农村生活污水净化试验研究——以广州市岑村河为例

针对农村生活污水处理难、基建投资成本高、技术复杂等问题,以广州市岑村河污水为例,开展了农村生活污水排放期间种植皇竹草(Pennisetum sinese Roxb)和美人蕉(Canna indica L.)处理污水的静态试验。结果表明,与不种植植物的对照相比,种植皇竹草和美人蕉处理的总氮(TN)、总磷(TP)的去除率分别提高了43.01、41.70和61.62、60.44个百分点,且种植皇竹草对污水的净化效果优于种植美人蕉,皇竹草对污水中化学需氧量(COD)、总磷、氨氮、总氮的去除率分别为79.86%、99.83%、98.86%、98.14%,而美人蕉则分别为57.51%、98.65%、98.18%、96.83%。

漆酶/天冬氨酸生物体系处理改善旧瓦楞纸纤维性能

利用漆酶/天冬氨酸体系对旧瓦楞纸(OCC)进行纤维改性,以提高OCC再生纸的物理性质,降低或避免OCC回用过程中的性能衰减。实验结果表明,漆酶/天冬氨酸体系处理OCC能明显提高其性能,最佳处理条件为漆酶200 mg(活性2000 U/g)、天冬氨酸1%(相对于绝干浆)、p H 5、反应温度40℃、反应时间2 h。最佳处理条件下的改性OCC再生纸相比于空白样而言,其抗张指数、撕裂指数、耐破指数分别提高了127. 91%、40. 05%、19. 74%。漆酶/天冬氨酸改性后的纤维酸不溶木素的含量比空白样纤维的酸不溶木素的含量降低了48. 40%。傅里叶变换红外光谱结果显示改性后OCC纤维素的红外结晶度指数相比于处理前有所降低。

Nitrogen and Phosphorus Runoff Losses from Orchard Soils in South China as Affected by Fertilization Depths and Rates

Fertilizers are heavily applied in orchards of the hilly and mountainous topography of South China and may increase nutrient loadings to receiving waters.A simple runoff collecting system was used to measure the effects of different fertilization treatments on total N and P concentrations of surface runoff in a Chinese chestnut (Castanea mollissima Blume) orchard in Dongyuan County,Guangdong Province,China.In such orchards,fertilizer was typically applied in two short furrows or pits on either side of each tree.Treatments included three application depths (surface,10cm and 20 cm),and three application rates (low,median and high).Results showed that 90.5% of the runoff water samples had a total N concentration higher than 0.35 mgL^(-1) and 54.2% had a total P concentration higher than 0.1 mgL^(-1).Fertilizer application at all depths and at all but the lowest rate significantly increased total N and P concentrations in runoff water.Fertilization with chemical compound fertilizer at a soil depth of 20cm produced significantly lower (P<0.05) total N concentration in runoff than both surface and 10-cm depth fertilization,and significantly lower (P<0.05) total P concentration in runoff than surface fertilization.Total N and P concentrations in runoff significantly increased with the application rate of organic fertilizers.With the exception of total P concentrations,which were not significantly different between the control and fertilization at a rate of 119 kg P ha-1 in organic form,all the other fertilization treatments produced significantly higher total N and total P concentrations in runoff than the control.A fertilization depth≥20cm and an application rate≤72 kg N ha^(-1) or 119 kg P ha^(-1) for compound organic fertilizer was suggested to substantially reduce N and P runoff losses from hillslope orchards and to protect receiving waters in South China.

