Stable sulfur isotope analysis of SO2 pollution impact on vegetation

Significance of the long-term biomonitoring studies for understanding the impact of pollutants on the environment based on a synthesis of 25-year biomonitoring in the Holy Cross Mountains, Poland

This review presents compiled results of complex biomonitoring studies that have been conducted in the Holy Cross Mountains, south-central part of Poland, since the 1990s. The significance of these studies results from several aspects: (i) a number and a variety of plant organisms used, e.g., mosses, lichens, coniferous and deciduous trees, and their tissues (wood, bark, needles, leaves, the aboveground parts of several vascular plants); (ii) applications of a broad scope of instrumental methods aiming at determining major and trace elements (including rare earth elements), organic compounds (PAHs, PCBs, phenols), and stable sulfur isotopes (δ³⁴S); and (iii) different methodological and environmental issues addressed. The comparison and interpretation of results derived from seventeen sampling campaigns carried out between 1994 and 2017 are a valuable source of information on the following: (i) bioaccumulative properties of organisms used in air quality monitoring, (ii) identification and variations of local and regional pollution sources and geochemical landscape patterns and processes over years, and (iii) establishing environmental factors that variously affected chemical composition of plants growing under physiological stress, including roadside vegetation and plants from acid mine drainage areas.

δ(34)S values and S concentrations in native and transplanted Pleurozium schreberi in a heavily industrialised area

Sulphur is an element found in surplus in anthropogenic areas and one of the minerals responsible for the development of acid rains. The analysis of stable S isotopes provides a powerful tool for studying various aspects of the biogeochemical circulation of sulphur. δ(34)S values and S concentrations were determined in a 90-day experiment with the native moss Pleurozium schreberi from rural, urban and industrial sites in Upper Silesia in southern Poland. At the same time P. schreberi from a control site was transplanted to the same rural, urban and industrial sites and the δ(34)S values and S concentrations were determined in the same 90-day experiment. (34)S enrichment (up to 4.7‰) in the mosses tested indicates that these plants responded to environmental pollution stress. Sulphur isotopic composition in the transplanted P. schreberi was related to S concentrations in this species after 90 days of the experiment. Higher δ(34)S values and S concentrations were noted in native mosses than in those transplanted from rural and urban sites while an opposite situation was reported in industrial sites. The transplanted P. schreberi was a better sulphur bioindicator than the native moss in more polluted industrial sites and worse in less polluted rural and urban sites.

Disentangling natural and anthropogenic sources of atmospheric sulfur in an industrial region using biomonitors

Despite reductions in atmospheric sulfur (S) concentrations due to abatement policies in some countries, modeling the dispersion of this pollutant and disentangling anthropogenic sources from natural ones is still of great concern. Lichens have been used as biomonitors of the impacts of S for over 40 years, but their potential as source-tracers of specific sources, including natural ones, remains unexplored. In fact, few attempts have been made to try to distinguish and spatially model different sources of S using lichens. We have measured S concentrations and isotopic values in lichens within an industrial coastal region where different sources of S, natural and anthropogenic, interplay. We detected a prevailing influence of natural sea-originated S that mixed with anthropogenic sources of S. We were then able to disentangle the sources of S, by removing the ocean influence on S isotopic values, enabling us to model the impact of different anthropogenic sources on S deposition and highlighting the potential use of lichens to evaluate the weight of different types of anthropogenic sources.

Indicating atmospheric sulfur by means of S-isotope in leaves of the plane, osmanthus and camphor trees

Foliar δ(34)S values of three soil-growing plant species (Platanus Orientalis L., Osmanthus fragrans L. and Cinnamomum camphora) have been analyzed to indicate atmospheric sulfur. The foliar δ(34)S values of the three plant species averaged -3.11±1.94‰, similar to those of both soil sulfur (-3.73±1.04‰) and rainwater sulfate (-3.07±2.74‰). This may indicate that little isotopic fractionation had taken place in the process of sulfur uptake by root or leaves. The δ(34)S values changed little in the transition from mature leaves to old/senescing leaves for both the plane tree and the osmanthus tree, suggestive of little isotope effect during sulfur redistribution in plant tissues. Significantly linear correlation between δ(34)S values of leaves and rainwater sulfate for the plane and osmanthus trees allowed the tracing of temporal variations of atmospheric sulfur by means of foliar sulfur isotope, while foliage δ(34)S values of the camphor is not an effective indicator of atmospheric sulfur.

Stable sulphur isotope ratios in the moss species Hylocomium splendens (Hedw.) B.S.G. and Pleurozium schreberi (Brid.) Mitt. from the Kielce area (south-central Poland)

Stable sulphur isotope determinations were performed on 18 moss samples collected at nine sites in forested areas of the city of Kielce. The delta(34)S of Hylocomium splendens varied from 4.4 to 7.1 per thousand, whereas the delta(34)S of Pleurozium schreberi was in the range of 3.7-9.1 per thousand. The Holy Cross Mountains mosses display a positive delta(34)S signature of airborne SO(2) and sulphates of anthropogenic origin, which is characteristic for this part of Europe. Some spatial variations in the delta(34)S of mosses are due to the interactions that occur between coal combustion emissions with diverse isotopic imprints, variations in wind direction and topographic features combined with biological fractionation.

Assessment of atmospheric sulfur with the epilithic moss Haplocladium microphyllum: evidences from tissue sulfur and delta34S analysis

The application of geochemical signals in mosses is more and more popular to investigate the deposition of atmospheric pollutants, but it is unclear whether records of atmospheric sulfur in mosses differ between their diverse habitats. This study aimed to investigate the influence of growing condition on tissue sulfur and delta34S of Haplocladium microphyllum. Epilithic and terricolous mosses in open fields, mosses under different canopy conditions were considered. We found that tissue sulfur and delta34S of mosses under different habitats were not consistent and could not be compared for atmospheric sulfur research with each other even collected at the same site, moss sulfur and delta34S records would be distorted by subsoil and upper canopies in different degrees, which possibly mislead the interpretation of atmospheric sulfur level and sources. Consequently, mosses on open rocks can be used reliably to assess atmospheric-derived sulfur in view of their identical sulfur and delta34S evidences.

Lichens and atmospheric sulphur: what stable isotopes reveal

Stable isotopes expand the range of applications for lichen biomonitoring of atmospheric sulphur.

Responses of Hawaiian Plants to Volcanic Sulfur Dioxide: Stomatal Behavior and Foliar Injury

Hawaiian plants exposed to volcanic sulfur dioxide showed interspecific differences in leaf injury that are related to sulfur dioxide-induced changes in stomatal condutance. Species with leaves that did not close stomata developed either chlorosis or necrosis, whereas leaves of Metrosideros collina closed stomata and showed no visual symptoms of sulfur dioxide stress.

Ecology of SO2 resistance: II. Photosynthetic changes of shrubs in relation to SO2 absorption and stomatal behavior

In an effort to predict SO₂ sensitivity of plants from their morphological and physiological features, the effects of SO₂ on photosynthesis were partitioned between stomatal and nonstomatal components for a drought deciduous shrub, Diplacus aurantiacus, and an evergreen shrub, Heteromeles arbutifolia. As predicted, the drought deciduous shrub had the higher gas conductance, and hence SO₂ absorptance. However, nonstomatal components also play a role in determining SO₂ sensitivity. Apparently a plant with a high intrinsic photosynthetic capacity will be more sensitive to SO₂ than one with a lower capacity.