Nature2010-Directional water collection on wetted spider silk

长江流域潜在蒸发量和实际蒸发量的关系王艳君;刘波;翟建青;苏布达;罗勇;张增信【摘要】For the scientific issue of "evaporation paradox", the relationship between actual and potential evaporation in the Yangtze River basin was studied in this paper. The results show that roughly when the dryness index R＜0.8, the actual evaporation is positively correlated with potential evaporation; when 0.8＜R＜1.0, their relationship is uncertain; and when R ＞1.0, their relationship is complementary.%针对“蒸发悖论”科学问题,从长江流域实际蒸发量变化的原因着手,探讨实际蒸发量与潜在蒸发量之间的关系.研究结果表明:一般情况下当干燥度指数R＜0.8时,实际蒸发量与潜在蒸发量为明显的正相关关系,当0.8＜R＜1.0时,实际蒸发量与潜在蒸发量主要表现为不确定关系,当R＞1.0时,实际蒸发量与潜在蒸发量为明显的互补关系.【期刊名称】《气候变化研究进展》【年(卷),期】2011(007)006【总页数】7页(P393-399)【关键词】蒸发悖论;蒸发互补;潜在蒸发量;实际蒸发量;长江流域【作者】王艳君;刘波;翟建青;苏布达;罗勇;张增信【作者单位】南京信息工程大学,南京210044;河海大学,南京210024;中国气象局国家气候中心,北京100081;中国气象局国家气候中心,北京100081;中国气象局国家气候中心,北京100081;南京林业大学,南京210042【正文语种】中文【中图分类】P426.2全球变暖已毋庸置疑。

**Nature's Balance**In the grand scheme of existence, the concept of Nature's Balance is not merely a phenomenon to be observed but a profound principle that governs the very essence of life on our planet.The words of the Roman philosopher Seneca ring true: "We are not born for ourselves alone; our country, our friends, have a share in us." This statement can be extended to our relationship with nature, as we are an integral part of a complex ecological web, not isolated entities.Nature's Balance is a delicate equilibrium maintained by countless interrelated factors. Take, for instance, the food chain. Predators keep prey populations in check, ensuring that no single species dominates and disrupts the ecosystem. The decline of wolves in certain areas has led to an overabundance of deer, which, in turn, has had detrimental effects on plant life.Another aspect of this balance is the water cycle. Rainfall replenishes rivers and lakes, which evaporate to form clouds and bring precipitation once again. This continuous process is essential for the survival of all living beings. The construction of dams and excessive water extraction for agriculture and industry can disrupt this cycle, causing droughts in some regions and floods in others.Climate, too, plays a crucial role in maintaining Nature's Balance. Even slight variations in temperature and precipitation patterns can have far-reaching consequences. The melting of polar ice caps due to global warming not only raises sea levels but also alters ocean currents and weather patterns worldwide.Despite the inherent resilience of nature, human activities have increasingly tipped the scales. Deforestation for agriculture and urbanization destroys habitats and reduces biodiversity. The excessive use of chemical fertilizers and pesticides pollutes soil and water, harming both wildlife and human health.Yet, there is hope. Conservation efforts around the world offer glimmers of a return to balance. Protected areas like national parks and wildlife reserves provide sanctuaries for endangered species to recover. Initiatives to promote sustainable agriculture and energy sources show that we can coexist with nature without causing irreparable harm.In conclusion, Nature's Balance is a precious and fragile state that wemust strive to preserve. As the ancient Indian saying goes, "When the last tree is cut, the last fish is caught, and the last river is polluted; when to breathe the air is sickening, you will realize, too late, that wealth is not in bank accounts and that you can't eat money." It is our responsibility to act now and ensure that future generations inherit a world in harmony with nature.。

小学上册英语第二单元真题试卷英语试题一、综合题(本题有100小题，每小题1分，共100分.每小题不选、错误，均不给分)1. A snail leaves a ______ (黏糊糊的) trail behind.2.My mom loves __________ (参与学校活动).3.Which vegetable is orange and long?A. PotatoB. CarrotC. BroccoliD. TomatoB4.The signing of the Treaty of Tordesillas divided the _____ territories.5.The ostrich lays the largest _______ (鸟蛋).6.Which season is cold?A. SummerB. AutumnC. WinterD. SpringC7.What do you call a person who studies human cultures?A. AnthropologistB. SociologistC. ArcheologistD. All of the aboveD8.The ______ is a skilled architect.9.I enjoy playing ________ (视频游戏) on my console.10.I love to eat ______ at lunchtime.11.The __________ (历史的回响) reverberates through ages.12.The flower pot is ______ (colorful) and bright.13.My friend, ______ (我的朋友), has a pet rabbit.14.The bear eats berries and fish in the ____.15.What do you call a baby goose?A. GoslingB. DucklingC. ChickD. CalfA16.What do we call the uppermost layer of the Earth?A. CrustB. MantleC. CoreD. LithosphereA17.What is the term for a young cassowary?A. ChickB. CalfC. KitD. PupA18.What do you call an animal that is active at night?A. DiurnalB. NocturnalC. CrepuscularD. SeasonalB19.The _____ (农场) is far away.20.What do we call the part of a plant that attracts pollinators?A. PetalB. LeafC. StemD. RootA21.What do we call the young of a cow?A. CalfB. KidC. LambD. Foal22. A chemical that helps to speed up a reaction is called a ______.23.What is the opposite of sweet?A. SourB. BitterC. SpicyD. Salty24.The owl’s eyes are very ______ (大) and round.25.What do you call the protective covering of a seed?A. ShellB. HuskC. PodD. CoatD26.What is 50 - 25?A. 15B. 20C. 25D. 3027.What do we call a massive star that has exhausted its nuclear fuel?A. Red GiantB. White DwarfC. Neutron StarD. Black Hole28.What is the opposite of happy?A. SadB. AngryC. ExcitedD. Tired29.The pufferfish can inflate to protect itself from _______ (捕食者).30.What is the name of the famous shipwreck that became a movie?A. TitanicB. LusitaniaC. Andrea DoriaD. Britannic31.What is 20 15?A. 3B. 4C. 5D. 6C32.What is the capital of Thailand?A. BangkokB. PhuketC. Chiang MaiD. PattayaA33.The ________ loves to swim in the pond.34.I wear ______ (glasses) to see better.35.I have a __________ in my class. (朋友)36.I enjoy _______ (与家人一起)露营。

俯冲带变质过程中的含碳流体刘景波【摘要】俯冲带含碳岩石通过俯冲过程的变质反应生成了含碳水流体、富硅酸盐的超临界流体和含碳熔体.不同类型流体的形成与岩石成分和岩石经历的温压条件相关.岩石中碳酸盐矿物脱碳反应的温压条件取决于岩石起初的流体成分:有水存在时,反应发生在低温条件下.在高压条件下,碳酸盐矿物在水或含盐水流体的溶解是生成含碳流体重要的机制,其导致的碳迁移作用可能超过脱碳变质反应的作用.高温条件下,含碳岩石的部分熔融可以生成含碳的熔体,这在热俯冲环境和俯冲带岩石底辟到上覆地幔的情况下是碳迁移重要载体.富硅酸盐的超临界流体可能是在第二临界端点上形成的超临界流体,目前在超高压岩石中观察到的非花岗质成分的多相固体包裹体被认为是这种流体结晶的产物,然而对其理解尚存在很多问题,需要进一步的实验研究.地表含碳岩石在俯冲带被带到深部,俯冲带地温特征的不同导致了不同类型含碳流体的形成,这些流体运移至上覆地幔引起岩石部分熔融产生含碳的岛弧岩浆,岩浆喷出到地表释放了其中的碳,这构成了俯冲带-岛弧系统的碳循环.【期刊名称】《岩石学报》【年(卷),期】2019(035)001【总页数】10页(P89-98)【关键词】俯冲带;碳循环;含碳流体;多相包裹体;熔体包裹体【作者】刘景波【作者单位】中国科学院地质与地球物理研究所,岩石圈演化国家重点实验室,北京100029;中国科学院大学地球与行星科学学院,北京100049【正文语种】中文【中图分类】P542.5;P588.3俯冲带-岛弧系统的碳循环模式可以概括这样一种图景：含碳岩石通过俯冲过程的变质作用形成含碳流体，含碳流体运移至上覆地幔楔交代其中的岩石导致部分熔融产生含碳的岛弧岩浆，岩浆上升到地表将碳以CO2形式释放到地表的物质圈层中去。

岛弧火山作用释放的CO2在碳同位素组成上证明了这种过程的存在。

岛弧岩浆的δ13 C在-0.1‰～-11.6‰之间，这种成分的碳是俯冲带的碳酸盐（δ13 C＝0‰）、蚀变大洋玄武岩及其下覆地慢岩的碳（δ13 C＝-5‰）和俯冲岩石中的有机碳（δ13 C＝-30‰）混合的结果（Sano and Marty，1995；Shaw et al.，2003；De Leeuw et al.，2007）。

小学上册英语第6单元真题(含答案)英语试题一、综合题(本题有100小题，每小题1分，共100分.每小题不选、错误，均不给分)1.We have a ________ (家庭聚会) every year.2.What is the term for a young quokka?A. KitB. PupC. CalfD. Chick答案:c3.I have a _____ (跳绳) that I use to exercise. 我有一根用来锻炼的跳绳。

