Site-level evaluation of satellite-based global terrestrial gross primary production and net primary production monitoring

Operational monitoring of global terrestrial gross primary production (GPP) and net primary production (NPP) is now underway using imagery from the satellite‐borne Moderate Resolution Imaging Spectroradiometer (MODIS) sensor. Evaluation of MODIS GPP and NPP products will require site‐level studies across a range of biomes, with close attention to numerous scaling issues that must be addressed to link ground measurements to the satellite‐based carbon flux estimates. Here, we report results of a study aimed at evaluating MODIS NPP/GPP products at six sites varying widely in climate, land use, and vegetation physiognomy. Comparisons were made for twenty‐five 1 km² cells at each site, with 8‐day averages for GPP and an annual value for NPP. The validation data layers were made with a combination of ground measurements, relatively high resolution satellite data (Landsat Enhanced Thematic Mapper Plus at ～30 m resolution), and process‐based modeling. There was strong seasonality in the MODIS GPP at all sites, and mean NPP ranged from 80 g C m^?2 yr^?1 at an arctic tundra site to 550 g C m^?2 yr^?1 at a temperate deciduous forest site. There was not a consistent over‐ or underprediction of NPP across sites relative to the validation estimates. The closest agreements in NPP and GPP were at the temperate deciduous forest, arctic tundra, and boreal forest sites. There was moderate underestimation in the MODIS products at the agricultural field site, and strong overestimation at the desert grassland and at the dry coniferous forest sites. Analyses of specific inputs to the MODIS NPP/GPP algorithm – notably the fraction of photosynthetically active radiation absorbed by the vegetation canopy, the maximum light use efficiency (LUE), and the climate data – revealed the causes of the over‐ and underestimates. Suggestions for algorithm improvement include selectively altering values for maximum LUE (based on observations at eddy covariance flux towers) and parameters regulating autotrophic respiration.     

Effects of land-rise on the development of a coastal ecosystem of the Baltic Sea and its implications for the long-term fate of 14C discharges

Due to the long half-lives of many radionuclides, safety assessments of nuclear waste facilities often need to consider the potential fate of radionuclides discharged to the environment in the future. In this study we explored the environmental fate of a hypothetical ¹⁴C release from a nuclear waste repository to a Baltic Sea bay in 2000 years. This was accomplished by connecting spatially linked biomasses and metabolic rates from a carbon flow model of the ecosystem at the site today to predicted changes in geomorphology and water exchange regimes. The employed extrapolation method was selected as shoreline displacement due to land-rise and sea level changes is the main process that affects the development of the coastal ecosystem around the repository in the coming 10 000 years. The modelling results indicate that the ecosystem will go through changes in several ecosystem properties in the coming 2000-year period, e.g. a decreased rate of primary production and changed feeding preferences of the fish community. Also, a decreased total biomass is expected and an ecosystem change altering the balance between producers and consumers towards a dominance of benthic plants. The changes of the ecosystem structure and carbon dynamics will also influence the potential fate of future discharges of ¹⁴C. We estimated an up to 1000 times higher ¹⁴C concentrations in biota compared to today. However, due to radioactive decay and reduced total biomass in the receiving ecosystem, the proportion of accumulated radionuclides is expected to decrease. Although the modelling approach used in this study is associated with several sources of uncertainty, it provides a way to both qualitatively and quantitatively assess likely effects of future discharges of contaminants.     

Testicular steroidogenesis is not altered by 137 cesium Chernobyl fallout,following in utero or post-natal chronic exposure

The testis is especially sensitive to pollutants, including radionuclides. Following the Chernobyl nuclear power plant accident, several of these radionuclides were emitted and spread in the environment. Subsequently, children presented some disruptions of the endocrine system. To determine whether these disruptions were due to 137 cesium (¹³⁷Cs) exposure, the effects of chronic contamination with low doses of ¹³⁷Cs in utero or from birth on testicular steroidogenesis in rats were studied. Contamination was continued for 9 months. No modification was observed in circulating level of hormones (17β-estradiol, testosterone, follicle-stimulating hormone, luteinizing hormone) following in utero or post-natal contamination. Expression of several genes involved in testicular steroidogenesis was affected (cyp19a1, fxr, sf-1), without modification of protein expression or activity. Our results suggest that growing organisms may be affected at the molecular level by ¹³⁷Cs contamination at this post-accidental dose.     

