Rice: Reducing arsenic content by controlling water irrigation

<正>Arsenic has long been recognized as a poison.Arsenic in water supplies that are used for both drinking and crop irrigation can expose many people chronically to elevated levels of arsenic.The main health concern for chronic exposure to arsenic is the development of cancer.Although the World Health Organization(WHO)recommends that total arsenic in drinking water should be under 10μg/L(or 10 ppb),(WHO,2011),some regions     

Effects of water management on arsenic and cadmiumspeciation and accumulation in an upland rice cultivar

Pot and field experiments were conducted to investigate the effects of water regimes on the speciation and accumulation of arsenic (As) and cadmium (Cd) in Brazilian upland rice growing in soils polluted with both As and Cd. In the pot experiment constant and intermittent flooding treatments gave 3-16 times higher As concentrations in soil solution than did aerobic conditions but Cd showed the opposite trend. Compared to arsenate, there were more marked changes in the arsenite concentrations in the soil solution as water management shifted, and therefore arsenite concentrations dominated the As speciation and bioavailability in the soil. In the field experiment As concentrations in the rice grains increased from0.14 to 0.21 mg/kg while Cd concentrations decreased from 0.21 to 0.02 mg/kg with increasing irrigation ranging from aerobic to constantly flooding conditions. Among the various water regimes the conventional irrigation treatment produced the highest rice grain yield of 6.29 tons/ha. The As speciation analysis reveals that the accumulation of dimethylarsinic acid (from 11.3% to 61.7%) made a greater contribution to the increase in total As in brown rice in the intermittent and constant flooding treatments compared to the intermittent-aerobic treatment. Thus, water management exerted opposite effects on Cd and As speciation and bioavailability in the soil and consequently on their accumulation in the upland rice. Special care is required when irrigation regime methods are employed to mitigate the accumulation of metal(loid)s in the grain of rice grown in soils polluted with both As and Cd.     

An investigation into the energy use in relation to yield of rice (Oryza sativa) in Assam, India

Energy use scenario and resulting rice yield of 576 farms belonging to six agroclimatic zones of Assam, India were investigated. Input energy from eight distinct sources, viz., human, animal, diesel, commercial chemical fertilizer, farm yard manure (FYM), seed, pesticide chemical and machinery were determined on the basis of collected data and using standard procedure. Based on the power sources used and application of commercial chemical fertilizer, four categories of farms were delineated: (i) animal power without commercial fertilizer (APNF), (ii) animal power with commercial fertilizer (APF), (iii) mechanical power without commercial fertilizer (MPNF) and (iv) mechanical power with commercial fertilizer (MPF). The best-fit curve of energy versus yield indicated that use of commercial chemical fertilizer and mechanical power resulted in higher rice yield at higher level of input energy. Moreover, as the use of energy increased the yield increased up to maxima and then declined at higher levels of energy. This was observed in all four categories of farms with variation in yield–energy values. The average values of energy input (MJ ha⁻¹) and corresponding yield (kg ha⁻¹) for the APNF, APF, MPNF and MPF type of farms were (5220, 1980); (9050, 3170); (5100, 2360) and (8320, 3800), respectively. Renewable energy dominated the rice cultivation in Assam contributing more than 50% of the total input energy with the exception of MPF category of farm where share of renewable and non-renewable were found to be almost equal. Among the farm operations, tillage was the highest energy consuming operation followed by threshing, harvesting and transplanting for all four categories of farms. However, it was observed that rice yield was not positively correlated with tillage energy.     

