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25381. 题目: Liquid and solids separation for target resource recovery from thermal hydrolyzed sludge
文章编号: N20010801
期刊: Water Research
作者: Dan Lu, Dan Wu, Tingting Qian, Jiankai Jiang, Shenbin Cao, Yan Zhou
更新时间: 2020-01-08
摘要: This study proposed an integrated process for biogas generation and biochar production from thermal hydrolysis pretreated sludge (THP sludge). In this study, the liquid and solids fractions of THP sludge were separately processed for the first time. The liquid fraction of THP sludge (THP-L) reached the biodegradability (262.6 ± 5.1 mL CH₄/g tCOD_feed) on the 15th day during anaerobic treatment, while the solids fraction of THP sludge (THP-S) only contributed 31.0% to the total methane production and required more than 30 days digestion time. We investigated the feasibility to convert THP-S into biochar to realize the higher value of the solids fraction. The results prove the produced biochar can be used as slow-release fertilizer. Preliminary energy analysis was performed to evaluate the energy efficiency of the integrated approach, namely, methane generation from THP-L coupled with biochar production from THP-S. The process realized energy surplus of 0.81 MWh/tonne dry sludge. In addition, THP-L digested sludge showed better dewaterability, lower yield stress and reduced viscosity during digestion. The proposed new sludge treatment process therefore has lower operating cost and higher value returns.
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25382. 题目: A synthesis of blue carbon stocks, sources and accumulation rates in eelgrass (Zostera marina) meadows in the Northeast Pacific
文章编号: N20010707
期刊: Global Biogeochemical Cycles
作者: C. Prentice, K.L. Poppe, M. Lutz, E. Murray, T.A. Stephens, A. Spooner, M. Hessing‐Lewis, R. Sanders‐Smith, J.M. Rybczyk, J. Apple, F.T. Short, J. Gaeckle, A. Helms, C. Mattson, W.W. Raymond, T. Klinger
更新时间: 2020-01-07
摘要: There is increasing urgency to implement climate change mitigation strategies that enhance greenhouse gas removal from the atmosphere and reduce carbon dioxide (CO₂) emissions. Recently, coastal “blue carbon” habitats ‐ mangroves, salt marshes, and seagrass meadows ‐ have received attention for their ability to capture CO₂ and store organic carbon (OC), primarily in their sediments. Across habitat types and regions, however, information about the sequestration rates and sources of carbon to local sediments remains sparse. Here, we compiled recently obtained estimates of sediment OC stocks and sequestration rates from 139 cores collected from temperate seagrass (Zostera marina) meadows in Alaska, British Columbia, Washington, and Oregon. Across all cores sediment OC content averaged 0.75%. Organic carbon stocks in the top 25 cm and one meter of the sediment averaged 1,846 and 7,168 g OC m^‐2, respectively. Carbon sequestration rates ranged from 4.6 to 93.0 g OC m^‐2 yr^‐1 and averaged 24.8 g OC m^‐2 yr^‐1. Isotopic data from this region suggest that OC in the sediments is largely from non‐eelgrass sources. In general, these values are comparable to those from other temperate Z. marina meadows, but significantly lower than previously reported values for seagrasses globally. These results further highlight the need for local and species‐level quantification of blue carbon parameters. While temperate eelgrass meadows may not sequester and store as much carbon as seagrass meadows elsewhere, climate policy incentives should still be implemented to protect existing sediment carbon stocks and the other critical ecosystem services associated with eelgrass habitats.

25383. 题目: Biochar as potential precursors for activated carbon production: parametric analysis and multi-response optimization
文章编号: N20010706
期刊: Environmental Science and Pollution Research
作者: Nor Adilla Rashidi, Suzana Yusup
更新时间: 2020-01-07
摘要: Accelerating greenhouse gas emission particularly carbon dioxide (CO₂) in the atmosphere has become a major concern. Adsorption process has been proposed as a promising technology for CO₂ adsorption from flue gas, and the carbonaceous adsorbent is a potential candidate for CO₂ adsorption at atmospheric pressure and ambient temperature. Biochar derived from palm kernel shell waste was applied as a potential precursor for activated carbon production. This research study employed the response surface methodology coupled with Box-Behnken design to optimize the parameters involved in producing exceptional activated carbon with high yield (Y₁) and CO₂ adsorptive characteristics (Y₂). Specifically, parameters studied include the activation temperature (750–950 °C), holding time (60–120 min), and CO₂ flow rate (150–450 mL/min). The activated carbon at the optimum conditions was characterized using various analytical instruments, including elemental analyzer, nitrogen (N₂) physisorption analyzer, and field emission scanning electron microscopy. Overall, utilization of biochar as the activated carbon precursor is practical compared with the traditional non-renewable materials, due to its cost efficiencies and it being more environment-friendly ensuring process sustainability. Besides, this research study that incorporates physical activation with CO₂ as the activating agent is attractive, because it directly promotes CO₂ utilization and capture, in addition to the absence of any chemicals that may result in the secondary pollution problems.

