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991.
992.
Due to easy volatilization of volatile organic compounds from water,it is difficult to monitor their aerobic biodegradation in the traditional single water system.Whether a two-liquid-phase system(TLPS) could overcome this obstacle and enhance the degradation of volatile contaminants? In this study,a TLPS composed of silicone oil and water was employed to investigate the biodegradation of volatile compounds,trichlorobenzenes(TCBs),by the adapted microorganisms in an activated soil.The degradation and volatilization of TCBs in TLPS and in a single water system were compared.The results showed that due to volatilization losses of TCBs,the mass balance of TCBs in a single water system was very low.In contrast,using TLPS could effectively inhibit the volatilization losses of TCBs and achieved a very good mass balance during the biodegradation process.Meanwhile,the TLPS could increase microbial activity and microbial growth during the degradation process.With TLPS,the TCB degradation was in descending order of 1,2,4-TCB> 1,2,3-TCB>> 1,3,5-TCB,which was related to the exposed concentration of the contaminants in soil.This study showed that TLPS could be employed as an effective tool to evaluate the biodegradation of volatile hydrophobic organic compounds,which could not be achieved with the traditional single water system. 相似文献
993.
本文概述了我国东南丘陵区红壤退化现状、原因和治理意义,总结了30年来不同阶段红壤退化治理的成果,分析了红壤区域进一步发展现代高效生态农业的途径。论文提出针对红壤区域保障粮食安全、保护生态环境和应对全球气候变化的多重目标,在常规化学农业基础上,充分利用区域水热资源优势,融合生态农业、循环农业和智慧农业等模式的科学理念和优势,创新区域现代高效农业的建设原理、关键技术、配套政策法规和管理体系;针对红壤退化的区域特征,开展流域尺度红壤退化的综合治理和适度规模经营,建立红壤流域智慧农业发展模式,促进红壤区域农业现代化。 相似文献
994.
995.
996.
Land-use effects on organic matter and physical properties of soil in a southern Mediterranean highland of Turkey 总被引:12,自引:0,他引:12
Forest and grassland soils in highlands of southern Mediterranean Turkey are being seriously degraded and destructed due to extensive agricultural activities. This study investigated the effects of changes in land-use type on some soil properties in a Mediterranean plateau. Three adjacent land-use types included the cultivated lands, which have been converted from pastures for 12 years, fragmented forests, and unaltered pastures lands. Disturbed and undisturbed soil samples were collected from four sites at each of the three different land-use types from depths of 0–10 cm and 10–20 cm in Typic Haploxeroll soils with an elevation of about 1400 m. When the pasture was converted into cultivation, soil organic matter (SOM) pool of cultivated lands for a depth of 0–20 cm were significantly reduced by, on average 49% relative to SOM content of the pasture lands. There was no significant difference in SOM between the depths in each land-use type, and SOM values of the forest and pasture lands were almost similar. There was also a significant change in soil bulk density (BD) among cultivation (1.33 Mg m−3), pasture (1.19 Mg m−3), and forest (1.25 Mg m−3) soils at depth of 0–20 cm. Only for the pasture, BD of the depth of 0–10 cm was significantly different from that of 10–20 cm. Depending upon the increases in BD and disruption of pores by cultivation, total porosity decreased accordingly. Cultivation of the unaltered pasture obviously increased the soil erodibility measured by USLE-K factor for each soil depth, and USLE-K factor was approximately two times greater in the cultivated land than in the pasture indicating the vulnerability of the cultivated land to water erosion. The mean weight diameter (MWD) and water-stable aggregation (WSA) were greater in the pasture and forest soils compared to the cultivated soils, and didn’t change with the depth for each land-use type. Aggregates of >4.0 mm size were dominant in the pasture and forest soils, whereas the cultivated soils comprised aggregates of the size ≤0.5 mm. I found that samples collected from cultivated land gave the lowest saturated hydraulic conductivity values regardless of soil depths, whereas the highest values were measured on samples from forest soils. In conclusion, the results showed that the cultivation of the pastures degraded the soil physical properties, leaving soils more susceptible to the erosion. This suggests that land disturbances should be strictly avoided in the pastures with the limited soil depth in the southern Mediterranean highlands. 相似文献
997.
The cost of soil lost from fields due to removal on harvested sugarbeet: a case study in Turkey 总被引:1,自引:0,他引:1
Abstract. Soil removed on sugarbeet ( Beta vulgaris L .) at harvest may be an important factor in soil degradation causing significant decline in soil productivity. This study evaluated soil losses on sugarbeet and estimated the cost of plant nutrients lost by this process. The losses were calculated using data from the agricultural reports published by the General Directorate of the Turkish Sugar Industry. Organic matter and plant available nutrient contents of soils removed from sugarbeet fields were determined. It was estimated that approximately 30 000 t of soil is lost annually in Erzurum, and 1.2 million t in the whole of Turkey. The cost of N, P and K losses is approximately 60 000 US$ annually for the study area. 相似文献
998.