Thiolated arsenicals in arsenic metabolism: Occurrence, formation, and biological implications

Arsenic (As) is a notoriously toxic pollutant of health concern worldwide with potential risk of cancer induction, but meanwhile it is used as medicines for the treatment of different conditions including hematological cancers. Arsenic can undergo extensive metabolism in biological systems, and both toxicological and therapeutic effects of arsenic compounds are closely related to their metabolism. Recent studies have identified methylated thioarsenicals as a new class of arsenic metabolites in biological systems after exposure of inorganic and organic arsenicals, including arsenite, dimethylarsinic acid (DMAV), dimethylarsinous glutathione (DMAIIIGS), and arsenosugars. The increasing detection of thiolated arsenicals, including monomethylmonothioarsonic acid (MMMTAV), dimethylmonothioarsinic acid (DMMTAV) and its glutathione conjugate (DMMTAVGS), and dimethyldithioarsinic acid (DMDTAV) suggests that thioarsenicals may be important metabolites and play important roles in arsenic toxicity and therapeutic effects. Here we summarized the reported occurrence of thioarsenicals in biological systems, the possible formation pathways of thioarsenicals, and their toxicity, and discussed the biological implications of thioarsenicals on arsenic metabolism, toxicity, and therapeutic effects.     

Rapid evaluation of arsenic contamination in paddy soils using field portable X-ray fluorescence spectrometry

Arsenic (As) in paddy fields is deteriorating food security and human health through rice ingestion. Rice is the dominant food source of arsenic exposure to half of the world''s population. Therefore, an in situ effective method for As risk evaluation in paddy soil is strongly needed to avoid As exposure through rice ingestion. Herein, we developed a rapid analytical methodology for determination of As in plant tissues using field portable X-ray fluorescence spectrometry (FP-XRF). This method was applied to rice roots in order to evaluate the As contamination in paddy soils. The results showed that rice roots with iron plaques were superior to rhizosphere soils for generating FP-XRF signals, especially for field sites with As concentrations lower than the soil detection limit of FP-XRF (30.0 mg/kg). Moreover, the strong linear relationships of As concentrations between the rice roots and corresponding leaves and grains proved that the rice root, rather than the soil, is a better predictor of As concentrations in rice grains. The research provides an efficient As monitoring method for As contaminated paddy fields by using wetland plant roots with iron plaques and XRF-based analytical techniques.     

青铜峡灌区水稻田化肥氮去向研究

青铜峡灌区是我国古老的特大型灌区和粮食主产区之一,灌区农田氮肥的过量施用已经导致化肥氮向水体流失.用15N示踪微区试验方法研究了青铜峡引黄灌区习惯灌溉量条件下水稻田化肥氮素去向.结果表明,施氮量为当地习惯施氮300kg.hm-2时,水稻吸收的化肥氮在籽粒中最多,氮肥的当季利用率为45.93%,吸收的土壤氮约占52.63%;作物中的回收率为27.90%,在0～90cm土壤中的残留率为23.31%,作物-土壤体系中的回收率为51.21%,氮肥的损失率为48.79%;氮肥除了被当季作物吸收和部分以矿质氮残留在土壤中外,灌区19×104hm2的水稻田化肥氮年流失量为2.78×104t,生产1000kg水稻(净籽粒),排放纯氮20.17kg;在0～90cm土壤层中均有化肥氮残留,残留化肥氮主要富集在表层0～30cm,在60～90cm检测到化肥氮,说明青铜峡引黄灌区在习惯灌溉量条件下,水稻田当季的化肥氮淋溶到90cm以下,成为浅层地下水的潜在污染源.     

Role of complex organic arsenicals in food in aggregate exposure to arsenic

For much of the world''s population, food is the major source of exposure to arsenic. Exposure to this non-essential metalloid at relatively low levels may be linked to a wide range of adverse health effects. Thus, evaluating foods as sources of exposure to arsenic is important in assessing risk and developing strategies that protect public health. Although most emphasis has been placed on inorganic arsenic as human carcinogen and toxicant, an array of arsenic-containing species are found in plants and animals used as foods. Here, we 2evaluate the contribution of complex organic arsenicals (arsenosugars, arsenolipids, and trimethylarsonium compounds) that are found in foods and consider their origins, metabolism, and potential toxicity. Commonalities in the metabolism of arsenosugars and arsenolipids lead to the production of di-methylated arsenicals which are known to exert many toxic effects. Evaluating foods as sources of exposure to these complex organic arsenicals and understanding the formation of reactive metabolites may be critical in assessing their contribution to aggregate exposure to arsenic.     

