生物流化床处理生活污水的动力学研究

本研究采用颗粒活性炭（Granule Activated Carbon,GAC）为填料,考察了生物流化床（Biological fluidized Bed,BFB）处理生活污水的动力学.研究结果表明,GAC-BFB内生物膜的表现产率YoA为2.3057gVSS/gCOD,微生物细胞衰减常数Kd为0.3056d-1;基质降解动力学中米氏常数Ks为0.2182mg/L,反应速率常数K为13.09 mg/（l·h）.GAC-BFB的微生物生长动力学拟合方程为1/θc=2.3057q-0.3056,R2=0.9549; GAC-BFB的基质降解动力学拟合方程为1/U =0.2182＊1/S ＋0.0764,R2 =0.9972,该微生物生长动力学拟合方程及基质降解动力学拟合方程能较好的反映GAC-BFB系统的出水水质状况,本研究所获得的动力学关系和动力学参数可作为GAC-BFB系统的设计依据.     

无锡职教园区餐厨垃圾理化性质调查分析研究

为提高餐厨垃圾厌氧消化效率,应用理化方法分别测试了无锡职教园区大中餐、小中餐、西餐、汤锅和食堂餐厨垃圾的容重、含水率、pH值、有机干物质、含油率、盐分、氮磷含量等指标,此外,应用餐厨垃圾厌氧发酵模拟试验分析其产沼气效率.通过理化性质试验获得不同类型餐厨垃圾理化指标的异同点.通过产沼气试验可知,容积负荷由1 kgVS/m3·d逐渐提升到4 kgVS/m3·d时,日产气量从2.91 L提高到9.01 L,沼气中甲烷含量在65％以上.     

Decontamination of anaerobically digested slurry in a paddy field ecosystem in Jiaxing region of China

Anaerobic digestion has become increasing popular for managing biowastes in rural China as it has the advantage of generating biogas, a renewable energy. A new challenge, however, is minimizing the environmental pollution resulting from the anaerobically digested slurry (ADS). The aim of this study was to assess the feasibility of using a paddy field to remediate ADS while simultaneously cultivating rice. A field experiment was trialed using six treatments based on varying nitrogen loadings over the period of a rice-growing season. These treatments were adjusted to the content of the N within the ADS and had loadings of 270, 405, 540 and 1080 kg N ha⁻¹. These treatments were compared to a negative control (no fertilizer) and a positive control (chemical fertilizer) that consisted of urea applied at 270 kg N ha⁻¹. The effects of these N sources and slurry remediation were monitored using standard methods to measure water quality, soil properties and changes in rice production. Rice grain yields were generally higher for all ADS treatments than for the urea N treatment. Standing water quality in the field could reach national discharge standards for all treatments within 7-8 days after each ADS irrigation. Groundwater quality and heavy metal concentrations in both soil and the rice grain were not affected by the ADS treatments. We suggest that the quantities of ADS irrigated in 867-1734 m³ ha⁻¹ was not only safe for food quality (rice grain) and the receiving environment (water and soil), but also beneficial to soil fertility and rice grain yield.     

The relationship between El Niño Southern Oscillations and cereal production in Sahel

The effect of drought on crop yield and water resources has been an important socio-economic concern in the Sahel region of Africa. The most severe droughts in the Sahel region occurred during the strong El Niño Southern Oscillation (ENSO) events. There is thus increased need to understand the stochastic relationship between such physical mechanism like ENSO and crop yield. In this paper, such a relationship is investigated using a wavelet approach. Our result shows that a statistically significant relationship exists between ENSO and cereal production in the region. In particular, El Niño events are devastation to millet yield with little or no impact on maize and sorghum production. This can be attributed to the lower length of growing period for maize and sorghum compared to millet. On the other hand La Niña events favor cereal production and mirrored sorghum yield during the La Niña years of 1973–1976. The potential value of ENSO-based rainfall forecast and socio-economic impact on local population in Sahel region are discussed.     

Impact of maximum sustainable yield on independent populations

We investigate a community of independent logistically growing populations under a common harvesting effort which leads to the total maximum sustainable yield (TMSY). It is surprising that in the case of two populations with approximately equal carrying capacities, TMSY is reached while both populations persist, although their biotic potential may differ substantially. In general, however, TMSY with a common harvesting effort implies suboptimal fishing of some populations, overfishing of others and extinction of the rest of the populations. Since extinction of populations is a rule rather than an exception and since a community of independent populations is more robust than an ecosystem with multiple trophic levels, we call for urgent retraction of all legal documents advocating MSY in ecosystems.     

