1. 题目: Adsorption of organic and inorganic arsenic from aqueous solution: Optimization, characterization and performance of Fe–Mn–Zr ternary magnetic sorbent
作者: Shuai-Wen Zou, Kok Yuen Koh, Zhihao Chen, Yu-Yang Wang, Yu-Ming Zheng, J. Paul Chen
摘要: Arsenic is a highly toxic pollutant and exists in inorganic and organic forms in groundwater and industrial wastewater. It is of great importance to reduce the arsenic content to lower levels in the water (e.g., <10 ppb for drinking) in order to minimize risk to humans. In this study, a Fe–Mn–Zr ternary magnetic sorbent was fabricated via precipitation for removal of inorganic and organic arsenate. The synthesis of sorbent was optimized by Taguchi method, which leads to an adsorbent with higher adsorption capacity. The adsorption of As(V) was pH dependent; the optimal removal was achieved at pH 2 and 5 for inorganic and organic As(V), respectively. Contact time of 25 h was sufficient for complete adsorption of both inorganic and organic As(V). The adsorption isotherm study revealed that the adsorbent performed better in sequestration of inorganic As(V) than that of organic As(V); both adsorption followed the Langmuir isotherm with maximum adsorption capacities of 81.3 and 16.98 mg g−1 for inorganic and organic As(V), respectively. The existence of anions in the water had more profound effect on the adsorption of organic As(V) than the inorganic As(V). The co-existing silicate and phosphate ions caused significantly negative impacts on the adsorption of both As(V). Furthermore, the existence of humic acid caused the deterioration of inorganic As(V) removal but showed insignificant impact on the organic As(V) adsorption. The mechanism study demonstrated that ion exchange and complexation played key roles in arsenic removal. This study provides a promising magnetic adsorptive material for simultaneous removal of inorganic and organic As(V).
2. 题目: Controls on organic matter accumulation in the Bakken Formation, Williston Basin, USA
期刊: Chemical Geology
作者: Zain Abdi, Susan M. Rimmer, Harold D. Rowe, Stephen Nordeng
摘要: The environmental processes and conditions controlling productivity and organic matter accumulation/preservation in the lower black shale (LBS) and upper black shale (UBS) members of the Devonian-Mississippian Bakken Formation were evaluated utilizing molybdenum (Mo), total organic carbon (TOC), total sulfur (ST), and iron (Fe) data. High-resolution (1- to 3-cm scale) chemostratigraphic records were generated for twelve drill cores, four of which closely flank the north-south-trending axis of the Nesson Anticline, proximal to the center of the Williston Basin in northwest North Dakota, USA. Degree of pyritization (DOPT) values (0.25 to 1.0) indicate that bottom waters were frequently dysoxic with intermittent aerobic and anoxic/euxinic conditions. However, the presence of organic sulfur in black shales can complicate the use of DOPT as a redox proxy requiring a multi-proxy approach to adequately elucidate depositional conditions. In such samples, the use of ST to approximate pyritic sulfur can lead to an overestimation of DOPT values. Total organic carbon contents of 2–20%, by weight, and consistently elevated Mo concentrations (>100 ppm) in both the LBS and UBS imply that the Williston Basin was often hydrographically unrestricted, allowing for ample nutrient resupply that resulted in enhanced primary productivity. Enhanced organic production (as indicated by the elevated TOC contents) was most likely supported by an abundant supply of nutrients in the basin. Using published Mo–TOC relationships from modern anoxic-euxinic basins, it is estimated that renewal time of the sub-chemoclinal water mass during accumulation of the LBS and UBS approximated 10 and 30 yr, respectively. Key differences between LBS and UBS redox proxies highlight different bottom-water redox conditions during deposition, suggesting differences in paleo-water mass geochemical characteristics and general circulation.
