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ABSTRACTThis study quantified the temporal properties of precipitation and actual evapotranspiration (ETa) in the Zoige basin of the Yellow River source region, China during the 1967–2011 period, as well as their influence to the area reduction of peatland. We extracted areas of different land-use and land-cover (LULC) types and obtained daily precipitation data. Then, we calculated annual precipitation (AP) and specific cumulative precipitation (SCP), which is the sum of precipitation to the date when an image was taken, and showed that the peatland areas were strongly affected by SCP. Using a modified Penman–Monteith equation, we calculated ETa for each LULC type and the area-weighted ones to show that the area-weighted total ETa was mainly contributed from grassland and peatland, which was between 450 and 550 mm. Temporal trends of the ratio of SCP to evapotranspiration showed that precipitation was generally greater than evapotranspiration rate not only during the summer but also over the 1967–2011 period. This trend failed to completely explain the continuous decrease of peatland area in the Zoige basin in decades. The draining effect of artificial ditches and natural gullies might play an additional role in causing peatland degradation but requires further process-based studies.

Interactions between graphene oxide (GO) and cell membranes play a crucial role in the nanotoxicity of GO toward organisms. However, little is known about interactions of GO with lipid membranes in the presence of heavy metals. This study investigated the attachment of GO and adsorption of heavy metals onto simulated cell membranes (spherical supported lipid bilayers, SSLBs) formed by cationic, neutral and anionic lipids, i.e., SSLB(+), SSLB(0) and SSLB(−), using batch experiments, density functional theory (DFT) calculations, and spectroscopic analyses. In the binary systems, the SSLBs bind with GO through hydrogen binding and with heavy metals viacomplexation. The attachment of GO or adsorption of heavy metals onto SSLBs decreased in the order SSLB(−) > SSLB(0) > SSLB(+), largely controlled by the type and number of functional groups in the SSLBs. Evidence from batch experiments, DFT calculations and spectroscopic analyses confirmed that in the ternary system GO first binds with metals, and then the GO–metal complexes attach to SSLBs viahydrogen bonding through GO rather than cation bridging through metals. Moreover, metal adsorption onto GO strengthens hydrogen bonding by withdrawing electrons from the GO surface. Therefore, in the ternary system, heavy metals promoted the GO attachment to SSLBs. However, GO suppressed the adsorption of heavy metals onto SSLBs by blocking the adsorption sites viasteric hindrance. This study highlighted the importance of molecular interactions on assessing the nanotoxicity of GO to cells in the coexistence of heavy metals.

The increase in population, the development of industry and agriculture, and the exploitation and utilization of natural resources have inevitably caused a series of ecological and environmental problems, including trace metal pollution. Quantifying the influence of human activities on the metal concentrations of an aqueous environment is helpful for understanding the process and the relationship between socioeconomic development and ecological environmental quality at the macro level. We investigated how human activities and natural variabilities influence the concentrations and distributions of trace metals in the aquatic environment of the heavily sediment-laden Yellow River (> 5000 km). The results showed that the relevant indicators of human activities, such as the population density, average GDP, the number of industrial enterprises above a designated size, percent cropland, percent impervious surface, and the proportion of total crops sown area, had significant positive effect on the concentrations and distributions of some metals in the water environment with a weight of 33∼64%. Moreover, percent grassland and percent wetland exhibited a significant negative correlation with metals. Rapid population growth and socioeconomic development have accelerated the production of metals and other pollutants, that eventually enter the aquatic environment via runoff or other methods through a series of migrations and transformations; thus, the scope of pollution has gradually increased. Some artificially constructed prevention, control and repair measures have played a role in mitigating the effects of environmental pollutants, including metals. This study contributes to the development of effective strategies for controlling metal pollution in the Yellow River basin.

