Limitations of soil enzymes as indicators of soil pollution
Soil enzyme activities are considered to be sensitive to pollution and have been proposed as indicators for measuring the degree of soil degradation. In this work we found that in three galician soils exposed to various degrees of pollution by tanning effluent, hydrocarbons or landfill effluent, the changes in the activities of individual enzyme did not allow precise quantification of soil degradation. Thus, the enzymatic activities in polluted soils with respect to that in control soils was between 37 and 260% for phosphomonoesterase, between 16 and 250% for β-glucosidase, between 28 and 194% for urease and between 24 and 251% for dehydrogenase. The degree of degradation was, however, clearly shown in all cases by the ratio Nc/Nk, where Nk is Kjeldahl nitrogen and Nc is a function of microbial biomass C and nitrogen mineralization capacity combined with three enzyme activities (phosphomonoesterase, β-glucosidase and urease). This ratio, Nc/Nk, exhibited all the attributes of a good pollution indicator and, in particular, was able to discriminate between the effect of the pollutant and any prior degradation of the sites. It is concluded that quantification of soil degradation can require that information on enzyme activities be supplemented with information on other biochemical soil properties.
 The use of microbial parameters in monitoring soil pollution by heavy metals
Microbial parameters appear very useful in monitoring soil pollution by heavy metals, but no single microbial parameter can be used universally. Microbial activities such as respiration, C and N mineralization, biological N2 fixation, and some soil enzymes can be measured, as can the total soil microbial biomass. Combining microbial activity and population measurements (e.g., biomass specific respiration) appears to provide more sensitive indications of soil pollution by heavy metals than either activity or population measurements alone. Parameters that have some form of “internal control”, e.g., biomass as a percentage of soil organic matter, are also advantageous. By using such approaches it might be possible to determine whether the natural ecosystem is being altered by pollutants without recource to expensive and long-running field experiments. However, more data are needed before this will be possible. Finally, new applications of molecular biology to soil pollution studies (e.g., genetic fingerprinting) which may also have value in the future are considered.
 Current status of agricultural soil pollution by heavy metals in China: A meta-analysis
In the last decades, agricultural soil pollution by heavy metals has been extensively investigated in China. However, nearly all studies were field monitoring in small regions and/or with limited samples, which may not represent soil pollution situation at the national scale. In this paper, attempt was made to provide a comprehensive report about heavy metal pollution in China based on meta-analysis of reviewed data. Given the characteristics of field monitoring studies, the weighted mean values based on “sampling number”, “study area”, and “standard deviation” were calculated to represent national mean values. In addition, subgroup analysis and cumulative meta-analysis were applied to explore the spatial and temporal variations as well as the influence of cropping systems. 336 articles published from 2005 to 2017 were reviewed in the analysis. Eight heavy metals (cadmium (Cd), chromium (Cr), mercury (Hg), lead (Pb), arsenic (As), copper (Cu), zinc (Zn) and nickel (Ni)) were analyzed. The contents of Cd and Hg were increased compared to background values, while, other six elements showed no significant accumulation. Little pollution was found in normal farmland, which was far from obvious anthropogenic emissions, but Cd and Hg in mining & smelting areas and industrial areas continued to accumulate significantly. Moreover, the accumulation had slowed down or decreased since 2012, which might be due to reduced use of coals, non-ferrous metals and agro-chemicals. Heavy metal contents were generally higher in southwest and south coastal areas but lower in northwest regions, whereas vegetable and paddy fields had higher concentrations than upland and other land use. This study provides information on soil pollution caused by heavy metals and its affected regions and cropping systems on a national scale. It can be useful for developing heavy metal pollution control and management strategies in China.
