Spatial and temporal variation of groundwater recharge in shallow aquifer in the Thepkasattri of Phuket,Thailand

Whether groundwater resources can be sustainably utilized is largely determined and characterized by hydrogeological parameters.Estimating the groundwater recharge is one of the essential parameters for managing water resources and protecting water resources from contamination.This study researched the spatial and temporal variation of groundwater recharge in the Thepkasattri sub-district through integrating chloride mass balance(CMB)and water table fluctuation(WTF)methods.The chloride content of representative rainfall and groundwater samples was analyzed.Besides,WTF method was adopted from groundwater level data from 2012 to 2015.According to the CMB method,the mean recharge was estimated to be 1172 mm per year,accounting for 47%of the annual rainfall.Moreover,the estimated recharge from the WTF method took 26%of annual rainfall in 2015.The recharge was underestimated according to the WTF method,because of the uncertainty in specific yield estimates and the number of representative wells in the study area.Moreover,the correlation between rainfall and water table fluctuation data indicated the positive linear relationship between two parameters.The spatial recharge prediction indicated that recharge was higher(1200-1400 mm/yr)in the eastern and western catchment,while that in the central floodplains was between 800 mm/yr and 1100 mm/yr.In addition,low recharge value between 450 mm/yr and 800 mm/yr was observed in the south-west part of Thepkasattri.The spatial variation of recharge partly reflects the influences of land use and land cover of the study area.     

Spatial and temporal radiogenic isotopic trends of magmatism in Cordilleran orogens

An intrinsic feature of Cordillera-style orogenic systems is a spatial trend in the radiogenic isotopic composition of subduction-related magmatism. Magmatism is most isotopically juvenile near the trench and becomes increasingly evolved landward. A compilation of radiogenic isotopic data from the central Andes, U.S. Cordillera, and Tibet (the most well-studied examples of modern and ancient Cordilleran systems) demonstrate such spatial trends are long-lived and persist throughout the life of these continental subduction margins. The consistency of the isotopic trend through time in magmatic products is surprising considering the plethora of orogenic processes that might be expected to alter them. In addition to longevity, spatial isotopic trends encompass a broad spectrum of geochemical compositions that represent diverse petrogenetic and geodynamic processes. The two end-members of the spatial isotopic trends are represented by melts sourced within isotopically juvenile asthenospheric mantle and melts sourced from isotopically evolved continental lithospheric mantle and/or lower crust. Mantle lithosphere generally thins toward the magmatic arc and trench in Cordilleran orogens because sub-lithospheric processes such as delamination, subduction erosion, and subduction ablation, operate to thin or remove the continental mantle lithosphere. With time, magmatic additions may impart the isotopic composition of the mantle source on the lower crust, giving rise to an isotopically homogenous deep lithosphere. The results of this analysis have significant implications for interpreting temporal and spatial shifts in isotopic composition within Cordilleran orogens and suggest that the continental mantle lithosphere may be a significant source of magmatism in orogenic interiors.     

水文响应单元空间离散化及SWAT模型改进

水文响应单元(Hydrological Response Units,HRU)是SWAT模型模拟的基本单元,传统方法划分的水文响应单元在空间分布上不连续且难以确定其明确的空间位置,不能反映HRU间的相互作用和进行精确空间分析。利用GIS工具对土地利用和土壤类型数据进行概化处理,提出了HRU空间离散化的方法,实现了水文响应单元在空间上的准确定位。在此基础上,针对SWAT模型中同一子流域所有HRU采取相同延迟的弱点进行改进,并选择太湖地区西苕溪流域对改进的SWAT模型进行水文模拟验证。改进后,校正期港口站Nash效率系数E_NS(Nash-Sutcliffe Efficiency)从0.64提高到0.67,验证期E_NS系数从0.70提高到0.76。研究表明:修正后的SWAT模型更能反映流域的水文特征,可以达到非常好的效果,考虑到HRU距离因素的径流延迟更为准确地刻画径流过程。实现HRU空间离散化将为模型改进和更小尺度的空间分析提供数据基础。     