The risk of leukaemia in young children from exposure to tritium and carbon-14 in the discharges of German nuclear power stations and in the fallout from atmospheric nuclear weapons testing

Towards the end of 2007, the results were published from a case–control study (the “KiKK Study”) of cancer in young children, diagnosed <5 years of age during 1980–2003 while resident near nuclear power stations in western Germany. The study found a tendency for cases of leukaemia to live closer to the nearest nuclear power station than their matched controls, producing an odds ratio that was raised to a statistically significant extent for residence within 5 km of a nuclear power station. The findings of the study received much publicity, but a detailed radiological risk assessment demonstrated that the radiation doses received by young children from discharges of radioactive material from the nuclear reactors were much lower than those received from natural background radiation and far too small to be responsible for the statistical association reported in the KiKK Study. This has led to speculation that conventional radiological risk assessments have grossly underestimated the risk of leukaemia in young children posed by exposure to man-made radionuclides, and particular attention has been drawn to the possible role of tritium and carbon-14 discharges in this supposedly severe underestimation of risk. Both ³H and ¹⁴C are generated naturally in the upper atmosphere, and substantial increases in these radionuclides in the environment occurred as a result of their production by atmospheric testing of nuclear weapons during the late 1950s and early 1960s. If the leukaemogenic effect of these radionuclides has been seriously underestimated to the degree necessary to explain the KiKK Study findings, then a pronounced increase in the worldwide incidence of leukaemia among young children should have followed the notably elevated exposure to ³H and ¹⁴C from nuclear weapons testing fallout. To investigate this hypothesis, the time series of incidence rates of leukaemia among young children <5 years of age at diagnosis has been examined from ten cancer registries from three continents and both hemispheres, which include registration data from the early 1960s or before. No evidence of a markedly increased risk of leukaemia in young children following the peak of above-ground nuclear weapons testing, or that incidence rates are related to level of exposure to fallout, is apparent from these registration rates, providing strong grounds for discounting the idea that the risk of leukaemia in young children from ³H or ¹⁴C (or any other radionuclide present in both nuclear weapons testing fallout and discharges from nuclear installations) has been grossly underestimated and that such exposure can account for the findings of the KiKK Study.     

全球不同气候带陆地植被净初级生产力变化趋势与可持续性

分析全球不同气候带陆地植被净初级生产力(NPP)的变化趋势与可持续性,对于估算全球陆地生态系统的结构、功能和碳源(汇)具有重要意义。运用Mann-Kendall突变检验、Theil-Sen斜率估计、Hurst指数分析全球不同气候带陆地NPP的变化趋势与可持续性。结果表明：(1)全球陆地NPP有明显的地域分异规律,呈现低纬高、高纬低,沿海高、内陆低的特点。约48.79%陆地生态系统的植被NPP得到了改善,其中显著改善的面积占全球陆地生态系统的8.45%,主要分布在北美洲北部和中部、亚马逊河流域西部、刚果盆地、欧洲南部、印度半岛西北部、中国黄土高原;轻微改善的面积占全球陆地生态系统的40.34%,主要分布在南美洲中南部、亚洲东部和澳大利亚大陆东部。(2)各气候带NPP变化趋势和突变点表现为：热带、亚热带、极地带的NPP呈不显著下降趋势(R²=0.111,P=0.176;R²=0.144,P=0.120;R²=0.002,P=0.854),热带无明显突变点,亚热带突变点为2015年,极地带突变点为2005年;干旱气候带的NPP...     

