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近日，发生于中国南方数省的超标镉大米风波持续发酵，引来舆论哗然。此事件不仅又一次触动了中国人对食品安全的敏感神经，同时也引发了人们对土壤污染问题的深深担忧。面对中国土壤污染的严峻形势，国土资源部表示将在全国范围内展开土壤抽样调查，绘制中国土壤污染地图，以此衡量人类活动导致的土壤重金属污染程度。但是有关该项调查的具体时间表以及结果是否会公布，相关部门则并未对外提及。一方是严峻的污染现状，另一方则是模糊的政府举动，谁来拯救饱受污染的土地以及生长于斯的民众，目前来看，似乎仍是一个无解的难题……
含镉大米凸显土壤重金属污染危机
2013年5月16日，中国广州市食品药品监管局的网站公布了第一季度餐饮食品抽验结果，其中一项结果显示：44.4%的大米及米制品抽检产品发现重金属“镉”超标。在食品安全办公室抽检的31个批次不合格大米中，显示有14个批次来自于中国湖南省，镉含量从每公斤0.26毫克到0.93毫克不等（中国的食品安全国家标准规定大米的镉限量不大于0.2mg/kg）。此抽检报告一经披露，便令素有“鱼米之乡”美誉的中国湖南省陷入了镉米危机。
受镉米事件影响，湖南大米滞销严重，米厂出现停工潮。据业界分析，湖南部分地区大米销量急降六成，米价也开始下跌。对于上述情况，当地许多农民及米厂老板表示实在不理解。“镉是什么？我都没听说过。”一位当地农民在接受媒体采访时这样说道。刘湘骥是湖南省攸县大同桥镇一家大米厂的老板。他告诉记者，他的大米厂从收谷、脱壳、碾米、抛光到包装所有程序都是物理性操作，不存在添加或产生镉等重金属污染的可能，污染物究竟从何而来，他也不得而知。
谜团：大米缘何会含镉
5月21日，镉大米来源地湖南攸县官方通报了不合格大米的镉含量范围，披露原稻主要收自当地农户，涉事米厂手续齐全，不存在生产环节重金属污染问题。
既然生产环节无污染、原稻来源也没有问题，那么，污染大米的镉又源自哪里？对此，更多业内专家表示这是一场迟早要来的危机。
南京农业大学农业资源与生态环境研究所教授潘根兴说，这些重金属的确不应该存在于农田，因为它们原本来自矿山。早在2007年，潘根兴和他的研究团队，在全国华东、东北、华中、西南、华南和华北六个地区的县级以上市场中，随机采购大米样品91个，结果表明：10%左右的市售大米镉超标。研究还表明，中国稻米重金属污染以南方籼米为主，尤以湖南、江西等省份最为严重。潘根兴表示，大米镉超标的关键在环境污染，“这取决于两个因素：土壤和品种。”
镉原本与人类没有亲密接触，但由于人在焙烧矿石及湿法取矿时，镉被释放到废水废渣中，并通过水源进入土壤和农田。自此，镉与人类形成了“剪不清，理还乱”的复杂关系，稻米成为其中的重要介质。有研究表明，水稻是对镉吸收最强的大宗谷类作物，其籽粒中镉含量仅次于生菜。
有关镉米的危害，最早于上世纪60年代在日本被发现。日本由于开矿致使镉严重污染农田，农民长期食用污染土壤上生长的稻米而导致镉中毒，患者骨头有针扎般剧痛，镉中毒因此被称为“痛痛病”，情况最严重的患者身上曾同时出现100多处骨折。
医学研究表明，镉主要在肝、肾部积累，并不会自然消失，经过数年甚至数十年慢性积累后，人会出现镉中毒症状。镉的拿手绝招是先损坏人体的肾功能，让骨骼生长代谢发生障碍，进而使骨骼出现各种病变，像骨痛病、软骨病、骨质疏松。
“镉污染大部分来自开矿。工厂排放废气中含有镉，可能会通过大气沉降影响较远的地方。”环保部南京环境科学研究所所长高吉喜表示，“即使冶炼厂距离远，其排放的废气扩散后也可能随降雨落到农田中。除此之外，农业投入品滥用、外源性污染、养殖业污染等，也使得土壤重金属污染趋势日益加剧。
土壤重金属污染严重
华中农业大学环境资源学院教授黄巧云是中国国内最早从事土壤重金属污染研究的学者之一，他认为：“镉米危机凸显了治理土壤污染的重要性与紧迫性。”据黄巧云介绍，污染土壤的重金属主要包括汞、镉、铅、铬和类金属砷等生物毒性显著的元素，以及有一定毒性的锌、铜、镍等元素。这些重金属污染物在土壤中移动性很小，既不易随水淋滤，也不为微生物降解，治理起来难度极大，更何况目前已经出现大面积的污染范围。
中国水稻研究所与农业部稻米及制品质量监督检验测试中心于2010年发布的《中国稻米质量安全现状及发展对策研究》称，中国已有1/5的耕地受到重金属污染，其中受到镉污染的耕地涉及11个省25个地区。在湖南、江西等长江以南地带，这一问题更加突出。南方省份土壤中由于重金属底值偏高，加之多年来经济结构偏重于重化工业，大量工业“三废”的排放加剧了土壤重金属污染形成。目前，华南部分城市约有一半的耕地已遭受镉、砷、汞等有毒重金属和石油类有机物污染。
“不仅污染加重，而且还在转移扩散。”潘根兴告诉记者，当前土壤污染还出现了有毒化工和重金属污染由工业向农业转移、由城区向农村转移、由地表向地下转移、由上游向下游转移、由水土污染向食品链转移的趋势，逐步积累的污染正在演变成污染事故的频繁爆发。仅2008年以来，全国已发生百余起重大污染事故，包括砷、镉、铅等重金属污染事故达30多起。
专家建议：换着产地吃大米
镉超标大米的消息持续刺激着公众敏感的神经，在饮食习惯上，专家建议不要长期食用一个地方出产的粮食，尽可能分散化，降低风险。
“换着产地吃大米”，专家的建议放到现实中，委实是退而求其次的无奈之举。不过建议仍回避不了两个问题：一、倘若镉大米的根源在于土壤污染，普通百姓又如何能确保自己所吃的大米是产自没有污染过的土壤？事实上，广州在此次抽检中发现“镉超标率达44.4%”，从而将矛头直指湖南。后经调查显示，受重金属污染的土地远非湖南一省。二、以“鸵鸟心态”（明知问题即将发生而不去想对策的逃避心理）来防范镉大米，也不是保障食品安全的上上之策。无奈的民众最终只能倚赖政府尽快给出明确的调查结果与防治措施，但是鉴于各种原因，某项调查结果迟而未宣，防治措施也由于污染状况复杂不能在一朝一夕内完成。 2006年7月18日，一场官方宣称耗资十亿元的土壤污染摸底战役在全中国悄然拉开，这项调查也是中国首次对土壤污染状况所做的综合性调查，由环保总局、国土资源部联合启动，直至2010年调查终于完成，但是纵然媒体和公众不断呼吁和追寻，调查数据和结果迄今未曾公布。对此，环保部在相关告知书中表示，此举系根据《政府信息公开条例》第14条，对“属于国家秘密”的全国土壤污染状况不予公开。
这场历时三年半的土壤污染调查，范围覆盖了除港澳台以外的所有省、直辖市、自治区的全部陆地。依照预期，各地的调查结果将绘成一张巨幅的中国土壤污染图谱。其意义不言而喻：土壤污染调查数据是所有后续治理工作的基础。
对于政府给出的保密解释，多名受访专家表示理解保密的苦衷，“在没有切实的处理办法和法规出台前，全国污染土壤状况一旦公布，将可能引起不必要的担忧和经济损失。”
