Ecological effects of atmospheric nitrogen deposition on soil enzyme activity

The continuing increase in human activities is causing global changes such as increased deposition of atmospheric nitrogen. There is considerable interest in understanding the effects of increasing atmospheric nitrogen deposition on soil enzyme activities, specifically in terms of global nitrogen cycling and its potential future contribution to global climate change. This paper summarizes the ecological effects of atmospheric nitrogen deposition on soil enzyme activities, including size-effects, stage-effects, site-effects, and the effects of different levels and forms of atmospheric nitrogen deposition. We discuss needs for further research on the relationship between atmospheric nitrogen deposition and soil enzymes.

Effects of six years of simulated N deposition on gross soil N transformation rates in an old-growth temperate forest

Elevated atmospheric nitrogen(N) deposition has been detected in many regions of China, but its effects on soil N transformation in temperate forest ecosystems are not well known. We therefore simulated N deposition with four levels of N addition rate(N0, N30, N60, and N120) for6 years in an old-growth temperate forest in Xiaoxing’an Mountains in Northeastern China. We measured gross N transformation rates in the laboratory usingN tracing technology to explore the effects of N deposition on soil gross N transformations taking advantage of N deposition soils. No significant differences in gross soil N transformation rates were observed after 6 years of N deposition with various levels of N addition rate. For all N deposition soils, the gross NH~+ immobilization rates were consistently lower than the gross N mineralization rates,leading to net N mineralization. Nitrate(NO~-) was primarily produced via oxidation of NH~+(i.e., autotrophic nitrification), whereas oxidation of organic N(i.e., heterotrophic nitrification) was negligible. Differences between the quantity of ammonia-oxidizing bacteria and ammonia-oxidizing archaea were not significant for any treatment, which likely explains the lack of a significant effect on gross nitrification rates. Gross nitrification rates were much higher than the total NO~- consumption rates,resulting in a build-up of NO~-, which highlights the high risk of N losses via NO~- leaching or gaseous N emissions from soils. This response is opposite that of typical N-limited temperate forests suffering from N deposition,suggesting that the investigated old-growth temperate forest ecosystem is likely to approach N saturation.

Response of soil fauna to simulated nitrogen deposition: A nursery experiment in subtropical China

We studied the responses of soil fauna to a simulated nitrogen deposition in nursery experimental plots in Subtropical China. Dissolved NH4NO3 was applied to the soil by spraying twice per month for 16 months, starting January 2003 with treatments of 0, 5, 10, 15 and 30 gN/（m^2·a）. Soil fauna was sampled after 6, 9, 13 and 16 months of treatment in three soil depths （0-5 cm, 5-10 cm, 10-15 cm）. Soil available N increased in correspondence with the increasing N treatment, whereas soil pH decreased. Bacterial and fungal densities were elevated by the N treatment. Soil fauna increased in the lower nitrogen treatments but decreased in the higher N treatments, which might indicate that there was a threshold around 10 gN/（m^2·a） for the stimulating effects of N addition. The N effects were dependent on the soil depth and sampling time. The data also suggested that the effects of the different N treatments were related to the level of N saturation, especially the concentration of NO3^- in the soil.

Short-term Effects of Nitrogen Deposition on Soil Physical and Chemical Properties of Tibetan Forest-Grassland Landscape Boundary