Spatial and temporal variation of heavy metals in a tropical estuary

The lower part of the Coatzacoalcos River has great industrial development in which high pollution has been reported. Surface sediments of this area were studied over a year to observe spatial and seasonal sedimentological and chemical variations. Higher metal concentrations were found during the dry season, Pajaritos Dock and Teapa sampling points showing the highest values. Ni (182 ppm) and Co (37 ppm) concentrations are elevated relative to other estuarine areas. Metal normalization against Al₂O₃ content shows contaminant input in areas where urban and industrial discharges exist. A cluster analysis of the data separates sediment samples from the different sampling trips, suggesting the dynamic nature of the sediments. Through the statistical t-test, metal enrichment of Cd, Cu, Cr, Ni, Pb, and Zn was evaluated and compared with metal concentration in sediments of the river higher parts. The percentage of bioavailable metals is a function of the physicochemical characteristics of the system.     

喜马拉雅山北坡典型冰川流域水文过程比较研究北大核心CSCD

2005年为喜马拉雅山中段的暖干年,夏季气温为历年最高。本文利用2005年珠穆朗玛峰绒布冰川下游水文观测资料及附近定日气象站资料、羊卓雍湖卡鲁雄曲冰川流域水文资料及附近浪卡子站气象资料,分析了两个流域的融水过程,建立冰雪消融数值模型,并进行了对比研究。结果表明:统计相关得到两流域气温和降水高度相关性(r>0.8),说明在区域尺度上两个地区的气候过程相似。绒布冰川消融强度比卡鲁雄曲冰川约大2倍,冰川退缩速率二者也差2.5倍,说明用冰川消融气温估计的水量损失基本反映两地冰川变化的事实。本文提出的冰雪融水模型,可以用于两个冰川区之间广大无资料冰川流域融水及冰川变化的估计,以及恢复珠穆朗玛和喜马拉雅山脉其他地区的长期水文过程及水资源变化的计算。     

中国农作物绿水占用指数估算及时空差异分析

从农作物生长消耗的绿水量入手,构造了农作物绿水占用指数,选取中国31个省区作为研究对象,通过对农作物绿水占用指数的计算,揭示中国各省区农业生态系统对绿水资源占用情况的空间分布特征,发现农作物绿水占用指数高的地区以黄淮海平原为核心集中分布,低的地区则主要分布在中国的西部。利用空间自相关分析方法,对中国1997～2007年农作物绿水占用指数的总体空间区域差异及时间演变趋势进行研究,结果显示,中国农作物绿水占用指数空间上存在着显著的集聚现象,但该现象逐年呈减弱趋势。结合局部自相关分析,对中国31个省区11年间的农作物绿水占用指数区域分异的时空演变规律进行探索,并对演变原因做出解释。     

Spatial and temporal trends of dust storms across desert regions of Iran

Dust storms are among natural and anthropogenic hazards for socioeconomic resources, especially in desert regions. In recent years, dust storms have become a serious problem, especially in desert regions of Iran. This study investigates temporal and spatial variation of dust storm frequency in desert regions of Iran. The number of dusty days (NDD) are collected from 22 stations across the region. The statistical analysis of NDD time series is carried out to show both spatial and seasonal pattern of dust storm occurrence in the region. The regional map of statistical characteristics indicates a north to south increasing dust storm frequency. The spatial map also reveals higher year-to-year variation in south eastern Iran. The seasonality of NDD shows the highest frequency for summer followed by the spring and autumn seasons. The popular Mann–Kendall and the bootstrap MK test to consider serial correlation are then applied for Trend assessment. Results showed both negative (across the north and northwestern regions) and positive trend (across south and south eastern regions) in the annual and seasonal NDD time series. This north-to-south gradient in the spatial and temporal frequency NDD may arise from harsh dry and gusty winds as well as intense land use change in the south eastern territories of Iran. However, more careful and detailed studies are required to connect environmental conditions to change in NDD frequency.     

