典型岩溶区溪流中硝酸盐动态变化及其影响因素研究

发布时间：2018-07-08 20:35

本文选题：岩溶区 + 地下河出口　；参考：《西南大学》2015年硕士论文

【摘要】：硝酸盐污染是水体污染中最常见也是危害最严重的污染之一。近年来,不断报道出河流、湖泊、城市地下水等受到硝酸盐污染,产生水体富营养化以及诱发食道癌等疾病并对人类健康造成严重危害。在西南岩溶区,已查明的地下河有2836条,总流量达1482m3.S-1,相当于一条黄河,对西南岩溶地区人民健康和社会经济发展有着重要作用的岩溶地下水资源,随着工农业生产的加剧、城镇化扩张等,也受到了严重的污染,西南地区岩溶地下水正面临着变成“下水道”的威胁,西南岩溶地下水污染已十分严重,地下水资源全面告急,保护岩溶地下水环境已经刻不容缓。我国西南岩溶区地上、地下双层结构,“三水”转换迅速,使得岩溶地下水对外界环境的反应非常敏感。同时,由于硝酸盐污染发生的随机性,机理过程的复杂性,排散的途径及排放污染物的不确定性,使得岩溶区水体中硝酸盐的时空分布非常难以监测、模拟和控制。因此,在岩溶区从不同时间尺度和空间尺度去探讨硝酸盐在岩溶水体中的动态变化及其影响因素显得十分必要,为全面了解硝酸盐在岩溶水体中的动态变化提供科学的认识,为防治岩溶区水体中的硝酸盐污染提供科学参考。本文以柳州官村地下河为为例,以官村地下河出口和受官村地下河补给的地表溪流为基础,对比探讨地表溪流中硝酸盐在不同时间尺度(季节、降雨、昼夜)上的动态变化及其影响因素。通过研究得到初步结论：(1)研究区溪流中N03-离子表现出明显的季节变化特征,地下河出口中NO3-离子含量为秋季冬季春季夏季,地表溪流中N03-离子含量为秋季冬季夏季春季,两个监测点都是旱季偏高,且两个监测点中N03"离子含量最高值都出现在11月份,主要是由于旱季流量偏低,最低值出现在4月份且春季NO3-离子含量剧烈变化,可能主要受到降雨过程的影响。溪流中NO3-离子在9、10、11、12、2、3、5、8月表现出氮的损失过程,损失量分别为2.46kgN.d-1、1.77 kgN.d-1、3.01 kgN.d-1、2.09 kgN.d-1、2.08 kgN.d-1、17.34 kgN.d-1,在1、4、6、7月表现出氮的增长过程,增长量分别为1.06 kgN.d-1、6.84 kgN.d-1、5.92kgN.d-、0.7 kgN.d-1。溪流中δ15N-NO3-与δ18O-NO3-表现出一定的正相关关系(R2=0.38,P0.05),且δ15N-NO3-与δ18O-NO3-的比值大部分落在了1：1的比值附近,说明溪流中在监测期间主要发生了氮的同化作用,只有很小的一部分落在了2：1的附近,说明反硝化作用对溪流中N03"离子的季节变化影响不大。另外,在一年中溪流中氮的损失量为28.75 kgN.d-1(未包括3、8月的损失量),而增长量为14.52 kgN.d-1,说明在一年的季节变化监测中,溪流中N03"离子主要发生了氮的损失过程,且主要受到水生植物的同化作用影响。而1、4、6、7月并没有发生氮的损失过程,可能主要是由于降雨淋溶作用的影响,使得累积于溪流周围土壤中的高浓度硝酸盐进入溪流中,从而覆盖了水生植物同化作用的影响。(2)地下河出口和地表溪流中硝酸盐降雨后的响应总体上表现出相似的变化趋势,但是地表溪流中硝酸盐也表现出与地下河出口不同的“异常”变化,且影响因素比地下河出口更加复杂,地表溪流中硝酸盐主要受到地下河出口补给水的影响,同时受到外界雨水以及土壤水的影响。而且不同的降雨强度以及降雨次数也会使得外界雨水和土壤水以不同的影响作用于地表溪流,首次降雨,外界土壤水中高浓度的N03"离子进入地表溪流使得地表溪流中NO3-离子升高,而多次降雨后,土壤水中N03"离子浓度逐渐下降,从而起到稀释作用。在两次降雨监测中,地下河出口和地表溪流中电导率和N03"离子在R2(2013年8月监测中第二次降雨)和2014年5月降雨过程中表现出更加快速的反应,而R1(2013年8月监测中第一次降雨)则相对缓慢,主要是由于R2和2014年5月降雨过程,雨强更大,降雨更加集中有关,也就是说降雨强度会影响电导率和N03"离子响应的时间长短及速率。雨强越大,电导率和NO3-离子反应越迅速。(3)2013年7月昼夜监测溪流中各物理化学参数(T、pH、DO、Spc、pCO2)以及NO3-离子都表现出有规律的昼夜变化趋势,其中水温、DO和pH表现出白天上升晚上下降,而电导率、pC02以及N03"离子则表现出白天下降而晚上上升的趋势。地下河出口补给对地表溪流各物理化学参数及N03"离子表现出有规律的昼夜变化趋势影响不大,且溪流的流量变动不大,没有表现出昼夜变化,可以说明在监测期间溪流流量也不是驱动溪流中各物理化学参数及N03"离子昼夜变化的因素。地表溪流中DO和pC02表现出显著的负相关关系(R2=0.81,P0.01),且温度对pC02的贡献率为27.48%～54.88%,水生植物对水体pC02的影响为45.12%～72.52%,说明监测期间溪流中水生植物的光合作用和呼吸作用是DO和CO2的昼夜变化的主要影响因素,同时,NO3-离子与DO表现出明显的负相关关系(R2=0.52,P0.01),说明DO浓度的昼夜变化影响着NO3-离子浓度的昼夜变化,溪流中N03"离子和pC02的变化存在很弱的相关性,说明脱气作用最溪流中NO3-离子的昼夜变化影响不大,同时说明溪流中水生植物的光合作用和呼吸作用是NO3-离子浓度有规律的昼夜变化的主要影响因素。NO3"离子总体上表现出下降趋势,但是在下午出现增长的趋势,在中午(12：30)达到增长的最大值3.72 mg.L-1,可见在白天NO3-离子不仅受到因光合作用增强而产生的同化作用影响,主要还受到硝化作用的影响。而在夜间水生植物呼吸作用占据主导作用,DO含量快速下降,因此同化作用和硝化作用在夜间受到抑制,反硝化过程开始发挥作用,因此NO3-离子出现下降过程。溪流中N的日变化量为2.59 kgN.d-1,下午以增长过程为主,增长量为0.99kgN.d-1,其余时间以损失过程为主,其中白天损失量为0.8 kgN.d-1,夜间损失量为0.8kgN.d-1,通过N的变化量计算各个作用所占的比例,下午以硝化作用为主,增长量为0.99kgN.d-1,占日变化量的38%,夜间以反硝化作用为主,损失量为0.8 kgN.d-1,占日变化量的31%,白天损失量为0.8 kgN.d-1,以同化作用为主,占日变化量的31%,因此可以说N以生物作用为主的日变化量中,硝化作用占38%,同化作用占31%,反硝化作用占31%。2014年7月昼夜监测溪流中各物理化学参数(T、pH、DO、Spc、pCO2)表现出有规律的昼夜变化趋势,其中水温、DO和pH表现出白天上升晚上下降,而电导率、pC02则表现出白天下降而晚上上升的趋势。但是溪流中NO3-离子并没有表现出与DO一致的昼夜变化,两者没有表现出相关性(R20.03),515N和δ18O同样没有表现出有规律的昼夜变化趋势,NO3-离子与δ15N表现出较小的相关性(R2=0.18,P=0.03),与δ18O没有表现出相关性(R2=0.01,P-=0.25),且δ515N和δ18O之间也没有表现出相关性(R2=0.008,P=0.25)。δ15N和δ18O没有表现出相关性,两者比值有很小的一部分落在1：1比值区间,有一部分落在2：1的比值区间,说明溪流中同化作用作用和反硝化作用对溪流中NO3-离子的昼夜变化产生了一定的影响,溪流中主要发生了氮的损失过程,损失量为2.71kgN.d-1,可能受到反硝化作用和同化作用一定的影响,但是溪流中δ15N-NO3-和δ18N-NO3-并没有表现出相关性变化,可能主要受到硝化作用和氮多种混合源的影响,同时N03"离子浓度与流量表现出一定的相关性(R2=0.25,P=0.03),说明随着时间和来源变化的上游补给也影响着溪流中N03"离子浓度的昼夜变化。同时说明是溪流中N03-离子的昼夜变化受到生物作用和随着时间和来源变化的上游补给的物理过程的共同影响。
