赵方杰,谢婉滢,汪 鹏
土壤与人体健康*
赵方杰,谢婉滢,汪 鹏
(南京农业大学资源与环境科学学院,南京 210095)
土壤可以通过多条途径对人体健康产生正面或负面的影响。本文从土壤通过食物链提供人体必需的矿质营养、人体来自于土壤-食物链的有害重金属暴露、以及土壤中抗生素抗性基因传播等方面探讨土壤与人体健康的关系。土壤对人体健康的影响具有非均等性,贫困地区与低收入群体往往更容易受到土壤对人体健康的负面影响。在未来人口增长与全球气候变化双重压力下,土壤与人体健康的关系将变得更为突出。本文还提出了消减土壤对人体健康负面影响的一些干预措施选项及未来的研究方向。
人体健康;矿质营养;重金属;抗生素抗性基因
众所周知,土壤具有多种功能,如农业生产和生态服务功能,这些功能对人类生存和生态环境起重要作用。土壤还和人体健康息息相关,健康的土壤是健康的人体的一个重要保障。
土壤可以通过多条途径影响人体健康,这些影响既有正面的,也有负面的,既有直接的,也有间接的[1-2]。例如,人体所必需的矿质养分大部分来自土壤,土壤中矿质养分缺乏也会导致人体养分缺乏;土壤中的各种污染物可以通过食物链传递进入人体,影响人体健康;土壤中存在多种人体致病菌,抗生素抗性基因的传播可能提高这些致病菌的风险;土壤的微生物组可能也会影响人体的微生物组,从而间接影响人体健康;土壤还会通过影响地下水和空气质量影响人体健康。
虽然土壤与人体健康关系密切,但是要确立并量化二者之间的因果关系难度很大。这是因为人群和食品的移动性,模糊了土壤与居民的直接联系,城市化和物联网的兴起,也使得食品来源更加多样化。历史上出现的一些地方病,由于人群和食品的流动而逐渐消失。此外,要确立土壤与人体健康的关系,需要大量的人体健康和流行病学数据,这些数据往往难于获取。
本文将举几个例子探讨土壤与人体健康的关系,并提出可能的干预措施及未来的研究方向。
人体需要至少20种矿质元素、13种维生素、9种氨基酸和2种脂肪酸[3]。土壤通过食物链向人体供应矿质营养,但是这个供应链并不能满足人体对某些矿质元素的需求,最典型的例子包括钠、碘、硒、铁、锌。其中,钠、碘和硒在地表岩石风化、土壤形成的漫长过程中容易淋失,迁移进入海洋,而且这三种元素均是动物必需而植物不需要的矿质元素,因此,土壤中这些元素的缺乏不会影响植物生长,但会影响人体健康。所以,人类早已知道需要通过食盐补充钠的供应。历史上,由于国家对食盐专卖权的控制,食盐成了国家税收和盐商致富的重要商品。不但人体需要补充钠,土壤中的一些食草动物也受钠不足的制约。Kaspari等在亚马逊热带雨林做过一个有趣的试验[4-5],向土壤添加食盐大幅度增加蚂蚁和白蚁的数量,加快凋落物的分解和土壤碳循环。为什么动物需要钠而植物不需要?钠在动物体内的主要功能是维持细胞内外的渗透压平衡,防止细胞内的溶解质渗漏。生命起源于海洋,海水中丰富的钠离子成为调节细胞渗透压平衡的最佳选择,演化到陆地上的动物保持了这一特性。与动物不同,陆地植物演化出通过液泡和细胞壁调节渗透压平衡和防渗漏的功能,而液泡里调节渗透压平衡的物质主要是钾离子和有机酸。
钠属于大量元素,碘则是人体需求量很少的微量元素。与钠相似,人们发现广大的内陆地区食品中碘含量不能满足人体需求,影响甲状腺功能,向食盐添加微量碘是解决人体缺碘的有效方法。Cao等[6]在新疆南部进行试验,通过向灌溉水添加碘酸钾提高土壤碘含量3倍、作物碘含量2倍,并使得动物和人体碘的摄入量显著增加。然而,人体碘需求有个安全阈值,当摄入碘过量也会引起甲状腺功能紊乱。
硒是另一个对人体健康有广泛影响的微量元素,人体含有20多种含硒的酶,硒对甲状腺激素代谢、抗氧化和免疫系统功能起重要作用[7]。不同国家推荐的硒摄入量为50~70mg·d–1。据估计,全球5亿~10 亿人口硒摄入量不足[8]。我国存在一个从东北黑龙江到西南川藏高原窄长的缺硒带,斜跨16个省或自治区,居住人口达1亿以上。这个地带土壤和农产品硒含量很低,两个与缺硒相关的地方病,即克山病(Keshan Disease)和大骨节病(Kashin-Beck Disease),均出现在这个地带[9-11]。克山病患者主要是15岁以下的儿童和育龄阶段的妇女,患者表现为心功能不全、心脏扩大、心律失常,血液和头发硒含量远低于正常人的水平,每周服用0.5~1 mg亚硒酸钠可有效防治克山病[9-10]。除了严重缺硒,病毒感染可能也是克山病的病因之一[7]。大骨节病是一种慢性和变形性骨关节病,主要影响儿童四肢和关节软骨,致其变性和深层细胞坏死。我国20世纪90年代有一百万至三百万患者,目前仍有六十多万患者[12]。大骨节病的病因仍然不清楚,但与缺硒、缺碘有关,谷物的霉菌毒素及饮用水较高的富里酸可能也是致病的原因[7,12-13]。
克山病和大骨节病主要发生在相对较为贫困的农民家庭,他们的食品种类少,来源单一,因此土壤缺硒很容易造成硒摄入量不足。目前市场上有多种富硒食品,但是由于经济原因,这些富硒食品很难到达最需要补硒的人群中。向克山病、大骨节病发病区域人群提供硒片是防治疾病的有效手段,但是对于占多数的硒摄入量不足但又没有显示病症的人群,这个方法相对难于执行。在食盐中添加硒也不合适,因为与缺钠或缺碘不同,缺硒是局部的,缺硒带周边甚至还有个别地区土壤富硒造成硒中毒现象。一种有效的办法是在缺硒带土壤施用少量硒肥,增加农产品硒含量。芬兰在20世纪80年代采取全国性措施,在复合肥中添加少量硒,相当于每公顷农田施用3~10 g硒,使得全国人口硒的平均摄入量由原来的25mg·d–1增加到110mg·d–1[14-16]。Broadley 等[17]在英国进行的大田试验表明,每公顷施用10 g硒(硒酸钠)可提高小麦籽粒硒含量10倍左右,达到对人体足够的水平。对于我国缺硒带,尤其是大骨节病流行较严重的川藏地区,在复合肥中添加少量硒可能是提高当地居民硒摄入量的有效办法。
为什么我国会存在一个斜跨东北—西南的缺硒带?Blazina 等[18]认为,缺硒带正好处于东亚夏季季风带来的降雨的边界,源自海洋的降雨是硒的重要来源,海水中的硒通过海洋浮游生物的甲基化挥发到大气中,在大气的传输过程中重新氧化成为无机硒酸盐、亚硒酸盐,随降雨沉降到土壤中,我国土壤硒含量呈现由东南沿海向缺硒带递减的规律,与东亚季风带来的降雨量分布规律相似,而缺硒带的西北面土壤硒含量主要受降尘影响。Jones等[19]在全球尺度上对土壤硒含量进行分析,得到影响硒含量的7个参数,包括干旱指数(潜在蒸腾量与降水量之比)、土壤黏粒含量、蒸腾量、成土母岩类型、土壤pH、降水量和土壤有机质含量,其中干旱指数的影响最大,干旱指数越高,土壤硒含量越低,包含这7个参数的模型可预测全球3万多份土壤硒含量变异的67%。他们用这个模型预测未来气候变化对全球土壤硒含量的影响,预测至2080—2099 年间,58% 土地硒含量将下降(平均降幅8.4%),20% 土地硒含量变化很小,此外22%土地硒含量将增加(平均增幅 5.7%),农田土壤硒含量下降的比例高达66%(平均降幅8.7%)。推测在未来气候变化情景中,缺硒人口的比例将会增加。