但是，无论最终调查数据如何，全国土壤污染状况已是不容忽视。2012年10月的一次国务院常务会议曾透露这次历时六年的普查的整体结论，“全国土壤环境状况必须引起高度重视，工矿业、农业等人为活动是造成土壤污染的主要原因。”既然如此，公众也只有企盼政府尽快出台相应的土壤防治法规及处理办法，唯有此土壤污染调查数据才有望公开，后续的治理工作才能随之有序进行。
土壤“排毒”
迫在眉睫
长期以来，比之大气污染和水污染，土壤污染所受到的重视程度似乎不如前两者。大气污染和水污染更有可视性、可感性，而土壤污染缺少直观的感受，问题的暴露也不在于一时，因此被称作“看不见的污染”。
鉴于近年来因土壤污染而造成的事故频频被曝出，外界对受重金属污染的土壤进行修复的呼声也逐渐高涨。不过，对此种说法“泼凉水”的人也不在少数。农业部环境保护科研监测所研究员、土壤学专家侯彦林告诉中国经济时报记者，对受污染的土壤治理不过是一种末端策略和不得已而为之的办法。他预计，基于土壤修复的技术、经济、社会等层面的原因，除尾矿开发外，土壤重金属修复在未来10到20年内很难形成产业。根治土壤污染的当务之急不是修复，而是国家下大力气控制好污染源。
严控污染源
在侯彦林看来，土壤污染修复不论是算经济账，还是生态账，其可行性和有效性均很有限。他甚至断言，相比大气和水污染的治理，土壤污染很难得到有效治理。
他举例指出，土壤修复的方法大概有如下几项，一是换土法。二是利用生物和植物修复。三是向土壤中加入石灰性物质等其它物质来改良土壤性能的钝化法。在他看来，以上三种方式的可操作性均有限。
就换土而言，侯彦林认为，撇开换土的成本不谈，“在某些污染地区就没有好土，怎么换？不像花盆换土，大田污染往往是少则几十万亩。”而如果要采取将上层的受污染土壤换到下层的方式，则如果放任污染源继续污染，那新土再过几年也同样会被污染。
土壤修复中“换土法”不可行，那植物吸收法和向土壤中加中和物质的钝化处理法又是否可行呢？侯彦林表示，当土壤中的有色金属含量过高时，植物可能根本就无法生长。植物修复法只适合于轻度土壤污染的情况，通过种植一些对重金属吸附性大的植物，达到修复土地的效果。而对于钝化处理法，侯彦林则认为，因土壤本身具有缓冲性，无论你放多少中和物质，放一年两年有效，三年后可能又回到原来状态。因此，所付出的经济成本是长期且不可估量的，而且加入的物质极有可能会对土壤造成新的危害。
“当前最重要的不是探讨如何修复受污染的土壤，而是如何去找出污染源，杜绝污染源。”侯彦林指出，只有在杜绝污染源的基础上进行的修复工作才能真正产生效果。对于轻度污染的土壤可采取上述几种修复方法，而对于中度和重度的土壤污染，则可通过调整产业结构的方法，比如，不以农业为主，通过种植一些非食用作物，如花草、树木等，或在城市郊区修建物流中心、公园、娱乐场所等，以改变土地的利用方式。
摸清土壤污染“家底”
除此之外，尽快摸清土壤污染“家底”，也是进行土壤后续修复工作的重要前提。中国地质大学地球科学院教授李长安认为，眼下最重要的是尽快启动中国“带病”土壤现状调查，掌握土壤“致病”原因，分类而治。同时，国家要尽快出台相关的法律法规，使土壤污染防治工作步入法制化轨道，像大气和地表水一样，建立土壤土质的污染监测站点，严厉打击污染土壤的行为，严惩肇事者。
土壤环境保护立法研究专家组组长、武汉大学环境法研究所所长王树义提出，应该为污染的土壤建立“污染档案”，保障公民对土壤环境的知情权；另外，还要建立土壤污染控制区，确定什么样的土地适合种植，什么样的土地适合居住。如果某个区域的土壤受到污染比较严重，就应该把它设为管制区，如果污染非常严重，就要完全禁止经济活动。
中科院武汉水生所副所长徐旭东则建议，可以采用立体治污的办法推动产业升级，阻止污染继续恶化。同时，严格保护粮食主产区的土壤环境，将保护重点放在遏制外源污染和侵蚀上，杜绝工业废物向粮食主产区排放。
国土资源部、中国地质调查局日前也发布了消息，决定全面会诊土壤重金属污染现状，绘制土壤重金属“人类污染图”。按照设想，该项目将在全国建立涵盖81个化学指标（含78种元素）的地球化学基准网：以120万图幅为基准网格单元，每一个网格都布设采样点位，每个点位都采集一个深层土壤样品和一个表层土壤样品。用表层含量减去深层含量，即能得出重金属元素的“人类污染图”。
此次国家绘制土壤重金属污染图，好比给一个病人绘出的病情图，知道病情后，才能有的放矢，由此可知此项调查的重要意义。但是，此番举动是否会如2006年启动的土壤污染调查一般没有下文，公众也不得而知，唯有期待不会再是一场空等。
Warning of Soil Pollution
Reported by Duan Ying Translated by Zhu Luqi and Guo Qi Recently， the “Cadmium Rice” scandals in several southern provinces of China have been in the spotlight and made public opinion seething with indignation. This event not only touches Chinese people’s sensitive nerves for food security， but also arouses wide concern about the issue of soil pollution. Facing the grim situation of soil pollution in China， Ministry of Land and Resources says that they will conduct a sampling survey all over China and make a map of soil pollution in China， in order to measure the degree of soil pollution by heavy metals caused by human activities. But it remains uncertain whether the detailed schedule for this survey will be announced. On one hand， it is the seriously contaminated soil； on the other hand， it is the ambiguous actions of governments. Who can save the people who suffer from soil contamination？ At present， it seems an intractable problem still.