4.The garden is full of ________ (植物).5.The __________ (历史的启示) can spark innovation.6.The chemical symbol for barium is ______.7.What is the opposite of "clean"?A. DirtyB. WetC. SmallD. Tall答案:A Dirty8.I enjoy _______ (看书) at the library.9.The ant can lift objects many times its _______.10.What is the capital of Mozambique?A. MaputoB. BeiraC. NampulaD. Tete答案: A11.Which fruit is red and often mistaken for a vegetable?A. BananaB. TomatoC. OrangeD. Grape答案: B12.The process of hydrolysis uses ______ to break bonds.13.What do you call the season when leaves fall from trees?A. SpringB. SummerC. FallD. Winter答案:C14.She likes to swim in the ___. (lake)15.My cousin is very __________ (有条理的) in her studies.16.Vinegar is an example of an _______.17.The sun rises in the ______ (east).18.She is drawing a ________ (图画).19.The _____ (lettuce) grows quickly in cool weather.20.What is the name of the famous American author known for his adventure novels?A. Mark TwainB. Ernest HemingwayC. F. Scott FitzgeraldD. John Steinbeck答案:A21. A ______ is a type of animal that can run very fast.22.The vegetables are very ___. (fresh)23. (20) River is known as the "Yellow River." The ____24.The ______ (小鸟) chirps cheerfully in the ______ (早晨).25. A sunny day is great for flying a __________. (风筝)26.The _______ can help create a sustainable environment.27.The ________ (文化节) highlights traditions.28.Baking soda is a common ______ used in baking.29.The capital of Armenia is ________ (亚美尼亚的首都是________).30. A polymer is a large molecule made up of many ________.31.The ______ is known for her support of the arts.32.I saw a _______ (蝴蝶) resting on a flower.33.The capital of Libya is _____.34.I like to visit the ______.35. A _______ (小水獺) plays in the river.36.What do you call the art of making paper flowers?A. OrigamiB. QuillingC. PapercraftD. Floral Design答案: A37.The process of combining two or more elements to form a compound is called_______.38.What do you call a fruit that is usually red and grows on a vine?A. PotatoB. TomatoC. CarrotD. Cucumber答案: B39.The _______ (鲸鱼) sings beautiful songs.40.The __________ is a famous city known for its canals. (威尼斯)41.My favorite animal is the _________ (大象).42.I love to visit ______ (自然保护区) to learn about wildlife and conservation efforts. It’s important to protect our planet.43. A ______ is a geographical area characterized by its unique features.44.I have a pet _____ that likes to chase balls.45._____ (落叶树) lose their leaves in the winter.46. A chemical reaction can create a new _______.47.I tell my __________ about my day. (妈妈)48.The process of turning a liquid into a gas is called ______.49.Abraham Lincoln was the ________ president of the United States.50.What do you call the study of the Earth?A. GeographyB. GeologyC. BiologyD. History答案: A51.In a chemical reaction, the substances that are produced are called _____.52.What is the term for the outer layer of the Earth?A. CoreB. MantleC. CrustD. Surface答案:c53.My brother loves going to ____ (amusement parks).54.ayas are famous for their ________ (雪山). The Hima55.I see a spider on the ___. (wall)56.I enjoy ________ (旅行) with my family.57.The term "viscosity" refers to a liquid's _______ to flow.58.Chemical reactions can be affected by _____, concentration, and surface area.59.In a chemical equation, reactants are found on the ______.60.The _____ is known for its spiral shape.61.I want to ________ (learn) English.62.My _____ (邻居) is very nice.63.The __________ (历史的协作) encourages partnership.64.George Washington was the commander of the Continental ________.65. A _______ (小孔雀) displays its feathers proudly.66.I have a toy _______ that can jump high and far, bringing me joy.67. A chemical reaction can produce a precipitate from ______.68.In ancient Rome, people used to watch _____ (gladiator) fights in the arena.69.I enjoy _______ (参加) sports activities.70.The __________ is essential for understanding the geology of an area.71. Age marks the beginning of human ________ (文明). The Suez72. A ________ (有机农业) avoids chemicals.73.My friend is a ______. He loves to read comics.74. A _____ can tell us about the history of our solar system.75.The birds are ______ in the bright blue sky. (flying)76. A ____ hops quickly and has large ears.77.I like to _______ (写作) stories.78.Hawaii is a group of ________ (夏威夷是一组________) in the Pacific Ocean.79.The antelope leaps gracefully across the _____.80.What is the capital of the Solomon Islands?A. HoniaraB. SuvaC. TarawaD. Funafuti答案: A. Honiara81.The _____ (小兔) hops in the grass.82.I like to ___ new things. (discover)83.The ______ is a symbol of peace.84.The __________ (历史的探索) invites curiosity.85.In a covalent bond, atoms share ______.86.The __________ (国家公园) protects natural beauty.87.The tortoise is much _________ than the hare. (慢)88.I think it's essential to be respectful to __________.89.Photosynthesis is how plants make their own ________.90.What is the freezing point of water?A. 0 degrees CelsiusB. 32 degrees CelsiusC. 100 degrees CelsiusD. 50 degrees Celsius答案:A.0 degrees Celsius91. A ____ is often found swimming in ponds and has smooth skin.92. A _______ can be used to demonstrate the principles of physics.93.The capital of Macedonia is __________.94.The country famous for chocolate is ________ (以巧克力闻名的国家是________).95.I love watching the ________ (星星) at night.96.What is the name of the famous novel written by George Orwell?A. Brave New WorldB. Moby DickC. 1984D. Animal Farm答案: C97.What is the capital of Iceland?A. OsloB. ReykjavikC. HelsinkiD. Copenhagen答案:B98.My brother is passionate about __________ (科学).99. A polymer is a large molecule made of many ______. 100.________ (生态影响) shapes landscapes.。

西双版纳绞杀植物斜叶榕的水分利用策略*王平元1刘文杰1李金涛1，2（1中国科学院西双版纳热带植物园，云南勐仑666303；2中国科学院研究生院，北京100049）摘要以斜叶榕为研究对象，通过测定其不同生长阶段木质部与各潜在水源的稳定氢、氧同位素组成，以及土壤水分含量、土壤水势、叶片水势等参数，揭示西双版纳地区不同生长阶段的绞杀榕（斜叶榕）在不同季节的水分利用策略.结果表明：浅层土壤（10 50cm ）的水势在干热季与雾凉季变化较大，较深土壤（51 120cm ）的水势在各季节无明显变化；雾凉季与干热季的土壤含水量之间无显著差异（P =0.64）；植物黎明前叶片水势与中午叶片水势随不同生长阶段而异；根据木质部水与各潜在水源的稳定氧同位素以及植物水势等其他参数判定，浅层土壤水是斜叶榕全年最主要的水分来源，不同生长阶段的斜叶榕在不同季节采取了不同的水分利用策略来应对环境的变化.关键词稳定同位素水分利用策略土壤水势叶片水势斜叶榕西双版纳文章编号1001－9332（2010）04－0836－07中图分类号Q948文献标识码AWater use strategy of Ficus tinctoria in tropical rainforest region of Xishuangbanna ，South-western China.WANG Ping-yuan 1，LIU Wen-jie 1，LI Jin-tao 1，2（1Xishuangbanna Tropical Bo-tanical Garden ，Chinese Academy of Sciences ，Menglun 666303，Yunnan ，China ；2Graduate Univer-sity of Chinese Academy of Sciences ，Beijing 100049，China ）.-Chin.J.Appl.Ecol .，2010，21（4）：836－842.Abstract ：Based on the measurement of the stable isotope ratios of hydrogen and oxygen in soil ，fog ，rain ，and plant non-photosynthetic tissues ，as well as the gravimetric soil water content ，soilwater potential ，and leaf water potential ，this paper studied the water use strategy of F.tinctoria at its different life stages in Xishuangbanna of Southwestern China.The water potential in shallow soil layer （10－50cm ）had a greater change between hot-dry season and foggy season ，whereas that indeeper soil layer （51－120cm ）had less change during the seasons.No significant difference was observed in the soil water content between foggy season and hot-dry season.The leaf water potentialat predawn and midday varied with life stage.From the measurement of the stable isotope ratios and other parameters ，it was found that shallow soil water was the main water source for F.tinctoria ，and F.tinctoria had different water use strategy at its different life stages.Key words ：stable isotope ；water use strategy ；soil water potential ；leaf water potential ；Ficus tinc-toria ；Xishuangbanna.