人体所需的微量元素中,铁和锌也经常缺乏。据估计,全球40% 的人口缺铁、33%的人口缺锌,主要影响发展中国家以禾谷类为主粮的人口[3,20-21]。有证据表明,绿色革命大幅度提高小麦产量的同时,也使得籽粒多种矿质养分含量显著下降[22]。缺铁、锌的主要原因是禾谷类中这两种元素含量普遍较低,而且由于植酸对铁、锌的结合,使得禾谷类中这两种元素对人体的有效性很低。土壤中铁的含量很高,但在中性至碱性条件下铁的有效性很低,有些农作物容易缺铁。稻田淹水后,土壤中部分铁被还原为溶解度高的亚铁,甚至可以导致水稻亚铁毒害,但是水稻籽粒中铁含量仍然较低,说明水稻对铁向籽粒的转运有着严格的控制。碱性土壤锌的有效性也低,土壤锌含量和pH是影响禾谷类锌含量的重要因素,向土壤施用锌肥或向作物叶面喷施锌肥可以显著提高籽粒锌含量[23]。叶面喷施锌、铁、硒、碘混合溶液显著提高小麦籽粒锌、硒、碘含量,铁含量也有小幅度增加[24]。对于禾谷类粮食,通过遗传育种降低植酸含量是提高铁、锌人体有效性的一种策略。
土壤中可能存在的污染物种类繁多,包括有机污染物、无机污染物、生物污染物、放射性核素等,这些污染物可能通过多条途径进入人体,影响人体健康。本文以我国土壤污染问题比较突出的无机污染物重金属为例讨论对人体健康的影响。
耕地土壤重金属污染物主要有镉、镍、砷、铜、汞、铅、铬、锌等,砷虽然不属于重金属,但由于其行为、来源、危害均与重金属相似,通常也被列为重金属考虑。土壤重金属污染不仅会引起生态环境质量恶化,还会通过食物链传递进入人体,危害人体健康。就重金属向农产品迁移行为而言,重金属可以划分为4类(表1)[25]。第一类是在土壤中溶解迁移能力较弱的元素,它们在土壤中生物有效性较低,如银、金、铬(III)、汞、锡等。第二类是在植物体内转运能力较弱的元素,如铝、汞、铅等,这些元素往往积累在根部,很少向植物地上部及可食部位转移。第三类是过量时会对植物生长造成明显毒害的元素,如铜、锰、锌等,对植物的毒害很大程度上会限制这些元素到达人们的餐桌。第四类是向农产品有较高迁移能力的元素,这些元素在对植物产生毒性之前可能就会对人体健康产生影响,如镉、硒、钼等。由于淹水稻田的厌氧条件和水稻对三价砷较强的吸收能力,稻米也会积累较高的砷[26],因此对于水稻而言,砷也归入第四类。根据这一概念,针对第二和第三类重金属,我们应该更多地关注其生态安全风险,而针对第四类重金属,我们应关注其对农产品安全以及人体健康的影响。我国的快速工业化导致了部分耕地土壤重金属污染严重,第四类重金属镉和砷处在我国耕地土壤污染物之前列,分别有7%和3%耕地土壤点位镉、砷超标[27]。土壤污染导致了农产品镉、砷超标问题严重,例如我国南方部分污染地区,稻米镉含量超标高达60%~80%[28-32],砷超标高达40%~50%[32]。因此,镉、砷已经成为威胁我国农产品安全最突出的两个污染元素。
表1 重金属从土壤向农产品迁移能力分类(基于Chaney等[25]提出的概念修改)
镉是一种对人体有毒有害元素。镉在人体滞留周期长,长达10~30年,主要在肾脏和骨骼中积累[33]。长期镉的摄入会导致严重的健康问题,例如,高镉的摄入会导致肾功能受损、骨质疏松以及癌症发病率升高等健康问题[34-38]。镉对人体毒害最为严重的疾病要数“痛痛病”。20世纪40、50年代,日本富山县神通川流域曾发生一种疾病。患者症状有全身发生骨痛、神经痛现象,行动困难,甚至呼吸都会导致疼痛,患病后期,患者骨骼软化,四肢弯曲,脊椎变形,骨质疏松,极容易导致骨折。患者痛不堪言,此病因此得名“痛痛病”(Itai-Itai Disease)[39]。该病在当地盛行20~30年,确诊患者410多例,其中死亡380多例[39]。“痛痛病”病因是由于当地居民长期食用镉污染的大米而导致的镉慢性中毒。此病一旦发生,尚无有效的治疗方法。“痛痛病”也被日本定为第一号环境公害事件。日本神通川流域发生的“痛痛病”具有以下特征:土壤镉有效性高、患者以大米为主食、患者主要为生育多胎的妇女。大米中铁、锌、钙等人体必需的矿质营养相比其他粮食比较缺乏,而生育多胎的妇女又特别容易缺乏这些矿质营养,可能导致妇女对镉的吸收效率增加[40],因而容易受镉的毒害。
结合当年日本爆发“痛痛病”地区的田间调研数据和流行病学资料,通过对比可以发现我国南方局部地区的稻米镉浓度已经接近甚至超过日本发病地区[41],需要引起警觉。当年日本发病地区的田间调查发现稻米镉平均含量为0.38 mg·kg–1(范围0.02~0.95 mg·kg–1;=2 446)[42]。Zhu等[28]在湖南省长-株-潭地区田间调查了近4万份稻米样品,发现稻米镉的平均含量高达0.43 mg·kg–1(范围0.005~4.80 mg·kg–1)。镉暴露高风险群体主要是自产自销型的农户家庭,他们食物来源较为单一,而且自产的粮食未经收购部门检验,长期食用镉污染的粮食人群特别容易受土壤污染的危害。值得注意的是,“痛痛病”是长期慢性暴露引起的,镉的健康风险具有隐蔽性,不能因现在未出现病例而掉以轻心。
我国目前的食品卫生标准规定稻米镉限量为0.2 mg·kg–1[43],这个标准严于联合国粮农组织(FAO)和世界卫生组织(WHO)2006年颁布的0.4 mg·kg–1限量标准[44]。通过镉摄入量的计算可知,成年人(60 kg 体重)每天食用250 g 含0.2 mg·kg–1Cd 的大米,镉的摄入量为0.83mg·kg–1体重·d–1,正好达到FAO/WHO制定的可容忍镉摄入限量(Tolerable Cd intake)[33]。我国卫生部2002年开展的中国居民营养与健康状况调查表明,我国农村与城市成年人人均米及其制品食用量分别为每天246 g和218 g,南方省份成年人食用量更高,人均260~430 g之间[45]。因此,我们认为不宜将我国稻米镉限量标准提高到FAO/WHO的限量水平。其实,FAO/WHO制定的小麦(欧美国家及我国北方人口的主粮)镉限量标准也是0.2 mg·kg–1。
