柳州市酸雨化学特征分析及人为硫源对碳酸盐岩风化的影响

发布时间：2018-05-07 11:09

本文选题：柳江流域 + 酸雨　；参考：《西南大学》2017年硕士论文

【摘要】：岩溶作用是一种发生在地球浅表层环境下的特殊地质过程,与大气圈、水圈、生物圈密切相关,因其地球化学过程中具有低温性、外放敏感性和生物参与性等特点,会导致岩溶水体DIC输入的多变(碳汇效应的稳定性受到影响)。作为岩溶碳汇的主控因子—水循环,对岩溶碳汇的影响较大,不同时期(丰水期、平水期、枯水期)所表现出来的碳汇特性也各不相同,同时,自然界除了碳酸外,人类活动造成的硫酸(酸雨)对碳酸盐的溶解也能增加水中的DIC浓度,且H2SO4参与的碳酸盐岩风化本质上是一个大气CO2的净释放过程,必须在碳汇计算中加以扣除,对全球碳循环的研究具有十分重要的意义,所以碳酸盐岩的硫酸风化机制及其与区域碳循环的关系也是近些年一直关注的热点问题。硫酸参与的化学风化过程来源主要包括石膏的溶解、硫化物氧化、大气降水以及人为排放,流域人类活动可以显著加速流域化学侵蚀,改变区域碳循环,干扰流域物质的生物地球化学循环,对西南岩溶流域碳酸盐岩的化学侵蚀具有重要贡献,大气酸沉降(酸雨)中的SO42-、NO3-等酸性离子绝大部分来源于人为排放的SO2、NOX气体,所以,以大气沉降为形式的人类活动对河流水化学组分带来的影响日益受到人们的关注。本文选取西南岩溶区域中酸雨问题较为突出的柳州地区作为研究区,设置沙塘林校(郊区)、柳州气象局、柳州环保局三个雨水采样点,分析柳州市酸雨化学特征及致酸物质来源,并在穿柳州市区而过的柳江设置监测断面,分别位于柳州的进出口,露塘与洛维,及柳州中部的水文站断面,用以分析降水中的硫源对该区域碳酸盐岩风化和碳汇效应的影响。研究结果表明,柳州市全年降水样品p H值的分布范围为4.16~6.61,酸雨率为67.6%,主要为弱酸雨(5p H5.6)与较重酸雨(4.5p H5),酸雨形势较为严峻。相对于90年代,主要致酸离子浓度均有大幅下降,脱硫除尘等措施也会使得NH4+、Ca2+等中和离子浓度下降,可能是p H值没有大幅度变化的原因,但降水离子浓度与电导率已充分说明柳州酸雨治理卓有成效。酸雨频率与p H值的变化趋势具有明显的季节性特征,酸雨主要集中于冬、春两季,这与我国大部分地区尤其是南方地区普遍存在的酸雨季节变化特征基本一致,与降水量的稀释作用有很大关系。通过富集因子(EF)分析降水中主要因子来源,表明K+中97.2%的地壳来源中绝大多数为木质燃烧等人为活动释放所得。CI-受人类活动影响明显,主要来自当地排放,如垃圾焚烧、汽车尾气排放(汽油中含有溴氯化物作为添加剂)等。SO42-的主要来源为人为来源,占到98.2%,SO42-主要源于煤炭燃烧释放的SO2气体氧化所得。NO3-的人为来源占到99.8%,主要包括燃料燃烧、大气中的化学反应以及汽车尾气排放等。Ca2+和Mg2+主要来为土壤来源,这与研究区的岩溶区背景相一致,但人为因素也能向大气中释放数量可观的碱性离子,且相对自然过程更为剧烈,如采石场进行石料开采过程中释放大量扬尘。确定影响研究区的2个较为稳定的水汽来源:1、西南方向百色、南宁等工矿业发达或人口密集型城市,西南方向的气流绝大部分都路经此地,尤其夏半年受西南季风影响大,春季几乎所有的酸雨水汽气团都来自于西南方向经南宁等城市径直抵达柳州,夏季占到44%,秋季与冬季多是东南方向气流登陆后经南宁等西南部城市再向东北抵达柳州;2、东南方向广东雷州半岛及珠三角地区,来源于西太平洋的气流经过此地径直到达柳州或经南宁等城市抵达柳州,夏季占到8%,秋季占到57%,冬季占到33%。对比相邻的酸雨区桂林降水的气流运移轨迹,中部酸雨带如江西、湖北、湖南、安徽等省份的工业发达人口稠密地区并未对柳州的酸雨造成直接影响。柳州水文站断面SO42-浓度变化趋势与降水量有很好的对应关系,说明降水对该流域SO42-的贡献较大,结合对该流域硫同位素的分析,以大气沉降为形式的人类活动势必对该流域的岩石风化及碳汇效应产生一定影响,比较汛期与枯水期降水对河水离子浓度的贡献率,枯水期降水对河水离子的贡献均有上升,造成这一现象的原因可能是人类活动信号被径流稀释,也有可能是汛期径流量增大导致化学风化加强,更多的风化产物进入水体降低了海盐源的相对贡献。其中SO42-来源于降水的比例高达到70%左右,柳州降水中SO42-的人为来源占到98.2%,则汛期与枯水期由人为来源带入该河段的SO42-比重分别达到65.9%和76.5%,均值为71.2%。硫酸风化碳酸盐岩所占的比例为32%,则该流域中人为硫源对碳酸盐岩的风化比例为22.8%。对比硫酸参与后碳酸盐岩的溶蚀速率与碳汇速率的变化,计算结果显示硫酸参与后,该流域风化速率增加了5.6%,相对于只考虑碳酸溶蚀,碳酸盐岩溶蚀产生的碳汇速率应减少19%,通过之前讨论的河水中SO42-的人为硫源比例为71.2%,可认为人为硫源造成的碳汇速率计算应减少13.53%。
[Abstract]:Karstification is a special geological process occurring in the shallow surface environment of the earth. It is closely related to the atmosphere, water circle and biosphere. Because of its low temperature, sensitivity and biological participation in the geochemical process, the DIC input of karst water will be changeable (the stability of carbon sequestration effect). The main controlling factor of the sinks, water cycle, has great influence on the carbon sink of karst, and the carbon sequestration characteristics are different in different periods (high water period, flat water period and dry water period). At the same time, in nature, the solution of sulfuric acid (acid rain) caused by human activities can increase the concentration of DIC in water, and the carbonate rocks of H2SO4 participate in the carbonate rock. Weathering is essentially a net release process of atmospheric CO2, which must be deducted in the calculation of carbon sink and is of great significance for the study of global carbon cycle. So the mechanism of sulphuric acid weathering and its relationship with the regional carbon cycle are also a hot point in recent years. The source of the chemical weathering process of sulphuric acid