*中国科学院“西部之光”人才计划项目和国家自然科学基金项目（30770368）资助.通讯作者.E-mail ：pingyuan0920@ 2009-06-05收稿，2010-02-04接受.稳定同位素技术作为生态学研究的一种重要手段，近年来在生态学的诸多领域得到了广泛的应用.由于同位素分馏过程的存在，自然界中的不同水源具有不同的同位素组成［1］.而在植物体内，除了一些排盐植物外［2］，在植物根系对土壤水分的吸收过程中，稳定氢氧同位素一般不发生分馏；水分在被植物根系吸收后沿木质部向上运输是通过液流方式进行的，不存在汽化现象，一般在植物体内不存在稳定氢氧同位素分馏现象［3－5］.因此，植物木质部水分的同位素组成能反映出植物利用不同水源的稳定同位素信息.如果不同来源的同位素组成差异显著，就可以通过对比植物木质部水分与各种水源的同位素组成确定植物究竟利用哪些来源的水分［6］.日趋成熟的稳定同位素示踪技术为植物在不同季节从不同深度土壤获取水分的研究提供了捷径，国内外有许多学者利用稳定同位素技术对不同生态系统的植物水分利用策略进行了研究，如Valentini 等［7］对不同生应用生态学报2010年4月第21卷第4期Chinese Journal of Applied Ecology ，Apr.2010，21（4）：836－842活型的植物研究发现，常绿地中海树种趋于利用雨水（浅层土壤中的水），而落叶树种则几乎毫无例外地依赖于地下水；Field等［8］对半附生植物Didymo-panax pittieri进行研究发现，该植物在其不同生长阶段采取了不同的水分获取策略，即：完全附生阶段从雾水和附生苔藓层中获取水分，乔木阶段从土壤中获取水分，而半附生阶段则同时采取以上两种方式.榕树是桑科（Moraceae）榕属（Ficus）植物的总称，主要分布在热带地区，尤以热带雨林最为集中［9］，在维持热带雨林的生物多样性甚至整个生态系统的平衡中都起着十分重要的作用，是国内外公认的热带雨林中的一类关键类群［10－12］.榕树物种的减少或灭绝将直接影响或改变整个热带雨林的物种多样性，没有榕树就形成不了热带雨林生态系统［9］.榕树的一些种类是热带雨林中的绞杀植物，如高山榕（F.altissima）、垂叶榕（F.benjamina）、丛毛垂叶榕（F.benjamina var.nuda）、钝叶榕（F.cur-tipes）和斜叶榕（F.tinctoria）等.它们的种子通过鸟类的传播在热带雨林中的多种树木上发芽、生长，成为绞杀植物，有的种类还绞杀同种其他树木或另一种榕树.绞杀现象是热带雨林的一个重要特征，也是热带雨林中物种间复杂关系的体现，具有重要的生态学意义［13］.被绞杀掉的树木死后，绞杀榕由于缺少支柱，很容易倒掉死亡，在它生长的地方就形成了一个林窗，有利于种子的萌发，使群落树种组成得以更新.同时，异质性环境也有利于森林中物种多样性的维持.另外，被榕树绞杀的多为多病的老树，所以，绞杀榕的存在有利于森林中树种的更新和森林生态系统的健康发展［14］.榕树中的对叶榕、斜叶榕等是热带雨林中的先锋树种，多出现在受到一定破坏的林段、林窗与路旁.它们的种子主要靠动物传播，能够传很远的距离，且萌发力强，在光照充足的环境中生长迅速，很快就能长满林窗或被破坏的林段，在热带雨林的恢复中起到重要作用［9］.绞杀榕的绞杀过程可分为3个明显的阶段：附生阶段、半附生阶段、乔木阶段.其中，我们根据缠绕在宿主树上与扎入土壤中树根的相对多少，将半附生阶段分为前期与后期.西双版纳地区具有特殊的气候条件，一年可以分为雨季、雾凉季与干热季，其中雾凉季降雨较少，而林下有大量滴落雾水补充土壤水，因此雾凉季的雾水有可能是绞杀榕的重要水分来源.本研究将以斜叶榕为研究对象，通过测定其木质部与各种潜在水源的氢氧同位素组成，以及不同生长阶段的叶片碳同位素组成，揭示西双版纳地区不同生长阶段的绞杀榕在不同季节的水分利用策略和生存机理，从而对热带雨林的保护提供参考.1研究地区与研究方法1.1自然概况西双版纳（21ʎ09ᶄ—22ʎ33ᶄN，99ʎ58ᶄ—101ʎ50ᶄE），受西南季风的影响，一年中有明显的雾凉季（11月—次年2月）、干热季（3—4月）和雨季（5—10月）之分，干热季与雾凉季又合称为干季.该地区年平均降雨量约1400mm，从图1可以看出，在雾凉季与干热季降水稀少，不足全年的13%，月均气温都在16ħ以上，温度较高，白天植物蒸散强烈，植物需水量增大，易受水分胁迫；雨季降雨占全年降雨量的87%以上.但干季几乎每日早晚都有浓雾出现（出现率>90%），且其总持续时间占干季时间的40%以上［15］.本文以西双版纳勐仑地区中国科学院西双版纳热带植物园内不同生长阶段的斜叶榕为研究对象，定期测定不同深度土壤水势、叶片黎明水势与中午水势、土壤含水量，并定期收集雨水、林下滴落雾水、不同深度土壤水、木质部水分（用于测定其稳定性同位素比率δD、δ18O）以及不同生长阶段斜叶榕的叶片（用于测定其稳定性同位素比率δ13C）.1.2研究方法1.2.1土壤水势的测定将土壤水势张力计（UIT，Germany）探头分不同层次（30、50、70cm）插入林下土壤中，测量土壤水势，3次重复，并在2007年8月、2007年12月与2008年2月、2008年4月分别测定雨季、雾凉季与干热季的土壤水势.土壤含水量图1西双版纳地区月均降水量（Ⅰ）与月均气温（Ⅱ）Fig.1Monthly precipitation（Ⅰ）and monthly average air temperature（Ⅱ）in Xishuangbanna（2007-05—2008-08）.7384期王平元等：西双版纳绞杀植物斜叶榕的水分利用策略的测定、土壤水分与木质部水分以及叶片的取样时间均同土壤水势的测定时间.1.2.2叶片水势的测定在黎明前（5：00—6：00）和中午（12：00—14：00）用枝剪剪取不同生长阶段样树的叶片，用Pump-Up无气瓶植物压力室测定叶片水势［16］.测定3片叶子，取平均值.于2007年10月与2008年3月分别测定雨季与干季的叶片水势. 1.2.3土壤质量含水量的测定用钻孔法钻取不同深度土壤样品（5、15、20、30、40、50、60、80、100、120 cm），实验室105ħ烘干，求取土壤的质量含水量.1.2.4大气降水的收集定期采集雾水样品，采集时间是干季9：00—10：00雾滴消失时，10d左右收集一次当日雾水水样并收集每次降雨水样.降雨水样采用中国科学院西双版纳热带雨林生态系统研究站采集的降水样品.1.2.5土壤水的取样用钻孔法钻取不同深度的土壤（5、15、20、30、40、50、60、80、100、120cm），同时取附生阶段与半附生阶段样树树干腐殖土.实验室内采用低温真空蒸馏法［17－18］提取土壤水.在数据处理时，我们认定表层土至50cm处为浅层土壤，50 cm以下为深层土壤.1.2.6植物木质部水分的取样8：00—9：00（干季为雾较浓重时），用枝剪剪取不同生长阶段样树的小枝样品（3 5个），实验室内采用低温真空蒸馏法［17－18］提取木质部水分.每个季节取样1 2次. 1.2.7叶片采集及δ13C的测定12：00—14：00，采摘不同生长阶段绞杀榕以及其宿主油棕（Elaeis gunieensis）林冠上的当年向阳叶片，分别在烘箱内60ħ烘干并研磨，过40目筛，用于叶片δ13C的测定.1.2.8雾水贡献比例的确定采用Brunel等［19］建立的同位素质量平衡模型计算植物利用不同来源水（雾水、雨水、地下水）的比例（P）.模型假设植物获得的水分来自两部分：雾水或土壤水（雨水）以及地下水，对植物利用来说，雾水和土壤水具有同等可利用性.例如：模型计算的雾水利用比例（Pf）值不是雾水或雨水对地下水的简单比值，而是一个加权的比值.模型如下：当存在两个水分来源时：δD1x1+δD2x2=δD（1）δ18O1x1+δ18O1x2=δ18O（2）x 1+x2=1（3）如果存在3个水分来源，则：δ18O1x1+δ18O2x2+δ18O3x3=δ18O（4）δD1x1+δD2x2+δD3x3=δD（5）x1+x2+x3=1（6）式中：δ18O与δD分别指植物木质部水分的氧与氢的稳定同位素值；δD1（δ18O1）、δD2（δ18O2）、δD3（δ18O3）分别指可能利用的水源1、2、3的稳定氢（氧）同位素组成；x1、x2、x3指植物利用水源1、2、3的比例.所有水样与树叶样品寄送中国科学院兰州分院测试中心地球化学部采用稳定性同位素气体质谱仪测定其稳定同位素值.2007年8月—2008年5月期间，共收集雨水样品11个，雾水样品5个，土壤水样品113个，木质部水样品27个，树叶样品31个.水样品的稳定性氢氧同位素比率采用同位素质谱仪（氢的测定用Finnigan MAT-251，氧的测定用Finni-gan MAT-252，USA）测定.氢氧稳定性同位素比率的值是以相对于V-SMOW（Vienna Standard Mean Ocean Water）的千分率（ɢ）给出，分别以δD和δ18O 表示，精度分别为ʃ2.5ɢ和ʃ0.5ɢ.树叶样品采用同位素质谱仪（Finnigan MAT-252，USA）测定，碳稳定性同位素比率的值是以相对于PDB（Pee Dee Bel-emnite，一种出自美国南卡罗来那州的碳酸盐陨石）的千分率（ɢ）给出，以δ13C表示，精度为ʃ0.5ɢ.质谱分析的方程表达式为：δɢ=［（R sample/R standard）－1］ˑ1000（7）其中，Rsample与Rstandard分别表示样品与标准物的D与H、18O与16O、13C与12C的丰度之比.对不同季节的土壤水势、土壤含水量、叶片水势进行方差分析，数据的处理分析采用统计软件SPSS 13.0.采用绘图软件SigmaPlot10.0对文中各图进行绘制.2结果与分析2.1土壤水势的季节变化从图2可以看出，干热季的30cm土壤处水势最低值达到－0.0305MPa，此时土壤含水状况最差，随着深度的增加，土壤水势逐渐增大；最大水势出现在雾凉季时30cm深度土壤处，为－0.0145MPa.对数据进行差异显著性比较可知，雨季与干热季之间不同深度土壤的水势差异不显著，与雾凉季之间差异显著，雾凉季与干热季之间差异也显著.在雨季，随着土壤深度的增加，土壤水势逐渐变大.在30cm 处，不同季节之间土壤水势变化较大，而随着土壤深度的增加，不同季节的土壤水势逐渐趋向一致，到70cm处，在各个季节的土壤水势几乎没有差异.838应用生态学报21卷图2不同土壤深度的土壤水势季节变化Fig.2Comparisons of soil water potential at different depthsamong different seasons（meanʃSD）.A：雨季Rainy season；B：雾凉季Foggy season；C：干热季Dry hotseason.下同The same below.2.2叶片水势的季节变化研究期间叶片黎明前、中午水势的季节变化如图3所示，在不同的生长阶段，雨季的叶片水势（包括黎明前与中午叶片水势）要明显大于干季的叶片水势，而干季时不同生长阶段叶片水势差异也较大.黎明前最低水势出现在干季时乔木阶段，为－0.35MPa，最高水势出现在雨季时半附生阶段前期，为－0.02MPa；中午最低水势出现在干季时附生阶段，为－0.4MPa；最高水势出现在雨季时半附生阶段后期，为－0.08MPa.图3雨季（A）与干季（B）叶片水势的季节变化Fig.3Comparisons of leaf water potential between rainy season（A）and dry season（B）（meanʃSD）.Ⅰ：附生阶段Epiphytic；Ⅱ：半附生阶段前期Early stage of hemiepi-phytic；Ⅲ：半附生阶段后期Late stage of hemiepiphytic；Ⅳ：乔木阶段Arborescent.下同The same below.2.3土壤含水量的季节变化雨季的土壤水分含量为（19.05ʃ2.14）%，雾凉季为（14.93ʃ4.96）%，干热季为（14.53ʃ2.16）%（图4）.雨季的土壤含水量极显著高于雾凉季与干热季（P<0.001），而雾凉季与干热季的土壤含水量则比较接近，差异不显著（P=0.64）.2.4不同生长阶段斜叶榕的水分利用来源2.4.1雨季不同生长阶段斜叶榕的水分利用在雨季，雨水的稳定氧同位素值为（－9.37ʃ3.09）ɢ，浅层土壤水为（－7.76ʃ3.07）ɢ，深层土壤水为（－8.47ʃ1.7）ɢ，树干腐殖土水为（－8.9ʃ0.76）ɢ.根据Brunel等［19］建立的同位素质量平衡模型，我们可以用图中不同水源与木质部水分δ18O值之间的距离比较来表示各水源与木质部水分δ18O值的接近程度，从而揭示利用各种水分的相对比例，与木质部水分δ18O值距离越小，则该水源被利用的比例越大.只要木质部水分与某种潜在可利用水源的稳定同位素值大致处于同一区域或者有部分交叉，我们就可以认为植物利用该水源.但从图5A可以看出，不同生长阶段木质部水分的δ18O值普遍低于各潜在水源，主要是因为在蒸馏时未能将木质部中的水分提取充分，从而导致同位素发生分馏，使所得数值偏低.但根据斜叶榕的生态与生理习性可知，附生阶段由于整个植株都在宿主树上，因此只能利用雨水与树干腐殖土水；半附生阶段（包括前期与后期）则可以利用雨水、树干腐殖土水以及浅层土壤水（根系较浅不能扎入深层土壤）；而乔木阶段则主要利用雨水与土壤水，由于斜叶榕的根系主要分布在土壤上层，加之浅层土壤水分含量较高，因此主要利用浅层土壤的水分.2.4.2雾凉季不同生长阶段斜叶榕的水分利用雨图4不同深度土壤含水量的季节变化Fig.4Soil water content at different depths among foggy，dryhot and rainy seasons（meanʃSD）.9384期王平元等：西双版纳绞杀植物斜叶榕的水分利用策略图5不同生长阶段植物木质部水分与各潜在水源δ18O关系Fig.5Relationship ofδ18O between stem xylem water and theavailable water sources in（meanʃSD）.a）可利用水源，指斜叶榕在不同生长阶段可以利用的水分来源，即图中的雨水（1）、树干腐殖土水（2）、深层土壤水（3）、浅层土壤水（4）、雾水（5）The available water sources，meant the water sources usedby F.tinctoria at different life stages，such as rain water（1），stem hu-mus water（2），deep soil water（3），shallow soil water（4）and fog drip（5）；b）木质部水Stem xylem water.水的稳定氧同位素值为（－1.1ʃ0.14）ɢ，雾水为（－1.24ʃ0.15）ɢ，浅层土壤水为（－7.44ʃ2.18）ɢ，深层土壤水为（－8.02ʃ1.35）ɢ，树干腐殖土水为（－2.78ʃ3.34）ɢ.从图5B可以看出，附生阶段木质部δ18O值与雨水、雾水以及树干腐殖土水最为接近；半附生阶段木质部δ18O值与树干腐殖土水、浅层土壤水、深层土壤水最为接近；而乔木阶段木质部δ18O值与浅层土壤水以及深层土壤水最接近.2.4.3干热季不同生长阶段斜叶榕的水分利用雨水的稳定氧同位素值为（－4.87ʃ1.81）ɢ，浅层土壤水为（－6.01ʃ2.37）ɢ，深层土壤水为（－7.55ʃ0.图5C图6Fig.6gler fig可以看出，附生阶段木质部δ18O值与雨水最为接近；半附生阶段木质部δ18O值与雨水、树干腐殖土水以及浅层土壤水最为接近；而乔木阶段木质部δ18O值与浅层土壤水最接近.2.5油棕以及不同生长阶段的绞杀榕叶片碳同位素δ13C从图6可以看出，在不同季节，油棕的δ13C值比较稳定，各季节变化不大；叶片δ13C的最大值出现在干热季时附生阶段，最小值则出现在雾凉季时半附生阶段；半附生阶段后期与乔木阶段斜叶榕叶片的δ13C值普遍较大，且变化不大，而在附生与半附生阶段前期，雾凉季叶片的δ13C值明显比另外两个季节要小；在雨季，各个生长阶段的斜叶榕的δ13C值之间差异不显著.2.6雾凉季雾水的贡献比例在雾凉季时常有滴落雾水存在，雾水的存在对附生阶段斜叶榕的生长起着极其重要的作用.