基于土地利用变化的农牧交错带典型流域生态风险评价——以洋河为例

为揭示土地利用变化对农牧交错带典型流域生态风险的影响,在Arc GIS技术支持下,以洋河流域1990、1995、2000和2008年遥感数据和土地利用数据为基础,定量分析洋河流域1990—2008年的土地利用动态变化特征;根据景观生态学理论,将研究区划分为525个生态风险评价单元,从土地利用变化和景观结构角度构建景观生态风险评价模型,评价洋河流域生态风险的时空变化特征。结果表明:耕地和草地面积占研究区总面积的67%以上;1990—2008年,洋河流域总体景观生态风险值(ERI)由0.197 3上升到0.238 4。低风险区(ERI≤0.17)面积减少3.53%,高风险区(ERI0.68)面积减少0.43%,较低(0.17ERI≤0.26)、中等(0.26ERI≤0.42)和较高(0.42ERI≤0.68)风险区面积均有增加,整体生态风险增加;洋河流域5种风险等级分布较集中,具体表现为洋河支流及其一级支流两侧地区生态风险相对较大(ERI0.26),而离河道越远的区域生态风险值越小(ERI≤0.26)。     

Assessment of metal and nutrient concentrations in river water and sediment collected from the cities in the Pearl River Delta,South China

The effects of anthropogenic activities, industrialization and urbanization on the accumulation of heavy metals and nutrients in sediments and water of rivers in the Pearl River Delta region were examined. Most sediments were seriously contaminated with Cd, Pb, and Zn in accordance with the classification by Hong Kong Environmental Protection Department. Total phosphorus (P) and nitrogen (N) concentrations in sediments ranged from 0.02% to 0.12% and 0.06% to 0.64%, respectively. High carbon (C), N, P and sulphur (S) levels at Yuen Long Creek were related to the discharge of industrial effluents along the river. The enrichment of P and ammoniacal-nitrogen (NH4+-N) in water were obvious. For most sites, the P concentration exceeded 0.1 mg/l, which is the recommended concentration in flowing water to encourage excessive growth of aquatic plants. Nine out of the 16 sites studied had NH4+-N concentration over 2 mg/l. The rivers in the south of Deep Bay (Hong Kong) had high nutrient exports compared with the rivers in the east region and western oceanic water. The concentrations of nitrate-nitrogen NO3--N in surface water were under the maximum contaminant level in public drinking water supplies (10 mg/l) except for one site. Although the concentrations of heavy metals in overlying water were low, their accumulations were significant. High contents of nickel (Ni) and zinc (Zn) in water were found at certain locations, suggesting the occurrence of some local contamination. These preliminary results indicated that river and sediment transported pollutants is likely one of the factors for the water quality degradation of Deep Bay water.     

Chemical composition and seasonal variation of acid deposition in Guangzhou, South China: comparison with precipitation in other major Chinese cities

With the aim of understanding the origin of acid rains in South China, we analyzed rainwaters collected from Guangzhou, China, between March 2005 and February 2006. The pH of rainwater collected during the monitoring period varied from 4.22 to 5.87; acid rain represented about 94% of total precipitation during this period. The rainwater was characterized by high concentrations of SO₄²⁻, NO₃⁻, Ca²⁺, and NH₄⁺. SO₄²⁻ and NO₃⁻, the main precursors of acid rain, were related to the combustion of coal and fertilizer use/traffic emissions, respectively. Ca²⁺ and NH₄⁺ act as neutralizers of acid, accounting for the decoupling between high SO₄²⁻ concentrations and relatively high pH in the Guangzhou precipitation. The acid rain in Guangzhou is most pronounced during spring and summer. A comparison with acid precipitation in other Chinese cities reveals a decreasing neutralization capacity from north to south, probably related to the role and origin of alkaline bases in precipitation.     

微波消解石墨炉原子吸收法测定土壤和沉积物中的铍

以氯化钯为基体改进剂,采用微波消解石墨炉原子吸收法测定土壤和沉积物中的铍,优化了微波消解条件,考察了共存元素对测定的干扰。方法在0μg／L～4．00μg／L范围内线性良好,检出限为0．01μg／g（以取样质量0．2000g、定容体积50mL计）,标准样品平行测定的RSD为3．5％～6．7％,实际样品的加标回收率为84．0％-113％。     

Unveiling the interaction mechanisms of key functional microorganisms in the partial denitrification-anammox process induced by COD

