12701. 题目: Impact of conventional agriculture on the concentration and quality of water-extractable organic matter (WEOM) in the surface horizons of Retisols—A case study from the Carpathian Foothills in Poland
In spite of many studies focused on the impact of land use changes on soil organic carbon (SOC) and the total nitrogen (TN) and soil organic matter (SOM) budget, less is known about the fate of water-extractable organic matter (WEOM) after the conversion of forestland to conventional farmland. The main aims of this study were: 1) to determine the concentration of water-extractable organic carbon (WEOC) and water-extractable total nitrogen (WETN) in topsoil horizons of forestland soils and cropland soils in the Carpathian Foothills in southern Poland and 2) to determine the quality of WEOM in topsoil horizons of forestland soils and cropland soils. Soil samples from topsoil horizons of forestland soils (Oi and Ah horizons) and cropland soils (Ap horizons) were collected and the concentration of WEOC and WETN was determined. In addition, the quality of WEOM was determined using ultraviolet-visible (UV–vis) spectroscopy and Fourier-transform infrared attenuated total reflectance (FTIR-ATR) spectroscopy. The results of this comparative study clearly indicate that conventional agriculture significantly affects the concentration and quality of WEOM in surface soil horizons of Retisols in the Carpathian Foothills in southern Poland. Surface horizons of arable soils (Ap horizons) are characterized by a significantly lower mean concentration of WEOC and WETN in comparison with surface horizons of forestland soils (Oi and Ah horizons), and reflect changes in the content of bulk SOC and TN due to soil tillage. Mean concentrations of WEOC and WETN in the studied Ap horizons of arable soils are 1.98 mg l−1 and 0.15 mg l−1, respectively while the mean concentrations of WEOC and WETN in the Ah horizons of forestland soils are 15.53 mg l−1 and 0.84 mg l−1, respectively. The studied Oi horizons of forestland soils are characterized by the highest mean concentration of WEOC (44.53 mg l−1) and WETN (6.22 mg l−1). Mean specific UV absorbance values at wavelength of 254 nm (SUVA254) was the highest for WEOM from Ap horizons indicating the highest transformation of WEOM in these horizons. Mean FTIR-ATR absorption bands of WEOM obtained from Oi and Ah horizons are much more intensive than the bands of WEOM from Ap horizons, which is related to significantly lower concentration of WEOM in the latter horizons in comparison with Oi and Ah horizons of forestland soils.
12702. 题目: Legacy of soil health improvement with carbon increase following one time amendment of biochar in a paddy soil – A rice farm trial
12703. 题目: Carbon mineralization and its temperature sensitivity under no-till and straw returning in a wheat-maize cropping system
Soil organic carbon (SOC) mineralization is regulated by temperature and moisture. No-till (NT) and straw returning (SR) have been widely adopted to sequester SOC, but information about the effects of temperature and moisture on SOC mineralization in NT and SR is limited, particularly SOC mineralization in different aggregate size classes. To identify the responses of SOC mineralization to temperature and moisture in NT and SR, undisturbed soils were sampled from a factorial experiment of tillage (NT and plow tillage [PT]) and straw (SR and straw removal [S0]) in a wheat-maize cropping system and incubated at moisture levels of 40%, 70%, and 100% at 15 °C and 25 °C. The results showed that maize season increased SOC mineralization but decreased its temperature sensitivity (Q10) compared with the wheat season under different moisture levels. Because NT and SR promoted macro-aggregation and low mineralization was observed in macro-aggregates, NT significantly decreased the absolute (per unit soil) and specific (per unit SOC) mineralization compared with PT, regardless of the soil temperature, moisture, depth, and sample date (P < 0.05). The SR significantly increased absolute SOC mineralization; Whereas, there was no significant difference in specific mineralization and was even 24.4% lower at 5–10 cm depth in the maize season than that of S0 (P < 0.05). However, macro-aggregates had 13.6%-37.3% and 11.9%-19.9% higher Q10 values than the micro-aggregates in the wheat and maize seasons, respectively. This led to a higher Q10 under NT and SR at 40% moisture level, indicating that NT and SR constrained SOC accumulation under global warming. Increases in moisture ranging from 40% to 100% could decrease Q10, thus no significant difference between NT and PT, and SR and S0 at 100% level. Conclusively, NT with SR decreases SOC mineralization but increases its Q10, indicating that the loss of SOC is currently low but could accelerate under future warming. Our study also provided an effective approach that increased moisture could constrain the improvement of Q10 induced by NT with SR.
