12561. 题目: Ten-year long-term organic fertilization enhances carbon sequestration and calcium-mediated stabilization of aggregate-associated organic carbon in a reclaimed Cambisol
作者: Xiaolei Huang, Zhixin Jia, Junjie Guo, Tingliang Li, Dasheng Sun, Huisheng Meng, Guanghui Yu, Xinhua He, Wei Ran, Shusheng Zhang, Jianping Hong, Qirong Shen
摘要: Soils play a vital role in the global carbon (C) cycle, yet little is known about the calcium (Ca)-mediated stabilization of soil organic carbon (SOC) in calcareous soils. With wet sieving, density fractionation and an incubation experiment from field soils, we investigated the effects of long-term fertilization on the Ca-mediated stabilization of aggregate-associated organic C and on the SOC stock at a soil depth of 0–20 cm in a reclaimed Cambisol on the Loess Plateau of China. Compared to the initial soil, after ten years the SOC stock increased by 50%, 76%, 94% and 110% in soils amended with no fertilizer (control), 100% chemical fertilizer, 50% chemical fertilizer plus 50% chicken manure compost and 100% chicken manure compost, respectively. The specific C mineralization rate (SCMR, rate per unit SOC) decreased as silt and clay > macroaggregate > microaggregate, indicating that SOC in microaggregates was more stable than in macroaggregates and the silt and clay fraction. The exchangeable Ca in the bulk soil (P < 0.001) and soil aggregates (P < 0.001) were positively correlated with the SOC, whereas the Ca carbonate (CaCO3) was negatively correlated with the SCMR (P < 0.001). The application of compost not only increased the exogenous C inputs but also promoted the transformation of CaCO3 to exchangeable Ca compared with the sole chemical fertilization. Furthermore, organic fertilization significantly increased the organic C in the heavy fraction (> 2.0 g cm−3) compared with the sole chemical fertilization, which was positively correlated with the mass proportion of macroaggregates (P < 0.001). These results indicate that organic fertilization can enhance the availability of Ca for C binding possibly by forming organo-Ca complexes, which in turn improve soil aggregation, and thus contribute to a long-term SOC sequestration in reclaimed soils of the Loess Plateau of China.
12562. 题目: In situ and laboratory soil spectroscopy with portable visible-to-near-infrared and mid-infrared instruments for the assessment of organic carbon in soils
作者: Christopher Hutengs, Michael Seidel, Felix Oertel, Bernard Ludwig, Michael Vohland
摘要: Mid-infrared (MIR) spectroscopy has been established as a rapid and cost-efficient laboratory analysis technique for soil organic carbon (SOC) concentrations. Current portable, high-performance handheld MIR instruments have opened the opportunity to take the technique from the laboratory to the field. We tested the potential of handheld MIR spectroscopy for SOC estimation with field spectral data against parallel VIS-NIR measurements and further evaluated the impact of soil state (in situ, dried, ground) on the accuracy of SOC prediction models. MIR and VIS-NIR data were collected for a set of 90 soils from 90 agricultural loess sites in Central Germany in the field, (i) in situ on the soil surface, and in the laboratory, on (ii) dried and sieved (<2 mm), and (iii) dried, sieved and ground sample material (~10 μm). Multivariate calibrations for SOC for each pre-treatment were evaluated with a repeated double cross-validation (rdCV) analysis and the Kennard-Stone (KS) calibration sampling approach. MIR calibrations were more accurate than VIS-NIR calibrations for samples measured under the same conditions in each case with lower RMSE values from 27 to 56% in the rdCV and from 15 to 61% in the KS approach. Sample pre-treatment in the laboratory had a pronounced effect on calibrations in the MIR as models developed on finely ground samples (R2rdCV = 0.86, RMSErdCV = 0.11%) were more accurate than those for dried and sieved samples (R2rdCV = 0.79, RMSErdCV = 0.13%), but differences in the VIS-NIR were negligible. SOC estimates with in situ MIR measurements were less accurate due to spectral variation induced by surface heterogeneity and soil moisture but compared favourably against VIS-NIR data (R2rdCV_MIR = 0.63, RMSErdCV_MIR = 0.17% vs R2rdCV_VIS-NIR = 0.39, RMSErdCV_VIS-NIR = 0.23%). Our findings show that portable MIR spectroscopy can achieve superior SOC calibrations to the VIS-NIR range with in situ data demonstrating its applicability for the on-the-go acquisition of spectral soil information in the field. Handheld MIR instruments thus have the potential to facilitate quantitative applications in proximal soil sensing, although with less accuracy than achievable with pre-treated samples in the laboratory.
