图1 监测点位及烟台主要港口分布图
纸质出版日期:2020-07-20,
收稿日期:2020-05-15
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使用单颗粒气溶胶质谱仪对烟台市3类典型船舶排放的源谱特征进行了分析,结果表明:船用柴油燃烧排放的气溶胶单颗粒以OC、EC类别为主;而重油燃烧中含Fe、V、K、Na等金属元素的类别占比较大,其中含V颗粒占比最大,且粒径主要集中在0.5 ~ 1.1 μm 段;而含Si、Fe、K、Pb等颗粒主要分布在0.8 ~ 1.4 μm粒径段。以含V颗粒作为船舶排放示踪物,对烟台市5个典型站点空气质量受船舶排放影响的分析显示:5站点均明显受到船舶排放的影响,春、夏季影响明显高于秋、冬季;百盛商城和万润化工两个距港口最近的监测点受船舶排放影响最大,春、夏季特定条件下含V颗粒占比接近40%。基于统计数据对烟台市船舶排放PM2.5进行估算,2017年烟台市内河和沿海船舶PM2.5的排放量约为463.6 t,与机动车尾气排放量相当,因此需要进一步重视船舶尾气排放对本地大气颗粒物的影响。
Single-particle aerosol mass spectrometer (SPAMS) was used to analyze the source features of 3 typical ship emissions in Yantai. The results showed that particle classes emitted by marine diesel oil were mostly composed of organic carbon (OC) and elemental carbon (EC), while those emitted by heavy fuel oil contained larger number of metal-containing particles such as Fe, V, K and Na. V-containing particle classes accounted for the largest proportion in heavy fuel oil emission, and were mainly concentrated in the small particle size range of 0.5-1.1 μm, while the metal-containing particles such as Si, Fe, K, and Pb were mainly distributed in larger size range of 0.8-1.4 μm. Based on the results, the V-containing particles were used as ship-emission tracer to study the impact of ship emissions on the air quality of 5 typical sites in Yantai. The results revealed that the five sites were obviously affected by ship emissions especially in spring and summer. The two sites Parkson Mall and Wanrun Chemical were the closest to the port, and suffered the most from the ship emissions. Under specific conditions in spring and summer, the V-containing particles proportion could reach up to 40%. Based on the statistical data, the PM2.5 emitted from inland and coastal ships in Yantai City were estimated to be 463.6 t in 2017, which was of the same order of magnitude as vehicle emission. Further attention should be paid to the impact of ship exhausts on local air quality.
近年来,随着中国经济持续增长、能源消费量持续增加,国内灰霾天气频发,大气污染形势严峻。我国的大气污染类型较为复杂,根据能源结构、污染特征的不同,一般分为偏燃煤污染型、偏机动车污染型、偏二次颗粒物污染型、偏钢铁污染型等;特殊情况下,又有偏沙尘污染型、偏烟花污染型等[
除了道路移动源以外,船舶尾气排放的污染物也不容忽视。国际环保组织自然资源保护协会(NRDC)的《中国船舶和港口空气污染防治白皮书》显示[
目前国内对船舶排放的研究仅局限于少数港口,多是侧重于排放清单研究且较多采用国外排放因子。上海港[
