Effects of Different Particle Sizes of Hydroxyapatite on the Distribution and Migration of Trace Elements (Copper and Cadmium) in a Smelter-Impacted Soil

To study the remediation effect of hydroxyapatite with different particle sizes, a field in situ experiment was carried out by adding conventional hydroxyapatite (0.25 mm) and microhydroxyapatite (3 μm) and nanohydroxyapatite (40 nm) to the contaminated soil and planting Elsholtzia splendens. The distribution and migration of copper (Cu) and cadmium (Cd) in soil were investigated after 4 years. The results show that the application of three different particle sizes of hydroxyapatite significantly raise the soil pH, total phosphorus, and soil organic carbon. Moreover, the addition of hydroxyapatite can reduce the EXC fraction of Cu and Cd by 73.7%–80.1% and 20.8%–35.2%, respectively. In addition, the concentrations of Cu and Cd in >2 mm, 0.25–2 mm, 0.053–0.25 mm, and <0.053 mm aggregate are significantly increased. This improvement indicates that there are risks which may cause the increasing of total Cu and Cd in the soil where the pollution sources still exist. Furthermore, the content of soil colloid is significantly increased, and the colloidal Cu and Cd distribution percentage have been significantly increased by 49.9%–120% and 30.3%–181%. This result illustrates that the application of hydroxyapatite may greatly increase the possibility of colloid and dust migration of Cu and Cd.

Optimization of fertility indices of podzolic soils via cultivation of phytomeliorants

Aim. To determine and estimate the impact of phytopotential of cultivated plants on the fertility indices of podzolic soils, the main factors, limiting the performance of crops, and to establish economic effi ciency of cultivating phytomeliorants, different in their physiological properties. Methods. Field, laboratory, mathematical-statistical. Results. Comprehensive four-year-long studies (2013–2017) established that the optimization of physical and chemical properties of podzolic soils is achieved via the application of phytomeliorant measures. First and foremost, these measures are aimed at preventing the decalcifi cation of soils, i.e. they condition the accumulation of an active Са 2+ ion, which promotes improving the soil characteristics due to progressing development of cumulative soil genesis. It was established that with the mass of alfalfa roots of 9.7 t/ha and sainfoin of 9.9 t/ha, the 0–100 cm layer of podzolic chernozem contains 148.6 and 109.2 kg/ha СаО respectively. Enriching the root-containing layer of soil with calcium compounds promotes replenishing the soil with active calcium, thus ensuring the optimization of the lime potential (pH – 0.5pCa). The latter affects both the acid-alkaline balance and the regulation of physical and chemical processes in soil. It was established that after three years of phytomelioration, the soil in variants with perennial grasses is characterized with higher buffer against acid-alkaline load compared to the control variant which is confi rmed with the indices of acid-alkaline buffer. Taking the abovementioned into consideration, one may assume that the very increase in the activity of calcium is one of buffer mechanisms of soil against acidifi cation. It was proven that phytomelioration is effi cient in terms of improving physical properties of soils, and soil structure, in particular, due to the decrease in the number of dusty and lumpy fractions. It was established that due to phytomeliorant measures the saturation of soil-colloid absorbing complex with calcium ensures intense improvement of water resistance of aggregates for two years. It was proven that optimal values of soil composition density for most crops of the Forest-Steppe zone may be achieved while cultivating Sudan grass for one year. The improvement of the main indices of soil fertility via phytomeliorative measures led to the increase in the performance of corn and barley and improvement of quality properties of grain. Conclusions. Phytomeliorative technology of cultivating podzolic soils ensures the balanced use of soils with simultaneous orientation towards preservation of resources, ecological safety and supplying the population with stable yield of crops with high quality of products.

Relations between soil properties and the 1 M NH 4 NO 3 soluble mobile element fraction

The aim of the present study was to establish whether the 1MNH4NO3extraction is a suitable method for determining the background concentrations of mobile element fractions in soils and for describing the relations among mobile element fractions and soil properties. The 1MNH4NO3extraction resulted As, Cr and Pb concentrations below the detection limit in 90% of the investigated soils. This shows that the mobile element content determined simply in 1MNH4NO3solution is probably inadequate for the determination of the mobile background concentrations of these elements. Therefore, in the risk assessment of soil contamination other soil properties and element fractions – like “total” (cc. HNO3+H2O2soluble) – should also be taken into consideration. The mobile Al concentration increased exponentially below pH 4. No correlation was found among 1MNH4NO3soluble mobile As, Cr, Cu and Pb element concentrations and any investigated soil property. Mobile Co, Mn, Al, Ni and Zn concentrations were determined mainly by soil pH. Soil colloid content correlated particularly with mobile Sr and B contents.