[Abstract]:Nitrate pollution is one of the most common and most serious pollution in water pollution. In recent years, it has been reported that rivers, lakes, urban groundwater, etc. are polluted by nitrate, produce water eutrophication, induce esophageal cancer and other diseases, and cause serious danger to human health. In the southwest karst area, 2836 underground rivers have been identified. The total flow rate is 1482m3.S-1, which is equivalent to a the Yellow River, the karst groundwater resources which have an important role in the people's health and social and economic development in the karst region of Southwest China. With the intensification of industrial and agricultural production, the expansion of urbanization and so on, the karst groundwater in Southwest China is facing the threat of "sewer", and southwest China is facing the threat of "sewer". The pollution of karst groundwater is very serious, and the groundwater resources are completely urgent. It is urgent to protect the karst groundwater environment. In the karst area of Southwest China, the underground double layer structure and the "three water" change quickly, making the karst groundwater reacting to the external environment very sensitive. It is very difficult to monitor, simulate and control the spatio-temporal distribution of nitrate in karst area. Therefore, it is necessary to explore the dynamic changes and influence factors of nitrate in karst water from different time scale and space scale in karst area. It provides a scientific understanding of the dynamic changes of nitrate in karst water body, and provides scientific reference for the prevention and control of nitrate pollution in the water of karst area. This paper takes the underground river in Guan village of Liuzhou as an example, based on the surface stream of the underground river outlet of Guan Cun and the underground river recharged by the underground river in the official village. The dynamic changes and its influencing factors on the time scale (season, rainfall, day and night) have been obtained. (1) the N03- ions in the stream of the study area show obvious seasonal variation, and the content of NO3- ions in the underground river exit is in the spring and winter in autumn and winter, and the content of N03- ions in the surface stream is two in autumn and winter in summer and winter. The monitoring points are all high in the dry season, and the highest value of N03 "ion content in the two monitoring points is in November, mainly due to the low flow in the dry season, the lowest value in April and the sharp change of the NO3- ion content in spring, which may be mainly affected by the rainfall process. The NO3- ion in the stream shows the loss of nitrogen in the month of 9,10,11,12,2,3,5,8. The loss amount is 2.46kgN.d-1,1.77 kgN.d-1,3.01 kgN.d-1,2.09 kgN.d-1,2.08 kgN.d-1,17.34 kgN.d-1 respectively, and the growth process of nitrogen in 1,4,6,7 month is 1.06 kgN.d-1,6.84 kgN.d-1,5.92kgN.d-, and the delta 15N-NO3- and delta 18O-NO3- in the 0.7 kgN.d-1. stream show a certain positive correlation. The ratio of O3- to delta 18O-NO3- falls near the ratio of 1:1, indicating that nitrogen assimilation occurs mainly during the monitoring of streams. Only a small portion of the stream falls near the 2:1, indicating that denitrification has little effect on the seasonal changes in the ions of N03 in the stream. In addition, the loss of nitrogen in a stream is 28.75 in a year. KgN.d-1 (excluding the loss of 3,8 months), and the increase of 14.52 kgN.d-1, indicates that in the seasonal variation monitoring of