[Objective] The paper was to study the effects of nitrogen deposition on soil nutrients and soil dissolved organic carbon in forest-grassland landscape in Linzhi, Tibet, and to provide scientific basis and basic data for understanding and assessing the effect of atmospheric nitrogen deposition on soil nutrients and soil dissolved organic carbon. [Method] From July 2014 to August 2015, in situ nitrogen deposition （CK0 kg· hm^2/a, LN25 kg·hm^2/a, MN 50 kg·hm^2/a, HN 150 kg· hm^2/a） was simulated in the forestgrassland boundary of Zhuqudeng village, Bujiu Township, LinzhiCounty, Tibet. The soil samples were collected for analyzing nutrient and dissolved contents in the soil layer of 0-20 and 20-40 cm. The effects ofdifferent nitrogen deposition levels on soil nutrients and dissolved organic carbon （DOC） were studied. [Result] Nitrogen deposition had significantimpacts on soil organic matter, total N, total P, total K, available N, available P, available K, exchangeable Ca, exchangeable Mg, pH, and DOC（P〈0.05）. （2） With the deepening of nitrogen deposition from CK, LN, MN to HN in the 0-20 cm boundary soil, the contents of organic matter, total N,total P, available P, exchangeable Ca, exchangeable Mg and DOC kept decreasing, and the content of total K and available N increased continuously. The pH increased in LN treatment and decreased in HN treatment, while the available K content was decreased in LN and HN treatment, butincreased in MN treatment. （3） The contents of organic matter, total N, total P, available N, available P, exchangeable Ca, exchangeable Mg andDOC all decreased at the soil layer of 20-40 cm under the same nitrogen deposition. The pH increased in LN treatment, but decreased in HN treatment; the content of total K decreased in LN treatment and increased in MN and HN treatments; the content of available K decreased in LN andHN treatments, but increased in MN treatment. （4） With the deepening of boundary soil layer （0-20 to 20-40 cm）, the organic matter, total N, totalP, available P, available K, exchangeable Ca, exchangeable Mg, DOC showed the same response to simulated nitrogen deposition, while the available N and total K responded differently. [Conclusion] Different levels of N deposition had certain impact on soil nutrient, and the variation of soilnutrients was not the same at different levels.

Laboratory-scale model of carbon dioxide deposition for soilstabilisation

Olivine sand is a natural mineral,which,when added to soil,can improve the soil’s mechanical properties while also sequester carbon dioxide(CO2)from the surrounding environment.The originality of this paper stems from the novel two-stage approach.In the first stage,natural carbonation of olivine and carbonation of olivine treated soil under different CO2pressures and times were investigated.In this stage,the unconfined compression test was used as a tool to evaluate the strength performance.In the second stage,details of the installation and performance of carbonated olivine columns using a laboratory-scale model were investigated.In this respect,olivine was mixed with the natural soil using the auger and the columns were then carbonated with gaseous CO2.The unconfined compressive strengths of soil in the first stage increased by up to 120% compared to those of the natural untreated soil.The strength development was found to be proportional to the CO2pressure and carbonation period.Microstructural analyses indicated the presence of magnesite on the surface of carbonated olivinetreated soil,demonstrating that modified physical properties provided a stronger and stiffer matrix.The performance of the carbonated olivine-soil columns,in terms of ultimate bearing capacity,showed that the carbonation procedure occurred rapidly and yielded a bearing capacity value of 120 k Pa.Results of this study are of significance to the construction industry as the feasibility of carbonated olivine for strengthening and stabilizing soil is validated.Its applicability lies in a range of different geotechnical applications whilst also mitigates the global warming through the sequestration of CO2.

Short-term Effects of Nitrogen Deposition on Soil Enzyme Activities in Tibet Grasslands

