Levels of Lead in Urban Soils from Selected Cities in a Central Region of the Philippines (7 pp)

Background Aims, and Scope. Lead (Pb) is a naturally occurring element that poses environmental hazards when present at elevated concentration. It is being released into the environment because of industrial uses and from the combustion of fossil fuels. Hence, Pb is ubiquitous throughout global ecosystems. The existence of potentially harmful concentrations of Pb in the environment must be given full attention. Emissions from vehicles are major source of environmental contamination by Pb. Thus, it becomes imperative that concentrations of Pb and other hazardous materials in the environment not only in the Philippines, but elsewhere in the world be adequately examined in order that development of regulations and standards to minimize risk associated with these materials in urban areas is continued. The objectives of this study were: (1) to determine the levels of Pb in soil from selected urbanized cities in central region of the Philippines; (2) to identify areas with soil Pb concentration values that exceed estimated natural concentrations and allowable limits; and (3) to determine the possible sources that contribute to elevated soil Pb concentration (if any) in the study area. Methods This study was limited to the determination of Pb levels in soils of selected urbanized cities located in central region in the Philippines, namely: Site 1 – Tarlac City in Tarlac; Site 2 – Cabanatuan City in Nueva Ecija; Site 3 – Malolos City in Bulacan; Site 4 – San Fernando City in Pampanga; Site 5 – Balanga City in Bataan; and Site 6 – Olongapo City in Zambales. Soil samples were collected from areas along major thoroughfares regularly traversed by tricycles, passenger jeepneys, cars, vans, trucks, buses, and other motor vehicles. Soil samples were collected from five sampling sites in each of the study areas. Samples from the selected sampling sites were obtained approximately 2 to 3 meters from the road. Analysis of the soil samples for Pb content was conducted using an atomic absorption spectrophotometer. This study was conducted from 2003 to 2004. Since this study assumed that vehicular emission is the major source of Pb contamination in urban soil, other information which the researchers deemed to have bearing on the study were obtained such as relative quantity of each gasoline type disposed of in each city within a given period and volume of traffic in each sampling site. A survey questionnaire for gasoline station managers was prepared to determine the relative quantity of each fuel type (diesel, regular gasoline, premium gasoline, and unleaded gasoline) disposed of or sold within a given period in each study area. Results and Discussion Analysis of soil samples for Pb content showed the presence of Pb in all the soil samples collected from the 30 sampling sites in the six cities at varying concentrations ranging from 1.5 to 251 mg kg–1. Elevated levels of Pb in soil (i.e. greater than 25 mg kg–1 Pb) were detected in five out of the six cities investigated. Site 4 recorded the highest Pb concentration (73.9 ± 94.4 mg kg–1), followed by Site 6 (56.3 ± 17.1 mg kg–1), Site 3 (52.0 ± 33.1 mg kg–1), Site 5 (39.3 ± 19.0 mg kg–1), and Site 2 (38.4 ± 33.2 mg kg–1). Soil Pb concentration in Site 1 (16.8 ± 12.2 mg kg–1) was found to be within the estimated natural concentration range of 5 to 25 mg kg–1. Site 1 registered the least Pb concentration. Nonetheless, the average Pb concentration in the soil samples from the six cities studied were all found to be below the maximum tolerable limit according to World Health Organization (WHO) standards. The high Pb concentration in Site 4 may be attributed mainly to vehicular emission. Although Site 4 only ranked 3rd in total volume of vehicles, it has the greatest number of Type B and Type C vehicles combined. Included in these categories are diesel trucks, buses, and jeepneys which are considered the largest contributors of TSP (total suspended particles) and PM10 (particulate matter less than 10 microns) emissions. Conclusion Only one (San Juan in Site 4) of the thirty sampling sites recorded a Pb concentration beyond the WHO permissible limit of 100 mg kg–1. San Juan in Site 4 had a Pb concentration of >250 mg kg–1. On the average, elevated Pb concentration was evident in the soil samples from San Fernando, Olongapo, Malolos, Balanga, and Cabanatuan. The average soil Pb concentrations in these cities exceeded the maximum estimated natural soil Pb concentration of 25 mg kg–1. Average soil Pb concentration in Site 1 (16.8 mg kg–1) was well within the estimated natural concentration range of 5 to 25 mg kg–1. Data gathered from the study areas showed that elevated levels of Pb in soil were due primarily to vehicular emissions and partly to igneous activity. Recommendation and Outlook The findings of this study presented a preliminary survey on the extent of Pb contamination of soils in urban cities in central region of Philippines Island. With this kind of information on hand, government should develop a comprehensive environmental management strategy to address vehicular air pollution in urban areas, which shows as one of the most pressing environmental problems in the country. Basic to this is the continuous monitoring of Pb levels and other pollutants in air, soil, and water. Further studies should be conducted to monitor soil Pb levels in the six cities studied particularly in areas with elevated Pb concentration. The potential for harm from Pb exposure cannot be understated. Of particular concern are children who are more predisposed to Pb toxicity than adults. Phytoremediation of Pb-contaminated sites is strongly recommended to reduce Pb concentration in soil. Several studies have confirmed that plants are capable of absorbing extra Pb from soil and that some plants, grass species in particular, and can naturally absorb far more Pb than others.     