SERS detection of arsenic in water: A review

Arsenic (As) is one of the most toxic contaminants found in the environment. Development of novel detection methods for As species in water with the potential for field use has been an urgent need in recent years. In past decades, surface-enhanced Raman scattering (SERS) has gained a reputation as one of the most sensitive spectroscopic methods for chemical and biomolecular sensing. The SERS technique has emerged as an extremely promising solution for in-situ detection of arsenic species in the field, particularly when coupled with portable/handheld Raman spectrometers. In this article, the recent advances in SERS analysis of arsenic species in water media are reviewed, and the potential of this technique for fast screening and field testing of arsenic-contaminated environmental water samples is discussed. The problems that remain in the field are also discussed and an outlook for the future is featured at the end of the article.     

不同pH值灌溉水对土壤Cd生物有效性及稻米Cd含量的影响

通过盆栽种植实验研究了pH值为3.5~6.5的灌溉水对稻田土壤pH值、土壤Cd生物有效性以及2种水稻品种各部位Cd含量的影响.结果表明:1不同pH值灌溉水对土壤pH值影响显著.灌溉水pH为3.5~6.5的处理下,湘晚籼土壤pH值下降了0.6~0.3个单位,威优46号土壤pH值下降了0.7~0.4个单位.2随着灌溉水pH值的升高,土壤交换态和TCLP提取态Cd含量(生物有效性)均有降低的趋势,但TCLP提取态Cd含量不显著.3随着灌溉水pH值从3.5上升到6.5,湘晚籼12号水稻植株各部位Cd含量均逐渐下降,而威优46号水稻植株各部位的Cd含量逐渐上升.与pH=3.5处理相比,浇灌pH值为4.5~6.5的灌溉水,湘晚籼12号根系、茎叶、谷壳和糙米中Cd含量分别下降32.3%~48.0%、16.5%~48.0%、40.0%~56.2%和45.6%~73.9%;相反,威优46号根系、茎叶、谷壳和糙米中Cd含量分别上升30.5%~446.3%、5.3%~201.1%、70.3%~316.7%和71.0%~177.2%.显然,升高灌溉水的pH值有利于降低湘晚籼12号(常规稻)糙米中的Cd含量,但不利于降低威优46号(杂交稻)糙米中的Cd含量.     

陕西泾惠渠灌区土壤-小麦体系中硒的空间分布特征

查明一个地区土壤和主食中硒含量及其空间分布特征,是探究该地区人体硒营养状况的重要基础.基于陕西泾惠渠灌区104个表层土壤样品和对应的小麦籽粒硒含量的测定,运用地统计的方法,对该地区硒含量的空间分布特征进行了分析,评价了土壤硒的有效性及其对人体硒摄入量的影响.结果表明:泾惠渠灌区土壤总硒含量变化为0.020~0.603 mg·kg-1,平均为(0.154±0.085)mg·kg-1,76.9%的地区处于临界缺硒状态,其中以阎良区土壤硒含量显著高于高陵区、临潼区、泾阳县和三原县;小麦籽粒硒含量为0.003~0.485 mg·kg-1,平均为(0.076±0.070)mg·kg-1,各地区间无显著差异,69.2%达到适度硒水平.造成土壤硒含量处于临界缺硒水平而小麦硒含量达到适度硒水平的原因是该地区土壤有效硒占土壤总硒含量的11.6%,硒的有效性相对较高.该灌区土壤和小麦的硒含量分布存在显著空间分布不均一性,在粮食硒强化中应综合考虑土壤供硒及作物硒吸收两个方面.     

中国粮食自给率研究——粮食、谷物和口粮自给率分析

由于统计口径与计算方法的不同,粮食自给率的计算结果往往差异较大,得出的中国粮食安全的结论也大相径庭,从而引起国内各界的广泛争议。为了准确分析当前中国的粮食安全情势,避免误判对相关决策造成误导,有必要对粮食的统计口径和自给率计算方法进行分析研究。本文选用三种粮食自给率计算方法—定额统计法、流向统计法和消费统计法,测算中国2000-2016年的粮食、谷物和口粮自给率,并对结果进行对比分析。结果显示：（1）定额统计法计算结果容易造成失真,流向统计法与消费统计法计算结果较为准确;（2）谷物和口粮自给率更能反映中国实际的粮食供需情况;（3）中国谷物自给率在98%以上,口粮自给率高于100%。然而,随着工业化和城市化进程的加快,城市发展对土地的需求越来越大,这会造成耕地被侵占、粮食需求激增等严重问题,口粮生产仍然不能放松,建议未来调整农业结构,稳定小麦、稻米生产。     