[Objective] The paper was to study the effects of nitrogen deposition on enzyme activity in different layers of soil. [Method] With grass-land located in Zhuqudeng Village, Bujiu Township, Linzhi City, the Tibet Autonomous Region, as the object, nitrogen deposition was simulated from July 2014 to August 2015. Four N addition treatments were established： control （0 kg·hm^2/a）, low N （LN, 25kg·hm^2/a）, medium N （MN, 50 kg·hm^2/a） and High N （HN, 150 kg·hm^2/a）, aiming at measuring enzyme activity （invertase, catalase, urease, amylase, cellulase, polyphenol oxidase and β-glucosi- dase） in different layers of grassland soil （0 -20 cm and 20-40 cm）. [Result] （1） Different levels of simulated nitrogen deposition had significant impact on invertase and β-glucosidase at the soil depth of 0-20 cm （P〈0.05）, but no significant impact on catalase, urease, amylase, cellulase and polyphenol oxidase（P〉0.05）; invertase, polyphenol oxidase and β-glucosidase had significant response to nitrogen deposition at the soil depth of 20- 40 cm （P〈0.05）, while catalase, urease, amylase and cellulose had no significant response （P〉0.05）. （2） The activities of invertase and polyphenol oxidase were enhanced at the soil depth of 0-20 cm, and that of β-glucosidase was inhibited. （3） With the deepening of nitrogen deposition, the ac- tivities of invertase and cellulose were enhanced at the soil depth of 20-40 cm; the activity of polyphenol oxidase was reduced in LN treatment, but increased in HN treatment; the activity of β-glucosidase was increased in LN treatment, but decreased in MN treatment. （4） With the deepening of soil layers, invertase and polyphenol oxidase responded similarly to simulated nitrogen deposition. [Conclusion] The results provide certain scientific basis and fundamental data for better understanding and evaluating the effects of nitrogen deposition on enzyme activity in grassland soil.

The Chemistry of Serpentine Soils Developed Over A Podiform Chromite Deposit,Western Sierra Nevada,USA

The Chinese Camp mining district in the western Sierra Nevada of California,USA,contains a serpentinized,ultramafic dunite intrusion with podiform chromite deposits.Serpentine soils have developed over this intrusion,creating a unique ecosystem of endemic vegetation and soils characterized by low Ca/Mg ratios and high Ni and Cr contents.The vegetation and red coloration make it easy to visually distinguish between soils developed over intruded,serpentinized bedrock and unmineralized,adjacent andesite bedrock(Fig.1).The purpose of our study was to compare soil chemistry and vegetative parameters among 3 study-design levels:1)undisturbed serpentine soil,2)undisturbed background soil(non-serpentine,developed over andesite),and 3)serpentine soil disturbed by mining activities.Within each of these l e v*e ls,3 random locations were chosen where weestablished 3,30-m transects(spaced 120-degrees apart).One soil sample was collected at a random location along each transect(0-15 cm depth after removing litter/O horizon).This scheme resulted in the collection of 9replicate soil samples per study-design level.Samples were analyzed for total metal content by ICP-AES/MS(inductively coupled plasma atomic emission spectroscopy/mass spectroscopy),p H,electrical conductivity,and total C/N/S.The vegetative parameter of%canopy cover was measured with a line-point intercept survey along each transect,using 0.6m intervals.Above-ground net primary productivity(ANPP)was estimated by harvesting all aboveground living plant material within a 0.5 m quadrant at 3 random locations along each transect,drying,and weighting the material.Significant differences among design levels were observed for ANPP,canopy cover,total P,total N,and Ca/Mg,where the median values for these parameters decreased in the order undisturbed background>undisturbed serpentine>mining-disturbed serpentine.The highest concentrations of Cr and Ni were found in undisturbed serpentine(medians of 1960 ppm and 2529ppm,respectively)followed by mining-disturbed serpentine(medians of 420 and 2120,respectively)then undisturbed non-serpentine(medians 47.0 and 32.2 ppm,respectively).Soil p H varied significantly among the design levels with a median 5.74 in undisturbed background,median 6.25 in undisturbed serpentine,and median of 7.17 in mining-disturbed serpentine.These data document the distinct differences in soil chemistry and vegetation parameters between undisturbed serpentine soil and adjacent,undisturbed background soil.Efforts toward mining reclamation must recognize these differences and include the correct baseline conditions in the reclamation plan.

