The term “Natural Attenuation” (NA) has been defined as “naturally occurring processes in soil and groundwater environments that act without human intervention to reduce the mass, toxicity, mobility, volume, or concentration of contaminants in those media” (Wiedemeier et al., 1999).

 

In practice, unfortunately, the term “natural attenuation” is often used synonymously with such terms as intrinsic bioremediation, self remediation, natural restoration, passive bioremediation, or intrinsic remediation. The negative result of this is that it is increasingly common to interchange “natural attenuation” with “remediation,"  when in fact they are not synonymous.

 

If contaminants have not yet reached receptors, and they are breaking down at a faster rate than they are traveling, natural attenuation may be appropriate.

 

1. Outer portions of contaminant plumes where contaminant concentrations are very low might be left to natural attenuation while the rest of the plume is subjected to extensive treatment.

2. After active remediation has run its course -- that is, if monitoring shows that active remedies are no longer bringing significant or even measurable improvements -- then natural attenuation might be relied upon to finish the job.

3. Natural attenuation may be enhanced through the application of oxygen or other substances. Under certain conditions, simply adding oxygen to the soil or groundwater may dramatically speed biodegradation. Adding oxygen and methane to the subsurface environment may enhance cometabolism. And injecting chemical nutrients into the soil or groundwater may accelerate anaerobic degradation. One might question, however, whether "enhanced natural attenuation" is "natural" at all.

4. EPA recommends that when monitored natural attenuation is adopted as a remedy, a contingency remedy selection should also be made. That contingency would be implemented, without further consideration of remedial alternatives, if monitoring shows that natural attenuation fails to perform as anticipated. The contingency remedy should not only specify the alternate strategy; it should contain clear criteria for triggering its implementation. Those criteria should address trends in contaminant concentrations at specified locations, indications of new releases, indicators of renewed contaminant migration, rates of degradation relative to remediation objectives, and proposed changes in land use.

EPA recommends, in its policy, that monitoring be designed to accomplish the following:

• Identify potentially toxic transformation products.

• Determine if the plume is expanding either laterally and vertically.

• Ensure that there is no effect on downstream receptors.

• Detect any new releases that could effect the remedy. Detect changes in hydrogeological, geochemical, or microbiological parameters that might reduce the effectiveness of natural attenuation. While EPA's Monitored Natural Attenuation guidance lists several factors that should be considered in monitoring performance, it does not explicitly require monitoring to prove that attenuation is due to biological activity, nor does it specify what level of certainty is adequate to verify that natural attenuation is occurring.

 

那些金色的日子

岁末狂欢地中海纪行

 

从法兰克福车站回酒店的车上很安静,没有了围着我叫导游叔叔的韬韬,没有了老邓爽朗的声音,没有了跑前跑后疯狂拍照的小白two夫妇的身影……车上甚至有些寂寞.身为导游,平日里不知道经历了多少迎来送往,平常的离别早不放在心上了,可是这次告别竟然真的微微伤感而且不舍.

2006年底跨年的时候,恺撒旅行社委托我带了这个为期十天的”狂欢地中海”团,从法兰克福出发途经施特拉斯堡,里昂横穿法国大陆到波尔多,随即转头向南进入西班牙经布尔格斯,马德里,萨拉哥萨到巴塞罗那,随后一路向北重新进入法国在普罗旺斯和蔚蓝海岸划了一个美丽的弧线途径了阿尔勒,马赛,戛纳,尼斯,摩纳哥再进入意大利,米兰之后穿过瑞士回到德国.十天里空间上穿越6个国家,时间上跨越新年,.因为是新开发的线路拿到行程之后我看的特别仔细,细看之下不由得惊叹一声:呃的神啊!!!!! 这该要飞奔多少公里啊!!!后来司机算出来的公里数还是吓了我一跳,居然有5600公里之多,拿给谁看都要吓一跳的行程,怪不得不敢让别人带了.一路顺利完成了之后我自己也有些庆幸.静下心来细细回味,发现在一路飞奔的十天里居然积累了那么多丰美的记忆和闪着光芒的瞬间,尽管有些疲惫,但是那是何其美妙的疲惫啊.在下一个旅程开始之前忍不住拿起笔来想写点东西来让自己留住些什么,好永不忘记.

一切的美丽好象都是从西班牙开始的,但是记忆不是.任何美好的旅游记忆里一定都会有一些亲切可爱的人被你记住,我何其有幸在着条道路上遇到如此一群可爱,热情,亲切并且热爱生活的游伴啊.记得在里昂遇到降温,路上结了冰溜滑无比,从地铁站到圣母院短短几百米的路居然走了半小时,大家相互扶持,过马路的时候手牵手拉起人桥,没有一个脱离队伍,从那个瞬间起,我们就不再是一个简单的旅行团而更象一个家庭.

