Effects of moisture and carbonate additions on CO_2 emission from calcareous soil during closed–jar incubation

Calcareous soil contains organic and inorganic carbon(C) pools,which both contribute to CO2 emission during closed-jar incubation. The mineralization of organic C and dissolution of inorganic C are both related to soil moisture,but the exact effect of water content on CO2 emission from calcareous soil is unclear. The objective of this experiment was to determine the effect of soil water content(air-dried,30%,70%,and 100% water-holding capacity(WHC)),carbonate type(CaCO3 or MgCO3),and carbonate amount(0.0,1.0%,and 2.0%) on CO2 emission from calcareous soil during closed-jar incubation. Soil CO2 emission increased significantly as the water content increased to 70% WHC,regardless of whether or not the soil was amended with carbonates. Soil CO2 emission remained the same or increased slowly as the soil water content increased from 70% WHC to 100% WHC. When the water content was ≤30% WHC,soil CO2 emission from soil amended with 1.0% inorganic C was greater than that from unamended soil. When the soil water content was 70% or 100% WHC,CO2 emission from CaCO3 amended soil was greater than that from the control. Furthermore,CO2 emission from soil amended with 2.0% CaCO3 was greater than that from soil amended with 1.0% CaCO3. Soil CO2 emission was higher in the MgCO3 amended soil than from the unamended soil. Soil CO2 emission decreased as the MgCO3 content increased. Cumulative CO2 emission was 3-6 times higher from MgCO3 amended soil than from CaCO3 amended soil. There was significant interaction effect between soil moisture and carbonates on CO2 emission. Soil moisture plays an important role in CO2 emission from calcareous soil because it affects both biotic and abiotic processes during the closed-jar incubation.

Influence of deep magma-induced thermal effects on the regional gas outburst risk of coal seams

The thermal effect caused by deep magma intrusion can not only accelerate the metamorphism of coal body,but also bring additional thermal field that changes the mechanical environment of coal seams,thereby affecting the permeability of coal seams.Different from shallow coal resources,deep coal resources are in a mechanical environment characterized by limited stress and strain.Thus,the thermal effect has a more significant influence on the distribution and permeability characteristics of deep coal seams.In this study,the evolution history of highly metamorphic coal seams in Yangquan mining area was analyzed,and the main effect of magmatic activity on coal seams was obtained.Based on the determined vitrinite reflectance data of typical mines in Yangquan mining area,the maximum paleotemperature was calculated by adopting the Barker’s method.Furthermore,the paleotemperature distribution in Yangquan mining area was summarized,and its relationship with the metamorphic degree was acquired.Then,a new permeability model considering the thermal strain was proposed to analyze the permeability evolution in deep coal seams at different ground temperatures.Finally,through a combination of the results of gas pressure and outburst number in Sijiazhuang Mine,Yangquan No.5 Mine and Xinjing Mine,the influence of ground temperature on the gas outburst risk in Yangquan mining area was explored.The following conclusions were drawn:The maximum paleotemperature in Yangquan area can be 303C.In addition,the paleotemperature in the south is higher than that in the north of Yangquan mining area.The various temperatures at different depths bring about different degrees of thermal stress to different coal seams,leading to different strains.Under the fixed displacement boundary conditions in the deep,the coal seam folds and bends to varying degrees.Moreover,the difference in the ground temperature raises the a value of coal seams and lowers the permeability,which promotes the formation of gas-rich zones and increases the risk of coal seam outburst.The research results can help mines to make proper gas disaster prevention plan for different zones.

Use of ^(15)N stable isotope to quantify nitrogen transfer between mycorrhizal plants

Aims Mycorrhizas(fungal roots)play vital roles in plant nutrient acquisition,performance and productivity in terrestrial ecosystems.Arbuscular mycorrhizas(AM)and ectomycorrhizas(EM)are mostly important since soil nutrients,including NH+4,NO
3 and phosphorus,are translocated from mycorrhizal fungi to plants.Individual species,genera and even families of plants could be interconnected by mycorrhizal mycelia to form common mycorrhizal networks(CMNs).The function of CMNs is to provide pathways for movement or transfer of nutrients from one plant to another.In the past four decades,both ^(15)N external labeling or enrichment(usually expressed as atom%)and ^(15)N naturally occurring abundance(d^(15)N,&)techniques have been employed to trace the direction and magnitude of N transfer between plants,with their own advantages and limitations.Important Findings The heavier stable isotope ^(15)N is discriminated against 14N during biochemical,biogeochemical and physiological processes,due to a greater atomic mass.In general,non-N2-fixing plants had greater d^(15)N values than N2-fixing(;0&)ones.Foliar d^(15)N often varied by 5 to 10&in the order:non-mycorrhizas/AMs>EMs>ericoid mycorrhizas.Differences in d^(15)N(&)or ^(15)N(atom%)values could thus provide N transfer information between plants.A range of between 0 to 80%of one-way N transfer had been observed from N2-fixing mycorrhizal to non-N2-fixing mycorrhizal plants,but generally less than or around 10%in the reverse direction.Plant-to-plant N transfer may provide practical implications for plant performance in N-limited habitats.Considering that N translocation or cycling is crucial,and the potential benefits of N transfer are great in both agricultural and natural ecosystems,more research is warranted on either oneway or two-way N transfers mediated by CMNs with different species and under field conditions.

