Rowan McLaughlin, Alan Cresswell, Tim Kinnaird, David Sanderson, Simon Stoddart, Caroline Malone
摘要: Geoarchaeological survey on the island of Gozo combined with test excavations and new chronometric dating of two Neolithic temple sites at Santa Verna and Ġgantija on the Xagħra plateau have revealed well-preserved buried soils which tell a new story of soil development and change for the early-mid-Holocene period. Micromorphological analysis has suggested that the earlier Neolithic climax soil type was a thick, well-developed, humic and clay-enriched argillic brown Mediterranean soil. With human intervention on the Xagħra Upper Coralline Limestone plateau from at least the early 4th millennium BCE, the trajectory of soil development quickly changed. Radical soil change was marked by the removal of scrub woodland, then consequent poorer organic status and soil thinning, and rubefication and calcification, no doubt exacerbated by Neolithic agricultural activities and a more general longer-term aridification trend. The beginnings of this transitional brown to red Mediterranean soil change process has been observed at Santa Verna temple by the early 4th millennium BCE, and appears to be much further advanced by the time of the latter use of Ġgantija temple in the early-mid-3rd millennium BCE. There is also evidence of attempts at amending these deteriorating soils during this period and into the 2nd millennium BCE, a practice which probably underpinned the viability of later Neolithic agricultural society in the Maltese Islands. The changes observed ultimately resulted in the creation of the thin, xeric, red Mediterranean soils on the Coralline Limestone mesa plateaux which are typical of much of Gozo and Malta today.
8276. 题目: Uranium Retention in a Bioreduced Region of an Alluvial Aquifer Induced by the Influx of Dissolved Oxygen
期刊: Environmental Science & Technology
作者: Donald Pan, Kenneth H. Williams, Mark J. Robbins, Karrie A. Weber
摘要: Reduced zones in the subsurface represent biogeochemically active hotspots enriched in buried organic matter and reduced metals. Within a shallow alluvial aquifer located near Rifle, CO, reduced zones control the fate and transport of uranium (U). Though an influx of dissolved oxygen (DO) would be expected to mobilize U, we report U immobilization. Groundwater U concentrations decreased following delivery of DO (21.6 mg O2/well/h). After 23 days of DO delivery, injection of oxygenated groundwater was paused and resulted in the rebound of groundwater U concentrations to preinjection levels. When DO delivery resumed (day 51), groundwater U concentrations again decreased. The injection was halted on day 82 again and resulted in a rebound of groundwater U concentrations. DO delivery rate was increased to 54 mg O2/well/h (day 95) whereby groundwater U concentrations increased. Planktonic cell abundance remained stable throughout the experiment, but virus-to-microbial cell ratio increased 1.8–3.4-fold with initial DO delivery, indicative of microbial activity in response to DO injection. Together, these results indicate that the redox-buffering capacity of reduced sediments can prevent U mobilization, but could be overcome as delivery rate or oxidant concentration increases, mobilizing U.
8277. 题目: Effects of anthropogenic nitrogen deposition on soil nitrogen mineralization and immobilization in grassland soil under semiarid climatic conditions
期刊: Environmental Monitoring and Assessment
作者: Ambreen Bhatti, Jawad Ahmad, Muhammad Qasim, Muhammad Riaz, Malcolm S. Cresser
摘要: Earlier studies by the authors on English soils under grassland strongly supported their hypothesis that soil/plant systems have naturally evolved to conserve nitrogen (N) by having a close match between the dynamics of mineral-N production in soils and the dynamics of plant N requirements. Thus, maximum mineral-N production in soils occurred in spring when plant N requirements were greatest and were very low in mid to late summer. Low temperature and a high C:N ratio of senescing material helped to conserve N in winter, but mobile N was associated with pollution inputs. We test the hypothesis that under the much more arid conditions of Pakistan, soil/plant systems naturally have evolved to conserve mineral-N, especially over the very dry and cooler months between October and February. When soils from a grassland site were incubated at ambient temperatures after removal of plant roots and exclusion of atmospheric N inputs, there was consistent evidence of immobilization of nitrate and immobilization and possibly volatilization of ammonia/ammonium. In the wetter months of July and August, the soil at 0–10 cm depth showed no evidence of significant ammonium-N production in July and only small ammonium production at 10–20 cm depth in August, but was associated with significant nitrate-N immobilization in August. Nitrate leaching only appeared likely towards the end of the rainy season in September. The results strongly suggest that, under grass, the retention of atmospheric N inputs over the long dry periods is regulating the pools of available N in the soils, rather than the N produced by mineralization of soil organic matter.
