1. 题目: Sediment and particulate organic carbon budgets of a subarctic estuarine fjard: Lake Melville, Labrador
期刊: Marine Geology
作者: C. Michelle Kamula, Robie W. Macdonald, Zou Zou A. Kuzyk
摘要: Sediment and particulate organic carbon (POC) budgets constructed for oceanic regions provide a means to quantify the burial of POC, providing a baseline against which future change can be measured. Here we developed the first mass balance budgets of sediment and POC (terrestrial and marine) for the Lake Melville system (LMS; Goose Bay and Lake Melville) in central Labrador using previously published data (210Pb-based mass accumulation rates, river discharge, and total suspended solids) together with measurements of %OC and δ13C signatures within dated sediment cores collected from the LMS basins and water from main tributaries and Groswater Bay. A two end-member mixing model was used to establish fractions of terrigenous and marine POC. Overall, our mass balance budgets show that the Churchill River is the major supply of sediment (16.7 ± 7.8 × 108 kg y−1) and POCterr (18.4 ± 6.6 × 106 kg y−1) to the LMS, accounting for 47% and 56% of the total input to the system, respectively. Although the Churchill River drains directly into Goose Bay along with the smaller Goose River, the majority of sediment (12.9 ± 7.8 × 108 kg y−1) and POCterr (11.8 ± 7.0 × 106 kg y−1) is transported eastward through the surface water plume into Lake Melville. Inputs of POCmar from autochthonous primary production, estimated by applying an empirical relationship between sediment-surface flux of POCmar and water depth, to Goose Bay (1.8 × 106 kg y−1) and Lake Melville (98.3 ± 4.7 × 106 kg y−1) increase with increasing distance from the Churchill River. To investigate the potential changes to the sediment load of the Churchill River to the LMS following impoundment at Muskrat Falls, we calculated the sediment increase using the median reservoir shoreline erosion potential. This approach showed that the delivery of sediment and POCterr to the LMS by the Churchill River may double during the two years following impoundment of the lower Churchill River.
2. 题目: Efficiency of crustacean zooplankton in transferring allochthonous carbon in a boreal lake
作者: Guillaume Grosbois, Dominic Vachon, Paul del Giorgio, Milla Rautio
摘要: Increased incorporation of terrestrial organic matter (t‐OM) into consumer biomass (allochthony) is believed to reduce growth capacity. In this study, we examined the relationship between crustacean zooplankton allochthony and production in a boreal lake that displays strong seasonal variability in t‐OM inputs. Contrary to our hypotheses, we found no effect of allochthony on production at the community and the species levels. The high frequency seasonal sampling (time‐for‐space) allowed for estimating the efficiency of zooplankton in converting this external carbon source to growth. From the daily t‐OM inputs in the lake (57 – 3027 kg C per day), the zooplankton community transferred 0.2% into biomass (0.01 – 2.36 kg C per day); this level was of the same magnitude as the carbon transfer efficiency for algal‐derived carbon (0.4%). In the context of the boundless carbon cycle which integrates inland waters as a biologically active component of the terrestrial landscape, the use of the time‐for‐space approach for the quantifying of t‐OM trophic transfer efficiency by zooplankton is a critical step toward a better understanding of the effects of increasing external carbon fluxes on pelagic food webs.
3. 题目: Mechanisms behind soil N dynamics following cover restoration in degraded land in subtropical China
期刊: Journal of Soils and Sediments
作者: Xiangzhou Zheng, Cheng Lin, Baoling Guo, Juhua Yu, Hong Ding, Shaoyun Peng, Jinbo Zhang, Eric Ireland, Deli Chen, Christoph Müller, Yushu Zhang
摘要: Purpose: Nitrogen (N) is an important nutrient for re-vegetation during ecosystem restoration, but the effects of cover restoration on soil N transformations are not fully understood. This study was conducted to investigate N transformations in soils with different cover restoration ages in Eastern China. Materials and methods: Soil samples were collected from four degraded and subsequently restored lands with restoration ages of 7, 17, 23, and 35 years along with an adjacent control of degraded land. A 15N tracing technique was used to quantify gross N transformation rates. Results and discussion: Compared with degraded land, soil organic carbon (SOC) and total N (TN) increased by 1.60–3.97 and 2.49–5.36 times in restoration land. Cover restoration increased ammonium and nitrate immobilization, and dissimilatory nitrate reduction to ammonium (DNRA) by 0.56–0.96, 0.34–2.10, and 0.79–3.45 times, respectively, indicating that restoration was beneficial for N retention. There were positive correlations between SOC content and ammonium and nitrate immobilization and DNRA, indicating that the increase in soil N retention capacity may be ascribed to increasing SOC concentrations. The stimulating effect of SOC on ammonium immobilization was greater than its effect on organic N mineralization, so while SOC and TN increased, inorganic N supply did not increase. Autotrophic and heterotrophic nitrification increased with increasing SOC and TN concentrations. Notably, heterotrophic nitrification was an important source of NO3−−N production, accounting for 47–67% of NO3−−N production among all restoration ages. Conclusions: The capacity of N retention was improved by cover restoration, leading to an increase in soil organic carbon and total N over time, but inorganic N supply capacity did not change with cover restoration age.
