National Scale In China Research Articles

CryoSat-2 radar altimetry for monitoring freshwater resources of China

Surface water bodies (lakes, reservoirs, and rivers) are key components of the water cycle and are important water resources. Water level and storage vary greatly under the impacts of climate change and human activities. Due to sparse in-situ monitoring networks, a comprehensive national-scale monitoring dataset of surface water bodies in China is not available. Over the last two decades, satellite altimetry has been used successfully for inland water monitoring. Here, we use CryoSat-2 radar altimetry to monitor water level variations of large lakes, reservoirs and rivers across China and demonstrate its potential to complement available in-situ monitoring datasets for the country.In this study, over 1000 lakes and reservoirs, and 6 large rivers are investigated. The results show that surface water varied greatly over the past 6years, e.g. in the Tibetan Plateau, the Junggar Basin, the Northeast China Plain, and the central Yangtze River basin. Estimated changes in volume indicate that surface water variation contributes significantly to terrestrial storage variation, especially in the Qaidam Basin and the Tibetan Plateau. CryoSat-2 is capable of measuring regional-scale river level at high spatial resolution and competitive accuracy as demonstrated by comparison with available in-situ gauging data. The results are encouraging with RMSE values ranging from 0.24 to 0.35m for the Heilongjiang-Amur River, 0.22 to 0.6m for the Yellow River and 0.22 to 0.5m for the Songhua River. Comparatively, accuracy is much lower over the Yangtze and Pearl Rivers (RMSE ~2.6m and ~3.3m), probably due to intensive inland waterway navigation. CryoSat-2 shows great potential for monitoring surface water at national scale in China.

The Spatial Structure of High Speed Railways and Urban Networks in China: A Flow Approach

AbstractThe high speed railway (HSR) has played a crucial role in the regional integration of urban networks in China. This paper analyses HSR passenger flows instead of commonly‐used time schedules for measuring different polycentricity in urban networks. Using 2013 origin/destination (O/D) passenger flow data, we analyse the spatial configurations of 99 HSR cities at the national scale in China. In addition, we compare the spatial configurations of three regional urban networks: the Pearl River Delta, the Yangzi River Delta and the Bohai Rim. The outcomes show that the three functional regions connected by HSR are the most dominant polycentric regions in China and that the Bohai Rim is less hierarchical than the other two. We conclude that the comprehensive Chinese HSR networks are largely polycentric, especially in the central and eastern regions.

The current status of heavy metal in lake sediments from China: Pollution and ecological risk assessment.

Heavy metal contamination in lake sediments is a serious problem, particularly in developing countries such as China. To evaluate heavy metal pollution and risk of contamination in lake sediments on a national scale in China, we collated available data in the literature of the last 10 years on lake sediments polluted with heavy metals from 24 provinces in China. Based on these data, we used sediment quality guidelines, geoaccumulation index, and potential ecological risk index to assess potential ecological risk levels. The results showed that approximately 20.6% of the lakes studied exceeded grade II level in Chinese soil quality standards for As, 31.3% for Cd, 4.6% for Cu, 20.8% for Ni, 2.8% for Zn, and 11.1% for Hg, respectively. Besides, the mean concentrations for As in 10.3% of lakes, Hg in 11.9% of lakes, and Ni in 31.3% of lakes surpassed the probable effect level. The potential ecological risk for toxic metals decreased in the order of Cd > Hg > As > Cu > Pb > Ni > Cr > Zn, and there were 21.8% of the lakes studied in the state of moderate risk, 10.9% in high risk, and 12.7% in very high risk. It can be concluded that Chinese lake sediments are polluted by heavy metals to varying degrees. In order to provide key management targets for relevant administrative agencies, based on the results of the pollution and ecological risk assessments, Cd, Hg, As, Cu, and Ni were selected as the priority control heavy metals, and the eastern coastal provinces and Hunan province were selected as the priority control provinces. This article, therefore, provides a comprehensive assessment of heavy metal pollution in lake sediments in China, while providing a reference for the development of lake sediment quality standards.