12563. 题目: Carbon input manipulations affecting microbial carbon metabolism in temperate forest soils – A comparative study between broadleaf and coniferous plantations
作者: Yun Wang, Chi Zhang, Guangna Zhang, Lizhi Wang, Yuan Gao, Xinli Wang, Bo Liu, Xingyun Zhao, Heping Mei
摘要: Large uncertainties exist about the relative importance of aboveground litter and root carbon input on soil organic carbon decomposition in different forest types. Here, we report on our detritus input and removal treatments conducted to investigate how changes in aboveground and belowground carbon inputs affect soil organic carbon content and various microbial carbon metabolic functions in different plantation types (oak vs. pine, broadleaf vs. coniferous). The results of our study showed that doubling aboveground litter significantly increased SOC content and labile carbon metabolism in the oak plantation but not the pine plantation. Root trenching and aboveground litter removal decreased SOC content and carbon metabolisms. The effect of root trenching on carbon metabolisms was weaker than litter removal in the oak plantation but not the pine plantation. Detritus input and removal treatments changed the diversity and function of labile carbon (starch, carbohydrates, and amines/amides) and the metabolic activity of soil microorganisms in oak plantation, but mainly influenced recalcitrant carbon (polymers) metabolism in the pine plantation. Detritus input and removal treatments influenced the composition of microbial carbon metabolic genes and functions mainly by modifying the soil environment and nutrient availability including moisture, pH, nitrate content, and available phosphorus content in the oak plantation, while it influenced carbon metabolism by altering soil moisture, and the ammonium, nitrate, and organic carbon content in the pine plantation. These findings indicate that different forest ecosystems could respond differently to different disturbances, and forest management should be adjusted accordingly.
12564. 题目: Flow-induced crystallization of biochar in bio-asphalt under various aging conditions
期刊: Science of The Total Environment
作者: Xinxing Zhou, Sanjeev Adhikari
摘要: Flow-induced crystallization (FIC) in polymers is an important problem that occurs on a very rapid time scale. This study aims to evaluate the flow-induced crystallization of bio-asphalt modified with different contents of biochar under various aging conditions. Small angle X-ray scattering and molecular dynamic simulations were performed to impose extensional deformation and the nucleation process. The rheological properties were measured using the dynamic shear rheometer (DSR) and the morphology of biochar modified bio-asphalt (BMBA) was measured using an optical microscope. The relative scattering intensity during crystallization appeared to peak at four strain rates: 13.2 s−1, 19.6 s−1, 25.4 s−1, and 27.3 s−1. The results showed that the addition of biochar could improve the flow-induced crystallization and enhance the high-temperature properties of bio-asphalt. Moreover, crystallization status of BMBA is lamellar crystals. Ultraviolet and pressure aging vessel aging could remarkably affect the crystallization status of BMBA and promote the formation of crystals.
12565. 题目: Why does nitrogen addition to forest soils inhibit decomposition?
期刊: Soil Biology and Biochemistry
作者: Mark TL. Bonner, David Castro, Andreas N. Schneider, Görel Sundström, Vaughan Hurry, Nathaniel R. Street, Torgny Näsholm
摘要: Enrichment of forest soils with inorganic nitrogen (N) tends to inhibit oxidative enzyme expression by microbes and reduces plant litter and soil organic matter decomposition rates. Without further explanation than is currently presented in the scientific literature, we argue that upregulation of oxidative enzymes seems a more competitive response to prolonged N enrichment at high rates than the observed downregulation. Thus, as it stands, observed responses are inconsistent with predicted responses. In this article, we present a hypothesis that resolves this conflict. We suggest that high rates of N addition alter the competitive balance between enzymatic lignin mineralisation and non-enzymatic lignin oxidation. Using metatransciptomics and chemical assays to examine boreal forest soils, we found that N addition suppressed peroxidase activity, but not iron reduction activity (involved in non-enzymatic lignin oxidation). Our hypothesis seems positioned as a parsimonious and empirically consistent working model that warrants further testing.
