2009年--外文翻譯--緩解湖泊富營養(yǎng)化放開氮控制并專注于磷的減排（節(jié)選）

1、<p>　　中文4700字，2980單詞，16700英文字符</p><p>　　出處：Progress in Natural Science 19 (2009) 1445–1451</p><p><b>　　原 文</b></p><p>　　Mitigation of Lake Eutrophication: Loosen Ni

2、trogen Control and Focus On Phosphorus Abatement</p><p>　　Haijun Wang, Hongzhu Wang</p><p><b>　　Abstract</b></p><p>　　Traditionally, nitrogen control is generally consid

3、ered an important component of reducing lake eutrophication and cyanobacteria blooms. However, this viewpoint is refuted recently by researchers in China and North America. In the present paper, the traditional viewpoint

4、 of nitrogen control is pointed out to lack a scientific basis: the N/P hypothesis is just a subjective assumption; bottle bioassay experiments fail to simulate the natural process of nitrogen fixation. Our multi-year co

5、mparative</p><p>　　KeywordsLake eutrophication; Cyanobacteria bloom </p><p>　　1. Introduction</p><p>　　Eutrophication of waters is the phenomenon of an ecosystem becoming more prod

6、uctive by nutrient enrichment, stimulating primary producers. It is usually characterized by algal blooms, causing water quality deterioration and fish kills. It is becoming a global environmental crisis. In China, the p

7、roblem of lake eutrophication is extremely severe, with frequent cyanobacteria blooms threatening the ecology of waters, economic development and society stability. The most representative case is the cy</p><p

8、>　　To mitigate eutrophication and cyanobacterial blooms, nutrient control is a fundamental process. Traditionally, besides phosphorus control, nitrogen control is generally considered a necessary practice. Abundant fu

9、nds have been spent on nitrogen removal during wastewater treatment processes. However, recent researches in China and North America suggest a change to the traditional practice of nitrogen removal for inland waters: to

10、mitigate eutrophication, it is not nitrogen but phosphorus that sh</p><p>　　In this paper, the traditional viewpoint of nitrogen control is pointed out first to lack a conclusive scientific basis. Then, new

11、researches are introduced to elaborate a general rule: reduction in nitrogen loading cannot decrease total phytoplankton biomass, but stimulates blooms of nitrogen-fixing cyanobacteria. Further analyses proceeded to elab

12、orate on the significance of this general rule for the strategy to control the source of nutrients. In the end, suggestions on lake restoration are p</p><p>　　2. The traditional viewpoint of nitrogen control

13、 lacks conclusive scientific bases</p><p>　　The traditional viewpoint of limiting nutrient control on phytoplankton biomass is based mostly on considerations of N/P (ratio of total nitrogen to total phosphor

14、us) and on bottle bioassay experiments. However, the following analyses indicate that both the hypothesis and the experiment are not conclusive.</p><p>　　2.1. The N/P hypothesis is a subjective assumption<

15、;/p><p>　　Generally, lakes have been regarded as limited by phosphorus if TN/TP was relatively large (such as TN/TP > 17), limited by nitrogen if TN/TP was relatively small (such as TN/TP < 10) and colimi

16、ted by nitrogen and phosphorus when TN/TP was intermediate (such as 10 < TN/TP < 17). However, the thresholds of TN/TP to indicate nutrient limitation vary greatly in the literature, being for instance 10–17, 10–30

17、, and 7–15. The variation itself implies that this method is not reliable. Some limnologists</p><p>　　By analyzing the regressions and scatterplots of phytoplankton Chlaorophyll with nitrogen and phosphorus,

18、 Sakamoto first proposed the N/P hypothesis. However, when probing into the evidence, we find that his conclusion is just a subjective judgment on the patterns of the scatterplots. In his analysis, he noted three points

19、with a N/P ratio larger than 15–17 deviating. He concluded that phosphorus became the critical limiting factor if the N/P ratio was larger than 15–17. In fact, there are ten p</p><p>　　Many researchers have

20、followed the principles espoused by Sakamoto to analyze the limiting nutrient and variations under different N/P ratios. However, all the analyses have been performed without strict statistical tests, failing to prove th

21、at the dependence of phytoplankton on nitrogen and phosphorus are significantly different under different N/P ratios.</p><p>　　In conclusion, through logical reasoning and empirical analyses, the N/P hypothe