one year, the N03 "ions in the stream occur mainly in the process of nitrogen loss and are mainly influenced by the assimilation of aquatic plants. And the loss process of nitrogen is not occurring in 1,4,6,7 months, probably mainly due to rainfall leaching. The effect is that the high concentration of nitrate accumulated in the soil around the stream enters the stream and covers the influence of the assimilation of aquatic plants. (2) the response of nitrate to the rain in the underground river outlet and the surface stream shows a similar trend in general, but the nitrate in the surface stream is also different from the underground river outlet. The "abnormal" change is more complex than the underground river outlet. The nitrate in the surface stream is mainly influenced by the supply water of the underground river outlet, and is affected by the external rain and the soil water. And the different rainfall intensity and the rainfall times also make the external rain and soil water affected by different effects on the ground. For the first time, the high concentration of N03 "ions into the surface stream of the soil water makes the NO3- ions in the surface streams increase, and the concentration of N03 ions in the soil water decreases gradually after several rainfall. In the two rainfall monitoring, the conductivity of the underground river and the surface streams and the N03" ions are in R2 (2013 8). The second rainfall during monthly monitoring and the rainfall in May 2014 showed a more rapid response, while R1 (the first rainfall in August 2013) was relatively slow, mainly due to the rainfall process in R2 and May 2014, which was stronger and more concentrated, which means that the intensity of rainfall would affect the time of electrical conductivity and the time of N03 "ion response. The greater the length and speed. The greater the intensity of the rain, the faster the electrical conductivity and the reaction of the NO3- ions. (3) all the physical and chemical parameters (T, pH, DO, Spc, pCO2) and NO3- ions in the day and night monitoring of the stream in July 2013 showed a regular day and night trend, in which the temperature, DO and pH showed a decline in the white sky at night, while the conductivity, pC02 and N03 "ions" showed The trend of daytime decline and evening rise. Underground river export recharge has little influence on the physical and chemical parameters of the surface streams and the regular diurnal changes of N03 "ions, and the flow of streams is not changed, and there is no day and night change. It can be shown that the stream flow is not a physical chemical reference in the driving stream during the monitoring. The factors of number and N03 "ion diurnal variation. DO and pC02 in surface streams show significant negative correlation (R2=0.81, P0.01), and the contribution rate of temperature to pC02 is 27.48% to 54.88%, and the effect of aquatic plants on water pC02 is 45.12% ~ 72.52%, indicating that the photosynthesis and respiration of aquatic plants during the monitoring are the day of DO and CO2. The main influence factors of night change, at the same time, NO3- ions and DO showed a significant negative correlation (R2=0.52, P0.01), indicating that the diurnal variation of the concentration of DO affects the diurnal variation of the concentration of NO3- ions, and there is a weak correlation between the changes of the N03 "ions and pC02 in the stream, and that the diurnal changes of the NO3- ions in the most