浙北地区土壤元素有效量及其影响因素研究

AVAILABLE ELEMENT CONTENTS AND FACTORS INFLUENCING THEIR AVAILABILITY IN NORTHERN ZHEJIANG

浙江省北部地区调查研究表明,受成土母质来源、土壤类型及其理化性质等因素的影响,土壤元素全量、有效量及其有效度表现为:1)低山丘陵岗地土壤中As,Cd,Mo,Pb和Se全量较高,As,Cd,Fe,Pb,Se和Zn有效量较高;而山前平原区土壤中Hg,Pb和Zn元素全量较高,由地表向深部的下降递度较小,显示为原始沉积成因特点。2)中酸性、富含有机质的红壤和水稻土中As,Cd,Cu,Fe,Mn,Pb,Se,Zn等元素有效度较高,水稻土Hg有效度最低;弱碱性或碱性、贫有机质的潮土和滨海盐砂土中As,Cd,Cu,Fe,Mn,Pb,Se,Zn等元素有效量较低,但B有效量及有效度均较高。3)统计分析表明,土壤中Mn,Cu,Zn,Mo,Cd,Pb,Se等元素全量与有效量间具显著正相关性,表明全量是有效量的重要影响控制因素;有机质含量与Fe,Cu,Zn,Cd,As和Pb有效度间为显著正相关,说明有机质较高有利于土壤元素活化;Fe,Cu,Zn,Cd,As,Pb和Se有效度与pH值为显著负相关,表明土壤酸性增强(酸化)会增加这类元素的生物有效性。

Based on representative 105 samples, the median values of total soil elements of As, B, Cd, Cu, Fe, Hg, Mn, Mo, Pb, Se and Zn in Northern Zhejiang are 9.3, 61.9, 0.19, 31.8, 32 200, 0.192, 485, 0.5, 31.5, 0.33 and 80.5 in ppm respectively; the median values of available contents of them are 0.036, 0.26, 0.114, 5.48, 120, 0.000 18, 123, 0.13, 5.54, 0.011 and 5.47 in ppm. Their median availabilities calculated by available to total contents are 0.37, 0.43, 59.82, 17.94, 0.35, 0.11, 26.20, 24.00, 17.06, 3.45 and 7.22 respectively.The median values of soil organic matter in hilly and mountainous areas, plains before mountains and river-net plains are 3.05,3.32 and 2.89 percent respectively, and median pH are 5.38, 6.36 and 6.95. It showed that the total and available contents of some elements in soils in different physiognomy units vary greatly: (1) total contents of Cd, Mo, and Se are higher in hilly and mountainous areas due to the stratum enriching in these elements; (2) the available contents and their availabilities of As, Cd, Fe, Pb, Se, and Zn are much higher in hilly and mountainous areas as soils are more acidic and have high content of organic matter; (3) total contents of heavy metals including Hg, Pb, and Zn are higher in plains before mountains due to lake and lagoon sediment environments which have the trend to contain abundant heavy metals. However, part of heavy metals in these areas probably comes from human activities as many middle to large cities are located in these areas. The median values of organic matter in perudic ferrisols, stagnic anthrosols, orthic anthrosols and orthic halosols are 2.81, 3.32, 1.58 and 0.84. Organic matter is enriched in stagnic anthrosols but poor in orthic anthrosols and orthic halosols. The median values of pH are 5.36, 6.55, 8.01 and 8.20 respectively. It is presented that soil types and their properties played an important role in element availability to control available contents: (1) red soil and stagnic anthrosols have higher availabilities of As, Cd, Cu, Fe, Mn, Pb, Se and Zn as the soils are rich in organic matter and acidic. Comparatively, orthic anthrosols and orthic halosols are weak alkaline to alkaline and lower in organic matter. Therefore available contents of As, Cd, Cu, Fe, Mn, Pb, Se, and Zn are much higher in perudic ferrisols and stagnic anthrosols than in orthic anthrosols and orthic halosols; (2) the available contents and availability of boron in orthic anthrosols and orthic halosols are higher than that in other soils mainly caused by pH; (3) the availability of Hg in stagnic anthrosols is very low because soil Hg in reduction environment caused by long-term irrigation may form un-soluble sulfide HgS. However, as Hg concentration in stagnic anthrosols is much high than that in other soils, available Hg is still higher than that in other soils. Statistical results presented that total soil concentrations of Mn, Cu, Zn, Mo, Cd, Pb, and Se have positive relationship with that of available contents. Organic matter played an important role in the availabilities of Fe, Cu, Zn, Cd, As, and Pb. Soil pH have evident influence as the solution of Fe, Cu, Zn, Cd, As, Pb, and Se are increased in acidic soils.