An integrative method to quantify contaminant fluxes in the groundwater of urban areas 总被引:2,自引:2,他引:2
Background, Aims, and Scope Groundwater in urban areas is often contaminated and emission sources can be located close to groundwater wells. The delineation
of contaminant plumes is difficult because of the various potential emission sources. Thus, detection, quantification and
remediation of contaminated sites in a city need more integrative approaches.
Methods A method has been developed which allows quantification of mass fluxes of contaminants in groundwater between control planes.
Budget zones along the flow path are defined to calculate a contaminant balance and to quantitatively reveal input areas.
Concentrations and water budgets are used to calculate mass balances for each contaminant. The city of Darmstadt (Germany)
was chosen to evaluate the method.
Results The groundwater monitoring wells (GMWs) upstream of the city showed anthropogenically superposed background values for all
naturally occurring inorganic species. The contaminant concentrations increased in the city (probably influenced by road traffic,
gas stations, leaking sewers, etc.). Downstream from the city, concentrations usually decreased. Organic compounds typical
for urban environments, such as polycyclic aromatic hydrocarbons (PAH), locally exceeded drinking water regulations. In GMWs
with high concentrations of organic contaminants in the city or downstream from industrial areas, a significant increase in
Fe2+ and Mn2+ could be observed, in some cases coinciding with a decrease in NO3, SO4 and an increase in NH4.
Discussion For typical urban contaminants, a positive budget was calculated in several zones, which shows that emissions from urban sources
are reaching the groundwater. Negative budgets can be mainly explained with diving plumes and degradation. The input calculated
from the individual budget zones is usually higher than the input estimated from urban emissions. Differences between the
calculated and the estimated input can be explained with additional sources or (bio)degradation processes.
Conclusions It was confirmed that high concentrations of contaminants do not necessarily correlate with high fluxes. Integrative approaches
can reveal areas of high contaminant mass input. The results obtained with the new method are plausible compared to the land
use and the estimated urban input. The concentration pattern of Fe2+, Mn2+, SO4 and NO3 is partly due to natural processes, triggered by the degradation of organic matter and organic contaminants.
Recommendations Since this method includes mass balances and flux calculations, avoiding an overestimation of single point contaminant concentration,
it is recommended to use this approach to quantify groundwater contamination in cities. Further research is focusing on the
role of urban soils as natural reservoirs for the input of contaminants. 相似文献
999.
Overuse of nitrogen (N) fertilizers may lead to many environmental issues via N leaching into groundwater and agricultural runoff into surface water. Biochar, a sustainable soil amendment agent, has been widely studied because of its potential to retain moisture and nutrients. However, recent studies have shown that biochar has a very limited ability to improve the retention of negatively charged nitrite (NO2-) or nitrate (NO3-). Although positively charged ammonium (NH4+) can be better held by biochar, it is usually susceptible to nitrification and can be easily transformed into highly mobile NO2-and/or NO3-. In practice, dicyandiamide (DCD) has been used to inhibit nitrification, preserving N in its relatively immobile form as NH4+. Therefore, it is likely that the effects of DCD and biochar in soils would be synergistic. In this study, the influences of biochar on the effectiveness of DCD as a nitrification inhibitor in a biochar-amended soil were investigated by combining the experimental results of incubation, adsorption isotherm, and column transport with the simulated results of different mathematical models. Biochar was found to stimulate the degradation of DCD, as the maximum degradation rate slightly increased from 1.237 to 1.276 mg kg-1 d-1 but the half-saturation coefficient significantly increased from 5.766 to 9.834 mg kg-1. Considering the fact that the availability of DCD for nitrification inhibition was continuously decreasing because of its degradation, a novel model assuming non-competitive inhibition was developed to simulate nitrification in the presence of a decreasing amount of DCD. Depending on the environmental conditions, if the degradation of DCD and NH4+ in biochar-amended soil is not significant, improved contact due to the mitigated spatial separation between NH4+ and DCD could possibly enhance the effectiveness of DCD. 相似文献
1000.
Bt棉棉子中Bt蛋白定量检测方法建立及变化规律研究 总被引:1,自引:1,他引:1
应用Envirologix试剂盒测定99B、33B棉子仁中Bt蛋白的含量,分别为4376.4ng·g1和4321.7ng·g1;测定系列稀释的棉子仁提取液,Envirologix试剂盒测得的OD450和Agdia试剂盒测得的OD630间的相关性很好,相关系数接近0.99;而Agdia试剂盒测得的系列稀释液的OD630与其Bt蛋白含量间有很好的相关性,相关系数大于0.99。据此,利用Agdia试剂盒测得99B、33B棉子、棉子仁、棉子壳在12个月的贮存过程中Bt蛋白含量的变化规律,棉子、棉子仁中Bt蛋白含量降低一半,棉子壳中Bt蛋白含量降低四分之一。 相似文献