NTP brief on BPA receives mixed peer review

NTP brief on BPA receives mixed peer review

Peer reviewers of a federal agency’s draft brief on bisphenol A recommend lowering levels of concern for some human-health risks.

Less than 2 months after the U.S. National Toxicology Program (NTP) released its much-awaited draft brief on the human-health risks of bisphenol A (BPA), the agency’s board of scientific advisers gave the report a somewhat mixed review. In a meeting held on June 11, the experts agreed with NTP’s concern over some of BPA’s human-health impacts. But, citing a lack of sufficient evidence, the board members suggested that NTP lower the levels of concern for two of the health risks of this estrogen-like chemical. The advisory board also pointed to a missing part of the BPA puzzle—exposure data for those most vulnerable to BPA: fetuses, infants, and children.


 
ISTOCKPHOTO
Manufacturers, including Nalgene, and retailers Wal-Mart and Target have responded to public concern by withdrawing certain BPA-containing products, such as baby bottles, from stores.

This is the latest chapter in the ongoing saga over this high-production-volume chemical. Used in polycarbonate plastics and epoxy-based resins, BPA is found in many consumer products, including baby bottles, reusable plastic bottles, dental sealants, and even the dyes on credit-card receipts.

According to data collected by the U.S. National Health and Nutrition Examination Survey (NHANES), 93% of Americans 6 years and older have BPA in their bodies. “It’s pretty amazing that we are seeing detectable levels in everyone,” notes Katherine Hammond, a member of NTP’s scientific advisory board and a public-health expert at the University of California Berkeley.

Although BPA’s toxic impacts on human development and reproduction at high doses are undisputed, its low-dose effects are highly controversial.

Different panels and organizations have reviewed BPA’s low-dose effects and arrived at varying conclusions. Last summer, a National Institutes of Health panel concluded that the evidence shows that some of the adverse effects are occurring “within the range of exposure to BPA of the typical human living in a developed country.” Another panel, convened by the NTP Center for the Evaluation of Risks to Human Reproduction (CERHR), concluded that available scientific evidence pointed to “some concern” for neural and behavioral effects in pregnant women, fetuses, and children. NTP uses a five-point scale of “negligible” to “serious” to rate “concern”.

However, the CERHR panel has been at the center of much debate. It drew severe criticism for hiring a contractor who had worked for chemical manufacturers to draft the CERHR report. NTP fired the contractor, Sciences International (SI), but the panel included the work done by SI in its final report. Researchers and environmental groups have also criticized the panel’s inclusion of two nonpeer-reviewed studies funded by the American Plastics Council.

And a U.S. congressional committee is investigating industry consultants; infant-formula manufacturers, for using epoxy-lined cans; and the U.S. Food and Drug Administration’s decision not to regulate BPA.

Meanwhile, in April, Canada became the first country to declare the compound toxic and ban it from use in baby bottles.

NTP released its draft brief in April. Its conclusions were not far from the CERHR panel’s results, except that it ratcheted up the level of concern for prostate, mammary, and early puberty effects from “minimal” to “some”.

Many scientists and environmentalists approved of NTP’s conclusions, but scientists representing industry groups were not pleased. In a public comment presented at the June 11 meeting, Steven Hentges, a representative of the American Chemistry Council, said that, unlike the earlier CERHR report, NTP’s evaluation was “inconsistent” and based on “inadequate studies.”

On June 11, as the board members prepared to cast their votes on NTP’s draft brief, some experts emphasized the urgent need to fill in the missing part in the BPA story. They said that the brief’s conclusions were based on current exposure data from NHANES, which did not include people at higher risk—infants and children below the age of 6, and people with liver and gut diseases, who cannot metabolize the compound.

The board agreed with NTP’s conclusions that existing scientific evidence pointed to “some concern” over neural and behavioral effects and impacts on the development of the prostate gland in male fetuses and infants. But it also recommended lowering the level of concern for mammary gland and early puberty effects of BPA to “minimal”.

It is unknown whether NTP will adopt the board’s recommendations in its final report, due to be released later this summer. Also unclear is whether NTP’s report would influence U.S. federal regulators’ decision not to regulate the chemical.