SOIL NITROGEN MINERALIZATION UNDER NORTHERN HARDWOOD FORESTS ALONG A SULFATE AND NITRATE DEPOSITION GRADIENT IN THE GREAT LAKES REGION

Net N mineralization (ammonification and nitrification) in the 0-10 cm mineral soil zone of five northern hardwood forest sites along a gradient of SO and NO deposition from northeastem Minnesota to central lower Michigan was measured by an in situ buried bag technique at monthly intervals from September 1987 to April 1990. Soil nitrification rates (36.9 to 46.7 kg N·ha-1·yr-1) increased from north to south among the five study sites and were strongly associated with soil temperature (r=0.87, p<0.001). The rates of soil ammonification (66.8 to 84. 1 kg N·ha-1·yr-1) and amounts of total N mineralized (103.7 to 130.6 kg N·ha-1·yr-1)did not show a clear regional trend across the gradient sites. Significant correlations between SO(r=0.82, p<0.001), No(r=0.77, p=0.003) deposition and the adjusted means of ammonium-N after removing the effects of soil temperature indicated that SO and NO deposition had significantly impacts on ammonification process. Soil pH did not correspond to the gradient of H+deposition, which was not correlated with either ammonification or nitrification rates across the study sites.

^137Cs tracing dynamics of soil erosion,organic carbon,and total nitrogen in terraced fields and forestland in the Middle Mountains of Nepal

The Middle Mountains is one of the regions of Nepal most vulnerable to water erosion, where fragile geology, steep topography, anomalous climatic conditions, and intensive human activity have resulted in serious soil erosion and enhanced land degradation. Based on the 137 Cs tracing method, spatial variations in soil erosion, organic carbon, and total nitrogen(TN) in terraced fields lacking field banks and forestland were determined. Soil samples were collected at approximately 5 m and 20 m intervals along terraced field series and forestland transects respectively. Mean 137 Cs inventories of the four soil cores from the reference site was estimated at 574.33 ± 126.22 Bq m-2(1 Bq(i.e., one Becquerel) is equal to 1 disintegration per second(1 dps)). For each terrace, the 137 Cs inventory generally increased fromupper to lower slope positions, accompanied by a decrease in the soil erosion rate. Along the entire terraced toposequence, 137 Cs data showed that abrupt changes in soil erosion rates could occur between the lower part of the upper terrace and the upper part of the immediate terrace within a small distance. This result indicated that tillage erosion is also a dominant erosion type in the sloping farmland of this area. At the same time, we observed a fluctuant decrease in soil erosion rates for the whole terraced toposequence as well as a net deposition at the toe terrace. Although steep terraces(lacking banks and hedgerows) to some extent could act to limit soil sediment accumulation in catchments, soil erosion in the terraced field was determined to be serious. For forestland, with the exception of serious soil erosion that had taken place at the top of slopes due to concentrated flows from a country road situated above the forestland site, spatialvariation in soil erosion was similar to the "standard" water erosion model. Soil organic carbon(SOC) and TN inventories showed similar spatial patterns to the 137 Cs inventory for both toposequences investigated. However, due to the different dominant erosion processes between the two, we found similar patterns between the <0.002 mm soil particle size fraction(clay sized) and 137 Cs inventories in terraced fields, while different patterns could be found between 137 Cs inventories and the <0.002 mm soil particle size fraction in the forestland site. Such results confirm that 137 Cs can successfully trace soil erosion, SOC and soil nitrogen dynamics in steep terraced fields and forestland in the Middle Mountains of Nepal.

Effect of six years of nitrogen additions on soil chemistry in a subtropical Pleioblastus amarus forest, Southwest China

