Lijin Station Research Articles

The hydrological regime and particulate size control phosphorus form in the suspended solid fraction in the dammed Huanghe (Yellow River)

The Huanghe River (Yellow River) had been the second largest river in the world in terms of sediment load to the sea; however, the river water discharge and sediment flux to the sea and their seasonal variability have been significantly altered by the dam activities and recent water–sediment regulation. These changes are believed to have important impacts on the flux of phosphorus that is generally transported in particulate form. In this article, the samples of suspended particulate matter (SPM) were collected at the Lijin Station during two high-discharge events in 2005 and were separated by particle size. Sequential extractions were applied to determine the forms of P in different particle size fractions and to assess the potential bio-availability of particulate phosphorus (PP). Based on the in-laboratory measurement, the impacts of different hydrological regimes on the source of PP and its bio-availability were also analyzed. The results indicate that exchangeable, organic, authigenic, and refractory P were preferentially associated with clay, very fine, and fine silt fractions. Detrital P was mainly associated with the medium and coarse silt fractions. Detrital P and authigenic P (two forms of calcium bound phosphorus) were the dominant fractions in all samples. Thus, the potential bio-available PP (exchangeable P and organic P) was mainly associated with the finer particles, such as clay. Higher content of exchangeable, organic, authigenic, and residual P and lower content of detrital P were found during the period of rainstorm compared to that of WSR. P forms and partitioning of P forms among different particle size fractions were assumed to depend on the sources of SPM. It is likely that the pathways and fates of PP forms were controlled by damming and by the related changes of hydrological regime. Therefore, anthropogenic changes of hydrological regime and particle size dominanted the amount and distribution pattern of bio-available P transportation to the estuary and the adjacent sea, which will have profound impacts on the marine ecosystems at the Huanghe River Estuary and even the Bohai Sea.

Size distributions of hydrocarbons in suspended particles from the Yellow River

Abstract Suspended particle samples from the Yellow River estuary were sorted into five grain size fractions to explore the effect of grain size distribution on organic matter content and composition. The n -alkanes and PAHs were determined for each size fraction. PAHs and n -alkanes were more abundant in the finer fractions and the loading decreases steadily with increasing of grain size. However, the total n -alkanes or PAHs normalized to organic C were lower in the smaller size fractions than those in the larger size fractions, suggesting n -alkanes or PAHs may be diluted by the addition of organic matter or gradually decreased by degradation in the smaller size fractions. The particulate n -alkanes in the Yellow River estuary consist of a mixture of compounds from terrigenous and riverine biogenic n -alkanes and more biogenic n -alkanes accumulate in finer particles. Particulate PAHs are related to combustion/pyrolysis processes of coal/wood, and the relative contribution of petrogenic PAHs increase with increasing grain size. The total particulate n -alkane and PAH discharges passing the Lijin Station are about 3.94 t d −1 and 0.52 t d −1 , respectively. Fine particles (

Changes in Runoff and Sediment Yield along the Yellow River during the Period from 1950 to 2006

In this paper, the changes in runoff and sediment yield have been assessed by using long-term observation data from 9 gauging stations on the Yellow River and 12 climate stations in the Yellow River watershed in China. It was observed that the annual precipitation depth at 3 climate stations in the headwater region of the Yellow River has an upward trend. However, in the lower section of the Upper Reach sub-watershed of the Yellow River, the annual precipitation depth has a slightly downward trend. In the Middle Reach sub-watershed, annual precipitation depth has a clear downward tendency. In the Lower Reach sub-watershed of the Yellow River, annual precipitation depth has a slightly upward tendency. Results indicate that, both annual sediment yield and annual runoff depth have a tendency of reduction in the past half century. The annual sediment yield in the Middle Reach is extremely high, with a long-term annual sediment yield of 1543.65 t/km^2 at the Longmen station and 1631.39 t/km^2 at the Tongguan station. In the Lower Reach, both annual runoff depth and sediment yield have a clearly downward trend. However, the long-term average annual sediment yield in the Lower Reach varies from 1035 to 1330 t/km^2 which is still extremely high but less than those at gauging stations on the Middle Reach. The average annual sediment yield decreased significantly in recent 10 years. Examplewise, for the Yellow River at Lijin Station, the average runoff depth of the recent 10 year s is only 1/3 of the long-term average value, and the average annual sediment yield of the recent 10 years is only 1/4 of the long-term average value. Additionally, the impacts of human activities on both runoff depth and sediment yield have been discussed.

