Concentrated flow can induce rill and ephemeral gully erosion in contour ridging systems. To better understand the morphological features of rills, deposition characteristics in contour ridging systems and their influencing factors, rainfall simulation experiments were conducted considering four factors: field slope, row grade, ridge height and seepage discharge. The results showed that a simplified power equation that considered the maximum rill depth and length predicts the erosion volume better than an equation that only accounts for rill length, with prediction accuracies of R 2 = 0.96 and R 2 = 0.61, respectively. The ridge height could promote seepage and extend the maximum rill width and depth. The relationships between seepage and rill width, and seepage and soil loss could be fitted with quadratic equations. Seepage exerted a positive effect when the rill width and total soil loss were <14.3 cm and 0.7 kg, respectively, and presented a negative effect when the rill width and total soil loss were greater. Seepage had a positive effect on the maximum rill depth. Sediment deposition was divided into two types: (i) deposition downstream of the rill and (ii) no deposition on the row sideslope. Greater row grades could result in deposition up to the ridge. The simple rill volume prediction equation could help predicting the soil loss induced by rill erosion in contour ridging systems. The effect of field slope, row grade, ridge height and seepage discharge on soil loss could provide guidance for choosing appropriate ridge morphology on slopeland to reduce rill erosion.
The objectives of this study were to identify the characteristics of groundwater in the petroleum contaminated site and to evaluate the applicability of house-type landfarm facilities heated with briquette stoves in winter season. The six monitoring wells were installed at the site where pH, dissolved oxygen, and temperature were all measured. Also groundwater contaminants, benzene, toluene, ethylbenzene, xylene and total petroleum hydrocarbon, were analyzed twice. House-type two landfarm facilities (12 m × 40 m × 4.8 m) each installed with four briquette stoves were constructed. During four rounds treatment process, VOCs, moisture, temperature were monitored and soil contaminants were analyzed. The pH was 6.37 and considered subacid and DO was measured to be 3.12 mg/L. The temperature of groundwater was measured to be 9.48 o C. The groundwater contaminants were detected only in the monitoring wells within the contaminated area or close to it showing that the groundwater contaminated area was similar to the soil contaminated area. During the landfarm process, 73.3% of VOCs concentration in interior gas was decreased and moisture was lowered from 17.7% to 13.4%. In the morning, at 8:00 am, the temperature was decreased showing soil (5.5 o C) > interior (4.8 o C) > exterior (3.5 o C). In the afternoon, at 2:00 pm, the temperature was soil (8.6 o C) < interior (9.9 o C) < exterior (11.5 o C) with solar radiation. The temperature difference between interior and exterior was 0.7 o C in the morning, but it was 1.6 o C in the afternoon. A total of 130 days were taken for four round landfarm processes. Each process was completed within 33 days showing 80% of cleanup efficiency (1 st order dissipation rate(k) = 0.1771).
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