而对于半附生阶段的斜叶榕，雾水仍可作为其水分来源的一部分，经三元混合模型计算可知，在雾凉季，半附生阶段前期的斜叶榕利用的水分大约有7%来源于雾水，其他的绝大部分依赖于浅层土壤水（大约90%）；而半附生阶段后期的斜叶榕几乎不利用雾水.3讨论西双版纳地区具有特殊的气候条件，降雨主要集中在雨季，干季时降雨极其稀少，但干季常有雾水出现，因此干季植物怎样获取水分以及利用哪种水分从而获得生存显得尤为重要.同时，由于斜叶榕具048应用生态学报21卷有特殊的生态习性，其生活史可以分为3个明显的生长阶段，各阶段潜在可利用水源不同，因此斜叶榕在不同季节不同生长阶段所利用的水源也可能存在不同.斜叶榕土壤最低水势出现在干热季较浅土壤30cm深度处，表明在干热季，30cm深度处的土壤水分含量极低，植物受水分胁迫严重.这可能是因为干热季降雨极其稀少，没有或很少有雾水补给，且气温较高，土壤蒸发与植物蒸腾非常大，导致浅层土壤水势较低.最高水势出现在雾凉季土壤30cm深度处，表明此时该处的土壤水分状况良好.这可能是因为雾凉季气温较低，植物蒸腾与土壤蒸发都较小，且浅层土壤有滴落雾水补给.在70cm深度处，各个季节的水势较高且趋向一致，说明在较深的土壤层水分含量较高并且变化较小，即斜叶榕很少利用深层土壤水.与土壤水势相比，叶片黎明前水势与中午水势明显偏低，显然这有利于植物从土壤中吸收水分.在各个生长阶段，雨季比干季的黎明前叶片水势要高，这可能是由于雨季多为阴雨天气，土壤含水量与空气相对湿度较高，叶片蒸腾较低，因而叶片水势较高.不同生长阶段的植物雨季与干季黎明前叶片水势的差异较大，说明不同生长阶段的绞杀榕对不同的水分状况表现不同的反应.黎明前叶片水势实际反映植物本身的吸水能力［20］，在不同季节，植物的黎明前叶片水势随不同生长阶段而异，说明不同生长阶段的绞杀榕在不同季节具有不同的吸水能力，最低水势出现在干季乔木阶段，说明此阶段其吸水能力最强.中午时的叶片水势反映叶片水分的亏缺情况［20］，最低水势出现在干季附生阶段，说明此时的叶片受水分胁迫最严重，这可能与干季时降水量较少以及气温较高有关.雨季中午叶片水势较高且差异不大，说明雨季时不同生长阶段的绞杀榕可利用水分状况良好且差异不大.由于在植物根系对土壤水分的吸收过程以及吸收后沿木质部向上运输过程中不存在稳定氢氧同位素分馏现象，各生长阶段斜叶榕木质部的稳定氧同位素值要普遍小于其各潜在水源，这可能是在取样过程或处理样品过程中出现同位素分馏现象造成的.在雨季，对于不同生长阶段的斜叶榕，雨水均为其主要水源；树干腐殖土水分也是附生阶段与半附生阶段的补充水源（树干腐殖土水分来源于雨水，同位素值与雨水接近）；浅层土壤水是半附生阶段与乔木阶段的主要水源之一，这可能是因为雨季降雨充足，植物易于直接从雨水或浅层土壤中获取所需水分.在雾凉季，斜叶榕附生阶段的主要水源是雨水、雾水、树干腐殖土水；在半附生阶段前期，由于斜叶榕的根未能延伸足够长从而吸收深层土壤的水分，因此，半附生阶段前期的斜叶榕只能吸收树干腐殖土水、雾水以及浅层土壤水，而浅层土壤水与树干腐殖土水是其主要水源；而在半附生阶段后期与乔木阶段，土壤水（包括浅层与深层土壤水）是其主要水源；由于雾凉季降水很少，树干腐殖土水分含量低，因此树干腐殖土水分是半附生阶段的补充水源而非主要水源；雾水也是半附生阶段的补充水源.对于半附生阶段前期，大约有7%的水分来源于雾水，这是因为半附生阶段前期时裸露在地表上的根较多，而在半附生阶段后期，由于大部分根扎入地下，因此几乎不利用雾水.根据刘文杰等［21］对西双版纳地区的雾水与土壤水的稳定同位素研究发现，浅层土壤水主要来自于雨水与雾水的补给，但干季浅层土壤水中包含更多的雾水［21］.同样，在本研究中，由于雾凉季降雨极其稀少，雾水成为浅层土壤水的主要补给水源，而浅层土壤水又是雾凉季斜叶榕半附生阶段以及乔木阶段的主要水分来源，因此，雾水虽然不会作为雾凉季斜叶榕最主要的直接水分来源，但由于其对浅层土壤水的补给作用，对雾凉季斜叶榕的生长也起着非常重要的作用.在干热季，由于附生阶段斜叶榕只有雨水与树干腐殖土水两个潜在可利用水源，且雨水与附生阶段木质部水的稳定同位素值接近，因此雨水是该阶段斜叶榕的主要水源；浅层土壤水是半附生阶段与乔木阶段的主要水源；由于干热季时降雨极少，树干腐殖质水分含量也极低，因此，雨水与树干腐殖土水是半附生阶段的补充水源；由于各生长阶段木质部同位素值与深层土壤水的同位素值相差较远，因此，各生长阶段几乎不利用深层土壤水，这是因为即使是乔木阶段斜叶榕的根也很浅，延伸不到深层土壤层.δ13C值与植物水分利用效率（WUE）呈正相关，与土壤水分含量呈负相关，油棕的δ13C比较稳定，说明油棕的水分来源也是稳定的水源，如深层土壤水，即使是在干季，受水分胁迫程度也较轻；半附生阶段后期与乔木阶段斜叶榕叶片的δ13C值普遍较大，且变化不大，说明这两个阶段植物需水量较大，且主要利用较稳定的水源，如土壤水；最大值出现在干热季的附生阶段，说明此时水分状况极差，WUE1484期王平元等：西双版纳绞杀植物斜叶榕的水分利用策略最大；雨季的各个生长阶段斜叶榕的δ13C变化不大，说明雨季时各生长阶段受水分胁迫较轻，WUE 较低.由于半附生阶段斜叶榕开始利用土壤水，乔木阶段的斜叶榕与油棕都主要利用土壤水，二者形成竞争，因此，斜叶榕生长到乔木阶段以后，根系逐渐发育完全，在与油棕的水分竞争中占据优势，油棕将逐渐死亡.综上所述，由于斜叶榕在不同季节内各生长阶段都具有不同的潜在水源，且各水源稳定同位素值存在差异，因此，根据稳定氧同位素以及植物水势等参数判定，斜叶榕不同生长阶段的植株在不同季节具有不同的水分利用来源，即在不同生长阶段采取不同的水分利用策略来应对环境的变化.参考文献［1］Hobson KA，Wasenaar LI.Stable isotope ecology：An introduction.Oecologia，1999，120：312－313［2］Lin GH，Sternberg L.Hydrogen isotopic fractionation by plant roots during water uptake in coastal wetlandplants//Ehleringer J，Hall A，Farqubar G，eds.StableIsotopes and Plant Carbon-Water Relations.San Diego，California：Academic Press，1993：497－510［3］Wershaw RL，Friedman I，Heller SJ.Hydrogen isotope fractionation of water passing through trees//Hobson F，Speers M，eds.Advances in Organic Geochemistry.New York：Pergamon Press，1966：55－67［4］Zimmermann V，Ehhalt D，Munnich KO.Soil-water movement and evapotranspiration：Changes in the iso-topic composition of water.Proceedings of the Symposi-um of Isotopes in Hydrology.Vienna，InternationalAtomic Energy Agency，1966：567－585［5］White JW，Cook 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Resources,Conservation and Recycling 54 (2010) 1074–1083Contents lists available at ScienceDirectResources,Conservation andRecyclingj o u r n a l h o m e p a g e :w w w.e l s e v i e r.c o m /l o c a t e /r e s c o n r ecPhysical geonomics:Combining the exergy and Hubbert peak analysis for predicting mineral resources depletionAlicia Valero ∗,Antonio ValeroCentre of Research for Energy Resources and Consumptions,CIRCE,University of Zaragoza,María de Luna 3,Zaragoza 50018,Spaina r t i c l e i n f o Article history:Received 14May 2009Received in revised form 19January 2010Accepted 24February 2010Keywords:ExergyHubbert peak ScarcityFuel mineralsNon-fuel mineralsa b s t r a c tThis paper shows how thermodynamics and in particular the exergy analysis can help to assess the degradation degree of earth’s mineral resources.The resources may be physically assessed as its exergy content as well as the exergy required for replacing them from a complete degraded state to the con-ditions in which they are currently presented in nature.In this paper,an analysis of the state of our mineral resources has been accomplished.For that purpose an exergy accounting of 51minerals has been carried out throughout the 20th century.This has allowed estimating from geological data when the peak of production of the main mineral commodities could be reached.The obtained Hubbert’s bell-shaped curves of the mineral and fossil fuels commodities can now be represented in an all-together exergy–time representation here named as the “exergy countdown”.This shows in a very schematic way the amount of exergy resources available in the planet and the possible exhaustion behaviour.Our results show that the peak of production of the most important minerals might be reached before the end of the 21st century.This confirms the Hubbert trend curves for minerals obtained by other authors using a different methodology.These figures may change,as new discoveries are made.However,assuming that these discoveries double,most of the peaks would only displace our concern around 30years.This is due to our exponential demand growth.The exergy analysis of minerals could constitute a universal and transparent tool for the management of the earth’s physical stock.© 2010 Elsevier B.V. All rights reserved.1.IntroductionThe 20th century has been characterized by the economic growth of many industrialized countries.This growth was mainly sustained by the massive extraction and use of the earth’s mineral resources.For instance,only in the US over the span of the last century,the demand for metals grew from a little over 160mil-lion tons to about 3.3billion tons (Morse and Glover,2000).The tendency observed worldwide in the present,is that consumption will continue increasing,especially due to the rapid development of Asia,the desire for a higher living standard of the developing world and the technological progress.But the physical limitations of our planet might seriously restrain world economies.However,inter-national worries are still very far removed from this fact.Currently,most attention is focused rather on the consequences of the use of natural resources,such as climate change,loss of biodiversity or pollution of soils and rivers,than on the depletion of minerals.Obvi-ously the former problems need and are slowly being solved with international agreements,dissemination campaigns,etc.Further-more,the huge amount of energy received every day from the sun (1353J/m 2s)helps restoring at least partially the damages caused∗Corresponding author.E-mail address:aliciavd@unizar.es (A.Valero).to the biosphere,atmosphere and hydrosphere.On the contrary,the natural reposition of the geosphere,which comes mainly from the earth’s interior energy (0.034–0.078J/m 2s—Skinner et al.,1999),is close to zero when compared to that of the other external earth’s spheres.As discussed in Valero and Valero (2010),during millions of years,nature has formed and concentrated minerals through a large number of geological processes such as magmatic separation,hydrothermal,sedimentary,residual,etc.