Editorial: Effect of root anatomy and apoplastic barrier development on cadmium uptake in rice

<正>Cadmium (Cd) is a toxic metal with high mobility from soil and known translocation into plants (Song et al., 2015).Because the main source of human exposure to Cd is from food consumption, there has been increased research examining Cd uptake in agricultural plants (Li et al., 2014; Rizwan et al., 2016; Song et al., 2015). Rice (Oryza sativa L.) has been identified as a major crop that contains relatively high     

分光光度法测定中药板蓝根中砷含量的方法探讨

对中药材板蓝根中砷含量测定的方法进行探讨。样品经HNO3-H2SO4消解，分光光度法测定回收率，并用该方法对来自不同产地板蓝根中砷的含量进行了测定。结果表明：砷的含量在0-25μg范围与吸光度呈良好的线性关系，r=0.9997,回收率平均值为95.0％。各地区板蓝根中砷的含量参考相关国家标准均未超标。     

Petroleum hydrocarbon concentrations in eight mollusc species along Tamilnadu coast, Bay of Bengal, India

Eight mollusc species and sediment samples collected from three different stations along Tamilnadu coast, Bay of Bengal, India were analysed for the levels of petroleum hydrocarbons to elucidate the status of the petroleum residues in mollusc meant for human consumption. The concentrations of petroleum hydrocarbons in sediments along Tamilnadu coast varied from 5.04–25.5 g/g dw (dry weight). High concentration of petroleum hydrocarbons in the sediment of Uppanar estuary (25.5 1.45 g/g dw) was perhaps land and marine based anthropogenic sources of this region. The petroleum hydrocarbon residues in eight mollusc species collected from Uppanar, Vellar and Coleroon estuaries varied between 2.44–6.04 g/g ww (wet weight). Although the concentration of petroleum hydrocarbons in sediment of the Uppanar region was markedly higher than the background, the petroleum hydrocarbon residues in mollusc collected from Uppanar estuary did not suggest bioaccumulation. The results signified that industrial growth has affected the aquatic environments and regular monitoring will help to adopt stringent pollution control measures for better management of the aquatic region.     

华北平原节水技术、灌溉用水量反弹效应与地区异质性——基于Malmquist和LMDI指数分析

很多地区节水技术的应用并未带来农业灌溉用水总量的下降。通过应用中国华北平原地级（直辖）市2000—2018年的面板数据,采用Malmquist指数和LMDI指数进行分解,测算出节水技术带来的农业灌溉用水反弹量和预期农业节水量。结果表明：中国华北平原节水技术引起的农业灌溉用水反弹效应均值为15.02%,这表明华北平原整体并未完全达到节水技术应用带来的预期农业节水量。节水技术应用放松了水资源约束,农户会扩大灌溉面积或高耗水高收益作物的种植,从而削弱节水技术的节水效果。黄河区的农业节水反弹效应程度最大,部分地区甚至会造成农业灌溉用水的增加。节水灌溉面积的增加是农业节水反弹效应的直接原因,农田灌溉水利建设投资的增加和水权市场建设的不完善则是根本原因。     

Attenuation of arsenic in a karst subterranean stream and correlation with geochemical factors: A case study at Lihu, South China