ABSTRACTAlthough initially designed and developed for studying large-scale open ocean dynamics, radar altimetry has proven to have the potential for monitoring coastal and inland water-level changes. However, for rough and heterogeneously reflecting surface, the shape of a waveform contains multiple peaks and traditional retracking methods do not perform well. In this study, we proposed a novel Multi-subwaveform Multi-weight Threshold Retracker (MSMWTR) method, which was applied to Jason-2 waveforms over the Yangtze River (about 1.70 km wide) during 2008–2015. Several traditional waveform retracking algorithms, including Ice-1, offset centre of gravity (OCOG) and 50% Threshold algorithms, were also used to compute water levels. By comparing retracked water levels with nearby Hankou daily gauge records, the results show that the proposed MSMWTR method can significantly improve the accuracy of the estimated water levels compared with other retrackers, especially in the dry season. After applying the MSMWTR algorithm, the root mean square of the errors decreased significantly from 9.06 to 0.34 m. The new method can significantly broaden the application of radar altimeter over relatively wide rivers.

AbstractThe water quality of East Lake, the largest urban lake in China, has continuously deteriorated as a result of urban development. To improve the lake's water quality, a diversion construction project is underway to divert water from the Yangtze River to the lake to accelerate the flow cycle and decrease nutrient concentrations. This study assessed the effects of proposed diversion schemes on water quality using the composite water quality identification index (CWQII) method and a 2-dimensional (2D) water quality model. The study results indicated that the water quality of the lake is strongly influenced by diversion schemes, including diverting locations, discharge, and time. The optimum diversion inlet was inlet 2 (located in Shuiguo Bay), and the most efficient discharge was 30 m3/s. Diverting from different inlet locations caused more obvious reduction rates of CWQII in summer (Jul) than in winter (Jan). After diversion, CWQII values throughout the entire lake were reduced, and the spatial distribution of CWQII became more homogeneous. The highest reduction of CWQII occurred near the inlet location. The CWQII method and 2D water quality model provided a relevant example for assessing the general water quality and designing optimal schemes for diversion projects to improve water quality in large shallow lakes.

The 270 km long section of the Upper Yellow River at the First Great Bend is comprised of single channel and multiple channel systems that alternate among anastomosing, anabranching, meandering and braided reaches. The sequence of downstream pattern changes is characterized as: anastomosing-anabranching, anabranching-meandering, meandering-braided and braided-meandering. Remote sensing images, DEM data and field investigations are used to assess and interpret controls on these reach transitions. Channel slope and bed sediment size are key determinants of transitions in channel planform. Anastomosing reaches have a relatively high bed slope (0.86‰) and coarser sediment bed material (d50= 3.5 mm). In contrast, meandering reaches have a low slope (0.30‰) and fine sediment bed material (d50= 0.036 mm). The transition from a meandering to braided pattern is characterized by an increase in channel width-depth ratio, indicating the important role of bank strength (i.e. cohesive versus non-cohesive versus channel boundaries). Interestingly, the braided-meandering and meandering-braided transitions are coincident with variable flow inputs from tributary rivers (Baihe and Heihe rivers respectively). Theoretical analysis of the meandering-braided transition highlights the key control of channel width-depth ratio as a determinant of channel planform.

The spatial distribution of valley setting (laterally-unconfined, partly-confined, or confined) and fluvial morphology in the source region of the Yangtze and Yellow Rivers is contrasted and analyzed. The source region of the Yangtze River is divided into 3 broad sections (I, II and III) based on valley setting and channel gradient, with the upstream and downstream sections being characterized by confined (some reaches partly-confined) valleys, while the middle section is characterized with wide and shallow, laterally-unconfined valleys. Gorges are prominent in sections I and III, while braided channel patterns dominate section II. By contrast, the source region of the Yellow River is divided into 5 broad sections (sections I–V) based on valley characteristics and channel gradient. Sections I, II and IV are alluvial reaches with mainly laterally-unconfined (some short reaches partly-confined) valleys. Sections III and V are mainly confined or partly-confined. Greater morphological diversity is evident in the source region of the Yellow River relative to the upper Yangtze River. This includes braided, anabranching, anastomosing, meandering and straight alluvial patterns, with gorges in confined reaches. The macro-relief (elevation, gradient, aspect, valley alignment and confinement) of the region, linked directly to tectonic movement of the Qinghai-Tibet Plateau, tied to climatic, hydrologic and biotic considerations, are primary controls upon the patterns of river diversity in the region.

