首页
十八嫂.十八哥
影响力0.00
经验值0.00
粉丝10
工艺专业主任
氯气外管路的补偿? 有搞设计的朋友帮助解决一下,“PVC缠绕的 玻璃 钢”DN250 氯气 室外管路的补偿应该如何考虑? 膨胀剂 多长加一个为合适? # + + 。 查看更多 2个回答 . 2人已关注
医院内安装液氧储槽的要求? 医院内安装 液氧 储槽的要求:需要向哪些部门报送什么资料?有没有国家相关的标准。 安监局认为是危险化学品建设项目,需要有设计资质的单位设计安装。还要搞三同时审查,有没有这方面的国家规定啊。 急求!!!!查看更多 2个回答 . 4人已关注
请问各位有煤焦油加工方案方面的资料吗? 我这里有好几百本煤化工的书籍,若你需要,可以在我的书籍目录里选,我可以发给你。QQ33614232查看更多 3个回答 . 1人已关注
上传附件出现错误? 请教各位,发帖时上传图片和附件老出现Server (IO) Error,该怎么解决?我用的浏览器为360浏览器 查看更多 5个回答 . 5人已关注
关于球罐的压力控制方案? 球罐的正常工作压力为0.2~0.4MPa,若采用分程控制能否满足P<0.2MPa时, 氮气 阀打开而去火炬阀关闭;P在0.2~0.4MPa时,双阀关闭;P大于0.4MPa时,去火炬阀打开,氮气阀关闭。 查看更多 8个回答 . 3人已关注
环境监测机构管理实务? 《环境监测机构管理实务》 吴景峰 编著 中国环境科学出版社 出版(2001) ISBN:7-80163-016-5 PDF档,共8.1MB。分3个压缩包。 [目录]: 第一章 概述 第二章 环境监测体系 第三章 环境监测机构 第四章 组织管理 第五章 质量体系管理 第六章 方法管理 第七章 设施与环境管理 第八章 记录与报告管理 第九章 协作与申诉管理 第十章 认可管理 [ ]查看更多 0个回答 . 2人已关注
请教大侠Aspen里怎么查2-乙基蒽醌(C14H16O2)及氢蒽醌 ...? 如题。查看更多 0个回答 . 2人已关注
加制氢新装置开工多长时间开始管道测厚? 加制氢新装置开工多长时间开始管道测厚? 查看更多 7个回答 . 3人已关注
哪可以购买HG21514~21535 2014人孔施工图? 请问各位大神,公司想买HG21514~21535 2014人孔施工图以及其他一些吊柱施工图,但不知道去哪购买,请各位大神明示,谢谢!查看更多 6个回答 . 2人已关注
英语学习--不变的誓言? Y: Yang Fuqing, host of Dialogue on CCTV 9   M: Andrew McEwan   J: Edmund Jocelyn   Y: The Long March undertaken by the Red Army from Oct. 16th 1934 to Oct. 19th 1935 is one of the greatest acts of heroism in the 20th century. Inspired by the spirit of the Long Marchers, two Englishmen, Edmund Jocelyn and Andrew McEwan<注1>, decided to retrace the route of the Long March. They set out from Yudu in Jiangxi province on Oct. 16th 2002. After walking a distance of 1,800 kilometers in 3 months, they arrived in Zunyi, where they are taking a short break before they continue their new Long March. They are now joining Dialogue to share with us their extraordinary experiences.   Y: Now you have finished about 1,800 kilometers, roughly 1/5 of the total length of the Long March. How would you describe your first part of the walk? How difficult was it?   M: The first week was easily<注2> the most difficult, lots of unexpected things. First of all, we were expecting very little rainfall on the way. And in the first week there was endless rainfall, which was kind of unseasonable, and then... eh...   J: I was sick. We set off and I was already feeling bad and I just felt worse the further we went. By the second day, I couldn't speak anymore. So Andy<注3> had to take over everything. He was always organizing and I just wrote notes for the next few days.   M: He was just about to get better when I got sick. I was throwing up<注4> along the road. So the first week was very tough.   Y: So as you continue you are getting used to the pains and the rest of the things?   J: Yeah. I mean, after this month or so, I think we started to get physically much stronger and things that seemed really difficult started to seem actually quite easy.   Y: Is it more of a physical challenge or a mental one?<注5>   M: Certainly it's a mental challenge. Physically it is quite demanding<注6> and I suppose that for most people it will be quite demanding. But I think mentally, basically what it comes down to is anybody can get up tomorrow morning and walk 20 or 30 kilometers. They can do it. But can they get up the next day and do exactly the same, and the next day, the same? I think that's the trick of the Long March—can you keep getting up when you are already tired and keep the pace in the same day. It's kind of boring sometimes.   