12641. 题目: Effect of alpha-hydroxy acids on transformation products formation and degradation mechanisms of carbamazepine by UV/H2O2 process
期刊: Science of The Total Environment
作者: Gang Lu, Jiangyong Hu
摘要: The role of dissolved organic matters (DOM) in the matrix of water on the degradation of refractory pharmaceutical has aroused broad concerns. However, The effect of alpha-hydroxy acids as vulnerable aliphatic acids in the water on the degradation of Carbamazepine (CBZ) has been lack of research. The decomposition kinetics and transformation products (TPs) of CBZ by UV/H2O2 process were studied in the existence of glycolic acid (GA) and lactic acid (LA) and the degradation pathways were proposed. Both GA and LA had significantly negative effects on the decomposition kinetics and mineralization of CBZ by UV/H2O2 process. The declination of steady-state OH concentration in the presence of GA and LA justified the negative effects. GA was demonstrated to be stronger at scavenging and competing OH with CBZ, compared with LA, with the rate constant of slightly less than the common OH scavenger methanol. One-step dosing mode of H2O2 was better than multi-step dosing mode for CBZ decomposition, especially in the presence of GA and LA. The identification of TP253a, TP253b, TP271a, TP271b, TP226, and TP180 in the absence and presence of GA and LA were performed by HPLC-MS/MS and two main degradation pathways were presented. Except for TP271a and TP271b, GA and LA retarded the abundance peaks of other four TPs, of which the formation kinetics rates and decay kinetics rates were negatively affected. Tailing peaks of all TPs caused by GA and LA inevitably resulted in the toxicity of the treated effluent of UV/H2O2 process even when CBZ was decomposed completely. Therefore, alpha-hydroxy acids play important roles in determining the fate and transformation of refractory pharmaceuticals in AOPs treatment.
12642. 题目: Formation of iodinated trihalomethanes and noniodinated disinfection byproducts during chloramination of algal organic matter extracted from Microcystis aeruginosa
期刊: Water Research
作者: Chao Liu, Mahmut S. Ersan, Michael J. Plewa, Gary Amy, Tanju Karanfil
摘要: The increasing occurrence of harmful algal blooms in surface waters may increase the input of algal organic matter (AOM) to the dissolved organic matter pool. The formation of iodinated trihalomethanes (I-THMs) and noniodinated disinfection byproducts (DBPs) in synthetic water containing AOM extracted from Microcystis aeruginosa was investigated under chloramination (preformed and in-situ formed chloramine, NH2Cl and Cl2-NH2Cl, respectively) and chlorination (Cl2) processes. AOM is much more favorable for iodine incorporation than natural organic matter (NOM). For example, the formation of I-THM from AOM is much higher than NOM isolate extracted from treated water (e.g., 3.5 times higher in the NH2Cl process), and thus higher iodine utilization and substitution factors from AOM were observed. Short contact time (2 min) chlorination in Cl2-NH2Cl process leading to the formation of halogenated intermediates favored I-THM formation, compared with NH2Cl process. However, further increasing chlorine contact time from 5 min to 24 h facilitated the conversion from iodide to iodate and thus I-THM formation decreased. Meanwhile, the formation of noniodinated THM4, haloacetonitriles (HANs), and haloacetaldehydes (HALs) increased. Factors including concentrations of AOM and bromide, pH and chlorine/nitrogen ratios influenced the formation of I-THMs and noniodinated DBPs. To evaluate the benefit of mitigating I-THM formation over the risk of noniodinated DBP formation, measured DBPs were weighed against their mammalian cell toxicity indexes. Increasing the chlorine exposure increased the calculated cytotoxicity based on concentrations of measured I-THMs and noniodinated DBPs since unregulated HANs and HALs were the controlling agents.