Long-term variation in mesohaline Chesapeake Bay macrobenthos: Spatial and temporal patterns

Macrobenthos, sediments, and environmental conditions were sampled in the mesohaline region of western Chesapeake Bay (1971–1984) and the Potomac River (1980–1984). The survey data were used to quantify variation in macrobenthos and the physicochemical environment due to seasonal dynamics, spatial pattern (regional and local), and annual as well as long-term trends. Field experiments were conducted to test hypotheses suggested by the analysis of the survey data. Long-term and regional changes in the physiochemical environment, particularly salinity and dissolved oxygen concentration, had major influences on regional and long-term abundance patterns of macrobenthos. Two major species groups were identified along the mesohaline salinity gradient: those characteristic of high and low mesohaline salinities. Salinity increased and dissolved oxygen concentration below the pycnocline declined over the 14 yr. Estuarine endemic and euryhaline marine species concomitantly decreased in abundance. Opportunist species responded to increasing salinity and declining oxygen levels with increases in abundance. Predation on macrobenthos by fish and crabs affected the amplitude of annual recruitment pulses. Food availability apparently determined the magnitude of summer macrobenthic mortality. Spring was a critical period for the establishment of distributional patterns. The macrobenthos of the upper Chesapeake Bay was relatively stable over the study period mainly due to the stability and predictability of physicochemical processes controlling recruitment patterns.     

Spatial and temporal variation of natural recharge in the semi-arid valley of Aguascalientes,Mexico

The investigation involves a temporal and spatial analysis to characterize recharge in the Aguascalientes valley in central Mexico. The results are based on a two-part methodological strategy using a geospatial and numerical analysis. Results from the geospatial analysis are based on the analytical hierarchical process (AHP) method, which involves developing a zoning map that qualifies the conditions for groundwater recharge in the valley. In addition, one-dimensional numerical modeling based on the van Genuchten equation was applied for various soil column configurations to estimate the transit time of recharge through the vadose zone. The analysis was performed over a 20-year period from 1995 to 2015. The results of the geospatial analysis indicate that the optimal area for groundwater recharge is the lower zone of the valley, particularly the portion influenced by surface discontinuities. The shortest estimated period of recharge for water to pass through the vadose zone is approximately 4.25 years.     

Chemistry and transport of soluble humic substances in forested watersheds of the Adirondack Park,New York

Studies were conducted in conjunction with the Integrated Lake-Watershed Acidification Study (ILWAS) to examine the chemistry and leaching patterns of soluble humic substances in forested watersheds of the Adirondack region. During the summer growing season, mean dissolved organic carbon (DOC) concentrations in the ILWAS watersheds ranged from 21–32 mg C l^?1 in O/A horizon leachates, from 5–7 mg C l^?1 in B horizon leachates, from 2–4 mg C l^?1 in groundwater solutions, from 6–8 mg C l^?1 in first order streams, from 3–8 mg C l^?1 in lake inlets, and from 2–7 mg C l^?1 in lake outlets. During the winter, mean DOC concentrations dropped significantly in the upper soil profile. Soil solutions from mixed and coniferous stands contained as much as twice the DOC concentration of lysimeter samples from hardwood stands. Results of DOC fractionation analysis showed that hydrophobia and hydrophilic acids dominate the organic solute composition of natural waters in these watersheds. Charge balance and titration results indicated that the general acid-base characteristics of the dissolved humic mixture in these natural waters can be accounted for by a model organic acid having an average_pK_a of 3.85, an average charge density of 4–5 μeq mg^?1 C at ambient pH, and a total of 6–7 meq COOH per gram carbon.     

贵阳城区大气污染物的时空变化和复合污染特征

选取贵阳市10个空气质量监测站发布的PM2.5、PM10、SO2、NO2、CO和O3实时浓度数据，通过时间序列分析法和插值法研究贵阳市大气污染物的时空变化和复合污染特征。结果表明:（1）贵阳市2014-2018年主要污染物PM2.5和PM10的年平均浓度逐渐下降，光化学污染物O3年平均浓度有所增加，空气质量逐渐转好，环境治理取得明显效果；（2）2018-2019自然年PM2.5、PM10、NO2和O3在春季污染最严重，SO2和CO在冬季污染最严重，反映出污染源、阶段性燃料燃烧和二次离子生成等因素对不同污染物的影响不同；（3）PM2.5和PM10日变化特征为“午峰晚峰”型，峰值发生的时间因季节而异，主要由不同季节人类作息的起止时间不同所致，O3日变化为单峰型，夜间O3浓度较低，从早晨8:00点开始随着太阳辐射的增大和温度的升高，在15:00-16:00点左右达到峰值；（4）PM2.5的空间分布呈现出部分郊区和工业区较高，市中心居民区较低的特征，指示城市建设向郊区推进。O3浓度呈现出市区低、郊区高的空间分布特征，反映郊区植被覆盖好，释放的天然源VOCs促进了O3生成；（5）主要污染物O3与颗粒物PM2.5和PM10在春季造成的复合污染最为严重，在夏季O3与PM10造成一定程度的复合污染，在秋冬季O3浓度最低，O3与颗粒物不产生复合污染；一天之内同一时刻O3与颗粒物不会产生叠加从而造成复合污染。      

