Southern Yangtze River Delta Research Articles

Multi-Scale Analysis of Ecosystem Service Trade-Offs/Synergies in the Yangtze River Delta

The transformation of ecosystem structure leads to changes in ecosystem services (ESs) and their relationship. However, most research in this area has focused on particular scales and timeframes, often overlooking the significance of spatial and temporal variations. Therefore, we used the equivalent value method to evaluate seven typical ESs in the Yangtze River Delta (YRD) between 2000 and 2020: food production (FP), water supply (WS), climate regulation (CR), environmental purification (EP), soil conservation (SC), biodiversity maintenance (BM), and aesthetic landscape (AL). We further employed the Spearman correlation coefficient and bivariate Moran’s I to evaluate the relationship of ESs and their spatial heterogeneity at grid, township, county and city scales. Our results show that (1) All ESs except AL exhibited a fluctuating upward trend from 2000 to 2020, resulting in a total increase in ecosystem service (ES) value of RMB 650.63 billion. (2) Approximately 70% of the ES pairs demonstrated a synergistic relationship, with the exception of FP and other ESs, which mainly showed a trade-off. (3) With the scale increased from grid to city level, the degree of trade-off between FP and other ESs strengthened at different levels, while the synergy degree of among other ESs gradually decreased. (4) The relationship between ESs demonstrated strong spatial heterogeneity, with FP and other ESs exhibiting trade-offs primarily in the northern and southern YRD, while other ES pairs exhibited mostly synergy in these regions. This study provides scientific information for governments to optimize land use distribution and improve ESs.

Spatially and Temporally Differentiated NOx and VOCs Emission Abatement Could Effectively Gain O3-Related Health Benefits.

The increasing level of O3 pollution in China significantly exacerbates the long-term O3 health damage, and an optimized health-oriented strategy for NOx and VOCs emission abatement is needed. Here, we developed an integrated evaluation and optimization system for the O3 control strategy by merging a response surface model for the O3-related mortality and an optimization module. Applying this system to the Yangtze River Delta (YRD), we evaluated driving factors for mortality changes from 2013 to 2017, quantified spatial and temporal O3-related mortality responses to precursor emission abatement, and optimized a health-oriented control strategy. Results indicate that insufficient NOx emission abatement combined with deficient VOCs control from 2013 to 2017 aggravated O3-related mortality, particularly during spring and autumn. Northern YRD should promote VOCs control due to higher VOC-limited characteristics, whereas fastening NOx emission abatement is more favorable in southern YRD. Moreover, promotion of NOx mitigation in late spring and summer and facilitating VOCs control in spring and autumn could further reduce O3-related mortality by nearly 10% compared to the control strategy without seasonal differences. These findings highlight that a spatially and temporally differentiated NOx and VOCs emission control strategy could gain more O3-related health benefits, offering valuable insights to regions with severe ozone pollution all over the world.

A Twenty-Year Assessment of Spatiotemporal Variation of Surface Temperature in the Yangtze River Delta, China

A good understanding of the processes of land surface temperature (LST) change is important for assessing regional climate change. In the present study, we obtained the MODIS MOD11A2 LST products over the Yangtze River Delta (YRD) from 2001 to 2020. In order to comprehensively assess the spatial and temporal variability of LST in the YRD region over the past two decades, the Theil–Sen Median trend analysis and Mann–Kendall test, BFAST01 trend decomposition, and landscape pattern analysis were used in this study. We show that the rate of linear change in LST in the YRD ranges from −0.019 °C/month to 0.046 °C/month. The BFAST01 trend decomposition identifies more details of LST change and monotonic increases, reversal increase, and interruption increase are the main warming trends. The distribution of the different trend types shows strong aggregation with high spatial heterogeneity. The LST breakpoints are mainly located in the northern and southern YRD, which frequently occurred during 2010–2013. Of the various land types, breakpoints occur most frequently in cropland and high NDVI (0.5–0.7) areas, and the intensity of most of them is within 2 °C. In addition, much stronger warming occurs in urban areas than in other land types. Our study provides a better understanding of the dynamics of LST in the YRD region over the past 20 years and highlights that breakpoints cannot be circumvented in regional temperature assessment.

Impact of COVID-19 on air quality in the Yangtze River Delta, China.

