Enhancing soil aggregation and acetamiprid adsorption by ecofriendly polysaccharides hydrogel based on Ca2+- amphiphilic sodium alginate.

Soil aggregation plays an important role in agricultural production activities. However, the structure of soil aggregation is destroyed by the natural environment and unreasonable farming management, resulting in the loss of water, fertilizers and pesticides in soil. At present, hydrogels have been widely reported to promote the formation of soil aggregation. In this paper, amphiphilic calcium alginate (ASA/Ca2+) was applied to promote the formation of soil aggregation and enhance pesticide retention. Initially, an ASA was obtained through the one-pot Ugi condensation (a four-component green chemical reaction). Then, ASA/Ca2+ hydrogel is prepared by Ca2+ cross-linking. The formation of soil aggregation was determined through the Turbiscan Lab Expert stability analyzer, Confocal Laser Scanning Microscope (CLSM), and Transmission Electron Microscope (TEM). And the effect of soil aggregation on acetamiprid environmental behavior was investigated by adsorption kinetics, adsorption isotherms, and leaching. The results shown that the three-dimensional network structure of ASA/Ca2+ hydrogel can promote the formation of soil aggregation. Aggregate durability index (ADI) was 0.55 in the presence of ASA/Ca2+ hydrogel, indicating that amphiphilic hydrogel can enhance the stability of soil aggregation. The adsorbing capacity of acetamiprid was 1.58 times higher than pure soil, and the release of acetamiprid only about 20% in the presence of ASA/Ca2+ hydrogel. These results would be helpful for the formation of soil aggregation and pesticides adsorption on soil aggregation. Thus, ASA/Ca2+ hydrogel is likely to improve soil quality, simultaneously it can minimize the mobility of pesticides in the agricultural system.

Interannual variation in methane emissions from tropical wetlands triggered by repeated El Niño Southern Oscillation.

Methane (CH4 ) emissions from tropical wetlands contribute 60%-80% of global natural wetland CH4 emissions. Decreased wetland CH4 emissions can act as a negative feedback mechanism for future climate warming and vice versa. The impact of the El Niño-Southern Oscillation (ENSO) on CH4 emissions from wetlands remains poorly quantified at both regional and global scales, and El Niño events are expected to become more severe based on climate models' projections. We use a process-based model of global wetland CH4 emissions to investigate the impacts of the ENSO on CH4 emissions in tropical wetlands for the period from 1950 to 2012. The results show that CH4 emissions from tropical wetlands respond strongly to repeated ENSO events, with negative anomalies occurring during El Niño periods and with positive anomalies occurring during La Niña periods. An approximately 8-month time lag was detected between tropical wetland CH4 emissions and ENSO events, which was caused by the combined time lag effects of ENSO events on precipitation and temperature over tropical wetlands. The ENSO can explain 49% of interannual variations for tropical wetland CH4 emissions. Furthermore, relative to neutral years, changes in temperature have much stronger effects on tropical wetland CH4 emissions than the changes in precipitation during ENSO periods. The occurrence of several El Niño events contributed to a lower decadal mean growth rate in atmospheric CH4 concentrations throughout the 1980s and 1990s and to stable atmospheric CH4 concentrations from 1999 to 2006, resulting in negative feedback to global warming.

ß-Cyclodextrin network crosslinked by novel phosphonium-based tetrakiscarboxylic acid derived from PH3 tail gas: Synthesis and application for rapid removal of organic dyes from wastewater.