Changes in surface energy partitioning in China over the past three decades

Surface energy balance and the partitioning of sensible heat flux (SHF) and latent heat flux (LHF) play key roles in land–atmosphere feedback. However, the lack of long-term observations of surface energy fluxes, not to mention spatially extensive ones, limits our understanding of how the surface energy distribution has responded to a warming climate over recent decades (1979–2009) at the national scale in China. Using four state-of-the-art reanalysis products with long-term surface energy outputs, we identified robust changes in surface energy partitioning, defined by the Bowen ratio (BR = SHF/LHF), over different climate regimes in China. Over the past three decades, the net radiation showed an increasing trend over almost the whole of China. The increase in available radiative energy flux, however, was balanced by differential partitioning of surface turbulent fluxes, determined by local hydrological conditions. In semi-arid areas, such as Northeast China, the radiative energy was transferred largely into SHF. A severe deficiency in near-surface and soil moistures led to a significant decreasing trend in LHF. The combined effect of increased SHF and decreased LHF resulted in significant upward trends in the BR and surface warming over Northeast China. In contrast, in the wet monsoon regions, such as southern China, increased downward net radiation favored a rise in LHF rather than in SHF, leading to a significant decreasing trend in the BR. Meanwhile, the increased LHF partly cancelled out the surface warming. The warming trend in southern China was smaller than that in Northeast China. In addition to impacts on heat-related events, the changes in the BR also reflected recent cases of extreme drought in China. Our results indicate that information regarding the BR may be valuable for drought monitoring, especially in regions prone to such conditions.

Characterization of effects of thermal property of aggregate on the carbon footprint of asphalt industries in China

In this study, the effects of the thermal properties of asphalt binders and aggregate materials were characterized in terms of the specific heat capacity (C) for energy consumption and environmental footprints of hot mix asphalt (HMA) and warm mix asphalt (WMA). Asphalt mixes produced using low-C aggregate are found to be more energy-efficient and environmental friendly, irrespective of the binder type and construction technology. Therefore, different fractions of aggregate blends were replaced with the aggregate provided from a low-C source or sustainable source. Analysis of energy consumption clearly indicated that the specific energy and environmental footprints decrease linearly as the low-C aggregate content increases. The amount of energy saving realized in the asphalt industries by the use of low-C aggregate is significant on a national scale in China. In this regard, China was chosen as a case study. Analysis of fuel requirement clearly indicated that the production of WMA using high thermal sensitivity aggregate can yield significant energy saving sufficient to fuel 44,007 to 664,880 Chinese households per year. Therefore, use of low C aggregate in asphalt mix production can be adopted as a strategy to produce WMA and HMA.

Point-surface fusion of station measurements and satellite observations for mapping PM2.5 distribution in China: Methods and assessment

Fine particulate matter (PM2.5, particulate matters with aerodynamic diameters less than 2.5μm) is associated with adverse human health effects, and China is currently suffering from serious PM2.5 pollution. To obtain spatially continuous ground-level PM2.5 concentrations, several models established by the point-surface fusion of station measurements and satellite observations have been developed. However, how well do these models perform at national scale in China? Is there space to improve the estimation accuracy of PM2.5 concentration? The contribution of this study is threefold. Firstly, taking advantage of the newly established national monitoring network, we develop a national-scale generalized regression neural network (GRNN) model to estimate PM2.5 concentrations. Secondly, different assessment experiments are undertaken in time and space, to comprehensively evaluate and compare the performance of the widely used models. Finally, to map the yearly and seasonal mean distribution of PM2.5 concentrations in China, a pixel-based merging strategy is proposed. The results indicate that the conventional models (linear regression, multiple linear regression, and semi-empirical model) do not obtain the expected results at national scale, with cross-validation R values of 0.49–0.55 and RMSEs of 30.80–31.51μg/m3, respectively. In contrast, the more advanced models (geographically weighted regression, back-propagation neural network, and GRNN) have great advantages in PM2.5 estimation, with R values ranging from 0.61 to 0.82 and RMSEs from 20.93 to 28.68μg/m3, respectively. In particular, the proposed GRNN model obtains the best performance. Furthermore, the mapped PM2.5 distribution retrieved from 3-km MODIS aerosol optical depth (AOD) products agrees quite well with the station measurements. The results also show that the approach used in this study has the capacity to provide reasonable information for the global monitoring of PM2.5 pollution in China.

Airborne persistent toxic substances (PTSs) in China: occurrence and its implication associated with air pollution.

