Integrative evaluation of data derived from biomonitoring and models indicating atmospheric deposition of heavy metals

Moss biomass as effective biosorbents for heavy metals in contaminated water

The study explored batch adsorption of Cd(II) and Pb(II) ions using moss biomass from Barbula consanguinea and Hyophila involuta, assessing removal efficiency concerning various parameters. Both moss species showed high removal rates for Cd(II) (87 % for B. consanguinea and 89 % for H. involuta) and Pb(II) (93 % for B. consanguinea and 94 % for H. involuta) from contaminated water, reaching equilibrium within 30 min. While Cd(II) removal was pH-independent, Pb(II) removal showed pH-dependence, peaking at pH 5.0-5.5. Adsorption isotherm analysis indicated that the Langmuir, Freundlich, Elovich, Sips, and Redlich-Peterson models best described Cd(II) and Pb(II) adsorption onto both moss species (except for Cd(II) adsorption onto H. involuta), with R 2  > 0.98. This confirms a heterogeneous surface with both monolayer and multilayer adsorption sites. The pseudo-second-order kinetic model confirmed chemisorption on moss biomass from both species. FTIR spectra identified major binding sites such as phenols, alkaloids, amines, alkenes, nitro compounds, and low-molecular-weight carbohydrates. EDS analysis validated the bonding of Cd(II) and Pb(II) ions to the biomass surface by displacing Ca(II) ions. According to the Langmuir model, moss biomass exhibited selective adsorption, favoring Pb(II) over Cd(II). B. consanguinea showed a higher adsorption capacity than H. involuta, which is attributed to its higher negative zeta potential. This study underscores the novelty of moss biomass for heavy metal removal in wastewater treatment, highlighting its sustainability, effectiveness, cost-efficiency, versatility, and eco-friendliness.

Simulation of Heavy Metals Migration in Soil-Wheat System of Mining Area

Heavy metals in the soil of mining areas have become a primary source of pollution, which could cause deleterious health effects in people exposed through soil-plant systems via multi-pathways. A long-term field experiment under natural conditions was carried out to explore the distribution characteristic and migration law of heavy metals in a soil-wheat system of a mining area in Xuzhou. According to the second level standard of environmental quality standards for soils of China (GB 15618-1995), 30.8 g of CrCl₃·6H₂O, 8.3 g of Pb(CH₃COO)₂·3H₂O, and 16.5 g of ZnSO₄·7H₂O were added into the soil of three experimental sites, respectively. The other experimental site with no additional compounds was used as the control site. The Cr, Pb, and Zn concentrations in the soil-wheat system were counted and their corresponding migration models were constructed. From 2014 to 2017, the mean concentrations of Cr (49.09 mg·kg⁻¹), Pb (20.08 mg·kg⁻¹), and Zn (39.11 mg·kg⁻¹) in the soil of the addition sites were higher than that of the control site. The mean concentrations of Cr, Pb, and Zn in wheat of the addition sites were greater than that of the control site with the values of 3.29, 0.06, and 29 mg·kg⁻¹. In comparison, the Cr, Pb, and Zn concentrations in the soil of all experimental sites were lower than the second level standard of environmental quality standards for soils of China (GB 15618-1995), whereas the Cr concentration exceeded its corresponding soil background value of Xuzhou in 2017. The Pb concentration in soil of the addition site was greater than its corresponding background value from 2014 to 2016. The Pb and Zn concentrations in wheat of all experimental sites were lower than the national hygienic standard for grains of China (GB2715-2005) and the national guidelines for cereals of China (NY 861-2004), but the Cr concentration significantly exceeded the national guidelines for cereals of China (NY 861-2004). By constructing the Identical-Discrepant-Contrary (IDC) gray connection models, the result showed that there was a non-linear relationship of Cr, Pb, and Zn concentrations in the soil-wheat system, and the absolute values of most correlation coefficients r were lower than 0.5 and the values of greyness fG(r) were more than 0.5. The curvilinear regression models could not reflect the relationship of Cr, Pb, and Zn concentrations in the soil-wheat system with the regression coefficient r2 values far less than 1. Due to the values of regression coefficient r2 being close to 1, this study suggested that the allocation estimation models could be used for simulating the Cr, Pb, and Zn migration in the soil-wheat system of a mining area in Xuzhou.

Modelling spatial patterns of correlations between concentrations of heavy metals in mosses and atmospheric deposition in 2010 across Europe

BACKGROUND

This paper aims to investigate the correlations between the concentrations of nine heavy metals in moss and atmospheric deposition within ecological land classes covering Europe. Additionally, it is examined to what extent the statistical relations are affected by the land use around the moss sampling sites. Based on moss data collected in 2010/2011 throughout Europe and data on total atmospheric deposition modelled by two chemical transport models (EMEP MSC-E, LOTOS-EUROS), correlation coefficients between concentrations of heavy metals in moss and in modelled atmospheric deposition were specified for spatial subsamples defined by ecological land classes of Europe (ELCE) as a spatial reference system. Linear discriminant analysis (LDA) and logistic regression (LR) were then used to separate moss sampling sites regarding their contribution to the strength of correlation considering the areal percentage of urban, agricultural and forestry land use around the sampling location. After verification LDA models by LR, LDA models were used to transform spatial information on the land use to maps of potential correlation levels, applicable for future network planning in the European Moss Survey.

