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1.
《China Geology》2018,1(3):435-449
Focusing on the Yangtze River economic zone, the previous geological researches are systematically summarized, resources and environment conditions and major geological problems which are needing to be concerned in land planning and construction are studied. The results show that the resource conditions of cultivated land, shale gas, geotherm, lithium and so on are superior in the Yangtze River economic zone, and the resources and environment conditions are conducive to develop the modern agriculture, clean energy industry and strategic emerging industries. 3×1013 m2 farmlands without heavy metal pollution are concentrated; there are three national level shale gas exploration and development bases with explored reserves of 5.441×1011 m3; geothermal availability is 2.4×109 t of standard coal each year, equivalent to 19% of the amount of coal in 2014; Asia’s largest energy lithium metal ore deposit is found. In some parts of Yangtze River economic zone, there are some major geological problems such as active faults, karst collapse, ground subsidence, landslide-collapse-debris flow, affecting the river-crossing channels, high-speed railway, urban agglomeration and green ecological corridor planning and construction. Those problems should be concerned, and the relevant suggestions and countermeasures are put forward. Meanwhile, the ideas to further support the development of the Yangtze River economic zone are put forward. 相似文献
2.
In the Patía River delta, the best-developed delta on the western margin of South America, a major water diversion started in 1972. The diversion of the Patía flow to the Sanquianga River, the latter a small stream draining internal lakes from the Pacific lowlands, shifted the active delta plain from the south to the north and changed the northern estuarine system into an active delta plain. The Sanquianga Mangrove National Park, a mangrove reserve measuring 800 km2, lies in this former estuary, where major hydrologic and sedimentation changes are occurring. Overall, major environmental consequences of this discharge diversion in terms of geomorphic changes along distributary channels and ecological impacts on mangrove ecosystems are evidenced by: (1) distributary channel accretion by operating processes such as sedimentation, overbank flow, increasing width of levees, sedimentation in crevasses, interdistributary channel fill, and colonization of pioneer mangrove; (2) freshening conditions in the Sanquianga distributary channel, a hydrologic change that has shifted the upper estuarine region (salinity <1%) downstream; (3) downstream advance of freshwater vegetation, which is invading channel banks in the lower and mixing estuarine zones; (4) die-off of approximately 5200 ha of mangrove near the delta apex at Bocas de Satinga, where the highest sediment accumulation rates occur; and (5) recurrent periods of mangrove defoliation due to a worm plague. Further analyses indicate strong mangrove erosion along transgressive barrier islands on the former delta plain. Here tectonic-induced subsidence, relative sea-level rise, and sediment starving conditions due to the channel diversion, are the main causes of the observed retreating conditions of mangrove communities. Our data also indicate that the Patía River has the highest sediment load (27 × 106 t yr−1) and basin-wide sediment yield (1500 t km−2 yr−1) on the west coast of South America. Erosion rates from the Patía catchment have been more pronounced during the decades of 1970–1980 and 1990–2000, as a result of land degradation and deforestation. The high sediment and freshwater inputs into the mangrove ecosystem create additional stress (both at ongoing background levels and, occasionally, at dramatic levels), which may periodically push local environmental parameters beyond the thresholds for mangrove survival. The future environmental state of the Sanquianga Mangrove National Reserve deserves more scientific and governmental attention. 相似文献
3.
