Heavy metals, such as cadmium, copper, lead, chromium and mercury, are important environmental pollutants, particularly in areas with high anthropogenic pressure. Their presence in the atmosphere, soil and water, even...Heavy metals, such as cadmium, copper, lead, chromium and mercury, are important environmental pollutants, particularly in areas with high anthropogenic pressure. Their presence in the atmosphere, soil and water, even in traces can cause serious problems to all organisms, and heavy metal bioaccumulation in the food chain especially can be highly dangerous to human health. Heavy metals enter the human body mainly through two routes namely: inhalation and ingestion, ingestion being the main route of exposure to these elements in human population. Heavy metals intake by human populations through food chain has been reported in many countries. Soil threshold for heavy metal toxicity is an important factor affecting soil environmental capacity of heavy metal and determines heavy metal cumulative loading limits. For soil-plant system, heavy metal toxicity threshold is the highest permissible content in the soil (total or bioavailable concentration) that does not pose any phytotoxic effects or heavy metals in the edible parts of the crops does not exceed food hygiene standards. Factors affecting the thresholds of dietary toxicity of heavy metal in soil-crop system include: soil type which includes soil pH, organic matter content, clay mineral and other soil chemical and biochemical properties; and crop species or cultivars regulated by genetic basis for heavy metal transport and accumulation in plants. In addition, the interactions of soil-plant root-microbes play important roles in regulating heavy metal movement from soil to the edible parts of crops. Agronomic practices such as fertilizer and water managements as well as crop rotation system can affect bioavailability and crop accumulation of heavy metals, thus influencing the thresholds for assessing dietary toxicity of heavy metals in the food chain. This paper reviews the phytotoxic effects and bioaccumulation of heavy metals in vegetables and food crops and assesses soil heavy metal thresholds for potential dietary toxicity.展开更多
Global food supply has for a long time been regarded as only a problem of food production. Since the turn of the century, however, other aspects have entered the debate, such as improving food quality, changing eating...Global food supply has for a long time been regarded as only a problem of food production. Since the turn of the century, however, other aspects have entered the debate, such as improving food quality, changing eating habits and avoiding food waste. The latter topic has become the subject of attention for the past I0 years and the interest in it has steadily grown. This paper focuses on food waste within the overall context. Apart from the purely quantitative （material） aspects, it draws our attention to the immaterial side of waste, which has to do with our value system. It hopes to sharpen our minds towards a responsible way of dealing with resources展开更多
The goal of this study was to investigate the behaviour of rainbow trout(n=30),Oncorhynchus mykiss,in small raceways when either self-feeders(T2) or hand-feeding(t2) were used.The method of food delivery in T2 was def...The goal of this study was to investigate the behaviour of rainbow trout(n=30),Oncorhynchus mykiss,in small raceways when either self-feeders(T2) or hand-feeding(t2) were used.The method of food delivery in T2 was defensible while that of t2 was indefensible.Fish in both raceways were subjected to restricted feeding(RF) for 25 days.Food was available in the morning(09:00-10:00) in the downstream area and in the afternoon(16:00-17:00) in the upstream area of the raceways.The results showed that the behaviour of rainbow trout was significantly different under interference competition(T2) for food compared with that under scramble competition(t2).RF in T2 fish limited food availability to meal times when feeding rewards were available while t2 fish only responded to the location of food delivery.The aggressive fish in T2 were dominant,and t2 fish at high densities showed intense social interactions under the indefensible pattern of food distribution;these interactions did not dampen to a minimum level to suppress the development of dominance hierarchies.Further,the stocking density did not break down the dominance hierarchies between the T2 fish.This suggests that decreased efficiency in the search for food or inefficient foraging,induced by interference competition at high densities,affected the behaviour of rainbow trout.展开更多
Achieving both high yield and high nitrogen use efficiency （NUE） simultaneously has become a major challenge with increased global demand for food, depletion of natural resources, and deterioration of environment. A...Achieving both high yield and high nitrogen use efficiency （NUE） simultaneously has become a major challenge with increased global demand for food, depletion of natural resources, and deterioration of environment. As the greatest consumers of N fertilizer in the world, Chinese farmers have overused N, and there has been poor synchrony between crop N demand and N supply because of limited understanding of the N uptake-yield relationship. To address this problem, this study evaluated the total and dynamic N requirement for different yield ranges of two major crops （maize and wheat）, and suggested improvements to N management strategies. Whole-plant N aboveground uptake requirement per grain yield （Nreq） initially deceased with grain yield improvement and then stagnated, and yet most farmers still believed that more fertilizer and higher grain yield were synonymous. When maize yield increased from 〈 7.5 to 〉 12.0 Mg ha-I, Nreq decreased from 19.8 to 17.0 kg Mg-1 grain. For wheat, it decreased from 27.1 kg Mg-1 grain for grain yield 〈 4.5 Mg ha-1 to 22.7 kg Mg-1 grain for yield 〉 9.0 Mg ha-1. Meanwhile, the percentage of dry matter and N accumulation in the middle-late growing season increased significantly with grain yield, which indicated that N fertilization should be concentrated in the middle-late stage to match crop demand while farmers often applied the majority of N fertilizer either before sowing or during early growth stages. We accordingly developed an integrated soil-crop system management strategy that simultaneously increases both grain yield and NUE.展开更多
