| 题名 | 渤黄海黑碳的区域地球化学行为 |
| 作者 | 方引1,2 |
| 学位类别 | 博士 |
| 答辩日期 | 2016-05-22 |
| 授予单位 | 中国科学院大学 |
| 授予地点 | 北京 |
| 导师 | 陈颖军 |
| 关键词 | 黑碳 通量 源解析 沉积记录 渤海和黄海 |
| 学位专业 | 博士，环境科学 |
| 中文摘要 | 黑碳（Black Carbon，BC）是生物质和化石燃料在不完全燃烧条件下产生的高度难熔性碳质颗粒物，因其涉及到气候变化、碳循环、空气质量和公共健康等诸多问题，已成为当前气候和环境等研究领域共同关注的焦点。渤黄海沿岸省市总面积约为我国国土总面积的9%，但贡献了我国BC排放总量的~40%，是我国高强度的BC排放源区。大量的BC可通过大气沉降和河流排放等方式进入渤黄海，使得其广阔的陆架区成为BC的重要“汇”。本研究通过在渤黄海采集多环境介质样品，包括191个表层沉积物、3根柱状沉积物、36条环渤海主要河流水体和渤海海峡2个站位分季节/层位水体，运用湿化学预处理结合热光反射检测的方法对BC进行定量分析，结合在环渤海地区开展的大气气溶胶中BC的研究工作，旨在全面了解BC在渤黄海的区域地球化学行为，为深入研究海岸带黑碳的生物地球化学过程和区域碳循环提供科学依据。形成的主要认识如下： 渤黄海表层沉积物BC的含量范围为0.02−3.55 mg/g，平均为0.85 ± 0.57 mg/g。BC含量的高值和低值分别出现在沉积物中值粒径的高值区和低值区，分别对应水动力条件较弱和较强的海区，表明渤黄海陆架水动力条件是影响BC含量空间分布的主导因素。BC的埋藏通量范围为4−1,100 μg/cm2/yr，平均为160 ± 200 μg/cm2/yr，与世界其它大陆架表层沉积物的BC埋藏通量处于同一数量级水平，但高于深海/大洋沉积物2–4个数量级。就不同海区而言，渤海BC的埋藏通量最高（260 ± 252 μg/cm2/yr）、北黄海次之（100 ± 84 μg/cm2/yr）、南黄海最低（67 ± 51 μg/cm2/yr），并且表现出明显地从近岸到远岸逐渐下降的趋势。BC的汇通量为~325 Gg/yr，其中渤海为~157 Gg/yr，北黄海为~41 Gg/yr，南黄海为~127 Gg/yr，渤海BC源强显著高于黄海。 基于正定矩阵因子分解受体模型（PMF受体模型）的源解析结果表明，渤黄海表层沉积物BC的来源包括煤炭燃烧、生物质燃烧和石油燃烧，贡献比例分别为~75%、~17%和~8%。因此，化石燃料燃烧（~83%）是BC的主要来源，其贡献比例约为生物质燃烧的5倍。空间分布上，化石燃料燃烧呈现随离岸距离越远贡献比例增加的趋势，生物质燃烧呈现随离岸距离越远贡献比例下降的趋势，这种现象在黄河入海口处表现得尤为突出。在离黄河入海口5–30 km范围内，化石燃料燃烧的贡献比例随离岸距离增加呈指数式增加，从~5 km处的~10%增加到~30 km处的~80%；生物质燃烧的贡献比例呈指数式下降，从~5 km处的~90%降至~30 km处的~20%。不同燃烧源BC的物理性质差异和区域特定水动力条件的共同作用是造成这种现象的主要原因。 渤海BC的输入路径包括大气沉降、河流输入和北黄海通过渤海海峡向渤海的输入，通量大小分别为93 ± 30 Gg/yr、85 ± 14 Gg/yr和4 ± 4 Gg/yr；输出路径包括沉积埋藏至海底沉积物和通过渤海海峡向北黄海的输出，通量大小分别为157 ± 41 Gg/yr和21 ± 6 Gg/yr；输入通量和输出通量之差~4 Gg/yr，即为渤海水体中BC的净增量。因此，渤海BC的收支/源-汇关系表现为：大气沉降和河流输入是渤海BC的主要输入路径，分别占渤海BC总输入通量的51%和47%，两者的贡献比例基本相当；沉积埋藏是渤海BC的主要输出路径，占总输入通量的86%；BC在渤海海峡处的交换模式表现为从渤海向北黄海的净输出，净输出通量为17 ± 7 Gg/yr，渤海可视为北黄海BC的“源”。 渤海、北黄海和南黄海柱样中BC的含量范围分别为0.59‒1.36 mg/g、0.56‒1.32 mg/g和0.51‒1.18 mg/g，平均为0.93 ± 0.15 mg/g、0.78 ± 0.19 mg/g和0.77 ± 0.17 mg/g。BC含量的时间序列变化与人类活动存在阶段性响应关系：BC含量在19世纪60年代初和20世纪80年代初上升的趋势，与“洋务运动”和“改革开放”政策带来的中国经济的快速发展直接关联；渤海柱样中BC含量在20世纪70年代末表现为百年尺度的最低值，可能与1976年黄河改道所导致的沉积物粒度组分“粗化”有关；北黄海和南黄海柱样中BC含量在~1996年下降的趋势，可能与1996年“煤炭法”的实施和高污染的民用煤炉被清洁的液化石油气炉或天然气炉取代有关。本研究采用的热光反射法可有效区分焦炭和烟炱这两种BC亚组分，焦炭/烟炱比值的时间变化指示了我国能源消耗从低温向高温燃烧方式的转变，即我国从农业经济向工业经济的转变；其空间变化指示了北黄海和南黄海中部泥质区BC可能主要来源于长距离迁移，而渤海中部泥质区BC则可能主要来源于近距离输送。本研究和国内外其它区域BC沉积记录的对比结果表明，不同国家或同一国家的不同地区获得的BC沉积记录存在一定程度的差异，但能源改变（包括结构和使用量）、经济社会发展状况、污染物排放控制措施的实施以及国家和政府关于能源的一些决策等在柱样中BC含量或通量的时间序列变化上都有相应的体现，证实了BC是一个很好的地球化学指标，可用于揭示人类活动对生态环境的影响历史。 |
| 英文摘要 | Black carbon (BC) has been of great interest due to its linkage with climate change, carbon cycle, air quality and public health. BC is the highly condensed carbonaceous residue produced exclusively from the incomplete combustion of biomass (including wood, grass, crop straw, and etc.) and fossil fuels (including coal and petroleum/oil). The provinces and municipalities adjacent to the Bohai Sea (BS) and Yellow Seas (YS) have the highest BC emission intensity, which contribute ~40% of the China’s total annual BC emission amount even if the area there is only ~9% of the Chinese territory. A significant amount of BC is predictably injected into the BS and YS through atmospheric deposition and riverine inputs, making the BS and YS continental shelf be an important BC sink. In this study, multi-medium samples, including 191 surface sediments, 3 sediment cores, 36 riverine water in Bohai Rim and 2 seawater sites with different seasons (i.e., spring, summer, autumn, and