[1] Characterizing the level and sources of atmospheric N deposition in a large-scale area is not easy when using physical monitoring. In this study, we attempted to use epilithic mosses (Haplocladium microphyllum (Hedw.)) as a bioindicator. A gradient of atmospheric N deposition from 13.8 kg N ha −1 yr −1 to 47.7 kg N ha −1 yr −1 was estimated on the basis of moss tissue N concentrations and the linear equation between them. The estimated results are reliable because the highest atmospheric N deposition occurred in the middle parts of the Yangtze River, where the highest TN concentrations were also observed. Moss d 15 N values in cities and forests were found in distinctly different ranges of approximately −10‰ to −6‰ and approximately −2‰ to 2‰, respectively, indicating that the main N sources in most of these cities were excretory wastes and those in forests were soil emissions. A negative correlation between moss d 15 N values and the ratios of NH 4 -N/NO 3 -N in deposition (y = −1.53 x + 1.78) has been established when the ratio increased from 1.6 to 6.5. On the basis of the source information, the negative moss d 15 N values in this study strongly indicate that NH y -N is the dominant N form in N deposition in the whole drainage basin. These findings are supported by the existing data of chemical composition of local N deposition.
[1] A considerable number of studies on rainwater sulfur isotopic ratios (d 34 S rain ) have been conducted to trace sulfur sources at a large number of sites in the past. If longitudinal studies on the isotope composition of precipitation sulfate were conducted, it is possible to relate that to changes in sulfur emissions. But direct measurement needs considerable labor and time. So, in this study, sulfur isotopic ratios in rainwater and mosses were analyzed at Guiyang and Nanchang to evaluate the possibility of using mosses as a substitute for rainwater. We found that present moss sulfur isotopic ratios were comparable to those of present rainwater. Additionally, we investigated the changes of atmospheric sulfur sources and sulfur concentrations using an isotopic graphic analysis at five industrial cities, two forested areas, and two remote areas in China. Our results indicate that atmospheric sulfur pollution in most of the industrial cities decreased, while at the two forested areas, no significant changes were observed, and a new anxiousness coming from new energy sources (e.g., oil) appeared in some cities. Studies on the change of ambient SO 2 concentrations support these results.
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