Yellow River Delta Area Research Articles

Influence of oil extraction on concentration distributions, migration, secondary formation and carcinogenic risk of NPAHs and OPAHs in air and soil in an oilfield development area in China

Oil extraction leads to environmental pollution from the oilfields and dweller activities, however, knowledge of the concentration distributions, migration, secondary formation and toxicity of nitrated/oxygenated polycyclic aromatic hydrocarbons (N/OPAHs) in oilfield regions is limited. In this research, atmospheric and soil samples in 7 different location types in an important oil industrial base in China were gathered. The ΣNPAHs and ΣOPAHs in the air ranged from 0.05 to 2.47 ng/m3 and 0.14–22.72 ng/m3, respectively, and in soil ranged from 0.22 to 17.81 ng/g and 9.69–66.86 ng/g, respectively. Both NPAHs and OPAHs in the atmosphere exhibited higher concentrations during winter. The atmospheric NPAH concentrations decreased exponentially with distance from urban area especially in the summer, revealing the impact of vehicles on the air in the Yellow River Delta area. High NPAH and OPAH concentrations were found only in soil near oil extraction facilities, indicating that the impact of oil extraction is limited to the soil near the extraction facilities. The air-soil exchanges of N/OPAHs were assessed through fugacity fraction analysis, and NPAHs were in the equilibrium-deposition state and OPAHs were in the net-deposition state in the winter. Higher incremental lifetime cancer risk (ILCR) occurred at the urban, industrial, and oilfield sites in the atmospheric samples, and the soil samples had the largest ILCR values in the oilfield sites. However, ILCR values for both air and soil did not exceed the threshold of 10−6.

InSAR and machine learning reveal new understanding of coastal subsidence risk in the Yellow River Delta, China

Coastal subsidence is a geological disaster that has devastating consequences. However, an accurate understanding of its risks involves more than simply assessing the amount or rate of land subsidence. The existing methods used to evaluate geological disaster risks depend on extensive data collection, entail substantial workloads, suffer from error estimation challenges, and lack regional adaptability. These limitations prevent us from fully understanding coastal subsidence risks in estuarine deltas. Therefore, in this study, we propose a new subsidence risk assessment method that addresses the challenges of traditional geological risk assessments in terms of spatial coverage, spatiotemporal resolution, and data collection difficulty. First, Sentinel-1 multitemporal interferometric synthetic aperture radar (MT-InSAR) and cluster analysis were used to estimate the subsidence hazards. Subsequently, Landsat-8 imagery and a random forest (RF) classifier were used to obtain land use and land cover (LULC), and the analytic hierarchy process (AHP) was used to obtain settlement vulnerability. Thereafter, subsidence susceptibility was derived from the sediment layer thickness. By combining subsidence hazard, vulnerability, and susceptibility, the first subsidence risk map with a 30 m resolution was generated. The results showed that 4.54 % of the Yellow River Delta (YRD) area was high-risk, 8.75 % was medium-risk, and 10.14 % was low-risk. Notably, the risk map shows a clear overlap between high-risk and saltwater mining areas in the YRD. The proposed method is expected to improve our understanding of the coastal subsidence risk in estuarine deltas. Considering that the risk in high-value economic areas in the YRD is increasing, whereas the risk in low-value economic areas may change owing to human activity, early preventive measures are required.

How government-public collaboration affects individual mitigation responses to flooding: A case study in Yellow River Delta area, China

In the top-down Chinese political system, flood management has traditionally been led by the government, with the general public playing a supporting role. Within this context, individual-level disaster prevention behaviors are strongly interacted with the government-public collaboration during the government-led flood management processes. This study aims to provide a comprehensive understanding of how government-public collaboration affects individuals’ flood mitigation responses in China. An online survey data with 550 respondents from the Yellow River Delta area was examined with regard to the individuals’ willingness to take positive mitigation actions, and ordinal logistic regression models were constructed to explore the influence of the government-public collaboration factors, which are digested into three aspects: public involvement, public awareness and political trust, that motivate individuals to take flood mitigation measures. The results demonstrate that public involvement and political trust are positively correlated with the likelihood of individuals’ adopting positive mitigation actions, while public awareness and self-reported preparedness were also positively correlated, although to a less significant degree. This study contributes to the current literature by increasing the understanding of how government-public collaboration determines individual mitigation actions in the Chinese collectivist cultural environment. The results of this study reveal that involving the public effectively and earnestly through various forms of community engagement are likely to promote individual-level disaster prevention behaviors, from this point of view, can help policymakers to guide local residents towards taking responsible flood risk management and preventative actions.

