贵州喀斯特地区辣椒镉的累积特性及土壤风险阈值研究

Cadmium accumulation properties of pepper and risk threshold of soils in Karst Area of Guizhou Province

辣椒(Capsicum annuum L.)是我国西南喀斯特重金属地质高背景区的特色农作物,属茄科,具有一定镉(Cadmium)富集能力。为明确贵州主产区辣椒Cd的富集状况,探究辣椒质量安全的土壤风险阈值,保障农产品安全生产。采集贵州省9个县区辣椒及土壤样品105组,利用ICP-MS检测Cd含量,研究土壤Cd分布,辣椒富集系数,并根据土壤pH建立回归模型推导基于辣椒质量安全的土壤Cd风险阈值。结果表明,有4个研究区土壤均值超过贵州省土壤Cd背景值(0.659 mg·kg^(-1)),超出率分别是:WS(25.8%)、HZ(42.2%)、LD(146%)、WN(439%);18.1%的辣椒超过国家食品安全Cd限值标准(GB2762—2017,0.05 mg·kg^(-1)),点位超标率为LD(20.8%)、TZ(7.69%)和WN(100%);辣椒Cd的生物富集系数(BCF)范围是0.019至0.108,均值0.046。由回归模型推算出酸性土(pH<6.5)、中性土(6.5≤pH≤7.5)、石灰性土(pH>7.5)中Cd风险阈值分别为1.00、1.26和2.50 mg·kg^(-1),分别为国家农用地土壤污染风险筛选值(GB15618—2018)的3.33、4.21、4.17倍,阈值准确率达91.1%;有效态Cd风险阈值为0.071、0.017和0.005 mg·kg^(-1),阈值准确率达86.1%。地质高背景区农田土壤Cd超标严重,但辣椒的生物富集系数相对较低,基于辣椒质量安全的土壤Cd风险阈值远高于国家标准。

Pepper(Capsicum annuum L.)is a characteristic crop in the karst geological high background area of heavy metals in Southwest China,and it belongs to the solanaceae and has certain cadmium enrichment ability.In order to clarify the enrichment status of pepper Cd in the main producing areas of Guizhou province,the Cd risk threshold of pepper in soil was studied,to ensure the safe production of agricultural products.105 groups of pepper and soil samples were collected from 9 counties in Guizhou province.Cd content was detected by ICP-MS,soil Cd distribution and pepper enrichment coefficients were studied,and the soil Cd risk threshold based on pepper quality safety was deduced by establishing a regression model according to soil pH.The results showed that soil Cd in 4 areas exceeded the background value of soil Cd in Guizhou Province(0.659 mg·kg^(-1)),and the exceeding standards rate were:WS(25.8%),HZ(42.2%),LD(146%),WN(439%).18.1%of peppers exceed Cd limit standard of the National Food Safety Standards(GB2762-2017,0.05 mg·kg^(-1)),and the exceeding standard rates,LD(20.8%),TZ(7.69%)and WN(100%)were found.The bioenrichment coefficient of pepper Cd ranged from 0.019 to 0.108,with a mean of 0.046.According to the regression model,the Cd risk thresholds of acidic soil(pH<6.5),neutral soil(6.5≤pH≤7.5)and calcareous soil(pH>7.5)were 1.00,1.26 and 2.50 mg·kg^(-1),respectively,which were 3.33,4.21 and 4.17 times of the risk screening value for soil contamination of agricultural land(GB15618-2018),and accuracy rate of the soil risk threshold reached 91.1%.The soil risk thresholds of available Cd were 0.071,0.017,and 0.005 mg·kg^(-1),and the threshold accuracy rate was 86.1%.Cd in soil of agricultural land exceeded the standard value seriously in high geological background areas,but the BCF of pepper was relatively low;the soil Cd risk threshold based on pepper quality and safety is much higher than the national standard.