Spatial and temporal variation of uranium in a shallow weathered rock aquifer in southern India

Uranium occurs naturally in groundwater and surface water. The objective of this study is to understand the causes for the occurrence of uranium and its spatio-temporal variation in groundwater in a part of Nalgonda district, Andhra Pradesh, south India. Uranium deposits occur in the southeastern part of this area. Groundwater samples were collected from 44 wells every two months from March 2008 to January 2009. The samples were analyzed for pH, ORP and uranium concentration. The uranium concentration in groundwater varies from 0.2 ppb to a maximum of 68 ppb with a mean of 18.5 ppb. About 21.6% of the samples were above the drinking water limit of 30 ppb set by USEPA. The uranium concentration varied with fluctuation in groundwater level, pH and ORP. Uranium concentration in groundwater changes depending on lithology, degree of weathering and rainfall recharge.     

Spatial and temporal variation of organic carbon in the northern South China Sea revealed by sedimentary records

Three sediment cores were taken from the Pearl River estuary and adjacent northern South China Sea (SCS). These sediment cores span the time interval 1900–2000 AD. The stratigraphy of the concentration, the ratio of total organic carbon (TOC) to total nitrogen (TN) and stable isotope (δ¹³C_org) of organic carbon (OC) from three high-resolution sediment cores were analyzed. The stratigraphic profiles of OC concentration, TOC/TN ratios and δ¹³C_org for the near past 100 yrs indicate that terrestrial organic matter decreases from 68.3% to 27.4% of the TOC in the Pearl River estuary, while Dapeng Bay (offshore east of Hong Kong) apparently had throughout little terrestrial organic matter input. The highest deposited OC occurs at the Humen River mouth and the OC concentrations are higher in the outer estuary than in the inner shelf of the northern SCS. The deposited OC at the River mouth increased with time, which could be caused by the high precipitation of land-derived organic matter and the high input of terrestrial organic matter, which is likely related to the rapid urbanization and industrial development in the Pearl River Delta since the 1970s. The OC concentrations did not exhibit an obvious increase with time in most areas of the Pear River estuary and adjacent inner shelf of the SCS, but the algal-derived OC concentration inferred from the δ¹³C_org values increased with time especially from 1980 to 2000 in the outer Pearl River estuary and Dapeng Bay. This increase is presumably caused by enhanced primary marine productivity supported by higher anthropogenic nutrient inputs.     

Assessing the applicability of conceptual hydrological models for design flood estimation in small-scale watersheds of northern China

Natural Hazards - The estimation of design flood is mainly focused on the peak flow and the volume, ignoring the underlying surface factor and flood rising and falling process. Three basic...     

Spatial and temporal variation of the nekton and hyperbenthos from a temperate European estuary with regulated freshwater inflow

The aquatic macrofauna of the Guadalquivir estuary were sampled (1 mm mesh persiana net) at 5 sampling sites located along the entire (except the tidal freshwater region) estuarine gradient of salinity (outer 50 km). A total of 134 fish and macroinvertebrate species was collected but only 62 were considered common or regularly present in the estuary. Univariate measures of the community structure showed statistically significant differences among sampling sites: species richness, abundance, and biomass decreased in the upstream direction, being positively correlated with the salinity. Temporal differences of these three variables were also statistically significant. While a clear seasonal pattern (minimum densities in winter and maximum in spring-summer) was observed for abundance and biomass, no such pattern existed for the number of species. Mysids was the most dominant group throughout the estuary (96% to 99% of abundance; 49% to 85% of biomass), although fish biomass was also important at the outer estuary (36% to 38%). Multivariate analyses indicated highly significant spatial variation in the macrofaunal communities observed along the salinity gradient. These analyses suggest that the underlying structure was a continuum with more or less overlapping distributions of the species dependent on their ability to tolerate different physicochemical conditions. There were also significant temporal (intermonthly + interannual) variation of the estuarine community; the relative multivariate dispersion indicated that monthly variation was more considerable (relative multivariate dispersion >1) at the outer part of the estuary during the wet year (last 20 km) and was higher in the inner stations during the dry year (32 to 50 km from the river mouth). Since a clear negative exponential relationship was observed between the freshwater input (from a dam located 110 km upstream) and water salinity at all sampling stations, it is concluded that the human freshwater management is probably affecting the studied estuarine communities. While the higher seasonal (long-term) stability of the salinity gradient, due to the human control of the freshwater input, may facilitate the recruitment of marine species juveniles during the meteorologically unstable early-spring, the additional (short-term) salinity fluctuations during the warm period may negatively affect species that complete their lifecycle within the estuary.     

