中国西南部东北寨和金牙金矿床的矿物成分     

Wang  KR 毛家衢 《山东地质信息》1997,(2):17-23

对中国西南部两个金矿床的矿物成分，进行了考察，这两个金矿床含有全部是显微或次显微颗粒的金或包裹体金。它们含有难以提炼的或低品位矿石，与美国内华达州卡林型相似。对采自两个矿床的矿石样品的矿物成分研究（如质子探针分析、扫描电子显微镜分析、电子探针分析、Ｘ－射线衍射分析、矿石显微镜研究）表明，最主要的含金矿物，在东北寨矿床是黄铁矿，在金牙矿床是毒砂和黄铁矿。两矿床中的金均与Ａｓ、Ｓ和Ｆｅ密切相关。  相似文献   

CO2和温度对皮马棉发育的影响     

Redd.  KR 刘荣花 《气象与环境科学》1997,(1):26-28

预报作物对大气ＣＯ２浓度变化和全球可能变暖的响应，是重要问题。ＣＯ２对作物发育过程的影响，是ＣＯ２和其它主要气候变量对作物发育的相互作用的结果，对此还报道甚少。本项试验的目的是要确定ＣＯ２环境的变化及ＣＯ２与温度间的相互作用对皮马棉发育速度的影响。皮马棉（ＧｏｓｙｐｉｕｍｂａｒｂａｄｅｎｓｅＬ．ｃｖ．ｓ－６）从播种开始就生长于有日光照射的作物生长箱内。白天／夜间气温控制在２０／１２～４０／３２℃，每隔５℃一个处理。白天ＣＯ２保持在３５０或７００μＬＬ－１。在第二个试验中，温度维持在３０／２２℃（白天／夜间），ＣＯ２为３５０、４５０、７００μＬＬ－１。并测定了主茎节发育所需天数、出苗到初现蕾的日数、营养枝和果枝数、座果数、结铃和现蕾数以及为植株所能保持的蕾铃数。发现主茎节的形成速率、现蕾和现花的早晚对大气ＣＯ２浓度不敏感，但对温度很敏感。果枝长出之前节位的发育要比果枝长出之后的节位发育慢。不同ＣＯ２浓度对长出节的快慢没有影响。分枝数目对温度和ＣＯ２都敏感。相比之下，生长在高ＣＯ２下的植株由于提供了一个较大的光合作用汇，其下部果枝上的棉铃数要多些。这也许就是我们观察到生长在高浓度ＣＯ２下的棉株上层节的铃数减少的  相似文献   

Does historical exposure to hydrocarbon contamination alter the response of benthic communities to diesel contamination?     

Carman KR  Fleeger JW  Pomarico SM 《Marine environmental research》2000,49(3):255-278

A microcosm experiment was used to compare the influence of diesel contamination on two benthic salt-marsh communities, one chronically exposed to petroleum hydrocarbons for decades (Louisiana [LA]) and the other relatively uncontaminated (Mississippi [MS]). Initial meiofaunal community composition of the two sites was similar. Higher organic content of MS sediments should have reduced bioavailability, and thus the toxicity of hydrocarbons relative to the LA site. Nevertheless, although responses to diesel contamination at the two sites were generally qualitatively similar, a species-specific and several community-response variables were influenced to a much greater degree in the MS community. In particular, the abundance of total nauplii, ostracods, and copepods were negatively impacted to a greater extent in MS than in LA, as was grazing by ostracods on benthic microalgae. Nematode:copepod ratios in contaminated sediments were much higher in MS than in LA sediments. Pseudostenhelia wellsi (a benthic copepod) nauplii suffered greater adverse effects of diesel in MS than in LA. We conclude that the MS community was more sensitive to diesel contamination than was the LA community. The differential sensitivity is presumably a manifestation of different tolerances to hydrocarbon contaminants, mediated by a higher proportion of more tolerant species and/or increased tolerance among individual species in LA. Although the MS site was more sensitive to diesel contamination, qualitative response of the LA and MS communities were similar, and comparable to previous studies of diesel contamination. The spatial and temporal consistency of diesel impacts on salt-marsh communities suggests that hydrocarbon contamination results in predictable community responses. Specifically, crustacean (e.g. copepods, ostracods, and nauplii) benthos are most sensitive to hydrocarbons. Reductions in abundance and grazing activity of crustaceans leads to enhanced algal biomass, reduced copepod diversity, and alters competitive interactions among meiofauna.  相似文献   

玻利维亚一个巨大的斑岩银矿波托西省里科山矿床     

Sutt.  KR  张新安 《国土资源信息化》1989,(2):21-22

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巴西的金山—Morro DE Ouro由于无需剥离,品位一致...     