长江上游干流流经青、藏、川、滇、鄂、渝6省市,支流涉及甘肃、陕西、贵州3省,流域面积为105.4×104km2,人口1.55亿,占全国国土面积的11.1%.长江上游地区经济发展相对落后,人均国民收入低,少数民族众多,与中下游经济发达地区差距很大.但上游地区蕴藏着巨大的经济开发潜能,丰富的水力和矿产等自然资源,以及农、林、牧等物产,对中下游地区经济发展有着巨大的支援作用.同时,由于自然地理上的相关性,又使上游地区的开发治理,对中下游地区的生态环境和可持续发展有着至关重要的作用.目前,长江上游森林植被大量减少,水源涵养能力下降,水土流失加剧:泥石流、滑坡、崩塌等地质灾害严重,旱、洪灾害频发;沿江大量排放废气、废水、污水,使大气和水体严重污染.随着上游地区生态环境的日益恶化,给中下游地区带来严重危害,河道、湖泊、水库淤积加速,洪涝灾害频繁发生,造成中下游地区经济建设和人民生命财产的重大损失.因此,必须尽快对长江上游地区进行全面综合治理,尽快开展新一轮国土资源大调查,制定各种自然资源的合理开发利用和保护方案;控制沿江污染源的排放,建立大气和水体污染监测系统;运用高新技术,建立上游重点地带地壳形变的动态监测和预警系统,防治地质灾害;充分利用上游地区丰富的水力资源,兴建多级水利设施,对地表水实施人工的时空控制,消除旱、洪灾害. 相似文献
4.
Mid-Holocene coastal hydrology and salinity changes in the east Taihu area of the lower Yangtze wetlands, China 总被引：1，自引：0，他引：1
During the mid-Holocene the eastern Taihu area, on China's Yangtze delta plain, was populated by advanced late Neolithic cultures supported by intensive domesticated rice cultivation. This agricultural system collapsed around 4200 cal yr BP, with severe population decline, the end of the Liangzhu culture, and about half a millennium of very low-scale human activity in the area before the re-establishment of agricultural production. Microfossil analyses from six sedimentary sequences, supported by AMS 14C dating, has allowed reconstruction of mid-Holocene hydrological conditions and salinity changes which would have had a major influence on agricultural viability and cultural history in the coastal wetlands. These data, allied to existing stratigraphic and sea-level records, show that chenier ridges that developed after ca. 7000 cal yr BP in the east of the area sheltered it from marine inundation and, although still connected to the sea through tidal creeks, low-salinity conditions persisted throughout the Neolithic period. There is no evidence that marine flooding caused the collapse of Liangzhu culture. Marine influence was stable and evolved slowly. Social and cultural causes may also have been important, but if environmental change triggered the collapse of Neolithic agricultural society here, other natural forces must be sought to explain this event. 相似文献
5.
Phytolith data from Poyang Lake, southern China, indicate that significant natural and human‐induced vegetational changes have occurred in the middle Yangtze River valley, the likely hearth of rice (Oryza sativa L.) domestication, during the Late Pleistocene and Holocene periods. During the Late Pleistocene (from >13,500 to ca. 10,500 yr B.P.) the climate was cooler and drier than today's. Oryza appears to have been a natural component of the vegetation at that time, but may not have been well adapted to the glacial climatic conditions. The early Holocene climate may have been wetter and more markedly seasonal that at present, and wild Oryza species may have been distributed further north than seen today. By 4000 yr B.P., rice agriculture appears to have been well developed in the middle Yangtze River Valley. Environmental factors such as atmospheric CO2 concentrations and the seasonality of precipitation and temperature in addition to overall cooler and drier Pleistocene climates may have significantly influenced human exploitation of Oryza during the Late Pleistocene and early Holocene in southern China. © 2000 John Wiley & Sons, Inc. 相似文献
6.
