Nutrient removal in tropical subsurface flow constructed wetlands under batch and continuous flow conditions

The aim of this investigation was to evaluate the influence of batch versus continuous flow on the removal efficiencies of chemical oxygen demand (COD), nitrogen (N) and total phosphorus (TP) in tropical subsurface flow constructed wetlands (SSF CW). The quantitative role of the higher aquatic plants in nutrient removal in these two operational modes was also investigated. Results indicated no significant difference (p > 0.05) in COD removal between batch and continuous flow modes for either the planted or unplanted treatments. Furthermore, the batch-loaded planted wetlands showed significantly (p < 0.05) higher ammonium removal efficiencies (95.2%) compared with the continuously fed systems (80.4%), most probably because the drain and fill batch mode presented systematically more oxidized environmental conditions. With respect to TP removal, for both planted and unplanted beds, there was significant enhancement (p < 0.05) in batch flow operation (69.6% for planted beds; 39.1% for unplanted beds) as compared to continuous flow operation (46.8% for planted beds; 25.5% for unplanted beds). In addition, at a 4-day hydraulic retention time (HRT), the presence of plants significantly enhanced both ammonia oxidation and TP removal in both batch and continuous modes of operation as compared to that for unplanted beds. An estimation of the quantitative role of aeration from drain and fill operation at a 4-day HRT, as compared to rhizosphere aeration by the higher aquatic plant, indicated that drain and fill operation might account for only less than half of the higher aquatic plant's quantitative contribution of oxygen (1.55 g O2 per m2 per day for batch flow versus 1.13 g O2 per m2 per day for continuous flow).     

四川省不同区域高速公路环境影响评价要点

高速公路项目由于其线路长、工程量大等特点,不可避免会对生态环境、土地资源、水土流失、人居环境等造成不利影响,本文根据四川各区域的地形地貌、水文地质、生物多样性等环境特点,提出了在不同地区高速公路建设中的环境影响评价要点,从而使环境影响评价内容更具有针对性。     

Differential Effects of Legume Species on the Recovery of Soil Microbial Communities, and Carbon and Nitrogen Contents, in Abandoned Fields of the Loess Plateau, China

Plant–soil interactions are known to influence a wide range of ecosystem-level functions. Moreover, the recovery of these functions is of importance for the successful restoration of soils that have been degraded through intensive and/or inappropriate land use. Here, we assessed the effect of planting treatments commonly used to accelerate rates of grassland restoration, namely introduction of different legume species Medicago sativa, Astragalus adsurgens, Melilotus suaveolens, on the recovery of soil microbial communities and carbon and nitrogen contents in abandoned fields of the Loess Plateau, China. The results showed effects were species-specific, and either positive, neutral or negative depending on the measure and time-scale. All legumes increased basal respiration and metabolic quotient and had a positive effect on activity and functional diversity of the soil microbial community, measured using Biolog EcoPlate. However, soil under Astragalus adsurgens had the highest activity and functional diversity relative to the other treatments. Soil carbon and nitrogen content and microbial biomass were effectively restored in 3–5?years by introducing Medicago sativa and Astragalus adsurgens into early abandoned fields. Soil carbon and nitrogen content were retarded in 3–5?years and microbial biomass was retarded in the fifth year by introducing Melilotus suaveolens. Overall, the restoration practices of planting legumes can significantly affect soil carbon and nitrogen contents, and the biomass, activity, and functional diversity of soil microbial community. Therefore, we propose certain legume species could be used to accelerate ecological restoration of degraded soils, hence assist in the protection and preservation of the environment.     

垃圾渗滤液发酵产氢和产甲烷特性研究

以实际垃圾渗滤液作为厌氧发酵基质,研究了初始pH为7.0、中温(37℃)条件下的发酵产氢、产甲烷特性。结果表明,利用垃圾渗滤液作为基质发酵产氢或甲烷时,氢气的最大累积产量为24.33mL(以每克COD计,下同),甲烷的最大累积产量为91.59mL,产氢发酵在初期存在明显的迟滞期,但是产甲烷发酵不存在明显迟滞期;产氢发酵的液相末端产物中含有大量的挥发性有机酸和乙醇,乙醇、乙酸、丁酸质量浓度分别为487.23、1 175.21、1 225.78mg/L,相比产氢发酵,产甲烷发酵的液相末端产物中乙醇、乙酸、丁酸质量浓度均较低,分别为256.38、106.73、107.42mg/L;产甲烷发酵的最终pH是6.32,接近中性,而产氢发酵的最终pH为4.21,呈明显酸性;产甲烷发酵对COD的去除率(41.78%)高于产氢发酵对COD的去除率(32.14%),可能是产氢发酵液相末端产物中的乙酸能被产甲烷菌利用,而被进一步降解。     