3. 题目: Characteristics of humic substance in lake sediments: the case of lakes in northeastern China
期刊: Journal of Hydrology
作者: Xinyu Song, Chunhao Zhang, Xinya Su, Longji Zhu, Zimin Wei, Yue Zhao
摘要: As an important part of lake ecosystems, sediments play a key role in the carbon cycle in lakes. Due to the complex sources of organic matter in sediments, the link between sequestration and transformation of humic substance is largely unknown. Therefore, it is essential to understand the characteristics of humic substance in lake sediments. In this study, the relationship between the characteristics of humic substance and environmental conditions was found in sediment samples from six typical lakes of northeast China. The structure of humic substance (HS), fulvic acid (FA) and humic acid (HA) tended to be simplified with decreasing lake depth. Pearson analysis indicated that characteristics of humic substances in deep lake sediments were dominantly determined by nutrient factors (e.g., NO3--N, NO2--N, NH4+-N) and physicochemical factors (e.g., pH, water temperature, dissolved oxygen), while the changes of HS in shallow lake sediments were dominantly determined by physicochemical factors (e.g., pH, water temperature, dissolved oxygen). Variation partitioning results also indicated that nutrient factors and physicochemical factors explained 64% and 24.2% of the variations of HS content in boreal deep lakes. In comparison, physicochemical factors explained most of the variation (35.6%) of HS composition, while nutrient factors only explained 3.4% of the variation in shallow lakes. Structural equation models further confirmed that complex components were transformed into simple components by nutrient and physicochemical factors with decreasing lake depth. This study suggests that changes in environmental conditions with lake depth may result in changes in the quality of HS in lake sediments.
4. 题目: Unraveling the Reaction Mechanism of Selective C9 Monomeric Phenol Formation from Lignin Using Pd-Al2O3-Activated Biochar Catalyst
期刊: Bioresource Technology
作者: Lakshmiprasad Gurrala, M. Midhun Kumar, Attada Yerrayya, Prabu Kandasamy, Pedro Castaño, T. Raja, Giovanni Pilloni, Changyub Paek, R. Vinu
摘要: The conversion of biomass-derived lignin to valuable monomeric phenols at high selectivity is of paramount importance for sustainable biorefineries. In this study, a novel Pd-Al2O3 supported on activated biochar catalyst is developed for lignin hydrogenolysis. The catalyst characterization revealed that the (111) planes of both of Pd0 and Al2O3 were exposed to the surface. The maximum lignin conversion of 70.4% along with high liquid yield (∼57 wt.%) was obtained at 240°C, 3 h and 3 MPa H2 pressure. The total monomeric phenols yield in the liquid was 51.6 wt.%, out of which C9 monomeric guaiacols constituted ∼30.0 wt.% with 38.0% selectivity to 4-propyl guaiacol. Using the reaction intermediate, coniferyl alcohol, chemoselective hydrogenation of Cα=Cβ is proved to occur over the Pd site, while dehydroxylation of Cγ–OH is shown to occur over the alumina site. An impressive carbon atom economy of 60% was achieved for the production of monomeric phenols.
5. 题目: Particle-size-based elution of petroleum hydrocarbon contaminated soil by surfactant mixture
期刊: Journal of Environmental Management
作者: Tong Zhang, Jujin Cheng, Hanyue Tan, Shuai Luo, Yuanyuan Liu
摘要: Surfactants are often used to elute the contaminants from soils in order to remediate the polluted soils. However, the heterogeneity of minerals and organic matters with soil particle size may result in adsorption and precipitation of surfactants and affect the distribution of petroleum hydrocarbons (PHCs). In this work, spiked soil samples and surfactant mixture consisting of Tween 80 (TW80) and sodium dodecyl sulfate were prepared. Results showed that the silt-clay-mixture held the high retention capacity of PHCs, and 30% total petroleum hydrocarbons (TPHs) was retained in the soil fraction of ‘<125 μm’ (high concentration), while 70% TPHs (low concentration) was retained in the soil fraction of ‘>125 μm’. TW80 was highly adsorbed on the montmorillonite and aluminosilicates of the soil, and the adsorption of TW80 in surfactant mixture could be relieved at mass ratio of 1:1. This study provides a novel strategy in the elution removal of PHCs from the contaminated soils, in which with the separation of soil particles by the size of 125 μm before elution, as high as 80% PHCs could be eluted from the soil by surfactant mixture.
