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721.
PHILIP A. LORING 《Conservation biology》2013,27(1):55-63
Many believe commercial fisheries in Alaska (U.S.A.) are sustainability success stories, but ongoing socioeconomic problems across the state raise questions about how this sustainability is being defined and evaluated. Problems such as food insecurity and the disenfranchisement of Alaska Natives from fishing rights are well documented, yet these concerns are obscured by marketing campaigns that convey images of flourishing fishing communities and initiatives to certify Alaska's fisheries as responsibly managed. Fisheries management mandates and approaches built on such metrics and technologies as maximum sustainable yield and systems of tradable quotas actually serve to constrain, circumscribe, and marginalize some Alaskans’ opportunities for effecting change in how the benefits of these fisheries are allocated. Beneath the narrative of sustainability, these management technologies perpetuate a cognitive ecological model of sustainability that is oriented to single‐species outcomes, that casts people as parasites, and thus assumes the necessity of trade‐offs between biological and social goals. Alternative cognitive models are available that draw metaphors from different ecological concepts such as keystone species and mutualisms. Such models, when used to inform management approaches, may improve societal outcomes in Alaska and elsewhere by promoting food security and sustainability through diversified natural resource harvest strategies that are more flexible and responsive to environmental variability and change. Perspectivas Alternativas sobre la Sustentabilidad de las Pesquerías Comerciales en Alaska 相似文献
722.
Maryam Mohammadnia Mahmoud Reza Sohrabi 《Journal of environmental science and health. Part. B》2020,55(4):293-300
AbstractIn the present work, dispersive micro-solid phase extraction (D-μ-SPE) method using magnetic graphene oxide tert-butylamine (GO/Fe3O4/TBA) nanocomposite, as an efficient sorbent, was applied for determining 2,4-dichlorophenoxyacetic acid (2,4-D) in water and food samples. Detection was carried out using high-performance liquid chromatography (HPLC) instrument. Influential parameters of D-μ-SPE such as sorbent and its amount, elution solvent and its volume, adsorption and desorption times and pH of sample solution were investigated and optimized. Under the optimized conditions, limit of detection and quantitation values were 0.007 and 0.02?μg/mL, respectively. Recovery data for several real samples were obtained within the range of 88.0–94.0% with a relative standard deviation (RSD) less than 7.5%. The proposed method was successfully applied to quantitative determination of 2,4-D in several vegetables and water samples. 相似文献
723.
724.
高原牧区草地变化对牧民粮食安全的影响——以青海省达日县为例 总被引:2,自引:1,他引:1
农业区和牧业区的粮食安全在概念上存在着一定的差别,在关注农业区粮食安全的同时,牧业区粮食安全的研究也值得重视。论文从青海省达日县牧区牧民食物能量折算入手,构建了最小人均草地面积和草地压力指数两个计算方法,并以乡为基本单元,对各乡粮食安全进行定量计算。计算结果表明:达日县1987-2007年最小人均草地面积和草地压力指数呈增加趋势,1997年粮食安全区、警戒区、短缺区、危机区4个等级均有分布,至2007年该区域已全部演变为粮食短缺区和危机区,主要原因是草地退化严重,人口数量增加,人均草地面积减少以及技术和物质投入不足,牧业生产条件恶化。 相似文献
725.
通过测定上海市售动物性食品中PCBs的浓度和生物有效性,评估该地区PCBs的人体日暴露量.结果表明,不同种类食品中PCBs的浓度在未检出~3734.3pg/g(湿重)之间,3~6氯PCBs为主要同系物.鱼类中PCBs浓度高于畜类、禽类和软体类.鱼类PCBs的浓度水平遵循以下两规律:海水鱼>淡水鱼;肉食性鱼>杂食性鱼>草食性鱼.采用模拟人体胃肠消化过程测得PCBs的生物有效性,由于食品中脂肪含量与PCBs的生物有效性具有显著的线性关系,故可用于计算样品中PCBs的生物有效性.该地区居民每天通过动物性食品摄入的PCBs量为24439.3pg/d,以PCBs的生物有效性计量为5034.5pg/d.对不同暴露源(包括灰尘和大气颗粒物)的分析表明,鱼类是PCBs人体暴露的主要贡献者,约占人体PCBs日暴露的60%. 相似文献
726.
