Modeling of productivity and nutrient extraction by the Vetiver and Tifton 85 grasses grown in horizontal subsurface flow constructed wetlands.

The objective of this study was to evaluate the productivity of shoot dry biomass and the capacity of nitrogen (N), phosphorus (P) and potassium (K) extraction by the Vetiver and Tifton 85 grasses when cultivated in horizontal subsurface flow constructed wetlands (HSSF-CWs) whose porous medium was saturated with solutions containing different nutrient availability. The grass shoots were cut every 30 days to determine the productivity and N, P and K contents in the plant tissue. Models of productivity and the extraction capacity of each nutrient were obtained as a function of the nutrient concentration. Based on the results obtained, it was verified that the productivity of shoot dry biomass and the extractions of N, P and K by the Vetiver grass increased linearly with the nutrient availability of the nutritive solution. In relation to Tifton 85, quadratic models of productivity and N and K extraction were adjusted. The maximum productivity, N, P and K extraction by Vetiver grass were 513.4, 8.2, 1.9 and 10.39 g m-2 month-1, respectively. In relation to Tifton 85 grass, these values were 739.4, 30.8, 3.0 and 15.59 g m-2 month-1 for productivity, N, P and K extraction, respectively.

Evapotranspiration of the Vetiver and Tifton 85 grasses grown in horizontal subsurface flow constructed wetlands.

Estimation of the Crop Evapotranspiration (ETC) in Horizontal Subsurface Flow Constructed Wetlands (HSSF-CWs) is of great importance for hydrological modeling of these systems. The objective of this work was to obtain the Crop Coefficient (KC) values of Vetiver (Chrysopogon zizanioides) and Tifton 85 (Cynodon spp.) grasses when grown in HSSF-CWs whose porous medium was saturated with solutions containing different nutrients concentrations. The water balance was performed every day in order to determine the KC of the grasses. It was verified that the KC values of the Vetiver grass were independent of the nutrient availability, expressed in terms of Electrical Conductivity (EC) of the nutrient solution. The KC value in the initial growth phase (Phase I) was 0.99, independent of the seasons. In Phase II, the KC were 0.95 and 1.36 for autumn and spring, respectively, and for Phase III were 1.12 in autumn and 1.60 in spring. In relation to the Tifton 85 grass, the KC values showed a quadratic behavior as a function of the EC, where the KC estimation models were obtained by the cluster analysis in Phase II and III. For Phase I, the KC value was 1.17, independent of the EC and the time of year.

Vetiver grass hedgerows significantly reduce nitrogen and phosphorus losses from fertilized sloping lands.

Runoff and over-use of fertilizers have been considered as two major factors accelerating the discharge of nitrogen (N) and phosphorus (P) from agricultural fields to surface water. The practice of vetiver grass hedgerows (VGH) can check sediments and runoff pollutants from agricultural fields. However, the efficiency of VGH in reducing N and P losses while maintaining optimum crop yields is still unclear under a recommended fertilization rate. A three-year field experiment was conducted on a 10 o sloping land to know how VGH can reduce the discharge of runoff nutrients to surface water bodies and maintain optimum crop yields, and to understand the relationships between changing soil properties and reduction of sediments N and P due to the adoption of VGH. Five fertilization treatments to VGH were examined under VGH plus organic fertilizer (VGH + OF), VGH plus inorganic fertilizer (VGH + IF), sole organic or inorganic fertilizer (OF or IF) and no VGH and fertilizer (Control). Runoff nutrient pollutants PO4-, NO3--N and NH4+-N were significantly (P < 0.01) reduced by VGH + OF compared to OF by 97%, 94% and 95% and VGH + IF compared to IF by 95%, 88% and 89% respectively for 2012, 2013 and 2014. Sediment nutrients N and P were significantly (P < 0.01) reduced by VGH + OF compared to OF by 98% and 99%, and VGH + IF compared to IF by 94% and 99%, respectively. Improved soil properties by VGH significantly (P < 0.01) reduced runoff pollutants and consequently increased maize yields. Our results imply that runoff erosion, rather than fertilization, is a major driving force for agriculture-derived water pollution. Adoption of VGH with a recommended fertilization rate could significantly reduce N and P nutrient losses from agricultural fields and consequently improve water quality as well as maintaining optimum crop yields on sloping lands.

The Potential Use of Vetiveria zizanioides for the Phytoremediation of Antimony, Arsenic and Their Co-Contamination.

Antimony (Sb) and arsenic (As) contaminations are the well reported and alarming issues of various contaminated smelting and mining sites all over the world, especially in China. The present hydroponic study was to assess the capacity of Vetiveria zizanioides for Sb, As and their interactive accumulations. The novelty of the present research is this that the potential of V. zizanioides for Sb and As alone and their interactive accumulation are unaddressed. This is the first report about the interactive co-accumulation of Sb and As in V. zizanioides. Highest applied Sb and As contaminations significantly inhibited the plant growth. Applied Sb and As alone significantly increased their concentrations in the roots/shoot of V. zizanioides. While co-contamination of Sb and As steadily increased their concentrations, in the plant. The co-contamination of Sb and As revealed a positive correlation between the two, as they supplemented the uptake and accumulation of each other. The overall translocation (TF) and bioaccumulation factors (BF) of Sb in V. zizanioides, were 0.75 and 4. While the TF and BF of As in V. zizanioides, were 0.86 and 10. V. zizanioides proved as an effective choice for the phytoremediation and ecosystem restoration of Sb and As contaminated areas.

