A total of 219 of agricultural soil and 48 of vegetable samples were collected from the midstream and downstream, Hengyang to Changsha, of Xiangjiang River of Hunan Province. The spatial distribution, accumulation characteristics and potential risk of heavy metals in the agricultural soils and vegetables were depicted in details by three different approaches, including total contents of 7 metal elements in soils and vegetables, GIS map of heavy metals in soils, and multi-analysis of the relationship between metals content of soils and egetables in this study. The results show that there are higher accumulations of heavy metals such as As, Cd, Cu, Ni, Pb and Zn in agricultural soils, and the contents of Cd (2.44 mg kg-1), Pb (65.00 mg kg-1) and Zn (144.13 mg kg-1) are 7.97, 3.69 and 1.63 times of background contents of the corresponding heavy metals in soils of Hunan Province, respectively. There are about 13.2% of As, 68.5% of Cd, 2.7% of Cu, 2.7% of Ni, 8.7% of Pb and 15.1% of Zn in all the collected soil samples from the investigated sites which have overran the contents for heavy metal of China Environmental Quality Standard for Soils (GB15618-1995, Grade II). The pollution characteristics of multi-metals in soils are mainly reflected by Cd. Contents of As, Cd, Cu, Pb and Zn in vegetable soils are significantly higher than those in paddy soils, respectively. The ratios of vegetable samples which As, Cd, Ni and Pb concentrations are higher than the Maximum Levels of Contaminants in Foods (GB2762-2005) are 95.8%, 68.8%, 10.4% and 95.8%, respectively. There are significantly positive correlations between the concentrations of Cd, Pb and Zn in vegetables and the content of them in vegetable soils (P < 0.01). It is very necessary to focus on potential risk of heavy metals for food safety and human's health in agricultural soils and vegetables in the midstream and downstream of Xiangjiang River, Hunan Province of China.
In order to reveal the characteristics and climatic controls on the stable isotope composition in precipitation over Northwest China, seven stations have been selected from the Chinese Network of Isotopes in Precipitation (CHNIP). During the year 2005, monthly precipitation samples have been collected and analyzed for the composition of δ18O . The established local meteoric water line "D = 7.05δ18O - 2.17, based on the 50 monthly samples obtained, could be treated as isotope input functions across the region. The deviations of the slope and the intercept from the Global Meteoric Water Line indicated the specific regional meteorological conditions over Northwest China. The monthly δ18O values were characterized by a strong correlation with the surface air temperature and a weak correlation with precipitation amount. However, if only the % values during summer period have been taken into account, the amount effect visualized. Spatial distributions of δ18O have properly portrayed the atmospheric circulation background in each month over Northwest China. The quantitative simulation of δ18O, which involved a Rayleigh fractionation model and a kinetic fractional model, demonstrated that the kinetic fractionation was the dominating function of condensation of raindrops. Furthermore, the raindrops suffered re-evaporation during the falling process, and the precipitation vapor has been mixed with a quantity of local recycled water vapor. A multiple linear regression equation and a δ18O-T relation were gained by using meteorological parameters to evaluate physical controls on the long-term values. The established δ18O-T relation, which has been based on the present-day precipitation, was the first step of quantitatively reconstructing the paleo-climate.
Eleven major humidity proxy records and other supplementary evidences including different natural archives such as ice-cores, sedimentary records, river terraces, lake-level fluctuations as well as historical documents are involved to reconstruct the humidity variability in the arid Northwest China during the Little Ice Age (LIA) from 1400 AD to 1920 AD. The result shows that as a whole, the LIA is a relatively humid period in this region, contrasting to last 100 years during global warming and medieval warming period. For instance, precipitation in high marginal mountains of the study area was of a high value reflected by the various proxy records from west Kunlun, Tianshan and Qilian mountains. Accordingly, the discharge of big endorheic rivers such as the Tarim and Keliya rivers increased; the surface areas of terminal lakes in desert field expanded, e.g., at Juyan Lake and Ebinur Lake; the water levels rose at lakes in intermontane basins, such as Bosten Lake, Balikun Lake and Qinghai Lake; the groundwater recharge rates in the Badain Jaran Desert were increased; and the water salinity of Sugan Lake also significantly decreased during the LIA. Furthermore, the humidity records with a relatively high resolution from the eastern-southern fringe of the arid Northwest China indicate that there is a secondary oscillation of wet and dry within the LIA. The relatively high humidity during the LIA in Northeast China possibly results from the increase of precipitation in this region due to the strengthening and southward shift of westerlies and the decrease of evapotranspiration caused by the cooling during that time.