12704. 题目: Soil redistribution reduces integrated C sequestration in soil-plant ecosystems: Evidence from a five-year topsoil removal and addition experiment
Soil redistribution is an important movement process of surface material that drastically affects the dynamic cycling of essential elements and soil productivity in the terrestrial ecosystem. Although a number of studies have focused on the soil organic carbon (SOC) pool under soil redistribution, few studies have comprehensively assessed the effects of soil redistribution on the ecosystem carbon pool. A five-year experiment of simulated topsoil redistribution (removal and addition, R-A) was conducted to explore the effects of soil redistribution on soil CO2 emissions, the SOC pool and the plant C pool in the semi-arid Loess Plateau of China. The soil properties, soil CO2 emissions, and crop parameters were measured after the topsoil removal (R20) treatment and topsoil addition (A20) treatment and in the undisturbed control (CK). Our results showed that 1) compared with the undisturbed control, the mean soil CO2 emissions of the R-A treatment decreased by 8% while the mean SOC pool increased by 3.0%; 2) the plant C pool was significantly reduced by 53.8% in 2015 and 5.8% in 2019 compared with the undisturbed control; 3) the ecosystem C pool (the sum of the SOC pool and plant C pool) of the R-A treatment was reduced by 10.3%, 3.7% and 1.1% compared with the ecosystem C pool of the undisturbed CK for 2015, 2016 and 2017, respectively, but increased by 0.6% and 1.9% from 2018 to 2019. During the first three experimental years, the decrease in the ecosystem C pool of the R-A treatment was caused by the reduced plant C pool in R20 exceeding the elevated plant C pool in A20. Over time, the soil bulk density (BD) decreased in R20 and the SOC, microbial biomass carbon (SMBC) and total nitrogen (TN) increased, which jointly improved the plant C pool in R20 and the ecosystem C pool by 2019. The gradual recovering pattern of the ecosystem C pool in the later years highlights the key role of plants in restoring soil properties and stabilizing ecosystem C cycling. Overall, our findings highlight that any attempt to assess the net impacts of soil redistribution, whether as a sink or source for atmospheric CO2, should comprehensively consider the changes in the SOC pool and plant C pool.
12705. 题目: Enhanced aqueous Cr(VI) removal using chitosan-modified magnetic biochars derived from bamboo residues
The purpose of this study was to fabricate a chitosan modified magnetic bamboo biochar (CMBB) for Cr(VI) detoxification from aqueous solution. Results showed that chitosan modification provided more active adsorption sites on the surface of magnetic bamboo biochar (MBB), and hence enhanced Cr(VI) removal from aqueous solution. The maximum adsorption capacities of MBB and CMBB for Cr(VI) at 25 °C were 75.8 and 127 mg g−1, respectively. Increasing solution pH inbibited Cr(VI) adsorption by adsorbents. However, CMBB maintained a high Cr(VI) removal efficiencies over a broader pH range (2–10), and could attain 36% of the maximum adsorption (40 mg g−1) even at a high pH of 10.0. Rising temperature enhanced the Cr(VI) removal by two adsorbents. The escalating ionic strength and coexist substances, including Na+, Ca2+, Fe3+, Cl−, SO42−, PO43− and humate, inhibited the adsorption efficiency of Cr(VI) on adsorbents. After the fifth adsorption-desorption cycle, the adsorption efficiencies of CMBB and MBB for Cr(VI) remained above 90% and less than 50%, respectively. All these results indicated that CMBB could be a practical adsorbent that can be utilized for the detoxification of Cr(VI) ions from wastewater.