is the source of the chemical weathering process. It mainly includes the dissolution of gypsum, sulfide oxidation, atmospheric precipitation and anthropogenic emissions. Human activities in the basin can significantly accelerate the chemical erosion of the basin, change the regional carbon cycle, and interfere with the biogeochemical cycle of the material in the basin, which has an important contribution to the chemical invasion of carbonate rocks in the southwest karst basin, and the SO42- in the acid precipitation (acid rain). Most of the acid ions, such as NO3-, are derived from the human emission of SO2, NOX gas. Therefore, the influence of human activities in the form of atmospheric sedimentation on the chemical composition of river water is increasingly concerned. In this paper, the Liuzhou area, which is more prominent in the southwest karst region, is selected as the research area, and the sand pond forest school (suburb) is set up. The Liuzhou Meteorological Bureau and the three rainwater sampling points of the Liuzhou Environmental Protection Bureau analyzed the acid rain chemical characteristics and the source of acid causing substances in Liuzhou City, and set up monitoring sections in the Liujiang River, which was passing through Liuzhou City, which were located in the import and export of Liuzhou, lowei and lowei, and the hydrological station section in central Liuzhou to analyze the sulfur source in the precipitation to the carbonate rock in the region. The result of the effect of weathering and carbon sequestration shows that the distribution range of P H value of the annual precipitation sample in Liuzhou is 4.16~6.61, the acid rain rate is 67.6%, mainly the weak acid rain (5p H5.6) and the heavier acid rain (4.5p H5), the acid rain situation is more severe. Compared with the 90s, the main acid ion concentration has a significant decrease, and the desulfurization and dust removal measures will also make The decrease of neutralization ion concentration, such as NH4+ and Ca2+, may be the reason why the P H value has not changed greatly, but the precipitation ion concentration and electrical conductivity have fully demonstrated that the acid rain control of Liuzhou is effective. The frequency of acid rain and the change trend of P H value have obvious seasonal characteristics, the main collection of acid rain in winter and spring two season, which is especially in most areas of our country. It is a common seasonal variation of acid rain in southern China, which is closely related to the dilution of precipitation. Through the enrichment factor (EF) analysis of the main source of factors in precipitation, it is shown that the overwhelming majority of the 97.2% of the crustal sources in the K+ are wood burning and others for the activity release of.CI-, which are mainly influenced by human activities. The main source of.SO42- from local emission, such as waste incineration, automobile exhaust emission, (gasoline containing bromide as additive) is human source, accounting for 98.2%. SO42- mainly originates from the SO2 gas oxidation of coal combustion released by SO2, which accounts for 99.8% of the human sources, mainly including fuel combustion, chemical reactions in the atmosphere and cars. .Ca2+ and Mg2+ are mainly the source of soil, which is in accordance with the background of the karst area in the study area, but human factors can also release a considerable amount of alkaline ions to the atmosphere, and the relative natural process is more intense. For example, a large amount of dust is released during the mining process of the quarry. 