Use of wood and cork in biofilters for the simultaneous removal of nitrates and pesticides from groundwater.

About 13% and 7% of monitored groundwater stations in Europe exceed the permitted levels of nitrates (50 mg NO3- L-1) or pesticides (0.1 µg L-1), respectively. Although slow sand filtration can remove nitrates via denitrification when oxygen is limited, it requires an organic carbon source. The present study evaluates the performance of the use of wood pellets and granulated cork as carbon sources in bench-scale biofilters operated under water-saturated and water-unsaturated conditions for more than 400 days. The biofilters were monitored for nitrate (200 mg L-1) and pesticide (mecoprop, diuron, atrazine, and bromacil, each at a concentration of 5 µg L-1) attenuation, as well as for the formation of nitrite and pesticide transformation products. Microbiological characterization of each biofilter was also performed. The water-saturated wood biofilter achieved the best nitrate removal (>99%), while the cork biofilters lost all denitrification power over time (from 38% to no removal). The unsaturated biofilter columns were not effective for removing nitrates (20-30% removal). As for pesticides, all the biofilters achieved high removal rates of mecoprop and diuron (>99% and >75%, respectively). Atrazine removal was better in the wood-pellet biofilters than the cork ones (68-96% vs. 31-38%). Bromacil was only removed in the water-unsaturated cork biofilter (67%). However, a bromacil transformation product was formed there. The water-saturated wood biofilter contained the highest number of denitrifying microorganisms, with Methyloversatilis as the characteristic genus. Microbial composition could explain the high removal of pesticides and nitrates achieved in the wood-pellet biofilter. Overall, the results indicate that wood-pellet biofilters operated under water-saturated conditions are a good solution for treating groundwater contaminated with nitrates and pesticides.

Assessment of a novel microalgae-cork based technology for removing antibiotics, pesticides and nitrates from groundwater.

Groundwater pollution has increased in recent years due to the intensification of agricultural and livestock activities. This results in a significant reduction in available freshwater resources. Here, we have studied the long term assessment of a green technology (1-4 L/day) based on a photobioreactor (PBR) containing immobilised microalgae-bacteria in polyurethane foam (PF) followed by a cork filter (CF) for removing nitrates, pesticides (atrazine and bromacil), and antibiotics (sulfamethoxazole and sulfacetamide) from groundwater. The prototype was moderately effective for removing nitrates (58%) at an HRT of 8 days, while its efficiency decreased at a HRT of 4 and 2 days (<20% removal). The combined use of PBR-CF enabled antibiotics and pesticides to be attenuated by up to 95% at an HRT of 8 days, but their attenuation decreased with shorter HRT, with pesticides being the compounds most affected (reducing from 97 to 98% at an HRT of 8 days to 23-45% at an HRT of 2 days). Pesticide transformation products were identified after the CF, supporting biodegradation as the main attenuation process. A gene-based metataxonomic assessment linked the attenuation of micropollutants to the presence of specific pesticide biodegradation species (e.g. genus Phenylobacterium, Sphingomonadaceae, and Caulobacteraceae). Therefore, the results highlighted the potential use of microalgae and cork to treat polluted groundwater.

Seasonal changes of whole root system conductance by a drought-tolerant grape root system.