12706. 题目: Adsorption and molecular weight fractionation of dissolved organic matters with different origins on colloidal surface
Dissolved organic matter (DOM) adsorption on colloid surface occurred ubiquitously in aquatic ecosystems, while variations in molecular weight (MW) distribution during adsorption remained poorly understood. In this study, the adsorption and MW fractionation of aquatic DOMs with different origins (e.g., macrophyte- and algae-derived, MDOM and ADOM, respectively) on colloid surface were examined using total organic carbon, absorption and fluorescence spectroscopy, and flow field flow fractionation (FlFFF) analysis. Both the total organic carbon and spectroscopic results showed the predominant adsorption of DOMs within the first 45 min, which behaved not synchronously with MW fractionation. Quantitative FlFFF analysis further indicated that the organic ligands with different MWs exhibited different adsorption affinities on colloid surface. It was found that 5–15 kDa and 50 kDã0.45 μm were preferential adsorption fraction for humic- and protein-like MDOM, respectively, while 0.3–2 kDa and 0.3–50 kDa were preferential adsorption fraction for humic- and protein-like ADOM, respectively. Therefore, the MW fractionation of DOMs upon adsorption was highly dependent on DOM origins as well as specific components. Results obtained herein can enlarge our insights into adsorption and the resultant behavior and fate of DOMs that were highly related with the MW fractionation in aquatic environments.
12707. 题目: Applying a new pomelo peel derived biochar in microbial fell cell for enhancing sulfonamide antibiotics removal in swine wastewater
A sequential anode-cathode double-chamber microbial fuel cell (MFC) is a promising system for simultaneously removing contaminants, recovering nutrients and producing energy from swine wastewater. To improve sulfonamide antibiotics (SMs)'s removal in the continuous operating of MFC, one new pomelo peel-derived biochar was applied in the anode chamber in this study. Results demonstrated that SMs can be absorbed onto the heterogeneous surfaces of biochar through pore-filling and π-π EDA interaction. Adding biochar to a certain concentration (500 mg/L) could enhance the efficiency in removing sulfamethoxazole, sulfadiazine and sulfamethazine to 82.44–88.15%, 53.40–77.53% and 61.12–80.68%, respectively. Moreover, electricity production, COD and nutrients removal were improved by increasing the concentration of biochar. Hence, it is proved that adding biochar in MFC could effectively improve the performance of MFC in treating swine wastewater containing SMs.
12708. 题目: Dual resource utilization for tannery sludge: Effects of sludge biochars (BCs) on volatile fatty acids (VFAs) production from sludge anaerobic digestion
Resource utilization of organic matters in tannery sludge has drawn great attention. In this paper, the influences of sludge biochars (BCs) on volatile fatty acids (VFAs) production from the anaerobic digestion of sludge supernatant (SST) were investigated. Experimental results demonstrated that the VFAs yields improved in the presence of BCs with rich functional groups. The maximum yield of VFAs was 1037.5 mg/g SCOD with the addition of BC-1 biochar (zeta potential -50.42 mV). BCs decreased ammonia nitrogen concentration, thus reducing inhibition for bacteria during the anaerobic digestion. Microbial community analysis indicated that the BCs affected microbial community structures and contributed to a favorable environment for bacteria. Especially, the BC-1 biochar with rich functional groups enhanced the relative abundance of acid-forming bacteria (Clostridiales). A dual strategy was proposed to improve the resource utilization efficiency for tannery sludge.
12709. 题目: Sludge pre-treatments change performance and microbiome in methanogenic sludge digesters by releasing different sludge organic matter
In this study, temporal impacts of thermal, alkaline/acid and thermal-alkaline sludge pre-treatments on digestion performance and microbiome were investigated and compared in methanogenic sludge digesters. Results showed that thermal and alkaline/acid pre-treatments were efficient in releasing intracellular and EPS organic matter, respectively. The thermal-alkaline pre-treatment showed synergistic impacts of both thermal and alkaline/acid pre-treatments by releasing the major portion of sludge organic matter from solid- to liquid-phase, which result in 60-65% organic carbon removal in subsequent sludge digestion and further optimizing digestion temperature had negligible improvement. The 16S rRNA gene-based analyses suggested that organic matter released from sludge pre-treatments is a major deterministic parameter in shaping sludge microbiome. Pre-treatment specific lineages were identified in different sludge digesters, whereas several taxa were identified as common functionally active populations in sludge digestion. This study provided mechanistic insights into impacts of pre-treatments on digestion performance and microbiome in methanogenic sludge digesters.
