Stable isotope tracers identify sources and transformations of mercury in rice (Oryza sativa L.) growing in a mercury mining area

Methylmercury (MeHg) contaminated rice is a global issue, particularly in mercury-polluted areas, posing a potential threat to human health. The sources and transformations of mercury (Hg) species in rice are critical points that are not yet fully understood. In this study, field experimental pots together with a stable Hg isotope tracing technique were used to provide direct evidence of the sources and transformations of Hg species in rice plants. Enriched inorganic Hg (IHg) isotope (200Hg(NO3)2) was spiked into paddy soils, and the concentrations of inorganic Hg tracer (I200Hg), MeHg tracer (Me200Hg), and ambient Hg species (IHg and MeHg) were measured in the tissues of rice plants and their corresponding soil samples during the rice growing season. Here, we show that, in addition to the atmosphere, the soil is an important source of IHg to rice grains and was previously largely underestimated. We also show that MeHg is formed in paddy soil via microbial IHg methylation, absorbed through the rice root, translocated from the root to above-ground parts, and finally accumulated in rice grains. Although in vivo methylation of IHg in rice plants is unlikely to occur during the rice growing season, we observed in vivo demethylation of MeHg in the above-ground parts of rice plants, possibly via photolytic demethylation. Promoting in vivo demethylation of MeHg may be an effective approach to mitigate MeHg accumulation in rice grains.

Evaluation of Erythrocyte Iron Incorporation in Beijing Prepubertal Children Using a Single Stable Isotope Tracer Method

Objective To analyze the rate of erythrocyte iron incorporation and provided guidance for the iron nutrition for prepubertal children.Methods Fifty-seven prepubertal children of Beijing were involved in this study and each subject was orally administered 3 mg of 57 Fe twice daily to obtain a total of 30 mg 57 Fe after a 5-d period. The stable isotope ratios in RBCs were determined in 14 th day, 28 th day, 60 th day, and 90 th day. The erythrocyte incorporation rate in children was calculated using the stable isotope ratios, blood volume and body iron mass.Results The percentage of erythrocyte 57 Fe incorporation increased starting 14 th day, reached a peak at 60 d(boys: 19.67% ± 0.56%, girls: 21.33% ± 0.59%) and then decreased. The erythrocyte incorporation rates of 57 Fe obtained for girls in 60 th day was significantly higher than those obtained for boys(P < 0.0001).Conclusions The oral administration of 57 Fe to children can be used to obtain erythrocyte iron incorporation within 90 d. Prepubertal girls should begin to increase the intake of iron and further studies should pay more attention to the iron status in prepubertal children.

Application of Isotope Tracer Technique in Source Apportionment of Heavy Metal Pollution in Soil

The formation of heavy metal pollution in soil is closely related to human production and life. In order to effectively control heavy metal pollution and repair damaged soil,the pollution source should be known and judged first. Based on the preliminary analysis of major sources of soil heavy metal pollution in soil,combined with relevant literatures on heavy metal pollution source of soil or sediment at home and abroad in recent years,application progress of isotope tracer technique,especially lead isotope tracer technique,in the study of heavy metal pollution sources in soils and sediments were reviewed. The key points of future isotope tracer technology in the field of heavy metal pollution source apportionment were prospected.

The Effect of the Sinking of Isotope Grains in Water Injection Profile Logging

In the process of oil field exploitation, radioactive isotope tracer water injection profile logging is a main method to determine the water-intake capacity of the target intervals. For those general water injection wells, whose perforated intervals are beyond the tubing shoe, the sinking speed of isotope grains is related to the density and salinity of the injection water and the tubing dimension. We studied the motion of the isotope grains in the water injection wells by both theoretical calculation and field experiment. The result shows that if the water injection quantity is over 20 m＆3/d, and the density of the isotope grains, whose diameter is 100-600 μm, is 1.06 g/cm^3, then the logging technique for this kind of water injection wells will be appropriate. Whether water injection profile logging is successful in the well, whose perforated intervals are beyond the tubing shoe, depends on the sinking speed of the tracer grains.

