Roberta Marchesini

Use of moss (Tortula muralis Hedw.) for monitoring organic and inorganic air pollution in urban and rural sites in Northern Italy

Abstract Concentrations of polycyclic aromatic hydrocarbons (PAHs) and trace metals, as well as stable nitrogen (N) isotope composition, were determined in moss tissues from an urban area and from rural sites in northern Italy. The total PAH contents were higher in the urban area. The percentage fraction of low molecular weight volatile PAHs on total PAHs was greater in rural sites. The mean concentration ratio (urban:rural) was, overall, much lower for trace metals than for PAHs. Among metals, only Pb levels were highest in the city center, and were, in turn, associated with a more positive δ15N signature in moss tissue. This indicates that exposure to slow-moving traffic in the city center resulted both in higher Pb deposition and a greater contribution of NOx, compared with NHx, in atmospheric N pollution. Most metals (namely Cd, Cr, Fe, Ni, V and Zn) were moderately enriched in moss tissues from the urban area, especially in the sectors downwind from the main emission sources. In contrast, Co and Cu contents in the urban area did not differ from those in rural sites. We concluded that organic (PAH) and inorganic (metal) pollution showed varying patterns which reflected differences as regards both emission sources and atmospheric transport pathways. Atmospheric deposition of PAHs peaked in close vicinity to urban emission sources. Conversely, the atmospheric deposition of metals, except Pb, was more diffuse over the territory.

Monitoring of heavy metal deposition in Northern Italy by moss analysis

A survey of heavy metal deposition in the mountainous territories of Northern Italy was carried out in 1995-96. Moss samples (mainly Hylocomium splendens) were collected in a dense network of sites (about 3.2 sites/1000 km(2)) and the data of metal concentrations in moss tissues were statistically correlated with environmental and climatic factors, as well as with bulk deposition of elements and elemental concentrations in the soil. Three main geographic patterns of metal concentration in mosses could be defined: (1) Fe, Ni, and Cr, all derived both by soil particulates and anthropogenic emissions connected with ferrous metal manufacturing, were mostly concentrated in Northwestern Italy; (2) Cu and Zn, as typical multi-source elements, showed rather high concentrations with little ranges of variation over the whole area and small peaks reflecting local source points; (3) Cd and Pb reflected long-distance transport and showed highest concentrations in the regions with highest precipitation, especially in the Eastern Alps.

Element concentrations in the forest moss Hylocomium splendens: variation associated with altitude, net primary production and soil chemistry

Net primary production (NPP) of the forest moss Hylocomium splendens increased significantly along an elevational gradient in the southern Alps of Italy. Extracellularly bound metals (Al, Ca, Co, Cr, Fe, Ni, Mo, Ni, Pb) showed declining concentrations in moss tissue with increasing altitude, presumably because the amount of exchange sites on the cell wall increases less than total biomass. Concentrations of intracellular elements did not vary (Cd, Cu, Mg, Na, Zn), or even increased (K) with altitude. The observed patterns were always independent of precipitation amount and soil concentrations of exchangeable elements. A higher soil nutrient status only enhanced K uptake by the moss. We concluded that variations in moss NPP, associated with elevational gradients, may significantly affect estimates of atmospheric deposition based on moss analysis in mountainous regions.

Reed (Phragmites australis) decline in a brackish wetland in Italy

A comparative field study was carried out at two sites (a healthy site and a declining site) in a brackish wetland in northern Italy, with the objective to investigate the symptoms and the possible causes leading to reed (Phragmites australis) decline in this area. The declining reed plants presented many of the symptoms (clumping habit, smaller size, weaker culms, abnormal rhizome and root anatomy, low starch levels in rhizomes) comprised within the so-called reed die-back syndrome, frequently observed in central European wetlands but never recorded previously in (Sub)Mediterranean regions. Soil nutrient levels did not differ much between the two sites, with nitrate concentrations in the soil being even higher at the healthy site (1.54 microg g(-1); die-back site 0.76 microg g(-1)). Hence, eutrophication did not seem to represent a major cause in determining reed decline in this area. High sulphate concentrations in saltwater associated with low soil redox potentials (-215 mV) due to waterlogging resulted in high soil sulphide concentrations. Concentrations of organic acids, especially acetic acid, did not differ remarkably between sites. High sulphide levels presumably accounted for abnormal anatomical formations (callus blocking aerenchyma channels), lower rates of net CO2 exchange and reduced reserve storage, observed at the die-back site. This was associated with a lower mechanical resistance of reed culms which accelerated reed mortality in the die-back areas. We concluded that high sulpihde levels in permanently waterlogged soils may result in die-back of reed stands in Mediterranean wetlands.