stream of degassing action have little influence. At the same time, it is indicated that photosynthesis and respiration of aquatic plants in the stream are the main influencing factors of the regular diurnal changes of NO3- ion concentration,.NO3 "ions generally show a downward trend, but the trend of growth in the afternoon, at 12:30), reaches the maximum value of 3.72 mg.L-1, which shows that NO3- ions are not only in the daytime. The effect of assimilation caused by enhanced photosynthesis is mainly influenced by nitrification. While the respiration of the aquatic plants occupies the leading role in the night, the DO content decreases rapidly. Therefore, the assimilation and nitrification are inhibited at night and the denitrification process begins to play a role, so the NO3- ion decreases. N in the stream. The daily change amount is 2.59 kgN.d-1. In the afternoon, the growth process is based on the growth process, the growth is 0.99kgN.d-1, the rest time is dominated by the loss process, of which the daytime loss is 0.8 kgN.d-1, the night loss is 0.8kgN.d-1, and the proportion of each function is calculated by the change of N. In the afternoon, the nitrification is the main factor, the increase is 0.99kgN.d-1, accounting for the daily change. 38% of the amount of denitrification at night, the loss amount is 0.8 kgN.d-1, accounting for 31% of the daily change and 0.8 kgN.d-1 in the daytime, which is dominated by assimilation, accounting for 31% of the daily change. Therefore, the denitrification is 38%, the assimilation is 31%, and the denitrification account for the day and night prison of 31%.2014 year in July. The physical and chemical parameters (T, pH, DO, Spc, pCO2) in a measured stream show a regular trend of day and night change, in which water temperature, DO and pH show a decline in the night, while the conductivity and pC02 show a trend of rising in the white world and at night. However, the NO3- separated from the stream does not show the same day and night change as DO. The correlation (R20.03), 515N and delta 18O did not show a regular day and night trend, NO3- ions and delta 15N showed a smaller correlation (R2=0.18, P=0.03), and did not show a correlation with delta 18O (R2=0.01, P-=0.25), and there was no correlation between Delta 515N and delta 18O. [Delta] and delta 18O did not show correlation. A small part of the ratio falls on the ratio interval of the 1:1 ratio, and some of them fall on the ratio range of the 2:1. It shows that the effect of assimilation and denitrification on the diurnal changes of NO3- ions in the stream have a certain effect on the stream, and the loss process of nitrogen in the stream is 2.71kgN.d-1, which may be affected by the anti nitrite. The effects of chemical and assimilation are certain, but the delta 15N-NO3- and delta 18N-NO3- in the stream do not show a correlation change, which may be mainly influenced by nitrification and multiple nitrogen sources, while the N03 "ion concentration and flow show a certain correlation (R2=0.25, P= 0.03), indicating the upstream recharge with time and source changes, too. The diurnal variation of N03 "ion concentration in a stream is influenced by the physical processes of the physical processes of the diurnal changes of the N03- ions in the streams by the biological action and the upstream recharge with time and source changes.
【学位授予单位】：西南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X523

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