Soil-water behaviour of sandy soils under semi-arid conditions in the Duero Basin (Spain)     

Antonio Ceballos  Jos Mart&#x;&#x;nez-Fernndez  Fernando Santos  Pilar Alonso 《Journal of Arid Environments》2002,51(4):501

This paper examines the soil-water behaviour of sandy soils representative of a broad area in the Duero river basin (Spain), with semi-arid bioclimatic characteristics. Soil-moisture measurements of the first 25 cm of soil profile were taken using time domain reflectometry (TDR) methodology. The infiltration process was studied by means of field experiments combining rainfall simulations and TDR techniques. Finally, a set of hydrodynamic variables was calculated in the laboratory (i.e. available soil-water content, soil-water-retention curves and hydraulic conductivity).The average available soil-water content is 0·07 cm³ cm⁻³, in accordance with the predominance of the sandy textural fraction (85%). The rainfall simulation experiments show that infiltration prevails over overland flow, with a steady-state infiltration rate higher than rainfall application (40mmh⁻¹) in most cases; a low water-retention capacity was also observed. The evolution of soil-moisture over time indicates a close dependence on intra-annual rainfall variability due to the low water-retention capacity of sandy soils. With a maximum water-storage capacity of around 0·18 cm³ cm⁻³, the soils studied show high sensitivity to dry spells and may remain with <50% of the available soil-water content for several months during the year.  相似文献   

THE AVAILABILITY OF DISSOLVED ORGANIC PHOSPHORUS COMPOUNDS TO MARINE PHYTOPLANKTON   总被引：12，自引：0，他引：12  

洪华生  王海黎  黄邦钦 《中国海洋湖沼学报》1995,13(2):169-176

The availability of three dissolved organic phosphorus (DOP) compounds as nutrient sources for experimentalcultare of three algae was studied. Results indicated that these compounds could be utilized byalgae, and that dissolved inorganic phosphorus (DIP) was first to be uptaken when various forms ofphosphorus (DIP and DOP) co-existed. Dicrateria zhanjiangensis' uptake of sodium glycerophosphatewas faster than that of D-ribose-5-phosphate. The increase of sodium glycerphosphate had little effecton the maximum uptake rate(V_(max)) of Chlorella sp., but increased the semisaturation constant(K_s) remarkably;the photosynthesis rates(PR) of Dicrateria zhanjiangensis and Chlorella sp. were rarely affected byusing various forms of phosphorus in the culture experiments. The possible DOP pathways utilizedby algae are discussed.  相似文献   

一种具有SA预报能力的GPS KALMAN滤波器     

朱海  姬光荣  蔡明华 《中国海洋大学学报(自然科学版)》1996,(2)

对GPS定位中的SA误差作了系统辨识。表明：SA误差可用时变AR（p）模型表述，AR（p）的时变参数可由RLS算法结合F判据建立的AR（p）模型辨识机获得。用该方法获得的模型对SA误差进行预报。在剔除野值后精度在10m之内。还提出了一种将以AR（p）模型表述的SA误差加入GPSKALMAN滤波器的方法，可得到一种具有SA预报能力的GPSKALMAN滤波器。  相似文献   

格陵兰岛稀土矿资源潜力及对中国的可利用性评价     

刘青枰  赵元艺  刘春花 《地质通报》2019,38(8):1386-1395

格陵兰地处北极,是全球最大的岛屿,经历了约40亿年的地质构造演化,矿产资源极丰富,尤其是以重稀土元素为特色的稀土矿资源。前人主要集中研究格陵兰岛黑色和多金属矿产资源,较少涉及稀土资源。通过研究,为保护中国有限的稀土资源,给中方企业和地勘单位实施"走出去"政策在格陵兰寻找潜在稀土资源提供基础资料。收集资料发现,格陵兰岛的稀土矿床主要集中在西南部、南部、中东部、中西部,其类型有碳酸岩型、碱性岩型、古砂矿型,可能有IOCG型。格陵兰岛稀土矿资源潜力巨大,通过分析格陵兰岛地质资料确定了4个远景区,由2个Ⅰ级、1个Ⅱ级和1个Ⅲ级组成。下一步重点关注格陵兰岛南部和西南部的2个Ⅰ级远景区,其次关注中东部和中西部Ⅱ级和Ⅲ级远景区。从多方面考虑,格陵兰岛稀土矿资源可利用性评价良好,格陵兰岛的稀土元素矿床值得中国企业关注。  相似文献   

提升地理信息数据可获取性对促进我国经济发展的意义   总被引：4，自引：3，他引：1  

叶嘉安  朱家松 《地理信息世界》2004,2(4):1-4

本文在分析我国现有地理信息数据可获取性的现状和问题基础上,提出了对现行地理信息数据政策的一些看法和建议。在经济比较发达、对外比较开放的城市和地区设立“地理信息数据开放特区”的建议,可使GIS在民用和国民经济领域的应用更加合理合法化,使GIS技术在提高经济发展的同时,能够更多地为广大人民服务。  相似文献   

