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Large rivers integrate the products of physical erosion and chemical weathering in different forms (dissolved, fine to coarse particles). The geochemical composition of these products carry important informations on the mechanisms controlling erosion and weathering at the basin scale : sources of the products, vegetation, climate, anthropogenic and tectonic factors, timescale involed. In the framework of a large franco-chinese project, the four largest rivers in China (Changjiang, Huanghe, Zhujiang, Heilongjiang) were sampled : vertical profiles, surface tributaries, bedload sediments and surface monthly time series over a year were collected at different locations along the stream of these rivers. We report major and trace elements concentrations and Nd-Sr isotopes in the suspended particulate matter and bedloads. The four river basins cover a large diversity of climatic, lithologic, tectonic and anthropic settings, that our results put in perspective as controls on erosion-weathering mechanism and its associated timescales. [ABSTRACT FROM AUTHOR]

In order to realize the rational development, scientific management and effective protection of water resources, the Chinese government adopts the water function zoning management system to protect water resources. Over the past decade, the water quality in China has become better, and the most areas whose water quality under the goal of water function zone has become better heading to the goal required by this system. However, water quality in a few areas that was better than the goal has getting close to the goal. As a result, this study presents the concept of the trend balance of water quality based on the water function zoning management system. To verify these trend balance points, this study takes the main stream of the Yangtze River as the research area and the time evolution trend of the Yangtze River water quality was studied based on the analysis of big data. The Dickey-Fuller Test was used to test the stability of the water quality time series. It was found that more than 90% of the river sections whose DO and TP have stabilized, and 60% of the sections whose CODMn, NH3-N, BOD5, Pb, and OIL have stabilized, indicating that the water quality of the main stream of the Yangtze River has a steady trend in time evolution. That proves the water quality of the mainstream of the Yangtze River exists trend balance points, which means the water quality will tend to be an equilibrium state that gradually approaches the control target of this system and ultimately fluctuates up and down. Keywords: water function zoning management system; the Yangtze River; big data [ABSTRACT FROM AUTHOR]

With rapid socio-economic development in the Pearl River Delta area, plenty of domestic,industrial, and agricultural effluent is discharged into the Pearl River estuary (PRE), whichresulted in the deterioration of water quality in the region. During two field surveys in March and September 2005 in the PRE, high chlorophyll-aareas were observed. The highest chlorophyll-a concentrations reached 8.34 mg m−3 and6.15 mg m−3 during the two surveys, respectively. Nutrient analysis indicated thatnitrates, phosphates, and silicate concentrations were high. The salinity was near30 psu. Phytoplankton cell density data demonstrated that the high chlorophyll-aconcentrations were related to bloom conditions. In order to find the possible causes of theeutrophication, data for environment factors during and before the observation periods wereobtained, including winds, currents, precipitation, salinity, and sea surface temperature(SST). Between 18 and 20 March 2005, there was a strong northwesterly wind with a speed of 9m s−1 and the surface current flowed southwestward. The salinity rose and the SST droppedduring that time. That suggests the probable occurrence of upwelling, which broughtnutrient-rich bottom cold water up to the sea surface. The precipitation during March 12-15reinforced river runoff, bringing more nutrients into the estuary. With respect to the case inSeptember, a similar situation was observed. 6 days before the event, northwesterly windsprevailed with the highest speed reaching 10 m s−1. The surface current movedsouthwestward. A precipitation rate of 1.3 mm h−1 was observed over the entire study area.Increased salinity was observed during the bloom period. These conditions areupwelling-favorable. It can be concluded that the anomalous high chlorophyll events were very likely related toupwelling during the observation period. The winds favored upwelling. Further, theprecipitation led to the supplement of nutrients from river runoff. The finding from this workis helpful for forecasting algal blooms in productive estuarine waters, like the PRE. Furtherefforts are required to better understand the mechanism of the linkage between highchlorophyll-a and environmental factors. [ABSTRACT FROM AUTHOR]