Soil chemistry influences plant health and carbon storage in forest ecosystems. Increasing nitrogen(N) deposition has potential effect on soil chemistry. We studied N deposition effects on soil chemistry in subtropical Pleioblastus amarus bamboo forest ecosystems. An experiment with four N treatment levels(0, 50, 150,and300 kg N ha-1a-1,applied monthly, expressed as CK,LN,MN, HN,respectively) in three replicates. After6 years of N additions, soil base cations, acid-forming cations, exchangeable acidity(EA), organic carbon fractions and nitrogen components were measured in all four seasons. The mean soil pH values in CK,LN,MN and HN were 4.71, 4.62, 4.71, and 4.40, respectively, with a significant difference between CK and HN. Nitrogen additions significantly increased soil exchangeable Al3+,EA, and Al/Ca,and exchangeable Al3+ in HN increased by 70%compared to CK. Soil base cations(Ca2+, Mg2+, K+, and Na+) did not respond to N additions. Nitrogen treatments significantly increased soil NO3--N but had little effect on soil total nitrogen, particulate organic nitrogen, or NH4~+-N. Nitrogen additions did not affect soil total organic carbon, extractable dissolved organic carbon,incorporated organic carbon, or particulate organic carbon.This study suggests that increasing N deposition could increase soil NO3--N, reduce soil pH, and increase mobilization of Al3+. These changes induced by N deposition can impede root grow and function, further may influence soil carbon storage and nutrient cycles in the future.

Characteristics of Bacillus cereus Spore Counts in Soils w ith Underlying Gold Mineralization in Northwestern Sichuan, China: Results from a Pilot Study

A pilot survey on a microbial mineral exploration method based on so il Bacillus cereus spore counts was carried out across three different gold mi ning regions, which vary in soil type, climate condition and geological setting in northwestern Sichuan, China. B horizon soils from these sites were analyzed for B. cereus spores, Au, Ag, Cu, Pb and Zn. The results show that the numbe rs of B. cereus spores generally increased in soils overlying gold mineraliz ation. Specifically, elevated spore counts were found in samples slightly offset from the outcrops of orebodies, whereas soils directly above the outcrops of or ebodies usually contained low spore counts. However, the background counts of B. cereus spores varied from place to place and were complicated by environmen tal and pedological factors, but the relative ratios of spore counts still were indicative of the underlying gold mineralization.

Solid components and acid buffering capacity of soils in South China

The effects of soil solid components on soil sensitivity to acid deposition by sequential extraction method were studied. A multiple regression equation of soil sensitivity was set up on the basis of stepwise regression analysis. The results showed that organic matter expressed dual effects that were decided by soil original pH value and exchangeable cation composition on acid buffering reactions. The hydrolysis of activated oxides was a very important proton buffering reaction when in low pH situation. The crystalline oxides also played a role in the buffering reactions, but the role was restricted by the rate of activation of oxides. Meanwhile, the results by stepwise analysis showed that factors that had significant effect on soil acid buffering capacity were content of montmorillite, soil original pH value, Al 0, Mn 0 and CEC in decreasing order. Finally, sixteen soils were classified into four types of sensitive with single index cluster and multiple fuzzy cluster analysis respectively.

Nitrogen additions inhibit nitrification in acidic soils in a subtropical pine plantation: effects of soil pH and compositional shifts in microbial groups

Plantation forests play a pivotal role in carbon sequestration in terrestrial ecosystems, but enhanced nitrogen(N) deposition in these forests may affect plantation productivity by altering soil N cycling. Hence,understanding how simulated N deposition affects the rate and direction of soil N transformation is critically important in predicting responses of plantation productivity in the context of N loading. This study reports the effects of N addition rate(0, 40, and 120 kg N ha^(-1) a^(-1)) and form(NH_4Cl vs. NaNO_3) on net N mineralization and nitrification estimated by in situ soil core incubation and on-soil microbial biomass determined by the phospholipid fatty acid(PLFA) method in a subtropical pine plantation. N additions had no influences on net N mineralization throughout the year. Net nitrification rate was significantly reduced by additions of both NH_4Cl(71.5) and NaNO_3(47.1%) during the active growing season, with the stronger inhibitory effect at high N rates. Soil pH was markedly decreased by 0.16 units by NH_4Cl additions. N inputs significantly decreased the ratio of fungal-to-bacterial PLFAs on average by 0.28(49.1%) in November. Under NH_4Cl additions, nitrification was positively related with fungal biomass and soil pH. Under NaNO_3 additions,nitrification was positively related with all microbial groups except for bacterial biomass. We conclude that simulated N deposition inhibited net nitrification in the acidic soils of a subtropical plantation forest in China,primarily due to accelerated soil acidification and compositional shifts in microbial functional groups. These findings may facilitate a better mechanistic understanding of soil N cycling in the context of N loading.