砷也是一种有毒有害的致癌物,长期摄入不仅会导致皮肤癌、膀胱癌和肺癌,还会引起心脑血管疾病、生长发育和代谢紊乱[46-48]。人体砷慢性中毒一个明显特征是皮肤斑点性损伤,这也是皮肤癌的一个前兆。人体砷摄入的主要途径是饮用水和膳食摄入。南亚及东南亚的一些国家由于抽提含砷量高的地下水饮用,造成了人类历史上最大的群体中毒事件[49]。在这些国家,地下水还用于稻田灌溉,导致土壤和稻米砷含量增加[50]。对于饮用水砷含量未超标且以大米为主粮的人群,食用大米砷的摄入量可能高于饮用水砷的摄入量。中国、欧洲和美国等国的饮用水无机砷的限量标准是10 µg·L–1[46],人均每天饮水大约1.5 L,即使饮用含砷为10 µg·L–1饮用水,每天摄入无机砷为15 µg。相比而言,我国人群通过膳食摄入无机砷的量每天达42.5 µg[51],已经是美国环保署制定的参考剂量(Reference Dose,RfD)的2.4倍,致癌风险为10万分之177。其中通过食用大米每天摄入无机砷为24.5 µg,占无机砷摄入总量的60%[51]。
通常认为无机砷对人体的毒性较有机砷毒性强,但是有机三价砷的毒性也很强,甚至强于无机砷。亚洲稻米中无机砷含量占总砷比例平均为78%,其他组份主要为二甲基砷(DMA)[52-53]。稻米中无机砷含量占比在全球范围存在很大的变异,亚洲和欧洲生产的稻米无机砷比例普遍要高于美洲[52],在我国也存在较明显的地理差异,呈现出无机砷比例南方稻米较北方稻米高[54]。导致稻米砷形态比例地理差异的原因不甚清楚,但可能与土壤微生物区系和土壤环境因素有关[52-55]。最近的研究表明,淹水还原条件下,水稻土中的硫酸盐还原菌是驱动砷甲基化的主要微生物类群,而有些产甲烷古菌又会将甲基砷脱甲基,这两个相反的过程决定了土壤中甲基砷的水平[56]。
膳食中砷的化学形态以无机砷为主。无机砷被人体吸收后,能够被亚砷酸甲基转移酶(AS3MT)转化为有机砷,并通过尿液排除体外,因此尿液中砷的化学形态比例为10%~20% 无机砷、10%~20% MMA(一甲基砷)和60%~80% DMA[57-60]。人体基因自然变异会导致尿液DMA % 差异,这种代谢效率差异也是导致砷对不同人体毒性(例如,皮肤损伤)差异的重要原因[59-60]。人体将无机砷甲基化的过程中可能会产生毒性很强的有机三价砷中间产物或巯基砷化合物。
砷毒害敏感的群体是婴幼儿和孕妇。婴幼儿单位体重无机砷的摄入量是成人的2倍~3倍,且婴幼儿身体对砷毒性更为敏感,婴儿期的砷暴露会影响生长、婴幼期的免疫能力和神经系统发育等一些终身的健康问题[61]。Signes-Pastor 等[62]发现婴儿断奶后食用辅助食品后尿液中砷的浓度是哺乳期的1.6倍。最新的一项研究也发现,吃大米类食品的婴儿尿液砷含量是不吃大米类食品婴儿的2倍~3倍[61]。因此需要对婴幼儿的大米辅助食品中砷的含量加强管理。世界卫生组织食品法典委员会和联合国粮农组织将大米无机砷的标准订为0.2 mg·kg–1[63],鉴于婴幼儿对砷的毒害更敏感,欧盟2016年把婴幼儿大米辅助食品中无机砷安全标准提高到更严格的水平,即不超过0.1 mg·kg–1[64]。我们国家婴幼儿谷类辅助食品无机砷的标准与大米砷标准一样,均为0.2 mg·kg–1,鉴于我国婴幼儿习惯米糊米汤作为辅食,结构过于单一,因此是否需要提高我国婴幼儿大米辅食砷的标准有待进一步论证。
土壤污染是导致农产品镉、砷含量超标的一个重要原因,解析并阻断污染源是当务之急。此外,土壤条件、田间管理措施、作物种类和栽培品种也是影响农产品镉、砷积累的重要因素。例如,土壤酸化可导致土壤镉有效性大幅度提高,是我国南方稻米镉含量超标的一个重要原因[28,65],施用石灰将土壤pH提高至6.5以上是降低稻米镉含量的有效措施[66]。稻田淹水导致土壤中的铁氧化物还原溶解,吸附态砷释放到溶液中,并且五价砷还原为有效性更高的三价砷,这些过程是水稻吸收较多砷的重要原因[26]。即使土壤砷含量在背景值范围内,稻米砷含量仍然可能超标。旱作或干湿交替是降低稻米砷含量的有效措施[67],但是会导致镉含量增加[68]。如何解决稻田砷、镉这对生物地球化学矛盾,达到同时阻控水稻对这两种有害元素的积累,仍需进一步的研究。水稻品种间镉、砷积累能力差异很大,通过多年多点筛选可以得到一些较为稳定的低积累品种[69]。从长远的角度看,需要通过分子遗传分析挖掘低积累的优异等位基因,在育种过程中将这些等位基因导入新品种中。近年来,对植物吸收与转运重金属的分子机制研究已经取得了很大进展[70],为通过生物技术降低农产品重金属含量开辟了道路。例如,Tang等[71]采用CRISPR/Cas9技术编辑水稻基因,创制了低镉杂交水稻材料。采用转基因技术过量表达水稻本身的基因,可以大幅度降低稻米镉含量,降幅达90%以上[72-73]。过量表达编码三价砷转运蛋白的或基因,也可显著降低稻米砷含量[74]。如何高效移除土壤中的重金属,也是一个重要的研究方向。采用镉超积累植物可以在较短时间内将中轻度污染农田土壤镉含量降低到环境质量标准以内[75-76]。
抗生素和抗生素抗性基因古已有之,土壤是二者的天然库。临床中使用的许多抗生素来源于可培养的土壤细菌或者真菌的次生代谢产物及其其衍生物[77]。作为微生物的次生代谢产物,天然条件下低浓度的抗生素往往并没有“抗生”的作用,它们在微生物中行使着其他重要的功能,例如作为信号分子调控微生物的基因表达[78]。抗生素对细菌的抑制或者杀灭效果随着其浓度的增加才显现。与抗生素同时存在的是抗生素抗性基因(Antibiotic resistance genes,ARGs),这些基因的表达使微生物产生对抗生素不同程度的耐性。在未受人类影响的环境中,ARGs大多只存在于产生抗生素的微生物以及以抗生素为营养底物的微生物中[79]。此外,许多微生物广泛存在多药物外排泵(Multidrug resistance efflux pumps),起到中间代谢产物解毒和信号传导等功能,这些外排泵对一些抗生素也会表现抗性[79]。因此,在从未受人类影响的土壤中也能够检测到ARGs[80-81],这些可以被认为是土壤环境中的本底ARGs。然而,随着人类活动对环境影响的加剧,土壤中ARGs的丰度、多样性以及环境传播能力均显著增加,给人类健康带来很大的风险。
抗生素自被发现后对细菌感染的良好疗效使人们对其产生了过度依赖。然而,由于管控措施的滞后,抗生素的不合理使用甚至滥用的现象在全世界范围都很普遍,这促使了ARGs在环境中的广泛传播,伴随而来的是抗生素疗效的锐减。大多数抗生素主要被用于人体细菌感染防治,因此抗性细菌和新型ARGs常常最早在人体内被发现[82]。抗生素、抗性细菌和ARGs随医疗废水和生活废水进入城市污水处理系统。然而,现有的污水处理工艺很难去除抗生素和ARGs[83],因而城市污水处理厂中水及城市污泥是环境抗生素和ARGs的重要污染源。污水灌溉及污泥回用可将城市源的抗生素及ARGs引入土壤[84-85]。
