Investigation of phenological stages and pollutants’ type on the efficiency of vegetative buffer strips

Non-point source pollution is considered as a serious issue especially in the field of eutrophication for surface waters. Vegetative buffer strips include a specific plant being passed by flow before entering the waterways, so it causes to reduce runoff volume, deposited pesticides and other pollutants of the flow through infiltration, absorption and sediment deposition. The present study has been carried out with aim to investigate the effect of pollutant type on the efficiency of vegetative buffer strips to reduce sediment transport. This study was conducted using 1×10 experimental plots and producing artificial runoff with a discharge rate as much as precipitation with 100-year return period as well as two plant species of vetiver grass and native turf grass during one year in Lalim region of Sari, Mazandaran, Iran. According to the results, vetiver buffer strip reaches its maximum efficiency of pollutants removal at phenological stages of vegetative growth and flowering; so that, runoff volume, sediment, nitrate and phosphate concentration were reduced by 80%, 87%, 81% and 93% respectively. Also, this efficiency reached its maximum amount for the turf-grass buffer strips at vegetative growth stage; so that, runoff volume, sediment, nitrate and phosphate concentration were reduced by 91%, 91%, 79% and 71% respectively. The mean concentration of the pollutants increased and the efficiency of vegetative buffer strips was reduced in the last months of the experiment those which showed the capability of vegetative buffer strips to play role as the source of nutrients and sediment. According to the findings, the studied vegetative buffer strips considerably affected the pollutants removal as well as runoff volume reduction and consequently water and soil conservation after two months. On the other hand, a strong correlation was observed among nitrate, phosphate and sediment removal; because, the nutrients are attached to the fine sediments.