4. 题目: Accumulation of germanium (Ge) in plant tissues of grasses is not solely driven by its incorporation in phytoliths
作者: Sabine Kaiser, Stephan Wagner, Christin Moschner, Claudia Funke, Oliver Wiche
摘要: Ge/Si ratios of plant phytoliths have been widely used to trace biogeochemical cycling of Si. However, until recently, information on how much of the Ge and Si transferred from soil to plants is actually stored in phytoliths was lacking. The aim of the present study is to (i) compare the uptake of Si and Ge in three grass species, (ii) localize Ge and Si stored in above-ground plant parts and (iii) evaluate the amounts of Ge and Si sequestrated in phytoliths and plant tissues. Mays (Zea mays), oat (Avena sativa) and reed canary grass (Phalaris arundinacea) were cultivated in the greenhouse on soil and sand to control element supply. Leaf phytoliths were extracted by dry ashing. Total elemental composition of leaves, phytoliths, stems and roots were measured by ICP-MS. For the localization of phytoliths and the determination of Ge and Si within leaf tissues and phytoliths scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX) and laser ablation inductively coupled mass spectrometry (LA-ICP-MS) was used. The amounts of Si and Ge taken up by the species corresponded with biomass formation and decreased in the order Z. mays > P. arundinacea, A. sativa. Results from LA-ICP-MS revealed that Si was mostly localized in phytoliths, while Ge was disorderly distributed within the leaf tissue. In fact, from the total amounts of Ge accumulated in leaves only 10% was present in phytoliths highlighting the role of organic matter on biogeochemical cycling of Ge and the necessity for using bulk Ge/Si instead of Ge/Si in phytoliths to trace biogeochemical cycling of Si.
5. 题目: The influence of tree and soil management on soil organic carbon stock and pools in dehesa systems
作者: Lizardo Reyna-Bowen, Pilar Fernandez-Rebollo, Jesús Fernández-Habas, José A. Gómez
摘要: This study evaluated the effect on SOC concentration, stock and fractions in a dehesa divided into two areas of similar soil type but different soil management. The first area was a pastured dehesa (P) with young Holm oaks, planted in 1995 (70 trees ha−1, 12 m × 12 m) and, since 2000, grazed by sheep (3 sheep ha−1) with an average period of grazing of six months a year. Prior to this it was managed in the same way as the second adjacent area. The second area was a cropped dehesa (C) with widely spaced mature Holm oak (14 trees in a 12-ha dehesa), on which a mixture of vetch and oats was cultivated every three years and tilled with a chisel plough. After 22 years both dehesas showed similar SOC stock distribution amongst areas with different soil management, with approximately 40 t ha−1 in the top 100 cm of the soil. The P dehesa only showed higher SOC stock than the C dehesa on the surface 0–2 cm (5.86 ± 0.56 t ha-1vs 3.24 ± 0.37 t ha−1). The influence of the trees, increasing SOC concentration and content when compared to the area outside the canopy projection, was only detected under the mature trees in the C dehesa. In the area outside the tree canopy, both systems showed a similar distribution of soil organic carbon among their different fractions, with the unprotected fraction being the dominant one, followed by the physically and chemically protected fractions. In the C dehesa, the mature trees’ presence significantly modified the distribution of soil organic carbon in their surroundings, increasing the relevance of the unprotected fraction. The distribution of soil organic carbon in the unprotected and physically and chemically protected fractions were strongly correlated to the overall organic carbon concentration in the soil, indicating the rapid response of these three fractions to management, with the biochemically protected fraction showing no correlation, suggesting a high resilience to the changes in carbon budget.