2 more stable factors affecting the study area are determined. Water vapor sources: 1, southwest direction Baise, Nanning and other industries and mining developed or densely populated cities, the southwest of the vast majority of the air flow through this area, especially in the summer half of the southwest monsoon, almost all of the acid rain and vapor in the southwest from Nanning and other cities directly to Liuzhou, summer accounts for 44%, autumn and the autumn. In winter, most of the south-east airflow was landed in the south-west cities of Nanning and then to Liuzhou in the northeast. 2, the southeast direction of Guangdong Leizhou Peninsula and the Pearl River Delta region, the West Pacific airflow reached Liuzhou or Nanning and other cities through the West Pacific, occupied 8% in summer and 57% in autumn, and in winter occupied 33%. contrast. There is no direct impact on the acid rain in Jiangxi, Hubei, Hunan, Anhui and other provinces such as Jiangxi, Hubei, Hunan, Anhui and other provinces of the central acid rain zone, such as Jiangxi, Hubei, Anhui and other provinces. The change trend of the concentration of the Liuzhou hydrological station has a good relationship with the precipitation, indicating that the precipitation has a great contribution to the SO42- in this basin. According to the analysis of sulfur isotopes in this basin, human activities in the form of atmospheric sedimentation are bound to have a certain influence on the rock weathering and carbon sequestration effect in the basin, compare the contribution rate of precipitation to the ion concentration in the flood season and the dry water period, and increase the contribution of precipitation to the river ion in the dry water period, which may cause this phenomenon. The signal of human activity is diluted by runoff, and it may also be the increase of chemical weathering in flood season. More weathering products enter the water body to reduce the relative contribution of the sea salt source. The proportion of SO42- from precipitation is about 70%, and the human source of SO42- in the precipitation in Liuzhou is 98.2%. The proportion of SO42- into the river reaches 65.9% and 76.5% respectively, the proportion of the mean value of 71.2%. sulphuric acid weathering carbonate rock is 32%, and the weathering ratio of human sulfur source to carbonate rocks in this basin is 22.8%. and the carbonatite dissolution rate and carbon sink rate change after the participation of sulphuric acid. The calculation results show that after the sulphuric acid participation, the basin is involved. The rate of weathering increased by 5.6%, and the carbon sink rate of carbonate rock dissolution should be reduced by 19% compared with carbonate dissolution only. The ratio of human sulfur source to SO42- in river water before discussion is 71.2%. It is considered that the carbon sink rate caused by artificial sulfur source should be reduced by 13.53%..

【学位授予单位】：西南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X517;P512.1

【参考文献】