Estimation of Iron Physiological Requirement in Chinese Children using Single Stable Isotope Tracer Technique

Objective This study is to obtain precise data on iron physiological requirements in Chinese children using single stable isotope tracertechnique.Methods Thirty boys(10.6±0.2 years)and 27 girls(10.4±0.2 years)were received oral 6 mg ^(57)Fe each day for 5 consecutive days.Venous blood samples were subsequently drawn to examine the change of total iron concentration and ^(57)Fe abundance at day 0,14,28,60,90,180,360,450,540,630,720.The iron physiological requirement was calculated by iron loss combined with iron circulation rate once ^(57)Fe abundance stabilized in human body.Results The iron physiological requirement was significantly lower in boys than those values in girls(16.88±7.12 vs.18.40±8.81μg/kg per day,P<0.05).Correspondingly,the values were calculated as 722.46±8.43μg/day for boys and 708.40±7.55μg/day for girls,respectively.Considering nearly 10%iron absorption rate,the estimated average iron physiological requirement was 6.0 mg/day in boys and 6.2 mg/day in girls.Conclusion This study indicate that iron physiological requirement could require more daily iron intake in girls as compare with the values in boys having the same body weight.These findings would be facilitate to the new revised dietary reference intakes.

RADIOACTIVE OR NATURAL TRACER TECHNIQUES FOR LEAK DETERMINING OF DAM ABUTMENT

Infiltration and localization of preferential infiltration zones at the dam abutment are measured using radioactive tracer tests of flow in boreholes, meanwhile interconnection between boreholes and the energing water points is analysed. The theory and practice of radioactive tracer synthetic detective method are described to give methods and calculation formulae used under the condition of stable flow in single well to measure permeability coefficient and hydrostatic heads. Major single hole techniques including measurement for seepage line, velocity, rate of seepage flow and relationship of recharge of groundwater in aquifers are introduced briefly.The possibilities offered by natural tracers are analysed, including electric-conduct,pH-value and temperature of water as well as stable isotopes (D, 18O) and tritium.Furthermore, the sensibilities of this theory and methods were confirmed by detecting seepage flow field of Xinanjiang Dam.

N2 fixation rate and diazotroph community structure in the western tropical North Pacific Ocean

In the present study, we report N2 fixation rate(15N isotope tracer assay) and the diazotroph community structure(using the molecular method) in the western tropical North Pacific Ocean(WTNP)(13°–20°N, 120°–160°E). Our independent evidence on the basis of both in situ N2 fixation activity and diazotroph community structure showed the dominance of unicellular N2 fixation over majority of the WTNP surface waters during the sampling periods.Moreover, a shift in the diazotrophic composition from unicellular cyanobacteria group B-dominated to Trichodesmium spp.-dominated toward the western boundary current(Kuroshio) was also observed in 2013. We hypothesize that nutrient availability may have played a major role in regulating the biogeography of N2 fixation.In surface waters, volumetric N2 fixation rate(calculated by nitrogen) ranged between 0.6 and 2.6 nmol/(L·d) and averaged(1.2±0.5) nmol/(L·d), with <10 μm size fraction contributed predominantly(88%±6%) to the total rate between 135°E and 160°E. Depth-integrated N2 fixation rate over the upper 200 m ranged between 150 μmol/(m^2·d)and 480 μmol/(m^2·d)average(225±105) μmol/(m^2·d). N2 fixation can account for 6.2%±3.7% of the depthintegrated primary production, suggesting that N2 fixation is a significant N source sustaining new and export production in the WTNP. The role of N2 fixation in biogeochemical cycling in this climate change-vulnerable region calls for further investigations.

A Review on the Structure and Biodegradation of Cellulose-Lignin Complexes

Cellulose is the most abundant organic macromolecule in nature and is renewable,degradable,and biocompatible.The structure of native cellulose has not yet been completely elucidated.Part of cellulose is tightly combined with lignin macromolecules through chemical bonds to form cellulose-lignin complexes(CLC).The existence of the CLC structure inhibits the complete separation of cellulose from lignocellulosic material,which not only increases the consumption of chemicals in the cooking process and causes environmental pollution,but also makes the cellulose subject to certain degradation during the deep delignification process.Therefore,elucidation of the relationship between the cellulose-lignin connection structure and performance is of great significance for efficient separation of cellulose.This article reviews the current research status of CLC and discusses the research progress regarding its biodegradation characteristics.