Transfer of radionuclides to ants, mosses and lichens in semi-natural ecosystems

There is a scarcity of data on transfer of both natural and anthropogenic radionuclides to detritivorous invertebrates for use in the assessment of radiation exposure. Although mosses and lichens have been extensively used in biomonitoring programs, the data on transfer of radionuclides to these species are limited, particularly for natural radionuclides. To enhance the available data, activity concentrations of ¹³⁷Cs, ²²⁶Ra and ²²⁸Ra were measured in ants, mosses and lichens and corresponding undisturbed soil collected from semi-natural ecosystems in Serbia and Montenegro and biota/soil concentration ratios (CR) calculated. Since the majority of internal dose to biota is expected to come from ⁴⁰K, the activity concentrations of this radionuclide were also determined. The mean CR values for ¹³⁷Cs, ²²⁶Ra and ²²⁸Ra in ants analyzed in this study were found to be 0.02, 0.06 and 0.02, respectively. The mean CR values of radionuclides in mosses were found to be 2.84 for ¹³⁷Cs, 0.19 for ²²⁶Ra and 0.16 for ²²⁸Ra, while those in lichens were found to be 1.08 for ¹³⁷Cs, 0.15 for ²²⁶Ra and 0.13 for ²²⁸Ra. The CR values obtained in this study were compared with default CR values used in the ERICA Tool database and also with those reported in other studies.     

Cytogenetic abnormalities in aquatic plant Elodea canadensis in anthropogenic contamination zone of Yenisei River

Chromosome abnormalities in ana-telophase cells of apical root meristem of aquatic plant Elodea. canadensis (elodea), sampled in 2011–2012 in the Yenisei River at a site with background level of contamination and at several sites on the stretch contaminated with artificial radionuclides, and with chemical pollutants from municipal and industrial discharges of the Krasnoyarsk city. Lowest rate (5.2%) of cells with chromosome abnormalities was registered at sampling site with background level of contamination upstream of the Krasnoyarsk, highest rate of cells with abnormalities (39.7%)—in roots of elodea sampled in bottom sediments with highest concentration of ¹³⁷Cs. Sum of rates of cells with abnormalities and rates of cells with all types of abnormalities positively correlated with total concentration of artificial and natural radionuclides, with concentration of artificial radionuclides and ¹³⁷Cs in bottom sediments of the Yenisei River (r ² = 0.91–0.96, p < 0.0005 for sum of rates of cells with abnormalities; r ² = 0.58–0.92, p < 0.05 for all types of abnormalities).     

Considerations on the behavior of long-lived radionuclides in the soil

The migration of radionuclides from waste repositories to the biosphere potentially leads to a contamination of soil. Due to the importance of food production, the mobilisation and accumulation behaviour of long-lived radionuclides in the soil plays a key role in performance assessment studies. In this paper, the main features and processes that control radionuclide behaviour in soil, such as pH, redox potential and sorption to organic and inorganic soil components, are discussed for the radionuclides ³⁶Cl, ⁷⁹Se, ¹²⁹I, ⁹⁹Tc, ²³⁷Np and ²³⁸U, that are usually most relevant in long-term safety assessments of nuclear waste. The interaction of radionuclide behaviour in soil with environmental factors, such as temperature and humidity as well as farming practices are discussed. The possible impact of future soil development on long-term behaviour in soil are taken into consideration. Due to the physiological constraints of plant growth, appropriate soil conditions for growth will probably not be substantially different from current requirements, bearing in mind that sustainable agriculture strives for optimal plant growth. Against this background, present-day parameters may in general be considered appropriate for roughly estimating the behaviour of radionuclides in the soil-plant system. Received: 18 October 2000 / Accepted: 20 March 2001     

Experience on the neutron activation of natural/enriched Re,Sm, and Ho nuclides in a reactor for the production of radiotherapeutic radionuclides

