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硒元素(Se)近些年一直是学者们关注的微量元素,同时是人体及动物必需的微量营养元素之一,近些年来. 硒在地壳中含量为0.05 mg·kg−1,属于稀有分散元素[1],而我国硒含量分布极为不均匀[2]. 缺硒是发生克山病和大骨节病的重要原因. 而过量的硒可引起中毒[3-5]. 人体摄取硒的主要来源为粮食、水果和蔬菜,而大多数植物获取硒的来源是通过土壤途径,因此研究土壤硒元素对于人体健康及农产品安全有重要意义.
近年来,土壤硒元素的研究成为国内外众多学者的关注热点,杨忠芳等[6]对海南岛土壤研究表明,土壤中黏土矿物、有机质、铁锰氧化物及风化淋溶程度是影响土壤中硒含量变化的主控因素. 而土壤中的硒并无法完全被植物吸收,能被植物吸收的被称为有效硒,周菲等[7]提出了新型有效硒的测定办法,其计算方法所得的特征参数能较好得表征土壤硒生物有效性的可行性. 王锐等[8]基于回归方程对硒的生物有效性进行研究,表明硒生物有效性受到土壤中P和S的含量以及pH的共同影响. 结合前人研究成果[9-11],本文研究土壤硒的分布特征及其影响因素和有效硒的研究对区域土壤治理开发有重要意义.
龙山县有“湘鄂川之孔道”之称,其大面积的土壤属于典型的富硒地带[12]. 本次研究基于龙山县土地质量地球化学调查成果,研究区域内硒的空间分布、垂向迁移及影响因素,探讨土壤有效硒影响因素,以期为富硒土壤合理开发利用和特色农产品种植提供科学依据.
湖南省龙山县耕地土壤硒含量特征及其影响因素
Characteristics and influencing factors of soil se content in cultivated land in Longshan County, Hunan Province
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摘要: 硒是人体及动物必需的微量营养元素之一. 在龙山县耕地区系统地采集了326件表层土壤样品进行分析测试,研究了区域内土壤硒含量空间分布特征、空间变异特性、垂向分布特点及其影响因素,分析了土壤有效态硒的影响因素. 结果表明,研究区土壤硒平均含量为0.33 mg·kg−1,土壤有机质平均含量为20.7 g·kg−1,土壤呈酸性. 土壤硒含量呈中等空间变异,垂向分布呈表层富集的规律. 研究区内硒含量主要受成土母质与土地利用的双重影响,有机质含量与硒含量呈显著正相关关系(P<0.01). 土壤硒形态以腐殖酸结合态与强有机结合态为主,有效硒组分占比较低,土壤硒的生物有效性受硒全量和酸碱度影响较大,可以通过人为方式适当调整土壤酸碱度,提高硒生物有效性,有效提升土地利用价值.Abstract: Se is one of the essential micronutrients for human body and animals. 326 surface soil samples were systematically collected in the cultivated area of Longshan County for analysis and testing. The spatial distribution characteristics, spatial variation characteristics, vertical distribution characteristics and influencing factors of soil Se content in the region were studied, and the influencing factors of soil available Se were analyzed. The results showed that the average content of Se in the study area was 0.33 mg·kg−1, and the average content of soil organic matter was 20.7 g·kg−1. The soil was acidic. The soil of Se content showed medium spatial variation, and the vertical distribution showed the law of surface enrichment. Se content is mainly affected by soil forming parent material and land use in the study area, and there is a significant positive correlation between organic matter content and Se content (P < 0.01). The forms of soil Se are mainly humic acid bound and strong organic bound, and the effective Se components account for a relatively low proportion. The bioavailability of soil Se is greatly affected by the total amount of Se and pH. the soil pH can be adjusted artificially to improve the bioavailability of Se, effectively improve the value of land use.