There are many prehistoric relics in the Gaomiao Basin. The location of the prehistoric relics closely relates to the natural environment, especially to rivers and terraces. At 5-4 ka BP, the climate of Gaomiao Basin was humid and warm. It was the period from the Majiayao culture to the Machang culture. During this period, the distribution of settlements in this region changed from T3 to T2. The distribution format was also changed from even-distribution to concentration with numbers and scales keeping expanding. Up to the time of Machang culture, the development of settlements reached the climax. Medium-sized settlements appeared, raised to the second level and became the center of the whole region. At 4 ka BP, the climate changed abruptly and the rapid decline in temperature led to the transition from Qijia Culture to Kayue Culture and then to Xindian Culture. What's more, the development of settlements declined. Therefore, the climate changes greatly impacted the transmutation of settlements. Meanwhile, the transmutation also responded to the climate changes sensitively.
This paper studies the variation of runoff of Red River Basin and discusses the influence of "corridor-barrier" functions of valleys and mountains on variation of runoff by using GIS and statistic methods based on the monthly precipitation, temperature and evaporation data from 1960 to 2000 at 32 meteorological stations in the Red River Basin, and the annual runoff data of the Yuanjiang, Lixian and Panlong rivers from 1956 to 2000. The results showed out: (1) Under the effect of "corridor-barrier" functions of valleys and mountains in the Red River, the patterns of annual precipitation and runoff depth present in spatial change a NW-SE distribution, which was similar with the trend of the Red River valley and Ailao Mountains. (2) In the long temporal scale averaged over years, the most obvious effect of the "corridor-barrier" functions was on runoff variation, and the second was on the precipitation, but not obvious on the temperature: the precipitation in Lixian River Basin was greater than that in the Yuanjiang and Panlong rivers of the eastern Ailao Mountains, but the standard deviation was smaller than the latter two, an indication of the "barrier" effect from Ailao Mountains. The mean temperature difference was not obvious among the three regions. (3) Under the superposed effect of climate changes and the "corridor-barrier" functions of valleys and mountains in the Red River Basin, the difference in runoff variation was obvious in the east-west direction: the runoff variation of the Yuanjiang River along the Fault presented an ascending trend, but the Lixian River on the west side of the Fault and the Panlong River on the east presented a descending trend; the annual runoff of the Yuanjiang River and Lixian River had a quasi-5a period, and the Panlong River a quasi-8a period; and the runoff variations were quite inconsistent in different periods among the three river basins.
Based on meteorologic data, historical sediment data and current & sediment data collected in October 2006 in the Yangtze River Basin, the analyses of monthly mean water and sediment discharge characteristics, meteorologic characteristics and the effect on suspended sediment concentration and suspended sediment grain diameter under the exceptionally low water discharge were carried out. The results showed that the sediment discharge decreased remarkably in the year of low water discharge, and the sediment discharge of flood season at Datong Hydrographic Gauging Station is only 19.8% of the mean value from 1985 to 2000. The mean suspended sediment concentration in October 2006 was 0.057 kg/m3 in the middle and lower Yangtze River, being only 20.6% of the mean value in October from 2003 to 2005. The mean suspended sediment median diameter in October 2006 was 4.8 µm, being only 26.3% of the mean value of historic records and 41.8% of the annual mean value recently. The synthetic analysis of suspended sediment concentration, suspended sediment diameter and scouring/silting characteristics showed that the vertical water and sediment exchange was intense in the reach from Chenglingji to Hukou, where the channel adjustment has taken place frequently in recent years. Under the background of the exceptionally low water discharge and the completion of the Three Gorges Project, the contribution of the suspended sediment concentration from Dongting and Poyang lakes to the main stream was greater than that of any other lakes and tributaries, and the contribution of Poyang Lake was greater than that of Dongting Lake. The influence of the suspended sediment diameter from the Hanjiang River and Chaohu Lake to the main stream was greater than that of any other lakes and tributaries, while the influence of Dongting and Poyang lakes was relatively small.