遗址资源域分析(Site Catchment Analysis)已被广泛应用于对史前经济和人类行为模式的研究中,有别于西方普遍采用的“遗址外”(off-site)研究模式,本文提倡一种以“遗址内”(on-site)为核心的研究方法。主要通过遗址所见大植物遗存,结合古环境研究成果,模拟复原当时的植被分布,进而讨论遗址资源域及其反映的生业经济特点。第一个案例是长江下游的田螺山遗址,属于河姆渡文化（6900～6500cal.aB.P.）,分析表明: 早期的水稻栽培活动是长期伴生于采集经济模式中的; 当时的采集经济具有广域性、专门性、季节性和强调储存性等特点; 这一时期聚落的选址会优先考虑生态环境的多样性,在步行一天的活动半径便可获得大部分植物资源,但也有一些资源分布于12小时半径之外,必须短期露营（可能与狩猎同时进行）方可获取。第二个案例是中原地区的颍河上游,分析以袁桥遗址为中心的仰韶文化聚落（6000cal.aB.P.）: 尽管 2～3 小时的步行范围内就有条件获取各类野生植物资源,仰韶文化时期的生业活动已经集中在更小空间范围内的作物栽培上。遗址资源域缩小、对小范围景观进行改造、聚落间产生土地分配和资源共享等社会关系问题——这些构成了农业聚落资源域的一般特点。比较两个案例,农业聚落的产生可以看作是一种景观环境上发生的变化。遗址资源域分析为我们提供了一个新的视角来理解早期农业社会的产生、发展及不同生业社会与周边景观的互动关系。 相似文献
7.
下扬子区三叠纪古生物和古地理变迁及其主要原因 总被引：1，自引：1，他引：1
根据下扬子区三叠系生物化石和沉积相的研究，该区三叠纪古地理环境先后经历陆表海，萨布哈潮坪－泻湖，下三角洲平原滨海河口湾及三角洲平原河，湖和沼泽一系列变迁，其主要原因是由于扬子板块从赤道以南附近持续向北进行跨气候带漂移抵达北回归线以北附近的结果。 相似文献
8.
本文系统梳理了长江经济带以往地质研究成果,对长江经济带资源环境条件和国土规划建设中应关注的重大地质问题进行了研究。研究结果表明,长江经济带耕地、页岩气、地热、锂等资源条件优越,0.3亿hm2无重金属污染耕地集中分布,拥有3个国家级页岩气勘查开发基地,探明储量5441亿m3,每年地热可利用量折合标准煤2.4亿t,相当于2014年燃煤量的19%,发现亚洲最大的能源金属锂矿床,资源环境条件有利于发展现代农业、清洁能源产业和战略新兴产业;长江经济带部分地区存在活动断裂、岩溶塌陷、地面沉降、滑坡崩塌泥石流等重大地质问题,影响过江通道、高速铁路、城市群和绿色生态廊道规划建设,应予以关注,本文提出了相关建议和对策,同时,提出了下一步支撑服务长江经济带发展地质工作设想。 相似文献
9.
《Applied Geochemistry》2000,15(5):599-609
The effects of agriculture on the isotope geochemistry of Sr were investigated in two small watersheds in the Atlantic coastal plain of Maryland. Stratified shallow oxic groundwaters in both watersheds contained a retrievable record of increasing recharge rates of chemicals including NO3−, Cl, Mg, Ca and Sr that were correlated with increasing fertilizer use between about 1940 and 1990. The component of Sr associated with recent agricultural recharge was relatively radiogenic (87Sr/86Sr=0.715) and it was overwhelming with respect to Sr acquired naturally by water–rock interactions in the oxidized, non-calcareous portion of the saturated zone. Agricultural groundwaters that penetrated relatively unoxidized calcareous glauconitic sediments at depth acquired an additional component of Sr from dissolution of early Tertiary marine CaCO3 (87Sr/86Sr=0.708) while undergoing O2 reduction and denitrification. Ground-water discharge contained mixtures of waters of various ages and redox states. Two streams draining the area are considered to have higher 87Sr/86Sr ratios and NO3− concentrations than they would in the absence of agriculture; however, the streams have consistently different 87Sr/86Sr ratios and NO3− concentrations because the average depth to calcareous reducing (denitrifying) sediments in the local groundwater flow system was different in the two watersheds. The results of this study indicate that agriculture can alter significantly the isotope geochemistry of Sr in aquifers and streams and that the effects could vary depending on the types, sources and amounts of fertilizers added, the history of fertilizer use and groundwater residence times. 相似文献
10.
