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181.
182.
采集了杭州市污染天和非污染天的PM2.5样品,并进一步获取了PM2.5中可溶铁(FeS)的浓度及%FeS.研究结果显示,采样期间气溶胶中总Fe(FeT)的浓度为(629±296)ng/m3(150~1167ng/m3),FeS的浓度为(51.4±30.5)ng/m3(4.2~90.5ng/m3),%FeS为(7.8%±3.5%)(1.5%~12.9%).污染天PM2.5、FeT和FeS的浓度均明显高于非污染天,且污染天%FeS为9.3%,高于非污染天的5.1%.本研究发现%FeS的差异主要与Fe的来源和大气酸化过程相关,污染天Fe受交通排放和工业排放等人为源的影响更大,且污染天大气酸化程度更强. 相似文献
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184.
采用四氧化三铁(Fe3O4)稳定化纳米Pd/Fe催化脱氯水溶液中的2,4-二氯苯氧乙酸(2,4-D),获得了良好的处理效果.实验考察了Fe3O4投加量、pH、钯化率、温度、搅拌速率等因素对2,4-D去除的影响.2,4-D去除率随Fe3O4投加量增加而提高,投加量为4.0 g·L-1时,反应210 min后,2,4-D去除率为93.5%,而未稳定的纳米Pd/Fe,去除率为47.3%.低pH可促进2,4-D还原脱氯,pH为2.6~4.1时,2,4-D在110 min内几乎完全去除.2,4-D去除率随钯化率增加而提高.随着钯化率由0.25%、0.50%增加到0.75%,210 min后,2,4-D的去除率也由51.4%、93.5%提高到99.9%.温度在16.5~30.0℃范围内,反应210 min后,2,4-D去除率均可超过90.0%.温度升高到35.0、40.0℃时,去除率显著下降.2,4-D去除率随着搅拌速率加快而提高.Fe3O4的加入可以使纳米Pd/Fe分散和稳定.此外,Fe0可通过Fe3O4将电子传递给H+和2,4-D,促进2,4-D的还原脱氯. 相似文献
185.
Arsenic dynamics in the rhizosphere and its sequestration on rice roots as affected by root oxidation 总被引:3,自引:0,他引:3
A pot experiment was conducted to investigate the effects of root oxidation on arsenic (As) dynamics in the rhizosphere and As sequestration on rice roots. There were significant differences (P 〈 0.05) in pH values between rhizosphere and non-rhizosphere soils, with pH 5.68-6.16 in the rhizosphere and 6.30-6.37 in non-rhizosphere soils as well as differences in redox potentials (P 〈 0.05). Percentage arsenite was lower (4%-16%) in rhizosphere soil solutions from rice genotypes with higher radial oxygen loss (ROL) compared with genotypes with lower ROL (P 〈 0.05). Arsenic concentrations in iron plaque and rice straw were significantly negatively correlated (R = -0.60, P 〈 0.05). Genotypes with higher ROL (TD71 and Yinjingmanzhau) had significantly (P 〈 0.001) lower total As in rice grains (1.35 and 0.96 mg/kg, respectively) compared with genotypes with lower ROL (IAPAR9, 1.68 mg/kg; Nanyangzhan 2.24 mg/kg) in the As treatment, as well as lower inorganic As (P 〈 0.05). The present study showed that genotypes with higher ROL could oxidize more arsenite in rhizosphere soils, and induce more Fe plaque formation, which subsequently sequestered more As. This reduced As uptake in aboveground plant tissues and also reduced inorganic As accumulation in rice grains. The study has contributed to further understanding the mechanisms whereby ROL influences As uptake and accumulation in rice. 相似文献
186.