基金Project supported by the Science and Technology Ministry of China (No. 2002CB410804) and the Education Ministry of China (No. IRT0536)
文摘Heavy metals, such as cadmium, copper, lead, chromium and mercury, are important environmental pollutants, particularly in areas with high anthropogenic pressure. Their presence in the atmosphere, soil and water, even in traces can cause serious problems to all organisms, and heavy metal bioaccumulation in the food chain especially can be highly dangerous to human health. Heavy metals enter the human body mainly through two routes namely: inhalation and ingestion, ingestion being the main route of exposure to these elements in human population. Heavy metals intake by human populations through food chain has been reported in many countries. Soil threshold for heavy metal toxicity is an important factor affecting soil environmental capacity of heavy metal and determines heavy metal cumulative loading limits. For soil-plant system, heavy metal toxicity threshold is the highest permissible content in the soil (total or bioavailable concentration) that does not pose any phytotoxic effects or heavy metals in the edible parts of the crops does not exceed food hygiene standards. Factors affecting the thresholds of dietary toxicity of heavy metal in soil-crop system include: soil type which includes soil pH, organic matter content, clay mineral and other soil chemical and biochemical properties; and crop species or cultivars regulated by genetic basis for heavy metal transport and accumulation in plants. In addition, the interactions of soil-plant root-microbes play important roles in regulating heavy metal movement from soil to the edible parts of crops. Agronomic practices such as fertilizer and water managements as well as crop rotation system can affect bioavailability and crop accumulation of heavy metals, thus influencing the thresholds for assessing dietary toxicity of heavy metals in the food chain. This paper reviews the phytotoxic effects and bioaccumulation of heavy metals in vegetables and food crops and assesses soil heavy metal thresholds for potential dietary toxicity.
文摘Global food supply has for a long time been regarded as only a problem of food production. Since the turn of the century, however, other aspects have entered the debate, such as improving food quality, changing eating habits and avoiding food waste. The latter topic has become the subject of attention for the past I0 years and the interest in it has steadily grown. This paper focuses on food waste within the overall context. Apart from the purely quantitative （material） aspects, it draws our attention to the immaterial side of waste, which has to do with our value system. It hopes to sharpen our minds towards a responsible way of dealing with resources
文摘The goal of this study was to investigate the behaviour of rainbow trout(n=30),Oncorhynchus mykiss,in small raceways when either self-feeders(T2) or hand-feeding(t2) were used.The method of food delivery in T2 was defensible while that of t2 was indefensible.Fish in both raceways were subjected to restricted feeding(RF) for 25 days.Food was available in the morning(09:00-10:00) in the downstream area and in the afternoon(16:00-17:00) in the upstream area of the raceways.The results showed that the behaviour of rainbow trout was significantly different under interference competition(T2) for food compared with that under scramble competition(t2).RF in T2 fish limited food availability to meal times when feeding rewards were available while t2 fish only responded to the location of food delivery.The aggressive fish in T2 were dominant,and t2 fish at high densities showed intense social interactions under the indefensible pattern of food distribution;these interactions did not dampen to a minimum level to suppress the development of dominance hierarchies.Further,the stocking density did not break down the dominance hierarchies between the T2 fish.This suggests that decreased efficiency in the search for food or inefficient foraging,induced by interference competition at high densities,affected the behaviour of rainbow trout.
基金supported by the National Basic Research Program(973 Program) of China(No.2015CB150402)the National Maize Production System in China(No.CARS-02-24)+1 种基金the Special Fund for Agroscientific Research in the Public Interest of China (No.201103003)the Innovative Group Grant of the NSFC,China(No.31421092)
文摘Achieving both high yield and high nitrogen use efficiency （NUE） simultaneously has become a major challenge with increased global demand for food, depletion of natural resources, and deterioration of environment. As the greatest consumers of N fertilizer in the world, Chinese farmers have overused N, and there has been poor synchrony between crop N demand and N supply because of limited understanding of the N uptake-yield relationship. To address this problem, this study evaluated the total and dynamic N requirement for different yield ranges of two major crops （maize and wheat）, and suggested improvements to N management strategies. Whole-plant N aboveground uptake requirement per grain yield （Nreq） initially deceased with grain yield improvement and then stagnated, and yet most farmers still believed that more fertilizer and higher grain yield were synonymous. When maize yield increased from 〈 7.5 to 〉 12.0 Mg ha-I, Nreq decreased from 19.8 to 17.0 kg Mg-1 grain. For wheat, it decreased from 27.1 kg Mg-1 grain for grain yield 〈 4.5 Mg ha-1 to 22.7 kg Mg-1 grain for yield 〉 9.0 Mg ha-1. Meanwhile, the percentage of dry matter and N accumulation in the middle-late growing season increased significantly with grain yield, which indicated that N fertilization should be concentrated in the middle-late stage to match crop demand while farmers often applied the majority of N fertilizer either before sowing or during early growth stages. We accordingly developed an integrated soil-crop system management strategy that simultaneously increases both grain yield and NUE.