25384. 题目: Biochar/iron (BC/Fe) composites for soil and groundwater remediation: Synthesis, applications, and mechanisms
文章编号: N20010705
期刊: Chemosphere
作者: Honghong Lyu, Jingchun Tang, Mengke Cui, Bin Gao, Boxiong Shen
更新时间: 2020-01-07
摘要: Biochar/iron (BC/Fe) composites, such as nano zero-valent iron (nZVI)/BC, iron sulfide/BC, and iron oxide/BC, have been developed and applied to deal with various contaminants owing to their excellent physicochemical properties. This work summarizes the progress in the preparation of BC/Fe composites, the properties and applications of BC/Fe, and the mechanism of the synergistic effect between Fe and BC in the composites. Various methods, including pyrolysis, hydrothermal carbonization, fractional precipitation, and ball milling, have been used to synthesize BC/Fe composites. In addition, the introduction of stabilizers, such as carboxymethyl cellulose (CMC), in the fractional precipitation process further prevents the agglomeration of Fe particles, which enhances the stability and fluidity of the resultant composites to facilitate the application of the composites in soil and water remediation. The application of BC/Fe composites in water and soil remediation is discussed in three aspects based on the interaction mechanisms, namely adsorption, reduction, and oxidation. Overall, the composites showed the synergistic effect of BC and Fe owing to the combination of the specific properties of Fe, such as reduction, catalysis, and magnetism, which can enhance the properties of BC with a larger surface area, abundant functional groups, and increased electron transfer efficiency. This review systemically summarizes the recent developments in BC/Fe composites to maximize the efficiency of BC/Fe application in soil and groundwater remediation. Key challenges and further research needs are also suggested.
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25385. 题目: Insights into the effects of long-term biochar loading on water-soluble organic matter in soil: Implications for the vertical co-migration of heavy metals
文章编号: N20010704
期刊: Environment International
作者: Qinya Fan, Jianxiong Sun, Guixiang Quan, Jinlong Yan, Jianhua Gao, Xinqing Zou, Liqiang Cui
更新时间: 2020-01-07
摘要: Although interest in biochar remediation is growing, the effects of long-term biochar loading on soil environments have not been clearly confirmed. The contents and characteristics of water-soluble organic matter (WSOM) from soils after eight years of biochar remediation were investigated, and the vertical co-migration of heavy metals controlled by interactions between WSOM, soil and contaminants were also analyzed. The results showed that biochar-leaching WSOM featured high aromaticity. Fluorescence excitation–emission matrix (EEM) spectrophotometry was employed, and three primary components, including fulvic-acid-like (FA_-like), tryptophan, and humic-acid-like (HA_-like) compounds, were identified in the EEM spectra via parallel factor analysis models. With increasing biochar loading, FA_-like and HA_-like greatly increased, but tryptophan showed a weak response. Furthermore, the WSOM was freeze dried and analyzed with Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, and the results demonstrated that the BC treatment increased oxygen-containing functional groups and enhanced the complexation capability of the WSOM. Finally, the Cd and Pb concentrations in the WSOM were investigated, and Cd was found to decrease in top-soil WSOM with added BC because of increased complexation, but the Pb content increased because exchangeable and carbonate Pb converted into organic Pb. Further, the Cd and Pb concentrations decreased in sub-soil WSOM. These findings suggest that more efforts should be devoted to studying the effects of long-term biochar loading on soil environments.

