Wheat straw return can lead to biogenic toluene emissions

As a common practice in agricultural system,straw return has been reported to release a large number of trace gases and attractedmuch attention.However,the role of straw return in toluene emission remains poorly understood.In this study we measured the emissions of toluene as well as other 50 volatile organic compounds(VOCs)from wheat straw return for 66 days under flooded and non-flooded conditions,respectively.The results showed that substantial toluene was released from the returned wheat straw particularly under flooded condition,and primarily derived from the secondary product.Toluene emissions from the returned wheat straw were 36.8 and 8.45 mg C/kg,sharing 28.0%and 8.6%of total VOCs released,and over 90% of toluene emissions occurred between days 24-56 and 0-17 under flooded and non-flooded conditions,respectively.The emission rates of toluene were relatively high but decreased sharply at the beginning 2 days,and then was steady until 24 days under the two moisture conditions.After the initial decrease these rose again to form one“peak emission window”between days 24-56 under flooded condition,while these were still very low and steady until the end under non-flooded condition.The toluene emission rates significantly positively correlated with microbial biomass C under flooded condition,but negatively associated with bacteria and fungus number,microbial biomass C,and CO_(2) flux under non-flooded condition,suggesting that microorganism might play an important role in toluene emissions from wheat straw return.A rough estimate indicated that straw return might be important for biogenic toluene.

Chemical signature and fractionation of trace elements in fine particles from anthropogenic and natural sources

The health effects of trace metal elements in atmospheric fine particulate matter(PM_(2.5))are widely recognized,however,the emission factor profiles and chemical fractionation of metal elements in different sources were poorly understand.In this study,sixteen metal elements,including Cd,Pb,V,Zn,Ba,Sb,As,Fe,Sr,Cr,Rb,Co,Mn,Cu,Ni and Sn frombiomass burning,bituminite and anthracite combustion,as well as dust,were quantified.The results showdifferent emission sourceswere associated with distinct emission profiles,holding important implications for source apportionment of ambient particulate metals.Specifically,Fe was the dominant metal species(28-1922 mg/kg)for all samples,and was followed by different metals for different samples.For dust,Mn(39.9 mg/kg_(dust))had the second-highest emission factor,while for biomass burning,itwas Cr and Ba(7.5 and 7.4mg/kg_(biomass),respectively).For bituminous coal combustion,the emission factor of Zn and Ba was 6.2 and 6.0 mg/kg_(bituminous),respectively,while for anthracite combustion the corresponding emission factor was 5.6 and 4.3 mg/kg_(anthracite),respectively.Moreover,chemical fractionation(i.e.,the exchangeable,reducible fraction,oxidizable,and residual fraction)and the bioavailability index(BI)values of the metal elements from different sources were further investigated to reveal the link between different emission sources and the potential health risk.The findings from this study hold important implications for source apportionment and sourcespecific particulate metal-associated health effects.

REMOTE SENSING OF AIR TEMPERATURE PROFILE AND SURFACE EMISSIVITY FROM HIRS2 DATA

A physical method,based on the simplification of surface radiation terms in remote sensing equations, has been suggested to retrieve the surface temperature,vertical temperature profile and surface emissivity from the first eight channel observations of TIROS-N/HIRS2.Analyses of several examples indicate that this method can obtain much more accurate temperatures in the lower atmosphere than a statistical technique, and that the surface temperature and emissivity retrieved are also reasonable.