To investigate the effect of nationwide restrictions due to COVID-19 on air quality in the Yangtze River Delta (YRD), China, we defined four periods named period I (January 1 to 23, 2020), period II (January 24 to February 23), period III (February 24 to April 7), and period IV (April 8 to May 31), which indicated normal period, lockdown period, regional work resumption period, and nationwide work resumption period, respectively. Hourly PM2.5, PM10, NO2, SO2, CO, and O3 in 41 cities in the YRD region were analyzed. Compared to period I, NO2 decreased by 58% during period II and increased in periods III and IV. SO2 remained constant during the four periods (7–8 μg/m3). Higher PM2.5 concentration was monitored during period II (41 μg/m3) when compared to period III (35 μg/m3), which was resulted from the enhanced secondary formation. Spatial distribution analysis further indicated that PM2.5 in the northern YRD during period II was higher than that during period III, whereas PM2.5 in the southern YRD in the period II was similar to that in period III. The results demonstrated that PM2.5 shows a nonlinear response to the reduction of its precursors, and this phenomenon varies in different areas. Compared to periods I (36 μg/m3) and III (64 μg/m3), relatively higher O3 during period II (64 μg/m3) was probably resulted from less NO emission and hence weakened NO titration effect. The study suggested that coordinated and balanced measures are needed to improve air quality.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10661-021-09342-1.

长三角地区休闲游憩服务供需关系研究

PDF HTML阅读 XML下载 导出引用 引用提醒 长三角地区休闲游憩服务供需关系研究 DOI: 10.5846/stxb201912052642 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（41971230）；中国科学院“美丽中国生态文明建设科技工程”专项（XDA23020201）；中央高校基本科研业务费青年项目（KJQN201847） Spatial variation of supply and demand relationships of recreational service in the Yangtze River Delta Author: Affiliation: Fund Project: the Strategic Priority Research Program of the Chinese Academy of Sciences，Grant No. XDA23020201 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:依托生态空间的休闲游憩服务是提升人类福祉至关重要的贡献者。但由于经济发展、城市扩张、人口增长等因素，区域休闲游憩服务供需矛盾突出，且供给与需求在空间上错位、不匹配等问题严重。研究休闲游憩服务供需关系对合理规划、管理区域生态用地，促进生态文明建设等方面具有重要的理论和现实价值。以长三角为例，基于土地利用与人口数据，提出不同可达半径下区域休闲游憩服务供需关系的评价方法，研究41个地级市不同可达半径下供需关系的空间分异规律。研究结果表明：（1）2015年长三角地区休闲游憩服务的供需比为1028%，供给远大于需求，但供需关系空间异质性明显，高供给区与高需求区明显错位，空间不匹配问题严重。（2）随着可达半径由0 km扩大至50 km，区域赤字区面积占比由43.14%减少至7.83%，休闲游憩服务需求未得到满足的人口占比由65.47%下降至10.64%。（3）根据41个地级市不同可达半径下休闲游憩服务供需关系的演变规律，将其划分为5种类型区，提出相应的发展建议。研究表明，快速城市化和城市扩张过程中，应强化城区内绿色空间的分散化配置；同时，在长三角经济一体化发展过程中，休闲游憩服务供需的盈余区、赤字区可以建立生态补偿和经济合作关系，促进长三角绿色发展的一体化。 Abstract:Recreational service that relies on ecological space is a vital contributor to improve human well-being. However, the spatial mismatch between supply and demand of recreational service poses a great concern in the Yangtze River Delta (YRD) region, primarily due to rapid economic development, urban expansion, population growth and other factors. It is therefore of great significance to explore the spatial variation of supply and demand relationships of recreational service for practically guiding spatial planning and management of regional ecological land in the YRD. Based on land use and gridded demographic data, this article proposed a spatially explicit approach to quantify and map the supply and demand relationships of recreational service in the YRD by considering the impact of different levels of ecological land accessibility. We also compared the supply and demand relationships of recreational service in 41 prefecture-level cities. The results showed that: (1) in 2015, the supply and demand ratio of recreational service was 1028% in the YRD, indicating that the supply was far greater than the demand for the service. There was also a spatial mismatch between the supply and demand of recreational service, where the supply-demand surplus regions were mainly located in the southern YRD, while the supply-demand deficit regions were primarily in the north. (2) With increasing ecological land accessibility from 0 km to 50 km, the proportion of supply-demand deficit area decreased from 43.1% to 7.8%, and the proportion of population in the deficit area decreased from 65.5% to 10.6%. (3) The 41 prefecture-level cities in the YRD were further divided into 5 groups according to their differences in the supply and demand relationships of recreational service. Based on these findings, we encourage that the decentralized allocation of ecological land should be promoted for the rapidly expanding urban areas of the YRD. It would also be beneficial for meeting the increasing demand for recreational service in different regions of the YRD through implementation of the payment for ecosystem service project between surplus and deficit regions in the future. 参考文献 相似文献 引证文献

