to extend the natural levee for agri- 

 culture. 



An undetermined area of marsh land 

 has been affected because of the con- 

 struction of canals. The topography and 

 hydrology of the marsh have been most 

 altered in the vicinity of dense canal 

 networks associated with major oilfields 

 such as Venice, Leeville, and Lafitte. 



Hydrological changes 



Hydrology has been altered in three 

 ways. (1) Upland runoff enters water 

 bodies rapidly and directly via canals, 

 bypassing wetlands that would otherwise 

 receive it. (2) Water exchange between 

 different parts of the basin is speeded 

 up because of the construction of new 

 canals or the deepening of natural 

 channels for the mid Barataria basin. 

 (3) Water flow over wetlands is blocked 

 because of spoil placement. These 

 alterations reduce the deposition of 

 suspended sediments and exacerbate the 

 existing sediment deficit in inland 

 marshes. Because sedimentation is the 

 single most important source of "new" 

 nutrients to the marshes (Delaune and 

 Patrick 1980b), a reduction of sediments 

 leads to lower marsh productivity. 



Toxic Substances in the Barataria Basin 



The possibility of toxic pollution 

 of waters and wetlands is great because 

 of their proximity to large urban cen- 

 ters, extensive agricultural areas, and 

 a high concentration of petrochemical 

 industries. There is input from indus- 

 trial plants, hazardous waste sites, 

 pesticides from agricultural runoff, 

 pesticides and heavy metals from urban 

 runoff, petroleum hydrocarbons from oil 

 exploration and production, and the 

 spraying of herbicides for aquatic weed 

 control. Figure 49 shows the locations 

 of major petrochemical plants in or near 

 the Barataria basin. 



The petrochemical industries within 

 the basin produce a variety of products 

 such as vinyl chloride, nitric acid, 

 hydrochloric acid, methyl-ethyl ketone, 

 styrene, sulfuric acid, acrylonitrile, 

 benzene, and various herbicides and 



pesticides (Mumphrey et al. 1978). All 

 manufacturing processes result in waste 

 materials as by-products. In many cases, 

 wastes are known to have leaked into the 

 environment (Dow and Garcia 1980). Over 

 sixty solid waste sites, pits, ponds, 

 and lagoons associated with industry 

 have been located within the Barataria 

 basin (USEPA 1980). 



Agricultural runoff also introduces 

 pollutants such as pesticides, organic 

 material, nutrients, and sediments into 

 receiving water bodies. Crop production 

 is not regulated to prevent pollutants 

 from entering water bodies (although 

 feedlot operations are regulated). 

 Agricultural pesticide usage (including 

 herbicides, insecticides, and fungi- 

 cides) in the Barataria basin is ap- 

 proximately 211,000 kg/yr (465,000 

 lbs/yr) (Hopkinson 1978). The percent- 

 age that reaches the wetland system is 

 unknown. The Barataria basin is cur- 

 rently losing soil at a rate of 327,000 

 mt/yr (360,495 tons/yr) from cropland 

 and 2,700 mt/yr (3,016 tons/yr) from 

 pastureland (Hopkinson 1978). As water- 

 borne erosion occurs, the soil with 

 adsorbed chemicals is transported from 

 agricultural areas into water bodies via 

 runoff. 



A typical moderate-sized city an- 

 nually discharges 45,000 to 113,000 kg 

 (100,000 to 250,000 lbs) of lead; 2,722 

 to 13,608 kg (6,000 to 30,000 lbs) of 

 mercury; 6,804 to 13,608 kg (15,000 to 

 30,000 lbs) of chromium; 38,555 to 

 40,823 kg (85,000 to 90,000 lbs) of 

 copper; 63,503 to 136,078 kg (140,000 to 

 300,000 lbs) of zinc; and over 4,536 kg 

 (10,000 lbs) of nickel. These sub- 

 stances originate from automobile use, 

 including gasoline combustion, tire and 

 brake wear, and oil loss. Other sources 

 of contamination in urban runoff in- 

 clude, rubber and metal lost from 

 vehicles, industrial combustion product 

 residue, and pesticides and herbicides 

 applied to lawns and parks (U.S. EPA 

 1977). 



Available data on toxic substances 

 in the Barataria basin are scarce. The 

 ability to monitor possible pollution 

 sources is limited because there is not 



118 



