Part I
Pro: So we’ve been talking about nutrients, the elements in the environment that are essential for living organisms to develop, live a healthy life and reproduce. Some nutrients are quite scarce; there just isn’t much of them in the environment. But fortunately they get recycled. When nutrients are used over and over in the environment, we call that a nutrient cycle. Because of the importance of nutrients and their scarcity, nutrient recycling is one of the most significant eco-system processes that we’ll cover in this course.
The three most important nutrient cycles are the nitrogen cycle, the carbon cycle and the one we are going to talk about today, the Phosphorus cycle.
我们最近一直在谈论营养物质，就是环境中那些对生物体的发育、健康生活和繁殖至关重要的元素。
1. nutrient |ˈnju:triənt|
noun. a substance that is needed to keep a living thing alive and to help it to grow 营养素；营养物
E.g.: Plants draw minerals and other nutrients from the soil.
植物从土壤中吸取矿物质和其他养分。
2. scarce|skeəs|
adj. if sth is scarce , there is not enough of it and it is only available in small quantities 缺乏的；不足的；稀少的
E.g.: Food was becoming scarce.
食物越来越紧缺。
3. ecosystem |ˈi:kəʊsɪstəm|
noun. all the plants and living creatures in a particular area considered in relation to their physical environment 生态系统
E.g.: We all have an interest in maintaining the integrity of the ecosystem.
维持生态系统的完整是我们共同的利益。
4. nitrogen 氮, oxygen 氧, hydrogen 氢, ammonia 氨, chlorine 氯
5. phosphorus cycle
the phosphorus cycle is the biogeochemical cycle that describes the movement of phosphorus through the lithosphere, hydrosphere, and biosphere 磷循环是生物地球化学循环，描述了通过岩石圈，水圈，生物圈的磷移动。因为磷和磷基化合物在地球上找到的典型范围的温度和压力下通常是固体，磷循环与许多其它的生物地球化学循环不同，大气没有起到磷移动的显著作用。
Part II
So the Phosphorus cycle has been studied a lot by ecologists because like I said, Phosphorus is an important nutrient and it’s not so abundant. The largest quantities are found in rocks and at the bottom of the ocean.
How does Phosphorus get there? Well, let’s start with the Phosphorus in rocks. The rocks get broken down into smaller and smaller particles as they are weathered. They are weathered slowly by rain and wind over long periods of time. Phosphorus is slowly released as the rocks are broken down and it gets spread around into the soil. Once it’s in the soil, plants absorb it through their roots.
Stu: So that’s the reason people mine rocks that contain a lot of Phosphorus to help with agriculture?
Pro: Uh-huh, they mine the rock, artificially break it down and put the Phosphorus into agricultural fertilizers. So humans can play a role in the first part of the Phosphorus cycle–the breaking down of rocks and the spreading of Phosphorus into the soil by speeding up the rate at which this natural process occurs. You see.
因此人类可以在磷循环的第一部分发挥作用——岩石分解和磷在土壤中的扩散，通过加快这一自然过程发生的速度。
1. particle |ˈpɑ:tɪkl|
noun. a very small piece of sth 颗粒；微粒
E.g.: fine particles of sand
细沙颗粒
2. weather |ˈweðə(r)|
verb. to change, or make sth change, colour or shape because of the effect of the sun, rain or wind (使)风化;(使)褪色;(使)受到侵蚀
E.g.: This brick weathers to a warm pinkish-brown colour.
这块砖经日晒雨淋退成了带粉红的暖褐色。
3. mine|maɪn|
verb. to dig holes in the ground in order to find and obtain coal, diamonds, etc. （在某地）开矿，采矿
E.g.: The area has been mined for slate for centuries.
这个地区开采板岩有数百年了。
4. fertilizer |ˈfɜ:təlaɪzə(r)|
noun. a substance added to soil to make plants grow more successfully 肥料
E.g.: Fertilizer enriches the soil.
肥料使土壤肥沃。
Part III
Now after the Phosphorus is in the soil, plants grow. They use Phosphorus from the soil to grow. And when they die, they decompose. And the Phosphorus is recycled back into the soil; same thing with the animals that eat those plants, or eat other animals that have eaten those plants. We call all of this–the land phase of the Phosphorus cycle. But a lot of the Phosphorus in soil gets washed away into rivers by rain and melting snow. And so begins another phase of the cycle. Can anyone guess what it is called? Nancy?
Stu: Well, if the one is called the land phase, then this has to be called the water phase, right?
Pro: Yes, that’s such a difficult point, isn’t it? In a normal water phase, rivers eventually empty into oceans, and once in the oceans, the Phosphorus gets absorbed by water plants like algae. Then fish eats the algae or eat other fish that have eaten those plants. But the water phase is sometimes affected by excessive fertilizers.
