摘要
南渡江流域新坡河塘疏浚底泥的利用方向规划为农田土地整治工程中耕作层的替代土,用来发展蔬菜种植业。为了探清该流域河塘疏浚底泥的养分水平及重金属污染状况,综合考虑河塘的形态、水域面积、断面特征、流速、底泥沉积量采取典型断面布设和网格法布点,将所调查的河塘分为上游和下游,共采集0~40cm深的底泥样品78个。通过室内底泥样品成分检测、养分灰色关联度评价、内梅罗综合污染评价、GIS空间分析等方法,分析和评价了河塘底泥的养分特征、肥力水平、重金属的含量、污染程度及空间格局分布特征,掌握了该流域底泥的养分条件、底泥重金属污染状况及底泥农业利用的风险。结果表明:1)底泥的全氮、全磷、全钾及有机质含量呈现空间异质性,下游的全氮、全磷均值含量较上游分别高出32.45%、11.88%,而下游的全钾、有机质均值含量较上游分别低14.64%、14.62%,上游段底泥养分数据的变异系数普遍高于下游段,底泥养分异质性是由河流流速、周边的自然环境及人为耕作活动造成。底泥中的全氮、全磷、有机质等养分指标达到1级(丰)水平,统计分析全钾含量为5级(缺)水平;整个河塘底泥养分要高于对照点,为底泥的农业土地利用提供了有利条件。2)底泥重金属污染物主要为Cd和Cu,其次为和Cr和Ni,Cd、Cu、Cr、Ni样品单因素污染超标率分别为76.92%、47.44%、56.41%、23.07%,且超标幅度分别为58.45%、104.58%、6.06%、68.48%;底泥重金属污染是因基性火山岩为成土母质,背景值偏高,土壤重金属被酸雨淋溶出,并随地表径流汇集在河塘中,造成了底泥的重金属超标。内梅罗综合污染指数评价可知河塘底泥是以轻微污染和中度污染为主,分别占样品数的46.15%、28.21%;底泥污染状况具有明显的空间异质性,轻微污染水平(3级)和中度污染水平(4级)的区域面积分别为62.05%、25.80%,以中、轻微污染水平的区域为主。河塘下游水面宽阔,流速减慢,造成底泥沉积量增加,污染加重及污染空间分布异质性强。应该根据底泥的污染等级及养分条件综合决定其农业土地利用。
Sediment, the major reservoir of contaminants in a lake, contains not only hazardous matter, but also nutrients like nitrogen, phosphorus, and organic matter. So the detoxification, recycling and reuse of sediment has been widely studied. Agricultural land use of sediment is a potentially feasible approach for contaminated site remediation and can achieve good economic and environmental benefits. The key concept is to control the pollutant content and soil burden according to the related environmental standards. Heavy metals reserved in agricultural soil would greatly affect the grain yield and quality, as well as food safety, and are one of the major environmental pollution sources threatening human health. In this article, the sediment content in Xinpo Pond of the Nandu River Valley was planned to be used as the substitute soil of plough horizon in farmland remediation engineering to develop vegetable farming. To investigate the nutrient content and the degree of heavy metal contamination of the pond sediment, the shape and dimension of the pond, characteristics of the cross-section, flow rate, and the amount of sediment were comprehensively explored. Typical cross-section and grid sampling methods were chosen to collect samples within the 0~40 cm depth of the sediment. Based on (a) farmland environmental quality evaluation standards for edible agricultural products as the heavy metals evaluation criteria and (b) the second national soil survey classification criteria as the nutrient evaluation criteria, adopting sample testing, statistical analysis, nutrients gray correlation analysis, Nemerow pollution index assessment and GIS spatial analysis, the nutrient characteristics, soil fertility, heavy metal content, pollution degree and spatial distribution of the pond sediment were analyzed. The results showed: 1) Total nitrogen, total phosphorus, total potassium and organic matter content of the sediment presented spatial heterogeneity. Sediment total nitrogen content was in the range of 0.1300 ~ 6.7600 g / kg with an average of 2.8717 g / kg; total phosphorus content was in the range of 0.1097 to 2.3108 g / kg with a mean of 1.1824 g/kg; total potassium content fell in the range of 2.3000 ~ 16.8000g/ kg with a mean of 9.3000 g/kg; and the organic matter content fell in the range of 22.7195 to 167.8769 g / kg with a mean of 92.9408 g/kg. Mean values of total nitrogen and total phosphorus at the lower reach outweighed those at the upper reach by 32.45% and 11.88%, respectively, while total potassium and organic matter content at the lower reach were lower than those at the upper reach by 14.64% and 14.62%, respectively. The variation coefficient of nutrient data from the upper reach sediment were generally higher than those from the lower reach sediment, resulting from the flow rate, ambient natural environment and farming activities. Total nitrogen, total phosphorus, and organic matter reached level 1 (abundant), and the total potassium content was in level 5 (scarce). From evaluation of sediment nutrient based on the analysis of grey correlation, the average fertility indices of Ponds sediment and control processing were 0.4703 and 0.4685, respectively. The nutrients in the sediment were higher than that of the control point, which supported agricultural application of the sediment. 2) The mean contents of Cr, Ni, Cu, Zn, Cd, Pb, As, and Hg in sediments of the study area were 135.5983, 51.0098, 78.5999, 113.3576, 0.4245, 30.5595, 5.3038, and 0.1739 mg/kg, respectively. Heavy metal contamination was mainly attributed to Cd and Cu, followed by Cr and Ni, whose exceeding rates were 76.92%, 47.44%, 56.41%, and 23.07%, respectively; their exceeding magnitudes were 58.45%, 104.58%, 6.06%, and 68.48%. Heavy metal contamination resulted from the fact that the soil parent materials are mafic volcanic rocks, which caused high background values of the metals in the soil. Heavy metals in the soil were flushed by acid rain into the pond through surface runoff. From the Nemerow Index evaluation, the sediment was mainly slightly polluted (46.15%of the samples) to moderately polluted (28.21% of the samples). Contamination of the sediment was also spatially distributed, among which 62.05% of the site was at the slightly contaminated level (level 3) and 25.80% of the site was at the moderately contaminated level (level 4). The watercourse at the lower reach was wider and the flow rate was slow, increasing the rate of sediment deposition, the deterioration of sediment contamination, and the heterogeneity of spatial distribution. Therefore, the patterns of agricultural land use should be critically determined according to the contamination levels and nutrient conditions of the sediment.
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2013年第3期213-224,J0007,共13页
Transactions of the Chinese Society of Agricultural Engineering
基金
海口市土地储备整理中心科技项目:河道底泥在土地整治工程中的资源化应用技术开发研究
南渡江土地整治工程中底泥农业利用工程示范
国家自然基金项目(40961033)
十二五国家科技支撑计划课题(2012BAC09B03)
关键词
底泥
养分
重金属
空间格局
污染评价
sediments, nutrients, heavy metals, spatial distribution, contamination evaluation