Sediment load reduction in Chinese rivers

In this paper, the changes in the annual runoff and sediment transport have been assessed by using the long term observation data from 10 gauging stations on 10 large rivers across China from far north to far south. It is found that the annual sediment yield has generally had a decreasing trend in the past half century. According to the changes in annual runoff and the sediment yield per area, rivers in China can be classified into the following three groups: 1) rivers with decreasing annual sediment transport and stable runoff; 2) rivers with both decreasing annual sediment transport and runoff and 3) rivers with greatly reduced annual sediment transport and decreasing annual runoff. The results indicate that, in all southern rivers (to the south of the Huaihe River including the Huaihe River), there has been little change in average annual runoff but a dramatic decrease in annual sediment transport. In the northern rivers, however, both the annual sediment yield and the runoff show significant evidence of reduction. To further investigate the recent changes in annual runoff and sediment transport, the short-term observation data from these 10 gauging stations in the recent 10 years have been assessed. Results show that both the annual sediment transport and the runoff have decreased significantly in the northern rivers in the past 10 years. Using the Yellow River at the Lijin Station as an example, the average annual runoff for the last 10 years is only 1/3 of the long term average value and the average annual sediment yield of the last 10 years is only 1/4 of the long term average value. More unusually, in the Yongding River the annual sediment yield has approached zero and the runoff has decreased significantly. In addition, the impacts of human activities on the changes in both runoff and sediment transport have been discussed.

Metals in suspended sediments from the Changjiang (Yangtze River) and Huanghe (Yellow River) to the sea, and their comparison

Thirty-five samples of suspended sediments were collected at Datong Station and Lijin Station, the basin-wide control stations of the Changjiang (Yangtze River) and the Huanghe (Yellow River) during flood and dry seasons in 2000 and 2001. Concentrations of 15 elements (Fe, Mg, Ca, Al, Na, K, Ti, Mn, Ba, Sr, Pb, Cu, Zn, V, and Ni) in these samples were measured by ICP-AES. The results indicated that Fe, Al, Ti, Mn, Ba, Cu, Zn, V and Ni concentrations in the Changjiang sediments in May (flood season) were quite close to those in November (dry season), whereas Mg, Ca, Na, K, Sr concentrations were slightly higher and Pb was relatively lower in the dry season. Ti, Ba, Sr and Zn concentrations in Huanghe sediments varied little in August (flood season) and December (dry season), while Mg, Ca, Al, Na and K concentrations were higher by approximately 30% and Fe, Mn, Pb, Cu, Zn, V and Ni concentrations were lower in flood season. Concentrations of most metals, except Ca, Na and Sr were much higher in Changjiang sediments than those in the Huanghe. Such differences of metal concentrations in sediments from these two rivers could be ascribed to their different sediment sources and weathering processes within their corresponding river basin. Particularly, since the 1980s, Pb and Zn concentrations in Changjiang sediments have increased significantly due to the releases of waste/contaminants from human activities, while the variations for these two elements in the Huanghe samples were very little due to the elevated river bed in the lower reaches.

Sedimentation in the Yellow River delta, part I: flow and suspended sediment structure in the upper distributary and the estuary

A 44-year data record measured by Lijin Hydraulic Station on the Yellow River shows that sediment concentration has been increasing while river discharge has been decreasing into the delta since the 1970s. These changes are important because flood waters of the Yellow River, which are heavily laden with sediment, must be used to supply Dongying City and Shengli Oil Company which are located on the delta. Based on the analyses of data of velocity, sediment concentration, salinity and sediment grain size from four cross-section measurements at Lijin Station and one 8-vessel simultaneous measurement cruise in the estuary, structural characteristics of the river flow and suspended sediments throughout the upper distributary and the estuary have been studied and discussed. Results show that when sediment concentrations of the Yellow River exceed 100 kg/m 3 in the lower layer of the river flow during the flood period, the river flow structure does not coincide with the logarithmic law of wall and becomes vertically layered, and the vertical distributions of suspended sediment do not coincide with the diffusion law. The channel length influenced by the tide wave is less than 15 km and there is no tidal intrusion flow; only weak osmosis of salinity occurs inside the river mouth during the flood period of the Yellow River. Simultaneous 8-vessel measurements and simulation using the method of Preissman show that there is a tidal sensitive zone inside the river mouth bar with a length of 6–7 km, when the discharge is as large as 1100 m 3/s, and an area of very active sedimentation. The tidal sensitive region near the river mouth becomes a low-velocity zone that traps a large amount of river sediment which rapidly forms a `plastic' bed at flood tide, and a high-velocity zone with a strong hydrodynamic action to erode the new bed and transport the sediments into the sea at ebb tide.