22、sis is found to be just a subjective assumption without conclusive evidence.</p><p>　　2.2. Bottle bioassay experiments are too small in scale to simulate the natural process of nitrogen fixation</p>&

23、lt;p>　　Bottle bioassay experiments have also long been used to demonstrate the limiting nutrient of phytoplankton in a waterbody. The experiments are usually performed in an enclosed container to discriminate the limi

24、ting nutrient by observing the growth of phytoplankton after nutrient addition. They generally last a period between several hours to 1 week. If growth of phytoplankton is stimulated by the addition of some nutrient, thi

25、s nutrient is considered to be the limiting factor. Due to their small</p><p>　　3. New researches find that nitrogen control fails to restrain total phytoplankton, but stimulates blooms of nitrogen-fixing cy

26、anobacteria</p><p>　　In May 2008, our article disproved the N/P hypothesis based on regional comparative studies. In August 2008, an article by researchers from North America indicated that nitrogen control

27、might stimulate nitrogen-fixing cyanobacteria based on a long-term whole-lake experiment. Accordingly, it appears that reduction in nitrogen loading cannot decrease the biomass of total phytoplankton. It is also logical

28、when comparing the cycling characteristics of nitrogen and phosphorus.</p><p>　　3.1. Regional research in the Yangtze Basin</p><p>　　To test the N/P hypothesis on a large scale, we analyzed the

29、relationships of Chlaorophyll a with total nitrogen and total phosphorus based on multi-year investigations of more than 40 Yangtze lakes.Almost all the TP-Chla regressions had higher R2 values and lower percentage predi

30、ctive error than those of TN-Chla regressions, indicating the superiority of TP over TN as a predictor.</p><p>　　Because different thresholds of TN/TP ratios have been proposed in the literature, we further

31、compared the differences of R2 values between TP-Chla and TN-Chla regressions over the complete TN/TP spectrum. The results showed that 28 R2 values of TP-Chla regressions were higher than those of TN-Chlaregressions ove

32、r the entire TN/TP spectrum. According to the traditional N/P hypothesis, these cases should be limited by phosphorus and have relatively high TN/TP ratios. However, they were not confin</p><p>　　For a given

33、 amount of TP, Chla varied regardless of the changes of TN. That is, within the TN/TP range of the present research, Chla/TP tends towards a specific value. However, for a given amount of TN, Chlaincreased rapidly with t

34、he increase in TP. Therefore, in the field, the total phytoplankton biomass is not determined by TN but by TP.</p><p>　　Our research disproved the traditional viewpoint of using N/P as an index to discrimina

35、te nutrient limiting phytoplankton. We are of the opinion that TP is the primary factor regulating phytoplankton Chla regardless of the concentration of TN.</p><p>　　3.2. Long-term whole-lake experiments in

36、Canada</p><p>　　In Lake 227, a small lake in the Experimental Lakes Area (ELA) of Ontario, Canada, researchers from Canada and the USA have performed whole-lake fertilization experiments for 37 years. The la

37、ke has been fertilized with constant phosphorus and decreasing nitrogen addition. In the end, nitrogen addition ceased. The lake remained highly eutrophic throughout the experiments, with frequent blooms of cyanobacteria

38、 and other algae.</p><p>　　For the first 6 years (1969–1974), the ratio of nitrogen to phosphorus added in fertilizer was 12:1 by mass. Lake 227 became highly eutrophic as the result of this fertilization, a

39、nd phytoplankton developed rapidly and formed blooms. The average Chla was 0.03 mg/L. The algal assemblage was dominated by small unicellular desmids with large populations of Limnothrix redekei. No nitrogen-fixing alga

40、was found. For the next 15 years (1975–1989), the ratio of nitrogen to phosphorus in fertilizer adde</p><p>　　In China, the blooming sequence of algae in Lake Chaohu, Lake Dianchi and Lake Erhai is similar t

41、o that in the Canadian experiment lake. Nitrogen-fixing cyanobacteria generally form blooms in spring, while non-fixersgenerally form blooms in summer. This phenomenon may imply that in these lakes a cyclical process of

42、denitrification and nitrogen fixation occurs, and it also indicates that nitrogen control does not exactly help the mitigation of eutrophication and cyanobacteria bloom.</p><p>　　4. To mitigate eutrophicatio

43、n, it is not nitrogen but phosphorus that should be reduced</p><p>　　The new-found general rule is of great practical value for lake management. It indicates that, for the practices of nutrient control, it i