12710. 题目: Co-hydrothermal carbonization of food waste- woody sawdust blend: interaction effects on the hydrochar properties and nutrients characteristics
The influence of co-hydrothermal carbonization (co-HTC) on the hydrochar properties and nutrients distribution derived from food waste (FW) and woody sawdust (WS) blend was assessed. The carbon retention, surface functional groups and morphology features involved in hydorchar were evaluated to study the interaction effects. Results suggested that hydrochar yield consistently decreased with increase of both FW ratio and HTC temperature. C retention from 260°C hydrochar was low (approximately 65%), but more microsphere structures was formed due to the enhanced carbonization degree of hydrochar. Hydrochar obtained at high FW blend ratio and temperature resulted in weaken oxygen-containing groups like -OH and C-O with enhanced C=C and C–(O, N). 10.43-60.45% of N and 82-94% of P were retained in hydrochar. NH4+-N (6.63%-15.63%) and organic nitrogen (70.4%-87.7%) were identified as main N-containing species in liquid phase, while total P content (14-166 mg/L) depended more on FW ratio.
12711. 题目: Removal of high-molecular-weight polycyclic aromatic hydrocarbons by a microbial consortium immobilized in magnetic floating biochar gel beads
A bacterial consortium immobilized in magnetic floating biochar gel beads is proposed to remove high-molecular-weight polycyclic aromatic hydrocarbons. The microbial consortium performed better than single strains and consisted of four strains of marine bacteria for degrading pyrene (PYR), two strains for benzo(a)pyrene (BAP), and three strains for indeno(1,2,3-cd)pyrene (INP), which were isolated from oil-contaminated seawater. The immobilized cells could biodegrade 89.8%, 66.9% and 78.2% of PYR, BAP and INP, respectively, and had better tolerance to pH, temperature and salinity than free cells. The Andrews model was used to explore the biodegradation kinetics, and when the initial concentrations of PYR, BAP, and INP were 7.80, 3.05, and 3.41 mg/L, the specific biodegradation rates reached maximum values of 0.2507, 0.1286, and 0.1930 d−1, respectively. The immobilized microbial consortium had a high HMW-PAH removal ability and good floatability and magnetic properties and could be collected by an external magnetic field.
12712. 题目: Inter‐community and on‐farm asymmetric organic matter allocation patterns drive soil fertility gradients in a rural Andean landscape
Soil fertility in agricultural landscapes is driven by complex interactions between natural and anthropogenic processes, with organic matter (OM) inputs playing a critical role. Asymmetric allocation patterns of these resources among communities and within individual farms can lead to soil fertility gradients. However, the drivers and consequences of such patterns in different socioecological contexts remains poorly documented and understood. The objective of this study was to address this gap by assessing asymmetric OM allocation patterns and the associated consequences for soil fertility management in three indigenous communities located in the Central Ecuadorian Andes. We found that both distance from homestead and perception of fertility were associated with asymmetric OM allocation patterns to fields as well as with soil fertility gradients within farms. For example, soil organic carbon (SOC), total nitrogen (N), available phosphorus (P), and exchangeable potassium (K) all decreased with distance from the homestead, while SOC, total N, and available P were positively correlated with a farmer's perception of soil fertility. We note that these fertility gradients remained even in the case of increased farm‐level OM inputs. Overall OM allocation patterns differed significantly among communities and were associated with significant differences in soil fertility, with the highest levels of available P and exchangeable K found in the community with the highest OM inputs. The results of this study indicate the importance of asymmetric OM allocation patterns encountered at different scales, both within farms and among neighboring communities, in rural Andean landscapes and their significant interactions with soil fertility gradients.
