Geochemical Implication of Rare Earth Elements in Process of Soil Development

The geochemical characteristics and behavior of rare earth elements (REE) in soils developed on the basalts in the northern part of Hainan Island erupted in different time were studied as well as the REE partition in the soil-formation process and its implication on soil development degree. The results show that the total REE content in soils is correlative with soil age significantly and can be selected as the index to show soil evolution. With the soil developing intensively, light rare earth elements (LREE) gain and heavy rare earth elements (HREE) lose. The trends of positive Ce-anomaly and negative Eu-anomaly are remarkable with soil development.

Contents and Distribution of Rare Earth Elementsin Main Types ofSoilsin China

Forty four soils representing the eight types of soils in China were sampled, and their total rare earths and La, Ce, Nd, Sm and Y contents were measured by spectrophotometric and ICP AES methods, averaging 264, 43 7, 86 2, 35 8, 8 38, and 21 8 μg·g -1 , respectively. Rare earth elements were accumulated and leached to a different extent in the various soil forming processes, but REE contents in the soils showed no zonal variation. The available rare earth contents in the sixty one soil samples, averaging 24 9 μg·g -1 , present a decreasing trend from the South to the North in China. About 17% of the total acid soil samples are lower than 10 μg·g -1 in available rare earths, whereas 77% of the total neutral and calcareous soil samples are below the value. Availability of soil REE is primarily affected by pH, Eh(redox potential), and clay contents in the soils.

Effect of Organic Manure on Phosphorus Adsorption－Desorption and Availability in Paddy Soil Derived from Red Earth

A field test with the traditional rotation of paddy rice/upland crop (wheat) was carried out on a paddysoil derived from red earth to elucidate the effect of organic manure on the phosphorus adsorption-desorptionby soil and its P availability Soil samples were taken from different treatments at rice harvesting stage andanalysed. The isothermal adsorption of P by the samples fitted very well with Langmuir equation, and hence,the parameters in the equation, i.e., maximum adsoaption (qm), constant related to bonding energy (k) andtheir product (k x qm) could be used as a comprehensive index to characterize the potential P adsorptivityof the soil.Organo-inorganic fertilization and organic manuring conld decrease qm and k, while mineral P appli-cation had little effect on them. The isothermal desorption of P was significantly correlated with initiallyadded and isothermally adsorbed P. Part of P added was fixed, which represented the P fixation capacityof soil, and organic manuring could obviously lower the P fixation. The content of soil available P had asignificant negative correlation with qm, k and fixed P. It is concluded that organic manure could increase theP availability of paddy soil derived from red earth by decreasing qm, k, maximum buffering capacity (MBC=k x qm) and fixation capacity.

Geochemical Characteristics of Rare Earth Elements in Different Types of Soils in China

The contents, distribution patterns, and specification of rare earth elements(REEs) in latosol(tropical zone), red earth(middle subtropical earth), yellow brown soil(northern subtropical earth), cinnamon soil(warm temperate zone), leached chernozem(temperate zone) and albic bleached soil(temperate zone) in China were determined with instrumental neutron activation analysis(NAA) and systematically studied. The results indicate that yellow brown soil, cinnamon soil, leached chernozem and albic bleached soil are characterized by light REEs(LREEs) enrichment and Eudepletion, while latosol and red earth are characterized by LREEs enrichment and Cedepletion. REEs exist mainly in a stable residual form in the six soils, and with increasing atomic number, the intermediate REEs(IREEs) of residual form have lower proportion than light and heavy REEs. For the six unstable forms, the proportions of watersoluble, exchangeable, specific absorption, and carbonate forms are lower. Appearent zonal distribution patterns of REEs were found in the form of FeMn oxides in different types of soils, and the general trend gradually decreases from southern to northern China. Proportions of REEs in bound organic matters are higher and follow the order: albic bleached soil>leached chernozem>red earth>latosol>yellow brown soil>cinnamon soil. Higher proportion of REEs exists in soils with higher proportion of organic matters. But their activation differs greatly with difference in relative proportions of loosely bound organic matter form and tightly bound organic matter form.

Effect of Rare Earths on Fractionation and Transformation of Soil Available Nitrogen

The effect of rare earths (RE) on fractionation and transformation of available nitrogen in a yellow cinnamon soil was studied with soil cultivation. The results show that under the dry condition, when the extraneous RE are added to the soil, both concentrations of soil ammonium N and hydrolysable N increase, and the concentrations of soil nitric N decrease. The concentrations of soil available N increase with the increase of RE concentrations in soils when the RE concentrations are low, but it decreases with the increase of high RE concentrations in soils. The NOEC (no observed effect concentration) of the extraneous RE to available N in the soils is 443.8 mg·kg -1 . Under the inundated condition, low RE concentrations in soil has no significant effect on soil ammonium N and hydrolysable N. However, when the soil RE concentrations are high, both of them decrease with the increase of RE concentrations. The NOEC of the extraneous RE to soil ammonium N and hydrolysable N are 171.2 and 256.9 mg·kg -1 , respectively.