Intraplate volcanos are different from interplate volcanos. Their origins have no direct causal connection with plate boundary condition or plate movement velocity, which have always been controversial. Northeast China widely develops Cenozoic intraplate volcanoes, such as Changbaishan volcano, Wudalianchi volcano, Aershan volcano, and Nuomin River volcano, making it a great place to study the mechanism of Intraplate volcanos. Among those volcanos, the Nuomin River volcano's causative mechanism is poorly understood due to the lack of detailed constraints on the upper mantle structure beneath this region. Previous studies show that there are obvious low-velocity anomalies in the upper mantle of Changbai Mountain and Aershan volcano and extend all the way to the top of mantle transition zone, while the low-velocity anomalies of the Nomin River volcano and the Wudalianchi volcano are much shallow. Similar to the adjacent Wudalianchi volcano, the Nomin River volcanic rock is potassic, however, it is quite different from the Aershan volcano which is sodic. The differences in the chemical composition and physical properties of these volcanoes suggest that they may underwent different asthenosphere and lithosphere deformation. Therefore, the deep structure study of the Nomin River volcano will provide necessary evidence for understanding the volcanic activity of the Cenozoic in the Northeast China. Seismic anisotropy determined by the splitting of shear waves is one of the most effective conventional methods for studying mantle flow and lithospheric deformation. A total of 82 pairs of shear wave splitting measurements and 219 null measurements are obtained at 40 temporary seismic stations. Delay times vary from 0.4 s to 1.4 s with an average value of 0.78±0.21 s; while fast directions trending N77°W to N18°E with a mean value of N6.9°W±9.87° at most of stations. Fossil anisotropy within lithosphere is believed to be the main origin of anisotropy since the fast directions are in line with extensional orientation of the Late Mesozoic lithosphere in this area. Meanwhile, solely null measurements are measured at 19 stations, indicating lithospheric thermal erosion by hot mantle upwelling. [ABSTRACT FROM AUTHOR]

Abstract The transverse mixing is a more dominant process in water-quality managementthan either vertical or longitudinal mixing, especially for two-dimensional process. Inthis study, a series of transient tracer experiments were performed based on theammonia solution and red ink instantaneously injected into an urban river in thenortheast of China. A three-dimensional sampling device was designed to track thetransport of pollutants, observe the behavior of real-time processes and collect thetrace data. The outcomes of the tests show that the concentration change in thetransverse section was close to a normal distribution as the tracer was released intothe center of the stream section. The average value of the transverse dispersioncoefficient (Ey) in the study was 0.0038 m2/s. However the dimensionless coefficientwas smaller than the value estimated from the empirical formula because of theoriginal characteristics of urban river destructed by human activities. The analysis ofexperiment found that the Ey was sensitive to the channel aspect ratio and affected bythe specific gravity of the contaminant. This paper presents a theoretical formulaof the Ey derived by the friction term, channel aspect ratio and specific gravity.The newly proposed theoretical formula can estimate the pollutant transport in theriver, which may be of significant support to the emergency treatment of urbanrivers. * The first two authors Lu Gao and Xiangzhou Xu contributed equally to this work. [ABSTRACT FROM AUTHOR]

Groundwater inflow to river and the related heavy metal fluxes were estimated in a mountainmining area named Dabaoshan, Southern China. Mining activities had been conducted over40 years there. Shallow aquifers were seriously contaminated by toxic heavy metals in thisarea as a result of the discharge of acid mine drainage. Contaminated aquifers are long-termpollution sources to the rivers, even after the mining activities were stopped. The naturaltracer 222Rn was used for the estimation of groundwater inflow to Hengshi River in the studyarea. Two rounds of field works were carried out in both wet and dry seasons from 2016to 2017. Total groundwater inflow was estimated to be 21.5×103 m3 day−1 inwet season and 1.9×103 m3 day−1 in dry season, respectively. Comparing withother areas, although groundwater inflow rate in Dabaoshan is much lower, themagnitudes of groundwater-driven inputs of heavy metals are much higher or atleast quite similar, especially for Cu, Zn and Mn fluxes. This study suggests thatfluxes of heavy metals via groundwater discharge processes are remarkable pollutionsources to rivers in the mountain mining area. Meanwhile, even for a gaining riverin mountain area, aquifers can still be influenced by the polluted river water. Theresults also demonstrated that concentrations of Cd, Co, Cu, Ni, Mn, Fe, Zn and Tlin groundwater increased where river water recharges to the surrounding aquifer. [ABSTRACT FROM AUTHOR]

