Changes on the Phytoavailability of Nutrients in a Mine Soil Reclaimed with Compost and Biochar

Water, Air, & Soil Pollution, 2016, 227:453

DOI: 10.1007/s11270-016-3155-x

Mine soils often contain high levels of metals that produce serious environmental problems and poor fertility conditions that limit their reclamation. The aim of this study was to evaluate the influence of a compost and biochar amendment on the nutrient phytoavailability in a mine soil from the depleted copper mine of Touro (Spain). For this purpose, a greenhouse experiment was carried out amending the mine soil with increasing proportions (20, 40, 80 and 100%) of the compost and biochar mixture and planting Brassica juncea plants. The results revealed that the mine soil had an extremely acid pH and low fertility conditions and was affected by copper contamination. The addition of compost and biochar to the mine soil increased soil pH values (from 2.7 to 8.7), total carbon (from undetectable values to 149 g kg−1) and total nitrogen (from undetectable values to 11,130 mg kg−1) contents and phytoavailable concentrations of K, Mg, Na and P and promoted plant growth, since B. juncea plants did not survive in the untreated mine soil. The application of amendment decreased the phytoavailable concentration of Al, Co, Cu, Fe and Ni in the soil, resulting in a reduction of copper toxicity. The use of compost and biochar as a soil amendment combined with B. juncea plants could be an efficient strategy for the reclamation of degraded soils with low fertility conditions.

Build-up of carbon fractions in technosol-biochar amended partially reclaimed mine soil grown with Brassica juncea

Journal of Soils and Sediments

May 2016, Volume 16, Issue 5, pp 1529–1537

DOI: 10.1007/s11368-016-1358-9

Soil organic carbon (SOC) and its labile fractions are strong determinants of physical, chemical and biological properties. The objective of the present work was to evaluate the effects of organic amendments (technosol made of wastes and biochar) and Brassica juncea L. on the soil C fractions in a reclaimed mine soil.

The studied soil was from a former copper mine that was subsequently partially reclaimed with vegetation and wastes. A greenhouse experiment was carried out to amend the mine soil with different proportions of technosol and biochar mixture and planting B. juncea. B. juncea plants can tolerate high levels of metals and can produce a large amount of biomass in relatively short periods of time.

The results showed that with the addition of biochar and wastes, soil pH increased from 2.7 to 6.18, SOC from undetectable to 105 g kg−1 and soil total nitrogen (TN) from undetectable to 11.4 g kg−1. Amending with wastes and biochar also increased dissolved organic carbon (DOC) from undetectable to 5.82 g kg−1, carbon in the free organic matter (FOM) from undetectable to 30.42 g kg−1, FAP (carbon in fulvic acids removed with phosphoric acid) from undetectable to 24.14 g kg−1 and also increased the humification ratio, the humification index, the polymerisation rate and the organic carbon in the humified fractions (humic acids, fulvic acids and humin). Soils amended and vegetated with B. juncea showed lower FOM values and higher humification index values than the soils amended only with biochar and wastes.

This study concludes that the combined addition of wastes and biochar has a greater potential for both increasing and improving organic carbon fractions in mine soils. The authors recommend the application of biochar and technosol made of wastes as a soil amendment combined with B. juncea on soils that are deficient in organic matter, since they increased all of the SOC fractions in the studied copper mine soil.

Assessing the influence of technosol and biochar amendments combined with Brassica juncea L. on the fractionation of Cu, Ni, Pb and Zn in a polluted mine soil

Journal of Soils and Sediments

February 2016, Volume 16, Issue 2, pp 339–348

DOI: 10.1007/s11368-015-1222-3

Soil metal pollution is a widespread problem around the world and remediation of these soils is difficult. The objective of this study was to investigate the effect of two different strategies on the chemical fractions of metals in a soil of a depleted copper mine: (1) amending with a mixture of a technosol made of wastes and biochar and (2) amending combined with planting vegetation (Brassica juncea).

A 3-month greenhouse experiment was carried out to evaluate the effects of organic amendments and vegetation on the metal fractionation of Cu, Ni, Pb and Zn in a mine soil of the depleted copper mine at Touro (Spain). We compared the influence of organic amendments alone (technosol + biochar) and combined with mustard plants (Brassica juncea L.).

The results showed that amending with a technosol made of wastes promoted plant growth (from 0.7 to 2.9 g of biomass produced) and reduced the CaCl2-extractable metal concentration in soil, reduced the mobility factor of Cu from 18.3 to 1.6, Ni from 47.5 to 2.3 and Pb from 17.9 to 2.1, and also reduced the concentration of metals in the mobile soil fractions. It was not possible to grow up Brassica juncea plants in the untreated settling pond soil due to the extremely degraded conditions of that soil. However, the application of the used technosol increased the Pb and Zn pseudototal concentrations in the amended soils.

We conclude that the combination of amending with wastes and planting B. juncea provides little additional benefit for remediating a metal-polluted soil compared with incorporation of wastes alone.