Y: Did you come up with any way to kill time when you got bored?   J: Yes, we entertain ourselves with various made-up<注7> games. Sometimes we are even too tired to think about that, though. We are always focused on the next rest. All we can think about is our stomach.   Y: Was food a problem?   M: Food isn't often a problem but it can be a problem. For example, I'm vegetarian<注8> and Ed is supporting me. I stayed a vegetarian more or less<注9> for the rest of the journey. Sometimes we have problems communicating the fact that we don't want to use pork, fat or the fact that we don't eat meat.   Y: I'm very surprised to learn that you could still log on the Internet. I suppose that helps make you feel connected with the world.   J: It's true that we've been able to get on the Internet surprisingly often. I remember the first time was when we were in a very small town in Hunan. We found a little guesthouse and we went up to the boss of the guesthouse and asked her, "Do you have an Internet bar<注10> in this town?" And you know what? The boss said "Oh, yes." and we were taken out to the street. I couldn't believe it. So since then we always asked. They turned up in the most unlikely places.   M: Yeah. Sometimes you'll be very surprised that it's one. It looks like a shed for pigs or cows. You open it up and there's an Internet bar. So we have been very pleasantly surprised. But actually what turned up is that we had a week without much contact. I think about once a week we get to have contact with the outside world.   J: We look forward to those times when we get to a slightly bigger town, because we have been climbing up mountains, going through villages in Guangxi and Guizhou. There, communication is really our problem. Mobiles don't work. The villages don't have phones, either. If you want to use the phone you have to go to the nearest post office or maybe a government building.   M: I think the best day for that was when we were going up the mountains. I think it was in Jiangxi. We didn't expect much, but to our surprise, they had some English football games on TV and we love English football. Ed is a Manchester City football fan, which has Sun Jihai in the team.<注11> It was Manchester City against Manchester United. Ed was very very keen to see this big game. There it was! Suddenly we were in a restaurant and saw the TV. So he was very happy.   Y: Watching the game makes you less homesick, I suppose?   M: Yeah, it helps.   Y: How would you compare your difficulties with those of the Red Army soldiers?   M: It's a good question, but the truth is that there is no comparison and we don't pretend that there is one. We are not trying to be a sort of superman, all we are doing is retracing the route. There's no comparison. I mean those guys had to fight battles. They were being attacked by the Kuomintang. They had planes above them. And I think, you know, their footwear was pathetic<注12> and clothes were quite thin sometimes. Most of the Chinese are fairly familiar with these stories but foreigners don't really know how difficult it was.   