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11.
根据化石组合和火山岩的同位素年龄,并结合区域火山岩资料,本文厘定江苏镇江(?)山火山岩系的时代属早白垩世晚期至晚白垩世早期,而火山活动主要是在晚白垩世,进而论证了下扬子区在晚白垩世期间普遍有零星的酸性岩浆活动。 相似文献
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不同施肥处理对红壤晚稻田CH_4排放的影响 总被引:1,自引:1,他引:0
选取不同施肥处理的双季稻田为研究对象,采用静态箱-气相色谱法对晚稻田CH4排放通量进行观测。结果表明,与不施肥对照(T1)相比,各施肥处理CH4排放通量均有不同程度增加。其中秸秆还田+化肥处理(T5)CH4平均排放通量为9.96mg.m-2.h-1,比增氮磷施肥处理(T4)和对照分别增加26.1%和120.0%;平衡施肥处理(T2)和减氮磷施肥处理(T3)CH4平均排放通量比对照增加20%左右。说明施化肥可能提高水稻植株运输能力,进而增加CH4排放,但并未发现施化肥处理(T1、T2、T3和T4)之间CH4排放存在显著差异。同时对相关环境因素的分析表明,各处理CH4排放通量与土壤5cm深处温度间存在指数函数关系,并与田间水层厚度呈正相关关系(P<0.05)。综合考虑温室效应和稻谷产量,认为T2为推荐施肥方式,即N、P2O5和K2O施用量分别为180、90和135kg.hm-2,在插秧前1d施入占总N量70%的碳铵和全部磷肥、钾肥(过磷酸钙和氯化钾)作为基肥,并在分蘖期(2008年7月19日)追施占总N量30%的尿素。 相似文献
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内蒙古巴尔哲碱性花岗岩稀有稀土矿床地质特征及成因探讨 总被引:1,自引:0,他引:1
内蒙古巴尔哲特大型碱性花岗岩稀有稀土矿床是国内首次发现的一种新类型工业矿床,其规模居亚洲第三位.含矿岩体为燕山期碱性花岗岩,岩体普遍矿化,岩体即是矿体,矿石品位富、稀有稀土元素种类多,其共生伴生矿物多达44种,工业矿物以羟硅铍钇铈矿、烧绿石、铌铁矿、锌日光榴石为主. 相似文献
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A 12-month prospective population study of antenatal patients was undertaken in a large district general hospital to assess ultrasound scanning in late pregnancy for the detection of non-lethal fetal renal abnormalities. The rate of false-negative antenatal scans during the study period was also assessed. Both 18–20 and 28–32 weeks' gestational scans were performed on 6497 pregnant women. Forty fetuses with a suspected abnormality were referred for postnatal examination and 29 neonates were found to have renal abnormalities. Of these, 21 were significant and eight were likely to be extrarenal pelves. In six, there was evidence of an abnormality at the early scan. Nine children, seven with reflux, presented within the study period, all with preceding normal antenatal scans. The incidence (0·46 per cent) of structural renal abnormalities is similar to that reported previously. A late scan is necessary for the antenatal detection of non-lethal renal abnormalities. 相似文献
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Johnny Boggs Ge Sun David Jones Steven G. McNulty 《Journal of the American Water Resources Association》2013,49(1):132-150
Boggs, Johnny, Ge Sun, David Jones, and Steven G. McNulty, 2012. Effect of Soils on Water Quantity and Quality in Piedmont Forested Headwater Watersheds of North Carolina. Journal of the American Water Resources Association (JAWRA) 1‐19. DOI: 10.1111/jawr.12001 Abstract: Water quantity and quality data were compared from six headwater watersheds on two distinct soil formations, Carolina Slate Belt (CSB) and Triassic Basins (TB). CSB soils are generally thicker, less erodible, and contain less clay content than soils found in TB. TB generated significantly more discharge/precipitation ratio than CSB (0.33 vs. 0.24) in the 2009 dormant season. In the 2009 growing season, TB generated significantly less discharge/precipitation ratio than CSB (0.02 vs. 0.07). Over the entire monitoring period, differences in discharge/precipitation ratios between CSB and TB were not significantly different (0.17 vs. 0.20, respectively). Storm‐flow rates were significantly higher in TB than CSB in both dormant and growing season. Benthic macroinvertebrate biotic index scores were excellent for all streams. Nutrient concentrations and exports in CSB and TB were within background levels for forests. Low‐stream nitrate and ammonium concentrations and exports suggested that both CSB and TB were nitrogen limited. Soils appear to have had a significant influence on seasonal and storm‐flow generation, but not on long‐term total water yield and water quality under forested conditions. This study indicated that watersheds on TB soils might be more prone to storm‐flow generation than on CSB soils when converted from forest to urban. Future urban growth in the area should consider differences in baseline hydrology and effects of landuse change on water quantity and quality. 相似文献
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Geert Munnichs 《Journal of Agricultural and Environmental Ethics》2004,17(2):113-130
This article discusses the conditions under which the use of expert knowledge may provide an adequate response to public concerns about high-tech, late modern risks. Scientific risk estimation has more than once led to expert controversies. When these controversies occur, the public at large – as a media audience – faces a paradoxical situation: on the one hand it must rely on the expertise of scientists as represented in the mass media, but on the other it is confused by competing expert claims in the absence of any clear-cut standard to judge these claims. The question then arises, what expertise can the public trust? I argue that expert controversies cannot be settled by appealing to neutral, impartial expertise, because each use of expert knowledge in applied contexts is inextricably bound up with normative and evaluative assumptions. This value-laden nature of expert contributions, however, does not necessarily force us to adopt a relativist conception of expert knowledge. Nor does it imply active involvement of ordinary citizens in scientific risk estimation – as some authors seem to suggest. The value-laden, or partisan, nature of expert statements rather requires an unbiased process of expert dispute in which experts and counter-experts can participate. Moreover, instead of being a reason for discrediting expert contributions, experts' commitment may enhance public trustworthiness because it enlarges the scope of perspectives taken into account, to include public concerns. Experts who share the same worries as (some of) the public could be expected to voice these worries at the level of expert dispute. Thus, a broadly shaped expert dispute, that is accessible to both proponents and opponents, is a prerequisite for public trust. 相似文献
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In the `Des Vieux Arbres' ecological reserve situated within northwestern Québec, 40 band dendrometers were installedon 7 of the major boreal tree species. The late Spring–early Summer daily radial activity registered in 1997 was related todaily weather variables. For each tree species, the daily mean i) cumulative radial increment and ii) radial activity indexedseries obtained by first-difference standardization were analyzed. The results indicate the existence of strong similarities among the 7 species. All showed strong synchronousfluctuations in radius during late winter and early spring. Thisperiod ended with a short but sharp increase in radial increments that marked the passage of water into the stem. Thisinitial swelling, less obvious in Pinus species was followed by a prolonged period of little change in radial activity. Meteorological data indicated that air temperature waspositively related to stem swelling during the late winter–earlyspring period. Both air and soil temperatures became negatively related to radial expansion once the passage of water has occurred in the stem. Starting in early June, all species registered a sustained increase in radial increments possiblyassociated with active cell division. After this, radial expansion was negatively related to air temperature and positively to rainfall. 相似文献