科研

            主要从事膜制备技术及膜反应器应用、污染环境修复、企业环境风险最小化等方向研究,与新加坡国立大学化工系膜材料实验室、清华大学污染控制与环境模拟国家重点实验室、南京大学污染控制与资源化研究国家重点实验室、武汉大学分析化学中心等多家单位有着良好的科研合作关系。
科研项目
·        科技部重大项目:松花江污染底质修复技术研究(2005-10),主要完成人
·        国际合作项目企业环境风险最小化方法研究与应用,主要完成人
·        863水专项“苏州市城市水环境质量改善技术研究与综合示范”专题三“苏州古城区水环境质量改善综合整治方案”中的第一子课题“苏州古城区水环境质量改善及水生态系统修复综合工程方案”,子课题负责人
·        氯代有机有毒物质的共代谢降解过程研究(新加坡国家科技基金RP3602037
·        高效中空纤维膜研制及其在水处理过程中的应用(新加坡国家科技基金RP960710A
·        973项目入湖小流域生态系统特征及水网区生源要素输移过程研究2002CB412303 )主要完成人
·        863项目“苏州市城市水环境质量改善技术研究与综合示范”(2003AA601070)主要完成人
·        教育部浅水湖泊重点实验室基金共代谢降解过程在污染环境修复中的应用,负责人
·        留学回国人员博士后基金水处理过程环境风险最小化研究,负责人
·        中国博士后基金膜介质固定化微生物对难降解有机物污染底泥的修复技术研究 20070410535,负责人
 

 

Answer to Carbon Emissions May Lie Under the Sea

Picture of oil rig

Go deep. Huge drilling platforms akin to oil rigs could help sequester carbon dioxide on the ocean floor.

Answer to Carbon Emissions May Lie Under the Sea

By Eli Kintisch
ScienceNOW Daily News
14 July 2008

Scientists may have found a way to chemically lock up a trillion metric tons of carbon dioxide, many times the expected global carbon emissions over the next century. The plan involves injecting the greenhouse gas into huge formations of the porous volcanic rock basalt that lie on the sea floor. The approach would be expensive, however, and a host of questions remain about the technique.

Scientists around the world are examining ways to permanently store vast quantities of carbon dioxide in geologic formations. The hope is that carbon emissions from power plants or factories can someday be sequestered instead of being emitted into the atmosphere. Until now, most small- or medium-scale studies have focused on underground aquifers or depleted oil or gas wells as possible storage sites. Although feasible, these reservoirs might have limited capacity locally and could cause environmental problems, such as leakage into ground water.

Now, researchers have detailed the potential for deep-sea basalt formations to provide even more places for humanity to quarantine its carbon waste. A team led by geophysicist David Goldberg of Columbia University’s Lamont-Doherty Earth Observatory in Palisades, New York, focused on a 70,000-square-kilometer region of the Juan de Fuca plate. This honeycomb of porous basalt lies under more than 200 meters of clay roughly 200 kilometers off the Oregon coast. Analysis of drilling data along with geochemical and seismic studies reveal that this region alone could hold more than 250 billion tons of carbon–more than 120 years worth of U.S. emissions.

In the group’s scheme, reported today in the Proceedings of the National Academy of Sciences, carbon dioxide would be injected in a liquidlike state into the sea floor, where it would be held below the clay sediments for decades to centuries. There, the carbon would react with the basalt to form chalk, a chemical reaction that laboratory and field tests on terrestrial basalt formations suggest is irreversible.

Goldberg says the technique has "enormous potential," but he notes that a lot more research needs to be done. His team would like to conduct field trials, for example, to gauge potential leakage and other possible environmental side effects.

The approach is also likely to be costly, Goldberg says, requiring huge drilling platforms akin to oil rigs and hundreds of kilometers of pipelines. "It’s going to require a much more significant infrastructure investment than other carbon-sequestration concepts," he says. But Goldberg thinks that the advantage of having the carbon dioxide sequestered so far from human populations may eventually prove worth the extra cost.

2008年全国优秀博士学位论文评选结果在京公布

2008年全国优秀博士学位论文评选专家审定会日前在京结束,入选的100篇优秀博士学位论文名单由教育部学位管理与研究生教育司予以公布,自公布之日开始,进入为期60天的异议期。

  为更好地保证所评选出的全国优秀博士学位论文的质量,提高评选结果的公正性和准确性,树立良好的学术风气和维护科学道德,自入选论文名单公布之日起60日内,有发现入选论文存在学术失范行为,或论文的主要研究成果不能成立等严重问题者,可以书面方式向教育部学位管理与研究生教育司提出异议。提出异议的书面材料应包括异议论文的题目、作者姓名、学位授予单位名称、异议内容,支持异议的具体证据或科学依据,以及提起异议者的真实姓名、工作单位、联系地址、联系电话等(如需保密,请注明)。有关材料请直接寄送教育部学位管理与研究生教育司(地址:北京市西单大木仓胡同35号,邮政编码:100816)。

  异议期结束后,全国优秀博士学位论文由教育部和国务院学位委员会批准。

 

http://www.edu.cn/xin_wen_gong_gao_1114/20080523/t20080523_298182.shtml

未命名文章

2、含汞废水怎样治理,含汞化合物有何特性?

