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土地利用变化下滨海滩涂磷素关键界面过程

作者:润色论文网  来源:www.runselw.com  发布时间:2019/10/29 8:18:25  

摘要:磷是滨海滩涂生态系统中必不可少的营养元素之一,探究其在水-土界面的吸附解吸、形态分布等是研究其生物地球化学过程的关键。近年来,随着沿海大开发的进行,滩涂围垦加剧,滨海滩涂土地利用变化剧烈,可能改变了滨海滩涂磷的生物地球化学循环,并由此可能产生一系列严重的环境问题。

本文以盐城滨海滩涂为典型研究区,系统分析了滨海滩涂由辐射沙洲-原生盐沼(自然演化)及原生盐沼-围垦农田(人为演化)两种演化模式下土壤磷关键生物地球化学过程的变化,重点分析了土壤理化性质、磷吸附特征、赋存形态、生物可利用性等随滩涂土地利用(辐射沙洲-原生盐沼-围垦农田)的变化,并通过土柱模拟实验,分析了淋洗脱盐对滩涂磷关键界面过程的影响,为揭示滩涂围垦的环境效应,进而揭示人类活动对海岸带生源要素、功能演替的影响机制及作用强度提供基础依据。

主要研究结论如下:

1)滩涂自然演化和人为演化过程均可使土壤理化性质发生显著改变,总体上自然演化的影响远高于人为演化。同时,滩涂由原生盐沼到围垦农田过程中,主要物化性质和土壤质量比较相近,总体变化不大。

2)自然演化过程促进了磷吸附容量的快速升高,并显著降低了磷释放风险;而围垦导致的人为演化过程对磷吸附容量影响不大,但可导致磷吸附阈值和饱和度上升,磷释放风险显著提高。

3)滩涂自然演化过程不影响TP、IP含量与分布,而人为演化则可显著提高TP含量和OP赋存比例。两者均可显著提高活性磷组分和磷赋存形态的含量和比例,相比而言,人为演化提高幅度远高于自然演化过程。

4) 滨海滩涂土壤生物可利用磷水平很低。随着滩涂的自然演化和人为演化,生物可利用性磷显著升高,人为演化对生物可利用磷升高幅度远高于自然演化过程。滩涂土壤生物可利用磷变化主要决定于Fe/Al-P和无定型金属氧化物,盐度在辐射沙洲和原生盐沼中有一定影响,在围垦农田中不再起关键作用。

5)单纯淋洗不改变滩涂土壤的磷吸附容量、吸附阈值和赋存形态,但可使磷饱和度和释放风险显著下降。

6)在滩涂土地利用变化过程中土壤粘粒变化是磷吸附过程、赋存形态转化等关键生物地球化学变化的主要驱动力,盐度、酸碱度等起到辅助作用。以上研究结果为认识围垦等人类活动对滩涂生源要素的影响过程,保护与合理开发滩涂资源提供了一定依据。

Phosphorus is one of the essentialnutrients in tidal flat ecosystem. Study its adsorption-desorption and morphologicaldistribution at the water-soil interface is the key to studying itsbiogeochemical processes. In recent years, with the development of the coastalareas, reclamation of tidal flats intensified and the land-use changes ofcoastal beach land use changed drastically. This may change the biogeochemicalcycle of phosphorus in coastal beaches and may cause a series of seriousenvironmental problems.

This paper takes Yancheng tidal flat as atypical study area, and systematically analyzes the changes of the keybiogeochemical processes of soil phosphorus under two evolutionary patterns:from radiation sandbanks to pristine salt marsh (natural evolution) and frompristine salt marsh to reclamation farmland (artificial evolution). The changesin soil physicochemical properties, phosphorus adsorption characteristics,occurrence forms, and bioavailability were analyzed with the changes in landuse (radiation sandbanks-pristine salt marsh-reclamation farmland) in the tidalflat. Through the soil column simulation experiment, the influence of leachingand desalination on the phosphorus critical interface process was analyzed, soas to provide the basis for revealing the environmental effect of tidal flatreclamation and revealing the influence mechanism of human activities on thesource elements and functional succession of coastal wetland.

The main conclusions are as follows:

1) The natural evolution and artificialevolution of tidal flat can significantly change the physical and chemicalproperties of soil. In general, the influence of natural evolution is muchhigher than that of artificial evolution. The main physical and chemicalproperties and soil quality are close to farmland when the tidal flat developsto the pristine salt marsh.

2) The natural evolution process promotedthe phosphorus adsorption capacity increased rapidly, and significantly reducethe phosphorus release risk; artificial evolution and reclamation rate leadingto little effect on phosphorus adsorption capacity, but can lead to phosphorusadsorption saturation threshold and increased risk of phosphorus releaseincreased significantly.

3) The natural evolution process of thebeach does not affect the content and distribution of TP and IP, while humanevolution can significantly increase the TP content and the proportion of OPaccumulation. Both of them could significantly increase the content of activephosphorus components and phosphorus occurrence forms. In comparison, theincrease in artificial evolution was much higher than that in the naturalevolution process.

4) The bioavailability of phosphorus incoastal beach soils is very low. With the natural evolution and artificialevolution of the tidal flat, the bioavailable phosphorus increasedsignificantly, and the artificial evolution of bioavailable phosphorus was muchhigher than the natural evolution process. The bioavailable phosphorus changesin the tidal flat soil are mainly determined by Fe/Al-P and amorphous metaloxides. The salinity has a certain influence on the radiation sandbanks and thepristine salt marsh, and it does not play a key role in the reclamationfarmland.

5) Pure leaching does not change theadsorption capacity, adsorption threshold and occurrence form of the soil inthe beach, but it can significantly reduce the risk of phosphorus saturationand release.

6) In the process of beach land use change,soil clay change is the main driving force of key biogeochemical changes suchas phosphorus adsorption, desorption and occurrence form. Salinity, pH and soon play an auxiliary role. The above results provide a certain basis for theunderstanding of the influence of human activities and other human activitieson the source elements of the tidal flat, and the protection and rationalexploitation of the beach resources.

关键词:滩涂;土地利用;磷;围垦;环境行为

tidal flat; land use; phosphorus;reclamation; environmental behavior

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