Influx,transport, and accumulation of cadmium in plant species grown at different Cd2+ activities

Abstract

Cadmium (Cd) has no known essential biological function, but it is toxic to plants, animals, and humans. A promising approach to prevent Cd from entering the food chain would be to select and/or create Cd‐accumulating plants to remediate contaminated soils or to develop Cd‐excluding plants to reduce Cd flow from soils into foods. The present study was undertaken to examine the differences in Cd influx, transport, and accumulation among five plant species in relation to plant tolerance to Cd toxicity. Ryegrass (Lolium perenne L.) had the least reduction in dry matter which may be due to its lowest Cd transport rate (TR) to shoots at all Cd levels among the plant species tested. White‐clover (Trifolium repens L.) was the most sensitive species to Cd toxicity, likely because of its highest Cd influx rate (IR) and high TR when plants were grown at low Cd²⁺ activity (≤8 μM). The high tolerance of cabbage (Brassica oleracea var. capitata L.) to moderate Cd toxicity (≤14 μM) appeared to be mainly due to the detoxification of Cd inside plant tissue since it recorded the highest TR and relatively high IR for Cd among the tested species. At Cd²⁺ activities up to 28 uM, the Cd uptake ratios of shoot/root for ryegrass were, on average, about 50‐fold and 27‐fold lower than that for cabbage and maize (Zea mays L.), respectively. These results showed that Cd could be easily transported into shoots of cabbage and maize, but was mainly confined to roots of ryegrass. We suggest that influx and transport rates, especially transport rate, could be used as plant physiological parameters for screening Cd‐excluding genotypes among monocotyledonous plants.     

L-asparaginase and L-glutaminase activities in submerged rice soil amended with municipal solid waste compost and decomposed cow manure

The field study was conducted to evaluate the effect of municipal solid waste compost (MSWC) as a soil amendment on L-asparaginase (LA) and L-glutaminase (LG) activities. Experiments were conducted during the wet seasons of 1997, 1998 and 1999 on rice grown under a submerged condition, at the Agriculture Experimental Farm, Calcutta University at Baruipur, West Bengal, India. The treatments consisted of control, no input; MSWC, at 60 Kg N ha^{? 1}; well-decomposed cow manure (DCM), at 60 Kg N ha^{? 1}; MSWC (30 Kg N ha^{? 1}) + Urea (U) (30 Kg N ha^{? 1}); DCM (30 Kg N ha^{? 1}) + U (30 Kg N ha^{? 1}) and Fertilizer, (at 60:30:30 NPK kg ha^{? 1}) through urea, single superphosphate and muriate of potash respectively). LA and LG activities alone and their ratio with organic-C (ratio index value, RIV), straw and grain yield were higher in DCM than MSWC-treated soils, due to higher amount of biogenic organic materials like water-soluble organic carbon, carbohydrate and mineralizable nitrogen in the former. The studied parameters were higher when urea was integrated with DCM or MSWC, compared to their single applications. The heavy metals in MSWC did not detrimentally influence the above-measured activities of soil. In the event of long term MSWC application, changes in soil quality parameters should be monitored regularly, since heavy metals once entering into soil persist over a long period.     

Performance evaluation of a completely stirred anaerobic reactor treating pig manure at a low range of mesophilic conditions

Many Chinese biogas plants run in the lower range of mesophilic conditions. This study evaluated the performance of a completely stirred anaerobic reactor treating pig manure at different temperatures (20, 28 and 38 °C). The start-up phase of the reactor at 20 °C was very long and extremely poor performance was observed with increasing organic loading rate (OLR). At an OLR of 4.3 g ODM L^?1 d^?1, methane production at 28 °C was comparable (3% less) with that at 38 °C, but the risk of acidification was high at 28 °C. At low OLR (1.3 g ODM L^?1 d^?1), the biogas process appeared stable at 28 °C and gave same methane yields as compared to the reactor operating at 38 °C. The estimated sludge yield at 28 °C was 0.065 g VSS g^?1 COD_removed, which was higher than that at 38 °C (0.016 g VSS g^?1 COD_removed).     

赤红壤地区茶叶施用有机无机复肥的效果初探

本试验比较了三种不同Ｎ／Ｋ２Ｏ的有机无机复肥和进口复肥在赤红壤茶园上的施用效果．结果表明，施用有机无机复肥能促进茶树生长，增大茶芽密度．提高茶叶产量，增加茶叶的茶多酚和氨基酸含量；且能增加土壤有机质含量，平衡土壤养分．有机无机复肥中的Ｎ／Ｋ２Ｏ对其肥效的发挥有重要作用，Ｎ／ｋ２Ｏ值以４．５为宜．     

淮北地区小麦高产的生态限制因素与对策

本文在对影响淮北地区小麦高产的生态限制因素进行系统分析的基础上，提出了科学治水、施肥，合理灌溉，培肥地力，优化小麦群体动态结构等高产配套措施．