史前文化的经济形态与自然环境密切相关,不同地区史前经济形态的差异反映了人类对环境的不同响应方式。通过对黄河流域4kaB.P.前后不同文化中农作物、动物以及人骨同位素等有关资料的综合分析,结果表明黄河上游、中游和下游地区史前经济形态对4kaB.P.气候变化的响应存在3种不同的模式:甘青地区从农业为主向农牧并重、畜牧成分显著增加的混合经济形式转变;山东地区从稻粟混作向以粟为主的农业经济转变;而中原地区则是以粟为主的农业持续稳定发展。究其原因,认为除了史前人类的文化传统和适应能力等因素之外,主要与气候变化的区域差异以及人类对气候变化的不同响应有关。 相似文献
11.
海河流域水资源严重短缺,地下水长期超采是制约社会经济可持续发展的主要瓶颈。开展流域地下水资源及开发利用潜力研究,对支撑服务地下水超采治理、地下水资源可持续利用和生态环境保护都具有重要意义。经系统评价,海河流域天然资源量252.99×10~8m~3,生态水位约束条件下的浅层地下水开采资源量172.98×10~8m~3,可更新的深层水可利用量4.68×10~8m~3。海河流域山区地下水质量总体较好,Ⅰ～Ⅲ类水占比40.83%,平原区浅层地下水质量较差,Ⅰ～Ⅲ类水占比14.10%,深层地下水质量优于浅层地下水,Ⅰ～Ⅳ类水占比74.25%。海河流域山区地下水开采潜力总体较小,燕山和太行山北部山区,地下水资源禀赋较差,基本无开采潜力,太行中部山区地下水开采程度较高,无开采潜力或开采潜力较小,太行南部山区地下水资源禀赋良好,开采潜力较大;平原区浅层地下水在不同水文地质单元开采潜力差异较大,山前平原浅层地下水长期超采形成大范围降落漏斗,无开采潜力或潜力较小,中东部平原浅层地下水资源禀赋较差,以微咸水为主,开采潜力较小,山东省鲁北平原区浅层地下水开采程度较低,聊城—德州一带开采潜力较大;雄安新区地下水总体无开采潜力。平原区深层地下水基本无开采潜力。 相似文献
12.
The effects of human activities on oasis climate and hydrologic environment in the Aksu River Basin,Xinjiang, China 总被引：1，自引：0，他引：1
Guoya Wang Yongping Shen Jiangang Zhang Shunde Wang Weiyi Mao 《Environmental Earth Sciences》2010,59(8):1759-1769
Under the influence of human activities, the differences in climate changes emerged obviously in the Aksu Oasis. The summer
air temperature in Aksu City increased at a rate of 0.20°C·(10 annum)−1, while the air temperature in Aler in summer decreased at a rate of −0.27°C·(10 annum)−1. Human intervention has become the dominant factor in the the changes of water resources in the Aksu Oasis. Compared with
the Xidaqiao hydrological station, which is located on the upper reaches of the Aksu River, the runoff ratio at the Aler hydrological
station increased in summer and decreased in spring. Though the natural water inflow has increased in the last 50 years, irrigation
diversion and water consumption for human activities have increased unceasingly due to the increased reclamation of land and
the development of extensive agriculture. The water quality at the Xidaqiao station is in Grade I at different periods, and
the water quality at the Aler station of the Tarim River is good because the river did not suffer from human disturbance before
the large-scale development of oasis agriculture; but the salinity of river water increased from 0.67 g L−1 in 1960 to 5.27 g L−1 in 2000 at the Aler station after farmland development, reclamation and salt washing in the oasis. The geographic distribution
of surface water resources has changed due to human activities and in turn affected groundwater replenishment, bringing about
changes to groundwater table and quality. 相似文献
13.
