数据驱动的双层次软件过程挖掘方法

为了解决软件过程数据因活动信息及案例属性的缺失而无法应用传统过程挖掘方法的问题,以软件过程数据为研究对象,提出了一种双层次的软件过程挖掘方法.在活动层,提出加权结构连接向量模型对过程日志进行向量化,通过平均活动熵来确定过程日志模糊聚类的结果,将聚类结果作为活动信息支持后续挖掘工作的开展;在过程层,以启发式关系度量为基础,针对非完全循环进行研究,提出了过程层单触发序列循环划分的日志完备性条件,并进一步给出了循环归属的度量方法.基于大量真实软件过程数据的实验结果表明了双层次的软件过程挖掘方法的可行性及正确性.

Review:Assessing potential dietary toxicity of heavy metals in selected vegetables and food crops

Heavy metals, such as cadmium, copper, lead, chromium and mercury, are important environmental pollutants, particularly in areas with high anthropogenic pressure. Their presence in the atmosphere, soil and water, even in traces can cause serious problems to all organisms, and heavy metal bioaccumulation in the food chain especially can be highly dangerous to human health. Heavy metals enter the human body mainly through two routes namely: inhalation and ingestion, ingestion being the main route of exposure to these elements in human population. Heavy metals intake by human populations through food chain has been reported in many countries. Soil threshold for heavy metal toxicity is an important factor affecting soil environmental capacity of heavy metal and determines heavy metal cumulative loading limits. For soil-plant system, heavy metal toxicity threshold is the highest permissible content in the soil (total or bioavailable concentration) that does not pose any phytotoxic effects or heavy metals in the edible parts of the crops does not exceed food hygiene standards. Factors affecting the thresholds of dietary toxicity of heavy metal in soil-crop system include: soil type which includes soil pH, organic matter content, clay mineral and other soil chemical and biochemical properties; and crop species or cultivars regulated by genetic basis for heavy metal transport and accumulation in plants. In addition, the interactions of soil-plant root-microbes play important roles in regulating heavy metal movement from soil to the edible parts of crops. Agronomic practices such as fertilizer and water managements as well as crop rotation system can affect bioavailability and crop accumulation of heavy metals, thus influencing the thresholds for assessing dietary toxicity of heavy metals in the food chain. This paper reviews the phytotoxic effects and bioaccumulation of heavy metals in vegetables and food crops and assesses soil heavy metal thresholds for potential dietary toxicity.

Spatial and temporal variation of nitrogen exported by runoff from sandy agricultural soils

The eutrophication problem has drawn attention to nutrient leaching from agricultural soils, and an understanding of spatial and temporal variability is needed to develop decision-making tools. Thus, eleven sites were selected to monitor, over a two-year period, spatial and temporal variation of runoff discharge and various forms of N in surface runoff in sandy agricultural soils. Factors influencing the variation of runoff discharge and various forms of N in surface runoff were analyzed. Variation of annual rainfall was small among 11 sites, especially between 2001 and 2002. However, variation of annual discharge was significant among the sites. The results suggest that rainfall patterns and land use had significant effect on discharge. The concentrations of total N, total kjeldahl N （TKN）, organic matter-associated N （OM-N）, NO3- -N, and NHn＋-N in the runoff ranged widely from 0.25 to 54.1, 0.15 to 20.3, 0.00 to 14.6, 0.00 to 45.3, and 0.00 to 19.7 mg/L, respectively. Spatial and temporal variations in the N concentration and runoff discharge were noted among the different sites. Annual loads of N in the runoff varied widely among monitoring sites and depend mainly on runoff discharge. High loads of total N, OM-N, NO3--N, and NHn＋-N in the runoff either in citrus groves or on vegetable farms occurred from June to October for each year, which coincided with the rainy season in the region. This study found that N in surface runoff was related to rainfall intensity, soil N level, and fertilizer use.

Extractability and Mobility of Copper and Zinc Accumulated in Sandy Soils

Extractability and mobility of Cu and Zn and their relationships with 1) accumulation of Cu and Zn and 2) soil pH were studied in three sandy soils (Wabasso, Ankona, and Winder) from commercial citrus groves in Florida, USA. The soils, with a broad range of Cu and Zn concentrations, were fractionated by a modified procedure of Amacher, while Cu and Zn mobility were evaluated using column leaching. The extractability of Cu and Zn increased with decreasing soil pH. Also with increasing total soil Cu and Zn for extractable Cu in the Wabasso sand a threshold level, where the metal extraction rate increased, was noted at 100 mg kg-1, whereas for extractable Zn in the Wabasso sand the threshold level was found at 60 mg kg-1 and in the Ankona sand at 120 mg kg-1. These results suggested that the release potential of Cu and Zn was greater in the Wabasso sand than in the Ankona sand. The column leaching experiment showed that at total soil Cu or Zn concentrations < 100 mg kg-1 all leachates had low Cu and Zn concentrations. However at total concentrations > 200 mg kg-1 for Cu and > 150 mg kg-1 for Zn with decreasing soil pH, the concentrations of both Cu and Zn in the leachates increased exponentially. Also in these sandy soils soluble Cu and Zn mainly originated from the exchangeable fractions, and pH was a key factor controlling Cu and Zn extractability and mobility.