Evolution and Optimization of Territorial-Space Structure Based on Regional Function Orientation

In accordance with the ecological civilization strategy, it is necessary to conduct in-depth analyses and provide a systematic elaboration of the characteristics of territorial-space structure (TSS). In the present paper, we examine Shandong Province and construct a framework for the evolution and optimization of TSS based on regional functions. The evolutionary process, pattern, and driving mechanisms of TSS are clarified using a geo-information atlas, the gravity center shift model, spatial autocorrelation analyses, and a geographic detector model. Furthermore, multi-scenario territorial-space simulations are carried out using the CA–Markov model, based on which an optimal pattern of territorial space is constructed. The results show that the comprehensive dynamic degree of territorial space in Shandong Province was valued at 0.56% from 2000 to 2020. Furthermore, six geo-information Tupu of TSS evolution changed, with a total area of 35,485 km2, distributed mainly in the Yellow River Delta, the central and southern Shandong Mountain area, and the Jiaodong Peninsula. The migration route of the TSS gravity center curved over time. Territorial spaces are characterized by the exchange of ecological and agricultural space, while urban spaces occupy agricultural ones. The level of economic development, policy, and the institutional environment are driving forces in the transformation of ecological into agricultural spaces, as well as in transforming agricultural space into ecological and urban spaces. The trade-off connection of TSSs is made evident after a multi-scenario simulation of territorial space considering the 2020–2025 timeframe. Based on the goal of regional function co-ordination, Shandong Province is divided into three and four types of single and complex TSS, respectively. The obtained results may provide scientific reference for the co-ordination between human–land relationships and the sustainable use of territorial space, and serve to guide territorial spatial planning.

Pore Pressure Response and Dissipation of Piezocone Test in Shallow Silty Soil of Yellow River Delta

Soil dilatancy and partial drainage have great influence on the consolidation coefficient assessment of silty soils with clay content of less than 30% in the Yellow River Delta using the CPTu. This paper discussed the effect of soil dilatancy and partial drainage on the pore pressure response and dissipation of piezocone test in shallow silty soil of the Yellow River Delta through variable penetration rate tests in a pressure chamber and a series of supplementary soil element tests. The results show that the pore pressure dissipation curve is affected by soil type and degree of consolidation. The soil dilatancy is the key factor affecting consolidation coefficient inversion of shallow silt and silty clays. The initial pore pressure is negative and the pore pressure increases to umax first, but the umax value is very small in the Yellow River Delta silt. The inversion method used for shear contractile soil cannot be used to invert the mechanical properties of shallow silty soil directly, and a new consolidation curve normalization method is proposed. This paper provides a reference for the consolidation coefficient inversion of CPTu data in the Yellow River Delta area.

Monitoring and analysis of land subsidence in modern Yellow River Delta using SBAS-InSAR Technology

Modern Yellow River Delta has become one of the areas with serious land subsidence disaster in the plain area of Shandong Province. In this paper, Small Baseline Subsets - Interferometry Synthetic Aperture Radar (SBAS-InSAR) technology was used to process the Sentinel-1A data from August 2018 to October 2019 in the modern Yellow River Delta, in order to obtain the range and rate of land subsidence in the study area. At the same time, use the Leveling results of the same period to verify the accuracy. By selecting four larger land subsidence rate as feature points to analyze the characteristics of surface time series deformation, the influencing factors of land subsidence in this area are found out. The results show that during the past 2018-2019 years, the land subsidence in the the Yellow River Delta area was mainly distributed in Xianhe Town, southern the Huanghekou Town, Hubin Town, Guangrao County and its surrounding areas, DaWang Town, Yingli Town, Yangkou Town and the western part of Binhai Township, the most serious subsidence area is located in Xianhe Town, with an annual settlement rate of -204.7 mm/a. The land subsidence in the Yellow River Delta is mainly affected by groundwater overdraft, and the distribution characteristics of land subsidence funnel and deep groundwater depression funnel are basically consistent. In addition, natural factors such as consolidation of Quaternary loose sediments and regional tectonic movement also exacerbate the occurrence of land subsidence.