Stability on the ^(109)Cd,^(65)Zn Complex with Humus Acids

The radioactive isotope tracer and ion exchange balanced method was used to study the stability of 109Cd, 65 Zn complexes with humus acids. In the 109Cd and 65 Zn single existing system with humic acids, the stability constants of the humic-109Cd(65Zn) complex compound was higher than the fulvic-109 Cd(65Zn) complex compound. The stability constant of the humic (fulvic) -65Zn was higher than that of the humic (ful-vic)-109Cd. In the 109Cd and 65 Zn coexisting system, the stability constant and the co-ordination number of the humic (fulvic)-65Zn complex obviously increased, but the stability constant and the co-ordination number of the humic (fulvic)-109Cd complex obviously decreased as compared with its respectively single existing system . The result showed that the humus matter with higher molecular weight could more effectively reduce plant availability of heavy metals than that with lower molecular weight in polluted soil by heavy metals. The humus matter could more effectively reduce plant availability of Zn than that of Cd. Application of humus-acid increased the harm of Cd and decreased the harm of Zn to plants in Cd-Zn coexisting system.

Characteristic analysis on oxygen isotopic tracer in the East China Sea and waters to east of the Ryukyu－gunto

Samlpes of O isotopic tracer ware collected at Sections P_3, P_(25), P_(CM-1/2-E) and P_(CM-1/2-W) in both the EastChina Sea and the area to the east Of the Ryukyu-gunto during October-November, 1991.Analytical results of the δ￣(18) O are as follows: (1) In the Kuroshio area, the δ￣(18) o isolines are almost parallel to the200 m isobath. The value of δ￣(18)O is nagative and reaches minimum on the main axis of the Kuroshio,and increases on both sides. (2) In the Taiwan Warm Current (TWC) area there is a high δ￣(18) O tongue extending to the northeast. (3)In the area near the coast, the distribution of δ￣(18)O isoline shows that the Changjiang River runoff diffuses seaward andthe land-ocean isotopic effect from the nearshore to the offshore. (4) The values of δ￣(18) O are from-1. 0 x 10￣(-3) to -0.5 x 10￣(-3) in the shelf. (5) There is a low core of δ￣(18) O value (< -1 .6 X 10￣(-3)) at the 600 m layer in the Kuroshioarea, which is quite in accord with the ekistence of a low salinity core (S 34. 30) between the 600 and 800 m layersin the same area. Finally, the correlations of the δ￣(18)O with the salinity and temperature, the upwelling and so on arediscussed.(This study was supported by the National Natural Science Foundation of China under contract No. 4907257.)Yuan Yaochu et al. The Northwest Pacific circulation and its impacts on the current near the Chinese coast, 1991-1993.

Insights on the mechanism for synthesis of methylenedianiline from aniline and formaldehyde through HPLC-MS and isotope tracer studies

The mechanism for synthesis of 4,4-methylenedianiline （MDA） via condensation reaction of aniline with formaldehyde has been studied extensively in this paper. The intermediate and by-products were isolated and identified. The combination of isotope labeling and HPLC-MS characterizations disclosed that the reaction proceeded through an SN2 reaction mechanism. Moreover, the effect of aniline/formaldehyde molar ratio on the formation of MDA was investigated. This work would be of significance to understand the reaction mechanism deeply and provide valuable information for further improving the yield of desired product.

Trace metal dynamics in an industrialized Brazilian river:A combined application of Zn isotopes,geochemical partitioning,and multivariate statistics

The Paraiba do Sul(PSR)and Guandu Rivers(GR)water diversion system(120 km long)is located in the main industrial pole of Brazil and supplies drinking water for 9.4 million people in the metropolitan region of Rio de Janeiro.This study aims to discern the trace metals dynamics in this complex aquatic system.We used a combined approach of geochemical tools such as geochemical partitioning,Zn isotopes signatures,and multivariate statistics.Zinc and Pb concentrations in Suspended Particulate Matter(SPM)and sediments were considerably higher in some sites.The sediment partition of As,Cr,and Cu revealed the residual fraction(F4)as the main fraction for these elements,indicating low mobility.Zinc and Pb were mostly associated with the exchangeable/carbonate(F1)and the reducible(F2)fractions,respectively,implying a higher susceptibility of these elements to being released from sediments.Zinc isotopic compositions of sediments and SPM fell in a binary mixing source process between lithogenic(δ^(66/64)Zn_(JMC)≈+0.30‰)and anthropogenic(δ^(66/64)Zn_(JMC)≈+0.15‰)end members.The lighterδ^(66/64)Zn_(JMC)values accompanied by high Zn concentrations in exchangeable/carbonate fraction(ZnF1)enable the tracking of Zn anthropogenic sources in the studied rivers.Overall,the results indicated that Hg,Pb,and Zn had a dominant anthropogenic origin linked to the industrial activities,while As,Cr,and Cu were mainly associated with lithogenic sources.This work demonstrates how integrating geochemical tools is valuable for assessing geochemical processes and mixing source effects in anthropized river watersheds.

