China Plain Area Research Articles

Experimental study on mechanical and hydraulic properties of xanthan gum improved low liquid limit silty soil

The low liquid limit silty soil in the North China plain area is generally unsuitable for direct use as roadbed and slope soil. In order to improve the performance of low liquid limit silty soil, xanthan gum was used as an improver. Through a series of tests, the improvement effect of xanthan gum on low liquid limit silty soil was studied. The test results showed that Xanthan gum as an improver could significantly improve the unconfined compressive strength of silty soil. With the increase in dosage and curing age, the unconfined compressive strength of improved silty soil continued to improve and eventually tended to stabilize. The optimal dosage and curing period were 2% and 7 days, respectively. In addition, Xanthan gum could greatly improve the permeability and disintegration of low liquid limit silty soil. The permeability coefficient of improved silty soil with a content of 0.75% Xanthan gum and a 7-day curing period was 4.73 × 10−4 m·s−1, which was only 1.10% of that of plain silty soil at the same curing period. After immersion in water for 12 h, the soil only experienced slight disintegration. The scanning electron microscope image showed that the gel generated by the hydration reaction of Xanthan gum could improve the compactness and integrity of the soil by filling the voids, thus significantly improving the mechanical and hydraulic properties of the low liquid limit silty soil.

Spatial-Temporal Variation of AOD Based on MAIAC AOD in East Asia from 2011 to 2020

In recent years, atmospheric aerosol pollution has seriously affected the ecological environment and human health. Understanding the spatial and temporal variation of AOD is essential to revealing the impact of aerosols on the environment. Based on the MAIAC AOD 1 km product from 2011 to 2020, we analyzed AOD’s distribution patterns and trends in different time series across East Asia. The results showed that: (1) The annual average AOD in East Asia varied between 0.203 and 0.246, with a decrease of 14.029%. The areas with high AOD values were mainly located in the North China Plain area, the Sichuan Basin area, and the Ganges Delta area, with 0.497, 0.514, and 0.527, respectively. Low AOD values were mainly found in the Tibetan Plateau and in mountainous areas north of 40° N, with 0.061 in the Tibetan Plateau area. (2) The distribution of AOD showed a logarithmic decreasing trend with increasing altitude. Meanwhile, the lower the altitude, the faster the rate of AOD changes with altitude. (3) The AOD of East Asia showed different variations in characteristics in different seasons. The maximum, minimum, and mean values of AOD in spring and summer were much higher than those in autumn and winter. The monthly average AOD reached a maximum of 0.326 in March and a minimum of 0.190 in November. The AOD showed a continuous downward trend from March to September. The highest quarterly AOD values in the North China Plain occurred in summer, while the highest quarterly AOD values in the Sichuan Basin, the Ganges Delta, and the Tibetan Plateau all occurred in spring, similar to the overall seasonal variation in East Asia.

Information diffusion theory-based approach for the risk assessment of meteorological disasters in the Yangtze River Basin

The Yangtze River Basin is one of the three plain areas in China, and it spans eleven regions and serves as an important economic belt. The Yangtze River Basin is a region with frequent meteorological disasters and is affected by south-east and south-west monsoons. With a dense population, the economy in the middle and lower reaches of the basin has rapidly developed, and the agricultural economy has made significant contributions to China. Therefore, it is of far-reaching significance to study the influence of meteorological disasters in the Yangtze River Basin. Using information diffusion theory, this research analyses the impacts of five frequent natural disasters (floods, drought, convective storms, low temperatures, and typhoons) on selected areas from 2001 to 2006 (Shanghai, Jiangsu, Anhui, Jiangxi, Hunan, Hubei, Chongqing, Sichuan, Yunnan, Tibet, and Qinghai). Three agricultural indicators: affected area (A), covered area (C), and demolished area (D), are adopted to illustrate the economic losses caused by natural disasters. The method based on the analytic hierarchy process (AHP) framework is used to calculate the weights of the five disaster categories. The results are that Shanghai is severely affected by typhoons; Jiangsu, Anhui, Jiangxi, Hubei, Chongqing, Tibet, and Hunan are under the highest pressure of floods; Yunnan and Qinghai are under the strongest influence of droughts. Generally, agriculture production in the Yangtze River Basin is greatly affected by flood and drought disasters. Finally, some suggestions for dealing with meteorological disasters are proposed.

