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41.
《Journal of environmental science and health. Part. B》2012,47(11):877-882
AbstractProblems related to weed management such as outbreaks of herbicide-resistant weeds have recently increased. An interesting approach to such problems is to use plant materials with phytotoxic activity. Burdock (Arctium lappa L.) is a biennial herb belonging to Asteraceae and is cultivated in several countries. The present study investigated the phytotoxic activity of burdock and its active substances. Extracts of both burdock leaves and roots inhibited the shoot and root growth of cress and barnyard grass, where the level of inhibition increased with increasing extract concentration. The leaf extracts had 2.0–2.5 times higher activity than the root extracts. Bioassay-guided separations of the leaf extracts led to isolation of a phytotoxic substance, onopordopicrin. Onopordopicrin significantly inhibited the shoot and root growth of cress and barnyard grass. The concentrations of the substance required for 50% growth inhibition were 0.27 and 0.26?mM for cress shoots and roots, respectively, and 1.86 and 0.35?mM for barnyard grass shoots and roots, respectively. The present results suggest that burdock leaves have high phytotoxic activity and onopordopicrin may play a major role in the activity. Burdock leaves may be a good resource for weed management. 相似文献
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43.
Robert Leconte Rangesan Narayanan Trevor C. Hughes 《Journal of the American Water Resources Association》1988,24(2):247-253
ABSTRACT: A general methodology to study the economics of dual water systems (defined here as a separate distribution system for untreated low quality local surface Water for outdoor municipal water supply) is summarized and the application of the method to a rapidly growing city is presented. In the first step, a cost-benefit criterion for evaluating dual systems is developed. The criterion is then extended to a dynamic case where the population to be served increases with time and where the dual system is allowed to expand. The optimal investment time to introduce the dual water supply project is obtained by maximizing social welfare. The model is applied to the city of West Jordan, Utah, where a dual system is currently being proposed. Model results indicate that for the city as a whole dual supply is not economically feasible. However, when the model is applied to a part of the city, it is found feasible and the optimal time to initiate the project would be in the year 1989. 相似文献
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45.
AFS-830型双道原子荧光光度计同时测定饮用水中砷、汞 总被引:1,自引:0,他引:1
主要探讨应用AFS-830型双道原子荧光光度计,在饮用水监测中同时测定水中砷、汞的方法和技术。此法是在硝酸介质,以硼氢化钠作还原剂,进行原子化,被测元素原子激发出荧光强度值在一定范围内与被测元素的浓度成正比。砷与汞的检出限分别为0.0618和0.0158ug/L。 相似文献
46.
The paper analyzes the influence of lead toxicity by anaerobic granule sludge inhibition and recovering experiments. The result shows that there are different inhibition types at different lead contents. Higher lead content leads to more inhibition granular sludge, and at the same time, the time of gas recovery is different. Lower lead content per microorganism results in sooner sludge recovery. Microorganisms have a good ability to resist lead toxicity. 相似文献
47.
In the last years many efforts were made to transform standardized algal test protocols into low-cost microplate assays. While advantages were pointed out frequently, limitations are not systematically addressed, thus hindering a widespread utilisation. In this study a group of organic substances with a wide distribution of volatility (log KAW from −6.53 to −2.13) and lipophilicity (log KOW from 1.26 to 4.92) was investigated with respect to the influence of these physicochemical properties on their algal toxicity in different assays. Therefore the EC50 values were determined with a microplate assay based on ISO 8692 protocol and the results were compared with those of an established algal growth inhibition test conducted in air tight glass vessels. Using the ratio of the EC50 values, a clear connection between biological response and volatility as well as lipophilicity of test substances could be detected. Chemicals with a log KOW higher than 3 or a Henry coefficient log KAW higher than −4 were identified as less effective in the microplate assay than in the comparative assay. The loss in nominal concentration due to physicochemical properties could be shown to contribute to this using HPLC analysis. Consequently, when using microplate assay’s one should be aware that lipophilic and volatile chemicals might be underestimated in their toxicity, which could be indicated from evaluating related physicochemical properties modelled from structural information prior to an experimental investigation. 相似文献
48.
Cu^2+和Zn^2+是污水处理工艺中经常遇到的金属离子。在驯化好的活性污泥系统中,研究了金属离子Cu^2+和Zn^2+在0~100mg/L浓度下对活性污泥生物脱氮系统的影响。试验发现Cu^2+>5mg/L、Zn^2+>30mg/L时,对硝化过程具有明显的抑制作用,在同样浓度的试验条件下cu“对硝化过程的抑制作用比Zn^2+大。Cu^2+≤0.5mg/L时对反硝化过程具有一定的促进作用,有助于提高TN的去除效果;Cu^2+>0.5mg/L时,对反硝化产生抑制作用,随着浓度的增加,TN去除率逐渐下降。Zn^2+不影响反硝化过程,仅在大于30mg/L时,对硝化过程产生抑制作用。重金属Cu^2+对生物脱氮系统的影响明显强于Zn^2+。 相似文献
49.
The dissipation of carbendazim and chloramphenicol alone and in combination and their effects on soil fungal:bacterial ratios and soil enzyme activities were investigated. The results revealed that carbendazim dissipation was little affected by chloramphenicol, whereas chloramphenicol dissipation was found to be retarded significantly by the presence of carbendazim. The inhibitory effect of carbendazim on the fungal:bacterial ratios was increased by the presence of chloramphenicol, and the inhibitory effect of chloramphenicol on neutral phosphatase was increased by the presence of carbendazim. Carbendazim increased soil catalase and urease activities, but this increase was partially diminished by the presence of chloramphenicol. Little interaction was observed between carbendazim and chloramphenicol with regard to their influence on soil invertase. The results obtained in this study suggest that combinations of fungicides and antibiotics may alter the compounds’ individual behaviors in soil and their effects on soil enzymes. 相似文献
50.
ROBYN S. WILSON 《Conservation biology》2008,22(6):1452-1460
Abstract: Despite advances in the quality of participatory decision making for conservation, many current efforts still suffer from an inability to bridge the gap between science and policy. Judgment and decision‐making research suggests this gap may result from a person's reliance on affect‐based shortcuts in complex decision contexts. I examined the results from 3 experiments that demonstrate how affect (i.e., the instantaneous reaction one has to a stimulus) influences individual judgments in these contexts and identified techniques from the decision‐aiding literature that help encourage a balance between affect‐based emotion and cognition in complex decision processes. In the first study, subjects displayed a lack of focus on their stated conservation objectives and made decisions that reflected their initial affective impressions. Value‐focused approaches may help individuals incorporate all the decision‐relevant objectives by making the technical and value‐based objectives more salient. In the second study, subjects displayed a lack of focus on statistical risk and again made affect‐based decisions. Trade‐off techniques may help individuals incorporate relevant technical data, even when it conflicts with their initial affective impressions or other value‐based objectives. In the third study, subjects displayed a lack of trust in decision‐making authorities when the decision involved a negatively affect‐rich outcome (i.e., a loss). Identifying shared salient values and increasing procedural fairness may help build social trust in both decision‐making authorities and the decision process. 相似文献