Seasonal variation of enrichment, accumulation and sources of heavy metals in suspended particulate matter and surface sediments in the Daliao river and Daliao river estuary, Northeast China

摘要

Suspended particulate matter (SPM) and sediment samples were collected from the Daliao river and Daliao river estuary (Northeast China) to clarify the changes of metal concentrations, enrichment and accumulation during the medium season, wet season and dry season, respectively. The results showed that concentrations, enrichment factor (EF) values and geo accumulation (I-geo) values for metals significantly changed during the time. Generally, metal concentrations in sediments during the dry season were higher than those during the medium season and wet season. SQGs results revealed that potential toxicity for aquatic organisms may frequently happen for most of the metals during the dry season, while during the wet season and medium season, adverse effects for aquatic organisms may occasionally happen. Enrichment factor values (EF values) showed that various range of EF values for metals were found and Cd, Pb, As and Zn showed the most sever enrichment among the studied metals. Seasonal mean EF values for metals in SPM showed the following orders: Pb (2.82) > Cd (2.53) > As (2.07) > Zn (2.05) > Mn (1.94) > Co (1.23) > Fe (1.20) > Ni (1.15) > Cr (1.12) > Cu (1.00) and showed the following decreasing order: medium season > dry season > wet season, while for Mn, Cd and Pb, it shows that dry season > medium season > wet season, indicating minor enrichment for all the elements. For sediments, seasonal mean EF values for metals are showed as follows: Cd (12.80) > Pb (9.62) > As (4.11) > Zn (3.15) > Co (2.32) > Cr (2.27) > Mn (2.05) > Fe (1.87) > Ni (1.46) > Cu (1.43), indicating severe enrichment for Cd, moderate severe enrichment for Pb, moderate enrichment for As and Zn and minor enrichment for Co, Cr, Mn, Fe, Ni and Cu, respectively. Geo-accumulation index (I-geo) results indicated that mean I-geo values for most of metals in sediment samples were below 0 which was classified as unpolluted except for Cd whose I-geo values was classified as unpolluted to moderately polluted sediment samples during the wet season and dry season, respectively. I-geo values in SPM for metals also showed seasonal variation and Cd, Pb, As and Zn displayed the highest seasonal mean I-geo values. Sources analysis for metals in sediments indicated that natural and anthropogenic sources both contributed to the metal accumulations in sediments and industrial and municipal sewage effluents discharged from the upstream cities may be the main anthropogenic sources for metals in the Daliao river and Daliao river estuary.