Impact of Heavy Metals on Species Richness, Abundance and Vertical Distribution of Soil Microarthropods in Waste Dump Sites at Delta Steel Company, Warri, Nigeria

Abstract

Impact of heavy metals in steel industry wastes on species richness, abundance and vertical distribution of soil micro arthropods (mites, collembolans) was investigated at Delta Steel Company premises, Warri, Nigeria. Sampling was conducted fortnightly with a bucket-type auger at 0-10cm, 10-20cm, and 20-30cm depth. Extraction was by modified Bukard model of the Berlese-Tullgren funnel. Results indicated that 21, 8 and15 taxa of microarthropods were recorded at the control, current- dump, and abandoned- dump sites respectively. Five taxa were present in the control but absent from the current- dump and abandoned- dump sites. Seven taxa recorded in the control and abandoned- dump were absent from the current -dump sites. Total abundance was 110 mites (76Cryptostigmata, 32 Mesostigmata, and two Prostigmata) and 12 Collembolans. Distributions among sites were: 65micro arthropods (control), 21 (current-dump), and36 (abandoned - dump). The concentrations of heavy metals were 147.30, 2.50, and 0.12mg/kg for iron, copper and lead, respectively (current- dump), 19.37, 0.09 and 0.02mg/kg for iron, copper, and lead, respectively (abandoned-dump) sites. At the control site, the concentration of iron was 1.65mg/kg; copper and lead were not measurable. A total of 49, 13, and 2 micro arthropods were recorded from depth of 0-10cm, 10-20cm, and 20-30cm, respectively in the control site. At the same respective depth, 6, 11and 5 micro arthropods and 19,11, and 6 micro arthropods were collected from current dump and abandoned dump sites respectively. The variations in abundance among the three sites were statistically insignificant (F=3.1; df 8; p>0.05). Variations in abundance occurred among depths but the correlation coefficient among them was insignificant(r=0.002). Average pH was 7.02, 4.95, and 5.14 at the control, current – dump, and abandoned-dump sites, respectively. Metal pollution from steel industry wastes produced an acidic soil and a decline in abundance at the top 10cm of soil.