Impact of Expansion Pattern of Built-Up Land in Floodplains on Flood Vulnerability: A Case Study in the North China Plain Area

Built-up land in floodplains (BLF) is a driver and a disaster-bearing body of flood risk from a socio-hydrological perspective. The relationship between BLF growth and flood vulnerability is the key to understanding and managing flood risk. However, previous studies have focused more on the relationship between BLF growth and flood exposure, ignoring flood vulnerability. We examined the BLF expansion pattern (patch size and expansion type) in the North China Plain Area from 1975 to 2014 (1975–1990–2000–2014) using GIS (geographic information system)-based landscape analysis and revealed its relationship with flood vulnerability. The results show that the BLF area experienced rapid growth (288.26%) from dispersion to coalescence. Small patches dominated the number and area of BLF growth, and edge-expansion patches were the expansion type with the most area growth. We discovered that flood vulnerability was significantly correlated with the growth in small (R = 0.36, p < 0.01), edge-expansion (R = 0.53, p < 0.01), and outlying patches (R = 0.51, p < 0.01). Large patches were not significantly correlated with flood vulnerability (R = 0.18, p > 0.1), but there was a negative trend. Infilling patch growth was significantly associated with flood vulnerability over a long period (R = 0.27, p < 0.05). In addition, we suggest nature-based soft adaptations or village merging for small patches and outlying patches. Our findings have important scientific significance for adequately understanding the interplay between BLF growth and flood risk. It has practical implications for the formulation of integrated flood risk management strategy and the sustainable development of floodplains.

Time-space analysis of groundwater in China plain area and its water quantity balance analysis

Taking the typical plain city of Shangqiu as an example, groundwater balance is analyzed by monitoring precipitation and groundwater level. A correlation analysis shows that there is a significant correlation between groundwater level change and precipitation. By formulating the groundwater balance evaluation criteria, it was found that the evaluation grade was grade III in 1997, and most of the years were at grade II. It is suggested that measures should be taken to adjust the industrial layout, optimize the planting structure, and strengthen the utilization of reclaimed water to realize the scientific utilization of groundwater resources.

Reconstruction of cropland change in North China Plain Area over the past 300 years

Abstract Land use and land cover change (LUCC) is not only a vital form of global change, but through biogeophysical and biogeochemical mechanisms, it also has a strong impact on the global and regional climate and environment change. The existing historical LUCC datasets still have many uncertainties that cause errors in climate and environment simulations. Reconstruction of historical LUCC on the regional scale is essential for improving the precision of global and national LUCC. In this study, we combined existing datasets with historical statistics and survey data to reconstruct cropland change in North China Plain Area over the past 300 years. Following systematic steps, a range of original methods from data sources and methods comparison, data re-calibration, time slices selection, data supplement, to cropland area fraction calculation were used. The cropland area at the county level was allocated into grid cells of 10 km × 10 km so as to achieve a high spatial resolution and precision. The results show that the cropland area change in North China Plain Area can be classified into two main stages: steady increase before 1954 and rapid decrease after 1954. The spatial distribution of cropland change over the past 300 years corresponded to the patterns of the total cropland change in North China Plain Area. From the late 17th century to the 1980s, the cropland area fraction in the plains increased and the cropland expanded to the hilly and coastal areas gradually. After that, the cropland area fraction in the plains decreased, especially in the southeastern of North China Plain Area. The total cropland area in North China Plain Area of our study is close to the results of most previous studies but the maps generated based on our dataset present local difference of cropland distribution more clearly than a recent important global dataset HYDE3.2. Our dataset of cropland area at 10 km × 10 km grid scale can also be used directly in climate and environment simulations to improve the data precision in North China Plain Area.

Recent Surface Deformation in the Tianjin Area Revealed by Sentinel-1A Data

In this study, we employed multitemporal InSAR (Interferometric Synthetic Aperture Radar) (MT-InSAR) to detect spatial and temporal ground deformations over the whole Tianjin region in the North China Plain area. Twenty-five ascending Sentinel-1A terrain observation by progressive scans (TOPS) synthetic aperture radar (SAR) scenes covering this area, acquired from 9 January 2016 to 8 June 2017, were processed using InSAR time series analysis. The deformation results derived from Sentinel-1A MT-InSAR were validated with continuously operating reference stations (CORS) at four sites and four stations of the Crustal Movement Observation Network of China (CMONOC). The overall results show good agreement, demonstrating the suitability of applying Doris with Sentinel-1A data to high-resolution monitoring of surface deformation. Significant deformation variations have been observed in different parts of Tianjin. These gradually increased from the central part of the metropolitan area to the nearby suburbs. The deformation rate of the main urban area is well-balanced and it is also relatively linear, with uplifting rates ranging from 0 to 20 mm/yr. However, due to the diversity of the geological conditions and anthropogenic activities, remarkable signs of subsidence were found in several parts of Tianjin. In particular, the south-western part of Wuqing District and western part of Beichen District showed subsidence rates of up to −136 mm/yr. We also found that, in addition to groundwater over-exploitation and lithological characteristics, additional factors also influence ground subsidence, including dynamic loads (e.g., railways), static loads (e.g., urban construction), and groundwater recharging.