6. 题目: Leveraging high-throughput hyperspectral imaging technology to detect cadmium stress in two leafy green crops and accelerate soil remediation efforts
期刊: Environmental Pollution
作者: Maria Zea, Augusto Souza, Yang Yang, Linda Lee, Krishna Nemali, Lori Hoagland
摘要: Cadmium (Cd) is a toxic metal that can accumulate in soils and negatively impact crop as well as human health. Amendments like biochar have potential to address these challenges by reducing Cd bioavailability in soil, though reliance on post-harvest wet chemical methods to quantify Cd uptake have slowed efforts to identify the most effective amendments. Hyperspectral imaging (HSI) is a novel technology that could overcome this limitation by quantifying symptoms of Cd stress while plants are still growing. The goals of this study were to: 1) determine whether HSI can detect Cd stress in two distinct leafy green crops, 2) quantify whether a locally sourced biochar derived from hardwoods can reduce Cd stress and uptake in these crops, and 3) identify vegetative indices (VIs) that best quantify changes in plant stress responses. Experiments were conducted in a tightly controlled automated phenotyping facility that allowed all environmental factors to be kept constant except Cd concentration (0, 5 10 and 15 mg kg−1). Symptoms of Cd stress were stronger in basil (Ocimum basilicum) than kale (Brassica oleracea), and were easier to detect using HSI. Several VIs detected Cd stress in basil, but only the anthocyanin reflectance index (ARI) detected all levels of Cd stress in both crop species. The biochar amendment did reduce Cd uptake, especially at low Cd concentrations in kale which took up more Cd than basil. Again, the ARI index was the most effective in quantifying changes in plant stress mediated by the biochar. These results indicate that the biochar evaluated in this study has potential to reduce Cd bioavailability in soil, and HSI could be further developed to identify rates that can best achieve this benefit. The technology also may be helping in elucidating mechanisms mediating how biochar can influence plant growth and stress responses.
7. 题目: Meta-analysis of the priming effect on native soil organic carbon in response to glucose amendment across soil depths
期刊: Plant and Soil
作者: Gokul Gaudel, Megharaj Poudel, Peter Semba Mosongo, Li Xing, Abraham Mulu Oljira, Yuming Zhang, Fiston Bizimana, Binbin Liu, Yuying Wang, Wenxu Dong, Jean Yves Uwamungu, Chunsheng Hu
摘要: Aims The priming effect (PE) on native soil organic matter induced by exogenous carbon addition influences soil carbon and nutrient cycling across the soil depths. Therefore, this study aimed to explore the effects of exogenous glucose-induced PE on native soil organic carbon (SOC) influenced by soil properties across soil depths, weather factors in different ecosystems and experimental variables. Methods We conducted a meta-analysis of 1231 experimental comparisons from 41 publications to explore the responses of native SOC to stable or radioactive carbon isotope (glucose) addition in laboratory incubation experiments representing various ecosystems and soil depths on the global scale. Results Overall, glucose addition had 110% positive PE on native SOC. The PE was higher in deep soil (197%) and lowest in topsoil (99%). Deep soil contains significantly lower SOC, dissolved organic carbon and microbial biomass carbon and a higher soil carbon/nitrogen ratio than topsoil. The PE positively correlated with soil carbon/nitrogen ratio and glucose addition rate but negatively correlated with microbial biomass carbon, dissolved organic carbon, SOC and incubation duration. Furthermore, PE positively related to mean annual temperature and precipitation in cropland while negatively correlated with mean annual precipitation in grassland ecosystem. Conclusions Low soil nutrients and high carbon/nitrogen ratio is the reason for higher PE in deep soil than topsoil. Furthermore, the experimental variables and weather factors provide a framework for understanding the magnitude and direction of PE on native SOC induced by glucose addition and highlight the need for future integrated approaches of studies on PE.
8. 题目: Strategy for Mitigating Antibiotic Resistance by Biochar and Hyperaccumulators in Cadmium and Oxytetracycline Co-contaminated Soil
期刊: Environmental Science & Technology
作者: Yuhao Fu, Mingyun Jia, Fang Wang, Ziquan Wang, Zhi Mei, Yongrong Bian, Xin Jiang, Marko Virta, James M. Tiedje
摘要: The global prevalence of antibiotic resistance genes (ARGs) is of increasing concern as a serious threat to ecological security and human health. Irrigation with sewage and farmland application of manure or biosolids in agricultural practices introduce substantial selective agents such as antibiotics and toxic metals, aggravating the transfer of ARGs from the soil environment to humans via the food chain. To address this issue, a hyperaccumulator (Sedum plumbizincicola) combined with biochar amendment was first used to investigate the mitigation of the prevalence of ARGs in cadmium and oxytetracycline co-contaminated soil by conducting a pot experiment. The addition of biochar affected the distribution of ARGs in soil and plants differently by enhancing their prevalence in the soil but restraining transmission from the soil to S. plumbizincicola. The planting of S. plumbizincicola resulted in an increase in ARGs in the soil environment. A structural equation model illustrated that mobile genetic elements played a dominant role in shaping the profile of ARGs. Taken together, these findings provide a practical understanding for mitigating the prevalence of ARGs in this soil system with complex contamination and can have profound significance for agricultural management in regard to ARG dissemination control.
