# A Systematic Review on Earthworms in Soil Bioremediation
## 3 Results
### Alloobe Organic Vermieremediation
The presence of earthworms and soil microorganisms resulted in a statistically higher reduction rate (94.9% and 95.7%) than sterilised treatments with earthworms alone (52.3% and 60.3%). _A. robustus_ showed significantly higher atrazine accumulation in tissues than _E. fetida_. Antibiotics are still used worldwide for bacterial infection treatments; because of the poor absorption rate in the intestines of animals and humans, these substances are discharged through excretions and can enter into water or soil ecosystems [113; 114]. A group of harmful antibiotics widely and globally consumed is represented by Tetracyclines (TCs) [115]. These substances are widely used because of their broad-spectrum activity and low cost [116]. In Europe, from 2010 to 2020, despite their consumption in the community sector having decreased (while in the hospital sector, it has remained unchanged), attention is still high on the dangers of TCs, above all due to antimicrobial resistance [117]. The study conducted by [PERSON] et al. [118] investigated the effects of two earthworms with different behaviours and ecological functions (_E. fetida_ and _A. robustus_) on TCs degradation in sterilised and natural soil. The authors demonstrated that indigenous soil microbes have weak power to mineralise TCs; no significant differences were found between treatments with sterilised and natural soil alone. On the contrary, earthworms in sterile treatment showed a good remedial capacity, which significantly increased in association with soil bacteria. Looking at Figure 3, on average, slightly higher reduction rates were observed for _A. robustus_ (61.9%) than for _E. fetida_ (57%). Also, [PERSON] et al. [100] tested the efficacy of _E. fetida_ versus TCs, obtaining statistically different results compared to the treatment alone at the higher dose applied (100 mg kg\({}^{-1}\)). According to [PERSON] et al. [119], using _Metaphire guiallelmi_ in soil vermiremediation experiments is a more suitable choice as it is commonly isolated in farmland and is more sensitive to some contaminants than _E. fetida_[120]. _M. guillelmi_ significantly accelerated the TCs degradation, with an average value of 83.17% compared to soil without earthworms (63.55%). At the same time, the enzyme activity established no oxidative damage due to TCs, demonstrating the efficient detoxification ability of the antioxidant system in this species. Microcosm experiments were conducted by [PERSON] et al. [121] to study the effects of _Pheretima guillelmi_ on the fate of Sulfamethoxazole (SMX), an antibiotic commonly detected in almost all environmental compartments. The authors found that the _P. guillelmi_ activities significantly reduced the SMX concentration in soil (99.55%) compared to the treatments without them due to their gut detoxification and stimulation of soil indigenous microbes. Polychlorinated biphenyls (PCBs) are a group of organic chemicals comprising carbon, hydrogen and chlorine atoms of anthropogenic origin, belonging to chlorinated hydrocarbons. These compounds are a source of concern because they are globally distributed, highly persistent and toxic [122, 123]. [PERSON] et al. [102] studied the _E. fetida_ removal ability of decachlorobiphenyl (DCB) in the vermicomposting process. Data in Figure 3 showed that earthworms and their symbiotic bacteria could significantly reduce high DCB concentrations, with a value of 65.24%. Among all the research articles (53) analysed in this review, only two experiments used a product of earthworms, the vermicompost, as an alternative method to the earthworms' presence. [PERSON] et al. [124] used _E. fetida_'s casts to accelerate the atrazine biodegradation pathway, testing combinations of sterilised and unsterilised soils and casts. The contribution of vermicompost both in physical (sterilised cast 44.23%) and biological (unsterilised 60.77%) terms was decisive for reducing the contaminant compared to sterilised soil alone.