The three grand cultural spheres of the Holocene Eurasian Continent

Concentrations and fluxes of uranium in two major Chinese rivers: The Changjiang River and the Huanghe River

Field-grown cotton shows genotypic variation in agronomic and physiological responses to waterlogging

Polychlorinated dibenzodioxins and dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) are toxic environmental pollutants that are often found in sediments. The Yangtze and Yellow rivers in China are two of the largest rivers in Asia and are therefore important aquatic ecosystems; however, few studies have investigated the PCDD/F and PCB content in the sediments of these rivers. Accordingly, this study was conducted to generate baseline data for future environmental risk assessments. In the present study, 26 surface sediments from the middle reaches of the Yellow and Yangtze rivers were analyzed for PCDD/Fs and dioxin-like (dl) PCBs by high-resolution gas chromatography and high-resolution mass spectrometry. The ranges of PCDD/F, dl-PCB, and WHO-TEQ content in sediments from the Yellow River were 2.1-19.8, 1.11-9.9, and 0.08-0.57 pg/g (dry weight), respectively. The ranges of PCDD/F, dl-PCB, and WHO-TEQ content in sediments from the Yangtze River were 6.1-84.9, 1.8-24.1, and 0.13-0.29 pg/g (dry weight), respectively. Total organic carbon and dl-PCB contents in the Yellow River were significantly correlated (Spearman's correlation coefficient, r = 0.64, P < 0.05). It is well known that total organic carbon plays a role in the transport and redistribution of dl-PCB. Principal component analysis indicated that PCDD/Fs may arise from pentachlorophenol, sodium pentachlorophenate, and atmospheric deposition, while dl-PCBs likely originate from burning of coal and wood for domestic heating. The dioxin levels in the river sediments examined in this study were relatively low. These findings advance our knowledge regarding eco-toxicity and provide useful information regarding contamination sources.

In this study, the concentrations of six toxic metals (Cd, Cr, Cu, Ni, Pb, and Zn) in surface sediments within the Yangtze, Yellow, Pearl, and Liaohe rivers, China, were analyzed, and their associated pollution statuses and potential ecological risks were assessed using the geoaccumulation index (Igeo), sediment quality guidelines (SQGs), and the potential ecological risk index (RI). Relatively high toxic metal concentrations were observed in the Pearl and Yangtze rivers, whereas relatively low concentrations were observed in the Yellow and Liaohe rivers. In the Yangtze, Pearl, and Liaohe rivers, the concentrations of these six toxic metals were higher than their background values. Based on the SQGs, the concentrations of Cd, Cr, and Cu in the four rivers were found to be higher than the threshold effect levels (TELs) but lower than the probable effect levels (PELs); however, the concentration of Ni exceeded the PEL in the Pearl River sediments. The Igeo index indicated that all four rivers were heavily contaminated with Cd. The RI of the Pearl and Yellow rivers was classed as high and low, respectively, and that of the Yangtze and Liaohe rivers as moderate. The pollution status of the sediments in the four major rivers was explored in relation to the geochemical background, the ecological toxicity of metals, and the sensitivity of the local benthic communities. These results provide meaningful information for directing river management priorities.

China is one of the ancient civilization countries. Owing to the blind reclamation, the vegetation had been destroyed, causing soil erosion and desertification, and making the civilization center move to the Changjiang (Yangtze) River valley from the Huanghe (Yellow) River. This movement began in the Qin and Han dynasties (221 B.C.-220 A.D.) because at that time the large-scale reclamation was felled, the grassland was reclaimed into farmland, the vegetation was seriously destroyed in the loess and north of the Huanghe River, and the climate was getting colder; and the turn from north to south occurred in the Sui and Tang dynasties (581–907 A.D.) and completed in the Song Dynasty (960–1279 A.D.). However, at present the vegetation damage of the Changjiang River valley is very serious too and the silt carrying capacity of the Changjiang River is increasing sharply; thus the Changjiang River is in danger of becoming a second Huanghe River, so we must pay attention to the protection of ecological environment.

