改性玉米淀粉对Cu2＋、Pb2＋和Zn2＋的吸附特性研究

以玉米淀粉为原料,经过交联、醚化、胺化和亲核加成等步骤合成了一种新型重金属吸附剂——二硫代氨基甲酸改性淀粉（DTCS）。改性淀粉的结构采用红外光谱和扫描电镜进行表征。DTCS是一种性能优良的重金属吸附剂,对Cu2＋、Pb2＋和Zn2＋的饱和吸附容量随着pH（pH=2~6）的增加而增大。在有EDTA络合剂存在和酸性废水pH小于3的情况下,DTCS对Cu2＋、Pb2＋和Zn2＋仍有较高的去除率,分别达到90%、75%和50%以上,说明DTCS在含重金属离子的实际废水体系具有一定的实用价值。     

Biodegradability of Chemically Modified Starch (RS4)/PVA Blend Films: Part 2

Biodegradable films were successfully prepared by using cornstarch (CS), chemically modified starch (RS4), polyvinyl alcohol (PVA), glycerol (GL), and citric acid (CA). The physical properties and biodegradability of the films using CS, RS4, and additives were investigated. The results of the investigation revealed that the RS4-added film was better than the CS-added film in tensile strength (TS), elongation at break (%E), swelling behavior (SB) and solubility (S). Especially, the RS4/PVA blend film with CA as an additive showed physical properties superior to other films. Furthermore, when the film was dried at low temperature, the properties of the films clearly improved because the hydrogen bonding was activated at low temperature. The biodegradation of films was carried out using the enzymatic, microbiological and soil burial test. The enzyme used in this study was amyloglucosidase (AMG), α-amylase (α-AM) and β-amylase (β-AM). At the enzymatic degradation test, the GL-added films had an approximately 60% degradation, while the CA-added films were degraded about 25%. The low degradation value on CA-added film is attributed to low pH of film added CA that deactivated the enzymatic reaction. The microbiological degradation teat was performed by using Bacillus subtilis and Aspergillus niger.     

城市生活垃圾中可生化单基质的厌氧消化

在厌氧消化系统中,发酵细菌最主要的利用基质是淀粉、纤维素、脂肪和蛋白质等。本试验分别选取米饭、黄豆、芹菜和肥肉为上述四种基质的代表物质,通过对各物质进行的厌氧消化试验,探讨了它们的厌氧消化性能。结果表明。米饭在发酵初期降解速率最快,酸化也最明显。同时将消化初始阶段的pH控制在6．5时能使消化进入产甲烷阶段,没控制的只能停留在水解产酸阶段。将黄豆厌氧消化初期的pH控制在6．5并不能使消化顺利进行。将芹菜厌氧消化的初始pH值控制在6．5时可以加快它的降解速率。肥肉的厌氧消化也只有在对其消化进程控制pH值时才能顺利被降解。同时肥肉在厌氧消化进程中表现出了高产甲烷性能,产甲烷阶段累积产气量达13758mL,占总产气量的93．59％．     

基于MUASB处理马铃薯深加工废液的试验研究

试验研究了在改装UASB(MUASB)装置中培养好氧颗粒污泥及其处理生活污水和高浓度马铃薯深加工废液的效果。试验结果表明:可以在4 d内快速培养出好氧颗粒污泥。成熟的颗粒污泥平均直径达2 mm。当马铃薯深加工废液浓度ρ(COD)、ρ(NH 4+-N)、ρ(TP)平均分别为12 817.16,106.10,26.37 mg/L时,处理效果分别超过64%、63%和67%。利用共聚焦激光扫描显微镜观测颗粒污泥,虽然球菌主要形成了一个相对凝结的区域,但是在颗粒污泥的边缘区域出现许多丝状菌。α多糖主要分布在颗粒的核心。在颗粒中还发现少量的β多糖和无生命的细胞。     

The influence of pH and organic matter content in paddy soil on heavy metal availability and their uptake by rice plants

The experiments were done to investigate the effect of soil pH and organic matter content on EDTA-extractable heavy metal contents in soils and heavy metal concentrations in rice straw and grains. EDTA-extractable Cr contents in soils and concentrations in rice tissues were negatively correlated with soil pH, but positively correlated with organic matter content. The combination of soil pH and organic matter content would produce the more precise regression models for estimation of EDTA-Cu, Pb and Zn contents in soils, demonstrating the distinct effect of the two factors on the availability of these heavy metals in soils. Soil pH greatly affected heavy metal concentrations in rice plants. Furthermore, inclusion of other soil properties in the stepwise regression analysis improved the regression models for predicting straw Fe and grain Zn concentrations, indicating that other soil properties should be taken into consideration for precise predicting of heavy metal concentrations in rice plants.     

Effects of water management on arsenic and cadmiumspeciation and accumulation in an upland rice cultivar

Pot and field experiments were conducted to investigate the effects of water regimes on the speciation and accumulation of arsenic (As) and cadmium (Cd) in Brazilian upland rice growing in soils polluted with both As and Cd. In the pot experiment constant and intermittent flooding treatments gave 3-16 times higher As concentrations in soil solution than did aerobic conditions but Cd showed the opposite trend. Compared to arsenate, there were more marked changes in the arsenite concentrations in the soil solution as water management shifted, and therefore arsenite concentrations dominated the As speciation and bioavailability in the soil. In the field experiment As concentrations in the rice grains increased from0.14 to 0.21 mg/kg while Cd concentrations decreased from 0.21 to 0.02 mg/kg with increasing irrigation ranging from aerobic to constantly flooding conditions. Among the various water regimes the conventional irrigation treatment produced the highest rice grain yield of 6.29 tons/ha. The As speciation analysis reveals that the accumulation of dimethylarsinic acid (from 11.3% to 61.7%) made a greater contribution to the increase in total As in brown rice in the intermittent and constant flooding treatments compared to the intermittent-aerobic treatment. Thus, water management exerted opposite effects on Cd and As speciation and bioavailability in the soil and consequently on their accumulation in the upland rice. Special care is required when irrigation regime methods are employed to mitigate the accumulation of metal(loid)s in the grain of rice grown in soils polluted with both As and Cd.     

