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Abstract Due to highly compressible soil and a large amount of human activity, the costal deltas are more prone to ground subsidence. Many major costal deltas in the world are facing subsidence and are consequently more susceptible to flooding, salinization and seawater infusion or even permanent submergence. Therefore, ground subsidence has been a significant problem in coastal delta areas worldwide. The Yellow River Delta (YRD) is the second largest river delta in China. On the one hand, the YRD contains a large area of wetlands rich in biodiversity, and on the other hand, industrial activities and urbanization are extensive due to abundant underground resources such as oil, gas and brine. Excessive land use has caused different degrees of ground subsidence in this area. However, a detailed and comprehensive description of the ground subsidence pattern over the YRD has not been provided. Also, widespread non-urban area in Yellow River Delta region, such as wetlands, farmland and coastal tidal areas, hinders the application of persistent scatterer interferometry method (PSI) for comprehensive subsidence measurement over the whole area. In this paper, we developed a multitemporal InSAR method to map ground subsidence over the YRD area by exploiting both persistent scatterers (PS) and distributed scatterers (DS). This method is characterized by employing the coherence-weighted phase-linking algorithm for fast and reliable optimal phase reconstruction of each DS point and a two-tier network of PS and DS for the robust analysis of land subsidence. To extract the detailed and comprehensive ground subsidence over the whole YRD, we apply our method to 30 ENVISAT ASAR images (2007–2010) and 49 Sentinel-1A (S-1A) images (2015–2018) and obtain measurements of the ground subsidence during these two periods. Forty-one Sentinel-1B (S-1B) images (2016–2018) are also exploited for cross-sensor consistency validation with the result derived from the S-1A dataset. Our method shows a great advantage over the PSI method, providing much higher measuring point (MP) density in mapping land subsidence over the YRD, including 15-fold higher density for the ASAR dataset, 5.1-fold for the S-1A dataset and 5.3-fold for the S-1B dataset, which enables a very detailed description of local ground deformation patterns. Cross-track consistency in the derived measurements from the S-1A and S-1B datasets shows a standard deviation of 9.6 mm/yr for the vertical subsidence rate. A quantitative validation of the derived subsidence results compared with leveling measurements suggests an accuracy of 4.58 mm/yr for the standard deviation term. By comparing the ground deformation over the YRD during the periods of 2015–2018 and 2007–2010, we find that the subsidence in this region shows an overall intensification trend and many new and severe subsidence depressions appear along the coastline, with a maximum vertical subsidence rate of 432 mm/yr. Subsequently, the overextraction of underground brine for salt production is identified as the primary factor causing the ground subsidence near the YRD coastal area. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate that the effects of different hydrodynamic conditions on sediment resuspension on a tidal mudflat in the Yellow River Estuary. A field experiment was conducted on an intertidal flat of the Yellow River Delta, China. The sediment resuspension concentrations and hydrodynamic conditions were obtained in the field from September 2–7, 2013. The resuspended sediment concentrations induced by wave loading were compared with those induced by coupled wave–current actions in Yellow River Delta. The results were as follows: (1) when the wave height was higher than 10 cm and the shear stress induced by the waves was greater than the critical stress of the seabed sediments, the surface seabed was eroded and sediment was resuspended. In addition, 60% of the significant wave heights were larger than 10 cm on the intertidal flat of the Yellow River Delta. (2) The contribution of waves to sediment resuspension was greater than 30% when the significant wave height is higher than 10 cm, and the average contribution of waves to sediment resuspension was 51%. The mechanism of wave-induced sediment resuspension and processes of sediment resuspension were described in this paper. [ABSTRACT FROM AUTHOR]

Aims: Groundwater is a major factor that affects the growth and distribution of Tamarix chinensis in the Yellow River Delta (YRD). The response relationship between the photosynthetic physiological processes of T. chinensis and the depth to groundwater (DGW) remains unclear. This paper aims to elucidate the response pattern of photosynthetic efficiency to the DGW and to determine the suitable DGW for the growth of T. chinensis.Methods: Three-year-old T. chinensis, a dominant species in the YRD, was used as the research object, and seven DGW treatments of 0-1.8 m under low salinity conditions were simulated to determine and analyse the biomass of T. chinensis, the light responses of leaf gas exchange parameters, and the photosynthetic productivity classification under different DGW treatments.Results: There were significant threshold effects of the DGW on the net photosynthetic rate (Pn), transpiration rate (Tr), and water use efficiency (WUE) of T. chinensis leaves, indicating that photosynthetic parameters had significant DGW threshold effects. Different DGW treatments significantly changed the water and salt conditions in the T. chinensis-planted soil column, thereby significantly affecting T. chinensis growth, photosynthetic capacity, and WUE. With increasing the DGW, the soil relative water content and soil salt content gradually decreased, while the soil solution absolute concentration and T. chinensis biomass first decreased and then increased, followed by another decrease. The growth and photosynthetic capacity of T. chinensis at a high DGW (≥1.2 m) were significantly higher than those at a low DGW (≤0.6 m). At the medium DGW of 0.9 m, the biomass, photosynthetic capacity, water consumption associated with transpiration, and water and light use efficiencies of T. chinensis all reached their highest values. When the DGW was increased from 0.9 m to 1.8 m or decreased from 0.9 m to 0.3 m, the reduction of Pn in T. chinensis changed from a stomatal to a non-stomatal limitation. At the shallow DGW (≤0.3 m) and the deep DGW (1.8 m), the reduction in Pn was largely affected by photosynthetically active radiation. The 1.03-1.44 m DGW was referred to as the “high-yield and high-efficiency DGW”, at which T. chinensis exhibited good growth, high photosynthetic capacity, and high-efficiency physiological water use characteristics.Conclusions: Differences in the DGW changed the soil water content and salt content, and the soil solution absolute concentration was a key factor that affected the growth and photosynthetic efficiency of T. chinensis. However, soil drought stress at the deep DGW and soil salt stress at the shallow DGW were the main factors that affected the photosynthetic physiological processes of T. chinensis. T. chinensis exhibited adaptability characteristics of adequate tolerance to drought stress but intolerance to salt and flooding stresses. [ABSTRACT FROM AUTHOR]