9. 题目: Effects of fire on soil organic carbon, soil total nitrogen, and soil properties under rotational shifting cultivation in northern Thailand
期刊: Journal of Environmental Management
作者: Noppol Arunrat, Sukanya Sereenonchai, Ryusuke Hatano
摘要: Fire has been used for land clearing under rotational shifting cultivation (RSC) in Northern Thailand for a long time. However, the effects of fire on soil organic carbon (SOC), soil total nitrogen (STN), and soil properties are not well understood. We determined SOC, STN, and soil properties of the topsoil layer (0–30 cm) along a fallow chronosequence under RSC and assessed how fire affects SOC, STN, and soil properties. Eight fields at Ban Mae Pok, Mae Chaem District, Chiang Mai Province, Northern Thailand, were investigated. The levels of SOC, STN, and soil properties were observed at three time points: pre-burning, post-burning (5 minutes after burning), and post-harvest (nine months after burning). The highest SOC and STN stocks, organic matter (OM), and clay content were observed for the longest fallow period (7 years fallow), whereas the shortest period (1 year fallow) resulted in the lowest SOC and STN stocks. Fire caused no significant changes in SOC, STN, and some soil properties (soil texture, available P, exchangeable K, exchangeable Ca, exchangeable Mg, bulk density, and OM) because of the low fire intensity and short fire duration. Only pH and electrical conductivity were significantly increased (p ≤ 0.05) after burning due to the demobilization of base cations in burnt vegetation and incorporation into the soil with ashes and wood charcoal. Although fire may still be necessary for RSC, maintaining the fire intensity below 380 °C to reduce SOC losses and appropriate post-fire management strategies to reduce STN losses are crucial.
10. 题目: Facile preparation of magnetic porous biochars from tea waste for the removal of tetracycline from aqueous solutions: Effect of pyrolysis temperature
作者: Bin Li, Yin Zhang, Jin Xu, Shisuo Fan, Huacheng Xu
摘要: Pyrolysis process significantly influences the physicochemical properties and potential application of magnetic porous biochars (MPBCs). However, the effects of pyrolysis temperature on the properties of MPBCs as well as substantial adsorption are still unclear. This study reported a facile method to obtain the MPBC from tea waste via pyrolysis of a mixture of hydrochar, KHCO3, and FeCl3·6H2O under different temperatures (500–800 °C), and explored further the adsorption toward tetracycline (TC). Results showed pyrolysis temperature obviously influenced the physicochemical properties of MPBCs, and MPBC pyrolyzed at 700 °C (MPBC-700) has a highest specific surface area (1066 m2 g−1) and pore volume (2.693 cm3 g−1). However, the adsorption potential increased consistently from 59.35 mg g−1 for MPBC-500 to 333.22 mg g−1 for MPBC-800, suggesting that the surface area and pore volume were not the only factors determining TC adsorption. Further analysis showed that the pore-filling, π-π interaction, complexation, and hydrogen bonding contributed together to TC adsorption. Moreover, all MPBCs possessed a high saturation magnetization, indicating the easy separation by an external magnet. Therefore, MPBCs (especially at 700 °C) can act as the excellent adsorbents for contaminant removal due to their high separation, adsorption, and reuse performance.
11. 题目: Hierarchical porous structure formation mechanism in food waste component derived N-doped biochar: Application in VOCs removal
作者: Yuxuan Yang, Chen Sun, Qunxing Huang, Jianhua Yan
摘要: Nitrogen-doped (N-doped) hierarchical porous carbon was widely utilized as an efficient volatile organic compounds (VOCs) adsorbent. In this work, a series of N-doped hierarchical porous carbons were successfully prepared from the direct pyrolysis process of three food waste components. The porous biochar from bone showed a high specific surface area (1405.06 m2/g) and sizable total pore volume (0.97 cm3/g). The developed hierarchical porous structure was fabricated by the combined effect of self-activation (Carbon dioxide (CO2) and water vapor (H2O)) and self-template. The emission characteristics of activation gas analyzed by Thermogravimetric-Fourier transform infrared spectrometer (TG-FTIR) and the transformation of ash composition in the biochar help to illustrate the pore-forming mechanism. Calcium oxide (CaO) and hydroxylapatite were confirmed as the major templates for mesopores, while the decomposition processes of calcium carbonate (CaCO3) and hydroxylapatite provided a large amount of activation gas (CO2 and H2O) to form micropores. The materials also obtained abundant N-containing surface functional groups (up to 7.84 atomic%) from pyrolysis of protein and chitin. Finally, the porous biochar showed excellent performance for VOCs adsorption with a promising uptake of 288 mg/g and a high adsorption rate of 0.189 min−1. Aplenty of mesopores distributed in the materials effectively improved the mass transfer behaviors, the adsorption rate got a noticeable improvement (from 0.118 min−1 to 0.189 min−1) benefited from mesopores. Reusable potentials of the hierarchical porous carbons were also satisfying. After four thermal regeneration cycles, the materials still occupied 84.8%–87.4% of the original adsorption capacities.
