Advanced Materials Research Vols. 610-613

Abstract: Concentrations and profiles of polycyclic aromatic hydrocarbons (PAHs) were measured in road dust and soil from different functional urban areas in Shanghai. The ΣPAHs concentrations varies from 99.4 to 66900 ng/g dw, where the highest one is found in dust from a chemical industry producing black carbon. The mean concentrations of ΣPAHs for dust increase in the following order of land uses: park and lake area DBahA > BbF > IDP > BkF > BaA > Chr, underlining the importance of BaP as a surrogate compound of a PAHs mixute.

Abstract: The action of freeze-thaw is one of the important influence factors which can cause the changes of soil physicochemical and biological characteristics. During the freeze-thaw period the variations of active organic matters in cropland black soil were studied through the in-situ monitoring and determining methods. The surface soil experienced a series of repeated freeze-thaw actions during the alternate from autumn to winter and from winter to spring. The soil active organic matter was in the trend of fluctuation increase from 8.68 mg kg^-1 to 9.81 mg kg-1 during the seasonal freeze-thaw period. The soil water soluble organic matter was also in a gradually increasing trend, which could increase 33.95% for the surface layer in early April of the next year when compared with that of January. The soil microorganism carbon content increased firstly and then decreased during the seasonal freeze-thaw period, which fluctuated at 912.51-1137.91 mg kg^-1. The research showed that the freeze-thaw action could improve the active organic matter and strengthen the adaptability and activity of microorganism, which could promote the mineralization of organic matter.

Abstract: Chlorinated polycyclic aromatic hydrocarbons (ClPAHs) are a group of halogenated contaminants found in the urban environment with a toxic potential similar to dioxins. Little is well-known on the distribution and characteristics of ClPAHs on urban surfaces. In this study, concentrations of 20 ClPAH congeners were measured in road dust and soil from crossroads along arterial traffic, park and lake areas, a chemical industrial complex, waste incineration power plants nearby, and a steel factory in Shanghai. ClPAHs are ubiquitous and log-normally distribute in urban surface with a range from 0.27 to 206 ng/g dw for dust, and with a range from 0.05 to 94.3 ng/g dw for soils. The highest mean concentration of total 20 ClPAHs is found in floor dust from a steel factory. ClPyr and ClPhe are predominant in road dust, which infers that ClPAHs detected in the urban surface dust samples originate from vehicle exhaust.

Abstract: Danjiangkou reservoir area is the main water source area and submerged area of the Middle Route South-to-North Water Transfer Project of China. Soil erosion is a significant influence factor in reservoir water quality and water transfer project success. The objective of this paper is to assess the soil erosion risk and mapping priority areas for controlling soil erosion of Danjiangkou reservoir area. The results indicated that the top three conservation priority levels cover almost all regions with severe erosion and prominent increase in erosion risk, with a total acreage of 3,531.543km2, accounting for 19.703% of the study area. These three levels to be managed as erosion control regions with appropriate conservation strategies in future projects. The study results will provide guidance in developing and implementing water conservation planning and to assist government agencies in decision-making for determining erosion control area, starting regulation project and making soil conservation measures.

Abstract: Large amount of sediment is brought into the canal system along with the Yellow River water irrigation, which causes deposition in ditches, encroachment of arable land, intensification of soil desertification, blocking of drainage riverway and other environmental damages. On the analysis of sediment properties as a natural resource, this article introduces sediment utilization approaches at present such as farmland improvement, embankment reinforcement, construction use and subsidence land filling, which produce ecological and economic benefits and set good examples for the future sustainable utilization of sediment resource in irrigation districts.

Abstract: With the application and promotion of genetically modified crops, the safe of Bt-transgenic crops on soil had become one of the hot spot. In present study, two parallel experiments were conducted to compare the impacts of transgenic cotton on the rhizosphere soil properties in northern China. The results showed that the pH value increased, except for the cotton 33B. Furthermore, the change extent varied with Bt transgenic cotton and non Bt cotton. In addition, organic total carbon、 total nitrogen and available nitrogen decreased, while these of GK-12 increased. In general, the effect was different from cotton cultivar. Available P and K in the rhizosphere zone increased among all cotton cultivars tested, and no significant difference was found between Bt and non-Bt cotton

