大气CO2体积分数升高对植物N素吸收的影响

从影响植物N素吸收的因素来看，大气CO2体积分数升高条件下植物净光合作用增强，碳同化产物增多，利于改善N素吸收的能量和物质基础：植物根系生长增强，生物量增多且空间分布加大，有利于N素吸收；但土壤有效N供应能力的变化存在增强和减弱两种观点。从植物N素吸收的实际情况来看，大气CO2体积分数升高条件下植物N吸收总量并末增加，植物体内N质量分数普遍降低，某些种类植物N吸收形态也发生了改变。因此要阐明大气CO2体积分数升高对植物N素吸收的影响机制，必须探明土壤有效N供应能力的变化：CO2体积分数升高条件下N矿化作用是否增强，微生物和植物间是否存在对有效N的竞争，此外，CO2体积分数升高条件下植物根系形态特征变化和N素吸收(包括主动和被动吸收)的生理机制及其与环境因素的关系也值得进一步研究。     

根际土壤中Cd、Pb形态转化及其植物效应

采用根袋盆栽试验和连续形态分析方法研究根际土壤中Cd、Pb形态转化及其植物效应。结果表明，(1)在低Cd质量分数(≤1mg／kg)污染条件下，根际土壤中cd主要以残渣态存在；在较高cd质量分数(≥5mg／kg)污染条件下，cd主要以交换态和碳酸盐结合态存在，即根际土壤中Cd由残渣态向交换态和碳酸盐结合态转化，Cd活性增强。(2)Pb在根际土壤中主要以有机结合态和铁锰氧化物结合态存在，交换态质量分数很低，并随Pb污染水平的提高，其主要存在形态未改变。(3)土壤中Cd、Pb总质量分数及各形态质量分数(残渣态除外)与小麦根、茎叶中Cd、Pb质量分数呈正相关性，而与鲜质量呈负相关性；当w(Cd)添加量≥5mg／kg时，小麦鲜质量明显下降；当w(Pb)≥500mg／kg时，小麦鲜质量下降。     

湖南南部铅锌矿区铅锌富集植物筛选研究

在湖南省桂阳县铅锌矿区采用调查和室内分析相结合的方法,采集植物和土壤样品112个,分别测定了土壤和植物样品的铅锌含量,筛选铅锌富集植物。结果表明：矿区土壤铅锌污染十分严重,矿区土壤铅和锌的平均质量分数分别为：2177.22、3165.89 mg·kg^-1。植物样品根系的铅锌质量分数分别为：264.00、666.11 mg·kg^-1,地上部铅锌质量分数平均为165.56、363.87 mg·kg^-1,植物根系的铅锌含量与土壤的铅锌含量呈显著正相关。通过对比分析,以地上部铅质量分数大于450 mg·kg^-1、锌质量分数大于750 mg·kg^-1、转运系数大于1、植物地上部形态高大为筛选条件,筛选出5种铅富集植物分别是：糯米团（Hyrtanandra）、水蓼（Polygonum hydropiper）、酸模（RumexacetosaLinn）、毛叶堇菜（Viola verecumda A.Gray）、地榆（Garden Burnet Root）;3种锌富集植物分别是：鬼针草（Bidens pilosa L.）、博落回（Macleaya cordata（Willd.） R. Brown）和糯米团;糯米团茎叶的铅锌质量分数分别为635.48、919.51 mg·kg^-1,可作为铅锌复合污染土壤修复的备选植物品种。     

污灌湿地系统土壤-植物中铬的赋存形态研究

采取逐级提取法对江苏盐城某污水灌溉湿地土壤中的铬的赋存形态以及其上生长的丰要植物芦苇的不同组织部位中的总铬进行了分析测定，并研究其生物有效性。结果表明：与对照点相比，污灌土壤中铬质最分数明显升高而受到不同程度的污染，其赋存形态质量分数由高到低顺序为残渣态（RES-）→铁锰态（（OFeMn-））→碳酸态（CARB-）→有机态（OM-）和交换态（EX-）之和。芦苇不同组织部位中铬分布研究表明根部质量分数远大于茎和叶，说明根系吸收为主要作用，而后迁移至其它易积累部位。对各种形态的铬与植物中的铬总量之间的相关性进行了分析，相关系数表明，植物中的生物富集量与各种赋存形态都有一定的线性关系，其中强有机质结合态与生物富集量具有最好的线性相关性。     