12643. 题目: Effects of carbon materials on the formation of disinfection byproducts during chlorination: Pore structure and functional groups
期刊: Water Research
作者: Min Zhang, Xuan Wang, Tingting Du, Huihui Wang, Huizhi Hao, Yingying Wang, Yao Li, Tianwei Hao
摘要: Release of carbon materials (CMs) into water and wastewater treatment systems occurs due to their increasing utilization as adsorbents for water treatment. When the CMs, mixed with natural organic matter (NOM), interact with disinfectants used during water treatment (e.g. chlorine), the released CMs can affect the formation of disinfection byproducts (DBPs). In this study, three common CMs were investigated to reveal their possible effects and the mechanisms of DBP formation during the chlorination of NOM. The experimental results indicate that DBPs generation decreased by 10–40% in the presence of CMs when Suwannee River humic acid (SRHA) was chlorinated. The adsorption of SRHA by CMs was hypothesized as the major cause for the DBPs inhibition. CMs could irreversibly adsorb DBP precursors in their mesopores through π-π bonding and hydrophobic effects. OH groups on the surface of CMs were shown to be critical for DBPs inhibition through linking with the OH or COOH groups on the surface of NOM via hydrogen bonding. The study also showed that water chemistry parameters, such as pH and salinity, can affect DBP formation by changing the adsorption of NOM onto CMs. With diverse NOM components, the presence of CMs resulted in decreased formation of trichloromethane from 57.1 μg/L to 23.8, 38.4, and 40.4 μg/L when coal-made activated carbon (CAC), wheat straw-made BC pyrolyzed at 300 °C (WSBC300), and multiwalled carbon nanotubes (MWCNTs), respectively, were added to surface water; and from 30.6 μg/L to 20.0, 19.2, and 13.2 μg/L when CAC, WSBC300, and MWCNTs, respectively, were added to wastewater.
12644. 题目: Deforestation releases old carbon
期刊: Nature Geoscience
作者: Alf Ekblad, David Bastviken
摘要: Deep soil carbon in tropical catchments can be rapidly mobilized to rivers upon land-use change to agriculture, suggest analyses of dissolved organic carbon. Such carbon stocks had been thought stable for millennia.
12645. 题目: Impact of different combinations of water treatment processes on the concentration of disinfection by-products and their precursors in swimming pool water
期刊: Environmental Science & Technology
作者: Bertram Skibinski, Stephan Uhlig, Pascal Müller, Irene Slavik, Wolfgang Uhl
摘要: To mitigate microbial activity in swimming pools and to ensure hygienic safety for bathers, pool systems have a recirculating water system ensuring continuous water treatment and disinfection by chlorination. A major drawback associated with the use of chlorine as disinfectant is its potential to react with precursor substances present in pool water to form harmful disinfection byproducts (DBPs). In this study, different combinations of conventional and advanced treatment processes were applied to lower the concentration of DBPs and their precursors in pool water by using a pilot-scale swimming pool model operated under reproducible and fully controlled conditions. The quality of the pool water was determined after stationary concentrations of dissolved organic carbon (DOC) were reached. The relative removal of DOC (Δccin–1) across the considered treatment trains ranged between 0.1 ± 2.9% and 7.70 ± 4.5%, where conventional water treatment (coagulation and sand filtration combined with granular activated carbon (GAC) filtration) was revealed to be the most effective. Microbial processes in the deeper, chlorine-free regions of the GAC filter have been found to play an important role in the degradation of organic substances. Almost all treatment combinations were capable of removing trihalomethanes to some degree and trichloramine and dichloroacetonitrile almost completely. However, the results demonstrated that effective removal of DBPs across the treatment train does not necessarily result in low DBP concentrations in the basin of a pool. This raises the importance of the DBP formation potential of the organic precursors, which has been shown to depend strongly on the treatment concept applied. Irrespective of the filtration technique employed, treatment combinations employing UV irradiation as a second treatment step revealed higher concentrations of volatile DBPs in the pool compared to those employing GAC filtration as a second treatment step. In the particular case of trichloramine, results confirm that its removal across the treatment train is not a feasible mitigation strategy because it cannot compensate for the fast formation in the basin.
