Temporal and Spatial Distribution Characteristics of Potential Evapotranspiration and Its Sensitivity to Meteorological Factors in Guizhou Province

[Objective] The study aims to discuss the changes of potential evapotran- spiration and its sensitivity to meteorological factors in Guizhou Province, so as to provide important references for assessment of water resources, research of agri- cultural water conservancy and climate change. [Method] Temporal and spatial dis- tribution characteristics of potential evapotranspiration in Guizhou Province from 1961 to 2010 were analyzed, and the sensitivity of potential evapotranspiration to meteo- rological factors in Guizhou Province was studied through correlation analysis. [Re- sult] On the whole, potential evapotranspiration in Guizhou Province was higher in the southwest and the west compared with the northeast and the east. In various seasons, it was the highest in summer, followed by spring and autumn, while it was the lowest in winter. In recent 40 years, annual potential evapotranspiration showed an obvious decreasing trend in most stations of Guizhou Province. The main meteo- rological factors influencing changes of potential evapotranspiration in Guizhou Province were sunshine duration, daily maximum temperature, and daily average relative humidity. [Conclusion] Daily average temperature was not the main meteoro- logical factor affecting changes of potential evapotranspiration in Guizhou Province, while sunshine duration, daily maximum temperature, and daily average relative hu- midity had important effects on potential evapotranspiration in Guizhou Province.

Spatial distribution and potential poverty-returning factors of former poverty-stricken villages in the Liangshan Mountains,China

Remote mountainous villages are at risk of falling back into poverty,despite having been lifted out of extreme poverty.However,there has been a lack of focus on the factors contributing to povertyreturn in these villages,which making it difficult to understand the risks and their underlying causes.This study investigates the spatial distribution of 546 key assistance villages(KAVs)in the Liangshan mountainous region,a former poverty-stricken area,using the average nearest neighbor(ANN)and kernel density estimation(KDE)methods.Linear regression and geographically weighted regression(GWR)models are then employed to analyze the relationship between the KAVs'economy and potential povertyreturning factors.The results show that KAVs are primarily located in elevation ranges of 1800-2500 m(31.87%),with slopes of 6°-15°(42.67%)and 2-3 km from the township(28.94%).The distribution of KAVs exhibits distinct spatial clustering,forming four gathering areas.Several factors impact the KAVs'economy positively,including the normalized difference vegetation index(NDVI),built-up area,grassland,and education facilities,while elevation has a negative effect.The built-up area has the most critical impact on the rural economy,followed by NDVI and elevation.Additionally,education facilities and grassland areas also have significant effects.The study suggests promoting the Ex-situ Poverty Alleviation Relocation Program(ESPARP)and increasing rural built-up areas,grasslands,and educational facilities as practical measures for preventing poverty return and promoting economic development promotion in remote mountain villages.

Spatial distribution of the potential forest biomass availability in Europe

Background: European forests are considered a crucial resource for supplying biomass to a growing bio-economy in Europe. This study aimed to assess the potential availability of forest biomass from European forests and its spatial distribution. We tried to answer the questions(i) how is the potential forest biomass availability spatially distributed across Europe and(ii) where are hotspots of potential forest biomass availability located?Methods: The spatial distribution of woody biomass potentials was assessed for 2020 for stemwood, residues(branches and harvest losses) and stumps for 39 European countries. Using the European Forest Information SCENario(EFISCEN) model and international forest statistics, we estimated the theoretical amount of biomass that could be available based on the current and future development of the forest age-structure, growing stock and increment and forest management regimes. We combined these estimates with a set of environmental(site productivity, soil and water protection and biodiversity protection) and technical(recovery rate, soil bearing capacity) constraints, which reduced the amount of woody biomass that could potentially be available. We mapped the potential biomass availability at the level of administrative units and at the 10 km × 10 km grid level to gain insight into the spatial distribution of the woody biomass potentials.Results: According to our results, the total availability of forest biomass ranges between 357 and 551 Tg dry matter per year. The largest potential supply of woody biomass per unit of land can be found in northern Europe(southern Finland and Sweden, Estonia and Latvia), central Europe(Austria, Czech Republic, and southern Germany),Slovenia, southwest France and Portugal. However, large parts of these potentials are already used to produce materials and energy. The distribution of biomass potentials that are currently unused only partially coincides with regions that currently have high levels of wood production.Conclusions: Our study shows how the forest biomass potentials are spatially distributed across the European continent, thereby providing insight into where policies could focus on an increase of the supply of woody biomass from forests. Future research on potential biomass availability from European forests should also consider to what extent forest owners would be willing to mobilise additional biomass from their forests and at what costs the estimated potentials could be mobilised.