Sutt.  KR 杨玉波 《世界地质》1992,11(4):114-117

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美国威斯康星州中部地下水的年龄指示物—氚     

Brad.  KR 王伟礼 《水文地质工程地质译丛》1993,(2):15-23

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Is one an upper limit for natural hydraulic gradients?     

Hart DJ  Bradbury KR  Gotkowitz MB 《Ground water》2008,46(4):518-520

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Assessing background ground water chemistry beneath a new unsewered subdivision     

Wilcox JD  Bradbury KR  Thomas CL  Bahr JM 《Ground water》2005,43(6):787-795

Previous site-specific studies designed to assess the impacts of unsewered subdivisions on ground water quality have relied on upgradient monitoring wells or very limited background data to characterize conditions prior to development. In this study, an extensive monitoring program was designed to document ground water conditions prior to construction of a rural subdivision in south-central Wisconsin. Previous agricultural land use has impacted ground water quality; concentrations of chloride, nitrate-nitrogen, and atrazine ranged from below the level of detection to 296 mg/L, 36 mg/L, and 0.8 microg/L, respectively, and were highly variable from well to well and through time. Seasonal variations in recharge, surface topography, aquifer heterogeneities, surficial loading patterns, and well casing depth explain observed variations in ground water chemistry. This variability would not have been detected if background conditions were determined from only a few monitoring wells or inferred from wells located upgradient of the subdivision site. This project demonstrates the importance of characterizing both ground water quality and chemical variability prior to land-use change to detect any changes once homes are constructed.  相似文献   

Natural turbidity variability and weather forecasts in risk management of anthropogenic sediment discharge near sensitive environments     

Orpin AR  Ridd PV  Thomas S  Anthony KR  Marshall P  Oliver J 《Marine pollution bulletin》2004,49(7-8):602-612

Coastal development activities can cause local increases in turbidity and sedimentation. This study characterises the spatial and temporal variability of turbidity near an inshore fringing coral reef in the central Great Barrier Reef, under a wide range of natural conditions. Based on the observed natural variability, we outline a risk management scheme to minimise the impact of construction-related turbidity increases. Comparison of control and impact sites proved unusable for real-time management of turbidity risks. Instead, we suggest using one standard deviation from ambient conditions as a possible conservative upper limit of an acceptable projected increase in turbidity. In addition, the use of regional weather forecast as a proxy for natural turbidity is assessed. This approach is simple and cheap but also has limitations in very rough conditions, when an anthropogenic turbidity increase could prove fatal to corals that are already stressed under natural conditions.  相似文献   

Results from a sixteen year study on the effects of oiling from the Exxon Valdez on adult pink salmon returns     

Brannon EL  Maki AW  Moulton LL  Parker KR 《Marine pollution bulletin》2006,52(8):892-899

For sixteen years following the 1989 Exxon Valdez oil spill adult returns of pink salmon in Prince William Sound, Alaska were monitored to assess spill effects on survival. No evidence of spill effects was detected for either intertidal or whole-stream spawning fish. From 1989 through 2004 mean densities for oiled and reference streams tracked each other, illustrating similar responses of oiled and reference stream adult populations to naturally changing oceanographic and climactic conditions. Hatchery fish strayed into the study streams, but similar incursions occurred in oiled and reference streams, and their presence was compensated for to eliminate their influence on determining the success of the returning natural populations. These results, showing no detectable effects of oiling on pink salmon spawning populations, are supported by published field studies on pink salmon incubation success in oiled streams.  相似文献