In recent years, China suffered from extensive air pollution due to the rapidly expanding economic and industrial developments. Its severe impact on human health has raised great concern currently. Persistent toxic substances (PTSs), a large group of environmental pollutants, have also received much attention due to their adverse effects on both the ecosystem and public health. However, limited studies have been conducted to reveal the airborne PTSs associated with air pollution at the national scale in China. In this review, we summarized the occurrence and variation of airborne PTSs in China, especially in megacities. These PTSs included polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), halogenated flame retardants (HFRs), perfluorinated compounds (PFCs), organochlorine pesticides (OCPs), polycyclic aromatic hydrocarbons (PAHs) and heavy metals. The implication of their occurrence associated with air pollution was discussed, and the emission source of these chemicals was concluded. Most reviewed studies have been conducted in east and south China with more developed economy and industry. Severe contamination of airborne PTSs generally occurred in megacities with large populations, such as Guangzhou, Shanghai and Beijing. However, the summarized results suggested that industrial production and product consumption are the major sources of most PTSs in the urban environment, while unintentional emission during anthropogenic activities is an important contributor to airborne PTSs. It is important that fine particles serve as a major carrier of most airborne PTSs, which facilitates the long-range atmospheric transport (LRAT) of PTSs, and therefore, increases the exposure risk of the human body to these pollutants. This implied that not only the concentration and chemical composition of fine particles but also the absorbed PTSs are of particular concern when air pollution occurs.

Spatial and temporal trends in the mortality burden of air pollution in China: 2004–2012

While recent assessments have quantified the burden of air pollution at the national scale in China, air quality managers would benefit from assessments that disaggregate health impacts over regions and over time. We took advantage of a new 10×10km satellite-based PM2.5 dataset to analyze spatial and temporal trends of air pollution health impacts in China, from 2004 to 2012. Results showed that national PM2.5 related deaths from stroke, ischemic heart disease and lung cancer increased from approximately 800,000 cases in 2004 to over 1.2 million cases in 2012. The health burden exhibited strong spatial variations, with high attributable deaths concentrated in regions including the Beijing–Tianjin Metropolitan Region, Yangtze River Delta, Pearl River Delta, Sichuan Basin, Shandong, Wuhan Metropolitan Region, Changsha–Zhuzhou–Xiangtan, Henan, and Anhui, which have heavy air pollution, high population density, or both. Increasing trends were found in most provinces, but with varied growth rates. While there was some evidence for improving air quality in recent years, this was offset somewhat by the countervailing influences of in–migration together with population growth. We recommend that priority areas for future national air pollution control policies be adjusted to better reflect the spatial hotspots of health burdens. Satellite-based exposure and health impact assessments can be a useful tool for tracking progress on both air quality and population health burden reductions.

Assessment of cadmium (Cd) concentration in arable soil in China.

Cadmium (Cd) concentration in arable soil has drawn broad public attention due to its direct effect on Cd concentration in food. However, there have been few studies of surveying Cd accumulation on the national scale in China. This paper collected 486 studies of Cd concentrations in Chinese arable soil. The results showed that the average Cd concentration was 0.27mg/kg, higher than its background value, indicating that Cd had been introduced into arable soil by human activity. The Cd concentrations in areas of mining and smelting, urban areas, and areas irrigated by wastewater were obviously higher than that inremote areas. Spatially, Cd concentrations were lower in the north than those in the south, and many hotspots existed throughout China due to mining and smelting activities. Most Cd in the arable soil were accumulated from external sources in all investigated provinces except Ningxia Hui Autonomous Region.

Quantitative evaluation of carcinogenic and non-carcinogenic potential for PAHs in coastal wetland soils of China

The levels, sources and health risks for PAHs collected at the national scale in China were discussed in the study. The total concentrations of 16 PAHs in nine coastal wetland soils ranged from 10.8 to 4870ngg−1. The sources of PAHs were apportioned by PCA, and both the carcinogenic and non-carcinogenic risks were quantitatively calculated with Monte Carlo simulation. A sensitivity analysis was performed to determine the greatest effect of input variables on the risk assessment. The results revealed that 16 PAHs mainly originated from coal combustion, natural gas combustion, diesel emission, and petrogenic source. The carcinogenic risk and non-carcinogenic risk for nine coastal wetlands were below the risk threshold value (10−6 for carcinogenic risk, and 1 for non-carcinogenic risk, respectively), indicating no potential adverse health effects developed. Ingestion and dermal contact were the major exposure routes for PAHs risks. Exposure duration and PAHs concentration contributed most to the total risks uncertainty. This study is the first attempt to provide information on health risk of PAHs in wetland soils from a national perspective. The findings support the feasibility of development and evaluation of an implementation strategy for PAHs risks management in coastal wetland soils.