(Chapman and Roberts,1983)forming the currently existing natural stock.The concen-trated mineral deposits serve as a material and fuel reservoir for man.And the more concentrated is a mineral deposit,the less effort is required for extraction.The mining of materials implies an obvious reduction of the natural stock in terms of the min-erals extracted from the mines and the fossil fuels required for the mining processes.Those extracted minerals are concentrated and further refined to obtain the desired raw materials,for which additional quantities of fuels and minerals are required.This way,the natural stock stored in the earth’s crust goes into the hands of society as man-made stock.When the useful life of products finishes,they become dispersed,ending up as wastes (either as pol-lution or disposed of in landfills).As Gordon et al.(2006)argue,the relative sizes of the remaining stock in the lithosphere and the stock transferred to wastes at any given time are measures of how far we have progressed toward the need for total reliance0921-3449/$–see front matter © 2010 Elsevier B.V. All rights reserved.doi:10.1016/j.resconrec.2010.02.010A.Valero,A.Valero/Resources,Conservation and Recycling54 (2010) 1074–10831075on recycling rather than on virgin ore to provide material for new products.Unfortunately,the Second Law of Thermodynamics reflected in Eq.(2),tells us that as the concentration of the resource in the earth’s crust tends to zero,the energy required to extract the min-eral tends to infinity.Consequently,from a practical point of view, it is impossible to recover resources again when they become dis-persed.In a not very distant future,it will be easier to extract metals from landfills than from the crust.This is why recycling is so important to society.But fossil fuels or many additives like Cr,Mo,Mn in steel or in paints,or the new age of high-tech metals such as In,Ge,Ta,etc.included in nanotechnol-ogy and microelectronics are impossible or extremely difficult to recycle.Georgescu-Roegen,1father of ecological economists,states that we can only recycle“carbojunk”.That means that we cannot recycle completely.Furthermore,the worldwide rush for strate-gic materials is causing dramatic consequences in less developed countries such as irreversible environmental damage,corruption and even wars.This effect is named by Humphreys et al.(2007)as the“natural resources curse”.Our technology is quite inefficient in the use of energy and mate-rials,since there is a lack of awareness of the limit.If resources are limited,their management must be carefully planned.But it is impossible to manage efficiently the resources on earth,if we do not know what is available and at which rate it is being depleted.Hence, we need management tools,accountability and political will to accomplish this.The Extractive Industries Transparency Initiative (2006)is becoming an internationally accepted standard for eco-nomic transparency in the oil,gas and mining sectors.But it is still insufficient,since physical and objective information about the remaining resources such as ore grades,quantity of energy and water required for extraction,the amount of waste rock and other physical parameters that would allow an objective analysis of our mineral capital is rarely published.Rational management tools for the efficient use of resources require a theoretical basis,naturally provided by thermodynamics. For a thermodynamicist,this is so obvious,that it is hard to believe that very little systematic effort has been devoted to it.The use of the Second Law through the exergy concept,allows to progress into something more than words.Concepts can be converted into num-bers,and then into objective and universal indicators.The objective of this paper is to contribute to put Second Law numbers to the natural resources depletion and in particular to mineral resources.Georgescu-Roegen was one of thefirst authors in realizing the links between the economic process and the Second Law of thermo-dynamics.In his seminal work The Entropy Law and the Economic Process(Georgescu-Roegen,1971),he states that“the entropy law itself emerges as the most economic in nature of all natural laws[...] and this law is the basis of the economy of life at all levels”.More authors such as Berry et al.(1978),Ruth(1995)or Roma(2006)and Roma and Pirino(2009)state that economic production processes should consider thermodynamic limits on material and energy use in order to be optimal in the long-run.Berry et al.(1978)developed a theorem forfixing the economically-efficient level of thermody-namic efficient production systems.As an example,Ruth(1995) determined the optimal extraction path and production of iron ore at each period of time,taking into account thermodynamic limits on material and energy efficiency,the treatment of technical change through the theory of learning curves and the evaluation of alterna-tive time paths from an economic and thermodynamic perspective. Roma(2006)and Roma and Pirino(2009)developed different mod-els for production processes,imposing energy rather than standard 1See the interview of Antonio Valero with Nicholas Georgescu-Roegen under: http://habitat.aq.upm.es/boletin/n4/aaval.html.monetary terms as a mean of exchange.As a result,the authors state that resources will be more efficiently used,reducing thereby entropic wastes.Parallelly,concerned environmentalists search for alternate indicators closer to nature or social descriptions.A plethora of measuring units(or numeraires)appear,almost one per indica-tor.In particular,those who account for minerals and fossil fuels, have a spectrum of definitions and measurement units that actu-ally impede to make a systematic and universally accepted account of what the earth’s crust provides annually and what remains.On the other side,it is obvious that money cannot be the best unit of measure for the assessment of resources,since currency changes from one country to another,its value depends on dif-ferent factors and moreover,it is impossible to quantify nature in monetary terms,without opening the door to arbitrariness.Nature does not sell anything that we could buy with money.It only can be compensated with counteractions like recovering,restoring and replacing techniques which obviously have an associated cost. These arguments are solid and obvious.However they are difficult to admit,due to the familiarity and omnipresence of money.The argument the cost is not measured with money or everything costs more than the money we pay should be placed over everything can be bought.So,which should be the unit of measure of cost?The answer to this question is in the Second Law of Thermodynamics:if the cost is a sacrifice of resources,and the already consumed resources have been consumed forever,one can deduce that we should see this fact as the base of the physical accountability.In thisfield,Thermody-namics provides tools such as energy,entropy or exergy,among others.The problem with energy is that it does not distinguish quality.Although exergy is also one-dimensional,it is sensible to quantity and quality of the interchanged energy and has energy dimensions.In fact,exergy