A modeling study of PM2.5 transboundary transport during a winter severe haze episode in southern Yangtze River Delta, China

The WRF-CHEM (Weather Research Forecast-Chemistry) model was used to investigate a severe haze episode in Zhejiang province in southern Yangtze River Delta, China, during 28 November to 10 December 2013 to obtain the characteristics of PM2.5 transboundary transport and its contributions to haze formation. The predicted temporal variations of PM2.5 and meteorological variables are in good agreement with in-situ observations in Zhejiang. Simulated wind direction and pollution levels in upwind areas have significant effects on modeled near-surface PM2.5 concentrations. Both the large-scale atmospheric circulations and local weather conditions contributed to the accumulation of pollutants in Zhejiang, featuring the weakened East Asia trough, the dominance of a weak high pressure system, a low wind speed and a low planetary boundary layer height (PBLH) during the heavily polluted period from 4 to 7 December. The near-surface PM2.5 concentration was highly positively correlated with the accumulated PM2.5 transport mass (R = 0.88 at a lag of 7 h) and moderately negatively correlated with the PBLH (R = −0.39) during this period, indicating that the horizontal transport across Zhejiang's boundary under stable meteorological condition played important roles in the high PM2.5 concentrations. The analysis of PM2.5 transboundary transport flux shows that the main transport pathway for outside pollutants affecting Zhejiang was mainly the northerly flow. There were strong input fluxes mainly within the planetary boundary layer on 4 and 6 December before the maximum concentration occurred in the early morning on 7 December. The contribution of PM2.5 transboundary transport to the aerosol pollution in the study domain was determined by a receptor-oriented model based on the conservation of mass formula for PM2.5. The PM2.5 transboundary transport across the Zhejiang's boundary contributed 62% to the total PM2.5 increase during the severe haze episode, and the primary emission and secondary PM2.5 formation contributed 15% and 23%, respectively. This result suggests that the joint efforts with neighboring provinces to mitigate pollutant emissions are important to improve air quality in Zhejiang during winter.

Estimating the contribution of atmosphere on heavy metals accumulation in the aboveground wheat tissues induced by anthropogenic forcing

The influence of atmosphere pollution on human health is receiving more and more concerns as strengthened anthropogenic activity had brought excessive pollutant into the atmosphere. To date, the quantitative estimation about the contribution of atmosphere on the accumulation of heavy metal in the edible cereal parts induced by anthropogenic forcing is scarce. Taking the Yangtze River Delta area, China as an example, this study estimates quantitatively the influence of atmosphere on the concentration of heavy metal in the aboveground wheat tissues induced by anthropogenic industrial activity at the regional scale. The results show that the aboveground wheat tissues in the southern Yangtze River Delta area accumulated much more heavy metals than that in the northern area, although there is no significant difference in the geological and climate conditions, soil types, agricultural manages, wheat cultivar and soil heavy metals concentrations (even heavy metals concentrations in wheat root) between the southern area and northern area. The mean concentrations of Pb, Zn, Cu and Cd in wheat grain in southern area have exceeded the thresholds of contamination levels. The present study suggests that the influence of atmosphere on the accumulation of Hg, Cd, Pb, Zn, Cu, Ni and Cr in the aboveground wheat tissues is greatly significant when high amounts of pollutant are measured in the atmosphere. Based on translocation coefficient of the element, it is estimated that atmospheric pollution induced by anthropogenic forcing might lead to the concentration of heavy metals in wheat straw and grain increase by approximately 100% and 354% (Hg), 64% and 293% (Pb), 122% and 160% (Cr), 50% and 38% (Cd) and 14% and 41% (Cu), respectively.