“Cadmium Rice” Reflects the
Crisis of Soil Pollution by Heavy
The market of rice produced in Hunan Province was also affected by the cadmium crisis. Many rice factories were in the condition of shutdown. According to the industrial analysis， the sales volume in Hunan Province was reduced by 60%， and the rice price started to decrease. Most of the farmers and factory directors were very confused， because they could hardly understand the situation they were facing. One of the local farmers told the reporter that “what is cadmium on earth？ I’ve never heard about it.” Liu Xiangji was the director of a rice factory in Datongqiao Town， You County， Hunan Province， and he told the reporter from Xinhua News Agency that his factory had always followed the rules of physical operation in every process： collecting， shelling， milling， polishing， and packing. There was no chance or possibility of cadmium pollution in the producing process， and he didn’t know where the pollution source came from.
Mystery： How Come Rice Contains Cadmium
On May 21， Authorities in You County， Hunan Province announced the amount range of cadmium in rice. They also disclosed that the crop was mainly collected from the local farmers， and the formalities of rice factories involved were all complete， which meant the heavy metal pollution was not from the producing process.
Given that there was no pollution in the producing process， and the crop was all clean， where was the source of the cadmium？ Responding to this situation， many experts believed that this was a crisis that would come sooner or later. Pan Genxing， Professor from the Institute of Agricultural Resources and Environment， Nanjing Agricultural University， told us that the heavy metals should not have been in rice field， because they were supposed to exist only in mines. Earlier in 2007， Pan Genxing and his research team conducted a sampling inspection by selecting 91 samples in the above-county-level markets in East， Northeast， and Central， Southwest， South and North areas of China. The result showed that about 10% of the rice commercially available was with cadmium exceeding the official limit. The research also showed that the heavy metal pollutions were mainly found in long-shaped rice produced in South China， especially in the Provinces of Hunan and Jiangxi. Pan Genxing also told us that the key of excessive cadmium in rice lies in environmental pollution. “It is up to two factors： soil and variety.”
Cadmium does not have such a close connection with mankind. However， in the processes of roasting ore and wet-method reclaiming， cadmium is released in sewage and waste residue， and then blended in soil and rice field. After that， cadmium and mankind start a complicated relation， with rice crop working as an important medium. There are studies showing that rice is highly capable of absorbing cadmium， and the cadmium amount in its seeds is only less than in lettuce.
The harm brought by “cadmium rice” was first found at 1960s in Japan. At that time， many rice fields were polluted by cadmium because of mining， and the farmers constantly fed by the polluted rice were cadmium poisoned. Those patients suffered huge pain in the bones， so cadmium poisoning was also known as “itai-itai”. The most serious patient even had more than 100 bone fractures at one time.
Medical research shows that cadmium is mainly accumulated in the liver and kidney， and it will not disappear by itself. After several years or decades of accumulation， people will have the symptoms of cadmium poisoning. The cadmium usually first destroys the functioning of kidney， which will lead to an impediment in the growth and metabolism of bones. The bones will gradually have various pathological changes like itai-itai disease， rickets， and osteoporosis.
“Cadmium pollution is mainly caused by mining. The gas emitted by factories contains cadmium， and can affect more areas because of atmospheric sedimentation”， said Gao Jixi， the Director of Nanjing Institute of Environmental Sciences， Ministry of Environmental Protection. “Even if a smelting plant was moved to some place more far away， the exhaust would still drop along the rains in rice field. Apart from that， the abuse of farm chemical， exogenic pollution， and livestock and poultry pollution， have also made the heavy metal pollution worse. ” Serious Heavy Mental Pollution of Soil
Huang Qiaoyun， Professor of the College of Environment and Resources， Central China Agricultural University， is one of the earliest scholars who study on soil heavy metal pollution. He thinks “cadmium rice crisis highlights the significance and urgency of the soil pollution management”. He told us that heavy mentals that cause soil pollution includes mercury， cadmium， lead， chromium and elements with significant toxicity like metalloid arsenic， as well as elements with certain toxicity such as zinc， copper and nickel. Those heavy metals’ mobility in the soil is very small. They can neither be water leached nor degraded by microorganism， which means the control of pollution is very difficult， not to mention the pollution is already widespread now.
The Quality and safety of Chinese Rice Situation and Development Strategies published by China National Rice Research Institute and Rice Product Quality Supervision and Testing Center of Ministry of Agriculture in 2010 claimed that 1/5 of arable land in China has been polluted by heavy metals， among which cadmium pollution involves 11 provinces and 25 areas. In Hunan Province， Jiangxi Province and South of the Yangtze River， this problem has been prominent. The soil of southern provinces was naturally higher in heavy metals. Due to the development of heavy and chemical industry， a large amount of “three industrial wastes” was emitted to soil and made the pollution more serious. At present， about half of the arable land in South China has been polluted by cadmium， arsenic， mercury and other toxic heavy metals and petroleum organics.
“The pollution is not only getting worse， but also in a trend of transfer-diffusion.” Pan Xinggen told the reporter that the contaminants in soil pollution also have trends of transferring from industry to agriculture， urban areas to countries， ground surface to underground， upper reaches to lower reaches， and water and soil to the food chain. The accumulated pollution is happening frequently and turning into incidents. In 2008 only， there were more than 100 pollution incidents in China， including more than 30 pollution incidents of arsenic， cadmium， lead and other heavy metals.
Experts’ Recommendation： Try Different Rice Products
The information about cadmium rice continues to stimulate the sensitive nerves of the public. In terms of food habit， experts suggest that we had better not stick to rice produced in one place. Variety in places of production can lower the risks. The recommendation of “try different rice products” from experts is actually one of few options available. However， two questions are still unavoidable： First， if the source of cadmium rice is in the soil， how can we ordinary people make sure the rice we eat is unpolluted？ In fact， the sampling inspection conducted in Guangdong shows that “44.4% of the products are with exceeding cadmium”， which means the spearhead of attack is aimed directly at Hunan Province. The afterward inspection shows that soil that has been severely polluted by heavy metals is not confined to Hunan Province. Second， the “ostrich policy” （a psychology of escaping to avoid the upcoming event） cannot help solve the problem of cadmium rice， and is certainly not the best strategy in guaranteeing food security. People cannot but to rely on governments’ inspections and prophylactic-therapeutic measures. But because of various reasons， the inspection result has remained a secret and the prophylactic-therapeutic measures cannot be come up with overnight.
