土壤中砷的形态及生物有效性研究

土壤中砷的可移动性主要取决于其存在形态,并决定了其生物有效性,生物对不同形态砷的吸收利用程度亦不同,本文阐述了土壤中砷的形态及生物吸收的研究进展,总结了砷的生物有效性研究概况,对影响砷生物有效性的主要因素展开分析。其不仅与重金属本身的化学形态和结合相态有关,还受土壤化学性质及土壤环境中的物理、化学及生物作用影响,砷的生物有效性是砷地球化学形态的一种表征。文中最后指出需要解决的问题与今后的发展方向。

小流域土壤侵蚀及径流过程自动测量系统的实验应用

流域内降雨-径流-土壤侵蚀过程中不同时空点处流量、流速、泥沙含量的获取是土壤侵蚀机理研究中的难点,其实时、准确测量为侵蚀模拟-预报模型的建立与检验提供必要的数据支持。该文针对这一问题,将量水堰及水位传感器、薄层水流流速测量系统、γ射线泥沙含量测量仪有机组合,构成流域土壤侵蚀过程测量系统。将该系统测量仪器布设于室内小流域模型各沟道出口及沟道内典型点处,在降雨强度25 mm/h,降雨历时5 m in条件下,系统测量的流域出口处流量及泥沙含量变化值与采用手工采样方法测量结果的决定系数R2分别为0.738,0.749,流速误差为8.7%,比较结果显示该系统具有较高的测量精度。在此测量精度范围内,同时测得各沟道口流量及泥沙含量动态变化过程及沟道中典型点处流速。流域内径流过程及径流含沙量的动态测量结果表明将该系统应用到土壤侵蚀动态过程的研究中是可行的。

湘中安化黑色页岩土壤玉米的元素地球化学分析

利用等离子质谱(ICP-MS)等分析技术,对产于安化东坪、烟溪黑色页岩土壤上的玉米进行元素地球化学分析。结果表明:尽管东坪、烟溪黑色页岩土壤重金属元素富集的程度及其元素组合特征明显不同,但生长在其上的玉米有相似的主量元素和重金属元素的富集特征。玉米中Cd、Cr、Sc、Tl、Zn等重金属相对富集,以Cd的富集尤为明显;而Ba、Co、Cu、Fe、Mo、Ni、Pb、Sb、U、V等重金属相对亏损。黑色页岩土壤重金属污染的环境地球化学效应表现为Sc、Cr、Cd、Tl等生物毒性重金属元素在玉米中富集,而Ba、V、Co、Ni、Mo、Rb、Sr等生物必需微量金属在玉米中亏损。

The Distribution Characteristics of Soil pH Values of Tobacco-growing Areas in Dali City and Its Correlation with Soil Nutrients

[Objective] The aim was to study the distribution characteristics of soil pH values and its correlation with soil nutrients in tobacco-growing areas. [Method] Soil nutrients of 43 samples from tobacco-growing areas in Dali City were analyzed.[Results] The results showed that average pH value of tobacco-planting soil in Dali City was 6.52, soil samples which suited for flue-cured tobacco cultivation accounted for 72.09% of total soil samples. In four soil types of tobacco-growing areas, the pH values in a descending order were as follows： alluvial soil〉 paddy soil 〉purple soil〉 red soil. At the altitude range of 1 780-2 200 m, soil pH values showed a gradual decreasing trend. The average contents of soil organic matters were relatively abundant and generally suited for high-quality tobacco cultivation; the average contents of soil alkali-hydrolyzable nitrogen, available phosphorus, exchangeable calcium and exchangeable magnesium were generally at medium and abundant level, however,their rations under the medium level in some tobacco-growing areas were 6.98%,11.63%, 2.33% and 4.65%, respectively; moreover, soil with lower available potassium contents occupied a large proportion, namely 58.14%. [Conclusion] Soil pH values had significant correlation with exchangeable magnesium and exchangeable magnesium, however, they had no significant correlation with other soil nutrients.

Nitrate and Ammonium Leaching in Variable-and Permanent-Charge Paddy Soils

A variable-charge （VC） and a permanent-charge paddy soil （PC） were selected to study nitrate-N （NO3^--N） and ammonium-N （NH4^＋-N） leaching with N isotopes for one consecutive year. An irrigation and intermittent drainage pattern was adopted to mimic natural occurrence of rainfall during the upland crop season and drainage management during the flooded rice season. Treatments to each soil type were no-N controls （CK）, ^15N-labeled （NH4）2SO4 （NS）, and milk vetch （NV） applied at a rate equivalent to 238 kg N ha^-1 to unplanted lysimeters, totaling six treatments in triplicates. Results indicated that the soil type dominated N leaching characteristics. In the case of PC, NO3^--N accounted for 78% of the total leached inorganic N; NS was prone to leach three times more than the NV, being 8.2% and 2.4% of added ^15N respectively; and 〉 85% of leached NO3-N came from of the total inorganic N in leachate. Moreover, NH4^＋-N native N in the soil. In the case of VC, NH4^＋-N made up to 92% leaching was detected throughout the whole incubation, and was particularly high during the flooded season. NO3^--N leaching in VC occurred later at a lower rate compared to that in PC. The findings of this study indicate that NO3^--N leaching during the drained season in permanent-charge paddy soils and NH4^＋-N leaching in variable-charge soils deserve more attention for regional environmental control.

