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以四川成都经济区农业生态系统中的重金属Cd为对象,对其在土壤中的输入输出通量进行初步探索。综合各方面的因素,确定以大气干湿沉降、灌溉水、化肥为输入途径和农作物为输出途径进行研究。经过计算,经济区大气干湿沉降通量平均值为17.76g/hm2·a,灌溉水和化肥通量明显较低,三者对土壤Cd污染的贡献率分别为86%、10%和4%。对于6个不同的地区,三者比例略有差别,大气干湿沉降所占比例最高达94%,最低也达到了77%。Cd通过农作物收割输出的量相对较小。土壤Cd年净增量主要受大气干湿沉降的制约,因此大气环境质量应是重点监控的对象。以耕作土体为研究介质,经估算,当前的Cd年平均通量可引起土壤Cd的质量分数升高0.006mg/kg。
Taking the heavy metal Cd in agroecosystem of Chengdu Economic Zone in Sichuan as an example, the input and output fluxes in soil were preliminary explored. Taking all factors into account, it is determined that wet-dry deposition of the atmosphere, irrigation water and fertilizer as the input channels and crops as output channels. After calculation, the mean value of dry-wet deposition flux in the economic zone is 17.76g / hm2 · a, and the flux of irrigation water and fertilizer is obviously lower. The contribution rates of the three to the soil Cd pollution are respectively 86%, 10% and 4% . For six different regions, the proportions of the three are slightly different. The proportion of dry-wet deposition in the atmosphere reaches up to 94% and the lowest reaches 77%. The amount of Cd harvested through crop harvesting is relatively small. The net annual increment of Cd in soils is mainly controlled by atmospheric wet and dry deposition, so the quality of atmospheric environment should be the focus of monitoring. Taking tillage soil as the research medium, it is estimated that the current annual average flux of Cd can cause the mass fraction of soil Cd to increase by 0.006mg / kg.