叶面喷施硒硅复合溶胶抑制水稻砷积累效应研究

砷是一种毒性较强的类金属元素,稻米砷污染是近年来环境科学关注的难点和热点问题。为了控制稻米对砷的吸收积累,利用水热合成法制备了一系列浓度硒掺杂硅复合溶胶。采用盆栽和大田试验结合的方法,研究了硒掺杂纳米硅溶胶对水稻（Oryza sativa L.）砷吸收积累的影响。结果显示,叶面喷施硒掺杂纳米硅溶胶可以有效缓解水稻砷毒害,增加稻米硒含量,抑制稻米砷积累。盆栽试验结果表明：叶面喷施质量分数1%的硒掺杂纳米硅溶胶（1%Se-Si处理）后,水稻籽粒干质量比对照增加了43.8%,砷含量下降了46%,硒含量由对照的0.050 mg·kg-1增加到0.272 mg·kg-1。且与喷施亚硒酸钠相比（1%Se处理）,喷施硒掺杂纳米硅溶胶更有利于水稻生长,抑制稻米砷积累。与喷施硒质量分数1%的亚硒酸钠（1%Se处理）相比,喷施质量分数1%的硒掺杂纳米硅溶胶（1%Se-Si处理）后,水稻籽粒干质量增加了65.4%,砷含量下降了33.1%。大田试验结果也表明：叶面喷施硒硅复合溶胶可以显著抑制稻米砷积累,且随着硒掺杂量的增加,稻米砷含量显著降低、硒含量显著增加;硒的最佳掺杂量质量分数为0.5%,叶面喷施这种硒掺杂硅溶胶,稻米总砷质量分数由对照的0.25 mg·kg-1下降到0.14 mg·kg-1,稻米中硒的质量分数为0.26 mg·kg-1,符合富硒大米标准。砷污染稻田上,叶面喷施硒硅复合溶胶不仅使稻米砷含量达标,而且可以生产出富硒大米。因此,叶面喷施硒硅复合溶胶可能是治理稻米砷污染的新途径。     

Roles of soluble minerals in Cd sorption onto rice straw biochar

Transforming to biochar provides an environmentally friendly approach for crop residue reutilization, which are usually applied as sorbent for heavy metal removal. As typical siliconrich material, the specific sorptive mechanisms of rice straw derived biochar(RSBC) are concerned, especially at the low concentration range which is more environmentally relevant. In the present study, Cd sorption onto RSBCs at the concentration of ≤ 5 mg/L was investigated. The sorptive capacity was positively corr...     

The risks of sulfur addition on cadmium accumulation in paddy rice under different water-management conditions

Recently, the application of sulfur (S) has been recommended to control the accumulation of cadmium (Cd) in rice in contaminated paddy soil. However, the effects of exogenous S on Cd transfer in paddy rice systems under different water-management practices have not been systematically investigated. Pot experiments were performed to monitor the composition of soil pore water and the Cd accumulation in iron plaque and rice tissue were compared under different S (0 and 200 mg/kg Na₂SO₄) and water (continuous and discontinuous flooding) treatments. Sulfur application significantly increased Cd concentrations in soil pore water under discontinuous flooding conditions, but slightly reduced them under continuous flooding. Moreover, the oxidation/reduction potential (Eh) was the most critical factor that affected the Cd levels. When the Eh exceeded −42.5 mV, S became the second critical factor, and excessive S application promoted Cd dissolution. In addition, S addition elevated the Cd levels in iron plaque and reduced the Cd transfer from the iron plaque to rice roots. In rice, S addition inhibited Cd transfer from the rice roots to the straw; thus, more Cd was stored in the rice roots. Nevertheless, additional S application increased the Cd content in the rice grains by 72% under discontinuous flooding, although this effect was mitigated by continued flooding. Under simulated practical water management conditions, S addition increased the risk of Cd contamination in rice, suggesting that S application should be reconsidered as a paddy fertilization strategy.     

Biochar affects methylmercury production and bioaccumulation in paddy soils: Insights from soil-derived dissolved organic matter

Biochar has been used increasingly as a soil additive to control mercury (Hg) pollution in paddy rice fields. As the most active component of soil organic matter, soil dissolved organic matter (DOM) plays a vital role in the environmental fate of contaminants. However, there are very few studies to determine the impact of biochar on the Hg cycle in rice paddies using insights from DOM. This study used original and modified biochar to investigate their effect on DOM dynamics and their potential impact on methylmercury (MeHg) production and bioaccumulation in rice plants. Porewater DOM was collected to analyze the variations in soil-derived DOM in paddy soils. The results showed that the addition of biochar, whether in original or modified form, significantly reduced the bioaccumulation of MeHg in rice plants, especially in hulls and grains (p<0.05). However, MeHg production in soils was only inhibited by the modified biochar. Biochar addition induced a significant increase in DOM's aromaticity and molecular weight (p<0.05), which decreased Hg bioavailability. Furthermore, enhanced microbial activity was also observed in DOM (p<0.05), further increasing MeHg production in the soil. Thus, the effect of biochar on the fate of Hg cycle involves competition between the two different roles of DOM. This study identified a specific mechanism by which biochar affects Hg behavior in rice paddy soil and contributes to understanding the more general influence of biochar in agriculture and contaminant remediation.