Study on the Spatial Pattern of an Extreme Heat Event by Remote Sensing: A Case Study of the 2013 Extreme Heat Event in the Yangtze River Delta, China

The intensity and frequency of extreme heat events are increasing globally, which has a great impact on resident health, social life, and ecosystems. Detailed knowledge of the spatial heat pattern during extreme heat events is important for coping with heat disasters. This study aimed to monitor the characteristics of the spatial pattern during the 2013 heat wave in the Yangtze River Delta (YRD), China, based on the remote sensing estimated gridded air temperature (Ta). Based on the land surface temperature (Ts), normalized difference vegetation index (NDVI), built-up area, and elevation derived from multi-source satellite data, the daily maximum air temperature (Ta_max) during the heat wave was mapped by the random forest (RF) algorithm. Based on the remotely sensed Ta, heat intensity index (HII) was calculated to measure the spatial pattern of heat during this heat wave. Results indicated that most areas in the YRD suffered from extreme heat, and the heat pattern also exhibited obvious spatial heterogeneity. Cities located in the Taihu Plain and the Hangjiahu Plain generally had high HII values. The northern plain in the YRD showed relatively lower HII values, and mountains in the southern YRD showed the lowest HII values. Heat proportion index (HPI) was calculated to qualify the overall heat intensity of each city in the YRD. Wuxi, Changzhou, and Shanghai showed the highest HPI values, indicating that the overall heat intensities in these cities were higher than others. Yancheng, Zhoushan, and Anqing ranked last. This study provides a good reference for understanding the pattern of heat during heat waves in the YRD, which is valuable for heat wave disaster prevention.

Modulations of surface thermal environment and agricultural activity on intraseasonal variations of summer diurnal temperature range in the Yangtze River Delta of China

Compared with interdecadal, interannual, or seasonal scales, the variations of diurnal temperature range (DTR) at the intraseasonal scale and their driving forces are less understood. Using surface meteorological observations and multi-source satellite retrievals during 2013–2017, together with Random Forest modeling, this study examines the intraseasonal variation of summer DTR in the Yangtze River Delta (YRD) region, China, and determines its potential driving factors [i.e., daily maximum/minimum surface air temperature (SATmax/SATmin), sunshine duration (SSD), rainfall, altitude, land vegetation cover, and land surface thermal environment including daytime/nighttime land surface temperature (LSTD/LSTN) and anthropogenic heat flux (AHF)]. It is found that the intraseasonal variation of DTR at both 8-day and monthly scales in the YRD exhibits regional differences and is modulated by different primary factors across the region. The evident intraseasonal variation of DTR, with a peak in June, in the northern YRD, is largely attributable to nighttime temperatures (SATmin and LSTN), which in turn are mainly attributable to different LSTN responses to the underlying surface cover changes associated with crop rotation. In contrast, as the YRD metropolitan area (MYRD) is covered by a large proportion of built-up surfaces, and the weather stations there are surrounded by a higher surface thermal environment and AHF, the MYRD has stably higher LST and SATmin in the whole summer season. Thus, the summer DTR in the MYRD exhibits marginal intraseasonal variations. In the southern YRD, there is also a distinct DTR characteristic, with a maximum in July and minimum in June, since this region is largely covered by forests with constantly high-density vegetation cover, and its DTR variation is mainly forced by SSD, which directly affects SATmax. The findings reported here have important implications for understanding the influences of human activities on regional climate and environmental change for other regions of the world that experience various external forcings.

Modified regional biogenic VOC emissions with actual ozone stress and integrated land cover information: A case study in Yangtze River Delta, China

The biogenic volatile organic compounds (BVOCs) emissions are influenced by ambient ozone (O3) concentrations and vegetation cover. In most studies, however, the interaction between O3 and plants has not been considered and there are uncertainties in land cover input and emission factors (EFs) in BVOCs emission estimation, particularly at the regional scale. In this study, an O3 exposure-isoprene (ISOP) response function was developed using meta-analysis, and the EFs of ISOP and land cover inputs were updated by integrating local measurement and investigation data in the Yangtze River Delta (YRD) region. Five different cases were developed to explore the impacts of O3 and input variables on the BVOCs emissions using the Model of Emissions of Gases and Aerosols from Nature (MEGAN). The impacts of those variables on O3 simulation were further examined with air quality modeling. We found that the ISOP emissions were restrained in the city cluster along the Yangtze River during the growing season due to their negative feedback to O3 exposure for deciduous broadleaf forests. The estimation of BVOCs emissions strongly depended on EFs, and the global EFs underestimated the ISOP emissions in July by 37%, mostly in southern YRD. Different land cover datasets with various fractions and spatial distributions of plant function types resulted in a variation of 200–400 Gg in ISOP emissions in July across YRD. Air quality modeling indicated that BVOCs contributed 10%, 12%, and 11% to the 1-h mean, the maximum daily 1-h average, and the maximum daily 8-h average O3 concentrations, respectively, for July across the YRD region. Due to the NOx restriction, the spatial distribution of BVOCs emissions was inconsistent with that of their contribution to O3 formation. The O3 simulation was more sensitive to the changed BVOCs emissions in the area with relatively large contribution of BVOCs to O3 formation.