天山南坡清水河与阿拉沟流域径流变化特征及其对气候变化的响应

依据1956-2012年天山南坡清水河流域的克尔古提水文站以及阿拉沟流域的阿拉沟水文站资料,采用Mann-Kendall非参数检验法和交叉小波变换法,分析了清水河与阿拉沟出山径流的趋势、突变、周期变化等特征,并进一步探讨了出山径流对气候变化的响应。结果表明：清水河与阿拉沟流域年径流量均呈上升趋势,其中1988年为径流突变年,该年前后年均径流变化态势不同,1988年以后径流升幅显著。同时,流域径流过程呈现多时间尺度的周期变化,以32 a以上大周期为主,2 a和8 a小周期变化为辅。因流域下垫面特征等差异,清水河出山径流对降水变化的响应程度强于阿拉沟,而阿拉沟出山径流对气温敏感性高于清水河。且受冰川径流调节作用与多年冻土退化的影响,阿拉沟径流过程对气温的滞后性强于清水河。     

新安江流域2000—2021年NDVI时空变化特征及其影响因素分析

新安江流域是长三角地区重要的生态屏障,对该流域的植被覆盖情况进行监测并掌握其动态变化特征,对该区生态环境保护具有重要意义。以新安江流域为研究区,利用2000—2021年MOD13Q1数据,针对归一化植被指数(NDVI)的时空变化特征及其变化的持续性,使用Theil-Sen Median趋势分析、Mann-Kendall检验和Hurst指数等方法进行分析,探讨了NDVI的变化趋势与岩性建造、土地利用类型之间的关系。结果表明:二十多年以来,新安江流域的年平均NDVI为0.5~0.9,总体呈波动上升趋势,最大值出现在每年7—9月,最小值出现在每年1—3月,呈现"山地高,丘陵和平原较低"的分布特征。NDVI变化类型以改善型为主,改善型区域面积占比>70％,且以持续改善型为主,其中轻微改善型和明显改善型面积占比达85.71％。第四系和白垩纪红层分布区,NDVI严重退化和轻微退化占比较高,NDVI退化情况较严重的土地利用类型为建设用地、草地和耕地。该研究结果可反映新安江流域NDVI的时空变化特征,对于该区生态环境保护与建设具有一定指导意义。     

Spatial and temporal variation in estuarine fish and invertebrate assemblages: Analysis of an 11-year data set

Protocols for monitoring wetland mitigation and restoration projects call for routine counts of animals, yet long-term spatial and temporal patterns are rarely examined. An analysis of monitoring data from three southern California estuaries spanning 11 years, four seasons, and multiple stations within the estuaries revealed differences in spatio-temporal patterns between fish and invertebrates. Ordination analysis showed that fish assemblages were more predictable from environmental variables than were invertebrate assemblages. Variation in the fish assemblage was, primarily due to seasonal differences that were driven by changes in temperature. Invertebrates showed little seasonal variation, but a much higher degree of interannual variation than fish. Streamflow and dissolved oxygen were significant predictors of the invertebrate assemblage, indicating that irregular disturbances such as flooding events had a more important effect on the invertebrate assemblage than predictable seasonal cues such as temperature. Variation in fish and invertebrates was high both between and within the three estuaries, indicating that differences exist on multiple spatial scales. The influence of spatial and temporal factors on estuarine invertebrate and fish communities should be considered in planning monitoring programs for wetland mitigation or restoration sites.