Analysis of pH Value and Primary Nutrients in Blueberry Garden Soil

In order to explore the soil nutrient characteristics and put forward the improvement measures, a field experiment was arranged and performed. The experiment was conducted to evaluate the pH value and primary nutrient status in blueberry garden soil by means of collecting 21 soil samples from the main production base of blueberries in Qingdao, according to the specific requirements of blueberries for soil pH and organic matter and the second national soil survey nutrient classification standard. Results showed that the blueberry garden soil had the following characteristics： acidic soil, low organic matter content with significant differences among different bases, moderate total nitrogen and alkaline hydrolysis nitrogen contents, high available phosphorus content and above moderate available potassium content. Then, it is found that the primary causes were the differences in soil basic fertility, excessive use of sulfur, inadequate inputs of organic matter, not thorough soil improvement, and imperfect fertilizer management in the blueberry gardens. Finally, the corresponding improvement measures were put forward, for example, increasing organic fertilizer and organic matter covering, as well as the application of CaCO_3 and formulated fertilization.

Relationship of Soil Qualities to Maize Growth Under Increasing Phosphorus Supply in Acid Soils of Southern Cameroon

A large array of soil properties influences plant growth response to phosphorus(P) fertilizer input in acid soils. We carried out a pot experiment using three contrasted acid soils from southern Cameroon with the following main objectives:i) to assess the main soil causal factors of different maize(Zea mays L.) growth response to applied P and ii) to statistically model soil quality variation across soil types as well as their relationships to dry matter production. The soils used are classified as Typic Kandiudox(TKO) ,Rhodic Kandiudult(RKU) ,and Typic Kandiudult(TKU) . Analysis of variance,regression,and principal component analyses were used for data analysis and interpretation. Shoot dry matter yield(DMY) was significantly affected by soil type and P rate with no significant interaction. Predicted maximum attainable DMY was lowest in the TKO(26.2 g pot-1) as compared to 35.6 and 36.7 g pot-1 for the RKU and TKU,respectively. Properties that positively influenced DMY were the levels of inorganic NaHCO3-extractable P,individual basic cations(Ca,Mg,and K) ,and pH. Their effects contrasted with those of exchangeable Al and C/N ratio,which significantly depressed DMY. Principal component analysis yielded similar results,identifying 4 orthogonal components,which accounted for 84.7% of the total system variance(TSV) . Principal component 1 was identified as soil nutrient deficiency explaining 35.9% of TSV. This soil quality varied significantly among the studied soils,emerging as the only soil quality which significantly(P < 0.05) correlated with maize growth. The 2nd,3rd,and 4th components were identified as soil organic matter contents,texture,and HCl-extractable P,respectively.

Characterization of Soil Quality Under Vegetable Production Along an Urban-Rural Gradient

Human activity and urbanization result in urban-rural environmental gradients. Understanding effect of the gradients on soil properties is necessary for management of the soils around urban areas. In this study, soil quality of some vegetable fields was characterized along an urban-rural gradient in Shaoxing County, Zhejiang Province. Fifteen soil physical and chemical properties were evaluated by using principal component analysis.Results showed that there was a great variation in the soil quality along the gradient. From rural to urban zones, soil organic matter, water-stable aggregates, cation exchangeable capacity (CEC), total N and P, and available K increased, whereas soil pH value decreased. In addition, Pb, Cu, Ni, Co, Zn and Cr in the soils tended to be accumulated toward the urban zone. Sequential chemical extraction showed that mobility of all the heavy metals in the soils tended to increase from the rural to the urban zones. The variation of soil properties accounted for by the first principal component was significantly explained by the difference in application rates of municipal wastes.

Effect of Reclamation Time and Land Use on Soil Properties in Changjiang River Estuary,China

The objective of this study is to analyze soil physical and chemical properties,soil comprehensive functions and impact factors after different years of reclamation.Based on the survey data taken from 216 soil sampling points in the Fengxian Reclamation Area of the Changjiang (Yangtze) River Estuary,China in April 2009 and remotely sensed TM data in 2006,while by virtue of multivariate analysis of variance (MANOVA),geo-statistical analysis (GA),prin-cipal component analysis (PCA) and canonical correspondence analysis (CCA),it was concluded that:1) With the in-crease in reclamation time,soil moisture,soil salinity,soil electric conductivity and soil particle size tended to decline,yet soil organic matter tended to increase.Soil available phosphorous tended to increase in the early reclamation period,yet it tended to decline after about 49 years of reclamation.Soil nitrate nitrogen,soil ammonia nitrogen and pH changed slightly in different reclamation years.Soil physical and chemical properties reached a steady state after about 30 years of reclamation.2) According to the results of PCA analysis,the weighted value (0.97 in total) that represents soil nutrient factors (soil nitrate nitrogen,soil organic matter,soil available phosphorous,soil ammonia nitrogen,pH and soil particle size) were higher than the weighted value (0.48 in total) of soil limiting factors (soil salinity,soil elec-tric conductivity and soil moisture).The higher the F value is,the better the soil quality is.3) Different land use types play different roles in the soil function maturity process,with farmlands providing the best contribution.4) Soil physi-cal and chemical properties in the reclamation area were mainly influenced by reclamation time,and then by land use types.The correlation (0.1905) of the composite index of soil function (F) with reclamation time was greater than that with land use types (-0.1161).