6. 题目: Biochar and bacteria inoculated biochar enhanced Cd and Cu immobilization and enzymatic activity in a polluted soil
期刊: Environment International
作者: Chen Tu, Jing Wei, Feng Guan, Ying Liu, Yuhuan Sun, Yongming Luo
摘要: The application of biochar in the remediation of heavy metal contaminated soil has received increasing global attention during the past decade. Although there has been some review work on the mechanism of heavy metals stabilization by biochar, the effects and mechanisms of interaction between biochar and functional microbes such as heavy metal tolerant, adsorption and transformation microbial strains remains unclear. In this paper, maize biochar and a heavy metal-tolerant strain Pseudomonas sp. NT-2 were selected to investigate the dynamic effects and potential mechanisms of biochar and bacteria loaded biochar on the stabilization of Cd and Cu mixed contaminated soil by a 75-day pot experiment. The results showed that, compared to the single biochar amendment, the application of biochar inoculated with NT-2 strain at the rate of 5% significantly increased the soil pH at the initial stage of incubation, and followed by a slight decline to a neutral-alkaline range during the reaction. The addition of NT-2 loaded biochar could also significantly increase the proportion of residual fraction of Cd and Cu, thus reduce the proportion of exchangeable and carbonate bound species in the soil, which lead to the decreasing of plant and human bioavailability of the metal in the soil indicated by DTPA and simulated human gastric solution extraction (UBM), respectively. Finally, the application of bacterial loaded biochar also markedly enhanced soil urease and catalase activities during the later stage of the incubation, and improved soil microbial community at the end of incubation, which indicates a recovery of soil function after the metal stabilization. The research results may provide some new insights into the development of functional materials and technologies for the green and sustainable remediation of heavy metal contaminated soil by the combination of biochar and functional microorganisms.
7. 题目: Characterizing the molecular weight distribution of dissolved organic matter by measuring the contents of electron-donating moieties, UV absorbance, and fluorescence intensity
期刊: Environment International
作者: Qian-Yuan Wu, Tian-Hui Zhou, Ye Du, Bei Ye, Wen-Long Wang, Hong-Ying Hu
摘要: Electron-donating moieties (EDM) have recently been used to characterize the redox properties and treatability of dissolved organic matter during water and wastewater treatment. In this study, size exclusion chromatography followed by a derivatization-spectrometric method was developed to determine the molecular weight (MW) distribution of EDM in dissolved organic matter. The relationships between EDM concentration and chromophore content (indicated by UVA254), fluorophore content (indicated by fluorescence), and dissolved organic carbon (DOC) concentration were analyzed for different MW fractions. In general, natural organic matter (NOM) showed higher total EDM concentration and higher EDM average MW than effluent organic matter (EfOM). For NOM, fractions with MW between 1.8 k and 6.9 k Da accounted for most of the EDM (45.4%–48.6%), followed by the fractions with MW < 1.8 k Da (25.6%–42.4%). By contrast, the EDM in EfOM occurred predominantly in fractions with MW < 1 k Da (51.8%–58.6%), with lower concentrations in fractions with MW > 1.8 k Da (<20.2%). The heterogeneous MW distribution of EDM was strongly correlated to the presence of chromophores, but not DOC or fluorophores. The EDM difference between MW fractions suggested that the fraction with MW 1.8–6.9 k Da (40.7%–47.1%) and the fractions with MW < 1 k Da (50.2%–58.8%) should be the dominant oxidant consumers in NOM and EfOM, respectively. When the EDM was normalized by the DOC for each MW fraction (EDMMW/DOCMW), the EDMMW/DOCMW of relatively high-MW fractions (>1.8 k Da) is 1.2–1.9 times of relatively low-MW (<1 k Da) fractions for both NOM and EfOM, which indicates that higher-MW fractions are more susceptible to chemical oxidations. The relationship between EDM change and UVA254 change varied for different MW fractions during advanced ozonation treatment, because of the different oxidation mechanisms in operation for MW fractions. The ozonation of EfOM fractions with higher MW (>1.8 k Da) and lower MW (<1 k Da) preferentially resulted in benzoquinone formation and ring-cleavage, respectively.
