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ARS Home » Pacific West Area » Tucson, Arizona » SWRC » Research » Publications at this Location » Publication #99349
Title: SEDIMENT AND NITROGEN TRANSPORT IN GRASS FILTER STRIPS 1230

Author
item Mendez, Aida
item DILLAHA, T - VPI&SU (VIRGINIA TECH)
item MOSTAGHIMI, S - VPI&SU (VIRGINIA TECH)

Submitted to: Journal of the American Water Resources Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/11/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Grass strips are planted between pollutant source areas, such as croplands, and receiving downslope waters. Their function is to retain pollutants. Their effectiveness in retaining nitrogen is not clear. For that reason, an 18-month field experiment was conducted to evaluate the effectiveness of grass filter strips in removing total suspended solids (TSS), total Kjeldah hnitrogen (TKN), ammonium-N (NH4-N), and nitrate-N (NO3-N) from runoff. Runoff from natural occurring rainfall events was automatically collected a the downslope edge of six experimental plots. Four plots consisted of a runoff source area (24.7 m long) and a grass filter and two plots had only runoff source area. All runoff source areas were equal in size. Two grass filters were 8.5 m long and the other two were 4.3 m long. Kruskal-Wallis statistical test indicated that the 8.5 m filters retained TSS, NH4-N, NO3- N, TKN, and FTKN and the 4.3 m filters retained TSS, TKN and NH4-N. According to Man-Kendall statistical test, the effectiveness of 8.5 m filters in retaining TSS, NO3-N, NH4-N, TKN and FTKN did not vary significantly, over the 18-month period, however the effectiveness of the 4.3 m filter appeared to change for the TKN yield and TSS, NH4-N, and FTKN concentrations.

Technical Abstract: An 18-month field experiment was conducted to evaluate the effectiveness of grass filter strips in removing sediment, organic N, ammonium-N (NH4-N), an nitrate-N (NO3-N) from runoff. Runoff from natural occurring rainfall event was automatically collected at the downslope edge of six experimental plots The six plots were 3.7 m wide and had a 24.7 m runoff source area. Two plot tconsisted of the source area and a 8.5 m grass filter, another two had a 4 m grass filter, and two plots had no filter. Runoff was analyzed for total suspended solids (TSS), total Kjeldahl nitrogen (TKN), filtered TKN (FTKN), NH4-N, and NO3-N. According to the Mann-Kendall nonparametric test for tren there was not a significant increasing or decreasing trend in the yields an concentrations of TSS, NO3-N, NH4-N, TKN and FTKN from the 8.5 m filters. For the 4.3 m filters, there were significant upward trends in TKN yield an downward trends in TSS, NH4-N, and FTKN concentrations. The Kruskal-Wallis test indicated that the median yields and concentrations of TSS, NH4-N, NO N, TKN, and FTKN from the 8.5 m filters and the median yields and concentrations of TSS, TKN and NH4-N, and the concentration of FTKN from th 4.3 m long grass filter were significantly smaller than the influent median yields and concentrations of those pollutants. The 8.5 m and 4.3 m filters reduced contaminated yields and concentrations from 42 to 90% and from 20 t 83%,respectively.