High-Spatial-Resolution Population Exposure to PM2.5 Pollution Based on Multi-Satellite Retrievals: A Case Study of Seasonal Variation in the Yangtze River Delta, China in 2013

To assess the health risk of PM2.5, it is necessary to accurately estimate the actual exposure level of the population to PM2.5. However, the spatial distribution of PM2.5 may be inconsistent with that of the population, making it necessary for a high-spatial-resolution and refined assessment of the population exposure to air pollution. This study takes the Yangtze River Delta (YRD) Region as an example since it has a high-density population and a high pollution level. The brightness reflectance of night-time light, and MODIS-based (Moderate Resolution Imaging Spectroradiometer) vegetation index, elevation, and slope information are used as independent variables to construct a random-forest (RF) model for the estimation of the population spatial distribution, before any combination with the PM2.5 data retrieved from MODIS. This enables assessment of the population exposure to PM2.5 (i.e., intensity of population exposure to PM2.5 and population-weighted PM2.5 concentration) at a 3-km resolution, using the year 2013 as an example. Results show that the variance explained for the RF-model-estimated population density reaches over 80%, while the estimated errors in half of counties are < 20%, indicating the high accuracy of the estimated population. The spatial distribution of population exposure to PM2.5 exhibits an obvious urban–suburban–rural difference consistent with the population distribution but inconsistent with the PM2.5 concentration. High and low PM2.5 concentrations are mainly distributed in the northern and southern YRD Region, respectively, with the mean proportions of the population exposed to PM2.5 concentrations > 35μg/m3 close to 100% in all four seasons. A high-level population exposure to PM2.5 is mainly found in Shanghai, most of the Jiangsu Province, the central Anhui Province, and some coastal cities of the Zhejiang Province. The highest risk of population exposure to PM2.5 occurs in winter, followed by spring and autumn, and the lowest in summer, consistent with the PM2.5 seasonal variation. Seasonal-averaged population-weighted PM2.5 concentrations are different from PM2.5 concentrations in the region, which are closely related to the urban-exposed population density and pollution levels. This work provides a novel assessment of the proposed population-density exposure to PM2.5 by using multi-satellite retrievals to determine the high-spatial-resolution risk of air pollution and detailed regional differences in the population exposure to PM2.5.

Characteristics of Single Aerosol Particles during Pollution in Winter in an Urban Area of Ningbo, China

ABSTRACT The size and composition of individual atmospheric particles were assessed using a single particle aerosol mass spectrometer in Ningbo, China, from 30 December 2016 to 12 January 2017. The particles were primarily carbonaceous and inorganic, with the majority (60%) being carbonaceous. All of the major particle types contained internally mixed secondary species, such as nitrate and sulfate. The temporal trends of the particle number concentrations and PM2.5 (particulate matter with an aerodynamic diameter < 2.5 µm) mass concentrations indicated that secondary formation in Ningbo severely affected the air quality. The sampling period was divided into three subperiods according to the PM2.5 mass concentration. During Period I, local emission and secondary formation were the primary contributors of the pollution, and during Periods II and III, the abundance of particles occurring with high-speed winds indicated that regional transport was a primary factor in these two pollution processes. Additionally, high PM2.5 mass concentrations were often observed at night during high relative humidity and low temperatures across the entire sampling period. These results demonstrate that stagnant meteorological conditions increase pollution during winter. Overall, this study enhances our understanding of particulate pollution in the southern Yangtze River Delta region and provides useful information on the formation and growth of atmospheric aerosols.