25386. 题目: Characterisation of the impact of dissolved organic matter on iron, manganese, and arsenic mobilisation during bank filtration
文章编号: N20010703
期刊: Journal of Environmental Management
作者: Ahmed Abdelrady, Saroj Sharma, Ahmed Sefelnasr, Maria Kennedy
更新时间: 2020-01-07
摘要: Bank filtration (BF) has been used for many years as an economical technique for providing high-quality drinking water. However, under anaerobic conditions, the aquifer release of undesirable metal(loid)s, such as iron manganese, and arsenic, reduces the bank filtrate quality and thus restricts the application of this technique. This study investigates the impact of the organic-matter composition of source water on the mobilisation of Fe, Mn, and As during the anaerobic BF process. A laboratory-scale column study was conducted at a controlled-temperature (30 ± 2 °C) using different feed water sources. The organic matter characteristics of the feed water were elucidated using excitation-emission spectroscopy techniques integrated with parallel factor framework clustering analysis (PFFCA) model. The experiment was performed at redox conditions between 66 mv and −185 mv. Moreover, batch studies were implemented to study the effect of natural organic matter type (humic, fulvic and tyrosine) and concentration on the mobilisation of the selected metal(loids). The laboratory experiments demonstrated that the mobilisation of Fe, Mn and As during the BF are varied with the organic water concentration and composition of the source water. The fluorescence results revealed that terrestrial and condensed structure humic compounds are more capable to release Fe into the filtrate water. In contrast, Mn exhibited an equal tendency of mobilisation towards all the humic compounds regardless of its origin and structure. However, at a humic concentration higher than 5 mg-C/L, Mn showed more affinity towards lower molecular weight humic compounds. Arsenic was found to be the least impacted by the alteration in the source water organic matter composition; its mobilisation was highly correlated with iron releasing process. On the other hand, the biodegradable organic matter at high concentration (>10 mg-C/L) was found to be highly effective to turn the infiltration area into Fe-reducing environment and thereby elevating Fe and As concentrations in the pumped water. In conclusion, this study revealed that the DOM composition and concentration of the raw water could play an important role in the mobilisation of metal(loids) during the BF processes.

25387. 题目: Regeneration and reuse of microbial extracellular polymers immobilised on a bed column for heavy metal recovery
文章编号: N20010702
期刊: Water Research
作者: Victor Ajao, Kang Nam, Paraschos Chatzopoulos, Evan Spruijt, Harry Bruning, Huub Rijnaarts, Hardy Temmink
更新时间: 2020-01-07
摘要: Microbial extracellular polymeric substances (EPS) have gained increasing attention for various water treatment applications. In this study, EPS produced from nitrogen-limited glycerol/ethanol-rich wastewater were used to recover Cu²⁺ and Pb²⁺ from aqueous solutions. Continuous flow-through tests were conducted on a column packed with silica gel coated with polyethyleneimine, to which EPS were irreversibly attached as shown by optical reflectometry. These immobilised EPS excellently adsorbed Cu²⁺ and Pb²⁺, with 99.9% of influent metal adsorbed before the breakthrough points. Metal desorption was achieved with 0.1M HCl, with an average recovery of 86% for Cu²⁺ and 90% recovery for Pb²⁺. For the first time, we successfully showed the possibility to regenerate and reuse the immobilised EPS for five adsorption-desorption cycles (using Cu²⁺ as an example) with no reduction in the adsorbed amount at the breakthrough point (q_bp). Based on the mass balance of the associated metal ions participating in the adsorption process, ion exchange was identified as the major mechanism responsible for Cu²⁺ and Pb²⁺ adsorption by EPS. The results demonstrate the potential of wastewater-produced EPS as an attractive and perhaps, cost-effective biosorbent for heavy metal removal (to trace effluent concentrations) and recovery (86–99%).