12566. 题目: Long term effects of intensive biomass harvesting and compaction on the forest soil ecosystem
期刊: Soil Biology and Biochemistry
作者: Tera E. Lewandowski, Jodi A. Forrester, David J. Mladenoff, Erika Marin-Spiotta, Anthony W. D’Amato, Brian J. Palik, Randall K. Kolka
摘要: Forest soil ecosystems can be negatively affected by intensive biomass harvesting due to losses of organic inputs and soil compaction, ultimately leading to reduced forest productivity. In this research, we revisited a site from the North American Long-Term Soil Productivity study (LTSP) located on a sandy Spodosol within the Huron National Forest in Michigan, USA, to measure the effects of aboveground organic matter removal of different intensities (three levels: bole only; whole tree harvest; or whole tree harvest and forest floor removal) and soil compaction (2 levels: no or moderate compaction) nearly 20 years following the initial treatments. The effects of harvesting on the soil microbial community (SMC) in surface and subsurface soils and on soil nutrient availability in surface soils were evaluated. Additionally, patterns of carbon and nitrogen distribution among soil organic matter pools in surface and subsurface soils were compared using a physical fractionation approach to isolate a free – light fraction (f-LF) of particulate organic matter external to aggregates, an occluded – light fraction (o-LF), which represents particulate organic matter released from the disruption of soil aggregates, and a heavy or mineral-associated fraction (HF). Whole-tree harvests had significantly different SMC compositions than bole-only harvests (P =0.02), a result driven by significantly lower abundance of arbuscular mycorrhizae and greater gram positive bacterial abundance in the whole-tree harvest relative to bole-only harvest conditions. Few differences in soil nutrient availability were apparent 20 years after organic matter manipulations, with the exception of reduced calcium availability where organic matter was removed. Soil compaction resulted in greater microbial biomass (0.19 versus 0.14 μmol g-1 soil), which may have also led to a reduced C:N ratio in the heaviest and oldest soil component and increased P availability as well. Nitrogen concentrations and stocks were greatest at the surface (0-10 cm depth) for the free and light soil fractions in bole-only removal treatments, in contrast to whole-tree harvest treatments where C and N concentrations and C stocks were greater in the subsurface soil (f-LF at 20-30 cm depth). The SMC, soil fraction size, and soil C and N stocks differed between surface and subsurface soils, highlighting the soil forming processes at work in this Spodosol, and the importance of sampling multiple depths to address research questions. These results demonstrate the long-term effects of forest management on soil biological, physical, and chemical properties and are useful in evaluating sustainable biomass harvesting practices for comparable forests.
12567. 题目: Inactivation of bacterial planktonic cells and biofilms by Cu(II)-activated peroxymonosulfate in the presence of chloride ion
期刊: Chemical Engineering Journal
作者: Hye-Jin Lee, Hyung-Eun Kim, Min Sik Kim, Charles-François de Lannoy, Changha Lee
摘要: The combination of Cu(II) with peroxymonosulfate (PMS) (i.e., the Cu(II)/PMS system) synergistically inactivated P. aeruginosa cells in the planktonic state, and in biofilms grown on RO membranes. The enhanced bacterial inactivation by the Cu(II)/PMS system appears to be due to the reactive oxidants produced by the catalytic reactions of the Cu(II)/Cu(I) redox couple with PMS. In the presence of chloride ion (Cl−), the Cu(II)/PMS system showed increased microbicidal effects on the planktonic P. aeruginosa cells, which was explained by the role of hypochlorous acid (HOCl) produced by the reaction of chloride with PMS. In addition, the combination of Cu(II) with HOCl showed synergistic microbicidal effects on the planktonic cells. Compared to planktonic cells, biofilm cells were more resistant to the Cu(II)/PMS treatment. Cl− did not significantly affect the inactivation of biofilm cells by the Cu(II)/PMS system. It is believed that the extracellular polymeric substances of biofilms play a role as oxidant sinks (particularly HOCl), protecting the cells inside the biofilm matrix. The HOCl-generating systems, such as PMS/Cl− and Cu(II)/PMS/Cl−, greatly degraded proteins and polysaccharides in biofilms. Experiments on the cross-flow filtration of NaCl solution showed that the Cu(II)/PMS treatment of fouled RO membranes resulted in partial recovery of permeate flux.
12568. 题目: Improving sewage sludge dewaterability with rapid and cost-effective in-situ generation of Fe2+ combined with oxidants
期刊: Chemical Engineering Journal
作者: Jialin Liang, Siwei Zhang, Maoyou Ye, Jinjia Huang, Xian Yang, Shoupeng Li, Shaosong Huang, Shuiyu Sun
摘要: Zero-valent iron (ZVI) combined with oxidants is a promising conditioning strategy for improving sewage sludge dewaterability. However, challenges, such as a low dewatering rate and utilization efficiencies of ZVI, restrict further application of ZVI/oxidant treatments. This study employs, for the first time, rapid and cost-effective in-situ generation of Fe2+ combined with common oxidants, namely H2O2, Na2S2O8, and KMnO4, to effectively improve sludge dewaterability. A comparative investigation of a standalone ZVI/oxidants treatment and when combined with a thermal and acid-wash (TA) pretreatment (TA/ZVI/oxidants) was systematically conducted to determine the sludge dewatering efficiency. Under the optimal operational conditions, the average water content of dewatered cake (Wc) was 18.47% less with the TA/ZVI/oxidants treatment when compared with the ZVI/oxidants treatment. The Wc values decreased to 54.81, 58.06, and 59.32 wt%, after the TA/ZVI/H2O2, TA/ZVI/Na2S2O8, and TA/ZVI/KMnO4 treatments, respectively. The potential mechanism by which the TA/ZVI/oxidants treatment enhanced dewatering was investigated by determining the characteristics of both the sludge and the ZVI surface structure. Results indicate that the TA/ZVI/oxidants process caused more Fe2+ dissolution, more strong oxidizing radicals and more strong flocculating Fe3+. The large amount of strong oxidizing radicals and strong flocculating Fe3+ caused cell lysis and disrupted the protein-like and polysaccharide-like materials in the EPS, thereby decreasing the particle size, negative zeta potential, viscosity and colloidal forces, which then released the bound water trapped within the net-like floc and led to improved sludge dewaterability. In the ZVI reuse experiment, the TA/ZVI/oxidants treatment remained highly effective for sludge dewatering even after four cycles. Furthermore, economic analysis indicates that the TA/ZVI/H2O2 treatment can save approximately 52.32% per year compared with using the traditional polyacrylamide (PAM) treatment.