44、s not nitrogen but phosphorus that should be reduced to mitigate eutrophication unless the nitrogen concentration is too high to the extent of being toxic to human beings or other organisms. In fact, this has been proved

45、 to be true by whole-lake experiments and practices of lake restoration. It should be so according to logical reasoning and cost comparison.</p><p>　　4.1. Whole-lake experiments indicate that phosphorus alon

46、e can effectively mitigate eutrophication</p><p>　　To explore the mechanism of eutrophication, whole-lake fertilization experiments were performed in two lakes in the Canadian Experimental Lakes Area, one in

47、 Lake 304 (3.62 ha in area) and the other one in Lake 226 (16.1 ha in area). The one in Lake 304 lasted 3 years (1971–1973). During the 3 years, prior to fertilization, phytoplankton Chla was generally below 0.01 mg/L. I

48、n the first two experimental years, 5.5 g/m2carbon, 5.2 g/m2 nitrogen, and 0.4 g/m2 phosphorus were added to the lakes each </p><p>　　4.2. Practices of lake restoration indicate that focus on phosphorus can

49、mitigate eutrophication effectively</p><p>　　Lake restoration practices in Europe and America also prove that the focus on phosphorus can effectively mitigate eutrophication. The most representative case is

50、the recovery of Lake Washington in Seattle, USA. It is the second largest natural lake in the state of Washington, with an area of 87.6 km2. During the 1930s, sewage entering the lake caused a rapid increase in phosphoru

51、s of lake water and severe eutrophication. Blooms of cyanobacteria occurred continuously from 1955 to 1976. Since 1936</p><p>　　In China, the Diversion Project of Lake Xihu is an experiment succeeding in eut

52、rophication mitigation, in which only phosphorus was controlled. The project has been put into practice since 2003. Water from the Qiantangjiang River was diverted to the various regions of Lake Xihu after preliminary tr

53、eatment. Nutrients from river water before the preliminary treatment were high, with TN and TP of 3.08 mg/L and 0.13 mg/L, respectively, in 2005. In the process of preliminary treatment, only flocculat</p><p&g

54、t;　　5. Suggestions on loosening or cancelling nitrogen control and abatement of lake eutrophication</p><p>　　To accelerate the solving of the eutrophication crisis, four suggestions are proposed as follows a

55、ccording to the above-mentioned reviews and relevant research.</p><p>　　5.1. Perform pilotscale experiments as quickly as possible: loosen or cancel nitrogen control in wastewater treatment</p><p&

56、gt;　　In China, the problems of lake eutrophication and cyanobacteria bloom are becoming more and more severe. The most fundamental restoration measure is pollutant control. However, many wastewater treatment plants do no

57、t run regularly due to the high costs. The complex process of nitrogen removal is the main reason. It is better to try to remove phosphorus only and not to remove nitrogen or remove less nitrogen than to leave these trea

58、tment plants unused. It is suggested to perform pilotscale experi</p><p>　　There may still be someone who disagrees with our viewpoint of “no need for nitrogen control to mitigate eutrophication”. In this ca

59、se, we may follow the principle of “No Argument” proposed by Mr. Xiaoping Deng and perform pilotscale experiments as quickly as possible to reduce or cancel nitrogen control to test this method as a practical restoration

60、 on a larger scale.</p><p>　　5.2. Revise discharging standard of pollutants and quality standards for surface water to delete nitrogen limits</p><p>　　When considering only the control on phytop

61、lankton, there is no need to control nitrogen for relevant water quality standards. However, the limits on nitrogen set by the present standards of our country are too strict. The limits of Discharging Standards of Pollu

62、tants for Municipal Wastewater Treatment Plant (GB 18918-2002) and Environmental Quality Standards for Surface Water (GB 3838–2002) on total nitrogen are 15–20 mg/L (standards of First Class A and B) and 0.2–1.0 mg/L (Cl

63、asses I–III), whi</p><p><b>　　譯 文</b></p><p>　　題目：緩解湖泊富營養(yǎng)化：放開氮控制并專注于磷的減排</p><p><b>　　摘要</b></p><p>　　傳統(tǒng)上，氮的控制被認為是降低湖泊富營養(yǎng)化和藍藻水華的重要組成部分，然而，最近這一觀點被