    含汞废水主要来源于有色金属冶炼厂、化工厂、农药厂、造纸厂、染料厂及热工仪器仪表厂等。从废水中去除无机汞的方法有硫化物沉淀法、化学凝聚法、活性炭吸附怯、金属还原法、离子交换法和微生物法等。一般偏碱性含汞废水通常采用化学凝聚法或硫化物沉淀法处理。偏酸性的含汞废水可用金属还原法处理。低浓度的含汞废水可用活性炭吸附法、化学凝聚法或活性污泥法处理,有机汞废水较难处理,通常先将有机汞氧化为无机汞,而后进行处理。

    各种汞化合物的毒性差别很大。元素汞基本无毒;无机汞中的升汞是剧毒物质,有机汞中的苯基汞分解较快,毒性不大;甲基汞进入人体很容易被吸收,不易降解,排泄很慢,特别是容易在脑中积累。毒性最大,如水俣病就是由甲基汞中毒造成的。

常见工业废水处理方法

1、含酚废水有何危害,怎样处理?  
    含酚废水主要来自焦化厂、煤气厂、石油化工厂、绝缘材料厂等工业部门以及石油裂解制乙烯、合成苯酚、聚酰胺纤维、合成染料、有机农药和酚醛树脂生产过程。含酚废水中主要含有酚基化合物,如苯酚、甲酚、二甲酚和硝基甲酚等。酚基化合物是一种原生质毒物,可使蛋白质凝固。水中酚的质量浓度达到0.1一0.2mg/L时,鱼肉即有异味,不能食用;质量浓度增加到1mg/L,会影响鱼类产卵,含酚5—10mg/L,鱼类就会大量死亡。饮用水中含酚能影响人体健康,即使水中含酚质量浓度只有0.002mg/L,用氯消毒也会产生氯酚恶臭。通常将质量浓度为1000mg/L的含酚废水.称为高浓度含酚废水,这种废水须回收酚后,再进行处理。质量浓度小于1000mg/L的含酚废水,称为低浓度含酚废水。通常将这类废水循环使用,将酚浓缩回收后处理。回收酚的方法有溶剂萃取法、蒸汽吹脱法、吸附法、封闭循环法等。含酚质量浓度在300mg/L以下的废水可用生物氧化、化学氧化、物理化学氧化等方法进行处理后排放或回收。

生物修复

生物修复的基本概念
  随着工农业生产的发展,工业生产中排放的废水、固体废弃物、农田中施用的农药、石油开采中的井喷及运输中的泄漏等对水体、土壤环境的污染日趋严重,从而引起人们的关注。微生物是自然界生态系统中的分解者,它可使进入环境的污染物不断地降解,最终转化为CO2、H2O等无机物,使污染的环境得以净化,然而在某些天然污染环境中往往因缺乏合适的降解微生物或因微生物数量(浓度)过低、缺乏使微生物生长所必要的营养(如N、P等),缺乏足够的溶解氧等条件,使污染环境的自净过程极其缓慢,甚至还会因污染速度大于净化速度,使污染物不断贮积,结果环境污染程度更趋严重。
  为了改善人类居住的环境,人们采用活性污泥法、生物膜法,通过建造大型污水处理厂来解决水体的污染;采用生物堆肥法来解决有机生活垃圾对环境的危害。实践证明这些方法是十分有效的,在上述治理工程中我们通过人工曝气来增加溶氧,以满足微生物降解有机污染物时耗氧的需要,并提高处理的负荷;在难降解的工业废水及有机垃圾处理中,通过投菌法添加高效降解菌来提高污水处理系统和垃圾堆肥场中高效降解微生物的数量,增强其降解污染物的活性和提高处理效果;在污染成分单一的工业废水处理中,通过添加合适的营养来促进微生物的生长,从而提高处理效果,缩短净化时间。上述环境工程技术在解决点源污染中卓有成效,并发挥了巨大的作用;但要将这类环境工程的方法用于治理受污染的地面水体、受石油污染的洋面、受污染的土壤地下水时,不可能为此兴建大型的处理厂,也几乎不可能将污染的土壤、水体运送至固定的处理厂处置。在这种情况下,人们设想在天然的环境下通过某些工程手段以强化污染物降解的生物净化作用,使污染物在被污染的河道、海洋、地下水、土壤中就地(on site)或现场得到净化处理。生物修复(Bioremediation)技术就是在这种背景下被开发,并在20世纪90年代得到迅速发展的一项污染治理工程技术。实践表明,生物修复技术具有以下优点:
1. 费用省,仅为现有环境工程技术的几分之一;
2. 环境影响小,不会形成二次污染或导致污染物转移;
3. 可最大限度地降低污染物浓度;
4. 可用于处理其他技术难以应用的场地,如受污染的土壤和地下水。

