【作者】 薛占军；

【导师】 刘树庆；

【作者基本信息】 河北农业大学 ， 土壤学， 2012， 博士

【摘要】 土壤是人类生存和发展的物质基础,其质量的优劣不仅影响着农作物的产量,而且还决定着农产品的安全品质和农业发展的可持续性。然而,在水资源日益短缺和水污染不断加剧的双重压力下,长期污灌土壤的生态环境污染问题日趋凸显,并严重制约着我国农业的可持续发展。因此,本研究以河北省主要不同区域（衡水、石家庄、沧州和保定）的污灌土壤为研究对象,分析了反映土壤质量的理化性质、酶活性、重金属及其各形态含量水平和农作物的重金属污染水平,评价了污灌土壤的肥力质量、环境质量、综合质量以及农作物的健康风险,指出了污灌土壤现存的主要问题,对于遏制污灌土壤环境质量的下降、调控污灌土壤肥力质量、确保污灌农作物产品安全均具有十分重要意义。所取得的主要研究结果如下:（1）河北省主要污灌土壤质地总体上属于壤土,其中衡水、石家庄和保定区域属于中壤土,沧州区域属于重壤土。对于0～20cm污灌土壤pH值而言,石家庄和保定区域50%以上的样本为中性,衡水和沧州区域80%以上的样本为碱性,但是不同区域90%以上的20～40cm污灌土壤样本仍为碱性。根据全国第二次土壤肥力状况普查结果和河北省土壤肥力状况的分级标准可知,河北省0～20cm污灌土壤的有机质、全钾和速效钾含量达中等偏上水平,全氮、速效氮、全磷和速效磷含量则处于低等水平,其中石家庄区域的相对等级水平最高。0-20cm污灌土壤脲酶、过氧化氢酶、碱性磷酸酶和转化酶活性与大部分理化性质指标显著相关,石家庄和保定区域污灌土壤酶活性最高,衡水和沧州污灌土壤酶活性最低,且突出表现在土壤脲酶活性上。20～40cm污灌土壤的养分含量和酶活性均明显降低,且不同区域间的差异也显著减小。基于模糊数学法的污灌土壤肥力质量评价结果显示,衡水、石家庄、沧州和保定区域0-20cm污灌土壤肥力质量综合指数分别为0.42、0.67、0.40和0.61,分别属于中等、较高、中等和较高的肥力等级水平。（2）河北省主要污灌土壤重金属含量的大小顺序为,Fe>Ti>Mn>Zn>V>Cr>Pb >Cu>Ni>Co>As>Sn>Cd>Hg（20～40cm土层的为Cu>Pb）,除Fe、Mn和As外,其余重金属元素平均含量的最高值均出现在石家庄区域。与河北省土壤背景值相比,大部分重金属元素的累积现象较明显,突出表现在Hg、Cd、Zn和Pb元素上,且存在不同程度超中国土壤环境质量II级标准、无公害和绿色食品产地标准的样本比例,最高为Cd的44.4%,最低为Pb的8.9%。主成分分析和聚类分析结果一致表明,污灌土壤中的Cd、Cr、Cu、Pb、Sn和Zn主要受人类生产活动的影响,而As、Fe、Mn、Co、Ti和V则主要受自然成土过程的影响。污灌土壤中的大部分重金属元素以残渣态和铁锰氧化态的形式存在,而可交换态（除Cd和Cr）的比例则最低。污灌土壤环境质量评价及预警结果显示,较高水平的Hg、Cd、Zn、Pb和Cu累积,在污染土壤环境的同时,也构成了严重的生态危害,其中石家庄污灌土壤的综合潜在生态风险达很强程度,预警级别达中度及重度的相对比例为57.15%;保定和沧州污灌土壤的生态风险达较强程度,预警级别达中度及重度的相对比例分别为25.00%和6.67%;衡水污灌土壤的生态风险达中等水平,94.44%的相对风险概率处于无警级别。（3）与中国食品卫生相关标准相比,污灌粮食籽粒（除棉花）主要存在Pb和Hg的超标问题,且小麦超标样本比例（8.5%和16.7%）略高于玉米的（6.0%和10.0%）;污灌叶菜类蔬菜（除菜花）主要存在Zn、Ni、Pb、Cd和Hg的超标,其中菠菜Pb和Cd的超标样本比例高达50%以上,而白菜、油菜、香菜和韭菜的超标样本比例主要集中在10%-30%之间;根菜类蔬菜主要存在Zn、Ni、Pb和Cd的超标,除大葱外,其它根菜类的超标比例均较高,其中芥菜和白萝卜的Pb超标比例均达100%,这主要与农作物对重金属的富集能力密切相关。污灌农作物健康风险评价结果显示,除芥菜Pb和玉米Ni的单一重金属健康风险指数（HRI）接近1外,其它农作物的HRI均小于1。但是,玉米、芥菜、菠菜、白萝卜、香菜和油菜可食部分所有重金属的综合健康风险指数THQ>1,表明这些污灌作物具有较高的健康风险,尤其是对儿童。结合污灌农作物可食部分重金属含量与土壤重金属形态间的相关性和食品卫生标准中重金属含量的最大允许量获得,种植粮食和蔬菜作物的污灌土壤重金属Pb、Zn、Cd、Cr的交换态临界含量分别为4.47 mg kg^-1、10.99 mg kg^-1、0.27 mg kg^-1、42.38 mg kg^-1和8.45 mg kg^-1、16.38 mg kg^-1、0.15 mg kg^-1、52.97 mg kg^-1;种植粮食作物的污灌土壤重金属Pb和Cr的碳酸盐态临界含量分别为1.75 mg kg^-1和8.83 mg kg^-1,种植蔬菜作物的污灌土壤重金属Zn的碳酸盐态临界含量分别为42.37 mg kg^-1;种植粮食作物的污灌土壤重金属Zn和Cr的铁锰氧化态临界含量分别为67.08 mg kg^-1和14.29 mg kg^-1,种植蔬菜作物的污灌土壤重金属Cr的铁锰氧化态临界含量为31.19 mg kg^-1。（4）采用Box-Cox转化法对污灌土壤养分化学、酶学和有效态重金属指标进行正态性检验及其转化后,基于主成分分析法（PCA）的污灌土壤质量综合分析评价显示,衡水区域的污灌土壤综合质量最优,石家庄区域的最差,保定和沧州的位列中等,且不同区域间存在显著差异（P<0.05）。由此可见,受人类生产活动影响的重金属Cd、Pb、Cr、Cu、Sn和Zn是降低石家庄区域污灌土壤环境质量和综合质量的主要因子,需进行重金属污染土壤的修复或种植低富集的农作物（如棉花、菜花和大葱）,提高其环境质量,避免农作物安全品质污染事故的发生;对于其它污灌区域,特别是衡水地区应注重土壤肥力质量的改善措施与良性种植模式的运用,同时建立长期的、动态的污灌土壤质量定位监测机制,减轻对人体健康的危害,逐步实现污灌土壤的可持续发展。更多还原

【Abstract】 As is well known, soil is the material foundation of human living and development. Soil quality affects not only crop yields but is also a significant factor governing food safety and agricultural sustainability. Under the double pressures from lack and contamination of water resource, the pollution problem of soil ecological environment deprived from long-term sewage irrigation has been showing seriously and restricting development of sustainable agriculture in China. Therefore, this study was carried out taking sewage-irrigated soil sampled from different area （HS, SJZ, CZ, BD） in low-plain region of Hebei province as research subject. The physicochemical properties, enzyme activities, heavy metal and its fraction in soil and content of heavy metal in crop were determined and analyzed. We assessed the fertility quality, environment quality, comprehensive quality of soil and health risk of crop. The main problems of sewage-irrigated soil in different sampling area of Hebei province were revealed. The results will play an important role in suppressing soil environment quality decrease, improving soil fertility, and