On July 18， 2006， a war of soil pollution inspection， whose cost was 1 billion dollars according to the official claim， started quietly in China. This inspection was the first comprehensive inspection towards the condition of soil pollution. It was organized jointly by Environmental Protection Administration and MLR， and finished in 2010. Although media and the public continue to ask for the result of the inspection， the relevant data and results haven’t been released yet. The Ministry of Environmental Protection said in a notice that， according to Article 14 in The Decree of Government Information Openness， the national soil pollution condition belongs to “national secrets” and should not be published.
This three-and-a-half-year inspect covers the entire land of China， except for Hong Kong， Marco， and Taiwan. The inspection results were supposed to be gathered and illustrated in the form of an atlas. It is self-evident： The inspection data of soil pollution is the foundation for control and management afterward.
The explanation of “keeping a national secret” provided by the governments is not satisfying， but many experts told us they can understand the governments’ worries： “Without practical measures and feasible regulations， the release of soil pollution conditions is likely to cause unnecessary worries and economic losses.”
Nevertheless， no matter what the inspection data look like， we can no longer afford to ignore the pollution of soil. An Executive Meeting of the State Council in October 2012 revealed some information about the inspection result. “The soil environment in our country is worth our high attention， and human activity including mine industry and agriculture are the main causes.” Given the situation， the only thing people can do is to look forward to the relevant regulations and measures for dealing with soil pollution. Only with these can the inspection data be released and further control work be done. Elimination of
Soil’s Toxicants is
Extremely Urgent
For a long time， there is no much attention paid to the soil contamination issue， compared to air pollution and water pollution， which are more visible and sensible， while soil contamination lacking intuitive knowledge and immediate exposure. Soil contamination is so called “invisible pollution.”
Seeing that accidents caused by soil contamination have become more frequent in recent years， the public voices have become higher for remediation of heavy metal contaminated soil. But there are also many opponents. Yanlin Hou， pedologist and researcher of Agro-Environmental Protection Institute in Ministry of Agriculture， told the reporter that it is a compelled and end strategy to treat contaminated soil. He anticipated that， except for utilization of tailing， remediation of heavy metal contaminated soil is less likely to become industrialized in a couple decades based on remediation technology， economic and social limitations. The top priority in treating soil contamination radically for China is to make great effort to control the source of contamination， instead of remediation.
Strict Control of Contamination Source
In Hou’s view， the feasibility and effectiveness of contaminated soil remediation is rather limited either economically or ecologically. Even more， he asserts that soil contamination is unlikely to be controlled effectively， comparing to control of air and water pollution.
He listed several ways of soil remediation. The first is replacement method， the second is remediation with creature and plant， and the third is deactivation by adding calcareous substances into soil to improve soil quality. In his opinion， the three methods listed above are all limited in practicability.
As for replacement method， Hou said， “There is no good soil at all in some contaminated areas. How can we do the replacement？ Not like replacing the soil in a flower-pot， the contaminated field is of at least hundreds of thousands of acres，” not to mention the cost of replacement. And if we replace the contaminated soil on surface layer with deep later soil， new replaced soil will be as well contaminated as long as the contamination source is still let alone.
Since the replacement method is not feasible， how about the plant absorption method and the deactivation method by adding neutralizing substance？ Hou said that plants may even not be able to grow when nonferrous metal content in soil is too high. The plant remediation method is only applicable to mild soil contamination through some plants which have high absorbability of heavy metal elements. And as for the deactivation method， Hou thinks that because soil has buffer action itself， no matter how much neutralizing substance is used， it may be effective in a couple years but will resume the original condition after three years. Therefore， the economic costs are immeasurable in long term， plus the new-added substance might cause additional harm towards soil. “What is most important now is not to discuss how to remediate the contaminated soil， but to find out the contamination source and eliminate it.” Hou said， only when the contamination source is eliminated， can remediation method actually be effective. For mild contamination situation， the methods listed above are applicable； and for moderate and serious level pollution， the soil can be remediated through industrial structure readjustment. For example， we can change agricultural use into other functions by planting non-food crops such as flowers and trees， or by building logistics centers， parks， entertainment venues， etc.
Investigating Soil Contamination Situation
Besides， it is an important prerequisite to investigate the situation of soil contamination for following remediation process. Changan Li， College of Earth Science professor from China University of Geosciences， thinks that the most important issue now is to initiate investigation in “sick soil” situation in China as soon as possible in order to identify the causes of “sick soil” and remediate by cause. Meanwhile， the government should carry out relative laws and regulations to lead pollution control and prevention work on the right track. Like air and surface water monitoring， there should also be soil monitoring stations that strictly crack down on soil contamination crimes and punish the perpetrators.
Leader of expert group of soil environment protection legislature research and director of Wuhan University Environmental Law Institute Shuyi Wang pointed out that “contamination file” should be set up for contaminated field to ensure citizen’s right to know the soil environment； besides， soil contamination control zone should also be set up to determine division of agricultural field and residential field. An area should be set as control zone if the soil has been heavily contaminated； and economic activities are completely prohibited in this area if the contamination is seriously heavy.
Furthermore， the deputy director of Chinese Academy of Science IHB （Institute of Hydro-Biology） in Wuhan， Xudong Xu suggests that to stop contamination situation getting worse， a three-dimensional pollution control method could be adopted to promote industrial upgrading. At the same time， soil environment should be strictly protected in major grain producing areas. We should focus on suppressing exogenous pollution and erosion； eliminate industrial waste being discharged into major grain producing areas. The Ministry of Land and Resources and the China Geological Survey released a piece of news a few days ago saying that they decide to hold a comprehensive consultation on heavy metal contaminated soil and draw a “human contamination map” of heavy metal elements in soil. According to this plan， the project will build up a global chemical reference net which covers 81 chemical indexes （include 78 chemical elements）： this net has 1.2 million mapsheets as basic grid cells， each of which is laid with a sampling site； each sampling site collects one deep layer soil sample and one surface layer soil sample. The “human contamination map” of heavy metal elements in soil is generated through minus deep layer content from surface layer content.