Study of the Non-Uniform Distribution of Earthquake Risk Within Potential Sources

Potential sources are aggregates of probable future epicenters.In this area,for source models currently,in common use for seismic risk analysis in China,the mean area of each potential source is about 3000-4000 km2.It is assumed that seismic risk has a uniform distribution within the range of each potential source,but studies have shown that the uniform distribution model to a large extent may give an underestimation of the seismic risk.In this paper,the relative distribution of historical epicenters in space within potential sources is discussed,a method is proposed to quantitatively describe the non-uniform distribution of strong earthquakes within potential sources,and some preliminary results are given.By using the results of this paper,seismic risk analysis and seismic zonation can be made more scientific and more reasonable.

Population Spatial Distribution Based on Luojia 1-01 Nighttime Light Image:A Case Study of Beijing

With the continuous development of urbanization in China,the country’s growing population brings great challenges to urban development.By mastering the refined population spatial distribution in administrative units,the quantity and agglomeration of population distribution can be estimated and visualized.It will provide a basis for a more rational urban planning.This paper takes Beijing as the research area and uses a new Luojia1-01 nighttime light image with high resolution,land use type data,Points of Interest(POI)data,and other data to construct the population spatial index system,establishing the index weight based on the principal component analysis.The comprehensive weight value of population distribution in the study area was then used to calculate the street population distribution of Beijing in 2018.Then the population spatial distribution was visualize using GIS technology.After accuracy assessments by comparing the result with the WorldPop data,the accuracy has reached 0.74.The proposed method was validated as a qualified method to generate population spatial maps.By contrast of local areas,Luojia 1-01 data is more suitable for population distribution estimation than the NPP/VIIRS(Net Primary Productivity/Visible infrared Imaging Radiometer)nighttime light data.More geospatial big data and mathematical models can be combined to create more accurate population maps in the future.

Spatial distribution of SiCln （n=O-2） in SICl4 plasma measured by mass spectroscopy

For a better understanding of the deposition mechanism of thin films in SiCl4 source gas, we have measured the spatial distributions of SiCln （n=0-2） radicals in SICl4 radio frequency glow discharge plasma utilizing a mass spectrometer equipped with a movable gas sampling apparatus. The experimental results demonstrate that the relative densities of SiCln （n=0-2） radicals have peak values at the position of 10 mm above the powered electrode along the axial direction; the relative densities of the Si and SiCIn （n=1, 2） radicals have peak values at the positions of 27mm and 7 mm away from the axis along the radial direction, respectively. Generally speaking, in the whole SICl4 plasma bulk region, the relative density of Si is one order of magnitude higher than that of SICl, and the relative density of SiCl is several times higher than that of SICl2. This reveals that Si and SiCl may be the primary growth precursors in forming thin films.

GFDL-ESM2M气候模式下京津冀地区未来潜在蒸散量时空变化

为探究未来潜在蒸散量时空变化特征,该研究以京津冀地区为例,基于美国GFDL提供的GFDL-ESM2M全球气候模式,得到京津冀地区92个格点2000-2050年的平均气温、最高气温、最低气温、太阳总辐射、平均相对湿度和近地面平均风速,应用Penman-Monteith公式计算京津冀地区未来92个格点的逐日潜在蒸散量(ET0),分析其时空分布特征及其与气象要素的相关关系。结果表明:未来年ET0总体呈增加趋势,RCP8.5情景下ET0上升速度最快,且随着时间推移增幅越来越大。夏季ET0增长速度最快,其次为春季、秋季与冬季,意味着未来ET0季节差异将愈加明显,可能出现更为严重的季节性干旱。ET0空间分布呈由西南向东北逐渐递减趋势,其中中部地区增速最快,增长趋势由中部向南北递减。不同气候情景下平均气温均呈逐年上升趋势,风速、太阳总辐射略微上升,而相对湿度下降。ET0与太阳总辐射的相关系数最大,呈由东北向西南递增趋势,其次为最高气温,呈由西北向东南递增趋势。ET0与相对湿度变化呈显著负相关,相关系数绝对值呈东北向西南递增趋势,ET0与风速相关度不明显。该研究可为农业需水预测与灌溉管理、科学应对气候变化提供基础支撑。