Y: Now that you've walked part of the Long March, do you still think it was incredible for the Red Army to finish the Long March?   J: Oh, I think it's even more incredible. Before I started, I thought, well, that's a pretty remarkable achievement. Now I really struggled to understand how they could possibly do it. Like what Andy said, they'd got to fight battles as well. I had been so tired some days that I could hardly stand up, let alone pick up the gun and go into battles with someone.   Y: Did you find it difficult to find the correct route of the Red Army?   M: As I've mentioned, the second day I had to take over the responsibilities of finding the route for a few days. It's always going to be an imperfect solution but sometimes you can get very lucky. People will help you find the original journey that takes you over the mountain. I think by and large<注13> we have been quite successful. Every day we change our schedule. The thing we do is we walk up to the local people and we ask them how to find the route. There aren't many people who really know. The map is completely useless.   J: Mostly, if you see a main road today, then you can be fairly sure that's the way the Red Army didn't go. Their path is going to be a footpath somewhere up in the mountains. The local people still know where the Red Army went and most of the paths are still being used. They are not overgrown<注14>. They can show them to us. Unfortunately they don't always get it right. Then we've got to be pretty careful whom we ask, because people are not always that local. In south Guizhou, for instance, we were completely misdirected. The road we took was even harder than the original Red Army's route.   M: We found out that the best way to do it is to average out<注15> the responses. If you have five people, the same question, and you get five different responses. Then you can sit down and decide which one seems the most likely and then try again. That's usually what we do. We average out all the different answers. Sometimes they are completely contradictory; sometimes they are all the same. The most dangerous is when they are all the same because that gives you a kind of false confidence that you are on the right route. Quite often we find that we are on the wrong route. The most dangerous thing you could do is make suggestion. You should never suggest, "Is it this way?" because you can be sure the person will say, "Oh, yeah, it is that way." So never ever suggest which way or suggest the place name. If you do that, you are sure to get lost. Let the person tell you and see if you understand.   Y: You must have been to a lot of very remote places where local people have never seen a foreigner before. What were their reactions when they saw you?   