measures the minimum quantity of use-ful energy required to provide a system for building it from its constituent elements found in the reference environment(R.E.). The reference environment is a hypothetical and homogeneous earth,where all substances have been reacted and mixed,without kinetic or potential energy and at ambient pressure and tempera-ture.Once the R.E.has been defined,the minimum thermodynamic cost or exergy of any material or energyflow can be calculated.This is very important,as exergy takes into account all physical manifes-tations that differentiate the system from its environment:height, velocity,pressure,temperature,chemical composition,concentra-tion,etc.And this is not a function of how much we appreciate things,but on the useful energy that can be released until its deple-tion.On the other hand,the exergy concept participates in all properties of the cost concept:it is additive and can be calculated from the production process.But the process should be considered as reversible in all its steps.The most important contribution of the exergy concept is in its ability to objectify all the physical manifestations in energy units, independently of the economic value.Any product,natural or arti-ficial resource,productive process or polluting emission can be valued from an exergy point of view.This is why a good number of researchers believe that exergy can contribute to the assessment of certain environmental concerns(Szargut,2005,Brodianski,2005, Wall,1977,Sciubba,2003,or Ayres et al.,2004).2.Theoretical backgroundThe most important features thatfix the value of a mineral resource are on one hand its chemical composition and on the other hand its concentration—both characteristics which can be assessed with the single indicator of exergy.1076 A.Valero,A.Valero /Resources,Conservation and Recycling 54 (2010) 1074–1083The chemical composition of a substance is the key factor for fixing the final use of the resource.Furthermore,it has a direct influence on the energy required for processing the mineral (Valero and Valero,2010).For instance,the energy required to extract pure copper from a sulphide is significantly smaller than from an oxide,therefore copper sulphides such as chalcopyrite (CuFeS 2)are pre-ferred as copper ores (see Gerst,2008).The chemical exergy in kJ/mol can be calculated using the following well known expression (Szargut et al.,1988):b ch =v k b 0chel,k+ G mineral(1)where b ch el,k is the standard chemical exergy of the elements that compose the mineral and can be easily found in tables,v k is the number of moles of element k in the mineral and G is the Gibbs free energy of the mineral.The minimum amount of energy –exergy –involved in con-centrating a substance from an ideal mixture of two components is given by the following expression (see for instance Faber and Proops,1991):b c =−RT 0ln(x i )+(1−x i )x iln(1−x i )(2)where b c is the concentration exergy,x i is the molar concentration of substance i,R is the gas constant (8.3145J/mol K)and T 0is the reference temperature (298.15K).The difference between the con-centration exergies obtained with the mineral concentration in a mine x m and with the average concentration in the earth’s crust x c is the minimum energy (kJ/mol)that nature had to spend to bring the minerals from the concentration in the reference state to the concentration in the mine.A more comprehensive expression of the reversible separation energy of an ideal mixture of components is provided by Tsirlin and Titova (2004).In their finite-time thermo-dynamics model,linear kinetics is additionally taken into account.However,in the timeless limit,Tsirlin and Titova’s model converges to Eq.(2).This way,the total replacement exergy (b t —kJ/mol),i.e.its natu-ral exergy,representing the minimum exergy required for restoring the resource from the R.E.to the initial conditions in the mineral deposit,is calculated as the sum of the chemical and concentration exergy components (Eq.(3)).b t =b ch +b c(3)Specific exergies (b t )are converted into absolute exergies (B t )by multiplying the quantities by the moles of the substance con-sidered.However,a study based only on reversible processes (minimum replacement exergies)would ignore technological limits.Results show that,in general,the real energy requirements are tens or even thousands of times greater than the exergy content of the mineral (Valero and Botero,2002).The calculation of the exergy replacement costs b ∗t of the resource,representing the actual exergy required to replace the resource from the R.E.to its initial conditions,with current available technology commonly have two contributions,b ∗t =k ch ·b ch +k c ·b c(4)its chemical cost (k ch ·b ch ),accounting for the chemical produc-tion processes of the substance,and its concentration cost (k c ·b c ),accounting for the concentration processes.Variable k (dimension-less)represents the unit exergy replacement cost of a mineral.It is defined as the relationship between the energy invested in the real obtaining process (E real process )for either refining (k ch )or concen-trating the mineral (k c ),and the minimum energy (exergy)required if the process from the ore to the final product were reversibleTable 1Unit exergy costs of seven base-precious metals (updated from Valero and Botero,2002).Metal k ck ch Ag 7041.81Au 422,879.01Cu 343.180.2Fe 97.4 5.3Ni 431.858.2Pb 218.825.4Zn125.913.2( b mineral ).k =E realprocessb mineral(5)The exergy cost concept developed by Valero et al.(1986)and Lozano and Valero (1993)is also named embodied exergy or cumulative exergy consumption (Szargut et al.,1988).Valero and co-workers focused on the physical roots of cost as well as on pro-viding the concept with a theoretical framework.Table 1shows as an example,the unit exergy replacement costs of some important minerals considered in this paper.These values have been updated by the authors from Valero and Botero (2002).A key study pointing out the actual relationship between ther-modynamic limits and the extraction of mineral resources is that of Chapman and Roberts (1983).These authors developed a com-prehensive treatise on the relationship between the abundance of resources and the energy required to extract them,models for the prediction of non-renewable resource depletion,thermodynamic limits for the exploitation of metals and the effect of recycling on the availability of materials.They observed a relationship between the cut-off ore grade,g ,expressed in weight percentage and the his-torical cumulative production of a given metal,T .This relationship can be expressed as,ln T =−m ln g +c,(6)where c reflects the relative abundance of the metal considered and m the degradation velocity.Values estimated from historical data for constant m can be found in Nguyen and Yamamoto (2007).According to Chapman and Roberts (1983),the energy (approxi-mately equal to its exergy cost b*)required for mining and milling may be expressed as:b ∗=e g(7)where e is the specific energy consumption for mining and milling the metal.A typical value for e is 0.4MJ/kg for open pit mining,and 1.0MJ/kg for underground mining.Eqs.