摘要
利用野外监测与数值模拟方法分析了2003年3—5月在太湖站、拖山站、东山站降水化学成分,计算了2003年春季太湖水气界面受纳的各离子平均沉降率,阴离子中SO24-浓度及沉降率最大,NO3-次之;阳离子中Ca2+浓度及沉降率最大,NH+4次之。由离子浓度相关性分析可知太湖降水化学受区域人为污染影响较大。利用后向轨迹方法对太湖站的降水进行分类,春季影响太湖流域的降水主要是海洋性降水,占总降水量的92.7%,其中SO24-、NO3-、NH4+分别占春季总沉降量的89.2%、88.1%、88.3%;大陆性降水过程对沉降负荷的贡献不大,但由于降水中离子浓度高,降水酸度大,其对生态系统的危害较大。对云下气团轨迹的分析表明,3种气团影响太湖降水化学组成,即NE方向的输送、SW方向的输送及局地气团。局地气团由于降水量小,降水中离子浓度高,降水酸度大,其对生态系统的影响较大。在远距离输送的气团中北方气团的降水离子浓度和沉降量明显高于南方气团。
Eutrophication in Taihu Lake region has become a serious problem as the economy in the Yangtze River Delta district developed rapidly. In addition to the materials from river point-sources and runoff area-sources, the nutritive elements input from the lake outskirt also increased step by step in recent years. The nutrition elements input from the ambient can influence the different ecosystems in the lake in different ways from what river point-sources and runoff area-sources do. The significance of this study on the ambient input of nutritive elements is to understand the element circulation and origins of the eutrophication in Taihu Lake. In this paper, chemical compositions in the precipitation collected in several stations in the lake between March and May 2003 were analyzed. The results show that the average pH value in the spring 2003 was 4.27, and the frequency of acid rain reached 100% , showing a worsen trend in acidity in outskirt of the lake region. Our result indicates that the largest ion of concentration and deposition flux was in SO4^2- and NO3^- for anions, and Ca^2＋ and NH4^＋ for cations. The mole ratio of SO4^2-/NO3^- in the rainfall was 1.4, while it was 3.98 during 1992-1993. Analysis on the correlation among ions suggests that the chemical composition of the rainfalls was influenced largely by anthropogenic emissions. We used backward trajectory method to identify different rainfalls, finding that most rainfall in the spring was oceanic types, taking 92.7% of the total. In the oceanic precipitation, the contribution to the total deposition fluxes of SO4^2- ,NO3^- , and NH4^＋ were 89.2% , 88.1% , and 88.3% respectively. Although continental rainfall contribution was minor to the total deposition flux, the ion concentrations were much higher than that from oceanic rainfall, resulting in a serious damage to the local ecosystem. Analysis on the air mass under cloud with backward trajectory method revealed that the air masses have influenced the chemical composition, including those from NE, SW directions and local ones. Although the local one weighed small, it impacted on the ecosystem mostly, demonstrated by the highest ion concentrations, followed by the NE air mass then SW ones.
出处
《海洋与湖沼》
CAS
CSCD
北大核心
2006年第3期249-255,共7页
Oceanologia Et Limnologia Sinica
基金
国家基金委与香港资助局合作项目"大气氮磷输入对湖泊水质的影响研究"课题资助
N-HKUST612/01号和40110734号。
关键词
降水化学
气团后向轨迹
天气形势
Precipitation chemistry, Air mass backward trajectory, Weather situation, Taihu Lake