M: That was certainly better than developed places, because people were so genuine and friendly with you. In a more developed place, people shout at you, they shout "Hello, Laowai", but in places which are very remote, people are very polite and courteous, and it's much more comfortable. People are a little careless, a little distant, but incredibly warm.<注16>   J: The kids are always distant. Sometimes we arrive at a little village just at the time when school finishes and all the children are coming out of school. We have been surrounded by maybe two or three hundred screaming kids.   Y: So meeting different people in different places must be a very big excitement for you.   J: Yeah. It's tremendous. That's why the great attractions of the journey is that every day we are moving into new places and meeting new people.   Y: And you've also talked to the locals about the Red Army, right?   J: Sure, because in every place the history is still there. Not just in the memories of very old people, but also their children, because they were listening to the stories from their parents.   M: The most exciting thing is when you sit down with an old person and with his family and the old person starts to tell the story, perhaps even in their local dialect and the family have to translate it into mandarin. And everybody listens to the old member of the family. They've never heard of these stories. They've never really asked about them. And so, by our arrival, we give this opportunity to kind of add these old stories.   Y: I'm sure you did a lot of research before you embarked on this journey. You must have read about the Red Army, their lives and even the lives of the local people they encountered. So how did you find the lives of the local Chinese along this route have changed?   M: There are a lot of changes, obviously. China's reform and opening has been going on for what is like some 20 years now. It's really quite remarkable when you go to this place in Jiangxi, which a journalist also trailed in the 1990s when following the Long March route. When he went there, he said they had no electricity, no glass in the windows, a very very poor place. But since the 1990s, they've built a major highway there. When we went there, we stayed in a place with hot running water and there was an Internet cafe across the road, a completely different place with completely different people. It's just a whole new type of place.   Y: I know you two are old friends from college years. Several years ago you all came to China to work. When did you develop your interest in China?   M: Well, I developed my interest in China virtually the first day I stepped off the plane in Beijing. Before that I had no interest at all. My reason for coming to China is to go to as remote and exotic<注17> and distant a place as I could possibly imagine. It was shut in the dark for me. So I had no real knowledge or interest in China before I came here and I couldn't even say "nihao" and that was about five years ago.   Y: You didn't learn anything about Chinese history or...   M: No, we never studied it in school and I certainly didn't study it in university. I knew a little bit about some of the politics but not very much.   