1. 生物修复发展简史
  早在50年代末和60年代初,美国康奈尔大学马丁、亚力山大与他的学生针对《寂静的春天》发表后人们对环境中农药的污染和残毒问题的关注而展开了农药在土壤中可降解性的研究,为后来生物修复技术在环境保护中的应用打下了基础,其后他坚持对不同的工业合成物及污染物在土壤中的可降解性进行研究。70年代以后可以说是环境技术和环境微生物学的大发展时期,这种势头一直延续到今天。在这段时期内,污染物的可降解性和分解途径等方面的研究有了较大的进展,如斯坦福大学的麦卡蒂和列利·杨等开始系统地研究芳香族化合物在厌氧及好氧条件下降解的途径及机理。当时埃克逊油轮在阿拉斯加的漏油事故为生物修复技术在治理海洋石油污染中的应用提供了一次良机,并得到了社会的认同。在治理过程中,亚特拉斯等微生物学家提出了切实可行的实地示范和治理方案,证实了环境中的土著微生物(Indigenous microorganizms)能够分解石油成分,而限制这些微生物在自然条件下分解石油的因素是环境中N、P营养成分相对贫乏。 与此同时,密歇根州立大学的杰姆斯实验室,首次从污染河泥中分离出了具有脱氯功能的厌氧微生物――蒂氏脱硫念珠菌(Desulfomonile tiedjei),后来又提出还原脱氯反应与微生物的能量代谢是结合在一起的理论。由于含氯有机物在好氧条件下很难分解,厌氧还原脱氯为此类化合物在自然条件下的分解提供了一条途径,也为人们对微生物代谢途径的了解增加了认识,后来许多学者从不同环境中分离出了能分解不同种类氯代有机物的微生物,其中包括能分解二噁英的细菌。
  鉴于土壤污染的严重危害,世界各发达国家纷纷制定了土壤修复计划。在受有机污染的土壤治理中,业已证明生物修复技术最有效可行可靠。荷兰在1980年已花了约15亿美元进行土壤修复工作,德国在1995年投资约60亿美元进行土壤修复工作,美国90年代计划用于土壤修复方面的投资约数百亿到数千亿美元。至1989年,在美国超级基金场地土壤污染处理的项目中,采用生物修复技术已占8.4%。美国已将生物修复治理作为首选考虑的方法之一。如果生物处理适用于某一污染地点的治理,就不再要求采用其他方法。欧洲各发达国家从80年代中期就对生物修复进行了研究,并完成了一些实际的处理工程,整个欧洲从事生物修复工程技术的研究机构和商业公司约近百个,实践表明生物修复技术是有效的,利用微生物分解有毒有害污染物的生物修复技术是治理大面积水体和土壤有机污染的廉价而实用的方法。
  1991年3月,在美国的圣地亚哥举行了第一届原位生物修复国际研讨会,来自北美、欧洲、亚洲和澳洲20个国家的700位学者与会,交流和总结了生物修复工作中的实践和经验,并出版了两本论文集,使生物修复技术的推广和应用走上了更加迅猛发展的道路。
  我国正面临土壤和水体污染日益严重的巨大压力,大面积区域污染主要以有机污染为主,如农药、固体废弃物及其渗滤液等。据统计,我国每年施用农药达50~60万吨,每年施用农药的农田在2.8亿公顷以上,其中约80%的农药直接进入环境,不仅影响到土壤环境质量和农作物品质,而且还进一步污染地面水体和地下水资源以及海洋环境,直接威胁人类的生存环境和身体健康。石油污染在我国也相当严重,同样也造成了土壤、水体(包括地表水、地下水和海洋)的污染,此外工业废水及固体废弃物的排放也与日俱增,其中不乏对生物和人体具有高毒性的环境优先污染物。这些污染物多途径地进入环境后较难降解消失,结果对生态系统造成极大的危害,因此对其进行治理是摆在我们面前急切需要解决的问题。可以预见,生物修复技术在我国具有广泛的市场和发展前景。在21世纪,生物修复技术将成为我国生态环境保护领域最有价值和最具生命力的生物处理技术。