不同地区土壤中分蘖期水稻根表铁氧化物的形成及其对砷吸收的影响 总被引:6,自引:5,他引:6
通过土壤盆栽试验研究了14种不同土壤中种植水稻后,其根表铁膜形成量的情况,及其对苗期水稻吸收和转运砷的影响.结果表明,生长在不同土壤中的水稻其根表铁膜的形成量有显著的差异,铁膜形成量最大为61.97 mg/g,最小仅为1.15mg/g,分析表明土壤中非晶质态氧化铁含量的不同是其主要的影响因素之一.同时测定了根表铁膜中砷的含量,铁膜上吸附的砷浓度最大为1 376 mg/kg,最小低于检测限,其与根表铁膜形成量之间存在着显著的正相关性(r=0.85,n=14,p0.05),而与土壤溶液中有效态的砷浓度无显著的相关性;水稻植株地上部砷浓度(0.400~12.98 mg/kg)和地下部砷浓度(3.860~576.2 mg/kg)与根表铁膜的形成量之间也都存在着显著的正相关性(r=0.88,n=14,p0.05;r=0.91,n=14,p0.05),与土壤溶液中有效态的砷浓度无显著的相关性;水稻根系对砷的吸收能力(SAU,0.005~0.670 mg/g)与根表铁膜形成量之间也为显著的正相关性(r=0.91,n=14,p0.05);根表铁膜形成量与砷的转运之间无显著的相关性.结果表明,在此次试验中土壤的非晶质态氧化铁的含量是水稻根表铁膜形成的影响因素之一,根表铁膜的存在成为了根际砷的富集库,起到了促进根际砷吸收的作用,但对砷的转运没有显著的影响. 相似文献
187.
投加铁锈或Fe(OH)3可明显改善含高浓度硫酸盐有机废水的厌氧处理能力,使趋于失败的升流式厌氧污泥床UASB恢复正常工作对SO42-为5000mg/L,CODCr为15000mg/L的合成脂肪酸废水,在水力停留时间为4d,由40%以下的COD去除率提高到投加铁锈或Fe(OH)3后的73%和82%,出口pH值由53上升到73,产甲烷气量由0.3L/d上升为22L/d.并提出了Fe(OH)3比铁锈在去除S2-干扰更有效,去除S2-干扰可使厌氧处理恢复正常 相似文献
188.
小兴凯湖表层底泥磷吸附容量及潜在释放风险 总被引:3,自引:0,他引:3
利用沉积物磷吸附指数(PSI)和磷吸附饱和度(DPS)研究了小兴凯湖表层沉积物的磷吸附容量,分析了沉积物中磷的吸附饱和度(DPS)与其他指标的相关关系,并讨论了不同采样点湖泊沉积物中磷的潜在释放风险.结果表明:13个采样点的表层沉积物的PSI为9.78~197.53(mg?L)/(100g?μmol),平均值为59.77(mg?L)/(100g?μmol);DPS为9.95%~24.47%,平均值为15.41%.PSI与草酸铵提取的磷(Pox)极显著正相关,与草酸铵提取的铁、铝(Feox,Alox)显著正相关,草酸铵提取的铁是影响PSI的主导因素;DPS主要受沉积物中原有吸附态磷的影响.此外,磷释放风险指数(ERI)8.99%~129.94%的计算结果表明:小兴凯湖表层沉积物中磷释放诱发富营养化的风险处于高度风险范围,其中,受农业面源污染影响较大的北岸区域相比其他区域发生富营养化的风险更高. 相似文献
189.
Photochemical reactions can alter the transformation of sedimentary organic matter into dissolved organic matter (DOM) and affect its ultimate fate in water ecosystems. In the present study, the photorelease of DOM and Fe from resuspended lake sediments was investigated under different O2 and NO3? concentration conditions to study the mechanisms of DOM and Fe photorelease. The amount of photoreleased Fe, which ranged from 0.22 to 0.70 μmol/L, was significantly linearly correlated with the amount of photoreleased DOM. O2 and NO3? could promote the photochemical release of DOM and Fe, especially during the initial 4 h irradiation. In general, the order of the photorelease rates of DOM and Fe under different conditions was as follows: NO3?/aerobic > aerobic ≈ NO3?/anaerobic > anaerobic. The photorelease rates of DOM and Fe were higher for the initial 4 hr irradiation than these for the subsequent 8 hr irradiation. The photorelease of DOM and Fe is thought to proceed via direct photodissolution and indirect processes. The relative contributions of indirect processes (>60%) was much greater than that of direct photodissolution (<40%). The photoproduced H2O2 under aerobic and anaerobic conditions indicated that hydroxyl radicals (?OH) are involved in the photorelease of DOM. Using ?OH scavengers, it was found that 38.7%, 53.7%, and 77.6% of photoreleased DOM was attributed to ?OH under anaerobic, aerobic, and NO3?/aerobic conditions, respectively. Our findings provide insights for understanding the mechanisms and the important role of ?OH in the DOM and Fe photorelease from resuspended sediments. 相似文献
190.