12569. 题目: Micron-scale distribution of metals in Cambrian metalliferous shales, South China: Insights into local biologically driven redox disequilibrium
期刊: Chemical Geology
作者: Anaïs Pagès, Steve Barnes, Susanne Schmid, Chris Ryan, David Paterson, Colin MacRae, Jamie Laird, Margaux Le Vaillant, Haifeng Fan, Hanjie Wen
摘要: Early Cambrian black shales of the Niutitang Formation are found across the Yangtze Platform in a 1600-km belt extending across south China. A thin organic matter-rich layer in the lowermost part of this formation contains exceptional concentrations in Mo, Ni, Se, Re, Os, As, Hg, Sb, Ag, Au, Pt, Pd, and Ag. Due to their extreme metal enrichment, these black shales provide a rare opportunity to study the interface between semi-metals, metals and biogenic material. We report the first detailed μm-scale investigation of metal distributions and associations in samples from two sites, Zunyi and Sancha, located hundreds of km apart, using a combination of analytical techniques including X-ray fluorescence (XRF) mapping, scanning electron microscopy (SEM), Synchrotron-based XRF mapping, electron probe micro-analyser (EPMA), particle induced x-ray emission (PIXE) probe and x-ray absorption near-edge structures (XANES) imaging. Strong μm-scale variations in metal and semi-metal distributions were highlighted by Synchrotron-based XRF mapping of samples from both sites. At both locations, U is present within phosphorite nodules. Arsenic, Mo and Se are particularly abundant in the organic-rich matrix, showing strong associations with organic matter. Nickel, however, shows different distributions between the two sites. It is mainly present in association with the organic matter at the Sancha site while it is found in abundance in millerite at the Zunyi site, suggesting slightly different local conditions at Zunyi favouring Ni-S associations over Ni-organic matter. At both sites, biogenic structures were re-mineralised with laminations dominated by different metals, indicating a likely control of organic matter over metal distributions. In addition, the XANES imaging highlighted different redox states of As over μm-scale areas. While As−1 appears to be mainly present in pyrite, As+3 was mainly detected in association within the carbon and MoS2 mixed layer phase (MoSC). Overall, the present results emphasize the complexity of metal associations in this mineralised layer, the significant role of organic matter in the accumulation and precipitation of metals and semi-metals in these metalliferous shales and highlight how biogenic activity can induce μm-scale variations in redox conditions in sediments.
12570. 题目: Detection of soil organic matter from laser-induced breakdown spectroscopy (LIBS) and mid-infrared spectroscopy (FTIR-ATR) coupled with multivariate techniques
作者: Xuebin Xu, Changwen Du, Fei Ma, Yazhen Shen, Ke Wu, Dong Liang, Jianmin Zhou
摘要: Spectroscopy is a useful method for soil monitoring because of its environmental friendliness, and its ability to produce rapid, nondestructive, simultaneous multi-element analysis. In this work, data fusion strategies for laser-induced breakdown spectroscopy (LIBS) and attenuated total reflectance Fourier-transform mid-infrared spectroscopy (FTIR-ATR), as well as a combination of multivariate calibration methods were investigated for prediction of soil organic matter (SOM) content. The root mean square error (RMSE) and residual prediction deviation (RPD) of the calibration and validation sets, systematic error, and residual assessment, were applied to evaluate the robustness and accuracy of these predictions. The results of a principal component analysis (PCA) indicated that baseline wander present in the spectral data could be effectively removed using morphological weighted penalized least squares (MPLS) and wavelet transform (WT) algorithms. The quantitative prediction ability of SOM content by a partial least squares regression (PLSR) model could be improved using principal component weighted mean (PCWM) and Euclidean distance weighted mean (EDWM) algorithms applied to parallel LIBS spectra. The prediction ability of SOM content was dramatically improved using mid-level data fusion based on the concatenation of latent variables of LIBS and FTIR-ATR spectra obtained by partial least squares algorithm. The considerable prediction accuracy and robustness were achieved using the PLSR model (RV2 = 0.792, RMSEV = 1.76 g kg−1, and RPDV = 2.16), the support vector regression (SVR) model (RV2 = 0.811, RMSEV = 1.68 g kg−1, and RPDV = 2.27), and the artificial neural network (ANN) model (RV2 = 0.830, RMSEV = 1.60 g kg−1, and RPDV = 2.39). The findings from this work suggest that the use of LIBS and FTIR-ATR spectra in combination with multivariate calibration can be a simple, fast, and nondestructive approach to monitor SOM. This strategy is potentially of great significance in the evaluation of soil fertility, the management of soil nutrients, and in guiding the agricultural production of precision agriculture.