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25388. 题目: Impact of DOM source and character on the degradation of primidone by UV/chlorine: Reaction kinetics and disinfection by-product formation
文章编号: N20010701
期刊: Water Research
作者: Yuru Wang, Marie Couet, Leonardo Gutierrez, Sébastien Allard, Jean-Philippe Croué
更新时间: 2020-01-07
摘要: The presence of Dissolved Organic Matter (DOM) can exert a strong influence on the effectiveness of the UV/chlorine process. This study examined the impact of five DOM isolates with different characteristics on the degradation kinetics of model contaminant primidone (PM) during UV/chlorine treatment. The formation of Disinfection By-Products (DBPs) from DOM after 15-min UV/chlorine treatment followed by 24 h chlorination was investigated and compared with chlorination alone. The use of chemical probes and radical scavengers revealed that ^•OH and ClO• were the main radical species responsible for the loss of PM at acidic and alkaline conditions, respectively. All tested DOM isolates significantly inhibited the decay of PM. A strong negative correlation (>0.93) was observed between the decay rate constants of PM and SUVA of DOM isolates, except for EfOM isolate, which induced the strongest inhibitory effect due to its higher abundance in sulfur-containing functional groups (i.e., sink of ^•OH/Cl^• radicals). Compared with chlorination, the formation of Adsorbable Organic Chlorine (AOCl) and Trichloromethane (TCM) during the UV/Chlorine process was enhanced and hindered for low SUVA isolates and high SUVA DOM, respectively. However, Dichloroacetonitrile (DCAN) formation was generally lower for all isolates except for Ribou Reservoir DOM at pH 8.4 because of its high reactive nitrogenous DBP precursors at caustic conditions. However, when normalized to the chlorine consumed, the UV/Chlorine process always led to a lower DBPs formation compared with chlorination alone.
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25389. 题目: N 2 O and CO 2 emissions from a dryland wheat cropping system with long-term N fertilization and their relationships with soil C, N, and bacterial community
文章编号: N20010601
期刊: Environmental Science and Pollution Research
作者: Weihong Qiu, Jinshan Liu, Baoyan Li, Zhaohui Wang
更新时间: 2020-01-06
摘要: In dryland cropping ecosystems, nitrogen (N) fertilization causes changes in soil biochemical cycling and influences the crop biomass and grain yield. Based on a long-term field experiment involving three N rates (0 (N0), 160 (N160), and 320 (N320) kg N ha⁻¹ year⁻¹), we measured nitrous oxide (N₂O) and carbon dioxide (CO₂) emissions from wheat fields and determined the soil organic carbon (SOC), total N, microbial biomass C (MBC), and N (MBN), mineralized C (C_min) and N (N_min) concentrations and the bacterial community composition. The results showed that N fertilization significantly (P < 0.05) increased N₂O and CO₂ emissions. N fertilization also significantly (P < 0.05) increased SOC by 13.2%, total N by 7.4%, MBN by 34.3%, C_min by 15.5%, and N_min by 27.8%, as well as the soil bacterial diversity and abundances of N cycling functional groups (by 149%). Additionally, N₂O and CO₂ emissions were positively and linearly correlated with NH₄-N and NO₃-N concentrations and positively correlated with SOC, total N, MBN, and the number of bacterial species, as well as most of the bacterial phyla and functional groups. These results suggest that N fertilizer applied to the dryland soils improved soil fertility and changed the soil bacterial community composition and function, thus increased N₂O and CO₂ emissions. Therefore, to mitigate greenhouse gas emissions and maintain soil fertility for wheat production, an optimized N fertilizer rate should be applied in the southern region of the Loess Plateau in China.

25390. 题目: Salinity affects topsoil organic carbon concentrations through regulating vegetation structure and productivity
文章编号: N20010504
期刊: Journal of Geophysical Research: Biogeosciences
作者: Lian Xue, Junyan Jiang, Xiuzhen Li, Zhongzheng Yan, Qian Zhang, Zhenming Ge, Bo Tian, Christopher Craft
更新时间: 2020-01-05
摘要: Estuarine salt marshes have been recognized as one of the most efficient carbon sinks in the biosphere, with considerable potential for climate change mitigation. However, there are still uncertainties about the response of soil carbon stocks to enhanced soil salinization caused by accelerated sea‐level rises and aggravated saltwater intrusion. We therefore conducted both field investigations in the Chongming Dongtan salt marsh of the Yangtze River Estuary, China, and manipulative experiments on marsh soils occupied respectively by the invasive Spartina alterniflora, and the native Phragmites australis and Scirpus mariqueter, to identify the effects of elevated soil salinity on top soil organic carbon (SOC) concentration. Our field data showed that SOC concentrations were significantly positively associated with soil salinity concentrations, annual net primary productivity and marsh surface elevation, but showed a significant negative relationship with median grain size. Compared with the two native species, S. alterniflora preferred more saline conditions and had a higher SOC concentration. Although raised flooding salinities (0–35 ppt) did not strongly affect SOC concentrations, elevated soil salinities significantly corresponded with low SOC concentrations and plant biomass in manipulative experiments. These findings indicated that soil salinity, plant species and soil texture were key factors controlling SOC concentrations in the studied salt marsh. Moreover, soil salinity could affect SOC concentrations through regulating vegetation spatial structure and plant biomass production. The further invasion of the S. alterniflora community will exert a positive influence on SOC concentrations in the Chongming Dongtan salt marsh.