The Yellow River (~5464 km) and the Yangtze River (~6300 km) are large rivers that originate from the Tibetan Plateau and flow into the western Pacific Ocean. The shelf seas of the western Pacific Ocean (e.g., Bohai, Yellow, and East China seas) serve as critical sites for investigating the evolution of these rivers. Distinguishing the material signals of the Yellow River from those of the Yangtze River is an essential step in this research. Therefore, we analyzed published zircon U-Pb ages (n = 1568 for the Yellow River and n = 1216 for the Yangtze River) and K-feldspar Pb isotopes (n = 380 for the Yellow River and n = 158 for the Yangtze River) from the middle and lower reaches of both rivers. The results indicate that the detrital material in the lower reaches of the Yellow River is primarily influenced by the western North China Craton and the Qinling Mountains, whereas the detrital material in the lower reaches of the Yangtze River mainly derives from the South China Block. The Qinling Mountains influence the material composition of the lower Yellow River, primarily due to the formation of overhanging rivers along the river’s course. These geological features inhibit the inflow of materials from the eastern North China Craton, thereby preventing the mixing from the Qinling Mountains. In contrast, the influence of the Qinling Mountains on the material composition of the lower Yangtze River is minimal. This limited impact is attributed to the influx of materials from the South China Block, which dilutes the contributions from the Qinling Mountains. Notably, substantial discrepancies exist in the U-Pb ages and Pb isotopic compositions of detrital zircons and K-feldspar from the lower Yellow River compared to those from the lower Yangtze River and the surrounding geological units. These disparities provide a robust foundation for investigating large river provenance tracing in the western Pacific Ocean shelf sea through the integration of these two analytical methods. However, the U-Pb age distributions of detrital zircons in the lower Yellow River have changed significantly over geological time. The U-Pb age data for detrital zircons collected from the eastern Sanmen Gorge of the middle Yellow River should be utilized to examine river evolution prior to the Quaternary period. Conversely, the U-Pb data from detrital zircons in the lower Yellow and the Yiluo rivers should be considered when discussing Quaternary river evolution. The zircon U-Pb age characteristics of the lower Yangtze River can be directly employed to analyze the evolution of large rivers in the western Pacific Ocean shelf sea during the Neogene.

Runoffs in the Yellow River and Yangtze River basins, China, have been changing constantly during the last half century. In this paper, data from eight river gauging stations and 529 meteorological stations, inside and adjacent to the study basins, were analyzed and compared to quantify the hydrological processes involved, and to evaluate the role of human activities in changing river discharges. The Inverse Distance Weighted (IDW) interpolation method was used to obtain climatic data coverage from station observations. According to the runoff coefficient equation, the effect of human activities and climate can be expressed by changes in runoff coefficients and changes in precipitation, respectively. Annual runoff coefficients were calculated for the period 1950–2008, according to the correlation between respective hydrological series and regional precipitation. Annual precipitation showed no obvious trend in the upper reaches of the Yellow River but a marked downward trend in the middle and downstream reaches, with declines of 8.8 and 9.8 mm/10 a, respectively. All annual runoff series for the Yellow River basin showed a significant downward trend. Runoff declined by about 7.8 mm/10 a at Sanmenxia and 10.8 mm/10 a at Lijin. The series results indicated that an abrupt change occurred in the late 1980s to early 1990s. The trend of correlations between annual runoff and precipitation decreased significantly at the Yellow River stations, with rates ranging from 0.013/10 a to 0.019/10 a. For the hydrologic series, all precipitation series showed a downward trend in the Yangtze River basin with declines ranging from about 24.7 mm/10 a at Cuntan to 18.2 mm/10 a at Datong. Annual runoff series for the upper reaches of the Yangtze River decreased significantly, at rates ranging from 9.9 to 7.2 mm/10 a. In the middle and lower reaches, the runoff series showed no significant trend, with rates of change ranging from 2.1 to 2.9 mm/10 a. Human activities had the greatest influence on changes in the hydrological series of runoff, regardless of whether the effect was negative or positive. During 1970–2008, human activities contributed to 83% of the reduction in runoff in the Yellow River basin, and to 71% of the increase in runoff in the Yangtze River basin. Moreover, the impacts of human activities across the entire basin increased over time. In the 2000s, the impact of human activities exceeded that of climate change and was responsible for 84% of the decrease and 73% of the increase in runoff in the Yellow River and Yangtze River basins, respectively. The average annual runoff from 1980 to 2008 fell by about 97%, 83%, 83%, and 91%, compared with 1951–1969, at the Yellow River stations Lanzhou, Sanmenxia, Huayuankou and Lijin, respectively. Most of the reduction in runoff was caused by human activities. Changes in precipitation also caused reductions in runoff of about 3%, 17%, 17%, and 9% at these four stations, respectively. Falling precipitation rates were the main explanation for runoff changes at the Yangtze River stations Cuntan, Yichang, Hankou, and Datong, causing reductions in runoff of 89%, 74%, 43%, and 35%, respectively. Underlying surface changes caused decreases in runoff in the Yellow River basin and increases in runoff in the Yangtze River basin. Runoff decreased in arid areas as a result of increased water usage, but increased in humid and sub-humid areas as a result of land reclamation and mass urbanization leading to decreases in evaporation and infiltration.