NITROGEN USE AND MANAGEMENT IN ORCHARDS AND VEGETABLE FIELDS IN CHINA: CHALLENGES AND SOLUTIONS

China is the largest producer and consumer of fruits and vegetables in the world.Although the annual planting areas of orchards and vegetable fields(OVF)account for 20%of total croplands,they consume more than 30%of the mineral nitrogen fertilizers in China and have become hotspots of reactive N emissions.Excess N fertilization has not only reduced the N use efficiency(NUE)and quality of grown fruits and vegetables but has also led to soil acidification,biodiversity loss and climate change.Studies using 15N labeling analysis showed that the recovery rate of N fertilizer in OVFs was only 16.6%,and a high proportion of fertilizer N resided in soils(48.3%)or was lost to the environment(35.1%).Nitrate accumulation in the soil of OVFs is the main fate of N fertilizer in northern China,which threatens groundwater quality,while leaching and denitrification are the important N fates of N fertilizer in southern China.Therefore,taking different measures to reduce N loss and increase NUE based on the main pathways of N loss in the various regions is urgent,including rational N fertilization,substituting mineral N fertilizers with organic fertilizers,fertigation,and adding mineral N fertilizers with urease inhibitors and nitrification inhibitors.

A novel method of determining the optimal polyhedral orientation for discrete global grid systems applicable to regionalscale areas of interest

The polyhedral discrete global grid system(DGGS)is a multi-resolution discrete earth reference model supporting the fusion and processing of multi-source geospatial information.The orientation of the polyhedron relative to the earth is one of its key design choices,used when constructing the grid system,as the efficiency of indexing will decrease if local areas of interest extend over multiple faces of the spherical polyhedron.To date,most research has focused on global-scale applications while almost no rigorous mathematical models have been established for determining orientation parameters.In this paper,we propose a method for determining the optimal polyhedral orientation of DGGSs for areas of interest on a regional scale.The proposed method avoids splitting local or regional target areas across multiple polyhedral faces.At the same time,it effectively handles geospatial data at a global scale because of the inherent characteristics of DGGSs.Results show that the orientation determined by this method successfully guarantees that target areas are located at the center of a single polyhedral face.The orientation process determined by this novel method reduces distortions and is more adaptable to different geographical areas,scales,and base polyhedrons than those employed by existing procedures.

PROGRESS ON IMPROVING AGRICULTURAL NITROGEN USE EFFICIENCY: UK−CHINA VIRTUAL JOINT CENTERS ON NITROGEN AGRONOMY

Two virtual joint centers for nitrogen agronomy were established between the UK and China to facilitate collaborative research aimed at improving nitrogen use efficiency(NUE)in agricultural production systems and reducing losses of reactive N to the environment.Major focus areas were improving fertilizer NUE,use of livestock manures,soil health,and policy development and knowledge exchange.Improvements to fertilizer NUE included attention to application rate in the context of yield potential and economic considerations and the potential of improved practices including enhanced efficiency fertilizers,plastic film mulching and cropping design.Improved utilization of livestock manures requires knowledge of the available nutrient content,appropriate manure processing technologies and integrated nutrient management practices.Soil carbon,acidification and biodiversity were considered as important aspects of soil health.Both centers identified a range of potential actions that could be taken to improve N management,and the research conducted has highlighted the importance of developing a systemslevel approach to assessing improvement in the overall efficiency of N management and avoiding unintended secondary effects from individual interventions.Within this context,the management of fertilizer emissions and livestock manure at the farm and regional scales appear to be particularly important targets for mitigation.

Tailoring the adsorption behavior of superoxide intermediates on nickel carbide enables high-rate Li-O_(2) batteries

Probing the relationship between the adsorption of superoxide species and the kinetics of Li-O_(2) chemistry is critical for designing superior oxygen electrodes for the Li-O_(2) battery,yet the modulation essence,especially at the atomic level,remains little understood.Herein,we reveal that the adsorption behaviors of superoxide species can be effectively regulated via a core-induced interfacial charge interaction,and we find that moderate adsorption strength can enable superior rate capability in a Li-O_(2) battery.More importantly,operando X-ray absorption near-edge structure and surface-enhanced Raman spectroscopy provide tools to monitor in situ the evolution of the superoxide intermediates and the electronic states of the catalyst's metal sites during the discharge and charge processes,and correlate these with the surface adsorption states.The concept of tuning adsorption behavior through interfacial charge engineering could open up new opportunities to further advance the development of the Li-O_(2) battery and beyond.