全球范围内将近一半的抗生素用于动物养殖业,抗生素在动物养殖业中的使用也极大地促进了环境ARGs的富集及传播。动物养殖业中的抗生素除了用于细菌感染治疗外,常以低于治疗剂量长期添加在饲料中,用于预防疾病以及促进动物生长[86]。在抗生素长期的选择压力下,动物粪便中常含有丰富的抗性细菌和ARGs。同时,抗生素由于不能被动物完全吸收或者代谢,会以较大比例汇集到动物粪便中[87]。堆肥或者厌氧发酵等工艺可以在一定程度上降低畜禽粪便中的抗生素和ARGs,但这些工艺的普及范围还不够广,并且对抗生素和ARGs的去除效率还需进一步提高[87]。因此,畜禽粪肥作为肥料可将动物源的抗生素及ARGs引入土壤。虽然城市源或者动物源的微生物会由于不适应土壤环境而逐渐消失,但抗生素产生的选择压力可促使其中的ARGs通过水平基因转移(horizontal gene transfer,HGT)被土壤微生物获取,成为土壤抗生素抗性组的成员[88-89]。有些重金属对ARGs具有共选择的作用,因此重金属污染也可能增加土壤微生物的抗生素抗性[90]。
随着抗生素和ARGs污染的加剧,土壤中ARGs的水平转移能力也增加[85,91-92]。HGT可使ARGs在不同种类的细菌之间转移,促使ARGs在不同环境间传播。环境中ARGs传播的加剧导致了超级细菌事件在世界范围内的频发。典型的例子如携带NDM-1抗性基因的致病菌(如,,,等)感染事件从印度到世界范围内的爆发,这些感染事件中大多数菌株对除粘菌素和替加环素以外的抗生素都产生了抗性[93]。粘菌素被用于对抗这些超级细菌的最后防线。然而仅过了几年,对粘菌素具有抗性的基因便在世界范围内的环境及人体样品中检出[94-95]。一些土壤抗性细菌中的ARGs与人体病原菌中对应的基因具有100%的序列相似性,说明土壤ARGs在一定的条件下可转移到人体致病菌中[91]。
此外,土壤中存在多种人体致病菌,例如可导致人体罹患破伤风的破伤风梭菌(),引起肠胃炎的产气荚膜梭菌()等[96]。抗生素在针对破伤风的治疗中起着重要的作用[97]。若感染人体的破伤风梭菌携带ARGs,将会加重治疗难度,引发严重的健康风险。由于有效检测措施的匮乏,明确由土壤ARGs传播直接导致的抗生素治疗失败的案例甚少见于报道。但这并不意味着土壤ARGs传播对人体健康就没有危害。
针对环境ARGs的传播的风险,我们应该遵循预警原则[98]。因为风险一旦变成危害,我们能够选择的抗生素已经很少。我们应尽快从多方面采取应对措施。首先,应从国家层面制定法律法规管理抗生素的销售和使用,严格区分人用和兽用抗生素,逐步取消抗生素作为疾病预防药物和促生长剂在养殖业中的使用。其次,在细菌感染治疗中,尽量选用窄谱抗生素,避免更容易产生抗性的广谱抗生素的使用。第三,针对城市污泥和动物粪便中的抗生素和ARGs污染,应开发经济有效的消除方法并进行推广,减少抗生素和ARGs在土壤及其他环境中的传播。第四,加强宣传教育,提高公众对抗生素和ARGs的正确认识,在大众层面合理使用抗生素。
人类面临着人口增长和全球气候变化两大挑战,二者均可能影响甚至重塑土壤与人体健康的关系。预计到21世纪中世界人口将增长至100亿左右,这将对土壤资源施加越来越大的压力,人类活动也将会排放更多的污染物进入土壤。与此同时,未来的全球气候变化对生态系统将产生很大影响,空气CO2浓度增加可能会对农产品中人体必需矿质养分含量起稀释作用,从而加剧人体矿质微量元素的缺乏[99-100]。与此相反,增温或增加CO2浓度可能会增加重金属镉在禾谷类作物籽粒中的积累[101-102]。保护土壤资源与土壤健康,是人类应对未来人口增长与全球气候变化两大挑战中必须优先考虑的一项任务。探讨双重压力下的土壤与人体健康关系,也是未来土壤学研究的重要方向。
从本文列举的几个例子可以看出,土壤对人体健康的影响具有非均等性,收入低的社会弱势群体可能更容易受到土壤对健康的负面影响。因此,研究土壤与人体健康关系时,必需更多地关注贫困地区与弱势群体。消除土壤对人体健康负面影响的技术或措施,也必需针对并适宜于这些地区与群体。这就意味着,这些措施具有公益性质,单靠市场机制往往解决不了问题,政府干预可能是必需的选项。
土壤与人类生存息息相关,但很多人对土壤的健康问题往往视而不见,或者习以为常。近年来,有机农业的兴起在某种程度上反映了人们对土壤健康的关注,虽然有机农产品是否比常规农产品更富营养尚无定论。互联网与新媒体的崛起,对信息传播起到极大的推动作用,但也使得很多似是而非、哗众取宠、甚至是反科学的言论盛行。向大众传播基于证据的科学知识,是科学家们越来越需要学会的一项重要任务。
[1] Oliver M A. Soil and human health:A review. European Journal of Soil Science,1997,48(4):573—592.
[2] Steffan J J,Brevik E C,Burgess L C,et al. The effect of soil on human health:An overview. European Journal of Soil Science,2018,69(1):159—171.
[3] Zhao F J,Shewry P R. Recent developments in modifying crops and agronomic practice to improve human health. Food Policy,2011,36:S94—S101.
[4] Kaspari M,Clay N A,Donoso D A,et al. Sodium fertilization increases termites and enhances decomposition in an Amazonian forest. Ecology,2014,95(4):795—800.
[5] Pennisi E. Ecosystems say ‘Pass the salt!’ Science,2014,343(6170):472—473.
[6] Cao X Y,Jiang X M,Kareem A,et al. Iodination of irrigation water as a method of supplying iodine to a severely iodine-deficient population in Xinjiang,China. Lancet,1994,344(8915):107—110.