Y: Do you think the situation will change?   M: Well, it's got to. Just as China is waking up, the West is waking up to<注18> China. There was a long time that China was closed. It was impossible for foreigners to know anything about China. We weren't allowed to come here. We weren't allowed to ask questions. And we weren't allowed to even walk around places.   J: China wasn't very important on the world stage. It didn't really act on it, didn't get involved. Now China is involved. There's got to be a recognition. We've got to know a bit more about it.   Y: I know you came up with the idea of retracing the route of the Long March during your last trip to Guizhou. What is the point for two Westerners to retrace this route?   J: Well, the point is to understand it more. It was a story and experience that captures their imagination, but one that we felt we didn't really have a very clear understanding of. We want to understand much more about the experience of them. Even if you have read about it, you read about it from a political viewpoint. It's all about political struggles and what the leaders did and said. What we are interested in was the experience of it.   M: To be honest, we find the politics a little boring sometimes and we don't really care too much about the politics. We are much more interested in the ground level experience, the people. That's not been very well covered in the past, although it has been covered by some people. We really feel that, from a western point of view, the story needs more people to ask questions about. In the West we all know about Napoleon's retreat, we all know about Hannibal<注19>, we know about all kinds of great events in history, but the Long March is really not given a lot of publicity in the West.<注20> People don't know that much about it. It's more of a kind of slogan. We hope people will get to know this story better. Maybe we can contribute to that process.   Y: Do you think it's worth it for you to spend the whole year on the road?   J: So far I've got no regret. I think it's been a remarkable experience. I feel like I've lived several years already in the last three months.   Y: Are you confident that you'll finish this journey?   J: Yeah, I'm confident.   M: I'm not. No, I'm always a little cautious. Basically, my approach to the whole thing since day one has been to be cautious. Just take it. One step at a time. Just each day, get through that. So to be honest, it's quite hard in the morning sometimes. I think when we finally leave Zunyi, we've had a nice break here. We've had a week to rest up. We stay in a nice comfortable place, just like when the leaders came here. I drank coffee for the first time in two months. I think after all that, to leave again is quite difficult the first day when you get up and set off again. You've got another 40 kilometers to walk. I think that's the hardest thing. The first kilometer and the last kilometer are the hardest of every day.   Y: So what's your next step?   J: The next step is to cross the Chishui<注21>, the Red River, for the first time. And then we will cross it again...   