The present study reviewed the methodologies currently applied to atmospheric nitrogen deposition observation in China, as well as analyzed the long-term trend of the nitrogen deposition observed in the Pearl River Delta (PRD) region, South China. The atmospheric nitrogen deposition flux decreased from the southeast coast to the northwest inland, and the ecosystems influencing by more human activities tended to be of higher deposition load. The wet deposition fluxes were in the range of 18~38kgN/(hm2·a) and 6~78kgN/(hm2·a) for forest ecosystem and cropland ecosystem, respectively. More specifically in cropland, the fluxes of bulk deposition and dry deposition were respectively 15~133kgN/(hm2·a) and 54~83kgN/(hm2·a). And the bulk deposition flux in the urban ecosystem had achieved to 101kgN/(hm2·a). In the PRD region, the deposition fluxes of total nitrogen and the ratio of NH4+-N/NO3--N were declining in the past years. This could be explained by the industrial structure adjustment and the huge energy consumption accompanied with urban development. In general, the measurements for nitrogen deposition observation in China are becoming more and more diversified, and the results are also becoming more convincing. However, the observation is very scarce in the remote areas and wet deposition and bulk deposition, while the study of dry deposition is still insufficient.
Water-soluble ions in particulate matter (PM) from leaf combustion were determined. The results showed that Cl-, SO42-, Na+, NH4+, K+, and Mg2+ existed in flaming PM from green leaves. The average content of total water-soluble ions was 45.02g/kg. Cl-, SO42-, and K+ were the major components. The mean emission factor (EF) for the total ions was 2.43g/kg. The ion types in smoldering PM from green leaf combustion were similar to those in flaming PM, except that NO3- was found instead of SO42-. The mean content for the total ions was 9.95g/kg. The main constituents were Cl- and NH4+. The mean EF for the all ions was 1.04g/kg. Ca2+ occurred in flaming PM from fallen leaves besides the ions found in flaming PM from green leaves. The average content of the total ions was 56.40g/kg. Their major components were Cland SO42-. In addition, the mean EF of the all ions was 0.96g/kg. The types of ions found in smoldering PM from fallen leaves were the same as in flaming PM. The mean content of the ions was 16.86g/kg. SO42- was the main component. The mean EF for the total ions was 1.43g/kg. Both contents in PM and EFs for most of the ions from green or fallen leaves varied with leaf types while burned under each condition. Flaming combustion was in favor of ion emission relative to smoldering one for green leaves. The situation was just opposite for fallen leaves.
In order to achieve the rapid recovery of biological iron and manganese removal process in the low-temperature (3~5℃), three kinds of recovery methods, including different filtration methods of the upper and lower flow, changing the the influent iron concentration and adding inorganic carbon, were adopted to study the recovery effect on the damaged biological filter column. The results showed that three recovery methods could effectively shorten the recovery time of biological filter column and the recovery times were 40, 54 and 35d, Compared with the conventional recovery mode of 2# filter column, the recovery times of 1# and 3# filter column were shortened by 26%, 35%. Although the recovery time was longer by the way to change the concentration of iron and manganese, but the manganese removal performance after the recovery of the filter column was more stable. From comprehensive consideration of the recovery effect and economic rationality, It was suggested that the best way to recover damaged filter column was iron and manganese concentration increased from low to high and adding inorganic carbon when the filtration rate to 2~3m/h.