12571. 题目: Removal of ametryn and organic matter from wastewater using sequential anaerobic-aerobic batch reactor: A performance evaluation study
期刊: Journal of Environmental Management
作者: Gajanuru Basappa Mahesh, Basavaraju Manu
摘要: The present study was aimed to investigate biodegradation of 2-(ethylamino)-4-(isopropylamino)-6-(methylthio)-s-triazine (ametryn) in a laboratory-scale anaerobic sequential batch reactor (ASBR) and followed by aerobic post-treatment. Co-treatment of ametryn with starch is carried out at ambient environmental conditions. The treatment process lasted up to 150 days of operation at a constant hydraulic retention time (HRT) of 24 h and an organic loading rate (OLR) of 0.21–0.215 kg-COD/m3/d. Ametryn concentration of 4 and 6 mg/L was removed completely within 48–50 days of operation with chemical oxygen demand (COD) removal efficiencies >85% at optimum reactor conditions. Ametryn acted as a nutrient/carbon source rather causing toxicity and contributed to methane gas production and sludge granulation in the anaerobic reactor. Biotransformation products of ametryn to cyanuric acid, biuret, and their further conversion to ammonia nitrogen and CO2 are monitored during the study. Adsorption of ametryn on to reactor sludge was negligible, sludge granulation, presence of ANAMMOX bacteria, and low MLVSS/MLSS ratio between 0.68 and 0.72. The study revealed that ametryn removal occurred mainly due to biodegradation and co-metabolism processes. Aerobic post-treatment of anaerobic effluent was able to remove COD up to 95%. The results of this study exhibit that anaerobic-aerobic treatment is feasible due to easy operation, economic, and highly efficient.
12572. 题目: Effects of photochemical and microbiological changes in terrestrial dissolved organic matter on its chemical characteristics and phytotoxicity towards cyanobacteria
期刊: Science of The Total Environment
作者: Amanda D. Neilen, Anthony R. Carroll, Darryl W. Hawker, Katherine R. O'Brien, Michele A. Burford
摘要: Previous studies have shown that under laboratory conditions, dissolved organic matter (DOM) leached from plants can be differentially more phytotoxic to cyanobacteria, compared to green algae. This study examined how DOM source and transformation processes (microbial and photochemical) affect its chemical composition and phytotoxicity towards a cultured species of cyanobacteria (Raphidiopsis raciborskii) using a factorial experimental design. To complement cyanobacterial bioassays, the chemical composition and associated changes in DOM were determined using spectroscopic (nuclear magnetic resonance (NMR) and absorbance) and elemental analyses. Sunlight exposed DOM from leaves of the terrestrial plants, Casuarina cunninghamiana and Eucalyptus tereticornis had the most phytotoxic effect compared to DOM not exposed to sunlight. This phytotoxic DOM was characterised by relatively low nitrogen content, containing highly coloured and relatively high molecular mass constituents. Both mixed effect model and PCA approaches to predict inhibition of photosynthetic yield indicated phytotoxicity could be predicted (P < 0.001) based upon the following parameters: C: N ratio; gilvin, and lignin-derived phenol content of DOM. Parallel proton-detected 1D and 2D NMR techniques showed that glucose anomers were the major constituents of fresh leachate. With ageing, glucose anomers disappeared and products of microbial transformation appeared, but there was no indication of the appearance of additional phytotoxic compounds. This suggests that reactive oxygen species may be responsible, at least partially, for DOM phytotoxicity. This study provides important new information highlighting the characteristics of DOM that link with phytotoxic effects.
12573. 题目: Effect of mixed solutions of heavy metal eluents on soil fertility and microorganisms
期刊: Environmental Pollution
作者: Zhongchuang Liu, Bangjun Lu, Hongyan Xiao, Dongsheng Liu, Xiang Li, Li-ao Wang, Oksana Urbanovich, Liubov Nagorskaya
摘要: This study analyzed the effect of heavy metal eluents (0.3 mol/L C6H8O7, 5 × 10−4 mol/L EDTA, and 0.01 mol/L Na2S2O3) on the content of organic matter, hydrolytic nitrogen, available phosphorus and potassium, and species composition of bacteria and fungi in vegetable soils. The obtained results documented that the treatment of the soil, consisting of shaking the sample with a mixture of eluents, significantly increased the content of organic matter, hydrolytic nitrogen, and available phosphorus and potassium. The mixed solutions of eluents increase the maximum available P in the soil by 279.3%, and hydrolytic N by 30.7%. The eluents affected, to a certain extent, the dominant species of microorganisms in the soil, but did not increase species richness and evenness in all soil samples.