The grain-size distribution of ancient alluvial systems is commonly determined from surface samples of vertically exposed sections of gravel deposits. This method relies on the hypothesis that the grain-size distribution obtained from a vertical cross section is equivalent to that of the riverbed, in direct contact with the flow. Such an hypothesis implies first that the sediments are uniform in size in the river bed, and second that the sampling method implemented on a vertical section leads to a grain-size distribution equivalent to the bulk one. Here, we present a field test performed on granulometric samples collected in an active, gravel-bedded, braided stream: the Urumqi River in China. We compare data from volumetric samples of a trench excavated in an active thread and from surface counts performed on the trench vertical faces. Based on this data set, we show that the grain-size distributions obtained from all the samples are similar and that the deposit is uniform at the scale of the river active layer, a layer extending from the surface to a depth of approximately 10 times the size of the largest clasts. As a consequence, the grid-by-number method implemented vertically leads to a grain-size distribution equivalent to the one obtained by a bulk volumetric sampling. This study thus supports that vertical surface counts provide an accurate characterization of the grain-size distribution of paleo-braided rivers. [ABSTRACT FROM AUTHOR]

Extended-range runoff forecast is important for water resources management and energy planning. Ensemble hydrological forecast by coupling climate model and river basin hydrological model is a popular method since the 21 century. An experimental extended-range runoff forecast is underway, using an extended-range climate model developed by National Climate Center, China Meteorological Administration, and a semi-distributed hydrological model HBV-D The skill of runoff forecast were explored with indices of MSSS, ACC and MCRPSS for three experimental 51-day periods (June 1 to July 21, July 1 to August 20, and August 1 to September 20) in flood season for two rivers located in southern and southern China,. The results indicate that ensemble forecast is skillful in terms of multi-year mean, and MCRPSS sore is positive even > 0.5 for most days during the three periods. However, MSSS and ACC are only positive for the former days of each period, and the skillful time slice length varies with period and river location. These suggest that ensemble forecast is potential for extended-range runoff forecast compared with determined forecast. Among the three periods, skill of ensemble forecast is the highest for August 1 to September 20 for both rivers, in terms of it temporal mean. And the skill is higher for the Beijiang River than the Yiluo River for June 1 to July 21and July 1 to August 20, while lower than the Yiluo River for August 1 to September 20. This suggests that extended-range ensemble runoff forecast is skillful by simple coupling climate model and hydrological model without any pre-processing and post-processing. [ABSTRACT FROM AUTHOR]

In recent years, satellite precipitation products had been widely used in runoff simulation, especially in the ungauged basin. However, the accuracy of different satellite data on real precipitation process varies greatly in different regions. The applicability of satellite precipitation products in a particular watershed needs to be scientifically demonstrated. In this study, the Yellow River Source Region was chosen as the research area, and precipitation data of 11 rainfall stations as the benchmark. Tropical Rainfall Measurement Mission (TRMM) Multisatellite Precipitation Analysis (TMPA) 3B42V7, Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks-Climate Data Record (PERSIANN-CDR), Global Precipitation Measurement (GPM) Integrated Multi-SatellitE Retrievals for GPM (IMERG) final run and Global Satellite Mapping of Precipitation (GSMaP) gauge products were evaluated in the accuracy as well as their runoff simulation capability under Variable Infiltration Capacity (VIC) hydrological model during 1998 to 2016 in daily temporal scale. Results show that these four satellite precipitation products can reflect the consistent spatial distribution of precipitation with rainfall stations in the Yellow River Source Region. In the long term (1998 to 2016) precision analysis, TRMM performs better than PRESIANN-CDR. In the short term (2014 to 2016) precision analysis, GSMaP shows a high precipitation assessment capability. Comparing the precipitation data of the rainfall gauge with the satellite precipitation data of its grid, it is found that 3B42V7 is generally underestimated for precipitation in the whole basin. PERSIAN-CDR and GSMaP overestimate the precipitation in the southeast and underestimate in the northwest. The runoff simulation capability of 3B42V7 and PERSIAN-CDR has been improved in recent years. GSMAP has demonstrated excellent runoff simulation ability in the Yellow River Source Region. Because of the overestimation of precipitation by PERSIANN-CDR, the simulated runoff process is much higher than the observed runoff. As a substitute for TRMM, IMERG has superior runoff simulation ability in the Yellow River Source Region. [ABSTRACT FROM AUTHOR]