Organic dyes, such as methyl orange (MO), Congo red (CR), crystal violet (CV) and methylene blue (MB), are common organic pollutants existing in wastewater. Therefore, the exploration of bio-based adsorbents for the efficient removal of organic dyes from wastewater has gained many attentions. Here, we report a PCl3-free synthetic method for the synthesis of phosphonium-containing polymers, in which the prepared tetrakis(2-carboxyethyl) phosphonium chloride-crosslinked ß-cyclodextrin (TCPC-ß-CD) polymers were applied to the removal of dyes from water. The effects of contact time, pH (1-11), and dye concentration were investigated. The selected dye molecules could be captured by the host-gest inclusion of ß-CD cavities, and the phosphonium and carboxyl groups in the polymer structure would respectively facilitate the removal of cationic dyes (MB and CV) and anionic dyes (MO and CR) via electrostatic interactions. In a mono-component system, over 99 % of MB could be removed from water within the first 10 min. Based on the Langmuir model, the calculated maximum adsorption capacities of MO, CR, MB, and CV were 180.43, 426.34, 306.57, and 470.11 mg/g (or 0.55, 0.61, 0.96 and 1.15 mmol/g), respectively. Additionally, TCPC-ß-CD was easily regenerated using 1 % HCl in ethanol, and the regenerative adsorbent still showed high removal capacities for MO, CR, and MB even after seven treatment cycles.

Improvement of transpiration estimation based on a two-leaf conductance-photosynthesis model with seasonal parameters for temperate deciduous forests.

Introduction: Conductance-photosynthesis (Gs-A) models, accompanying with light use efficiency (LUE) models for calculating carbon assimilation, are widely used for estimating canopy stomatal conductance (Gs) and transpiration (Tc) under the two-leaf (TL) scheme. However, the key parameters of photosynthetic rate sensitivity (gsu and gsh) and maximum LUE (ϵmsu and ϵmsh) are typically set to temporally constant values for sunlit and shaded leaves, respectively. This may result in Tc estimation errors, as it contradicts field observations. Methods: In this study, the measured flux data from three temperate deciduous broadleaved forests (DBF) FLUXNET sites were adopted, and the key parameters of LUE and Ball-Berry models for sunlit and shaded leaves were calibrated within the entire growing season and each season, respectively. Then, the estimations of gross primary production (GPP) and Tc were compared between the two schemes of parameterization: (1) entire growing season-based fixed parameters (EGS) and (2) season-specific dynamic parameters (SEA). Results: Our results show a cyclical variability of ϵmsu across the sites, with the highest value during the summer and the lowest during the spring. A similar pattern was found for gsu and gsh, which showed a decrease in summer and a slight increase in both spring and autumn. Furthermore, the SEA model (i.e., the dynamic parameterization) better simulated GPP, with a reduction in root mean square error (RMSE) of about 8.0 ± 1.1% and an improvement in correlation coefficient (r) of 3.7 ± 1.5%, relative to the EGS model. Meanwhile, the SEA scheme reduced Tc simulation errors in terms of RMSE by 3.7 ± 4.4%. Discussion: These findings provide a greater understanding of the seasonality of plant functional traits, and help to improve simulations of seasonal carbon and water fluxes in temperate forests.

An early warning signal for grassland degradation on the Qinghai-Tibetan Plateau.

Intense grazing may lead to grassland degradation on the Qinghai-Tibetan Plateau, but it is difficult to predict where this will occur and to quantify it. Based on a process-based ecosystem model, we define a productivity-based stocking rate threshold that induces extreme grassland degradation to assess whether and where the current grazing activity in the region is sustainable. We find that the current stocking rate is below the threshold in ~80% of grassland areas, but in 55% of these grasslands the stocking rate exceeds half the threshold. According to our model projections, positive effects of climate change including elevated CO2 can partly offset negative effects of grazing across nearly 70% of grasslands on the Plateau, but only in areas below the stocking rate threshold. Our analysis suggests that stocking rate that does not exceed 60% (within 50% to 70%) of the threshold may balance human demands with grassland protection in the face of climate change.

Light-tuning amphiphility of host-guest Alginate-based supramolecular assemblies for photo-responsive Pickering emulsions.

