摘要
为明确不同母质环境下稻田根系土有效Cd及其活度(RCd)的分布规律及制约因素,在南京沿江冲积平原-丘陵岗地区典型水稻田采集了 300个根系土样,系统分析土壤RCd与根系土 Cd总量及其有效态、pH值、SOM(土壤有机质)含量、CEC(阳离子交换量)等的相关关系,并通过多元回归分析构建不同区块的RCd与其影响因素的预测模型.结果表明:平原区土壤全Cd、有效Cd含量及RCd平均值分别为(0.40±0.07)、(0.13±0.05)mg/kg和(32.87±11.71)％,丘陵区分别为(0.17±0.07)、(0.09±0.03)mg/kg和(53.60±14.26)％;有效Cd与其总量呈极显著正相关(p＜0.01),二者相关系数为0.55,但随着土壤pH值升高相关性减弱;相同母质来源的有效Cd与其pH值、SOM含量均出现极显著负相关(p＜0.01),其中丘陵区相关系数分别为-0.29、-0.39,平原区分别为-0.58、-0.29;RCd与Cd全量在丘陵区呈极显著负相关,但在平原区相关性很弱,与有效Cd呈极显著正相关,尤其是在平原区二者相关系数达0.80,与SOM含量和CEC均呈极显著负相关,与粒度几乎没有相关性;提升土壤pH值、SOM含量和CEC可制约土壤Cd的活度,尤其当土壤pH值≥7.5、SOM含量＞20 g/kg及CEC＞20 cmol/kg时,可显著抑制重金属Cd的活度;采用对数模型和多元回归分析,分别建立了全区、丘陵区、平原区土壤中的Cd活度与其影响因子的定量关系模型,可较好地预测当地农田根系土中重金属Cd的活度,为当地耕地土壤管护及安全利用措施的制定提供依据.
Abstract
In order to clarify the distribution rules and constraints of effective Cd and its activity(RCd)in root soil of paddy fields un-der different parent material conditions,300 root soil samples were collected from the paddy fields in the study area,and the correlation between soil RCd and the total amount,available state,pH,SOM,CEC,etc.of root soil Cd was systematically analyzed.The prediction models of RCd and its influencing factors in different blocks were constructed by multiple regression analysis.The results showed that,firstly,the average contents of total Cd,available Cd and RCd were(0.40±0.07)mg/kg,(0.13±0.05)mg/kg and(32.87±11.71)％in plain area,and(0.17±0.07)mg/kg,(0.09±0.03)mg/kg and(53.60±14.26)％in hilly area,respectively.Secondly,there was a significant positive correlation between available Cd and total Cd(p＜0.0 1),and the correlation coefficient was 0.55,but it decreased with the increase of soil pH.Thirdly,the available Cd from the same parent material was negatively correlated with pH value and SOM(p＜0.01),and the correlation coefficients were-0.29 and-0.39 in hilly area and-0.58 and-0.29 in plain area,respectively.Fourthly,RCd was extremely significant negative with the total amount of Cd in hilly areas,but weak in plain areas;it was extremely significant positive with available Cd,especially in plain areas,where the correlation coefficient was 0.80;it showed a very significant negative correlation with both SOM and CEC.Fifthly,there was almost no correlation with grain size.Sixthly,increasing soil pH,SOM and CEC can restrict the activity of soil Cd,especially when the soil pH was above or equal to 7.5,the content of SOM was above 20 g/kg and the content of CEC was above 20 cmol/kg,it can significantly inhibit the activity of heavy metal Cd.Seventhly,logarith-mic model and multiple regression analysis were used to establish quantitative relationship models of Cd activity and its influencing factors in the whole region,hilly region and plain region,respectively,which could better predict the heavy metal Cd activity in local farmland root soil.
万方数据