滨海4种盐生植物根际土壤酶活性特征与主要养分的关系

植物可直接或间接地影响土壤酶的活性,根际土壤酶的种类和活性对土壤养分的速效化产生影响,从而影响植物的吸收利用。以滨海盐土和轻度盐化潮土为材料,利用根袋法研究滨海盐生植物对根际与非根际土壤养分含量以及酶活性的影响,为盐生植物在滨海盐渍土壤中的修复利用提供理论依据。结果表明：在两种土壤中,植物根际过氧化氢酶,脲酶和蛋白酶的活性表现出相反的变化,滨海盐土中,根际土3种酶的活性均高于非根际土;而轻度盐化潮土中的根际土3种酶活性均低于非根际土。在两种土壤中,根际土全氮质量分数比非根际土高,但全磷却比非根际土低。根际土速效态养分的变化则与全态养分的变化相反,4种植物的根际土速效氮质量分数均显著低于非根际土。除芦苇外,根际土速效磷质量分数均高于非根际土。滨海盐土中碱性磷酸酶、过氧化氢酶和转化酶和土壤中几种主要养分的相关性最紧密,较好地体现了4种滨海盐生植物根际的养分状况,也说明盐生植物对滨海盐土酶活性有较大的影响。对比4种植物根际土壤中的酶活性,在高盐质量分数的滨海盐土中,盐地碱蓬对根际土壤酶活性的影响最大     

矿区周围土壤中重金属危害性评估研究

分别用总量法和连续萃取法对广东大宝山矿周围土壤、植物和沉积物中重金属的总量和化学形态进行了详细分析。结果发现，矿山废水流入的横石河沉积物中Pb、Zn、Cu和Cd的质量分数分别为1841．02、2326．28、1522．61和10.33mg／kg；经此河水灌溉的稻田中重金属(Cu、Cd、Pb和Zn)的质量分数也远远超出了土壤环境二级标准值，其中Cu、Cd超标倍数分别为14．01和4．17倍。结果还表明，生长在矿区周围的植物也受到不同程度重金属的污染且不同植物吸收和积累重金属的能力相差很大。用Tessier连续法对土壤中重金属进行萃取发现，虽然重金属主要存在于残余态中，但在Fe-Mn氧化态、有机结合态中的质量分数也很高．说明这些土壤确实受到了有毒有害重金属元素的严重污染。     

有机肥施用对珠三角菜地土壤磷污染风险的初步研究

通过田间小区试验研究有机肥施用量对菜心产量、土壤磷形态的影响,分析土壤磷形态之间的相关性,评估菜地红壤磷污染风险。结果表明,有机肥施用并未提高菜心的产量和生物量,而超过一定使用量之后,反而降低菜心产量和生物量;土壤无机磷形态以Fe-P和Al-P为主,占土壤无机磷质量分数的90%以上。有机肥施用提高土壤各形态无机磷的质量分数,且有机肥用量越高,土壤Fe-P、Al-P、Ca-P和O-P质量分数越高。有机肥过量施用显著提高土壤速效磷和水溶性磷质量分数;分别对Olsen-P和CaCl2-P与各形态磷进行逐步回归分析,只有Olsen-P和CaCl2-P与Ca-P具有线性关系（p〈0.05）,方程为Y1=36.95＋0.622 1X,Y2=-0.102 5＋0.048 6X。表明施用有机肥下,Ca-P是菜地土壤有效磷的最直接来源,可以作为红壤磷污染风险评价指标。     

凉水和宝天曼地区乔木叶片氮素再吸收过程中δ15N的变化

植物自然丰度的稳定性N同位素(δ15N)在植物N吸收和N转运过程中会发生变化,但植物叶片在凋落之前的N素的再吸收如何影响δ15N变化还不清楚.本研究以凉水地区的14个常见树种和宝天曼地区的16个常见树种为研究对象,测定各树种新鲜叶和凋落叶及其对应土壤中的C、N质量分数和δ15N值.结果表明,凉水树种新鲜叶N质量分数和δ15N值显著高于宝天曼树种,这与凉水土壤的N质量分数和δ15N值都高于宝天曼土壤相对应.此外,凉水树种叶片N吸收率(47%)与宝天曼树种(40%)无显著差异.宝天曼树种凋落叶中的δ15N显著高于新鲜叶中的δ15N值,即叶片N再吸收过程中存在N同位素的分馏效应,而凉水树种凋落叶与新鲜叶中的δ15N无显著性差异.本研究首次报道在植物叶片N再吸收过程中存在显著的同位素分馏效应,而且分馏效应的程度与N再吸收率显著负相关.此外,植物叶片N再吸收过程中是否存在同位素分馏效应可能取决于叶片的N再吸收率;乔木新鲜叶片N质量分数和δ15N值在地区间的差异可能取决于土壤N质量分数和δ15N值的地区差异;叶片N再吸收率可能与N在叶片中的存在形态有关,而与土壤N质量分数不相关.     