Monitoring temporal trends of air pollution in an urban area using mosses and lichens as biomonitors

Monitoring air quality by using living organisms as biomonitors has received increasing attention in recent years. However, rather few studies were based on the concomitant use of passive biomonitoring (based on the different sensitivity of living organisms to air pollution) and active biomonitoring (based on their capacity to accumulate pollutants in the tissues). We carried out a repeated survey of an urban area in Northern Italy, with the objective of comparing temporal trends of different kinds of air pollutants with bioindication (passive biomonitoring) and bioaccumulation (active biomonitoring) techniques. During a five-year interval, temporal patterns of moss metal concentrations underwent significant changes probably due to intercurring variations in the importance of different pollution sources. Nitrogen (N) concentration in moss tissues also decreased and was paralleled by increasing diversity of epiphytic lichens. Increasing δ(15)N in moss tissues suggested a higher contribution of oxidized N species compared with reduced N species.

Nutrient and carbon relations in subalpine dwarf shrubs after neighbour removal or fertilization in northern Italy

Two subalpine dwarf-shrub heath communities with differing levels of soil nutrient availability were subjected to a 3-year experimental manipulation, including nutrient addition or removal of one of the two co-dominant species from each community. The main objective of our study was to assess the relative importance of interspecific competition versus nutrient limitation in relation to soil fertility. We also aimed to investigate if and to what extent current-year shoot size, leaf-based rates of net photosynthesis and foliar nutrient status accounted for the observed changes in the aboveground biomass of the shrubs. At the end of the experiment, neighbour removal increased the aboveground biomass of all shrubs, especially in the more fertile community, while fertilization did not. We concluded that: (1) competition is more effective than nutrient limitation in structuring the vegetation of subalpine heathlands; and (2) competition intensity is stronger in the more fertile community. The observed patterns of variations in aboveground biomass were not consistently related to net photosynthetic rates, size of individual shoots and foliar nutrient status. Hence, we also concluded that the growth response of dwarf shrubs to altered environmental conditions is primarily determined by developmental plasticity.

Growth Response of Sphagnum capillifolium to Nighttime Temperature and Nutrient Level: Mechanisms and Implications for Global Change

Individuals of Sphagnum capillifolium were cultured for 2 mo under six different combinations of nighttime temperature and nutrients. Low nighttime temperature caused a five-fold reduction of growth. Growth was also reduced when the plants were cultured without any addition of nutrient in the growing medium, but only when nutrient deficiency was coupled with high nighttime temperature. Growth reduction was associated with decreased rates of net photosynthesis, but was not accompanied by a degradation of photosynthetic pigments and/or variations in the pigment ratios, nor was the ultrastructure of chloroplasts significantly altered. The decline in the net photosynthetic rate may be due to a limitation in the enzymatic reactions at unfavorable temperatures. Nitrogen and, especially, phosphorus appeared to limit growth of Sphagnum capillifolium at optimal temperatures. A nighttime temperature of 50C was above the lower threshold triggering the synthesis of red wall-pigments, known to be promoted by nighttime chilling. Climate warming is expected to increase the growth rates of Sphagnum, but the consequences on the carbon balance of peatlands cannot be predicted because temperature rise may also enhance breakdown of peat.

Re-cultivation of Neochloris oleoabundans in exhausted autotrophic and mixotrophic media: the potential role of polyamines and free fatty acids

Neochloris oleoabundans (Chlorophyta) is widely considered one of the most promising microalgae for biotechnological applications. However, the large-scale production of microalgae requires large amounts of water. In this perspective, the possibility of using exhausted growth media for the re-cultivation of N. oleoabundans was investigated in order to simultaneously make the cultivation more economically feasible and environmentally sustainable. Experiments were performed by testing the following media: autotrophic exhausted medium (E+) and mixotrophic exhausted medium after cultivation with glucose (EG+) of N. oleoabundans cells grown in a 20-L photobioreactor (PBR). Both exhausted media were replenished with the same amounts of nitrate and phosphate as the control brackish medium (C). Growth kinetics, nitrate and phosphate consumption, photosynthetic pigments content, photosynthetic efficiency, cell morphology, and lipid production were evaluated. Moreover, the free fatty acid (FFA) composition of exhausted media and the polyamine (PA) concentrations of both algae and media were analyzed in order to test if some molecules, released into the medium, could influence algal growth and metabolism. Results showed that N. oleoabundans can efficiently grow in both exhausted media, if appropriately replenished with the main nutrients (E+ and EG+), especially in E+ and to the same extent as in C medium. Growth promotion of N. oleoabundans was attributed to PAs and alteration of the photosynthetic apparatus to FFAs. Taken together, results show that recycling growth medium is a suitable solution to obtain good N. oleoabundans biomass concentrations, while providing a more sustainable ecological impact on water resources.