12646. 题目: Stokes Shift and Specific Fluorescence as Potential Indicators of Organic Matter Hydrophobicity and Molecular Weight in Membrane Bioreactors
期刊: Environmental Science & Technology
作者: Kang Xiao, Bingjun Han, Jianyu Sun, Jihua Tan, Jinlan Yu, Shuai Liang, Yuexiao Shen, Xia Huang
摘要: Hydrophobicity and molecular weight (MW) are two fundamental properties of dissolved organic matter (DOM) in wastewater treatment systems. This study proposes fluorescence Stokes shift and specific fluorescence intensity (SFI) as novel indicators of hydrophobicity and MW. These indicators originate from the energy gap and photon efficiency of the fluorescence process and can be readily extracted from a fluorescence excitation–emission matrix (EEM). The statistical linkages between these indicators and hydrophobicity/MW were explored through investigation of DOM across 10 full-scale membrane bioreactors treating municipal wastewater. Stokes shift was found to exhibit a general rule among the hydrophobicity components in the order of hydrophilic substances (HIS) < hydrophobic acids (HOA) < hydrophobic bases (HOB). The Stokes shift of 1.2 μm–1 is a critical border, above which the relative fluorescence correlated significantly with the HOA-related content (Pearson’s r = 0.8). With regard to MW distribution (<1, 1–10, 10–100, and >100 kDa), SFI was found to be the most sensitive to the change of MW of <1 kDa proportion, especially at the excitation/emission wavelengths of 200–320/310–550 nm (r > 0.9). Hydrophobicity-related π conjugation and MW-dependent light exposure might be responsible for the correlations. These fluorescence indicators may be useful for convenient monitoring of DOM in wastewater treatment systems.
12647. 题目: Mobilization of aged and biolabile soil carbon by tropical deforestation
期刊: Nature Geoscience
作者: Travis W. Drake, Kristof Van Oost, Matti Barthel, Marijn Bauters, Alison M. Hoyt, David C. Podgorski, Johan Six, Pascal Boeckx, Susan E. Trumbore, Landry Cizungu Ntaboba, Robert G. M. Spencer
摘要: In the mostly pristine Congo Basin, agricultural land-use change has intensified in recent years. One potential and understudied consequence of this deforestation and conversion to agriculture is the mobilization and loss of organic matter from soils to rivers as dissolved organic matter. Here, we quantify and characterize dissolved organic matter sampled from 19 catchments of varying deforestation extent near Lake Kivu over a two-week period during the wet season. Dissolved organic carbon from deforested, agriculturally dominated catchments was older (14C age: ~1.5 kyr) and more biolabile than from pristine forest catchments. Ultrahigh-resolution mass spectrometry revealed that this aged organic matter from deforested catchments was energy rich and chemodiverse, with higher proportions of nitrogen- and sulfur-containing formulae. Given the molecular composition and biolability, we suggest that organic matter from deforested landscapes is preferentially respired upon disturbance, resulting in elevated in-stream concentrations of carbon dioxide. We estimate that while deforestation reduces the overall flux of dissolved organic carbon by approximately 56%, it does not significantly change the yield of biolabile dissolved organic carbon. Ultimately, the exposure of deeper soil horizons through deforestation and agricultural expansion releases old, previously stable, and biolabile soil organic carbon into the modern carbon cycle via the aquatic pathway.
12648. 题目: Seasonal changes in the chemical composition and reactivity of dissolved organic matter at the land-ocean interface of a subtropical river
期刊: Environmental Science and Pollution Research
作者: Liyang Yang, Qiong Cheng, Wan-E Zhuang, Hui Wang, Wei Chen
摘要: Dissolved organic matter (DOM) is a critical component in aquatic ecosystems, yet its seasonal variability and reactivity remain not well constrained. These were investigated at the land-ocean interface of a subtropical river (Minjiang River, SE China), using absorption and fluorescence spectroscopy. The annual export flux of dissolved organic carbon (DOC) from the Minjiang River (5.48 × 1010 g year−1) was highest among the rivers adjacent to the Taiwan Strait, with 72% occurring in spring and summer. The freshwater absorption coefficient a280, DOC-specific UV absorbance SUVA254 and humification index HIX were higher, while the spectral slope S275–295 and biological index BIX were lower in summer than in winter. This suggests intensified export of terrestrial aromatic and high molecular weight constituents in the rainy summer season. Six fluorescent components were identified from 428 samples, including humic-like C1–C3, tryptophan-like C4 and C6, and tyrosine-like C5. The freshwater levels of four components (C1, C2, C4, and C6) were lower while that of C5 was higher in the wet season than in the dry season, suggesting contrasting seasonal variations of different constituents. Laboratory experiments were performed to assess the effects of photochemical and microbial degradation on DOM. Photo-degradation removed chromophoric and fluorescent DOM (CDOM and FDOM) effectively, which was stronger (i) for high molecular weight/humic constituents and (ii) during summer under higher solar radiation. Microbial degradation under laboratory controlled conditions generally showed little effect on DOC, and had smaller impact on CDOM and FDOM in winter than in summer. Overall, this study showed notable seasonal changes in the chemical composition and reactivity of DOM at the land-ocean interface, and demonstrated the significant effects of photo-degradation.