● The availability of PD-anammox was investigated with higher NO₃^––N concentration. ● NO₃^––N concentration affects NO₃^––N accumulation during denitrification. ● COD concentration is determinant for N removal pathways in PD-anammox process. ● The synergy/competition mechanisms between denitrifiers and anammox was explored. Partial denitrification-anammox (PD-anammox) is an innovative process to remove nitrate (NO₃^––N) and ammonia (NH₄⁺–N) simultaneously from wastewater. Stable operation of the PD-anammox process relies on the synergy and competition between anammox bacteria and denitrifiers. However, the mechanism of metabolic between the functional bacteria in the PD-anammox system remains unclear, especially in the treatment of high-strength wastewater. The kinetics of nitrite (NO₂^––N) accumulation during denitrification was investigated using the Michaelis-Menten equation, and it was found that low concentrations of NO₃^––N had a more significant effect on the accumulation of NO₂^––N during denitrification. Organic matter was a key factor to regulate the synergy of anammox and denitrification, and altered the nitrogen removal pathways. The competition for NO₂^––N caused by high COD concentration was a crucial factor that affecting the system stability. Illumina sequencing techniques demonstrated that excess organic matter promoted the relative abundance of the Denitratesoma genus and the nitrite reductase gene nirS, causing the denitrifying bacteria Denitratisoma to compete with Cadidatus Kuenenia for NO₂^––N, thereby affecting the stability of the system. Synergistic carbon and nitrogen removal between partial denitrifiers and anammox bacteria can be effectively achieved by controlling the COD and COD/NO₃^––N.     

镉胁迫对小白菜（Brassica campestris L.）抗氧化机理的影响

采用水培的方法,研究了不同Cd2 水平(0、1、2.5、5、10、15mg·L-1)对小白菜(Brassica campestris L.)抗氧化酶(SOD、POD、CAT)活性、非酶物质(SH、GSH、PCs)含晕以及生长的影响.结果表明,小白菜叶片和根系SOD活性随Cd处理质量浓度的增加呈降低的变化趋势,POD、CAT活性以及MDA含量随Cd处理质量浓度的增加而增加.小白菜的生物量、根长、株高、叶绿素质量分数随Cd处理质量浓度的增加显著降低(P<0.05),表明Cd抑制了小白菜的生长,破坏了叶绿素的合成.小白菜地上、地下部镉质量分数均随Cd处理质量浓度的增加而显著增加(P<0.05).当Cd处理质量浓度为15 mg·L-1,小白菜地上、地下部镉质量分数分别达到637.5、1 663.0 mg·kg-1,表明小白菜对Cd有良好的富集效果.小白菜根系与叶片中SH、GSH和PCs含量均随Cd处理质量浓度增加而增加的变化趋势,表明SH、GSH和PCs在解毒小白菜Cd毒害中起着重要作用.     

基于生态足迹法的区域水资源生态承载力计算与评价——以珠海市为例

研究了人类社会对水资源的消耗、对自然生态环境的影响以及该影响的量化方法和量化指标,将生态足迹法引入区域水资源承载力系统,构建珠海市水资源生态承载力计算模型,分析计算水资源供给对区域经济社会发展的生态承载力,并对该地区的水资源生态承载力进行生态盈亏和敏感性评价.结果表明,总体上珠海市水资源系统呈现生态亏损,亏损率为37%,水资源生态承载呈现超载现象,珠海市城市化进程中流动人口增长对区域水资源的生态承载压力较大.研究结果还表明,将生态足迹模型运用到地区水资源承载力中具有较高的可信度,对地方尺度具有适用性.     

水泥分解炉内生活垃圾与煤粉燃烧特性分析和技改建议

将生活垃圾制备成垃圾衍生燃料（RDF）,再投入水泥分解炉内进行燃烧处理是生活垃圾无害化处置的重要途径。与煤粉相比,RDF在分解炉内的燃烧与运动特性存在较大差异,从而对分解炉的正常运转产生较大影响。通过检测分析、热工计算和计算流体动力学模拟（CFD）等手段,对比了RDF与煤粉在燃烧、运动特性等方面存在的差异。结果表明,与煤粉相比,RDF的水分、灰分含量偏高,固定碳含量偏低, 单位RDF燃烧理论空气量只有煤粉的14.5%。入炉煤粉的特征粒径为20 μm,RDF为10 mm;粒径小于10 mm的RDF喂入分解炉后随烟气向下游流动,但大于10 mm的直接向下运动,并在分解炉缩口和中部形成循环。经过空气干燥、粉磨后的RDF颗粒着火温度为235~242 °C,煤粉着火温度为375 °C,然而考虑实际使用时入炉RDF水分含量高、尺寸大等,其在分解炉内燃烧速度通常较煤粉慢。为此,建议水泥企业在对RDF进行准确的工业分析和元素分析基础上,通过热工标定、CFD模拟等手段优化RDF处置尺寸与喂入位置,确保RDF在分解炉内完全燃烧。     

基于结构和工艺流程革新的AO工艺提标改造

通过实验进行了基于结构造和工艺流程革新的AO工艺提标改造研究。改造前后的对比实验结果表明,提标改造后的D-A2O反应器在（24±2）℃温度下COD、TN、NH3-N、TP去除率分别可达92.24%、84.77%、98.65%和92.11%,比AO反应器相应污染物去除率分别提高了5%、14%、14%和20%,出水水质优于GB 18918-2002中一级A标准;同时,本升级改造后形成的D-A2O反应器于不同温度下具有较强的稳定性,且污泥龄（SRT）可延长至30~35 d。根据小试结果粗略估算,将AO改造成D-A2O技术所需增加的基建投资费用小于AO工艺原有基建费用4%,可节约污水处理运行费用约6%。结果表明,提标改造在技术上和经济上均具有可行性。