64、中國和北美的研究人員所反駁。在本文中，指出了氮控制的傳統(tǒng)觀點缺乏科學的依據(jù)：N/P的假設(shè)只是一種主觀臆斷；瓶生物測定實驗無法模擬固氮的自然過程。通過對超過40個長江流域湖泊的多年比較研究表明，磷是決定浮游植物生長的關(guān)鍵因素，無論氮濃度還是總浮游植物生物量都是由總磷而不是由總氮濃度來控制的。北美的長期全湖實驗認為氮控制不會減少浮游植物生物量，這些研究成果概括而論，即是氮含量的減少可能不會減少總浮游植物生物量，因為它可以刺激固氮藍藻水華。為

65、了減輕水體富營養(yǎng)化，應(yīng)該減少水體中磷的含量，而非氮含量，除非氮濃度過高，而對人類或其他生物產(chǎn)生了直接毒性影響。最后，本文提供了關(guān)于如何減少對氮，以及如何減輕水體富營養(yǎng)化控制的細節(jié)。</p><p>　　關(guān)鍵詞 湖泊富營養(yǎng)化；藍藻水華 </p><p><b>　　1．引言</b></p><p>　　水體的富營養(yǎng)化是營養(yǎng)物質(zhì)富集，刺激初級生產(chǎn)

66、者大量繁殖的現(xiàn)象。其特點通常是藻類大量繁殖，從而引起水質(zhì)惡化，魚類死亡。它正在成為全球性的環(huán)境危機。在中國，湖泊富營養(yǎng)化的問題極其嚴重，影響了經(jīng)濟發(fā)展和社會穩(wěn)定。最有代表性的個案，是發(fā)生在2007年的太湖水華事件，造成江蘇省無錫市5萬市民的飲用水和生活用水的短缺。因此，對中國和世界而言，緩解湖泊富營養(yǎng)化和藍藻水華都具有重要意義。</p><p>　　為了減輕水體富營養(yǎng)化和藍藻水華，營養(yǎng)控制是基本的過程。傳統(tǒng)上，除

67、了控制磷，氮的控制通常被認為是必要的做法。在污水處理過程中雄厚的資金都用在脫氮上。然而，最近在中國和北美的研究提出了改變內(nèi)陸水域脫氮的傳統(tǒng)做法：通過對磷減排以減輕水體富營養(yǎng)化。這一發(fā)現(xiàn)對湖泊的恢復至關(guān)重要。</p><p>　　在本文中，我們指出傳統(tǒng)的氮控制觀點缺乏確鑿的科學依據(jù)。然后，通過新的研究引入來闡述一般原則：減少氮含量不能降低總浮游植物生物量，但能刺激固氮藍藻水華。最后，提出了湖面恢復的詳細建議。<

68、;/p><p>　　2．傳統(tǒng)的氮控制觀點缺乏確鑿的科學依據(jù)</p><p>　　傳統(tǒng)的限制浮游植物生物量營養(yǎng)控制的觀點的主要依據(jù)是N/P（總氮總磷比）的考慮和對瓶生物測定實驗。但是，下面的分析表明，這兩個假設(shè)與實驗不是決定性的。</p><p>　　2.1．N/P的假設(shè)是主觀臆斷</p><p>　　通常認為，如果TN/TP較大（例如TN/TP&

69、gt; 17），湖泊的富營養(yǎng)化受磷的控制；如果TN/TP較?。ɡ鏣N/TP< 10），湖泊的富營養(yǎng)化受氮的控制；如果TN/TP出于中間（例如10<TN/TP<17），湖泊的富營養(yǎng)化同時受到受磷和氮含量的控制。然而，用以指示營養(yǎng)限制的TN/TP閾值，在不同的文獻中有很大的差別，例如：10-17、10-30和7-15，因而這種方法是不可靠的。一些湖泊學家已經(jīng)使用了由Redfield提出的C:N:P比為準則，以評估營養(yǎng)限制

70、。同樣，Redfield的比值并不是通用的最佳比例，只是作為平均物種的特異性比率，不同淡水浮游植物物種中最適N/P比值變化很大，從4.1到133.3。顯然，這幾乎是不可能設(shè)置特定“截止”比例，以確定多品種的社區(qū)的限制性營養(yǎng)物質(zhì)。</p><p>　　通過分析浮游植物葉綠素N和P的回歸和散點圖，坂本首次提出了N/P假說。然而，本試驗結(jié)果表明，他對散點圖模式結(jié)論只是主觀判斷。他通過在N/P回歸線上找出了三個點，得出結(jié)