Drawing this soil heavy metal contamination map is just like drawing a patient’s condition graph. Only by knowing the condition of a patient， can a doctor target the disease with right treatment. This investigation project is of great importance towards soil environment. However， whether this project can come to a result， or become fruitless， just like the soil contamination investigation initiated in 2006， we have no idea. The only thing we can do is to hope.
含镉大米凸显土壤重金属污染危机
2013年5月16日，中国广州市食品药品监管局的网站公布了第一季度餐饮食品抽验结果，其中一项结果显示：44.4%的大米及米制品抽检产品发现重金属“镉”超标。在食品安全办公室抽检的31个批次不合格大米中，显示有14个批次来自于中国湖南省，镉含量从每公斤0.26毫克到0.93毫克不等（中国的食品安全国家标准规定大米的镉限量不大于0.2mg/kg）。此抽检报告一经披露，便令素有“鱼米之乡”美誉的中国湖南省陷入了镉米危机。
受镉米事件影响，湖南大米滞销严重，米厂出现停工潮。据业界分析，湖南部分地区大米销量急降六成，米价也开始下跌。对于上述情况，当地许多农民及米厂老板表示实在不理解。“镉是什么？我都没听说过。”一位当地农民在接受媒体采访时这样说道。刘湘骥是湖南省攸县大同桥镇一家大米厂的老板。他告诉记者，他的大米厂从收谷、脱壳、碾米、抛光到包装所有程序都是物理性操作，不存在添加或产生镉等重金属污染的可能，污染物究竟从何而来，他也不得而知。
谜团：大米缘何会含镉
5月21日，镉大米来源地湖南攸县官方通报了不合格大米的镉含量范围，披露原稻主要收自当地农户，涉事米厂手续齐全，不存在生产环节重金属污染问题。
既然生产环节无污染、原稻来源也没有问题，那么，污染大米的镉又源自哪里？对此，更多业内专家表示这是一场迟早要来的危机。
南京农业大学农业资源与生态环境研究所教授潘根兴说，这些重金属的确不应该存在于农田，因为它们原本来自矿山。早在2007年，潘根兴和他的研究团队，在全国华东、东北、华中、西南、华南和华北六个地区的县级以上市场中，随机采购大米样品91个，结果表明：10%左右的市售大米镉超标。研究还表明，中国稻米重金属污染以南方籼米为主，尤以湖南、江西等省份最为严重。潘根兴表示，大米镉超标的关键在环境污染，“这取决于两个因素：土壤和品种。”
镉原本与人类没有亲密接触，但由于人在焙烧矿石及湿法取矿时，镉被释放到废水废渣中，并通过水源进入土壤和农田。自此，镉与人类形成了“剪不清，理还乱”的复杂关系，稻米成为其中的重要介质。有研究表明，水稻是对镉吸收最强的大宗谷类作物，其籽粒中镉含量仅次于生菜。
有关镉米的危害，最早于上世纪60年代在日本被发现。日本由于开矿致使镉严重污染农田，农民长期食用污染土壤上生长的稻米而导致镉中毒，患者骨头有针扎般剧痛，镉中毒因此被称为“痛痛病”，情况最严重的患者身上曾同时出现100多处骨折。
医学研究表明，镉主要在肝、肾部积累，并不会自然消失，经过数年甚至数十年慢性积累后，人会出现镉中毒症状。镉的拿手绝招是先损坏人体的肾功能，让骨骼生长代谢发生障碍，进而使骨骼出现各种病变，像骨痛病、软骨病、骨质疏松。
“镉污染大部分来自开矿。工厂排放废气中含有镉，可能会通过大气沉降影响较远的地方。”环保部南京环境科学研究所所长高吉喜表示，“即使冶炼厂距离远，其排放的废气扩散后也可能随降雨落到农田中。除此之外，农业投入品滥用、外源性污染、养殖业污染等，也使得土壤重金属污染趋势日益加剧。
土壤重金属污染严重
华中农业大学环境资源学院教授黄巧云是中国国内最早从事土壤重金属污染研究的学者之一，他认为：“镉米危机凸显了治理土壤污染的重要性与紧迫性。”据黄巧云介绍，污染土壤的重金属主要包括汞、镉、铅、铬和类金属砷等生物毒性显著的元素，以及有一定毒性的锌、铜、镍等元素。这些重金属污染物在土壤中移动性很小，既不易随水淋滤，也不为微生物降解，治理起来难度极大，更何况目前已经出现大面积的污染范围。
中国水稻研究所与农业部稻米及制品质量监督检验测试中心于2010年发布的《中国稻米质量安全现状及发展对策研究》称，中国已有1/5的耕地受到重金属污染，其中受到镉污染的耕地涉及11个省25个地区。在湖南、江西等长江以南地带，这一问题更加突出。南方省份土壤中由于重金属底值偏高，加之多年来经济结构偏重于重化工业，大量工业“三废”的排放加剧了土壤重金属污染形成。目前，华南部分城市约有一半的耕地已遭受镉、砷、汞等有毒重金属和石油类有机物污染。
“不仅污染加重，而且还在转移扩散。”潘根兴告诉记者，当前土壤污染还出现了有毒化工和重金属污染由工业向农业转移、由城区向农村转移、由地表向地下转移、由上游向下游转移、由水土污染向食品链转移的趋势，逐步积累的污染正在演变成污染事故的频繁爆发。仅2008年以来，全国已发生百余起重大污染事故，包括砷、镉、铅等重金属污染事故达30多起。
专家建议：换着产地吃大米
镉超标大米的消息持续刺激着公众敏感的神经，在饮食习惯上，专家建议不要长期食用一个地方出产的粮食，尽可能分散化，降低风险。
“换着产地吃大米”，专家的建议放到现实中，委实是退而求其次的无奈之举。不过建议仍回避不了两个问题：一、倘若镉大米的根源在于土壤污染，普通百姓又如何能确保自己所吃的大米是产自没有污染过的土壤？事实上，广州在此次抽检中发现“镉超标率达44.4%”，从而将矛头直指湖南。后经调查显示，受重金属污染的土地远非湖南一省。二、以“鸵鸟心态”（明知问题即将发生而不去想对策的逃避心理）来防范镉大米，也不是保障食品安全的上上之策。无奈的民众最终只能倚赖政府尽快给出明确的调查结果与防治措施，但是鉴于各种原因，某项调查结果迟而未宣，防治措施也由于污染状况复杂不能在一朝一夕内完成。 2006年7月18日，一场官方宣称耗资十亿元的土壤污染摸底战役在全中国悄然拉开，这项调查也是中国首次对土壤污染状况所做的综合性调查，由环保总局、国土资源部联合启动，直至2010年调查终于完成，但是纵然媒体和公众不断呼吁和追寻，调查数据和结果迄今未曾公布。对此，环保部在相关告知书中表示，此举系根据《政府信息公开条例》第14条，对“属于国家秘密”的全国土壤污染状况不予公开。
这场历时三年半的土壤污染调查，范围覆盖了除港澳台以外的所有省、直辖市、自治区的全部陆地。依照预期，各地的调查结果将绘成一张巨幅的中国土壤污染图谱。其意义不言而喻：土壤污染调查数据是所有后续治理工作的基础。
