Variation Characteristics Of Stable Isotopes In Different Water Bodies And Its Implication For Climate In Chongqing China

Measuring water stable isotope(δD,δ18O)method is used among scientific fields to study the climate change and its driving mechanism.Rivers, reservoirs, lakes, groundwater and other water bodies are derived in atmospheric precipitation, whereas the precipitation is directly affected by climate change. Climate change is studied by using stable isotopes in different water bodies,as water stable isotope gives many climatic informations, both discussing water stable isotope Implications of climate change, and further understanding the hydroloogy cycle mechanism between different water bodies.Chongqing is located in Southwest China, in summer the region has more precipitation that is affected by the southwest monsoon and the East Asian monsoon.The southwest region of China has many mountainous, especially in Chongqing is known as "mountain city", the dual effects of the terrain and climate make water system developed, the water resource rich of the region. Chongqing not only has the characteristics of climate environment in Southwest China, but also has the unique characteristics of the local climate because of the terrain. Studying the water hydrogen and oxygen isotopic composition and variation of Chongqing, for Chongqing region and the southwest region climate change research has important significance.The author investigated hydrogen and oxygen isotopes of water in precipitation and the reservoir named Longtanzi from Maan Creekin in Beibei district of Chongqing.182 precipitation samples and 41 reservoir water samples were collected from two years(December 2013 to November 2015),and the samples were processed and analyzed.The author simultaneously recorded meteorological data, analyzed the change characteristics and rules between hydrogen and oxygen isotopes in precipitation and reservoir water.Through the research, preliminary draw the following conclusions:(1) the changes in the scope of Beibei District δD,δ18O values of precipitation were in the range of global atmospheric precipitation and atmospheric precipitation of Chinese.It was found that the correlation betweenδDandδ18Oin the precipitation is extremely significant,namely, δD=8.82δ18O+18.97,r=0.99,n=101,P<0.01.The slope and intercept of local meteoric water line was greater than global meteoric water line and China meteoric water line. Humid and rainy is the most primary climate characteristics in Chongqing.Air humidity larger rainfall in the condensation process in low temperature and evaporation is not strong, so in Chongqing area of the meteoric water line slope and intercept are relatively large. Area in winter and summer half year atmospheric drop waterline equation: in the winter half year δD=8.00 δ18O+17.17, r=0.95, n=66, P<0.01; summer half year δD=8.44 δ18O+14.28,r=0.99,n=116,P<0.01, the slope and intercept of the two difference smaller.But δD andδ18O values in rain water exhibited significant seasonal variations,having lower values in summer and higher one in winter,that shows different seasons, the source of water.(2) the linear relationship between δD,δ18O of the precipitation and rainfall: δD and rainfall(P) between the correlation as the δD=-1.77P-0.82,r=-0.71,n=23,P<0.01;δ18O and precipitation amount of correlation between(P) as the δ18O=-1.78P-2.46,r=-0.66,n=23,P<0.01.There was a significant negative correlation between the δD,δ18O and precipitation(P), and the precipitation amount effect of the δD and δ18O in the precipitation was very pronounce.But the study area not only affected by the rainfall influence, but also with the local climate characteristics and source of water vapor and water vapor transport process. The linear relationship between δD and δ18O of the precipitation and temperature: δD and temperature(T) correlation: δD=-3.18T+30.51,r=-0.71,n=23,P<0.01; the correlation between δ18O and temperature(T), δ18O=-0.30T+0.28, r=0.60, n=23, P<0.01, δD and δ18O and temperature(T) showed significant negative correlation.Because of Chongqing city is in the southwest of China’s low latitude and the summer is influenced by the southeast monsoon and the southwest monsoon, so the precipitation amount effect of the δD and δ18O in the precipitation was very pronounce,that concealed the temperature effect.(3) the linear correlation analysis of reservoir water during all the year, the winter and summer of δD and δ18O is extremely significant. All the year: δD=8.41 δ18O+12.87(r=0.99, n=41, P< 0.01); in winter : δD=8.44δ18O+12.98(r=0.99, n=19, P< 0.01); in summer: δD=8.39δ18O +12.83(r=0.99, n=22, P<0.01). Seasonal variation of hydrogen and oxygen isotopes in water of reservoir is small. The differ of three linear equations(annual, winter and summer) in the slope, intercept is small. The variation of reservoir water δD and δ18O for summer half year than in winter half year. The results show that the factors of precipitation source, temperature, humidity and the change of meteorological are more complex in summer. In winter both water supply and meteorological factors are relatively stable. Also hydrogen and oxygen isotope of reservoir water are almost in below the LMWL, that shows the change of reservoir water stable isotope is influenced by evaporation effects.The trends between hydrogen and oxygen isotopes of reservoir water and rainfall and temperature are not synchronous.The peak period of the former in 1-2 months after the peak period of the latter. That Indicates the hydrogen and oxygen isotopes of reservoir water inherit atmospheric precipitation characteristics of hydrogen and oxygen isotopes at the same time, and both of them exist difference.Reservoir water as a relatively static water have specific instructions to climate.(4) there is obvious seasonal variation in the precipitation of d in the study area. In summer, d value of the atmospheric precipitation is low; in winter, d value of the atmospheric precipitation is higher.atmospheric precipitation deuterium excess is indicative function for moisture source area. Whether it is winter or summer, d of precipitation values are greater in Chongqing than the world of regional atmospheric precipitation.What is indicating that the evaporation rate is fast and evaporation plays an important role in water cycle process in the area of Chongqing.(5) compared to the linear equation of reservoir water and atmospheric precipitation δD and δ18O the former’s slope and intercept difference are very small, and both of them have the same change trend approximately.It shows there is close contact between precipitation and reservoir and reservoir water mainly accept recharge of meteoric water. However, whether it is annual, winter or summer, the δD,δ18O and d values change range and amplitude of reservoir are far less than the value of the δD,δ18O and d of precipitation,and the former is more stable than the latter. The result suggests that the reservoir is not only affected by precipitation, but also influenced by soil water and groundwater supplies.