M: And then again.   J: And then again!   M: So that'll make it four times.   J: That's still just a small step on the way. And then we will head for Yunnan, Sichuan and the things that everybody is waiting for us to do.   M: They can't wait for us to get stuck in the grassland and snow mountain.   Y: A lot of challenges. Good luck to you for the rest of the journey.   1.马普安和李爱德,英国青年学者,于1997年到北京,曾在《中国日报》等报刊担任英文顾问。于2000年5月到贵州旅游时,偶然萌发了重走长征路的念头。经过充分准备,俩人于2002年10月16日从江西于都出发,沿着红一方面军的长征路线徒步前进。同年12月16日,进入贵州黎平境内。他们计划用368天走完8个省、2个自治区,最后抵达陕北吴起镇。   2. easily:无疑。   3. Andy为Andrew的昵称,下文中的Ed为Edmund的昵称。   4. throw up:<俚>呕吐。   5. physical:身体的,体力的;mental:精神的,心理的。   6. demanding:要求高的。   7. made-up:虚构的,指自己编的,想出来的。   8. vegetarian:素食者。   9. more or less:几乎,大约。   10. Internet bar:网吧,与下文中的Internet cafe意思相同。   11. Manchester City:曼彻斯特城队,简称曼城队;Sun Jihai:孙继海,大连人,中国国家足球队队员。2001年签约曼城队。下一句中的Manchester United指曼彻斯特联队,简称曼联队。该队是英国足坛的一支老牌劲旅,成立于1878年。   12. pathetic:可怜的,这里形容很破旧。   13. by and large:大体上,总的说来。   14.. overgrown:植被(或杂草)蔓生的。   15. average out:算出……的平均值,这里指综合各种回答得出最可能的结果。   16.人们有点随便,不会靠你太近,但却十分热情。   17.exotic:异国情调的。   18. wake up to:认识到,意识到。   19. Hannibal:汉尼拔[247-183BC]迦太基统帅,率大军远征意大利[218],从而发动第二次布匿战争,曾三次重创罗马军队,终因缺乏后援而撤离意大利[203],后被罗马军队多次击败,最终服毒自杀。   20.但是在西方,对于长征没有太多的介绍。publicity:宣传文章(或电影)。   21. Chishui:赤水,河流名,位于贵州省,红军长征时曾四渡赤水。下文中的3个again意思是说像红军那样过赤水河四次。查看更多 0个回答 . 1人已关注
讨论计算综合能耗? 各位大侠: 现在国家发布了清洁生产标准,可是行业不全。 我们想计算综合能耗,比如 二甲醚 、苯精制产品的综合能耗,有统一标准么!查看更多 1个回答 . 2人已关注
TCS合成中的问题? 1。怎样有效的解决硅粉输送中的磨损问题,采用什么办法可以不用换阀门和管路。 2。在 合成炉 中加氢气稀释 氯化氢 是否可以帮助TCS的合成。我个人认为加氢气从化学平衡的角度讲可以抑制STC和DCS的生成,但同样也抑制TCS的生成。但可以控制氢气和氯化氢的配比问题,关键比例一般控制在多少最有利TCS的生成。 3.在经济衡算中,三氯氢硅的收率是多少比购买三氯氢硅要划算。查看更多 5个回答 . 1人已关注
真空精馏出现了怪事? 精馏塔 ,负压操作,真空度-0.069,真空 调节阀 打为自动,高于这个真空就自动关闭。 实际操作中,在真空调节阀关闭的情况下,真空度突然增大,并在两个小时内几乎达到绝对真空。塔釜和回流槽的液位也瞬间降为0,请教各位大侠,这是怎么回事?查看更多 9个回答 . 2人已关注
大流量大全压风机有哪些型? 风机流量为27630m3/h,全压为533990Pa是什么类型风机 通用名是什么查看更多 2个回答 . 4人已关注
ISO1940标准? 求 ISO1940离心 压缩机 转子动平衡标准 查看更多 1个回答 . 1人已关注
关于水环境方面的一些概念和资料汇编? 关于水环境方面的一些概念和资料汇编 1、环境 2、水体(water body) 3、地表水 4、地下水 5、水体污染(water body pollution) 6、水质(water quality) 7、底质 8、底质污染 9、水体自净能力 10、水体自净过程的特征 11、水环境容量 12、污径比 13、水环境功能区划 14、水体富营养化 15、水生态系统的环境特征 16、水生态系统的营养结构特点 17、水生态系统的物质循环 18、污染物在水体中的运动特性 19、对流迁移运动 20、扩散运动 21、衰减转化运动 22、环境影响评价 23、建设项目的环境影响报告书内容 24、专项规划的环境影响报告书内容 25、环境影响分类 26、环境影响评价分类 27、环境影响预测与评价 28、环境质量 29、环境标准 30、环境目标 31、环境背景值(环境本底值) 32、水土保持 环境 环境是指以人类为主体的外部世界,主要是地球表面与人类发生相互作用的自然要素及其总体。它是人类生存发展的基础,也是人类开发利用的对象。环境是以人类为主体的客观物质体系,它具有整体性、区域性、变动性等最基本的特性。 环境包括:大气、水、土地、矿藏、森林、草原、野生动物、野生植物、水生物、名胜古迹、风景游览区、温泉、疗养区、自然保护区、生活居住区等。 水体(water body) 水体是地表水圈的重要组成部分,指的是以相对稳定的陆地为边界的天然水域和人工水域。包括有一定流速的江河、溪流、沟渠;相对静止的湖泊、水塘、沼泽、水库;受潮汐影响的三角洲与海洋;地下水和极冰。将水体当作完整的生态系统或综合自然体来看待,其中包括水相和固相物质,水中的悬浮物质、溶解物质、底泥和水生生物。 水体按照类型划分,可分为:海洋水体和陆地水体。海洋水体包括海和洋;陆地水体包括地表水体(如河流、湖泊、沼泽等)和地下水体。 地表水 暴露于地球表面的天然水体及人工积水。包括淡水,如河流水、湖泊水、水库水等;咸水,如海水等。 地下水 埋贮在地球表面以下的水体。包括浅层地下水、深层地下水等。 水体污染(water body pollution) 当污染物进入河流、湖泊、海洋或地下水等水体后,其含量超过了水体的自然净化能力,使水体水质和水体底质的物理、化学性质或生物群落组成发生变化,从而降低了水体的使用价值和使用功能的现象,被称作为水体污染。 水质(water quality) 水质主要指水相的质量,通过水体的物理(色度、悬浮物等)、化学(有机和无机物含量)和生物(细菌、微生物、浮游生物、底栖生物)的特征及组成状况,反映了水体环境自然演化过程和人类活动影响的程度。 