71、論認為，如果在N/P比大于15-17，磷成為至關(guān)重要的制約因素。事實上， N/P處于這個水平有十個點，其中有七個點正好落在回歸線上。顯然，這種基于次要點的推理是不正確的。同樣，他的另一個結(jié)論是基于兩個離群點，當N/P小于9-10，在分析lg(TN)和lg(chla)回歸關(guān)系，認為浮游植物是由氮限制，顯然是不正確的。因此，這個最早的經(jīng)驗證據(jù)不支持N/P假說。</p><p>　　許多研究人員用Sakamoto信奉的

72、理論來分析不同N/P比例下限制性營養(yǎng)物和變異性。然而，所有的分析并未進行嚴格的統(tǒng)計測試，未能證明在不同的N/P比值下浮游植物對氮磷的依賴程度有顯著差異。</p><p>　　總之，通過邏輯推理和實證分析，發(fā)現(xiàn)N/P的假設(shè)無確切證據(jù)，只是主觀臆斷。</p><p>　　2.2．瓶生物測定實驗的規(guī)模太小，難以模擬固氮的自然過程</p><p>　　瓶生物測定實驗也早就被

73、用來證明浮游植物在水體的限制性營養(yǎng)物。該實驗通常是在封閉的容器中，觀察營養(yǎng)物添加后浮游植物的生長來鑒別限制性營養(yǎng)物。通常持續(xù)幾個小時到1周。如果浮游植物的生長是通過加入某些養(yǎng)分的刺激，這種營養(yǎng)物被認為是限制因素。由于時間和空間規(guī)模較小，這些實驗不能模擬真正的開放系統(tǒng)，如生物固氮等一些重要的過程。因此，瓶子的生物測定實驗不能證明長期存在的氮限制的領(lǐng)域。</p><p>　　3．新的研究發(fā)現(xiàn)，氮控制無法抑制浮游植物總

74、量，但能刺激固氮藍藻水華</p><p>　　2008年5月，筆者發(fā)表文章反駁基于區(qū)域比較研究的N/P假說。2008年8月，一篇北美研究人員的文章表明，基于長期的全湖實驗中氮的控制可能會刺激固氮藍藻。因此，減少氮含量不能減少總浮游植物的生物量。這也比較合乎的氮和磷的循環(huán)特征。</p><p>　　3.1．長江流域研究</p><p>　　為了測試N/P假說，研究人員

75、對超過40個長江流域的湖泊進行了調(diào)查研究并分析了葉綠素同總氮和總磷之間的關(guān)系。幾乎所有的TP-Chla回歸曲線都有較高的R2值和較低的百分比，表明在預(yù)測總營養(yǎng)限制方面，總磷比總氮有更好的優(yōu)勢。</p><p>　　由于TN/TP比值不同的閾值已經(jīng)在文獻中提出，進一步比較了完整TN/TP回歸曲線上的TP-Chla的值和TN-Chla值的不同。結(jié)果表明，在整個TN/TP曲線中，有28組P-Chla值均較TN-Chla

76、值均更高。按照傳統(tǒng)的N/P的假說，這些情況下，應(yīng)通過磷的限制控制水體富營養(yǎng)化。然而，這些情況并不局限于較高的TN/TP比值的任何特定區(qū)域，但是均勻分布于5和50之間。這進一步表明TN/TP用在營養(yǎng)限制預(yù)測方面的失敗。</p><p>　　在總磷含量確定的情況下，葉綠素a的變化同總氮無關(guān)。也就是說，在本研究的TN/TP范圍內(nèi)，Chla/TP趨于特定的值。然而，對于總氮含量確定的情況下，總磷的增加會引起葉綠素a含量的

77、迅速增加。因此，在該領(lǐng)域，總浮游植物生物量不是由總氮而是由總磷決定。</p><p>　　本研究推翻了以N/P為指標來區(qū)分養(yǎng)分限制浮游植物的傳統(tǒng)觀點。試驗結(jié)果表明總磷是調(diào)節(jié)浮游植物葉綠素的首要因素，和總氮量無關(guān)。因此，減少了氮含量不能減少總浮游植物的量。</p><p>　　3.2．加拿大長期全湖實驗</p><p>　　在湖227（位于加拿大安大略省的實驗湖泊區(qū)一