In the Central Andes of Argentina, evidences of early human occupations come from the Precordillera, a low mountain system which was under periglacial conditions prior to 14,000 14C yr BP, when the Cordillera Principal and Cordillera Frontal were glaciated. The corridors for human migration across the Andes may have opened before 13,000 14C yr BP. The Pleistocene/Holocene transition gave rise to a substantial variability of environments and consequently of natural resources for early people, who found in the Precordillera new ecosystems with suitable conditions for living. The first human groups arrived ca. 11,000 14C yr BP at Agua de la Cueva rockshelter, located at 2900 m above sea level in the western flank of the Precordillera. The occurrence of raw material outcrops close to the site and the archaeofaunistic record indicate a local and likely seasonal exploitation of mountain resources. These early people lived in a shrub steppe environment under cooler and probably wetter conditions in which camelids were the most important food resource. Since 9000 14C yr BP, warmer and drier conditions were dominant. Except for a lower intensity of human occupations, the site function of Agua de la Cueva seems to have remained the same. 相似文献
14.
J. B. Adams G. C. Bate T. D. Harrison P. Huizinga S. Taljaard L. van Niekerk E. E. Plumstead A. K. Whitfield T. H. Wooldridge 《Estuaries and Coasts》2002,25(6):1382-1393
The National Water Act (Act 36 of 1998) in South Africa recognizes basic human water requirements as well as the need to sustain the country's freshwater and estuarine ecosystems in a healthy condition for present as well as future generations. In this Act, provision is made for a water reserve to be estimated prior to the authorization of water use (e.g., for agriculture, large volume residential and industrial uses) through licensing. This reserve is the water required to satisfy basic human needs (i.e., 25 1 person?1 d?1) and to protect aquatic ecosystems to ensure present and future sustainable use of the resource. This led the Departments of Water Affairs and Forestry and estuarine scientists throughout South Africa to develop a method to determine the freshwater inflow requirements of estuaries. The method includes documenting the geographical boundaries of the estuary and determining estuarine health by comparing the present state of the estuary with a predicted reference condition with the use of an Estuarine Health Index. The importance of the estuary as an ecosystem is taken from a national rating system and together with the present health is used to set an Ecological Reserve Category for the estuary. This category represents the level of protections afforded to an estuary. Freshwater is then reserved to maintain the estuary in that Ecological Reserve Category. The Reserve, the quantity and quality of freshwater required for the estuary, is determined using an approach where realistic future river runoff scenarios are assessed, together with data for present state and reference conditions, to evaluate the extent to which abiotic and biotic conditions within an estuary are likely to vary with changes in river inflow. Results from these evaluations are used to select an acceptable river flow scenario that represents the highest reduction in freshwater inflow that will still protect the aquatic ecosystem of the estuary and keep it in the desired Ecological Reserve Category. The application of the Reserve methodology to the Mtata estuary is described. 相似文献
15.
为提升对长江流域水文地质和地下水资源的认知程度,突破以往单独从地表水或地下水角度进行评价的局限性,长江流域水文地质调查工程以地球系统科学理论和水循环理论为指导,充分考虑地表水与地下水的转化关系,将水文地质单元和地表水流域有机结合,划分长江流域地下水评价单元,建立典型地下水资源评价模型,开展了新一轮长江流域地下水资源评价。评价结果表明:(1)长江流域水循环要素时空分布不均,降水以中游最多,并由东南向西北递减;地表径流主要集中在夏季,且长江北岸比南岸集中程度更高;蒸散发量总体上呈现东部高于西部的特征,最大值集中在长江中游一带;长江流域地下水位总体保持稳定,丰枯季水位变化总体不大,一般小于2 m;长三角超采区的地下水漏斗面积已明显减小,相关环境地质问题得到了有效控制。(2)2020年长江流域的地下水资源总量2421.70亿m~3/a,其中山丘区地下水资源量2092.79亿m~3/a,平原区地下水资源量331.35亿m~3/a;地下水储存量较2019年整体略有增加趋势,其中四川盆地最为明显,共增加23.72亿m~3。(3)长江流域的水质上游优于下游,优质地下水主要分布在赣南地区和大别山南麓一带,部分地区水质较差的主要原因是原生劣质水的广泛分布。长江流域地下水开发利用水平整体很低,局部地区由于过往不合理的开发所引发的环境地质问题已得到缓解,岩溶塌陷、地面沉降等问题得到了较好控制。建议适当开发利用赣南地区和大别山南麓一带优质的基岩裂隙水。 相似文献
16.