Does the long-term application of calcium superphosphate lead to an increase of the soil rare earth element contents？

In order to test whether the long-term application of calcium superphosphate leads to an increase of the soil rare earth element contents, superphosphate fertilized soils were sampled and compared with superphosphate-free soils. Spectrophlame inductively coupled argon plasma atomic emission spectrophotometer （ICP-AES） was applied to quantify the rare earth elements （REEs）. The total rare earth element contents in calcium superphosphate from Zhijin County, west part of Guizhou Province, China （produced by the sulphuric acid treatment of the apatites） are about 2.54 mg/g. Between 38 and 189 gREEs/hm^2 per year （available for plants, estimated by 2% citric acid） will be introduced into the soil solution when applying 320 kg superphosphate/hm^2 per year. The long-term application of the latter will increase the REE content by about 18% in the soil surface layer in these areas. A statistically significant increase of the content of the rare earths in some cultivated soils should not be neglected.

Accumulation of Rare Earth Elements in Spinach and Soil under Condition of Using REE and Acid Rain Stress

The content and distribution characteristics of REE in spinach and soil under using REE and acid rain stress were studied by pot experiments. The results show that the content of REE is 0 527～0 696 (μg·g -1 ) in the above ground portion of spinach, 2 668～3 003 (μg·g -1 ) in the under ground portion of spinach and 229 09～250 30 (μg·g -1 ) in the soil. With the acidity of acid rain increasing, the leaching of REE in plants and soil is strengthened and the amount of REE reduces with decreasing of pH value. After REE are used, though plants show the selective absorption to Ce group elements (especially spraying on leaves), regardless under acid rain stress or using REE or not, the distribution model of REE in the above ground and under ground portion of plants is basically the same with the control. Plants also follow the Oddo Harkins rule of the REE of distribution abundance, light rare earth elements is enriched, the minus of Eu is abnormal and admeasure of Ce is a rich model. The results show that REE in plants mainly come from soil and are affected by it.

Spatial-temporal variations in near-surface soil freeze-thaw cycles in the source region of the Yellow River during the period 2002–2011 based on the Advanced Microwave Scanning Radiometer for the Earth Observing System(AMSR-E) data

Detecting near-surface soil freeze-thaw cycles in high-altitude cold regions is important for understanding the Earth＇s surface system, but such studies are rare. In this study, we detected the spatial-temporal variations in near-surface soil freeze-thaw cycles in the source region of the Yellow River（SRYR） during the period 2002–2011 based on data from the Advanced Microwave Scanning Radiometer for the Earth Observing System（AMSR-E）. Moreover, the trends of onset dates and durations of the soil freeze-thaw cycles under different stages were also analyzed. Results showed that the thresholds of daytime and nighttime brightness temperatures of the freeze-thaw algorithm for the SRYR were 257.59 and 261.28 K, respectively. At the spatial scale, the daily frozen surface（DFS） area and the daily surface freeze-thaw cycle surface（DFTS） area decreased by 0.08% and 0.25%, respectively, and the daily thawed surface（DTS） area increased by 0.36%. At the temporal scale, the dates of the onset of thawing and complete thawing advanced by 3.10（±1.4） and 2.46（±1.4） days, respectively; and the dates of the onset of freezing and complete freezing were delayed by 0.9（±1.4） and 1.6（±1.1） days, respectively. The duration of thawing increased by 0.72（±0.21） day/a and the duration of freezing decreased by 0.52（±0.26） day/a. In conclusion, increases in the annual minimum temperature and winter air temperature are the main factors for the advanced thawing and delayed freezing and for the increase in the duration of thawing and the decrease in the duration of freezing in the SRYR.

Rare earth elements in tropical surface water,soil and sediments of the Terengganu River Basin,Malaysia

The 14 stable rare earth element(REE) concentrations and distribution patterns were investigated for surface waters(n=51),soils(n=52) and sediments(n=42) from the tropical Terengganu River basin,Malaysia.The chondrite normalized REE patterns of soils developed on four geological units showed enrichment of LREE,a pronounced negative Eu,and depletion of HREE with an enrichment order granite>>metasedimentary>alluvium>volcanic.The REE patterns in sediments reflected the soil REE patterns with an ove...