12. 题目: An efficient, green and sustainable potassium hydroxide activated magnetic corn cob biochar for imidacloprid removal
作者: Yongfei Ma, Siyu Chen, Yong Qi, Lie Yang, Li Wu, Liuyang He, Ping Li, Xuebin Qi, Feng Gao, Yongzhen Ding, Zulin Zhang
摘要: The extensive use of imidacloprid (IMI) has led to its being frequently detected in natural water, also caused the potential damage to the ecosystem. Development of efficient, green and sustainable technique is demanded to eliminate this problem. A novel biochar (KMCBC) derived from agriculture waste of corn cob was first time co-modified by potassium hydroxide (KOH), ferric chloride (FeCl3) and zinc chloride (ZnCl2), which showed the greater adsorption amount (410 mg g−1 at 298 K) for imidacloprid (IMI). Pseudo-second-order kinetic and Langmuir isotherm models fitted well with the experimental data, together with the physicochemical characterization analysis, demonstrating that the adsorption process of IMI by KMCBC might be mainly controlled by micropore filling, π-π electron donor-acceptor and functional groups interactions (H-bonding and complexation). Additionally, the thermodynamics parameters suggested that IMI adsorption in this study was a spontaneous, endothermic and randomly increasing process. Besides, KMCBC owned the easy separation performance and promising environmental safety, also exhibited a high selective adsorption capacity regardless of solution pH (its optimum adsorption performance for IMI was obtained at pH = 5), inorganic ions strength and humic acid (HA) concentrations. The regenerated KMCBC (synergistic ultrasound/ethanol) could sustainably and efficiently adsorb IMI in the reuse cycles. Therefore, this study provided an efficient, green and sustainable adsorbent of KMCBC for IMI removal.
13. 题目: Activation of organic chloramine by UV photolysis: A non-negligible oxidant for micro-pollutant abatement and disinfection by-product formation
期刊: Water Research
作者: Yan Wang, Huiyu Dong, Wenlei Qin, Jin Li, Zhimin Qiang
摘要: Due to the wide-presence of organic amines in natural waters, organic chloramines are commonly formed during (pre-)chlorination. With the increasing application of UV disinfection in water treatment, both the activation mechanism of organic chloramine by UV photolysis and its subsequent impact on water quality are not clear. Using sarcosine (Sar) as an amine group-containing compound, it was found that organic chloramines (i.e., Cl-Sar) would be firstly formed during chlorination even in the presence of natural organic matter. Compared with self-decay of Cl-Sar, UV photolysis accelerated Cl-Sar decomposition and induced N-Cl bond cleavage. Using metoprolol (MTP) as a model micro-pollutant, UV-activated Cl-Sar (UV/Cl-Sar) can accelerate micro-pollutant degradation, attributed to reactive radicals formation. HO• and Cl• were important contributors, with a total contribution of 45%‒64%. Moreover, the degradation rate of MTP by UV/Cl-Sar was pH-dependent, which monotonically increased from 0.044 to 0.065 min‒1 under pHs 5.5‒8.5. Although the activation of organic chloramine by UV could accelerate micro-pollutant degradation, UV/Cl-Sar treatment could also enhance disinfection by-products formation. Trichloromethane (TCM) formation was observed during MTP degradation by UV/Cl-Sar. After post-chlorination, TCM, 1,1-dichloropropanone, 1,1,1-trichloropropanone, and dichloroacetonitrile were detected. Their individual and total concentrations were all positively proportional to UV/Cl-Sar treatment time. The total concentration with 30 min treatment (66.93 μg L‒1) was about 2.3 times that with 1 min treatment (28.76 μg L‒1). Finally, the accelerated effect was verified with Cl-glycine and Cl-alanine. It is expected to unravel the non-negligible role of organic chloramine on water quality during UV disinfection.