Modelling Soil Erosion and Sedimentation in the Oued Haricha Sub-Basin (Tahaddart Watershed, Western Rif, Morocco): Risk Assessment

This study evaluates the annual loss of soil in the sub-basin of Oued Haricha (Tahaddart basin, Western Rif, NW Morocco). The integration of revised (RUSLE) and modified (MUSLE) soil loss empirical equations of Wischmeier and Smith in combination with GIS permits the modelling of soil erosion at the scale of parcels. The characteristics of precipitation and runoff, the soil properties, the culture system and the current working practices of soil in the sub-basin of the Oued Haricha are collected from local data. The digital terrain model is used to generate topographic factors. The combination of different RUSLE factors shows that the annual soil is 62.72 t/ha/year and corresponds to an average level of risk. The total losses calculated by MUSLE method are valued at 221,468 t/year. The rates of loss due to linear erosion are 82,652 t/year. These soil losses represent 20.33% of the total losses, and confirm that the losses on the slopes outweigh the losses due to the river system. Sedimentation module shows that the areas of high erosion (greater than 200 t/ha/year) are concentrated in the reliefs with average and high slope and occupy 38% of the total area. The deposition areas occupy the centre of sub-basin and constitute 9.12% of the total area. These deposits were concentrated on the edges of major rivers and the outlet of the sub-basin and contributed to siltation of the April 9, 1947 dam.

海陆交互相沉积软土中超深基坑支护设计与实践

海滨地区城市工程建设受软土工程特性影响,尤其在基坑工程中面临巨大挑战。以珠海地区海陆交互相沉积软土中某基坑工程为例,提出了“截水-降水-回灌协同控制”“非对称双翼栈桥”“非对称换撑传力框架柱”等基坑支护优化设计理念。根据基坑工程地质条件及施工部署,综合采用了卸土减载、SMW工法桩、排桩、钢筋混凝土内支撑等多种支护结构形式,并在地下水控制、土方挖运平台及非对称换撑等优化设计中进行合理的平面和空间结合,既保证了基坑支护结构及周边环境安全,又实现了土方快速挖运及地下结构的便捷施工,可为类似基坑工程的设计与施工提供参考。

Dynamics of soil inorganic nitrogen and their responses to nitrogen additions in three subtropical forests, south China

Three forests with different historical land-use, forest age, and species assemblages in subtropical China were selected to evaluate current soil N status and investigate the responses of soil inorganic N dynamics to monthly ammonium nitrate additions. Results showed that the mature monsoon evergreen broadleaved forest that has been protected for more than 400 years exhibited an advanced soil N status than the pine （Pinus massoniana） and pine-broadleaf mixed forests, both originated from the 1930＇s clear-cut and pine plantation. Mature forests had greater extractable inorganic N pool, lower N retention capacity, higher inorganic N leaching, and higher soil C/N ratios. Mineral soil extractable NH4^＋-N and NO3-N concentrations were significantly increased by experimental N additions on several sampling dates, but repeated ANOVA showed that the effect was not significant over the whole year except NH4^＋-N in the mature forest. In contrast, inorganic N （both NH4^＋-N and NO3^--N） in soil 20-cm below the surface was significantly elevated by the N additions. From 42% to 74% of N added was retained by the upper 20 cm soils in the pine and mixed forests, while 0%-70% was retained in the mature forest. Our results suggest that land-use history, forest age and species composition were likely to be some of the important factors that determine differing forest N retention responses to elevated N deposition in the study region.