Ecosystem‐scale carbon allocation among different land uses: implications for carbon stocks in the Yellow River Delta

AbstractThe reclamation area of the Chinese Yellow River Delta (YRD) has experienced frequent land use changes in recent decades. The consequence of such land use changes on the stocks and allocation of ecosystem‐scale carbon is not known. Here, we assessed carbon stocks and allocation of four representative land uses in the YRD area: (1) purple alfalfa (LAL), (2) reed and Aeluropus littoralis (RAE), (3) cotton (ECO), and (4) Chinese tamarisk (CTA). The results showed that the overall carbon stocks, and carbon stocks of aboveground, litter, roots, and soil were notably different among different land uses. The native CTA land had the largest overall carbon stock (belowground and aboveground) and had the strongest potential to allocate the carbon to the soil carbon pool (95.72%), followed by the natural grassland (RAE). Alfalfa grassland (LAL) also had a large carbon stock due to its large aboveground biomass, litter, and roots, but the relative allocation proportion of soil carbon stock was lower than that of the other land uses examined. Cotton (ECO) had the lowest soil carbon and total carbon stocks among four land uses. In combining our data on the carbon pool with changes of land use in the YRD area, we argued that land reclamation in the YRD area was likely to turn this area from a carbon sink to carbon source with the release of soil organic carbon. Therefore, cautions should be taken to reduce carbon release, if the reclaimed land be used to plant crops.

Satellite-Observed Evolution Dynamics of the Yellow River Delta in 1984–2018

The Yellow River delta (YRD) is regarded as one of the most rapid sedimentation deltas in the worldwide and the youngest land in China. Existing studies more focused on evolutions of river mouth region, thus provided limited knowledge on the evolution of the entire YRD and its corresponding trajectories of shrinkage and expansion. Here, we used 1984–2018 Landsat images and the change detection analysis algorithm to track annual area change trajectories of present YRD with the help of Google Earth Engine cloud platform. Results showed that entire YRD area documented a significantly shrinking trend with slope of –18.5 km2/decade ( p p p < 0.01). Their mean coast erosion distance ranged from 2 to 4 km in 1984–2018. Area changes in the two regions contributed more to shrinkage of entire YRD. Besides, the expanding rate of current river mouth region was gradually slowdown due to decreases of sediment discharges, although area of new river mouth was still seemingly expanding. The significantly shrinking phenomena of the present YRD should be paid more attention.

Migration and Diffusion of Heavy Metal Cu from the Interior of Sediment during Wave-Induced Sediment Liquefaction Process

Sediments are an important sink for heavy metal pollutants on account of their strong adsorption capacity. Elevated content of Cu was observed in the Chengdao area of the Yellow River Delta, where the surface sediment is mainly silt and is prone to be liquefied under hydrodynamic forces. The vertical transport of fine particles, along with pore water seepage, during the liquefaction process could promote the migration and diffusion of Cu from the interior of sediment. The present study involved a series of wave flume experiments to simulate the migration and diffusion of Cu from the interior of sediment in the subaqueous Yellow River Delta area under wave actions. The results indicated that sediment liquefaction significantly promoted the release of Cu from internal sediment to overlying water. The variations of Cu concentrations in the overlying water were opposite to the suspended sediment concentrations (SSCs). The sediment liquefaction caused high initial rises of SSCs, but led to a rapid decline of dissolved Cu concentration at the initial period of sediment liquefaction due to the adsorption by fine particles. Afterwards, the SSCs slightly increased and then gradually decreased. Meanwhile, the dissolved Cu concentration generally kept increasing under combined effects of intensively mix of sediment and overlying water, pore water seepage, and desorption. The dissolved Cu concentration in the overlying water during sediment liquefaction phase was 1.5–2.2 times that during the consolidation phase. Sediment liquefaction also caused vertical diffusion of Cu in sediment and the diffusion depth was in accordance with the liquefaction depth. The results of the present study may provide reference for the environmental management in the study area.

Mapping the Yellow River Delta land subsidence with multitemporal SAR interferometry by exploiting both persistent and distributed scatterers

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.

Priority conservation pattern of wetlands in the Yellow River basin based on systematic conservation planning.