14. 题目: Potential role of organic matter in the transmission of antibiotic resistance genes in black soils
期刊: Ecotoxicology and Environmental Safety
作者: Sen Li, Junjie Liu, Qin Yao, Zhenhua Yu, Yansheng Li, Jian Jin, Xiaobing Liu, Guanghua Wang
摘要: The degradation of black soil is a serious problem with the decrease in soil organic matter (SOM) content in northeast China, and animal manure as a reservoir of antibiotic resistance genes (ARGs) is commonly amended into soil to sustain or increase the SOM content. However, the potential effect of SOM content on soil resistome remains unclear. Here, a soil microcosm experiment was established to explore the temporal succession of antibiotic resistance genes (ARGs) and bacterial communities in three black soils with distinct difference in SOM contents following application of poultry manure using high-throughput qPCR (HT-qPCR) and MiSeq sequencing. A total of 151 ARGs and 8 mobile genetic elements (MGEs) were detected across all samples. Relative abundance of ARGs negatively correlated with SOM content. Manure-derived ARGs had much higher diversity and absolute abundance in the low SOM soils. The ARG composition and bacterial community structure were significantly different in three soils. A random forest model showed that SOM content was a better predictor of ARG pattern than bacterial diversity and abundance. Structural equation modeling indicated that the negative effects of SOM content on ARG patterns was accomplished by the shift of bacterial communities such as the bacterial diversity and abundance. Our study demonstrated that SOM content could play an important role in the dissemination of ARGs originated from animal manures, these findings provide a possible strategy for the suppression of the spread of ARGs in black soils by increasing SOM content.
15. 题目: Distribution and functional groups of soil aggregate-associated organic carbon along a marsh degradation gradient on the Zoige Plateau, China
作者: Yulin Pu, Shanxin Lang, Aobo Wang, Shirong Zhang, Ting Li, Hongyu Qian, Guiyig Wang, Yongxia Jia, Xiaoxun Xu, Dagang Yuan, Yun Li
摘要: Alpine marsh wetlands in the Qinghai-Tibetan Plateau are ecological hotspots for global carbon (C) cycling in Central Asia; however, the soil C sinks are increasingly limited by marsh degradation. To assess the physical mechanisms by which changes in the soil C sequestration occur, the distribution and functional groups of soil organic C (SOC) in aggregates along a marsh degradation gradient on the Zoige Plateau in China were investigated using soil samples collected from differently degraded marshes. Our results showed that, beyond the state of light degradation, the large aggregate content decreased significantly by 31.1–55.2%, while the micro-aggregate content increased significantly by 23.1–93.1%. The SOC content in the aggregates decreased significantly by 39.1–84.8% and the dominant aggregate size for SOC preservation decreased to small or micro-aggregate. Marsh degradation also decreased the relative ratio of aliphatic-C while increasing that of alcohol and phenolic-C, and polysaccharide-C. Index I (relative decomposition of SOC in aggregates) was 73.5–429.0% higher for degraded marshes than for relatively pristine marsh (RPM), while Index Ⅱ (relative recalcitrance of SOC in aggregates) was 13.8–79.5% lower in comparison. Therefore, we concluded that marsh degradation probably reduces the organic C sequestration capacity of soil by increasing the decomposition of SOC in aggregates after both the dominant aggregate size for SOC preservation and aggregate stability decreased. This result represents the physical mechanism by which the decrease in SOC content occurs in response to marsh degradation in alpine regions.
16. 题目: Modeling and elucidation the effects of iron deposits on chlorine decay and trihalomethane formation in drinking water distribution system
期刊: Water Research
作者: Pei Hua, Quan Gao, Zhenyu Wang, Shanshan Jiang, Keila Roberta Ferreira de Oliveira, Dhiogo Okumoto Macedo
摘要: Iron deposits stimulate chlorine consumption and trihalomethane (THM) formation in drinking water distribution systems through distinct mechanisms. In this study, a second-order chlorine decay model with a variable reaction-rate coefficient was developed to quantitatively evaluate the influences of iron deposits on chlorine reactions by considering the characteristics of dissolved organic matter (DOM), the type and dosages of deposits, as well as the initial chlorine concentrations. Based on a reliable prediction of residual chlorine, the concept that THM formation had a linear relationship with chlorine consumption was further validated by chlorination of DOM in the presence of iron deposits. Due to the catalysis influences, the reactivity of DOM towards chlorine decay or THM formation was accelerated. Although iron deposits activated the reactivity of DOM with bromine and chlorine, THM slightly shifted toward chlorinated species. Due to the adsorption influences, the maximum chlorine demand increased with the increasing deposit dosages whereas the extent of enhancement mainly relied on the DOM properties. Low-molecular-weight DOM with a hydrophilic characteristic was prone to be elevated by iron deposits. Based on the model simulation, approximately 20% of chlorine consumption and 37% of THM formation were contributed by deposits after 168 h reaction. The data provided herein emphasize the role of iron deposits in chlorine consumption and THM formation, which assist the water quality management in drinking water distribution systems.
