The Influence To Rainwater Chemical By Different Water Conservation Forests In Liuxihe

Acid rain in Pearl River Delta is becoming worse and causes serious ecological problems, special for the surface water quality. In Liuxihe national forest park which is the most important land of water source for Guangzhou, Phyllestachys pubescens, Lichi and Boradleaf forests were selected for study, the purifying functions of three forest types to acid rain were analysed by water samples collections(rainwater,throughfall,stemflow,interflow,surface runoff and total runoff),the water quality analysis and assessment.1.The seasonly rainfall in Liuxihe varied greatly,the correlation between pH and rainfall were negative, pH was low in rainy season;and oppositely, pH was high in dry season and normal river flow period. The yearly volume-weighted average pH was 4.52, the frequency of acid rain was 52%. The main cations were Ca2+ and NH4+, their yearly volume-weighted average concentrations were 48.47μeq/L and 27.13μeq/L respectively, the heavy mental ions such as Zn2+(1.46μeq/L),Pb2+(0.08μeq/L)and Cu2+(0.06μeq/L)were few. The main anion was SO42-, 81.75μeq/L, about 61.29% of the total anions. Other anions such as Cl-,F-,NO3-,the volume-weighted average concentrations were 35.81μeq/L,7??eq/L and 7.73μeq/L respectively. The acid rain type in Liuxiheis was sulfuric acid type, SO42- was the main anion pollutant.2. The component matters in rainwater are from some different category sources. The majority of Mg2+(34.8%) and Cl-(25.11%), the small fraction of Ca2+(0.71%),K+(1.51%)and SO42-(1.16%) were from ocean sources. And the sparisity of F-,NO3-,Al3+,P,Pb2+,Cu2+,Zn2+ from ocean sources could indeed be ignored. The main mental elements such as Al,Cu,Zn,Pb came from ores which were mined and epurated in surrounding area; N amd P came form the waste gas and fugitive dust raising which were produced by chemical fertilizer plant; SO42- was carried form other areas by near-distance or middle-distance transportation.3. When rain crossed the canopy layer, the concentration of Ca2+,Mg2+,K+ increased greatly, they are leached from forest canopy. NH4+,F+,Cu2+,Zn2+ were absorbed by the canopy layer, so the concentration decreased. The change of NO3- and SO42- concentration showed different rules in broadleaf forest and Phyllestachys pubescens forest, the concentration in broadleaf forest decreased, in Phyllestachys pubescens forest, it slightly increased, the change of concentration Pb2+ showed the opposite rule due to the different species characteristics. The canopy layer of Broadleaf forest absorbed NO3- and SO42- better, the concentration of Pb2+ in thoughfall increased because of the dry deposition of Pb on the canopy layer.4. The concentrations of most ions such as SO42-,NH4+and NO3- in the soil surface water were higher than these in thoughfall, The reason of rising may be caused by litter decomposition. The concentration of Al3+ increased because of soil acidification. The concentrations of some ions such as Ca2+,Mg2+,Zn2+,Cu2+ and Pb2+ decreased, after crossing soil surface indicated that the soil surface had the strong ability to absorb and purify pollutants. Because the soil and vegetation of forest ecology system had strong ability to absorb and purify the pollutants of atmospheric deposition, the concentration of all the ions except F- in total runoff increased. The concentrations of NO3- and Al3+ in total runoff of Lichi forest were much higher than these in rainfall. NO3- was more because of artificial disturbance, indicated soil acidification of Lichi forest was serious, and the concentration of Al3+ was much higher than other forests.5. The purification ability to ions is different among different forest types. The purification ability to anions such as SO42-,NO3- and cations such as NH4+,Ca2+,Mg2+,Al3+,heavy mental cations, The purification ability of broadleaf forest was best,Lichi forest was worst.6. Under the condition of storm especially typhoon storm, the concentration of Pb in total runoff was stable, because its concentrate was low and the forests a??bed it greatly. Some other ions such as Al3+,Cu2+,Zn2+,NH4+,their concentration peaks were behind the flood peak, having hysteresis. It showed that these mental cations were difficult to remove and run out, they easily accumulated. Nitration could not happened and achieved in time, so NH4+ was removed by water moving and its concentration was high in total runoff. Other ions such as NO3-,Ca2+,Mg2+,K+, their concentration peaks were front of the flood peak, they were easy to remove. The COD concentration peaks were behind flood peak, it had good relation with the main pollutions. The main pollutant of total runoff in broadleaf forest was NH4+, and Al3+ pollutant in the rest forests.7. By the comprehensive evaluation to the runoff water quality of three forest types, it can be found that the water quality has a seasonal fluctuation. In dry season,the water quality of broadleaf forest and Phyllestachys pubescens forest is relatively bad, the single water quality is over standard, the comprehensive water quality belongs toⅡandⅢclass. The main pollutant of broadleaf forest is P which is produced by litter decomposition; In Phyllestachys pubescens forest, the main pollutions are N and P. Because its ability of preserving fertilizer is bad, so N and P which are produced by rock weathering and litter decomposition are easily loss. The human activity occurring in summer has great influence to Lichi forest, the water quality of total runoff in Lichi forest is bad because of excessive N. In a word, except Lichi forest, the water quality of total runoff is good in Liuxihe, It belonged to the first and the second class of water quality standard all the year.