不同类型植物篱对长江上游坡耕地土壤养分含量及坡面分布的影响

在调查分析长江上游现有坡耕地植物篱的配置方式、生长状况和室内分析植物篱-坡耕地系统中土壤养分含量和颗粒组成的基础上,对3种坡耕地-植物篱系统中土壤养分含量及其分布特征进行了研究,结果表明：在坡耕地-植物篱系统中,植物篱能显著改善和提高植物篱带内表层土壤的养分含量,不同植物篱带内土壤有机质、全氮、水解氮、全磷、速效磷、全钾、速效钾平均质量分数比带间坡耕地土壤分别提高了59.1%、83.5%、56.2%、83.3%、149.6%、14.0%、153.1%,植物篱带内土壤阳离子交换量比带间坡耕地土壤提高了21.6%。植物篱带内比带间坡耕地土壤沙粒质量分数减小了9.4%,粘粒质量分数增加了21.6%,在植物篱系统中土壤粘粒质量分数与土壤养分含量在3种植物篱系统内表现出一致的规律性,自篱间坡耕地至植物篱带呈增加的趋势,至植物篱带下土壤粘粒和土壤养分含量减小。     

不同退化程度喀斯特生态系统根际土壤的养分分布特征

以贵州中部喀斯特地区由乔木林、灌木林和灌草丛等不同退化程度生态系统中的优势物种根际土壤为研究对象,测定其C、N、P全量及有效态质量分数,分析各优势物种根际土壤的养分变化。结果表明：3个生态系统中不同优势物种根际各类土壤养分质量分数变化较大,其中,土壤C、N、P养分为乔木林中园果化香根际土壤质量分数最高,白枥根际养分质量分数最低。可溶性有机碳质量分数为乔木林中最低,其平均水平不超过10 mg·kg-1。土壤磷素的供给能力为乔木林的园果化香和刺秋相对较强,其中园果化香中达到1.5%。而且优势树种间根际土壤有效态养分质量分数的差异明显高于全量养分,说明喀斯特地区根际土壤养分差异性主要受植被因素的影响,土壤有效态养分较全量养分对植被群落演替的响应更为灵敏,而且根际土壤养分质量分数和形态的变化与土壤有机碳质量分数有显著的正相关关系,这进一步说明喀斯特地区植被类型的变化对土壤养分的循环利用具有重要的影响作用。     

An innovative approach for iodine supplementation using iodine-rich phytogenic food

Iodine, as one of the essential trace elements for human body, is very important for the proper function of thyroid gland. In some regions, people are still suffering from iodine deficiency disorder (IDD). How to provide an effective and cost-efficient iodine supplementation has been a public health issue for many countries. In this review, a novel iodine supplementation approach is introduced. Different from traditional iodine salt supplement, this approach innovatively uses cultivated iodine-rich phytogenic food as the supplement. These foods are cultivated using alga-based organic iodine fertilizer. The feasibility, mechanics of iodine absorption of plants from soil and the bioavailability of iodine-rich phytogenic food are further discussed.     

The geochemistry of iodine — a review

Iodine has long been recognised as an important element environmentally. Despite this there are many gaps in our knowledge of its geochemistry and even where information is available much of this is based on old data which, in the light of recent data, are suspect.Iodine forms few independent minerals and is unlikely to enter most rock-forming minerals. In igneous rocks its concentration is fairly uniform and averages 0.24 mg/kg. Sedimentary rocks tend to have higher concentrations with average iodine contents of:-recent sediments 5–200 mg/kg, carbonates 2.7 mg/kg, shales 2.3 mg/kg and sandstones 0.8 mg/kg. Organic-rich sediments are particularly enriched in iodine.Soils, generally, are much richer in iodine than the parent rocks with the actual level being decided mainly by soil type and locality. Little soil iodine is water-soluble and much iodine is thought to be associated with organic matter, clays and aluminium and iron oxides. Most iodine in soils is derived from the atmosphere where, in turn, it has been derived from the oceans. Seawater has a mean iodine content of 58 g/L, while non-saline surface waters have lower and very variable levels. Subsurface brines and mineral waters are generally strongly enriched in iodine.Marine plants are frequently enriched in iodine while terrestrial plants have generally low contents. Iodine is essential for all mammals.Consideration of the geochemical cycle of iodine reveals that its transfer from the oceans to the atmosphere is probably the most important process in its geochemistry.     