Selection of appropriate organic additives for enhancing Zn and Cd phytoextraction by hyperaccumulators

Chelant-enhanced phytoextraction is one of the most promising technologies to remove heavy metals from soil. The key of the technology is to choose suitable additives in combination with a suitable plant. In the present study, laboratory batch experiment of metal solubilization, cress seeds germination were undertaken to investigate the metal-mobilizing capability and the phytotoxicity of organic additives, including ethylene diamine triacetic acid （EDTA）, citric acid, acetic acid, oxalic acid, glutamine and monosodium glutamate waste liquid （MGWL） from food industry. Experiments in pots were carried out to study the effects of the additives on Zn and Cd phytoextraction. Furthermore, a leaching experiment with lysimeter was performed to evaluate the environmental risks of additive-induced leaching to underground water. The results showed that EDTA had a strong mobilizing ability for Zn and Cd, followed by mixed reagent （MR） and MGWL. MGWL and acetic acid at 5 mmol equivalent per liter resulted in seed germination index less than 2%. Experiments in pots verified the phytotoxicity of acetic acid and MGWL. Addition of the mixed reagent at 6--10 mmol/kg significantly increased Zn phytoextraction by Thlaspi caerulescens. The same for EDTA and the mixed reagent at 10 mmol/kg by Sedum dfredii. But only mixed reagents could significantly increase Cd phytoextraction by the studied hyperaccumulators. This suggested that the strong chelant was not always the good agent to enhance phytoextraction. S. alfredii combined with 2--10 mmol/kg soil MR was preferred for phytoremediation of Cd/Zn contaminated soils in southern China, this could result in high phytoextraction of Cd/Zn and reduce the leaching risk to underground water than EDTA assisted phytoextration.

Impact of fertilization on chestnut growth, N and P concentrations in runoff water on degraded slope land in South China

Growing fruit trees on the slopes of rolling hills in South China was causing serious environmental problems because of heavy application of chemical fertilizers and soil erosion. Suitable sources of fertilizers and proper rates of applications were of key importance to both crop yields and environmental protection. In this article, the impact of four fertilizers, i.e., inorganic compound fertilizer, organic compound fertilizer, pig manure compost, and peanut cake （peanut oil pressing residue）, on chestnut （Castanea mollissima Blume） growth on a slope in South China, and on the total N and total P concentrations in runoff waters have been investigated during two years of study, with an orthogonal experimental design. Results show that the organic compound fertilizer and peanut cake promote the heights of young chestnut trees compared to the control. In addition, peanut cake increases single-fruit weights and organic compound fertilizer raises single-seed weights. All the fertilizers increased the concentrations of total N and total P in runoff waters, except for organic compound fertilizer, in the first year experiment. The observed mean concentrations of total N varied from 1.6 mg/L to 3.2 mg/L and P from 0.12 mg/L to 0.22 mg/L, which were increased with the amount of fertilizer applications, with no pattern of direct proportion. On the basis of these experiment results, organic compound fertilizer at 2 kg/tree and peanut cake at 1 kg/tree are recommended to maximize chestnut growth and minimize water pollution.

Chemical Composition of Root and Stem Saps in Relation to Cadmium Resistance and Accumulation in Brassica parachinensis

Sap mixtures of the xylem, phloem, and vacuoles from low and high Cd accumulator varieties of Brassica parachinensis L. H. Bailey were analyzed under Cd stress to understand the biochemical mechanisms of Cd accumulation in plants. Low Cd accumulator ('Teqing-60') and high Cd accumulator ('Chixin-2') plants were grown in Cd-treated soil in pots in a greenhouse. Percentage of cell wall-bound Cd was estimated. pH level and the concentrations of amino acids, organic acids, anions, and cations in both stem and root saps were determined for the calculation of Cd speciations using the computer program GEOCHEM. The results showed that 'Teqing-60' had a significantly higher (P≤0.05) percentage of Cd bound to cell walls in roots and a significantly higher (P≤0.05) pH in the root sap. 'Teqing-60' also contained a higher concentration of total amino acids in both roots and stems compared with the high Cd accumulator variety 'Chixin-2'. However, between the two accumulators, for stems and for roots, there were no significant differences in non-amino organic acids. GEOCHEM calculations showed that Cd in the root sap of 'Teqing-60' mainly combined with amino acids, especially alanine. Compared with 'Chixin-2', in the root sap of 'Teqing-60', much lower levels of Cd as free ions or bound to simple ligands were found, indicating that less 'Teqing-60' is transferred to stems and leaves. Cadmium activity in the shoot sap of 'Teqing-60' was much lower than that in 'Chixin-2'; therefore, 'Teqing-60' exhibited higher Cd resistance. However, direct determination of the Cd complexes from xylem and phloem sap is needed to verify these results.