2. 生物修复的原理
  受污染的环境中有机物除少部分是通过物理、化学作用被稀释、扩散、挥发及氧化、还原、中和而迁移转化外,主要是通过微生物的代谢活动将其降解转化。因此,在生物修复中首先须考虑适宜微生物的来源及其应用技术。其次,微生物的代谢活动需在适宜的环境条件下才能进行,而天然污染的环境中条件往往较为恶劣,因此我们必须人为提供适于微生物起作用的条件,以强化微生物对污染环境的修复作用。

2.1 用于生物修复的微生物及其他生物
  (1) 土著微生物
  由于微生物的种类多、代谢类型多样,“食谱”广,凡自然界存在的有机物都能被微生物利用、分解。例如,假单胞菌属的某些种,甚至能分解90种以上的有机物,可利用其
中的任何一种作为唯一的碳源和能源进行代谢,并将其分解。对目前大量出现,且数量日益上升的众多人工合成有机物,虽说它对微生物是“陌生”的,但由于微生物有巨大的变异能力,这些难降解、甚至是有毒的有机化合物,如杀虫剂、除草剂、增塑剂、塑料、洗涤剂等,都已陆续地找到能分解它们的微生物种类。据报道,能够降解烃类的微生物有70多个属、200余种;其中细菌约有40个属。可降解石油烃的细菌即烃类氧化菌广泛分布于土壤、淡水水域和海洋。表4-24中列举了某些难降解有机物和重金属及其相应的降解转化微生物。
 难降解有机污染物和重金属及其相应的降解转化微生物
污染物 降解菌 参考文献
五氯酚 Flavobacterium属 (Hu Zhong-Cheng 1994)
Phanerochaete soidida (Lamar,R.T. etal. 1994)
Pnanarochaete chrysosporium (Kang Guyoung et.al 1994)
Trametes verscolor (Logan,B.E. et.al 1994)
氯酚 Rhodotorula glutinis (Katayama-Hirayama et.al 1994)
多环芳烃(PAH)类 Bacillus属,Mycobacterium属 (Maue,G. et.al 1994)
Nocardia属,Sphingomonas属
Alcaligenes属,Pseudomonas属
Flavobacterium属
高分子PAH   Mycobacterium sp. strain PYR-1 (Kelley,I. et.al 1995)
2-硝基甲苯 Pseudomonas sp. JS42   (Haigler,B.E. et.al 1994)
蒽醌染料 Bacillus subtilla   (Itoh,K. et.al 1993)
甲基溴化物 Methylocoocus capsulatus (Oremland,R.S. et.al 1994)
氯苯 Pseudomonas sp. (Nishino,S.F. et.al 1994)
多氯联苯(PCB)   Pseudomonas属,Alcaligenes属   (Dercova,K. et.al 1993)
石油化合物   Bacteroides属,Wolinella属   (Jun,E.H. et.al 1994)
Desulfomonas属, Desulfobacter属
Desulfococcus属,Megasphaera属
Acinetobacter sp. (Kwon,K.K. et.al 1994)
n-十六烷 Acinetobacter sp. (Espeche,M.E. 1994)
间硝基苯甲酸 Pesudomonas sp. (Nadeau,L.J. 1995)
3-羟基丁酸聚合物及其与 Acidovorax facilis (Mergaert,J. et.al 1993)
3-羟基戊酸聚合物的共聚体 Variovorax paradoxus
Bacillus属,Streptomyces属
Aspergillus fumigatus
Penicillium 属
氯化愈创木酚 Acinetobacter junii   (Gonzalez,B. et.al 1993)
农药:莠去津,扑灭津,西玛津 Rhodococcus sp. B-30   (Behki,R.M. et.al 1994)
β硫丹 Aspergillus niger (Mukhenee,I. et.al 1994)
1,4-二氧六环 Actinomyces CB1190   (Perales,R.E. et.al 1994)
2,4-二氯苯氧乙酸(2,4-D) Pseudomonas capacia (Daugherty,D.D. et.al 1994)
2,4,5-三氯苯氧乙酸(2,4,5-T) Burkholdena cepacia AC1100   (Saubaras,D.L. et.al 1995)
高浓度脂类   Pseudomonas sp. (Chappe,P. et.al 1994)
Aeromonas hydrophila
Staphylococcus sp.