Iodine deficiency status in the WHO Eastern Mediterranean Region: a systematic review

Iodine deficiency is a global public health issue because iodine plays a major role in the thyroid hormone synthesis and is essential for normal neurological development. This review summarizes the publications on iodine status in the WHO Eastern Mediterranean Region (EMR) countries. All related studies available in main national and international databases were systematically searched using some specific keywords to find article published between 1909 and 2015. The prevention of iodine deficiency disorders (IDDs) in the WHO EMR countries is currently under control without significant side effects. Mild to severe IDDs exist in some countries of the Middle East, due to lack of effective iodine supplementation program, but the Islamic Republic of Iran, Jordan, Bahrain and Tunisia have achieved the goal of universal salt iodization. Overall, despite enormous efforts to control IDDs, still IDD remains a serious public health problem in some countries of the region, requiring urgent control and prevention measures.     

Concentration of lodine and bromine by plants in the seas of Japan and Okhotsk

Iodine and bromine content were measured in 24 species of red (Rhodophyta), brown (Phaeophyta) and green (Chlorophyta) seaweeds and 2 species of higher water plants (Embryophyta) from the Sea of Japan, as well as in 12 species of the abovecited taxa and 1 species of flowering plant from the Sea of Okhotsk. Iodine was determined by photometric extraction with brilliant green, and bromine by neutron activation of samples. Phaeophyta and Rhodophyta were richest in iodine and bromine content. Representatives of the order Ceramiales (Rhodophyta) had high iodine and bromine contents. Thus, iodine concentrations in Ptilota filicina, Campylaephora hypnaeoides and Myriogramme yezoensis, a new iodine concentrator discovered by us, amount to 0.42, 0.094 and 0.75%, respectively. Bromine content in representatives of the family Rhodomelaceae was 3.36 and 3.74% in Japan Sea and Okhotsk Sea Rhodomela larix, respectively. Polysiphonia japonica (Rhodomelaceae) is a newly discovered concentrator of bromine (3.20%). Many species of the order Laminariales (Phaeophyta) were characterized by high iodine contents: Laminaria japonica, L. cichoriodes, L. inclinatorhiza, Cymathaere japonica and Alaria marginata. The Br:I ratio for all the species except those that concentrated iodine, was more than 1. Seaweeds that grow at greater depths showed increased iodine and bromine contents. A tendency toward increased iodine content was observed in species growing further to the North. Iodine and bromine were accumulated selectively by various organs of Sargassum pallidum.     

Organoiodine formation during humification in peatlands

Although two billion people in the world are suffering from iodine deficiency there is little information on the chemical fate of iodine in the terrestrial environment. Here we show that peatlands play a major role in terrestrial iodine cycling. Chemical data from two peat profiles from Patagonia, Chile imply that transformation of iodine from its inorganic form to organoiodine compounds during early humification in peatlands is a key process in storage of iodine in the terrestrial environment. Once bound in peat, iodine remains stable for thousands of years. In the earths peatlands, net accumulation of iodine since the last glacial period is estimated to be 12–36 teragrams (1 Tg=10¹² g). These data suggest that peatlands are a major reservoir of iodine in terrestrial ecosystems. Our novel model of iodine distribution in the terrestrial environment demonstrates the key role of peatlands in burial and reemission of organically bound iodine.     

Soils and geomedicine

Geomedicine is the science dealing with the influence of natural factors on the geographical distribution of problems in human and veterinary medicine. Discussions on potential harmful impacts on human and animal health related to soil chemistry are frequently focused on soil pollution. However, problems related to natural excess or deficiency of chemical substances may be even more important in a global perspective. Particularly problems related to trace element deficiencies in soils have been frequently reported in agricultural crops as well as in livestock. Deficiencies in plants are often observed for boron, copper, manganese, molybdenum, and zinc. In animals deficiency problems related to cobalt, copper, iodine, manganese, and selenium are well known. Toxicity problems in animals exposed to excess intake have also been reported, e.g., for copper, fluorine, and selenium. Humans are similar to mammals in their relations to trace elements and thus likely to develop corresponding problems as observed in domestic animals if their supply of food is local and dependent on soils providing trace element imbalances in food crops. In large parts of Africa, Asia, and Latin America, people depend on locally grown food, and geomedical problems are common in these parts of the world. Well-known examples are Keshan disease in China associated with selenium deficiency, large-scale arsenic poisoning in Bangladesh and adjacent parts of India, and iodine deficiency disorders in many countries. Not all essential elements are derived only from the soil minerals. Some trace elements such as boron, iodine, and selenium are supplied in significant amounts to soils by atmospheric transport from the marine environment, and deficiency problems associated with these elements are therefore generally less common in coastal areas than farther inland. For example, iodine deficiency disorders in humans are most common in areas situated far from the ocean. There is still a great need for further research on geomedical problems.     