8. 题目: Simultaneous removal of arsenic, cadmium, and lead from soil by iron-modified magnetic biochar
期刊: Environmental Pollution
作者: Xiaoming Wan, Chongyang Li, Sanjai J. Parikh
摘要: Effective and economically viable method to remove elevated metal(loid)s from farm and industrial lands remains a major challenge. In this study, magnetic biochar-based adsorbents with Fe3O4 particles embedded in a porous biochar matrix was synthesized via iron (Fe) treated biochar or thermal pyrolysis of Fe treated cedar sawdust. Application and separation of the adsorbent to a multi-contaminated soil slurry simultaneously removed 20–30% of arsenic, cadmium and lead within 24 h. Fast removal of multi-metal(loid)s result from the decrease in all operationally defined fractions of metal(loid)s, not limited to the exchangeable fraction. The direct removal of arsenic-enriched soil particles was observed via micro X-ray fluorescence maps. Furthermore, through comparison of biochars with different production methods, it has been found that magnetization after pyrolysis treatment leads to stronger metals/metalloids adsorption with a higher qe (bound sorbate) than other treatments but pyrolysis after magnetization stabilized Fe oxides on the biochar surface, indicating a higher biochar recovery rate (∼65%), and thus a higher metal(loid)s removal efficiency. The stability of Fe oxides on the surface of biochar is the determining factor for the removal efficiency of metal(loid)s from soil.
9. 题目: Evaluation of biochar pyrolyzed from kitchen waste, corn straw, and peanut hulls on immobilization of Pb and Cd in contaminated soil
期刊: Environmental Pollution
作者: Congbin Xu, Jiwei Zhao, Wenjie Yang, Li He, Wenxia Wei, Xiao Tan, Jun Wang, Aijun Lin
摘要: Biochar has a wide range of feedstocks, and different feedstocks often resulted in different properties, such as element distribution and heavy metal immobilization performance. In this work, batch experiments were conducted to assess the effectiveness of biochar pyrolyzed from kitchen waste (KWB), corn straw (CSB), and peanut hulls (PHB) on immobilization of Cd and Pb in contaminated soil by planting swamp cabbage (Ipomoea aquatica Forsk.) with a combination of toxicological and physiological tests. The results showed that biochar could all enhance the soil pH, and reduce extractable Pb and Cd in soil by 22.61%–71.01% (KWB), 18.54%–64.35% (CSB), and 3.28%–60.25% (PHB), respectively. The biochar led to a drop in Cd and Pb accumulation in roots, stems, and leaves by 45.43%–97.68%, 59.13%–96.64%, and 63.90%–99.28% at the dosage of 60.00 mg/kg, respectively. The root length and fresh weight of swamp cabbage were promoted, while superoxide dismutase (SOD) and peroxidase (POD) decreased after biochar treatment. The distribution of heavy metal fractions before and after biochar treatment indicated that biochar could transform Cd and Pb into a state of lower bioavailability, thus inhibiting Cd and Pb uptake by swamp cabbage. Biochar with different feedstocks could be ranked by the following order according to immobilization performance: KWB > CSB > PHB.
10. 题目: Removal of atrazine by biochar-supported zero-valent iron catalyzed persulfate oxidation: Reactivity, radical production and transformation pathway
期刊: Environmental Research
作者: Zhao Jiang, Jiaojiao Li, Duo Jiang, Yan Gao, Yukun Chen, Wei Wang, Bo Cao, Yue Tao, Lei Wang, Ying Zhang
摘要: Atrazine is a widely used herbicide whose presence poses a potential threat to agriculture and human living environment. This work studied the degradation performances and mechanisms of zero-valent iron and biochar composite (ZVI/BC) activated persulfate (PS) for atrazine. The results showed that the removal percentage of atrazine reached 73.47% within 30 min. Furthermore, the optimal parameters (175 mg/L ZVI/BC, 2 mM PS and initial pH of 3) were obtained through response surface methodology. Meanwhile, the high atrazine removal percentage (83.77%) was obtained under the optimal conditions. Radical quenching studies and electron spin resonance revealed that active substances produced during PS activation, as well as that SO4·− and HO· were dominant active species for the atrazine degradation. According to iron corrosion products and XPS analysis, the reaction mechanism of ZVI/BC-PS system was proposed as that ZVI loaded on the composites further activated PS to produce SO4·− and HO· which accompany with the valent changing of iron and finally causing degradation of atrazine. In addition, the degradation pathways of atrazine in ZVI/BC-PS system included dealkylation, alkyl oxidation and dechlorination-hydroxylation by the results of GC-MS and LC-MS. These findings demonstrated that ZVI/BC activated persulfate may be an efficient technique for the degradation of atrazine.