《Applied Geochemistry》2004,19(9):1471-1482
Ground-water chemistry data from coastal plain environments have been examined to determine the geochemical conditions and processes that occur in these areas and assess their implications for aquifer susceptibility. Two distinct geochemical environments were studied to represent a range of conditions: an inner coastal plain setting having more well-drained soils and lower organic carbon (C) content and an outer coastal plain environment that has more poorly drained soils and high organic C content. Higher concentrations of most major ions and dissolved inorganic and organic C in the outer coastal plain setting indicate a greater degree of mineral dissolution and organic matter oxidation. Accordingly, outer coastal plain waters are more reducing than inner coastal plain waters. Low dissolved oxygen (O2) and nitrate (NO3−) concentrations and high iron (Fe) concentrations indicate that ferric iron (Fe (III)) is an important electron acceptor in this setting, while dissolved O2 is the most common terminal electron acceptor in the inner coastal plain setting.The presence of a wide range of redox conditions in the shallow aquifer system examined here underscores the importance of providing a detailed geochemical characterization of ground water when assessing the intrinsic susceptibility of coastal plain settings. The greater prevalence of aerobic conditions in the inner coastal plain setting makes this region more susceptible to contamination by constituents that are more stable under these conditions and is consistent with the significantly (p<0.05) higher concentrations of NO3− found in this setting. Herbicides and their transformation products were frequently detected (36% of wells sampled), however concentrations were typically low (<0.1 μg/L). Shallow water table depths often found in coastal plain settings may result in an increased risk of the detection of pesticides (e.g., alachlor) that degrade rapidly in the unsaturated zone. 相似文献
17.
Construction of two dams in 1958 and 1982 decreased freshwater inflow to the Nueces River and Nueces Delta marsh, which has become a reverse estuary where salinity increases upstream rather than downstream as would occur in a normal estuary. In 1995, an overflow channel was dug to breach the banks of the Nueces River to restore inundation of the marsh via Rincon Bayou, which is the main stem channel of the delta. Previous studies demonstrated a restoration of a normal salinity gradient and positive affects on benthos in the upper reaches of Rincon Bayou. The present study was performed to determine how far downstream the overflow channel had beneficial effects. A transect of eight stations was established and sampled quarterly between October 1998 and October 1999. Benthic characteristics were measured to assess ecological change. There were 12 precipitation and freshwater inflow events between the month preceding and ending sampling. The largest were in fall and restored normal salinity patterns. The macrobenthic community was different in three zones. The upper four stations (<6.4 km from the overflow channel) were highly variable in water inundation and salinity. The broad salinity range caused the lowest diversity and allowed short-lived pioneer speciesStreblospio benedicti, Laeonereis culveri, and Chirominid larvae to dominate. Biomass blooms occurred during fall inflow events in the upper reaches. The central stations (11.4 to 14.3 km from the overflow channel) were brackish, had more narrow salinity ranges, and were more diverse.Mulinia lateralis, Mediomastus ambiseta, Cerapus tubularis, andAmpelisca abdita were dominant species. The third zone, the lower portion of Nueces Bay (27 km from the overflow channel), was distinct from other stations in the transect, because it had the greatest marine influence. It is in a later successional stage, with a more diverse community of larger organisms, e.g.,Polydora caulleryi, Tharyx setigera, andMysella planulata, which were dominant species and contributed to the larger biomass there. Overall, the overflow channel restored normal salinity patterns in the upper reaches (<14 km) of Rincon Bayou and freshwater pulses (>106 m3) in fall increased benthic productivity indicating ecological functions were restored as well. This restoration however, only occurs intermittently for short time periods because the freshwater events are isolated and inflow volumes during the current study were too small to affect the lower Rincon Bayou or Nueces Bay. 相似文献
18.