25391. 题目: Responses of soil respiration and its temperature sensitivity to nitrogen addition: A meta-analysis in China
文章编号: N20010503
期刊: Applied Soil Ecology
作者: Haibing Xiao, Zhihua Shi, Zhongwu Li, Ling Wang, Jia Chen, Jian Wang
更新时间: 2020-01-05
摘要: Annual atmospheric nitrogen (N) deposition in China increased approximately 8 kg N ha⁻¹ from the 1980s to the 2000s, which may have greatly affected soil respiration (R_s) and its temperature sensitivity (Q₁₀). Although numerous individual studies have been conducted, the responses of R_s to simulated N deposition remain controversial. To reconcile the conflicting results of R_s and expand our knowledge about the response of Q₁₀ to N addition, a dataset with 333 independent observations in China was compiled, and a meta-analysis was performed. Our results showed that N addition increased R_s by 7.1% (P < 0.05) across all biomes. The positive response degree of R_s in croplands (27.0%, P < 0.05) was significantly greater than those in the grassland and forest biomes, which indicated that R_s in anthropogenic ecosystems might be more sensitive to N enrichment. In contrast to low and medium N levels (≤20 g m⁻² yr⁻¹), high N addition levels (>20 g m⁻² yr⁻¹) inhibited R_s due to a decrease in plant fine root biomass (RB). Compared with ammonium nitrate, urea is more likely to stimulate the release of soil C. Regression models showed that the R_s response ratio (RR) was positively correlated with pH and the RRs of microbial biomass carbon (MBC) and RB. Increases in both plant roots and microbial biomass induced by N addition directly promoted R_s, and N enrichment likely increases R_s in soil with a high pH. The temperature sensitivity parameter, Q₁₀, decreased by 3.7% (P < 0.05) across all biomes and showed an overall negative response for different biomes (except wetlands and deserts), N addition levels and N types. The Q₁₀ response ratio was positively correlated with the RR of pH. Soil acidification induced by proton release during N fertilizer transformation might accelerate the decomposition of recalcitrant organic matter and further decrease the Q₁₀ value. Our study provides valuable information to Chinese environmental policy- and decision-makers in their attempts to evaluate the effects of N deposition on terrestrial ecosystem C cycle.

25392. 题目: Air pre-oxidation induced high yield N-doped porous biochar for improving toluene adsorption
文章编号: N20010502
期刊: Chemical Engineering Journal
作者: Ziheng Jin, Bangda Wang, Liang Ma, Pengbo Fu, Lingling Xie, Xia Jiang, Wenju Jiang
更新时间: 2020-01-05
摘要: In this study, high yield Nitrogen (N)-doped porous biochar for enhanced toluene adsorption was developed via a novel air pre-oxidation (APO) treatment. Stillage and ammonium phosphate were used as the carbon precursor and in situ nitrogen additive, respectively. A range of APO conditions, including temperature (150–400 °C), air flow rate (0–240 mL/min) and time (0.5–3.0 h) were explored for biochar production. The optimized biochar exhibited high yield (55.5%), N content (6.51 at%), surface area (762.9 m²/g) and pore volume (0.444 cm³/g), which significantly exceeded biochar produced without APO. The toluene adsorption capacity of APO treated biochar reached 437.8 mg/g, which was significantly higher than that produced without APO (296.4 mg/g). APO treatment improved the structural characteristics and surface chemistry of biochar, thereby improving its adsorption properties. Possible mechanisms were also discussed for both the APO induced biochar preparation process and toluene adsorption by APO treated biochar.