12574. 题目: Evidence-based analysis on the toxicity of disinfection byproducts in vivo and in vitro for disinfection selection
期刊: Water Research
作者: Feilong Dong, Jianing Chen, Cong Li, Xingmao Ma, Jingjing Jiang, Qiufeng Lin, Chenhong Lin, Hongyan Diao
摘要: Disinfection is a key step in drinking water treatment process to prevent water-borne infections. However, reactions between chlorine, one of the most common disinfectants, and natural organic matter (NOM) often lead to the formation of hazardous disinfection byproducts (DBPs). However, the cytotoxicity of some DBPs is still poorly understood. Such knowledge is critical for proper selection of disinfection processes. We investigated the effects of DBPs on mouse acute liver injury. The exacerbation of liver damage increased with the DBPs concentrations, likely due to the increased hepatic macrophages. Haloacetonitriles (HANs) and haloketones (HKs) are more toxic to Human Hepatocellular (Hep3B) cells than trihalomethanes (THMs). Cytotoxicity of DBPs were governed by the halogen type (brominated DBPs > chlorinated DBPs) and the numbers of halogen atoms per molecule. Then, we used the pilot-scale WDS to study the best conditions for reducing the formation of DBPs. The result showed that the formation of DBPs followed the order: stainless-steel (SS) > ductile iron (DI) > polyethylene (PE) pipe. Higher flowrate promoted the formation of DBPs in all three pipes. The results suggest that the formation of DBPs in chlorine disinfection can be reduced by using PE pipes and low flow rate in water distribution systems (WDS).
12575. 题目: Balancing carbon, nitrogen and phosphorus concentration in seawater as a strategy to prevent accelerated membrane biofouling
期刊: Water Research
作者: Siqian Huang, Nikolay Voutchkov, Sunny Jiang
摘要: Membrane biofouling remains a significant challenge in seawater reverse osmosis desalination for drinking water production. This study investigated nutrient imbalance as the cause of biofouling in lab-scale experiments and carried out a year-long field-testing at a seawater desalination pilot plant. Lab experiments showed that growth medium with excess of organic carbon (C) but with low nitrogen (N) and phosphorus (P) accelerated the formation of bacterial biofilm. Balancing C to N and P ratios by adding N and P to growth medium increased the proliferation of free-living cells but reduced attached form of bacteria as biofilm. The cell excretion of excess C in the form of extracellular polysaccharides (EPS) was considered as a strategy for nutrient storage for future use. Cell enzyme activity assays indicated some of the bacteria had enhanced enzyme activities to degrade polysaccharides in the absence of organic C in growth medium, possibly using EPS in the biofilm. A year-long field study indicated that accelerated biofouling of seawater reverse osmosis (SWRO) membranes was associated with the elevated content of total organic carbon (TOC) in the intake seawater. Adding N and P to the intake seawater to balance the increase of TOC resulted in reduction of membrane biofouling. Microbial community analysis of the biofouling layer using 16S rRNA gene sequencing indicated biofouling communities varied with seasonal changes. Dosing of N and P did not induce dramatic changes in the fouling microbial community growing on the membrane surface. The outcome of this work implies that membrane biofouling associated with the elevated concentration of TOC in intake seawater is caused by imbalance of C:N:P in the source seawater which occurs often during algal blooms. Addition of N and P to rebalance the nutrients can prevent accelerated SWRO membrane biofouling.
12576. 题目: Stimulation of heterotrophic and autotrophic metabolism in the mixing zone of the Kuroshio Current and northern South China Sea: implications for export production
期刊: Journal of Geophysical Research: Biogeosciences
作者: Yibin Huang, Edward Laws, Bingzhang Chen, Bangqin Huang
摘要: To evaluate the influences of the Kuroshio Current intrusion on the biogeochemistry of the northern South China Sea (NSCS), we conducted field observations of the responses of microbial metabolism to the intrusions of the Kuroshio Current into the NSCS. We used an isopycnal mixing model to quantitatively assess the extent of the Kuroshio intrusion into the NSCS and found that bacterial abundance, production, and growth efficiency were unimodal functions of the fraction of Kuroshio water. Values were maximal at ~60% Kuroshio water and decreased monotonically as the percent of Kuroshio water deviated from 60%. The patterns of gross primary production and nitrate concentration were similar, but the peaks occurred at ~50% Kuroshio water. The Kuroshio intrusion, however, had little impact on bacterial and community respiration. The observed elevation of nitrate concentrations at ~50% Kuroshio water was quantitatively consistent with estimates of the amount of inorganic nitrogen released by remineralization of dissolved organic nitrogen by bacteria. Based on these observations, we hypothesize that dissolved organic matter (DOM) in the Kuroshio water stimulates bacterial activity, and catabolism of the DOM releases inorganic nutrients that stimulate primary production in the NSCS basin. The concomitant elevation of net community production subsequently enhances export production and thereby strengthens the biological pump in the nitrogen‐limited NSCS basin. Recognition of this mechanism underscores the role of horizontal currents in regional carbon and nitrogen cycles and broadens understanding of the processes that sustain export production in the oligotrophic ocean.
