A category of chromium (Cr)-containing fertilizers is represented by the fertilizers deriving from byproducts of tanning process. Their use is widespread because of their good agronomic response due to the high conten...A category of chromium (Cr)-containing fertilizers is represented by the fertilizers deriving from byproducts of tanning process. Their use is widespread because of their good agronomic response due to the high content of slow release or- ganic nitrogen (N) and carbon (C). They do not represent an environmental hazard because only the non-toxic form of Cr(III) is present. Productive processes may involve chemical, enzymatic or thermal hydrolysis. The final product is characterized by different contents of peptides and free amino acids depending on the type of hydrolysis. Legislation concerning Cr-containing fertilizers is controversial because often do not consider any scientific evidences;nevertheless, the European Union, the United States and countries as Italy, do not set the restriction to Cr(III) and generally only the presence of the toxic form, Cr(VI), is limited. Depending on its two main oxidation forms, Cr issue has been studied for many years. Several authors confirmed that Cr(VI) is carcinogenic, while Cr(III) is an essential trace element in human and animal diet. In soil Cr(III) has low mobility, whereas Cr(VI) is highly water soluble. However Cr(VI) in soil is quickly reduced to Cr(III);on the contrary oxidation of Cr(III) to Cr(VI) is rarely possible because particular conditions must occur. Only a very small fraction of Cr in soil is available to plant uptake and its translocation in edible parts is limited because it is immobilized in roots as Cr(III). Therefore risks of environmental pollution using these fertilizers are negligible;on the contrary they have positive environmental and agronomical effects. The aim of this review is to deal with the category of the organic fertilizers containing Cr derived from tannery processes focusing on its chemical, productive, legislative, environmental and agronomical aspects. Special attention is given to the ambiguous issue of Cr briefly summarizing the most important studies of the last forty years.展开更多
Donkey hides are used in a form of Traditional Chinese medicine called ejiao, the demand for ejiao is currently so high the global donkey population is currently in decline. Africa’s donkey population is considered a...Donkey hides are used in a form of Traditional Chinese medicine called ejiao, the demand for ejiao is currently so high the global donkey population is currently in decline. Africa’s donkey population is considered a key source for the trade, with Kenya being highlighted as being particularly affected. In Kenya donkeys play a vital contribution to people’s livelihoods;this study aimed to explore the potential impact of the donkey hide trade on small holder farmer’s livelihoods. The study was conducted in five counties in Kenya;data was collected using household survey questionnaires, focus group discussions and key informant interviews. When household survey participants (n = 421) were asked if the number of donkeys in their herd had decreased within the last two years 34.2% (n = 144) reported a decrease, of those 43.8% (n = 63) reported the selling of donkeys as the primary cause of reduction in herd size. Increased money spent on the transportation of farm produce, water and firewood was the most frequently reported effect of the loss of donkeys (62.5%, n = 263). Some focus group discussion participants said that they had previously sold their donkeys to raise money for school fees, likewise 43% (n = 97) of focus group discussion participants said that they would sell their donkeys to pay medical bills. Results from the study suggest that small holder farmers are choosing to sell their donkeys for an instant boost in income, but long-term this is unlikely to be a sustainable livelihood option.展开更多
文摘A category of chromium (Cr)-containing fertilizers is represented by the fertilizers deriving from byproducts of tanning process. Their use is widespread because of their good agronomic response due to the high content of slow release or- ganic nitrogen (N) and carbon (C). They do not represent an environmental hazard because only the non-toxic form of Cr(III) is present. Productive processes may involve chemical, enzymatic or thermal hydrolysis. The final product is characterized by different contents of peptides and free amino acids depending on the type of hydrolysis. Legislation concerning Cr-containing fertilizers is controversial because often do not consider any scientific evidences;nevertheless, the European Union, the United States and countries as Italy, do not set the restriction to Cr(III) and generally only the presence of the toxic form, Cr(VI), is limited. Depending on its two main oxidation forms, Cr issue has been studied for many years. Several authors confirmed that Cr(VI) is carcinogenic, while Cr(III) is an essential trace element in human and animal diet. In soil Cr(III) has low mobility, whereas Cr(VI) is highly water soluble. However Cr(VI) in soil is quickly reduced to Cr(III);on the contrary oxidation of Cr(III) to Cr(VI) is rarely possible because particular conditions must occur. Only a very small fraction of Cr in soil is available to plant uptake and its translocation in edible parts is limited because it is immobilized in roots as Cr(III). Therefore risks of environmental pollution using these fertilizers are negligible;on the contrary they have positive environmental and agronomical effects. The aim of this review is to deal with the category of the organic fertilizers containing Cr derived from tannery processes focusing on its chemical, productive, legislative, environmental and agronomical aspects. Special attention is given to the ambiguous issue of Cr briefly summarizing the most important studies of the last forty years.
文摘Donkey hides are used in a form of Traditional Chinese medicine called ejiao, the demand for ejiao is currently so high the global donkey population is currently in decline. Africa’s donkey population is considered a key source for the trade, with Kenya being highlighted as being particularly affected. In Kenya donkeys play a vital contribution to people’s livelihoods;this study aimed to explore the potential impact of the donkey hide trade on small holder farmer’s livelihoods. The study was conducted in five counties in Kenya;data was collected using household survey questionnaires, focus group discussions and key informant interviews. When household survey participants (n = 421) were asked if the number of donkeys in their herd had decreased within the last two years 34.2% (n = 144) reported a decrease, of those 43.8% (n = 63) reported the selling of donkeys as the primary cause of reduction in herd size. Increased money spent on the transportation of farm produce, water and firewood was the most frequently reported effect of the loss of donkeys (62.5%, n = 263). Some focus group discussion participants said that they had previously sold their donkeys to raise money for school fees, likewise 43% (n = 97) of focus group discussion participants said that they would sell their donkeys to pay medical bills. Results from the study suggest that small holder farmers are choosing to sell their donkeys for an instant boost in income, but long-term this is unlikely to be a sustainable livelihood option.