The role of root systems in drought tolerance is a subject of very limited information compared with above-ground responses. Adjustments to the ability of roots to supply water relative to shoot transpiration demand is proposed as a major means for woody perennial plants to tolerate drought, and is often expressed as changes in the ratios of leaf to root area (A(L):A(R)). Seasonal root proliferation in a directed manner could increase the water supply function of roots independent of total root area (A(R)) and represents a mechanism whereby water supply to demand could be increased. To address this issue, seasonal root proliferation, stomatal conductance (g(s)) and whole root system hydraulic conductance (k(r)) were investigated for a drought-tolerant grape root system (Vitis berlandieri×V. rupestris cv. 1103P) and a non-drought-tolerant root system (Vitis riparia×V. rupestris cv. 101-14Mgt), upon which had been grafted the same drought-sensitive clone of Vitis vinifera cv. Merlot. Leaf water potentials (ψ(L)) for Merlot grafted onto the 1103P root system (-0.91±0.02 MPa) were +0.15 MPa higher than Merlot on 101-14Mgt (-1.06±0.03 MPa) during spring, but dropped by approximately -0.4 MPa from spring to autumn, and were significantly lower by -0.15 MPa (-1.43±0.02 MPa) than for Merlot on 101-14Mgt (at -1.28±0.02 MPa). Surprisingly, g(s) of Merlot on the drought-tolerant root system (1103P) was less down-regulated and canopies maintained evaporative fluxes ranging from 35-20 mmol vine(-1) s(-1) during the diurnal peak from spring to autumn, respectively, three times greater than those measured for Merlot on the drought-sensitive rootstock 101-14Mgt. The drought-tolerant root system grew more roots at depth during the warm summer dry period, and the whole root system conductance (k(r)) increased from 0.004 to 0.009 kg MPa(-1) s(-1) during that same time period. The changes in k(r) could not be explained by xylem anatomy or conductivity changes of individual root segments. Thus, the manner in which drought tolerance was conveyed to the drought-sensitive clone appeared to arise from deep root proliferation during the hottest and driest part of the season, rather than through changes in xylem structure, xylem density or stomatal regulation. This information can be useful to growers on a site-specific basis in selecting rootstocks for grape clonal material (scions) grafted to them.

Individual traits as determinants of time to death under extreme drought in Pinus sylvestris L.

Plants exhibit a variety of drought responses involving multiple interacting traits and processes, which makes predictions of drought survival challenging. Careful evaluation of responses within species, where individuals share broadly similar drought resistance strategies, can provide insight into the relative importance of different traits and processes. We subjected Pinus sylvestris L. saplings to extreme drought (no watering) leading to death in a greenhouse to (i) determine the relative effect of predisposing factors and responses to drought on survival time, (ii) identify and rank the importance of key predictors of time to death and (iii) compare individual characteristics of dead and surviving trees sampled concurrently. Time until death varied over 3 months among individual trees (from 29 to 147 days). Survival time was best predicted (higher explained variance and impact on the median survival time) by variables related to carbon uptake and carbon/water economy before and during drought. Trees with higher concentrations of monosaccharides before the beginning of the drought treatment and with higher assimilation rates prior to and during the treatment survived longer (median survival time increased 25-70 days), even at the expense of higher water loss. Dead trees exhibited less than half the amount of nonstructural carbohydrates (NSCs) in branches, stem and relative to surviving trees sampled concurrently. Overall, our results indicate that the maintenance of carbon assimilation to prevent acute depletion of NSC content above some critical level appears to be the main factor explaining survival time of P. sylvestris trees under extreme drought.

Uptake of microcontaminants by crops irrigated with reclaimed water and groundwater under real field greenhouse conditions.

The use of reclaimed water for agricultural irrigation has emerged as a new strategy for coping with water scarcity in semiarid countries. However, the incorporation of the organic microcontaminants in such water into the diet through crop uptake poses a potential risk to human health. This paper aims to assess the presence of organic microcontaminants in different crops irrigated with groundwater and reclaimed water (secondary or tertiary effluents) in a greenhouse experiment. The determination of microcontaminants in water and vegetation samples was performed by solid-phase extraction and matrix solid-phase dispersion procedure with GC-MS/MS, respectively. The presence of nitrates in the groundwater used for irrigation increased biomass production by a higher proportion than the harvest index. The concentration of microcontaminants in lettuce, carrots, and green beans ranged from less than the limit of quantitation to 571 ng g(-1) (fresh weight). Tributyl phosphate and butylated hydroxyanisole exhibited the highest concentration levels in crops. The concentration and frequency of detection of microcontaminants were lower in green bean pods than in green bean roots and leaves. Although the concentrations were generally low, the simultaneous presence of a variety of microcontaminants should be taken into consideration when assessing the risk to human health.