12577. 题目: Vertical dynamics of dissolved organic carbon in relation to organic input quality and microaggregate formation in a coarse textured Ultisol
期刊: European Journal of Soil Science
作者: Benjapon Kunlanit, Frank Rasche, Aunnop Puttaso, Georg Cadisch, Patma Vityakon
摘要: Against the background of current understanding about dissolved organic carbon (DOC) adsorption onto clay surfaces, it remains elusive if bulk DOC or its fractions contribute to microaggregate formation in the top layers of coarse–textured soils. We therefore investigated the effects of long–term inputs of biochemically contrasting organic residues on the chemical characteristics and vertical distribution of DOC in a coarse–textured Ultisol. During 2007–2008, DOC samples were extracted from soil profiles of a long–term residue quality field experiment initiated in 1995. In this field experiment, groundnut stover, dipterocarp and tamarind leaf litter, as well as rice straw of contrasting biochemical quality were applied yearly at 10 Mg ha−1. Groundnut, dipterocarp and tamarind produced large amounts (7.1–11.8 g C m−2) of high molecular weight (HMW; > 10 kDa) DOC was found in high concentrations (30–50 mg C kg−1) in the topsoil (0–15 cm). Rice straw, however, produced large amounts (3.5 g C m−2) of low molecular weight (LMW; < 1 kDa) DOC during the initial stage of decomposition. While the HMW DOC was retained in the topsoil (0–15 cm), the LMW DOC was rapidly translocated to lower soil depths (60–80 cm). This translocation was facilitated by the low adsorption potential of the rice–straw–derived LMW DOC onto colloidal surfaces of the topsoil. There was a significant positive correlation of C in the HMW DOC to that in fine particles inferring their contribution to microaggregate formation and thus C accumulation. It was concluded that biochemical quality of residues as determinant of concentration and chemistry of DOC and its vertical dynamics along the soil profile must be considered for SOC accumulation in coarse–textured soils. Furthermore, we found reasonable indications that HMW DOC contributes to microaggregate formation in topsoils.
12578. 题目: The sensitivity of soil microbial respiration declined due to crop straw addition but did not depend on the type of crop straw
期刊: Environmental Science and Pollution Research
作者: Shutao Chen, Jing Wu
摘要: An incubation experiment was conducted to investigate whether the type of crop straw added to soil influenced the temperature sensitivity of soil microbial respiration. The soil for incubation was collected from a winter wheat-soybean rotation cropland. Five temperature levels (5, 10, 15, 20, and 25 °C), five crop straw types (soybean, peanut, rice, winter wheat, and maize), and a control (CK, no crop straw addition) were established. Soil microbial respiration rates were measured on days 1, 2, 3, 5, 7, 10, 14, 20, and 27 after crop straw addition using an infrared CO2 analyser. Soil enzyme activities of invertase, urea, and catalase and the dissolved organic carbon (DOC) content were measured after incubation. Estimated Q10 (temperature sensitivity of soil microbial respiration) ranged from 1.472 ± 0.045 to 1.970 ± 0.020 and showed no significant (P > 0.05) difference between straw addition treatments, but there was significantly (P < 0.001) higher temperature sensitivity (1.970 ± 0.020) for CK. A significant (P = 0.002) relationship was found between the Q10 of cumulative soil microbial respiration and basal soil microbial respiration (soil microbial respiration at 0 °C). Moreover, a marginally significant (P < 0.1) relationship was found between the Q10 at different incubation stages and basal soil microbial respiration. A quadratic function was used to explain the relationship between estimated basal microbial respiration and the lignin content. Soil microbial respiration was positively correlated with the activities of invertase, urease, and catalase and the dissolved organic carbon (DOC) content in all treatments. This study indicated that crop straw addition significantly (P < 0.001) reduced the Q10 of soil microbial respiration and that the types of crop straw added to soil did not significantly (P > 0.05) change the Q10 value.