17. 题目: Vertical profile and radiative forcing of black carbon in a winter pollution period over Chengdu, China
期刊: Atmospheric Research
作者: Yuan Liang, Zhang Xiaoling, Che Yuzhang, Xia Xiang'ao, Liu Xuan, Zhao Tianliang, Song Minghao
摘要: The vertical distributions of BC mass concentration (mBC) during a winter pollution period in 2017 over Chengdu, a megacity in the Sichuan Basin, China, were measured by a micro-aethalometer equipped on a tethered balloon. This observation experienced severe air pollution with an averaged ground BC of 11.1 μg·m−3, which is higher than two times the annual mean in Chengdu for 2018. The available 68 BCE vertical profiles are grouped in to five types: Type A (18%) is the uniform vertical distribution of BC with an unrecognizable mixing layer (ML) height; BC in Type B (26%) is also uniformly distributed in the ML while decreases rapidly above the ML; Type C (7%) is a unimodal distribution with BC peak within the ML when the suspended temperature inversion forms; BC in Type D (29%) is accumulated in the near-ground layer and quickly decreases with height; Type E (20%) is the bimodal or trimodal distribution with BC peaks around the top of ML. Types A and B dominate from noon to afternoon, and Types C–E play critical roles during the evening and night. The different vertical patterns of BC are mainly associated with the evolution of the ML and the local emissions. For all the five types, the calculated radiative forcing of BC (fBC) is negative at the surface but positive at the top of profile (TOP), indicating the net absorption of radiation by the atmosphere due to BC. The absolute values of fBC at the surface and the TOP are increased with the increase of columnar BC loading, and there is no significant difference in fBC at the TOP and the surface among different patterns when the same BC loading is considered. However, the vertical distribution of atmospheric heating rate contributed by BC (hBC) is highly related to BC's vertical profile. The uniform distributed BC can result in a positive gradient of hBC with altitude, and thus, enhance the stability of the atmosphere. The plateau terrain induced small-scale secondary circulation and relatively lower thermal inversion in the west of the Sichuan basin have an essential effect on the vertical distribution of aerosols and can contribute to an accumulation of aerosols at 0.8–1.4 km above ground level. This study would hopefully have a preliminary understanding of the vertical distribution of BC in the Sichuan Basin, and a vital implication for accurately estimating direct radiative forcing by BC in this region.
18. 题目: Dual role of boron-doped diamond (BDD) anode in effluent organic matter degradation and ultrafiltration membrane fouling mitigation
作者: Weichen Zeng, Langming Bai, Heng Liang, Guibai Li, Han Zhang, Jinlong Wang, Zhendong Gan, Dachao Lin, Yuanqing Guo, Penghui Shao
摘要: Ultrafiltration (UF) is effective in retaining macromolecules during tertiary treatment, but membrane fouling caused by effluent organic matter (EfOM) limits its application. This study employed electrochemical oxidation (EO) as a pretreatment method for UF in tertiary treatment to investigate the effects of anode materials on membrane fouling alleviation and EfOM degradation. Compared with the dimensionally stable (DSA) and platinum (Pt) anodes, EO with a boron-doped diamond (BDD) anode exhibited better performances for membrane fouling mitigation due to the higher hydroxyl radical production activity of the BDD anode. It was observed that the current density and electrolysis time were closely related to membrane fouling when using a BDD anode, where increasing the current density or electrolysis time led to a significant improvement of specific flux. The BDD-based pre-oxidation efficiently removed 64% DOC, 76% UV254, and 95% fluorescence organic matter in EfOM, among which the concentrations of DOC and UV254 were positively correlated with the total fouling index (TFI). Meanwhile, 70% SMX in the secondary effluent was removed by the BDD anode. Furthermore, the BDD anode also mitigated membrane fouling by decomposing high molecular weight organic matter into smaller fractions and enhancing the electrostatic repulsion between membrane and EfOM. Therefore, the BDD-based EO process is a promising pretreatment strategy for UF to alleviate membrane fouling and improve the permeate quality.