对于政府给出的保密解释，多名受访专家表示理解保密的苦衷，“在没有切实的处理办法和法规出台前，全国污染土壤状况一旦公布，将可能引起不必要的担忧和经济损失。”
但是，无论最终调查数据如何，全国土壤污染状况已是不容忽视。2012年10月的一次国务院常务会议曾透露这次历时六年的普查的整体结论，“全国土壤环境状况必须引起高度重视，工矿业、农业等人为活动是造成土壤污染的主要原因。”既然如此，公众也只有企盼政府尽快出台相应的土壤防治法规及处理办法，唯有此土壤污染调查数据才有望公开，后续的治理工作才能随之有序进行。
土壤“排毒”
迫在眉睫
长期以来，比之大气污染和水污染，土壤污染所受到的重视程度似乎不如前两者。大气污染和水污染更有可视性、可感性，而土壤污染缺少直观的感受，问题的暴露也不在于一时，因此被称作“看不见的污染”。
鉴于近年来因土壤污染而造成的事故频频被曝出，外界对受重金属污染的土壤进行修复的呼声也逐渐高涨。不过，对此种说法“泼凉水”的人也不在少数。农业部环境保护科研监测所研究员、土壤学专家侯彦林告诉中国经济时报记者，对受污染的土壤治理不过是一种末端策略和不得已而为之的办法。他预计，基于土壤修复的技术、经济、社会等层面的原因，除尾矿开发外，土壤重金属修复在未来10到20年内很难形成产业。根治土壤污染的当务之急不是修复，而是国家下大力气控制好污染源。
严控污染源
在侯彦林看来，土壤污染修复不论是算经济账，还是生态账，其可行性和有效性均很有限。他甚至断言，相比大气和水污染的治理，土壤污染很难得到有效治理。
他举例指出，土壤修复的方法大概有如下几项，一是换土法。二是利用生物和植物修复。三是向土壤中加入石灰性物质等其它物质来改良土壤性能的钝化法。在他看来，以上三种方式的可操作性均有限。
就换土而言，侯彦林认为，撇开换土的成本不谈，“在某些污染地区就没有好土，怎么换？不像花盆换土，大田污染往往是少则几十万亩。”而如果要采取将上层的受污染土壤换到下层的方式，则如果放任污染源继续污染，那新土再过几年也同样会被污染。
土壤修复中“换土法”不可行，那植物吸收法和向土壤中加中和物质的钝化处理法又是否可行呢？侯彦林表示，当土壤中的有色金属含量过高时，植物可能根本就无法生长。植物修复法只适合于轻度土壤污染的情况，通过种植一些对重金属吸附性大的植物，达到修复土地的效果。而对于钝化处理法，侯彦林则认为，因土壤本身具有缓冲性，无论你放多少中和物质，放一年两年有效，三年后可能又回到原来状态。因此，所付出的经济成本是长期且不可估量的，而且加入的物质极有可能会对土壤造成新的危害。
“当前最重要的不是探讨如何修复受污染的土壤，而是如何去找出污染源，杜绝污染源。”侯彦林指出，只有在杜绝污染源的基础上进行的修复工作才能真正产生效果。对于轻度污染的土壤可采取上述几种修复方法，而对于中度和重度的土壤污染，则可通过调整产业结构的方法，比如，不以农业为主，通过种植一些非食用作物，如花草、树木等，或在城市郊区修建物流中心、公园、娱乐场所等，以改变土地的利用方式。
摸清土壤污染“家底”
除此之外，尽快摸清土壤污染“家底”，也是进行土壤后续修复工作的重要前提。中国地质大学地球科学院教授李长安认为，眼下最重要的是尽快启动中国“带病”土壤现状调查，掌握土壤“致病”原因，分类而治。同时，国家要尽快出台相关的法律法规，使土壤污染防治工作步入法制化轨道，像大气和地表水一样，建立土壤土质的污染监测站点，严厉打击污染土壤的行为，严惩肇事者。
土壤环境保护立法研究专家组组长、武汉大学环境法研究所所长王树义提出，应该为污染的土壤建立“污染档案”，保障公民对土壤环境的知情权；另外，还要建立土壤污染控制区，确定什么样的土地适合种植，什么样的土地适合居住。如果某个区域的土壤受到污染比较严重，就应该把它设为管制区，如果污染非常严重，就要完全禁止经济活动。
中科院武汉水生所副所长徐旭东则建议，可以采用立体治污的办法推动产业升级，阻止污染继续恶化。同时，严格保护粮食主产区的土壤环境，将保护重点放在遏制外源污染和侵蚀上，杜绝工业废物向粮食主产区排放。
国土资源部、中国地质调查局日前也发布了消息，决定全面会诊土壤重金属污染现状，绘制土壤重金属“人类污染图”。按照设想，该项目将在全国建立涵盖81个化学指标（含78种元素）的地球化学基准网：以120万图幅为基准网格单元，每一个网格都布设采样点位，每个点位都采集一个深层土壤样品和一个表层土壤样品。用表层含量减去深层含量，即能得出重金属元素的“人类污染图”。
此次国家绘制土壤重金属污染图，好比给一个病人绘出的病情图，知道病情后，才能有的放矢，由此可知此项调查的重要意义。但是，此番举动是否会如2006年启动的土壤污染调查一般没有下文，公众也不得而知，唯有期待不会再是一场空等。
Warning of Soil Pollution
Reported by Duan Ying Translated by Zhu Luqi and Guo Qi Recently， the “Cadmium Rice” scandals in several southern provinces of China have been in the spotlight and made public opinion seething with indignation. This event not only touches Chinese people’s sensitive nerves for food security， but also arouses wide concern about the issue of soil pollution. Facing the grim situation of soil pollution in China， Ministry of Land and Resources says that they will conduct a sampling survey all over China and make a map of soil pollution in China， in order to measure the degree of soil pollution by heavy metals caused by human activities. But it remains uncertain whether the detailed schedule for this survey will be announced. On one hand， it is the seriously contaminated soil； on the other hand， it is the ambiguous actions of governments. Who can save the people who suffer from soil contamination？ At present， it seems an intractable problem still.
