卤素离子对溶解性黑碳光化学活性的影响

溶解性黑碳(DBC)是天然有机质的重要组分,但其在河口水环境中的光化学活性尚不清楚.为解决这个问题,以大豆秸秆溶解性黑碳为目标物,使用山梨酸能量转移同分异构方法研究河口水卤素离子浓度条件下激发三重态DBC (³DBC^*)的生成速率(F_T)、淬灭速率(k_s')、稳态浓度([T]_ss)变化规律,并使用2,4,6-三甲基苯酚电子转移探针方法研究卤素离子对³DBC^*电子转移过程的影响.结果表明,卤素离子及其离子强度作用对F_T无显著影响,但k_s'因离子强度和Br^-重原子效应而减小,导致³DBC^*的[T]_ss增加.高浓度DBC光化学实验证实离子强度作用引起DBC分子聚集,导致³DBC^*的电荷转移过程减弱,从而抑制³DBC^*的淬灭.山梨酸探针实验表明,卤素离子及其离子强度作用对³DBC^*的能量转移无直接影响,主要是通过抑制³DBC^*的淬灭,增加[T]_ss.进一步研究发现卤素离子及其离子强度作用对低能态³DBC^*(E_T < 250kJ/mol)无显著影响,但抑制高能态³DBC^*(E_T > 250kJ/mol)的电子转移,且随卤素离子和离子强度的增加而愈发明显.     

Water balance characterization of the early 21st century drought in the western United States

Monthly temperature and precipitation data for 923 United States Geological Survey 8-digit hydrologic units are used as inputs to a monthly water balance model to compute monthly actual evapotranspiration, soil moisture storage, and runoff across the western United States (U.S.) for the period 1900 through 2020. Time series of these water balance variables are examined to characterize and explain the dry conditions across the western U.S. since the year 2000. Results indicate that although precipitation deficits account for most of the changes in actual evapotranspiration and runoff, increases in temperature primarily explain decreases in soil moisture storage. Specifically, temperature has been particularly impactful on the magnitude of negative departures of soil moisture storage during the spring (April through June) and summer (July through September) seasons. These effects on soil moisture may be particularly detrimental to agriculture in regions already stressed by drought such as the western U.S.     

Bioenergy production from roadside grass: A case study of the feasibility of using roadside grass for biogas production in Denmark

This paper presents a study of the feasibility of utilising roadside vegetation for biogas production in Denmark. The potential biomass yield, methane yields, and the energy balances of using roadside grass for biogas production was investigated based on spatial analysis. The results show that the potential annual yield of biomass obtainable from roadside verges varies widely depending on the local conditions. The net energy gain (NEG) from harvest, collection, transport, storage and digestion of roadside vegetation was estimated to range from 60,126–121,476 GJ, corresponding to 1.5–3.0% of the present national energy production based on biogas. The estimated values for the energy return on invested energy (EROEI) was found to range from 2.17 to 2.88. The measured contents of heavy metals in the roadside vegetation was seen not to exceed the legislative levels for what can be applied as fertilizer on agricultural land, neither does it reach levels considered as inhibitory for the anaerobic fermentation process. From a practical point of view, few challenges were identified related to the acquisition and processing of the roadside vegetation. Considering the positive net energy gains, further energy investments for management of these challenges can be made. Despite the somewhat low EROEI values, the use of this resource could however result in other positive externalities, such as improved biodiversity of the verges and recycling of nutrients.     