1964-2017年山西省潜在蒸发量时空变化及其影响因素分析

采用Penman-Monteith模型计算出山西省潜在蒸发量,运用小波分析、Mann-Kendall非参数检验和地统计等方法分析了山西省潜在蒸发量的时空分布特征,并且利用主成分分析法分析了其影响因素。结果表明:(1)山西省多年平均潜在蒸发量为1 148.6 mm,存在以27 a为主周期和9 a,45 a左右为次周期的周期变化;(2)山西省多年平均潜在蒸发量空间分布特征表现为由中部向南北两边递减,北部地区潜在蒸发量低于南部地区,地势低的地方潜在蒸发量较高;(3)山西省潜在蒸发量西北部和东南部呈现下降趋势,东北部及西南部呈增加趋势,东北部增加趋势尤为显著;(4)平均水气压和相对湿度是影响山西省潜在蒸发量的主导因素,潜在蒸发量与平均水气压、相对湿度和海拔高度呈负相关,与温度、风速、日照时数及纬度呈正相关。

Changes in global potential vegetation distributions from 1911 to 2000 as simulated by the Comprehensive Sequential Classification System approach

Vegetation classification models play an important role in studying the response of the terrestrial ecosystem to global climate change. In this paper, we study changes in global Potential Natural Vegetation (PNV) distributions using the Comprehensive Sequential Classification System (CSCS) approach, a technique that combines geographic information systems. Results indicate that on a global scale there are good agreements among maps produced by the CSCS method and the globally well-accepted Holdridge Life Zone (HLZ) and BIOME4 PNV models. The potential vegetation simulated by the CSCS approach has 6 major latitudinal zones in the northern hemisphere and 2 in the southern hemisphere. In mountainous areas it has obvious altitudinal distribution characteristics due to topographic effects. The distribution extent for different PNV classes at various periods has different characteristics. It had a decreasing trend for the tundra and alpine steppe, desert, sub-tropical forest and tropical forest categories, and an increasing trend for the temperate forest and grassland vegetation categories. The simulation of global CSCS-based PNV classes helps to understand climate-vegetation relationships and reveals the dynamics of potential vegetation distributions induced by global changes. Compared with existing statistical and equilibrium models, the CSCS approach provides similar mapping results for global PNV and has the advantage of improved simulation of grassland classes.

Energy properties and spatial plume profile of ionic liquid ion sources based on an array of porous metal strips

An ionic liquid ion source(ILIS)is a kind of high brightness ion source capable of providing high-speed positive or negative ion beams.This paper presents a miniaturized ILIS based on an array of porous metal strips.The porous emitter array,integrated with seven 10 mm long strips,is fabricated using wire electrical discharge machining(WEDM)combined with electrochemical etching.The assembled ILIS is 30 mm×30 mm×17.5 mm in size and weighs less than 25 g.A series of experiments,including anⅠ-Ⅴcharacteristic test,a retarding potential analyzer(RPA)test,and a spatial plume distribution test,have been conducted in vacuo to characterize the performance of the ILIS.Results show that the emitted current is up to about 800μA and ion transparency is as high as 94%.Besides,RPA curves reveal that the total fragmentation rate of the emitted particles accounts for 48.8%in positive mode and 59.8%in negative mode.Further,with the increase in applied acceleration voltage,the voltage loss rises while the energy efficiency decreases.It is also found that the plume perpendicular to the strips has a higher divergence than the one parallel to the strips.A numerical simulation by COMSOL reveals that the electric field distribution between the two electrodes results in such a spatial plume profile.