Hexachlorocyclohexanes in tree bark across Chinese agricultural regions: spatial distribution and enantiomeric signatures.

The environmental issue caused by atmospheric hexachlorocyclohexanes (HCHs) has been a worldwide concern due to their long-range transport potential. Tree bark is an excellent passive sampler for monitoring atmospheric pollutants. In this study, bark samples from agricultural regions across China were collected and analyzed to elucidate the contamination status of atmospheric HCHs and the enantiomeric composition of chiral α-HCH. Average contents of α-HCH, β-HCH, γ-HCH, δ-HCH, and ∑HCHs in bark were 1.16, 2.51, 1.67, 0.368, and 5.71 ng/g (dry basis), respectively. Jing-Jin-Tang region was identified as the "hot-spot" of bark HCHs in China. Their residues were likely from the combined sources of historical applications of technical HCHs and lindane through long-distance transport. HCH contents were found inversely correlated with annual precipitation and temperature, but positively correlated with PM10 or PM2.5 due to the bioaccumulation of both vapor- and particle-phase HCHs by tree bark. Most bark samples preferentially accumulated (+)-α-HCH, and the enantiomeric fractions (EFs) of α-HCH were positively correlated with α-HCH concentrations and the elevations of sampling locations. Compared to atmospheric analysis, tree bark analysis and enantiomeric signatures provide valuable time-integrated information on the spatial distribution and transport pathways of atmospheric HCHs on the national scale in China.

Status, Influences and Risk Assessment of Hexachlorocyclohexanes in Agricultural Soils Across China

Large amounts of hexaclorocyclohexanes (HCHs) were historically applied to Chinese soils. However, there has been limited information on the residue patterns of HCHs in soils at a national scale in China. In this study, surface soil samples were collected from agricultural fields across China, and the concentrations of HCHs and enantiomeric fractions (EFs) of α-HCH were measured. The results showed that the average concentrations of α-HCH, β-HCH, γ-HCH, and total HCHs in Chinese agricultural soils were 0.190, 1.31, 0.236, and 1.74 ng g(-1), respectively. Residues of HCHs likely originated from past usage of technical HCHs. The isomers of α-HCH and γ-HCH tended to accumulate in the sites with lower total HCH concentrations, lower temperature, higher elevation, and less wet precipitation when compared to β-HCH. Enantiomeric analysis showed a preferential degradation of (-)-α-HCH. Human health risks via various exposure routes to HCHs in soils were further estimated. Overall, the mean hazard index (HI) linked to noncarcinogenic risks was below 1, suggesting an absence of noncarcinogenic risks of HCHs in Chinese soils. In addition, the cancer risk values were all below 10(-4), which indicates low or very low risks.

Survey and analysis of consumers' behaviour of waste mobile phone recycling in China

Abstract The aim of this paper is to investigate the behaviour of consumers toward waste mobile phone recycling on a national scale in China. With this goal in mind, a questionnaire survey was performed on a nationwide scale to explore consumers' behaviours, attitudes and willingness to pay (WTP) for recycling waste mobile phones. There were 1035 effective questionnaires, and the questionnaire was analysed with principal component analysis and multinomial logistic regression analysis. The results revealed that the actual service life of mobile phones in China is generally shorter than three years. Due to the current level of economic development and the traditional concept, only 47.9% of consumers agreed to pay for waste mobile phone recycling, and most consumers' WTP was 0–5% of the recycling costs. The main factors affecting the consumers' WTP were region, education level and monthly income. Therefore, mobile phone producers and the government should mostly share the responsibility of waste mobile phone recycling. With an improvement in public environmental awareness, it may be possible for consumers to afford recycling fees in the future, through either a prepaid deposit, or purchasing the product with the fee embedded in the price. In addition, it is important to support environmental education to promote environmental awareness.