78、個小湖泊），加拿大和美美的研究人員已進行了37年的全湖施肥實驗。該湖已被施以恒定量的磷肥和不斷減少的氮肥。在最后停止施加氮肥，整個實驗中，該湖仍然高度富營養(yǎng)化，同時藍藻等藻類大量繁殖。</p><p>　　對于前6年（1969-1974年），在肥料中加入的氮磷比例為12:1。湖227變得高度富營養(yǎng)化，而浮游植物發(fā)展迅速，形成水華。葉綠素a平均含量為0.03mg/L。藻組合的主導力量是小的單細胞Desmids和大量

79、的Limnothrix redekei，未發(fā)現(xiàn)固氮藻類。在接下來的15年中（1975年至1989年），添加到湖泊中肥料的氮磷比例下降至5:1。</p><p>　　在中國，藻類在巢湖，滇池和洱海大量繁殖的順序是相似的，在加拿大實驗湖，固氮藍藻通常在春天繁殖；微囊藻通常在夏季形成水華。這種現(xiàn)象可能意味著，在這些湖泊脫氮和固氮循環(huán)的過程發(fā)生時，氮的控制并不完全有利于富營養(yǎng)化和藍藻水華的緩解。</p>&

80、lt;p>　　4．磷的減少而非氮的減少以減輕富營養(yǎng)化</p><p>　　新發(fā)現(xiàn)的一般規(guī)則對湖泊管理很高的實用價值。它表明，對于通過營養(yǎng)控制的做法來減輕水體富營養(yǎng)化，應(yīng)當降低磷的含量而非氮的含量，除非氮濃度過高而產(chǎn)生對人體或其他生物體的直接毒性。事實上，根據(jù)邏輯推理和成本的比較，已經(jīng)證明了湖泊恢復全湖實驗和做法是正確的。</p><p>　　4.1．全湖實驗表明，單獨減少磷能有效地減

81、輕水體富營養(yǎng)化</p><p>　　為了探索富營養(yǎng)化的機制，在加拿大的實驗湖泊區(qū)——湖304（面積3.62公頃），另在湖226（面積16.1公頃）進行了全湖施肥實驗。湖304在3年（1971-1973年）之前施肥，浮游植物葉綠素a含量普遍低于0.01mg/L。在前兩個實驗?zāi)?，每年加入到湖泊?.5 g/m2的碳，5.2 g/m2的氮，和0.4 g/m2的磷。藻類變化發(fā)生在這2年，葉綠素a最大濃度分別為0.05mg

82、/L和0.12mg/L。第三年，停止施加磷肥，但碳和氮含量不變。藻類繁殖停止，葉綠素a含量恢復到施肥前的水平。在226湖實驗持續(xù)了至少14年（1973年至1986年）。使用塑料分隔窗簾分為??大致相等的兩部分（北部地區(qū)和南部地區(qū)）。在南湖地區(qū)，湖泊每年新增6.05g/m2的碳和3.16g/m2氮，總浮游植物生物量維持不變，葉綠素a含量維持在約0.01mg/L。在北部湖區(qū)，不僅碳和氮的面積添加率與南部地區(qū)相同，且前10年中每年0.59g/

83、m2磷的添加量也與南部地區(qū)相同。藍藻大量繁殖。第十個年頭后，不再施加磷肥，藻類立刻停止增長，葉綠素a含量降至0.01mg/L。與第一個實驗相比較，第二個實驗中設(shè)置的控制和持續(xù)時間較</p><p>　　4.2．湖泊修復實踐表明，專注于磷能有效地減輕水體富營養(yǎng)化</p><p>　　在歐洲和北美的湖泊修復實踐也證明，專注于磷能有效地減輕水體富營養(yǎng)化。最有代表性的案例是西雅圖的華盛頓湖，它是華

84、盛頓州第二大天然湖，面積87.6km2。在20世紀30年代，含磷污水進入湖中造成湖水嚴重富營養(yǎng)化。在1955年至1976年水華持續(xù)發(fā)生。1968年后所有污水不再排入湖中。污水改道后，總磷于1963年，1968年和1979年，分別下降0.07mg/L，0.03mg/L和0.02mg/L，氮的變化較小，硝酸鹽含量分別為0.44mg/L，0.37mg/L和0.30mg/L，總凱氏氮濃度分別為0.29mg/L，0.31mg/L和0.20mg/L