底质 底质又称沉积物,系指江、河、湖、海底部的表层沉积物质,是水环境的重要组成部分之一。 底质污染 底质污染主要是由于工厂、矿山、城镇等排放的废水、废渣及大气污染物的沉降和蓄积而形成的。底质中的污染物质可在一定外界条件下,如水温、酸度、水流状况等条件下重新进入水体,对水体产生二次污染。底质中的污染物质也可被水体中的水生生物吸收,通过食物链作用对人体产生间接危害。 通过底质监测,有助于了解污染物质存在的状况及其对水体的可能产生的危害;通过分层测定底质中污染物含量和污染物垂直分布状况,从而了解底质及水体的污染历史。 水体自净能力 水体自净能力的定义有广义和狭义两种。广义定义指受污染的水体经物理、化学与生物作用,使污染的浓度降低,并恢复到污染前的水平;狭义定义是指水体中的 氧化物 分解有机污染物而使水体得以净化的过程。 影响水体自净过程的因素很多,其中主要因素有:收纳水体的地理、水文条件、微生物的种类与数量、水温、复氧能力以及水体和污染物的组成、污染物浓度等。 水体自净过程的特征 废水和污染物进入水体后,即开始自净过程,自净机制包括物理自净、化学和物理化学自净、生物和生化自净。该过程由弱到强,直到趋于恒定。自净过程的主要特征:1)污染物浓度逐渐下降;2)一些有毒污染物可经各种物理、化学和生物作用,转变为低毒或无毒物质;3) 重金属 污染物以溶解态被吸附或转变为不容性化合物,沉淀后进入底泥;4)部分复杂有机物被微生物利用和分解,变成二氧化碳和水;5)不稳定污染物转变成稳定的化合物;6)自净过程初期,水中溶解氧含量急剧下降,到达最低点后又缓慢上升,逐渐恢复至正常水平;7)随着自净过程及有毒物质浓度或数量的下降,生物种类和个体数量逐渐随之回升,最终趋于正常的生物分布。 水环境容量 水环境容量是指水体在规定的环境目标下允许容纳的污染物量。容量大小与水体特征、水质目标及污染物特性有关。水体中蕴藏着宝贵的水环境容量资源,可以通过水体所具有的存储、输移降解污染物的能力而使自身有所净化。 污径比 即一定水体内认为排放的污水流量与河流径流量的比值。一般,河流的污径比越小,稀释能力越强,稀释容量越大,水质不易被污染;反之则水质易受污染。我国南方的大江大河径流量大,污径比小,如长江和珠江的污径比在1%左右,总体上水质尚好;北方的一些河流污径比大,如辽河、海河、滦河等均在10%左右;一些城市河流的污径比很大,污染严重。 水环境功能区划 根据水域功能的重要程度、使用目的和保护目标,在经济、技术可行性分析的基础上,对生活饮用水源地、风景名胜区水体、重要渔业水体和其它具有特殊经济文化价值的水体划定保护区,并采取措施保证保护区内的水质符合规定用途的水质标准。 水环境功能区划是实现水环境综合开发、合理利用、积极保护、科学管理的基础,是运用法律的、行政的、经济的手段,使水环境保护工作兼收环境、技术、经济效益的必要前提。 水环境功能区划的指导思想是:高功能水域高标准保护,低功能水域低标准保护,专业用水区依专业用水标准保护,补给地下水水源地的水域依保证地下水使用功能标准保护。总的划分原则是:饮用水水源地优先保护,地表水环境质量宏观控制,统筹安排专业用水区,充分考虑经济、技术约束,突出陆上污染源合理布局,合理利用水环境容量。 论文关于水环境方面的一些概念和资料汇编来自 www.66wen.com 免费论文网 水体富营养化 在人类活动的影响下,生物所需要的氮、磷等营养物质大量进入湖泊、河口、海湾等缓流水体,引起藻类及其它浮游生物迅速繁殖,水体溶解氧含量下降,水质恶化,鱼类及其它生物产生变异现象,称为水体富营养化。 天然水体中氮和磷的含量在一定程度上是浮游生物数量的控制因素。生活污水、化肥和食品等工业废水以及农田排水都含有大量的氮、磷及其它 无机盐 类。天然水体接纳这些废水后,水中营养物质增多,促使自养型生物旺盛生长,某些藻类的个体数量迅速增加,而藻类的种类逐渐减少。水体中的藻类本来以硅藻和绿藻为主,蓝藻的大量出现是富营养化的征兆,随着富营养化的发展,最后变为蓝藻为主。 水生态系统的环境特征 水的密度大于空气,许多小型生物如浮游生物可以悬浮在水中,并且决定了水生生物在结构上的许多特点。水的比热较大,导热率低,水温的升降变化比较缓慢,温度相对稳定。水的另一重要物理特性是4℃时密度最大,因此水面结冰而底层的水温始终保持在冰点以上,水生生物可在冰层下生活。水体中的氧气含量较陆地环境少,光照条件也比陆地差。因此,水中溶解氧的含量和光照常常成为水生生物生活和分布的限制因子。 水生态系统的营养结构特点 水生态系统的生产者,除一部分水声高等植物外,主要是体型微小而数量很大的富有植物。这类生产者的特征是代谢率高、繁殖速度快,种群更新周期短,能量的大部分用于新个体的繁殖,因此生物量低。在淡水水体中,消费者一般是体型微小、生物学分类较低的变温动物,新陈代谢过程中所需热量比较常温动物少,热能代谢受外界环境变化的影响较大。分解者在系统中的作用较差,物质循环在很大程度上是由浮游生物通过自溶来完成的,尤其在迅速生长期和繁殖期间,自溶在物质循环中的作用更为重要。 水生态系统的物质循环 水生态系统初级生产者对光能的利用率比陆地生态系统低。根据有关研究,实际用于总生产力的有效太阳能仅为太阳总有效能量的1.22%,除去生产者自身呼吸消耗的0.7%以外,初级生产者净生产力的有效太阳能只有0.52%。然而,初级生产转为次级生产的效率,水生态系统并不比陆地生态系统低,淡水生态系统中的这种转化效率一般在10%以上。所以,分解者的作用远不如陆生生态系统重要。水域中只有10%~40%的初级生产量是由分解者分解的,而陆生生态系统、尤其是森林生态系统中,初级生产的90%左右是由分解者分解的。 水生态系统中的动植物尸体及其排泄物主要有三个去向:1)通过自溶归还环境并被重新利用;2)由分解者分解并被重新利用;3)下沉,部分被水生物所利用,部分随水体运动重新返回上层被再利用。 污染物在水体中的运动特性 污染物进入水体后,随着水的对流迁移运动、污染物的扩散运动和污染物质的衰减转化运动,使污染物在水体中得到稀释和扩散,从而降低了污染物在水体中的浓度。 对流迁移运动 对流迁移运动是指污染物在水流作用下产生的迁移作用,这种作用只改变水流中污染物的位置,并不能降低污染物的浓度。 扩散运动 污染物在水体中的扩散运动包括三个方面的内容,分子扩散、湍流扩散和弥散。分子扩散是由分子的随机运动引起的质点扩散现象,是各向同性的。湍流扩散是水体湍流场中质点的各种状态的瞬时值相对于其平均值的随机脉动而导致的扩散现象,湍流扩散系数是各向异性的。弥散运动是由于横断面上实际的流速不均匀引起的,由空间各点湍流流速的时均值与流速时均值的系统差别所产生的扩散现象。在用断面平均流速描述实际运动时,必须考虑一个附加的、由流速不均匀引起的弥散作用。 三种扩散运动的扩散系数在河流中的取值数量级分别为:分子扩散系数为10-5~10-4m2/s;湍流扩散系数为10-2~100m2/s;弥散系数为101~104m2/s。 衰减转化运动 进入水体中的污染物可分为两大类:保守物质和非保守物质。 保守物质进入水体后,随着水流运动不断变换空间位置,还由于扩散作用不断向周围扩散而降低其初始浓度,但不会改变其总量。重金属、很多高分子有机化合物都属于保守物质,它们对水环境有害,或暂时无害但能在水体中积累,从长远看是有害的。对于保守物质,水体对它们没有净化能力。 