Agriculture is one of the major fields, where sewage sludge can be used. Its high nutrient content can contribute to the improvement of important soil properties, such as nutrient content, water balance and soil structure. However, sewage sludge may contain hazardous components, such as pathogens and pollutants. Therefore, it is important to monitor the effects of its field application. In this paper, we assessed the impacts of two low-dose (2.5 m3/ha) municipal sewage sludge compost applications (in 2013 and in 2017) in a 5.6 ha arable land in southeast Hungary (near Újkígyós), located in the Hungarian Great Plain. The nutrient and the heavy metal contents in the upper soil layer (0-30 cm) of the studied Chernozem soils were compared between two sampling campaigns in 2013 (before the compost applications) and in 2018 (after the compost applications). Basic soil properties (pH, salinity, humus content, carbonate content, Arany yarn number) complemented with nutrient content (K2O, P2O5, NO2+ NO3) and heavy metal content (Cd, Co, Cr, Cu, Ni, Pb and Zn) analyses were performed. The results show that no significant change can be noticed in the baseline parameters over the 5-year period. The slight increase in the P2O5, NO2+ NO3 content is closely related to the beneficial effects of the sewage sludge deposition. The soil-bound heavy metal load did not increase significantly as a result of the compost treatments, only nickel showed a slight increase in the topsoil. In all cases the heavy metal concentrations did not reach the contamination thresholds set by Hungarian standards. The results provided positive evidences proving that low dose municipal sewage sludge compost disposal on agricultural land is safe, and can be considered as a sustainable soil amendment for agriculture in compliance with legal requirements.

Sewage sludge contains organic matter and micro and macronutrients which are potentially useful for agricultural usage. However, it can be harmful when containing undesirable amounts of organic pollutants, heavy metals, or pathogens. Our study focused on examining the changes in the extractable nutrient, organic matter and heavy metal contents of a Chernozem soil and the alteration of the soil biological activity as a consequence of low-dose municipal sewage sludge compost applications (0.5 t/ha). Sampling campaigns were done in 2018 near Újkígyós (SE Hungary) during which composite soil samples (0–30 cm and 30–60 cm) and groundwater samples were collected for assessing changes in the nutrient and heavy metal concentrations as a result of compost amendments’ use. Additionally, upper soil (0–50 cm) and subsoil (50–80 cm) were sampled for assessing biological parameters, considered to be aerobic and anaerobic soil layers, respectively. Soil samples were analyzed for the basic pedological parameters (pH, organic matter, carbonates and texture), nutrients (K2O, P2O5, N-forms and organic matter) and heavy metal concentrations following standard extraction procedures. The microbial properties were characterized by colony-forming units (CFUs) and enzyme activity measurements. The results of the nutrient analyses show significantly increased soil-bound K2O, P2O5 and NO2− + NO3− contents linked to the sewage sludge treatments. However, neither the organic matter nor the heavy metal content varied significantly in the sludge-amended soil compared with a control site. The microbiological analyses revealed that the sewage sludge treatments tended to increase the aerobic CFUs, but not that of the anaerobic microbes. The average catalase enzyme activity in both the aerobic and anaerobic samples and the average dehydrogenase activity only in the aerobic layers showed a slight but not significant increase in the compost-amended soils. Overall, these results convincingly demonstrated that amending soils with low doses of municipal sewage sludge composts (lacking any industrial sources) can be a sustainable fertilizing practice taking advantage of their high N, P and K contents that are slowly converted to their bioavailable forms thus preventing their excessive leaching in the groundwater.

Wind-eroded sediment, as an environmental transport pathway of toxic elements and pesticids, can result in environmental and human exposure far beyond the agricultural areas where it has been applied. In our research we quantified the pesticide residues moving in the soil near Szeged (Hungary) on the original soil surface of agricultural areas with a portable wind tunnel. Before the experiments, a portion of the sample area was treated with chlorpyrifos and pendimethalin. A control area was also selected. In 2017-2019, a total of 42 wind event experiments were conducted by examining the topsoil samples. During the experiments, moving soil particles were trapped at various heights (5-10 cm, 20-25 cm and 50-55 cm) and the pesticide concentrates by GC-MS were measured. The enrichment ratios (ER) were calculated, and statistical analyzes were also carried out (SPSS). The measurements obtained that the pendimethalin ER is much higher in the rolled fraction (mean: 13.7) than chlorpyrifos (mean: 2.9). Our measurements showed that the enrichment of chlorpyrifos and pendimethalin can be detected in the rolling and suspended soil particles.

<p>Land application of sewage sludge is an increasingly popular means of the reuse of sewage sludge as it allows for recycling of valuable components, such as organic matter, N, P and other nutrients. Indeed, sewage sludge amendment to the soil modifies the soil’s physico-chemical properties, such as plant-available macro/micro nutrient contents, organic matter content. Additionally, sewage sludge applications can significantly increase the amount of microbial biomass in the soil and can also increase the soil enzyme activities. The aim of the present study is to investigate the impact of low-dose municipal sewage sludge compost amendment on the nutrient status and the biological activity in Chernozem soils. </p><p>The study area, located near Újkígyós (SE Hungary), is a 5.6 ha arable land, where 2.5 m<sup>3</sup>/ha/year municipal sewage compost has been regularly disposed since 2013. The pH (in H<sub>2</sub>O) and humus content of soils were measured according to standard procedures. The macronutrients P<sub>2</sub>O<sub>5</sub> and K<sub>2</sub>O were extracted using ammonium-lactate, while the nitrogen forms (NO<sub>2</sub><sup>-</sup> + NO<sub>3</sub><sup>-</sup> -N) were extracted with KCl-solution. The nutrient content was then determined by a flow injection analysis photometer. In order to determine the bacterial composition and enzyme activity of the soil samples, the number of living cells (CFUs), the catalase enzyme activity (CAT) and the dehydrogenase activity (DHA) were determined. The CO<sub>2</sub> emission was measured by an EGM-5 Portable High Precision CO<sub>2</sub> Meter in the field.  </p><p>The sewage sludge compost applied to Chernozem soils improved soil properties by adding slowly decomposing organic matter, abundant in plant macronutrients (N, K, P). The anaerobic microorganisms and the DHA enzyme activity in the anaerobic soil layers did not increase in the compost-amended soils. The aerobic microorganisms (CFUs) and CAT activity tended to be higher in treated soils compared to the non-amended (control) site, however not significantly. These results suggest that the soil biological activity is only moderately affected by the low-dose municipal sewage sludge compost applications. According to our field CO<sub>2</sub> emission measurements, the yearly application of the sewage sludge compost in a low-dose seemingly did not affect the soil respiration rates, compared to a local control site.</p><p>The research was funded by the ‘Thematic Network for the Sustainable Use of Re-sources – RING2017’ project (program code: EFOP-3.6.2-16-201700010).</p>

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