不同种养结合区农田系统氮磷平衡分析

山东禹城和湖南桃源是位于我国不同地区均以种养生产为主的两个县(市),根据养分平衡原理对这两个县级区域尺度的农田系统氮、磷收支状况进行了计算分析,结果表明:自1980年以来,单位面积耕地上氮磷的输入量与输出量均表现为不断增加,但是,因为输入增长高于输出增长,导致农田系统产生较多氮磷养分盈余,两个地区存在明显差异。禹城农田系统氮磷盈余量呈逐年增长趋势,氮盈余量从133.8 kgN·hm^-2增加到目前的450 kgN·hm^-2以上,磷盈余量从6.2 kgP₂O₅·hm^-2增加到目前的148.9 kgP₂O₅·hm^-2;在其11个乡镇中有10个表现为氮盈余、9个表现为磷盈余,其中氮盈余量最多的高达841.8 kgN·hm^-2,磷盈余量最多的达到297.8 kgP₂O₅·hm^-2。桃源农田系统氮磷盈余量表现为先增后降,氮盈余量从100 kgN·hm^-2左右增加到2002年达到峰值253.7 kgN·hm^-2后,逐渐下降到目前的150.0 kgN·hm^-2左右,磷盈余量从20.0 kgP₂O₅·hm^-2左右增加到2002年的峰值95.9 kgP₂O₅·hm^-2后,下降到目前的34.4 kgP₂O₅·hm^-2;在其40个乡镇中有36个表现为氮盈余、26个表现为磷盈余,其中氮盈余量最高的达到561.7 kgN·hm^-2,磷盈余量最高的为171.1 kgP₂O₅·hm^-2。农田系统氮磷养分大量盈余主要是源于投入化肥量和承载粪便量较高,山东禹城明显高于湖南桃源,所以,为了减少养分盈余损失,应根据农田作物生长养分需求尽可能地减少化肥投入,并根据耕地粪便承载容量在区域内外合理调配畜禽粪便的施用。     

Fate and removal of typical pharmaceutical and personal care products in a wastewater treatment plant from Beijing: a mass balance study

The fate and removal of pharmaceuticals and personal care products (PPCPs) in wastewater treatment plants (WWTPs) has received great attention during the last decade. Numerous data concerning concentrations in the water phase can be found in the literature, however corresponding data from sludge as well as associated mass balance calculations are very limited. In the present study, the adsorbed and dissolved concentrations of 9 PPCPs were investigated in each unit of a WWTP in Beijing, China. Based on the calculation of mass balance, the relative mass distribution and removal efficiency of each target compound was obtained at each process. The amount of PPCPs entering into the WWTP ranged from 12 g·d^–1 to 3848 g·d^–1. Five target compounds (caffeine, chloramphenicol, bezafibrate, clofibric acid, and N,N-diethyl-meta-toluamide) were effectively removed, with rates of 57%–100%. Negative removal efficiencies were obtained for sulpiride, metoprolol, nalidixic acid, and carbamazepine, ranging from -19% to -79%. PPCPs mainly existed in dissolved form (≥92%) in both the raw influent and the final effluent. The sludge cake carried a much lower amount of PPCPs (17 g·d^–1) compared with the discharged effluent (402 g·d^–1). In A²/O treatment tanks, the anaerobic and anoxic tanks showed good performance for PPCPs removal, and the amount of adsorbed PPCPs was increased. The results reveal that both the dissolved and the adsorbed phases should be considered when assessing the removal capacity of each A²/O tank.     

水平衡模型及其在水价政策的应用

基于物质平衡模型,构建了经济系统水平衡模型及部门的水平衡模型,并利用水平衡模型核算A市工业和居民用水、排水的真实状况,评估水价政策的执行效果,以期为我国水价政策的制定、实施和完善提供参考.结果表明,循环用水具有节水和减排的双重效果:工业的用排比和无处理排水量远高于居民,A市工业水用排比是居民的2.9倍,工业无处理排水量是居民的3.6倍;对用水和排水监管不严,导致实际水费收入远低于应征水费收入.在2009年的水价标准下,A市少征收水费11802万元,有效的水价政策必须建立在严格监管的基础之上.     

