Estimates of dry and wet deposition using tissue N contents and 15 N natural abundance in epilithic mosses in atmospheric NH y ‐dominated areas

Measurement of dry N deposition by physical methods is time‐consuming because it is usually difficult to measure directly. In this study, an alternative approach has successfully been proposed by coupling isotopic ratios with tissue N contents of epilithic mosses. The method is to use moss N contents to quantitatively estimate total N (TN) deposition and then to use 15 N natural abundance in mosses to discriminate dry and wet deposition in atmospheric NH y ‐dominated areas (NH y /TN > 0.75). On the basis of the isotopic balance between atmospheric NH y and moss tissue N and the correlation between atmospheric NH y concentrations and their isotopes, both wet and dry N deposition can be estimated. By the approach, we have estimated rainwater ammonium concentrations and contribution percentage of wet deposition to total N deposition ( f wet ) in some areas of southern China. The results indicated that rainwater ammonium concentrations increased relative to those reported previously in most cities, owing to stronger anthropogenic activity. The f wet values estimated in most sites were found to be slightly higher than those reported, because faster transformation rates due to higher SO 2 emission later in acid rain areas of southern China favored deposition in the form of wet deposition instead of dry deposition. The largest uncertainty of the approach comes from the influence of NO x in the atmosphere, and thus it cannot be used in areas where NO x deposition is high. The presented isotopic approach represents a new application of moss biomonitoring for estimating atmospheric N deposition in NH y ‐dominated areas.