This study presents findings of the first systematic analysis of aquatic biotic assemblages in the source region of the Yellow and Yangtze Rivers. It provides an initial basis with which to select representative organisms as indicators to assess the aquatic ecological status of rivers in this region. Macroinvertebrates are considered to be good indicators of long-term environmental changes due to their restricted range and persistence over time. Field investigations of macroinvertebrates were conducted in August 2009 in the source region of the Yellow River, and in July 2010 in the source region of the Yangtze River. Altogether 68 taxa of macroinvertebrates belonging to 29 families and 59 genera were identified. Among them were 8 annelids, 5 mollusks, 54 arthropods and 1 other animal. In the source region of the Yellow River, taxa number, density and biomass of macroinvertebrates were 50, 329 individuals m−2and 0.3966 g dry weight m−2, respectively. Equivalent figures for the source region of the Yangtze River were 29, 59 individuals m−2and 0.0307 g dry weight m−2. The lower benthic animal resources in the source region of the Yangtze River are ascribed to higher altitude, higher sediment concentration and wetland degradation. Preliminary findings of this exploratory study indicate that hydroelectric power stations had a weak impact on benthic dwellers but wetland degradation caused by a series of human activities had a catastrophic impact on survival of macroinvertebrates. Ecological protection measures such as conservative grazing and vegetation management are required to minimize grassland degradation and desertification, and reduce soil erosion rate and river sediment discharge.

Abstract: Eutrophication can shift lakes from a clear, macrophyte-dominated state to a turbid, algae-dominated state, and different habitat condition supports different fauna. Macrozoobenthos are good indicators of water environment, and studies on macrozoobenthic assemblage characteristics can help us to know which state a lake is in, thus provide the basis for its eutrophication control. In this study, a systematic investigation on macrozoobenthos was conducted in 17 Yangtze-isolated lakes to explore the macroecological laws of macrozoobenthic assemblages. Detrended correspondence analysis (DCA) revealed that variance of benthic assemblage structure occurred in two types of lakes. In macrophytic lakes, altogether 51 taxa of macrozoobenthos were identified. The average density and biomass of total macrozoobenthos were 2231 individuals·m−2 and 1.69 g dry weight·m−2, respectively. Macrozoobenthic assemblage was characterized by dominance of scrapers (i.e. gastropods). In algal lakes, altogether 20 taxa of macrozoobenthos were identified. The average density and biomass of total macrozoobenthos were 2814 individuals·m−2 and 1.38 g dry weight·m−2, respectively. Macrozoobenthic assemblage was characterized by dominance of collector-gatherers (i.e. oligochaetes). Wet biomass of submersed macrophytes (B Mac) and phytoplankton chlorophyll a concentration (Chl a) were demonstrated as the key factor structuring macrozoobenthic assemblages in macrophytic and algal lakes, respectively.

Deep-going analysis of the temporal and spatial variations of the major ions in rivers can reveal the sources of nutrients to a certain extent, which is of great value for the development of specialized governance strategies to control nutrient flows into rivers. The Yellow River stem and its reservoirs were selected as the study area, which is the most sediment-laden river in the world. A systematic survey of the Yellow River main steam was conducted from April to May and September to October 2019. The Yellow River was divided into three regions via cluster analysis of ion composition data, which represent the three states of natural and man-made influences. Based on the analysis of hydrochemical characteristics, the results indicated that: (1) the ion and nutrient concentrations in Region Ⅰ were generally low, the concentrations in Region Ⅱ were higher than those in Region I, and the concentrations in Region Ⅲ remained consistently high. (2) the transportation of phosphorus is mainly controlled by the erosion of rainfall runoff and the adsorption of sediment in the Yellow River Basin; nitrogen is mainly derived from point source pollution during spring, but there is combined impact of point and nonpoint sources during autumn; and (3) ultimately, six indicators (Na+, K+, Mg2+, Cl-, SO42-and HCO3-) were used to qualitatively analyze pollution sources. Of these, K+, Mg2+, and HCO3-were selected as nonpoint source pollution tracers, and Na+, Cl-, and SO42-were selected as point source pollution tracers. Our results improve the understanding of applicability of hydrochemical characteristics method, and are important for water resource management in the Yellow River Basin.