Global estimates for the CO2 flux from river waters to the atmosphere have substantially increased over the last decade. More data from under- represented landscape are needed to refine these estimates. Rivers draining karst landscape are generally oversaturated with CO2 and thus should outgas CO2 to the atmosphere, but this has not been well quantified, largely because it has been assumed that karst systems are a sink for atmospheric CO2 by carbonate weathering. To qualify and compare the rates of CO2 emissions from karst fluvial drainages, we deployed floating chambers to estimate instantaneous CO2 emissions in karst and non-karst catchments in SW of China. CO2 flux (FCO2) from karst system can be greater than non-karst, spanning the reported ranges of global FCO2 obtained by direct measurement. Karst sites FCO2 is positively-correlated with the product of ū and pCO2, as with non-karst sites. Pool our data and all available direct measurements from global rivers, we find a single model (using multiple regression and log transformed ū and pCO2) describes the FCO2 from river waters This model has a geographically wider and lithologically more diverse reach, and also includes ingress. Carbonate lithology covers a significant part of the Earth's surface, thus studying CO2 degassing from karst fluvial systems is an essential step toward more accurate estimation of global CO2 evasion from inland waters. By upscaling we can quantify the significance of CO2 evasions from global karst rivers to the global budget. [ABSTRACT FROM AUTHOR]

The Lancang River Basin, a window for China’s external cooperation is facing the disruptionof the nutrient balance of aquatic ecosystem. Phosphorus is a crucial limiting factor of theaquatic ecosystem in the Lancang River. This study proposed a framework for estimating thetotal phosphorus (TP) load and spatial distribution in the Lancang River Basin in the absenceof measured data. Because the difference of the sources of TP load, both integrated empiricalmodel based on social-economic data and distributed mechanism model (ie. ULSE) are usedin the accounting process. The uncertainties of some key parameters in this frameworkand some input data were also analyzed. Moreover, the TP load in Lancang RiverBasin was compared with those of some large-scale basins, i.e., the Yangtze River,the Yellow River, the Pearl River, the Huai River, the Hai River, and the SonghuaRiver. Results showed that the annual average TP load is in the range of 1.6×104t to3.9×104t, increasing from the upper reaches to the lower reaches, and the lower reachesaccounted for about 60% of that in the whole basin. Among them, natural soil erosion isthe dominant source of TP load with large uncertainty, accounting for about 69%of the whole basin. Compared with other large-scale basins, the TP load in theLancang River Basin is at a very low level, mainly because the land use types inthe basin are natural forest and grassland, and the farmland area is less than 10%,which is less affected by human activities. The data set of TP load in Lancang RiverBasin is given in this paper, which can be used to guide the integrated watershedmanagement, as well as provide a more scientific basis for the relationship between upperreaches and lower reaches, and also offer some data support and reference for futureresearch. Keywords: Lancang River Basin, total phosphorus load, spatial distribution, uncertaintyanalysis. [ABSTRACT FROM AUTHOR]

How did the pesticide or pollutant behave in the cold river water in the Northeast of China? This study presents a laboratory experiment on the distribution of the low-concentration nitrobenzene in the cold water.Water in a stainless-steel container with the height of 1 m was kept still without any disturbances in two groups of the solutions, while the container wall was regularly tapped in the third group. The experimental results show that, after the water samples were kept motionless for more than 120 h, the nitrobenzene kept on uniformly distributed in the cold water with the temperature close to 0°C and the initial content were 19.8 μg/L, 240 μg/L or 2446 μg/L. Furthermore, no deposition occurred even though minor disturbances came. In both conditions above mentioned, the differences of the nitrobenzene contents in different depths were not more than 10%. The results imply the fate of the pesticide or pollutant containing nitrobenzene in the river of the cold area: most of them will flow away in the river water without influence on the local environment as the contaminant content is enough low. [ABSTRACT FROM AUTHOR]