Spatial and temporal variability of agricultural pollutants in an agricultural headwater stream within a multipond syste

Abstract： The spatial and temporal variability of nutrients and suspended solids were investigated for two years in a 1.8 km agricultural headwater stream, located by Chaohu Lake, southeastern China. The stream form was greatly modified by human activities into channelized, pond and estuary shapes. The stream could be divided into 4channelized reaches(1.3 km), a pond reach(0.15 km) and 3 estuary reaches(0.36 km). It was found that nutrients and TSS concentrations in the stream showed temporal variability, and higher concentrations occurred in months with high precipitation and intensive agricultural activities. And, retention of total nitrogen (TN), nitrate (NO-3-N),ammonium( NH+4 -N ) and total suspended solids (TSS) predominantly occurred in the pond reach and estuary reaches with larger width and Iow current velocity. Pollutants retained in these reaches accounted for more than 50%of those retained in whole stream. The retention mostly happened in the rain-runoff events and it was 7 to 27 times than that in base flow. The results showed that the channelized reach was the most important source for pollutants release under either runoff or base flow, and its release accounted for more than 90% of whole stream release.There was a high spatial variability of nutrients retention in different channelized reaches. The channelized reach directly discharging into the pond did always retain nutrients and TSS under base flow and runoff conditions, whereas the other channelized reaches performed differently in different hydrological conditions. The high spatial and temporal variability of nutrients and TSS in the stream indicated that anthropogenic disturbance of the agricultural headwater stream, such as channelization and excavation, would be expected to decrease the capacity of nutrients retention in the stream. 作 者： MAO Zhan-po    Yin Cheng-qing    SHAN Bao-qing   作者單位： MAO Zhan-po(State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences,Beijing 100085, China;China Institute of Water Resources and Hydropower Research, Beijing 100038, China)

Yin Cheng-qing(State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences,Beijing 100085, China)

SHAN Bao-qing(China Institute of Water Resources and Hydropower Research, Beijing 100038, China) 

期 刊： 環(huán)境科學學報(英文版)  ISTICSCI   Journal： JOURNAL OF ENVIRONMENTAL SCIENCES  年，卷(期)： 2004, 16(4)  分類號： X52  Keywords： retention    release    nutrients    variability    stream forms