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25393. 题目: A novel PARAFAC model for continental hot springs reveals unique dissolved organic carbon compositions
文章编号: N20010501
期刊: Organic Geochemistry
作者: Joshua Nye, Everett Shock, Hilairy Hartnett
更新时间: 2020-01-05
摘要: Dissolved organic carbon in hot springs reflects a range of sources and biogeochemical processes. We evaluated ∼200 continental hot spring samples, with a range in pH and temperature, collected from the Tengchong hydrothermal region, Yunnan Province, China and Yellowstone National Park, Wyoming, USA. Dissolved organic carbon concentrations ranged from 16.7 µM to 2.97 mM. Acidic springs displayed the highest values and widest range in carbon concentration. Alkaline springs had a narrower range and lower average concentrations. Carbon composition was evaluated using ultraviolet absorption and 3D fluorescence spectroscopy. Total fluorescence was correlated (p < 0.05) with dissolved organic carbon (DOC) concentration. Fluorescence excitation-emission matrices were deconvolved using parallel factor analysis. We validated a five-component model that represented >97% of the total fluorescence. Our model includes three humic-like components, one protein-like component, and one novel component exclusively observed in highly acidic springs. The closest spectral match to the novel component is an acid-soluble lignin produced during high-temperature, acid digestion of wood pulp. Humic-like components were dominant in mid-pH springs (4 < pH < 7) indicating these springs had greater terrestrial carbon input. Acidic springs also exhibited evidence for terrestrial carbon input. Alkaline springs, in contrast, consistently had low dissolved organic carbon content and low fluorescence intensity suggesting that these springs had little terrestrial input. This absence of terrestrial carbon implies a predominantly hydrothermal fluid source. A comparison of the traditional fluorescence indices with our five model components suggest that these indices may have limited utility in continental hot springs with multiple organic matter sources and alteration processes.

25394. 题目: Dibutyl phthalate adsorption characteristics using three common substrates in aqueous solutions
文章编号: N20010417
期刊: Frontiers of Environmental Science & Engineering
作者: Tiancui Li, Yaocheng Fan, Deshou Cun, Yanran Dai, Wei Liang
更新时间: 2020-01-04
摘要: In recent years, the presence and adverse impacts of phthalic acid esters in aquatic environments have gained increasing attention. This work investigated the adsorption behavior of a typical phthalic acid ester, dibutyl phthalate (DBP), onto steel slag, gravel, and shell sand (substrates commonly used in constructed wetlands). The influence of dissolved organic matter (DOM) on DBP adsorption was investigated using humic acid as a proxy for DOM. The results demonstrated that the adsorption of DBP to three substrates reached equilibrium within 96 h, and the adsorption kinetics were well fitted by a pseudo-second-order model. The DBP adsorption isotherms were best fitted by the Langmuir adsorption model. The DBP adsorption capacity decreased in the order of steel slag>gravel>shell sand, with values of 656 mg/kg, 598 mg/kg, and 6.62 mg/kg at 25°C, respectively. DBP adsorbed to the surface of all substrates in a monolayer via an endothermic process. The DBP adsorption capacities of steel slag and gravel decreased as the DOM content increased. The DBP adsorption mechanisms to steel slag and gravel mainly involved the surface coordination of DBP with −OH or −COOH groups and electrostatic interactions. The results of this work suggest that steel slag and gravel may be ideal substrates for use in constructed wetlands to treat wastewater polluted with DBP.

25395. 题目: Identification of important precursors and theoretical toxicity evaluation of byproducts driving cytotoxicity and genotoxicity in chlorination
文章编号: N20010416
期刊: Frontiers of Environmental Science & Engineering
作者: Qian-Yuan Wu, Yi-Jun Yan, Yao Lu, Ye Du, Zi-Fan Liang, Hong-Ying Hu
更新时间: 2020-01-04
摘要: Chlorination, the most widely used disinfection process for water treatment, is unfortunately always accompanied with the formation of hazardous disinfection byproducts (DBPs). Various organic matter species, like natural organic matter (NOM) and amino acids, can serve as precursors of DBPs during chlorination but it is not clear what types of organic matter have higher potential risks. Although regulation of DBPs such as trihalomethanes has received much attention, further investigation of the DBPs driving toxicity is required. This study aimed to identify the important precursors of chlorination by measuring DBP formation from NOM and amino acids, and to determine the main DBPs driving toxicity using a theoretical toxicity evaluation of contributions to the cytotoxicity index (CTI) and genotoxicity index (GTI). The results showed that NOM mainly formed carbonaceous DBPs (C-DBPs), such as trichloromethane, while amino acids mainly formed nitrogenous DBPs (N-DBPs), such as dichloroacetonitrile (DCAN). Among the DBPs, DCAN had the largest contribution to the toxicity index and might be the main driver of toxicity. Among the precursors, aspartic acid and asparagine gave the highest DCAN concentration (200 g/L) and the highest CTI and GTI. Therefore, aspartic acid and asparagine are important precursors for toxicity and their concentrations should be reduced as much as possible before chlorination to minimize the formation of DBPs. During chlorination of NOM, tryptophan, and asparagine solutions with different chlorine doses and reaction times, changes in the CTI and GTI were consistent with changes in the DCAN concentration.