Seasonal and spatial distribution of trace metals in alpine soils of Eastern Tibetan Plateau,China

The distribution of trace metals in remote alpine region is an effective way to understand the impacts of regional human activity and vegetation on the alpine ecosystem. In this study, the concentrations of cadmium(Cd), copper(Cu), lead(Pb), and zinc(Zn) in the soils of Gongga Mountain, Eastern Tibetan Plateau, were investigated to reveal their seasonal and spatial distribution and enrichment state, and to decipher the effects of atmospheric deposition and vegetation on their distributions among five vegetation zones. The results showed that the concentrations of Cd, Pb, and Zn were higher in the O horizon than in other horizons despite the seasonal changes, whereas Cu was enriched in the C horizon. The enrichment states of the metals studied in the soils decreased in the order of Cd > Pb > Zn > Cu. Cd and Pb were mainly sourced from atmospheric deposition; Zn was from both atmospheric deposition and parent materials, whereas Cu was mainly from parent materials.Seasonally, the trace metals were generally higher in May and December but lower in September, implying the impact of vegetation on the distribution of trace metals under the plant uptake and the litter decomposition. Spatially, the higher enrichment of Cu, Pb, and Zn in the soils existed in the mixed broadleafconiferous forests and coniferous forests(approximately 3000 m above sea level). The results suggested that atmospheric deposition and biological processes are main factors controlling the seasonal and spatial distribution of trace metals in the soils of the remote alpine ecosystem.

Three-dimensional cellular automata based particle flow simulations of mechanical properties of talus deposit

Based on three-dimensional cellular automata （CA）, a new stochastic simulation model to simulate the microstructures and particle flow of talus deposit is proposed. Ill addition, an auto-modeling program CARS is developed, with which nunaerical simulations can be conducted conveniently. For the problem of simulating mechanical behaviors of talus deposit, spatial anangement or sphere shapes should be considered. In the new modeling method, four sphere anangement models are developed for the particle flow simulation of talus deposit. Numerical results show that the talus deposit has the mechanical characteristics of typical stress-strain curves, as other rock-like materials. The cohesion of talus deposit decreases with increasing rock content, while the internal friction angle increases with increasing rock contents. Finally, numerical simulation is verified with the results of field test.

砂岩型铀矿找矿中土壤氢气测量方法影响因素研究

放射性元素衰变过程中水辐解会产生大量氢气,而氢气质量轻、迁移快的特点使其在地表就能够被探测到异常,进而能够指导铀矿找矿工作。在已知的巴音戈壁盆地塔木素砂岩型铀矿床、二连盆地巴润砂岩型铀矿床和图门勘探区开展了土壤氢气测量试验研究,从测孔深度、孔闲置时间、测量点距、气体动态平衡情况、最佳采集时间等方面分析了土壤氢气测量方法对铀矿勘查的影响,经与已知地质资料和钻孔资料对比分析得出结论:铀矿化程度、厚度及埋深情况与地表氢气浓度异常呈正相关关系,矿化程度越高、厚度越大、埋深越浅则土壤氢气浓度越高;断裂构造上方均有较好的土壤氢气异常显示,且土壤氢气浓度异常受断裂宽度、断裂含矿或不含矿等因素影响较大;总结了一套有效可行的土壤氢浓度采集方案和工作方法,为铀矿找矿工作提供了新思路和新方法。

土壤光释光测量方法在特拉敖包砂岩型铀矿产地的试验研究

文章以探索新型铀矿放射性勘查技术方法的试验效果为目的,在特拉敖包砂岩型铀矿产地开展了土壤光释光测量方法的试验研究。通过数据处理,综合地质、钻孔和物探相关先验信息,分析评价了土壤光释光测量方法在砂岩型铀矿勘查中的应用效果。试验结果显示:土壤光释光测量等效剂量数据非正态分布,不适宜采用逐步剔除法进行数据异常下限的计算;对数处理后的数据符合近似正态分布,可根据数据分布特征进行异常下限的估算。在铀矿体上方及其附近,存在土壤光释光测量等效剂量异常,表明该方法在砂岩型铀矿勘查领域具有较好的发展前景。通过对异常成因的分析,提出通过不同深度样品等效剂量差的矿致释光异常识别方法。