水胺硫 动性球菌属   (赵金辉等 1995)
甲胺磷 Pseudomonas sp. WS-5 (肖华胜等 1995)
单甲脒 Pseudomonas mendocina DR-8   (刘志培等 1995)
洁霉素 Aeromonas sp. (罗国维等 1995)
重金属: CoPseudomonas (Yasmin,S. et.al 1991)
Pb Ca Cr Desulfovibrio desulforicans (Kafkewitz,D. et.al 1994)
镅(Am) 钚(Pl) Citrobacter sp. (Macaskie,L.E. et.al 1994)
Ni2+ Desulfovibrio sp. (吴乾箐等 1995)
Cr6+ Desulfovibrio sp. (汪频等 1994)
Cd Rhizopus oryzae (Huang,C. et.al 1994)
有机汞   Bacillus sp.   (Nakamura,K. et.al 1994)
  天然的水体和土壤是微生物的大本营,存在着数量巨大的各种各样微生物,在遭受有毒有害的有机物污染后,可出现一个天然的驯化选择过程,使适合的微生物不断增长繁殖、数量不断增多。另外,有机物的生物降解通常是分步进行的,整个过程包括了多种微生物和多种酶的作用,一种微生物的分解产物可成为另一种微生物的底物,在有机污染物的净化过程中我们还可以看到生物种群的这一生态演替,我们可据此来判断净化的阶段和进程。由于土著微生物降解污染物的巨大潜力,因此在生物修复工程中充分发挥土著微生物的作用,不仅必要而且有实际的可能。
  (2) 外来微生物
  在废水生物处理和有机垃圾堆肥中我们已成功地用投菌法来提高有机物降解转化的速度和处理效果,如应用珊瑚色诺卡氏菌来处理含腈废水,用热带假丝酵母来处理油脂废水等。因此,在天然受污染的环境中,当合适的土著微生物生长过慢,代谢活性不高,或者由于污染物毒性过高造成微生物数量反而下降时,我们可人为投加一些适宜该污染物降解的与土著微生物有很好相容性的高效菌。
  目前用于生物修复的高效降解菌大多系多种微生物混合而成的复合菌群,其中不少已被制成商业化产品。如光合细菌(Photosynthetic Bacteria,缩写为PSB),这是一大类在厌氧光照下进行不产氧光合作用的原核生物的总称。目前广泛应用的PSB菌剂多为红螺菌科(Rhodospirillaceae)光合细菌的复合菌群,它们在厌氧光照及好氧黑暗条件下都能以小分子有机物为基质进行代谢和生长,因此对有机物有很强的降解转化能力,同时对硫、氮素的转化也起了很大的作用,目前国内有很多高校科研院所和生物技术公司有PSB菌液、浓缩液、粉剂及复合菌剂出售,经应用于水产养殖水体及天然有机物污染河道的治理已显示出一定的成效。由玉垒环境生物技术公司生产的玉垒菌,是以一类高温放线菌为主的复合菌剂,其中的YL活性生物复合剂H15经用于苏州河支流新泾港程家桥河段后,180天内对底泥中有机物(在有外来污染物不断进入的条件下)降解率为20%左右,对促进底泥的矿化也显示出一定的效果。美国CBS公司开发的复合菌制剂,内含光合细菌、酵母菌、乳酸菌、放线菌、硝化菌等多种微生物,经对成都府南河、重庆桃花溪等严重有机污染河道的试验,对水体的COD、BOD、NH3-N、TP及底泥的有机质均有一定的降解转化效果。美国Polybac公司推出了20余种复合微生物的菌制剂,可分别用于不同种类有机物的降解,氨氮硝化等。日本anew公司研制的EM生物制剂,由光合细菌、乳酸菌、酵母菌、放线菌等共约10个属80多种微生物组成,已被用于污染河道的生物修复。其他用于生物修复的微生物制剂尚有DBC(Dried Bacterial Culture)及美国的 LLMO(Liquid Live Microorganisms)生物活液,后者含芽孢杆菌、假单胞菌、气杆菌、红色假单胞菌等七种细菌。
  (3) 基因工程菌
  自然界中的土著菌,通过以污染物作为其唯一碳源和能源或以共代谢等方式,对环境中的污染物具有一定的净化功能,有的甚至达到效率极高的水平,但是对于日益增多的大量人工合成化合物,就显得有些不足。采用基因工程技术,将降解性质粒转移到一些能在污水和受污染土壤中生存的菌体内,定向地构建高效降解难降解污染物的工程菌的研究具有重要的实际意义。
  70年代以来,发现了许多具有特殊降解能力的细菌,这些细菌的降解能力由质粒控制。到目前为止,已发现自然界所含的降解性质粒多达30余种,主要有4种类型:假单胞菌属中的石油降解质粒,能编码降解石油组分及其衍生物:如樟脑、辛烷、萘、水杨酸盐、甲苯和二甲苯等的酶类;农药降解质粒,如2,4-D、六六六等;工业污染物降解质粒,如对氯联苯、尼龙寡聚物降解质粒等;抗重金属离子的降解质粒。
  利用这些降解质粒已研究出多种降解难降解化合物的工程菌,Chapracarty等为了消除海上溢油污染,将假单胞菌中不同菌株的CAM,OCT,SAL,NAH四种降