中国居民碘营养健康风险评估

我国碘元素的天然分布极不均匀,因此对地域差异缺乏考虑的全民食盐加碘政策(USI)并非碘缺乏病的最适宜的防控策略,甚至还增加了"碘过量"导致的潜在健康风险。近年来,中国卫生部多次调整食盐加碘政策,但亟需从健康风险评估的角度对该政策进行科学的论证和解读。通过解析全国碘缺乏病监测数据中8～10岁儿童尿碘浓度的数据,采用有阈值的剂量效应曲线,评价了中国居民碘营养健康状况,并计算出全国31个省级地区8～10岁儿童因碘过量导致的"亚临床甲状腺功能减低(亚甲减)"的发病率,最后利用5%基准剂量(benchmark dose,BMD),并结合我国居民膳食营养结构的调查结果,提出了考虑地域差异的分层次的食盐加碘量推荐值上限。研究表明,我国居民尿碘浓度分布有明显的区域性特征,尿碘浓度几何平均值和几何标准差分别为168.17和2.24μg·L-1,由于碘摄入过量导致的亚甲减发生率为4.00%。低水碘地区(水碘浓度低于150μg·L-1)的食盐加碘量推荐值上限为29.62mg·kg-1;中、高水碘地区(水碘浓度高于150μg·L-1)的居民通过非碘盐途径摄入的碘量已高于日可耐受最大摄入量,不宜再食用加碘食盐。这些结果基本支持了我国调整后的现行食盐加碘政策,即各地区根据当地人群实际碘营养水平,选定适合本地的食用盐加碘量。     

Medical geology in tropical countries with special reference to Sri Lanka

Sri Lanka provides an ideal opportunity for the study of the effect of geology on human health. The vast majority of the people of Sri Lanka still live in rural areas within areas termed geochemical provinces. Very broadly, one could say that a geochemical province has characteristic chemical composition in soil, water stream sediments and rocks, enabling their delineation from others. The chemical composition is presumed to be have an impact on the health of the inhabitants of the particular geochemical province, particularly because of the fact that their food and water are obtained mostly from the terrain itself. This leads to the concept of “diseases of geochemical origin”. Among these are dental fluorosis, iodine deficiency disorders (IDDs) and selenium-based diseases. The Dry Zone of Sri Lanka has several areas rich in groundwater fluoride, the ingestion of which leads to dental fluorosis. Iodine deficiency diseases are more common in the Wet Zone, though their aetiologies are more complicated. Interestingly, it has also been observed that significant proportions of the female population of Sri Lanka are selenium-deficient, which could well be related to the geological environment. Chronic renal failure (CRF) has been observed in some areas of the Dry Zone of Sri Lanka, where there is a relationship of CRF with the mineral content of drinking water. This subject matter falls under the auspices of Medical Geology, a scientific discipline still in its infancy, and much more concerted studies are needed to attract the attention of medical research.     

Geochemistry of trace elements in paddy (rice) soils of Sri Lanka – implications for iodine deficiency disorders (IDD)

Iodine Deficiency Disorders (IDD) are a common health problem prevalent in the wet zone of Sri Lanka with a prevalence of >25 of the population. In comparison, in the dry zone of Sri Lanka IDD occurs in <10 of the population. Seventy soil samples from 14 villages selected on the basis of the incidence of goitre, were collected and analysed for 13 trace elements using ICP-MS. In order to identify any prevailing differences in antecedent chemical environments, soil samples from each pre-selected village were classified into three groups in terms of their geographical location. Among the elements investigated, the total soil concentrations of Rb, Sr, Ba, Mn and Co are lower in the wet zone of Kalutara. In contrast, total soil Rb, Sr, Ba and Mn contents are higher in the dry zone of Anuradhapura. Further soil total Mo and Nb levels are relatively similar in all pre-selected study locations. The high endemic goitre regions (IDD >25 of the population) show low levels of Rb, Sr, Ba, and Mn and higher levels of V, Cr, Co, Ni, Cu, Zn and Pb as compared with moderate and non-goitre areas. Factor analysis was used to exploit the correlation structure present in data and yielded three groups in all cases. This indicated that most transition group elements and iodine are associated with the Mn phase in the low IDD areas whereas iodine shows a high affinity for the organic phase in high IDD regions. The variable distribution of trace elements, therefore, must be due to differences in mobility and capacity for incorporation into the structure of secondary minerals or organic phases.