广西中东部9县区农田土壤As输入通量研究

对广西中东部9县区农田土壤中的As输入通量进行了初步研究。综合各方面因素,计算获取了大气干湿沉降、施肥和灌溉水输入通量。结果表明,研究区大气干湿沉降和施肥As输入通量基本相当,平均值分别为9.92 g/(hm^2·a)和7.83 g/(hm^2·a),灌溉水通量最高,平均值为14.98 g/(hm^2·a),三者对土壤As污染的贡献率分别为30.31%、23.92%和45.77%。9个不同县区大气干湿沉降、施肥和灌溉水As输入通量占比略有不同,其中6个县区灌溉水和施肥输入通量占主导地位,另外3个县区大气干湿沉降输入通量比例较高。因此,灌溉水是研究区农田土壤As的主要输入途径,应重视灌溉水水质控制。在未考虑农田土壤As输出通量的情况下,以当前的As年平均输入通量估算得到耕层土壤As的质量分数每年升高0.01 mg/kg。与土壤As含量现状相比,As年增量比例很小,因此判断在短期内,外源输入对土壤As分布现状影响不大。该区土壤p H值较低,铁氧化物含量较高,因此外源输入农田土壤的As生物有效性较低。

Arsenic Input Flux in Farmland Soil of 9 Counties in the Middle East of Guangxi

The input fluxes of As in farmland soil of 9 counties in the middle east of Guangxi were studied.By integrating various factors, the authors took the atmospheric wet and dry depositions, fertilizers and irrigation water as As inputs.Calculation results show that the atmospheric wet and dry depositions and the fertilizers fluxes are about the same, which of the average fluxes are 9.92 g/(hm²·a) and 7.83 g/(hm²·a), while the irrigation water flux is much higher,which of the average flux is 14.98/g/(hm²·a).They contribute 30.31%, 23.92% and 45.77% of As in soil respectively. Their proportions are somewhat different among 9 counties of the study area.The irrigation and fertilizers in 6 counties are dominant, and the proportion of atmospheric wet and dry depositions is higher in the other 3 counties.Therefore, the irrigations is the main input way of As in the study area.Adequate attention should be paid to the water quality controlling.Ignoring the outputs, it is estimated that the As content in farmland soil may increase by 0.01 mg/kg due to the present average flux of arsenic.The proportion of annual As increment in farmland soil is very small, so outside-sourced As will cause little change in As distribution in soil in a short time.The soil of the study area has low pH value and high iron oxides content, so the bioavailability of As is low when it is imported into farmland soil.