湖北长湖表层沉积物营养盐和重金属分布特征及污染评价

Distribution Characteristics and Pollution Assessment of Nutrients and Heavy Metalsin Surface Sediments of Changhu Lake in Hubei Province

2019年9月采集了长湖马洪台区、后港区、毛李区、湖心区和出湖口区共25个表层沉积物样品,分析表层沉积物营养盐和重金属的空间分布和污染特征,并对重金属来源进行初步分析。结果表明,长湖表层沉积物中Corg和TN空间分布特征相似,含量高值区基本位于马洪台区,其次为毛李区,含量低值区基本位于后港区、湖心区和出湖口区;TP含量表现为后港区和湖心区最高,马洪台区次之,毛李区和出湖口区最低。重金属As、Pb、Cr、Cu、Ni在空间分布上具有一致性,含量高值区主要集中在后港区和湖心区,毛李区次之,马洪台区和出湖口区含量最低;Cd和Hg在马洪台区含量最高,略高于土壤背景值;Zn含量在各区域变化不明显,整体上低于或接近于土壤背景值。营养盐污染评价中,后港区、湖心区和马洪台区整体上处于重度污染,毛李区处于中度污染,出湖口区处于轻度污染,其中P是造成长湖水体富营养化的主要因素。重金属潜在生态风险评价中,后港区和湖心区污染较为严重,处于中等生态风险水平,其中As是主要的生态风险贡献因子,在后港区和湖心区处于较重生态风险水平;Cd与Hg在马洪台区处于中等生态风险水平;其余重金属均处于低生态风险水平。分析结果表明,重金属As、Cr、Cu、Ni和Pb之间相关性显著,具有相似的来源,可能主要来源于后港镇工农业废水;Cd和Hg主要来源于船只燃油排放;Zn主要受自然源的影响。该研究成果可为长湖污染控制和生态修复提供科学依据。

In September 2019,25 surface sediment samples were collected from Changhu Lake,and the spatial distribution and pollution characteristics of nutrients and heavy metals were analyzed.The results showed that the spatial distribution characteristics of Corg and TN in the surface sediments of Changhu Lake were similar.The high content area was basically located in the Mahongtai area,followed by the Maoli area,and the low content area was basically located in the Hougang area,the central area of the lake and the outlet area.The TP content was the highest in the Hougang area and the central area of the lake,followed by the Mahongtai area,and the lowest in the Maoli area and the outlet area.The spatial distribution of heavy metals As,Pb,Cr,Cu and Ni was consistent.The high content areas were mainly concentrated in the Hougang area and the lake center area,followed by the Maoli area,and the lowest content was in the Mahongtai area and the lake outlet area.The contents of Cd and Hg were the highest in Mahongtai area,which were slightly higher than the background values.The content of Zn did not change significantly in each region,and was lower than or close to the background value as a whole.In the evaluation of nutrient pollution,Hougang District,Lake Center District and Mahongtai District were in severe pollution as a whole,Maoli District was in moderate pollution,and the outlet area was in mild pollution.Among them,P was the main factor causing severe pollution in Hougang District,Lake Center District and Mahongtai District.In the potential ecological risk assessment of heavy metals,the pollution in Hougang District and the central area of the lake was more serious and at a medium ecological risk level.Among them,As was the main ecological risk contribution factor,and it was at a heavy ecological risk level in Hougang District and the central area of the lake.Cd and Hg were at a medium ecological risk level in Mahongtai District,and the remaining heavy metals were at a low ecological risk level.In addition,the results of source analysis showed that heavy metals As,Cr,Cu,Ni and Pb may be mainly derived from industrial and agricultural wastewater in Hougang Town,and Cd and Hg were mainly derived from ship fuel emissions.Zn was mainly affected by natural sources.The research results can provide scientific basis for pollution control and ecological restoration of Changhu Lake.