Evolution Process And Spatial Distribution Of Nitrogen-containing Ions In Snowpack Of Glaciers In The Chinese Tianshan Mountains

Nitrogen cycle plays an important role in the global biogeochemical cycle, andthe snow and ice of glaciers are widely regarded as information storage ofatmospheric environment. So the nitrogen-containing ions in snow and ice, especiallyfor nitrate (NO3-) and ammonium (NH4+), are indicators of paleoclimate evolution,anthropogenic activities and future environment change. Based on the snow and icesamples collected at accumulation zone of the Urumqi Glacier No.1(abbreviated asUG1, henceforth) from April2004to March2007, the snow-ice evolution process wasanalyzed systemically, which was useful for interpreting the chemical record in icecores at the mid-and low-latitude glaciers, especially in the Central Asia. In order toinvestigate the spatial distribution of nitrogen-containing ions and the regionalatmospheric nitrogen cycle, five glaciers in the Chinese Tianshan Mountains wereselected and sampled from2004to2009: the Qingbingtan Glacier No.72of TomurPeak (QG72), the Haxilegen Glacier No.51at Kuytun River (HG51), the UrumqiGlacier No.1(UG1), the Glacier No.4at Sigong River of Bogda Peak (SG4) and theMiaoergou Flat-topped Glacier in Hami (MG3), respectively, from west to east. Theresult was showed as follows:(1) According to the samples of Urumqi Glacier No.1, the concentrations ofnitrate and ammonium in surface snow vary seasonally, which are higher in the wetseason (from April to October) and lower in the dry season (from November toMarch). In the dry season with low temperature, precipitation and evaporation, theconcentration profile keeps at a steady situation, and sublimation and dry deposition isthe main effects in post-depositional process. However, in the wet season with hightemperature, large amount of meltwater is presented, and elution effect is significantin post-depositional process. In the profile of snowpack, a transition layer appears at adistance of70~80cm to ice layer. During the elution period, the obvious changes ofthe peak concentration, ionic load and peak spacings can be found in snowpack,which are much stronger at the upper section, generally. Observed at the snow-iceinterface, the mean concentrations in the dry season are higher at snow bottom thanthose at ice top, but the situation in the wet season are contrary.(2) According to the samples collected at five typical glaciers, the concentration order of nitrate in snowpack is HG51<UG1<MG3<QG72<SG4, and theconcentration order of ammonium is QG72<HG51<MG3<UG1<SG4. Calculatedwith the HYSPLIT air trajectory model, the air mass at the sampling sites mainlytransports from west to east. The air mass in summer is influenced by regional dust,which is different from other seasons. In addition, the spatial distribution of nitrateand ammonium is also affected by the urban pollution (both industry and domesticpollutant) and agricultural emission (crops growing, straw burning, nitrogenousfertilizer using, livestock husbandry, etc.).