11. 题目: Microstructural and biochemical diversity of forest soil organic surface layers revealed by density fractionation
作者: Jörg Prietzel, Sigrid Hiesch, Gertraud Harrington, Svenja Müller
摘要: Particularly on sites with shallow, nutrient-poor soils, forest soil organic surface layers (O layers) are important for the storage of plant-available nutrients and water, and thus for forest vitality and productivity. O layers can contain up to 70 mass percent of inorganic compounds (minerals) which may be spatially separated from or closely associated with soil organic matter (SOM). O layer SOM may differ in biochemical properties and resistance against mineralization, depending on the extent of organo-mineral association. Moreover, type and intensity of SOM-mineral mixing in O layers conveys information about biological activity. Here, for the first time we present detailed density fractionation results to distinguish SOM constituents in O layers with different chemical properties and likely also different degrees of organo-mineral association. Additionally, we characterized spatial association patterns of the SOM fractions. We investigated samples of Of (Oe) and Oh (Oa) horizons of temperate forest soils with different parent materials (basalt, gneiss, andesite, Pleistocene gravel, dolomite). The samples were distinguished into six density fractions (ρ < 0.8 g cm−3; 0.8–1.0 g cm−3; 1.0–1.2 g cm−3; 1.2–1.4 g cm−3; 1.4–1.6 g cm−3; >1.6 g cm−3) by sequential treatment with deionized H2O (ρ = 1.0 g cm−3), 1-propanol (ρ = 0.8 g cm−3), and sodium polytungstate (SPT) solution of increasing density (ρ = 1.2, 1.4, 1.6 g cm−3). The procedure is characterized by a mass recovery of 93 ± 5% and an organic carbon (OC) recovery of 90 ± 9%. In each fraction, we analyzed the concentrations of C, N, metal cations (Fe, Al, Ca, Mg), C speciation (13C NMR spectroscopy), as well as abundances of 13C and 15N. For selected fractions, we additionally determined the radiocarbon age and acquired microscopic images. From the Of to the Oh horizons, the contribution of heavy fractions (>1.4 g cm−3) to total soil mass and total SOC increased, indicating augmented organo–mineral association with progressive SOM decomposition state. Compared to bulk soil, heavier fractions >1.4 g cm−3 were characterized by smaller SOC concentrations, whereas concentrations of Al and Fe were increased for fractions >1.4 g cm−3 in the of and >1.6 g cm−3 in the Oh horizon. The SOM in the heavy fractions was enriched in N, carboxyl C, and alkyl C, but depleted in O/N-alkyl C and aryl C. Smaller mean particle sizes and C/N ratios as well as increased alkyl C / O/N-alkyl C ratios and 13C and 15N abundances indicate an advanced SOM decomposition state and enrichment of microbial-derived SOM in heavier fractions. However, according to its 14C signature, in contrast to high-density (ρ > 1.6 g cm−3) SOM in the mineral soil, forest floor SOM with high density is a rapidly cycling SOM pool with a turnover time <50 years.
12. 题目: Irreversible fouling in hollow-fiber PVDF MF/UF membranes filtering surface water: Effects of precoagulation and identification of the foulant
期刊: Journal of Membrane Science
作者: Katsuki Kimura, Keita Kume
摘要: In this study, microfiltration (MF) and ultrafiltration (UF) of surface water were compared in terms of irreversible fouling and effective pretreatment. Hollow-fiber MF/UF membranes made from the same polymer (polyvinylidene fluoride (PVDF)) were examined with multiple samples of surface water used for drinking water production. Experiments were carried out in a realistic style: with a constant flow rate and periodic backwashing. Regardless of the source of the feed water, evolution of fouling was less significant in the case of UF. In the case of MF, anion exchange followed by coagulation using poly-aluminium chloride (PACl) efficiently mitigated membrane fouling, whereas PACl coagulation alone was sufficient for UF. Artificial alteration of the composition of natural organic matter (NOM) in the feed water was carried out by MF/UF with different pore sizes, and it was revealed that different fractions of NOM were responsible for evolution of irreversible fouling in MF and UF: large biopolymers and small biopolymers were responsible for irreversible fouling in MF and UF, respectively. The mechanism of fouling mitigation by coagulation was also investigated. Cake (coagulated flocs) deposited on the membrane surface mitigated irreversible fouling in UF, whereas it did not affect irreversible fouling in MF. It was postulated that advection flow caused by membrane filtration made more adsorption sites available inside the flocs for removal of small biopolymers (i.e., UF foulants).