12649. 题目: Peatland Volume Mapping Over Resistive Substrates With Airborne Electromagnetic Technology
期刊: Geophysical Research Letters
作者: Sonia Silvestri, Craig W. Christensen, Asgeir O. K. Lysdahl, Helgard Anschütz, Andreas A. Pfaffhuber, Andrea Viezzoli
摘要: Despite the importance of peatlands as carbon reservoirs, a reliable methodology for the detection of peat volumes at regional scale is still missing. In this study we explore for the first time the use of airborne electromagnetic (AEM) to detect and quantify peat thickness and extension of two bogs located in Norway, where peat lays over resistive bedrock. Our results show that when calibrated using a small amount of field measurements, AEM can successfully detect peat volume even in less ideal conditions, that is, relatively resistive peat over resistive substrata. We expect the performance of AEM to increase significantly in presence of a conductive substratum without need of calibration with field data. The organic carbon content retrieved from field surveys and laboratory analyses combined with the 3‐D model of the peat extracted from AEM allowed us to quantify the total organic carbon of the selected bogs, hence assessing the carbon pool.
12650. 题目: Impact of prolonged rice cultivation on coupling relationship among C, Fe, and Fe-reducing bacteria over a 1000-year paddy soil chronosequence
期刊: Biology and Fertility of Soils
作者: Yalong Liu, Yuqi Dong, Tida Ge, Qaiser Hussain, Ping Wang, Jingkuan Wang, Yong Li, Georg Guggenberger, Jinshui Wu
摘要: Long-term soil chronosequences are valuable model systems for investigating pedogenesis and investigating the process of element coupling. Here, we assessed the coupling relationships among C, Fe, and Fe-reducing bacteria (Anaeromyxobacter, Geobacter, and Shewanella) in a paddy soil chronosequence of approximately 50 to 1000 years. Soils of the chronosequence originated from tidal marsh under nearly identical landscape and climate conditions. During 1000 years of rice cultivation, soil organic carbon (SOC) contents in surface horizons (0–20 cm) increased from 10.4 to 21.8 g kg−1. In contrast, total Fe contents declined from 59.6 to 45.1 g kg−1 during the initial 50 years of paddy rice cultivation and then further decreased at a low rate of 0.004 g kg−1 soil year−1 (equivalent to 10 kg ha−1 soil year−1). Organically complexed Fe oxides (Fep) increased from 219 to 642 mg g−1 with increasing time of pedogenesis, but free total Fe oxides (Fed) and amorphous Fe oxides (Feo) declined at early stage of soil development, followed by a slow accumulation at later stages of the chronosequence. Gene copy numbers of Anaeromyxobacter and Geobacter increased from 4.6 × 105 and 3.6 × 106 copies g−1 to 3.8 × 107 and 3.6 × 107 copies g−1 dry soil with continuous paddy rice cultivation, while concurrently Shewanella gene abundance decreased gradually from 4.5 × 105 to 9.3 × 104 copies g−1 dry soil. Using structural equation modeling (SEM), different coupling relationships were observed among C, Fe, and Fe-reducing bacteria for the first 300 years of paddy chronosequence and thereafter. Overall, all Fe-reducing bacteria did not show consistent variation. With the stable microbial community and iron oxide fractions, the microbially mediated dissimilatory coupling relationship between C and Fe becomes simple during 1000 years of paddy soil development.
