湘中典型灌区稻田镉污染调查与灌溉水镉生态拦截研究

发布时间：2018-01-09 02:20

本文关键词：湘中典型灌区稻田镉污染调查与灌溉水镉生态拦截研究　出处：《中南林业科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：一般认为除污灌外,灌溉水源带入土壤的Cd很少。我国农田灌溉水质标准(GB5084-2005)规定,灌溉水总Cd不得高于0.01mg/L。我国南方稻田灌溉定额高达15000 m3/hm2,年平均用水将近9000 m3/hm2,即使灌溉水源符合标准,每年随灌溉水进入稻田的Cd总量仍然不可低估。灌溉水中低浓度、高通量的Cd对于土壤Cd的贡献仍然没有引起足够的重视,针对灌溉水中镉污染的净化模式的研究不多。本课题以湘中某灌区农田为研究对象,调查了灌溉水、农田土壤、水稻糙米中镉,采集了灌渠底泥,分析了底泥镉形态和有机质状况,研究其与灌溉水、土壤、糙米Cd的相关性。构建人工湿地系统,结合吸附材料筛选,建立一种人工湿地结合吸附材料对灌溉水中的镉进行净化的技术模式。主要研究结果如下:(1)调查了水稻生育期湘江某支流灌溉水Cd的平均浓度为6.354 ug/L,汇入湘江水体Cd平均浓度为4.006 ug/L。沿湘江某取水口灌渠对应采集了 19个点的灌溉水、农田土壤、水稻糙米样本,研究表明,早稻灌溉水Cd平均浓度为0.447 ug/L,晚稻灌溉水Cd1.759ug/L,灌溉水Cd绝大部分无超标。早稻、晚稻期间稻田土壤 Cd 分别为 0.556 mg/kg、0.694 mg/kg,超标 1.85 倍、2.31 倍,糙米中 Cd超标2.82倍。单因子污染评价表明,灌溉水只有2.2%的样点轻度污染;而土壤样点大部分受到Cd污染,轻度、中度以及重度污染分别占比63.2%、18.4%、15.8%;糙米中受Cd污染最为严重,轻度、中度以及重度污染分别占比16.7%、44.4%、36.2%。(2)沿灌渠采集底泥底泥样品13个,其Cd平均含量为1.351 mg/kg,Cd的交换态、铁锰态以及有机结合态,分别占51.04%、28.18%以及18.95%,底泥中Cd的活性较高。底泥胡敏酸、富啡酸、胡敏素分别为2.32、7.48、9.12 g/kg,DOC、氨氮以及DON的平均含量为0.34、0.10、0.07 g/kg。底泥中胡敏酸含量和早稻灌溉水中Cd浓度呈显著正相关关系(p0.05);底泥中水溶态的Cd含量和晚稻灌溉水Cd含量呈显著正相关关系p0.05),交换态的Cd与早稻土壤中Cd含量呈极显著正相关关系(P0.01);而底泥中有机结合态的Cd与富啡酸、DOC、DON都呈极显著正相关关系(p0.01),铁锰态Cd也与富啡酸呈极显著正相关关系(p0.01)。(3)改性玉米秸秆炭和花生壳炭对水体中Cd具有良好的吸附性能,两种改性生物炭具有相似的吸附机制均符合准二级动力学方程,说明其吸附以化学吸附为主;改性玉米秸秆炭和改性花生壳炭对Cd2+的吸附过程均可以采用Langmuir和Freundlich等温吸附方程来描述。由Langmuir方程拟合得出的理论最大吸附量分别为68.97、55.55mg/g,且经6%的NaOH溶液解吸4次后,对Cd2+的吸附量仍有31.40、24.10 mg/g,可以循环利用。(4)在晚稻生育时期,用人工湿地系统处理灌溉水,4次采样Cd浓度平均浓度为4.157ug/L。经过三级人工湿地处理后,7、8、10月三次采样时期,出水Cd浓度平均降低79.01%。4次采样灌溉水经过人工湿地处理后出水浓度平均为0.764 ug/L,已经远远低于国家农田灌溉水质标准(GB5084-2005)Cd10ug/L的限制,表明人工湿地系统能拦截灌溉水中Cd,有效降低了灌溉水中Cd的浓度。(5)用人工湿地系统处理灌溉水进行田间小区试验,不处理灌溉水水稻糙米中Cd最高为0.621 mg/kg,灌溉水净化水稻糙米中Cd的平均含量为0.503 mg/kg。灌溉水经过人工湿地系统处理后的各试验小区内水稻糙米中Cd含量均有所下降,平均降低23.76%,其中以T2处理即人工湿地系统+改性玉米秸秆炭处理试验小区内水稻糙米中Cd含量最低,下降29.66%,为0.437 mg/kg。虽然试验小区内水稻糙米中Cd的含量有所降低,但所有糙米中Cd含量仍超过国家食品安全标准(GB2762-2012)Cd≤0.2 mg/kg的限制,灌区土壤Cd控制仍然需要多措施配套应用。
[Abstract]:Generally the decontamination irrigation, irrigation water into the soil to little Cd. Our standards for irrigation water quality (GB5084-2005), total Cd of irrigation water shall not be higher than 0.01mg/L. in South China rice irrigation quota of up to 15000 m3/hm2, the average annual water nearly 9000 m3/hm2, even if the source of irrigation water standard, the amount of Cd per year into the paddy fields with irrigation the water is still not be underestimated. The irrigation water of low concentration, high throughput Cd for soil Cd contribution is still not attracted enough attention, not much research on purifying mode for cadmium contaminated irrigation water. In this paper a Hunan in irrigation area as the research object, the investigation of irrigation water, soil, rice cadmium, collected irrigation sediment, analysis of sediment Cadmium Forms and organic matter, and the study of irrigation water, soil, rice correlation Cd. The construction of artificial wetland system, combined with adsorption material screening, the establishment of a Artificial wetland combined with adsorption material for irrigation water purification technology model of cadmium. The main results are as follows: (1) investigated the average concentration of rice growing period in Xiangjiang on a tributary of the irrigation water Cd is 6.354 ug/L, the water flow into the Xiangjiang Cd average concentration of 4.006 ug/L. along Xiangjiang water intake channel corresponding to the 19 points of the acquisition irrigation water, soil and rice samples, research shows that rice irrigation water Cd average concentration was 0.447 ug/L, rice Cd1.759ug/L irrigation water, irrigation water Cd almost no exceed the standard. During the period of early rice, late rice