Effect of Exogenous Rare Earths on Microbial Characteristics in Paddy Soil

An incubation study was performed to elucidate exogenous rare earth elements (RE) influencing on microbial biomass, microbial ecophysiological parameters c_(mic)/c_(org), metabolic quotient q_(CO_2) and respiratory rate in relation to temporal availability in paddy soil. Six samples were added different concentrations between 0 and 2000 mg·kg^(-1) REEs in soil. Results show that exogenous RE have slight stimulative effects on microbial indices in paddy soil at low concentration in the early stage after adding RE, while having inhibitory effects at high concentration. The inhibition is strengthened with increasing RE concentration and is weakened with increasing incubation time. Principal component analysis of the BIOLOG data indicates that microbial community structures have changed, carbon sources consumption of microorganisms in paddy soil becomes much more rapid after 8 weeks, and under RE stress, the change of microbial community structures is a long-term effect.

Characterization of Clayey Soils from Congo and Physical Properties of Their Compressed Earth Blocks Reinforced with Post-Consumer Plastic Wastes

Physical properties of compressed earth blocks reinforced with plastic wastes are compared to those of nonreinforced ones. These bricks are made with two clayey soils from two deposits of Congo located in Brazzaville and Yengola. Mineralogical and geotechnical analysis revealed that the soil of Brazzaville is mainly composed of kaolinite whereas that of Yengola is a mixture of kaolinite and illite. The amounts of clay (46 and 48%, respectively) are higher than those usually recommended for bricks’ production without stabilizers. Despite this difference of mineralogical compositions, the physical properties of these soils are quite similar. The compressive strength of the resulted bricks compacted with an energy of 2.8 MPa is about 1.5 MPa, which is the lower limit value allowed for adobes. Reinforcing with polyethylene waste nets increased the strength by about 20 to 30% and slightly enhanced resistance to water, Young’s modulus and strain to failure. However, the reinforcement had no significant effect either on bricks’ curing length or on their shrinkage.

Correlations between Light Rare Earth Elements in Soil and Navel Orange Tree System in Gannan Area

The total content of light rare earth elements( LREEs) in the soil of navel orange orchards of Gannan area is greater than that of heavy rare earth elements( HREEs). Appropriate content of LREE can not only promote the growth of navel oranges,and it is also conducive to human health. On the basis of exploring the correlations between the content of LREE in the soil of navel orange orchards of Gannan area and the contents of LREE in navel orange leaves and fruit,the influence mechanism of LREEs on the quality of navel oranges was revealed. In this study,with two Newhall navel orange orchards with different soil LREEs background levels in Xinfeng County as the research object,the changes in the content of LREE( lanthanum,La; cerium,Ce; praseodymium,Pr; neodymium,Nd) in leaves and fruit of navel orange at different growth stages were analyzed using Inductively Coupled Plasma-Mass Spectrometry( ICP-MS),and the correlations between the content of LREE in the soil,navel orange leaves and navel orange fruit were studied. The results showed that the contents of the four kinds of LREEs in the soil ranked as Ce > La > Nd > Pr,and there were significant differences among them( P < 0. 01). Navel orange leaves and fruit have selective and heterogenic absorption for LREEs. At different growth stages,La showed the highest accumulation amount in the leaves and fruit of navel orange; and the content of LREE in the leaves of navel orange increased first and then decreased,while that in the fruit of navel orange showed continuous decrease. During the migration of LREEs from soil to leaves to fruit,the content of LREE decreased rapidly as the migration distance increased. The accumulation amount of LREE in navel orange was positively correlated with the content of LREE in the soil. The correlation between the content of LREE in the leaves and fruit of navel orange was greatest. Among the four kinds of LREEs,the correlation of La was greatest,followed by Ce,indicating that the accumulation amount of LREE in the navel orange body was affected by the element types.

Accumulation and Fractionation of Rare Earth Elements in Soil-Rice Systems

Accumulation and fractionation of rare earth elements （REEs） were studied through applications of exogenous REEs in soils with pot-cultured rice for 2 years. The results show that the biomass of rice consistently decreases at sprouting and maturity stages when the amount of exogenous REEs are over 400 mg· kg^- 1. It illustrates that the endurance of rice to exogenous REE exposure is much weaker than that of wheat. The distribution patterns of REEs in rice of the control are similar to that in the soil, both exhibiting light REE （LREE） enrichment and positive Tb in the roots and the aboveground parts. Applications of exogenous REEs ranging from 400 to 1200 mg· kg^- 1 have significant effects on the distribution patterns of REEs in roots, some effects in stems and leaves, and almost no effects in grains. Accumulation rates of REEs in different organs follow the order of roots 〉 leaves 〉 stems 〉 panicle axes and crusts 〉 grains. The roots take up different REEs at almost the same rates, except for the selective accumulation of Th. In the aboveground parts, the accumulation rates of middle REEs （MREEs） and heavy REEs （HREEs） are higher than those of LREEs, there are significant selective accumulations of Eu and Tb. Accumulation rates of REEs in the roots, stems and leaves increase with the increasing applications of exogenous REEs, but they change slightly in the panicle axes, crusts and grains, demonstrating that it is easier for the roots, stems and leaves to accumulate exogenous REEs. Selective accumulation and fractionation of exoge nous Nd are also observed in rice organs including grains.