Yellow River basin is a significant habitat for biodiversity conservation in China. Here, we established a integrated classification system of wetlands based on climate types and geomorphological units, with which as the coarse-filter surrogates of biodiversity elements to complement the fine-filter surrogates of distribution of focal bird species. Then, we applied the theoretical framework of systematic conservation planning (SCP), with those two biodiversity surrogates as protection objects and watershed as planning units. We calculated social and economic costs (including roads, railroads, towns, rural settlements, dams) and set targets of 30% to input Marxan to figure out the optimal set of planning units, which met the protection target with the minimum of social economy cost and land resources. We identified a conservation priority pattern by calculating the irreplaceability of each unit by Marxan. Then, we compared the priority pattern with the existing reserve system to analyze conservation gap in the Yellow River basin. The results showed that most marsh wetlands were concentrated in the upper reaches of the Yellow River. The coverage of reserves in the source area was large. Some rare wetland types in Inner Mongolia, Gansu and Sichuan were separated from the protection system. The main wetland types in the middle reaches of the Yellow River were riverine wetlands, with low protection coverage rate and large conservation gaps. After protection network system being optimized, the protection effect was improved by29.1%-37.6%. The wetland in the lower reaches of the Yellow River was mainly concentrated in the Yellow River Delta area. The protection system was good and the conservation gaps was small. Overall, riverine wetlands in the middle reaches of the Yellow River basin had the highest area proportion of conservation gaps which needed more attention. Based on the priority conservation pattern, our results provided scientific suggestions for the protection planning and management of wetlands in the Yellow River basin, which would lay a foundation for the water ecological protection of the Yellow River basin from the macro scale.

Classification of the Yellow River delta area using fully polarimetric SAR measurements

ABSTRACTIn this study, an analysis of the polarimetric synthetic aperture radar (SAR) capabilities to classify coastal areas is undertaken. The Yellow River delta (China) is selected as the test case since it represents an extraordinary environmental and economical area, which is characterized by a very heterogeneous scattering scenario, as witnessed by official reference data, provided by the Chinese government, that classified 12 different kinds of environment. Experimental results, obtained applying two well-known unsupervised classifiers, namely the H/α-based and the Freeman–Durden model-based algorithms, to a fully polarimetric SAR scene collected by Radarsat-2 in 2008 are compared and critically discussed. Both provide a satisfactory global accuracy (larger than 60% in average) with reference to the inland Yellow River delta area, but there are subareas that result in misclassifications and severe classification ambiguities. This study also suggests including single-polarization intensity information to improve the classification accuracy and to partly solve ambiguities.

Response of Hydrodynamic Characteristics to Seabed Erosion and Deposition in Yellow River Delta Area

The Yellow River carries large amount of sediment into the sea, of which 70%-80% will deposit at the offshore of the Yellow River Delta. Under the hydrodynamic forces, such as waves, tides and currents, seabed may be eroded or deposited in varying degree. But, the current situation of seabed erosion and deposition in Yellow River delta is not yet clear. In this study, a long-term observation was carried out in Yellow River delta from 9th, December, 2014 to 10th February, 2015. We analyzed the effects of hydrodynamic forces, including waves, tide and currents, on the process of seabed erosion and deposition from the monitoring data. Results showed that the degree of seabed erosion and deposition are closely related to the velocity of underflow, wave height and water depth, etc.

Analysis of relationships between land surface temperature and land use changes in the Yellow River Delta

This study analyzed land use and land cover changes and their impact on land surface temperature using Landsat 5 Thematic Mapper and Landsat 8 Operational Land Imager and Thermal Infrared Sensor imagery of the Yellow River Delta. Six Landsat images comprising two time series were used to calculate the land surface temperature and correlated vegetation indices. The Yellow River Delta area has expanded substantially because of the deposited sediment carried from upstream reaches of the river. Between 1986 and 2015, approximately 35% of the land use area of the Yellow River Delta has been transformed into salterns and aquaculture ponds. Overall, land use conversion has occurred primarily from poorly utilized land into highly utilized land. To analyze the variation of land surface temperature, a mono-window algorithm was applied to retrieve the regional land surface temperature. The results showed bilinear correlation between land surface temperature and the vegetation indices (i.e., Normalized Difference Vegetation Index, Adjusted-Normalized Vegetation Index, Soil-Adjusted Vegetation Index, and Modified Soil-Adjusted Vegetation Index). Generally, values of the vegetation indices greater than the inflection point mean the land surface temperature and the vegetation indices are correlated negatively, and vice versa. Land surface temperature in coastal areas is affected considerably by local seawater temperature and weather conditions.

