ABSTRACT
Phosphorus is an essential element for food production, but the distribution of its global reserve is highly uneven. With the increasing demand for products from all sectors of the phosphorus supply chain, the international phosphorus material trade is becoming increasingly intensive. However, the evolution of the global phosphorus trade network and potential supply risks caused by the trade structure and trade stability are rarely evaluated. By employing the complex network theory, a phosphorus material trade network and a quantitative evaluation index of the trade risk using the external supply risks are proposed to evaluate the supply risk in different countries from 2000 to 2020. According to the network analysis of global phosphorus trades for phosphate rock, phosphorus fertilizer and phosphoric acid, the number of trading countries and trading links has generally increased during the last twenty years. However, the trade structure was found to be significantly altered due to the stresses on the phosphorus reserve scarcity and trade restrictions from countries such as the United States and China. Correspondingly, Morocco has become the largest phosphorus-exporting country since 2016, while India was the world's largest phosphorus-importing country between 2008 and 2015. The topological network characteristics indicate that the phosphorus trade is well connected and more stable over time, but high supply risks were also identified, especially in developing countries in Africa within their phosphate rock and phosphorus fertilizer trade, which might threaten their food security. The obtained findings would be helpful for phosphorus trading countries to manage their trade risks in a timely manner.
Subject(s)
Fertilizers , Phosphorus , Phosphates , Morocco , Risk AssessmentABSTRACT
OBJECTIVE: To optimize the conditions of purifying the total alkaloids in Aconitum szechenyianum with macroporous adsorption resin, and compare the content of total alkaloids and aconitine in A. szechenyianum from different producing areas, in order to provide basis for further studies. METHOD: The orthogonal experiment method was adopted for optimizing the conditions of purifying the total alkaloids in A. szechenyianum with macroporous adsorption resin. The content of total alkaloids and aconitine were determined by using the titration method. The total alkaloids in A. szechenyianum from different producing areas were purified under optimum processing conditions. Aconitine was determined by HPLC. RESULT: Different processing conditions showed different influences on the purification of total alkaloids. The optimum conditions were resin type HPD-722, ethanol concentration of 80% , and ethanol elution volume of 80 mL x min(-1). The contents of aconitine in A. szechenyianum from different producing areas--Qinghai, Maxianshan, Ningxia and Yongdeng were 0.493 5, 0.883 5, 1.527 8, 1.664 4 mg x g(-1), respectively. CONCLUSION: The optimum processing conditions used in this essay could be used for purifying the total alkaloids and aconitine. A. szechenyianum from Yongdeng and Gansu contains the highest content of aconitine.