[7] Fairweather-Tait S J,Bao Y,Broadley M R,et al. Selenium in human health and disease. Antioxidants & Redox Signaling,2011,14(7):1337—1383.
[8] Combs G F. Selenium in global food systems. British Journal of Nutrition,2001,85(5):517—547.
[9] Chen J. An original discovery:Selenium deficiency and Keshan disease(an endemic heart disease). Asia Pacific Journal of Clinical Nutrition,2012,21(3):320—326.
[10] Chen X,Yang G,Chen J,et al. Studies on the relations of selenium and Keshan disease. Biological Trace Element Research,1980,2(2):91—107.
[11] Tan J A,Zhu W Y,Wang W Y,et al. Selenium in soil and endemic diseases in China. Science of the Total Environment,2002,284(1/3):227—235.
[12] Guo X,Ma W J,Zhang F,et al. Recent advances in the research of an endemic osteochondropathy in China:Kashin-Beck disease. Osteoarthritis and Cartilage,2014,22(11):1774—1783.
[13] Stone R. A medical mystery in middle China. Science,2009,324:1378—1381.
[14] Eurola M,Ekholm P,Ylinen M,et al. Effects of selenium fertilization on the selenium content of cereal grains,flour,and bread produced in Finland. Cereal Chemistry,1990,67(4):334—337.
[15] Varo P,Alfthan G,Ekholm P,et al. Selenium intake and serum selenium in Finland—Effects of soil fertilization with selenium. American Journal of Clinical Nutrition,1988,48(2):324—329.
[16] Hartikainen H. Biogeochemistry of selenium and its impact on food chain quality and human health. Journal of Trace Elements in Medicine and Biology,2005,18(4):309—318.
[17] Broadley M R,Alcock J,Alford J,et al. Selenium biofortification of high-yielding winter wheat(L.)by liquid or granular Se fertilisation. Plant and Soil,2010,332(1/2):5—18.
[18] Blazina T,Sun Y,Voegelin A,et al. Terrestrial selenium distribution in China is potentially linked to monsoonal climate. Nature Communications,2014,5. DOI:10.1038/ncomms5717.
[19] Jones G D,Droz B,Greve P,et al. Selenium deficiency risk predicted to increase under future climate change. Proceedings of the National Academy of Sciences of the United States of America,2017,114(11):2848—2853.
[20] The World Bank. Repositioning nutrition as central to development//A strategy for large-scale action. Washington:The International Bank for Reconstruction and Development/The World Bank,2006.
[21] White P J,Broadley M R. Biofortification of crops with seven mineral elements often lacking in human diets- iron,zinc,copper,calcium,magnesium,selenium and iodine. New Phytologist,2009,182(1):49—84.
[22] Fan M S,Zhao F J,Fairweather-Tait S J,et al. Evidence of decreasing mineral density in wheat grain over the last 160 years. Journal of Trace Elements in Medicine and Biology,2008,22:315—324.
[23] Cakmak I,Kutman U B. Agronomic biofortification of cereals with zinc:A review. European Journal of Soil Science,2018,69(1):172—180.