Evaluation of asthma control and patient’s perception of asthma: findings and analysis of a nationwide questionnaire-based survey in China

Background: Little is known about asthma control and perception of asthma among asthmatic patients on a national scale in China due to the difficulty of conducting a survey of the large, vastly distributed population of the country. We know that the medical insurance system may not evenly cover all patients and that socioeconomic status varies greatly across cities. Objective: This study marks the first survey conducted on a national scale that was aimed at obtaining baseline information on asthma control and patients’ perceptions of asthma and providing a point of reference for future studies. Methods: This face-to-face, questionnaire-based survey was conducted from April 2007 to March 2008 in 3069 asthmatic patients from the respiratory outpatient clinics of 36 general hospitals located in 10 geographically dispersed cities. Results: Per the Global Initiative for Asthma (GINA) guidelines, 28.7% and 45.0% of our patients achieved complete or partial asthma control, respectively. Of patients in the study, only 21.8% had used a peak flow meter (PFM) and 6.6% of these patients used it daily. Inhaled corticosteroids (ICS) plus a long-acting β2 agonist and ICS were the two most common medication regimens and were used in 45.6% and 30.4% of patients, respectively. Asthma had a significant effect on patients’ life and work. A considerable number of hospitalizations, emergency department visits and sick days were also observed. Conclusions: Despite improvements in asthma control and ICS and PFM compliance compared with past literature, the current level of asthma control countrywide continues to fall short of the goals set in the GINA.

Economical assessment of forest ecosystem services in China: Characteristics and implications

China is an important country in the world in terms of forestry and the function of its forest ecosystem. It is an essential issue to account the value of the forest ecosystem services (FESs) of China in both ecological economy and environmental policy making. However, a big challenge exists because of the variety in climate types, forest vegetation, and silvicultural measures. In the current study, the monetary value of some important China's FESs, such as water conservation, soil conservation, carbon sequestration and oxygen release, nutrient accumulation, atmosphere environment purification, and biodiversity conservation, was estimated to be about 10.01 trillion RMB/year (1.48 trillion US dollars/year) in 2008, wherein the largest fraction was water conservation (40.51%). A four-fold variation used to exist in the FESs per unit area by the provinces which are geographically used as assessing units. This value of FESs was about 33% of the gross domestic product (GDP) of China in 2008. The values of FESs are unevenly distributed across the country, decoupling from GDP among different provinces. The value of China's FESs will continue to have a fast increasing trend due to massive forestation in the future decades. Beyond that, it is clear that how much ecological benefits human obtained from forest, what kind of ecological benefits offered by forest, and which are predominant or potential FESs types in province under different natural and social conditions according to ecological location quotient (ELQ). Compared with the Engel's coefficient (EC) of individual and the willingness to pay index (WTP) of governmental to FESs, we can conclude that insofar as we have a thorough understanding of the value and functions of FESs, and bring the government WTP and individual EC into full play, and promote the high environmental protection consciousness, it will have large potential WTP for improving the environment quality based on the low level WTP of the government in reality. Moreover, these results show important implications in making a policy for ecological complementary on the national scale in China and in assessing FESs in other countries, and will be useful to scientists, managers, policy makers and people who are concerned with relationship between human and natural systems.

Spatial simulation of topsoil TN at the national scale in China

Based on 5336 typical soil profiles collected during the second national soil survey period,the correlation between topsoil total nitrogen(A horizon) and 11 environmental factors were analyzed and spatial distribution of topsoil nitrogen(TN) at national scale in China was simulated with the combination of multiple regression model and HASM model.Results indicated that,mean absolute error and mean relative error of the predicted value for 350 validation points were 0.67 g·kg-1 and 61.06%;compared with ordinary kriging method,the two errors were reduced by 0.05 g·kg-1 and 17.53% respectively.Besides,simulation result for northwest China,where the density of sample points was much smaller,was much closer to the actual situation.Thus,a combined method of multiple regression model and HASM model,which took the influence of environmental factors into account,can be used as an effective method for simulating spatial distribution of soil properties at a large scale.

Spatial patterns and effects of soil organic carbon on grain productivity assessment in China

AbstractIn this paper, we present an assessment of the content and effects of cropland soil organic carbon (SOC) on grain productivity at the national scale in China using a Web‐based Land Evaluation System. Homogeneous 5 km × 5 km grid data sets of climate, crop, soil and management parameters were created and grain production in 2005 was simulated. Attempts were made to incorporate SOC into the land evaluation procedure and to quantify the potential effects of SOC deficiency on grain productivity. Results were statistically analysed and the modelling approach was validated. National cropland SOC maps were generated. At the national scale, the cropland SOC content averaged 1.20, 0.58, 0.41, 0.31 and 0.26% for the five 20‐cm sections consecutively from the surface downwards. At the regional scale it tended to decline slightly from northeast (1.63%) to southwest (1.11%). On average, 64% of grain yield was lost due to SOC deficiency for the humid provinces and 7% for the arid and sub‐arid ones. Soil management options are suggested based on the simulation results.