14C-tracer technique and closed incubation method were used to study straw 14C decomposition and distribution in different fractions of newly formed humus under different moisture regimes. Decomposition of straw 14C w...14C-tracer technique and closed incubation method were used to study straw 14C decomposition and distribution in different fractions of newly formed humus under different moisture regimes. Decomposition of straw 14C was faster during the initial days, and slower thereafter. Decay rate constants of straw 14C varied from 3.29x10-3 d-1 to 7.06x10-3 d-1. After 112 d incubation, the amount of straw 14C mineralized was 1.17～1.46 times greater in submerged soils than in upland soils. of the soil residual 14C, 9.08%～15.73%was present in humic acid (HA) and 31.01%～37.62% in fulvic acid (FA). Submerged condition favored the formation of HA, and HA/FA ratio of newly formed humus (labelled) was greater in submerged soils than in upland soils. Clay minerals affected the distribution of straw 14C in different humus fractions. Proportion of 14C present in HA to 14C remaining in soil was greater in Vertisol than in Ultisol.展开更多
Laboratory incubation was conducted to investigate transformation of straw 14 C in Ultisol and Vertisol under aerobic condition for 112 d at 30 oC. Dried and ground 14 C labeled rice and maize...Laboratory incubation was conducted to investigate transformation of straw 14 C in Ultisol and Vertisol under aerobic condition for 112 d at 30 oC. Dried and ground 14 C labeled rice and maize straws were mixed with the soils at the rate of 2.5 g kg -1 . Decomposition of the straw C and native soil C both revealed two stages, being faster during the initial days, and slower thereafter. About 37.33%～48.80% of the straw C and 4.22%～6.83% of the native soil C decomposed by the end of the incubation. The kinds of the straws only slightly influenced the rates of their decomposition in soils, however, some retardation was found in Ultisol at the initial decomposition stage due to its lower pH. Positive priming effects were observed in the soils applied with straw, and the rate of priming effect ranged from 7.23% to 13.80%. Net losses of native soil C were found under such incubation conditions, except Ultisol with rice straw. Soil biomass C and 14 C decreased gradually with incubation time, and seemed to be consistent with the decomposition patterns of straw C and native soil C. The ratio of biomass 12 C to biomass 14 C ranged from 1.35 to 3.37. Soil biomass C occupied 1.17%～2.32% of the total soil organic C, and the proportion of biomass 14 C to the residual 14 C varied from 7.3% to 14.3%.展开更多
The ring-and side-chain-<sup>14</sup>C-labeled probimane, 1,2-bis （4-morpholinomethy1-3,5-dioxopiperazin-1-yl） propane were synthesized from acetic acid-1-<sup>14</sup>C in 4 steps and from &...The ring-and side-chain-<sup>14</sup>C-labeled probimane, 1,2-bis （4-morpholinomethy1-3,5-dioxopiperazin-1-yl） propane were synthesized from acetic acid-1-<sup>14</sup>C in 4 steps and from <sup>14</sup>C-formaldehyde in 1 step respectively. The radiochemical yeild for the ring labeling was 28.1%; for the side-chain labeling was 18.5%.展开更多
The syntheses of N-Methyl-14C benzyl amine and N-Methyl-14C benzyl nitrosamine are reported. Specific activities were approximately 920 MBq/mmol. Chemical and radiochemical purity checked by HPLC were more than 95%.
文摘14C-tracer technique and closed incubation method were used to study straw 14C decomposition and distribution in different fractions of newly formed humus under different moisture regimes. Decomposition of straw 14C was faster during the initial days, and slower thereafter. Decay rate constants of straw 14C varied from 3.29x10-3 d-1 to 7.06x10-3 d-1. After 112 d incubation, the amount of straw 14C mineralized was 1.17～1.46 times greater in submerged soils than in upland soils. of the soil residual 14C, 9.08%～15.73%was present in humic acid (HA) and 31.01%～37.62% in fulvic acid (FA). Submerged condition favored the formation of HA, and HA/FA ratio of newly formed humus (labelled) was greater in submerged soils than in upland soils. Clay minerals affected the distribution of straw 14C in different humus fractions. Proportion of 14C present in HA to 14C remaining in soil was greater in Vertisol than in Ultisol.
文摘Laboratory incubation was conducted to investigate transformation of straw 14 C in Ultisol and Vertisol under aerobic condition for 112 d at 30 oC. Dried and ground 14 C labeled rice and maize straws were mixed with the soils at the rate of 2.5 g kg -1 . Decomposition of the straw C and native soil C both revealed two stages, being faster during the initial days, and slower thereafter. About 37.33%～48.80% of the straw C and 4.22%～6.83% of the native soil C decomposed by the end of the incubation. The kinds of the straws only slightly influenced the rates of their decomposition in soils, however, some retardation was found in Ultisol at the initial decomposition stage due to its lower pH. Positive priming effects were observed in the soils applied with straw, and the rate of priming effect ranged from 7.23% to 13.80%. Net losses of native soil C were found under such incubation conditions, except Ultisol with rice straw. Soil biomass C and 14 C decreased gradually with incubation time, and seemed to be consistent with the decomposition patterns of straw C and native soil C. The ratio of biomass 12 C to biomass 14 C ranged from 1.35 to 3.37. Soil biomass C occupied 1.17%～2.32% of the total soil organic C, and the proportion of biomass 14 C to the residual 14 C varied from 7.3% to 14.3%.
文摘The ring-and side-chain-<sup>14</sup>C-labeled probimane, 1,2-bis （4-morpholinomethy1-3,5-dioxopiperazin-1-yl） propane were synthesized from acetic acid-1-<sup>14</sup>C in 4 steps and from <sup>14</sup>C-formaldehyde in 1 step respectively. The radiochemical yeild for the ring labeling was 28.1%; for the side-chain labeling was 18.5%.
文摘The syntheses of N-Methyl-14C benzyl amine and N-Methyl-14C benzyl nitrosamine are reported. Specific activities were approximately 920 MBq/mmol. Chemical and radiochemical purity checked by HPLC were more than 95%.