12651. 题目: Effect of NaCl on nitrification performance and extracellular polymeric substance characteristic of Klebsiella sp. TN-10
期刊: Environmental Science and Pollution Research
作者: Dan Li, Yao Jin, Jun Huang, Chongde Wu
摘要: Klebsiella sp. TN-10, isolated from tannery wastewater, exhibited excellent nitrification ability cultivated in media with NaCl contents ranging from 0 to 35 g/L. Analysis of antioxidative enzyme activities of TN-10 stressed by NaCl showed that the stain produced more superoxide dismutase (SOD) and catalase (CAT) to fight against salt stress conditions. Moreover, the auto-aggregation index of TN-10 decreased with the increment of NaCl contents, which is consistent with results of zeta potentials. Extinction-emission matrix (EEM) and Fourier-transform infrared (FT-IR) spectrum analyses showed that the compositions of extracellular polymeric substances (EPS) by TN-10 after NaCl shock were similar. Furthermore, proteins and polysaccharides were the main components of EPS, and the contents were greatly influenced by salinity. Then, circular dichroism (CD) spectrum was used to calculate the contents of each protein secondary structure. These results provided further insights into the knowledge of nitrification characteristics, auto-aggregation performance, and EPS compositions of TN-10 during NaCl shock.
12652. 题目: Soil Organic Carbon Stocks across Hydrologic Schemes in Freshwater Wetlands of the Chi River Basin, Northeast Thailand
作者: Utain Chanlabut, Bhuvadol Gomontean, Akeapot Srifa
摘要: The role of freshwater wetlands as soil organic carbon (SOC) stocks has been well documented for temperate regions but less is well known in tropical regions. In this study, SOC stocks were compared within three different hydrologic schemes in six freshwater wetlands of the Chi River Basin in tropical Northeast Thailand. The SOC concentration exhibited a decrease with increased depth and significantly differed among the hydrologic schemes (9.15 ± 0.84, 8.66 ± 0.67, and 5.53 ± 0.49 g C kg−1 for the intermittently flooded zone, saturated zone, and permanently flooded zone, respectively). The SOC stocks at 50 cm depth were significantly highest in the intermittently flooded zone (69.05 ± 10.86 Mg C ha−1), followed by the saturated zone and the permanently flooded zone (66.06 ± 7.75 and 43.39 ± 5.83 Mg C ha−1, respectively). Total SOC stocks among wetlands ranged from 123.30 to 291.29 Mg C ha−1. These differences indicate the spatial variability of SOC within wetland locations and among wetlands. The study demonstrates an important ecosystem service of these wetlands as carbon stocks, and it will be useful for management and policy planning of the wetlands in the Chi River Basin.
12653. 题目: Accelerating waste sludge hydrolysis with alkyl polyglucose pretreatment coupled with biological process of thermophilic bacteria: Hydrolytic enzyme activity and organic matters transformation
期刊: Journal of Environmental Management
作者: Pengtao Gao, Liang Guo, Jian Sun, Yi Wang, Zonglian She, Mengchun Gao, Yangguo Zhao
摘要: A novel pretreatment method combining thermophilic bacteria (TB) with alkyl polyglucose (APG) was employed to pretreat waste sludge for enhancing the sludge hydrolysis. TB combined with APG pretreatment was effective in the releasing of soluble chemical oxygen demand (SCOD), protein and carbohydrate in extracellular polymeric substances (EPS) when the dosage of APG was below 0.1 g/g TSS. The enhancement of SCOD, carbohydrates and protein in dissolved organic matter (DOM) was promoted by the synthetic effect of APG and TB, which provides more carbon and energy source to the subsequent biochemical processes in sludge digestion. Excitation-emission matrix (EEM) fluorescence spectroscopy revealed that the combined pretreatment was beneficial for the decrease of non-biodegradable materials and the increase of biodegradable materials in DOM, resulting in the enhancement of the biodegradation of waste sludge. The combined use of TB and 0.4 g/g TSS APG achieved the maximal activities of protease (1.8) and α-glucosidase (1.9), and the activities of protease and α-glucosidase were positively correlated to the dosage of APG. The combined pretreatment was advantageous for the sludge reduction and sludge stabilization.