ensuring food safety for the sewage-irrigated area of Hebei province. The major findings were summarized as follows:（1） The sewage-irrigated soil in Hebei province was loam, including medium loam for HS, SJZ, BD and heavy loam for CZ. As far as pH of 0～20cm soil samples were concerned, the proportion of 6.5～7.5 reached more than 50% in SJZ and BD, whereas more than 80% of soil samples were alkaline（7.5～8.5） in CZ and HS. Additionally, more than 90% of 20～40cm soil samples were still alkaline in the all sewage-irrigated area.According to soil fertility standard of the second national soil survey and current situation of soil fertility in Hebei province, the organic matter, total potassium and available potassium contents of 0～20cm sewage-irrigated soil were in the medium-high level. The total nitrogen and phosphorus, available nitrogen and phosphorus content were in low level. Among the four sewage-irrigated area, the organic matter, nitrogen, phosphorus and potassium content in SJZ were the highest. The urease, catalase, alkaline phosphatase and invertase activities were correlated with mostly physicochemical properties in a significant or very significant way. On the whole, enzyme activities of sewage-irrigated soil in BD and SJZ were higher, but the lower soil enzyme activities were recorded in HS and CZ, especially for urease activity. The physicochemical properties and enzyme activities of sewage-irrigated soil were lower in 20～40cm soil layer than in 0～20cm soil layer and decreased in significant difference of four sewage-irrigated areas.The present situation of fertility quality of 0～20cm sewage-irrigated soil was evaluated by using fuzzy mathematical method. The results showed that soil fertility quality index（SFQI） for HS, SJZ, CZ and BD was 0.42、0.67、0.40 and 0.61, respectively in moderate, higher, moderate and higher fertility level.（2） The contents of heavy metals in sewage-irrigated soil sampled from low-plain region of Hebei province followed the order of Fe>Ti>Mn>Zn>V>Cr>Pb> Cu> Ni>Co> As>Sn>Cd>Hg（Cu>Pb in 20～40cm）. Except for Fe, Mn and As, the average concentrations of other heavy metals in SJZ were the highest. Compared with the background values of heavy metals in Hebei province, an accumulation level of heavy metals was significant in the sewage-irrigated soils, especially for Hg, Cd, Zn and Pb, which were beyond the permissible limits set by the State Environmental Protection Administration（SEPA） and Ministry of Agriculture（MA） in China. The proportion of soil samples was exceeded by 44.4% for Cd and 8.9% for Pb, respectively. The principal component analysis（PCA） in combination with cluster analysis （CA） revealed that heavy metal contamination had different origination. The primary inputs of Cd, Cr, Cu, Pb, Sn and Zn in sewage-irrigated soils were due to anthropogenic sources, whereas As, Fe, Mn, Co, Ti and V were mainly of pedogenic source. A considerable proportion of the mostly heavy metals resided in residual fractions, whereas Cd and Cr dominated the exchangeable fraction.An assessment of soil environmental quality and its warning results revealed that the study area was higher enrichment level with respect to Hg, Cd, Zn, Pb and Cu, which led the contamination of soil and posed severely ecological risk. The degree of comprehensive ecological risk in SJZ was very strong; and moderately to strongly warned with 57.15% relative level. The degree of comprehensive ecological risk in CZ and BD was stronger; and moderately to strongly warned with 25.00% and 6.67% relative level, respectively. The degree of comprehensive ecological risk in HS was moderate; and no warned with 94.44% relative level.