Using Nd-Sr isotopes and rare earth elements to study sediment provenance of the modern radial sand ridges in the southwestern Yellow Sea

The radial sand ridges (RSRs) in the southwestern Yellow Sea off the Jiangsu Coast, East China have been intensively studied at least since 1975. Despite decades of studies, the provenance of the RSR sediments remains uncertain. In this study, the Nd-Sr isotopic and REE geochemical compositions of residual sediments (i.e., the acid-insoluble fractions) were investigated to determine the provenance of the RSR sediments. The Nd isotopic composition, PAAS-normalized REE patterns and characteristic parameters (e.g., Sm/Nd, (La/Sm)N, (Gd/Yb)N) were merely associated with source rocks but not with particle sorting while the Sr isotopic composition and REE contents of residual sediments were affected by particle sorting in addition to source rocks. The onshore RSR sediments originated mainly from mixing of the fine-grained sediments from various parts of the offshore RSR in terms of REE geochemical and isotopic analyses. Isotopic and REE geochemical comparison further reveals that the RSRs off the Jiangsu Coast were fed chiefly by the dispersal of surface sediments from the Yangtze River Mouth. Surface sediments from the Yangtze River Mouth were directly dispersed to the RSRs along the Jiangsu Coast and significantly affected the seaward part of the offshore RSR and the old Yellow River Delta area by a northward branch of the Changjiang Diluted Freshwater Plume. Only minor quantities of surface sediments from the modern Yellow River Mouth were introduced into the RSRs by the Jiangsu Coastal Current and mainly contaminated the landward part of the offshore RSR area. Our findings highlighted the potential of the Nd isotopes with REE geochemistry to trace the provenance of coastal sediments.

Vertical migration of fine-grained sediments from interior to surface of seabed driven by seepage flows–‘sub-bottom sediment pump action’

A scientific hypothesis is proposed and preliminarily verified in this paper: under the driving of seepage flows, there might be a vertical migration of fine-grained soil particles from interior to surface of seabed, which is defined as ‘sub-bottom sediment pump action’ in this paper. Field experiments were performed twice on the intertidal flat of the Yellow River delta to study this process via both trapping the pumped materials and recording the pore pressures in the substrate. Experimental results are quite interesting as we did observe yellow slurry which is mainly composed of fine-grained soil particles appearing on the seabed surface; seepage gradients were also detected in the intertidal flat, under the action of tides and small wind waves. Preliminary conclusions are that ‘sediment pump’ occurs when seepage force exceeds a certain threshold: firstly, it is big enough to disconnect the soil particles from the soil skeleton; secondly, the degree of seabed fluidization or bioturbation is big enough to provide preferred paths for the detached materials to migrate upwards. Then they would be firstly pumped from interior to the surface of seabed and then easily re-suspended into overlying water column. Influential factors of ‘sediment pump’ are determined as hydrodynamics (wave energy), degree of consolidation, index of bioturbation (permeability) and content of fine-grained materials (sedimentary age). This new perspective of ‘sediment pump’ may provide some implications for the mechanism interpretation of several unclear geological phenomena in the Yellow River delta area.

Combined application of polymer coated potassium chloride and urea improved fertilizer use efficiencies, yield and leaf photosynthesis of cotton on saline soil