 Management of Increasing Soil Pollution in the Ecosystem
The present paper is a mini review of the increasing soil pollution in the environment and the possible handy options available, to curb its rate. Soil being a non-renewable resource, must be protected from all types of pollutants. The health of all life forms is associated with the health of soil. Any degradation in the quality of soil can significantly produce many undesirable changes in the environment. Adoption of suitable strategies to protect our motherland from contamination is must for all of us to save ourselves and continuation of natural cycles in the ecosystem.
 Effects of Watering Regimes on the Intrinsic Qualities of Bioremediated Waste Engine Oil-Polluted Soil
Five (5) kg of sun-dried top-soil was each placed into large perforated bowls and mixed thoroughly with waste engine oil (WEO) to obtain similar concentrations of 2.5% w/w oil in soil. The polluted soil was thereafter amended with 4g NPK (15:15:15) fertilizer to enhance microbial activity. Having previously determined the soil’s water holding capacity to be 215 ml/kg soil, the entire setup was divided into 6 sets according to watering regimes. One set was irrigated with 1000 ml distilled water only once a week (1PW); the other sets were irrigated twice in a week (2PW), once a month (1PM), and the other twice a month (2PM). One set was deprived of moisture throughout the duration of the study (NWT), while the control experiment was carefully irrigated daily to saturation (CTRL). The entire experimental set up was left for three months in a well ventilated screen house with inherent room temperature range (28 – 30ºC). Results of the present study showed reductions in heavy metal contents, but in differing degrees. One week after pollution (WAP) concentration of Fe was 1097.34 mg/kg, Mg was 18.4mg/kg, Cu was 5.63 mg/kg and Ni was 2.95 mg/kg. Total hydrocarbon content (THC) was 3425.63mg/kg. However, 3 months later when polluted soil was subjected to varying soil watering regimes, Fe in soil was 875.43mg/kg, Cu was 3.83 mg/kg and THC was 1095.54mg/kg respectively in the control, compared to values for Fe (687.3 mg/kg), Cu (3.83 mg/kg) and THC (445.45 mg/kg) respectively, when soil was wetted once a week. The contamination factor (CF) values presented for Fe, Mg, Cu, and Ni were all less than unity (CF < 1) an indication, that these heavy metals were remediated to levels below when soil was not yet exogenously polluted. There were reductions in polyaromatic hydrocarbon (PAH) contents of the soil. At one WAP total PAH was 923.90mg/kg as against 458.59 mg/kg 3 months later. When soil was wetted once a week, total PAH was 85.98mg/kg, 104.89 mg/kg when irrigated twice a week, 170.74 mg/kg when irrigated twice a month and 302.60mg/kg when soil receive no wetting at all. Comparatively total concentration of PAH was lowest at 1PW. Bacterial isolates of the oil polluted soil subjected to watering treatment once a week were Bacillus subtilis, Pseudomonas sp., and Serratia marcescens, whereas fungal species included Aspergillus niger, Penicillium sp. and Trichoderma sp.
 Trasar-Cepeda, C., Leiros, M.C., Seoane, S. and Gil-Sotres, F., 2000. Limitations of soil enzymes as indicators of soil pollution. Soil Biology and Biochemistry, 32(13), pp.1867-1875.
 Brookes, P.C., 1995. The use of microbial parameters in monitoring soil pollution by heavy metals. Biology and Fertility of soils, 19(4), pp.269-279.
 Huang, Y., Wang, L., Wang, W., Li, T., He, Z. and Yang, X., 2019. Current status of agricultural soil pollution by heavy metals in China: A meta-analysis. Science of The Total Environment, 651, pp.3034-3042.
 Sarkar, D., Rakesh, S., Ganguly, S. and Rakshit, A., 2017. Management of increasing soil pollution in the ecosystem. Advances in Research, pp.1-9.
 Ikhajiagbe, B., Anoliefo, G.O., Oshomoh, E.O. and Agbonrienrien, B., 2013. Effects of watering regimes on the intrinsic qualities of bioremediated waste engine oil-polluted soil. Annual Research & Review in Biology, pp.107-123.