Tropical Biofuels Getting Less and Less Green

Picture of rainforest

Knockdown fight. New research suggests that using tropical rainforests to grow biofuels could be even trickier than previously estimated.

A new analysis suggests that biofuels grown in the tropics are not a much greener source of energy than drilling for oil–at least in the short term. The research paints an even gloomier picture of biofuels than previous studies, which have begun to cast doubts on the greenhouse gas benefits that these alternatives to petroleum might provide.

Proponents see plant-based biofuels as a carbon-friendly alternative to fossil fuels. That’s because plants that produce, say, palm oil or corn ethanol recycle carbon dioxide from the atmosphere as they grow. In contrast, petroleum production introduces new carbon into the air that was previously sequestered deep within Earth.

Two studies published earlier this year in Science, however, suggest that the carbon benefits from biofuels are delayed for centuries when farmers knock down carbon-absorbing forests in order to grow the plants. One paper, for example, estimated that cutting down Brazilian rainforest to grow soybeans for diesel fuel would result in a so-called carbon debt that would take 319 years to repay–essentially rendering the fuel as carbon-unfriendly as gasoline in the short term.

But critics, including the U.S. Department of Energy, have charged that such analyses underestimate the yield of biofuel crops, especially those grown in the tropics.

To get a better sense of just how green biofuels are, Holly Gibbs, a tropical land-use scientist at the University of Wisconsin, Madison, and colleagues used newly available data on the yields of 10 crops in various seasons and ecosystems within South American, African, and Asian rainforests. Even when Gibbs assumed that the plants would perform in the top 10% of all global varieties–with corn ethanol varieties, for example, producing more than seven times as much ethanol as current species in Africa–the picture remained gloomy. For example, corn grown with high yields in tropical forests (thanks to fertilizer, irrigation, and sophisticated farming) repaid its carbon debt in 100 years: five times faster than corn grown at normal yields. But the improvement is still a "losing proposition," Gibbs says, given the goal of stemming carbon emissions immediately. What’s more, she notes, such yields would be hard to achieve throughout the developing world anyway given the cost of world-class agriculture.

To make biofuels more efficient, Gibbs suggests growing biofuel crops in places where trees wouldn’t have to be cut down, such as in West African scrublands where cocoa plantations once grew. Otherwise, growing, say, oil palm trees on land that was previously carbon-rich peatland forests in Southeast Asia can create a nearly millennium-long carbon debt, the team reports online today in Environmental Research Letters. The paper highlights the short-term risk of ramping up production of tropical biofuels and cutting down carbon-rich forests to grow them, says Gibbs.

The new studies offer a set of estimates more precise than before for the carbon tradeoff that biofuels entail, says Princeton University agricultural expert Timothy Searchinger, an author of one of the Science papers. "Forests and grasslands have a lot of carbon, so there is really no way to transform those lands into biofuel crops that produce net benefits," he says.

 

 

A Trickle on the Moon

Picture of volcanic glass bits

Beady clues. Water molecules lurk in these volcanic glass bits from the moon’s surface.