[24] Zou C,Du Y,Rashid A,et al. Simultaneous biofortification of wheat with zinc,iodine,selenium and iron through foliar treatment of a micronutrient cocktail in six countries. Journal of Agricultural and Food Chemistry,2019,67:8096—8106.
[25] Chaney R L. Health risks associated with toxic metals in municipal sludge//Bitton G. Sludge:Health risks of land applications. Ann Arbor,Michigan:Ann Arbor Science Publisher,1980:59—83.
[26] Zhao F J,McGrath S P,Meharg A A. Arsenic as a food-chain contaminant:Mechanisms of plant uptake and metabolism and mitigation strategies. Annual Review of Plant Biology,2010,61:535—559.
[27] Ministry of Environmental Protection,Ministry of Land and Resources. National Soil Pollution Survey Bulletin. http://www.gov.cn/foot/2014-04/17/content_2661768. htm. [环境保护部,国土资源部. 全国土壤污染状况调查公报. http://www.gov.cn/foot/2014-04/17/content_ 2661768.htm.]
[28] Zhu H H,Chen C,Xu C,et al. Effects of soil acidification and liming on the phytoavailability of cadmium in paddy soils of central subtropical China. Environmental Pollution,2016,219:99—106.
[29] Du Y,Hu X F,Wu X H,et al. Affects of mining activities on Cd pollution to the paddy soils and rice grain in Hunan Province,central south China. Environmental Monitoring and Assessment,2013,185(12):9843—9856.
[30] Wang M,Chen W,Peng C. Risk assessment of Cd polluted paddy soils in the industrial and township areas in Hunan,southern China. Chemosphere,2016,144:346—351.
[31] Chen H,Yang X,Wang P,et al. Dietary cadmium intake from rice and vegetables and potential health risk:A case study in Xiangtan,southern China. Science of the Total Environment,2018,639:271—277.
[32] Williams P N,Lei M,Sun G,et al. Occurrence and partitioning of cadmium,arsenic and lead in mine impacted paddy rice:Hunan,China. Environmental Science & Technology,2009,43(3):637—642.
[33] Joint FAO/WHO Expert Committee on Food Additives. Joint FAO/WHO Expert Committee on Food Additives seventy-third meeting. http://www.who.int/foodsafety/ publications/chem/summary73.pdf. Geneva:World Health Organization,2010.
[34] European Food Safety Authority. Cadmium dietary exposure in the European population. EFSA Journal 2012,10(1):2551—2588.
[35] Nordberg G,Jin T,Bernard A,et al. Low bone density and renal dysfunction following environmental cadmium exposure in China. Ambio,2002,31(6):478—481.
[36] Jin T,Nordberg G,Ye T,et al. Osteoporosis and renal dysfunction in a general population exposed to cadmium in China. Environmental Research,2004,96(3):353—359.
[37] Zhang W L,Du Y,Zhai M M,et al. Cadmium exposure and its health effects:A 19-year follow-up study of a polluted area in China. Science of the Total Environment,2014,470:224—228.
[38] Nordberg G F,Nogawa K,Nordberg M,et al. Chapter 23 - Cadmium // Handbook on the toxicology of metals. 3rded. Burlington:Academic Press,2007:445—486.
[39] Kasuya M. Present status of Itai-itai disease patients as of January 14,2001,Kankyo Hoken Report. 2002:41—54.
[40] Reeves P G,Chaney R L. Nutritional status affects the absorption and whole-body and organ retention of cadmium in rats fed rice-based diets. Environmental Science & Technology,2002,36(12):2684—2692.
[41] Wang P,Chen H,Kopittke P M,et al. Cadmium contamination in agricultural soils of China and the impact on food safety. Environmental Pollution,2019,249:1038—1048.
[42] Nogawa K,Sakurai M,Ishizaki M,et al. Threshold limit values of the cadmium concentration in rice in the development of itai-itai disease using benchmark dose analysis. Journal of Applied Toxicology,2017,37(8):962—966.
[43] National Health and Family Planning Commission of China,China Food and Drug Administration. National food safety standard:Maximum levels of contaminants in food. GB2762—2017. [中华人民共和国国家卫生和计划生育委员会,国家食品药品监督管理总局. 食品安全国家标准—食品中污染物限量:GB2762—2017.]
[44] Codex Alimentarius Commission. Report of the 29th Session of the Codex Alimentarius Commission,ALINORM 06/29/41. Rome:Codex Alimentarius Commission,FAO,2006.
[45] Ministry of Environmental Protection. Exposure factors handbook of Chinese population:Adults. Bejing:China Environmental Science Press,2013:849. [环境保护部. 中国人群暴露参数手册(成人卷). 北京:中国环境出版社,2013:849.]
[46] National Research Council. Arsenic in drinking water:2001 update. Washington,DC:National Academy Press,2001 .
[47] Smith A H,Steinmaus C M. Health effects of arsenic and chromium in drinking water:recent human findings. Annual Review of Public Health,2009,30:107—122.
[48] Chen Y,Parvez F,Gamble M,et al. Arsenic exposure at low-to-moderate levels and skin lesions,arsenic metabolism,neurological functions,and biomarkers for respiratory and cardiovascular diseases:Review of recent findings from the Health Effects of Arsenic Longitudinal Study(HEALS)in Bangladesh. Toxicology and Applied Pharmacology 2009,239(2):184—192.
[49] Fendorf S,Michael H A,van Geen A. Spatial and temporal variations of groundwater arsenic in south and southeast Asia. Science,2010,328(5982):1123—1127.
[50] Meharg A A,Rahman M. Arsenic contamination of Bangladesh paddy field soils:Implications for rice contribution to arsenic consumption. Environmental Science & Technology,2003,37(2):229—234.
[51] Li G,Sun G X,Williams P N,et al. Inorganic arsenic in Chinese food and its cancer risk. Environment International,2011,37(7):1219—1225.
[52] Zhao F J,Zhu Y G,Meharg A A. Methylated arsenic species in rice:Geographical variation,origin,and uptake mechanisms. Environmental Science & Technology,2013,47(9):3957—3966.
[53] Zhu Y G,Sun G X,Lei M,et al. High percentage inorganic arsenic content of mining impacted and nonimpacted Chinese rice. Environmental Science & Technology,2008,42(13):5008—5013.
[54] Chen H,Tang Z,Wang P,et al. Geographical variations of cadmium and arsenic concentrations and arsenic speciation in Chinese rice. Environmental Pollution,2018,238:482—490.