winter) and layers (surface, middle and bottom) were collected for analyzing BC using the method of wet-chemical treatment combined with thermal/optical reflectance (TOR) detection. Together with the extensive investigations of atmospheric BC conducted in the Bohai Rim, the objective of this study was to have a comprehensive understanding of the regional BC geochemical behaviors in the BS and YS, which might provide some scientific basis for the deep study of coastal BC biogeochemical processes and regional carbon cycle. The main conclusions are as follows. The BC concentrations in the BS and YS ranged from 0.02 to 3.55 mg/g, with an arithmetic mean value of 0.85 ± 0.57 mg/g. High and low BC values took place in sea areas characterized by weak and strong hydrodynamic conditions, respectively, indicating that the regional hydrodynamic condition might be an important factor affecting the spatial distribution of the BC concentrations in the BS and YS. The BC burial flux in the BS and YS ranged from 4 to 1100 μg/cm2/yr, and averaged 160 ± 200 μg/cm2/yr. The BC burial flux in the BS and YS was comparable to those detected in other continental shelf regimes, but was 2–4 orders of magnitude higher than those in the pelagic regimes. For the sub-regions, the BS had the highest burial flux, reaching up to 260 ± 252 μg/cm2/yr, followed by that in the NYS (100 ± 84 μg/cm2/yr) and the SYS (67 ± 51 μg/cm2/yr). In contrast to the BC concentration, the BC burial flux decreased with the increasing distance from the coastline in the BS and YS. The BC sink flux in the entire BS and YS was estimated to be ~325 Gg/yr. For the sub-regions, the BC sink fluxes were sorted in the order of BS (~157 Gg/yr) > SYS (~127 Gg/yr) > NYS (~41 Gg/yr), and it can be therefore concluded that the source intensity of BC input into the BS was significantly higher than that of the YS. Positive Matrix Factorization (PMF)-based source apportionment showed that the main sources of BC to the BS and YS continental shelf surface sediments consisted of coal combustion, biomass burning and oil combustion, with each accounting for ~75%, ~17% and ~8%. Therefore, the fossil fuels combustion was the main source (~83%) of BC in the BS and YS surface sediments, which was nearly five-fold to that from biomass burning. Spatially, the percentage of the fossil fuels combustion-derived BC increased with the increasing distance from the nearshore areas, and the resultant was the declined percentage of the biomass burning-derived BC. These trends were more pronounced in the Yellow River estuary. Within 5–30 km away from the Yellow River estuary, with the increasing distance from the Yellow River mouth, the percentage of the fossil fuels combustion-derived BC increased exponentially from ~10% to ~80%, and that of the biomass burning-derived BC declined exponentially from ~90% to ~20%. This spatial trend was to a large extent attributed to the differences in physical properties between these two BC sources and the regional hydrodynamic conditions. The BC inputs into the BS include atmospheric deposition (including dry deposition and wet deposition), riverine discharge, and import from the NYS through the Bohai Strait, with each contributing 93 ± 30 Gg/yr, 85 ± 14 Gg/yr, and 4 ± 4 Gg/yr. The outputs consist of sequestration to bottom sediments and