Sanitary landfill improved CNPS microbial functional gene abundance compared to non-sanitary landfill

Abstract

The landfill soil microbes related to nutrient cycling, such as carbon (C), nitrogen (N), phosphorus (P), and sulfur (S) cycling, are changed by continuous waste decomposition. Monitoring the changes that occur in CNPS functional genes in different types of landfill cover soils as a whole is vital to our understanding of microbial function in element cycling. The high-throughput quantitative polymerase chain reaction–based chip (HT-Q-PCR) method was used to explore differences in the abundance of 71 CNPS functional genes in cover soils (0–20 cm, 20–40 cm, and 40–60 cm) from two types of landfills (sanitary and non-sanitary) and to examine the soil pH and the concentrations of C, N, P, S, and 6 heavy metals. The absolute abundances of CNPS functional genes varied greatly, with the highest gene abundance reaching 5.28 × 109 copies per gram of soil, and 11% (8/71) of the genes not detected. Among the detected genes, there was a much higher functional gene abundance in the sanitary landfill than in the non-sanitary landfill cover soils, and the difference in gene abundance became more significant with increasing sampling depth. In addition to landfill type and sampling depth, the soil pH, soil dissolved organic carbon (DOC), available N (AN), and available S (AS) correlated significantly to functional gene abundance. Conversely, soil heavy metals, such as Cu, Cd, Cr, Zn, and Ni, had no effects on functional gene abundance, which might be due to their low contents. Our results suggest that sanitary landfill increases soil CNPS gene abundance compared to that of non-sanitary landfill. The findings provide suggestions for landfill treatment and ecological protection, especially regarding vegetation restoration.