(6)and (7)show empirically what Second Law tells us about the natural exponential behaviour of the exergy needed for extract-ing a material from a mixture as a function of its ore grade (Eq.(2)).The lower the ore grade,the more effort per unit of material is needed to extract it.Even if the earth’s crust is plenty of ele-ments and minerals,its concentration may be so low that the exergy required to extract them from the bare rock becomes economically prohibitive,making it impossible in practice.Following this behaviour,it is natural to resort to the well known Hubbert peak (traditionally used for estimating the peak of produc-tion of fossil fuels—Hubbert (1962))for its application to minerals.Basically,Hubbert (1962)found that the production of fossil fuel trends had a strong family resemblance.The curves started slowly and then rose more steeply tending to increase exponentially with time,until finally an inflection point was reached after it became concave downward.The observed trends are based on the fact that no finite resource can sustain for longer than a brief period such aA.Valero,A.Valero/Resources,Conservation and Recycling54 (2010) 1074–10831077Fig.1.The exergy replacement cost loss of the main non-fuel mineral commodities on earth in the20th century. rate of growth of production;therefore,although production ratestend initially to increase exponentially,physical limits prevent theircontinuing to do so.So for any production curve of afinite resourceoffixed amount,two points on the curve are known at the outset,namely that at t=0and again at t→∞.The production rate will bezero when the reference time is zero,and the rate will again be zerowhen the resource is exhausted,after passing through one or sev-eral maxima.The second consideration is that the area under theproduction curve must equal the quantity of the resource available(R).In this way,the production curve of a certain resource through-out history takes the ideal form of a bell-shaped curve representedby Eq.(8).f(t)=Rb0√e−(t−t0)/b0(8)where parameters b0and t0are the unknowns and R the economic proven reserves of the commodity.The model was successful in predicting the peak of oil extraction in the US lower48states and the subsequent decline in produc-tion.Recently,several authors used Hubbert’s model to predict the evolution of crude oil extraction at the planetary level(Deffeyes, 2001;Bentley,2002;Campbell and Laherrere,1998).According to these estimates,the corresponding production peak could take place within thefirst decade of the21st century or not much later. And as Campbell and Laherrere(1998)argue,from an economic perspective,when the world runs completely out of fuels is not directly relevant:what matters is when production begins to taper off.Beyond that point,prices will rise unless demand declines com-mensurately.Bardi and Pagani(2008)examined the world production of57 minerals reported in the USGS database.They came to the conclu-sion that the bell-shaped curve can be used globally and for most minerals,not only for oil extraction.Moreover,we think that the bell-shaped curve is better suited to minerals,if it isfitted with exergy over time instead of mass pro-duction of the metal commodity over time.Oil quality keeps nearly constant with extraction,whereas other non-fuel minerals do not (mineral’s concentration decreases as the mine is being exploited). Therefore exergy is a much better unit of measure than mass,since it accounts not only for quantity,but also for ore grades and mineral composition.Furthermore,if the Hubbert model is applied to the exergy replacement costs explained before,the technological factor of extracting and refining the mineral is also taken into account.In short,the well known bell-shaped curve can befitted to the exergyor exergy replacement cost consumption data provided,in order to estimate when mineral production will start declining.With our proposal,the yearly exergy replacement cost loss of the commodity calculated with Eq.(5)is represented versus time f(t).With a least squares procedure,the points are adjusted to the curve given by Eq.(8).The maximum of the function is given by parameter t0,and it verifies that f(t0)=R/b0√.3.The exergy loss of world’s mineral reserves in the20th century3.1.Non-fuel mineralsWith the help of historical data compiled by the USGS(2007), and the equations presented above,we have calculated the exergy(B t)and exergy replacement cost(B∗t)destroyed due to non-fuel mineral extraction throughout the20th century of the51most important mineral commodities(see Table2).Furthermore,the average degradation velocities and the latest degradation velocities in minimum exergy and exergy cost terms(˙B t and˙B∗t)registered (from1996to2006)are calculated.The concentration factor has been assumed to be constant and equal to the average ore grades estimated in Valero(2008).Obviously,a better approximation would take into account the evolution of the ore grades with his-tory.But unfortunately this information is generally not compiled and there is only available data for Australia(Mudd,2007).The depletion degree of the commodities shown in Table2(%R and% R.B.)has been obtained as the ratio between the exergy destroyed due to extraction,and the total exergy of the reserves or reserve base of the considered commodity.The latter are obtained as the published reserves or reserve base of the commodity in2006,plus the exergy destroyed from1900to2006.2Finally,the resources to production ratio R/P with exergy units is provided,as a measure of the years until depletion of the commodity.It has been assumed that production remains as in year2006,and that reserves do not increase after that year.****2According to the USGS,reserve base is defined as that part of an identified resource that meets specified minimum physical and chemical criteria related to current mining and production practices,including those for grade,quality,thick-ness,and depth.The reserve basefigure is larger than that of the“reserves”one, which is defined as that part of the reserve base which could be economically extracted or produced at the time of determination.1078 A.Valero,A.Valero/Resources,Conservation and Recycling54 (2010) 1074–1083Table2The exergy and exergy replacement cost loss of the main mineral commodities in the world and average degradation velocities(Valero et al.,2010). Mineral1900–20061996–20062006B t B∗t ˙B t˙B∗t˙B t˙B∗t%R loss%R.B.loss R/P,years R.B./P,yearsAluminium 5.64E+05 1.22E+07 5.27E+03 1.14E+05 1.85E+04 4.01E+0514.912.0135173 Antimony 5.13E+02 5.71E+03 4.80E+00 5.34E+01 1.18E+01 1.31E+0272.856.61632 Arsenic 5.75E+027.23E+03 5.37E+00 6.76E+01 6.91E+008.70E+0174.666.22030 Barite 1.53E+03N.A. 1.43E+01N.A. 3.47E+01N.A.61.025.224111 Beryllium 6.88E−01 3.60E+01 6.43E−03 3.37E−017.97E−03 4.17E−01N.A.N.A.N.A.N.A. Bismuth7.61E+00 1.24E+027.12E−02 1.16E+00 1.54E−01 2.50E+0041.124.756119 Boron oxide 4.04E+03N.A. 3.78E+01N.A. 1.69E+02N.A.39.221.14096 Bromine 2.41E+02N.A. 2.26E+00N.A.7.96E+00N.A.N.A.N.A.N.A.N.A. Cadmium 6.51E+01 3.54E+03 6.08E−01 3.31E+01 1.28E+00 6.98E+0166.845.12562 Cesium 6.62E−02N.A. 6.18E−04N.A.N.A.N.A. 1.20.8N.A.N.A. Chromium 4.53E+04 1.03E+05 4.23E+029.62E+02 1.32E+03 3.00E+03N.A.N.A.N.A.N.A. Cobalt 2.20E+02 1.10E+04 2.05E+00 