The northern piedmont of the Tianshan Mountains, which is characterized by three parallel ridges of anticlines, known as Fold-and-Thrust zones I-III from the mountains towards the foreland basin, and north-flowing rivers, is a typical region containing many scientific problems attracting a lot of geologists and geographers. Under the special geological setting, the terraces developing along these rivers contain a lot of information on climatic changes and tectonic movement. However, previous studies on fluvial terraces in the northern piedmont of the Tianshan Mountains are still divergent. This work tries to solve the problem and well understand the sequences and ages of fluvial terraces along the northern piedmont of the Tianshan Mountains. The seven fluvial terraces named as T1 to T7 developed along major river channels in the northern piedmont of the Tianshan Mountains, and some main and consecutive terraces correspond to some fans. The fans corresponding to T7, T6, T5 and T2 are respectively named as F1, F2, F3 and F4. Because the center of the upheaval migrated from south to north in the process, some fans developed one by one. But the limit of the anticlines leads to the anomalistic shape of some fans between two anticlines. According to the ESR age, OSL age, and loess-paleosol series, the highest terrace (T7), corresponding to the oldest alluvial fan (F1) which is covered by thick loess and strongly dissected, is dated as 0.54 Ma BP. The higher terrace (T6) corresponds to F2, and the surface of T6 and F2 is also covered by thick loess and dissected by gullies, some of which were abandoned. The age of T6 is estimated as 0.3-0.2 Ma on the basis of the ESR age and loess-paleosol series.
Based on the theory of RS and GIS, the thesis focuses on the effect the topography has on the landscape pattern of a city and makes a dynamic analysis of the landscape pattern from space-time angles.The paper shows that in the rapid process of urbanization, the whole dynamic characteristic landscape pattern is influenced by landforms, while the method of taking advantage of the urban land is influenced by different topographic features. Because of the degree of influence of human activities on landscape declines with the raising of hypsography, during the initial stage of urbanization, the lower and more smooth region intersects with farm landscape and city landscape where the diversity is higher, which result in the Yantian District in Shenzhen where mountainous regions are the majority had the lower level of landscape diversity index, while the landscape diversity index of Futian District where the topography is smooth had higher ones. However, with the quickening up of the urbanization, landscape diversity in Futian District decreases quickly because of most of the farm landscape changing into city landscape, but the index of Yantian District decreases slightly, and that of Longgang District even increases. The index time development curve there presented an "anti-U" shaped pattern which is almost similar to Kuznets curves. The index that has changed for a long time at hand in elevation belt and slope shows two situations: firstly, in the perpendicular space, the characteristic of landscape diversity index, the "anti-U" shaped curve, cannot form until urbanization reaching to some extent, what's more, the characteristic will tend to be more obvious and stable eventually with the furthering of the urbanization. Secondly, in time, the characteristic of low height and low slope diversity index also presents the "anti-U" shaped curve which is similar to Kuznets curves, and with the furthering of the urbanization, both of height and slope will move upward.
Recent studies have demonstrated the importance of LUCC change with climate and ecosystem simulation, but the result could only be determined precisely if a high-resolution underlying land cover map is used. While the efforts based on satellites have provided a good baseline for present land cover, what the next advancement in the research about LUCC change required is the development of reconstruction of historical LUCC change, especially spatially-explicit historical dataset. Being different from other similar studies, this study is based on the analysis of historical land use patterns in the traditional cultivated region of China. Taking no account of the less important factors, slope and population patterns were selected as the major drivers of reclamation in ancient China, and were used to design the Chinese Historical Cropland Data Gridding Model (at a 60 km×60 km resolution), which is an empirical model for allocating the historical cropland inventory data spatially to grid cells in each political unit. Then we use this model to reconstruct the cropland distribution of the study area in 1820, and test the result by prefectural cropland data of 1820, which is from the historical documents. The statistical analyzing result shows that the model can simulate the patterns of the historical cropland's distribution in the traditional cultivated region efficiently.
