Invasion risk to Yangtze River Estuary posed by resting eggs in ballast sediments from transoceanic ships

Soil salt-water dynamics in the Yangtze River Estuary (YRE) is complex and soil salinity is an obstacle to regional agricultural production and the ecological environment in the YRE. Runoff into the sea is reduced during the impoundment period as the result of the water-storing process of the Three Gorges Reservoir (TGR) in the upper reaches of the Yangtze River, which causes serious seawater intrusion. Soil salinity is a problem due to shallow and saline groundwater under serious seawater intrusion in the YRE. In this research, we focused on the temporal variation and spatial distribution characteristics of soil salinity in the YRE using geostatistics combined with proximally sensed information obtained by an electromagnetic induction (EM) survey method in typical years under the impoundment of the TGR. The EM survey with proximal sensing method was applied to perform soil salinity survey in field in the Yangtze River Estuary, allowing quick determination and quantitative assessment of spatial and temporal variation of soil salinity from 2006 to 2017. We developed regional soil salinity survey and mapping by coupling limited laboratory data with proximal sensed data obtained from EM. We interpreted the soil electrical conductivity by constructing a linear model between the apparent electrical conductivity data measured by an EM 38 device and the soil electrical conductivity (EC) of soil samples measured in laboratory. Then, soil electrical conductivity was converted to soil salt content (soil salinity g kg−1) through established linear regression model based on the laboratory data of soil salinity and soil EC. Semivariograms of regional soil salinity in the survey years were fitted and ordinary kriging interpolation was applied in interpolation and mapping of regional soil salinity. The cross-validation results showed that the prediction results were acceptable. The soil salinity distribution under different survey years was presented and the area of salt affected soil was calculated using geostatistics method. The results of spatial distribution of soil salinity showed that soil salinity near the riverbanks and coastlines was higher than that of inland. The spatial distribution of groundwater depth and salinity revealed that shallow groundwater and high groundwater salinity influenced the spatial distribution characteristics of soil salinity. Under long-term impoundment of the Three Gorges Reservoir, the variation of soil salinity in different hydrological years was analyzed. Results showed that the area affected by soil salinity gradually increased in different hydrological year types under the impoundment of the TGR.

Download Full-text

Iron plaque formation and rhizosphere iron bacteria in Spartina alterniflora and Phragmites australis on the redoxcline of tidal flat in the Yangtze River Estuary

Geoderma ◽

10.1016/j.geoderma.2021.115000 ◽

2021 ◽

Vol 392 ◽

pp. 115000

Author(s):

Qiqiong Zhang ◽

Zhongzheng Yan ◽

Xiuzhen Li

Keyword(s):

Spartina Alterniflora ◽

Phragmites Australis ◽

Tidal Flat ◽

Yangtze River ◽

River Estuary ◽

Plaque Formation ◽

Yangtze River Estuary ◽

The Yangtze River ◽

Iron Bacteria ◽

The Yangtze River Estuary

Download Full-text

Numerical Study on the Expansion and Variation of Changjiang Diluted Water in Summer and Autumn

Journal of Marine Science and Engineering ◽

10.3390/jmse9030317 ◽

2021 ◽

Vol 9 (3) ◽

pp. 317

Author(s):

Wanli Hou ◽

Menglin Ba ◽

Jie Bai ◽

Jianghua Yu

Keyword(s):

Yangtze River ◽

Sea Water ◽

Numerical Study ◽

River Estuary ◽

Ocean Model ◽

Theoretical Research ◽

Yangtze River Estuary ◽

Hydrodynamic Characteristics ◽

Changjiang Diluted Water ◽

Transportation Route

In view of the expansion and directional change mechanisms of Yangtze River water diluted with sea water in the shelf region (also known as Changjiang diluted water [CDW]) during summer and autumn, a three-dimensional hydrodynamic model of the Yangtze River Estuary (YRE) and its adjacent waters was established based on the Finite Volume Community Ocean Model (FVCOM). Compared with the measured data, the model accurately simulates the hydrodynamic characteristics of the YRE. On that basis, the influence of the expansion patterns of the CDW in both summer and autumn was studied. It was found that, in 2019, the CDW expanded to the northeast in the summer and to the southeast in the autumn, and that the route of the CDW is mainly controlled by the wind, not the runoff. Current seasonal winds also change the transportation route of the CDW by affecting its hydrodynamic field. Typhoons are frequent in both summer and autumn, causing abnormalities in both the transportation route and expansion of the CDW. During a typhoon, a large amount of the CDW is transported in a continuous and abnormal manner, accelerating the path turning of the CDW. This paper enhances the existing theoretical research of the CDW and provides a reference with respect to the expansion of diluted water all over the world.

Download Full-text