85、。同時，總浮游植物生物量顯著下降。葉綠素a含量在1963年，1968年和1979年的夏天分別為0.03mg/L，0.01mg/L和0.002mg/L。藍藻的主導地位也有所下降，從1962-1968年90％以上的水平降至1976-1978年20％以下的水平。因此，磷減排是解釋華盛頓湖富營養(yǎng)化的恢復的主要原因。</p><p>　　在中國，西湖的引水工程是僅用磷控制成功地減輕富營養(yǎng)化的經(jīng)典案例。該項目已于2003年付

86、諸實施，錢塘江水經(jīng)過初步處理轉(zhuǎn)移到西湖的各個區(qū)域。初步治理前河水養(yǎng)分較高，總氮和總磷含量分別為3.08mg/L和0.13mg/L。在初步治理的過程中，只有絮凝和沉淀的產(chǎn)生。在這個過程中不能有效地除去氮。在轉(zhuǎn)入小南湖后，該地區(qū)2005年的水的TN和TP濃度分別為2.07mg/L和0.04mg/L。然而，湖內(nèi)浮游植物生物量仍然偏低。改道后（2005-2006年），各地區(qū)的葉綠素a含量與轉(zhuǎn)移（2002-2003年）之前相比下降了11-82％的

87、水平。進一步的相關(guān)性表明，葉綠素a含量的變化在很大程度上取決于總磷的變化。這表明，專注于磷減排可以有效地控制在中國的湖泊浮游植物。</p><p>　　5．對放松或取消氮控制的建議</p><p>　　為了加快水體富營養(yǎng)化危機的解決，根據(jù)上述審查和相關(guān)研究提出如下建議。</p><p>　　5.1．盡可能快地進行在污水處理中放松或取消氮控制嘗試性實驗</p&g

88、t;<p>　　在中國，湖泊富營養(yǎng)化和藍藻水華的問題正變得越來越嚴重，最根本的修復措施是污染物控制，然而，許多廢水處理廠由于成本過高不能做到定期有規(guī)律的運行，脫氮工藝復雜是主要原因。可以嘗試只去處磷或者去除少量的氮，這比讓那些污水處理廠閑置要強得多。故建議進行嘗試性實驗，在我國各地區(qū)污水處理廠放寬控氮，同時監(jiān)測水體富營養(yǎng)化和藍藻水華的發(fā)展，以測試水處理的效率，并在全國各地推廣經(jīng)驗。預(yù)計污水處理的成本將大大降低。</p

89、><p>　　可能仍有人不同意“放松控氮，以減輕水體富營養(yǎng)化”的觀點。在這種情況下，可會遵循鄧小平先生提出的“擱置爭議”的原則，進行嘗試性實驗，盡快減少或取消氮控制，將此方法作為較大規(guī)模的實際水體恢復方案。</p><p>　　5.2．修改地表水質(zhì)量標準和污染物的排放標準，刪除氮的限制</p><p>　　僅考慮對浮游植物的控制，而不去考慮控制氮為相關(guān)的水質(zhì)標準。然而，

90、我國目前氮的限制標準過于嚴格。城鎮(zhèn)污水處理廠污染物（GB18918-2002）和地表水環(huán)境質(zhì)量標準對總氮的排放標準的限值（GB3838-2002）是15~20mg/L（第一類A和B標準）和0.2-1.0mg/L（I-III類），而有關(guān)硝酸鹽飲用水水質(zhì)的限制標準（GB 5749-2006）是10~20mg/L。顯然，各種對氮的限制措施可以大大放寬或取消，以達到經(jīng)濟實用的管理目標。然而，某些形式的氮濃度足夠高時會對人類和水生生物產(chǎn)生直接的毒

91、性。工業(yè)銨對水生動物特別是魚類毒性很大，可引起窒息，抑制ATP的產(chǎn)生，并對免疫系統(tǒng)產(chǎn)生危害。亞硝酸鹽可通過轉(zhuǎn)換攜氧載體的形式，使其不能與氧結(jié)合而造成魚類和龍蝦缺氧，最終死亡。因此，放松或取消對氮的限制之前，很有必要探索高氮對湖泊生態(tài)系統(tǒng)的影響，并確定最大允許濃度。有人建議資助一些相關(guān)機構(gòu)進行區(qū)域比較湖沼學研究和全湖實驗探索研究高氮對水生生物和湖泊生態(tài)系統(tǒng)的完整性和彈性效果的方法和強度。再與上述試驗作品組合，并根據(jù)不同水域的功能修改排放標