烟台市地处山东半岛东北部,扼渤海、邻国际主航道、处连结东三省、环渤海与长三角等最活跃经济带之海上交通要冲,背靠京津鲁冀经济发达区域,隔海与日本韩国相望,占据东北亚国际经济圈核心地带,是中国“一带一路”倡议的15个支点港口城市、全国首批14个沿海开放城市。烟台港是中国大陆沿海25个主枢纽港之一,形成了以芝罘湾港区、西港区、龙口港区、蓬莱港区等四大港区为主体,以莱州华电港、潍坊寿光港、东营广利港、滨州套尔河港为支点,以几内亚博凯港为海外桥头堡的现代化港口集群。2019年,烟台港完成吞吐量3.01亿吨,位列全国沿海港口第8,连续多年保持全国铝矾土进口第一港、化肥进出口第一港地位。已有研究表明,烟台市砣矶岛空气质量较明显地受到船舶尾气的影响[
根据烟台市功能区划分及污染源分布情况,选取了百盛商城、福山环保局、万润化工、盛泉工业园、长岛国家背景站5个受体点位,分别在冬、春、夏、秋四季代表性月份开展单颗粒气溶胶飞行时间质谱仪连续在线监测,其中百盛商城和万润化工开展全年连续监测,另外三个点位每个季节于代表性月份开展顺序监测。5个监测点位及烟台市主要港口分布见
图1 监测点位及烟台主要港口分布图
Fig.1 Location of monitoring sites and main ports of Yantai
点位 | 冬季 | 春季 | 夏季 | 秋季 |
---|---|---|---|---|
百盛商城 | 2016/12/01-2017/2/28 | 2017/3/1-5/31 | 2017/6/1-8/31 |
2016/11/21-30 2017/9/1-11/30 |
万润化工 |
2017/1/3-2/28 2017/12/01-12 | 2017/3/1-5/31 | 2017/6/1-8/31 | 2017/9/1-11/30 |
福山环保局 | 2017/1/3-1/18 | 2017/3/31-4/17 | 2017/8/17-31 |
2017/9/1-3 2017/11/3-11/21 |
盛泉工业园 |
2017/2/5-2/27 2017/12/01-19 | 2017/4/18-5/19 | / |
2017/9/5-9/27 2017/11/23-30 |
长岛国家背景站 | 2017/2/22-28 | 2017/3/1-22 | / | 2017/9/29-11/1 |
1)百盛商城与万润化工两站点为四季连续在线监测
本研究选取了3艘典型船舶进行源谱采集,包括一艘货船、一艘客船,以及一艘渔船。其中货船和客船均使用船用重油作为燃料,而渔船使用船用柴油作为燃料。
气溶胶单颗粒源谱利用真空瓶进行采集[
SPAMS的工作原理、基本性能和质量控制已有文献进行了详细的阐述[
采集的所有源谱颗粒的粒径及质谱信息输入到MATLAB r2011a上的SPAMS Data Analysis V3.1软件包进行处理。首先,通过自适应共振理论神经网络算法(ART-2a)对采集到的颗粒进行自动分类[
图 2 货船、客船、渔船排放颗粒物平均质谱图
Fig.2 Average mass spectrum of particles emitted by
freighter, ferry and fishing boat
船型 (燃料类型) | 货船(重油) | 客船(重油) | 渔船(柴油) | |
---|---|---|---|---|
颗粒类别 | EC | 0.3% | 12.4% | 25.4% |
OC | 22.1% | 3.0% | 66.6% | |
Na-ECOC | 20.5% | 2.4% | 0.7% | |
Na-rich | 16.3% | 18.9% | 1.2% | |
K-rich | 11.6% | 2.1% | 2.0% | |
Ca-rich | 0.4% | 7.0% | 0.3% | |
V-OC | 27.0% | - | 0.2% | |
Fe-V-OC | 0.8% | 37.0% | 0.2% | |
Fe-rich | - | 1.6% | 1.0% | |
Si-rich | - | 1.5% | 2.2% | |
Pb-rich | - | 0.3% | 0.2% | |
Fe-OC | 1.0% | 13.9% | 0.2% |
图 3 不同类型船舶排放单颗粒类别粒径分布图
Fig.3 Size distribution of single particle classes emitted by different ships(a. freighter, b.ferry, c.fishing boat)
从不同粒径的颗粒物组成来看,货船排放颗粒物类别在不同粒径段的占比分布波动较大,各类颗粒物在不同粒径段均有分布,其中V-OC颗粒主要分布在0.5 ~ 1.1 μm。客船排放颗粒物中,Fe-V-OC颗粒主要分布在0.4 ~1.0 μm,且随粒径增大占比逐渐减少,而V-OC颗粒与货船类似,几乎均匀分布在0.5 ~ 1.0 μm粒径段;Fe-OC和Ca-rich颗粒主要分布在0.4 ~ 1.0 μm,占比均呈先升高后降低的趋势;Si-rich、Fe-rich、K-rich及EC颗粒主要集中在0.8 μm以上粒径段中,且占比随粒径增大而增加。渔船排放颗粒物中,0.6 ~ 0.8 μm粒径段以OC为主,0.4 ~ 0.5 μm以EC为主。其余粒径段中,OC、EC占比互有高下,但均为主要类别;与客船类似,Si-rich、Fe-rich、K-rich颗粒,主要分布在0.8 μm以上粒径段中,且占比随粒径增大而增加。