Estimation of biogenic VOC emissions and its impact on ozone formation over the Yangtze River Delta region, China

Biogenic volatile organic compounds (BVOCs) play an important role in the formation of tropospheric ozone. In the present work, biogenic emissions over the Yangtze River Delta (YRD) region for year 2014 were developed based on the interpretation of remote sensing image and MODIS data using the Model of Emissions of Gases and Aerosols from Nature (MEGAN). Impact of BVOCs emissions over the YRD region on ozone formation was investigated based on the Weather Research and Forecasting (WRF)-Community Multi-scale Air Quality (CMAQ) modeling system for July 2014. Two parallel scenarios-with and without BVOCs emissions-were developed to evaluate the influence of BVOCs emission on ozone formation. Biogenic emissions were estimated to be 18.86 × 105 ton yr−1 over the YRD region for year 2014, with higher emissions in the southern YRD region than the northern region, and higher emissions in summer than other seasons. Model evaluation showed fairly good model performances, with the index of agreement (IOA) of meteorological parameters and ozone concentrations of 0.80–0.95 and 0.76–0.91, respectively. Ozone concentrations mainly concentrated in the northwest, which is the downwind of the YRD region in summer. Impact of biogenic emissions on ozone formation exhibited a strong spatial pattern: high contributions were observed in the middle YRD region, including Bengbu, Tongling, Hefei, Huzhou, Nanjing and Zhenjiang, with the maximum hourly ozone contribution of 18.43–36.18μg/m3 during July 18 to 23. Ozone concentrations in rural areas would be more likely to be influenced by BVOCs emissions than urban areas.

Emissions, Chemical Composition, and Spatial and Temporal Allocation of the BVOCs in the Yangtze River Delta Region in 2014

Based on the land surface vegetation data interpreted via remote sensing and the meteorological conditions predicted via the WRF model, the MEGAN model was applied to calculate the regional BVOC emissions in the Yangtze River Delta (YRD) in 2014. The chemical components and the temporal and spatial allocations were further analyzed. Results show that the annual BVOC emissions in the YRD were 1886 kt, in which isoprene emissions were 704.2 kt (accounting for 37.3%), monoterpenes 303 kt (16.1%), and other VOCs 878.8 kt (46.6%). Seasonal variation of the BVOC emissions was very significant. The BVOC emissions had a strong seasonal pattern, with maximum emissions in summer, accounting for 60.9% (1088 kt) of the total, whereas the minimum emissions occurred in winter, accounting for 3.2% (57 kt). Spatially, the southern YRD produced more BVOC emissions than the northern part did. In Zhejiang, Anhui, Jiangsu, and Shanghai, the BVOC emissions were 842 kt (44.6%), 760 kt (40.3%), 272 kt (14.4%), and 12 kt (0.7%), respectively. This is mainly related to the distribution of vegetation types.

Assessment of Heavy Metal Pollution and Health Risks in the Soil-Plant-Human System in the Yangtze River Delta, China.

Heavy metal (HM) contamination and accumulation is a serious problem around the world due to the toxicity, abundant sources, non-biodegradable properties, and accumulative behaviour of HMs. The degree of soil HM contamination in China, especially in the Yangtze River Delta, is prominent. In this study, 1822 pairs of soil and crop samples at corresponding locations were collected from the southern Yangtze River Delta of China, and the contents of Ni, Cr, Zn, Cd, As, Cu, Hg, and Pb were measured. The single pollution index in soil (SPI) and Nemerow composite pollution index (NCPI) were used to assess the degree of HM pollution in soil, and the crop pollution index (CPI) was used to explore the degree of HM accumulation in crops. The bioaccumulation factor (BAF) was used to investigate the translocation of heavy metals in the soil-crop system. The health risks caused by HMs were calculated based on the model released by the U.S. Environmental Protection Agency. The SPIs of all elements were at the unpolluted level. The mean NCPI was at the alert level. The mean CPIs were in the following decreasing order: Ni (1.007) > Cr (0.483) > Zn (0.335) > Cd (0.314) > As (0.232) > Cu (0.187) > Hg (0.118) > Pb (0.105). Only the mean content of Ni in the crops exceeded the national standard value. The standard exceeding rates were used to represent the percentage of samples whose heavy metal content is higher than the corresponding national standard values. The standard exceeding rates of Cu, Hg, and Cd in soil were significantly higher than corresponding values in crops. Meanwhile, the standard exceeding rates of Ni, As, and Cr in crops were significantly higher than corresponding values in soil. The chronic daily intake (CDI) of children (13.8 × 10−3) was the largest among three age groups, followed by adults (6.998 × 10−4) and seniors (5.488 × 10−4). The bioaccumulation factors (BAFs) of all crops followed the order Cd (0.249) > Zn (0.133) > As (0.076) > Cu (0.064) > Ni (0.018) > Hg (0.011) > Cr (0.010) > Pb (0.001). Therefore, Cd was most easily absorbed by crops, and different crops had different capacities to absorb HMs. The hazard quotient (HQ) represents the potential non-carcinogenic risk for an individual HM and it is an estimation of daily exposure to the human population that is not likely to represent an appreciable risk of deleterious effects during a lifetime. All the HQs of the HMs for the different age groups were significantly less than the alert value of 1.0 and were at a safe level. This indicated that citizens in the study area face low potential non-carcinogenic risk caused by HMs. The total carcinogens risks (TCRs) for children, adults, and seniors were 5.24 × 10−5, 2.65 × 10−5, and 2.08 × 10−5, respectively, all of which were less than the guideline value but at the alert level. Ingestion was the main pathway of carcinogen risk to human health.