12713. 题目: Photoformation of persistent free radicals on a montmorillonite-humic acid complex simulated as particulate organic matter in an aqueous solution
12714. 题目: Quantitative determination of redox-active carbonyls of natural dissolved organic matter
Natural dissolved organic matter (DOM) is ubiquitous in environment and plays an important role in numerous environmental processes. Although the molecular basis of the reactivity of DOM remains poorly understood due to its extreme complexity, redox-active carbonyls (aromatic ketones/aldehydes and quinones) within DOM are believed vitally important. Except the rough determination of total carbonyls (including non-redox active –COOR) based on inflexible 13C chemical shift range by expensive and time-consuming solid-state nuclear magnetic resonance (NMR), there is no ready method to quantify redox-active carbonyls in DOM. Here we show that after treatment with sodium borohydride (NaBH4) by selectively eliminating redox-active carbonyls, quenched fluorescence of carbon quantum dots (CD) by DOM recovered dramatically, and displayed a good linear relationship between redox-active carbonyls detected and DOM concentration (R2 ≥ 0.977), thus allowing first quantitative determination of the redox-active carbonyls of DOM. Eight DOM isolates present 0.59%–0.90% redox-active carbonyls by the current method. And this method is robust from coexisting proteins and salts. This method could provide better or equal instructive results compared with solid-state NMR for total carbonyls or electrochemical method for electron-accepting capacities (EAC). Our results provide the underlying structural basis of many important geochemical processes that mediated by DOM. We posit that this method could apply to other complex molecular systems such as the atmospheric aerosols and extracellular polymeric substances (EPS), too.
12715. 题目: Estimating contributions of black and brown carbon to solar absorption from aethalometer and AERONET measurements in the highly polluted Kathmandu Valley, Nepal
We estimated the individual contributions of black carbon (BC) and brown carbon (BrC) to the aerosol absorption coefficient (σap) and absorption aerosol optical depth (AAOD) in the highly polluted Kathmandu Valley, Nepal, by applying the absorption Ångström exponent (AÅE) method to multi-wavelength aethalometer and AERONET sun/sky radiometer measurements. The elevated σap levels observed during the winter and pre-monsoon periods were primarily due to increased usage of diesel generators and low-grade fuel/coal. The AAODBC and AAODBrC values were substantially higher during the pre-monsoon period, almost two-fold higher than winter levels, due to seasonally increased biomass-burning activities from agricultural residue burning and forest fires. The overall contribution of BC to σap was approximately 80%–95%, whereas BrC accounted for 5%–20% at 520 nm. However, the BrC contribution to σap at 370 nm was substantially higher during the winter, ranging from 29.3% to 34.0%. The portioning of AERONET measurements indicates that BC contributed 80% (69%) while BrC contributed 20% (31%) to AAOD of carbonaceous aerosols at 520 nm (370 nm). Although the observation principles and techniques are completely independent, the BC and BrC absorption for simultaneous daytime data points shows a strong correlation between surface aethalometer-based and column AERONET-based estimates. The contributions of BC and BrC to absorption in Kathmandu Valley are similar to those observed under open biomass and garbage-burning conditions; however, the BrC absorption at both 370 and 520 nm is approximately 2- to 3-fold higher than those observed for urban areas in East Asia.
12716. 题目: Variation in quantity and quality of rainwater dissolved organic matter (DOM) in a peri-urban region: Implications for the effect of seasonal patterns on DOM fates
Dissolved organic matter (DOM) is a ubiquitous group of organic compounds in rainwater that plays vital roles in the biogeochemical cycle. However, little is known about its chemical composition, optical characterization, potential sources, and controlling mechanisms in peri-urban atmospheric rainwater. One-year rainfall samples were collected between September 2018 and August 2019 in a Nanjing suburb. Stoichiometric, ultraviolet–visible (UV–Vis) absorption, and three-dimensional fluorescence excitation-emission matrix (EEM) with parallel factor analysis (PARAFAC) analyses were utilized to characterize DOM. Several proxies for DOM concentration, including dissolved organic carbon (DOC), dissolved organic nitrogen (DON), and absorption coefficient (a254), exhibited power-function relationships with the rainfall amount (r2 = 0.33–0.55, p < 0.001). Particularly, the DOC and a254 value showed significant seasonal variability, with lower value in two wet seasons (winter and summer) than in the dry seasons (autumn and spring). The annual wet depositional (WD) flux of DOC in the Xianlin (XL) site was calculated as 1.68 g C m−2 yr−1, agreeing with the range of global WD flux values. Two terrestrial humic-like components (C1–C2), one microbial humic-like component (C3), and one tryptophan-like component (C4) were identified by EEM-PARAFAC in rainwater DOM. The results of the specific absorption indices (SUVA254, SR) and PARAFAC component analyses revealed that summer DOM samples had lower fluorescence intensities, aromatic contents, and molecular sizes. Principal component analysis (PCA) based on DOM indices showed that rainwater DOM had predominantly terrestrial humic origins, while this characteristic became slightly weaker in summer. The quantity and quality of rainwater DOM were closely related to meteorological variables (i.e., air mass, rainfall amount, and solar radiation) as well as anthropogenic activities. This study could improve the understanding of the quantity and quality of rainwater DOM on carbon budgets and biogeochemical cycling from some new insights of optical proxies about different fates of rainwater DOM under complex controlling mechanisms.