paddy soil Cd were 0.556 mg/kg, 0.694 mg/kg, exceed the standard 1.85 times, 2.31 times, 2.82 times exceed the standard in brown rice Cd. Show that the single factor pollution evaluation, light pollution point of irrigation water is only 2.2%; and most soil samples polluted by Cd, mild, moderate and severe pollution accounted for 63.2%, 18.4%, 15.8%; brown rice by Cd The most serious pollution, mild, moderate and severe pollution accounted for 16.7%, 44.4%, 36.2%. (2) along the canal sediment collection 13 sediment samples, the average content of Cd is 1.351 mg/kg, exchangeable Cd, iron manganese and organic bound, respectively 51.04%, 28.18% and 18.95%, higher activity in the sediment Cd. The sediment Hu Min acid, fulvic acid and humin were 2.32,7.48,9.12 g/kg, DOC DON, the average content of ammonia nitrogen and Hu Min acid and rice irrigation water Cd concentration has a significant positive correlation between 0.34,0.10,0.07 g/kg. (P0.05) in the sediment; sediment water soluble Cd content and Cd content in rice irrigation water a significant positive correlation between the P0.05 exchange), there are significant positive correlation between the content of Cd and Cd in rice soil state (P0.01); Cd and fulvic acid in organic sediment, DOC, DON were significantly positive correlation (P0.01), iron manganese Cd and fulvic acid were A significant positive correlation (P0.01). (3) modified corn straw charcoal and peanut shell charcoal has good adsorption properties for Cd in water, two kinds of modified biochar with similar adsorption mechanisms were pseudo two order kinetics equation, indicating that the adsorption was mainly chemical adsorption; modified corn straw charcoal and the process of the adsorption of Cd2+ by modified peanut shell charcoal can be used Langmuir and Freundlich isothermal adsorption equation to describe the theory. The maximum adsorption capacity obtained by the Langmuir equation for 68.97,55.55mg/g and NaOH respectively, by 6% after 4 times of desorption solution, the adsorption capacity of Cd2+ is 31.40,24.10 mg/g, can be recycled. (4 in the late growth period,) using artificial wetland treatment system of irrigation water, 4 sampling Cd concentration the average concentration was 4.157ug/L. after three artificial wetland treatment after 7,8,10 months, three sampling period, the effluent Cd concentration decreased by an average of 79.01%.4 samples were Irrigation water after artificial wetland treatment after the effluent concentration was 0.764 ug/L, far less than the national irrigation water quality standards (GB5084-2005) Cd10ug/L, showed that the artificial wetland system can intercept the irrigation water Cd, effectively reducing the concentration of irrigation water is Cd. (5) conducted a field experiment with artificial wetland treatment system of irrigation water. Don't Cd up to 0.621 mg/kg in rice irrigation water, irrigation water purification average content in brown rice Cd decreased to 0.503 mg/kg. irrigation water through the Cd content in each experimental plot after treatment of the artificial wetland system in rice have been reduced by 23.76% on average, among which T2 is modified corn + artificial wetland system straw carbon Cd content in brown rice test area decreased by 29.66%, the lowest was 0.437 mg/kg., although the content of experimental plots in brown rice of Cd decreased, but all of brown rice In the content of Cd is still more than the national food safety standard (GB2762-2012) Cd = 0.2, mg/kg limit, soil Cd control still needs more supporting measures.

【学位授予单位】：中南林业科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S273;X56

【相似文献】