[55] Zhao F J,Harris E,Yan J,et al. Arsenic methylation in soils and its relationship with microbial arsm abundance and diversity,and as speciation in rice. Environmental Science & Technology,2013,47(13):7147—7154.
[56] Chen C,Li L,Huang K,et al. Sulfate-reducing bacteria and methanogens are involved in arsenic methylation and demethylation in paddy soils. The ISME Journal,2019,13:2523—2535.
[57] Buchet J P,Lauwerys R,Roels H. Comparison of the urinary excretion of arsenic metabolites after a single oral dose of sodium arsenite,monomethylarsonate,or dimethylarsinate in man. International Archives of Occupational and Environmental Health,1981,48(1):71—79.
[58] Chung J Y,Yu S D,Hong Y S. Environmental source of arsenic exposure. Journal of Preventive Medicine and Public Health,2014,47(5):253—257.
[59] Pierce B L,Tong L,Dean S,et al. A missense variant in FTCD is associated with arsenic metabolism and toxicity phenotypes in Bangladesh. PLoS Genetics,2019,15(3):e1007984.
[60] Pierce B L,Kibriya M G,Tong L,et al. Genome-wide association study identifies chromosome 10q24.32 variants associated with arsenic metabolism and toxicity phenotypes in Bangladesh. PLoS Genetics,2012,8(2):e1002522.
[61] Karagas M R,Punshon T,Sayarath V,et al. Association of rice and rice-product consumption with arsenic exposure early in life. JAMA Pediatrics,2016,170(6):609—616.
[62] Signes-Pastor A J,Woodside J V,McMullan P,et al. Levels of infants’ urinary arsenic metabolites related to formula feeding and weaning with rice products exceeding the EU inorganic arsenic standard. PLoS One,2017,12(5):e0176923.
[63] Joint Food and Agriculture Organization of the United Nations/World Health Organization Codex Alimentarius Commission. Report of the eighth session of the codex committee on contaminants in foods. 2014.
[64] European Commission. Amending Regulation(EC)No 1881/2006 as regards maximum levels of inorganic arsenic in foodstuffs. 2015/2016.
[65] Zhao F J,Ma Y,Zhu Y G,et al. Soil contamination in China:Current status and mitigation strategies. Environmental Science & Technology,2015,49(2):750—759.
[66] Chen H,Zhang W,Yang X,et al. Effective methods to reduce cadmium accumulation in rice grain. Chemosphere,2018,207:699—707.
[67] Li R Y,Stroud J L,Ma J F,et al. Mitigation of arsenic accumulation in rice with water management and silicon fertilization. Environmental Science & Technology,2009,43:3778—3783.
[68] Arao T,Kawasaki A,Baba K,et al. Effects of water management on cadmium and arsenic accumulation and dimethylarsinic acid concentrations in Japanese rice. Environmental Science & Technology,2009,43(24):9361—9367.
[69] Duan G L,Shao G S,Tang Z,et al. Genotypic and environmental variations in grain cadmium and arsenic concentrations among a panel of high yielding rice cultivars. Rice,2017,10:9. DOI:10.1186/s12284-017- 0149-2.
[70] Clemens S,Ma J F. Toxic heavy metal and metalloid accumulation in crop plants and foods. Annual Review of Plant Biology,2016,67:489—512.
[71] Tang L,Mao B,Li Y,et al. Knockout ofusing the CRISPR/Cas9 system produces low Cd-accumulatingrice without compromising yield. Scientific Reports,2017,7,14438. DOI:10.1038/s41598-017- 14832-9.
[72] Ueno D,Yamaji N,Kono I,et al. Gene limiting cadmium accumulation in rice. Proceedings of the National Academy of Sciences of the United States of America,2010,107(38):16500—16505.
[73] Lu C,Zhang L,Tang Z,et al. Producing cadmium-free Indica rice by overexpressing OsHMA3. Environment International,2019,126:619—626.
[74] Sun S-K,Chen Y,Che J,et al. Decreasing arsenic accumulation in rice by overexpressing OsNIP1;1 and OsNIP3;3 through disrupting arsenite radial transport in roots. New Phytologist,2018,219(2):641—653.
[75] Li Z,Wu L,Hu P,et al. Repeated phytoextraction of four metal-contaminated soils using the cadmium/zinc hyperaccumulator. Environmental Pollution,2014,189:176—183.
[76] Zhao F J,Lombi E,McGrath S P. Assessing the potential for zinc and cadmium phytoremediation with the hyperaccumulator. Plant and Soil,2003,249(1):37—43.
[77] Charlop-Powers Z,Owen J G,Reddy B V B,et al. Global biogeographic sampling of bacterial secondary metabolism. eLife,2015,4:e05048. DOI:10.7554 /eLife.05048
[78] Fajardo A,Martinez J L. Antibiotics as signals that trigger specific bacterial responses. Current Opinion in Microbiology,2008,11(2):161—167.
[79] Martinez J L. Antibiotics and antibiotic resistance genes in natural environments. Science,2008,321:365–367.
[80 ]Allen H K,Moe L A,Rodbumrer J,et al. Functional metagenomics reveals diverse β-lactamases in a remote Alaskan soil. The ISME Journal,2008,3(2):243—251.
[81] Lang K S,Anderson J M,Schwarz S,et al. Novel florfenicol and chloramphenicol resistance gene discovered in Alaskan soil by using functional metagenomics. Applied and Environmental Microbiology,2010,76(15):5321—5326.
[82] Yong D,Toleman M A,Giske C G,et al. Characterization of a new metallo-β-lactamase gene,NDM-1,and a novel erythromycin esterase gene carried on a unique genetic structure insequence type 14 from India. Antimicrobial Agents and Chemotherapy,2009,53(12):5046—5054.
[83] Michael I,Rizzo L,McArdell C S,et al. Urban wastewater treatment plants as hotspots for the release of antibiotics in the environment:A review. Water Research,2013,47(3):957—995.
[84] Wang F H,Qiao M,Su J Q,et al. High throughput profiling of antibiotic resistance genes in urban park soils with reclaimed water irrigation. Environmental Science & Technology,2014,48(16):9079—9085.
[85] Xie W Y,McGrath S P,Su J Q,et al. Long-term impact of field applications of sewage sludge on soil antibiotic resistome. Environmental Science & Technology,2016,50(23):12602—12611.
