Incubation, macrocosm and field studies were carried out to observe any increase in the concentration of arsenic （As） in soil and its subsequent uptake by plants due to disposal of As-filter sludge into soil from tw...Incubation, macrocosm and field studies were carried out to observe any increase in the concentration of arsenic （As） in soil and its subsequent uptake by plants due to disposal of As-filter sludge into soil from two different arsenic removal media. One of the media was iron based and the other was activated alumina based. For the incubation study, sludge @ 1 T.ha^-1 and 0.5 T.hal from the two sources wer applied to soils and incubated for 180 days with five individual incubation periods viz., 15, 30, 60, 90 and 180 days. At the end of each incubation period the soils were extracted with 1M HCI. For the macrocosm study, a leafy vegetable-lpomoea aquatica L. and rice （Oryza sativa L.） were grown in pots treated with sludge @ 1 T·ha^-1 and 0.5 T·ha^-1 soils. For the field study, two leafy vegetables viz., red amaranthus （Amaranthus gangeticus L.） and Kalmi （Ipomoea aquatiea L.） were grown on soils treated with the sludge @ 1 T.ha^-1 in plots of 1 m^2 sizes. Arsenic was found to have increased under upland and lowland conditions that contributed to an increased accumulation of the element in the plants. The increase of As was found to be relatively higher under upland condition than under submerged condition. Arsenic accumulation in plants was found to be the highest in the roots followed by straw and grain. Similar observation has been made under field condition too. Increased concentration of Fe an AI has also been observed which could be a new environmental hazard. The study reveals that the filters used for making As-safe drinking water cannot be safely disposed of to the soil, particularly to the agricultural soils.展开更多
Azadirachta indica A. Juss, Dalbergia, sissoo Roxb., and Melia azedarach L. are little studied species in nutrient return capabilities from leaf litter decomposition to maintenance of the soil fertility despite their ...Azadirachta indica A. Juss, Dalbergia, sissoo Roxb., and Melia azedarach L. are little studied species in nutrient return capabilities from leaf litter decomposition to maintenance of the soil fertility despite their importance in agroforestry practices of Bangladesh. A leaf litter decomposition experiment was conducted using a litterbag teeh7 nique to assess the nutrient reaun efficiency of these species. The de- composition rate of leaf litter was highest for M. azedarach and lowest for D. sissoo. Rainfall and temperature of study sites showed a significant （p〈0.05） positive relationship with the rate of leaf litter decomposition. The highest decay constant was observed for M. azedarach （6.67）. Nitrogen and Phosphorus concentration in leaf litter showed a decreased trend sharply at the end of the first month, whereas rapid decrease of Potassium concentration was reported within 10 days. Conversely, higher concentration of nutrient was observed at the later stages of decomposition. All three species showed a similar pattern of nutrient release （K 〉 N 〉 P） during the decomposition process of leaf litter. Among the studied species, D. sissoo was best in terms of N and P return and A. indica was best in terms of K return.展开更多
文摘Incubation, macrocosm and field studies were carried out to observe any increase in the concentration of arsenic （As） in soil and its subsequent uptake by plants due to disposal of As-filter sludge into soil from two different arsenic removal media. One of the media was iron based and the other was activated alumina based. For the incubation study, sludge @ 1 T.ha^-1 and 0.5 T.hal from the two sources wer applied to soils and incubated for 180 days with five individual incubation periods viz., 15, 30, 60, 90 and 180 days. At the end of each incubation period the soils were extracted with 1M HCI. For the macrocosm study, a leafy vegetable-lpomoea aquatica L. and rice （Oryza sativa L.） were grown in pots treated with sludge @ 1 T·ha^-1 and 0.5 T·ha^-1 soils. For the field study, two leafy vegetables viz., red amaranthus （Amaranthus gangeticus L.） and Kalmi （Ipomoea aquatiea L.） were grown on soils treated with the sludge @ 1 T.ha^-1 in plots of 1 m^2 sizes. Arsenic was found to have increased under upland and lowland conditions that contributed to an increased accumulation of the element in the plants. The increase of As was found to be relatively higher under upland condition than under submerged condition. Arsenic accumulation in plants was found to be the highest in the roots followed by straw and grain. Similar observation has been made under field condition too. Increased concentration of Fe an AI has also been observed which could be a new environmental hazard. The study reveals that the filters used for making As-safe drinking water cannot be safely disposed of to the soil, particularly to the agricultural soils.
基金supported by Bangladesh Academy of Science and University Grants Commissions of Bangladesh
文摘Azadirachta indica A. Juss, Dalbergia, sissoo Roxb., and Melia azedarach L. are little studied species in nutrient return capabilities from leaf litter decomposition to maintenance of the soil fertility despite their importance in agroforestry practices of Bangladesh. A leaf litter decomposition experiment was conducted using a litterbag teeh7 nique to assess the nutrient reaun efficiency of these species. The de- composition rate of leaf litter was highest for M. azedarach and lowest for D. sissoo. Rainfall and temperature of study sites showed a significant （p〈0.05） positive relationship with the rate of leaf litter decomposition. The highest decay constant was observed for M. azedarach （6.67）. Nitrogen and Phosphorus concentration in leaf litter showed a decreased trend sharply at the end of the first month, whereas rapid decrease of Potassium concentration was reported within 10 days. Conversely, higher concentration of nutrient was observed at the later stages of decomposition. All three species showed a similar pattern of nutrient release （K 〉 N 〉 P） during the decomposition process of leaf litter. Among the studied species, D. sissoo was best in terms of N and P return and A. indica was best in terms of K return.