Assessment of the potential health risks of heavy metals in soils in a coastal industrial region of the Yangtze River Delta.

Soil heavy metal contamination is a serious environmental problem. Human beings may be directly exposed to heavy metals in soils through the inhalation of soil particles, dermal contact, and oral ingestion, which can seriously threaten health. This study assesses the health risks associated with heavy metals in soils by determining the concentrations of eight heavy metals (Cr, Pb, Cd, Hg, As, Cu, Zn, and Ni) based on 2051 surface-soil samples collected from the southern Yangtze River Delta of China. The mean concentrations were higher than the corresponding background values in Zhejiang Province and China as a whole, indicating an accumulation of heavy metals. The health risk assessment suggests that the non-carcinogenic and carcinogenic risks in the study area were not significant. The non-carcinogenic risk for children was the highest, followed by those for adults and seniors; the non-carcinogenic risk for the entire population was less than 1.0, the predetermined threshold. Carcinogenic risk for adults was the highest, followed by those for seniors and children; a few sample points had a value larger than the threshold of 1.0E-04. Arsenic represented the greatest contribution to non-carcinogenic and carcinogenic risk. Meanwhile, ingestion of heavy metals in soil was the main exposure pathway for carcinogenic risk, followed by inhalation and dermal exposure. The spatial method of Getis-Ord was used to identify hot spots of health risk. Hot spots with high hazard index (HI) and total carcinogenic risk (TCR) for children, adults, and seniors were mainly distributed in core urban areas, such as Jiangbei, Haishu, Yinzhou, Jiangdong, and the urban areas of some other counties, which coincided with industrial, mining, and urban areas of the study area and were strongly influenced by anthropogenic activities. These results provide a basis for heavy metal control in soil, source identification, and environment management in the Yangtze River Delta and other rapidly developing industrial regions in China.

Application of portable XRF and VNIR sensors for rapid assessment of soil heavy metal pollution.

Rapid heavy metal soil surveys at large scale with high sampling density could not be conducted with traditional laboratory physical and chemical analyses because of the high cost, low efficiency and heavy workload involved. This study explored a rapid approach to assess heavy metals contamination in 301 farmland soils from Fuyang in Zhejiang Province, in the southern Yangtze River Delta, China, using portable proximal soil sensors. Portable X-ray fluorescence spectroscopy (PXRF) was used to determine soil heavy metals total concentrations while soil pH was predicted by portable visible-near infrared spectroscopy (PVNIR). Zn, Cu and Pb were successfully predicted by PXRF (R2 >0.90 and RPD >2.50) while As and Ni were predicted with less accuracy (R2 <0.75 and RPD <1.40). The pH values were well predicted by PVNIR. Classification of heavy metals contamination grades in farmland soils was conducted based on previous results; the Kappa coefficient was 0.87, which showed that the combination of PXRF and PVNIR was an effective and rapid method to determine the degree of pollution with soil heavy metals. This study provides a new approach to assess soil heavy metals pollution; this method will facilitate large-scale surveys of soil heavy metal pollution.