We examined high frequency fluctuations in water quality parameters in two tropical coastal plain estuaries in response to
changing tidal flow conditions. The variability in total suspended sediments (TSS), volatile suspended solids (VSS), total
organic carbon (TOC) concentrations, and indicators of water quality, including pH, temperature, salinity, and dissolved oxygen,
over one spring tidal cycle during the early wet monsoon season was measured in two estuaries in eastern Sumatra. The relatively
high rainfall experienced throughout the year, in combination with the recent extensive vegetation clearing and modification
of the landscape, resulted in significant concentrations of TSS, VSS, and TOC being discharged to coastal waters. Maximum
values are reached on the ebb tide (TSS > 1,013 mg l−1; VSS > 800 mg l−1; TOC >60 mg l−1). The influence of freshwater discharge and tidal flow on water properties of the lower estuaries is also marked by the variability
in salinity, dissolved oxygen, and pH over the tidal cycle, with minimum values for each of these parameters following maximum
current velocities and after the completion of the strong ebb tide. Estimation of seaward sediment fluxes, which are of significant
interest in a region where rapid environmental change is occurring, would require further examination of sedimentary processes,
such as resuspension and advection of sediment, as well as a consideration of neap-spring tidal variations and the effect
of seasonality on estuarine circulation. 相似文献
19.
The rapid expansion of agriculture, industries and urbanization has triggered unplanned groundwater development leading to severe stress on groundwater resources in crystalline rocks of India. With depleting resources from shallow aquifers, end users have developed resources from deeper aquifers, which have proved to be counterproductive economically and ecologically. An integrated hydrogeological study has been undertaken in the semi-arid Madharam watershed (95 km2) in Telangana State, which is underlain by granites. The results reveal two aquifer systems: a weathered zone (maximum 30 m depth) and a fractured zone (30–85 m depth). The weathered zone is unsaturated to its maximum extent, forcing users to tap groundwater from deeper aquifers. Higher orders of transmissivity, specific yield and infiltration rates are observed in the recharge zone, while moderate orders are observed in an intermediate zone, and lower orders in the discharge zone. This is due to the large weathering-zone thickness and a higher sand content in the recharge zone than in the discharge zone, where the weathered residuum contains more clay. The NO3 ? concentration is high in shallow irrigation wells, and F? is high in deeper wells. Positive correlation is observed between F? and depth in the recharge zone and its proximity. Nearly 50 % of groundwater samples are unfit for human consumption and the majority of irrigation-well samples are classed as medium to high risk for plant growth. Both supply-side and demand-side measures are recommended for sustainable development and management of this groundwater resource. The findings can be up-scaled to other similar environments. 相似文献
20.
长江中下游丰富的新石器时代文化遗址,为研究该地区新石器时期气候环境变化、古人类活动和文化演化等提供了丰富的材料。浙江余姚田螺山遗址是河姆渡早期文化保存比较完整的一处新石器时代遗址。文章通过对田螺山遗址剖面植硅体、硅藻和炭屑等的分析,探讨了田螺山遗址河姆渡文化早期的原始农业和古人类活动的文化环境背景。7000～6600cal.aB.P.期间,植硅体和炭屑含量较低,淡水-半咸水硅藻丰富,推测为淡水或泻湖沉积环境,受海水影响较小; 从6600cal.aB.P.开始,水稻植硅体和炭屑含量增加说明田螺山先人已经开始大量种植水稻; 晚期（约6000cal.aB.P.后）海绵骨针和硅藻海水种含量的增长说明该时期田螺山地区明显受到海水影响。研究结果表明,河姆渡文化早期,田螺山地区就已经开始水稻栽培,原始农业形态基本是以稻作农业为主; 田螺山遗址河姆渡文化之前和之后都可能存在相对海面较高或受海水影响的时期,其与河姆渡文化在田螺山地区兴起与消失有着一定的关系。 相似文献