Abstract: Evapotranspiration (ET) constitutes the dominant water loss from many different types of wetlands. The relative importance of ET is apparent in its influence over water depth, temperature and salinity. However, direct measurement of ET, especially for wetland, is difficult, costly, and rarely available. In this study, the Penman-Monteith model was selected to estimate the reference evapotranspiration for short and tall canopies, moreover, Hargreaves equation was also used to simulate the ET_ref and test the precision of Penman-Monteith method. The results show that the reference evapotranspiration are maximal between June and August and minimal in winter, and ET_rs is larger than ET_os in the whole simulation periods. H ET₀ and ET_os have the same variation trend, but the former was smaller than the latter during May to September. Finally, there is a strong correlation between ET_os and ET_rs, with the correlation coefficient are 0.98 and 0.99 at daily and monthly means scale.

Abstract: Study on the distributive characteristics of the soil microorganisms at floodplain on wetland of Mongolian plateau. Using the Plate dilution method to determine the 0~10cm, 10~20cm, 20~30cm, 40~50cm and 50~60cm soil samples, soil aerobic bacteria, bacillus type bacteria, fungus and actinomycetes bacteria number, the results show that with the deepening of the soil depth, the number of aerobic bacteria number reduced, the peak value of the number of aerobic bacteria in the 0~10cm soil layer, the minimum number in the 50~60cm soil, 0~10cm and the other four soil there was a significant difference, there was no significant difference between the other four soil layers. The Bacillus type bacteria have a high ratio of total aerobic bacteria in 0~10cm, the surface of the soil with a high ammonification quality but also the best. The peak of the number of fungus in 0~10cm, followed by 10~20cm and 30~40cm and 20~30cm, 40~50cm, 50~60cm no isolated fungus. There is no actinomycetes separation in the 10-3 cfu.g-1dry soil dilution.

Abstract: To analyze reclaimed water irrigation effects upon soil quality, including indicators of secondary salinization and heavy metal accumulation, a field experiment in the typical reclaimed water irrigated area (Xin-he irrigated area, Tongzhou District) was carried out in this study. The treated soils for sampling and analyzing were irrigated with reclaimed water and well water. Soil heavy metal contents were determined by ICP-AES, while those of soil salt ions were determined by DX 600. Results show that, reclaimed water irrigated soil has a significant increase in salt ion contents than well irrigated soil, with an increasing order of Na⁺ >K⁺ >Mg ²⁺ >Ca ²⁺ . And Ca ²⁺ 、Mg ²⁺ 、Na⁺ accumulations at 40~80 cm and140~180 cm are relatively critical. Vertical trends of sodium adsorption ratio(SAR) values of soil extraction are the same in districts irrigated with reclaimed water and well water, however, SAR values of reclaimed water irrigated soil are significantly higher than well irrigated soil, with an average of 5~6 times bigger. But values are still in the suitable level for crops. Although heavy metals(Cu、As、Ni、Pb and Zn) slightly accumulate at 140~200cm, values are still consistent with soil environmental standard grade of 1or 2. And contents of heavy metals have no obvious differences between soils irrigated with reclaimed water and well water at 0~140cm.

Abstract: An incubation experiment was carried out to study various available N pools and enzyme activities in the soil near fertilizers under controlled temperature and soil moisture. Fertilizers added into soil were chemical fertilizer supplied as urea, organic fertilizer as rapeseed straw, and mixture of urea and rapeseed straw in a ratio of 7:3, respectively. 30 days after incubation, NH+4-N, NO-3-N and 1 N NaOH- hydrolyzed N increased in the soil at < 2.5 cm from the fertilizers in two lateral directions, and progressively decreased as the distance to the fertilizers increased. The results indicated the intensive available N release from the fertilizers and easy movement of fertilizer N. Taking into account of dense roots in cultivated soil layers and easy migration of N fertilizers, broadcast application of N fertilizers could be efficient in the middle growing periods of crops. There was neither obvious influence of urea application on urease activity nor significant correlation between urease activity and NH4+-N in the soil. Therefore, it seems reasonable to suggest that urea hydrolysis catalyzed by urease might be fast, unlikely the rate-limiting step in the process of urea transformation into NH4+-N. Further study showed the high activities of saccharase and protease in the soil only at 0.25 cm from the organic fertilizers added either in pure rape straw or mixture with urea. Saccharase and protease on the interface between organic fertilizer and soil could thus accelerate N release of organic fertilizers as available forms through organic N decomposition, resulting in the high available N pools in the soil near organic fertilizers.