Spatial distribution of health risks for residents located close to solvent-consuming industrial VOC emission sources

Emissions derived from the consumption of organic solvents have been proven to be the primary industrial source of volatile organic compounds(VOCs).In conjunction with epidemiologic studies, water-based paints(WBPs) and solvent-based paints(SBPs) were selected as representatives of newly developed solvents and traditional solvents, respectively,to simulate the effects of consuming solvents emitted during industrial production.And non-carcinogenic and carcinogenic risks to residents near emission sources were studied in detail.The results showed that the spatial distribution of health risks varied with meteorological conditions and type of emission source, and the prevailing wind direction strongly affected the distribution range and shape of the influenced area.The areas of influence maximized on heavy-polluting days for both WBP and SBP emission sources with the total span reaching 804 m and 16 km, respectively;meanwhile, the areas of influence for carcinogenic risk resulting from WBP emission sources were 1.2 and 2.3 times greater than those measured on fine and rainy days, respectively, and 1.8 and 2.9 times greater for SBP emission sources.Compared with WBPs, the total spans of negatively influenced regions resulting from SBP emission sources were 10.4, 12.5 and 19.9 times greater on fine, rainy and heavypolluting days, respectively.Therefore, carcinogenic risk was the dominant health threat for populations residing close to solvent-consuming industrial emission sources.The findings suggest that newly developed solvents are capable of significantly reducing consequent health threats, nevertheless, they could still pose occasional threats to nearby residents under specific meteorological conditions.

中国东部沿海管道海岸-断裂带复合效应

低频扰动地磁场在大地中感应出地磁感应电流(GIC)和地面感应电势(ESP),直接影响埋地管道管地电位(PSP)。为研究中国东部沿海地区海岸和断裂带复合效应对日东线管道PSP的影响,基于傅里叶变换和反变换的思想提出了管道傅里叶-有限元法,该方法采用地面磁场时频转换理论,建立低频地磁扰动下管道PSP计算模型以获取实时信息。本文首先建立了三维海岸-断裂带理论模型探索沿海地区的电场分布与断裂带电导率之间的关系;然后根据大地电磁测深数据构建了中石油日东线所在地区的大地三维电导率模型,应用地磁台磁场数据作为大地导体边界条件计算磁扰动期间实时管道PSP时空分布,以2016年10月12-14日期间的磁扰动为例对日东线PSP的计算值和实测值进行对比分析。在空间分布特性上分析了管道PSP的两种基本分布形态以及重要节点处受管道参数变化的影响,在时间分布特性上不仅验证了计算模型的准确性,还揭示了海岸-断裂带复合效应对沿海管道PSP的影响,为管道腐蚀防护提供了理论依据。

The Major Ore Clusters of Super-Large Iron Deposits in the World, Present Situation of Iron Resources in China, and Prospect

The metamorphosed sedimentary type of iron deposits（BIF） is the most important type of iron deposits in the world, and super-large iron ore clusters of this type include the Quadrilatero Ferrifero district and Carajas in Brazil, Hamersley in Australia, Kursk in Russia, Central Province of India and Anshan-Benxi in China. Subordinated types of iron deposits are magmatic, volcanic-hosted and sedimentary ones. This paper briefly introduces the geological characteristics of major super-large iron ore clusters in the world. The proven reserves of iron ores in China are relatively abundant, but they are mainly low-grade ores. Moreover, a considerate part of iron ores are difficult to utilize for their difficult ore dressing, deep burial or other reasons. Iron ore deposits are relatively concentrated in 11 metallogenic provinces（belts）, such as the Anshan-Benxi, eastern Hebei, Xichang-Central Yunnan Province and middle-lower reaches of Yangtze River. The main minerogenetic epoches vary widely from the Archean to Quaternary, and are mainly the Late Archean to Middle Proterozoic, Variscan, and Yanshanian periods. The main 7 genetic types of iron deposits in China are metamorphosed sedimentary type（BIF）, magmatic type, volcanic-hosted type, skarn type, hydrothermal type, sedimentary type and weathered leaching type. The iron-rich ores occur predominantly in the skarn and marine volcanic-hosted iron deposits, locally in the metamorphosed sedimentary type（BIF） as hydrothermal reformation products. The theory of minerogenetic series of mineral deposits and minerogenic models has applied in investigation and prospecting of iron ore deposits. A combination of deep analyses of aeromagnetic anomalies and geomagnetic anomalies, with gravity anomalies are an effective method to seeking large and deep-buried iron deposits. China has a relatively great oresearching potential of iron ores, especially for metamorphosed sedimentary, skarn, and marine volcanic-hosted iron deposits. For the lower guarantee degree of iron and steel industry, China should give a trading and open the foreign mining markets.

