Seasonal variation of transport pathways and potential source areas at high inorganic nitrogen wet deposition sites in southern China

This study attempts to identify the dominant transport pathways,potential source areas,and their seasonal variation at sites with high inorganic nitrogen(IN)wet deposition flux in southern China.This is a long-term study(2010-2017)based on continuous deposition measurements at the Guangzhou urban site(GZ)and the Dinghushan Natural Reserve site(DHS)located in the Pearl River Delta(PRD)region.A dataset on monthly IN concentration in precipitation and wet deposition flux were provided.The average annual fluxes measured at both sites(GZ:33.04±9.52,DHS:20.52±10.22 kg N/(ha·year))were higher,while the ratios of reduced to oxidized N(GZ:1.19±0.77,DHS:1.25±0.84)were lower compared with the national mean level and the previous reported level throughout the PRD region.The dominant pathways were not always consistent with the highest proportional trajectory clusters.The transport pathways contributing most of deposition were identified in the north and northnortheast in the dry season and in the east-southeast,east,and south-southwest in the wet season.A weighted potential source contribution function(WPSCF)value>0.3 was determined reasonably to define the potential source area.Emission within the PRD region contributed the majority(≥95%at both sites)of the IN deposition in the wet season,while the contribution outside the region increased significantly in the dry season(GZ:27.86%,DHS:95.26%).Our results could help create more effective policy to control precursor emissions for IN fluxes,enabling reduction of the ecological risks due to excessive nitrogen.

Characterization,reactivity,source apportionment,and potential source areas of ambient volatile organic compounds in a typical tropical city

Based on one-year observation,the concentration,sources,and potential source areas of volatile organic compounds(VOCs)were comprehensively analyzed to investigate the pollution characteristics of ambient VOCs in Haikou,China.The results showed that the annual average concentration of total VOCs(TVOCs)was 11.4 ppb V,and the composition was dominated by alkanes(8.2 ppb V,71.4%)and alkenes(1.3 ppb V,20.5%).The diurnal variation in the concentration of dominant VOC species showed a distinct bimodal distribution with peaks in the morning and evening.The greatest contribution to ozone formation potential(OFP)was made by alkenes(51.6%),followed by alkanes(27.2%).The concentrations of VOCs and nitrogen dioxide(NO_(2))in spring and summer were low,and it was difficult to generate high ozone(O_(3))concentrations through photochemical reactions.The significant increase in O_(3)concentrations in autumn and winter was mainly related to the transmission of pollutants from the northeast.Traffic sources(40.1%),industrial sources(19.4%),combustion sources(18.6%),solvent usage sources(15.5%)and plant sources(6.4%)were identified as major sources of VOCs through the positive matrix factorization(PMF)model.The southeastern coastal areas of China were identified as major potential source areas of VOCs through the potential source contribution function(PSCF)and concentration-weighted trajectory(CWT)models.Overall,the concentration of ambient VOCs in Haikou was strongly influenced by traffic sources and long-distance transport,and the control of VOCs emitted from vehicles should be strengthened to reduce the active species of ambient VOCs in Haikou,thereby reducing the generation of O_(3).

Application of Characteristics of Seismogenic Structures in the Determination of Parameter of Potential Seismic Source Areas

The characteristics of seismogenic structures are an important basis for delineating the potential seismic source areas and determining the annual occurrence rate of earthquakes. The potential seismic source area does not only have the intension that “this area has the possibility for destructive earthquakes to occur in the future" but also means that earthquakes of high magnitude interval have the characteristics of similar recurrence. When determining the seismic activity parameters of a statistical unit, some active tectonic blocks in the unit may have different background earthquakes. In order to better reflect the heterogeneity in space of seismic activities, it is necessary to divide the potential seismic source areas into three orders. By analyzing the recurrence characteristics of earthquakes of high magnitude interval in the potential source area and calculating the occurrence probability of earthquakes of high magnitude interval in the potential seismic source area in the time window for prediction, the average annual occurrence rate of earthquakes can be obtained by the method of probability equivalent conversion in the time window for prediction. This would be helpful for considering the recurrence characteristics of strong earthquakes in potential source areas within the framework of seismic risk analysis of China. Besides, the insufficient frequency of characteristic earthquakes of the next high magnitude interval in the potential source area and the heterogeneity of strong earthquakes on seismogenic structures are analyzed to see their application in seismic risk analysis.

Expected magnitude and distance of potential source area and the estimating method

Magnitude and distance of major potential source are needed in order to determine duration time of artificial ground motion and to determine the type of response spectrum (near field or far field) when using the seismic intensity zonation map. The magnitude probabilistic distribution function of seismic belt and the magnitude and space joint distribution function for given intensity of the site in a potential Source are provided. Then the basicformula of calculating expected magnitude and expected distance are developed. Several examples for calculating expected magnitude and expected distance in northern China are discussed. These results show that expected magnitude and expected distance are related not only to geometry of potential source and magnitude but also to the intensity of the site with certain exceeding probability.

Characterization of Fe-containing particles in Chengdu,southwest China,using single-particle aerosol mass spectrometry

Single-particle aerosol mass spectrometry was used to study the characteristics of Fecontaining particles during winter in Chengdu,southwest China.The mass concentrations of PM_(2.5)and PM_(10)during the study period were 64±38 and 89±49μg/m~3,respectively,and NO_(2)and particulate matter were high compared with most other regions of China.The Fecontaining particles were divided into seven categories with different mass spectra,sources and aging characteristics.The highest contribution was from Fe mixed with carbonaceous components(Fe-C,23.1%)particles.Fe was more mixed with sulfate than nitrate and therefore the contribution of Fe mixed with sulfate(Fe-S,20.7%)particles was higher than that of Fe mixed with nitrate(Fe-N,12.5%)particles.The contributions from Fe-containing particles related to primary combustion were high in the small particle size range,whereas aged Fecontaining particles and dust-related particles were mostly found in the coarse particle size range.The air masses mainly originated from the west and east of Chengdu,and the corresponding PM_(2.5)concentrations were 79±36 and 55±36μg/m~3,respectively.The west and east air masses showed stronger contributions of Fe-containing particles related to biomass burning(Fe-B)and fossil fuel combustion(Fe-C and Fe-S)particles,respectively.The southwest area contributed the most Fe-containing particles.Future assessments of the effects of Fe-containing particles during heavy pollution period should pay more attention to Fe-C and Fe-S particles.Emission-reduction of Fe-containing particles should consider both local emissions and short-distance transmission from the surrounding areas.