Removal efficacy and mechanism of nitrogen and phosphorus by biological aluminum-based P-inactivation agent (BA-PIA)

In this study,aluminum-based P-inactivation agent(Al-PIA)was used as a high-efficiency microbial carrier,and the biological Al-PIA(BA-PIA)was prepared by artificial aeration.Laboratory static experiments were conducted to study the effect of BA-PIA on reducing nitrogen and phosphorus contents in water.Physicochemical characterization and isotope tracing method were applied to analyze the removal mechanism of nitrogen and phosphorus.High-throughput techniques were used to analyze the characteristic bacterial genus in the BA-PIA system.The nitrogen and phosphorus removal experiment was conducted for 30 days,and the removal rates of NH_(4)^(+)-N,TN and TP by BA-PIA were 81.87%,66.08%and 87.97%,respectively.The nitrogen removal pathways of BA-PIA were as follows:the nitrification reaction accounted for 59.0%(of which denitrification reaction accounted for 56.4%),microbial assimilation accounted for 18.1%,and the unreacted part accounted for 22.9%.The characteristic bacteria in the BA-PIA system were Streptomyces,Nocardioides,Saccharopolyspora,Nitrosomonas,and Marinobacter.The loading of microorganisms only changed the surface physical properties of Al-PIA(such as specific surface area,pore volume and pore size),without changing its surface chemical properties.The removal mechanism of nitrogen by BA-PIA is the conversion of NH_(4)^(+)-N into NO_(2)^(−)-N and NO_(3)^(−)-N by nitrifying bacteria,which are then reduced to nitrogen-containing gas by aerobic denitrifying bacteria.The phosphorus removal mechanism is that metal compounds(such as Al)on the surface of BA-PIA fix phosphorus through chemisorption processes,such as ligand exchange.Therefore,BA-PIA overcomes the deficiency of Al-PIA with only phosphorus removal ability,and has better application prospects.

Effects of mountain pine beetle-killed forests on source water contributions to streamflow in headwater streams of the Colorado Rocky Mountains

Natural or human-influenced disturbances are important to the health and diversity of forests, which in turn, are important to the water quantity and quality exported from a catchment. However, human-induced disturbances （prescribed fire and harvesting） have been decreasing, and natural disturbances （fires and insects） have been increasing in frequency and severity. One such natural disturbance is the mountain pine beetle （MPB）, （Denclroctonus ponderosae） an endemic species. A recent epidemic resulted in the mortality of millions of hectares of lodgepole pine （Pinus contorta） forests in Colorado, USA. Beetle-induced tree mortality brings about changes to the hydrologic cycle, including decreased transpiration and interception with the loss of canopy cover. This study examined the effect of the mountain pine beetle kill on source water contributions to streamflow in snowmelt- dominated headwater catchments using stable isotopes （2H and ~80） as tracers. Study catchments with varying level of beetle-killed forest area （6% to 97%） were sampled for groundwater, surface water, and precipitation. Streams were sampled to assess whether beetle-killed forests have altered source water contributions to streamflow. Ground- water contributions increased with increasing beetle-killed forest area （p = 0.008）. Both rain and snow contributions were negatively correlated with beetle-killed forest area （p = 0.035 and p = 0.011, respectively）. As the beetle-killed forest area increases, so does fractional groundwater contribution to streamflow.