根据以上分析,含V颗粒仍可以作为船舶重油燃烧的示踪物,因此以钒(V+、VO+)作为船舶尾气排放的示踪离子,对船舶排放对各站点PM2.5的影响进行分析。由于51V+容易受到OC峰51C4H3+的干扰,而一般51C4H3+会与其他OC质谱峰如27C2H3+、37C3H+、43C3H7+、63C5H3+、77C6H5+一同出现。因此,为对含V颗粒进行精确识别,从环境空气受体颗粒物中,筛选出同时含有质荷比51V+和67VO+的颗粒,从中扣除同时含有27C2H3+、37C3H+、43C3H7+、63C5H3+、77C6H5+等有机碳信号峰的颗粒物,定义为含V颗粒,以指示船舶尾气排放。
图 4 五个点位不同季节含V颗粒日均占比分布
Fig.4 Distribution of average daily proportion of V-containing particles at five sites in different seasons
点位 | 冬季 | 春季 | 夏季 | 秋季 | 全年 | |||||
---|---|---|---|---|---|---|---|---|---|---|
最大比例 | 平均比例 | 最大比例 | 平均比例 | 最大比例 | 平均比例 | 最大比例 | 平均比例 | 最大比例 | 平均比例 | |
百盛商城 | 18.8 | 0.6 | 20.6 | 1.1 | 37.5 | 2.1 | 14.3 | 0.4 | 37.5 | 1.0 |
万润化工 | 3.7 | 0.5 | 36.0 | 1.2 | 22.5 | 2.0 | 29.7 | 0.7 | 36.0 | 1.1 |
福山环保局 | 5.5 | 0.3 | 3.0 | 0.5 | 6.7 | 0.8 | 7.5 | 0.4 | 7.5 | 0.5 |
盛泉工业园 | 7.7 | 0.3 | 12.5 | 1.0 | / | / | 6.9 | 0.6 | 12.5 | 0.6 |
长岛国家背景站 | 1.9 | 0.5 | 3.3 | 0.7 | / | / | 9.1 | 0.7 | 9.1 | 0.6 |
图 5 烟台市2017年各月份风向占比
Fig.5 The proportion of wind direction in each month of 2017 in Yantai city
从空间变化来看,百盛商城和万润化工点位的含V颗粒占比明显高于其余点位,福山环保局点位的占比最低。冬春季节,百盛商城点位受船舶影响程度高于万润化工,日均占比出现多个峰值;而夏秋季节,万润化工点位受到的影响高于百盛商城,尤其是夏季,最高单日占比高达13.2%,远高于其他几个点位。从地理位置看(
选取百盛商城和万润化工两个全年观测点位,对含V颗粒占比较高的6月份进一步分析。根据烟台市24 h后气团轨迹,将6月份每日受到的气团影响分为内陆气团(西南/西/西北风)、海洋气团1(北/东北/东风)和海洋气团2(东南/南风)三种。此外,部分时段由于风速较小,受本地影响为主,归为静稳天(
图 6 烟台市2017年6月每日24 h后向气团轨迹
Fig.6 24 h daily backward trajectory of air masses in Yantai City in June 2017
参考《非道路移动源大气污染物排放清单编制技术指南(试行)》[
E=(Y×EF)×10-6
式中,E 为内河及沿海船舶的PM2.5排放量,单位为t;Y 为燃油消耗量,单位为kg;EF 为排放系数,单位为g/kg燃料。《指南》中提供的柴油、燃料油的PM2.5排放系数EF分别为3.65 g/kg 燃料和5.60 g/kg 燃料,由于暂无烟台市船舶用油的分配情况,因此本研究暂取均值4.624 g/kg 燃料。燃油消耗量按以下公式估算:
Y=(0.065×Z客+Z货)×YX
其中,Z客为客运周转量,单位为万人公里; Z货为货物周转量,单位为104 t·km;YX 为油耗系数,单位为kg/(万t·km),按《指南》推荐取为50。根据烟台市2018年统计年鉴[
交通运输部公布的2017年国内规模以上港口货物、旅客吞吐量快报数据中[
1)烟台市不同类型船舶排放特征有较大区别。使用重油作为燃料的货船和客船,排放颗粒物中Fe、V、K、Na等金属元素特征较为明显,而使用柴油作为燃料的渔船排放颗粒物则以OC、EC成分为主。含V颗粒仍可以作为使用重油作为燃料的船舶的示踪物。
2)不同类型船舶排放颗粒物粒径组成差异较大。货船排放颗粒物的粒径范围最宽,峰值粒径最大,渔船排放颗粒物的粒径范围最窄,峰值粒径最小。指示重油燃烧的含V颗粒主要集中在0.5 ~1.1 μm 小粒径段,而Si、Fe、K、Pb等含金属元素类别主要分布在大粒径段。
3)以含V颗粒指示船舶排放,结果显示:烟台五个站点均明显受到船舶排放的影响,其中百盛商城和万润化工两个距离港口较近的点位受到的影响最大。受海洋气团影响,五个点位均在春夏季受船舶影响较大,而秋冬季的影响相对较小。虽然从含V颗粒平均占比来看,整体占比并不大(0.3% ~2.1%),但特定情况下,尤其是春夏两季,港区下风向的市区会受到港口船舶尾气排放的明显影响,含V颗粒占比峰值最大接近40%。
4)对烟台市船舶排放PM2.5进行估算,得出2017年烟台市内河和沿海船舶PM2.5的排放量约为463.6 t,与机动车尾气排放量相当,需要进一步重视船舶尾气排放对本地大气颗粒物的影响。
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