Agrochemical loading in drains and rivers and its connection with pollution in coastal lagoons of the Mexican Pacific

Abstract

The state of Sinaloa in Mexico is an industrialized agricultural region with a documented pesticide usage of 700 t year; which at least 17 of the pesticides are classified as moderately to highly toxic. Pollutants in the water column of rivers and drains are of great concern because the water flows into coastal lagoons and nearshore waters and thereby affects aquatic organisms. This study was done in four municipalities in the state of Sinaloa that produce food intensively. To investigate the link between pollution in the lagoons and their proximity to agricultural sites, water was sampled in three coastal lagoons and in the rivers and drains that flow into them. Seawater from the Gulf of California, 10 km from the coast, was also analyzed. Concentrations of nutrients, organochlorines, and organophosphorus pesticides were determined. Nutrient determination showed an unhealthy environment with N/P ratios of <16, thus favoring nitrogen-fixing cyanobacteria. The organochlorine pesticides showed a clear accumulation in the coastal lagoons from the drains and rivers, with ΣHCH showing the highest concentrations. In the southern part of the region studied, pollution of the coastal lagoon of Pabellones could be traced mainly to the drains from the agricultural sites. Accumulation of OC pesticides was also observed in the Gulf of California. Tests for 22 organophosphates revealed only five (diazinon, disulfoton, methyl parathion, chlorpyrifos, and mevinphos); diazinon was detected at all the sites, although methyl parathion was present at some sites at concentrations one order of magnitude higher than diazinon.

Environmental Policy in Mexico

“…This is definitely less costly than expenditures into water treatment facilities -as seen in San Luis Potosí (United States of America, Department of Commerce, 2016b) -or new conveyance architecture, and it can conceivably reduce reliance upon existing infrastructure by having local communities assume their share of their burden (through best practices) so that waste and effluents are minimized. Best practices, enforced at the local or communal level, would certainly aid a state such as Sinaloa inasmuch as this state has long struggled with the improper and promiscuous use of dangerous pesticides on arable land (Arellano-Aguilar et al, 2017). The literature definitely points to the value of allowing locals to police their own, not least of all because of the reduced strain this creates for over-taxed state bureaucracies.…”

Hexachlorocyclohexanes, Cyclodiene, Methoxychlor, and Heptachlor in Sediment of the Alvarado Lagoon System in Veracruz, Mexico

“…The presence of organochlorine compounds represents an environmental risk because of their bioaccumulation in the food chain and the alteration of aquatic ecosystems in both fresh and coastal waters [7,11]. Likewise, the contaminating effect of these compounds in productive activities such as fishing should be considered, and this effect is associated with the fact that the consumption of aquatic organisms with a certain concentration of these compounds represents a potential risk to public health (bioaccumulation and biomagnification) and can alter the quality of these ecosystems [7].…”

“…Five pesticides (aldrin, dieldrin, endrin, mirex, and chlordecone) have been banned in Mexico, five are not marketed and are banned (chlordane, lindane, DDT, sulfluramide, and endosulfan), and finally six others have never been approved for use (heptachlor, HCB, toxaphene, pentachlorobenzene, and α-, and β-HCH) [7]. However, despite being banned, the presence of these compounds indicates their regular use, and degradation products of the original compounds are found in the environment [7]. for the aquatic biota that is in direct contact with the sediment in these sampling sites, particularly the molluscs, which act as a link between higher trophic levels like humans, which are indicative of pollution [31].…”

“…Five pesticides (aldrin, dieldrin, endrin, mirex, and chlordecone) have been banned in Mexico, five are not marketed and are banned (chlordane, lindane, DDT, sulfluramide, and endosulfan), and finally six others have never been approved for use (heptachlor, HCB, toxaphene, pentachlorobenzene, and α-, and β-HCH) [7]. However, despite being banned, the presence of these compounds indicates their regular use, and degradation products of the original compounds are found in the environment [7]. The authors of [11] indicated that these sites are located in the central part of the Alvarado lagoon system, where the circulation of water bodies is minimal since these sites also have a low depth of approximately 1.5 m. They also pointed out that this area of the lagoon presents silt-like sediment, which contributes to a greater accumulation of organic matter, because this type of soil, rich in humus, absorbs a greater quantity of pesticides than sandy soils.…”

“…For its transport capacity, the presence of these compounds has been determined in various aquatic ecosystems of Mexico, becoming a risk to public health and the environment [5][6][7][8]. They have been found mainly among the coastal ecosystems located in the southeast region of the Gulf of Mexico.…”