export to the NYS through the Bohai Strait, and the fluxes were 157 ± 41 Gg/yr and 21 ± 6 Gg/yr, respectively. The difference between the inputs and the outputs, ~4 Gg/yr, was thus the BC internal sink, i.e., net increase in the BS seawater. It can be therefore concluded that atmospheric deposition and riverine discharge were the main BC input patterns to the BS, with each accounting for 51% and 47%. Sequestration to bottom sediments was the major BC output pattern, accounting for ~88% of the input BC. Water exchange in the Bohai Strait led to net BC transport from the BS to the NYS. The net export flux was 17 ± 7 Gg/yr, and the BS could be considered as a source of BC to the NYS. Sediments cores in the BS, NYS and SYS had BC concentrations ranges of 0.59‒1.36 mg/g, 0.56−1.32 mg/g, and 0.51−1.18 mg/g, with mean values of 0.93 ± 0.15 mg/g, 0.78 ± 0.19 mg/g, and 0.77 ± 0.17 mg/g, respectively. The temporal trends of BC concentrations in these three cores closely followed the regional historical anthropogenic activities in China. The increasing trends occurring at the beginning of the 1860s and 1980s each corresponded well to the rapid economic development induced from the “Westernization Movement” and the “Reform and Open” Policy. The lowest BC concentration detected in the core of BS in the late 1970s might stem from the shift of the Yellow River mouth, which made the grain size of the sediments coarser. The decreasing trends since ~1996 in the NYS and SYS cores was associated with the enforcement of the Coal Law and the substitution of high polluted domestic coal stoves with clean liquid petroleum gas/natural gas stoves during this period. The TOR method used in the present work has been demonstrated to effectively discriminate between char and soot, the two subtypes of BC with different formation mechanisms and physicochemical properties. The temporal trends of char/soot indicated that the energy structure in China has changed from low-temperature to high-temperature combustion processes, implying that China has shifted from an agricultural economy to an industrial economy. The spatial trends of char/soot indicated that BC in central mud areas of the NYS and SYS was from long range transport, and BC in central mud area of the BS was from short range transport. By comparing results from the present work and other sedimentary records retrieved around the world, we found that there were differences of sedimentary records in different countries or in different regions within a country. Of particular notable was that, however, energy consumption (including energy amount and structure), levels of economic and social development, pollution emission control measurements, energy strategies implemented by the countries and governments, and etc. could be well mirrored from the temporal trends of BC concentrations and fluxes. This study confirmed that BC was a good geochemical indicator, which could be used to reveal the influential history of anthropogenic activities on ecological environment. |
| 语种 | 中文 |
| 学科主题 | 地球科学 ; 环境科学 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.yic.ac.cn/handle/133337/13826]  |
| 专题 | 中科院烟台海岸带研究所知识产出_学位论文 |
| 作者单位 | 1.中国科学院烟台海岸带研究所 2.中国科学院大学 |
| 推荐引用方式 GB/T 7714 | 方引. 渤黄海黑碳的区域地球化学行为[D]. 北京. 中国科学院大学. 2016. |
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