怠速起停对汽油车油耗及颗粒数量排放的影响

以一辆配置怠速起停系统的国V缸内直喷汽油车为研究对象,使用底盘测功机试验系统、全流稀释采样系统和固态颗粒计数系统,试验研究怠速起停对缸内直喷汽油车油耗与颗粒数量排放的影响,并分析起动温度、试验循环等因素的影响.结果表明,NEDC循环车辆冷机起动时,车辆怠速起停系统开启的百公里油耗降低了5.1%,颗粒数量排放升高了16.7%;车辆热机起动,怠速起停开启产生的百公里油耗降幅增大到7.3%,颗粒数量排放升幅减小至9.3%;WLTC循环热机起动,车辆怠速起停系统开启的百公里油耗降幅减少到1.7%,颗粒数量排放升幅减少到6.2%.怠速起停有利于降低汽车的百公里油耗,但不利于缸内直喷汽油车颗粒数量排放的控制.     

成都市道路移动源排放清单与空间分布特征

以成都市为例开展了路网、交通流、道路行驶工况和机动车保有量等数据的收集工作,运用自下而上的方法,基于实测校正和本地化的IVE模型计算了不同区域机动车在高速路、主干道、次干道和支路的排放因子,应用GIS技术建立了1 km×1 km的成都市高时空分辨率道路移动源排放清单.结果表明,2016年成都市道路移动源CO、VOCs、NO_x、SO_2、PM_(10)和NH_3排放量分别为4.2×10~5、4.5×10~4、7.2×10~4、0.4×10~3、1.1×10~4和6.2×10~3t.CO排放主要贡献车型为小型客车、中型客车和大型客车,VOCs排放主要源于小型客车和摩托车,NOx和SO2排放主要产生于小型客车和重型货车,PM10排放主要贡献车型为重型货车,NH3排放主要由小型客车贡献.污染物排放量空间分布呈现出由城市中心向卫星城市、远郊区递减趋势,中心城区和二圈层区域路网密集,排放呈片状分布,三圈层则呈带状分布.排放清单机动车技术分布数据可靠性较高,而交通流数据和排放因子存在一定不确定性.     

京津冀地区汽车运输碳排放影响因素研究

以空间相关性和空间异质性为基础,构建SLM-STIRPAT、SEM-STIRPAT和GWR-STIRPAT模型,对京津冀地区汽车运输碳排放进行测算和影响因素分析.结果表明：京津冀地区汽车运输碳排放存在显著空间相关性和空间异质性.人口对汽车运输碳排放呈正向影响;人均GDP对货运碳排放和总量碳排放呈正向影响,对客运碳排放呈负向影响,城镇化水平对汽车运输碳排放呈负向影响.第三产业增加值对客运碳排放和总量碳排放呈正向影响,对货运碳排放呈负向影响,人口对张家口市汽车运输碳排放影响最为显著;人均GDP对秦皇岛市和沧州市的汽车运输碳排放影响最为显著;城镇化水平对秦皇岛市的汽车运输碳排放影响最为显著;第三产业增加值对秦皇岛市的汽车运输碳排放影响最为显著.     