12654. 题目: Emergent properties of organic matter decomposition by soil enzymes
期刊: Soil Biology and Biochemistry
作者: Bin Wang, Steven D. Allison
摘要: Plant residues and soil organic matter are predominantly decomposed by exoenzymes. Many soil carbon models now represent enzymatic decomposition, but the mathematical formulation of this process has been debated over the last 15 years. Some models apply the traditional “forward” Michaelis-Menten equation to represent enzyme kinetics, whereas others apply the “reverse” Michaelis-Menten equation, which assumes that kinetic rates saturate at high enzyme concentrations. Recently the equilibrium chemistry approximation (ECA) has been proposed as an alternative to both Michaelis-Menten formulations. However, because of methodological limitations, in-situ enzyme kinetics—especially in the context of soil system heterogeneity—have been difficult to verify experimentally. Therefore, the overarching goal of our study was to evaluate different enzyme kinetic formulations using model-based evidence at microbial to ecosystem scales. We used a spatially explicit individual- and trait-based microbial model, DEMENT, to circumvent methodological challenges. Although DEMENT assumes forward Michaelis-Menten kinetics at local scales, at the grid scale we found saturating relationships between degradation rate and both substrate concentrations and enzyme concentrations that fit the forward and reverse Michaelis-Menten equations, respectively, at specific successional stages during decomposition. Although forward and reverse Michaelis-Menten equations emerged under some conditions, only the ECA adequately represented decay rates emerging from the spatial-temporal variation in substrate and enzyme concentrations throughout the decomposition process. Our results support a more widespread adoption of the ECA equation in soil biogeochemical modelling at ecosystem scales.
12655. 题目: Alleviation of atrazine toxicity to maize seedlings grown in soils with amendment of biochar derived from wheat under different temperatures
期刊: Environmental Science and Pollution Research
作者: Yifan Wang, Yi Tang, Qun Jiang, Xinyuan Zhang, Weiling Xie, Ruizhen Li, Wenzhu Liu, Jiaming Kang, Ying Zhang
摘要: The effects of different biotransformation temperatures (250, 550, and 850 °C) and different dose (0–1%) of biochar on the physiological characteristics of maize seedlings under the stress of atrazine were studied. The results show that atrazine significantly inhibits the growth of maize seedlings, while biochar can alleviate the toxicity of atrazine to seedlings. Compared with the low temperature of biochar, the addition of BC850, the germination rate of maize was significantly increased. The biochars prepared at higher temperatures and adding 1% dose could significantly increase the plant height, while the effect of biochar on root growth of maize seedlings was not significant. According to the data, with the increase of biochar application, the accumulation of atrazine in maize leaves and roots gradually decreased. At the maximum application rate of 1%, the content of atrazine in maize leaves decreased by 58.94%, 60.70%, and 62.75%. The content of atrazine in maize roots decreased by 52.93%, 54.57%, and 55.42%, respectively. Meanwhile, the addition of biochar could slightly increase the chlorophyll content, but the change was not significant statistically, while the content of chlorophyll b increases with the application amount. The content of malondialdehyde (MDA) in roots and leaves decreased first and the increased with the dose of biochar from 0 to 1%. Compared with the atrazine treatment, the content of MDA in leaves and roots decreased significantly, and the lipid peroxidation of maize significantly decreased. With the addition of three kinds of biochar, the soluble content of plant tissues increased gradually, BC550 biochar has the most noticeable remediation effect. Given the toxicity of atrazine in soil, the quality and yield of agricultural products, and the potential health risks to human beings, biochar can be the soil remediation product.