Phosphorus removal from secondary effluents through integrated constructed treatment system.

The treatment capacity of an integrated constructed treatment system (CTS) was explored which was designed to reduce phosphorus (P) from secondary effluents. The integrated CTS was combined with vertical-flow constructed wetland, floating bed and sand filter. The vertical wetland was filled from the bottom to the top with gravels, steel slag and peat. Vetiverzizanioides (L.) Nash was selected to grow in the vertical constructed wetland while Coixlacrymajobi L. was grown in floating bed. The results suggested that integrated CTS displayed excellent removal efficiency for chemical oxygen demand (COD), dissolved phosphorus (DP), and total phosphorus (TP). The average COD removal efficiency of the integrated CTS was 90.45% after 40 days of operation, the average DP and TP removal efficiencies of the integrated CTS were 97.43% and 96.40%, respectively. The integrated CTS has good potential in removing COD as well as P from secondary effluents.

Economic incentive for applying vetiver grass to remediate lead, copper and zinc contaminated soils.

The application of vetiver grass (Chrysopogon zizaniodes) for phytoremediation of heavy metal contaminated soils can be promoted by economic return through essential oil production. Four levels of lead (0, 500, 2000, and 8000 mg kg(-1) dry soil), copper (0, 100, 400, and 1600 mg kg(-1) dry soil) and zinc (0, 400, 1600, and 6400 mg kg(-1) dry soil) were used to study their effects on vetiver growth, essential oil composition and yield. This study also investigated the effect of nitrogen concentrations on vetiver oil yield. Vetiver accumulated high concentrations of Pb, Cu and Zn in roots (3246, 754 and 2666 mg kg(-1), respectively) and small amounts of contaminants in shoots (327, 55, and 642 mg kg(-1), respectively). Oil content and yield were not affected at low and moderate concentrations of Cu and Zn. Only the application of Pb had a significant detrimental effect on oil composition. Extraction of vetiver essential oils by hydrodistillation produced heavy metal free products. High level of nitrogen reduced oil yields. Results show that phytoremediation of Cu and Zn contaminated soils by vetiver can generate revenue from the commercialization of oil extracts.

Tolerance and accumulation of lead in Vetiveria zizanioides and its effect on oil production.

Experiments were conducted to evaluate lead tolerance and accumulation in vetiver grass Vetiveria zizanioides (L.), grown in hydroponics and a pot study and to examine the effect of lead on vetiver oil production. Elevated concentrations of lead decreased the length of shoots and roots of plants. However, vetiver grown in highly contaminated soils showed no apparent phytotoxicity symptoms. Lead concentrations in the shoots and roots of vetiver plants grown in hydroponics were up to 144 and 19530 mg kg(-1) and those grown in soil were 38 and 629 mg kg(-1), respectively. Lead had an effect on vetiver oil production and composition by stimulating oil yield and the number of its constituents. Oil yield ranged from 0.4-1.3%; the highest yields were found in plants grown in nutrient solution with 100 mg Pb l(-1) for 5 weeks (1.29%) and 7 weeks (1.22%). The number of total constituents of vetiver oil also varied between 47-143 compounds when lead was presentin the growth medium. The highest number (143) was found in plants grown in soil spiked with 1000 mg Pb kg(-1). The predominant compound was khusimol (10.7-18.1%) followed by (E)-isovalencenol (10.3-15.6%). Our results indicated that lead could increase the oil production of vetiver.

Potential of vetiver (vetiveria zizanioides (L.) Nash) for phytoremediation of petroleum hydrocarbon-contaminated soils in Venezuela.

Venezuela is one of the largest oil producers in the world. For the rehabilitation of oil-contaminated sites, phytoremediation represents a promising technology whereby plants are used to enhance biodegradation processes in soil. A greenhouse study was conducted to determine the tolerance of vetiver (Vetiveria zizanioides (L.) Nash) to a Venezuelan heavy crude oil in soil. Additionally, the plant's potential for stimulating the biodegradation processes of petroleum hydrocarbons was tested under the application of two fertilizer levels. In the presence of contaminants, biomass and plant height were significantly reduced. As for fertilization, the lower fertilizer level led to higher biomass production. The specific root surface area was reduced under the effects of petroleum. However, vetiver was found to tolerate crude-oil contamination in a concentration of 5% (w/w). Concerning total oil and grease content in soil, no significant decrease under the influence of vetiver was detected when compared to the unplanted control. Thus, there was no evidence of vetiver enhancing the biodegradation of crude oil in soil under the conditions of this trial. However, uses of vetiver grass in relation to petroleum-contaminated soils are promising for amelioration of slightly polluted sites, to allow other species to get established and for erosion control.