[86] Castanon J I. History of the use of antibiotic as growth promoters in European poultry feeds. Poultry Science,2007,86(11):2466–2471.
[87] Xie W Y,Shen Q,Zhao F J. Antibiotics and antibiotic-resistance from animal manures to soil:A review. European Journal of Soil Science,2018,69:181—195.
[88] Zhu Y G,Johnson T A,Su J Q,et al. Diverse and abundant antibiotic resistance genes in Chinese swine farms. Proceedings of the National Academy of Sciences of the United States of America,2013,110(9):3435—3440.
[89] Xie W Y,Yuan S T,Xu M G,et al. Long-term effects of manure and chemical fertilizers on soil antibiotic resistome. Soil Biology & Biochemistry,2018,122:111—119.
[90] Yu Z,Gunn L,Wall P,et al. Antimicrobial resistance and its association with tolerance to heavy metals in agriculture production. Food Microbiology,2017,64:23—32.
[91] Forsberg K J,Reyes A,Wang B,et al. The shared antibiotic resistome of soil bacteria and human pathogens. Science,2012,337(6098):1107—1111.
[92] Graham D W,Knapp C W,Christensen B T,et al.Appearance of β-lactam resistance genes in agricultural soils and clinical isolates over the 20thcentury. Scientific Reports,2016,6:21550.https://doi.org/10.1038/srep 21550.
[93] Rolain J M,Parola P,Cornaglia G. New Delhi metallo-beta-lactamase(NDM-1):towards a new pandemia? Clinical Microbiology and Infection,2010,16(12):1699—1701.
[94] Liu Y Y,Wang Y,Walsh T R,et al. Emergence of plasmid-mediated colistin resistance mechanism MCR-1 in animals and human beings in China:A microbiological and molecular biological study. The Lancet Infectious Diseases,2016,16(2):161—168.
[95] von Wintersdorff C J H,Wolffs P F G,van Niekerk J M,et al. Detection of the plasmid-mediated colistin- resistance genein faecal metagenomes of Dutch travellers. Journal of Antimicrobial Chemotherapy,2016,71(12):3416—3419.
[96] Palmer J S,Hough R L,West H M,et al. A review of the abundance,behaviour and detection of clostridial pathogens in agricultural soils. European Journal of Soil Science,2019,70:911—929.
[97] Brook I. Current concepts in the management ofinfection. Expert Review of Anti- infective Therapy,2008,6(3):327—336.
[98] Manaia C M. Assessing the risk of antibioticresistance transmission from the environment to humans:Non-direct proportionality between abundance and risk. Trends in Microbiology,2017,25:173—181.
[99] Myers S S,Zanobetti A,Kloog I,et al. Increasing CO2threatens human nutrition. Nature,2014,510(7503):139—143.
[100]Loladze I. Rising atmospheric CO2and human nutrition:toward globally imbalanced plant stoichiometry? Trends in Ecology & Evolution,2002,17(10):457—461.
[101]Ge L Q,Cang L,Liu H,et al. Effects of warming on uptake and translocation of cadmium(Cd)and copper(Cu)in a contaminated soil-rice system under Free Air Temperature Increase(FATI). Chemosphere,2016,155:1—8.
[102]Guo H,Zhu J,Zhou H,et al. Elevated CO2levels affects the concentrations of copper and cadmium in crops grown in soil contaminated with heavy metals under fully open-air field conditions. Environmental Science & Technology,2011,45(16):6997—7003.
Soil and Human Health
ZHAO Fangjie, XIE Wanying, WANG Peng
(College of Resources and Environmental Sciences,Nanjing Agricultural University,Nanjing 210095, China)
Soil can exert both positive and negative impacts on human health. In this paper, three aspects of the relationship between soil and human health are discussed: 1) supply of essential mineral nutrients from soil to humans; 2) human’s exposure to toxic heavy metals and metalloids via their transfer from soil to the food chain; and 3) the spread of antibiotic resistance genes in soil. Although soils, through the food chain, are a main source of many essential mineral nutrients for humans, for some nutrients the supply may not meet the requirements of humans, especially those elements that are required by animals but not by plants. Selenium is a typical example, which is deficient in the diets of many people due to low levels of this element in the soil. Agronomic biofortification through additions of selenium in fertilizers is an effective way to increase selenium intake in the population living in the low selenium areas. Human activities have caused contamination of soil with various types of organic and inorganic contaminants. Heavy metals and metalloids such as cadmium and arsenic can be transferred readily from soil to the edible organs of crop plants, posing a risk to human health. Soil contamination coupled with soil acidification has resulted in increased availability of cadmium in soil and elevated accumulation of this toxic metal in food crops. A number of strategies can be used to reduce the accumulation of heavy metals and metalloids in food crops, including methods to immobilize contaminants in soil, cultivar selection, breeding and genetic engineering to reduce heavy metal uptake or translocation in crop plants, phytoextraction of heavy metals and metalloids with hyperaccumulators to clean up contaminated soil. Overuse of antibiotics in humans and in animal production has resulted in increased antibiotic resistance in microorganisms in the environment, which may lead to the evolution of superbugs of human pathogens. Animal manures may contain high levels of antibiotic resistant microbes and resistance genes, which can disseminate into agricultural soil via manure applications. Urgent actions should be taken to control the overuse of antibiotics in animal production. Effective methods are also needed to decrease the abundance and diversity of antibiotic resistance microbes and genes in animal manures before application to soil. It is recognized that the impacts of soil on human health are uneven across the whole population; people living in poor areas or having a low income are often more vulnerable to the negative effects of soil on human health. The relationship between soil and human health will become more prominent in the future with the dual challenges of increasing population and global climate changes. Options to alleviate the negative impacts of soil on human health and future research directions are also discussed.
Human health; Mineral nutrients; Heavy metals; Antibiotic resistance genes
S153;X18
A
10.11766/trxb201907200376
赵方杰,谢婉滢,汪 鹏. 土壤与人体健康[J]. 土壤学报,2020,57(1):1–11.
ZHAO Fangjie,XIE Wanying,WANG Peng. Soil and Human Health[J]. Acta Pedologica Sinica,2020,57(1):1–11.
* 国家自然科学基金项目(21661132001,41671309)资助 Supported by the National Natural Science Foundation of China(Nos. 21661132001,41671309)
赵方杰(1963—),男,福建安溪人,博士,教授。E-mail:Fangjie.Zhao@njau.edu.cn
2019–07–20;
2019–09–16;
2019–12–24
(责任编辑:卢 萍)