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611.
This paper aims to identify the land-use factors benefiting sustainable land management in terms of environmental conservation. For evaluating the impacts of land use on the environment, the following parameters were used: chemical fertiliser and pesticide use, land-use structure and diversity. The farmers' income, land tenure and farming scale were selected for their influence on agricultural sustainability. The analysis shows a rapid increase in use of chemical fertiliser and pesticide in the past 40 years, and an observable increase in land-use diversity. The amount of chemical fertiliser used per unit area in large-scale farming was lower than that at small scales, but large-scale farming consumes more pesticide than small-scale farming. A significant negative correlation was observed between the proportions of the holdings possessing land and the holdings using the chemical fertiliser. In order to achieve sustainable agriculture, it is necessary to manage crop systems and land use towards selecting new strains and varieties of crops and fruits with a lower demand for chemical fertiliser and a higher resistance to disease and pests, balancing large- and small-scale farming, and ensuring land tenure and economic incentives. 相似文献
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蓝藻藻泥好氧堆肥腐熟后还田是其打捞后资源化利用的主要途径。堆肥后仍有一定数量的微囊藻毒素(microcystin,MC)残留,大量还田是否会对作物生长和人类健康产生安全风险尚不明确。将青菜(Brassica chinensis)暴露于不同MC含量的石英砂和菜地土壤,观测植株生长状况及体内MC含量,并观测不同含量的MC在菜地土壤中的降解速率。结果发现:砂培实验结束时,青菜成株的株高和生物量随着MC暴露浓度的增加而显著降低,而植株地上部MC的含量则显著增加。在MC浓度为0.386mg·kg-1的处理中,青菜地上部MC-LR(L为亮氨酸)和MC-RR(R为精氨酸)的浓度分别达到27.45μg·kg-1(鲜质量)和1.35μg·kg-1(鲜质量)。MC-LR和MC-RR在青菜地上部的富集系数都随着砂培基质中MC浓度的增加而显著降低,且前者显著高于后者。土培青菜生长过程中吸收和累积的MC数量显著小于砂培实验。MC在菜地土壤中降解56d后,MC-LR和MC-RR的降解率均达90%以上。按普通有机肥的一般用量(2.5kg·m-2)施用充分腐熟的蓝藻堆肥成品种植青菜,食用后每人每天摄入的MC含量远低于WHO制定的饮用水中MC的指导值。研究为评估现行蓝藻堆肥工艺中残留的MC对作物生长和生物安全风险提供了科学依据。 相似文献
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RBCA、CLEA及CalTOX模型在苯并[a]芘污染场地健康风险评估中的应用比较 总被引:4,自引:0,他引:4
为探讨不同模型对污染场地健康风险评估结果的影响,以苯并[a]芘为例,采用RBCA、CLEA和CalTOX模型对某工业污染场地表层土壤进行健康风险评估,分析了评估结果的差异和原因,同时对模型的主要暴露参数进行了敏感性分析,并推导出基于风险概率分布的土壤修复限值。结果表明,RBCA、CLEA和CalTOX模型计算的苯并[a]芘致癌总风险分别为2.40×10-4、6.32×10-4和7.04×10-6,且经口摄入和皮肤接触2个途径对人体健康造成的危害最大。降解作用是影响CalTOX模型风险评估结果不同于RBCA和CLEA模型的重要因素,3个模型间参数取值及方法学的差异也会导致风险评估结果不同。各模型暴露参数的敏感性排序也有差异。采用基于风险概率分布的方法推导土壤修复限值,RBCA、CLEA和CalTOX模型所得结果分别为0.18、0.08、0.13(不考虑降解作用CalTOX模型)和10.74(考虑降解作用CalTOX模型)mg·kg-1,为各模型直接推导值的1.5~2.6倍。基于风险概率分布的方法可有效降低风险评估过程中参数不确定性的影响,为工业污染场地土壤修复值的制定提供参考。 相似文献
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Species immigration history can structure ecological communities through priority effects, which are often mediated by competition. As competition tends to be stronger between species with more similar niches, we hypothesize that species phylogenetic relatedness, under niche conservatism, may be a reasonable surrogate of niche similarity between species, and thus influence the strength of priority effects. We tested this hypothesis using a laboratory microcosm experiment in which we established bacterial species pools with different levels of phylogenetic relatedness and manipulated the immigration history of species from each pool into microcosms. Our results showed that strong priority effects, and hence multiple community states, only emerged for the species pool with the greatest phylogenetic relatedness. Community assembly also resulted in a significant positive relationship between bacterial phylogenetic diversity and ecosystem functions. Interestingly, these results emerged despite a lack of phylogenetic conservatism for most of the bacterial functional traits considered. Our results highlight the utility of phylogenetic information for understanding the structure and functioning of ecological communities, even when phylogenetically conserved functional traits are not identified or measured. 相似文献
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A detailed nitrogen (N) budget has been developed for an urban ecosystem based on the method of material flow analysis. How increased human activity and urbanisation influences N cycling have also been analysed. Total N input and output in the urban ecosystem of Zhengzhou City (ZUE) was calculated at 304.8?Gg was 275.3?Gg year?1, resulting in an N accumulation of 29.5?Gg year?1. Industry and human life activities, which respectively accounted for 43.8% and 34.2% of total N inputs and 52.6% and 29.1% of total N outputs, were the core of N flow in the urban ecosystem. Humans activities mediated more than 98% N inputs into the ZUE, 73.2% of N was released into the atmosphere and 11.7% into hydrosphere. This very large volume of released N could contribute to regional problems. High energy consumption, insufficient wastewater treatment facility practices, and low N use efficiency are the primary causes of pollution. The major challenge ahead for the urban ecosystem is how to manage high-intensity N pollutant inputs to the urban ecosystems coupled with incomplete N cycling and removal. Based on the analysis of the N budget and loading, this study also proposes an N management strategy for the ZUE. 相似文献