非保守物质进入水体后,除了随着水流运动变换空间位置,并不断扩散而降低浓度外,还因污染物自身的衰减而加速浓度的下降。非保守物质的衰减有两种方式:一是由其自身的运动变化规律决定的;另一种是在水环境因素的作用下,由于化学的或生物的反应而不断衰减。例如:可生化降解的有机物在水体中微生物作用下的氧化分解过程。 环境影响评价 定义1:本法所称环境影响评价,是指对规划和建设项目实施后可能造成的环境影响进行分析、预测和评估,提出预防或者减轻不良环境影响的对策和措施,进行跟踪监测的方法与制度。—《中华人民共和国环境影响评价法》 定义2:是指在一项工程动工兴建之前,对它的选址、设计以及在建设施工过程中和建成投产后,可能对环境造成的影响进行预测和估计,又称环境影响分析。—《中国大百科全书&#8226;环境科学卷》 定义3:环境影响评价是对建设项目、区域开发计划及国家政策实施后,可能对环境造成的影响进行预测和估计。环境影响评价的目的是确保拟开发项目在环境方面是合理的、适当的,并且确保任何环境损害在项目建设前期得到重视,同时在项目涉及中予以落实。—《世界银行工作指南第四号附件A》 定义4:环境影响评价是对拟议中的可能对环境产生影响的人为活动(包括制定政策和经济社会发展规划,资源开发利用、区域开发和单个建设项目等)进行环境影响的分析和预测,并进行各种替代方案的比较(包括不行动方案),提出各种减缓措施,把对环境的不利影响减少到最低程度的活动。—国家环保总局 建设项目的环境影响报告书内容 建设项目的环境影响报告书应当包括下列内容: 建设项目概况; 建设项目周围环境现状;建设项目对环境可能造成影响的分析、预测和评估;建设项目环境保护措施及其技术、经济论证;建设项目对环境影响的经济损益分析;对建设项目实施环境监测的建议;环境影响评价的结论。专项规划的环境影响报告书内容专项规划的环境影响报告书应当包括下列内容:实施该规划对环境可能造成的影响的分析、预测和评估;预防或者减轻不良环境影响的对策和措施;环境影响评价的结论。环境影响分类1.按影响的来源分可分为直接影响、间接影响和累积影响。直接影响于人类活动在时间上同时,在空间上同地。间接影响在时间上推迟,在空间上较远,但是在可合理预见的范围内。累积影响是指一项活动的过去、现在及可以预见的将来的影响具有累积性质,或多项活动对同一地区可能叠加的影响,当建设项目的环境影响在时间上过于频繁或在空间上过于密集,以至于各项目的影响得不到及时消除时,都会产生累积影响。2.按影响效果分,环境影响可分为游离影响和不利影响。这是一种从受影响对象的损益角度进行划分的方法。有利影响是指对人群健康、社会经济发展或其他环境的状况和功能有积极的促进作用的影响。反之,对人群健康有害、或对社会经济发展或其他环境状况有消极阻碍或破坏作用的影响,则为不利影响。需注意的是,不利与有利是相对的,是可以相互转化的,而且不同的个人、团体、组织等由于价值观念、利益需要等的不同,对同一环境的评价会不尽相同。环境影响的有利和不利的确定,要综合考虑多方面的因素,是一个比较困难的问题,也是环境影响评价工作中经常需要认真考虑、调研和权衡的问题。3.按影响性质划分,环境影响可分为可恢复影响和不可恢复影响。可恢复影响是指人类活动造成的环境某特性改变或价值丧失后可能恢复,反之,就是不可恢复影响。一般认为,在环境承载力范围内对环境造成的影响是可恢复的;超出了环境承载力范围,则为不可恢复的影响。4.另外,环境影响还可分为短期影响和长期影响,地方、区域影响和国家和全球影响,建设阶段影响和运行阶段影响等。环境影响评价分类环境影响评价分类,一般分为环境质量评价(主要是环境现状质量评价)、环境影响预测与评价以及环境影响后评估。这是一个不断评价和不断完善决策的过程。环境质量评价:是依据国家和地方制订的环境质量标准,用调查、监测和分析的方法,对区域环境质量进行定量判断,并说明其与人体健康、生态系统的相关关系。环境质量评价根据不同的时间域,可分为环境质量回顾评价(过去的环境质量)、环境质量现状评价和环境质量预测评价。在空间域上,可分为局地环境质量评价、区域环境质量评价和全球环境质量评价等。涉及建设项目的环境质量评价主要是环境质量现状评价。环境影响预测与评价环境影响后评估:可认为是环境影响评价的延续,是在开发建设活动实施后,对环境的实际影响程度进行系统调查和评估,检查对减少环境影响的落实程度和实施效果,验证环境影响评价结论的正确可靠性,判断提出的环保措施的有效性,对一些评价时尚未认识到的影响进行分析研究,以达到改进环境影响评价技术方法和管理水平,并采取补救措施,达到消除不利影响的作用。环境质量是表示环境本质属性的一个抽象概念。有两种理解,一种是认为环境质量表示环境状态惯性的大小,即环境状态从一种变化到另一种的难易程度的表示;另一种则认为环境质量是环境状态品质优劣的表示。环境标准是国家根据人群健康、生态平衡和社会经济发展对环境结构、状态的要求,在综合考虑本国自然环境特征、科学技术水平和经济条件的基础上,对环境要素间的配比、布局和各环境要素的组成所规定的技术规范。环境标准是评价环境状况和其它环境保护工作的法定依据。环境标准的种类,按照适用范围和地区可分为国际标准、国家标准和地方标准等;按其性质可分为环境质量标准、污染物排放标准等。这些环境标准组成了环境标准体系。环境目标环境目标是为了改善、管理、保护环境而设定的、拟在一定期限内力求达到的环境质量水平与环境结构状态。环境目标是社会发展总目标的一个组成部分,它必须与社会发展总目标中的其它目标相适应、相匹配,此外,它也是制定环境战略、环境规划的前提和出发点。环境背景值(环境本底值)是指不受污染的情况下,环境各组成要素:空气、水、土壤、岩石、植物、农作物、食品等的化学成分。它反映了这些环境要素在自然界存在和发展过程中,其自身原有的化学成分特征。水土保持是指对自然因素和人为活动造成水土流失所采取的预防和治理措施。 查看更多 0个回答 . 3人已关注
Aspen11.1模拟导热油therm66? 请问使用ASPEN11.1如何模拟导热油therm66,计算出来的数据与文献中差别较大,如何解决 查看更多 1个回答 . 5人已关注
求凝汽式汽轮机安全阀的原理及内部构造? 求凝汽式 汽轮机 安全阀 的原理及内部构造?附带的图形资料如下:查看更多 3个回答 . 4人已关注
来自吸收塔的富载H2S甲醇中压闪蒸后,闪蒸出的循环气温 ...? 各位专家:来自 吸收塔 的富载H2S 甲醇 中压闪蒸后,闪蒸出的循环气温度是多少?进入中压闪蒸段(压力1.0MPag)的各种物料都在 -30--35℃,怎么闪蒸循环气温度变成了-12℃,是写错了还是怎么的? 查看更多 4个回答 . 2人已关注
熔盐的特性? 请教:380~450摄氏度的熔盐有什么特性 , , - 查看更多 0个回答 . 3人已关注
简介
职业:苏州开元民生科技股份有限公司 - 工艺专业主任
学校:山东轻工学院 - 化学工程学院
地区:辽宁省
个人简介:风很大,买了烤地瓜暖手,见到了你,我愿意把烤地瓜给你,那你愿意把手给我吗 。查看更多
已连续签到天,累积获取个能量值
  • 第1天
  • 第2天
  • 第3天
  • 第4天
  • 第5天
  • 第6天
  • 第7天
 
这是一条消息提示
 
提醒
您好,您当前被封禁天,这天内您将不能登陆盖德问答,离解封时间还有
我已了解
提醒
提问需要5个能量值,您当前能量值为,请完成任务提升能量值
去查看任务