12579. 题目: Lake-specific controls on the long-term stability of mining-related, legacy arsenic contamination and geochemical baselines in a changing northern environment, Tundra Mine, Northwest Territories, Canada
期刊: Applied Geochemistry
作者: Clare B. Miller, Michael B. Parsons, Heather E. Jamieson, Graeme T. Swindles, Nawaf A. Nasser, Jennifer M. Galloway
摘要: Climate change is influencing the biogeochemistry of northern lake ecosystems. These changes may affect the mobility of naturally occurring metal(loid)s and long-term stability of anthropogenic contaminants. Arsenic (As) concentrations in lake sediments in the Courageous Lake Greenstone Belt, Northwest Territories, Canada, are elevated from the operation of two high-grade, low-tonnage historical gold mines (Tundra Mine and Salmita Mine) and the weathering of mineralized bedrock. In sensitive sub-Arctic environments, it is not currently known how the cumulative effects of resource extraction and climate warming will impact geochemical baselines and the long-term stability of legacy contaminants. In this study, measurements of As concentration and speciation in waters and sediments are combined with multivariate analyses of climate proxies (sediment particle size and organic matter composition) from five lakes downstream of the former Tundra Mine site. Data from lake sediment cores were divided into geochemically distinct populations using a combination of radiometric dating and constrained incremental sum-of-squares cluster analysis to define geochemical baselines, examine the lake-specific controls on As distribution, and determine climate-related factors that may influence the long-term stability of As. Median As concentrations in near-surface impacted sediments (median: 110 mg kg−1; range: 31 to 1,010 mg kg−1; n = 22) and pre-mining sediment (median: 40 mg kg−1; range: 28–170 mg kg−1; n = 102) exceed the Canadian Council of the Ministers of the Environment Probable Effects Level of 17 mg kg−1. Near the Tundra Mine, the long-term stability of As in the near-surface sediment is influenced by the source of As (direct disposal and weathering of waste rock, tailings overtopping and seepage, discharge of treated tailings effluent, weathering and airborne deposition of tailings and waste rock, and natural weathering of mineralized bedrock), lithology of the sediment, and composition of sediment organic matter. This study demonstrates that in lakes impacted by weathering of waste rock and mineralized bedrock, As in sediments is primarily hosted by Fe-(oxy)hydroxides and may be more susceptible to remobilization with climate warming relative to those lakes impacted by direct discharge of mine wastes where As-bearing sulphides are the most abundant As host. Continued climate warming is expected to increase the natural loading of metal(loid)s and organic matter to lake sediments; however, the effects of these changes on the long-term stability of legacy contaminants will vary between lakes.
12580. 题目: Insights into the retention behaviour of europium(III) and uranium(VI) onto Opalinus Clay influenced by pore water composition, temperature, pH and organic compounds
期刊: Applied Geochemistry
作者: Ralf Kautenburger, Kristina Brix, Christina Hein
摘要: In the scientific community, a consensus exists to store high-level radioactive waste (HLW) in deep geological formations for several hundred thousand years to protect humanity and the environment. After a container damage followed by the release of HLW components, the retention of the radionuclides can be affected by diverse chemical reactions in the geosphere. In this study, geochemical effects possibly influencing the retention of the radionuclides were investigated. Therefore, the retention behaviour of U(VI) and Eu(III) (as homologue for trivalent actinides) onto Opalinus Clay (OPA) as a potential host rock for a HLW disposal was analysed at different geochemical conditions. For these experiments, a wide range of metal concentrations in presence and absence of natural clay organic matter (NOM) (lactate or humic acid) in different types of background electrolytes (0.01 mol L−1 sodium perchlorate and 0.4 mol L−1 synthetic OPA pore water) were investigated. Inductively coupled plasma mass spectrometry (ICP-MS) was used as a high specific and very sensitive method for elemental trace analysis. For the speciation of Eu3+-NOM-complexes, a method with high separation performance, capillary electrophoresis, was hyphenated with ICP-MS. The performed batch experiments simulate a potential water intrusion into the waste disposal. The retention (determined as log Kd values) of the metal ions strongly depends on the pH value, the presence of competing cations, temperature and NOM. At a pH value of pH 7.6 in synthetic OPA pore water, which is relevant for a disposal in OPA formations, the sorption of Eu(III) onto OPA (4 g L−1) is significantly higher (log Kd = 3.35 ± 0.04 at 25 °C and 4.85 ± 0.08 at 60 °C) than the retention of uranyl (log Kd = 2.17 ± 0.21 at 25 °C and 2.86 ± 0.01 at 60 °C) due to the formation of an uncharged aqueous calcium-uranyl-carbonate-complex (Ca2UO2(CO3)3(aq)) which does not sorb onto OPA. Modelling metal retention data onto OPA with PHREEQC reveals a very good agreement with most measurement results. At elevated temperatures, PHREEQC modelling could not performed due to lack of data, especially for possible secondary minerals. The observed increased Kd values at elevated temperature revealed in this study might be assumed advantageous for the safe storage of HLW in a future repository.