湖南省油菜秸秆资源作为生物质产业原料的潜力量化评估

油菜(Brassica napus L.)秸秆作为重要的生物质资源,在环境保护和经济效益方面有着显著优势,具有高纤维素含量、利用成本低等优点,合理的利用可为相关产业原料的供应提供重要保障。湖南省作为中国油菜主产区,理论上具备产业化开发的潜力。全面了解生物质产量潜力和原料品质的区域差异是合理利用秸秆资源的前提与基础。因此,该研究对湖南省油菜秸秆资源产量潜力和原料品质空间异质性进行研究,基于此对油菜秸秆作为未来生物质产业原料的潜力进行评估。结果表明:湖南省油菜秸秆年产量为660.47万t,其中以湘北(35.71%)和湘中地区(32.43%)贡献最大,产量潜力分别达到了235.84万t和214.21万t。湖南省油菜秸秆生物质原料品质存在较高的异质性,所有表征指标的变异系数(coefficient of variation,CV)值均很高(>0.50)。生物质原料品质差异主要表现在重金属含量方面(CV>5.00)。此外,油菜秸秆生物质在灰分含量(CV=3.02)、木质素含量(CV=1.17)和纤维素聚合度(CV=1.15)方面也具有较为明显的差异。基于测定的多项品质指标,该研究通过构建基于隶属函数的生物质生产潜力指数进行原料品质指标的归一化处理。从生物质生产潜力指数上看,湖南省油菜秸秆最适合生产半纤维素基产品,尤其是湘北地区的油菜秸秆(潜力指数为0.60)。总体上看,具备较高产量潜力和较优原料品质的湘北地区可作为全省油菜秸秆产业的先行原料供应区。

1981—2018年吉林省玉米水分盈亏及旱涝时空分布

吉林省作为我国玉米主产区和重要的商品粮基地,明确吉林省玉米水分盈亏指数及旱涝灾害的时空分布特征,有助于提高农业生产的稳定性和抗灾能力。该文采用吉林省逐日气象站点数据,通过计算月尺度下的潜在蒸散量,构建水分盈亏指数来分析吉林省潜在蒸散量和旱涝灾害的时空分布特征,运用趋势分析法和小波分析法来探究水分盈亏指数的趋势性及周期性变化。结果表明:多年平均潜在蒸散量和各月份平均潜在蒸散量均有由西北至东南逐渐递减的趋势,5—9月潜在蒸散量分别占生长周期内总平均潜在蒸散量的26.3%、24.5%、21.1%、16.8%和11.3%。5月和9月发生中旱及以上频率大于50%的地区主要位于白城市西部,四平市西部和长春市中部地区。8月和9月中涝及以上频率高值区位于吉林省东部及东南部地区。

中国33个城市土壤重金属污染空间分布特征与潜在风险

收集整理了中国33个城市的表层土壤重金属(As、Co、Cr、Cu、Mn、Ni、Pb、Zn、Cd、Hg)含量,城镇化指标(GDP、常住人口、机动车保有量),大气环境监测指标(空气质量指数AQI、PM_(2.5)、PM_(10)、SO_(2)、NO_(2)、CO和O_(3)),研究了33个城市土壤重金属污染空间分布特征和潜在风险。结果表明:各个城市土壤重金属As、Co、Cr、Cu、Mn、Ni、Pb、Zn、Cd、Hg的平均含量分别是中国土壤元素背景值的1.12、1.75、1.21、1.69、1.16、1.13、1.75、1.66、4.18、2.87倍。土壤重金属地累积指数(I_(geo))均值排序为Cd(1.48)>Hg(0.93)>Pb(0.23)>Co(0.22)>Cu(0.17)>Zn(0.14)>Cr(-0.31)>Mn(-0.37)>Ni(-0.41)>As(-0.42)。中国八大社会经济区域内梅罗污染指数顺序为西南地区(7.07)>长江中游地区(6.84)>北部沿海地区(6.81)>东部沿海地区(4.09)>南部沿海地区(3.82)>东北地区(3.12)>黄河中游地区(2.76)>大西北地区(3.73)。不同重金属元素单项潜在生态风险系数大小顺序为Cd>Hg>As>Pb>Co>Cu>Ni>Cr>Mn>Zn,潜在生态风险指数平均值为665.15。城市土壤中Cu、Mn、Pb和Zn之间相关性较好,但是与城镇化指标、大气环境监测指标之间不存在显著相关性。