Various Pickering emulsions-based system have been increasing demand for potential applications in a wide variety of fields. However, tunable emulsifiers and controllable Pickering emulsions with the ability to respond to external triggers remains an outstanding challenge. Here, we demonstrate the photo-tuning amphiphilicity in Pickering emulsions using ß-cyclodextrin-grafted alginate and azobenzene derivative supramolecular self-assemblies as photoactivatable emulsifiers. Specifically, the photoisomerization of a host-guest system between ß-cyclodextrin and azobenzene derivative was employed to tailor the polarity of the microenvironment, resulting in the reversible variation of hydrophilic/hydrophobic balance. The photoactivatable emulsifier based on supramolecular self-assemblies could effectively destabilize o/w emulsions by tailoring the amphiphilic balance at oil-water interface under an external UV irradiation, leading to the oil-water separation from Pickering emulsion. The light regulating demulsification is further showcased here by the photodelivery of hydrophobic model drug. Finally, this study provides a sustainable yet eco-friendly formulation for the fabrication of stimuli-responsive Pickering emulsions.

Optimization of extraction technology of poly-mannuronic acid to a green delivery system for the water-insoluble pesticide, λ-Cyhalothrin.

Poly-mannuronic acids (PMs) have been considered as great biodegradable polymers as a green carrier for the potential pesticide deliver. In this work, the response surface design and microwave-assisted degradation were employed to obtain the optimum extraction conditions (i.e., 81 °C, 4.1 h, acid concentration 17.65 g/L). Meanwhile, the Ugi multi-component reaction makes the PM to be amphiphilic, called Ugi-PM, which induces the aggregation in aqueous solution at the concentration of 0.0895 g/L. The corresponding chemical structure and thermal stability of PM and Ugi-PM were determined by the FTIR, 1H NMR and thermogravimetric analysis (TG). Furthermore, the construction of novel emulsion-based delivery system using synthetic Ugi-PM was explored to prepare the pesticide of λ-Cyhalothrin. Interestingly, with the Ugi-PM concentration at 0.5 wt%, the stability of the Ugi-PM emulsion and the sustainable release of λ-Cyhalothrin are better than other concentrations and our previous system without degradation (Ugi-Alg emulsion). It is possible that electrostatic repulsion and steric hindrance derived from the hydrophobic Ugi-PM can promote the stability and flexible structure may be the reason for excellent sustained release of Ugi-PM emulsions in the pesticide deliver. The above-mentioned preparation progress is an efficient way to provide a valuable pesticide formulation.

Climate-driven increase of natural wetland methane emissions offset by human-induced wetland reduction in China over the past three decades.

Both anthropogenic activities and climate change can affect the biogeochemical processes of natural wetland methanogenesis. Quantifying possible impacts of changing climate and wetland area on wetland methane (CH4) emissions in China is important for improving our knowledge on CH4 budgets locally and globally. However, their respective and combined effects are uncertain. We incorporated changes in wetland area derived from remote sensing into a dynamic CH4 model to quantify the human and climate change induced contributions to natural wetland CH4 emissions in China over the past three decades. Here we found that human-induced wetland loss contributed 34.3% to the CH4 emissions reduction (0.92 TgCH4), and climate change contributed 20.4% to the CH4 emissions increase (0.31 TgCH4), suggesting that decreasing CH4 emissions due to human-induced wetland reductions has offset the increasing climate-driven CH4 emissions. With climate change only, temperature was a dominant controlling factor for wetland CH4 emissions in the northeast (high latitude) and Qinghai-Tibet Plateau (high altitude) regions, whereas precipitation had a considerable influence in relative arid north China. The inevitable uncertainties caused by the asynchronous for different regions or periods due to inter-annual or seasonal variations among remote sensing images should be considered in the wetland CH4 emissions estimation.

Methane emissions from rice paddies natural wetlands, and lakes in China: synthesis and new estimate.