Effect of Compost Amendment on Heavy Metals, Nitrogen and Phosphorus in a Peat-Based Container Medium

A laboratory study was conducted to evaluate the effect of compost amendment on mobility and leaching potential of heavy metals, nitrogen (N) and phosphorus (P) from a peat-based commercial container medium containing 700 g kg-1 peat, 200 g kg-1 perlite and 100 g kg-1 vermiculite at varying amendment rates of compost (0, 0.25, 0.50, 0.75 and 1.00 L L-1). Increasing compost amendment significantly and linearly increased the pH (P < 0.01), the total concentrations of organic carbon (P < 0.05), copper (Cu) (P < 0.01), cadmium (Cd) (P < 0.01), and lead (Pb) (P < 0.01), and increased the bulk density (P < 0.01) of the medium. The electrical conductivity (EC), and total N and P of the medium increased significantly (P < 0.01) and quadratically with increasing compost amendment. The relationship of the C/N ratio of the medium with the compost amendment rate was decreasing, significant (P < 0.01) and cubic, while that of the total Zn was increasing, significant (P < 0.01) and cubic. Extractable P, NO3-N, and NH4-N increased initially with an increasing compost amendment of up to 0.50 L L-1 and then decreased with further increasing compost rate. Increasing compost rates resulted in a highly significant (P < 0.01) and linear increase in total Cd, Cu, and Pb, and a highly significant (P < 0.01) and cubic increase in total Zn in the medium. Increasing compost rates also significantly (P < 0.01) increased extractable Cu (linearly) and Zn (quadratically), but significantly (P < 0.01) decreased extractable Pb (linearly). There was no significant effect of compost amendment on the extractable Cd concentration in the medium. However, with increasing compost rates from 0.25 to 1.00 L L-1, extractability of P, Cd, Cu, Pb and Zn (extractable concentration as a percent of total) was decreased, indicating that compost amendment could lower the leachability of these elements from the medium.

坑内钻探在广西大厂巴力-龙头山矿区的应用效果

广西大厂巴力-龙头山矿区,在深边部找矿、生产勘探等领域广泛应用了坑内钻探。多年实践证明,在矿山生产过程中,坑内钻探继承了地表钻探的功能,采用坑内钻探不但能够在深边部探矿,快速控制矿体提高储量级别等方面取得显著效果,而且在缩短探矿耗时、降低能源消耗,降低成本,减少废石排放,降低矿山井下通风污染和水资源重金属污染等方面也起到不可或缺的作用。

Microbial Biomass and PLFA Profile Changes in Rhizosphere of Pakchoi(Brassica chinensis L.) as Affected by External Cadmium Loading

The effects of root activity on microbial response to cadmium(Cd) loading in the rhizosphere are not well understood.A pot experiment in greenhouse was conducted to investigate the effects of low Cd loading and root activity on microbial biomass and community structure in the rhizosphere of pakchoi(Brassica chinensis L.) on silty clay loam and silt loamy soil.Cd was added into soil as Cd(NO_3)_2 to reach concentrations ranging from 0.00 to 7.00 mg kg^(-1).The microbial biomass carbon(MBC) and community structure were affected by Cd concentration,root activity,and soil type.Lower Cd loading rates(<1.00 mg kg^(-1)) stimulated the growth of pakchoi and microorganisms,but higher Cd concentrations inhibited the growth of microorganisms.The content of phospholipid fatty acids(PLFAs) was sensitive to increased Cd levels.MBC was linearly correlated with the total PLFAs.The content of general PLFAs in the fungi was positively correlated with the available Cd in the soil,whereas those in the bacteria and actinomycetes were negatively correlated with the available Cd in the soil.These results indicated that fungi were more resistant to Cd stress than bacteria or actinomycetes,and the latter was the most sensitive to Cd stress.Microbial biomass was more abundant in the rhizosphere than in the bulk soil.Root activity enhanced the growth of microorganisms and stabilized the microbial community structure in the rhizosphere.PLFA analysis was proven to be sensitive in detecting changes in the soil microbial community in response to Cd stress and root activity.

Effect of Lead on Soil Enzyme Activities in Two Red Soils

Enzyme activities have the potential to indicate biological functioning of soils. In this study, soil urease, dehydrogenase, acid phosphatase and invertase activities and fluorescein diacetate(FDA) hydrolysis were measured in two red soils spiked with Pb2+ranging from 0 to 2 400 mg kg-1to relate the enzyme activity values to both plant growth and the levels of available and total Pb2+concentrations in soils, and to examine the potential use of soil enzymes to assess the degrees of Pb contamination. Soil samples were taken for enzyme activities assaying during 3 month's incubation and then after planting of celery(Apium graveolens L.) and Chinese cabbage(Brassica chinensis L.). Enzyme activities in the red soil derived from arenaceous rock(RAR) were generally lower than those in the red soil developed on Quaternary red earths(REQ). At high Pb2+loadings, in both incubation and greenhouse studies, urease activity and FDA hydrolysis were significantly inhibited. But there were no significant relationships between soil dehydrogenase, acid phosphatase or invertase activity and soil Pb2+loadings in both RAR and REQ soils. The growth of celery and Chinese cabbage increased soil urease activity and FDA hydrolysis, but had minimal effect on dehydrogenase and invertase activities. There were positive correlations between celery biomass and soil urease activity and FDA hydrolysis. These results demonstrate that urease activity and FDA hydrolysis are more sensitive to Pb2+than acid phosphatase, dehydrogenase and invertase activities in the RAR and REQ soils.