（3） Concentrations of Pb and Hg in grain seeds（except for cotton seed） selected from the sewage-irrigated soil were beyond the safe limit of pollutants in food of China （GB2762–2005）; and the contamination with Pb and Hg was at its higher level in wheat seed（8.5% and 16.7%） than in maize seed（6.0% and 10.0%）. Concentrations of Zn, Ni, Pb, Cd and Hg in leafy vegetables （except for cauliflower） selected from the sewage-irrigated soil were beyond the safe limit of pollutants in food of China （GB2762–2005）; more than 50% leafy vegetable samples contaminated with Pb and Cd were found in edible parts of spinach; and between 10% to 30% leafy vegetable samples contaminated with Zn, Ni, Pb, Cd and Hg appeared to all edible parts of Chinese cabbage, rape, parsley, and chives. Concentrations of Zn, Ni, Pb and Cd in root vegetables （except for scallion） selected from the sewage-irrigated soil were beyond the safe limit of pollutants in food of China （GB2762–2005）; and all the root vegetable samples contaminated with Pb were found in edible parts of mustard and white radish, which were related to higher enrichment factor of heavy metals in root vegetables grown in sewage-irrigated soil.The health risk index（HRI） of single heavy metal for crops grown in sewage-irrigated soil suggested that the consumption of mustard and maize posed a higher health risk for Pb and Ni, respectively; but other vegetables were free of health risks. However, the combined total health quotients （THQ） exceeded the safe level（THQ>1） and were not free of risk for maize, mustard, spinach, white radish, parsley and rape. In all crops THQ for children were higher than that for adults.The species of crops, available fraction of heavy metal and food health standard were all taken into consideration for establishing available heavy metal fraction thresholds based on soil-plant system in the sewage-irrigated area. The threshold values of exchangeable fraction of Pb、Zn、Cd and Cr were 4.47 mg kg^-1, 10.99 mg kg^-1, 0.27 mg kg^-1 and 42.38 mg kg^-1 for grain growing soil, 8.45 mg kg^-1, 16.38 mg kg^-1, 0.15 mg kg^-1 and 52.97 mg kg^-1 for vegetable growing soil, respectively. The threshold values of carbonate fraction of Pb and Cr were 1.75 mg kg^-1 and 8.83 mg kg^-1 for grain growing soil; and 42.37 mg kg^-1 of Zn for vegetable growing soil. The threshold values of iron/manganese oxide fraction of Zn and Cr were 67.08 mg kg^-1 and 14.29 mg kg^-1 for grain growing soil; and 31.19 mg kg^-1 of Cr for vegetable growing soil.（4） Principal component analysis （PCA） output using Box-Cox normalization on raw dataset of physicochemical properties, enzyme activities, available heavy metals in 0～20cm sewage-irrigated soil demonstrated that comprehensive soil quality in HS was the best; the worst comprehensive soil quality was found in SJZ; and the moderately comprehensive soil quality was recorded in BD and CZ. The difference in four sewage-irrigated areas was also significant （P<0.05）.Therefore, the effective remediation technologies, strict protection measures, stringent guidelines and an integrated system for sewage-irrigated soil are needed to enhance its environmental quality and avoid polluted accidents in the SJZ area, because the lowest environmental quality and comprehensive quality and highest fertility quality of soil were found in SJZ. Additionally, the physicochemical properties, enzyme activities, heavy metals concentrations and so on, which reflect status of soil quality, should be long-term and periodically monitored in the sewage-irrigated soils together with the improvement measures of soil fertility and practice of perfect cropping pattern to minimize possible impacts on human health and get the agricultural sustainability in sewage-irrigated soil.更多还原