典型街道环境空气质量分析

根据对深南东路环境空气的监测及车流量、气象条件的调查,分析机动车及气象因素对深圳市环境空气质量的影响。根据分析可知,机动车尾气是深圳市环境空气中污染物的主要来源,但污染程度不断变化的主要原因是风速,深圳市环境空气中污染物浓度与风速有着非常显著的负相关。     

汽车排放检测新技术研究

介绍了机动车排放检测新技术简易工况法的检测原理、检测方法、检测设备及其技术特点,通过进行怠速法、双怠速法、简易工况法的实车对比测试,证明了简易工况法比现行国家标准怠速法的技术更先进和有效,它能模拟实际路况反映汽车尾气排放的污染程度,能区分在用车中的高排放车、超标率和达标车,根据检测数据辅助不合格车辆进行有效的治理。以减低机动车污染物的排放,增强机动车的性能,配合I/M制度的实施。     

高排放车遥感筛选在台湾的应用

机动车尾气遥感监测是一项较新的技术。文章介绍了台湾地区在机动车尾气遥感监测法规、标准制订、实施方面的成功经验,以及我国其他大城市可以从中借鉴的经验。     

不同类型机动车尾气挥发性有机化合物排放特征研究

机动车尾气主要成分包括一氧化碳、氮氧化物、碳氢化合物、铅及苯并[a]芘等.其中,挥发性有机化合物由于其对光化学烟雾的贡献及对人体健康的影响而成为近年来大气化学研究的热点.文章首次对北京市9种车辆、5种燃料在不同工况下排放挥发性有机化合物特征进行了定量研究.结果表明,车型、燃料、净化器及工况等因素对排放量产生影响,电喷车比化油器车排放低,其中,夏利比富康与奥迪排放量高;LPG与汽油车排放量最高,柴油车与CNG车排放最低.其中,-10#柴油车比0#柴油车排放更低;使用净化器可以降低挥发性有机化合物排放量;不同工况对排放量的影响随车型、燃料类型的不同而不同.因此,使用清洁燃料、安装净化器和使用电喷装置,可减少尾气中挥发性有机化合物含量.     

Contribution of motor vehicle emissions to organic carbon and fine particle mass in Pittsburgh, Pennsylvania: Effects of varying source profiles and seasonal trends in ambient marker concentrations

We present estimates of the vehicular contribution to ambient organic carbon (OC) and fine particle mass (PM) in Pittsburgh, PA using the chemical mass balance (CMB) model and a large dataset of ambient molecular marker concentrations. Source profiles for CMB analysis are selected using a method of comparing the ambient ratios of marker species with published profiles for gasoline and diesel vehicle emissions. The ambient wintertime data cluster on a hopanes/EC ratio–ratio plot, and therefore can be explained by a large number of different source profile combinations. In contrast, the widely varying summer ambient ratios can be explained by a more limited number of source profile combinations. We present results for a number of different CMB scenarios, all of which perform well on the different statistical tests used to establish the quality of a CMB solution. The results illustrate how CMB estimates depend critically on the marker-to-OC and marker-to-PM ratios of the source profiles. The vehicular contribution in the winter is bounded between 13% and 20% of the ambient OC (274±56–416±72 ng-C m⁻³). However, variability in the diesel profiles creates uncertainty in the gasoline–diesel split. On an OC basis, one set of scenarios suggests gasoline dominance, while a second set indicates a more even split. On a PM basis, all solutions indicate a diesel-dominated split. The summer CMB solutions do not present a consistent picture given the seasonal shift and wide variation in the ambient hopanes-to-EC ratios relative to the source profiles. If one set of source profiles is applied to the entire dataset, gasoline vehicles dominate vehicular OC in the winter but diesel dominates in the summer. The seasonal pattern in the ambient hopanes-to-EC ratios may be caused by photochemical decay of hopanes in the summer or by seasonal changes in vehicle emission profiles.     

青藏铁路临界翻车风速研究

分析了青藏铁路沿线不同季节大风平均风速、最大风速和超过8级风天数。由于空气密度随海拔上升而减小,大风对铁路运输安全的影响与低海拔地区差异较大。笔者利用车辆动力学原理建立了列车的临界翻车风速模型,研究了高寒铁路不同海拔地区和冻土地区的临界翻车风速。研究结果表明:青藏高寒铁路临界翻车风速随海拔升高而增大,而随冻土路基病害出现而降低的规律。参考英、日等国大风标准,结合青藏高原的特点,根据危险翻车风速和临界翻车风速,首次提出青藏高原铁路海拔4000m地区安全行车标准。