城市化对北京夏季极端高温影响的数值研究

利用一个耦合了城市冠层模式（UCM）的区域数值模拟系统（WRF／NCAR）,引入由LandsatTM提取的京津冀区域30m分辨率下垫面GIS数据集代替美国USGS地表分类数据,对2009年6月24—25日出现在北京地区的一次超过40℃极端高温天气过程进行了高分辨率数值模拟,用以考察WRF／UCM系统对北京“城市热岛”及城市高温天气的模拟效果,并分析了城市化对北京地区城市高温和地表能量平衡的影响及其日变化特征。结果表明：采用精细化下垫面分类数据集后能更好地模拟出主要高温区的分布特征,并能较好再现夜间的“城市热岛”效应。城市化发展对近地层气温的影响主要表现在会促使城区及其下风向近郊区气温的升高,增幅可达0．5～2℃,这与城市热岛及其下游效应有关。城市下垫面的高粗糙度对近地层风速表现出明显的阻挡效应,表现在模拟的10m风场减弱明显。考虑了城市下垫面属性的敏感性试验更好地再现了城区温度的日变化,其模拟的日间最高温度与实际观测值更为接近,也较好地模拟出了城区具有较高最低温度的特征。通过城区与郊区能量平衡过程差异的分析表明,城市化可以显著改变能量平衡中各项所占的比重。地表对近地层大气热量输送过程的变化表明随着城市下垫面的日愈扩大,会显著增强白天地表对大气的向上感热输送,增大城区日间出现高温的可能。夜间,模式反映出地表能量收入来自土壤热通量的向上输送,同样由于城区的潜热通量小,收入的能量仍主要以感热形式加热大气,夜间城区具有较高的最低温度并表现出较强的热岛特征,主要与夜间感热加热的持续相关。     

造纸废水短流程动态平衡水循环利用工艺

斜网脱水机、洗浆机及抄纸机产生的废水短流程逆向分段回用于水力碎浆机、配浆池和成浆池,同时在纸机抄造系统中加入与废水蒸发量相当的新鲜水,实现了废水动态平衡与短流程循环利用"零"排放的目标。河南滑县光明纸业责任有限公司采用该工艺以来,每年可节约水资源61万t,减排COD量为43 t,年减少污泥量510 t,故该工艺具有良好的应用前景。     

铅蓄电池生产企业的清洁生产审核

介绍了某铅蓄电池生产企业按照清洁生产审核程序的7个阶段开展的清洁生产审核工作,分别对企业含铅废气、含铅废水和含铅危险废物污染源进行了排查,采用铅平衡核算、与清洁生产标准进行指标对比等方法查找问题并进行原因分析,提出改进方案。实施清洁生产方案后企业废水产生量为0.10 m3/(kV.A.h)(以生产单位电功率铅蓄电池产生的废水量计),总铅产生量为0.35 g/(kV.A.h),铅尘处理系统除尘效率达98%以上,年减少含铅废酸液产生量50 t,年减排铅尘3.2 kg,年节约成本50万元以上。     

The effect of Oja-titun market effluent on the chemical quality of receiving OPA reservoir in Ile-Ife, Nigeria

The effect of market effluent from the Oja-titun market in Ile-Ife, Nigeria on the chemical quality of the Opa Reservoir located 3.5 km downstream was investigated between February and November 2000. Water samples were collected in February, May, August and November from 16 sites, four along each of the market drainage channels (MDC), market stream, tributary stream and the Opa River and Reservoir. The peak level of each variable-biochemical oxygen demand, temperature, total alkalinity, Na(+), K(+), Ca(2+), Mg(2+), PO(4)(3+), SO(4)(2+), Cl(-), NO(3)(-), Pb and Zn-occurred at the MDC, and decreased significantly downstream, except pH, conductivity and dissolved oxygen, which increased. Seasonal fluctuation in most variables was pronounced. Generally, there were high values in the early dry and dry seasons and low values in the rainy and early rainy seasons. Comparison of the reservoir water with international limitation standards for drinking water supply showed that the quality of the reservoir water was very low and that treatment required to achieve minimum limitation standards for drinking water would be both intensive and expensive. The study concluded that the stream borne effluent from the market impacts significantly on the chemical quality of the reservoir water although other tributaries within the Reservoir's catchment are other possible sources of pollutants in the reservoir.