Sources of methane (CH4 ) become highly variable for countries undergoing a heightened period of development due to both human activity and climate change. An urgent need therefore exists to budget key sources of CH4 , such as wetlands (rice paddies and natural wetlands) and lakes (including reservoirs and ponds), which are sensitive to these changes. For this study, references in relation to CH4 emissions from rice paddies, natural wetlands, and lakes in China were first reviewed and then reestimated based on the review itself. Total emissions from the three CH4 sources were 11.25 Tg CH4  yr(-1) (ranging from 7.98 to 15.16 Tg CH4  yr(-1) ). Among the emissions, 8.11 Tg CH4  yr(-1) (ranging from 5.20 to 11.36 Tg CH4  yr(-1) ) derived from rice paddies, 2.69 Tg CH4  yr(-1) (ranging from 2.46 to 3.20 Tg CH4  yr(-1) ) from natural wetlands, and 0.46 Tg CH4  yr(-1) (ranging from 0.33 to 0.59 Tg CH4  yr(-1) ) from lakes (including reservoirs and ponds). Plentiful water and warm conditions, as well as its large rice paddy area make rice paddies in southeastern China the greatest overall source of CH4 , accounting for approximately 55% of total paddy emissions. Natural wetland estimates were slightly higher than the other estimates owing to the higher CH4 emissions recorded within Qinghai-Tibetan Plateau peatlands. Total CH4 emissions from lakes were estimated for the first time by this study, with three quarters from the littoral zone and one quarter from lake surfaces. Rice paddies, natural wetlands, and lakes are not constant sources of CH4 , but decreasing ones influenced by anthropogenic activity and climate change. A new progress-based model used in conjunction with more observations through model-data fusion approach could help obtain better estimates and insights with regard to CH4 emissions deriving from wetlands and lakes in China.

Inter-annual variations of methane emission from an open fen on the Qinghai-Tibetan Plateau: a three-year study.

The study aimed to understand the inter-annual variations of methane (CH(4)) emissions from an open fen on the Qinghai-Tibetan Plateau (QTP) from 2005 to 2007. The weighted mean CH(4) emission rate was 8.37±11.32 mg CH(4) m(-2 )h(-1) during the summers from 2005 to 2007, falling in the range of CH(4) fluxes reported by other studies, with significant inter-annual and spatial variations. The CH(4) emissions of the year of 2006 (2.11±3.48 mg CH(4) m(-2 )h(-1)) were 82% lower than the mean value of the years 2005 and 2007 (13.91±17.80 mg CH(4) m(-2 )h(-1) and 9.44±14.32 mg CH(4) m(-2 )h(-1), respectively), responding to the inter-annual changes of standing water depths during the growing season of the three years. Significant drawdown of standing water depth is believed to cause such significant reduction in CH(4) emissions from wetlands in the year 2006, probably through changing the methanogen composition and decreasing its community size as well as activating methanotrophs to enhance CH(4) oxidation. Our results are helpful to understand the inter-annual variations of CH(4) emission and provide a more reasonable regional budget of CH(4) emission from wetlands on the QTP and even for world-wide natural wetlands under climate change.

Detecting one-hundred-year environmental changes in Western China using seven-year repeat photography.

Due to its diverse, wondrous plants and unique topography, Western China has drawn great attention from explorers and naturalists from the Western World. Among them, Ernest Henry Wilson (1876 -1930), known as 'Chinese' Wilson, travelled to Western China five times from 1899 to 1918. He took more than 1,000 photos during his travels. These valuable photos illustrated the natural and social environment of Western China a century ago. Since 1997, we had collected E.H. Wilson's old pictures, and then since 2004, along the expedition route of E.H. Wilson, we took 7 years to repeat photographing 250 of these old pictures. Comparing Wilson's photos with ours, we found an obvious warming trend over the 100 years, not only in specific areas but throughout the entire Western China. Such warming trend manifested in phenology changes, community shifts and melting snow in alpine mountains. In this study, we also noted remarkable vegetation changes. Out of 62 picture pairs were related to vegetation change, 39 indicated vegetation has changed to the better condition, 17 for degraded vegetation and six for no obvious change. Also in these photos at a century interval, we found not only rapid urbanization in Western China, but also the disappearance of traditional cultures. Through such comparisons, we should not only be amazed about the significant environmental changes through time in Western China, but also consider its implications for protecting environment while meeting the economic development beyond such changes.