Situated in the hinterland of the Qinghai-Xiang Plateau, the eco-environment of the source regions of the Changjiang (Yangtze) River and the Huanghe (Yellow) River are getting worse in recent years and has attracted increasing attention of researchers around the world. This paper discusses several major problems concerning the eco-environment of the source regions. The authors hold that the two eco-environment extents of the source region of the Changjiang River should be demarcated with the confluence of the Deng’ailongqu River to Zhidoi as its boundary, or 1.15×104 km2 larger than the hydrological source area; while that of the Huanghe River should be delimited with Medotangumaxia in Darlag County as its limit, or 1.84×104 km2 larger than the hydrological source area. The eco-environment of the source regions with vegetation, soil, wetland, lake and river as the main elements, has always been affected by climatic changes, freezethaw processes (including frozen soil freeze-thaw processes and glacial snow cover freeze-thaw processes), rodent damage and human activities. From an evaluation angle of fragile ecosystem, a study index system is established and several important issues for future research are suggested.

Asymmetric response of vegetation GPP to impervious surface expansion: Case studies in the Yellow and Yangtze River Basins

A China-Japan Cooperative JICA Atmospheric Observing Network over the Tibetan Plateau (JICA/Tibet Project): An Overviews

In the vast valley of the Yellow River in the northern part of China, where wheat production has been a primary cultivation for its agriculture, and thereby wheaten food (or wheat powder made food) has been a traditional food for the livelihood of the local peeple since a long time ago, which is in the sharply contrast to the production form and lifestyle in the Yangtze River basin, southern part of China. The wheaten foods in the northern of China are vafious, but mainly are composed of steamed bread, noodles, steamed stuffed bun, and dumpling (jiaozi). This paper focuses on the history regarding mantou and the civil folk culture concerned. In north China, mantou is not only the most popular ＂food＂, but also a usually perceived ＂sacrifice＂ used at the ceremony for Gods and ancestors. Meanwhile, it is also an important ＂gift＂ for the important festivals and rituals, such as the ceremonies of born day, matured year, marriage day, and funerals. The more important is its civil root feature derived from the prolonged logic line of folk lifestyle, presenting as food-sacrifice-gift. Then it becomes an ＂artwork＂, taking the forms as ＂flower mantou ＂or called ＂wheaten flower＂. The ＂flower mantou＂ or ＂Wheaten flower＂ is an real art but exists in a flash time in the lifestyle of the local people. Its symbolic meanings are, however, very rich in representing perfectly the values of the local people, including their outlooks on life, views on happiness and aesthetic awareness. Dangjia village, one of the villages of Hancheng City, Shaanxi Province, is located in the northeast part about 9 kilometers from the city center, the Yellow River is 3.5 kilometers to the east of the village and the No.108 national road is 1.5 kilometers to the west of the village. The surrounding geography of Dangjia village is the joint area of the Loess Plateau and the Qin plain, so it is a typical loess landscape. The village's location is on a river tableland and faces a small river named Bishui river, which finds its way to the Yellow River. There are many fruit trees, Chinese prickly ash trees, vegetable plots and arable land on the both sides of the river and the plateau of the southern part of the village. There are two family names mainly, Dang and Jia, but a few other family names in this village, marriage linkage has been kept between these two families for generations, so, it is a typical village for its clan marriage. In 2006, the households there were 392 and the total population was 1373, with total farmland of 2220 Chinese mu, averagely 7 mu for one family. Apart from the income from agricultural activities ( as productions of wheat, corn and Chinese prickly ash for the major income, most of the villagers heavily rely on their family members who work outside of the village or young laborers who do the odd-jobs in small towns or large cities. The middle reaches of the Yellow River where Dangjia village locates is one of the important wheat production areas in China, wherefore wheaten food is the main food for the local people there. Over a long period of time, the local females have created a very special culture presented by various ritual steamed bread or flower steamed bread. In this paper, steamed bread (Mantou) refers to the steamed food made of leavened dough, which is named ＂Mo＂ or ＂Memo＂ in Shaanxi dialect. ＂Huamo＂(flower steamed bread) means the steamed bread with various models or various colors, whereas, ritual steamed bread refers to the steamed bread or flower steamed bread used as gifts among the local people, and the so called steamed food is the general name for the all kinds of the ＂Mo＂ mentioned above.