Conventional potassium fertilizers had been used widely, but few studies paid attention to controlled-release potassium fertilizer. The objective of this study was to explore the effects of polymer coated potassium chloride (PCPC) -an innovation product, especially the interaction application of PCPC and polymer coated urea (PCU) on cotton yield, fiber quality, leaf photosynthesis and fertilizer use efficiencies under salinity stressed conditions. A two-year experiment was conducted in two nearby fields with the similar fertility but varying salinity, using a split-plot design in the Yellow River Delta area of China. The main plots were assigned to the types of K fertilizers (K1-180kgha-1K from potassium sulfate, K2-90kgha-1K from potassium sulfate+90kgha-1K from PCPC, K3-54kgha-1K from potassium sulfate+126kgha-1K from PCPC, hereafter referred to as 0, 50% and 70% PCPC), while the types of N fertilizers (N1-220kgha-1N from urea, N2-110kgha-1N from urea+110kgha-1N from PCU, N3-66kgha−1N from urea+154kgha-1N from PCU, hereafter referred to as 0, 50% and 70% PCU) were assigned to the subplots. The results indicated that the lint yield, number of bolls, boll weight, lint percentage, fiber qualities, leaf photosynthesis and fertilizer use efficiencies were significantly affected by the types of K, N fertilizers and their interaction. The K and N release characteristics of PCPC and PCU under field condition were closely matched to the nutrients requirements of cotton growth. The contents of soil available K and inorganic N were significantly augmented from the first bloom stage to the initial boll-opening stage by using PCPC and PCU compared to potassium sulfate and urea treatments. Meanwhile, PCPC and PCU interaction increased lint yields by 11.16–26.44% and 14.17–32.11% in comparison with potassium sulfate and urea in 2014 and 2015, respectively, and the maximum lint yield was achieved by the combination of 70% PCPC and 50% PCU. Besides, the boll number and boll weight were improved 5.2–18.2% and 4.75–10.29% by the PCPC and PCU treatments compared to both potassium sulfate and urea treatments, respectively. The potassium recovery efficiency (KRE) and nitrogen recovery efficiency (NRE) of PCPC and PCU treatments were significantly raised by 24.34–33.77% and 19.68–36.25%, respectively, compared with potassium sulfate and urea treatments in 2014 and 2015. PCPC owned the great potential to alter the current application of potassium fertilizer due to its ubiquitous traits. The interaction of PCPC and PCU at optimal dose was significant on cotton growth in saline soil. Consequently, the application of 70% PCPC in combination with 50% PCU is recommended to increase cotton yield and fertilizer use efficiency, and to improve the fiber quality and leaf photosynthesis properties in the Yellow River Delta area of China.

Effects of rice-duck mutualistic organic farming on rice quality in the Yellow River Delta, China.

Three cultivation models including rice-duck mutualistic, manual weeding and conventional rice farming were designed in the Yellow River Delta area to study the effects on rice milling quality, appearance quality, cooking and eating quality, and sanitation quality. The results showed that compared to conventional rice farming, the rice-duckmutualistic treatment increased grain width and brown rice rate, milled rice rate, head rice rate and reduced the chalkiness. This was mainly due to the increase of panicle numbers and grain mass and the decrease of the inferior grains. Due to the application of organic manure, the gel consistency increased, amylose and protein contents decreased, and the rice taste improved under rice-duck mutualistic and manual weeding cultivation treatments. As no chemical fertilizers and pesticides were applied under rice-duck mutualistic and manual weeding treatments, pesticide residues were greatly reduced or even not detected. Rice duck farming could improve the quality of rice and protect the environment, which would be a good ecological technology for high quality rice production.

The magnetic properties of sediment and sedimentary environment in the Huanghe Delta area after the last glacial maximum

On the basis of measuring the magnetic parameters of sediment in Core YDZ1, combined with a grain size analysis and Carbon-14 dating, the magnetic properties of sediment and sedimentary environment in the Huanghe (Yellow River) Delta area after the last glacial maximum have been studied. The results show that the ferrimagnetic minerals of a pseudo single domain and multi domain particles dominate the magnetic properties of sediment in Core YDZ1. The imperfect anti ferrimagnetic minerals have more contribution on sediment in a depth of 24.0–22.1 m, and more stable-single domain and pseudo single domain particles exist. The susceptibility of anhysteretic remanent magnetization and the ratio of the susceptibility of anhysteretic remanent magnetization to saturation isothermal remanent magnetization show a decrease trend below depth of 24 m, a marked increase trend in a depth of 24.0–13.5 m, and a rapid decrease at depth of 13.5 m, then a fluctuation trend upward. The above two magnetic parameters and the ratio of the susceptibility of anhysteretic remanent magnetization to the mass susceptibility can be regarded as the proxy indicators for the content of clay (<4 μm) and the fine-grained size (<32 μm). The sedimentary environment after the last glacial maximum in the Huanghe Delta area has experienced the fluvial facies, the tidal flat facies, the neritic facies, the pro delta facies, the delta front facies and the floodplain facies. Thickness of the Holocene transgression layer is 10.5 m and the depth of substrate is about 24 m according to the YDZ1 core. The sedimentary dynamic has a variation trend with strongweak- strong, which has been proved by the Flemming triangular schema.

Effect of sampling on spatial variability in soil salinity in the Yellow River Delta Area

Effect of sampling on spatial variability in soil salinity in the Yellow River Delta Area