In recent years, much effort has been concentrated on the use of Β-emitting radionuclides for the treatment of various cancers. The reports suggested the application of¹⁸⁶Re and¹⁵³Sm as radiotherapeutic radionuclides for the treatment of palliative widespread skeletal métastases, whereas¹⁶⁶Ho was suggested as an agent for radiation synovectomy. Hence, a study on the production of¹⁸⁶Re,¹⁵³Sm, and¹⁶⁶Ho radionuclides was carried out by neutron activation of the appropriate target materials using a Pakistan Atomic Research Reactor (PARR-1) at a neutrons flux of 1 x 10⁴ n/cm² s. These radionuclides were then converted to appropriate radiopharmaceuticals for their use on animals and patients. The targets of natural Re (metal), natural Sm₂O₃, enriched Sm₂O₃ (99.06%), Sm(NO₃)₃ (solid), Sm(NO₃)₃ (liquid), and Ho₂O₃ were irradiated in the PARR-1. After irradiation, the purity of these radionuclides were checked by a multichannel analyzer, Canberra series 85 (MCA) coupled with HPGe detector and then measured in radioisotope calibrator Capintec ionization chamber model CRC-5RH. The effect of the irradiation time and amount of target material was investigated on the production yields of the radionuclides. The results showed an increase in the specific activity of Re with an increase in the irradiation time from 1 to 72 h, whereas a decrease in the specific activity was observed with increase in the amount of Re from 10 to 100 mg. Similar results were obtained for¹⁵³Sm and¹⁶⁶Ho radionuclides. The results further indicated that the specific activity of powder target was much less than the liquid targets for¹⁵³Sm. Their conversion to the appropriate radiotherapeutic radiopharmaceuticals were also carried out by investigating the experimental conditions and acceptable quality of¹⁸⁶Re-HEDP and¹⁵³Sm-EDTMP complexes were prepared. These complexes were then used on animals and patients which showed good performance.     

Dextranase production by recombinant Pichia pastoris under operational volumetric mass transfer coefficient (kLa) and volumetric gassed power input (Pg/V) attainable at commercial large scale

Abstract

Most of the reported bioprocesses carried out by the methylotrophic yeast Pichia pastoris have been performed at laboratory scale using high power inputs and pure oxygen, such conditions are not feasible for industrial large-scale processes. In this study, volumetric mass transfer (k_La) and volumetric gassed power input (Pg/V) were evaluated within values attainable in large-scale production as scale-up criteria for recombinant dextranase production by Mut^S P. pastoris strain. Cultures were oxygen limited when the volumetric gassed power supply was limited to 2?kW m^?3. Specific growth rate, and then dextranase production, increased as k_La and Pg/V did. Meanwhile, specific production and methanol consumption rates were constant, due to the limited methanol condition also achieved at 2?L bioprocesses. The specific dextranase production rate was two times higher than the values previously reported for a Mut⁺ strain. After a scale-up process, at constant k_La, the specific growth rate was kept at 30?L bioprocess, whereas dextranase production decreased, due to the effect of methanol accumulation. Results obtained at 30?L bioprocesses suggest that even under oxygen-limited conditions, methanol saturated conditions are not adequate to express dextranase with the promoter alcohol oxidase. Bioprocesses developed within feasible and scalable operational conditions are of high interest for the commercial production of recombinant proteins from Pichia pastoris.     

Complex Spatiotemporal Responses of Global Terrestrial Primary Production to Climate Change and Increasing Atmospheric CO2 in the 21st Century

Quantitative information on the response of global terrestrial net primary production (NPP) to climate change and increasing atmospheric CO₂ is essential for climate change adaptation and mitigation in the 21^st century. Using a process-based ecosystem model (the Dynamic Land Ecosystem Model, DLEM), we quantified the magnitude and spatiotemporal variations of contemporary (2000s) global NPP, and projected its potential responses to climate and CO₂ changes in the 21^st century under the Special Report on Emission Scenarios (SRES) A2 and B1 of Intergovernmental Panel on Climate Change (IPCC). We estimated a global terrestrial NPP of 54.6 (52.8–56.4) PgC yr⁻¹ as a result of multiple factors during 2000–2009. Climate change would either reduce global NPP (4.6%) under the A2 scenario or slightly enhance NPP (2.2%) under the B1 scenario during 2010–2099. In response to climate change, global NPP would first increase until surface air temperature increases by 1.5°C (until the 2030s) and then level-off or decline after it increases by more than 1.5°C (after the 2030s). This result supports the Copenhagen Accord Acknowledgement, which states that staying below 2°C may not be sufficient and the need to potentially aim for staying below 1.5°C. The CO₂ fertilization effect would result in a 12%–13.9% increase in global NPP during the 21^st century. The relative CO₂ fertilization effect, i.e. change in NPP on per CO₂ (ppm) bases, is projected to first increase quickly then level off in the 2070s and even decline by the end of the 2080s, possibly due to CO₂ saturation and nutrient limitation. Terrestrial NPP responses to climate change and elevated atmospheric CO₂ largely varied among biomes, with the largest increases in the tundra and boreal needleleaf deciduous forest. Compared to the low emission scenario (B1), the high emission scenario (A2) would lead to larger spatiotemporal variations in NPP, and more dramatic and counteracting impacts from climate and increasing atmospheric CO₂.     