Nitrogen transformations during pig manure composting

Composting is now suggested as one of the environmentally and friendly alternative method for disposal of solid organic wastes, as it leads to minimization, stabilization, and utilization of organic waste. Transformations of nitrogen were investigated in co-composting of pig manure with different amendments, such as sawdust and leaves. Samples were analyzed for pH, total-N, soluble NH4-N, soluble NO3-N and soluble organic-N. The total-N increased after 63 days of composting, as well as the soluble NO3-N and soluble organic-N. Soluble NH4,-N increased significantly and showed peak values at day 7, thereafter decreased sharply and gradually to lower levels. Seed germination index (GI) showed that co-composting of pig manure with sawdust reached maturity after 49 days of composting, while co-composting of pig manure with sawdust and leases required shorter time for 35 days. Soluble NH4-N was significantly negatively ( P < 0.05) , while soluble NO3-N and soluble organic-N were significantly positively ( P < 0.05), correlated with seed germination index (GI). Addition of leaves in co-composting of pig manure with sawdust had no significant impacts on nitrogen transformations, but it was beneficial for maturity of pig manure compost.

实际污染土壤和模拟污染土壤垂直电动修复效果对比

为加深对电动修复技术理论的理解及提供实际污染土壤修复技术科学依据,以实际污染土壤和人为污染土壤为研究对象,采用垂直电动修复技术,着重对比了实际污染土壤和人为污染土壤的电流强度、pH和土壤中重金属迁移率。结果表明:1)电动修复过程中,实际污染土壤和人为污染土壤具有相似的电流峰形,但是人为污染土壤电流值约为实际污染土壤电流值的2倍,指示人为污染发生了更多的离子迁移。2)电动修复结束后,距离阳极越近的土壤pH越低,阴极附近区域的土壤pH显著升高,实际污染土壤和人为污染土壤pH变化规律相似,阴极pH的升高可起到深层固定重金属的效果。3)对于实际污染土壤,垂直电动修复技术对0~5 cm土层Cd、Pb、Cu和Zn造成一定的向下迁移,Cd和Zn在5~10 cm土层也有一定迁移,但该土层中Pb和Cu产生积累,其余土层变化不明显。4)对于人为污染土壤,Cd迁移明显且在最底层(35~40 cm)积累,Zn、Cu在表层(0~20 cm)有一定迁移,但是Pb只在最表层(0~5 cm)有一定迁移,其余土层变化不明显。5)对比实际污染土壤和人为污染土壤,实际污染土壤具有明显较低的重金属迁移率,人为污染土壤重金属由于老化时间较短(2个月),Cd和Zn具有较高的迁移率。因此,人为污染土壤的研究结果不一定适用于实际污染土壤。

Cadmium and Zinc Accumulation in Maize Grain as Affected by Cultivars and Chemical Fixation Amendments

A field experiment was conducted to investigate the effects of soil amendments(lime,nano-Si foliar solution and used diatomite) on the growth and metal uptake of three maize(Zea mays L.) cultivars grown in a Cd and Zn-contaminated acidic soil.The addition of lime significantly increased the maize grain yields and decreased the concentrations of Zn and Cd in the grains and shoots of maize when compared with the control.Among the three maize cultivars,Yunshi-5 accumulated the lowest amounts of Cd and Zn in the grain.The concentrations of Zn and Cd in the grain of Yunshi-5 conformed to the Chinese feed standards.These data revealed that a combination of low metal-accumulating maize and chemical fixation could effectively provide a barrier to prevent metals from entering the human food chain.