Inherited disturbances of phenylalanine metabolic kinetics in essential hypert ension

Objective To clarify whether the disturbances in metabolic kinetics of the essential aminoacid, phenylalanine (phe), are implicated in the genetic pathogenesis of essential hypertension (EH).Methods 1. L-(2, 3D3)-leucine, L-(2, 3D3)-isoleucine, L-15N-lysine, L-(2, 3D3)-valine and L-(2, 3D3)-phe were used for simultaneously studying comparative metabolic kinetics using stable isotope tracer methods with a GC-MS system. Study groups were the offspring with both parents suffering EH (n=10, FH+), 2 or more than 2 parents and grand-parents with EH and stroke (n=12, FS+) and those without genetic predisposition of EH and stroke (n=12, F) groups. 2. By comparing the radioactive counts of ［3H］-phe, and their weight transformation in blood after 1.5?Ci/kg i.v. administration at defined intervals and in tissues obtained after being sacrified among spontaneously hypertensive rats (SHR), 2 kidney-1 clip hypertensive rats (2K1C) and their normotensive controls (WKY). 3. The time transport and concentration transport of ［3H］-L-phe in cpm between the cultured vascular smooth muscle cell of 5th generation in SHR and WKY were compared.Results A single and unique disturbance of metabolic kinetics in phe were found in FH+, FS+ and SHR. The plasma pool or apparent volume of distribution was enlarged, and the turnover rate constants between plasma and cell tended to show a decrease. The pharmacokinetics of phe in 2K1C was not changed. Only phe content in heart and aorta, the vital organs for predicting BP, were higher in SHR than in WKY tissues studied. Both the time and concentration transport were higher in SHR, e.g., an increment in the net-uptake of L-phe by vascular tissue.Conclusion A unique aberrant of metabolic kinetics of phe might be implicated in the inherited pathogenesis of EH and stroke both from clinical and animal studies.

Characteristics of Cd isotopic compositions and their genetic significance in the lead-zinc deposits of SW China

Up to now, the evaporation and condensation, as well as the biological absorption and inorganic absorptions, have been proved to be major factors in Cd isotope fractionation. And Cd isotopes have been widely applied in studies on the universal evolution and marine environment and so on. However, only a few researches have been conducted in applying Cd isotopes to trace the source of metallogenic material and the evolution of the ore-forming fluid in a complex mineralization environment, especially in a hydrothermal ore-formation system. We measured the Cd isotopic compositions of sphalerite, galena, and ores from five lead-zinc deposits in SW China, and found that the ~14/11~Cd values varied from -1.53%o to 0.34%0, with a total range of 1.87%o, which is greater than most of measured geological samples. Meanwhile, through contrasting the Cd content with Cd isotopic compositions of different deposits, it may be concluded that different genetic lead-zinc deposits have different Cd content and isotopic compositions, which could be a tool for the studies on the origin of ore deposits. Also, the biominera]iza- tion and crystal fractionation may also result in Cd isotope fractionation. In a word, although the research of Cd isotopes is presently at the preliminary stage （especially in hydrothermal ore-formation system）, this study demonstrated that Cd isotopes can give a clue in tracing the evolution of ore-forming fluid and metallogenic environment.

Insight into the Dual Cycle Mechanism of Methanol-to-OIefins Reaction over SAPO-34 Molecular Sieve by Isotopic Tracer Studies

Methanol-to-olefins(MTO)reaction is one of the important non-petroleum routes to produce light olefinsover acidic molecular sieves.In this study,the complete reaction course of MTO on SAPO-34 molecular sieve with retained organics evolution from induction period to deactivation period was investigated systematically at different weight hourly space velocities(WHSV)of methanol.By the aid of 12C/3C-methanol isotopic switch experiment,the dual cycle mechanism involving aromatics-based cycle and alkenes-based cycle was evaluated during the whole reac-tion process.The detailed reaction route varied with the evolution of the retained organics in the catalyst at different reaction stages.The aromatics-based cycle and alkenes-based cycle alternately dominate the reaction process.In the efficient reaction period,aromatics-based cvcle is the main reaction mechanism,while in the induction and deactiva-tion periods.the contribution of alkenes-based cvcle mechanism will become more important.

Nuclear Technique and Agriculture in China

Nuclear technique is a powerful scientific tool in agricultural research, an area with fruitful achievements in China. Application of nuclear technique in agriculture (Nuclear Agricultural Sciences) based on the development of related science and technology is a high-tech area, and also a significant aspect of non-electrical power application of nuclear technique. As an important component of agricultural science and technology, Nuclear technique application in agricultural field has achieved a lot and made remarkable contributions to the economic, social and ecological development of China. The current paper reviews the achievements, and presents the situation of the application of nuclear technique in the Chinese a-griculture briefly. The author strongly suggests that Chinese government should pay more attention to the study on the application of nuclear technique in agriculture, in order to promote its development and contribute more to the Chinese society and agriculture.