Radioactivity in mushrooms from selected locations in the Bohemian Forest,Czech Republic

¹³⁷Cs is one of the most important radionuclides released in the course of atmospheric nuclear weapon tests and during accidents in nuclear power plants such as that in Chernobyl, Ukraine, or Fukushima, Japan. The aim of this study was to compare ¹³⁷Cs and ⁴⁰K concentrations in particular species of mushrooms from selected locations in the Bohemian Forest (Czech: ?umava), Czech Republic, where a considerable contamination from the Chernobyl accident had been measured in 1986. Samples were collected between June and October 2014. Activities of ¹³⁷Cs and ⁴⁰K per dry mass were measured by means of a semiconductor gamma spectrometer. The ¹³⁷Cs values measured range from below detection limit to 4300?±?20 Bq kg^?1, in the case of ⁴⁰K from 910?±?80 to 4300?±?230 Bq kg^?1. Differences were found between individual locations, due to uneven precipitation in the course of the movement of the radioactive cloud after the Chernobyl accident. There are, however, also differences between individual species of mushrooms from identical locations, which inter alia result from different characteristics of the soil and depths of mycelia. The values measured are compared with established limits and exposures from other radiation sources present in the environment. In general, it can be stated that the values measured are relatively low and the effects on the health of the population are negligible compared to other sources of ionizing radiation.     

汾河上游流域生态系统服务变化及驱动因素

随着社会经济的发展,人类对生态系统服务选择的加剧,生态系统服务面临的形势更加严峻。以汾河上游流域为研究区,以遥感影像、气象、土壤、统计数据及专题地图等为数据源,基于Arc GIS平台,采用CASA、In VEST等模型,评价了2000年和2008年汾河上游流域泥沙截持、产水量、NPP、固碳释氧、粮食生产五项生态系统服务变化情况;同时,整合人口、居民点、道路定量评价了研究区2000和2008年人类活动强度,并采用SPSS典型相关分析方法(CCA),对生态系统服务的自然与人文驱动因素进行了分析。结果表明:2000—2008年间,研究区5项生态系统服务变化明显。其中,泥沙截持服务减少43.30 t/hm~2,减少范围占整个流域87.5%,只有北端局部区域有所增强;产水服务增加4.74 t/hm~2,产水服务增加的区域占到了流域总面积的89.6%; NPP生产服务增加0.86 t/hm~2,NPP增加的区域占研究区的93.7%,仅边缘零星区域NPP减少;固碳释氧服务与NPP生产服务呈现一致的时空格局,增加量达2.18 t/hm~2,仅流域边缘零星分布减少的斑块;粮食生产服务总体上有所降低,下降幅度为15.65 kg/hm~2,粮食生产减少的区域占到整个流域的65%。同期,该区域人类活动强度有所增强,人类活动指数(HAI)由0.19增加到0.21,呈现出北低南高的空间格局。相关性分析表明,2000—2008年前,人类活动与泥沙截持和产水服务呈现极显著的正相关(r=0.637**和r=0.656**)。典型相关分析则(CCA)表明:影响泥沙截持服务的主要驱动因子是坡度,影响产水量的主要因素是降雨量和温度; 2000—2008两年间生态系统服务变化量的典型相关分析表明泥沙截持和产水服务受日照时数、相对湿度、降雨等自然因子的影响,NPP生产/固碳释氧的主要影响因子为温度和坡向。     

Simulation of Diffusive Transport of Radionuclides in the Soil of a Radioactive Waste Disposal Site