Numerical simulation and analysis of the Yangtze River Delta Rainstorm on 8 October 2013 caused by binary typhoons

Torrential rainfall associated with the 23rd Typhoon Fitow in 2013 hit the Yangtze River Delta (YRD) region of China, resulting from mutual effects of residual low pressure cyclonic circulation of Fitow and the 24th Typhoon Danas, which imposed great challenge to forecasters. In this study, the Weather Research and Forecasting (WRF) model was used to simulate the rainstorm under the background of binary typhoons of Fitow and Danas. Three sensitivity experiments of typhoon intensity changes of binary typhoons were carried out. It was found that the Typhoon Danas was the main factor in this torrential rain event, in which its accompanied strong eastward low-level jet was the major moisture conveyor belt through which the warm and moist air was brought into the heavy rainfall zone and the static instability was maintained and enhanced over the YRD. The convergence line formed by periphery easterly flow of Typhoon Danas and southward cold air, together with the local frontogenesis mainly due to convergence, was an important trigger factor of this rainstorm. The large scale forcing was the major uplift mechanism, and the underlying frontal uplift played a secondary role for rainstorm in the north YRD, while uplift mechanism for rainstorm in the southern YRD is mainly local underlying frontal uplift induced large CAPE release resulting in local strong buoyancy uplift that led to strong upward motion. Not only did the convergence of twin typhoons directly provide dynamic conditions for the rainstorm, but also the dynamic lifting was enhanced by binary typhoons through strengthening the coupling of upper-level and low-level jet. The sensitivity tests revealed that the rainstorm in YRD was sensitive to both typhoons' intensity, and the rainfall in the south YRD was more sensitive than that in the north. A conceptual model of YRD rainstorm under binary typhoon situation was proposed based on the above-mentioned factors.

Sand creep as a factor in land subsidence during groundwater level recovery in the southern Yangtze River delta, China

A number of areas worldwide are suffering from the land subsidence, including the southern Yangtze River delta, the most developed area in China. Land subsidence is mainly induced by excessive groundwater pumping and has caused numerous problems, for example, flooding, structural cracking, and ground fissuring. Although several countermeasures have been adopted to mitigate the land subsidence problem in the southern Yangtze River delta, commonly using groundwater recharge, land subsidence is still developing even when groundwater levels are rising. The observation data of land subsidence in each stratum show that the deformation of the pumped aquifer is even greater than that in the adjacent aquitards when groundwater levels are recovering. Laboratory test results on the aquifer sand in Shanghai and Changzhou (two cities in the studied area, which have the most sufficient observation data about the land subsidence and groundwater level developing with time) proved that sand creep deformation is significant and is partially responsible for the land subsidence without groundwater level drawdown. Considering the difficulty and cost of collecting borehole samples from deep pumped aquifers to obtain the essential parameters for the existing sand creep calculation models, a simplified method was then proposed to calculate the sand creep deformation in the pumped aquifer. The relationship between the sand creep rate and the time can be recognized as linear using double logarithmic coordinates and the slope can be assumed to be one. In the proposed method, the laboratory test data are not necessary. Finally, case histories from Shanghai and Changzhou were used to verify the effectiveness of the proposed method.

Investigation into the daily precipitation variability in the Yangtze River Delta, China

AbstractIn this article, by using the daily precipitation data measured at 58 meteorological stations, spatial and temporal variability of daily precipitation including zero rainfall values (called “precipitation”) and without zero rainfall values (called “rain”) and four precipitation extrema (P0, P20, P50, and P100 representing the daily precipitation with the magnitude smaller than 0.1 mm, bigger than 20 mm, 50 mm, and 100 mm per day, respectively) in the Yangtze River Delta (YRD) during 1958–2007 were analyzed, and the effects of urbanization were further investigated. Results indicate that (i) differing from the downward trends in 1958–1985, daily precipitation and rain in 1986–2007 show slowly downward trends in the mid YRD but show upward trends in the northern and southern YRD. (ii) Spatial and temporal variability of the rain is more complex than daily precipitation. Both of them become smaller but show more obvious fluctuations in 1986–2007. (iii) Urbanizations cause not only the urban rainfall island problem but also more obvious fluctuations of rain intensity in the mid YRD, reflecting more uncertainty of daily precipitation variability. (iv) Urbanizations have little effects on the variability of P0 and P100 but cause notable increases of P20 and P50. (v) The spatial variability of daily precipitation and precipitation extrema in 1958–1985 clearly shows a breakpoint at 30°20′N latitude, but the breakpoint disappears afterward because of the effects of urbanization. Copyright © 2012 John Wiley &amp; Sons, Ltd.