The Characteristics of Adsorption and Desorption of Rare Earth Elements by the Main Types of Soils of China

The adsorption-desorption behavior of the mixed rare earth elements(RE)on the main types of soils of China,kaolinite and synthetic oxides was studied.The isothermal adsorption of RE was fitted to Langmuir.Freundlich and Temkin equations.The main factors determining the RE adsorption capacity of the soils are the type of clay mineral and the content of amorphous iron oxide in the soils.The above two fac- tors and the pH of soil determine the RE adsorption ability of the soils.The soil and synthetic iron,manga- nese oxides strongly adsorb RE specifically.

Grey Interrelation Analysis for the Use of Rare Earths and the Elements in Soil in Growing Cotton

The method of grey interrelation analysis is adopted for the analysis of the relationship between the amount of rare earths applied and the factors of the soil in increasing cotton production in Kazuo County, Liaoning Province. The results show that there is an intimate relation between the use of the RE and the elements in the soil. The pH value, total K, and total P are the main factors influencing the relation, and the total N, hydrolytable N, organic matter, K2O and P2O5 are the secondary factors. This provides a scientific basis for the use of the RE.

Calculation of passive earth pressure of cohesive soil based on Culmann's method

Based on the sliding plane hypothesis of Coulumb earth pressure theory, a new method for calculation of the passive earth pressure of cohesive soil was constructed with Culmann＇s graphical construction. The influences of the cohesive force, adhesive force, and the fill surface form were considered in this method. In order to obtain the passive earth pressure and sliding plane angle, a program based on the sliding surface assumption was developed with the VB.NET programming language. The calculated results from this method were basically the same as those from the Rankine theory and Coulumb theory formulas. This method is conceptually clear, and the corresponding formulas given in this paper are simple and convenient for application when the fill surface form is complex.

Regularity of Erosion and Soil Loss Tolerance in Hilly Red-Earth Region of China

The observations from 14-yr long-term investigation on the soil-water losses in the sloping red-earth (slope 8°- 15°) showed that soil-water losses were closely correlated with land slope and vegetative coverage. Runoff rate in sloping red-earth could be reduced doubly by exploitation, while the soil erosion was enhanced doubly during the first two years after exploitation. Subsequently, it tended to be stable. Soil erosion was highly positively correlated with land slope, i. e. soil erosion increased by 120 t km-2 yr-1 with a slope increase of 1°. On the contrary, soil erosion was highly negatively correlated with vegetative coverage, i. e. soil erosion was limited at 200 t km-2 yr-1 below as the vegetative coverage exceeded 60%. Furthermore, soil erosion was highly related with planting patterns, i. e. soil erosion in contour cropping pattern would be one sixth of that in straight cropping. Based on the view of soil nutrient balance and test data, it was first suggested that the soil loss tolerance in Q2 red clay derived red-earth should be lower than 300 t km-2 yr-1.

Achieving Cooler Soil as an Effective Heat Sink for Earth-to-Air Heat Exchanger (EAHE) Cooling Technology in Malaysia Tropical Climate

This research is intended to explore the capacity of Malaysia soil in becoming a more effective heat sink for the application of Earth-to-Air Heat Exchanger (EAHE) Cooling Technology in Malaysia. EAHE Cooling Technology consists of buried pipes underground where the ambient air is channeled through from the pipe inlet and produces cooler air at its outlet. Within the buried pipes, heat exchange process occurs between the air and the soil that surrounding the pipe. This building cooling technology has been applied in many countries, mostly in temperate or hot and arid climate where the diurnal temperature is large. However, minimal resources were found on the study of EAHE application to buildings in Malaysia, hence there is room to develop. A parametric study on EAHE cooling application in Malaysia was done through field experiment and concluded that among many parameters affecting the technology performance, the soil temperature which surrounded the pipe was the most influential factor. The study recommended to further reduce the soil temperature to achieve a cooler outlet temperature. In response to that, this research conducted a parametric study of soil temperature under three different soil surface conditions: bare, shaded with timber pallettes and insulated with used tyres at 1.0 m and 1.5 m underground. The data was logged for a month and the result has shown significant reduction in the soil temperature underground below the shaded and insulated soil surface as compared to below bare soil surface condition. The insulated soil surface produced the best result where the soil temperature was reduced up to 26.9°C. The main contribution of this paper is to highlight that the soil surface treatment can be used to reduce solar heat gain within the soil underground and thus improving the performance of EAHE Cooling Technology particularly for the application in Malaysia tropical climate.