The diffusive transport of ¹³⁷Cs, ⁹⁰Sr, and ⁶⁰Co in the clay of a radioactive waste disposal site at PINSTECH was studied to assess the safety of the underlying permeable zone against the release of these radionuclides from buried waste containers in the clay. Diffusion coefficients of these radionuclides were estimated by reservoir to sediment diffusion method via their stable counterparts in a laboratory experiment. A curve-fitting procedure was applied on the measured concentration-time profiles of the reservoir using the one-dimensional solute transport equation with a nonlinear least squares technique. Distribution coefficients were determined in laboratory batch experiments. Diffusive transport simulations were performed with the estimated values of diffusion coefficients and distribution coefficients using the one-dimensional solute transport equation describing Fickian diffusion, equilibrium adsorption, and radioactive decay. The transport simulation results showed that ¹³⁷Cs, ⁹⁰Sr, and ⁶⁰Co will transport distances of 4.33, 3.77, and 1.51 meters, respectively, in the clay before their activity concentrations will drop to clearance levels set by the International Atomic Energy Agency (IAEA), below which the waste is treated as non-radioactive. This showed that concentrations more than clearance levels will not be able to transport to the permeable zone at a minimum depth of seven meters from the ground surface if the waste containers are disposed in a trench below which a clay layer with a thickness of 4.33 meters or more exists.     

Naturally occurring radionuclides in food and drinking water from a thorium-rich area

This paper focuses on a survey of uranium and thorium decay chain radionuclides in food and drinking water from the thorium-rich (monazite-bearing) region of Buena, which is located in the state of Rio de Janeiro, Brazil. The radionuclide concentration values in the food and drinking water from Buena reached values higher than 100-fold the international reference values. The daily intake of radionuclides by the local population is similar to that of another high background radiation area in Brazil, but the intake is higher than that of residents from a normal background radiation area. Approximately 58?% of the food consumed by Buena inhabitants is produced locally. Based on that figure, locally produced food and the dilution of total radionuclides in the diet of residents caused by food importation are both highly relevant to a population’s intake of radionuclides. The concentration values for ²¹⁰Pb and the radium isotopes in drinking water from Buena are among the highest values to be reported in the literature. ²²⁸Ra is the most important radionuclide ingested with both food and water among the inhabitants of Buena.     

Radioecological indexes of fallout measurements from the Fukushima nuclear accident

Fallout from the Fukushima nuclear accident has been monitored for about 1 month in Thessaloniki, Northern Greece. Three different radionuclides, one short-lived, one relatively long-lived and one long-lived fission product were identified in air, grass and milk samples. The ¹³¹I, ¹³⁷Cs and ¹³⁴Cs activity concentrations in air reached 497, 145 and 126 μBq m⁻³, respectively on 4 April, 2011. These radionuclides are of particular concern regarding their transfer from the environment to population through the ingestion pathways for the assessment of the Fukushima accident consequences. Radioecological indexes (eco-indexes) of fallout measurements in the air–grass–cow-milk–man pathway for ¹³¹I were determined, as they are related to radiological impact of the Fukushima derived radionuclides on the public and environment.     

The use of technetium-99m as a radioisotopic label to assess cell-mediated immunity in vitro

We have developed a radioisotopic microassay of cell-mediated immunity employing target cells prelabeled with technetium-99m (^99mTc), a high specific activity metastable gamma emitter. Labeling kinetics, release and reutilization, subcellular localization, and effects of ^99mTc on DNA and protein synthesis have been investigated. Target cells were optimally labeled with 10 mCi of ^99mTc at 37 °C for 10 min. Cyclic freezing and thawing released less than 10% of total bound radioisotope. Spontaneous leakage of ^99mTc by monolayer cells was negligible over 48 hr and that which was released appeared to be nonreutilizable. Cell fractionation revealed that nuclear, mitochondrial, and microsomal fractions all were labeled with ^99mTc. The incorporation of ³H-thymidine and ³H-amino acids was not impaired in ^99mTc-labeled cells.The alloimmune reactivity of C57BL/6 mice which had received A/J skin allografts was studied by means of the ^99mTc microcytotoxicity assay. Cell-mediated immunity was clearly evident at 7 days postgrafting, peaked at 14 days, and had declined to background levels by 21 days. These findings correlated well with initial acceptance and ultimate rejection of the allografts. The rapid labeling time without dependence upon cell division for incorporation, high specific activity, low spontaneous release, and nonreutilizability are important advantages of ^99mTc over other radionuclides which have been employed in in vitro assays of cell-mediated immunity.     