有机-中性化技术对旱作土壤镉有效性的长期影响     

杜葱远  林珍珠  梁巧凤  陈炎辉  王果 《福建地理》2009,(1):15-22

采用连续提取法测定了土壤中镉（Cd）的形态,以研究石灰或钙镁磷肥与猪粪或泥炭混施对田间条件下Cd污染土壤中Cd有效性的抑制效果．处理的第1年,猪粪使石灰对土壤Cd有效性的抑制率从18．2％提高到22．3％,使钙镁磷肥的抑制率从37．1％提高到50．8％;泥炭使石灰的抑制率从18．2％提高到57．1％,使钙镁磷肥的抑制率从37．1％提高到49．3％．处理的第4年,猪粪使石灰对土壤Cd有效性的抑制率从32．3％提高到44．2％,使钙镁磷肥的抑制率从38％提高到51．6％;泥炭使石灰的抑制率从32．3％提高到45．4％,使钙镁磷肥的抑制率从38％降低到8．2％．上述结果表明猪粪和泥炭在施用后第1年均可增强石灰和钙镁磷肥对土壤Cd有效性的抑制效果．到第4年,猪粪仍然促进了石灰和钙镁磷肥对Cd有效性的抑制效果,而泥炭增强了石灰的抑制效率但降低了钙镁磷肥的抑制效果．研究结果证明了有机-中性化技术对cd污染土壤的修复效果．石灰和钙镁磷肥大幅度提高了土壤Cd的碳酸盐结合态与专性吸附态,从而降低了土壤Cd的有效态（水溶态＋交换态）．  相似文献   

Biodiversity loss in benthic macroinfaunal communities and its consequence for organic mercury trophic availability to benthivorous predators in the lower Hudson River estuary, USA     

Daisuke Goto  William G. Wallace 《Marine pollution bulletin》2009,58(12):1909-1915

Organic mercury such as methylmercury is not only one of the most toxic substances found in coastal ecosystems but also has high trophic transfer efficiency. In this study, we examined implications of chronically altered benthic macroinfaunal assemblages for organic mercury trophic availability (based on organic mercury intracellular partitioning) to their predators in the Arthur Kill-AK (New York, USA). Despite low species diversity, both density and biomass of benthic macroinvertebrates in AK were significantly higher than those at the reference site. Disproportionately high biomass of benthic macroinvertebrates (mostly polychaetes) in the northern AK resulted in a more than twofold increase (‘ecological enrichment’) in the trophically available organic mercury pool. These results suggest that altered benthic macroinfaunal community structure in AK may play an important role in organic mercury trophic availability at the base of benthic food webs and potentially in mercury biogeochemical cycling in this severely urbanized coastal ecosystem.  相似文献   

Physiological disturbance of the Manila clam,Ruditapes philippinarum,by altered environmental conditions in a tidal flat on the west coast of Korea     

《Marine pollution bulletin》2014,78(1-2):137-145

To examine the influence of habitat alteration by tideflat reclamation on the physiological ecology of Ruditapes philippinarum, seasonal variations in its condition, gross biochemical composition, and reproductive cycle were compared for a yearly cycle between a reclaimed flat (Gomsohang, GS) and a natural flat (Hajun, HJ) in Gomso Bay, Korea. Concentrations of chlorophyll a and seston (as well as its energy value as food available to the clam) were consistently higher at HJ than at GS. Condition, dry tissue weight, and energy reserves (proteins and carbohydrates) of the clams were much higher at HJ than at GS during spring–summer, when fast growth and gametogenic development occur. Furthermore, their spring gametogenic development and spawning were advanced at HJ compared with GS. Our results suggest that the Manila clam encounters nutritionally stressful environmental conditions in altered habitats after tideflat reclamation that lead to lowered nutrient accumulation and a changing reproductive cycle.  相似文献   

High Ni Levels in Soil Can Modify Growth Performance and Mineral Status of Wheat Cultivars          下载免费PDF全文

Muhammad Sabir  Khalid Rehman Hakeem  Tariq Aziz  Muhammad Zia‐ur‐Rehman  Irfan Rashid  Munir Ozturk 《洁净——土壤、空气、水》2014,42(9):1263-1271

  相似文献   

Desertification Reversion in Relation to Land Use Change and Climate in Naiman County, Inner-Mongolia, China     

XueYong Zhao  XiaoAn Zuo  Gang Huang  YingXin Huang  ShaoKun Wang  YaYong Luo  WenDa Huang  Hao Qu  Wei Mao  Jie Lian 《寒旱区科学》2010,2(1):0015-0020

Analyses of desertified land and land use change in Naiman County of Inner-Mongolia showed that there was a fluctuated in-crease of rain-fed cropland in the period from 1951 to 1960, then decreased until the middle of the 1990＇s, then increased again, while irrigated cropland consistently increased. The woodland and build-up land consistently increased while grassland area de-creased. The area of water body increased from 1975 to 1995 and then decreased while river beach decreased. Wetland change fluctuated with a maximum of 303.53km2 in 1995 and a minimum of 62.08 km2 in 2002. Invasion of cropland into river beach does not only change land coverage on the beach, but also the hydrological process of the river systems and deeply influence wa-ter availability. The correlation between cropland and underground water table is negative and significant. Increase of irrigated cropland is the primary cause of water availability reduction. Water table reduction is negatively correlated to cropland. The total desertified land has decreased since 1975. A rapid increase occurred before 1959, but it is difficult to assess the change of deserti-fication due to lack of data from 1959 to 1975. Changes of different types of desertified lands were different. There is no signifi-cant correlation between land use and different types of desertified land, but there is a significant negative correlation between woodland and total desertified land. The correlation between grassland and total desertified land is positive and significant. There is a significant correlation between different land cover and key factors such as water body and annual precipitation, river beach and runoff, area of shifting dune and annual precipitation, and cropland and underground water table. Desertification reversion in Naiman County is fragile and will be even much more fragile due to population growth, rapid land use and climate change. This will lead to continued invasion of irrigated cropland into more fragile ecosystems and reduction of water availability.  相似文献