“Cadmium Rice” Reflects the
Crisis of Soil Pollution by Heavy
The market of rice produced in Hunan Province was also affected by the cadmium crisis. Many rice factories were in the condition of shutdown. According to the industrial analysis， the sales volume in Hunan Province was reduced by 60%， and the rice price started to decrease. Most of the farmers and factory directors were very confused， because they could hardly understand the situation they were facing. One of the local farmers told the reporter that “what is cadmium on earth？ I’ve never heard about it.” Liu Xiangji was the director of a rice factory in Datongqiao Town， You County， Hunan Province， and he told the reporter from Xinhua News Agency that his factory had always followed the rules of physical operation in every process： collecting， shelling， milling， polishing， and packing. There was no chance or possibility of cadmium pollution in the producing process， and he didn’t know where the pollution source came from.
Mystery： How Come Rice Contains Cadmium
On May 21， Authorities in You County， Hunan Province announced the amount range of cadmium in rice. They also disclosed that the crop was mainly collected from the local farmers， and the formalities of rice factories involved were all complete， which meant the heavy metal pollution was not from the producing process.
Given that there was no pollution in the producing process， and the crop was all clean， where was the source of the cadmium？ Responding to this situation， many experts believed that this was a crisis that would come sooner or later. Pan Genxing， Professor from the Institute of Agricultural Resources and Environment， Nanjing Agricultural University， told us that the heavy metals should not have been in rice field， because they were supposed to exist only in mines. Earlier in 2007， Pan Genxing and his research team conducted a sampling inspection by selecting 91 samples in the above-county-level markets in East， Northeast， and Central， Southwest， South and North areas of China. The result showed that about 10% of the rice commercially available was with cadmium exceeding the official limit. The research also showed that the heavy metal pollutions were mainly found in long-shaped rice produced in South China， especially in the Provinces of Hunan and Jiangxi. Pan Genxing also told us that the key of excessive cadmium in rice lies in environmental pollution. “It is up to two factors： soil and variety.”
Cadmium does not have such a close connection with mankind. However， in the processes of roasting ore and wet-method reclaiming， cadmium is released in sewage and waste residue， and then blended in soil and rice field. After that， cadmium and mankind start a complicated relation， with rice crop working as an important medium. There are studies showing that rice is highly capable of absorbing cadmium， and the cadmium amount in its seeds is only less than in lettuce.
The harm brought by “cadmium rice” was first found at 1960s in Japan. At that time， many rice fields were polluted by cadmium because of mining， and the farmers constantly fed by the polluted rice were cadmium poisoned. Those patients suffered huge pain in the bones， so cadmium poisoning was also known as “itai-itai”. The most serious patient even had more than 100 bone fractures at one time.
Medical research shows that cadmium is mainly accumulated in the liver and kidney， and it will not disappear by itself. After several years or decades of accumulation， people will have the symptoms of cadmium poisoning. The cadmium usually first destroys the functioning of kidney， which will lead to an impediment in the growth and metabolism of bones. The bones will gradually have various pathological changes like itai-itai disease， rickets， and osteoporosis.
“Cadmium pollution is mainly caused by mining. The gas emitted by factories contains cadmium， and can affect more areas because of atmospheric sedimentation”， said Gao Jixi， the Director of Nanjing Institute of Environmental Sciences， Ministry of Environmental Protection. “Even if a smelting plant was moved to some place more far away， the exhaust would still drop along the rains in rice field. Apart from that， the abuse of farm chemical， exogenic pollution， and livestock and poultry pollution， have also made the heavy metal pollution worse. ” Serious Heavy Mental Pollution of Soil
Huang Qiaoyun， Professor of the College of Environment and Resources， Central China Agricultural University， is one of the earliest scholars who study on soil heavy metal pollution. He thinks “cadmium rice crisis highlights the significance and urgency of the soil pollution management”. He told us that heavy mentals that cause soil pollution includes mercury， cadmium， lead， chromium and elements with significant toxicity like metalloid arsenic， as well as elements with certain toxicity such as zinc， copper and nickel. Those heavy metals’ mobility in the soil is very small. They can neither be water leached nor degraded by microorganism， which means the control of pollution is very difficult， not to mention the pollution is already widespread now.
The Quality and safety of Chinese Rice Situation and Development Strategies published by China National Rice Research Institute and Rice Product Quality Supervision and Testing Center of Ministry of Agriculture in 2010 claimed that 1/5 of arable land in China has been polluted by heavy metals， among which cadmium pollution involves 11 provinces and 25 areas. In Hunan Province， Jiangxi Province and South of the Yangtze River， this problem has been prominent. The soil of southern provinces was naturally higher in heavy metals. Due to the development of heavy and chemical industry， a large amount of “three industrial wastes” was emitted to soil and made the pollution more serious. At present， about half of the arable land in South China has been polluted by cadmium， arsenic， mercury and other toxic heavy metals and petroleum organics.
“The pollution is not only getting worse， but also in a trend of transfer-diffusion.” Pan Xinggen told the reporter that the contaminants in soil pollution also have trends of transferring from industry to agriculture， urban areas to countries， ground surface to underground， upper reaches to lower reaches， and water and soil to the food chain. The accumulated pollution is happening frequently and turning into incidents. In 2008 only， there were more than 100 pollution incidents in China， including more than 30 pollution incidents of arsenic， cadmium， lead and other heavy metals.
Experts’ Recommendation： Try Different Rice Products
The information about cadmium rice continues to stimulate the sensitive nerves of the public. In terms of food habit， experts suggest that we had better not stick to rice produced in one place. Variety in places of production can lower the risks. The recommendation of “try different rice products” from experts is actually one of few options available. However， two questions are still unavoidable： First， if the source of cadmium rice is in the soil， how can we ordinary people make sure the rice we eat is unpolluted？ In fact， the sampling inspection conducted in Guangdong shows that “44.4% of the products are with exceeding cadmium”， which means the spearhead of attack is aimed directly at Hunan Province. The afterward inspection shows that soil that has been severely polluted by heavy metals is not confined to Hunan Province. Second， the “ostrich policy” （a psychology of escaping to avoid the upcoming event） cannot help solve the problem of cadmium rice， and is certainly not the best strategy in guaranteeing food security. People cannot but to rely on governments’ inspections and prophylactic-therapeutic measures. But because of various reasons， the inspection result has remained a secret and the prophylactic-therapeutic measures cannot be come up with overnight.