19. 题目: Reduction in mercury bioavailability to Asian clams (Corbicula fluminea) and changes in bacterial communities in sediments with activated carbon amendment
作者: Mark Xavier Bailon, Minoh Park, Kurt Louis Solis, Yeong Na, Dhiraj Kumar Chaudhary, Sungpyo Kim, Yongseok Hong
摘要: Activated carbon (AC) amendment is considered as one of the alternatives for managing and remediating mercury (Hg) contaminated sediments because of its high sorptive capacity and potential to immobilize the contaminant. For this study, the underlying mechanisms that control the reduction of Hg bioavailability in AC-amended estuarine sediments were investigated in box microcosm set-ups with 28-day Asian clam bioassay experiments. The application of diffusive gradients in thin film technique (DGT) revealed that the total mercury and methylmercury levels in sediment pore water decreased by 60%–75% in 1%–3% AC-amended sediments. This decrease subsequently led to a linear reduction in the Hg body burden in Asian clams, even at 1% sorbent mixing. These observations implied that AC amendment reduced the net flux of Hg into the pore water and overlying water, resulting in reduced Hg bioaccumulation in benthic organisms. The addition of AC to sediment also led to reduced dissolved organic carbon and several biogeochemical indicators (HS−, Mn, and Fe) in the pore water. Furthermore, the 16 S rRNA gene amplicon sequencing analysis revealed noticeable alterations in the microbial communities after AC amendment. The predominant phylum was Firmicutes in control sediment, Bacteroidetes in 1% AC-amended sediment, and Proteobacteria in both 2% and 3% AC-amended sediment samples. The genera-level analysis showed that the relative abundance of the Hg-methylators decreased as the level of AC amendment increased. These observations suggested that AC amendment decreased Hg bioavailability not only by physicochemical sorption but also by changing geochemical species and shifting the microbial community composition.
20. 题目: Extrapolymeric substances (EPS) in Mucilaginibacter rubeus P2 displayed efficient metal(loid) bio-adsorption and production was induced by copper and zinc
作者: Yuan Ping Li, Le Xing You, Xiao Jun Yang, Yan Shuang Yu, Hai Ting Zhang, Bing Yang, Jon Chorover, Ren Wei Feng, Christopher Rensing
摘要: Strains of the genus Mucilaginibacter, belonging to the phylum Bacteroidetes, have been noted for exhibiting high genome plasticity and for the vigorous production of extracellular polymeric substances (EPS). Here we analyzed the composition and properties of EPS generated by M. rubeus P2, isolated from a gold-copper mine and exhibiting extremely high resistance to multiple heavy metals. Production of EPS increased significantly upon exposure to elevated concentrations of Cu(II) and Zn(II), but not Au(III). In addition, the EPS produced by M. rubeus P2 displayed extremely high bio-adsorption of As(III), Cu(II) and Au(III), but not of Zn(II). Moreover, EPS production in Mucilaginibacter rubeus P2 exposed to 1 mM of Cu(II) was 8.5 times higher than EPS production in the same strain without metal (loid)-exposure. These findings constitute the basis for a future use of these EPS-overproducing bacteria in bioremediation of heavy metal contaminated environments. The functional groups, especially –SH, C￼O, and N–H/C–N in the fingerprint zone of glutathione (GSH) and polysaccharides-like components of EPS, were the main components of EPS involved in both Zn(II) and Cu(II) binding and removal. Around 31.22% and 5.74% of Cu(II)-treated EPS was shown to exist as (C￼O) structures and these structures were converted into C–OH and O–C–O upon exposure to Cu(II), respectively. In contrast, (C–OH/C–O–C/P–O–C) groups in EPS were observed to be positively correlated to increasing concentrations of Zn(II) in strain P2. Furthermore, the complete genome of M. rubeus P2 helped us to identify 350 genes involved in carbohydrate metabolism, some of which are predicted to be involved in EPS production and modification. This work describes the first detailed biochemical and biophysical analysis of EPS from any strain of Mucilaginibacter with unique heavy metal binding properties. The results will be useful for a better understanding of how microorganisms such as M. rubeus P2 adapt to heavy metal polluted environments and how this knowledge can potentially be harnessed in biotechnological applications such as industrial waste water purification, bioremediation of heavy metal contaminated soil and beneficial plant microbe interactions. The toolbox provided in this paper will provide a valuable basis for future studies.