1.03E+02 5.70E+00 2.86E+0219.511.5104193 Copper 2.96E+04 3.07E+06 2.76E+02 2.87E+047.94E+028.24E+0450.334.53262 Feldspar8.77E+02N.A.8.20E+00N.A. 3.51E+01N.A.N.A.N.A.N.A.N.A. Fluorspar9.95E+03N.A.9.30E+01N.A. 2.03E+02N.A.48.632.14590 Gallium 2.75E−01N.A. 2.57E−03N.A. 1.31E−02N.A.N.A.N.A.N.A.N.A. Germanium 6.52E−01N.A. 6.09E−03N.A. 1.24E−02N.A.N.A.N.A.N.A.N.A. Gold9.98E−018.17E+049.33E−037.64E+02 1.93E−02 1.58E+0375.458.91737 Graphite 3.26E+04N.A. 3.05E+02N.A.7.13E+02N.A.31.015.583204 Gypsum 1.40E+04N.A. 1.30E+02N.A. 3.51E+02N.A.N.A.N.A.N.A.N.A. Helium 1.32E+02N.A. 1.23E+00N.A. 4.11E+00N.A.N.A.N.A.N.A.N.A. Indium 5.45E−01N.A. 5.10E−03N.A. 3.35E−02N.A.34.326.41928 Iodine 1.12E+01N.A. 1.05E−01N.A. 3.86E−01N.A. 3.8 2.26001080 Iron 4.60E+06 3.22E+07 4.30E+04 3.01E+05 1.04E+057.26E+0527.714.984185 Lead 6.01E+03 2.35E+05 5.62E+01 2.19E+038.99E+01 3.51E+0372.555.12349 Lithium9.32E+03 3.49E+048.71E+01 3.26E+02 3.26E+02 1.22E+0362.338.11233 Magnesium 1.01E+04 1.01E+049.45E+019.45E+01 2.96E+02 2.96E+02N.A.N.A.N.A.N.A. Manganese 1.08E+05 1.04E+06 1.01E+039.75E+03 1.82E+03 1.76E+0451.98.739437 Mercury9.24E+00 3.16E+038.63E−02 2.95E+01 2.75E−029.40E+0092.269.431162 Molybdenum9.58E+02 1.80E+048.95E+00 1.68E+02 2.62E+01 4.92E+0237.521.447103 Nickel 4.48E+03 3.55E+05 4.18E+01 3.32E+03 1.31E+02 1.04E+0440.022.94295 Niobium 1.57E+02N.A. 1.46E+00N.A. 6.90E+00N.A.19.818.16167 Phosphate rock 5.47E+047.08E+04 5.12E+02 6.62E+02 1.19E+03 1.54E+0326.111.3127352 PGM 2.41E−01N.A. 2.25E−03N.A.8.35E−03N.A.14.413.0137154 Potash 1.30E+05 2.02E+05 1.22E+03 1.89E+03 2.94E+03 4.56E+0312.8 6.3285619 REE 6.65E+01N.A. 6.22E−01N.A. 2.85E+00N.A. 2.4 1.47151220 Rhenium 6.10E−027.43E+00 5.70E−04 6.95E−02 2.71E−03 3.30E−0124.27.453212 Selenium8.72E+00N.A.8.15E−02N.A. 1.77E−01N.A.48.231.053110 Silver 1.76E+01 1.69E+04 1.65E−01 1.58E+02 3.24E−01 3.11E+0278.563.41328 Strontium 1.83E+03N.A. 1.71E+01N.A.8.52E+01N.A.56.041.91221 Tantalum 4.71E+00 1.31E+03 4.41E−02 1.22E+01 2.30E−01 6.38E+0114.210.794130 Tellurium 4.65E−01N.A. 4.35E−03N.A.7.03E−03N.A.25.813.5159356 Thorium 1.58E+00N.A. 1.47E−02N.A.N.A.N.A. 1.2 1.0N.A.N.A. Tin 2.11E+03 1.08E+05 1.97E+01 1.01E+03 2.92E+01 1.51E+0375.262.72036 Uranium 2.47E+027.29E+04 2.31E+00 6.81E+02 4.68E+00 1.38E+0334.829.996120 Vanadium 4.40E+02 4.96E+03 4.11E+00 4.64E+01 1.56E+01 1.76E+028.9 3.2231675 Wolfram 3.01E+02 2.28E+04 2.81E+00 2.13E+02 6.02E+00 4.56E+0248.530.23269 Zinc 4.98E+049.09E+05 4.65E+028.49E+03 1.13E+03 2.06E+0468.144.41848 Zirconium 3.03E+02 2.91E+05 2.83E+00 2.72E+038.52E+008.18E+0343.829.23261 TOTAL 5.68E+06 5.11E+07 5.31E+04 4.78E+05 1.34E+05 1.29E+0625.614.292191Values are expressed in ktoe and ktoe/year for the degradation velocities.As shown in Table2,in reversible exergy terms,the exergy degradation of the non-fuel mineral capital on earth is clearly dom-inated by the extraction of two commodities:iron and aluminium, representing around81and10%of the total exergy consumption, respectively.The exergy destroyed due to non-fuel mineral extrac-tion between1900and2006is at least5.68Gtoe.As expected, the general consumption pattern has followed an exponential-like behaviour.This is reflected in the drastic change of the exergy degradation velocity(˙B),passing from around10Mtoe/year in 1910,to180Mtoe/year in2006.In irreversible terms,i.e.analyzing the exergy replacement costs (actual exergy)of the commodities,we observe in Fig.1that copper acquires a more important role.Copper is responsible for6%of the total exergy degradation costs on earth,while iron and aluminium, 63and24%,respectively.The irreversible exergy destruction of all analyzed commodities is at least51Gtoe.This means that with current technology,we would require a minimum of a third of all current fuel oil reserves on earth(178Gtoe(BP,2007))for the replacement of all depleted non-fuel mineral commodities. Excluding iron and aluminium,which eclipse the rest commodi-ties,we observe in Fig.2that in decreasing order,the production of manganese,zinc,nickel,zirconium,lead,chromium,uranium, tin and gold contribute also significantly to the planet’s non-fuel mineral capital degradation.Again,an exponential behaviour of the exergy costs of all commodities is observed.The average exergy cost degradation velocity in the20th century is at least0.5Gtoe/year.However in the last decade,this velocity increased to1.3Gtoe/year.According to the depletion ratios(%R loss and%R.B.loss)in Table2,man has depleted in just one century around26%of its world non-fuel mineral reserves,and around14%of its reserve base. The estimated years until the depletion of the total reserves and reserve base are around92and191years,respectively.It must be pointed out that these are only minimum numbers,as it has been。

小学上册英语第2单元真题英语试题一、综合题(本题有100小题，每小题1分，共100分.每小题不选、错误，均不给分)1.I have a ______ of crayons in different colors. (box)2.My cousin, ______ (我的表妹), loves to act in school plays.3.The girl is very ________.4.My ________ (玩具名称) is a dinosaur that dances.5. ________ (画画) after school. She love6.My sister enjoys making ____ (gifts) for friends.7. A flamingo gets its color from the food it ________________ (吃).8. A ____ is often seen resting on leaves during the day.9.The __________ (历史的影响力) can be profound.10.What is the value of 3 + 2 + 1?A. 4B. 5C. 6D. 7B11.What is the main ingredient in soap?A. WaterB. OilC. FatD. LyeD12.The _____ (海豚) loves to surf the waves.13. A __________ can be used to predict weather patterns.14.What is the tallest mountain in the world?A. K2B. EverestC. KilimanjaroD. DenaliB15.Sedimentary rocks are formed from __________ materials.16.My mom is great at ____ (cooking) different dishes.17.What is 12 x 3?A. 36B. 24C. 30D. 18A18.What is the color of grass?A. RedB. BlueC. GreenD. Yellow19.What do we call the period before a baby is born?A. PregnancyB. ChildhoodC. AdolescenceD. Adulthood20.What do we call the art of making sculptures and statues?A. PaintingB. SculptureC. DrawingD. PhotographyB21. A chemical that can act as both an acid and a base is called ______.22.What is the capital of Costa Rica?A. San JoséB. AlajuelaC. CartagoD. LiberiaA23.ta Stone unlocked the mysteries of ________ (古埃及文字). The Russ24.Chemical bonds hold _______ together in a molecule.25.Which fruit is red and often mistaken for a vegetable?A. BananaB. TomatoC. GrapesD. OrangeB26.What is 20 ÷ 4?A. 4B. 5C. 6D. 7B27.What do we call the act of providing assistance to someone in need?A. HelpingB. AssistingC. AidingD. SupportingA28.My teacher has a ______ (鹈鹕) that catches fish.29.The ______ (小鸟) builds its nest high up in the tree branches.30.What do we call the process of a seed developing into a plant?A. GerminationB. PhotosynthesisC. PollinationD. FertilizationA31.Which animal is known as the king of the jungle?A. LionB. TigerC. BearD. ElephantA32. A ______ (生态旅游) can educate visitors about plants.33.The country known for its bamboo is ________ (中国).34.________ (植物适应) to their environment.35.Dolphins are very _________. (聪明)36.Herbs can enhance the flavor of ______ (食物).37.I like to ________ cartoons.38.What do you call the process of making cheese?A. FermentationB. PasteurizationC. CurdlingD. CreamingC39.ts can regenerate from small ______ of their stems. (某些植物可以从小块茎部再生。