12656. 题目: Increasing organic carbon biolability with depth in yedoma permafrost: ramifications for future climate change
期刊: Journal of Geophysical Research: Biogeosciences
作者: J.K. Heslop, M. Winkel, K.M. Walter Anthony, R.G.M. Spencer, D.C. Podgorski, P. Zito, A. Kholodov, M. Zhang, S. Liebner
摘要: Permafrost thaw subjects previously frozen organic carbon (OC) to microbial decomposition, generating the greenhouse gases (GHG) carbon dioxide (CO2) and methane (CH4) and fueling a positive climate feedback. Over one‐quarter of permafrost OC is stored in deep, ice‐rich Pleistocene‐aged yedoma permafrost deposits. We used a combination of anaerobic incubations, microbial sequencing, and ultrahigh‐resolution mass spectrometry to show yedoma OC biolability increases with depth along a 12‐m yedoma profile. In incubations at 3 °C and 13 °C, GHG production per unit OC at 12 m depth versus 1.3 m depth was 4.6 and 20.5 times greater, respectively. Bacterial diversity decreased with depth and we detected methanogens at all our sampled depths, suggesting that in situ microbial communities are equipped to metabolize thawed OC into CH4. We concurrently observed an increase in the relative abundance of reduced, saturated OC compounds, which corresponded to high proportions of C mineralization and positively correlated with anaerobic GHG production potentials and higher proportions of OC being mineralized as CH4. Taking into account the higher global warming potential (GWP) of CH4 compared to CO2, thawed yedoma sediments in our study had 2 times higher GWP at 12 m depth versus 9.0 m depth at 3 °C and 15 times higher GWP at 13 °C. Considering yedoma is vulnerable to processes that thaw deep OC, our findings imply it is important to account for this increasing GHG production and GWP with depth to better understand the disproportionate impact of yedoma on the magnitude of the permafrost carbon feedback.
12657. 题目: Mineralogy dictates the initial mechanism of microbial necromass association
期刊: Geochimica et Cosmochimica Acta
作者: Courtney A. Creamer, Andrea L. Foster, Corey Lawrence, Jack McFarland, Marjorie Schulz, Mark P. Waldrop
摘要: Soil organic matter (SOM) improves soil fertility and mitigates disturbance related to climate and land use change. Microbial necromass (the accumulated cellular residues of microorganisms) comprises the majority of soil C, yet the formation and persistence of necromass in relation to mineralogy is poorly understood. We tested whether soil minerals had different microbial necromass association mechanisms. Specifically, we tested whether microbial necromass directly sorbed to mineral surfaces or was consumed by live microorganisms prior to mineral association. Applying Raman microspectroscopy with 13C enriched microbial necromass to quantify microbe-mineral interactions, we show that mineralogy alters the initial mechanism of microbial necromass association. In the presence of K-feldspar (lower abiotic C preservation potential), microbial necromass required assimilation by live microorganisms for mineral retention. In contrast, with amorphous aluminum hydroxide (higher abiotic C preservation potential) microbial necromass was retained predominately through abiotic sorption, and was subsequently protected from microbial decomposition. Despite different mechanisms, both minerals retained similar quantities of microbial necromass under biotic conditions. Mineralogy determined not only the quantity of mineral-associated C, but the distinct pathway of microbial necromass association. These findings show the utility of Raman microspectroscopy as a technique to study microbe-mineral interactions, and imply that heterogeneity in mineral-organic interactions could result in gradients of organic matter stability.
12658. 题目: Co-occurrence of geogenic and anthropogenic contaminants in groundwater from Rajasthan, India
期刊: Science of The Total Environment
作者: Rachel Coyte, Anjali Singh, Kirin Emlet Furst, William Mitch, Avner Vengosh
摘要: Northwest India suffers from severe water scarcity issues due to a combination of over-exploitation and climate effects. Along with concerns over water availability, endemic water quality issues are critical and affect the usability of available water and potential human health risks. Here we present data from 243 groundwater wells, representing nine aquifer lithologies in 4 climate regions that were collected from the Northwestern Indian state of Rajasthan. Rajasthan is India's largest state by area, and has a significant groundwater reliant population due to a general lack of surface water accessibility. We show that the groundwater, including water that is used for drinking without any treatment, contains multiple inorganic contaminants in levels that exceed both Indian and World Health Organization (WHO) drinking water guidelines. The most egregious of these violations were for fluoride, nitrate, and uranium; 76% of all water samples in this study had contaminants levels that exceed the WHO guidelines for at least one of these species. In addition, we show that much of the groundwater contains high concentrations of dissolved organic carbon (DOC) and halides, both of which are risk factors for the formation of disinfectant byproducts in waters that are treated with chemical disinfectants such as chlorine. By using geochemical and isotopic (oxygen, hydrogen, carbon, strontium, and boron isotopes) data, we show that the water quality issues derive from both geogenic (evapotranspiration, water-rock interactions) and anthropogenic (agriculture, domestic sewage) sources, though in some cases anthropogenic activities, such as infiltration of organic- and nitrate-rich water, may contribute to the persistence and enhanced mobilization of geogenic contaminants. The processes affecting Rajasthan's groundwater quality are common in many other worldwide arid areas, and the lessons learned from evaluation of the mechanisms that affect the groundwater quality are universal and should be applied for other parts of the world.