Net primary production, carbon storage and climate change in Chinese biomes

Net primary production (NPP) and leaf area index (LAI) of Chinese biomes were simulated by BIOME3 under the present climate, and their responses to climate change and doubled CO₂ under a future climatic scenario using output from Hadley Center coupled ocean‐atmosphere general circulation model with CO₂ modelled at 340 and 500 ppmv. The model estimated annual mean NPP of the biomes in China to be between 0 and 1270.7 gC m^‐2 yr^‐1 at present. The highest productivity was found in tropical seasonal and rain forests while temperate forests had an intermediate NPP, which is higher than a lower NPP of temperate savannas, grasslands and steppes. The lowest NPP occurred in desert, alpine tundra and ice/polar desert in cold or arid regions, especially on the Tibetan Plateau. The lowest monthly NPP of each biome occurred generally in February and the highest monthly NPP occurred during the summer (June to August). The annual mean NPP and LAI of most of biomes at changed climate with CO₂ at 340 and 500 ppmv (direct effects on physiology) would be greater than present. The direct effects of carbon dioxide on plant physiology result in significant increase of LAI and NPP. The carbon storage of Chinese biomes at present and changed climates was calculated by the carbon density and vegetation area method. The present estimates of carbon storage are totally 175.83 × 10¹² gC (57.57 × 10¹² gC in vegetation and 118.28 × 10¹² gC in soils). Changed climate without and with the CO₂ direct physiological effects will result in an increase of carbon storage of 5.1 and 16.33 × 10¹², gC compared to present, respectively. The interaction between elevated CO₂ and climate change plays an important role in the overall responses of NPP and carbon to climate change.     

Variability of water content and of depth profiles of global fallout 137Cs in grassland soils and the resulting external gamma-dose rates

¹³⁷Cs from global fallout of nuclear weapon testings in the 1950s and 1960s was determined in successive layers (0–30 cm) of eight undisturbed grassland soils in Bavaria, Germany. The maximum activity concentration was found in soil layers between 4 and 15 cm below the surface. Using the vertical distribution of the cesium activity, which varied considerably from site to site, the mean residence half-time of ¹³⁷Cs from global fallout in each soil layer was evaluated with a compartment model. These values ranged from 1.0 to 6.3 years/cm. The mean residence half-time averaged over all soil layers and all sites was 2.7±1.4 years/cm and, thus, about twice the corresponding residence half-time of the Chernobyl-derived ¹³⁷Cs as determined in the same soil layers (also in 1993). The dose rate of the external gamma-radiation due to ¹³⁷Cs from global fallout in the soil determined from the depth distributions varied between 0.34 and 0.57 (mean: 0.45±0.07) nGy/h per kBq/m². The effect of soil water content on the dose rate was studied by considering four states of the soil, from water content zero to complete water saturation of the total pore volume. It was shown that the difference between the dose rates at the permanent wilting point and the field capacity, which both represent the most relevant water contents of soils, was only 10% of the dose rate at the permanent wilting point for all sites. Received: 8 September 1997 / Accepted in revised form: 15 December 1997     

Methods to label monoclonal antibodies for use in tumor imaging

The use of radiolabeled monoclonal antibodies as a diagnostic tool in nuclear medicine has grown rapidly over the past several years. Early studies utilized antibodies labeled with radionuclides of iodine (i.e. ¹²⁵I and ¹³¹I) although these radionuclides are not ideal for use in tumor imaging. Recent advances and the development of new chemical methods has made it possible to label antibodies with other radionuclides (i.e. ⁷⁷Br, ¹¹¹In and ^99mTc). The advantages and disadvantages associated with all of the different radionuclides and labeling methods will be discussed.