8278. 题目: Phytolith content in Vietnamese paddy soils in relation to soil properties
作者: Minh N. Nguyen, Stefan Dultz, Andrew Meharg, Quang V. Pham, Anh N. Hoang, Than T.N. Dam, Van T. Nguyen, Khai M. Nguyen, Huan X. Nguyen, Nghia T. Nguyen
摘要: Understanding of the fate of phytolith in soils is important because of its role as an agronomical nutrient resource and for carbon sequestration. Accumulation of phytolith derived silica occurs in paddy soils when phytolith input, here through straw incorporation, is higher than silica removal through crop offtake, dissolution and leaching. Phytolith dissolution is thought to be the main reason for diminishing of phytolith derived silica in soil, with this dissolution being highly dependent on soil chemical properties. In this study, phytolith content from 78 paddy soils sampled in the Red River (RRD) and Mekong River (MRD) Deltas, Vietnam, were quantified and related to pH, electrical conductivity (EC), oxalate-extractable Al and Fe (Alox and Feox), organic carbon (OC) and clay content. Average phytolith contents within the topsoil (0–20 cm) were 4.8 ± 1.98 and 7.74 ± 2.97 mg g−1 for the RRD and MRD, respectively. Positive correlation coefficients obtained for Alox, OC, clay content and EC, implying that these parameters might enhance phytolith resistance to dissolution. Soil pH had a negative correlation coefficient with phytolith content. Lower pH and higher Alox content explained the predominance of the phytolith in the MRD compared to the RRD. Soil pH adjustment can be proposed as an active management strategy to maintain phytolith added Si, source for crops and for carbon sequestration.
8279. 题目: Evaluation of the anaerobic biodegradation of linear alkylbenzene sulfonates (las) using oecd 308 water/sediment systems
期刊: Journal of Hazardous Materials
作者: Carmen Corada-Fernández, Eduardo González-Mazo, Pablo A. Lara-Martín
摘要: Linear alkylbenzene sulfonates (LAS) are the most widely used anionic surfactants in household detergents and cleaning products. We have evaluated LAS anaerobic degradation in sediments following OECD 308 guidelines. Four different classes of sediments were collected from non-polluted areas and tested to check the influence of: fine and coarse texture, low and high organic carbon content, and freshwater and marine origin. The concentrations of LAS and possible degradation metabolites in sediment and water phases were monitored by high resolution mass spectrometry over an incubation period of 160 days. LAS removal was between 0 and 63%, depending on the sediment used, and it was accompanied by formation of sulfophenyl carboxylic acids (SPCs). The best results were observed for marine sediments having low organic carbon and silt + clay contents (0.5% and 13%, respectively), whereas degradation was negligible in freshwater sediments. The large differences in degradation observed across the sediments tested were attributed to their physicochemical properties influencing LAS bioavailability and the heterogeneity of microbial communities. Further research is also needed to address some shortcomings observed during the application of the OECD 308 and to ensure that test results obtained with these guidelines model anaerobic biodegradation under realistic environmental conditions.
8280. 题目: Interpreting the effects of natural organic matter on antimicrobial activity of Ag2S nanoparticles with soft particle theory
期刊: Water Research
作者: Yulei Liu, Tao Yang, Lu Wang, Zhuangsong Huang, Juan Li, Haijun Cheng, Jin Jiang, Suyan Pang, Jingyao Qi, Jun Ma
摘要: Natural organic matter (NOM) ubiquitously exists in natural waters and would adsorb onto the particle surface. Previous studies showed that NOM would alleviate the toxicity of nanomaterials, while the mechanism is seldom quantitatively interpreted. Herein, the effects of humic substances [Suwannee River fulvic acid (SRFA) and Suwannee River humic acid (SRHA)] and biomacromolecules [alginate and bovine serum albumin (BSA)] on the aggregation and antimicrobial effects of silver sulfide nanoparticles (Ag2S-NPs) were investigated. The aggregation kinetics of Ag2S-NPs in electrolyte solutions were in agreement with the results based on Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. The dynamic light scattering (DLS) results showed that the SRFA, SRHA, alginate and BSA molecules coated on the Ag2S-NPs surfaces. The NOM coating layer prevented salt-induced coagulation of Ag2S-NPs, and the effects of BSA and SRHA on Ag2S-NPs stabilizing were more obvious than that of SRFA and alginate. Flow cytometry results showed that BSA and SRHA were more effective on alleviating the Ag2S-NPs induced cell (Escherichia coli) membrane damage than SRFA and alginate. After interpreting the electrophoretic mobility (EPM) data of the NOM coated Ag2S-NPs by Ohshima's soft particle theory, it was found that the thickness of the NOM coating layers followed the orders of BSA > SRHA > alginate > SRFA. The E.coli cell membrane damage level was negatively correlated with the thickness and softness of the coating layer. NOM coating may physically alleviate the contact between NPs and E. coli cells and thus attenuate the extent of cell membrane damage caused by the NP-cell interaction. This work provides a new perspective for quantitatively interpreting the influence of NOM on the environmental behaviors and risks of nanomaterials.