氢氧化铁用于污水污泥原位恶臭控制的研究

考察了添加不同剂量氢氧化铁对于污水污泥处置过程中的恶臭污染的控制效果。结果表明,在厌氧发酵32d时,添加0.05%、0.10%、0.25%(质量分数,下同)的氢氧化铁分别使污水污泥处理中硫化氢的平均去除率(与未添加氢氧化铁相比)达到81.3%、93.7%、97.5%;氢氧化铁的添加对污水污泥厌氧发酵中氨气的释放量没有明显影响。利用冷扩散连续萃取法考察了厌氧发酵过程中污水污泥中硫的形态分布,发现在氢氧化铁的作用下生成了硫化亚铁、二硫化亚铁、单质硫,从而降低了硫化氢的释放速率,有效控制了污水污泥厌氧发酵中的恶臭。氢氧化铁是一种可以用于污泥处理的高效除臭剂。     

特大型城市客运交通碳排放与减排对策研究

本文基于对现有城市交通碳排放测算方法的比较分析,以上海市为例,采用IPCC"自下而上"法对特大型城市客运交通CO2排放进行了测算,结果显示:轨道交通是碳排放效率最高的客运方式,出租车最低;客运交通CO2排放总量增长迅速,且碳源结构发生了较大变化;近年客运交通CO2排放增量主要来自私人载客汽车,同时公务交通在客运交通碳排放中始终占较大比重。由此本文认为,控制客运交通碳排放的关键在于对以私人载客汽车和单位载客汽车为主的个体交通的管理和控制,形成以公共交通为主的交通结构。在此基础上,为了将控制碳排放纳入到城市交通政策目标中去,本文就主要城市交通政策对客运交通碳排放产生的影响进行了深入分析,并得出结论:以往的交通供给、需求管理政策对于抑制客运交通碳排放增长的作用有限;而就目前城市空间发展政策的实施效果而言,也不利于降低居民出行的碳排放水平。文章最后分别从交通供给、需求管理以及城市空间角度给出了控制客运交通碳排放的对策。     

滇中城市经济圈资源环境支撑能力综合评价

滇中城市经济圈作为云南省优先开发区,其社会经济发展与资源环境保障之间的矛盾日益突出。科学评价滇中城市经济圈的资源环境基础,是制定滇中城市经济圈发展战略的客观依据。为了克服传统资源环境单要素评价方法的不足,从资源环境多要素视角出发对滇中城市经济圈的资源环境支撑能力进行了综合评价,明确资源环境系统的优劣势,从而为滇中城市经济圈的可持续发展提供资源环境保障。     

Tracking nitrogen losses in a greenhouse crop rotation experiment in North China using the EU-Rotate_N simulation model

Vegetable production in China is associated with high inputs of nitrogen, posing a risk of losses to the environment. Organic matter mineralisation is a considerable source of nitrogen (N) which is hard to quantify. In a two-year greenhouse cucumber experiment with different N treatments in North China, non-observed pathways of the N cycle were estimated using the EU-Rotate_N simulation model. EU-Rotate_N was calibrated against crop dry matter and soil moisture data to predict crop N uptake, soil mineral N contents, N mineralisation and N loss. Crop N uptake (Modelling Efficiencies (ME) between 0.80 and 0.92) and soil mineral N contents in different soil layers (ME between 0.24 and 0.74) were satisfactorily simulated by the model for all N treatments except for the traditional N management. The model predicted high N mineralisation rates and N leaching losses, suggesting that previously published estimates of N leaching for these production systems strongly underestimated the mineralisation of N from organic matter.     

医疗废物焚烧处理核心技术的开发及应用

国内已建成的医疗废物焚烧设施目前普遍存在进料系统不稳定、玻璃结渣和高浓度HCl气体的排放的问题。这些技术难点已成为医疗废物焚烧处置行业发展的瓶颈。本文介绍了可解决上述问题的"可调节医疗废物恒流量进料技术"、"医废焚烧防玻璃结渣技术"和"含高浓度氯化氢医废尾气处理技术"三项医疗废物焚烧处理核心技术的主要特点及技术指标与应用实例。     

秦皇岛市天然矿泉水水质特征及开发利用前景研究

秦皇岛市天然矿泉水主要赋存在早太古代的花岗岩和变质岩的构造裂隙与风化裂隙之中,有锶、偏硅酸、锶及偏硅酸、锶溴及偏硅酸等4种类型。矿泉水水源地数量较多,水质优良,但开采程度较低,开发利用前景广阔。