之后一切都很神奇,法国一直都阴霾着,一跨过西班牙的边境,毫无预兆地,金子般的阳光瞬间铺洒下来,天空也变得无比澄澈高远.金色阳光里的布尔格斯小城也仿佛如同黄金打造一般熠熠生辉.小城的夜里西班牙人挤满街道,和餐馆,习惯了寂寞清冷的德国夜生活的我们着实不太习惯,但是却也着实喜悦和享受.同行的报社范主编说,一个布尔格斯就值得了整个5000公里的奔驰,可他不会想到更美妙的奇遇还在后面等待呢.多么美妙的西班牙啊,广阔的田野,起伏的群山,热情拥挤的人群,久远奇妙的历史,迷人的传说,飘香的美味……更不要说开阔博大的马德里,虔诚安静的萨拉哥萨,丰富美妙的巴塞罗那…….还有那些瞬间的记忆呢.记得我们离开马德里去萨拉哥萨的路上,汽车绕过最后一道山梁,广阔的卡斯蒂里亚平原上迷漫着浓雾,从高处看去正如一片云海没有边际,见惯了美景的我也惊诧地说不出话来,车上更是一阵阵惊喜的叹息.还记得同一天下午穿出浓雾走在驶向巴塞罗那的路上我忧心忡忡,因为想带大家看看我去过的海边小城siegst,又担心夕阳沉落的太快赶不上那里的落日,于是催促司机飞奔,终于,在夕阳沉落之前,湛蓝的地中海如锦缎一般铺展在我们的眼前,大家一路小跑冲向海滩,他们如孩子般惊喜快乐的样子我永远也忘不了……

离开西班牙我们进入南法,神奇的普罗旺斯,蔚蓝海岸依然赐给我们无比美好的阳光,sete渔村的海浪灯塔,阿尔勒古老苍凉的城桓和梵高久远的往事,马赛加德尔圣母院的清晨远眺,花开四季的圣堡德旺斯,摩纳哥华美的灯火,尼斯旖旎的海浪……美丽到绝望啊.记得在圣堡的旺斯,那个岩石也仿佛会闪烁光芒的绝美小城,我盯上了来自斯图加特的小杨小姜,他们拥有的全团最好的一部相机佳能400D,于是给他们200张照片的指标,完不成不许上车,一下车小杨就如同上足了发条一般冲了出去,见什么拍什么,果然不辱使命,他的作品是这一程中最杰出的,被我在博客里疯狂引用,至今深深感谢.当然我想谁都忘不了那个奇妙的新年之夜,饱餐了海鲜的团友齐聚在尼斯的盎格鲁大道上挤在法国人群里等待新年,不知道是被一点点酒精还是被心里的快乐点燃,我们一群人在海边大声唱歌,,旁若无人,新年嘛,一群离家在外的游子用歌声宣泄一下快乐和想念谁又能说什么呢,我们的快乐甚至感染了周围的法国人,好多人过来跟我们一起蹦蹦跳跳的.歌声在回去的路上也没有止息,好象我们唱完了所有会唱的歌.

神奇的旅程结尾也神奇,阳光一直送我们到意大利的热那亚,进入山区之前我们在路边休息的时候还能远远看到地中海,大片的乌云渐渐聚集,最后几道阳光在消失在海的远方.仿佛伤感的离别.

我很感谢命运给了我这样美妙的职业和一个好奇的心灵,这些地方我都去过不止一次了,但每一次重游都依然欣喜而快乐.一路上客人们都习惯了我的大惊小怪,还常拿我的话开玩笑,每当我遇到语言无法形容的美景的时候便会说”让我死在这里吧!”因此这一路上常有人问我:曹导,你想不想死在这里?......更过分的是范主编,他后来引申我的话来形容这一程的感觉时候说简直是”死去活来”!!

不能写了,否则整版给我也写不完啊.我在自己的博客上连载了四天还没写完,我想我的客人们也会记忆很久吧.每次想到这些日子,那些交织着阳光和海洋的金色记忆一定也会让他们微笑吧.这注定将是被我们长久想念的一段旅程.翻开地图,你就会发现这个世界上有那么多自己想去的地方在等待你,导游其实更可怜,见得越多就更知道世界之广大,纵使用一生的时光也看不完这个世界的一个角落,于是情不自禁地加快了脚步,于是被我们私底下叫做”狂奔地中海”的这个行程就有了存在下去的理由:让人们在有限的时光里尽力延展生命的宽度.