13. 题目: Two-year study of biochar: Achieving excellent capability of potassium supply via alter clay mineral composition and potassium-dissolving bacteria activity
期刊: Science of The Total Environment
作者: Mengyang Zhang, Muhammad Riaz, Bo Liu, Hao Xia, Zeinab El-desouki, Cuncang Jiang
摘要: At present, there has been renewed interest in biochar research, but most of them were focused on the short-term effects of biochar and the information of long-term application of biochar is still lacking. In addition, the nutrient mechanism of biochar has rarely been the subject of research. This research explored the effect of potassium (K) nutrient and the response of bacterial communities to biochar in yellow-brown soil based on two-year experiment. In this study, we used peanut shell biochar obtained by pyrolysis at 400 °C, and at the same time, 0%, 20%, 40%, 100% conventional potassium fertilizer were used. The results indicated that the effective improvement of biochar on acidic soil was long-term and 2% biochar replaced 40% conventional potassium fertilizer. Biochar accelerated the conversion of slowly-available K to available K by changing the composition of clay minerals and promoting the growth of K-dissolving bacteria. From the perspective of bacterial community, biochar significantly increased the relative abundance of Sphingomonas, Gaiella, and Elev-16S-1332, which improved the potential ability of soil to degrade pollutants and inhibit pathogens. The pH, organic matter, cation exchange capacity (CEC), and available phosphorus and potassium were important environmental factors that caused significant effects in the bacterial community of yellow-brown soil. Overall, the study demonstrates that biochar is not only an effective alternative to potash fertilizer but also improves soil bacterial communities.
14. 题目: The impact of biodegradable carbon sources on nutrients removal in post-denitrification biofilm reactors
期刊: Science of The Total Environment
作者: Artur Mielcarek, Joanna Rodziewicz, Wojciech Janczukowicz, Joanna Struk-Sokołowska
摘要: Wastewater from households wastewater treatment plants (HWWTP) is discharged to the ground or to the surface waters. Special consideration should be given to the improvement of HWWTP effectiveness, particularly in relation to nutrients. The addition of biodegradable carbon sources to biofilm reactor, can enhance microbial activity but may also lead to filling clogging. The study aimed to compare 3 different organic substrates: acetic acid (commonly applied)and two untypical - citric acid and waste beer, under the same operational conditions in a post-denitrification biofilm reactor. The study investigated the impact of a type of organic substrate, low pH and time on: (1) biofilm growth, (2) the characteristics of extracellular polymeric substances (EPS), (3) the kinetics of nutrients removal and (4) reactor clogging. Results were referred to (5) the effectiveness of nutrients removal. The study demonstrated that low pH assured the development of a thinbiofilm. Citric acid ensured the lowest biomass volume, being by 53% lower than in the reactor with acetic acid and by as much as 61% lower than in the reactor with waste beer. The soluble EPS fraction prevailed in the total EPS in all reactors. The content of the tightly bound EPS fraction ranged from 26.93% (citric acid) to 36.32% (waste beer). Investigations showed also a high ratio of exoproteins to polysaccharide in all fractions, which indicated a significant role of proteins in developing a highly-proliferating biofilm. The treated wastewater met requirements of Polish regulations concerning COD and nitrogen concentrations.
