滨海盐田土壤碳时空分布特征及碳收支

doi:10.19657/j.geoscience.1000-8527.2024.044

摘要/Abstract

摘要：

滨海盐田存在土壤盐碱化、瘠薄与有机碳含量低等障碍问题,有关滨海盐田土壤碳方面的系统研究目前依然缺乏典型实例剖析。为了揭示滨海盐田以及用地类型发生转变后土壤的有机碳时空分布特征、影响因素及碳收支,选取江苏省连云港市徐圩新区和青口盐场的土壤为研究对象,采取表层(0~20 cm,2004年和2019年两期数据)土壤及深层(150~200 cm,2004年一期数据)土壤样品,进行了土壤有机碳(SOC)、总碳(TC)及总氮(TN)的测试。结果表明,SOC储量呈增加趋势,碳汇区面积占比69.4%,碳源区占比30.6%,不同用地类型SOC含量与平均固碳速率差异较大。2004年表层SOC含量分布在低、中两个等级区间,2019年SOC含量在中等级分布频率最高。近15年盐田1区(用地类型保持不变)SOC含量增加了0.12%,盐田2区(耕地)SOC含量增加了0.42%,盐田3区(建设用地)SOC含量增加了0.13%。平均固碳速率最高值出现在耕地类型,数值达到了5.83×10⁴ kg·km^-2·a^-1。盐田1区土壤有机碳的分解主要通过微生物的异氧呼吸途径来实现,有机碳的有氧矿化主要通过真菌与细菌的有氧矿化来实现。滨海盐土具有高含量的SO₄^2-与Ca²⁺,有机碳的厌氧矿化主要通过SO₄^2-还原来实现,因此无机碳的增加速率较大,达到3.64 g·m^-2·a^-1。盐田1区两期数据SOC/TN平均值均为9.9,说明土壤环境稳定。盐田3区SOC/TN稍有下降,推测原因是土壤微生物量及酶活性提高导致SOC的矿化速率增加。在环境问题日益严重和土壤质量趋向恶化的情况下,本文的研究成果为滨海盐田及其土地利用类型转变后的土壤碳循环研究提供了新的基础依据。

关键词: 有机碳, 无机碳, 徐圩新区, 青口盐场, 碳循环

Abstract:

There are issues of soil salinization, inferiority, and low organic carbon content in coastal salt pans and those relevant studies are relatively lacking. This study aims to reveal the spatial and temporal distributions, influencing factors, and carbon cycling of the organic carbon in soils of coastal salt pans and land use types after the transformation. We select the soils from Xuwei New Area and Qingkou Salt Farm in Lianyungang, Jiangsu as the research objects. The soil samples were collected from the surface layer (0-20 cm, two phases of data in 2004 and 2019) and deep layer (150-200 cm, phase I data in 2004). The soil organic carbon (SOC), total carbon (TC), and total nitrogen (TN) were measured in the study. The results show that the SOC stock was increasing with the area of carbon sink area accounting for 69.4% and the area of carbon source area accounting for 30.6%. However, the SOC content and average carbon sequestration rate varied greatly among different site types. The SOC content was only distributed in the two grade intervals, low and medium in 2004, and medium in 2019, the SOC content was distributed in medium grade with the highest frequency. In the past 15 years, the SOC content was increased by 0.12% in salt pans 1 (land type remained unchanged), 0.42% in salt pans 2 (cropland), and 0.13% in salt pans 3 (construction land). The highest average carbon sequestration rate was found in the cropland type, with a value of 5.83×10⁴ kg·km^-2·a^-1. The decomposition of soil organic carbon in salt pans 1 was mainly caused through the heteroxic respiration pathway of microorganisms. Aerobic mineralization of organic carbon is mainly achieved through aerobic mineralization by the fungi and bacteria. The anaerobic mineralization of organic carbon is mainly caused by SO₄^2- reduction, so the rate of increase of the inorganic carbon is higher, reaching to 3.64 g·m²·a^-1. The average SOC/TN value of the two phases of data in salt pans 1 is 9.9 positive, indicating a stable soil environment. The slight drop in SOC/TN in salt pans 3 is presumed to be caused by the decrease in the mineralization rate of SOC due to the increase of soil microbial load and enzyme activities. With the increasing environmental issues such as deteriorating soil quality, the results of this study provide an important reference for the soil geochemical cycle in coastal salt pans and their land use types after the transformation.

Key words: organic carbon, inorganic carbon, Xuwei new area, Qingkou salt farm, carbon cycle

中图分类号:

S153.6
X142

苟富刚, 王光亚, 蔡露明. 滨海盐田土壤碳时空分布特征及碳收支[J]. 现代地质, 2024, 38(02): 497-508.

GOU Fugang, WANG Guangya, CAI Luming. Spatial and Temporal Distribution of the Soil Carbon and Carbon Balance in Coastal Salt Pans[J]. Geoscience, 2024, 38(02): 497-508.

