Epidemiological studies demonstrated that the exposure of different air pollutants including particulate matter (PM) has been related to adverse effect on immune system. Current study was designed to investigate cytokines in blood plasma of adolescent persons continuously exposed to different degrees of ambient air pollutions. Tumor necrosis factor-α (TNF-α), interleukin 6 (IL-6), IL-12p40, and IL-10 were chosen as cytokines of proinflammatory and anti-inflammatory immune response. The peripheral venous blood was taken from adolescents living in the cities of Stara Zagora region, Southeast Bulgaria, that is, in Stara Zagora, Kazanlak, and Chirpan. The quantity of cytokines in plasma samples was determined by enzyme-linked immunosorbent assay. Results demonstrated that youths living in Stara Zagora showed significantly smaller quantity of TNF-α, compared with adolescents from Kazanlak and Chirpan. Moreover, adolescents living in Stara Zagora showed significantly higher quantity of IL-10 than students from Kazanlak and Chirpan. Analysis of the data of air quality gives reason to assert that PM10 and PM2.5 have been the main atmospheric pollutants around the monitoring points. The complex air quality assessment based on these criteria determined that the highest air pollution was in the city of Stara Zagora, followed by Chirpan and the relatively unpolluted town was Kazanlak. We concluded that air pollutants, mostly PM2.5, can modulate cytokine production and can change the balance between proinflammatory TNF-α and anti-inflammatory IL-10 production. Increased levels of IL-10 combined with decreased level of TNF-α in adolescents living in Stara Zagora can serve as a biomarker for suppression of T helper 1 (Th1) cell-mediated immunity and exacerbation of Th2 humoral immune response and could be a prerequisite for the development of allergic and autoimmune diseases.

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Municipal green waste (MGW) has significantly increased with the development of urban green areas, and its utilization by composting is a good alternative to solve the problem. This paper presents the results from the quality assessment of two industrial composts (from the composting facility of a regional nonhazardous waste landfill) based on their physicochemical properties, hygienic safety (microbiological parameters), fertilizing potential (by fertilizing index, FI) and heavy metal polluting potential (by clean index, CI). Compost 1 (C1) was made from MGW (100%) and Compost 2 (C2) was made from MGW (75%) and discarded green peppers (25%). The evaluation of physicochemical parameters was conducted according to Bulgarian Standards (BDS) methods and microbiological analysis using selective, chromogenic detection systems. It was found that the EC, P, K, Mg, Cu, Cr and Ni were lower for C1 (p < 0.05–0.001). On the other hand, Pb concentration was higher compared to C2 (p < 0.001); the concentrations of Cd, Hg and the E. coli were very low for both composts; presence of Salmonella was not detected. The estimated quality indexes (FI and CI) classified C1 as Class B compost (very-good-quality compost with medium fertilizing potential) and C2 as Class A compost (best-quality compost with high soil fertility potential and low heavy metal content). The C1 and C2 composts meet the requirements of EU and Bulgarian legislation and can be used as soil fertilizers.

The temporal concentration variations and spatial distribution of nitrogen compounds (nitrate, nitrite, ammonium) in the natural surface waters of Stara Zagora Region, Bulgaria, over a period of 1 year were assessed in the present study. Nitratenitrogen concentrations in all surface water samples, except for the December value -21.8 mg/L in Zetyovo Reservoir, were within the permissible national quality standards. NO2 --N could be classified as a priority pollutant of Chirpan and Zetyovo Reservoirs waters. The greatest extent of NH4 + -N pollution was registered in Chirpan Reservoir surface waters. The correlation study revealed appreciable mutual relationship only between NH4 + -N and NO2 --N in the surface waters. The hierarchical cluster analysis (HCA) exhibited divergent apportionment of nitrogen compounds in the surface water bodies. bs_bs_banner Water and Environment Journal. Print

Municipal solid waste (MSW) landfills are among the major sources of greenhouse gas (GHG) emissions affecting global warming and the Earth’s climate. In Bulgaria, 53 regional non-hazardous waste landfills (RNHWL) are in operation, which necessitates conducting studies to determine the environmental risk from the emitted GHGs. This study attempted to assess the CH4 and CO2 emissions from three gas wells of a cell (in active and closed phases, each of 2.5 years duration) in an RNHWL, Harmanli (41°54′24.29″ N; 25°53′45.17″ E), based on monthly in situ measurements by portable equipment, using the Interrupted Time Series (ITS) ARMA model. The obtained results showed a significant variation of the CH4 and CO2 concentrations (2.06–15.1% v/v) and of the CH4 and CO2 emission rates (172.81–1762.76 kg/y) by gas wells (GWs), months and years, indicating the dynamics of the biodegradation of the deposited waste in the areas of the three GWs. Throughout most of the monitoring period (2018–2022), the CH4 concentrations were higher than the CO2 concentrations (% v/v), while CO2 emissions were lower than CH4 emissions (kg/y), a fact that could be explained by the differences in the mass of the two gases. The emissions rates of both gases from GW2 dominated over those from GW1 and GW3, giving a reason to determine the zone of GW2 as a hotspot of Cell-1. On the whole, CH4 and CO2 emission rates were higher in the winter (December–February) and partly in the spring (March–May) compared to summer–autumn (June–November). However, the CH4 and CO2 concentrations and emissions decreased drastically after the Cell-1 closure. The CH4/CO2 ratio (0.68–2.01) by months and gas wells demonstrated a great sensitivity, making it a suitable indicator for the assessment of organic waste biodegradation level in the landfills. The ITS ARMA model confirmed the negative and significant effect of the cell closure on CH4 and CO2 emissions; the correlations found between predicted and observed values were strong and positive (0.739–0.896).