| With the development of industry and the increaseing of population, the active nitrogen created by the people has became the main source of nitrogen pollution and nitrogen deposition in the atmosphere. Owing to the special physiological structure, mosses have been widely used in indicating and monitoring of atmospheric pollution deposition. By contrasting nitrogen isotope in mosses with that of nitrogen source in Nanchang, we further confirmed that the reliability of the isotopes in mosses can indicate the source of atmospheric nitrogen. We studied the nitrogen contents and nitrogen isotopes in mosses in Lushan Mountain, which extend the application of nitrogen isotopes in mosses to environmental monitor and atmospheric nitrogen deposition. This paper has not only discussed the response of the vascular plants to atmospheric nitrogen deposition, but also tentatively investigated the nitrogen isotopic fractionation during assimilated by vascular plants.1,δ15N in mosses under different nitrogen sources815N in mosses would changed much when the mosses strongly influenced by the different source of nitrogen.δ15N in mosses influenced by nitrogen source of excreta and vehicle were-8.05±1.08%o and+0.9±1.6%o respectively, which confirm the δ15N of moss can be used to indicate the atmosphere nitrogen deposition.δ15N in mosses which come from industrial park was-1.67±1.35%o, indicating that N produced by coal combustion and fertilizer are the main nitrogen source of industrial park.δ15N in mosses in the center district of Nanchang was-2.7±1.4%o, suggesting that nitrogen source in the park of center district of Nanchang was vehicle gas, excreta and sewage.δ15N in mosses collected in the residential area (-6.19±1.89‰) reflected the special environmental characteristic of residential area:the relatively high concentration of NHx caused by high-population. Analyzing δ15N in mosses collected in the different functional zones and that at the nitrogen point sources, we can draw a conclusion that the nitrogen absorbed by the mosses were not only strongly influenced by its environment, but indicate the different nitrogen forms. 2,Nitrogen content in mosses under the different nitrogen source reflect the nitrogen depositionNitrogen content in mosses was higher at the toilet (3.21±0.20%) than the other place, indicating the nitrogen deposition was higher in the toilet than the other place. In the industrial park, nitrogen content in mosses(2.98±0.34%) was similar to that in the center district of Nanchang(2.91±0.27%), illustrating the nitrogen deposition in the center district of Nanchang and in the industrial park was similar, and nitrogen deposition was high in the center district of Nanchang. Nitrogen content in mosses in the residential area (3.05±0.49%) was similar to the vegetable field (3.03±0.36%), and both of them were much higher than that in mosses of industrial park and center district of Nachang, indicating the nitrogen deposition were higher in risidential area and vegetable field than both industrial park and center district of Nachang. It was resulted from the relativity high nitrogen deposition and relativity high-population in the residential. The lowest nitrogen content in moss growed in the side of road2.69±0.42%, this may be caused by high NOx concentration.3,Indicator of atmospheric nitrogen source in Mt.Lushan by nitrogen isotope in mossesAt low altitude area (the altitude was lower than800m) in Mt. Lushan,δ15N in mosses varied from-4.37‰～+0.65%o, indicating the main nitrogen source came from the agriculture. At high altitude area (the altitude was higher than800m) in Mt. Lushan,δ15N in mosses varied from-3.87‰～-1.34%o, indicating the main nitrogen source came from the soils. The δ15N values in the mosses were mainly concentrated between-4‰and-2‰, suggesting that atmospheric nitrogen deposition in Mt. Lushan mainly comes from the nitrogen release of agricultural and natural soil. Additional,δ15N in mosses (+1.68‰) collected from a garage at the foot of Mt. Lushan just indicated that it strongly influenced by NOx driven by vehicle.4,Indicator of atmospheric nitrogen deposition in Mt.Lushan by nitrogen content in mossesThis work investigated the nitrogen contents in mosses collected along altitude from273m to1400m in Mt. Lushang, and found there was a good linear relation between nitrogen contents in mosses and the altitude (y=3.11-7.85x10-4). It showed that total nitrogen contents in mosses gradually decreased with the increase of altitude in Mt. Lushan. This tendency indicated that the active nitrogen created by the people gradually decreased with the increase of altitude during the process of atmospheric vertical diffusion. According to the quantitative relationship reported previously between the total nitrogen contents in mosses and atmospheric nitrogen deposition, atmospheric nitrogen deposition was estimated to be24.61kg(hm2·a)-1at the summit and41.72kg (hm2·a)-1at the foot of Mt. Lushan. From this, we can draw a conclusion that the nitrogen deposition at the foot of Mt. Lushan was intensely influenced by nitrogen source of agricultural activity and at the summit of Mt. Lushan dominated by nitrogen release of natural soil.5,Characteristics of nitrogen contents in vascular plantsThis study analyzed the nitrogen contents and δ15N values of8evergreen vascular plants collected at Nanchang university. Although all of them lived in the same growing environment, there was a widely different between them. Nitrogen contents in Ligustrum sinense Lour (3.66±0.13%) were double times as much as those in Camellia sinensis(L.)D.ktze (1.54±0.13%), Yucca gloriosa Linn (1.56±0.17%) and Rhododendron simsii Planch (1.61±0.12%). It suggested that there were distinct discrepancy between nitrogen assimilation and the contents of nitrogen-containing compound in leaves in the plants. The similarity in growing environment and obvious difference in nitrogen contents also implied that if plants were not influenced by environment stress, nitrogen contents in vascular plants was decided by its gene. In terms of the nitrogen contents in Ligustrum sinense Lour (3.66±0.13%), Ligustrum sinense Lour may be used as a main plant species planted in the area of serious nitrogen pollution. This was a very useful message for choosing tree species in landscape design of industrial park. By the way, the nitrogen contents in Euonymus japonicus cv.Aureo-marginatus (2.08±0.26%) was much closer to those in mosses (2.17±0.12%) than the others. If taking the nitrogen contents in mosses as an indicator of atmospheric nitrogen deposition, the Euonymus japonicus cv.Aureo-marginatus was the best ideal plant that can be used to reflect the atmospheric nitrogen deposition. This work provided a new reference for choosing a new plant "indicator" to indicate atmospheric nitrogen deposition. 6,Characteristics of nitrogen isotopes in vascular plantsδ15N values in Ligustrum sinense Lour (1.22±2.88%o) was much higher than those in Rhododendron simsii Planch (-3.23±1.24%o) and Yucca gloriosa Linn (-4.84±1.20‰). This may be caused by the isotopic fractionation during the process of nitrogen assimilation by plants. By contrast with the815N values (-5.34±0.08‰) in mosses collected in the same place where the evergreen planted,815N values in all of the plants were higher than those in mosses, further making sure that isotopic fractionation occurred during the nitrogen assimilation by plants. And we found that evergreen plants, in most cases, having higher nitrogen contents would have more positive δ15N values, indicating that the more nitrogen assimilated, the more isotopic fractionation will take place if the vascular plants were not influenced by environment stress. |
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