RESULTS

Correlations between concentrations of heavy metals in moss and in modelled atmospheric deposition were found to be specific for elements and ELCE units. Land use around the sampling sites mainly influences the correlation level. Small radiuses around the sampling sites examined (5 km) are more relevant for Cd, Cu, Ni, and Zn, while the areal percentage of urban and agricultural land use within large radiuses (75-100 km) is more relevant for As, Cr, Hg, Pb, and V. Most valid LDA models pattern with error rates of < 40% were found for As, Cr, Cu, Hg, Pb, and V. Land use-dependent predictions of spatial patterns split up Europe into investigation areas revealing potentially high (= above-average) or low (= below-average) correlation coefficients.

CONCLUSIONS

LDA is an eligible method identifying and ranking boundary conditions of correlations between atmospheric deposition and respective concentrations of heavy metals in moss and related mapping considering the influence of the land use around moss sampling sites.

(Persistent) Organic pollutants in Germany: results from a pilot study within the 2015 moss survey

BACKGROUND

Since 1990, every 5 years, moss sampling is conducted within the European moss monitoring programme to assess the atmospheric deposition of airborne pollutants. Besides many other countries, Germany takes regularly part at these evaluations. Within the European moss monitoring 2015, more than 400 moss samples across Germany were taken according to a harmonized methodology for the assessment heavy metal and nitrogen input. In a pilot programme, eight of these sites were chosen for additional investigations on a broad range of organic contaminants to evaluate their accumulation in moss and thereby their presence in atmospheric deposition in Germany. Target compound classes comprised polycyclic aromatic hydrocarbons (PAH), polychlorinated dibenzodioxins and -furans (PCDD/F), dioxin-like and non-dioxin-like polychlorinated biphenyls (dl-PCB, ndl-PCB), polyfluorinated alkyl substances, classical flame retardants as well as emerging chlorinated and brominated flame retardants. In total, 120 target compounds were analysed. For some analytes, comparisons of accumulation in moss and tree leave samples were possible.

RESULTS

Except for certain flame retardants, PFAS, and ndl-PCB, substances of all other compound classes could be quantified in moss samples of all sites. Concentrations were highest for PAH (40-268 ng g-1) followed by emerging flame retardants (0.5-7.7 ng g-1), polybrominated diphenyl ethers (PBDE; 0.3-3.7 ng g-1), hexabromocyclododecane (HBCD; 0.3-1.2 ng g-1), dl-PCB (0.04-0.4 ng g-1) and PCDD/F (0.008-0.06 ng g-1).

CONCLUSIONS

Results show the widespread atmospheric distribution and deposition of organic contaminants across Germany as well as the suitability of moss as bioaccumulation monitor for most of these compound classes. Compared to nearby tree leaf samples, accumulation potential of moss appeared to be higher for pollutants of high octanol-air partition coefficient (KOA) and octanol-water partition coefficient (KOW).

Evaluation of the impact of reducing national emissions of SO2 and metals in Poland on background pollution using a bioindication method

Changes in environmental pollution by S, Cd, Cu, Pb and Zn in 2006–2014 were evaluated using a bioindication method. This method was based on measurements of pollutants in Scots pine (Pinus sylvestris L.) needles. The measurements were performed in the Chojnowskie Forests, a region recognized as a background area for central Poland. The changes in the contents of sulfur (S) and metals in needles were not comparable with the changes in the global emissions of the pollutants in Poland. On average, the pollution level in the study area decreased by 9.9% for S, 61.4% for Pb, 22.5% for Cd, 11.7% for Zn and 10.4% for Cu. During the same period, global emissions in Poland decreased by 38.1% for S, 8.0% for Pb, 63.2% for Cd, 11.7% for Zn and 14.0% for Cu. Therefore, the differences in the changes in emissions and the needle contents of each element should be examined separately which was not a goal of this study. However, the discrepancy between these results did not prevent the use of bioindication methods. Evaluation of pollutant contents in plants reflected their incorporation in biological processes rather than air or soil pollution levels.

Using Moss to Assess Airborne Heavy Metal Pollution in Taizhou, China

Bryophytes act as bioindicators and bioaccumulators of metal deposition in the environment. To understand the atmospheric deposition of heavy metals (cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), nickel (Ni), lead (Pb), and zinc (Zn)) in Taizhou, East China, samples of moss (Haplocladium microphyllum) were collected from 60 sites selected by a systematic sampling method during the summer of 2012, and the concentrations of these heavy metals were determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES). The results suggested that the concentrations of these metals varied moderately among different sites, indicating a similar contamination level for each element throughout the monitoring region. The mean values under investigation were higher than those from neighboring cities, such as Wuxi, Xuzhou, and Nanjing, and much higher than those in Europe based on a 2010 survey. Significant (p < 0.01) correlations were identified among some of the heavy metals, suggesting that these originated from identical sources. There was no statistically significant correlation between Hg and all the other elements. Spatial distribution maps of the elements over the sampled territory were created using Arc-GIS 9.0. The potential ecological risk index indicated that the air was heavily polluted by Cd and Hg, and that there was a considerable potential ecological risk from all the heavy metals studied.