Effects of sewage irrigation on agro-environment--A case study from Shijiazhuang Sewage Ir-rigation Areas

Effects of sewage irrigation on crops，soil and ground water in Shijiazhuang Sewage Irrigation Areas are studied．The results show those of the sewage in Shijiazhuang is polluted moderately by organic matter，seriously by sulphide，lightly by heavy meta1． The ground water that is 100 to 200m distant from the sewage channel is polluted．In past forty years，the heavy metal contents in seeds of wheat and corn planted in the sewage-irrigated land are lower than those of the National Foods-Heavy Metals Limited Staodard．those in surface soil are all lower than the second degree standard of the National Soil Environmental Assessment Standard．The contents of soil organic matter and total nitrogen can be improved by irrigating sewage reasonably．