Arsenic （As） pollutants generated by human activities in karst areas flow into subterranean streams and contaminate groundwater easily because of the unique hydrogeological characteristics of karst areas. To elucidate the reaction mechanisms of arsenic in karst subterranean streams, physical-chemical analysis was conducted by an inductively coupled plasma mass spectrometer and an X-ray fluorescence spectrometer. The results show that inorganic species account for most of the total arsenic, whereas organic arsenic is not detected or occurs in infinitesimal amounts. As（III） accounts for 51.0% ± 9.9% of the total inorganic arsenic. Arsenic attenuation occurs and the attenuation rates of total As, As（III） and As（V） in the Lihu subterranean stream are 51%, 36% and 59%, respectively. To fully explain the main geochemical factors influencing arsenic attenuation, SPSS 13.0 and CANOCO 4.5 bundled with CanoDraw for Windows were used for simple statistical analysis and redundancy analysis （RDA）. Eight main factors, i.e., sediment iron （SFe）, sediment aluminum （SAI）, sediment calcium （SCa）, sediment organic matter （SOM）, sediment manganese （SMn）, water calcium （WCa^2＋）, water magnesium （WMg^2＋）, and water bicarbonate ion （WILCOX） were extracted from thirteen indicators. Their impacts on arsenic content rank as： SFe〉SCa〉WCa^2＋〉SAl〉wHCO3^-〉SMn〉SOM〉WMg^2＋. Of these factors, SFe, SAl, SCa, SOM, SMn, WMg^2＋ and WCa＆2＋ promote arsenic attenuation, whereas WHCO3^- inhibits it. Further investigation revealed that the redox potential （Eh） and pH are adverse to arsenic removal. The dramatic distinction between karst and non-karst terrain is that calcium and bicarbonate are the primary factors influencing arsenic migration in karst areas due to the high calcium concentration and alkalinity of karst water.     

富硅肥料和水分管理对稻米镉污染阻控效果研究

在已筛选出的施硅方式(基施和叶面喷施相结合)基础上,选择典型单一镉污染稻田土壤(pH=4.97,总Cd 4.1 mg·kg~(-1)),并结合2种稻田水分管理方式,进一步开展不同水肥管理方式对常规早稻(湘早籼45)和杂交晚稻(丰源优299)的3个生育期内各部位中Cd含量及成熟期生物量的影响研究.实验设计4个处理:不施硅肥+常规间歇淹水措施(CK)、不施硅肥+全生育期淹水措施(W)、2种硅肥配施+常规间歇淹水措施(SiLsi)、2种硅肥配施+全生育期淹水措施(SiLsi+W).结果表明,4个处理下,早晚稻试验结果基本一致,但各试验处理对晚稻的阻镉效果更加明显;与CK相比,各处理都能显著降低水稻籽粒中Cd的含量且不会明显影响水稻产量,其中以SiLsi+W对籽粒的降Cd效果最佳(晚稻精米中Cd的含量为0.12 mg·kg~(-1),达到了国家粮食安全生产标准:Cd0.2 mg·kg~(-1)),分别使晚稻谷壳、糙米和精米的降Cd幅度达到93.65%、86.70%和91.18%,W和Si Lsi处理的降Cd效果次之.因此,SiLsi+W可作为一种有效的稻米镉污染控制技术.     

新疆奎屯地区高砷地下水DOM三维荧光特征

新疆奎屯地区是中国大陆第一个地方性砷（As）中毒病区,为了解析该地区高As地下水中溶解性有机物（DOM）的组分和来源,探索其在As迁移转化过程中的作用,利用三维荧光光谱结合平行因子分析法对奎屯地区水样进行研究.结果表明：该地区地下水As含量范围在1.30~400.68μg/L,平均值为61.18μg/L,有68.99%的地下水为高As地下水.地下水中DOM含有3种组分：类腐殖质C1（260（325） nm/425nm）,占2.78%;类色氨酸C2（275nm/350nm）,占18.74%;微生物源的还原性醌类C3（260（375） nm/475nm）,占54.12%.研究区水体DOM的荧光指数在1.2~1.52之间,均值为1.36,水中DOM以陆源为主.该地区地下水整体呈现还原-弱碱性环境,地下水中As的释放过程主要有铁氧化物矿物还原和脱硫酸作用,水中的DOM参与了铁、硫酸盐的还原反应过程,类色氨酸C2主要在微生物呼吸过程中充当电子供体角色,还原性醌类C3担任了电子飞行过程中的电子穿梭体,增强了As从含水层沉积物中释放到地下水的迁移性能.