On July 18， 2006， a war of soil pollution inspection， whose cost was 1 billion dollars according to the official claim， started quietly in China. This inspection was the first comprehensive inspection towards the condition of soil pollution. It was organized jointly by Environmental Protection Administration and MLR， and finished in 2010. Although media and the public continue to ask for the result of the inspection， the relevant data and results haven’t been released yet. The Ministry of Environmental Protection said in a notice that， according to Article 14 in The Decree of Government Information Openness， the national soil pollution condition belongs to “national secrets” and should not be published.
This three-and-a-half-year inspect covers the entire land of China， except for Hong Kong， Marco， and Taiwan. The inspection results were supposed to be gathered and illustrated in the form of an atlas. It is self-evident： The inspection data of soil pollution is the foundation for control and management afterward.
The explanation of “keeping a national secret” provided by the governments is not satisfying， but many experts told us they can understand the governments’ worries： “Without practical measures and feasible regulations， the release of soil pollution conditions is likely to cause unnecessary worries and economic losses.”
Nevertheless， no matter what the inspection data look like， we can no longer afford to ignore the pollution of soil. An Executive Meeting of the State Council in October 2012 revealed some information about the inspection result. “The soil environment in our country is worth our high attention， and human activity including mine industry and agriculture are the main causes.” Given the situation， the only thing people can do is to look forward to the relevant regulations and measures for dealing with soil pollution. Only with these can the inspection data be released and further control work be done. Elimination of
Soil’s Toxicants is
Extremely Urgent
For a long time， there is no much attention paid to the soil contamination issue， compared to air pollution and water pollution， which are more visible and sensible， while soil contamination lacking intuitive knowledge and immediate exposure. Soil contamination is so called “invisible pollution.”
Seeing that accidents caused by soil contamination have become more frequent in recent years， the public voices have become higher for remediation of heavy metal contaminated soil. But there are also many opponents. Yanlin Hou， pedologist and researcher of Agro-Environmental Protection Institute in Ministry of Agriculture， told the reporter that it is a compelled and end strategy to treat contaminated soil. He anticipated that， except for utilization of tailing， remediation of heavy metal contaminated soil is less likely to become industrialized in a couple decades based on remediation technology， economic and social limitations. The top priority in treating soil contamination radically for China is to make great effort to control the source of contamination， instead of remediation.
Strict Control of Contamination Source
In Hou’s view， the feasibility and effectiveness of contaminated soil remediation is rather limited either economically or ecologically. Even more， he asserts that soil contamination is unlikely to be controlled effectively， comparing to control of air and water pollution.
He listed several ways of soil remediation. The first is replacement method， the second is remediation with creature and plant， and the third is deactivation by adding calcareous substances into soil to improve soil quality. In his opinion， the three methods listed above are all limited in practicability.
As for replacement method， Hou said， “There is no good soil at all in some contaminated areas. How can we do the replacement？ Not like replacing the soil in a flower-pot， the contaminated field is of at least hundreds of thousands of acres，” not to mention the cost of replacement. And if we replace the contaminated soil on surface layer with deep later soil， new replaced soil will be as well contaminated as long as the contamination source is still let alone.
Since the replacement method is not feasible， how about the plant absorption method and the deactivation method by adding neutralizing substance？ Hou said that plants may even not be able to grow when nonferrous metal content in soil is too high. The plant remediation method is only applicable to mild soil contamination through some plants which have high absorbability of heavy metal elements. And as for the deactivation method， Hou thinks that because soil has buffer action itself， no matter how much neutralizing substance is used， it may be effective in a couple years but will resume the original condition after three years. Therefore， the economic costs are immeasurable in long term， plus the new-added substance might cause additional harm towards soil. “What is most important now is not to discuss how to remediate the contaminated soil， but to find out the contamination source and eliminate it.” Hou said， only when the contamination source is eliminated， can remediation method actually be effective. For mild contamination situation， the methods listed above are applicable； and for moderate and serious level pollution， the soil can be remediated through industrial structure readjustment. For example， we can change agricultural use into other functions by planting non-food crops such as flowers and trees， or by building logistics centers， parks， entertainment venues， etc.
Investigating Soil Contamination Situation
Besides， it is an important prerequisite to investigate the situation of soil contamination for following remediation process. Changan Li， College of Earth Science professor from China University of Geosciences， thinks that the most important issue now is to initiate investigation in “sick soil” situation in China as soon as possible in order to identify the causes of “sick soil” and remediate by cause. Meanwhile， the government should carry out relative laws and regulations to lead pollution control and prevention work on the right track. Like air and surface water monitoring， there should also be soil monitoring stations that strictly crack down on soil contamination crimes and punish the perpetrators.
Leader of expert group of soil environment protection legislature research and director of Wuhan University Environmental Law Institute Shuyi Wang pointed out that “contamination file” should be set up for contaminated field to ensure citizen’s right to know the soil environment； besides， soil contamination control zone should also be set up to determine division of agricultural field and residential field. An area should be set as control zone if the soil has been heavily contaminated； and economic activities are completely prohibited in this area if the contamination is seriously heavy.
Furthermore， the deputy director of Chinese Academy of Science IHB （Institute of Hydro-Biology） in Wuhan， Xudong Xu suggests that to stop contamination situation getting worse， a three-dimensional pollution control method could be adopted to promote industrial upgrading. At the same time， soil environment should be strictly protected in major grain producing areas. We should focus on suppressing exogenous pollution and erosion； eliminate industrial waste being discharged into major grain producing areas. The Ministry of Land and Resources and the China Geological Survey released a piece of news a few days ago saying that they decide to hold a comprehensive consultation on heavy metal contaminated soil and draw a “human contamination map” of heavy metal elements in soil. According to this plan， the project will build up a global chemical reference net which covers 81 chemical indexes （include 78 chemical elements）： this net has 1.2 million mapsheets as basic grid cells， each of which is laid with a sampling site； each sampling site collects one deep layer soil sample and one surface layer soil sample. The “human contamination map” of heavy metal elements in soil is generated through minus deep layer content from surface layer content.
Drawing this soil heavy metal contamination map is just like drawing a patient’s condition graph. Only by knowing the condition of a patient， can a doctor target the disease with right treatment. This investigation project is of great importance towards soil environment. However， whether this project can come to a result， or become fruitless， just like the soil contamination investigation initiated in 2006， we have no idea. The only thing we can do is to hope.