15. 题目: Water quality changes and organic matter removal using natural bank infiltration at a boreal lake in Finland
期刊: Hydrogeology Journal
作者: M. Jylhä-Ollila, H. Laine-Kaulio, P. Niinikoski-Fusswinkel, J. Leveinen, H. Koivusalo
摘要: Managed aquifer recharge (MAR) refers to intentional infiltration of surface water to an aquifer for facilitating natural water treatment and storage. MAR is often used as a treatment to remove natural organic matter from water in drinking water production. The sustainability of MAR depends on how the aquifer capacity to remove organic matter will evolve over the long term. This report explores the behavior of MAR systems by using a natural lake–aquifer system as a surrogate. Natural infiltration of lake water to groundwater has been going on for millennia at the research site in Finland chosen for this study. According to the measurements, the mean concentration of total organic carbon (TOC) in lake water was 3.0 mg/L. Within the distance of 3 m from the lake bank (retention time 7–15 days), already 46% of TOC was removed. At greater distances along the flow paths within the aquifer, 80–90% of TOC was removed. The observed TOC removal in the aquifer was slightly higher than the reported values at MAR sites, indicating that MAR can be an effective solution to the problem of removing natural organic matter in the long term. Signs of accumulation of organic matter were not observed in the aquifer, which suggests that biodegradation was the main removal method, and the role of sorption was minor. Several processes had an impact on oxygen levels in the aquifer, which led to spatial and seasonal changes in the redox conditions and in the iron and manganese concentrations in groundwater.
16. 题目: Nitrifier adaptation to low energy flux controls inventory of reduced nitrogen in the dark ocean
期刊: Proceedings of the National Academy of Sciences
作者: Yao Zhang, Wei Qin, Lei Hou, Emily J. Zakem, Xianhui Wan, Zihao Zhao, Li Liu, Kristopher A. Hunt, Nianzhi Jiao, Shuh-Ji Kao, Kai Tang, Xiabing Xie, Jiaming Shen, Yufang Li, Mingming Chen, Xiaofeng Dai, Chang Liu, Wenchao Deng, Minhan Dai, Anitra E. Ingalls, David A. Stahl, Gerhard J. Herndl
摘要: Ammonia oxidation to nitrite and its subsequent oxidation to nitrate provides energy to the two populations of nitrifying chemoautotrophs in the energy-starved dark ocean, driving a coupling between reduced inorganic nitrogen (N) pools and production of new organic carbon (C) in the dark ocean. However, the relationship between the flux of new C production and the fluxes of N of the two steps of oxidation remains unclear. Here, we show that, despite orders-of-magnitude difference in cell abundances between ammonia oxidizers and nitrite oxidizers, the two populations sustain similar bulk N-oxidation rates throughout the deep waters with similarly high affinities for ammonia and nitrite under increasing substrate limitation, thus maintaining overall homeostasis in the oceanic nitrification pathway. Our observations confirm the theoretical predictions of a redox-informed ecosystem model. Using balances from this model, we suggest that consistently low ammonia and nitrite concentrations are maintained when the two populations have similarly high substrate affinities and their loss rates are proportional to their maximum growth rates. The stoichiometric relations between the fluxes of C and N indicate a threefold to fourfold higher C-fixation efficiency per mole of N oxidized by ammonia oxidizers compared to nitrite oxidizers due to nearly identical apparent energetic requirements for C fixation of the two populations. We estimate that the rate of chemoautotrophic C fixation amounts to ∼1 × 10 13 to ∼2 × 10 13 mol of C per year globally through the flux of ∼1 × 10 14 to ∼2 × 10 14 mol of N per year of the two steps of oxidation throughout the dark ocean.
17. 题目: Advanced landfill leachate biochemical effluent treatment using Fe-Mn/AC activates O 3 /Na 2 S 2 O 8 process: process optimization, wastewater quality analysis, and activator characterization
期刊: Environmental Science and Pollution Research
作者: Zhanmeng Liu, Liang Pan, Fengping Hu, Yunqi Hu
摘要: A novel catalyst of Fe-Mn/AC was prepared and used as a heterogeneous catalyst to activate O3/Na2S2O8 for landfill leachate biochemical effluent treatment. The experimental results indicated that the highest COD (84%) and color (98%) removal was obtained at Fe-Mn/AC dosage 1.2 g/L, O3 concentration 1.2 g/L, Na2S2O8 dosage 6 g/L, initial pH 10, and reaction time 100 min. Three-dimensional and excitation emission matrix (3D-EEM) fluorescence spectrometry, Fourier transform infrared spectroscopy (FTIR), and gas chromatography mass spectrometry (GC/MS) of wastewater samples before and after treatment demonstrated that the leachate biochemical effluent contained a large amount of humic and fulvic acid organic compounds. After treatment with this coupling system, both the pollution level of dissolved organic matter (DOM) and the fluorescence intensity declined. The micro morphology of Fe-Mn/AC was characterized using scanning X-ray diffraction patterns (XRD), electron microscope spectra (SEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectroscopy. It can be concluded that the microscopic morphology of the catalyst is porous. The main active components are amorphous MnO2 and multivalent iron oxides. Furthermore, the Fe-Mn/AC catalyst showed great reusability; the removal efficiency of COD was only reduced from 84% to 79% at the fourth reaction. Moreover, the COD removal efficiency could recover to 81% after catalyst regeneration.
