[Effects of exogenous dissolved organic matter and temperature on copper forms in red soil].

A simulating incubation test was conducted to evaluate the effects of exogenous dissolved organic matter (DOM) and incubation temperature on the copper forms in red soil. Comparing with the control, adding different amount of DOM increased the content of soil exchangeable Cu, but decreased the content of soil Fe-Mn bound Cu. With increasing time of incubation, the content of soil exchangeable Cu in all DOM-added treatments had a decreasing trend. By the end of the incubation, treatment 250 mg DOM x L(-1) had the highest contents of soil exchangeable Cu and carbonate bound Cu, while treatment 500 mg DOM x L(-1) had the highest content of soil Fe-Mn bound Cu. In the treatments with DOM addition, the content of soil organic bound Cu increased by 10.67%-23.66%, compared with the control. At incubation temperature 25 degrees C and 45 degrees C, the contents of soil exchangeable Cu and Fe-Mn bound Cu decreased with increasing time of incubation; while at 5 degrees C, an opposite trend was observed. At these three temperatures, the content of soil carbonate bound Cu in treatments with DOM addition increased with incubation time. The content of soil organic bound Cu increased with increasing temperature, but that of soil residual Cu decreased at lower temperature (5 degrees C).

[Arsenic accumulation in different agricultural soils in Shouguang of Shandong Province].

The study on the soil arsenic (As) accumulation under different types of agricultural use in Shouguang of Shandong Province showed that farmland soils had an average As content of 9. 63 mg x kg(-1) , with the highest being 15. 15 mg x kg(-1) . Compared with the local background value (9. 3 mg As x kg(-1)) , 53. 1% of soil samples was detected as As enrichment. The soil As content was high in the west, east and north parts of Shouguang, relatively lower in the middle part, and the lowest in the south part. Different agricultural use had an obvious effect on the soil As content, which was decreased in the order of wheat/maize land > cotton field > protected vegetable land > uncovered vegetable land. Such a difference in soil As content was mainly affected by agricultural activities. With the increasing year of vegetable planting, soil As content had an increasing trend, because the As input from pig dung and chicken feces was the main source of soil As in protected vegetable land. Soil As enrichment could be reduced to some degree by applying soybean cake fertiliz-