Ecological vulnerability assessment of wetlands is a very important early-stage task for wetland protection, pollution treatment, ecological restoration and water resources utilization. On the basis of the study of vulnerability evolution mechanism of wetland ecosystem in the Yellow River Delta, this paper proposes a Pressure-Support-State-Response Model (PSSR) for ecosystem vulnerability assessment and employs a single-factor evaluation method. The proposed model is applied to assessing ecosystem vulnerability of wetland in Yellow River Delta (a case study of Dongying City). Research results show that: from 2005 to 2009, the ecosystem vulnerability of wetlands in Yellow River Delta was 0.62, and 0.68 from 2010 to 2014; the ecosystem vulnerability grade is moderately vulnerable during the two periods. Generally speaking, regional ecosystem vulnerability slightly decreases. More efforts should be made to protect and restore the ecosystem and prevent it from deterioration and wetlands degradation. This study may provide a theoretical support for wetland protection, management, exploitation and policy making in the Yellow River Delta. [ABSTRACT FROM AUTHOR]

Soil salinization can limit the development of agriculture in the Yellow River Delta. In this paper, saline and alkaline farmland in the Yellow River Delta was chosen as the research object, and effects of soil salinity on soil microbial biomass nitrogen (SMBN) under different conditions were investigated to study the response of soil nitrogen turnover to salt stress. There were four salinity gradients (SI: 0.1%; S2:0.5%; S3: 0.9%; S4:1.3%), and four substrates were added to the soiL The results showed that after the addition of various substrates, SMBN in treatments with high soil salinity (S3 and S4) was obviously lower than that in treatments with low soil salinity (SI and S2). In comparison with treatment SI, the average of SMBN in treatments S3 and S4 decreased by 35.8% and 46.7% respectively when there was no substrate added to them; it declined by 55.6% and 56.1% respectively as the carbon source was added to them; it reduced by 24.6% and 28.3% when the nitrogen source was added to them; it dropped by 43.8% and 57.0% respectively as the carbon and nitrogen source were added to them. Compared with treatments without substrates, the addition of the nitrogen source could not improve SMBN; the addition of the carbon source or carbon and nitrogen source could enhance SMBN obviously, and it increased by 60.9% and 66.1% (or 110.8% and 140.2%) in treatments with low soil salinity (SI and S2), while it changed slightly in treatments with high soil salinity (S3 and S4). In order to increase SMBN, it is needed to apply oiganic fertilizer or chemical fertilizer and oiganic fertilizer to maintain or improve soil fertility. [ABSTRACT FROM AUTHOR]

The paper analyzed total factor productivity of Binzhou City, and key factors that influence its economic growth and effluent discharge. The results shoved that (i) production efficiency of the city during 2005-2013 kept stable, mean of Malmquist-Luenberger index was 1.044,9 without considering effluent discharge, and the average annual increase rate was 4.49%, and that vitas 1.020,4 considering effluent discharge, the average annual increase rate was 2.04%, and the increase rate reduced by 2.45%. (ii) GDP growth showed significant negative correlation and positive correlation with capital input and energy input, but insignificant negative correlation and positive correlation with labor force input and technological progress. (iii) Effluent discharge showed insignificant negative correlation and positive correlation with capital input and energy input, but significant negative correlation and positive correlation with labor force input and technological progress. [ABSTRACT FROM AUTHOR]

This paper presents a social-economic-natural approach to measure regional sustainability in the Yellow River Delta region of China based on emergy theory. In this study, Dongying, as the core city of the Yellow River Delta High-efficient Eco-Economic Zone (YRDHEZ) in China, was chosen as the study area. The reason we chose this city is because of its fast economic growth, quick urbanization, and rich natural capital. Using GIS technology, we assessed the emergy of the study area in the year 2009 with consideration of natural capitals. Compared with many previous emergy studies on the urban and regional levels, the natural capital especially the Net Primary Production (NPP) of the ecosystem were included rather than only assessing the natural capitals based on statistical data of agriculture products. The results showed that total emergy used (U) of Dongying was 1.14E+23 solar emergy joule (sej) in 2009. While the emergy value of NPP was 1.95E+22 sej accounting for 60% of Indigenous renewable production (R 1 ). A series of indices based on emergy flows of Dongying were also calculated. The Emergy Sustainable Index (ESI) of Dongying was 0.79 in 2009 which was higher than several other cities from previous studies. However, the biggest proportion among all used sources was the nonrenewable source (N) which indicated that its economic development relied heavily on the consumption of N. The results of this study may provide a reference standard for measuring regional sustainability and also provide policy makers with a reference for adjusting regional developing policies with systematic consideration of the social-economic-natural complex system. [ABSTRACT FROM AUTHOR]

Taking the Yellow River Delta for example, this paper applied remote sensing and GIS to explore land use changes in the local area from 1980 to 2010. The results showed that arable land, and urban and rural construction land were major land use types in the Yellow River Delta, unused land also took a large ratio; land use changes occurred mainly in coastal regions, in terms of change matrix, 25.46% of the grassland was reclaimed as arable land, unused land also witnessed great changes, specifically, 11.14% turned to arable land, 23.25% to construction land. This study provided references for the land use planning and development of the local area. [ABSTRACT FROM AUTHOR]