Four species of trees were selected to evaluate the tolerance to heavy crude oil contamination by means of a tolerance index integrating germination, height, biomass and survival as variables. Fresh seeds to Cedrela odorata (tropical cedar), Haematoxylum campechianum (tinto bush), Swietenia macrophylla (mahogany) and Tabebuia rosea (macuilis) were planted in a Vertisol to which heavy crude petroleum was added at four different treatments (C0, 0; C1, 18,940; C2, 44,000; and C3, 57,000 mg kg⁻¹), with the control being uncontaminated soil. The experiment was carried out in a greenhouse during 203 days with a completely random design. The presence of petroleum in soil stimulated and increased germination of S. macrophylla and C. odorata, accelerated the germination of T. rosea and did not affect the germination of H. campechianum. The height and biomass of all species was reduced in the presence of petroleum in the soil. The survival of S. macrophylla and H. campechianum was not affected by petroleum at any concentration studied. On the other hand, C. odorata and T. rosea showed high mortality at all concentrations. The tolerance index showed that S. macrophylla was best at tolerating petroleum in soil and could be employed as a productive alternative for the advantageous use of contaminated sites. The use of tree species could be important because of the great potential of trees for phytoremediation due to their long life, biomass and deep roots that can penetrate and remediate deeper soil layers.

The effect of chronic high groundwater nitrate loading on riparian forests is poorly understood. The growth patterns of northern white cedar (Thuja occidentalis) and related plant–soil processes were examined at four riparian sites in southern Ontario, Canada which have similar vegetation, soils, and hydrology but have differed in adjacent land use for >60 years. Fertilized cropland at two riparian sites produced groundwater-fed surface flows with high mean NO3–N concentrations of 9 and 31 mg l−1, whereas mean concentrations were <0.5 mg l−1 at two control sites down slope from forest. Tree-ring analysis at the two nitrate-rich sites indicated a positive growth trend in 1980–2004 and an absence of a positive growth trend in the 1945–1970 period that preceded high rates of synthetic nitrogen fertilizer use on cropland. However, a significant increase in growth also occurred in 1980–2004 at the two control riparian sites suggesting that high groundwater nitrate inputs did not influence tree growth. Cedar foliar and litter N content did not differ significantly between the high nitrate and control sites. Litter decomposition rates measured by the litterbag technique at a nitrate-enriched and control site were similar. Litter from a high nitrate and a control site produced a similar rate of potential denitrification in lab incubations of riparian surface peat. This study indicates that prolonged nitrate inputs in groundwater did not increase nitrogen uptake and growth of white cedar or stimulate decomposition and denitrification as a result of changes in the quality of plant material. In the absence of anthropogenic nitrate inputs, riparian wetland soils are typically high in ammonium and low in nitrate, and as a consequence, white cedar may have a limited ability to utilize nitrate.

Background, aim, and scope Carbonyl compounds have been paid more and more attention because some carbonyl species have been proven to be carcinogenic or a risk for human health. Plant leaves are both an important emission source and an important sink of carbonyl compounds. But the research on carbonyl compounds from plant leaves is very scarce. In order to make an approach to the emission mechanism of plant leaves, a new method was established to extract carbonyl compounds from fresh plant leaves. Materials, methods, and results The procedure combining derivatization with ultrasonication was developed for the fast extraction of carbonyl compounds from tree leaves. Fresh leaves (< 0.01 g) were minced and ultrasonicated in acidic 2,4-dinitrophenylhydrazine (DNPH)-acetonitrile solution for 30 min and then holding 30 min to allow aldehydes and ketones in leaves to react completely with DNPH. Conclusions The extraction process was performed under room temperature and only took 60 min. The advantages of this method were very little sample preparation, requiring short treatment time and usual equipment. Four greening trees, i.e., camphor tree (Cinnamomum camphora), sweet olive (Osmanthus fragrans), cedar (Cedrus deodara), and dawn redwood (Metasequoia glyptostroboides), were selected and extracted by this method. Seven carbonyl compounds, including formaldehyde, acetaldehyde, acetone, acrolein, p-tolualdehyde, m/o-tolualdehyde, and hexaldehyde were determined and quantified. The most common carbonyl species of the four tree leaves were formaldehyde, acrolein, and m/o-tolualdehyde. They accounted for 67.3% in cedar, 50.8% in sweet olive, 45.8% in dawn redwood, and 44.6% in camphor tree, respectively. Camphor tree had the highest leaf level of m/o-tolualdehyde with 15.0 ± 3.4 µg g⁻¹(fresh leaf weight), which indicated that camphor tree may be a bioindicator of the level of tolualdehyde or xylene in the atmosphere. By analyzing carbonyl compounds from different tree leaves, it is not only helpful for further studying the relationship between sink and emission of carbonyls from plants, but also helpful for exploring optimum plant population in urban greening.