18. 题目: Effect of Fe–Mn–Ce modified biochar composite on microbial diversity and properties of arsenic-contaminated paddy soils
作者: Guogang Zhang, Xuewei Liu, Minling Gao, Zhengguo Song
摘要: In this study, we investigated the mechanism of decrease in arsenic (As) bioavailability after addition of biochar (BC) supplemented with iron (Fe)- manganese (Mn)- cerium (Ce) oxide (FMCBC) to As-contaminated paddy soil. We explored the effects of these composites on the oxidation, reduction, microbial community, and soil enzyme activity of As-contaminated paddy soil. Results showed that FMCBCs improve soil pH, significantly improve the redox capacity of soil, and reduce bioavailable forms of As. FMCBCs can convert As from a specifically or non-specifically bound form into amorphous hydrous oxide bound- and crystalline hydrous oxide bound form. The application of FMCBCs increased soil enzyme activity (urease, catalase, alkaline phosphatase, and peroxidase), and greatly influenced the relative abundance of certain microorganisms (Proteobacteria, Acidobacteria, and Gemmatimonadetes), which improved soil enzyme heavy metal tolerance and prevented their denaturation. Thus, FMCBCs can not only change the form and distribution of As in soil but also create an environment suitable for microbial growth, consequently affecting the geochemical cycling of As in soil.
19. 题目: Reviews and syntheses: The mechanisms underlying carbon storage in soil
作者: Isabelle Basile-Doelsch, Jérôme Balesdent, and Sylvain Pellerin
摘要: Scientific research in the 21st century has considerably improved our knowledge of soil organic matter and its dynamics, particularly under the pressure of the global disruption of the carbon cycle. This paper reviews the processes that control C dynamics in soil, the representation of these processes over time, and their dependence on variations in major biotic and abiotic factors. The most recent advances in soil organic matter knowledge are:
20. 题目: Characterizing the interactions between sediment dissolved organic matter and zinc using multispectroscopic techniques
期刊: Environmental Pollution
作者: Weiwei Lü, Xin Yao, Haoyu Ren, Huanguang Deng, Min Yao, Baohua Zhang
摘要: Sediment dissolved organic matter (DOM) was collected in November 2018 from Lake Dongping, China. The lake was divided into the entrance of the Dawen River, the open region of the lake, the tourism district and the macrophyte-dominated region based on principal component analysis (PCA) of 9 DOM-related parameters. Multispectroscopic tools were used to investigate the binding of zinc (Zn) with four kinds of DOM collected from the entrance of the Dawen River (EDOM), the open area of the lake (ODOM), the macrophyte-dominated area (mainly dominated by Potamogeton crispus L.) (PDOM) and the tourism district (TDOM). Three fluorescent components, the humic-like (components 1 and 3) and protein-like (component 2) components, were found by excitation-emission matrix spectra with parallel factor analysis. The EDOM, ODOM and TDOM were controlled by protein-like components, and the PDOM was controlled by humic-like components. Different components respond differently to Zn addition. The binding order of the tyrosine-like fraction > the tryptophan fraction > the humic-like fraction was identified by Synchronous fluorescence (SF) spectra and two-dimensional correlation spectroscopy (2D-COS). The fluorescence intensity of the protein-like component was suppressed, and the humic-like component was enhanced with the addition of Zn. The effective quenching constants (log K) of the protein-like component in PDOM were clearly higher than those in the EDOM, ODOM and TDOM, indicating higher metal binding potential in PDOM than in other kinds of DOM in Lake Dongping. The %Fmax (the amounts of each component measured as % of the total fluorescence maxima for the three components) of the humic-like components exhibited a gradual increase in all kinds of DOM with the addition of Zn, suggesting that the addition of Zn increased the humification of DOM.