25396. 题目: High seasonal variability in sediment carbon stocks of cold‐temperate seagrass meadows
文章编号: N20010415
期刊: Journal of Geophysical Research: Biogeosciences
作者: Martin Dahl, Maria E. Asplund, Diana Deyanova, João N. Franco, Alan Koliji, Eduardo Infantes, Diana Perry, Mats Björk, Martin Gullström
更新时间: 2020-01-04
摘要: Seagrass meadows have a high ability to capture and store atmospheric CO₂ in the plant biomass and underlying sediment, and thereby function as efficient carbon sinks. The seagrass Zostera marina is a common species in the temperate Northern Hemisphere, a region with strong seasonal variations in climate. How seasonality affects carbon storage capacity in seagrass meadows is largely unknown, and therefore, in this study, we aimed to assess variations in sedimentary total organic carbon (TOC) content over a one‐year cycle in seagrass meadows on the Swedish west coast. The TOC was measured in two Z. marina sites, one wave exposed and one sheltered, and at two depths (1.5 and 4 m) within each site, every second month from August 2015 to June 2016. We found a strong seasonal variation in carbon density, with a peak in early summer (June), and that the TOC was negatively correlated to the net community production (NCP) of the meadows, presumably related to organic matter degradation. There was seasonal variation in TOC content at all sediment sections, indicating that the carbon content down to 30 cm is unstable on a seasonal scale and therefore likely not a long‐term carbon sink. The yearly mean carbon stocks were substantially higher in the sheltered meadow (3965 and 3465 g m^‐2) compared to the exposed one (2712 and 1054 g m^‐2) with similar seasonal variation. Due to the large intra‐annual variability in TOC content, seasonal variation should be considered in carbon stock assessments and management for cold‐temperate seagrass meadows.

25397. 题目: Predicting Cr(VI) adsorption on soils: the role of the competition of soil organic matter
文章编号: N20010414
期刊: Environmental Science: Processes Impacts
作者: Zhenqing Shi, Shimeng Peng, Xiaofeng Lin, Yuzhen Liang, Suen-Zone Lee, Herbert E. Allen
更新时间: 2020-01-04
摘要: Cr(VI) has posed a serious risk for the environment and human beings because of its pollution and toxicity. It is essential to understand the equilibrium behavior of Cr(VI) in soils. In this study, the adsorption of Cr(VI) on fourteen soils was studied with batch experiments and quantitative modeling. The batch experiments included the adsorption edge and adsorption isotherm experiments, investigating the adsorption of Cr(VI) with varying soil properties, solution pH, and initial Cr(VI) concentrations. The experimental data were then modeled using the surface complexation models in Visual MINTEQ of CD-MUSIC by considering the adsorption of Cr(VI) and ions onto Fe (hydr)oxides and Al (hydr)oxides, and the Stockholm Humic Model and the fixed charge site model by accounting for the adsorption of the cations to soil organic matter and clay, respectively. Particularly, the modeling method of this study introduced an important parameter RO⁻ to account for the amount of soil organic matter irreversibly adsorbed on soil minerals. Overall, the model predicted reasonably well for the equilibrium partition of Cr(VI) under various conditions with a root-mean-square-error of 0.35 for the adsorption edge data and 0.19 for the adsorption isotherm data. According to the model calculations, ferrihydrite dominated the binding of Cr(VI) at pH of 3.0–7.0. The content of ferrihydrite and reactive soil organic matter was found to be the main factor influencing RO⁻. The modeling results help to understand and predict Cr(VI) adsorption on different soils and are beneficial to environmental risk assessment and pollution remediation.