在磷进入土壤后，植物就会生长，它们利用土壤中的磷来生长。当这些植物死去时，它们会分解。磷又被回收到土壤中；吃这些植物的动物或吃其他吃过这些植物的动物也是如此。
1. decompose |ˌdi:kəmˈpəʊz|
verb. to be destroyed gradually by natural chemical processes 腐烂
E.g.: As the waste materials decompose, they produce methane gas.
废物腐烂时会产生沼气。
2. phase |feɪz|
noun. a stage in a process of change or development 阶段；时期
E.g.: The wedding marked the beginning of a new phase in Emma's life.
婚礼标志着埃玛生活新阶段的开始。
3. empty |ˈempti|
verb. to flow or move out from one place to another 流入；涌进
E.g.: The Rhine empties into the North Sea.
莱茵河注入北海。
4. algae |ˈældʒi:|
noun. very simple plants with no real leaves, stems or roots that grow in or near water, including seaweed 藻；海藻
E.g.: The green covering on top of the water in the pond is algae.
池塘水面上绿色的东西是水藻。
Part IV
If not all of Phosphorus gets used by the crops and large amounts of Phosphorus gets into the rivers, this could cause rapid growth of water plants in the river, which can lead to the waterways getting clogged with organisms, which can change the flow of the water. Several current studies are looking at these effects and I really do hope we can find a way to deal with this issue before these ecosystems are adversely affected. Ok?
Of course, another way that humans can interrupt the normal process is fishing. The fishing industry helps bring Phosphorus back to land. In the normal water phase the remaining Phosphorus makes its way, settles to the bottom of the ocean and gets mixed into ocean sediments.
But remember, this is a cycle. The Phosphorus at the bottom of the ocean has to somehow make its way back to the surface, to complete the cycle, to begin the cycle all over again. After millions of years, powerful geological forces, like underwater volcanoes, lift up the ocean sediments to form new land. When an underwater volcano pushes submerged rock to the surface, a new island is created. Then over many more years the Phosphorus-rich rocks of the new land begin to erode and the cycle continues.
数百万年后，强大的地质力量，如水下火山，将海洋沉积物抬升，形成新大陆。
1. clog |klɒg|
verb. to block sth or to become blocked （使）阻塞，堵塞
E.g.: The narrow streets were clogged with traffic.
狭窄的街道上交通堵塞。
2. adverse |ˈædvɜ:s|
adj. negative and unpleasant; not likely to produce a good result 不利的；有害的；反面的
E.g.: This drug is known to have adverse side effects.
众所周知，这种药具有不良副作用。
3. make your way
to move or get somewhere; to make progress 去；前往；到…地方去；前进
E.g.: He made his way to the marketplace, as he had been instructed to do.
他按照指示去了市场。
4. submerge|səbˈmɜ:dʒ|
verb. to go under the surface of water or liquid; to put sth or make sth go under the surface of water or liquid（使）潜入水中，没入水中，浸没，淹没
E.g.: The fields had been submerged by floodwater.
农田被洪水淹没了。
5. erode |ɪˈroʊd|
verb. to gradually destroy the surface of sth through the action of wind, rain, etc.; to be gradually destroyed in this way 侵蚀；腐蚀；风化
E.g.: The cliff face has been steadily eroded by the sea.
峭壁表面逐渐被海水侵蚀。
Part V
Stu: What about, well, you said that the nitrogen cycle is also an important nutrient cycle. And there is a lot of nitrogen in the atmosphere, so I was wondering, is there a lot of Phosphorus in the atmosphere, too?
Pro: Good question, George. You’re right to guess that Phosphorus can end up in Earth’s atmosphere. It can move from the land or from the oceans to the atmosphere, and vice versa. However, there’s just not a substantial amount of it there, like there is with nitrogen. It’s a very minimal quantity.
1. end up
to find yourself in a place or situation that you did not intend or expect to be in 最终成为；最后处于
E.g.: If he carries on driving like that, he'll end up dead.
如果他继续这样开车，总有一天会把命都丢掉。
2. vice versa |ˌvaɪs ˈvɜ:sə|
adv. used to say that the opposite of what you have just said is also true 反过来也一样；反之亦然
E.g.: You can cruise from Cairo to Aswan or vice versa (= also from Aswan to Cairo) .
你可以乘船从开罗游览到阿斯旺，也可以从阿斯旺游览到开罗。
3. substantial |səbˈstænʃl|
adj. large in amount, value or importance 大量的；价值巨大的；重大的
E.g.: He ate a substantial breakfast.
他吃了一顿丰盛的早餐。
4. minimal |ˈmɪnɪməl|
adj. very small in size or amount; as small as possible 极小的；极少的；最小的
E.g.: There's only a minimal amount of risk involved.
所冒的风险极小。