图/表 12

图1 江苏省连云港市采样点分布及用地类型

Fig.1 Distribution of sampling locations and site type map of Lianyungang, Jiangsu

表1 江苏省连云港市不同用地类型土壤地球化学参数统计

Table 1 Statistics of the soil geochemical parameters for the different land types of Lianyungang, Jiangsu

用地类型		SOC (%)	SIC (%)	SOCD (kg/m²)	含盐量 (%)	TN (10^-3)	pH	C/N	个数	SOC变异系数
2004年	研究区整体	0.69	0.93	1.55	—	0.73	8.2	10.1	84	0.247
	盐田1区	0.67	0.73	1.50	—	0.71	8.2	9.9	37	0.212
	盐田2区	0.79	1.08	1.76	—	0.76	8.2	11.6	10	0.253
	盐田3区	0.69	0.83	1.54	—	0.75	8.3	9.8	37	0.266
2019年	研究区整体	0.89	—	2.00	1.69	0.90	8.4	9.9	288	0.429
	盐田1区→盐田1区	0.79	—	1.77	2.94	0.80	8.5	9.9	73	0.432
	盐田2区→耕地	1.21	—	2.84	0.46	1.28	8.5	9.4	60	0.285
	盐田3区→建设用地	0.82	—	1.79	2.62	0.81	8.4	10.2	155	0.419
背景值 (1.5~2.0 m)	研究区整体	0.53	0.70	1.54	—	0.63	8.2	10.1	84	0.150
	盐田1区	0.56	0.67	1.50	—	0.55	8.2	16.4	37	0.212
	盐田2区	0.52	0.78	1.76	—	0.73	8.3	8.0	10	0.253
	盐田3区	0.51	0.63	1.54	—	0.69	8.2	9.1	37	0.267

图2 江苏省连云港市2004年(a)和2019年(b)SOC含量分布频率统计

Fig.2 Frequency statistics of the SOC content distribution of Lianyungang, Jiangsu in the years of2004 (a) and 2019 (b)

表2 研究区土壤有机碳相关参数分级

Table 2 Classification of the soil carbon related parameters for the study area

级别	极高	高	中上	中	低	极低
有机质 (10^-3)	>40	30~ 40	20~ 30	10~ 20	6~ 10	<6.0
有机碳 (%)	>2.3	1.7~ 2.3	1.2~ 1.7	0.6~ 1.2	0.3~ 0.6	<0.3
有机碳密度 (kg/m²)	>6.0	4.5~ 6.0	3.0~ 4.5	1.5~ 3.0	1.0~ 1.5	<1.0

图3 连云港滨海盐田区2004年和2019年SOC含量空间分布及变化特征

Fig.3 Spatial distribution and change characteristics of the SOC content of the Lianyungang coastal salt pans in 2004 and 2019

图4 连云港滨海盐田区2004年与2019年SOCD含量空间分布及变化特征

Fig.4 Spatial distribution and change characteristics of the SOCD content of the Lianyungang coastal salt pans in the years of 2004 and 2019

表3 连云港滨海盐田区不同用地类型碳储量及变化分区统计(2019年数据)

Table 3 Carbon stock and change zoning statistics of different land types of the Lianyungang coastal salt pans (data in 2019)

区域		面积 (km²)	2004年SOC储量 (10⁷ kg)	2019年SOC储量 (10⁷ kg)	碳增量 (10⁷ kg)	平均固碳速率 (10⁴ kg·km^-2·a^-1)
全区		348.7	53.25	65.54	12.29	2.35
用地类型	盐田1区(用地类型不变)	42.2	5.86	7.08	1.22	1.92
	盐田2区(盐田→耕地)	25.5	4.33	6.56	2.23	5.83
	盐田3区(盐田→建设用地)	281.0	43.05	51.90	8.84	2.10

图5 滨海盐田碳的循环过程

Fig.5 Carbon cycling processes in the coastal salt pans

表4 不同用地类型含盐量(平均值)特征

Table 4 Salinity (mean) characteristics of different land types

用地类型	含盐量 (%)	SOC (%)	Na⁺ (mg/kg)	Cl^- (mg/kg)	Ca²⁺ (mg/kg)	SO₄^2- (mg/kg)	Na⁺与Cl^-合计 (%)
不分类(全部样本)	1.69	0.89	7918	13688	520	2367	83
盐田1区→盐田1区	2.94	0.79	9291	15859	660	2372	86
盐田2区→耕地	0.46	1.21	2844	4375	99	780	74
盐田3区→建设用地	2.62	0.82	9052	15817	628	3087	83

图6 连云港滨海地区SOC与无机碳(SIC)关系拟合(2004年数据)

Fig.6 Fitting of SOC to SIC of in the Lianyungang coastal area (data in 2004)

图7 连云港滨海地区不同用地类型含盐量与SOC含量对比(a)和拟合(b)

Fig.7 Comparison of the salinity and SOC content of different land types in the Lianyungang coastal area and fitting curves

图8 连云港滨海地区SOC与TN的关系拟合

Fig.8 Fitting of SOC versus TN in the Lianyungang coastal area

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