727.
基于价值链增值的农地整治项目前期阶段效率测度研究 总被引:1,自引:0,他引:1
在研究国内外农地整治项目效率相关问题的基础上,对农地整治项目前期阶段工作效率的内涵进行了界定,剖析了其价值链,并围绕着价值链增值这一核心建立了包含项目选址、可行性论证、勘测、权属调整及规划设计5 个准则层在内的农地整治项目前期阶段工作效率指标体系。依据标杆管理原理和项目特征设置了32 个效率指标的基准标杆、实际最优标杆及理论拓展标杆,构建了基于距离函数法的农地整治项目前期阶段工作效率测度模型。以鄂州市华容区蒲团高产农田建设示范项目为例,对其前期阶段的工作效率进行了测度,针对测度结果分析了项目前期阶段工作中存在的问题,并有针对性地提出了建议,也为其它农地整治项目前期阶段工作效率测度提供了参考依据。 相似文献
728.
以具有代表性的异味特征-异味阈值为研究对象,采用三点比较式臭袋法测定了醇类、醛类、酮类、酸类和硫醇类5个系列常见异味化合物的异味阈值,研究了异味阈值与碳链长度之间的关系,并以官能团疏水性参数量化表征官能团结构,研究了异味阈值与官能团类型之间的关系.研究发现,分子碳链长度和官能团类型都能影响异味阈值的大小,其中异味阈值与碳链长度关系为y=axb或lgy=cx+d(y:异味阈值,x:碳原子数);异味阈值与官能团疏水常数π参数关系为y=aebx或lgy=cx+d(y:异味阈值,x:官能团疏水性参数).所得模型能定量描述碳链长度和官能团类型对异味阈值的影响,为异味机理的进一步探索提供了有力支撑.此外,对异味阈值与上述两因素的多元线性拟合及残差分析结果表明,碳链长度和官能团类型能够影响化合物异味阈值,但二者并非异味阈值的完全决定因素,研究决定异味阈值的全面结构因素,需大量后续工作. 相似文献
729.
Trace-element contamination poses a serious threat to China's ecology, environment, food safety, and human health. Human exposure to potentially toxic trace elements is predominantly attributed to the consumption of vegetables, especially leafy vegetables, grown on metal-contaminated soil. In the present study, the concentrations of Cd in Chinese cabbage were found to decrease at an exponential rate from the outermost layer to the inner core, while there was a small change in Pb content from the 1st to the 16th layer of the plant, suddenly decreasing at the 17th layer. Although there was a little difference between the maximum permissible concentration (MPC) and the mean Cd content in the plant, from the 1st layer to the 10th layer in the edible part of Chinese cabbage, Cd concentrations were 1.1–2.5 times higher than the MPC. The Pb concentration in the whole plant was 1.9 times higher than the MPC, while the 17th layer to the 25th layer of Chinese cabbage was safe for consumption. Health risk assessment indicated that the surface layer of Chinese cabbage might cause harm to human health, especially to children, in view of cancer risk and non-cancer risk. 相似文献
730.
The factors affecting the solubilisation of metals during digestion of food have been examined in a two‐stage model system comprising simulated gastric and intestinal juices. The solubilisation of iron, copper and zinc was examined in digests of white and wholemeal bread. Zinc solubility was principally governed by pH and the simulated digestion had little additional effect. In contrast both iron and copper solubility were markedly affected by digestion of the bread. In the case of copper the enzymolysis increased solubility appreciably at neutral pH. All of the cadmium in a simulated gastric digest of canned crab meat was associated with soluble low molecular weight species of less than 1000 daltons. Cadmium solubility resulted from the acidic conditions of the digest rather than enzymatic solubilisation of binding proteins. Ninety percent of the cadmium in the digest became rebound to the insoluble fraction on adjustment to pH7.0. Subsequent simulated intestinal digestion increased the level of soluble cadmium to 20%; 1.0–1.5% was associated with soluble species in the range 26,000–37,000 daltons and 15.0–20.0% with soluble species of less than 3,000 daltons. 相似文献