12717. 题目: Chemical fractionation of organic matter and organic phosphorus extractions from freshwater lake sediment
Lake sediment organic matter (OM) is composed of a variety of organic compounds differing in their biolability and origin. Sources of sediment OM can include terrestrial input from the watershed and algal/microbial metabolic byproducts residing in the water column or sediment. Dissolved organic phosphorus (DOP) is a critical component of OM in freshwater eutrophic lakes, often acting as a source for bioavailable phosphorus that fuels harmful algal and/or cyanobacterial blooms. Parallel extractions of lake sediment collected from Missisquoi Bay, a eutrophic bay in Lake Champlain, were conducted with the goal of identifying OM and organic P sediment constituents using ultrahigh-resolution mass spectrometry from various extractants. Extractants converged into two groups based on the characteristics of their extracted OM; stronger extractants were composed of highly acidic and alkali media, while milder extractants represented weaker acids and bases. Sediment treated with the strong extractants afforded highly oxygenated and unsaturated OM thought to be stable with mostly lower heteroatomic content. In contrast, milder extractants yielded highly aliphatic and saturated compounds with lower masses and greater heteroatom functionally, sharing characteristics with labile molecules. Extracted organic P molecules mirrored the bulk OM in terms of lability, mass, and oxygenation within their corresponding extractants. Milder extractants resulted in greater organic P formulae assignments than the stronger extractants, with NaHCO3 resulting in the most aliphatic organic P formulae. We recommend the use of acetic acid to probe lake sediment for overall molecular characterization, spanning the greatest ranges of O/C and H/C ratios and representing both labile and mineral-associated OM. Other extractants should be implemented for a more targeted analysis. For instance, the use of NaHCO3 for organic P characterization, while using NaOH when interested in sediment geochemistry; both of which are critical for understanding the factors contributing to internal P loading.
12718. 题目: Sludge-derived biochar as efficient persulfate activators: Sulfurization-induced electronic structure modulation and disparate nonradical mechanisms
Sulfurized biochar derived from sewage sludge (SSB) was facilely synthesized and manifested upgraded performance in activation of peroxymonosulfate (PMS) and peroxydisulfate (PDS) for bisphenol A (BPA) elimination. The incorporated zigzag-edge sulfur effectively activated the sp2-hybridized graphene lattice, leading to the creation of more Lewis acid and basic sites in SSB. Singlet oxygen (1O2) generated from PMS oxidation at the Lewis acid sites was confirmed to be the dominated reactive species for BPA removal in the SSB/PMS system, whereas electron-transfer reactions comprising surface-confined complexes originated from the intimate contact between PDS and Lewis basic sites played the decisive role in the SSB/PDS system. Nineteen intermediates were identified in the two systems and degradation pathways of BPA were deduced accurately as well. This work not only provides a novel modification strategy for the cost-effective and environment friendly biochar-based catalysts but also deepen the insight into mechanisms of persulfate activation with carbonaceous materials.
12719. 题目: Persistence of soil organic carbon caused by functional complexity
12720. 题目: Materials and pathways of the organic carbon cycle through time