12659. 题目: Preparation of biochar via pyrolysis at laboratory and pilot scales to remove antibiotics and immobilize heavy metals in livestock feces
期刊: Journal of Soils and Sediments
作者: Renqiang Tian, Chunxing Li, Shengyu Xie, Futian You, Zhihong Cao, Zhihong Xu, Guangwei Yu, Yin Wang
摘要: Purpose: Pyrolysis is the most effective method to completely remove antibiotics and immobilize heavy metals from livestock feces. However, the effect of the pyrolysis temperature on antibiotic removal at laboratory and pilot scales is still unclear. Materials and methods: The pyrolysis technique was used to convert pig manure (PM) and chicken manure (CM) into biochar at different temperatures from 300 to 700 °C in a laboratory-scale test. The performance of antibiotic removal and heavy metal immobilization in livestock feces was studied, and the optimal temperature of 600 °C was selected for the pilot-scale verification. Results and discussion: The results showed that the removal of the antibiotics tylosin (TYL), tetracycline (TC), chlortetracycline (CTC), doxycycline (DOXY), sulfamethazine (SMZ), sulfadiazine (SDZ), and sulfamethoxazole (SMX) was satisfactory, and all seven typical antibiotics were completely removed at 600 °C. In addition, the heavy metals zinc (Zn), copper (Cu), chromium (Cr), lead (Pb), nickel (Ni), cadmium (Cd), and arsenic (As) in the manure were well immobilized, and higher temperatures (above 600 °C) favored their immobilization. The results of heavy metal immobilization and antibiotic removal of the pilot-scale test were similar to those of the laboratory-scale test. Conclusions: Laboratory- and pilot-scale experiments showed that the current study provided a safe method and technology for treating and recycling livestock feces into biochar via the pyrolysis process.
12660. 题目: Toxicity of aluminum to Ceriodaphnia dubia in low-hardness waters as affected by natural dissolved organic matter
期刊: Environmental Toxicology and Chemistry
作者: John Besser, Danielle Cleveland, Chris Ivey, Laura Blake
摘要: We conducted a series of 7‐d toxicity tests with Ceriodaphnia dubia in dilutions of low‐hardness natural waters, which contained dissolved organic carbon (DOC) concentrations up to 10 mg/L. Stream waters were mixed with well water to achieve 2 target hardness levels (20 and 35 mg/L) and 4 DOC concentrations. Tests with Al‐spiked waters were conducted in a controlled CO2 atmosphere to maintain pH in the range, 6.0‐6.5. Results were used to estimate effect concentrations for survival and reproduction, expressed as total (unfiltered) Al concentrations. There were small differences in total‐Al thresholds between waters with 20 and 35 mg/L hardness, but effect concentrations for C. dubia survival (LC50) and reproduction (EC20) increased log‐linearly with increasing DOC concentrations in the range, 0.3 mg/L to 6 mg/L. Slopes of these regressions were similar to slopes from data used to revise the USEPA water quality criterion for Al, but toxic effects occurred in the present study at total‐Al concentrations 8‐ to 10‐fold greater than toxicity values used for criteria development. This difference probably reflects the long equilibration (aging) times of Al test waters used in the present study (up to 192 hr) compared to very short (3 hr) equilibration times in other studies used for criteria development. These results confirm the importance of DOC as a control on Al toxicity in low‐hardness waters, but they also demonstrate that total‐Al concentrations are not predictive of Al toxicity, except under defined water quality (pH, hardness, DOC) and exposure conditions (e.g., aging of test waters).