Strain Mesorhizobium sp.CCNWGX035:A Stress-Tolerant Isolate from Glycyrrhiza glabra Displaying a Wide Host Range of Nodulation

Thirty-nine rhizobial isolates were isolated from the root nodules of Glycyrrhiza uralensis and Glyeyrrhiza glabra, growing in the arid and semiarid regions of northwestern China, to test their taxonomic position and stress tolerance and to select one promising putative inoeulant strain for further studies. On the basis of 113 physiological and biochemical characteristics, the isolates were clustered into three groups. One isolate CCNWGX035 was found to have high tolerance to NaC1, pH, and temperature. By sequencing the 16S rDNA, isolate CCNWGX035 was placed in genus Mesorhizobium. Nodulation tests demonstrated that the isolate not only formed nitrogen-fixing nodules on its original host plant Glyeyrrhiza glabra, but also on Sophora vieiifolia, Lotus cornieulatus, Trifolium repens, Melilotus suaveolens, and Sophora alopecuroides. On the basis of sequence analysis of the nodA gene, isolate CCNWGX035 was closely related to strains of the genus Mesorhizobium, exhibiting some novel characteristics of root nodule bacteria.

Performance analysis of semi-active cab’s hydraulic system of the vibratory roller using optimal fuzzy-PID control

In order to evaluate the performance of semi-active cab’s hydraulic mounts(SHM)of the off-road vibratory roller with the optimal fuzzy-PID(proportional integral derivative)control,a nonlinear dynamic model of the vehicle interacting with off-road terrains is established based on Matlab/Simulink software.The weighted root-mean-square(RMS)acceleration responses of the driver’s seat heave and the cab’s pitch angle are chosen as objective functions.The SHM is then optimized and analyzed via the optimal fuzzy-PID control under different operation conditions.The simulations results show that the driver’s ride comfort and the cab shaking are greatly affected by the off-road terrains under various operating conditions of the vehicle,especially at the speed from 8 to 12 km/h on a very poor terrain surface of Grenville soil ground under the vehicle travelling.With SHM using the optimal fuzzy-PID control,the driver’s ride comfort and the cab shaking are clearly improved under various operation conditions of the vehicle,particularly at the speed from 6 to 7 km/h of the vehicle traveling.

Polychlorinated biphenyis in Beijing soil of China

The concentrations of polychlorinated biphenyls （PCBs） have been determined in soils collected in Beijing of China. According to Principle Component Analysis （PCA） of PCBs, the possible sources were studied. Relationship between PCBs and soil organic materials revealed that higher chlorinated PCBs are more inclined to be adsorbed by particles rich of organic materials. But the low chlorinated homologues are dominant in Beijing soils, which is very different from the foreign studies. It was concluded that the application of relatively low chlorinated commercial PCBs in China was the main reason leading to this homologue composition character. Besides, the relatively short pollution history is also one of the main reasons. PCA of PCBs data in Beijing soil and atmospheric deposition samples revealed that some other emission sources such as atmospheric deposition, automobile exhaust; chemical and petrochemical industry and steel industry may be the important reasons of elevated PCBs concentrations in Beijing soil

Minimum Data Set for Assessing Soil Quality in Farmland of Northeast China

Soil quality assessment provides a tool for agriculture managers and policy makers to gain a better understanding of how various agricultural systems affect soil resources. Soil quality of Hailun County, a typical soybean （Glycine max L. Merill） growing area located in Northeast China, was evaluated using soil quality index （SQI） methods. Each SQI was computed using a minimum data set （MDS） selected using principal components analysis （PCA） as a data reduction technique. Eight MDS indicators were selected from 20 physical and chemical soil measurements. The MDS accounted for 74.9% of the total variance in the total data set （TDS）. The SQI values for 88 soil samples were evaluated with linear scoring techniques and various weight methods. The results showed that SQI values correlated well with soybean yield （r = 0.658＊＊） when indicators in MDS were weighted by the regression coefficient computed for each yield and index. Stepwise regression between yield and principal components （PCs） indicated that available boron （AvB）, available phosphorus （AvP）, available potassium （AvK）, available iron （AvFe） and texture were the main factors limiting soybean yield. The method used to select an MDS could not only appropriately assess soil quality but also be used as a powerful tool for soil nutrient diagnosis at the regional level.