Mega-reservoir regulation: A comparative study on downstream responses of the Yangtze and Yellow rivers

Impact of European Black Carbon on East Asian Summer Climate

Regional characteristics of recent precipitation indices in China were analyzed from a daily rainfall dataset based on 494 stations during 1961 to 2000. Some indices such as precipitation percentiles, precipitation intensity, and precipitation persistence were used and their inter-decadal differences were shown in this study. Over the last 40 years, precipitation indices in China showed increasing and decreasing trends separated into three main regions. A decreasing trend of annual precipitation and summer precipitation was observed from the southern part of northeast China to the mid-low Yellow River valley and the upper Yangtze River valley. This region also showed a decreasing trend in precipitation intensity and a decreasing trend in the frequency of persistent wet days. On the other hand, increasing trends in precipitation intensity were found in the Xinjiang region (northwest China), the northern part of northeast China, and southeast China, mainly to the south of the mid-low Yangtze River. The indices of persistent wet days and strong rainfall have contributed to the increasing frequency of floods in southeast China and the Xinjiang region in the last two decades. Persistent dry days and weakening rainfall have resulted in the increasing frequency of drought along the Yellow River valley including North China. Regional precipitation characteristics and trends in precipitation indices indicate the climate state variations in the last four decades. A warm-wet climate state was found in northwest China and in the northern part of northeast China. A warm-dry climate state extends from the southern part of northeast China to the Yellow River valley, while a cool-wet summer was found in southeast China, particularly in the mid-low Yangtze River valley over the last two decades.

River sediments are valuable archives of the environmental conditions within their catchments. The Yangtze and Yellow Rivers are the most active fluvial systems for sediment transport in East Asia, and they are regarded as potential sediment sources for the radial sand ridges (RSRs) in the southwestern Yellow Sea. We used the geochemical compositions of size‐fractioned sediment samples from the Yangtze and Yellow Rivers to characterize chemical weathering, the fractionation behavior of provenance tracers, and the sources of RSRs. For the Yangtze and Yellow River sediments, the (Rb + Sr)/Ti ratio is a reliable chemical weathering proxy that is grain‐size independent. The chemical indices of Chemical Index of Alteration, Rb/Sr, (Rb + Sr)/Ti, and acid‐leached elements from common grain‐size fractions together reveal that the Yangtze River basin undergoes stronger chemical weathering than the Yellow River basin, indicating that the chemical weathering is dominated by latitudinally‐dependent climatic variations. The dissolution and precipitation of amorphous Fe‐Mn oxides can result in the significant fractionation of La/Y, La/Sc, Nb/Co, La/Co, (La/Sm)N, (La/Yb)N, Ti/Sc, Zr/Y, Zr/Co, and Cr/Ta, whereas Zr/Ti and Zr/Nb are largely unaffected. Based on the robust provenance tracers of Zr/La, La/Hf, (La/Yb)N, Zr/Nb, Ti/Zr, and Hf/Ta, we conclude that the RSRs in the southwestern Yellow Sea are mainly derived from Yangtze River sediments, and that part of the clay fraction is from the Yellow River. In future research, we suggest that established geochemical indicators of chemical weathering and sediment provenance can be applied to the deposits of the Yangtze and Yellow River Deltas, the Yellow Sea, and the East China Sea.