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Key words:
- top soil /
- Se /
- spatial distribution /
- influencing factors /
- Longshan, Hunan Province
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表 1 研究区土壤硒含量参数统计
Table 1. Statistics of soil Se content parameters in the study area
元素/指标
Elements/Indicators平均值
Mean最大值
Maximum最小值
Minimum标准差
Standard deviation变异系数
Variation coefficient全国土壤背景值[15]
National soil background valueSe/(mg·kg−1) 0.33 0.69 0.18 0.10 0.30 0.22 pH — 8.18 4.01 0.94 0.18 — OM/(g·kg−1) 20.7 36.2 9.22 4.12 0.20 — 注:pH无量纲;“—”表示无数据. Note: pH is dimensionless; "—" means no data 表 2 研究区土壤硒划分标准
Table 2. classification standard of soil Se in the study area
含量等级
Content gradeSe含量/(mg·kg−1)
Se土壤中样品所占比例/%
Samples in soil Proportion面积/km2
Area缺乏 ≤0.125 0 0 边缘 0.125—0.175 0 0 适量 0.175—0.4 87.06 48.82 高 0.4—3.0 12.94 7.26 过剩 >3.0 0 0 表 3 研究区土壤硒理论半方差模型及其拟合参数
Table 3. theoretical semivariance model of soil Se and its fitting parameters in the study area
最优模型
Best Model块金值
C0基台值C0+C 块金系数C0/(C0+C) 变程/km
Range预测误差
Prediction ErrorMS RMSS Se 球面模型 0.534 1.236 0.432 8.159 0.0045998 1.0251987 表 4 不同成土母质土壤中Se元素参数统计
Table 4. statistics of Se element parameters in soils with different soil forming parent materials/mg·kg−1
时代
Times地层名称
Stratum name岩性
Lithology样本数
Sample size平均值/(mg·kg−1)
Mean变化范围/(mg·kg−1)
Variation
range标准差/
(mg·kg−1)
Standard
deviation变异系数
Variation
coefficient寒武系
Cambrian System高台组上段 灰岩、灰绿色页岩、白云岩 40 0.33 0.22—0.61 0.067 0.20 高台组下段 灰岩页岩互层 17 0.31 0.24—0.39 0.039 0.13 奥陶系
Ordovician System大湾组 灰岩、钙质页岩 38 0.26 0.18—0.43 0.045 0.17 志留系
Silurian system帽溪组 黄绿色页岩、泥质粉砂岩、页岩 158 0.35 0.19—0.69 0.099 0.28 罗惹坪组 泥岩、灰岩 73 0.29 0.19—0.46 0.055 0.19 表 5 不同土地利用类型土壤中Se含量参数统计(mg·kg−1)
Table 5. Statistics of Se content parameters in soils of different land use types
土地利用方式
Land use mode平均值
Mean样本数
Sample size变化范围
Variation range标准差
Standard deviation变异系数
Variation coefficient旱地 0.34 210 0.18—0.69 0.091 0.273 水田 0.31 94 0.19—0.55 0.117 0.375 林地 0.29 22 0.21—0.48 0.054 0.184 表 6 研究区土壤硒不同形态含量特征
Table 6. characteristics of different forms and contents of soil Se in the study area
元素形态
Elemental均值/
(mg·kg−1)
Mean最小值/
(mg·kg−1)
Minimum最大值/
(mg·kg−1)
Maximum标准偏差/
(mg·kg−1)
Standard deviation变异系数
Variation
coefficient占比
Proportion水溶态SOL-Se 0.010 0.007 0.015 0.002 16.81% 2.89% 离子交换态EX-Se 0.006 0.004 0.010 0.001 19.03% 1.57% 碳酸盐结合态CA-Se 0.005 0.003 0.012 0.002 42.62% 1.49% 腐殖酸结合态HA-Se 0.133 0.046 0.318 0.069 51.98% 37.36% 铁锰结合态FMO-Se 0.009 0.002 0.022 0.003 39.04% 2.49% 强有机结合态OM-Se 0.092 0.050 0.179 0.036 38.64% 25.87% 残渣态RES-Se 0.083 0.033 0.274 0.038 46.26% 23.38% 表 7 有效硒与硒全量、有机质、pH的偏相关分析结果
Table 7. partial correlation analysis results of Available Se and total Se, organic matter and pH
因变量
Dependent
variable控制变量
Control
variable自变量
Independent
variable相关系数
Correlation
coefficient控制变量
Control
variable自变量
Independent
variable相关系数
Correlation
coefficient有效硒
Available SepH 有机质 0.08 硒全量 有机质 0.42 有机质 pH 0.37 有机质 硒全量 0.68 -
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