丽江高地质背景区马铃薯安全生产的土壤镍铬风险阈值

Soil Nickel and Chromium Risk Thresholds for Safe Potato Production in High Geochemical Background Areas of Lijiang

  • 摘要: 为探讨丽江镍铬高地质背景区马铃薯生产安全, 分别以古城区和玉龙县2个区域的农田土壤及丽薯7号马铃薯为试验材料, 马铃薯可食部位铬(Cr)含量以GB 2762-2022《食品安全国家标准食品中污染物限量》〔w(Cr) < 0.5 mg·kg-1〕为标准, 镍(Ni)含量以《食品卫生理化检验标准手册(1998)》中Ni限值(蔬菜: 0.3 mg·kg-1)为标准, 以生态环境效应法、物种敏感度分布(SSD)法推导马铃薯质量安全的土壤Cr、Ni风险阈值。结果表明: 丽江市采样区土壤Cr、Ni总量超过GB 15618-2018《土壤环境质量农用地土壤污染风险管控标准(试行)》中农用地土壤污染风险筛选值, T4~T6采样点土壤Cr总量(545~907 mg·kg-1)均超过筛选值且T5采样点(907 mg·kg-1)超过管制值1.30倍, T3~T6采样点土壤Ni总量(202~1 210 mg·kg-1)均超过筛选值。T6采样点中马铃薯可食部位Ni含量超过《食品卫生理化检验标准手册(1998)》3.23倍, 可食部位Ni含量与自然污染土壤总Ni含量呈显著正相关(P<0.05), 与产量呈显著负相关; 可食部位Cr含量与土壤总Cr含量不呈现相关性, 与产量呈显著负相关(P<0.05)。马铃薯可食部位Cr含量与外源添加配制土壤有效态Cr含量呈显著正相关(P<0.05), 可食部位Ni含量与土壤Ni、有效态Ni含量均呈显著正相关(P<0.05), 产量与土壤Ni含量不相关。基于马铃薯减产10%的标准通过建立线性回归模型, 确定了土壤(pH值>7.5)中Ni的风险阈值为631 mg·kg-1, 外源添加配制土壤盆栽试验数据以线性回归模型与SSD法拟合推导土壤总Cr含量(pH值>7.5)分别为1 809和1 547 mg·kg-1, 土壤pH值介于6.5~7.5之间推导总Ni含量阈值分别为231和393 mg·kg-1。采样区土壤总Cr、Ni含量超标严重, 但马铃薯可食部位超标率相对较低且超标倍数小, 基于马铃薯质量安全和产量减产10%条件下推导土壤Cr含量阈值(1 547 mg·kg-1)是农用地土壤污染风险管制值的1.19倍。现行农用地土壤Ni、Cr标准应用丽江高Cr、Ni含量背景研究区较为严苛, 基于高背景情形下推导的风险阈值为该地区马铃薯安全生产提供了科学依据。

     

    Abstract: To investigate the safe production of potatoes in the high chromium (Cr) and nickel (Ni) geochemical background areas in Lijiang, farmland soil samples from two regions (Gucheng District and Yulong County) and the potato variety Lishu-7 were used as experimental materials. The chromium content in edible potato parts was evaluated against the maximum permissible limit for contaminants in foods (GB 2762-2022, Cr < 0.5 mg·kg-1), while the nickel content was assessed according to the Ni limit for vegetables (0.3 mg·kg-1) specified in the Standard Manual of Physicochemical Testing for Food Hygiene (1998). The eco-environment effect method and species sensitivity distribution (SSD) method were applied to derive soil Cr and Ni risk thresholds to ensure potato quality and safety. The results show that the total Cr and Ni concentrations in the soil samples collected from Lijiang exceeded the soil pollution risk screening values for agricultural land (GB 15618-2018). Total Cr concentrations ranged from 545 to 907 mg·kg-1 in naturally contaminated soil (T4-T6), all exceeding the screening value, with T5 (907 mg·kg-1) surpassing the risk control value by 1.30 times. In T6, Ni content in edible potato parts exceeded the food standard by 3.23 times. Ni content in edible parts showed a significant positive correlation (P < 0.05) with total Ni in naturally contaminated pot soils and a significant negative correlation with yield. Cr content in edible parts showed no correlation with total soil Cr but was significantly negatively correlated with yield. In artificially spiked soils, Cr content in edible parts was significantly positively correlated with available Cr (P < 0.05), and Ni content was significantly positively correlated with both total and available Ni (P < 0.05). Yield showed no correlation with soil Ni content. Based on a 10% yield reduction and a linear regression model, the risk threshold for Ni in soil (pH>7.5) was determined to be 631 mg·kg-1. Using data from pot experiments with artificially spiked soils, risk thresholds for total Cr in soil (pH < 7.5) were derived as 1 809 mg·kg-1 (linear regression) and 1 547 mg·kg-1 (SSD method). For soils with pH between 6.5 and 7.5, total Ni thresholds were 231 mg·kg-1 and 393 mg·kg-1 respectively. Although total Cr and Ni concentrations in the sampled soils significantly exceeded standard limits, the exceedance rate and magnitude in the edible potato parts were relatively low. Based on both potato quality safety and ≤10 % yield reduction, the derived soil Cr threshold (1 547 mg·kg-1) was 1.19 times the existing risk control value for agricultural soils. This study suggests that the existing national standards for Ni and Cr in agricultural soils may be overly stringent for the high Ni and Cr geological background area of Lijiang. The risk thresholds derived under high background conditions provide a scientific basis for safe potato production in this region.

     

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