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25398. 题目: Absorption characteristics of CDOM in treated and non-treated urban lakes in Changchun, China
文章编号: N20010413
期刊: Environmental Research
作者: Lili Lyu, Zhidan Wen, Pierre-Andre Jacinthe, Yingxin Shang, Ning Zhang, Ge Liu, Chong Fang, Junbin Hou, Kaishan Song
更新时间: 2020-01-04
摘要: In urban settings, one may find (i) lakes that are non-treated (NT) and impacted by recurrent discharges of pollutants and nutrients, and (ii) lakes that, through restoration measures and active management, are treated (T) from external inputs. The optical properties of chromophoric dissolved organic matter (CDOM) have been used to assess the anthropogenic impact on lakes ecology, but their application in comparative assessments of urban lakes has not been attempted. For 2 years, we measured nutrients and CDOM properties in water samples collected from NT and T lakes in the city of Changchun, China. Significant differences in CDOM properties were found between the two types of lakes, and these results were supported by redundancy analysis. The NT lakes were eutrophic while the T lakes were mesotrophic, with mean trophic status index (TSI) of 74.2 and 50.3, respectively. The CDOM absorption coefficient at 350 nm, a(350), was 2-fold higher in NT than in T lakes (6.59 vs 3.21 m^-1). In the NT lakes, CDOM components predominantly comprised large molecular weight (MW > 1000-Da) humus-like substances of allochthonous origin, whereas in the T lakes CDOM was dominated by low MW (<1000-Da) substances from autochthonous production. Seasonal fluctuation has a great influence on the CDOM concentration, but a little influence on its molecular composition. The CDOM concentration were higher in summer than in other seasons. Weather conditions (rainfall, temperature) and biophysical processes (biodegradation, photo-bleaching) likely contributed to these variations. We found the water quality of the treated lakes was getting better from 2016 to 2018. In summary, the study results, not only revealed seasonal effects, but most importantly documented the impact of human activities on the characteristics of CDOM in urban lakes. Most specifically, the sharp difference between the lakes in regard to a(350) (2-fold lower in T than in NT lakes) demonstrated the suitability CDOM absorption coefficient as an early indicator of the impact of treatment measures on the hydrochemistry of DOM in urban lakes.

25399. 题目: Stability of Marine Organic Matter Respiration Stoichiometry
文章编号: N20010412
期刊: Geophysical Research Letters
作者: T. Tanioka, K. Matsumoto
更新时间: 2020-01-04
摘要: The magnitude of biological consumption of oxygen during organic matter remineralization critically depends on how much organic carbon is remineralized per unit dissolved oxygen consumed (respiratory quotient, RQ) but the global distribution and the mechanisms that control RQ are not well understood. Here, we estimate RQ in the surface ocean by using two independent methods, one using satellite‐derived macromolecular composition of phytoplankton and another using objectively gridded nutrient data. Both methods yield mean RQ of ~0.7 with small spatial variability consistent with previous estimates. This pattern is likely to be a result of phytoplankton protein content universally exceeding those of carbohydrates and lipids. At face value, the relative stability of RQ suggests that the remineralization stoichiometry will not affect the ongoing deoxygenation of the world ocean. However, the possibility that RQ may increase in the future (e.g., organic matter becoming more carbohydrate‐dominated) and thus ameliorate deoxygenation cannot be ruled out.

25400. 题目: Burial and origin of permafrost derived carbon in the nearshore zone of the southern Canadian Beaufort Sea
文章编号: N20010411
期刊: Geophysical Research Letters
作者: H. Grotheer, V. Meyer, T. Riedel, G. Pfalz, L. Mathieu, J. Hefter, T. Gentz, H. Lantuit, G. Mollenhauer, M. Fritz
更新时间: 2020-01-04
摘要: Detailed organic geochemical and carbon isotopic (δ¹³C and Δ¹⁴C) analyses are performed on permafrost deposits affected by coastal erosion (Herschel Island, Canadian Beaufort Sea), and adjacent marine sediments (Herschel Basin) to understand the fate of organic carbon in Arctic nearshore environments. We use an end‐member model based on the carbon isotopic composition of bulk organic matter to identify sources of organic carbon. Monte Carlo simulations are applied to quantify the contribution of coastal permafrost erosion to the sedimentary carbon budget. The models suggest that 36 % of all carbon released by local coastal permafrost erosion is efficiently trapped and sequestered in the nearshore zone. This highlights the importance of sedimentary traps in environments such as basins, lagoons, troughs and canyons for the carbon sequestration in previously poorly investigated, nearshore areas.