Impact of synoptic weather patterns on 24 h-average PM2.5 concentrations in the North China Plain during 2013–2017

North China Plain area (NCP) is one of the most densely populated and heavily polluted regions in the world. In the last five years, frequently happened fine particulate matter (PM2.5) serious pollution events were one of the top environmental concerns in China. As PM2.5 concentrations are highly influenced by synoptic flow patterns and local meteorological conditions, a two-stage hierarchical clustering method based on dynamic principal component analysis (DPCA) and standard k-means clustering algorithm was employed to classify synoptic wind fields into 6 patterns over the NCP area using the data of 5 PM2.5 seasons (Sept. 15th–Apr. 15th) from 2013 to 2017. Among the six identified synoptic patterns, pattern of uniform pressure field (U) and that of zonal high pressure (ZH) accounted for 78.21%, 65.55%, 63.56%, 57.11%, 59.13% and 58.27% studied heavy smog pollution events in Beijing, Tianjin, Tangshan, Baoding, Shijiazhuang and Xingtai city. The two particular patterns were associated with uniform pressure field and sparsely latitudinal isobar in 850 hPa level, respectively. They were also characterized by high relative humidity, low temperature, low-speed northerly wind in Tianjin and Tangshan, and southerly wind in the other cities. Under the continuous control of pattern ZH, the values of 24 h–average PM2.5 were found to increase at a rate of 31.78 μg/m3 per day. To evaluate the contribution of meteorological factors and precursors to PM2.5 levels, linear mixed-effects models (LMMs) were applied to establish relations among 24 h–average PM2.5 concentrations, concentrations of main precursors, local meteorological factors and synoptic patterns. Results show that the variations of precursors, local meteorological factors and synoptic flow patterns can explain 51.67%, 19.15% and 14.01% changes of the 24 h–average PM2.5 concentrations, respectively. This study illustrates that dense precursor emissions are still the main cause for heavy haze pollution events, although meteorological conditions play almost equal roles sometimes.

Study on the North China Rural Water Supply Project O&M Cost Standard Rating

For the purpose of further regulating the set-up standard of rural water supply project operation and maintenance cost, O&M cost accounting method should be identified; with North China plain area as the study target, water supply projects at 722 places are selected randomly for study. On the basis of survey data, multiple regression analysis means is employed to analyze relations between O&M cost and operation cost, annual actual output of water supply, personnel cost, electric tariff and water supply facility O&M frequency, and three O&M calculating models are established. O&M cost check computation has high reliability through personnel cost and electric tariff, operation cost and personnel cost, personnel cost and pump, purification equipment, electromechanical equipment, instrument and meter, valve and transmission and distribution pipe network maintenance frequency to some extent. Meanwhile, three O&M calculating models should be selected flexibly in combination with project conditions in actual application.

Soil nutrient loss due to tuber crop harvesting and its environmental impact in the North China Plain

Soil loss due to crop harvesting (SLCH) is a soil erosion process that significantly contributes to soil degradation in croplands. However, little is known about soil nutrient losses caused by SLCH and its environmental impacts. In the North China Plain area, we measured the losses of soil organic carbon (SOC) and nitrogen as well as phosphorus due to SLCH and assessed their relationship with soil particle size composition, agronomic practices and soil moisture content. Our results show that the losses by harvesting potato of SOC, total nitrogen (TN), available nitrogen (AN), available phosphorus (AP) and total phosphorus (TP) were 1.7, 1.8, 1.8, 15.9 and 14.1 times compared by harvesting sweet potato, respectively. The variation of SOC, N and P loss by SLCH are mainly explained by the variation of plant density (PD) (17–50%), net mass of an individual tuber (Mcrop/p) (16–74%), soil clay content (34–70%) and water content (19–46%). Taking into account the current sewage treatment system and the ratio of the nutrients adhering to the tubers during transportation from the field (NTRP/SP), the loss of TN and TP by harvesting of potato and sweet potato in the North China Plain area amounts to 3% N and 20% P loads in the water bodies of this region. The fate of the exported N and P in the sewage treatment system ultimately controls the contribution of N and P to the pollution of lakes and rivers. Our results suggest that a large amount of SLCH-induced soil nutrient export during transportation from the field is a potential pollutant source for agricultural water for vast planting areas of tuber crops in China, and should not be overlooked.

Settlement extraction in the North China Plain using Landsat and Beijing-1 multispectral data with an improved watershed segmentation algorithm

In this paper we present an improved watershed segmentation algorithm for settlement mapping from medium resolution satellite data over plain areas in China. The algorithm can increase the computational efficiency of the fastest reported watershed segmentation algorithm by 30–40%. We apply this method to a selected study area in southern Hebei Province, China. We acquired a Landsat Enhanced Thematic Mapper Plus (ETM + ) image over this area in May 2000, two Landsat Thematic Mapper (TM) images in August 2004 and April 2005, and two Beijing-1 satellite images in May 2006 and May 2007. The three types of images have three similar spectral bands (green, red and near-infrared) with similar spatial resolution (30–32 m). Only the red and near-infrared bands were used in image segmentation for settlement area extraction. The extracted settlement results are compared with manual interpretation results by two people. We assumed the human interpretation results are of higher accuracy than the segmentation results. Our results indicated that our settlement area extraction method is effective. With high quality images, the overall accuracies are nearly 94%, the kappa coefficient can be greater than 0.85.