Credit: NASA

A team of researchers has discovered the first evidence of water on the moon. A new type of chemical analysis has spotted the telltale signs of water molecules inside tiny beads of volcanic glass brought to Earth decades ago by the Apollo astronauts. The find may force astronomers to rethink their theories of how the moon formed, and it might mean that future missions could mine water from the lunar soil, helping to sustain colonists and fuel voyages to other planets.

Soon after it coalesced, about 4.5 billion years ago, Earth took at hit from a Mars-sized object. The resulting cloud of debris eventually condensed to form the moon–or so the current thinking goes. But if the moon came from Earth, and Earth is awash with water, where is the lunar water?

Many planetary scientists think any water blown away from Earth by the impact would have been instantly vaporized by the high temperatures of the collision. Nevertheless, some researchers continue to believe that the moon does contain some water, perhaps locked deep within its interior. Over the years, they’ve intensely scanned tiny glass beads–brought back by the Apollo missions in the 1960s and 1970s–that had been ejected from inside the moon by volcanic eruptions about 3 billion years ago. Up to now, however, these samples have shown no evidence that the liquid ever existed on the moon.

A team led by geochemist Alberto Saal of Brown University decided to use a more sensitive method. The technique, called secondary ion mass spectrometry, was developed to detect trace amounts of volatile gases such as chlorine and fluorine in Earth soil samples. Applying it to the lunar samples, the team found trace amounts of water–about 46 parts per million–in the volcanic beads. Because the water was embedded in the beads, it can’t be a contaminant picked up since the samples arrived on Earth, the researchers report tomorrow in Nature.

Saal declines to speculate about how much water the moon contains or if any of it is still present in liquid form. Extrapolating the results to estimate the amount of lunar water would be like predicting "the final score of the game after we saw the first touchdown in the first 5 minutes of the first quarter," he says. Meanwhile, he and his team will be studying as many lunar glass beads as possible to refine their analysis.

Planetary scientist David Stevenson of the California Institute of Technology in Pasadena calls the findings important and says they open up a new possibility. "It is likely that at the time of the giant impact, Earth had water and the impacting body had water," he says, so some of that water might still be trapped in the moon.

Rain on the Martian Plain?

 

 

Picture of channels

Before the rains came. Martian water may have carved out channels like these early in its history, but eventually the torrents were replaced by light rain.

Martian soil data collected by five robotic missions indicates that rain fell on the Red Planet billions of years ago. The findings provide no new insight into the possibility of martian life, but they do suggest that further clues to Mars’s past could be found right here on Earth.

There’s little doubt now that Mars once was wet. The twin Mars Exploration rovers–Spirit and Opportunity–have been finding signs of water-associated minerals for 4 years now. And less than 2 weeks ago, the Phoenix Mars Lander struck water ice while digging at the north polar region (ScienceNOW, 20 June). What remains to be determined is where this wetness came from and how long it lasted. Preliminary investigations by Mars mission scientists, as well as high-resolution images taken by orbiters, have suggested that water on Mars surged up from deep below the surface, sometimes carving extensive channels and gullies (see photo).

Now, a team led by geologist Ronald Amundson of the University of California, Berkeley, has found indications of rain by studying our own planet’s geochemistry. Analyzing soil samples collected by five previous missions, including the 1976 Viking and 1997 Pathfinder landers, the researchers found a distinctive pattern of chloride and sulfate deposits. In all of the samples, the data show that the sulfates tend to stay nearer to the surface, whereas chloride concentrations increase with depth. That’s the same pattern found in extremely arid places on Earth such as Antarctica’s dry-valley regions and Chile’s Atacama Desert. In these areas, rain is light and infrequent, but over millions of years it can change the chemical makeup of soil by depositing sulfates near the surface and by transporting the more soluble chlorides farther into the soil.

So the picture emerging is that by about 3 billion years ago, the biggest bodies of water on the martian surface, which were derived from groundwater, had mostly frozen or evaporated, the researchers report online this month in Geochimica et Cosmochimica Acta. Then a prolonged period of intermittent drizzle and dew began. That climate apparently continued long enough to alter the chemistry of surface minerals, creating the pattern detected by the analyses.

It’s a convincing argument, says planetary scientist Itay Halevy of Harvard University: "Atmospherically delivered water and downward migration of salts, both common processes on Earth, played a part in the formation of martian soils, too." Moreover, the results "provide further chemical support for what previous studies have found: that during early parts of Mars’s history, liquid water existed on the surface for geologically significant periods of time."