中国农产品进口潜力及来源结构:一项进口多元化战略的实证研究

扩大农产品进口有助于保障我国农产品供给,也有利于实现农业产业升级、提高可持续发展能力,科学测度中国农产品进口潜力则显得格外重要。基于1995-2019年世界双边贸易数据,构建进口潜力标准化指标测算分析农产品进口潜力和分布特点,并采用贸易边际方法进一步讨论未来农产品进口潜力来源结构。结果表明:(1)从总规模看,入世前农产品进口不足,入世后进口增加,2009年开始进口明显过度;(2)从国家(地区)分布看,中国从欧盟、北美自由贸易区、南美洲等国家(地区)进口农产品过度,从东盟进口适度,从印度和韩国进口不足,未来农产品进口重点区域在亚洲内部;(3)从产品分布看,动物类产品进口过度,食品加工类产品进口适度,果蔬类产品进口不足;(4)从来源结构看,农产品进口数量过度,进口种类适度,进口价格不足。提出要坚持“立足国内供给、适度进口调剂”安全战略,积极实施农产品进口多元化战略,对农产品进口实行国别管理,实施区域性贸易战略;对农产品进口分品种理性看待并分类实施;积极调整进口来源结构,减少对进口数量的依赖,重视优质、高附加值农产品进口,促进农产品进口增长方式转型。

广东省热带气旋潜在风险指数时空分布特征

热带气旋在广东省内造成的影响具有显著的时空不均匀性,采用统计方法对1949—2022年间热带气旋登陆广东省情况进行分析,并根据PRITC V1.0数据集提供的数据对1949—2018年间热带气旋潜在风险指数的时空分布特征开展分析。结果表明:热带气旋主要在6—10月登陆广东,数量占登陆总数的94.2%;主要在粤西三市登陆,占比47.8%;珠江口以西登陆的热带气旋强度较珠江口以东更大。1970年以来,逐年平均指数10 a滑动平均呈上升趋势。热带气旋给广东省带来的降水影响超过大风影响。累计潜在风险指数最高的城市为湛江、汕尾、阳江、江门;且湛江、茂名、汕头的风雨综合指数10 a滑动平均基本呈增加趋势;结果可为各地区水公共安全防御工作提供参考。

2020年7月一场梅雨暴雨的异常空间分布及形成机制

利用GPCP逐日降水资料、NCEP/NCAR和ERA5再分析资料,研究了2020年7月17—19日长江梅雨大暴雨异常空间分布及成因。结果表明,强降水主雨带在长江下游呈纬向分布,与长江干流位置重合、走向一致、长江中游雨带为西南—东北走向。中高层大气环流出现“两脊一槽”的异常大气环流型,南亚高压主体强盛东伸,副高西北侧水汽通道持续维持,为暴雨的形成和维持提供了有利环流背景。17—18日高空西风急流呈纬向分布、副高控制华南、低空西南急流持续加强并东移;19日高空西风急流转为“V”型分布,江淮气旋形成,长江中下游位于高空急流入口区南侧、副高的西北侧和低空西南急流出口区北侧。“两脊一槽”和“V”型大气环流配置结构使得上层的“抽吸”作用和下层的抬升活动相重叠,伴有江淮气旋的辐合作用,导致强烈的上升运动,易产生大暴雨。过程内高低空急流和副高位置和形态的变化是暴雨空间分布出现变化的主要原因。诊断结果显示,热力因子对抬升活动起主要作用,位涡垂直输送和非绝热加热随气压变化项均有利于位涡增强,假相当位温在500 hPa与850 hPa之差的峰值、强上升运动和位涡高值区与强降水中心重合为本次大暴雨形成提供了有利的热力与动力条件。假相当位温在500 hPa与850 hPa之差的谷值具有较好前期预报指示意义。

中国天然石英砂矿床时空分布规律与成矿资源潜力分析

中国天然石英砂矿产地分布主要受新生代流域、海岸盆地、山间盆地及断陷盆地控制,成矿时间分布局限,形成时代主要集中于新近纪中新世至第四纪全新世,其中以全新世为主导,是中国天然石英砂矿的主要成矿时代,矿石质量较好。中国天然石英砂矿资源较丰富,地理分布较广,集中度高。矿床主要集中分布在广东、海南、广西、福建和山东的沿海地带。